This invited plenary contribution presents some of our recent results in the area of optical nonlinear devices. It also briefly reviews the origins and past developments of what became a field of photonics. In conclusion it makes an attempt to suggest where photonics research might be directed in the future, which would truly materialize its inherent pervasiveness.

History and recent developments of terahertz devices utilizing lattice and molecular vibration are presented. In particular, semiconductor Raman oscillator and amplifier, parametric generation of terahertz wave using polariton-phonons in dielectrics and semiconductors are discussed, together with future important applications in the field of medicine, biology, and pharmacy.

A novel approach is proposed to all-optically route packets/datagrams in a core optical network. An encapsulation scheme is designed in which network destination addresses are converted into Cartesian-like addresses specifying a device by its physical location. The scheme is termed Cartesian Optical Routing Environment (CORE) routing. CORE allows the all-optical routing of packets along a serial point-to-point path in a network. Routing decisions are made by bitwise comparing an incoming packet's CORE destination address to the physical address of the local router using simple optical logic that is currently achievable. The comparison has three possible results: destination greater than, less than or equal to the local address. Based on the results of the comparison, the packet is either all-optically switched along the serial point-to-point path, or passed to the electronic component of the local router for further processing. This novel protocol solution is based on earlier work that proposed Cartesian routing as an alternative to IP routing. The optical logic and circuitry required to perform the routing functions are also considered based on the work in reference 2. The proposed scheme is evaluated using network traffic information from the Candian high-speed optical research and education network, CA*net3.

Applications of optical code division multiplexing (OCDM) to multi-tera bit/s photonic network are reviewed. The experimental demonstrations include a high spectral efficiency OCDM/WDM transmission as a link technology and a transparent virtual optical code/wavelength path (VOCP/VWP) network as a node technology.

MIMO channel signal transmission is one of the key technologies to realize broadband mobile communication systems with the bit rate of up to 100 Mbit/s. Space Division Multiplexing (SDM) with multiple antennas in MIMO channel transmission is a promising technology to achieve a high capacity system with very high peak throughput. In this paper, we describe the receiver constructions for MIMO-SDM systems with iterative signal processing. We also introduce the recent research activities of dual polarized antennas for MIMO-SDM channel signal transmission, required microwave propagation characteristics, and so on.

A cylindrical microwave resonant cavity in TE₀₁₁ mode in a microwave spectrometer is used to identify phase transitions in liquid crystal 4-methoxybenzilidene-4'-butylanine (MBBA). The microwave dielectric response in this liquid crystal is studied at microwave frequencies of 9.52 and 10.1 GHz. The method of cooling the sample as described in this paper is very effective in producing the metastable modification in this liquid crystal. Dielectric relaxation in this molecule is studied by using Debye's theory of polar molecules, and Slater's perturbation equations are used to calculate the real and imaginary parts of the dielectric constant. The microwave spectrometer is also used to study the behavior of nanotubes as a function of frequency. There seems to be a very high absorption of microwaves at certain frequencies in samples of carbon nanotubes studied in this experiment. We have attempted to calculate the rates of absorbance of microwaves first by using sample of pure polycarbonate and then compared the results obtained with various blends. The reduction in the amplitude and the overall attenuation of the microwave signal applied is the measure of the absorption of microwaves in these samples.

The Mars Exploration Rover (MER) mission is designed to investigate Martian geology, investigate the role of water, and seek information on the climate history of the red planet at two sites. The Telecommunications Subsystem consists of the Radio Frequency Subsystem (RFS) operating at 7.1/8.4GHz (X-band), the Ultra High Frequency (UHF) Subsystem operating at 401/437MHz, the RFS and UHF Antenna Subsystem and the Radar Altimeter Subsystem (RAS) operating at 4.3 GHz (C-band). Science data return is enhanced through UHF relay communications with the Mars Odyssey (ODY) orbiter up to 128 kbps. Relay communications will also be demonstrated with the ESA Mars Express orbiter.

For determination of the limitng error rate in mobile indoor optical diffusion networks, which are working in infrared spectral area, is one of crucial parameters the knowledge of the light distribution within the overlaying premises. Because it is general knowledge that the achievement of the secure discriminating level at receiving logic 1 and logic 0 requires to capture the satisfactory quantity energy, that is the bigger by the bigger is the demands on the error rate decreasing and what higher is the data signaling rate. This contribution describes the experimental results of the light distribution inside a model rooom. Measuring configuration consists of diffuse source and receiver. Position of the source is especially the corner of pico-cell. Measurements have been achieved in the empty room, the room with obstacles and for different surface walls. Results are processed graphically in shape putting detailed statement about spatial luminosity distribution with determination of critical zones. The operating LED wavelength is about 700 nm.

Different circuit-level approaches to study the effects of nonlinear distortion on coded division multiple access (CDMA) wireless communication systems are analyzed. These techniques are used to predict spectral regrowth and baseband signal vector constellation at the output of a nonlinear device. To demonstrate and verify their capability, a simple MESFET amplifier has been tested with a W-CDMA waveform. The active device was widely characterized including the extraction of large-signal model parameters. Measurements were satisfactorily compared with the simulated results.

In this paper some generalized sub-optimum unequally spaced channel allocation techniques have been suggested for minimizing Four Wave Mixing (FWM) effect in Dense Wavelength Division Multiplexed (DWDM) fiber optic systems. These techniques are sub-optimum because their use will not reduce the FWM noise power generation at the frequencies matching the channel frequency to zero, but these are useful in reducing the FWM noise substantially. The major advantage of our techniques of USCA is that these can be applied to a small as well as a large number of channels with equal ease. Also the use of our techniques will not increase the operating bandwidth requirement of the system under the condition that the minimum inter channel separation used in our allocation technique is not less than the inter-channel separation required for good channel selectivity at the receiver. Efficiency of these techniques in minimizing the detrimental effect of FWM in DWDM fiber optic systems has been studied and compared with that of equally spaced channel allocation systems.

Bluetooth is the new emerging technology for wireless communication. It can be used to connect almost any device to another device. The traditional example is to link a Personal Digital Assistant (PDA) or a laptop to a mobile phone. That way you can easily take remote connections with your PDA or laptop without getting your mobile phone from your pocket or messing around with cables. A Class 3 Bluetooth device has range of 0,1 - 10 meters. The architecture of Bluetooth is formed by the radio, the base frequency part and the Link Manager. Bluetooth uses the radio range of 2.45 GHz. The theoretical maximum bandwidth is 1 Mb/s, which is slowed down a bit by Forward Error Correction (FEC). Bluetooth specification designates the frequency hopping to be implemented with Gaussian Frequency Shift Keying (GFSK). The base frequency part of the Bluetooth architecture uses a combination of circuit and packet switching technologies. Bluetooth can support either one asynchronous data channel and up to three simultaneous synchronous speech channels, or one channel that transfers asynchronous data and synchronous speech simultaneously. The Link Manager is an essential part of the Bluetooth architecture. It uses Link Manager Protocol (LMP) to configure, authenticate and handle the connections between Bluetooth devices. Several Bluetooth devices can form an ad hoc network. In these piconets, one of the Bluetooth devices will act as a master and the others are slaves. The master sets the frequency-hopping behavior of the piconet. It is also possible to connect up to 10 piconets to each other to form so-called scatternets. Bluetooth has been designed to operate in noisy radio frequency environments, and uses a fast acknowledgement and frequency-hopping scheme to make the link robust, communication-wise. Bluetooth radio modules avoid interference from other signals by hopping to a new frequency after transmitting or receiving a packet. Compared with other systems operating in the same frequency band, the Bluetooth radio typically hops faster and uses shorter packets. This is because short packages and fast hopping limit the impact of microwave ovens and other sources of disturbances. Use of Forward Error Correction (FEC) limits the impact of random noise on long-distance links. Bluetooth transmissions are secure in a business and home environment. Bluetooth has built in sufficient encryption and authentication and is thus very secure in any environment. In addition to this, a frequency-hopping scheme with 1600 hops/sec. is employed. This is far quicker than any other competing system. This, together with an automatic output power adaption to reduce the range exactly to requirement, makes the system extremely difficult to eavesdrop. Information Integrity in Bluetooth has these components: Random Number Generation, Encryption, Encryption Key Management and Authentication.

This work analyzes the ring network availability based on SDH technology. Two protection mechanisms are specially analyzed: Path Protection and Self Healing Ring with two and four fibers. Calculation of availability is made using the data pertaining to the failures of optical cables and equipment which are obtained during years-long observation of SDH network of HPT Mostar as well as those obtained from manufacturers.

The possible improvement in the performance of networks without electro/optical conversion has been investigated by introducing optical memories. In particular, different buffering methods are presented, where optical signal is stored in the memory blocks. The need to process signals at electrical level limits the performance of transmission links or computing systems. This limit can be overcome through the introduction of all optical processing, thus avoiding the electro/optical conversion.

Fiber Bragg gratings with phase-only sampling has been shown to greatly increase the reflectivity of multi-channel designs when compared to equivalent amplitude sampling. A new 21 channel grating design that exhibits excellent channel to channel uniformity is presented in this paper. When used as a dispersion compensator it cancels the chromatic dispersion of an 80 km long section of standard telecommunication fiber (SMF-28) in the 40GBd data link. The individual channels are separted by 200 GHz, thus covering the whole C-band.

Paper is engaged in determination of the minimum received optical power on photodetector for defined transmission rates. The relationship between amplitude noise and transmission rate in FSO communication systems is shown. It means for diffused optical access networks that it is always necessary to determine the lay-out of the light intensity in area which entails in other words that by this distribution it is also determined three-dimensional distribution of the transmission rates.

Several aspects of thickness monitoring and turning-point prediction during deposition of the narrow band pass optical filters (NBPF) for dense-wavelength-division-multiplexing (DWDM) applications are discussed. Simplification of the method using a recurrent approach, relative transmittance fitting is presented. Partial coherence, effects of monochromator bandpass and divergence of the testing incident beam are also included. We show that the partial coherence effects in thin film structure are significant and can not be neglected. The proposed method is applicable for precise thickness monitoring and deposition control of any complex multilayer coating.

Besides the common fiber technologies like splicing, polishing and coating there is a demand for specific methods for advanced packaging solutions in the field of telecom and medical applications. We present here three of such methods for lensing glass fibers that can be used to increase optical performance and reliability as well as to reduce the packaging efforts. These technologies are very useful for micro optical assembly, i.e. fiber connectors for high power applications, collimators and telecom transceivers and endoscope imaging or sensor systems. At the Fraunhofer Institute for Reliability and Microintegration Berlin special photonic packaging solutions are developed. Optical interconnects have been obtained a great importance for optical data transfer. Optical fibers are necessary for disturbance free communication of high data rates via long distances. Optical system components perform generation, distribution, transformation, amplifying and processing of optical signals. That's why optical systems are a assembly of different kinds of functional basic elements such as optical fibers, splitters, switches, modulators, transmitters and detectors. Furthermore, industrial applications need a reliable and cost effective coupling of optical fibers to those systems.

A coverage estimation based cellular system design in microcell structure under shadowing and multipath conditions is presented. The effect of the signal weakening conditions is examined by log-normal shadowing/Rayleigh fading distribution. By taking the application values of GSM operating systems and cellular phones, area reliability and cell radius are calculated and reliable RF coverage is investigated.

We present results of a study of the static characteristics of regenerative amplifiers based on Mach-Zehnder interferometers with semiconductor optical amplifiers in each arm. Specifically we consider a series of regenerative amplifiers and single regenerative amplifiers with feedback. Small amounts of feedback lead to produce hysteresis in the transfer functions of the regenerators. Including an SOA in the feedback loop allows the feedback to be controlled optically and leads to an all-optical latch design.

This contribution deals with design, fabrication and test of a micromachined Fabry-Perot-Interferometer in first order configuration. Main application fields are chemical analysis, infrared sensing and spectral imaging. Some of the most important properties of a FPI filter are the full width half maximum (FWHM) and the tunable spectral range which are generally limited by the curvature and tilt of the mirrors and by their reflectance.

A simple mutual pulse injection-seeding scheme is developed to produce tunable single wavelength and dual-wavelength optical short pulses by using two Fabry-Perot laser diodes. The operating wavelength of the optical pulses is flexibly selected by adjusting a tunable filter or cascaded fiber Bragg gratings, and the pulse intensity is enhanced by using an erbium-doped fiber amplifier. The sidemode suppression ratio achieved by the system for single wavelength operation is larger than 26 dB over the wavelength region of 25 nm and higher than 31 dB within 18 nm wavelength range. In the dual-wavelength case, the sidemode suppression ratio achieved is better than 25 dB over the wavelength-tuning range of 12.1 nm. The system is robust, flexible and convenient for wavelength tuning.

Semiconductor optical amplifiers (SOAs) are useful nonlinear components, which are the key elements for all-optical gates. This paper is devoted firstly to nonlinear elements based on SOAs. Secondly, a novel configuration using two cascaded SOAs will be presented. Besides the simplicity of this assembling, the gain nonlinearity is accentuated by the mutual gain modulation of the two SOAs which is an interesting feature to improve XGM applications. The reported results point essentially on static characteristics and applications. A spatial evolution of the XGM across the two SOAs cavities is simulated to evaluate and optimize the performances of this configuration. All-optical functions, such as a switch and a NOR gate, will be presented by using two SOAs of 500 μm and 750 μm lengths.

Laterial p-i-n photodiodes have been produced in a standard, unmodified commercial GaAs integrated circuit process (Vitesse Semiconductor Inc. HGaAs IV and V). The devices were modelled using the MEDICI simulation package, achieving a very good fit to both capacitance and DC light response measuremnts. The simulation recreated an interesting feature of the devices, wherein the detectors go from a low-performance to high-performance regime abruptly at a specific reverse bias. An analysis of the simulated behavior of the depletion region in the nominally intrinsic region of the device provided a partial answer to the physics behind this bias point. A second generation of devices of different geometries was fabricated and tested. The newer fabrication process showed a lower performance transition (~0.6 V) than the previous process (~4 V) for an identical layout geometry. Preliminary high-speed measurements of the newer devices are quite encouraging.

Two-beam spectral interference at the output of a slightly dispersive Michelson interferometer is used to measure the phase spectra of transparent thin films over a wide range of wavelengths. First, using a Fourier transform method in processing of the recorded spectral interferograms the ambiguous spectral fringe phase function is obtained. Then, using a simple procedure based on the linear dependence of the optical path difference between beams of the interferometer on the refractive index of material of the interferometer optical element, the ambiguity of the spectral fringe phase function is removed and the thickness of the interferometer optical element and the phase spectrum of the transparent thin films are determined. Knowing both the thickness of the interferometer optical element and the phase spectrum of the transparent thin films for a given configuration, the theoretical spectral interferogram is compared with the recorded one and good agreement between these interferograms is confirmed.

A spectral-domain white-light interferometric technique employing a low-resolution spectrometer at the output of a tandem configuration of the compensated (non-dispersive) Michelson interferometer and a two-mode highly birefringent optical fiber is used to measure intermodal dispersion characteristics of the optical fiber. The technique utilizes the fact that the spectral interference fringes are resolved in this configuration only in the vicinity of the so-called equalization wavelength at which the optical path difference (OPD) in the interferometer is the same as the intermodal group (OPD). The white-light spectral interferometric technique is used to measure the wavelength dependences of both the difference between propagation constants of X-polarized and Y-polarized LP modes and the intermodal group OPDs for an elliptical-core (highly birefringent) optical fiber. The measured intremodal dispersion characteristics of the optical fiber are compared with those corresponding to the results of an adequate theoretical analysis using the known parameters of the optical fiber.

The paper presents a novel kind of Hadamard transform optic. First investigations are made with a micro mirror array in a Hadamard transform spectrometer (HTS) whereby the usually used detector array is replaced by the micro mirror array. All the mirrors are imaged onto a single detector. The measurement is performed using a Hadamard matrix, i.e. while each detector reading a certain combination of mirrors given by the matrix is reflecting the light towards the detector. All the rest of them are reflecting the light beside it. The consequence is an improvement of the signal to noise ratio (SNR). The novelty of the realized spectrometer is that in contrast to other applications the mirrors are not statically switched but they are forced to oscillate at their resonant frequency. By this way a special Hadamard matrix can be used that improves the SNR best.

Ellipticity of optical beams can be compensated by means of diffraction gratings. Holographic gratings are a simple alternative, which is noted for the possibility of recording gratings with curved and non-equidistant grooves. Using spherical wave fronts off-axis diffractive imaging elements can be recorded. They can be used for a beam transformation. The usual transformation task is to collimate beams emitted by edge-emitting diode lasers. Holographic recording and reconstruction, taking into account aberrations of the third order and assuming a recording layer to be on a spherical substrate, are described. Experiments verifying theoretical presumptions were carried out. Fraunhofer diffraction pattern with a very narrow central maximum was obtained.

We highlight the self-similar properties of the reflection coefficient of optical-Cantor prefractals multilayers. These properties are first illustrated by means of numerical results obtained using the characteristic matrix method and then are analytically investigated by resorting to the small reflection approximation.

In this paper, the analytical solution of nonlinear wave equation, describing the propagation of non-diffracting wave beams in a medium with dielectric constant's nonlinear variation in paraxial approximation, is obtained. The obtained analytical solution gives good fit with the results of numerical integration.

We present the influence of an assist light beam injection at the gain transparency wavelength inside Semiconductor Optical Amplifiers (SOAs), which is proposed as a useful method to enhance the SOAs static and dynamic characteristics. Experimental static measurements demonstrate 4.6 dB improvement in saturation output power of SOA measured at -3 dB while maintaining a high level gain. A shorter gain recovery time is obtained which is essential for all-optical high bit-rate applications. Moreover, photodetection dynamic response shows an enlargement in the SOA photodetection bandwidth which implies a carrier lifetime reduction.

An approach for modeling the saturated single-pass gain in an Ytterbium doped fiber amplifier has been proposed. This approach accounts for both two- and three-level schemes, as well as coupled spectral and power effects. A simple approximation considering an average value of depleted pump power over the fiber length allows to obtain analytic expressions for input and output pump, amplified spontaneous emission (ASE) and signal power in the fiber.

Modern optical analytics require more and more compact and cost-effective modules for analysis of surfaces, solids, thin films, powders, pastes, gels, liquids and alike. Thereby a fast and non-invasive measurement is often necessary. Microsystem technology, more precisely Micro-Opto-Electro-Mechanical System (MOEMS) technology is suitable for the realization of such modules. Different miniaturized optical analyzers employing MOEMS have been developed at the Fraunhofer Institute for Reliability and Microintegration (IZM) in collaboration with the Center for Microtechnologies (ZfM) and the company COLOUR CONTROL Farbmesstechnik GmbH. These devices are based on the principle of spectral sensing in the infrared range. Due to the requirement of compact dimensions and short optical paths a high packaging accuracy is necessary. In the development process different setups with a continuous packaging improvement have been realized. The first packaging principle was based on particularly assembled laser-cut stainless steel sheets and optical standard components. The design requires exact positioning of the functional elements to attain a sufficient optical resolution. The reduction of the active components by means of monolithic combinations was one improvement. Further progress could be achieved by a package made of aluminum cast, whose models were provided using modern methods of rapid prototyping. Consequently adjustment tolerances will be minimized and the vibration stability will be increased. During the development process, simulations and characterization of the system are essential to obtain necessary improvements. Thereby an evaluation of the packaging accuracy regarding its influence on the defocus was made. According to precision and reproducibility, the optical and electrical performance are being tested.

The paper deals with autocorrelation function for black body radiation. It is going on its interpretation with using Wiener-Chinchin's theorem for black body radiation spectrum which we usually meet commonly. The point of view presents autocorrelation function as the third derivation of Langevin function known from polar orientation of dipoles. In the second chapter of the paper, partial autocorrelation functions for each of modes, which create spectral power density of the black body radiation in sum, have been presented.

This paper deals with adjustment of certain optical parameters of nano and micro-structured particles of silica by which Mastersizer 2000 as a device for size distribution particle measurement has been used. The optical method process may be used by looking for unique refractive and absorption index of investigated particles. Optical properties, i.e. refractive index and absorption index of the silica have been found and related to inter-particle silica bindings in the form of Hamaker constants. For the optical properties calculations using the Mastersizer 2000 Mie Scattering solutions representing the electric and magnetic induction, i.e. silica's permeability and permittivity from Maxwell's equations have been exercised.

Radiation modes for general planar multilayered structure are defined and their specific functional expressions are derived. Radiated fields from arbitrary field sources, surface and/or volume sources, can be uniquely expanded in terms of these radiation modes, the expansion coefficients of which are calculated using orthonormality properties for the corresponding radiation modes, once the source field distribution causing radiation is obtained by some numerical techniques such as, e.g., the FD-TD method. Practical application of this radiation mode theory is the evaluation of radiation, radiation into substrate region as well as into free space region, from multilayered Microwave Integrated Circuit (MIC) elements. General algorithm for evaluating radiated power and radiation patterns, using the present radiation modes together with the FD-TD method, is briefly summarized for multilayered MIC elements. Validity and accuracy of this method are discussed and numerically examined for ten-layered MIC microstrip line right-angled bends.

We present theoretical study, technological realization and characterization of fabricated devices: TIR switches, electro-optical directional coupler switches and DOS switches because of their good linearity, low noise figure and short switching time which make them particularly suitable for microwave applications.

Circularly bent gradient-index planar waveguides with finite cladding thicknesses are analyzed by the modal matching method. The waveguides assume the refractive index profiles of different shapes, namely, the parabolic and the truncated parabolic profiles. Numerical results of propagation characteristics together with pure bend loss are shown. In addition, feasibility of interferometric devices using bent planar waveguide is discussed.

A numerical variational procedure for determining the field propagating in an optical fiber near to the cutoff frequency is presented. The obtained field representation is used to evaluate the cutoff frequency shift of the LP₁₁ mode occurring in optical fibers when cabling effects are taken into acount.

The nonlinear characteristics of TM surface waves at microwave frequencies in a layered structure of left-handed metamaterial filme, a nonlinear antiferromagnet cover, and a linear dielectric substrate have been performed. The complex wave number of TM surface wave is computed by solving the dispersion equation in order to find out the reduced phase and attenutation constants. The effects of the frequency and nonlinearity of antiferromagnet on the reduced phase and attenuation constants have been examined. The power flow has also been studied as a function of the reduced phase and attenuation constants.

In this paper, mode transitions inside the waveguides with step discontinuities are studied. These transitions are applied to design the corrugated horn antenna directly connected with band pass filter (BPF) in millimeter wave regime. The used rectangular waveguide at the input port is a WR-22 standard waveguide for the frequencies from 40.5 GHz to 43.5 GHz. The RF system used for transmitter and receiver requires wide beam width and wide bandwidth characteristics for coverage and return loss, respectively. Also the antenna needs the high front-to-ratio in radiation pattern.

In this paper, a novel structure in coplanar waveguide (CPW) technology which exhibits an equivalent negative magnetic permeability is described. Such a structure consists in a conventional coplanar waveguide that is loaded with split ring resonator (SRR) cells. Due to the configuration of the magnetic field components in the coplanar waveguide, by adequately placing the SRR cells, quasi-static resonance occurs. In the vicinity of such resonance frequency, the magnetic permeability exhibits a negative value in a certain frequency range. Full wave simulation results as well as measurement from fabricated prototypes validate initial assumptions, providing a new method to implement band rejection filters with very small size.

One of the most important problem of modern optical fiber transmission systems is their bandwidth limitation due to polarization mode dispersion. There are a lot of dispersion compensation methods leading to increase of the bandwidth of transmitted signals. One of them is based on application of Faraday phenomenon caused in optical fiber by external magnetic field. In the paper we present results of measurements of polarization parameters of light passing through different kind of optical fibers. One of the polarization parameters named degree of polarization and its changes allows to conclude about polarization mode dispersion. Hence we can utilize our results for design of a magneto-optical system for dynamic polarization mode dispersion compensation.

A rigorous method to analyze the electromagnetic scattering from a layered crossed-arrays of circular cylinders is presented. The crossed arrays consists of a stacking sequence of two orthogonal arrays in which the cylinder axes are rotated by 90° in each successive layer.

In this paper we analyze the frequency response of one-dimensional periodic dielectric gratings under plane wave excitation using a vectorial modal method in combination with the Generalized Scattering Matrix Technique. A very fast and efficient CAD tool has been developed for the analysis of the scattering of such structures, which allows modifying all the electrical and geometrical parameters, as grating period, thickness, frequency, polarization and angle of incidence. We show that ideal reflection (band-stop) filters with high efficiency can be designed by combining guided-mode resonance effects in periodic dielectric gratings with antireflection effects of thin-film structures, providing a symmetrical line shape with near-zero reflectivity over appreciable frequency bands adjacent to the resonance frequency. A reflection filter example employing common dielectric materials illustrates bandwidth control by grating modulation. Moreover, it is shown that the resonance frequency of the filter can be controlled by the angle of incidence. Finally, it is shown a double-band reflection filter using a structure with two gratings with different periods, with the center frequencies determined by the resonances of the individual single-layer waveguide gratings.

Lamellar grating type semiconductor periodic waveguides with rectangular cross-section are analyzed numerically using Fourier series expansion method, and the wavelength characteristics of reflected and transmitted powers of both guided and radiation modes are investigated for several values of the groove depth and length of the grating waveguide. Then the effects of the radiation fields are made clear, and the preferred parameters for the stable propagation of the reflected dominant guided mode are recommended.

Nanometric diffraction grating structure exhibits the same macroscopic properties as the effective layer of uniaxial continuous material. Power reflectance of such dielectric lamellar structure was computed using RCWA theory. Angular spectra of power reflectance were subsequently used as the input to the optimization procedure in order to find effective indices of refraction. The spectral dependence of effective parameters was obtained as well as the fill factor dependence. The results were confronted with the simple model of effective permitivitties. The results support the idea, that the effective media models should include the role of the substrate.

Fourier modal method for rectangular dot gratings made of anisotropic and conducting materials is reformulated by taking into account Li's Fourier factorization rules. Diffraction efficiencies computed by the present formulation are compared with the conventional one, and numerical results show that convergence of the presented formulation is superior to that of the conventional one.

The reflection and transmission problem of plane wave from periodic arrays of composite cylindrical objects wih internal scatterers using the aggregate T-matrix approach and the lattice sums technique has been studied. The array element per unit cell consists of a circular dielectric cylinder with N parallel eccentric cylindrical inclusions. Reflection characteristics for the asymmetrical proflie in terms of the array plane for the lowest three upgoing and downgoing space harmonics have been investigated. The difference between the upgoing and downgoing space harmonics for the TM wave could be vividly observed.

This paper presents specific experimental ellipsometric data fit of dielectric 2D grating, which can be characterized as very shallow structure. The grating pattern is of squared shape, with sharp edges and depth to period ratio about 1/1000. The rigorous coupled wave analysis (RCWA) was used for characterization of grating response on optical wavelengths. Boundary conditions were formulated using transfer matrix method. Material parameters of the patterned dots are supposed to be known from additional experiments. The task of the fit si to find unknown thickness of all parts of dots.

The parameters of two dispersion models for Si₃N₄ dots of multilayer 2D grating are established by the fitting procedures. The Gauss-Newton and Levenberg-Marquardt fitting algorithms are compared. Spectral ellipsometric measurements as the resource of experimental data are reported. In the objective function, various weighting coefficients corresponding to ellipsometric angles are tested.

This paper presents a new numerical technique for solving design shape optimization problems. The idea is to apply a standard optimization algorithm within a hierarchy of discretizations such that a coarse optimized design is used as the initial guess at the next finer discretized level. We give a comparison with the standard optimization approach which proceeds only on the finest discretization. The method is used for 3-dimensional optimal shape design of an electromagnet that arises in the research on magneto-optic effects.

A novel technique for the fast calculation of the scalar and dyadic Green's functions of a rectangular cavity resonator is presented. The integral equations satisfied by the quasi-static Green's functions are efficiently solved by combining classical image theory and a decomposition strategy: the proposed technique expresses the electric and magnetic potential produced by the periodic set of images in terms of two rapidly convergent series. The key feature of the presented method lies in the introduction of an auxiliar distribution of Gaussian sources which makes the convergence of the periodic potential to be exponential, thus dramatically reducing the computation effort of the implemented tool. Consequently, the proposed approach becomes an essential algorithm to be readily used in computer-aided-design tools for the efficient electromagnetic characterization of passive microwave devices.

The theory of scattering in free space by a novel structure of a two-dimensional dielectric-metallic post is developed with the use of a combination of a modified iterative scattering procedure and an orthogonal expansion method. The far scattered field patterns for open structures are derived. The rotation of the post affects its scattered field characteristic, which permits to make adjustments in characteristic of the posts arrays.

First, we derive an approximate solution for the wedge diffraction of an incident spherical wave by using the source and image coefficients. Next, we propose an approximation for the multi-edge diffraction by including the principal part of the diffraction and ignoring the higher order of multiple diffractions. Numerical examples are shown for statistics of diffraction phenomena.

Spreadsheet EXCEL is known as the software commonly oriented on statistic or economics. Its application in the electromagnetic field theory is rather rare. But many of the features of EXCEL are applicable in the calculations in electromagnetism. Some of them are described in this paper. Implementation of basic numerical methods into EXCEL is given here as well.

This paper describes a novel technique for the very efficient and accurate commputation of the coupling integrals of waveguide step discontinuities between arbitrary cross section waveguides. This new technique relies on solving the Integral Equation (IE) that provides the well-known Boundary Integral -- Resonant Mode Expansion (Bi-RME) method by the Nystrom approach, instead of using the traditional Galerkin version of the Method of Moments (MoM), thus providing large savings on computational costs. Comparative benchmarks between the results provided by the new technique and the original BI-RME method are successfully presented.

A study of the impact of the magnetic dot-vacancy and biasing field on the basic magnetic properties of magnetic dot array is reported. Magnetic bias is a constant magnetic field applied simultaneously with the remagnetization field, which is oriented perpendicularly to the remagnetization field. Simulations, which are presented, deal with the magnetic dot arrays in rotating magnetic field and in-line remagnetization field with the dot-vacancies in various positions. The results led us to conclude, that amplitude of two-fold magnetization contribution increases with asymmetry of the position of dot-vacancy regarding to the center of array. The non-zero bias and the presence of magnetic defect are resulting in asymmetric behavior of magnetization response. For characterization of asymmetrical hysteresis loops was defined the specific coefficient of asymmetry. This quantitative characterization of asymmetry allows to determine the range of relevant biases leading to external two-fold contributions to magnetic anisotropy of array.

In this paper is presented new method of an integral transformation of alternating periodic functions for the determination of circuit parameters of an electromagnetic phenomenon. This integral transformation is based on the electromagnetic physical laws: Ohm's law, induction law, equation of continuity, Kirchhoff's laws and the mathematical definition of the scalar (inner) product time varying quantities. The new method is an effective tool for the production of the circuit models of electromagnetic phenomena.

The paper deals with a new method of an integral transformation of alternating nonharmonic periodic functions. The presented integral transformation serves for the determination of circuit parameters of an electromagnetic phenomenon. In the paper are calculated circuit parameters by means of measured voltage and current waveform. Then, on the basis ones, are developed Kirchhoff's current law and Kirchhoff's voltage law for root means square values of the current and the voltage under nonsinusoidal conditions.

In this paper, the propagation characteristics of nonlinear surface waves at a lateral antiferromagnetic/nonmagnetic superlattices (LANS) substrate and a nonlinear dielectric cover have been investigated. LANS super-lattices (antiferromagnetic-non magnetic) which are linear frequency-dependent gyromagnetic media, described with an effective-medium theory. We found that the nonlinear magnetic waves are reciprocal for H_o = O and nonreciprocal for H_o ≠ O. We also calculate and illustrate the variation of the wave index with the power flow for various values of the magnetic fraction f₁. We found that the nonlinearity interface is a very frequency dependent.

The paper is oriented on modelling, construction and testing of new design of magnetic defectoscope for nondestructive inspection of pipes. This defectoscope is determined for protection of tube in steam generator of electric power station. This approach allows shifting the accuracy limit to be better than 0.3% for internal and external defects.

Integrated optoelectronic devices are expected to become a key component of the future microelectronic and communication technology. This has led to great interest in the development of silicon-based light emitters. One of the most promising techniques for fabricating such emitters uses ion-beam synthesis (IBS) to form semiconductor nanoclusters in a layer of thermally-grown silicon dioxide. Following the preparation of metal-oxide-semiconductor (MOS) structures incorporating nanocluster-rich oxide layers, blue-to-violet electroluminescence (EL) has been observed at room temperature (RT) for implants using germanium ions and heat treatments involving furnace and/or rapid thermal processing. The power efficiency of the EL is quite high, up to 5 x 10^-3, making the blue/violet light emission visible with the naked eye. It has been proven that light emission is caused by one and the same luminescent center. The microstructure of the ion-implanted and annealed oxide layers has been characterized by cross-sectional transmission electron microscopy (XTEM). The presence of second-phase nanoclusters has been found to modify considerably the charge injection and charge transport in the oxide. The optical properties of the nanocluster-rich oxide layers have been correlated with the process of charge trapping using a combination of current-voltage (I/V) and capacitance-voltage (C/V) measurements. The results obtained have enabled the nature of the EL to be elucidated. Finally, opto- and microelectronic application aspects are outlined.

This paper analyses the temperature dependence of device characteristics. The degradation of the device performance due to thermal stress has been explained in detail. The paper also includes a theoretical explanation to the significant temperature effects on transconductance and cut off frequency for microwave frequency application.

We report on fabrication of the GaN layers deposited onto silicon, silica-on-silicon and quartz glass substrates by RF magnetron sputtering. The GaN layers were also doped with erbium ions to achieve active optical properties. The fabricated layers were characterized by a number of methods and the results are discussed on the bases of quality of the deposited GaN structures.

The paper solves the optimization problem of thermal donors (TD) removing in Si-single crystal wafers produced in the TEROSIL company. TD are removed during subsequent annealing process by temperature 620°C and time 20 min. Amount of the residual TD is determined by electrical resistivity measurement. The first results indicate possibility to modify the annealing process in order to increase its effectiveness.

A generalization of the Tauc-Lorentz model dielectric function of amorphous semiconductors and dielectrics is presented in which the exponential Urbach tail is included. The generalized parameterization of the optical functions includes only six fitting parameters. The real part of the dielectric function is calculated using analytical Kramers-Kronig dispersion relations. The model is applied to hydrogenated amorphous silicon.

A computerized optical fiber variable pressure sensing system has been developed. The approach is based on the birefringence effect on a single mode fiber and uses a computer data collection system with 486 DX PC computer, a DAS 1600 A/D converter, linear amplifier and the GUI software for graphic processing. The system works very well over a wide temperature range from -50°C to 150°C.

The precise microwave characterization of dielectric materials is an important issue for emerging technologies of the 21^st century. In this paper recent advances in resonant techniques for permittivity and dielectric loss tangent measurements of low and medium loss dielectrics at microwave frequencies are presented.

In this paper we report on measurements of electric field intensities of microwave field above surface of microwave circuits using miniaturized coaxial antennas. During the scanning process the antenna is driven at various distances above the sample surface according to topographic data acquired prior to the field measurement. A position/signal difference method is used to increase the spatial resolution of the antenna to about 20 μm (λ/10⁴) -- one order of magnitude better than contemporary microwave scanning systems. For measurement of the tangential field components parallel to the sample surface the antenna is tilted by about 45° relative to the sample surface. By its rotation about the vertical axis various components of the field are measured, vertical and horizontal electric field intensities are recalculated. Performance of our scanning system utilizing these methods is tested using a PCB surface capacitor, a microstrip filter and a microstrip transmission line.

In this communication, we present an extensive theoretical analysis of nonlinear wave guide structure sensor and derive the conditions of the maximum sensitivity of TE nonlinear surface plasmons. The theoretical requirements for reaching high sensitivity of the proposed nonlinear waveguide sensor will be determined. Exact maximum sensitivity expressions for nonlinear surface plasmons in sensing schemes will be obtained, which will allow the designer to find the work basis of maximum sensitivity and to create the right dimensioning of the proposed structure. We believe that the theoretical predictions and numerical modeling could realize future versatile sensors. The above concepts could be experimentally demonstrated and carried out.

Differential absorption measurement for acetylene is achieved by using a Fabry-Perot laser diode in a self-seeding scheme. The two wavelengths from the laser output can be selected conveniently by switching the repetition frequency. The system has flexible wavelength tunability, larger sensitivity than that based on DFB, and high potential for multi-point, multiple gas sensing.

The paper describes implementation of smart sensors (SS) at the distributed measurement systems. To the main advantages of smart sensors bleong: -- compact form with common supply and standard output signals, with good functionality at hard conditions, -- minimization and compensation of the disturb influence to measuring transducers and to the output signal (temperature influence, static characteristic non-linearity, transfer disturbing), -- local signal processing with duplex communication, function testing and data validation. Some results will be present with design, structure and properties of small displacement smart sensors with two types of optical fiber transducers. These sensors are interconnected with controllers by ILAN or WLAN with PC computers and SCADA/MMI program support that enable to reach very good functional parameters with higher flexibility, reliability, testing and maintenance.

Liquid core optical fiber waveguides are capillaries that contain a liquid core -- liquid sample for spectroscopic analysis. The sensitivity of absorbance spectroscopy can be improved by extending optical pathlength. Liquid core waveguides provide for long optical pathlengths by constraining light propagation within a liquid medium which has a higher refractive index than the surrounding solid tubing. We present a simple optic method that allows to extend the sensitivity of conventional spectroscopic measurement. For long pathlength absorbance spectroscopy measurement the Teflon AF waveguide capillary cell for low refractive index liquids was designed. For ultraviolet, visible and near infrared region this type of fiber optic sensor with liquid core was designed. Benefit of this solution is possibility to use of small volume samples, long pathlengths by constraining light propagation within a liquid medium which has a higher refractive index than the Teflon AF tubing, sensitivity increase of conventional absorbance spectroscopy by two or more orders of magnitude. No preconcentation is required in chemical analysis. The analytical procedures employed in long pathlength absorbance spectroscopy are amenable to miniaturization and autonomous operation.

Discrete wavelet transformation (DWT) is mostly used for image processing and data compression. This paper shows that DWT may be of good use at one-dimension data processing. With certain conditions met, compared to discrete Fourier transformation (DFT) or discrete cosine transformation (DCT), transformed data provide less coefficients fit for further use. These properties are demonstrated on the data obtained from a tin dioxide gas-based sensors TGS 813 and TGS 822. Organic liquid vapors (acetone, ethanol, hexane) mixed with air were used at the tests.

A non-quasi-static (NQS) model suitable for simulating the small signal-performance of monolithic MESFET and HEMT devices, which is consistent with a large-signal model, is described. The hallmark of the model is that it incorporates NQS effects not only in the capacitors of the equivalent circuit, but also in the conductances, employing the same relaxation time in both types of elements. A parameter extraction technique which provides a correct identification of parasitic and intrinsic elements is also presented. The single relaxation-time NQS model has been successfully applied to predict the small-signal performance of monolithic MESFET and HEMT devices in the 1 to 40 GHz band at a wide variety of bias conditions. The close agreement obtained between measured and simulated S-parameters at all bias points validates the proposed model and proves that it represents the main devices' behavior aspects.

Rain induced attenuation degrades the performance of communication systems. Thus the knowledge of rain-induced attenuation at the frequency of operation is necessary to design a reliable communication system at a particular location. Attenuation of radio waves by rain depends on the shape, size and distribution of raindrops and rate of rainfall (mm/hr). Hence this research work has been undertaken to study rain-induced effects on microwave propagation at 20 and 30 GHz at Amritsar for planning future earth-space communication links at these frequencies. Present research work envisaged collection of propagation data over line of sight links, radiometric data and meteorological data in the form of rainfall and raindrop size distribution. The data thus collected, using proposed experimental setup, have been analyzed for developing empirical models which are required to develop a statistical model for the prediction of rain induced slant path attenuation for our location which will help us to design an efficient and reliable terrestrial and satellite communication systems which will work for 99.99% of time.

Both types of industrial lasers, CO₂ and Nd:YAG, are used for welding with wide range of maximal power values. Successful results of laser welding depend on many different factors: energy, diameter, mode structure, polarization and focus position of laser beam; thickness, accurate positioning and gap of welded parts, kind of shielding gas. With LASAG Nd:YAG pulsed laser system KLS 246-102 we made optimization of welding parameters for different metals 0.5 mm thick and some types of the weld geometry. Our experimental results were used for welding of the side joint of the steel motor covers. These precious parts are used in automobile racing models. Finite elements model is used to predict a heat affected zone.

Microwaves of 2450 MHz have been attracting attention from researchers of various fields. The most distinguished characteristics of microwave from conventional heating are volumetric and selectivity. Due to these characteristics, when combined with convective air, microwave-assisted drying can greatly reduce drying time and energy usage to achieve certain moisture content. These characteristics also make it possible to combine this highly efficient heating method with vacuum drying by passing the energy through a microwave-transparent vacuum chamber. Microwaves also have various applications in chemistry such as extraction of natural products from plant materials and microwave-assisted synthesis. In this paper, the work conducted in our lab on the applications of microwave energy in agriculture and chemistry is briefly reviewed.

Laser cladding is one of the technologies of material surface treatment. A series of laser-clad specimens have been produced using continual 2,5 kW CO₂ laser. There is introduced a description of the powder injection laser cladding method in the present paper. For some numerical calculations of laser beam induced temperature field in treated material were used the finite difference method and the finite element method. Results of this modeling led to an optimalization of cladding process parameters. Some layers of Ni-based alloy K50, Stellit6 alloy and SiC powders were applied on low-carbon CSN 11 373 and CSN 12 010 steels. Shape characteristics and some properties such as microhardness of clad layers in comparison with substrate values were analyzed.

The paper is aimed at some recent results of both the theoretical end experimental research of interaction of the laser beam with rock materials. The topic of the theoretical research is to determine the amount of energy transferred into rock like material more preciously. The experimental task is to identify the temperature fields in the vicinage of the impact zone to be able to reconstruct the heat flow and losses. Some problems of these tasks are discussed in the paper.

The optical method appropriate for studying of the specific surfaces created by abrasive water jets has been assembled and tested. It is based on shadow visualization of random rough surfaces and it makes possible to obtain the shadowing function from distribution of light and shadows. Evaluation of shadowing functions and spectral analyses of signals obtained from surface were performed. Values of a stochastic distribution of light intensity in shadows were quantified using calibration of the experimentally obtained shadowing functions thus defining height distributions of measured profiles of roughness and/or waviness.

Results of concurrent measurements of both attenuation due to rain at different frequencies on terrestrial line-of-sight paths and rain intensity measured in many countries all over the world are included i the data bank of the Study Group 3 ITU-R. These data can be accepted for the testing of various methods presented occasionally in professional journals and conferences for the calculation of rain attenuation distribution from measured rain intensity data. At TESTCOM, software was developed which can be used for choosing the best method for rain attenuation distribution calculation. Data from 62 terrestrial line-of-sight paths collected in 16 countries were used for 36 testing methods. Statistical parameters of testing procedure were calculated and encountered risks are described. The real proposal of cumulative distributions of attenuation due to rain at 19 GHz frequency band in the Czech Republic based on both the 5-year results of observation at TESTCOM and the above mentioned software is shown in detail and discussed. Rain attenuation calculation methods based on measured propagation and rain intensity data are of fundamental importance for the realistic calculation of new both the Point-to-Point and the Point-to-Multipoint systems.

This paper describes the measurement of zenith path attenuation due to rain in winter and monsoon seasons of the year 2001 at Amritsar (31° 38' N 74° 52' E) India, using zenith looking radiometer operating at 19.9 GHz frequency. The effective rain height has been obtained from the analysis of the radiometric data and point rainfall intensity. Specific attenuation for various rain rates in the present study has been evaluated from measured drop size data using lognormal drop size distribution. The average effective rain height at Amritsar has been estimated to be 3.4 km, and compared with that of predicted by ITU-R.

Computer Aided Design (CAD) is an essential tool in circuits and systems design and modeling. With the current advances in computer technology, it is becoming more feasible to obtain good and accurate models in a reasonable time. For transistors, it is important to have accurate small- and large-signal models to achieve good predictions of system behavior. Automating the model selection process helps to speed the design cycle. In this paper, we describe the process of generating optimal large-signal model for MESFETs based on an optimal small-signal topology and using I-V and transconductance measurement data. This is achieved by, first, generating an optimal small-signal model and topology for a MESFET based on a given S-parameter experimental data, and using TopFinder, a CAD tool we developed. The methodology is demonstrated on a GaAs power FET based on Curtice, Materka, or Statz DC models. The optimal large-signal model is decided upon by using a least-square optimality metric that combines both the fitting of the I-V curves as well as their derivatives. The metric showed that the Materka model based on an optimal small-signal topology was roughly 50% better than the Curtice model.

Medical applications of microwaves (i.e. a possibility to use microwave energy and/or microwave technique and technology for therapeutical purposes) are a quite new and a very rapidly developing field. Microwave thermotherapy is being used in medicine for the cancer treatment and treatment of some other diseases since early eighties. In this contribution we would like to offer general overview of present activities in the Czech Republic, i.e. clinical applications and results, technical aspects of thermo therapeutic equipment and last but not least, prospective diagnostics based on microwave principals ant technology and instrumentation.

A detailed dosimetry in the inner ear is performed using the FDTD algorithm with a subgridding method. A head model is exposed to a mobile phone radiation and the electromagnetic field in the region of the inner ear is computed with increased numerical resolution by factor of 3, 5 and 7. Results show that increase of the numerical resolution without increase of the geometrical resolution does not give more detailed SAR distribution in the inner ear. Therefore a new model of the cochlea with increasing the geometrical resolution from 1 mm to 1/7 mm and dosimetry in this model is presented.

Paper deals with new results in the field of intracavitary microwave applicators used for Benign Prostatic Hyperplasia (BPH) treatment. We demonstrate here that it is necessary to use more sophisticated applicators than a simple monopole radiating structure. One of the good possibilities for safe and efficient treatments we propose here is a helix structure.

Thermotherapy is one of the standard methods of the complex cancer treatment. In many studies, the improvement in local tumor control and free life survival has been shown. Goal of this project was realization of Evanescent Mode Waveguide applicator and its comparison with Waveguide Applicator, which is clinically used. The optimization of the Evanescent Mode Applicator has been studied with aid of numerical methods (FDTD).

This contribution outlines possibilities of the numerical method for the evaluation of electromagnetic field and the temperature distribution in front of the applicator's aperture. This modeling is useful for having basic idea about the distribution of the temperature inside the treated area.

Blindness is a sensory disability which is difficult to treat but can to some extent be helped by artificial aids. The paper describes the design aspects of one such visual aid, which is based on the principle of 'air sonar.' Such a visual aid is also known as a sonocular perception system. The blind person will wear "ultrasonic eyeglasses" which has ultrasonic sensor (transmitter and receiver) array embedded on it. The ultrasonic sound from the transmitter array is reflected back by objects in the 3-D visual field in front of the blind subject. The received signal is processed to extract information about these objects. This information is presented stereophonically for auditory perception. Experimental results and inferences regarding design issues and the system implementation are also presented. We also present performance results of a novel method to efficiently transform the visual field information into auditory signal to aid navigation.

This paper is focused on the design, the construction and the evaluation of the resonant loop, which can be used as a part of the regional microwave applicator for medical application (microwave thermotherapy).

In the paper the model of heat transfer processes in biological tissues is presented. But using of the model is bounded. It describes temperature field of skin surface only in area influenced by VHF electric field (40,68 MHz). But there are experimentally observed cases when the model can not predict temperature rise in areas nearest to exposed ones.

Recently, dielectric resonator antennas (DRA) have been studied and found to be efficient radiator for wideband applications. The DRA has many advantages over microstrip antennas such as wideband, small size and high radiation efficiency. The stacked dielectric resonator is considered as an example of wide band DRA. A small linear array is considered to show that the mutual coupling has no significant effect beyond the neighboring four elements. Also, a single fed hexagonal DRA is considered for circular polarization.

This paper presents the wire antenna composed of multi-step rectangular loop above the ground plane. The antenna has good characteristic when it has the surrounding length of one wavelength. We consider about theoretical composition in need of that the antenna has good characteristics and it is examined by numerical analysis and measurement whether the composition is appropriate. The antenna has high directivity in vertical plane and there is no side lobe in horizontal plane. If the antenna is composed in many side plane, it is useful as antenna for broadcasting.

This study checks the compliance of reference levels around a GSM antenna, out of the reference parallelpiped that include inside of it the surface in which reference levels are reached, according to far-field approximations. This surface's shape is the same as radiation pattern's. We will see the real shape of the limiting surfaces around several configurations of antennas for mobile communications and its relation with the radiation pattern. To sum up, this study is focused on the analysis of the limiting surfaces, and the regulation's compliance when far-field is used or not.

In this paper, we present a new compact Planar Inverted F Antenna (PIFA) applicable to PCS system. The principle aim in design is to broaden the bandwidth. To overcome the narrow bandwidth characteristic, that is typical of a patch antenna, a type of tapered patch is employed. In specific case, bandwidth of about 15.2% was achieved experimentally. And when the tapered type PIFA was applied to a specially designed mobile phone structure, the Specific Absorption Rate (SAR) value was less by 40% than that of the conventional structure.

Recent topics on ESPAR (Electronically Steerable Parasitic Array Radiator) antennas, which we have proposed as an adaptive antenna for mobile user terminals, are described. The measurement characteristics of a 2.4 GHz 7-element ESPAR antenna are given along with its design criteria. Experimental work on an ad hoc network with 2.4 GHz ESPAR antennas is now proceeding and preliminary results are given. The design and fabrication of a beam-steerable 60 GHz planar microstrip antenna for the TV receiver of an indoor multi-channel video transmission system are presented as another example of user terminal applications. Beam steering is realized by varactor phase shifters at low cost.

This paper introduce the two types of submillimeter-wave horn antennae designed by the authors and present the experimental results obtained by an evaluative testing system that has also been developed by the authors. Submillimeter-wave components are widely used in radio-astronomical observation apparatuses. It should be noted, however, that, because the submillimeter-waves radiating from astronomical objects are extremely weak, there is a need to minimize (1) the various losses possibly occurred in the wave-receiving unit of observation apparatus, and (2) the quantity of the unwanted electromagnetic waves mixing in. With a view to achieving this objective, therefore, the authors provide in this paper their theoretical and experimental analyses of the submillimeter-wave horn antenna as well. It is a well-known fact that a corrugated horn antenna possesses very low levels of cross-polarized field intensity and high levels of radiation gain. It is for this reason that the authors have chosen to use corrugated horn antennae or, to be more specific, two types of such antennae -- one designed by the authors for use in the range of 280 GHz to 360 GHz frequencies and tested actually to ascertain its characteristics, and the other designed for use in the range of 385 GHz to 500 GHz frequencies and tested actually to ascertain its characteristics. Note that (1) the measurements of the antenna beam patterns have been found to largely correspond to those of the numerical analyses, (2) it may therefore, be safely assumed that the corrugated horn antennae presented here are functionally as efficient as they were designed, and (3) it may well be concluded that the measuring system developed by authors for evaluating submillimeter-wave horn antennae doubtless serves its useful purposes.

Intensive development of cellular personal communications system has been observed lately. Thus, protection of a man, and especially protection of his head against non-ionizing electromagnetic radiation generated by cellular telephones is becoming one of the most important problems. The results of elaborated microstrip antennas which have minimized radiation towards the user's head are presented in this paper.

A circularly polarized waveguide antenna using a simple feed structure is proposed and investigated. The feed probe forms L character put on a sidewall of the waveguide so that circular polarization can be generated by the traveling wave on the L-probe. This paper describes the proposed scheme and the experimental CP characteristics of waveguide antenna. Finally, simulated results by finite-difference time-domain (FDTD) method are presented.

The bandwidth (BW) of a rectangular microstrip antenna (RMSA) with a single feed is usually small. Various techniques can be used to increase the BW of RMSA. Broad BW can be achieved with dual feed RMSA, when it is fed with same magnitude and 180° phase difference at its two ports. The main problem in dual feed antenna with equal and opposite phase is to design its feed network. In this paper, a feed network consisting of two branch line couplers and a ratrace coupler has been proposed. To improve the network loss due to the dissipation of nearly 3 dB power in the terminating load, an array of two dual feed antennas is also proposed.

Broadband rectangular microstrip antenna (RMSA) with a pair of rectangular slots, which are symmetrically placed with respect to the feed probe, is proposed which improves the bandwidth of the RMSA without increasing its size. Further increase in the bandwidth is obtained by increasing the number of pairs of slots. A compact configuration of broadband RMSA using a single slot is proposed which gives 50% reduction in the size.

In the present paper efforts have been made to optimize InAlAs/InGaAs/InP HEMT by enhancing the V_c-V_off using pulsed doped structure from uniformly doped to delta doped for its microwave frequency applications. Contours have been shown to predict the cause of enhanced performance of the device using delta doped in comparison to uniformly doped structure. The detailed design criteria to select the proper design parameters have also been discussed in detail to exclude parallel conduction without affecting the device performance. The optimized value of V_c-V_off is then used to predict the transconductance and cut-off frequency of the device. From the analysis the maximum-transconductance of 1.41 S/mm for channel depth of 200 Å and a cut-off frequency of 627 GHz for channel depth of 300 Å can be achieved corresponding to gate length of 0.1 μm with breakdown voltage of 14.8 V.

History and recent developments of terahertz devices utilizing lattice and molecular vibrations are presented. They are semiconductor Raman oscillator and amplifier, parametric generators of terahertz wave using polariton-phonons in dielectrics and semiconductors. We also present the recent advancements in the fabrication and performance of terahertz electronics devices: ISIT and ZTUNNETT diode. They are fabricated with molecular layer epitaxy (MLE), which is the most advanced nanotechnology having atomic accuracy.

High efficiency power amplifier design criteria, in the microwave and millimeter wave frequency range, are reviewed and discussed. An approach to clarify the relevance of both input and output harmonic terminations is presented. Starting from power balance expressions, design criteria to improve efficiency for high frequency application are derived. In order to validate the approach, experimental harmonic source pull results, and comparisons among performances of single-stage amplifiers, synthesized utilizing different design methodologies, are presented.

The use of Electromagnetic Bandgap (EBG) structures has proven to be effective in the implementation of many devices in planar circuit technology, such as filters, couplers and antenna design. In this paper, a low pass filter based in EBG structures in coplanar waveguide (CPW) technology is proposed. The device consists in a periodically loaded CPW with shunt capacitive elements. This way, a low pass frequency response is obtained. The capacitive elements are formed by t-shaped fingers that extend from the central conductor strip to both ground planes. Further enhancement is achieved by introducing a second periodicity in the central conductor strip, modulating the width of the strip. By doing so, effective rejection of undesired frequency harmonics is achieved. Full wave simulation results as well as measurement from fabricated prototypes confirm the performance of the proposed low pass filter, which exhibits low insertion losses in the passband, high rejection slope and effective rejection of undesired harmonics. Another advantage is the small footprint, due to the inherent slow-wave nature of the device.

In the paper, electromagnetic bandgap (EBG) structures in coplanar waveguide (CPW) technology are presented. In order to design this type of circuits, a custom Finite Difference Time Domain (FDTD) code is employed. Due to the fact that simulation is performed in the time domain, a wide frequency response can be obtained in a reasonable amount of time, being a numerically efficient technique. Simulation of several proposed designs are presented and these results are validated with measurements from fabricated prototypes. The results show that the use of FDTD techniques is adequate for the design of EBG devices in planar circuit technology in general.

The sections of ferrite coupled lines with longitudinal magnetization (FCL) play important role in novel class of integrated nonreciprocal devices. The circulator is designed for instance as a cascade of a section of FCL and T-hybrid. In this paper a slot line FCL is developed and applied in design of the circulator. The simulated behavior of the FCL indicates the Faraday's rotation phenomenon performing a periodical exchange of em wave energy between the coupled lines of the structure. It also predicts that a section of FCL with pi/4 rotation is useful for circulator design. The FCL circulator was designed and produced in finline technology. The measured parameters of the circulator agree well with the ones theoretically predicted.

In this paper, electromagnetic bandgap structures are applied to a conventional coplanar waveguide. The EBG is obtained by etching a continuous sinusoidal perturbation pattern either on the central conductor strip or the both ground planes of the CPW. By doing so, a rejected frequency band appears. Since the frequency response of the device can be approximated by the Fourier Transform of the perturbation function, the application of a sinusoidal perturbation gives allows in principle a unique rejected band, without the presence of frequency harmonics. Full wave simulation results are presented for simple reflectors as well as for combination of several simultaneous perturbation functions, tailoring the desired frequency selective behavior.

In this paper, we propose a new synthesis method which allows the design of equi-ripple dual-band impedance transformers and is based on a straightforward generalization of the well-known Chebyshev synthesis of single band transformer. As compared to a single-band Chebyshev transformer encompassing both required passbands, the proposed design yields significantly better performance.

A new monocycle generator using transistors and Schottky Diode is introduced. It generates ultra-short pulses for Ultra-Wide Band (UWB). The pulse-shaping circuit consist of a rectifying diode and a resistor to achieve substantial removal of the pulse ringing. The pulse width is depended on time delay of one of transistor input. An ultra-short monocycle pulse of 900 ps pulse width, 240 mV_{p_p} amplitude, -10dB ringing level, and good symmetry has been demonstrated. Good agreement between the measured and ADS simulation.

In this research we discuss an approach for signal selection-separation by using distance. We introduce term distance filter, method for its analysis is applied. Expression for the distance filter characteristic approximation has been found. By using of technique to be presented in this paper the problem of estimation of number of interferences at the receiver input has been solved.

In this paper the technique for estimation of RI influence on system's characteristics is discussed. To estimate interfering influence statistical model of EM environment has been used. At researching, main attention was focused at investigation of the system's tracking filter. The technique to be offered enables us to estimate accuracy characteristics of the system at mass and random interfering influence on it. Research is illustrated by the numerical example.

A 5 GHz fully monolithic Voltage Controlled Oscillator for Wireless Local Area Network applications is presented. It is designed using 0.35 μm CMOS process. The proposed structure uses MOS transistor accumulation mode varactors and small value spiral inductors. Unlike the conventional cross coupled CMOS VCO circuit, the use of common source output stage is exploited to observe its effects on phase noise optimization. The principle of operation of common source topology and its trade-offs with design performance parameters are reviewed. At 2.6 V supply, design simulations indicates phase noise performance of -110.3dBc/Hz at 1 MHz offset and turning range of 15.7% spanning from 4.6 GHz to 5.4 GHz with 2.5 V variation in control voltage. Circuit is simulated using Advanced Design System. Circuit theory with design optimization followed by detailed simulation results and layout is discussed.