In this paper, we present the fabrication and experimental results of impedance-graded composites containing carbon nanotubes, carbon fibers, microballoons along with Frequency Selective Surface (FSS). Samples with different FSS patterns were used along with these composites and experiments were carried out to find the effect of the FSSs. It is found that both the FSS pattern and its location in the composite are critical for the reflection property of the sample.
Radar absorbing material is a very effective means of RCS reduction in the content of stealth technology. In this paper, we present our design of multi-layer microwave absorber with fractal Frequency Selective Surface embedded. Micro-genetic algorithm is employed for the optimization of the design. Two designs are presented in the paper with regard to different frequency spectrum. The experimental result shown here indicates more than 15 dB reduction at X- band in the reflection of a flat surface, by the use of this configuration with lossy dielectrics, which is in good agreement with the simulation result.
A novel approach to improve the performance of a capacitive shunt switch using high dielectric constant materials and monolithic integration based on copper interconnection process is investigated here. To get a high isolation and low actuation voltage, a high dielectric constant material (Ba0.65Sr0.35TiO3) was used in the MIM (metal- insulator-metal) structure, which determines switching isolation characteristics. The realized dielectric constant of this BST thin film was 367 for a thickness of 1500Å. When the BST film is used between the membrane and transmission line instead of silicon nitride, the air gap can be reduced into 1.85 μm with isolation ratio of 4500:1 and actuation voltage of 18 V. In case of 0.85 μm air gap, it is expected to give the isolation ratio of over 2000:1 and actuation voltage less than 7 V. We have also investigated a monolithic integration process of RF MEMS switch with CMOS circuitry using a back-end-of-line process of Cu interconnection technology. This process integration is based on the 6 level Cu interconnection process that includes the MIM capacitor structure.
Photoelectronic DUal Base Transistor (PDUBAT) is a novel kind of photoelectronic negative resistance devices, which features 'N' type negative resistance and small negative resistance RN. PDUBAT consists of a vertical NPN bipolar transistor and a P type diffusion region with large area over a specific distance. The base and collector of the vertical NPN BJT with a large P diffusion region form a lateral PNP BJT. The emitter and collector of the vertical NPN BJT are connected to the ground and voltage supply respectively, while the P diffusion region is left floated to detect input light signal. When the device is exposed to light, a large number of electron-hole pairs are generated at the PN junction under the P diffusion region. The holes travel along the base of the lateral PNP BJT and become the driving current of the vertical NPN BJT. In experiments, we found that PDUBAT acts as a pulse oscillator without the load of inductors, whose frequency and magnitude are modulated by the intensity of incident light. The oscillating frequency increases while the magnitude decreases with the increasing of light intensity. The manufacturing process of PDUBAT is compatible with that of JBTs, so that it can be incorporated with the ICs.
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