A next generation of Smart antennas with point-to-point communication and jam, spoof protection capability by verification of spatial position is offered. A directional antenna array (DAA) with narrow irradiation beam provides counter terrorism protection for communications, data link, control and GPS. Communications are “invisible” to guided missiles because of 20 dB smaller irradiation outside the beam and spatial separation. This solution can be implemented with current technology. Directional antennas have higher gain and can be multi-frequency or have wide frequency band in contrast to phase antenna arrays. This multi-directional antenna array provides a multi-functional communication network and simultaneously can be used for command control, data link and GPS.
Regular micro and nano radars cannot provide reliable tracking of low altitude low profile aerial targets in urban and
mountain areas because of reflection and re-reflections from buildings and terrain. They become visible and vulnerable
to guided missiles if positioned on a tower or blimp. Doppler radar cannot distinguish moving cars and small low
altitude aerial targets in an urban area. A new concept of pocket size distributed radar technology based on the
application of UAV (Unmanned Air Vehicles), UGV (Unmanned Ground Vehicles) is proposed for tracking of low
altitude low profile aerial targets at short and medium distances for protection of stadium, camp, military facility in
urban or mountain areas.
Proc. SPIE. 8045, Unmanned Systems Technology XIII
KEYWORDS: Defense and security, Safety, Detection and tracking algorithms, Receivers, Geographic information systems, Signal processing, Sensing systems, Algorithm development, Collision avoidance, Global Positioning System
Military and other national security agencies have been denied unfettered access to the National Air Space (NAS)
because their unmanned aircraft lack a reliable and effective collision avoidance capability. To overcome the constraints
imposed on UASs use of the NAS, a new, conformable collision avoidance system has been developed - one that will be
effective in all flyable weather conditions, overcoming the shortfalls of other sensing systems. Upon implementation this
system will achieve collision avoidance capability for UASs deployed for national security purposes and will allow
expansion of UAS usage for commercial or other civil purposes.
Narrow band polarization measurements were taken from a bridge in San Diego Harbor using the Advanced Coherent
Technologies Multi-mission Adaptable Narrowband Imaging Spectrometer (MANTIS) multichannel imaging system.
MANTIS was capable of simultaneously collecting four channels of imagery through a narrowband green (532 nm) filter
together with linear polarizers oriented at 0, 45, 90, and 135 degrees. This configuration enabled the collection of the
first three Stokes Vector elements. The data is being gathered to explore methods of calculating the sea surface Mueller
Matrix. Models, methods, and measurements are presented. Of specific interest is the deviation of the modeled data
from the measured data and its causes. The data and a model are used to estimate the contribution of upwelled polarized
PAR Government Systems Corporation (PAR) with Advanced Coherent Technologies, LLC (ACT) has developed
affordable, narrow-band polarimetry sensor hardware and software based upon the PAR Mission Adaptable Narrowband
Tunable Imaging Sensor (MANTIS). The sensor has been deployed in multiple environments. Polarimetric imagery of
the clear blue sky and the sea surface has been collected. In addition, a significant amount of calibration data has been
collected to correctly calibrate the sensor for real-time Stokes Vector imaging. Data collected with the MANTIS
polarization sensor has been compared to modeled data. The sensor hardware and software is described and some
representative collected calibration data are presented and compared to a developing model.
Wide dynamic range gating photosensor modules has been design for LIDAR-RADAR applications on base R7400U
(active area 8 mm. diameter) R7600U (active area 18x18 mm.) Hamamatsu photomultiplier tubes. The photomultiplier
tubes R7400U, series have two kinds of photocathode: low resistance semitransparent multialkali photocathodes and
semitransparent bialkali photocathodes with large resistance. Different kinds of photocathodes require different approach
to gating circuits design. High-speed pulse gating (gating rise time 10 nsec, setting time 40 nsec for 99%) has been used
for enhancing of target contrast at ocean optic application for both kinds: semitransparent bialkali and semitransparent
multialkali photocathodes. Wide dynamic range (50 dB of optical power) has been achieved by optimizing of applied to
dynodes voltages. Compression up to 30 dB has been used for following output signal digital processing. Hamamatsu
photosensitive modules were used in the two system receivers in pulsed LIDAR system. The system was mounted on
the bow of the R/V New Horizon and collected data from August 25 thru September 8, 2005 as part of the LOCO field
test in Monterey Bay. Approximately 4 million LIDAR profiles were collected during this period. During the field test
the profiles were processed to show relative changes in water optical properties and to reveal water column structure in
New approach to high-speed detection and modulation based on application of capacitance modulation is offered. Application of capacitance modulation allows to increase sensitivity and noise immunity of high-speed photodetectors in microwave range.
Subject: INTEVAC hybrid photomultiplier vacuum tube IPD-280 with 18 mm GaAsP photocathode, imaging electron optics, ion trap and 0.5, 1.0 diameter Schottky barrier anode.
Problem: Large area intensified photodiodes (IPDs) have parameters (high sensitivity, gain, speed of operation, bandwidth, low noises), which are ideal for Ocean optic applications. However, these IPDs have not enough dynamic range and lifetime.
Target of objective investigation: Identify the cause for small dynamic range and short lifetime of IPDs and optimize them for Ocean Optic applications.
The voltages applied to photocathode and focusing electrodes have been experimentally optimized for maximal IPD sensitivity,dynamic range, pulse rise, and transit time. The photoelectrons trajectories and ions have been simulated using SIMION 3D 7,0 software for various voltages applied to the focusing electrodes. The uniformity of the photocathode has been tested to determine the impact of ions on the photocathode. Electron and ion currents investigations have been made for both negative and positive voltages applied to the ion trap electrode. Optimizing the regime for electron focusing and minimizing the ion current impact to photocathode was determines as result of the investigation. Reducing the voltages applied to photocathode and focusing the electrodes from 8 KV to 4-6 KV decreased the ion current. In this regime, the gain of IPD does not decrease significantly and the rise time and transit time of IPD remined practically the same.
The original approach for the optical information processing for the hyperspectral remote sensing systems is developed on the union basis of the two mathematical tools: fuzzy logic and neural network. The optical information processing includes the complicated calculations and final results can give a large error. It is well known that there are large number of input parameters and some there uncertainty in the case of information processing of hyperspectral remote sensing systems. The using of statistical and determined models give the result having quite a large error of optical information processing and the given calculations take a lot of time to compute. Therefore the neoro-fuzzy logic application can be more expediency for processing of opto-electronic signals.
RL Associates in conjunction with Hybrid Technologies is developing a narrow linewidth optical filter employing extremely thick volume holographic diffraction gratings. The gratings are written in MEMPLEX, a new holographic materia invented by Laser Photonics Technology, Inc. and licensed to Hybrid Technologies. MEMPLEX has the following characteristics: (1) Excellent optical clarity, (2) Preparable at any thickness up to 10 mm, (3) Large dynamic range for plane wave holograms, (4) Hard, freestanding, stable, polishable and coatable. We have written and characterized numerous gratings in 1.8 mm thick samples to study the effect of writing geometry on the spectral linewidth and field-of-view of a single grating in the reflection geometry. We have succeeded in writing some very efficient gratings at 15 degrees internal write angles with external slant angles of 5 degrees. These gratings exhibit linewidths of < 0.2 nm and diffraction efficiencies of better than 70 percent. The measured angular acceptance of these gratings ranges from 0.1 to 0.24 degrees. We have also written some initial angle multiplexed gratings which include 3 efficient gratings in the same volume in an attempt to increase the angular acceptance. In this manner we hope to achieve a highly efficient optical filter with extremely narrow spectral linewidth and wide angular acceptance. Filters based on thick volume holograms show great promise in Lidar applications and should result in superior S/N ratios.
Experiments with two laser radar systems were conducted off the coast of Key West Florida in May of 2001. The purpose of the test was to observe the effect of the water optical properties on the Lidar return signal decay rate and compare the performance of the two systems. The first lidar system, the Shipborad K-meter Survey System (KSS) was configured to transmit linearly polarized light and to receive backscattered light in both channels. The second system, the Airborne KSS, is designed to conduct global surveys from patrolling P3-C aircraft. For this test the Airborne KSS was specially configured to operate from the deck of a ship and both systems were operated in conjunction with each other. The shipboard KSS was configured with a remotely controlled mechanical iris in both receiver channels to allow the use of different fields of view in each channel. Several oceanographic in-situ instruments were used to measure such water properties as optical transmission and absorption, backscatter coefficient, diffuse attenuation , temperature, and salinity as functions of depth. This in-situ dat was then compared with the lidar measurements.
Current Laser Line Scanner (LLS) sensor performance is limited in turbid water and in bright solar background conditions. In turbid water, backscattered and small angle forward scattered light reaching the receiver decreases underwater target contrast and resolution. Scattered solar energy reaching the detector also decreases detection sensitivity by increasing receiver noise. Thus, a technique which rejects unwanted, scattered light while retaining image-bearing photons is needed to improve underwater object detection and identification. The approach which we are investigating is the application of radar modulation and detection techniques to the LLS. This configuration will enable us to use optical modulation to discriminate against scattered light. A nonscanning mock-up of an existing LLS, the Electro-Optic Identification sensor, has been developed with off-the-shelf components. An electro-optic modulator will be added to this system to create a modulated LLS prototype. Laboratory tank experiments will be conducted to evaluate the performance of the modulated LLS as a function of water clarity and solar background levels. The new system will be compared to its unmodulated counterpart in terms of target contrast.
Experiments with a blue-green laser radar system were conducted off the coasts of Ireland and Scotland in June, 1999. The purpose of this test was to measure the effect of the water optical properties on the polarization state and decay rate of the lidar return signal. The lidar system, the K-meter Survey System (KSS), was configured to transmit linearly polarized light and to receive cross-polarized light in one channel and both polarization in the other channel. Several oceanographic ground truth instruments were used to measure the water optical properties, including transmission, absorption, backscatter coefficient, diffuse attenuation, temperature and salinity, as a function of depth. The KSS was mounted on the bow of one of the UK survey vessels, the HMS Roebuck, and the oceanographic instruments were deployed with a deck-mounted winch. The results presented in this paper were obtained both inside and outside of the continental shelf. Since these regions were characterized by different water optical properties, the sensitivity of the lidar return signal in terms of decay rate and polarization to different water clarities was determined.
Many single shot, single pixel underwater LIDAR systems employ high performance photo-multiplier tubes (PMTs) in their receivers. While PMTs offer high gain with a low noise factor, the dynamic range of the output signal is limited by signal induced artifacts. These artifacts include decaying signals with long time constants and short duration `ghost reflection' signals. This paper will characterize the signal-induced artifacts for various single pixel PMTs with different photo-cathode materials and dynode materials.
Past laboratory experiments established the ability of the modulated pulse lidar system to improve underwater target contrast. Due to the limitations of the laboratory environment in assessing the performance of then we detection scheme, a system was designed and constructed for use in an ocean experiment which was carried out in December, 1995. Results from the field test confirm the capability of modulated pulse lidar to reduce backscatter clutter and enhance underwater target contrast. In addition, the existence of microwave subcarrier interference effect confirmed that the microwave signal integrity was maintained throughout the range of measurements.
Testing has been conducted on 8 by 8 avalanche photo diode (APD) arrays derived from large area (16 mm) APDs, both produced by Advanced Photonics, Inc. The array structure was produced using a novel reverse etching process. Tests have been conducted measuring cross- talk, bandwidth, rise and fall times, gain, effective pixel size, and noise characteristics. Measurements have been made as functions of wavelength, optical intensity, and bias voltage. Cross-talk between pixels was characterized under both CW and pulsed (3 nsec) conditions. The effective pixel size was measured by scanning a very small laser spot (.25 mm) across the pixel under test while monitoring the output current. The measured pixel size was approximately 1 mm. This matched very well with the expected physical pixel size of 1 mm. The pulse response was measured by injecting a 3 nsec laser pulse into the pixel under test. The measured response shows that the signal decays approximately 3 orders of magnitude in 60 nsec. The rise time of the pixel is on the order of 5 nsec. Cross-talk between pixels was measured by injecting an optical signal into a pixel. The current output of an adjacent pixel was measrued as the optical power input was increased. The cross-talk a CW optical input is on the order of 1000 to 1. The pulsed cross-talk is on the order of 100 to 1. The cross talk ratio remains constant with varying optical input intensities. The pulsed wavelength response of the APD was characterized at 440 nm and 700 nm. The APD exhibited no difference between the two wavelengths.
In pulsed blue-green laser radar applications, the signal return amplitude can have a
dynamic range of 9 orders of magnitude in 200 ns. Signal compression is required to match
this range to the input capabilities of the digitizing or processing devices, typically 2 or 3 orders
of magnitude. The compression of the dynamic range of the signal by photomultiplier space
charge control (P5CC) results in an adjustable compression range, variable gain, bandwidth
in excess of 100 MHz, and extended input dynamic range, with no loss of photomultiplier
sensitivity (i.e. photon counting operations are still achievable).