This PDF file contains the front matter associated with SPIE Proceedings Volume 7308, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

A space-based synthetic aperture radar (SAR) designed to provide quantitative information on a global scale implies severe requirements to maximize coverage and to sustain reliable operational calibration. These requirements are best served by the hybrid-polarity architecture, in which the radar transmits in circular polarization, and receives on two orthogonal linear polarizations, coherently, retaining their relative phase. This paper summarizes key attributes of hybrid-polarity dual- and quadrature-polarized SARs, reviews the associated advantages, formalizes conditions under which the signal-to-noise ratio is conserved, and describes the evolution of this architecture from first principles.

TerraSAR-X, Germany's first national remote sensing satellite, is implemented in a public-private partnership between the German Aerospace Centre (DLR) and EADS Astrium, Infoterra GmbH. This radar satellite, launched at June 15th 2007 supplies high-quality radar data for purposes of scientific observation of the Earth for a period of at least five years. The first part of the paper describes the key features of the TerraSAR-X mission, the high-resolution X-Band Synthetic Aperture Radar which allows the operation in Spotlight, Stripmap and ScanSAR mode with various polarizations. The second part of this paper deals with the interpretation of TerraSAR-X images under dual-use aspects, especially for security and reconnaissance purposes. Examples for relevant and characteristic target categories are listed and attributes for a precise description are defined. As a measure for resolution and interpretation the public NIIRS-table (National Image Interpretation Rating Scale) is used. As an application example the characteristic scenario of a military airport including railway and route connections are extracted. Finally the applicability of the NIIRS-table is discussed in this particular case.

Imagery data acquired by recently launched space borne SAR systems demonstrate a very good spatial resolution (e.g. one meter with TerraSAR-X). The designs of such complex systems make it compulsory to do SAR end-to-end simulations to optimize image quality (e.g. spatial and radiometric resolution, ambiguity suppression, dynamic range, etc.). The most complex, critical and challenging modules have to be designed for the generation of SAR raw data and SAR image generation, because the limits of computability and memory requirements are reached very quickly. Moreover, the analysis of SAR images is a demanding task, because of their sensor specific effects. Therefore, a simulation tool is under development to analyze realistic target features and make the scattering processes transparent to the user. With the method presented in this paper, SAR images of complex scattering bodies can be generated in a very efficient way. This is done by directly localizing scattering centers and identifying their persistency along the synthetic aperture. Thus the usual raw data generation and processing steps are dropped. The resulting images show a very good similarity to reality, because scattering centers due to multipath propagation effects are also handled. Furthermore this toolkit makes it possible to visualize the scattering centers and their evolution, by mapping them on the 3D structure of the scattering body. This results in transparency of the whole scattering process, which greatly improves the understanding of the image effects. The paper presents this new approach for the application of inverse SAR (ISAR) and first simulation results.

Goleta has been developing low-cost and lite-weight MMW SAR / MTI radars for small UAS applications. Initial models of two different radars have been built, the LUAVR and the LCLPR. The current LUAVR (Lite-weight UAV radar) configuration weighs in at 18-lbs and the first LCLPR version (Low-Cost Low-Power Radar) weighs in at a little under 2-lbs. Initial testing was done from the roof of a van simulating a low flying UAV. Currently the LUAVR is flying in an ultra-lite as part of a UAS demonstration system. The system is comprised of both airborne and ground segments with a data link connecting the two. SAR and MTI Imagery have been generated.

With a vertical accuracy better than 1 m and collection rates up to 7000 km²/h, airborne interferometric synthetic aperture radars (InSAR) bridge the gap between space borne radar sensors and airborne optical LIDARs. This paper presents the latest generation of X-band InSAR sensors, developed by Intermap Technologies^TM, which are operated on our four aircrafts. The sensors collect data for the NEXTMap^(R) program - a digital elevation model (DEM) with 1 m vertical accuracy for the contiguous U.S., Hawaii, and most of Western Europe. For a successful operation, challenges like reduction of multipath reflections, very high interferometric phase stability, and a precise system calibration had to be mastered. Recent advances in sensor design, comprehensive system automation and diagnostics have increased the sensor reliability to a level where no radar operator is required onboard. Advanced flight planning significantly improved aircraft utilization and acquisition throughput, while reducing operational costs. Highly efficient data acquisition with straight flight lines up to 1200 km is daily routine meanwhile. The collected data pass though our automated processing cluster and finally are edited to our terrain model products. Extensive and rigorous quality control at every step of the workflow are key to maintain stable vertical accuracies of 1 m and horizontal accuracies of 2 m for our 3D maps. The combination of technical and operational advances presented in this paper enabled Intermap to survey two continents, producing 11 million km² of uniform and accurate 3D terrain data.

The flight testing phase is vital in the development of an airborne SAR system, but can be time consuming and expensive, especially for UAS based systems. As part of a SAR design methodology, we are using a small, manned aircraft as a surrogate for UASs and other platforms. Prototypes of new systems can be easily installed on the testbed in order to quickly and inexpensively obtain sensor and motion data. These data can be used to aid in system-specific algorithm development, as well as further refinement of the system hardware as necessary.

A millimeter-wave imaging system has been developed operating at a center frequency of 94 GHz. The system has a single stationary mounted transmit and receive lensed horn antenna and two moving mirrors in x and y. The beam is generated by a FMCW-radar module. The final beam aperture is an off-set parabolic mirror which focuses the beam to a small spot at 2 m distance. Key component of the FMCW radar module is a MMIC, which includes a VCO, a MPA/HPA, two Lange-couplers, an LNA , a Wilkenson splitter, and an I/Q-mixer. This MMIC is fabricated using IAF's 100 nm metamorphic HEMT process.

BAE Systems recently developed a rotorcraft brownout landing aid system technology (BLAST) to satisfy the urgent need for brownout landing capability. BLAST uses a W-band monopulse (MP) radar in conjunction with radar signal processing and synthetic display techniques to paint a three-dimensional (3-D) perspective of the landing zone (LZ) in real time. Innovative radar signal processing techniques are developed to process the radar data and generate target data vectors for 3-D image synthesis and display. Field tests are conducted to characterize the performance of BLAST with MP and non-MP (only using the sum channel of the MP radar) modes in clear and brownout conditions. Data processing and analysis are performed to evaluate the system's performance in terms of visual effect, signal-to-noise ratio (SNR), target height estimation, ground-mapping effect, and false alarm rate. Both MP and non-MP modes reveal abilities to sufficiently display the 3-D volume of the LZ; the former shows advantage over the latter in providing accurate ground mapping and object height determination.

In this paper, we will describe the development of a 228 GHz heterodyne radar system as a vital signs sensing monitor that can remotely measure respiration and heart rates from distances of 1 to 50 meters. We will discuss the design of the radar system along with several studies of its performance. The system includes the 228 GHz transmitter and heterodyne receiver that are optically coupled to the same 6 inch optical mirror that is used to illuminate the subject under study. Intermediate Frequency (IF) signal processing allows the system to track the phase of the reflected signal through I and Q detection and phase unwrapping. The system monitors the displacement in real time, allowing various studies of its performance to be made. We will review its successes by comparing the measured rates with a wireless health monitor and also describe the challenges of the system.

A novel signal-processing approach is reported for vibrometry in synthetic aperture radar (SAR) imaging systems. The approach exploits the conventional deramp process; however, in place of Fourier-transform processing we utilize the fractional Fourier transform (FRFT) as a processing tool. The FRFT is geared toward non-stationary signals and chirped sinusoids particularly. A simplified mathematical expression is developed to describe the reflectivity of the aimed patch of ground containing vibrating targets as a function of space and time. Under the approximation that the velocities of vibrating point targets are constant during each probing chirped pulse, it is shown that the returned echo after the deramp process is a superposition of sinusoids that are chirped according to the Doppler effects induced by the vibrating point targets. By applying the multiangle centered discrete fractional Fourier transform (MA-CDFRFT) to the demodulated echoes, the instantaneous velocities of the vibrating point targets are estimated from the two coordinates of each peak in the MA-CDFRFT's frequency-angle plane. By repeating this process where a sequence of successive pulses are used to interrogate the vibrating targets, the velocities of the targets are estimated in each pulse, thereby generating a piecewise-linear estimate of the history of the vibration velocity in time. Theoretical performance evaluation of the proposed technique is carried out using real SAR-system parameters and simulated vibrating targets. The interplay amongst minimum detectable velocity, maximum detectable vibration frequency, pulse duration and chirp rate is determined analytically.

During the flight test of a Raytheon radar sensor in West Texas through 2007, Raytheon collected a wide variety of SAR images that showed evidence of atmospheric lensing. We have characterized the type of image artifacts that lensing creates, as well as the circumstances under which they occur. We also present evidence of a correlation between the artifacts and the presence of a humidity gradient detected in radiosonde measurements. The purpose of this presentation will be to show how these effects can be recognized in SAR images as well as indications of when they will be most severe.

Since the 1940s, radar development has focused on narrow-beam, scanning sensors. A wide field of view has advantages in terms of extended acquisition time for any target, and when combined with a high Doppler sampling frequency can yield high-resolution Doppler spectra. Unambiguous range and Doppler can be achieved under certain circumstances, resulting in enhanced ability to evaluate the characteristics of targets and clutter. Holographic radar has a range of applications in which the ability to discriminate targets among clutter is key. An example of such an application is in mitigation of wind farm interference with Air Traffic Control radar.

The Stokes matrices of about 1 billion pixels of fully polarimetric single look and multilook SIR-C L-band data were analyzed. The Stokes matrix is a 4×4 real symmetric matrix. The Jacobi eigenvalue algorithm was used to determine the eigenvalues and eigenvectors of each matrix. A remarkable result is that all 1 billion pixels did not have more than one eigenvector which satisfied the Stokes vector property where (equation) and S₀ >0. Less than 1 percent of the pixels had no eigenvectors which satisfied this property. The equality condition corresponds to cases where the eigenvector describes a fully polarized Stokes vector. Images were generated from the fraction of the polarized part and unpolarized part of these Stokes vectors, the sine of the ellipticity as well as the eigenvalue. Images were generated as well from the phase statistics generated from the Mueller scattering matrix. These images strongly correlate with the span imagery. The reported resolution for the multilook SIR-C data is 25 m. Each resolution cell is populated by a large number of scattering centers at this relatively low resolution. RADARSAT-2, which was launched on Dec 14, 2007, is capable of much higher resolution fully polarimetric data. Application of this type of analysis to such data will allow consideration of the signatures of the more dominant scatterers in a resolution cell.

This paper describes a vehicle mounted 8-channel radar system suitable for buried landmine and IED detection. The system is designed to find Anti Tank (AT) landmines and buried Improvised Explosive Devices (IEDs). The radar uses field-proven ground penetrating radar sub-system modules and is scalable to 16, 32 or 64 channels, for covering greater swathe widths and for providing higher cross track resolution. This offers the capability of detecting smaller targets down to a minimum dimension of 100mm. The current rate of advance of the technology demonstrator is 10 kph; this can be increased to 20 kph where required. The data output is triggered via shaft encoder or via GPS and, for each forward increment; the data output is variable from a single byte per channel through to the 512 samples per channel. Trials using an autonomous vehicle, combined with a COFDM wireless link for data and telemetry back to a base station, have proven successful and the system architecture is described in this paper. The GPR array can be used as a standalone sensor or can be integrated with off-the-shelf software and a metal detection array.

In this paper we look at the scattering of electromagnetic waves from thin wires. We propose a vehicle mounted search radar system that rotates 360° about the vertical axis. Our wire of interest is lying on a lossy ground plane. It is generally flat but has many bends, which gives it a vertical extent. The system is designed using a wire scattering simulator to predict the response of a test wire to various illuminations. The simulator makes use of the Method of Moments technique to predict the scattering of E&M waves in 3D. Several approximations make the tool fast and versatile. Among these is the general assumption of the wire as a metal filament (with infinitesimal radius). To include a lossy ground plane we suggest the use of the NEC2 simulator. In the development of this problem, we first look at scattering from a 3D thin wire. The conclusion of the simulation phase of this work is that the cardinal flash or glint response of the wire must be observed for the wire to be detectable. This response occurs when the wire is illuminated directly from the side. Because this scenario occurs at an unknown location as the vehicle passes by the wire, our design suggests the use of a spinning search radar. A brief experiment is performed using a search radar as a validation of concept. The observed glint response is shown and suggestions are made for how a practical system could reduce false alarms. We conclude the paper with a preferential configuration for a search radar suggested by simulation for this given application.

This paper describes a system that is capable of detecting dangerous objects carried under ones clothing from a standoff position. The system is autonomous and renders a decision regarding a persons screening results to an operator. That decision is reached on the basis of processing many parameters extracted from both the frequency and time domain responses of the radar return in an artificial neural net. This system has been extensively tested and been shown to be highly accurate.

The U.S. Department of Defense Humanitarian Demining (HD) Research and Development Program focuses on developing, testing, demonstrating, and validating new technology for immediate use in humanitarian demining operations around the globe. Beginning in the late 1990's, the U.S. Army Countermine Division funded the development of the NIITEK ground penetrating radar (GPR) for detection of anti-tank (AT) landmines. This work is concerned with signal processing algorithms to suppress sources of artifacts in the NIITEK GPR, and formation of three-dimensional (3D) imagery from the resultant data. We first show that the NIITEK GPR data correspond to a 3D Synthetic Aperture Radar (SAR) database. An adaptive filtering method is utilized to suppress ground return and self-induced resonance (SIR) signals that are generated by the interaction of the radar-carrying platform and the transmitted radar signal. We examine signal processing methods to improve the fidelity of imagery for this 3D SAR system using pre-processing methods that suppress Doppler aliasing as well as other side lobe leakage artifacts that are introduced by the radar radiation pattern. The algorithm, known as digital spotlighting, imposes a filtering scheme on the azimuth-compressed SAR data, and manipulates the resultant spectral data to achieve a higher PRF to suppress the Doppler aliasing. We also present the 3D version of the Fourier-based wavefront reconstruction, a computationally-efficient and approximation-free SAR imaging method, for image formation with the NIITEK 3D SAR database.

Current methods of demining are mostly ground or vehicle based and therefore extremely time consuming, risky and also do not produce low false alarm rates. Detection of landmines using airborne and satellite based sensors are a viable risk free alternative. However extracting mine like features from data captured using airborne and satellite based sensors using signal and image processing techniques with low false alarm rates is a subject of active research. Microwave remote sensing in X-band (10 GHz, 3 cm) frequency has the capability for both subsurface penetration and resolution of landmines as well as non-lethal targets. In the present study, a set of experiments under laboratory conditions have been carried out using dummy landmines without explosives buried to different depths up to 10 cm in dry smooth sand. The data generated through the experiments is processed through a series of image processing steps and a region of interest segmented using Otsu and Maximum Entropy based thresholding methods. The region of interest is masked and the average observed backscatter containing the mine further processed through an electromagnetic model developed and optimized using genetic algorithm for estimation of depth. The method does not have any requirement of separate training and test data set to train the optimizer and validate the results. The results under laboratory conditions indicate satisfactory results both for detection of shallow buried landmines and estimation of depth.

High-power transmitters are one of the critical elements in a radar system. The radar waveform needs to be amplified without distortion to the desired output power level by the high-power transmitter. In addition to affecting the overall performance of the radar system, the design of the transmitter affects many other factors, such as size, weight, power consumption, operating cost, reliability and maintenance. This paper provides basic guidelines for designing a radar transmitter and addresses the critical requirements faced by the hardware designer. Available technologies and recent advances that enable designers to meet these requirements are discussed. Vacuum electron devices and solid state technologies are examined, as well as the design trade-offs that must be considered when selecting the more suitable of the two approaches. Specific devices, such as the Traveling Wave Tube (TWT) and other vacuum electron device-based transmitters, including the Microwave Power Module (MPM), solid state amplifier, Active Electronic Scanned Array (AESA), and a combination of these technologies are discussed in detail. Techniques for achieving the critical requirements of a modern radar system, such as good spectral purity, excellent amplitude and phase stability and very low spurious, are also discussed. In particular, this paper emphasizes the practical design of reliable hardware for achieving high microwave power in the 1 to 40 GHz power range.

This paper presents three different types of ultra-wideband (UWB) antennas for RF micro-radar applications in range of 1-3 GHz and discusses performance characteristics of each antenna. The electromagnetic radiation properties of antennas are analyzed based on their gain, bandwidth, voltage standing wave ratio (VSWR), conductivity, and form and size factors. In addition, the performance of each antenna is investigated with different feed line configuration to determine influence of feed line configuration upon the performance of each UWB antenna. The antennas were modeled using electromagnetic simulation software, FEKO. The software simulates the performance of each antenna via Method of Moment (MoM) technique that is a powerful method for analysis of electromagnetic radiation characteristics of RF antennas. This paper presents the simulation-based performance comparison of the three selected UWB antennas under the same operational bandwidth.

Recent developments in communications and RF technology have enabled system concept formulations and designs for low-cost radar systems using state-of-the-art software radio modules. One of the major benefits of using these RF communications products is the potential for generating frequency-agile waveforms that are re-programmable in real-time and potentially adapt to a scattering environment. In addition, recent simulation results [1] indicate that this type of system enables the development and implementation of multi-function RF systems that yield good performance within embedded shared-spectrum environments. This paper investigates the design and implementation of software radar systems via implementation of commercially available software radio modules. Specifically, the potential for developing alternative multi-tone radar systems that provide significant levels of information with respect to embedded indoor scattering environments is discussed. This approach is developed via the transform domain waveform synthesis/design and implementation of OFDM (Orthogonal Frequency Domain Multiplexing) waveforms and shows good potential for the future development of cooperative multi-function RF systems.

Interferoceiver is a true correlation receiver and capable of overcoming severe problems caused by conventional super heterodyne receivers, such as range inaccuracy, Doppler range ambiguity, fratricides, excessive clutter contamination, undue inter system interference, etc. We had discussed the above capabilities in our early publications. In this paper, we will present the experimental progresses on interferoceiver as well as encountered obstacles. The technological revolution in radar and electronic warfare is within sight.

An S-Band, half-wave length, probed-fed, two-patch (uniformly linear array 2 x 1 configuration) array antenna is presented. The array was constructed using an air dielectric between the patch and ground plane. The two-metal patches have coaxial feeds with type N (or HN) connectors and are supported by two metal posts positioned for bandwidth enhancement. In addition, these patches are separated at prescribed distance and locations for obtaining electrical performance in terms of antenna pattern and gain. The array can produce a maximum achievable gain of 11.5 dBi with broad azimuthal angle. The antenna's architecture is low profile and suitable for platform integration such as airborne as well as ground radar systems. The design is unique, reproducible, and affordable for manufacturing a low cost radar system. The paper will present the design of the antenna, experimental data, and its implementation.

This paper presents a time-domain, Moving-Target-Indication (MTI) processing formulation for detecting slow-moving personnel behind walls. The proposed time-domain MTI processing formulation consists of change detection and tracking algorithms. We demonstrate the effectiveness of the MTI processing formulation using data collected by the Army Research Laboratory's (ARL's), Ultra-Wideband (UWB), Synchronous Impulse Reconstruction (SIRE) radar. During the collection of the data, the SIRE radar remains stationary and is positioned broadside to the wall and 38 degrees off the broadside position. We have collected data for multiple operational scenarios including: personnel walking inside wood and cinderblock structures, personnel walking in linear and non-linear trajectories, and multiple personnel walking within the building structure. We analyze the characteristics of moving target signatures for the multiple operational scenarios and describe the detection and tracking algorithms implemented to exploit them.

With recent advances in both algorithm and component technologies, through-the-wall radar imaging (TWRI) is emerging as an affordable sensor technology in civil and military settings. Design of appropriate waveforms is important for improving the performance of TWRI systems. We present optimal waveforms, based on the matched illumination concept, for detection of targets inside enclosed structures using a monostatic multi-antenna radar system. We evaluate the effect of these optimal detection waveforms on the performance of through-the-wall radar imaging. The design flexibility for transmit signal duration and its role in the ultimate range resolution of the TWRI system is investigated. Supporting examples based on numerical electromagnetic modeling are also provided.

Through-the-wall radar imaging is of value in several civilian and defense applications. One of the challenges in through-the-wall radar imaging is the strong wall reflections which tend to persist over a long duration of time. In order to image weak and close by targets behind walls, the wall reflections should be suppressed, or at least be significantly alleviated. In this paper, we apply spatial filters across the antenna array to remove the spatial zero-frequency and low-frequency components which correspond to wall reflections. The application of spatial filters recognizes the fact that the wall EM responses do not significantly differ when viewed by the different antennas along the axis of a real or synthesized array aperture which is parallel to the wall. The proposed approach is tested with experimental data using solid wall, multi-layered wall, and cinder block wall. It is shown that the wall reflections can be effectively reduced by spatial preprocessing prior to beamforming, producing similar imaging results to those achieved when a background scene without the target is available.

In this paper, a compact and low-cost electronic circuit system is designed to time reverse short impulses in microwave regime. The proposed system consists of three major parts: (i) Fourier transform, to obtain discrete spectra of input impulses; (ii) Digital signal processing, to digitize spectral samples resulted from the first part and process them; and finally (iii) Inverse Fourier transform, to synthesize time-reversed impulses using discrete continuous wave elements. This architecture is composed of commercially available semi-conductor components, including oscillators, multipliers/mixers, band-pass-filters, amplifiers, and switches. Thus, it can embody a system-on-chip implementation of real-time time-reversal. Its performance is demonstrated by Advanced Design System simulations, with time-reversal of impulses with around 1.4 ns temporal width and [22, 29] GHz spectral coverage in noisy environments as examples.

Multiplicative noise poses a big challenge for SAR imaging system, in which energy from the sidelobes of large RCS man-made and natural clutter objects spread throughout the resulting SAR imagery. Detection of small RCS targets is very difficult since their signatures might be obscured or even embedded in this multiplicative noise floor that is proportional to the RCS of surrounding clutter objects. ARL has developed a Recursive Sidelobe Minimization (RSM) technique that is combined with the standard backprojection image formation algorithm to suppress the multiplicative noise floor in the resulting SAR imagery. In this paper, we present the Recursive Sidelobe Minimization (RSM) technique. Although the technique is originally developed and tested using data from the Army Research Lab (ARL) UWB Synchronous Impulse Reconstruction (SIRE) forward-looking radar, it is also applicable for other SAR data sets with different configurations.

Detection of moving objects around corners, with no direct line-of-sight to the objects, is demonstrated in experiments using a coherent test-range radar. A setting was built up on the test-range ground consisting of two perpendicular wall sections forming a corner, with an opposite wall, intended to mimic a street scenario on a reduced scale. Two different wall materials were used, viz. light concrete and metallic walls. The latter choice served as reference, with elimination of transmission through the walls, e.g. facilitating comparison with theoretical calculations. Standard radar reflectors were used as one kind of target objects, in horizontal, circular movement, produced by a turntable. A human formed a second target, both walking and at standstill with micro-Doppler movements of body parts. The radar signal was produced by frequency stepping of a gated CW (Continuous Wave) waveform over a bandwidth of 2 or 4 GHz, between 8.5 and 12.5 GHz. Standard Doppler signal processing has been applied, consisting of a double FFT. The first of these produced "range profiles", on which the second FFT was applied for specific range gates, which resulted in Doppler frequency spectra, used for the detection. The reference reflectors as well as the human could be detected in this scenario. The target detections were achieved both in the wave component having undergone specular reflection in the opposite wall (strongest) as well as the diffracted component around the corner. Time-frequency analysis using Short Time Fourier Transform technique brought out micro-Doppler components in the signature of a walking human. These experiments have been complemented with theoretical field calculations and separate reflection measurements of common building materials.

A backscattered signal is coherently or incoherently polarized depending on the nature of the scattering surface and the bandwidth of the incident signal. In various applications, and more realistic scenarios, multi spectra or Ultra Wide Band (UWB) have certain advantages over narrow band signals especially in target detection or resolution. Under these circumstances, we investigate the depolarizing effects of wide band signals to understand the relationship of coherency or incoherency with various scattering mechanisms such as reflection/transmission or diffraction. In other words, these major scattering mechanisms may depolarize a signal incoherently in one instance while coherently in another. In this paper we present results showing that the coherency or incoherency of a signal is highly dependent on the nature of the scatterer in relationship to the bandwidth of the incident signal. We use the Finite Difference Time Domain (FDTD) methodology to analyze signals scattering off various homogenous or inhomogeneous surfaces.

Extracting biometric characteristics using radar requires a detailed understanding of the RF scattering phenomenology associated with humans. The gross translational Doppler signals associated with walking are well documented in the literature. The work reported in this paper seeks to understand the micro-Doppler signals generated by human motion associated with ancillary activities such as breathing, heartbeat, and speech. We will describe procedures for anechoic chamber and outdoor measurements at UHF and Ku-band of humans engaged in a range of activities, such as lying, sitting, standing, speaking, and walking. In addition, we will analyze and discuss the various biometric signatures that we collected.

There is a connection between radar theory and the formalism of quantum mechanics that has not been explored by many radar engineers. We illustrate this for a number of other radar observables that are also equivalent to taking the expected value of certain operators. We then compare this to an approach to waveform design based on the ambiguity function. We note that the key to understanding measurement of more complicated interactions is the kernel. Additional signal interactions can be simply interpreted as additional operators in this kernel. This approach may be the key to understanding the underlying interactions found within return signals.

Ground Surveillance Radars (GSRs) can build a virtual wall around facilities or on a border. They provide operators and agents with much more time to assess, prioritize and apprehend intruders than a traditional fence system. The extra response time is one of the important features of the wide area surveillance concept, along with added benefits for both the operators and the response teams. These are described in detail in the paper. But all GSRs are not alike. There are two primary GSR technologies - Frequency Modulated Continuous Wave (FMCW) and Pulse Doppler. Most pulse Doppler radars are derivatives of legacy military battlefield radar technology being applied for wide area surveillance, while a new generation of FMCW radar technology has been developed for this new type of surveillance, applied to high value site security, airports, military bases, ports and borders. The purpose of this paper is to explore the benefits of each type of radar for the wide area application.

Large-scale weather radar signatures are easier to identify compared to smaller-scale events. The location of such signatures can be predicted and tracked. Thus, large-scale signatures are useful in forecasting. Identification of these signatures in radar imagery can be facilitated through the use of smoothing filters. In particular, processing of radar imagery using directional smoothers has been shown to be more effective in retaining the storm front characteristics compared to isotropic smoothers. Moreover, efficient directional smoothing techniques have been developed that are capable of quickly processing large amounts of data. An advantage of smoothers operating in the spatial domain is that they are capable of involving logical operations in order to determine which pixels should be processed or neglected. This paper extents a recently introduced computationally efficient separable/steerable Gaussian-based smoothing technique in three aspects. First, the technique is generalized so that computationally efficient filters having shapes other than Gaussian with respect to their main orientation can be designed. Second, it is shown that the technique presented in this work is more efficient that the commonly used angular harmonic expansion. Third, a technique that combines directional and isotropic filtering is introduced. The technique is capable of revealing directional structures hidden in large-scale signatures, and thus be employed as a preprocessing step in forecasting applications.

Position-Adaptive Radar concepts have been formulated and investigated at the AFRL within the past few years. Adopting a position-adaptive approach to the design of distributed radar systems shows potential for the development of future radar systems that function under a variety of new and challenging environments. Specifically, we investigate notional control geometries and trajectories for multi-platform SUAV applications by integrating additional electromagnetic scattering-based metrics within more generic overall objective functions for multi-SUAV controls systems. We show that the formulation of these new categories of objective functions lead to realizations of multiplatform SUAV trajectories that position adaptively converge to a set of RF leakage points. After position-adaptive convergence to a set of leakage points, we show that an embedded scatterer (i.e. a metal cylinder) can be imaged by applying radar processing techniques derived for sparse apertures.

By means of data from highly resolved tower-turntable ISAR measurements this paper gives an overview of our work on an ATR process from the raw data acquisition to the final ATR performance evaluation. Main objectives are the radar imaging, the ATR robustness against small changes in the articulation of targets (e.g. military vehicles) and changes in the incidence angle. The recognition process is based on a template matching method. The two-dimensional templates are generated by extracting the most robust scatterers from the RCS image.

In this paper the structure and operational peculiarities of reconstructed, Ka-band, combined scatterometer-radiometer system are discussed. The developed system is suitable for spatio-temporally collocated, high precise measurements of the absolute values of water surface, snow, bare and vegetated soils microwave reflective (radar backscattering coefficient) and emissive (brightness temperature) characteristics at ~37GHz, under test-control laboratory conditions from low altitude measuring platforms.

In this paper the structure and operational features of Ku-band, multi-polarization, combined scatterometer-radiometer system and the results of preliminary, spatio-temporally collocated measurements of bare soil and waved pool water surface microwave reflective (radar backscattering coefficient) and emissive (brightness temperature) characteristics angular dependences at ~15GHz are presented.

We present an effective quadratic time-frequency S-method based approach in conjunction with the Viterbi algorithm to extract m-D features. The effectiveness of the S-method in extracting m-D features is demonstrated through the application to indoor and outdoor experimental data sets such as rotating fan and human gait. The Viterbi algorithm for the instantaneous frequency estimation is used to enhance the weak human micro-Doppler features in relatively high noise environments. As such, this paper contributes additional experimental micro-Doppler data and analysis, which should help in developing a better picture of the human gait micro-Doppler research and its applications to indoor and outdoor imaging and automatic gait recognition systems.

In this paper, we present a time-frequency-based detection scheme for the high-frequency surface-wave radar (HFSWR) for the detection of maneuvering air targets in the presence of strong sea-clutter. The performance of the proposed method is evaluated using both synthetic and experimental data. In addition, the proposed time-frequency detection scheme is examined in detail with different signal-to-noise ratio and various examples are considered. The time-frequency-based detection method is then compared with the Fourier-based detector. Results clearly demonstrate that the time-frequency-based detector can significantly improve the detection performance of the HFSWR and add considerable physical insight over what can be achieved by conventional Fourier-based detector currently used by HFSWRs. These results distinctly suggest that the Fourier-based detector is optimal for stationary signals, whereas the Time-Frequency-based detector is optimal for non-stationary signals.

This paper presents two different test methods for camouflage layers (CL) like nets or foam based structures. The effectiveness of CL in preventing radar detection and recognition of targets depends on the interaction of CL properties as absorption and diffuse scattering with target specific scattering properties. This fact is taken into account by representing target backscattering as interference of different types of GTD contributions and evaluating the impact of CL onto these individual contributions separately. The first method investigates how a CL under test alters these individual scattering contributions and which "new" contributions are produced by "self-scattering" at the CL. This information is gained by applying ISAR imaging technique to a test structure with different types of scattering contributions. The second test method aims for separating the effects of absorption and "diffuse scattering" in case of a planar metallic plate covered by CL. For this, the equivalent source distribution in the plane of the CL is reconstructed from bistatic scattering data. Both test methods were verified by experimental results obtained from X-band measurements at different CL and proved to be well suited for an application specific evaluation of camouflage structures from different manufacturers.

The Defense Research and Development Canada establishment located at Valcartier has an ongoing project to improve the detection capability of a optical surveillance system presently used by the Canadian Forces, To improve the detection capabilities of the system, we demonstrated and tested a new Range-Doppler imager specialty adapted to the existing infrared imaging system to provide information gathered by the radar to be fuse with the infrared image. Operating in W band (92-94 GHZ), the range resolution of the radar is better than 40cm for a maximum range of 2km. To obtain the Doppler signature of the scene, the radar is mounted on a 1.5m rail directed attached to the cameras pan-and-tilt. To produce the range-Doppler image, the radar is moved on the rail at constant speed. As the motion of the radar is highly linear, no correction is required in the range-Doppler processing to obtain a well focused image. The field of view of the radar is matched to the infrared camera one to facilitate the fusion process.

This work investigates the plausibility of target detection using a pulsed linear frequency modulated (LFM) noise waveform conglomerate. The results were generated from simulation and demonstrated that the proposed transmit waveform structure possesses the ability to successfully mask any "chirp-like" characteristic making recognition and/or corruption by unintended 2nd-party passive receivers virtually impossible. Due to the fact that the pulsed LFM noise transmit signal was digitally stored as a reference, we were able to employ classical correlation mixing techniques that enabled the target detection approach to successfully resolve targets at range in the presence of interference. In addition, the process of using various binary random signal modulation schemes for the purpose of masking conventional pulsed radar waveform is also investigated. This work describes research involving target detection using a pulsed linear frequency modulated (LFM) waveform modulated by various discrete random signals. The results include a measure of correlation assessing the effectiveness of the various random signal modulators, Monte Carlo simulations identifying the loss introduced by the random signal modulators during the transmit process, matched filter receiver analysis analytically comparing the probability of detection performance when the random signal modulators are considered, and ambiguity functions to assess the uncertainty of the transmit waveform as a function of Doppler and time.

High computing requirements for the synchronous impulse reconstruction (SIRE) radar algorithm present a challenge for near real-time processing, particularly the calculations involved in output image formation. Forming an image requires a large number of parallel and independent floating-point computations. To reduce the processing time and exploit the abundant parallelism of image processing, a graphics processing unit (GPU) architecture is considered for the imaging algorithm. Widely available off the shelf, high-end GPUs offer inexpensive technology that exhibits great capacity of computing power in one card. To address the parallel nature of graphics processing, the GPU architecture is designed for high computational throughput realized through multiple computing resources to target data parallel applications. Due to a leveled or in some cases reduced clock frequency in mainstream single and multi-core general-purpose central processing units (CPUs), GPU computing is becoming a competitive option for compute-intensive radar imaging algorithm prototyping. We describe the translation and implementation of the SIRE radar backprojection image formation algorithm on a GPU platform. The programming model for GPU's parallel computing and hardware-specific memory optimizations are discussed in the paper. A considerable level of speedup is available from the GPU implementation resulting in processing at real-time acquisition speeds.

Recent investigations into multi-sensor fusion have yielded a variety of data fusion algorithms. Some fuse imagery from multiple sensors at the pixel level, while others fuse outputs of detection algorithms-such as radar prescreeners or hyperspectral anomaly detectors-at the feature level. Many of the feature-level fusion algorithms build upon the foundation of Bayesian probability, and they assign probability to the event that a certain feature value is due either to a target or to clutter. A few of the feature-level fusion algorithms, however, exploit tools developed within the framework of the Dempster-Shafer (DS) theory of evidence. In these formulations some of the probability can be assigned to a third hypothesis representing uncertainty, and the algorithm developer must specify an uncertainty function that maps feature values to probability "mass" for this third hypothesis. Unfortunately, the DS paradigm lacks a standard method for assignment of mass to the "don't know" hypothesis for a particular input feature. In this paper we define a feature-level DS fusion algorithm and determine a method for specifying its uncertainty function. We begin by developing and describing a measure of performance based on the area under the receiver operating characteristic (ROC) curve. We then incorporate this measure of performance into a training procedure that exploits the dynamics of the particle swarm and is capable of discovering locally optimal uncertainty functions. We exercise the training algorithm using simulated data, and analyze the performance of its hypothesized optimal uncertainty function. Next we apply the newly developed training techniques to data produced by separate prescreener algorithms operating on measured Hyperspectral Imager (HSI) and synthetic aperture radar (SAR) data from the same scene. Finally, we quantify the performance of the entire DS fusion procedure using ROC curves.

This paper analyzes the application of ultra-wideband ground-penetrating radar (GPR) in a down-looking configuration for the detection of buried targets. As compared to previous studies, where target detection algorithms have been developed based on the radar range profiles alone (pre-focus data), we investigate the potential performance improvement by forming synthetic aperture radar (SAR) images of the targets. This becomes important in scenarios with small signal-to-noise or signal-to-clutter ratios. Our three-dimensional (3-D) image formation algorithm is based on the backprojection technique. We apply this method to radar scattering data obtained through computer simulation by the finite-difference time-domain (FDTD) technique. Our analysis demonstrates the advantages of using focused SAR images versus the pre-focus range profiles. We also perform a parametric study of several physical factors that could affect the image quality.