The authors are utilizing an X-band radar to recover the natural resonance frequencies of a tractor trailer truck (18 wheeler) moving at highway speed. The aspect at which the truck is observed will be from the front and the radar will be raised above the roadway. The natural resonant frequency of the tractor and trailer can be as low as 1 Hz, and as high as 5 Hz depending on the gross weight of the cargo and how the cargo is arranged within the trailer. The condition of the truck's shock absorbers and other suspension stiffening members may also determine the natural resonance frequency of the tractor and trailer. The technical challenge is recovering the 1 to 3 Hz resonance induced signal that is imposed on the normal Doppler shifted signal of the truck when it is moving at 70 Miles Per Hour (MPH) using an X-band homodyne radar. This paper discusses: 1) the research goals; 2) the instrumentation being used for a test target; 3) tests that have been conducted using controlled test targets; and 4) signal processing methods that are being used to extract the micro-Doppler signal components.

This paper discusses the experimental design and analysis of low power 24.1 GHz propagation effects on roadways around the Atlanta, Georgia metropolitan area. The transmitter used was a 24.1 GHz Safety Warning System (SWS) transmitter operating in the continuous wave (CW) mode. The Federal Communications Commission (FCC) has licensed the Safety Warning System for Part 90 operation. A Part 90-compliant transmitter was used during the tests. The receiver was a modified Bel 855Sti radar detector that was calibrated in an anechoic chamber. The receiver was placed in a Ford F-150 truck and driven toward the transmitter. Three distinct propagation environments are characterized including a rural road, state route, and interstate highway. Shadowing effects from terrain features such as hills are examined as well as the effects of other vehicles, including large tractor-trailers. Signal strength is analyzed as a function of distance to the transmitter and using probability distribution function (pdf) modeling. It was found that the Weibull distribution provided the best statistical description for both the line of sight and shadowing cases. In many instances, the statistics of the received signal would change rapidly depending on the terrain features and interaction with surrounding traffic. The results provide insight into how the unlicensed 24.1 GHz band in the United States might be used for low power, intelligent transportation system (ITS) applications.

Radar return data from airborne jet aircraft were collected to determine the presence of consistent, dominant radar returns of point scatterers on aircraft simulating landing conditions. Radar return data on additional targets of opportunity, such as propeller aircraft and helicopters, were also collected for dominant radar returns. These measurements were performed by integrating two separate X-band radars into one system with the ability to simultaneously track and image aircraft. Selected processed data from both radar systems were analyzed and compared for all three types of aircraft, and the results are presented.

Next generation reconnaissance and Automatic Target Detection/Recognition (ATD/R) performance goals will impose new image quality requirements on integrated SAR hardware and software systems. Signal processing techniques using demonstrated non-parametric autofocus methods such as the Phase Gradient Autofocus algorithm and developments in robust super-resolution signal processing offer the opportunity for reducing overall system cost through utilization of less costly hardware options in integrated system design. Traditional requirements on image quality from integrated hardware-software SAR systems have used image quality metrics based on the characteristics of the overall system impulse response function. An additional class of image quality metrics is available based on the performance of the ATD/R algorithms that are to utilize the imagery. The performance of a given SAR system by these measures is expected to be context-sensitive and dependant on both target and clutter characteristics in a manner not necessarily readily characterizable solely in terms of system impulse response function measures of image quality. A simulation illustration of these issues is presented for a test case in which a range of SAR sensor hardware options are processed through a representative texture metric mechanization. Potential performance dependencies on target and clutter characteristics are reviewed and the efficacy of supplementing impulse response function image quality metrics with additional appropriate predictors of ATD/R performance is reviewed.

Performance in an MPRF mode of an airborne pulse-Doppler radar is limited by the presence of surface clutter. Analysis of the behavior of clutter and noise data collected from an experimental radar system is performed and compared with the results of simulations. The suitability of the Weibull distribution in representing the statistical behavior of real and simulated data, as input to a CFAR thresholding scheme, is assessed.

There has been considerable interest in evaluating the use of a low frequency, ultra-wideband (UWB) imaging radar to detect tactical vehicles concealed by foliage. This interest stems from the fact that while high-frequency imagery has shown near-literal imaging capability for targets positioned in open areas, it cannot penetrate tree canopy effectively. However, at low frequencies, the tree canopy is effectively transparent. We examine the issues related to foliage penetrating (FOPEN) radar by first considering VHF scattering from a T-72 tank over soil using a method of moments (MoM) analysis. The MoM analysis considers arbitrary dielectric and perfectly conducting targets in a layered medium, with the lossy, dispersive layers representing the typical layered character of many soils. The solution obtained via the MoM is based on a full-wave formulation of Maxwell's equations. For the clutter, we model both tree trunks as well as a full tree model (trunk and branch structure). The tree trunk is modeled as a dielectric body of revolution (BoR), again using a MoM half-space analysis, while the 'tree' is modeled as an arbitrary dielectric target.

We present an algorithm based on hidden Markov models (HMM) to detect several types of unexploded ordinance (UXO). We use the synthetic aperture radar (SAR) images simulated for 155 mm artillery shell, 2.75 in rocket and 105 mm mortar to generate the codebook. The algorithm is used on the data collected at Yuma Proving ground (YPG). YPG is seeded with several types of UXOs for testing purposes. The data is collected using an ultra wideband SAR mounted on a telescoping boom to simulate the airborne radar. The algorithm has detected all the targets for which it is trained for and it also detected other UXOs that are similar in shape.

Law enforcement and emergency services all face the difficult task of determining the locations of people within a building. A handheld radar able to detect motion through walls and other obstructions has been developed to fill this need. This paper describes the attributes and difficulties of the radar design and includes test results of the radar's performance. This discussion begins by summarizing key user requirements and the electromagnetic losses of typical building materials. Ultra-wideband (UWB) short pulse radars are well suited for a handheld sensor primarily because of their inherit time isolation in high clutter environments and their capability to achieve high resolution at low spectral center frequencies. There are also constraints that complicate the system design. Using a technique referred to as time-modulation allows the radars to reject range ambiguities and enhances electromagnetic compatibility with similar radars and ambient systems. An outline of the specifications of the radar developed and a process diagram on how it generates a motion map showing range and direction of the people moving within structures is included. Images are then presented to illustrate its performance. The images include adults, child, and a dog. The test results also include data showing the radar's performance through a variety of building materials.

A systematic theory for estimating ultra-wideband antenna parameters and performance is not yet published. Because the radiation of short duration signals is significantly different from the long duration narrowband signals, we analyzed the processes in linear antennas and give a physical interpretation. We considered a series excited antenna modeled as one branch of a symmetrical radiator of length L, and having a large number of elementary radiators of size (Delta) L. By examining the radiation from each element (Delta) L, we can sum the results and provide a far field estimate at different angles from the antenna axis. The result shows the field is a function of time and angular position from the antenna, instead of position, as in the narrowband case. For a given radiator size L, the radiation because axial for small values of c(tau) . As (tau) increases for a constant length, the pattern becomes normal to the antenna axis.

This manuscript develops the mathematical basis and the physical radar principles and computer simulation results which are the basis for the three techniques developed. The three techniques developed to attain the objective are unique and based on extensive mathematical development and computer simulation of radar principles and employ real radar data. The object of this paper is to further process the radar data from two synthetic arrays and determine very accurately the range, relative radial velocity and angular position of the target (within the resolution of a doppler bin or better). The target may or not be in the presence of clutter.

Adopting a digital beamforming (DBF) architecture for phased array radars offers the advantage that multiple spatial channels are available the digital computer thereby enabling the use of a wide range of advanced array signal processing algorithms. Many of these algorithms rely on the ability to digitally re-steer beams in the vicinity of the nominal receive sum beam. At the current level of technology, DBF can only be practically implemented at a subarray level for large arrays operating at high frequencies. As a consequence, analog phase shifters at the element level may be set to point the beam in one location while digital re-steering is being used to move the beam to another location. In this paper, the performance impacts of digital re-steering are evaluated in terms of dispersion loss, and a simple correction factor is derived to compensate for a beam pointing error that results from digitally re-steering a beam to a location different from the location used to set the element level phase shifters.

The focus of this paper is the exploitation of the synchronization properties of coupled, nonlinear oscillators for inertialess beam steering. A discussion of experimental and analytic work concerning a novel antenna architecture that utilizes interactions between nonlinear active elements for phase-shifterless beam shaping is presented. The problems of static and dynamic beam steering of 1- and 2-dimensional rectangular arrays are addressed. In addition, recent progress providing sidelobe reduction via the oscillator amplitude dynamics is reported.

The sliding window process in Constant False Alarm Rate (CFAR) detection creates high threshold levels at both up- range and down-range next to a strong clutter point. If the clutter point is stable, these high threshold levels reduce the probability of detection (Pd) unnecessarily. In this paper, a CFAR pre-process is described which removes the high threshold levels near strong clutter and restores the desired Pd.

The standard reflective multipath analysis is summarized briefly, and developed to include other effects, often neglected in text-book analyses, such as curved earth, spatially-extended targets, and frequency agility. In the main part of the paper we show that refractive multipath also exists, given certain atmospheric temperature profiles which may occur quite frequently. The circumstances that give rise to such anomalous multipath are discussed, and the pattern factors are calculated. These are quite different from the pattern factors expected for standard reflective multipath.

Today, such an aspect of Remote Sensing, as a development methods and devices for sea surface fluctuation parameters remote measurement, is of huge interest. A very important stage of such problem solving is statistical characteristics computer-modeling researching of back-scattered signals (in decameter wave range) from sea surface. The height and length of sea waves are evaluated, via amplitude of envelope and frequency characteristics of the radio pulse signals scattered from the rough sea. The obtained results can be used in oceanography, meteorology and for marine environment.

The co-registration of complex SAR images is a key problem in SAR interferometry, especially when the relative acquisition geometry is not known with sufficient accuracy and the approximate terrain elevation changes cannot be considered a priori. This article presents a new multi-stage co-registration strategy using dynamic programming technique for the globally consistent matching. In the primary stage, coarse co-registration results are obtained based on the cross-correlation algorithm which can always give a robust answer. Then in the following fine registration stages, scaling factor is used to correct the systematic misregistration errors in the range direction while a pixel by pixel dynamic programming procedure is used to give a smooth offset-surface of the azimuth direction, which is usually tied to topography. The dynamic programming technique considers the global compatibility of the matching results and optimizes the entire scan area rather than search for the optimum for each point separately, and thus a more smoothly consistent result. Another advantage of this approach is that it gives estimates for co-registration based on a pixel by pixel basis. Subpixel accuracy is achieved and both spaceborne and airborne interferometric data of DLR are used to show the potential of the proposed co-registration strategy.

Transformations of the statistical characteristics of the scattered signals from the low-altitude targets are analyzed, caused by the multipath propagation over sea surface and multiple reflections at path `target-surface- target'. It is shown that the target movement over the diffuse scattering surface leads to change of radar cross- section probability density function in comparison with Swerling's models. The differences of the experimental distributions from models increased with radar wavelength shortening.