3.1 Clutter Processing Using K-Distributions for Digital Radars with Increased Sensitivity
By: Lisa Ann Osadciw
Syracuse University
and: John F. Slocum
Lockheed-Martin | Abstract: This paper presents a unique false alarm mitigation approach for non-homogeneous clutter, which is problematic for digital radars with increased sensitivity. A clutter map is formed containing estimates of the two parameters for the K-distribution. The map applies the new thresholds to the data. The false alarm rate is reduced by a factor of 1000 due to the improved accuracy in modeling the clutter distribution tail. |
3.2 Sub-array Level Simulation of an Active Electronically Scanned Array Radar for Integrated System Design
By: N.W. Ramsey, C. McComb, and D.W. Greig
BAE Systems Avionics Ltd. | Abstract: An overview of a complete simulation of an Active Electronically Scanned Array (AESA) radar system is given. The Airborne Radar Environment Simulation (ARES) tool has been developed to represent signals emanating from the radar's environment at the sub-array level. This data forms the input to a test bed simulation in which signal processing algorithms can be developed, in particular Adaptive Beam Forming (ABF) and Space-Time Adaptive Processing (STAP) techniques which make use of the sub-array signals. Examples of the outputs from the simulations are presented. The philosophy and methodology of radar systems design and development using simulations is discussed. |
3.3 Anomalous Propagation Limitations to High-Resolution SAR Performance
By: Mark Denny and Iain Scott
BAE Systems Avionics Ltd. | Abstract: We show that the performance of future high-resolution SAR modes will be limited by anomalous propagation effects, rather than by platform measurement errors, or focusing algorithm limitations, or RF wavelength. This is established by calculating the phase history distortions that result from specified atmospheric temperature profiles. Simulations show the effects of such phase distortions upon SAR images. |
3.4 Angle-of-Arrival of a Radar Beam in Atmospheric Turbulence
By: R. W. McMillan, R.A. Smith, and M. Shipman
U. S. Army Space and Missile Command
and: E.J. Holder and J.C. Kerce
Georgia Institute of Technology
and: J. Williams
Technovative Applications, Inc. | Abstract: Atmospheric turbulence has been shown to have measurable effects on the angle-of-arrival (AOA) of radar beams, but these effects are on the order of a few microradians, which is a negligible level for most applications. In this paper, we present a theory describing this phenomenon and compare this theory to one-way measurements made over a 3.5 km path and two-way measurements made over a 25 km path using an X-band interferometric radar. |
3.5 An Efficient Beamforming Method Using a Combination of Analog True Time and Digital Delay
By: L Morgan H Andersson
Ericsson Microwave Systems AB | Abstract: In order to produce controllable deep zeroes in antenna patterns for signals with bandwidths comparable to antenna dimension you have to use beam forming by "True Time Delay" (TTD). The motivation for this investigation is to see if by combining digital and analog delays a method could be found that produces long delays digitally and short delays with analog electric circuits without reducing system bandwidth. |
3.6 Bistatic Reflectivity Measurements on Various Terrain at X, Ku, Ka and W-Band Frequencies
By: Brenda L. Matkin, James H. Mullins, and Tommy J. Ferster
U. S. Army Aviation and Missile Command
and: Perry J. Vanderford
Simtech, Inc. | Abstract: Data that realistically represents the phenomenology of bistatic reflectivity is essential to the design of radar systems intended to sense land based targets and low flying aircraft. A need exists to further characterize clutter phenomenology in order to design and project the performance of current and future systems. This paper provides an overview of X, Ku, Ka and W-Band bistatic measurements made at the Research, Development and Engineering Center at Redstone Arsenal. The data collection includes both on-axis (zero degrees) and off-axis (10 and 30 degrees) measurements of the bistatic reflectivity response of sand, gravel, sod and flat plates. The results of reflectivity from gravel, grassy sod, smooth sand and flat plates will be presented. Modeling and statistical analysis of the data is discussed. This work has application to tactical missile systems that must complete their engagements at low altitudes in a clutter environment. |
3.7 Efficient Determination of Thresholds via Importance Sampling for Monte Carlo Evaluation of Radar Performance in Non-Gaussian Clutter
By: Dennis L. Stadelman
Syracuse Research Corporation
and: Donald D. Weiner and Andrew D. Keckler
Syracuse University | Abstract: An efficient importance sampling simulation method is presented for estimating the thresholds to achieve very low probabilities of false alarm for radar receivers in clutter modeled as a non-Gaussian, spherically invariant random vector. Thresholds at false alarm probabilities of 106 and lower are estimated with only 10,000 trials for both known and unknown clutter covariance matrix cases. |
3.8 The Dynamics and Radar Cross Section Density of Chaff Clouds
By: Sherman W. Marcus
RAFAEL, Ltd. | Abstract: A new chaff cloud model is described which is based on fundamental principles with modifications based on laboratory observations. Excellent approximations to the exact physical model have been developed which can rapidly predict the chaff fiber density and orientation as a function of location, time and fiber characteristics. Using this information, the time varying RCS density is determined for any frequency and polarization anywhere within the chaff cloud. The results are consistent with full-scale observations, and the computational speed allows the model to be integrated into existing real time radar simulations. |
3.9 Robust Multichannel Detection in Heterogeneous Airborne Radar Disturbance
By: James H. Michels, Muralidhar Rangaswamy, and Braham Himed
Air Force Research Laboratory | Abstract: This paper presents the performance of several multichannel adaptive processing detection methods including a model-based approach, which exhibits robustness in correlated disturbance ranging from Gaussian to K-distributed with high tailed probability density functions modeled as compound-Gaussian clutter. Specifically, we consider detection in dense signal environments where training data contains multiple discrete signals in the spatial-temporal domain. For this problem, we compare methods featuring robustness to such processes with recently proposed non-homogeneity detection (NHD) methods, a pre-processing approach for training data selection prior to detection algorithm implementation. Issues considered here include robust detection with respect to clutter texture power variations and multiple signal environments, constant false alarm rate (CFAR) performance, and efficient estimation with limited training data. |
3.10 Sparse Mutual Coupling Matrix and Sensor Gain/Phase Estimation for Array Auto-Calibration
By: Amin G. Jaffer
Raytheon | Abstract: This paper develops a method for estimating the sparse array mutual coupling matrix and sensor gains/phases using a signal source at unknown directions. The sparsity of the mutual coupling matrix results from the recognition that the mutual coupling between array elements is inversely related to their separation and may be negligible for elements separated by a few wavelengths. In the present work we remove the restriction that the signal test source directions must be known as required in an earlier recent work by the author. A fast converging iterative method is developed which estimates the directions and the sparse mutual coupling matrix and sensor gains/phases. Computer simulation results are presented to demonstrate the utility of the method. |