2004 IEEE Radar Conference

Innovative Radar Technologies - Expanding System Capabilities

 
 
 April 26-29, 2004 Wyndham Philadelphia at Franklin Plaza Philadelphia, Pennsylvania
 
 
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Poster 4: STAP and Signal Processing

Wed, 28 April 2004, 3:20 PM - 4:10 PM


4.1 Cramer-Rao lower bounds for bearing estimation in STAP performance analysis
4.2 Efficient Tapering Methods for STAP
4.3 Analysis of terrain scattered interference mitigation
4.4 An alternating transmit approach for STAP with short antenna arrays
4.5 A method of sidelobe cancellation using wavelet packets
4.6 A multiple hypotheses testing approach to radar detection and pre-classification
4.7 Estimating the number of signals in presence of colored noise
4.8 Efficient exhaustive search for optimal-PSL binary codes
4.9 The Earth Rotation Effect on a LEO L-Band GMTI SBR and Mitigation Strategies

4.1 Cramer-Rao lower bounds for bearing estimation in STAP performance analysis
By: Gregory A Showman
Georgia Tech Research Institute
and: William L. Melvin
Georgia Tech Research Institute
and: Daren J. Zywicki
Georgia Tech Research Institute

The performance of space-time adaptive processing (STAP) radar is a strong function of array geometry and the particular algorithm implemented. Traditionally, detection performance has been of paramount importance, but recently interest has grown in the accuracy of target direction of arrival (DOA) estimates. This paper describes an evaluation of the Cram?r-Rao Lower Bound (CRLB) for DOA accuracy. The CRLB is useful for bounding the bearing estimation performance of candidate array architectures and STAP algorithms, but often generates counter-intuitive results. Anomalous characteristics of the CRLB are investigated, explained, and placed in the context of maximum likelihood estimation (MLE) properties. The end product is a tool that can be applied to comparative analyses with confidence. The paper concludes by demonstrating the utility of the CRLB in both array and algorithm studies.

4.2 Efficient Tapering Methods for STAP
By: Unnikrishna S Pillai
Polytechnic University
and: Joseph R. Guerci
DARPA/SPO
and: Radhakrishnan S Pillai
C & P Technologies, Inc.

The sample support problem in space-time adaptive processing (STAP) arises from the requirement to adapt to a changing interference environment where the available wide-sense-stationary sample support is severely limited for direct implementation of adaptive algorithms. In this paper we outline several approaches to address the sample support problem by utilizing efficient covariance matrix tapering (CMT) methods to retain the a-priori known structure of the covariance matrix. By combining efficient tapering approaches along with terrain knowledge based STAP and other pre-processing schemes such as subarray ? subpulse, relaxed projection method, it is possible to reduce the data samples required in non-stationary environment and consequently achieve superior target detection. In addition, the application of Khatri-Rao product to the data domain implementation of CMT is also introduced thus expanding the class of robust algorithms for real-time STAP implementation.

4.3 Analysis of terrain scattered interference mitigation
By: Anders Nelander
Swedish Defence Research Agency (FOI)

Terrain scattered interference mitigation for airborne radar has been studied at FOI and deconvolution methods for interference suppression have been proposed. This paper describes an analysis of the terrain scattered interference mitigation performance for different conditions and limitations. The direct path signal must be accurately estimated without strong multipath errors. A time limited impulse response is required to avoid too much suppression of target signals. Small relative Doppler shift errors are required between the direct path and the terrain scattered paths. Several strong jamming signal sources can not be resolved and suppressed. Receiver blocking gives errors in the impulse response estimate. Clutter signals must be suppressed for accurate impulse responses. Numerical stability must be ensured in the inverse filtering and deconvolution operations.

4.4 An alternating transmit approach for STAP with short antenna arrays
By: Pierfrancesco Lombardo
University of Rome "La Sapienza"
and: Fabiola Colone
University of Rome

The approach of alternating the transmission between a leading and a trailing antenna sub-aperture from pulse to pulse (ALTX) is presented for radar systems equipped with digital beam forming. ALTX is shown to improve detection and DOA estimation performance with respect to standard transmission with the whole antenna aperture for systems with a short antenna array and a limited number of receiving channels.

4.5 A method of sidelobe cancellation using wavelet packets
By: Patrick E. Cahill
Naval Research Laboratory
and: Karl Gerlach
Naval Research Laboratory
and: Feng-ling Lin
Naval Research Laboratory

Classical methods of performing sidelobe cancellation include an approach whereby the main and auxiliary channels are divided into a prescribed number of contiguous subbands. This is known as a band-partitioned (BP) sidelobe canceler (SLC). A method of BP sidelobe cancellation using wavelet packets (WP) has been developed. The use of a wavelet packet decomposition is a simple, well-defined way to implement a paraunitary tree-structured filter bank. The performance of this method is compared to the method used in [1], which is a special case of a uniform DFT filter bank. It will be shown that the WP analysis filters provide better separation between adjacent narrowband channels, leading to an increase in performance of the BP SLC algorithm.

4.6 A multiple hypotheses testing approach to radar detection and pre-classification
By: Maria S. Greco
Dept. of
and: Fulvio Gini
Dept. of "Ingegneria della Informazione", University of Pisa, Italy
and: Alfonso Farina
Alenia Marconi Systems

This work presents a single-scan-processing approach to the problem of detecting and pre-classifying a radar target that may belong to different target classes. The proposed method is based on a hybrid of the Maximum A Posteriori (MAP) and Neyman-Pearson (NP) criteria and guarantees the desired constant false alarm rate (CFAR) behavior. The targets are modeled as subspace random signals having zero mean and given covariance matrix. Different target classes are discriminated based on their different signal subspaces, which are specified by their covariance matrices. Performance is investigated by means of numerical analysis and Monte Carlo simulation in terms of probabilities of false alarm, detection and classification. The extra signal-to-noise power ratio necessary to pre-classify a target once a detection has occurred is also derived.

4.7 Estimating the number of signals in presence of colored noise
By: Pinyuen Chen
Syracuse University
and: Gerard J. Genello
Air Force Research Laboratory
and: Michael C. Wicks
Air Force Research Laboratory

In this paper, statistical ranking and selection theory is used to estimate the number of signals present in colored noise. The data structure follows the well-known MUltiple SIgnal Classification (MUSIC) model. We are dealing with the eigen-analyses of a matrix, using the MUSIC model and colored noise. The data matrix can be written as the product of a covariance matrix and the inverse of second covariance matrix. We propose a multi-step selection procedure to construct a confidence interval on the number of signals present in a data set. Properties of this procedure will be stated and proved. Those properties will be used to compute the required parameters (procedure constants). Numerical examples are given to illustrate our theory.

4.8 Efficient exhaustive search for optimal-PSL binary codes
By: Gregory E. Coxson
Lockheed Martin MS2
and: Jon C. Russo
Lockheed Martin ATL

This paper describes an exhaustive search for minimum Peak Sidelobe Level (PSL) binary codes, combining several devices for efficiency. These include combinatoric tree search techniques, the use of PSL-preserving symmetries to reduce search space, data representations and operations for fast sidelobe computation, and a partitioning scheme for parallelism. All balanced 64-bit minimum PSL codes are presented, and the upper limit on known consecutive lengths to have PSL=4 codes is extended to 70.

4.9 The Earth Rotation Effect on a LEO L-Band GMTI SBR and Mitigation Strategies
By: Peter Zulch
Air Force Research Laboratory
and: Mark Davis
Air Force Research Laboratory
and: Robert Hancock
CAE Soft Corp.
and: Sid Theis
CAE Soft Corp.
and: Larry Adzima
Stiefvater Consultants

Space Based Radars (SBR) have been used to accomplish a number of civilian and military missions. Most recently, SBR concepts are being considered to perform ground moving target indication (GMTI) radar modes. Unlike airborne surveillance platforms, SBR clutter returns are affected by the high satellite velocity and Earth rotation. The phenomenology of the Earth?s rotation, and its impact on clutter Doppler returns, will be discussed for a Low Earth Orbit (LEO) L-band radar concept. The Air Force?s Research Laboratory Space Time Adaptive Processing Tool (RLSTAP) high fidelity Radar modeling tool is used to provide simulated data in order to demonstrate the Earth rotation effects, and resulting clutter rejection impact on slow moving target detection.

 
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