925 research outputs found
Classification Schemes for the Radar Reference Window: Design and Comparisons
In this paper, we address the problem of classifying data within the radar
reference window in terms of statistical properties. Specifically, we partition
these data into statistically homogeneous subsets by identifying possible
clutter power variations with respect to the cells under test (accounting for
possible range-spread targets) and/or clutter edges. To this end, we consider
different situations of practical interest and formulate the classification
problem as multiple hypothesis tests comprising several models for the
operating scenario. Then, we solve the hypothesis testing problems by resorting
to suitable approximations of the model order selection rules due to the
intractable mathematics associated with the maximum likelihood estimation of
some parameters. Remarkably, the classification results provided by the
proposed architectures represent an advanced clutter map since, besides the
estimation of the clutter parameters, they contain a clustering of the range
bins in terms of homogeneous subsets. In fact, such information can drive the
conventional detectors towards more reliable estimates of the clutter
covariance matrix according to the position of the cells under test. The
performance analysis confirms that the conceived architectures represent a
viable means to recognize the scenario wherein the radar is operating at least
for the considered simulation parameters.Comment: Accepted by IEEE Transactions on Aerospace and Electronic System
Model Order Selection Rules For Covariance Structure Classification
The adaptive classification of the interference covariance matrix structure
for radar signal processing applications is addressed in this paper. This
represents a key issue because many detection architectures are synthesized
assuming a specific covariance structure which may not necessarily coincide
with the actual one due to the joint action of the system and environment
uncertainties. The considered classification problem is cast in terms of a
multiple hypotheses test with some nested alternatives and the theory of Model
Order Selection (MOS) is exploited to devise suitable decision rules. Several
MOS techniques, such as the Akaike, Takeuchi, and Bayesian information criteria
are adopted and the corresponding merits and drawbacks are discussed. At the
analysis stage, illustrating examples for the probability of correct model
selection are presented showing the effectiveness of the proposed rules
Learning Strategies for Radar Clutter Classification
In this paper, we address the problem of classifying clutter returns in order
to partition them into statistically homogeneous subsets. The classification
procedure relies on a model for the observables including latent variables that
is solved by the expectation-maximization algorithm. The derivations are
carried out by accounting for three different cases for the structure of the
clutter covariance matrix. A preliminary performance analysis highlights that
the proposed technique is a viable means to cluster clutter returns over the
range.Comment: 12 pages, 13 figure
Forward-Looking Radar Clutter Suppression Using Frequency Diverse Arrays
This thesis introduces a new array structure, the Frequency Diverse Array (FDA), where each channel transmits and receives at a different frequency. The resulting range-dependent FDA antenna pattern is proposed to improve forward-looking clutter suppression. The planar FDA radar data model is derived and analytically verified to be equivalent to the constant frequency data model when each element frequency is set to the same value. The linear FDA at high platform altitude provides significant benefits? by reducing the range ambiguous clutter contribution, improving target detection by up to 10 dB. At low altitudes without range ambiguous clutter the linear FDA achieved a small but consistent performance improvement of 1 to 2 dB attributed to sample support data homogeneity. Planar FDA showed up to a 20 dB detection improvement for a high altitude platform with an airborne target. The simulation results show the FDA provides considerable benefit for low relative velocity targets, improving ground target detection for platforms such as Joint Surveillance and Target Attack Radar System (JSTARS) and Unmanned Aerial Vehicles (UAV)
Radar Signal Processing for Interference Mitigation
It is necessary for radars to suppress interferences to near the noise level to achieve the best performance in target detection and measurements. In this dissertation work, innovative signal processing approaches are proposed to effectively mitigate two of the most common types of interferences: jammers and clutter. Two types of radar systems are considered for developing new signal processing algorithms: phased-array radar and multiple-input multiple-output (MIMO) radar. For phased-array radar, an innovative target-clutter feature-based recognition approach termed as Beam-Doppler Image Feature Recognition (BDIFR) is proposed to detect moving targets in inhomogeneous clutter. Moreover, a new ground moving target detection algorithm is proposed for airborne radar. The essence of this algorithm is to compensate for the ground clutter Doppler shift caused by the moving platform and then to cancel the Doppler-compensated clutter using MTI filters that are commonly used in ground-based radar systems. Without the need of clutter estimation, the new algorithms outperform the conventional Space-Time Adaptive Processing (STAP) algorithm in ground moving target detection in inhomogeneous clutter.
For MIMO radar, a time-efficient reduced-dimensional clutter suppression algorithm termed as Reduced-dimension Space-time Adaptive Processing (RSTAP) is proposed to minimize the number of the training samples required for clutter estimation. To deal with highly heterogeneous clutter more effectively, we also proposed a robust deterministic STAP algorithm operating on snapshot-to-snapshot basis. For cancelling jammers in the radar mainlobe direction, an innovative jamming elimination approach is proposed based on coherent MIMO radar adaptive beamforming. When combined with mutual information (MI) based cognitive radar transmit waveform design, this new approach can be used to enable spectrum sharing effectively between radar and wireless communication systems.
The proposed interference mitigation approaches are validated by carrying out simulations for typical radar operation scenarios. The advantages of the proposed interference mitigation methods over the existing signal processing techniques are demonstrated both analytically and empirically
Airborne Radar Interference Suppression Using Adaptive Three-Dimensional Techniques
This research advances adaptive interference suppression techniques for airborne radar, addressing the problem of target detection within severe interference environments characterized by high ground clutter levels, levels, noise jammer infiltration, and strong discrete interferers. Two-dimensional (2D) Space-Time Adaptive Processing (STAP) concepts are extended into three-dimensions (3D) by casting each major 2D STAP research area into a 3D framework. The work first develops an appropriate 3D data model with provisions for range ambiguous clutter returns. Adaptive 3D development begins with two factored approaches, 3D Factored Time-Space (3D-FTS) and Elevation-Joint Domain Localized (Elev-JDL). The 3D adaptive development continues with optimal techniques, i.e., joint domain methods. First, the 3D matched Filter (3D-MF) is derived followed by a 3D Adaptive Matched Filter (3D-AMF) discussion focusing on well-established practical limitations consistent with the 2D case. Finally, a 3D-JDL method is introduced. Proposed 3D Hybrid methods extend current state-of-the-art 2D hybrid methods. The initial 3D hybrid, a functional extension of the 2D technique, exhibits distinct performance advantages in heterogeneous clutter. The final 3D hybrid method is virtually impervious to discrete interference
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