Space/time/frequency methods in adaptive radar - New Jersey ...

ABSTRACTSPACE/TIME/FREQUENCY METHODS IN ADAPTIVE RADARbyChristopher D. PeckhamRadar systems may be processed with various space, time and frequency techniques.Advanced radar systems are required to detect targets in the presence of jammingand clutter. This work studies the application of two types of radar systems.It is well known that targets moving along-track within a Synthetic ApertureRadar field of view are imaged as defocused objects. The SAR stripmap mode istuned to stationary ground targets and the mismatch between the SAR processingparameters and the target motion parameters causes the energy to spill over toadjacent image pixels, thus hindering target feature extraction and reducing theprobability of detection. The problem can be remedied by generating the imageusing a filter matched to the actual target motion parameters, effectively focusingthe SAR image on the target. For a fixed rate of motion the target velocity canbe estimated from the slope of the Doppler frequency characteristic. The problemis similar to the classical problem of estimating the instantaneous frequency of alinear FM signal (chirp). The Wigner-Ville distribution, the Gabor expansion, theShort-Time Fourier transform and the Continuous Wavelet Transform are comparedwith respect to their performance in noisy SAR data to estimate the instantaneousDoppler frequency of range compressed SAR data. It is shown that these methodsexhibit sharp signal-to-noise threshold effects.The space-time radar problem is well suited to the application of techniquesthat take advantage of the low-rank property of the space-time covariance matrix.It is shown that reduced-rank methods outperform full-rank space-time adaptive