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

7processing. This is explained by the presence, in addition to thermal noise effects,of errors resulting from the estimation process. Reduced-rank processing suppressesestimation errors at the cost of a bias in the SNR. The net effect, however, is asignificant performance improvement for cases when the interference may be modeledas low-rank. Reduced-rank methods are clearly important for STAP radar, where alarge number of degrees of freedom may be available. For a uniform array and forfixed PRF, the space-time clutter covariance matrix is essentially low-rank due tothe inherent oversampling nature of the STAP architecture. Hence, the space-timeradar problem is well suited to the application of techniques that take advantage ofthe low-rank property.This work is organized as follows: Chapter 2 introduces time-frequencyanalysis, including the Fourier transform, the short-time Fourier transform, theGabor expansion, the Wigner-Ville transform, and the Continuous Wavelet transform.These time-frequency analysis techniques are then applied to the problem ofestimating SAR target parameters. The space-time adaptive processing signalenvironment is introduced in Chapter 3. Reduced rank processing of STAP systemsis presented in Chapter 4 with numerical results of simulated and real data presentedand compared in Chapter 5. Finally, conclusions are presented in Chapter 6.