Adaptive reconstruction for azimuth signal of multichannel HRWS SAR imaging system

Abstract

The reconstruction of azimuth signal in multichannel synthetic aperture radar (SAR) for high-resolution and wide-swath (HRWS) imaging requires exact steering vectors. The information of ambiguities and system parameters are used to create the steering vectors. The knowledge of ambiguities involves ambiguity number and index; the system parameters include the pulse repetition frequency (PRF), platform velocity, and channel spacing. However, in some cases, the knowledge of ambiguities is Doppler-variant and there exist errors in the system parameters, which may degrade the reconstruction performance. In this work, an adaptive reconstruction method is developed. Firstly, we discuss the azimuth sampling of multichannel SAR and derive the equation of ambiguity index. We then utilize the azimuth cross-correlation to determine the aliasing number. Afterwards, based on the spatial spectrum estimation methods, an equivalent system parameter is adaptively calculated. With the aliasing number and the equivalent parameter, we can obtain the ambiguity information of each Doppler bin. Therefore, the steering vectors are constructed and the azimuth ambiguities can be suppressed. Compared with state-of-the-art reconstruction methods, our method achieves excellent performance even in highly nonuniform sampling case. Without relying on any system parameters, the proposed method has better practicality and applicability. We conduct extensive experiments including simulations and real data processing to verify the effectiveness and evaluate the performance of the proposed method.

Wideband Waveform Generation Using MDDS and Phase Compensation for X-Band SAR

“…In addition to verifying the reliability of the waveform generator, a pulse-to-pulse correlation analysis was performed. Generating a coherent waveform can reduce azimuth distortion and increase the reliability of the reference signal [26,27]. Signals with phase error, signals with compensated error, and pre-distorted signals were correlated, with the results demonstrating that a difference of 0.4% exists in 90 signal samples.…”