Application of Super-sva to Stepped-chirp Radar Imaging with Frequency Band Gaps between Subchirps

It is well-known that the stepped-frequency chirp signal (SFCS) technique is one of the very effective approaches for achieving high range resolution in radar [1–5]. The SFCS is a train of subchirp pulses with up-stepped or down-stepped carrier frequencies. However, there exists a rang-Doppler coupling problem (RDCP) when applying this signal to practical radar system because longer time is needed for transmitting a complete burst compared with that needed for transmitting just a single chirp. In radar system design, if carrier frequency step (∆f) can be larger than the bandwidth of subchirp (Bm), it will be very helpful for using less number of subchirps to obtain high resolution and at the same time reduce the influence of RDCP on imaging quality. However, the spectrum of transmitted signal will not be continuous but with band gaps existing when ∆f > Bm, and it will lead to high grating lobes in range profile. In this paper, the SuperSVA technique is applied to solve the grating lobe problem arisen from band gaps in SFCS. Simulation and experiment results for moving train imaging are presented to show that the algorithm works very well. Received 28 March 2011, Accepted 26 April 2011, Scheduled 29 April 2011 Corresponding author: Wenshuai Zhai ([email protected]). † Also with The Key Laboratory of Microwave Remote Sensing, Chinese Academy of Sciences, and Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China. ‡ Also with Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China.