For a space-based radar system with hybrid baseline, the problem of clutter angle-Doppler spectral broadening poses a significant challenge to clutter cancellation in the terrain fluctuant observation scene. To improve the robustness of clutter suppression, this article proposed a homogeneous sample selection method based on a novel concept of generalized spatial spectrum density function (GSSDF). This method can be summarized as three crucial steps. First, the GSSDF was constructed by the prior information of digital elevation model (DEM) data, radar system parameters, and the backscattering model. Then, the angle of deflection (AOD) and the equivalent bandwidth (EBW) of GSSDF were adopted to measure the diffusion of clutter spectral. Subsequently, the sample selection criterion was established by a new threshold detection strategy, but the key here is that an appropriate detection threshold of the AOD and EBW can be determined by the characteristic of filter response. To summarize, this approach ensures that the training samples sharing similar clutter properties can be selected to estimate clutter covariance matrix (CCM), thereby enhances clutter suppression capability. Finally, the experimental results demonstrated that the proposed method can obtain better clutter suppression performance than the other contrast methods.

Air-space based bistatic radar is a new radar concept of space-based radar, has strong anti-jamming ability and can economize satellite payloads. However, given the fact that the transmitter and receiver of the radar system are placed on airplane platform and satellite platform respectively, the Doppler frequency is determined by two platforms, which makes the clutter characteristic more complicated. This paper considers the actual beam exposure range, establishes the clutter model of air-space based bistatic radar and analyzes the performance of space-time adaptive processing (STAP) in different configurations. Experiment results show that system performance is greatly influenced by configuration and that air-space based bistatic radar is feasible in certain configurations. This can provide references for the study of air-space based bistatic radar.

Space-borne bistatic radar has stronger viability than monostatic radar. And larger radar cross section (RCS) makes anti-stealth capability of space-borne bistatic radar stronger. However, space-borne bistatic radar is also in down-looking working state, which will suffer serious clutter interference. Since the transmitter and receiver are not placed on the same platforms, bistatic configurations cause clutter characteristics more complicated. It is mainly manifested in resolution spatial variation and tanglesome space-time distribution. In this paper, we first establish the signal model of spaceborne bistatic radar based on satellite-earth relation. Then, we focus on arbitrary orbital plane configuration to study resolution spatial variation and space-time distribution characteristics against bistatic geometric relationships. Last, we adopt the full link evaluation model to evaluate the performance of space-time adaptive processing (STAP) under corresponding bistatic geometric relationships. This paper can provide significant references for system design of space-borne bistatic radar.