This study investigates the target detection problem of multistatic radar in the presence of deception jamming. A detection algorithm based on non-coherent integration is presented to determine whether a target exists in each probed spatial resolution cell (SRC). This algorithm can suppress the jamming to some extent because the spatial divergence of the jamming signal inhibits the effective energy accumulation for detection. However, a jamming signal influences more SRCs than a target. Given that the power of deception jamming is usually larger than that of the target, the global statistics of the SRCs can still exceed the detection threshold with a certain probability, which leads to many false targets. Therefore, a discriminator is presented to distinguish the jamming signals from the target echoes and noises. Subsequently, a joint target detection and deception jamming suppression method that can simultaneously detect targets and suppress the jamming is derived to eliminate the interference in the relative SRCs. Simulation results show that the proposed algorithm can suppress the deception jamming while accurately detecting multiple targets.

A space-based bistatic radar system, typically composed of a satellite as transmitter and an aircraft as receiver, has a larger surveillance area, stronger resistance to damage, and more superior early warning capability for high-speed targets when compared with monostatic radar system. However, the echo signal is more challenging to process because of the high speed of both receiver and transmitter. There are two main problems to be solved in space-based bistatic radar signal processing: constructing geometric model in line with the actual situation to derive the echo signal model and improving detection ability on the basis of the longtime coherent integration algorithm. This article addresses the problem of space-based bistatic radar echo signal modeling and coherent integration for detecting high-speed maneuvering targets. A novel algorithm based on generalized second-order keystone transform and modified product cubic phase function (GSKT-MPCPF) is proposed. First, the bistatic radar system model is constructed and the signal scattered from the moving target is derived. Aiming at seeking a general algorithm which is suitable for space-based bistatic radar system, the GSKT-MPCPF is presented to correct the linear range migration (LRM), the quadratic range migration (QRM), and the Doppler frequency migration (DFM), and estimate the motion parameters of targets simultaneously. The simulations of mono-target and multitargets validate the proposed method. Furthermore, we perform comparisons with several relative algorithms and results show that the proposed algorithm has superior performance.

The mainlobe jamming suppression technique is one of the key techniques of radar electronic counter- countermeasure (ECCM). In the view of multistatic radar, the interference signals received with different view angles would be highly coherent, on the contrary, the target echoes would be independent due to the radar cross section (RCS) of target would randomly fluctuate as the variation of view angle. As a consequence, After the interference signals have been aligned, a steering vector can be found of interference signals, the energy of the interference signals will be concentrated in a single-rank subspace whereas the energy of the target echo signals will be scattered throughout the whole signal space of the multistatic radar. By exploiting this phenomenon, a new mainlobe interference suppression method for multistatic radar is proposed. In this method, the projection matrix is trained based on the time domain sampling data. The interference signals received by multiple node radars with different view angles can be effectively suppressed through the noise subspace projection operation. Then, a general likelihood ratio test detector used for the residual signals after projection operation is derived. The results of simulations indicate that the proposed method can effectively suppress various kinds of mainlobe jamming and improve the detection performance. Furthermore, this method is adaptive to the variation of the interference pattern and the geometric configuration of the node array.

Near space is the key to integrating “sky” and “space” into the future. A synthetic aperture radar (SAR) that works in this area would initiate a technological revolution for remote sensing applications. This study mainly focused on ground moving target imaging (GMTIm) for a near-space hypersonic vehicle-borne SAR (NS-HSV-SAR) with squint angle. The range history, parameter coupling, and Doppler ambiguity of the squint-looking NS-HSV-SAR are more complicated than traditional side-looking airborne or space-borne SARs. Thus, a precise range model is presented on the basis of phase error analyses. Then, all potential distributions of echo’s azimuth spectrum are derived, and a GMTIm method is proposed on the basis of a detailed analysis of the echo characteristics. The proposed method consists of three steps. Firstly, a prior information-based pre-processing function was created to decrease the Doppler ambiguity and range migration effects. Secondly, a blur matched keystone transform was developed to correct the residual range walk migration. Thirdly, a time-saving chirp Fourier transform was investigated for azimuth focusing. Implementation considerations, including the curvilinear trajectory of the NS-HSV-SAR, multiple moving target imaging, and applicability and limitation of the method, are discussed. Finally, simulation results are presented to validate the effectiveness of the proposed method.

In this paper, we investigate an approach for embedding communication symbols into radar waveform, while holding constant envelope with spectral containment. To achieve this approach, a new frequency modulation (FM) scheme is proposed, where the proposed FM is the addition of communication frequency modulation term (CFMT) and the base radar FM. For communication information modulation, the CFMT is designed to be a linear combination of multiple sub-FM terms and the information-bearing communication symbols are carried out by the coefficients of different sub-FM terms. This technique is based on these sub-FM terms comprising of the CFMT mathematically orthogonal to each other in the inner product domain. In addition, in order to mitigate the interference caused by the radar FM on the demodulation procedure, the CFMT is designed mathematically orthogonal to the radar FM. Therefore, the resulting FM of emission is actually a group of orthogonal FM terms. Besides, a weighted coefficient is introduced to make a tradeoff between the degrees of range sidelobe modulation (RSM) and the communication bit error rate (BER) performance. The performance of the designed radar-embedded communication waveform, including ambiguity function, spectral, weighted coefficient design and the demodulation procedure is analyzed. The results show that a satisfactory communication BER performance can be achieved without sacrificing the radar performance.

Elevation frequency scanning synthetic aperture radar (EF-SCAN SAR) can isolate range ambiguities in the range-frequency domain. Therefore, range ambiguity suppression can be accomplished through range-frequency bandpass filtering, which can outperform spatial filtering-based ambiguity suppression. In this article, the analytic space-time signal model of an intrapulse frequency scanning array is derived. Based on the analysis of the characteristics of this signal model, waveform design criteria for EF-SCAN SAR are developed to effectively separate the range ambiguities in the range frequency domain. The ground echo model of EF-SCAN SAR is also developed based on this space-time signal model. The impact of intrapulse frequency scanning on the performance of high-resolution and wide-swath (HRWS) imaging is analyzed based on the derivation and analysis of the echo spectrum. Finally, an imaging algorithm for EF-SCAN SAR is developed based on this analysis. Numerical simulations verify the effectiveness of the proposed waveform design criteria and imaging algorithm.