A chirp-mismatch echo signal can be generated by exchanging the I and Q baseband signals of a received SAR signal. In this paper, the basic generation principles of a chirp-mismatch echo signal are analyzed. Then, a suppression jamming method with controllable jamming position and coverage area is proposed. This method firstly performs chirp-mismatch processing on the received SAR signals, then controls the range jamming coverage and center position through range shift-frequency modulation and time delay, and controls the azimuth jamming coverage and center position through motion modulation and azimuth shift-frequency modulation. Theoretical analysis and simulation results show that this method can effectively control the location and coverage of a jamming result without convolution modulation, and it is easy to implement in engineering. The simulation results verify the correctness of the theoretical model, which can provide a basis for the implementation and application of SAR jamming based on the active radar transponder.

LuTan-1 (LT-1) is a bistatic synthetic aperture radar (BiSAR) system consisting of two identical L-band SAR satellites. The bistatic mode of LT-1 plays a critical role in generating high-precision digital elevation models (DEMs), which requires precise geometric calibration of initial range and azimuth times for both SARs to ensure the reliability and quality of geolocation. However, existing geometric calibration methods predominantly focus on monostatic SAR systems, with limited literature on slave SAR calibration in bistatic systems. This research addresses this gap by establishing geometric calibration models for both SARs based on signal echo history and the range–Doppler model. The geometric errors are effectively resolved using corner reflector data from Xinjiang, China. Through statistical analysis of LT-1 SAR images acquired between July and November in bistatic mode, this paper has demonstrated range delay accuracy of better than 5 ns and azimuth time accuracy of better than 0.1 ms. This level of precision translates into a positional accuracy better than 0.8 m. The proposed models have been successfully applied to geometric calibration, providing precise geolocation for LT-1, thus enhancing its utility for a wide range of Earth observation applications. This paper is the first endeavor to present the assessment of the geometric calibration and geolocation accuracy of LT-1 and discuss the results of the bistatic geometric calibration of the master and slave SARs in a BiSAR formation.

The digital beamforming synthetic aperture radar (DBF-SAR) is proposed by scholars as a promising solution to overcome the constraint of the minimum antenna area of the traditional single-channel SAR to achieve high resolution and wide swath (HRWS) by scan-on-receive (SCORE) in the elevation multiple channel. However, the inevitable channel imbalance between the elevation channels of DBF-SAR will degrade the DBF-SAR image quality. In this paper, we present a method to estimate the sampling time delay error, amplitude error and phase error based on the external calibration data. For the sampling time delay deviation, we adopt to calculate the statistical average of the position deviation of several external calibration points in the reference channel image with that of the error channel image. To avoid noise interference, we image the DBF-SAR original echo-carrying amplitude information to obtain the amplitude error between channels by dividing the absolute values of the complex image data of the error channel. Due to the phase error between channels, the image contrast will decrease. Therefore, the problem of estimating the phase error can be transformed into the problem of maximizing the image contrast. So, in this paper, we use the gradient descent method to optimally estimate the phase error. Finally, the effectiveness of the method is verified by the simulation of airborne measured data and simulation data.

With the development of synthetic aperture radar (SAR) imaging technology, the research of SAR jamming method has become an important topic in the field of electronic countermeasures. According to the jamming effect, SAR jamming methods can be mainly divided into suppression jamming and deception jamming. Since the effect is relatively single and the power demand is high, the suppression jamming method is easy to detect and identify. Meanwhile, deception jamming requires high-precision reconnaissance of signal parameters and complex algorithm design, so it is difficult to develop the system. Therefore, it is of great research value to design a smart, controllable and easy-to-implement jamming method. Based on this, a new jamming method combining sine function secondary modulation and phase coded modulation is proposed in this paper. This method utilizes the sine function secondary modulation signal and the periodic or non-periodic phase-coded signal to perform azimuth modulation and range modulation on the intercepted SAR signal respectively and utilizes two-dimensional shift-frequency modulation to achieve position control, thereby generating the desired jamming signal. Through changing the modulation parameters, the proposed method can produce six different types of jamming effects and meet the requirements of suppression jamming and deception jamming. The simulation results based on airborne SAR raw echo data verify the correctness of the theoretical model.

In this paper, a fast generation method for deceptive jamming signal against synthetic aperture radar (SAR) based on template space domain processing is proposed. The first advantage of this algorithm is that the computational complexity of the real-time processing stage of the jammer is independent of the size of the jamming template, secondly, the hardware consumption, especially the storage capacity, during the initialization stage is smaller, and finally, it has a relatively small requirement for SAR parameters, which is beneficial for achieving real-time jamming process. It is very suitable for situations with high real-time processing requirements for the limited size and weight of SAR jammers. Firstly, the distances between SAR and the jammer, as well as between SAR and the center of the false target, are used to construct the jammer's frequency response (JFR). And then, through the space-frequency transform of the preprocessed jamming template image, a transformation equivalent JFR can be obtained at specific locations in the two-dimensional (2-D) Fourier transform domain of the preprocessed jamming template. By designing reasonable parameters of the range dimension in the pre-processing process, the JFR can be obtained solely through the 1-D sinc interpolation process of the azimuth dimension. Then, theoretical analysis is conducted on the slant range error and its impact, as well as the quantization error of space-frequency domain transformation algorithms. The simulation results and computational complexity analysis have verified that the algorithm exhibits superior performance in terms of imaging quality and efficiency.

Due to inaccurate reconnaissance parameters of the jammer and the decline in equipment performance over long-term usage, the false targets generated by the jammer usually have problems such as defocusing, abnormal brightness, and distortion, which fail to reach the ideal state. Therefore, experts or specialized assessment methods are needed to evaluate the interference effect. However, the human eye is not sensitive to minor changes. In such cases, the results obtained by some evaluation methods may be inconsistent with expert judgments. Therefore, this paper proposes an evaluation method that integrates three features of image edge information, brightness variation, and texture structure. This method mainly achieves two purposes: (1) Maintain a high evaluation effect when the image error does not change significantly, and be consistent with the expert’s judgment. (2) When the image error changes significantly, it can conduct effective effect evaluation like other methods, and has stronger universality and robustness. Furthermore, its robustness is reflected in the ability to reliably evaluate even in the presence of severe image distortion, without relying on geometric correction. Simulation experiments are conducted under three error conditions, and result comparisons verify the advantages and robustness of the proposed method. Finally, the effectiveness of proposed method is verified using real jamming data.