A novel approach with photonic-assisted simultaneous self-interference cancellation and IQ demodulator is proposed and experimentally demonstrated for In Band Full Duplex (IBFD) communication system. In this scheme, the X branch of the integrated dual-polarization dual-parallel Mach-Zehnder modulator (DP-DPMZM) is used to generate upper and lower sidebands of the local oscillator signal with a phase difference of 90 ° through bias voltage control, and the received communication signal and the reference signal are loaded on the Y branch, which is used to achieve self-interference cancellation (SIC) by adjusting the delay and amplitude of the reference signal and the bias voltage of Y branch. All the sub-MZMs are worked on Carrier Suppression Double Sideband (CS-DSB) mode, and the upper and lower sidebands, which are separated by dense wavelength division multiplexer (WDM) or some other kind of optical bandpass filter, are used to realize IQ demodulation through two polarization beam splitters (PBS) and balanced photodetectors (BPDs) by adjusting the polarization state. Experimental results demonstrate good gain characteristics of the system during the down-conversion from 10GHz to 30GHz, as well as, the spurious-free dynamic range (SFDR) of 100.7 dB•Hz2/3 is obtained. At the same time, the cancellation results show more than -30 dB cancellation depth from 10 GHz to 25GHz. Besides, IBFD demodulation performance based on 16-QAM under 200Msps, whose carrier frequencies are from 10 GHz to 30GHz, are all demodulated without and with self-interference. All the average depths of communication signal self-interference cancellation have reached over -20 dB when signal-to-interference ratio (SIR) is 0dB, -5dB, -10dB, and all the demodulated error vector magnitudes (EVMs) satisfy the 3GPP-specified EVM limit for 16-QAM signals.

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.

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.

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.

Due to the weakening effects on the reconnaissance and detection ability of target imaging radar system, SAR jamming has attracted wide attentions in the research field of electronic countermeasures. Generally, SAR jamming methods can be mainly classified as suppression jamming and deceptive jamming based on the generated jamming effects. The suppression jamming methods are easy to implement but have the problems of high power demand and limited jamming effects. The deceptive jamming methods can realize rich jamming types but have the problems of high demand of parameter reconnaissance precision and algorithm complexity. Hence, it is urgent to study easy-to-implement, flexible, and controllable jamming methods to cope with the increasingly complex electromagnetic countermeasure environment. Based on this, a controllable active jamming method against SAR system based on the secondary modulation is proposed in this paper. This method first performs range periodic phase modulation, range sine function modulation and range shift-frequency modulation on the intercepted SAR signals, then further performs azimuth periodic phase modulation, azimuth sine function modulation and azimuth shift-frequency modulation so as to generate the desired jamming signals. This method combines the periodic phase modulation with the sine function modulation to achieve both the suppression jamming effects and the deceptive jamming effects. Through changing the modulation parameters, nine different types of two-dimensional jamming effects can be generated. Meanwhile, the jamming coverage and the jamming position can be accurately controlled. Finally, the correctness of proposed theoretical model is validated by the jamming simulations based on the airborne SAR original echo data.

Suppression jamming and deceptive jamming are effective methods to protect targets from detection of synthetic aperture radar (SAR). However, the energy of traditional jamming is significantly attenuated after processing by ground moving target indication (GMTI) of three-channel SAR, increasing the likelihood of exposing real moving targets. In this paper, a multiple targets jamming method based on a three-step modulation is proposed. First, two additional phases are compensated to the intercepted signal to mimic the position offsets and energy broadening characteristics of real moving targets. Next, a system function and a positioning template are applied to generate multiple false targets for deceptive jamming or control the position of multiple sub-areas for suppressing jamming. Then, a multi-scale noise template is modulated into the signal to complete multi-area suppression jamming. This multiple targets jamming method for three-channel SAR-GMTI can generate multiple false moving targets, which have the same energy broadening and position offsets as real moving targets at the same speed. It can also generate multi-area suppression jamming with arbitrary shapes, which simultaneously achieves significant structural disruption effects on multiple moving targets. After the cancellation process of the displaced phase center antenna (DPCA) method, the jamming energy can be significantly retained. Moreover, the implementation of this method only requires one jammer, and the algorithm complexity is lower compared to some other jamming methods. In addition, the accurate multi-area suppression jamming brings high utilization of jamming energy. The theoretical analysis and simulation experiments have validated the effectiveness of the proposed method.