# Research on the Compound Jamming Method against FDA-MIMO Beamforming
## 1 Introduction  
In modern information-based high-tech warfare, the electromagnetic environment is increasingly complex, electronic jamming and electronic anti-jamming are composed of a radar countermeasures system, and the enemy and our two sides are fighting fiercely in the field of radar countermeasures to obtain control of the electromagnetic spectrum, which is also the key to gain strategic advantage and victory in electronic warfare. Frequency diverse array (FDA) was first proposed at the 2006 IEEE radar annual conference [1] due to its unique range dimension dependence. By adding a frequency offset to the array element, which is much smaller than the carrier frequency, the FDA makes the transmit beam have range-angle dimension dependence [2, 3]. By combining the FDA with multiple-input multiple-output (MIMO), it has more flexible range dimension freedom [4, 5] and has good application potential against main lobe deceptive jamming [6, 7, 8, 9, 10, 11, 12, 13, 14, 15]. With the development of new system radars such as the FDA and advanced anti-jamming technologies, the interfering party has to adopt more advanced technical means to counter the opponent's radar system. Therefore, how to protect one's own targets and effectively interfere with the opponent's radar system and advanced anti-jamming measures have become urgent problems in modern warfare. At present, the use of appropriate jamming strategies and advanced and flexible jamming technology is still the main technical means adopted by both sides of the confrontation. The use of a single false target deceptive jamming for countermeasures often fails to achieve the jamming effect, so it is necessary to use a combination of multiple jamming styles to improve one's own electronic jamming capability. With the development of digital radio frequency memory (DRFM), whichhas replaced the traditional analog jamming with digital jamming, the jamming signal has a strong correlation with the original signal, which makes jamming have the dual characteristics of suppression and deception, thus jamming the radar system with a good jamming effect. In recent years, domestic and foreign scholars have carried out a lot of research on the radar jamming technology of the FDA. In [16], [PERSON] deduced the expression of the FDA deceptive jamming signal and established a deceptive jamming model. A space-time adaptive method for joint-domain localization was proposed in [17]. However, the authors of [16; 17] ignored the time delay, so the jamming model was incomplete. Considering the time delay problem, the study in [18] re-derived the FDA deceptive jamming model. In response to the problem that the enemy's passive radar performs direction finding through the signal of the jammer, which poses a threat to the jammer, [PERSON] proposed the FDA radar cross direction-finding positioning deceptive jamming method and the angle deceptive jamming method of amplitude comparison monopulse direction finding of adjacent antennas in [19]. The research in [20; 21] corrected the deceptive jamming signal flow and studied the deceptive jamming method based on FDA-MIMO. The study in [22] proposed a new deceptive jamming method that can hide real targets and generate multiple false targets at the same time. In [23], considering the FDA-MIMO robust adaptive beamforming (RAB) design and proposes an improved worst-case performance optimization (IWCPO) algorithm using the eigenspace. In [24], the weight vector was used to control the range-angle dimension-dependent transmit and receive beamforming pattern of FDA-MIMO, to suppress the main lobe jamming. To address the application of jamming technology in static scene jamming signals, the study in [25] proposed a deceptive jamming method combining static and moving targets for synthetic aperture radar (SAR). [PERSON] analyzed the range, angle, and doppler resolution capabilities of the FDA radar signals by using ambiguity functions in [26] and applied them to SAR deceptive jamming and imaging.