With advances in radar localisation, especially the emergence and development of passive localisation, there is an urgent demand for countermeasure technology. To counteract the passive direction‐of‐arrival (DOA) location, this article studies the DOA location deception effect of a frequency diverse array (FDA) on an interferometer. By analysing the phase distribution model of the uniform linear FDA (ULFDA) signal and the DOA location principle of the one‐dimensional phase interferometer, it was found that the phase difference the FDA produces does not conform to the direction‐finding law of the interferometer, which provides a potential capability for the FDA to achieve localisation deception for the interferometer. Based on the proposed DOA location deception model and the instantaneous signal‐to‐noise‐ratio (ISNR), the CRLB and RMSE of the angle and x ‐intercept deviation are investigated. The results show that, compared with conventional phased array signals, the FDA signal can achieve DOA location deception on the interferometer, and by properly configuring the frequency increment sequence, the FDA can perform better DOA location deception on the interferometer, which means that the FDA provides promising potential for radar security.

Frequency diverse array (FDA) can generate a range-angle-dependent beampattern due to the introduction of the tiny frequency offsets across array elements. However, the range-angle-coupled beampattern is detrimental to the estimation of the target parameter, and even the normal function of the FDA. In fact, the main purpose of the FDA beampattern synthesis is to achieve beampattern decoupling, mainlobe attenuation avoidance and sidelobe suppression. Furthermore, these conditions can be summarized as the chaotic degree modulation of the beampattern. In this paper, the 2-D fuzzy entropy is first employed in the FDA beampattern synthesis. The proposed FDA can generate a dot-shaped beampattern with high fuzzy entropy in the near-target field and low fuzzy entropy in far-target field. In addition, by introducing time-variant weights, the time modulation is suppressed in the fuzzy entropy-based FDA. The results of the numerical simulation demonstrate the superiority of the proposed beampattern synthesis method.

Considering the signal model of the frequency diverse array (FDA), the amplitude and phase characteristics cannot be ignored. The beampattern mainly reflects the amplitude characteristics. Existing investigations show that the angle‐range dependence of the beampattern offers the FDA several benefits regarding detection and location. However, for the FDA, the phase characteristics that have not been studied are significant when considering the imaging and anti‐jamming. In this work, the authors investigate the phase characteristics of the FDA based on the proposed generalised FDA structure. Then, based on the structure, the authors derive the general closed form of the signal model, the phase‐radiation function, and the phase‐radiation pattern. Moreover, the periodicity of the phase radiation pattern is analysed using the recursive algorithm as compared with the rational analysis. Finally, using the three‐point method, the phase centre of the generalised FDA is derived. Furthermore, the proposed signal model and the derived phase characteristics of the FDA are verified by extensive numerical results.

In this article, we combine the frequency diverse array (FDA) with the vortex electromagnetic wave theory and propose a beamforming method in the generation of range-time-dependent orbital angular momentum (OAM) based on the circular FDA (CFDA). First, we establish a CFDA-based OAM-generating structure, based on which the feasibility of CFDA to generate OAM is verified. Then, we analyze the range-time-dependent characteristics of the generated OAM. Furthermore, concerning the field of radar imaging and target detection, we investigate beamforming with the CFDA-based OAM. Two main issues are addressed: beam collimation and sidelobe suppression. Therefore, according to the derived angular offset between the mainlobe direction and the beam axis, we steer the beam at the target through the phase shifter. Moreover, the sidelobe is suppressed by selecting an appropriate antenna pattern. Finally, based on the analysis of beam collimation and sidelobe suppression, we establish the CFDA configuration for beamforming. Numerical examples and simulations show the superiority of the proposed beamforming method.