The technology of anti-informational interference is a research hotspot in radio detectors. According to the workflow of first interception and then interference for the jammer, improving low interception can fundamentally improve the anti-jamming ability of the radio detector. Airspace low interception is one of the most promising research directions. FDA-MIMO technology holds significant potential for application in this field. Therefore, this paper investigates the design principle of an FDA-MIMO radio detector with low beam entropy. From the perspectives of information acquisition and countermeasure, the spatial low interception of a radio detector is defined by beam entropy. In this paper, the power peak point and drop point are set in a relatively close range ($\Delta r$), ensuring the rapid attenuation of beam amplitude over short distances. Consequently, the design principle of the FDA-MIMO low interception point beam based on the array frequency offset setting formula is obtained, and the optimal beam convergence is realized. Simulation results show that the half-power beam widths of FDA-MIMO point-like beams are 1 m in the distance dimension and 9 degrees in the beamwidth dimension, with a beam entropy of 11. Compared with other classical frequency offset setting methods, the proposed method demonstrates significantly superior beam performance, particularly in terms of low intercept characteristics. The design principle proposed in this paper provides theoretical support for the low intercept beam design of the FDA-MIMO radio detector, thereby reducing the probability of jammers acquiring signal parameters and enhancing both the low intercept performance and anti-jamming capabilities of the radio detector.

Correlation estimation between echo signal and leakage signal is indispensable when designing transceiver distance or processing leakage signal in frequency modulated continuous wave (FMCW) radar system. Although many contributions investigate methods for correlation estimation of leakage signal, almost all of them consider a random process and are difficult to quantify the relation. Differently, in this work, we propose a correlation estimation method utilizing information geometry theory to explore a certain condition that makes the correlation degree of leakage signal and echo signal least. Through this method, the random issue of estimation in signals correlation calculation process could be transformed into a deterministic issue. The validity of proposed method is proved by both simulation and measurement results. The optimal correlation condition, determined conveniently by our proposed method, will benefit for antennas distance design and future signal processing to cancel leakage signal.

A stop condition without prior information, applied to compressed sensing recovery in millimeter-wave detection system considering the deceptive jamming signal, is proposed in this paper. The input observation signal is extended to the case consisting of the interference that is correlated to the recovery signal. By making the sufficient statistics of the input parameters and observation values generated from the iterative process, the recovery algorithm can be stopped more appropriately. The main contribution of this paper is to propose a stop criterion to improve the efficiency of the algorithm for random modulated signal recovery. Furthermore, different modulated parameters of the random modulated signal are investigated to verify the feasibility and adaptability of the proposed method. The comparable results show greater performance and the algorithm efficiency is improved by 53.2.