Sidelobe Randomization Technique using Frequency Diverse Subarray for Secure MmWave Wireless Communications

In order to solve the sensitive eavesdropping problem outside the target region, we propose a novel sidelobe randomization method called random frequency offset increment combination technique (RFOICT) based fixed region beamforming (FRB) using frequency diverse subarray. The FRB-based RFOICT consists of a conventional phased-array followed with frequency offset modulate at each branch. The main idea of FRB-based RFOICT is to generate an angle-and-range double confined beam and convert the leakage signal in the sidelobe into the artificial noise by exploiting the degree of freedom of frequency while keeping the mainlobe a constant. The statistical features of mean and variance of the received beampattern gain is summarized using a simplified statistical model. An expression of secrecy rate is derived as a function of the frequency offset increment. Simulation results show that the proposed FRB-based RFOICT provides robust PLS performance with lower transmission power compared with the current sidelobe randomization techniques.