Solving Ambiguity in Target Detection for BPSK-Based MIMO FMCW Radar System

In a binary phase shift keying (BPSK)-based multiple-input and multiple-output (MIMO) frequency-modulated continuous wave (FMCW) radar system, real and ghost targets are detected simultaneously, causing ambiguity in target detection. In this paper, we define the targets that are inevitably generated by the BPSK modulation as ghost targets and propose a method for suppressing them. The proposed ghost target suppression method consists of two main steps. First, at the receiving end, a received signal is demodulated using a specific code orthogonal to binary codes used to modulate transmitted signals. Due to the Doppler shift caused by the spectrum of the code used at the receiving end, only ghost targets remain in the demodulated received signal. Then, by subtracting the demodulated signal including the ghost targets from the initially received signal, only the information of the actual targets can be restored. We verify the performance of the proposed method through simulations and actual signal measurements. In addition, the target estimation performance of the proposed method is compared with that of the time-division multiplexing MIMO FMCW radar system.