Solving Doppler-Angle Ambiguity of BPSK-MIMO FMCW Radar System

Abstract

In a multiple-input multiple-output (MIMO) radar system, binary phase-shift keying (BPSK) modulation is widely used to separate signals transmitted from multiple transmit (Tx) antennas. However, when the BPSK modulation is applied to the frequency-modulated continuous-wave (FMCW) radar system, there is an issue of Doppler-angle ambiguity due to the properties of the modulation scheme. In other words, the maximum detectable velocity is reduced in proportion to the number of Tx antennas, and the angle estimation performance can be degraded when a moving target induces a Doppler phase shift. Therefore, in this paper, we propose a method for solving the Doppler-angle ambiguity in the BPSK-MIMO FMCW radar system. The proposed method involves comparing and arranging the phases of signals corresponding to the same target in the range-velocity detection results. By arranging the phases to form an arithmetic sequence, the signals from each Tx antenna can be distinguished and the unambiguous velocity and angle of the target can be estimated. In addition, by using a general phase-shift keying (PSK) modulation scheme, the proposed method can be applied to an arbitrary MIMO system regardless of the number of Tx antennas.INDEX TERMS Doppler-angle ambiguity, binary phase-shift keying (BPSK), frequency-modulated continuous-wave (FMCW), multiple-input multiple-output (MIMO)

Novel Multiplexing Scheme for Resolving the Velocity Ambiguity Problem in MIMO FMCW Radar Using MPSK Code

“…6 and the highest peak was determined as the true peak. Similarly, Detected peaks with an orthogonal code in [23] binary phase modulation with Hadamard code was used in [24] and the MPSK code was used in [25]. To resolve the velocity ambiguity problem, detected target peaks including the ghost target peaks by an orthogonal code are matched to each Tx antenna element and true peaks are found.…”

“…Second, since we use inverse matrix of the circulant matrix A of the MPSK code, it must be invertible. For example, if the set of MPSK code of {0, 1/4, 2/4, 3/4} is applied to the Tx antenna array with N Tx = 4 as in [25], true target peaks cannot be found since the circulant matrix of the MPSK code is not invertible. Therefore, the MPSK code with invertible circulant matrix must be designed.…”

“…However, this method requires significant amount of computation, especially when N Tx increases. To mitigate the above issues in BPM, the M phase-shift keying (MPSK) code for the MIMO radar was first proposed in [25]. This method finds an arithmetic sequence of the phase of each peak to separate Tx signals.…”

The algorithm of elimination of the ambiguity of radial velocity measurements for the automotive radar

“…A method for eliminating the ambiguity of angle and radial velocity measurements in the MIMO FMCW radar system with binary phase manipulation is proposed in [15]. The method involves comparing and ordering the phases of signals corresponding to the same target.…”

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

“…In the BPSK-based MIMO FMCW radar system, signals to which the binary phase modulation is applied are transmitted. A decrease in the maximum detectable velocity can be avoided through the binary phase modulation, but ghost targets are detected along the Doppler axis [15], [16]. To distinguish between real and ghost targets in this system, the intensity of the received signal can be used [15].…”