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 occurrence 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.
Highlights
F REQUENCY-modulated continuous-wave (FMCW) radars are widely used as automotive sensors to obtain information about a surrounding target such as its range, velocity, and angle
In the multiple-input multiple-output (MIMO) frequency-modulated continuous-wave (FMCW) radar system, the signals transmitted from multiple transmit (Tx) antennas are required to be separated at the receiving (Rx) antenna end [2], [3]
The proposed method does not require additional hardware and can be implemented in the existing digital signal processor of the radar system. This is because two-dimensional (2D) fast Fourier transform (FFT) for the range-velocity estimation is an essential signal processing that should be performed in the FMCW radar system, and only an algorithm that arranges the phase values needs to be implemented
Summary
F REQUENCY-modulated continuous-wave (FMCW) radars are widely used as automotive sensors to obtain information about a surrounding target such as its range, velocity, and angle. In the MIMO FMCW radar system, the signals transmitted from multiple transmit (Tx) antennas are required to be separated at the receiving (Rx) antenna end [2], [3] Various multiplexing methods, such as time-division multiplexing (TDM) [4], [5], frequency-division multiplexing (FDM) [6]– [8], and code-division multiplexing (CDM) [9], [10], can be used to maintain the orthogonality of the transmitted signals. The proposed method does not require additional hardware and can be implemented in the existing digital signal processor of the radar system This is because two-dimensional (2D) fast Fourier transform (FFT) for the range-velocity estimation is an essential signal processing that should be performed in the FMCW radar system, and only an algorithm that arranges the phase values needs to be implemented. By applying Fourier transform to each dimension of the radar data cube, the range, velocity, and angle of the target can be estimated
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