Fast-Chirp FDMA MIMO Radar System Using Range-Division Multiple-Access and Doppler-Division Multiple-Access

Frequency-division multiple-access (FDMA) in frequency-modulated continuous-wave (FMCW) radar comprises range-division multiple-access (RDMA) and Doppler-division multiple-access (DDMA). In this article, we present a method using RDMA and DDMA to realize multiple-input multiple-output (MIMO) functionality for FMCW radars. We use single-sideband modulation and quadrature phase shift keying (QPSK) modulation to implement RDMA and DDMA, respectively. These two approaches enable the simultaneous transmission of fast chirp waveforms from multiple transmitting (TX) antennas. Compared to existing works, our proposed system shows the following advantages. First, in RDMA FMCW radar, we apply overlapping binary masking to improve the unambiguous range. Second, in DDMA FMCW radar, we introduce a phase compensation method to reduce the image signals from the nonideality of QPSK symbols. Finally, we leverage these advantages of combining both RDMA and DDMA to balance the performance for FMCW MIMO radar in angular resolution, unambiguous range, and unambiguous velocity. In particular, the FMCW radar system combining RDMA and DDMA allows us to increase the numbers of TX antennas in MIMO applications. We verify our proposed radar system with measurement data on a prototype using three TX and four receiving antennas.