A 15/30/60-GHz 1TX/4RX Radar Chipset Achieving 6° Angular Resolution Using Frequency Dimension for Virtual Aperture Expansion

The angular resolution of a millimeter-wave frequency-modulated continuous-wave (FMCW) radar can be significantly improved by stimulating antenna arrays with multiple frequencies, thus diversifying electrical distances under a fixed physical distance across antenna elements to expand the virtual aperture. With three different stimulating frequencies, the radar array that includes N transmitters (TX) and N receivers (RX) can form a virtual array of $\mathrm{N}^{6}$ elements in addition to the multiple-input and multiple-output (MIMO) operation, which creates only $\mathrm{N}^{2}$ virtual elements. As a proof-of-concept, we demonstrate a single-channel TX chip and a dual-channel RX chip in 65-nm CMOS technology. The chips can operate at 15, 30, and 60 GHz with $\gt23 \%$ bandwidth. The TX has 11.8, 10.1, and 12.0 dBm output power, while the RX has 9.8, 12.6, and 12.4 dB noise figure and -0.7, 1.5, and -0.2 dBm out-of-band (OOB) input 1-dB compression point (IP1dB), measured at 15, 30, and 60 GHz respectively. In the system demonstration, we use 1 TX chip and 2 RX chips to form a 1 TX and 4 RX demonstration board. The over-the-air (OTA) demonstration shows a 6° angular resolution, which is improved by $4 \times$ compared to the conventional 1 TX and 4 RX radar system.