A CMOS Code-Modulated Path-Sharing Multi-Antenna Receiver Front-End

This paper presents the design and implementation of a novel multi-antenna receiver front-end, which is capable of accommodating various multi-antenna schemes including spatial multiplexing (SM), spatial diversity (SD), and beamforming (BF). The use of orthogonal code-modulation at the RF stage of multi-antenna signal paths enables linear combination of all mutually orthogonal code-modulated RF received signals. The combined signal is then fed to a single RF/baseband/ADC chain. In the digital domain, all antenna signals are fully recovered using matched filters. Primary advantages of this architecture include a significant reduction in area and power consumption. Moreover, the path-sharing of multiple RF signals mitigates the issues of LO routing/distribution and cross-talk between receive chains. System-level analyses of variable gain/dynamic range, bandwidth/area/power trade-off, and interferers are presented. Designed for the 5-GHz frequency and fabricated in 0.18 $mu$m CMOS, the 76 mW 2.3 mm$^{2}$ two-antenna receiver front-end prototype achieves a 10$^{-2}$ symbol error rate (SER) at 64, 77, and 78 dBm of input power for SM, SD, and BF, respectively, while providing 21–85 dB gain, 6.2 dB NF, and 10.6 dBm IIP3.