A CMOS code-modulated path-sharing multi-antenna receiver front-end for spatial multiplexing, spatial diversity and beamforming

This paper presents the design of a novel 5 GHz multi-antenna RF front-end, which is capable of performing spatial multiplexing, spatial diversity, and beamforming. The use of a unique code-modulation scheme at the RF stages of the signal paths enables linear combination of all mutually orthogonal code-modulated received signals. The combined signal is then fed to a single RF/baseband/ADC chain, resulting in a significant reduction of power consumption and area, as well as mitigating the issue of LO routing/distribution. In the digital domain, all antenna signals are fully recovered. Fabricated in 0.18 mum CMOS, the 76 mW 2.3 mm² two-antenna receiver front-end achieves a 10^-2 SER at -64, -77, and -78 dBm of input power for SM, SD, and BF, respectively, while providing 85 dB gain, 6.2 dB NF, and -10.6 dBm IIP3.