Mixer-First MIMO Receiver with Multi-Port Impedance Tuning for Decoupling of Compact Antenna Systems

This paper introduces mutual impedance tuning for N-path mixer-first MIMO receivers, useful for dynamic decoupling of coupled-antenna systems. A two-port mixer-first MIMO receiver is realized in 45-nm SOI CMOS and includes polyphase baseband resistive-coupling networks. This coupled response is upconverted to radio frequency to realize tunable mutual impedance. The two receivers consume 16 mW and operate over 0.1-3 GHz. Each receiver achieves 3–6 dB noise figure and 14–40 dB conversion gain. When connected to two antennas placed an eighth-wavelength apart, measurements show that N-path decoupling improves signal-to-noise ratio by 7 dB.