Mixer-First MIMO Receiver With Reconfigurable Multi-Port Decoupling and Matching

This article presents architectures to realize mutual impedance tuning for N-path mixer-first multiple-input multiple-output (MIMO) receivers. A coupled response at baseband is upconverted to radio frequency to realize the tunable mutual impedance. This enables the dynamic decoupling of coupled-antenna systems. The impedance of a multi-port receiver is analyzed and shown to be able to provide a wideband tunable and broadband coupled response with an array of RC baseband networks. A two-port mixer-first MIMO receiver is realized in a 45-nm silicon on insulator (SOI) CMOS and includes polyphase baseband resistive-coupling networks. 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. The MIMO system with N-path decoupling was measured with two cases: two monopole antennas and a two-port single-aperture antenna. Signal-to-noise ratio was increased by 7 and 5.2 dB, respectively.