A Scalable 60GHz 4-Element MIMO Transmitter with a Frequency-Domain-Multiplexing Single-Wire Interface and Harmonic-Rejection-Based De-Multiplexing

This work demonstrates a 60GHz 45nm RF-SOI 4-element scalable MIMO TX with a single-wire interface (SWI) to alleviate the challenge of supporting high data-rate I/O in a large-scale tiled MIMO mm-wave array. Frequency-domain multiplexing is used on the single wire to simultaneously support the signals of all 4 MIMO channels while breaking the trade-off between channel-to-channel isolation and single-wire bandwidth. Harmonic-rejection mixing (HRM) is used to demultiplex the 4 modulated signals simultaneously from the single-wire, each with 2GHz bandwidth (total BW of 8GHz). A novel two-stage wideband HRM achieves high channel-to-channel isolation with low power overhead. The single-wire interface can support 8GHz total IF bandwidth across the 4 channels with 30-40dB SFDR. Each TX in the array achieves 20-35dB conversion gain and 8.8-10.9dBm OP1dB while maintaining a channel-to-channel isolation >30dB. System level measurements show the ability of the MIMO chip to form multiple simultaneous independent beams carrying independent signals.