Design of an 8x8 MIMO Broadband RF Subsystem for Future WLAN

This article describes a broadband 8x8 MIMO RF subsystem with large area coverage for next generation wireless local area networks (WLAN) in the 5 GHz band. Measurements demonstrate the capability to operate over a long range of 80 m at a high data rate of 1 Gbps, due to its 23 dBm transmitter, -70 dBm sensitivity, 50 dB dynamic range receiver and 8 dBi high gain antenna. The EVM of transmitter and receiver are 2.6 and 3.2 percent, respectively, for an 80 MHz 64 QAM signal. The 8x8 RF subsystem has been successfully integrated into an IEEE 802.11ac prototype system. Because broadband OFDM signals employed in 802.11ac WLAN standards are more sensitive to non-ideal RF system characteristics such as phase noise, I/Q imbalance and interference, their effects are analyzed and mitigations are incorporated. Design details, fabrication considerations and measurement results are presented.