A 28nm CMOS Dual Band Concurrent WLAN and Narrow Band Transmitter with On-chip Feedforward TX-to-TX Interference Cancellation Path for Low Antenna-to-Antenna Isolation in IoT Devices

Abstract: A dual-band, concurrent 2.4G WLAN and 2.4G narrow band (NB) transmitter (TX) with on-chip feedforward TX-to-TX interference cancellation path for low antenna-to-antenna isolation in IoT devices is proposed. An on-chip cancellation path generates a replica signal of the same magnitude but 180° out-of-phase with respect to the “aggressor” TX signal appeared at the “victim” TX output. With cancellation path properly calibrated, the measured IMD3 product is reduced by 25 dB. Additionally, the maximum output power during concurrent transmission, while meeting the FCC out-of-band emission specification, improves from 10 to 17 dBm across all WLAN channels. With this proposed architecture, the issue of TX-to-TX interference in multi-radio coexistence is finally addressed, opening the door to future high power concurrent multi-band transmitters in reconfigurable IoT devices.