Pulling Mitigation in Wireless Transmitters

A new architecture to mitigate the unwanted pulling effect of a transmitter VCO pulled by its own transmitted signal or by other on-chip locked oscillators is presented. The proposed auto-calibration technique can run online without disturbing the transmitter functionality, and with no significant overhead on power consumption and area. When a 16QAM signal is transmitted and the TX-VCO is heavily pulled, the calibration improves the modulation mask by over 15 dB and lowers the transmitted EVM from 11% to 2.4%. Furthermore, the presented calibration technique suppresses unwanted sidebands caused by a mutual pulling between the TX-VCO and another nearby oscillator by more than 20 dB, where center frequencies of the two 4 GHz oscillators are spaced by only 3 MHz.