Frequency translation through fractional division for a two-channel pulling mitigation

We present a two-channel RF generation system for a 2 GHz basestation transmitter that avoids pulling due to various parasitic coupling paths, especially between a strong RF output and a sensitive LC-tank of an RF oscillator. This is achieved through a fractional frequency translation by means of a programmable fractional divider realized as a dynamic edge selector of eight oscillator phases. This way, the integer harmonic frequency relationship of victims/aggressors within and between the RF transmission channels is avoided, thus rendered harmless in the creation of injection pulling spurs. The proposed method can push the injection pulling spurs far away from the carrier and at an infinitesimal power level below -80 dBc. The pulling mitigation for two RF channels has been verified in a 65-nm CMOS testchip that occupies 0.56×1.46 mm2 area and emits -156 dBc/Hz noise floor. An RF oscillator is realized as a class-C topology without tail current source.