An EDGE transmitter with mitigation of oscillator pulling

We propose a polar transmitter architecture that is robust to modulation-induced injection pulling of its RF oscillator by means of a built-in self compensation. A mathematical model is presented for the injection pulling mechanism, which incorporates a digitally-controlled delay circuit that minimizes injection pulling by adjusting the overall phase shift in the parasitic path between the final amplitude modulation stage (aggressor) and the RF oscillator (victim). The technique is verified in a 65-nm CMOS GSM/GPRS/EDGE SoC demonstrating compliant error vector magnitude (EVM) and modulation spectral-mask performance over process and temperature.