A 11.4dBm 90nm CMOS H-Bridge resonating polar amplifier using RF Sigma Delta Modulation

Abstract

Using RF Sigma Delta Modulation (RFSDM), a class-D polar amplifier in H-Bridge configuration can work in resonating mode and minimize the switching loss for high efficiency polar transmitters. The high oversampling ratio envelop bit stream created by the low pass RFSDM is phase modulated and digitally mixed with quantized RF carrier to give a modulated RF digital signal. By taking the advantage of high speed and accurate digital CMOS process, this ‘information combination’ architecture can achieve high efficiency and reduce the need for external filter components. A polar power amplifier based on this concept is implemented in 90nm CMOS process and achieved a peak output power of 11.4dBm with 19.3% efficiency at 1.0V power supply. The total area is 0.72mm2 including an on-chip filter matching network designed for 2.4GHz to 2.7GHz band.