A Frequency Tuneable Switched-Capacitor PA in 65nm CMOS

A frequency tuneable, switched capacitor power amplifier (SCPA) is introduced that allows it to operate in relatively narrow channel bandwidths (10's of MHz) while enabling operation across a much wider frequency band (>1GHz). An SCPA is connected in series with a fixed inductor and a digitally programmable capacitor (DPC) that allows frequency tuning of the SCPA resonance. A prototype is fabricated in a 65nm CMOS process and embedded with the DPC on a printed circuit board for validation. The measured prototype operates from supply voltages of 1.2 and 2.4 V and achieves linear operation over 58.8% fractional bandwidth (1.4-2.5 GHz) with less than 1.7 dB output power variation. Due to its linearity, no digital pre-distortion is required to achieve measured ACLR<-30 dBc and EVM<3.9%-rms over all operating frequencies when transmitting an LTE 64-QAM, 20 MHz OFDM symbol at >14.1 dBm.