A transformer combined quadrature switched capacitor power amplifier in 65nm CMOS

This paper presents a transformer combined, quadrature switched-capacitor power amplifier (Q-SCPA) that amplifies in-phase (I) and quadrature (Q) signals separately and combines them in a power-combining transformer. The unit SCPA utilizes a class-G dual-supply architecture to improve efficiency at backoff. This counteracts losses associated with the signal combination. Unlike polar/EER counterparts, the Q-SCPA requires no wideband phase modulator or delay matching circuitry. The Q-SCPA delivers a peak (average) output power of 26 (18.5) dBm with a peak (average) PAE of 22% (18%) for a 20 MHz, 64 QAM OFDM signal with a simulated EVM of 4 % in the S-band.