A Quadrature Switched Capacitor Power Amplifier

Abstract

This paper presents an all-digital class-G quadrature switched-capacitor power amplifier (Q-SCPA) implemented in 65 nm CMOS. It combines in-phase ( I ) and quadrature ( Q ) signals on a shared capacitor array. The I / Q signals are digitally weighted and combined in the charge domain. Quadrature summation results in a 3 dB signal loss; Hence the Q-SCPA utilizes a class-G dual-supply architecture to improve efficiency at backoff. Unlike polar/EER counterparts, the Q-SCPA requires no wideband phase modulator or delay matching circuitry. The Q-SCPA delivers a peak output power of 20.5 dBm with a peak PAE of 20%. It is measured with a 10 MHz, 64 QAM LTE signal, and achieves an ACLR of $ , with an ${\bf EVM} 4%-rms.