A multi-path multi-rate CMOS polar DPA for wideband multi-standard RF transmitters

A two-path digital power amplifier (DPA) in 1.2V 65nm CMOS is presented. This highly reconfigurable and frequency agile block is designed to be used as an envelope modulator in a wideband multi-standard polar transmitter. Each path is composed of a 12-bit DPA ensuring the modulation of the envelope of the RF signal. The DPAs are controlled by envelope code words (ECW) at different sample rates. This diversity strongly attenuates the images produced by the direct digital to RF conversion, avoiding passive filtering. The baseband sample rate conversion can easily be reconfigured. The proposed front-end can manage spurious emissions depending on the standard, the carrier frequency and the required power. The DPAs also integrate active input impedance compensation cells in order to limit the input impedance modulation when switching the DPA cells. The two-path DPA covers a 0.9-1.9 GHz bandwidth with 16.7dBm output 1dB compression point and 12.4% PAE. 64-QAM presents -28dB EVM while active area occupies 1 × 0.25 mm².