An Intrinsically Linear Wideband Polar Digital Power Amplifier

This paper presents an intrinsically linear wideband polar digital power amplifier (DPA) operating in semi class-E/F-2 mode. Without using any type of digital pre-distortion (DPD), the proposed architecture achieves high linearity by accurately controlling its AM-AM and AM-PM characteristic curves through nonlinear sizing, overdrive-voltage control, and multiphase RF clocking without compromising the achievable output power or efficiency. Measurement results of the fabricated prototype in 40-nm bulk CMOS show -46 and -40 dBc adjacent channel power ratio (ACPR) for 20- and 40-MHz orthogonal frequency-division multiplexing (OFDM) signals, respectively. The measured error vector magnitudes (EVM) are -36 dB and -33 dB, respectively. Measured results indicate a P-SAT, peak drain efficiency (DE), and power-added efficiency (PAE) of 14.6 dBm, 44%, and 26%, respectively, using a 0.5-V supply for the output stage at 2.2 GHz.