An Intrinsically Linear Wideband Polar Digital Power Amplifier

Abstract

This paper presents an intrinsically linear wideband polar digital power
amplifier (DPA) operating in semi class-E/F2 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 20and 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 PSAT, 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.