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<sub>2</sub> 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 <italic>nonlinear sizing</italic>, <italic>overdrive-voltage control</italic>, and <italic>multiphase RF clocking</italic> 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 <inline-formula> <tex-math notation="LaTeX">$P_{\mathrm{ SAT}}$ </tex-math></inline-formula>, 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.

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