Design of a tunable linearity-enhanced Doherty power amplifier based on varactor diode networks

This article presents a tunable linearity-enhanced technique using varactor diode networks (VDNs) to enhance the linearity of Doherty power amplifiers (DPAs) under broadband high peak-to-average power ratio (PAPR) signals. By adjusting the bias voltages of varactor diodes in the input matching network (IMN), the technique compensates for AM–AM and AM–PM distortions from nonlinear capacitances of transistors and DPA load modulation, enhancing linearity and enabling tunability in both single-tone and modulated modes. An asymmetric DPA operating within 1.9–2.4 GHz is designed for validation. A 20 MHz LTE signal (9 dB PAPR) is used to measure. At 9 dB output power back-off, the drain efficiency reaches 44.3%. The adjacent channel power leakage ratio (ACPR) reaches –38.7 dBc. The AM–PM distortion is within 4.75°.