Bandwidth‐extended single‐input switchable Doherty power amplifier based on dual compensating reactance with adjusted drain voltage

Abstract

This study presents a switchable Doherty power amplifier (S-DPA) based on dual compensating reactance and adjusted drain voltage with 124% fractional bandwidth (FBW) using single-input architecture. The proposed S-DPA can be operated in wideband mode (WB-MOD) and dual-band mode (DB-MOD) with a larger power back-off region through one-click switching directly. The needed back-off impedance in both operation modes is achieved by using the dual compensating reactance for bandwidth extension. Meanwhile, a load modulation enhancement technique through adjusting the drain voltage of both the carrier and peaking amplifiers is proposed for proper load modulation in DB-MOD. To verify the proposed techniques, an S-DPA was designed and fabricated. Measurement results show that the proposed S-DPA has an efficiency of 51.3%–70.3% at saturated power of higher than 43.4 dBm over the frequency band of 0.8–3.4 GHz with 124% FBW. The 6-dB back-off efficiency in WB-MOD (1.3–2.9 GHz) is 45.3%–56.1% and the 8-dB back-off efficiency in DB-MOD (0.8–1.3 GHz & 2.9–3.4 GHz) is 41.6%–57.9%. 80-MHz modulated signals with 6.2-dB and 8.2-dB peak to average power ratios are used to evaluate the modulated signal performance in two modes. The DPA can achieve an average efficiency of up to 56% with high linearity after digital pre-distortion linearisation.