3–3.6-GHz Wideband GaN Doherty Power Amplifier Exploiting Output Compensation Stages

Abstract

We discuss the design, realization and experimental characterization of a GaN-based hybrid Doherty power amplifier for wideband operation in the 3-3.6 GHz frequency range. The design adopts a novel, simple approach based on wideband compensator networks. Second-harmonic tuning is exploited for the main amplifier at the upper limit of the frequency band, thus improving gain equalization over the amplifier bandwidth. The realized amplifier is based on a packaged GaN HEMT, and shows, at 6 dB of output power back-off, a drain efficiency higher than 38 % in the 3-3.6 GHz band, gain around 10 dB, and maximum power between 43 dBm and 44 dBm, with saturated efficiency between 55 % and 66 %. With respect to the state of the art, we obtain, at a higher frequency, a wideband amplifier with similar performances in terms of bandwidth, output power, and efficiency, through a simpler approach. Moreover, the measured constant maximum output power of 20 W suggests that the power utilization factor of the 10 W (Class A) GaN HEMT is excellent over the amplifier band.

A 25 W 70% Efficiency Doherty Power Amplifier at 6 dB Output Back-Off for 2.4 GHz Applications with VGS, PEAK Control

“…The control on VGS for the peak branch elevates the total gain on the Doherty region in comparison with one without this kind of control [9], [10]. In other words, the conduction angle of the peak device is increased up to reach the same as the main device.…”

A Broadband High-Efficiency Doherty Power Amplifier With Integrated Compensating Reactance

“…On the other hand, the impedance Z P1 should also be transformed to the optimum load impedance Z P when the amplifier is in saturation. When those four impedances have been determined, the design parameters of the OMN, i.e., S 22 and θ 21 , can be obtained according to (10)- (14), (16) and (17). An optimized OMN that can achieve two-point matching can then be designed accordingly.…”

High Efficiency Power Amplifiers for Modern Mobile Communications: The Load-Modulation Approach

“…In particular, the offset line at the output of the Auxiliary amplifier forces the necessary almost-ideal open-circuit condition at low power levels, while the one at the output of the Main stage keeps under control the load matching within the whole Doherty region, thus maximizing the power efficiency. An alternative method to compensate for parasitic effects, which is nowadays often preferred to offset lines, is the co-design of the device output matching networks and output combiner, where the correct load modulation is imposed as an additional constraint for circuit optimization [56][57][58]. This approach has the advantage of reducing the circuit size.…”