A Reactance Compensated Three‐Device Doherty Power Amplifier for Bandwidth and Back‐Off Range Extension

Abstract

This paper proposes a new broadband Doherty power amplifier topology with extended back-off range. A shunted /4 short line or /2 open line working as compensating reactance is introduced to the conventional load modulation network, which greatly improves its bandwidth. Underlying bandwidth extension mechanism of the proposed configuration is comprehensively analyzed. A three-device Doherty power amplifier is implemented for demonstration based on Cree's 10 W HEMTs. Measurements show that at least 41% drain efficiency is maintained from 2.0 GHz to 2.6 GHz at 8 dB back-off range. In the same operating band, saturation power is larger than 43.6 dBm and drain efficiency is higher than 53%.

A Broadband Three-Way Series Doherty Power Amplifier with Deep Power Back-Off Efficiency Enhancement for 5G Application

“…The Doherty power amplifier (DPA) is the most widely used architecture for improving the OBO efficiency of PAs due to its intrinsic linearity and low baseband overhead [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. A DPA typically comprises a Main PA and an Auxiliary PA, with its OBO efficiency enhanced through active load modulation between these two sub-PAs.…”

“…Nevertheless, a two-way parallel DPA is restricted to providing efficiency improvements within 6 dB OBO, which is insufficient for the 5G NR waveform. To extend the OBO range, N-way (where N = 3 or 4) parallel DPAs have been developed, achieving a deep OBO range of up to 9-12 dB [20][21][22][23]. However, N-way parallel DPAs typically have a larger impedance transformation ratio (ITR) due to the need for impedance matching between R opt /N and 50 Ω at the combining node, resulting in a reduced bandwidth and efficiency, as well as significant area overhead [9,20].…”

A Compact Octave Tunable Switched-Power-Combining PA

“…Alternatively, Doherty-based amplifiers can deliver higher back-off efficiency using various powercombining and bandwidth-enhancing techniques. To improve the back-off efficiency, several three-stage Doherty amplifiers are proposed [6]- [9]. Such an architecture results in significant enhancement in back-off efficiencies (40% at 10 dB back-off).…”

“…Such an architecture results in significant enhancement in back-off efficiencies (40% at 10 dB back-off). The required complex structure to split and combine the RF power, however, limits their bandwidth [7], [9], and results in larger form factor [6], [8]. Load-modulated balanced amplifiers [5], [10] also enhance the efficiency of amplifiers by injecting an additional control signal with predetermined amplitude and phase.…”

Design of a 12dB back-off asymmetric Doherty power amplifier using reactive output impedance

“…At present, there are mainly two methods to increase the OPBO range. The first one is the multi-stage DPA using multiple active devices [23,24], while the other is the asymmetric DPA [25,26]. The multi-stage DPA needs more than two active devices, making its design more complex and costly [27].…”