K-Band GaAs MMIC Doherty Power Amplifier for Microwave Radio With Optimized Driver

Abstract

In this paper, a Doherty power amplifier for K-band point-to-point microwave radio, developed in TriQuint GaAs 0.15-m PWR pHEMT monolithic technology, is presented. Highly efficient driver stages on both the main and auxiliary branches have been designed and optimized to boost gain with minimal impact on power-added efficiency. The selected architecture enables a modular combination to reach higher power levels. Matching network structures have been designed, according to simple equivalent circuit approaches, to obtain the desired 10% fractional bandwidth. The fabricated power amplifier (PA) exhibits, at 24 GHz in continuous-wave conditions, an output power of 30.9 dBm, with a power-added efficiency of 38% at saturation and 20% at 6 dB of output power back-off, together with a gain of 12.5 dB. System-level characterization at 24 GHz, in very demanding conditions, with a 28-MHz channel 7.5-dB peak-to-average ratio modulated signal, showed full compliance with the standard emission mask, adopting a simple predistorter, with average output power of 23.5 dBm, and average efficiency above 14%. The measured performance favorably compare with other academic and commercial K-band PAs for similar applications.Index Terms-Doherty power amplifiers (DPAs), gallium arsenide (GaAs), monolithic microwave integrated circuits (MMICs), point-to-point radio.

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

“…At present, watt-level working DPA examples are limited to Ku-band (below 18 GHz) for implementations in the most widely-available 0.25 µm gate-length GaAs [84] or GaN [58,85] technologies. Few examples of watt-level DPAs working in the K-band (below 27 GHz) are also available, resorting to more performing 0.15 µm GaAs [86] or GaN [87] gate-length technologies, while, above K-band power, levels around 0.5 W are proven to be attainable in [88,89] also resorting to 0.15 µm GaAs pHEMTs. These examples indicate that technological advancements in compound semiconductor processes are crucial to allow for the application of the DPA architecture to next-generation communication systems.…”

A 4-W Doherty Power Amplifier in GaN MMIC Technology for 15-GHz Applications

“…To test the linearizability of the DPA, system level characterization has been performed [3]. Adopting a microwave arbitrary waveform generator (ESG4433B of Keysight), a typical point-to-point 256-quadrature amplitude modulated signal, with 28-MHz channel bandwidth and PAPR of 7.4 dB is applied to the DPA.…”

The Doherty Power Amplifier: Review of Recent Solutions and Trends

“…The MMIC and the full module have area of 2.5 mm 2.7 mm and 7 mm 15 mm, respectively. The design procedure of a K-band DPA with embedded drivers is shown in [72]: the measured results on the realized hardware, see a microscope picture in Fig. 16, show a saturated output power exceeding 1 W, together with gain higher than 9 dB over a 10% bandwidth.…”

“…Microscope picture of the GaAs MMIC DPA designed following the guidelines of[72] for K-band point-to-point radios. Size: 3 mm 1.43 mm.…”