Background The escalating demand for ultra-high-power radio frequency(RF) sources in scientific research (e.g., particle accelerators), industrial heating, and advanced medical equipment necessitates breakthroughs in solid-state microwave amplifier technology. While GaN HEMT devices offer superior power density, extending their operation to lower UHF bands while maintaining extreme efficiency remains a critical challenge due to thermal management limitations and waveform engineering complexities.
Purpose This study aims to design and fabricate an ultra-high-power, high-efficiency solid-state microwave amplifier operating in the UHF band based on GaN HEMT technology, specifically targeting continuous-wave(CW) output exceeding 2500W with a drain efficiency greater than 85%.
Methods Utilizing a 0.8 μm GaN HEMT process, comprehensive electro-thermal co-design and simulation were conducted. At the device level, source-drain spacing, field plate structures, and substrate thinning were optimized to enhance breakdown voltage. At the assembly level, AuSb solder sintering processes were refined to improve die-attach yield on Cu-diamond heat sinks, minimizing voids. At the circuit level, a hybrid PCB stack-up with varying dielectric constants and harmonic tuning networks were implemented to shape quasi-square voltage and half-sinusoidal current waveforms, thereby reducing power dissipation.
Results Under a CW operating condition of 325 MHz with a drain voltage of 50V and gate voltage of -3V, the fabricated amplifier achieved a saturated output power of >2500 W, a power-added efficiency (PAE) of >85%, and a power gain of >19 dB. The thermal resistance was successfully reduced to 0.20 ℃/W, and the efficiency outperformed comparable LDMOS-based technologies by over 10%.
Conclusions The successful demonstration of this GaN HEMT amplifier not only validates the feasibility of extending high-performance GaN devices into the low-frequency UHF regime but also provides a robust technological solution for applications requiring multi-kilowatt RF power, such as industrial heating, medical systems, and large-scale scientific facilities.
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