Design of Broadband High-Efficiency Power Amplifier Based on Low-Pass Filter Network

This letter proposes an improved power amplifier (PA) design method based on a filter network. A high-order Butterworth low-pass filter is used as a prototype of the output matching network of the PA, and the proposed matching method reorganizes the matching network to take in transistor parasitic and packaging parameters. In this method, the high-order filter with large circuit area is converted into a compact microstrip matching network containing transistor package and parasitic parameters, and the circuit size is reduced. The Butterworth filter has good frequency selectivity and stability in the wideband range, the reconfigured microstrip matching network takes the transistor packaging and parasitic parameters into account, which provides theoretical support for the design of wideband high-efficiency PAs. To verify the proposed method, a wideband PA module is designed and fabricated with a 10-W gallium nitride (GaN) high electron mobility transistor (HEMT) device. Measurement results show that, over the frequency band between 2.1 GHz and 3.4 GHz, 9.5–11.8 dB gain, a drain efficiency (DE) of 61.7%–75.7%, and 39.5–41.5 dBm output power have been achieved.