A Highly Efficient Power Amplifier at 5.8 GHz Using Independent Harmonic Control

An optimal design of a highly efficient power amplifier (PA) is described using independent fundamental and second harmonic impedance control technique. In fabrication of a power amplifier, a tuning method is indispensable because the simulation models of the device and capacitor have some difference with the actual value. To achieve a high drain efficiency, the fundamental and harmonic impedances need to be accurately optimized. However, as the operating frequency is increased, the matching circuit becomes sensitive and it is difficult to realize the accurate optimum matching. To solve the problem, the matching circuit of the PA adopts the independent harmonic control circuit using the characteristic of a quarter-wavelength microstrip line. A power amplifier with the concept is designed and implemented using a Cree GaN HEMT CGH40035 at 5.8 GHz. The peak output power, drain efficiency and gain are 47.2 dBm, 70.2%, and 10.2 dB.