Impedance Mismatch Approach to Design RF Power Amplifier With Harmonic Suppression

This letter presents the design of a PCB based RF power amplifier (PA) with improved harmonic suppression without the use of any external filter at the output. The proposed stepped impedance microstrip line input and output matching networks offer optimum impedance matching at the fundamental design frequency, whereas at harmonics, the impedances are of no match with the impedances required for higher harmonics power. The designed PA delivers 12.5 watt of CW power in Class-AB mode of operation at 2.45 GHz with measured power added efficiency (PAE) and drain efficiency (DE) of 62.7% and 63.5%, respectively. The first three harmonics of the PA are suppressed at least by 38.9 dBc as well. Measured Gain and input return loss of the amplifier are within 19 ± 0.6 dB and better than 12 dB, respectively, over 2.38–2.65 GHz. © 2025 Wiley Periodicals LLC.