In radio frequency power amplifier designs, the desired current and voltage waveforms are achieved through the tuning of the fundamental and harmonic impedance values in the matching networks. Analytical design methods have been often used to design power amplifiers. But nonlinear behavior of the high-frequency power transistors and inevitable trade-offs between the efficiency, output power, gain, linearity, and bandwidth performances require additional effort and time to optimize the design. Therefore, a reliable optimization technique for designing high-performance power amplifiers is needed. This study reviews several popular and easy-to-apply studies that are reported for designing nonlinear microwave circuits such as power amplifiers.