A novel balanced power amplifier (BPA) using compact coupler with rhombus resonators is presented. In this design, a new method is presented to analyze the proposed rhombus‐shaped resonator based on the LC equivalent circuit. A new class F power amplifier is designed to improve performances of the BPA. The results show that the performance of the proposed BPA is improved by using the proposed harmonic suppressed coupler at the design structure. The designed BPA operates at 1.25 GHz and delivers 29 dB output power with a gain of 17.9 dB and drain efficiency (DE) of 65.2%. The presented BPA is realized using ATF‐34143 transistors in GaAs pHEMT technology and fabricated on the RT/Duroid 5880 substrate with a thickness of 31 mil.