Design of a compact harmonic control circuit for Class-F power amplifier for L-band applications

A harmonic control circuit (HCC) is one of the most important block in the Class-F power amplifiers, which should pass the signal at operating frequency and even harmonics and suppress the signals at odd harmonics. Long open stubs are usually used to suppress odd harmonics in the conventional Class-F power amplifiers, which resulted in the large size of the power amplifiers. In the proposed design a compact harmonic control circuit using coupled lines and bended lines are designed at 1GHz. The proposed HCC passes signals at 1 GHz with less than 0.1 dB insertion loss (IL) and also, passes signals at 2 GHz (second harmonic) with less than 0.1 dB IL, and also suppresses signals at 3 GHz (third harmonic) with more than 35 dB attenuation level, and also passes signals at 4 GHz (fourth harmonic) with less than 0.1 dB IL. With these good preferences the proposed HCC can be easily used in Class-F power amplifiers.