Input-Output Harmonic Controlled Broadband Class-B/J Power Amplifier

In this paper, we propose a novel methodology for Class B/J Power Amplifier design. Class B/J Power Amplifiers (PA) have been widely used for high efficiency broadband radio applications. Their consistent broadband performance helps designers achieve high efficiency and high output power over a wide bandwidth. However, the conventional Class B/J design approach considers only the impact of the load harmonics. Nevertheless, proper source harmonic control is instrumental in maintaining the ‘continuous’ broadband performance of a Class B/J PA. The optimum design space at second harmonic source is proposed and validated to ensure high efficiency across the broadband frequency range. The validation of the impact of the source harmonics on the Class B/J mode is carried out using load pull measurements and the high-efficiency source harmonic design space for broadband operation is identified. As a proof-of-concept, the paper presents a broadband Class B/J PA with input-output harmonic control. The implemented PA demonstrates drain efficiency between 60-73% with output power of more than 40 dBm over the 2.2-3.4 GHz band, thereby achieving 42% fractional bandwidth. The achieved gain flatness is +/- 0.4 dB which satisfies 5G radio standards.