Methodology to Design Multi-Octave Power Amplifier Using Extended Class B to Class J Continuous Mode

Abstract

This paper presents the design of a multi-octave power amplifier (PA) using extended class B to class J continuous mode. In a multi-octave PA, an overlapping exists between the higher harmonic frequencies of the lower octave and the fundamental frequency of the higher octave. Therefore, a PA mode with overlapping between fundamental and second harmonic impedances is suitable to design a multioctave PA. An extended class B to class J continuous mode consists of overlapping between fundamental and second harmonic impedances. However, the design of a multi-octave PA is not straightforward. The impedance selected in each octave is important to design a highly-efficiency multi-octave PA. Therefore, this paper presents a methodology to choose the appropriate load in each octave to design extended class B to class J continuous mode PA. This paper also presents a valid range of design variables for the transistor’s reliable operation. The proof of concept PA has been designed using 10 W Wolfspeed GaN HEMT CGH40010F. The designed PA operates from 0.75 to 2.75 GHz. The corresponding fractional bandwidth is 114.2%. The measured drain efficiency, power added efficiency, and output power are 60-73.6%, 53-67.8%, and 39.3-42.3 dBm, respectively. The measured carrier to third-order intermodulation distortion is better than -15 dBc when tested with a 20 MHz spacing two-tone signal.