Frequency-Agile Class-J Power Amplifier With Clockwise Fundamental- and Second-Harmonic Loads

A novel frequency-agile power amplifier (PA) designed with a modified class-J theory enforcing constant maximum and minimum instantaneous drain voltages for all frequencies is presented. The resulting high-efficiency class-J mode that requires a reconfigurable drain supply exhibits clockwise fundamental- and second-harmonic load impedance trajectories versus frequency facilitating the PA design. This clockwise-loaded class-J (CLCJ) mode enables frequency-agile capability with enhanced efficiency when the proper drain supply voltage codesigned with the clockwise fundamental and harmonic loads is applied. The CLCJ PA designed from 0.8 to 2.4 GHz exhibits the measured drain efficiency in 57%-78% and 61%-86% ranges when operated in low and high compressions, respectively. To validate the frequency agility, 3G (2.84 MHz), 4G (20 MHz), and 5G (100 MHz) modulated signals were measured at different operating frequencies from 0.8 to 2.4 GHz. At 2 GHz, the average drain efficiency improved from 53% to 68% for CW signals and from 56.6% to 66.3% for a frequency-modulated 30-MHz chirp radar signal with second-harmonic injection.