Improvement of Intermodulation Distortion Asymmetry Characteristics With Wideband Microwave Signals in High Power Amplifiers

This paper presents the improvement techniques of intermodulation-distortion asymmetries with wide carrier-spacing signals in L/S-band high power amplifiers. We proposed a novel circuit technique to directly connect LC series resonant circuits to the gate and drain electrodes of the transistor die in a package for baseband terminations with a wide frequency range. By applying this circuit technique to a 28-V operation 200-W GaAs heterojunction field-effect transistor (HJFET) amplifier, the third-order intermodulation distortion (IMD3) asymmetries were improved even if the two-tone carrier spacing (Deltaf) exceeds 100 MHz. In addition, we analyzed the IMD3 asymmetries of a Doherty amplifier through the IMD3 vector combination of the main and peak amplifiers. A newly developed 28-V operation 200-W GaAs HJFET Doherty amplifier with source and load baseband terminations also delivered flat IMD3 characteristics against the Deltaf over 50 MHz.