High power, broadband Class-J PA with internally pre-matched FET

Abstract

In the broadband design of a Class-J power amplifier using GaN HEMT, the operation of Class-B due to zero crossings of 2nd harmonic frequency load impedance poses problems of low output power and efficiency characteristics. Therefore, a broadband power amplifier should be designed to be operated only with Class-J or Class-J*. This study was designed to implement a matching circuit that meets the Class-J conditions in a wide frequency band. Towards this end, the second harmonic load matching network using stub lines with low characteristic impedance and the fundamental load pre-matching network to increase the low output impedance of the power amplification device with high output power were implemented using high-permittivity ceramic materials. With the use of a field effect transistor (FET) in which the internal matching circuit with these two functions is integrated, a Class-J power amplifier with high power and broadband characteristics was implemented. The measurement results confirmed the following characteristics: 1.1 GHz (1.9–2.9 GHz) small-signal bandwidth (1 dB bandwidth), 46.7–48.1 dBm output power, 61.9-72.6% drain efficiency, and 56.9–66.5% power added efficiency.