Tunable Class-F high power amplifier at X-Band using GaN HEMT

Abstract

Class-F type amplification stands on proper termination of harmonics such as short for even harmonicsand open for odd harmonics. Moreover, termination of only the first few harmonics is practical for high-frequencycircuits, while obtaining satisfactory short and open terminations at high frequencies is a challenging design issue. In thepresent study, a topology of harmonics termination for Class-F load network with 2nd and 3rd harmonics and its relativeanalytical analysis are presented. The proposed output termination structure for Class-F type amplification providesan improved short termination of 2nd harmonic; therefore, the efficiency of the power amplifier increases. In addition,the topology implemented with the microstrip lines has a tunable structure, and it is suitable for very high-frequencyapplications due to its straightforward architecture. An X-Band high power amplifier for a small satellite transmitteris designed and fabricated with the proposed method. A 0.25 µm GaN on SiC HEMT having a total gate width of1.25 mm is used. The PA achieves the peak P AE of 55% at 8.1 GHz while the output power is 36 dBm at the3 − dB compression point. The Class-F PA has higher than 50% P AE and 35.5 dBm output power in the band of7.9 − 8.2 GHz . The measured linear power gain is 16.2 dB .