This paper describes high power density and low distortion characteristics of a novel InGaP channel field-modulating plate FET (InGaP FP-FET) under high voltage operation of over 50 V. The developed InGaP FP-FET exhibited an extremely high breakdown voltage of 100 V with an impact ionization coefficient about 103 times smaller than that of GaAs. These superior breakdown characteristics indicate that the InGaP FP-FET is one of the most desirable device structures for high-voltage high-power operation. The InGaP FP-FET delivered an output power density of 1.6 W/mm at 1.95 GHz operated at a drain bias voltage of 55 V. As power operation moves from class A to class AB, both 3rd-order intermodulation distortion (IM3) and power-added efficiency (PAE) at higher output-power region were improved, resulting from a suppressed gate leakage current near the power saturation point. These results promise that the developed InGaP FP-FET is suited for applications in which both high efficiency and low distortion are required.

This paper describes a high power GaN-FET amplifier which is developed for wideband code division multiple access (W-CDMA) base stations. We design a bias network which is symmetrically arranged to the RF line (two way bias network) in order to reduce impedance at a baseband frequency of the multi-carrier W-CDMA signal. As a result, the amplifier with the two way bias network successfully suppressed memory effects. Therefore, the application of a DPD technique to the GaN-FET amplifier with the two way bias network demonstrates almost 20 dB linearity improvement in IM3 and considerable improvement in higher order IMD, resulting in low IMD of less than -50 dBc at the highest ever reported W-CDMA average output power of 76 W.

This paper describes amplification with improved linearity by employing a linearizing circuit in an input circuit of an internally-matched Ku-band high power amplifier. The linearizing circuit is composed of series L, C, R and an FET with grounded source and drain, and is connected between the input signal line and ground. This linearizing circuit was applied to a Ku-band 10 W output power amplifier utilizing a 25.2 mm gate-width double-doped Heterojunction FET. The power amplifier demonstrated a 8 dB reduction of the third-order intermodulation at about 6 dB output power backoff point from the 2 dB output compression point.

A buried gate AlGaAs/InGaAs heterojunction FET (HJFET) with gate breakdown voltage of 30 V was examined for high drain bias (higher than 10 V) operation. High breakdown voltage was realized due to the optimization of the narrow recess depth. A 1.4 mm HJFET has exhibited an output power of 30.2 dBm (1050 mW) with 50% power added efficiency (PAE) and 12.1 dB linear gain at 12 GHz with a 13 V drain bias. An internal matching circuit for a 16.8 mm HJFET was designed using a large-signal load impedance determined from load-pull measurement. The 16.8 mm internally-matched HJFET has delivered 38.9 dBm (7.8 W) output power with 46% PAE and 11.6 dB linear gain at 12 GHz with a drain bias of 13 V. This is the first report of higher than 10 V operation of an X- and Ku-band power HJFET with the excellent power performance.