This paper presents a class-E power amplifier (PA) with a novel harmonic tuning circuit (HTC) based on composite right-/left-handed transmission lines (CRLH TLs). One of the issues of conventional harmonically tuned PAs is the limited PAE bandwidth. It is shown by simulation that class-E amplifiers have potential of maintaining high PAE over a wider frequency range than for example class-F amplifiers. To make full use of class-E amplifiers with the superior characteristics, an HTC using double CRLH TL stub structure is proposed. The HTC is not only compact but also enhances the inherently wide operation frequency range of class-E amplifier. A 2-GHz 6W GaN-HEMT class-E PA using the proposed HTC demonstrated a PAE bandwidth (≥65%) of 380MHz with maximum drain efficiency and PAE of 78.5% and 74.0%, respectively.

A highly efficient power MOSFET has been developed for 3.6 V RF power amplifiers for use in GSM (Global Systems for Mobile communications) cellular telephone systems (880-915 MHz). It was fabricated using a 0.45-µm CMOS LSI process with an Al-shorted metal-silicide/Si gate structure instead of a conventional 0.8-µm Mo-gate. The resulting power MOSFET has an on-state resistance of 6.9 Ωmm, a breakdown voltage of 13 V, and a cut-off frequency of 11 GHz. The RF performance of the device achieved an output power (Pout) of 1.8 W, a power gain of 10 dB, and a power-added efficiency (ηadd) of 60%. In addition, an RF power module using our proposed power MOSFET achieved an output power of 4 W and a total efficiency of 50%.

We report on 1.9-GHz performance of the Buried-Channel self-aligned WN/W-gate GaAs MESFET (BC-MESFET) for use in digital mobile telephone handsets with low power consumption. The BC-MESFET incorporates undoped i-GaAs epitaxial-grown surface layer on the ion-implanted channel. Both the power and noise performance of the BC-MESFET are superior to the conventional MESFET. The 0.6-µm gate power BC-MESFET exhibits a high power-added efficiency of 57% at 1-dB gain compression, which leads to low power dissipation of the handset. This power performance is attributed to high breakdown voltage which the undoped i-GaAs surface layer has brought about. The BC-MESFET has also shown a minimum noise figure of below 0.4 dB. Taking the IC-oriented fabrication process of the BC-MESFET into consideration, these FET performances demonstrate that the BC-MESFET is suitable for the single-chip MMIC that integrates RF front-end blocks for the 1.9-GHz small-size mobile telephone handset with long battery lifetime.

This paper describes 950 GHz power performance of double-doped AlGaAs/InGaAs/AlGaAs heterojunction field-effect transistors (HJFET) operated at a drain bias voltage ranging from 2.5 to 3.5 V. The developed 1.0 µm gatelength HJFET exhibited a maximum drain current (Imax) of 500 mA/mm, a transconductance (gm) of 300 mS/mm, and a gate-to-drain breakdown voltage of 11 V. Operated at 3.0 V, a 17.5 mm gate periphery HJFET showed 1.4 W Pout and -50.3 dBc adjacent channel leakage power at a 50 kHz off-carrier frequency from 950 MHz with 50% PAE. Harmonic balance simulations revealed that the flat gm characteristics of the HJFET with respect to gate bias voltage are effective to suppress intermodulation distortion under large signal operation. The developed HJFET has great potential for small-sized digital cellular power applications operated at a low DC supply voltage.

A 170-mW class GaAs Power MESFET and a 10-mW class MMIC pre-amplifier operating at very low drain bias have been developed for use in personal handy phones (PHP). The MESFET provided P0(1dB)22.5 dBm, ηadd38.8% at VDS3 V with IDS0.14 A (0.4 IDSS) at 1.9 GHz, and also provided P0(1dB)22.4 dBm, ηadd32.6% at VDS2 V with IDS0.24 A (0.6 IDSS). The MMIC using the same MESFET structure had a linear power gain of 13 dB, a linear output power of more than 10 dBm, and P0(1dB)13.7 dBm, ηadd24.3% at VDD3 V with ID30 mA at 1.9 GHz. The MESFET had a buried p-layer and our improved LDD n self-aligned structure both of which were optimized so as to satisfy a high V(BR)GDO of more than 10 V, a minimized bias dependence of S-parameters and low VK of less than 0.5 V.