A monolithic linear power amplifier IC operating with a single low 2.7-V supply has been developed for 1.9-GHz digital mobile communication systems, such as the Japanese personal handy phone system (PHS). Refractory WNx/W self-aligned gate GaAs power MESFETs have been successfully developed for L-band power amplification, and this power amplifier operates with high efficiency and low distortion at a low voltage of 2.7 V, without any additional negative voltage supply, by virtue of small drain knee voltage, high transconductance and sufficient breakdown voltage of the power MESFET. An output power of 23.0 dBm and a high power-added efficiency of 30.8% were attained for 1.9-GHz π/4-shifted QPSK (quadrature phase shift keying) modulated input when adjacent channel leakage power level was less than -60 dBc at 600 kHz apart from 1.9 GHz.

A GaAs SPDT switch IC operating at a low power supply voltage of 2.7 V has been developed for use in 1.9 GHz band personal handy phone system (PHS). In combination with MESFETs with low on-resistance and high breakdown voltage, the switch IC adopts parallel-LC resonant circuits and utilizes both stacked FETs and an additional shunt capacitor at the receiver side in order to realize low insertion loss, high isolation and low distortion characteristics. An insertion loss of 0.55 dB and an isolation of 35.8 dB were obtained at 1.9 GHz. The IC also achieved an output power of 25.0 dBm at 1 dB gain compression point, a second order distortion of -54.3 dBc and an adjacent channel leakage power of -66 dBc at 600 kHz apart from 1.9 GHz at 19 dBm output power.

Two approaches to the design of resonant-type switches with low distortion characteristics operating at a 2-V power supply voltage have been proposed for use in the 1. 9-GHz-band personal handy phone system (PHS). One approach is to use three stacked FETs at the receiver side. They are composed of a dual-gate FET and a single-gate FET. An insertion loss of 0. 41 dB and an isolation of 44. 0 dB were obtained at 1. 9 GHz. A third-order distortion value of -52 dBc was achieved at 19 dBm output power. Another approach is to insert a capacitor in the resonator. A third-order distortion of -49 dBc at 19-dBm output power when two stacked FETs were used at the receiver side. The layout area of the resonator is drastically reduced as compared with the above-mentioned case.

A GaAs linear power amplifier operating with a single 3-V supply has been developed for 5.8-GHz ISM band applications. Two kinds of refractory WNx/W self-aligned gate MESFETs, a P-pocket MESFET and an asymmetric MESFET with a buried p-layer (BP- MESFET ) have been compared in terms of DC characteristics, small signal characteristics and power performances at 5.8 GHz. To obtain both high gain and high efficiency in the case of single 3-V supply operation at 5.8 GHz, we used a highly efficient and linear P-pocket MESFET for the output-stage power FET and a high-gain asymmetric MESFET with a buried p-layer (BP- MESFET ) for the driver-stage FET. The bias condition for 1-mm output-stage P-pocket MESFET was set near class-AB, so as to obtain sufficient output power with high PAE. The two-stage power amplifier MMIC module which can include all matching and biasing circuits, has been designed and fabricated. The amplifier exhibits a high power gain of 17.9 dB and a high power-added efficiency of 25.7% with a sufficient output power of 18.7 dBm at the 1-dB compression point. This self-aligned gate GaAs MESFET technology is promising for near-future 5.8-GHz applications, because of such good power performance and good mass-producibility.

A GaAs power MESFET amplifier with a low-distortion, 10-dB gain-variable attenuator has been developed for 1. 9-GHz Japanese personal handy phone system (PHS). Independently of its gain, a very low 600-kHz adjacent channel leakage power (ACP) with sufficient output power was attained. In single low 2. 4-V supply operation, an output power of 21. 1 dBm, a low dissipated current of 157 mA and a high power-added efficiency (PAE) of 37. 2% were obtained with an ACP of -55 dBc.

A GaAs power amplifier IC has been developed for 1. 9-GHz digital mobile communication applications, such as the handsets of the Japanese personal handy phone system (PHS), which was assembled into a very small 0. 012-cc surface mount plastic package. This power amplifier using refractory WNx/W self-aligned gate MESFETs with p-pocket layers can operate with high efficiency and low distortion with a single 3-V supply. A very low dissipated current of 119 mA was obtained with an output power of 21. 1 dBm and a low 600-kHz adjacent channel leakage power (ACP) of -63 dBc for π/4-shifted quadrature phase shift keying (QPSK) modulated input.