Hiromasa Fujimoto

Source second-harmonic control for high efficiency power amplifiers

A novel technology that drastically improves output power and efficiency of amplifiers has been developed, where source and load second-harmonic impedances, as well as the fundamental impedances, are optimally terminated in the input and output matching circuits. A record high 74% power-added efficiency (PAE) with 31.4 dBm (1.4 W) output power at a frequency of 930 MHz has been achieved as a single-stage saturated amplifier using an ion-implanted GaAs MESFET under the low supply voltage of 3.5 V. As a single-stage linear amplifier, an excellent PAE of 59% with 31.5 dBm output power has been realized at V/sub d/=4.7 V and f=948 MHz. Saturated and linear two-stage power modules operating at 900 MHz band with 31 dBm (1.25 W) output power have been demonstrated for analog and digital cellular applications respectively, the volume of which is as small as 0.4 cc. The saturated power module has achieved a PAE of 66% at V/sub d/=3.5 V, and the linear one has realized a PAE of 50% at V/sub d/=4.7 V.

A 3.5V, 1.3W GaAs power multichip IC for cellular phone

A GaAs power multichip IC (MCIC) operating at 3.5 V for cellular phone has been developed. The MCIC can deliver an output power over 1.3 W with a power-added efficiency of 60% from 890 to 950 MHz. It is comprised of two GaAs MESFETs, three GaAs passive matching chips and a printed board on which biasing networks are fabricated. These components are mounted on an aluminum nitride (AlN) package. The volume of the MCIC is only 0.4 cc, half that of conventional power hybrid ICs. This MCIC will contribute to realization of high performance and very compact cellular phones.<<ETX>>

High-efficiency low adjacent channel leakage GaAs power MMIC for 1.9 GHz digital cordless phones

We report on the fabrication of highly efficient GaAs MESFETs, the design for low distortion, and the performance of this MMIC. Two power MESFETs and input, interstage, and output matching circuits were integrated in a very small chip size of 1.0 mm/spl times/1.5 mm. This MMIC achieved an output power of 22 dBm at 1.9 GHz with high power added efficiency of 49.5% and low adjacent channel leakage power of -56 dBc under the low operating voltage of 3.0 V. This result represents one of the highest efficiencies that have been reported. This MMIC has a promising future for 1.9 GHz digital cordless phone applications. >

High isolation and low insertion loss switch IC using GaAs MESFET's

A novel RF switch IC using GaAs MESFETs has been developed for digital communication systems. The new IC is composed of a three-stage SPST switch and a thin film termination resistor, which realizes a high isolation and a low return loss. In addition, a high power handling capability and a low insertion loss are simultaneously realized with two kinds of pinch-off voltages using the orientation effect of GaAs MESFETs. According to these technologies, the excellent performance is achieved as follows: the isolation of 60 dB, the return loss of 20 dB, the 1 dB power compression of 27 dBm and the insertion loss of 1.6 dB at a frequency of 1.9 GHz with control voltages of 0/-5 V. The new switch IC contributes to a variety of communication system using high-quality digital modulation. >

A 3.5 V, 1.3 W GaAs power multi-chip IC for cellular phones

A GaAs power multi-chip IC (MCIC) operable at a voltage of 3.5 V designed for cellular phones has been developed. The MCIC is able to deliver an output power of 1.3 W with a power-added efficiency of 60% in a frequency range from 890 to 950 MHz. This consists of two GaAs MESFETs, three GaAs passive matching chips, and a printed circuit board on which biasing networks are disposed. These are mounted on an aluminum nitride (AlN) package, occupying a half volume of conventional power hybrid ICs, i.e., only 0.4 cc. In order to improve the low voltage operation characteristics, a GaAs power MESFET operable at a low voltage of 3.5 V with an output power of 32 dBm and a power-added efficiency of 65% is developed, and microstrip lines having high impedance characteristics are incorporated also in order to minimize the conductor loss of matching network. The MCIC would be highly useful to develop compact cellular phones with advanced characteristics. >

A high performance GaAs MMIC transceiver for personal handy phone system (PHS)

A high performance GaAs MMIC transceiver has been developed for the Personal Handy phone System (PHS), Japans digital cordless telephone system. The MMIC includes a T/R switch, a Low Noise Amplifier (LNA) and a Power Amplifier (PA), which offers significant advantages in RF performance in comparison with silicon devices. In receive mode, the power gain and the noise figure including T/R switch are 15 dB and 2.4 dB, respectively. In transmit mode, the MMIC including T/R switch exhibits an overall power added efficiency (PAE)-of 25.5% and produces an output power of 21 dBm with an adjacent channel leakage power (Padj) of ¿56.2 dBc (600 kHz offset) at 1.9 GHz for ¿/4-shift QPSK modulated signal. A very small chip size of 1.0 mm × 2.7 mm is also realized. This is one of the smallest GaAs MMICs that have been reported with the same functionality.

Direct Chip Mounting GaAs Power Module using an AIN Substrate

A new power amplifier module (PAM) in which GaAs power MESFETs are mounted directly on an aluminum nitride (AIN) substrate has been developed for analog cellular phones. This module occupies a volume of 0.2cc, only 1/4 as large as that of conventional one, and can deliver an output power (Pout) of 31dBm with a power-added efficiency (PAE) of 58% at a low operating voltage of 3.5V around 900MHz band. Furthermore, a new microwave probe card has been introduced into on-wafer RF power measurement of the FETs in order to improve the yield of the PAMs. Using this probe card, the maximum output power of 30.9dBm has been obtained, and gain deviation between on-wafer and packaged FETs is only 1.4dB. This new concept PAM and the developed on-wafer measurement technique must promise advanced high-performance PAM.