Paul Saunier

AlGaAs/InGaAs heterostructures with doped channels for discrete devices and monolithic amplifiers

AlGaAs/InGaAs/GaAs-type heterostructure with one or two doped channels have been used to fabricate both discrete devices and monolithic amplifiers for millimeter-wave operation. Maximum current densities of 1 A/mm and maximum transconductances of 530 mS/mm were obtained. 0.25*50 mu m discrete devices delivered a power density of 1 W/mm with 2.9-dB gain and 25% efficiency at 60 GHz. A 100- mu m monolithic one-stage amplifier demonstrated 93 mW (0.93-W/mm power density) at 31.5 GHz with 4.2-dB gain and 29% efficiency. A record 34% efficiency was achieved with a 53.7-mW output power and 4.8-dB gain. >

GaAs Dual-Gate FET for Operation Up to K-Band

A high-frequency equivalent circuit model of a GaAs dual-gate FET and analytical expressions for the input/output impedances, transconductance, unilateral gain, and stability factor are presented in this paper. It is found that the gain of a dual-gate FET is higher than that of a single-gate FET at low frequency, but it decreases faster as frequency increases because of the capacitive shunting effect of the second gate. A dual-gate power FET suitable for variable gain amplifier applications up to K-band has been developed. At 10 GHz, a I.2-mm gatewidth device has achieved an output power of 1.1 W with 10.5-dB gain and 31-percent power-added efficiency. At 20 GHz, the same device delivered an output power of 340 mW with 5.3-dB gain. At K-band, a dynamic gain control range of up to 45 dB was obtained with an insertion phase change of no more than +-2 degrees for the first 10 dB of gain control.

A heterostructure FET with 75.8-percent power added efficiency at 10 GHz

The authors report the performance of a new AlGaAs/GaAs heterostructure FET (HFET) designed to have very high efficiency at the X-band with high drain bias. The combination of low doped AlGaAs under the gate and highly doped GaAs channel and superlattice buffer layers allows high gate-drain and source-drain breakdown voltage, constant transconductance, and moderate-to-high maximum channel current. These characteristics make the devices ideal for Class B and Class F operation. The 1200*0.25- mu m HFET devices have demonstrated a power-added efficiency (PAE) of 75.8% with 603 mW of output power and 8.8 dB of gain with a 9-V drain bias at 10 GHz. Other 1200*0.25- mu m HFET devices have demonstrated a 63.2% PAE with 8.3 dB of gain and 851 mW of output power with a 12-V drain bias. At 14 volts, 50% PAE was measured with 7.4-dB gain and 1.1 W of output power.<<ETX>>

A high efficiency Ka-band monolithic GaAs FET amplifier

A monolithic three-stage Ka-band GaAs FET power amplifier has been designed and fabricated on MBE (molecular-beam epitaxy)-grown material with a highly doped (8*10/sup 17/ cm/sup -3/) channel. Devices with gate length of 0.25 mu m and gate width of 50 mu m, 100 mu m, and 250 mu m were cascaded. The gate and drain bias networks were also integrated. A maximum small-signal gain of 26 dB was obtained with 4 V on the drain and 0 V on the gate. When biased for large-signal operation, the amplifier was capable of generating 112 mW output power with 16-dB gain and 21.6% power-added efficiency at 34 GHz. It is believed that this is a record efficiency for a GaAs MMIC (microwave monolithic integrated circuit) amplifier at this frequency.<<ETX>>

Performance comparison of 1 watt Ka-band MMIC amplifiers using pseudomorphic HEMTs and ion-implanted MESFETs

We have demonstrated a high-gain, high-efficiency Ka band three-stage MMIC power amplifier providing >1 watt CW output power, >20 dB power gain, with an average 35% power-added efficiency (378 peak) over a 26.5 to 28 GHz band using 0.25 /spl mu/m AlGaAs/InGaAs pseudomorphic HEMT (HEMT) process technology. The pHEMT amplifiers exhibit third-order intermodulation products >29 dBc with the output power backed off by 5 dB. As an alternate low-cost solution, we processed three wafers of the Ka-band monolithic amplifier designed with pHEMT technology using direct ion-implanted 0.2 /spl mu/m GaAs MESFETs achieving >1 watt CW output power, >18 dB power gain, with an average 24% power-added efficiency (27% peak) over the band. The MESFET amplifiers demonstrate third-order intermodulation products >21 dBc with the output power backed off by 5 dB. All amplifier results reported here contain no de-embedding of fixture and connector losses. This paper presents 0.25 /spl mu/m pHEMT and 0.2 pm MESFET device results, as well as amplifier design and performance over a 26.5 to 28 GHz band.

High-efficiency broadband monolithic pseudomorphic HEMT amplifiers at Ka-band

The design and performance of high-efficiency, broadband (up to 7 GHz), monolithic Ka-band amplifiers using doped channel power pseudomorphic high-electron-mobility transistors (HEMTs) are discussed. Amplifiers with output powers as high as 500 mW and power-added-efficiencies as high as 40% were demonstrated.<<ETX>>

Monolithic GaAs Dual-Gate FET Variable Power Amplifier Module

The design, fabrication, and microwave performance of a monolithic four-stage GaAs dual-gate FET amplifier are described. A linear gain of 23 dB with 250 mW output power has been measured at 18 GHz. The highest power obtained was 500 mW with 21 dB gain at the same frequency. By varying the second gate bias voltage, a dynamic gain control range of more than 60 dB has been observed. The chip size is 6.45mm x 2.1mm x 0.1mm.

Embedded transmission-Line (ETL) MMIC for low-cost high-density wireless communication applications

A new embedded transmission-line (ETL) monolithic-microwave integrated-circuit (MMIC) approach which allows flexibility in mixing different transmission-line types (i.e., coplanar and striplines) for maximum MMIC design flexibility and permits the feasibility of eliminating backside processing for low production cost is described. This ETL MMIC approach is an enabling technology allowing for low-cost batch fabrication, and high-density integration of microwave and RF components (including silicon mixed-signal products) for emerging wireless communication applications. Designs and performance results of a number of ETL MMICs are described in this paper.

Four-watt, Kt-band MMIC amplifier

The 4-watt, 28-percent-efficient, 20-GHz power amplifier results reported at last years symposium have been significantly improved to 4 watts and 38-percent efficiency by using 0.25-/spl mu/m pHEMT device technology. The 1992 paper reported amplifier results for our 0.25-/spl mu/m HFET technology. In 1993, the amplifier was minimally redesigned to accommodate our latest pHEMT device improvements. The results, reported here are for a packaged Kt-band amplifier, include connector losses (no de-embedding), and are the best power and efficiency numbers reported to date for this frequency. The gain and bandwidth of this two-stage amplifier have also increased with the improved device technology, by 4.5- to 13.5-dB power gain across the 17.5- to 21-GHz band. The Kt-band amplifier features a mostly monolithic approach, with a portion of the input- and output-matching networks on alumina. AM/PM measurements for this amplifier demonstrate capability for transmitting QPSK information. This paper presents discrete 0.25-/spl mu/m pHEMT device results at 18 and 20 GHz, as well as amplifier design and performance over a >3-GHz band.<<ETX>>

High-efficiency Kaband monolithic pseudomorphic HEMT amplifier

A monolithic three-stage Ka-band amplifier has been designed and fabricated on a doped channel heterostructure. Devices with gate length of 0.2 micron and gate width of 50, 100, and 250 micron were cascaded. The gate and drain bias networks were also integrated. The small signal gain is 31 dB and the amplifier is capable of an output power of 190 mW with 23 dB gain and 30.2 percent power added efficiency at 31 GHz. This is a record efficiency for a multistage MMIC at this frequency.