GaAs m.e.s.f.e.t. linear power-amplifier stage giving 1 W

A balanced GaAs m.e.s.f.e.t. power stage has been developed for the 7?8 GHz satellite communication frequency band. At 7.5 GHz, the output power at 1 dB comparession 1 W with a power added efficiency of 37%. The small-signal gain was 6.65 ± 0.45 dB across the frequency band. The small-signal gain, phase, group delay and input and output v.s.w.r. as function of frequency are described. Large-signal gain saturation and 3rd-order intermodulation distrotion measurements are also presented.     

Performance of GaAs m.e.s.f.e.t. oscillators in the frequency range 8?25 GHz

Performance results of microstrip GaAs m.e.s.f.e.t. oscillators operating in the frequency range 8?25 GHz are reported. It is shown that output powers as high as 500 mW and efficiencies as high as 45% can be achieved.     

Dual-gate m.e.s.f.e.t. self-oscillating X-band mixers

GaAs dual-gate m.e.s.f.e.t.s have been successfully used as self-oscillating down-convertors in X-band. A single device replaces the preamplifier, mixer and local oscillator. The best conversion gain achieved by mixing from 10 GHz down to 1 GHz was 12 dB. The input (gate 1) to output (drain) port isolation amounted to 16 dB. Slug-tuner and `disc?-resonator circuits were tested and showed comparable gain and noise performance. Best d.s.b. noise figures of 5.5 dB could be realised at an i.f. of 1 GHz with an associated conversion gain of 4 dB.     

GaAs power m.e.s.f.e.t.s. with a graded recess structure

A new recess structure device was developed to improve the field distrubution and therfore the performance of GaAs power m.e.s.f.e.t.s. The linear gain and the output power were improved by 1?2 dB for this structure. The highest output powers obtained are 15 W with 4 dB associated gain at 6 GHz, and 4.3 W with 3 dB associated gain at 11 GHz.     

Novel f.e.t. power oscillator

An X-band GaAs f.e.t. oscillator is described that uses a novel configuration, designated `reverse-channel oscillator?. This provides output powers of up to 0.94 W at 8 GHz and efficiencies as high as 37%. At a higher frequency this configuration provided approximately 300 mW output at 17.5 GHz.     

7.9?8.4 GHz GaAs m.e.s.f.e.t. amplifier

A 4-stage balanced GaAs m.e.s.f.e.t. amplifier has been developed for the 7.9?8.4 GHz satellite-communication frequency band. Linear gain of 26±0.5dB and 150 mW power at 1 dB compression were obtained across the design band. The small-signal gain, phase linearity, group delay and noise figure are described as a function of frequency. Large-signal gain saturation, 3rd-order intermodulation distortion, gain and phase against temperature and a.m.-to-p.m. conversion data are also presented.     

X-band performance of GaAs power f.e.t.s

The results of X-band measurements on GaAs power f.e.t.s are reported. These devices are fabricated with a simple planar process. Devices with output powers of 1 W or more at 9 GHz with 4 dB gain have been fabricated from more than a dozen slices. The highest output powers observed with 4 dB gain are 1.78 W at 9 GHz and 2.5 W at 8 GHz. Devices have been operated with 46% power-added efficiency at 8 GHz.     

Microwave capability of 1.5 ?m-gate GaAs m.o.s.f.e.t.

1.5 ?m-gate GaAs m.o.s.f.e.t.s have been fabricated by anodic oxidation, and the microwave capability has been examined. The maximum oscillation frequency fmax is 22 GHz and the noise figure is 6.1 dB at 8 GHz. The results are comparable to those of GaAs m.e.s.f.e.t.s.     

X and Ku band GaAs m.e.s.f.e.t.

A GaAs Schottky-barrier f.e.t. (m.e.s.f.e.t.) with a 1 ?m gate has been built, which is suitable for X band and Ku band applications. The unilateral power gain over the X band is above 9 dB and the noise figure is only 5 dB at 10 GHz.     

Microwave power amplification with InP f.e.t.s

InP f.e.t.s were fabricated from v.p.e. layers, with an Al gate of 1.5 ?m × 308 ?m. The power output at 9 GHz, with 4 dB gain, was 1.15 W/mm gate width. This result is believed to be higher than the best published results obtained with equivalent GaAs f.e.t. structures.     

K-band f.e.t. amplifiers

Single-stage f.e.t. amplifiers operating in K-band have been constructed using the Varian VSX 9305 0.5 ?m-gate GaAs f.e.t. An amplifier gain of 9±1 dB was obtained over the frequency band 18.5?20.5 GHz and gain of 8±1 dB was observed from 23.0 to 26.0 GHz. An amplifier noise figure of 5.6 dB was measured at 24 GHz.     

A 4?8 GHz dual gate m.e.s.f.e.t. amplifier

A two-stage dual-gate f.e.t. amplifier with small signal gain of 20 ± 0.75 dB, covering an octave bandwidth (4?8 GHz) and having a dynamic gain control range in excess of 60 dB is reported. The gain frequency response, input and output v.s.w.r. are described as a function of second-gate voltage. The performance of the dual-gate f.e.t. amplifier as a fast r.f. switch is also presented.     

Low-noise microwave f.e.t.s fabricated by molecular-beam epitaxy

The growth of m.b.e. GaAs suitable for f.e.t. fabrication is reported. The m.b.e. structure consists of an n+ = 2.5×1018 cm?3 contact layer on top of an n+ = 3.5×1017 cm?3 active layer. Using this material, f.e.t.s. have been fabricated that have a minimum noise figure of 1.5 dB with an associated gain of 15 dB at 8 GHz. These are the best results yet reported for low-noise m.b.e. GaAs f.e.t.s.     

Microwave InxGa1?xAsyP1?y/InP f.e.t

Microwave performance of InxGa1?xAsyP1?y quaternary alloy metal-semiconductor field effect transistors (m.e.s.f.e.t.s) is reported. Liquid-phase epitaxy (l.p.e.) using a step cooling technique has been employed to grow submicrometre quaternary layers having room-temperature bandgaps of 0.9, 1.0, 1.05, 1.15 and 1.2eV. F.E.T.s having gate dimensions of 1×200 ?m and a channel length of 5 ?m have been fabricated using 1.15 and 1.2 eV quaternary alloys. A maximum d.c. transconductance of about 10 mS and a maximum available gain of about 7 dB at 10 GHz have been obtained.     

High-speed 1 ?m GaAs m.e.s.f.e.t.

By minimising parasitic series resistances, a GaAs m.e.s.f.e.t. with 1 ?m gate length was fabricated, possessing the highest known r.f. power gain, measured up to 18 GHz, for GaAs m.e.s.f.e.t.s.     

New structure of enhancement-mode GaAs microwave m.o.s.f.e.t.

This letter proposes a new feasible device structure of an enhancement-mode GaAs deep-depletion m.o.s.f.e.t. as an attractive alternative to the junction-gate f.e.t.s and describes its microwave properties. The device has been fabricated on a high-resistance epitaxial n?-layer by simple readily available technology without requiring the sophisticated control of the channel thickness needed for the conventional junction-gate f.e.t.s. The 'normally-off nature of the device can be explained on the basis of the substrate space-charge region extending over then?-layer. The microwave performance of the device can be favourably compared with that of currently achievable junction-gate normally-off f.e.t.s. Unilateral gain drops to zero at a frequency slightly above 7 GHz.     

New estimate of the minimum noise figure of a m.e.s.f.e.t.

New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 ?m gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.     

High-efficiency millimetre-wave silicon impatt oscillators

High-efficiency impatt devices and oscillators have been fabricated from epitaxially grown silicon for operation in the frequency range 40?140 GHz. These devices have produced world state-of-the-art efficiencies and demonstrated the expected relative frequency insensitivity of silicon. Single drift devices have given efficiencies of approximately 8%; and double drift device efficiencies as high as 13.5% at 50 GHz and 12% at 90 GHz. Initial measurements show that the sideband phase noise levels follow a constant deviation law.     

Low-noise GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s with optimum noise figures of 1.6 dB at 6 GHz have been fabricated by projection photolithography. An equation has been developed for the calculation of optimum noise figure which gives good agreement between calculated and measured values.     

GaAs f.e.t. mixer operation with high intermediate frequencies

GaAs f.e.t. mixer operation is investigated at 6 GHz when the intermediate frequency is around 1 GHz. A 3 dB improvement in noise figure is measured, compared with 30 MHz i.f. operation. Other characteristics, such as conversion gain and dynamic range, are similar. Broadband operation is also investigated. With 0.5 ?m gate device, on s.s.b. noise figure of 5.6 dB is achieved with a conversion gain of 10 dB.