Common-gate GaAs f.e.t. oscillator

Frequency tuning, power and noise characteristics of a common-gate GaAs f.e.t. oscillator were investigated. By changing the common-gate lead inductance, the frequency was changed by almost two octaves. The f.m. noise of the low-Q factor f.e.t. oscillator was at the same level as that of a medium-Q factor GaAs impatt oscillator.     

Broadband varactor-tuned GaAs f.e.t. oscillator

A broadband varactor-tuned GaAs f.e.t. oscillator (7.4 to 13.1 GHz) is presented, together with measured and predicted performance characteristics. The circuit uses tuning in series with both the gate and the source leads of the device to maintain optimum oscillation conditions across the band.     

11 GHz and 12 GHz multiwatt internal matching for power GaAs f.e.t.s

Multiwatt internal-matching techniques for multichip power GaAs f.e.t.s at 11 GHz and 12 GHz bands have been developed, adopting a lumped-element input circuit and a semidistributed output circuit. The internally matched device for the 11 GHz band exhibits 4 W power output with 3.4 dB associated gain, and the 12 GHz device 3.6 W power output with 3 dB associated gain.     

High peripheral power density GaAs f.e.t. oscillator

Peripheral power density (p.p.d.), i.e. the output power per Unit gate width is defined as a figure of merit for GaAs f.e.t. oscillators. An X-band oscillator circuit using series and shunt feedback is described and its performance characteristies indicated. It is shown that this GaAs f.e.t. oscillator circuit configuration has the highest peripheral power density.     

High efficiency GaAs Schottky-barrier gate f.e.t. oscillator

A high efficiency high p.p.d. GaAs f.e.t. oscillator was developed. An output power of 63 mW with an efficiency of 39.7% and a p.p.d. of 0.21 mW/?m was easily produced at 9.3 GHz using a HP FET 1101 A-HPAC 100 A. The design of this oscillator was effected using a large signal method by means of a time-domain analysis program IMAG III, which computes the transient response of a nonlinear f.e.t. network.     

Simplified GaAs m.e.s.f.e.t. model to 10 GHz

A simplified design-oriented equivalent circuit for the GaAs m.e.s.f.e.t. is presented. Its relation to a common, but more complex, model is derived and characteristics are compared. Element values are easily determined from measurements, and the simple model shows good agreement with measured parameters to 10 GHz for 1 ?m-gate m.e.s.f.e.t.s.     

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.     

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.     

10 GHz/10 W internally matched flip-chip GaAs power f.e.t.s

A flip-chip GaAs power f.e.t. delivering 10 W power output with 3 dB gain has been realised at 10 GHz by using a newly developed internal matching technique, in which the f.e.t. chips are directly connected to the lumped capacitors in the matching networks.     

Circuit model for the GaAs m.e.s.f.e.t. valid to 12 GHz

A new equivalent circuit is given for the GaAs m.e.s.f.e.t., which includes resistive loss in the feed back elements. The circuit values are given for several 1 ?m-gate GaAs m.e.s.f.e.t.s. A method for fitting s12 to the measured data is described. Finally, the gain and stability factor of several GaAs m.e.s.f.e.t.s. are extrapolated to 24 GHz from the present model.     

Dual gate GaAs m.e.s.f.e.t. phase shifter with gain at 12 GHz

A dual gate m.e.s.f.e.t. phase shifter is described with 4 dB insertion gain at 12 GHz and more than 100° linear continuous phase shift as a function of the d.c. voltage applied to the controlling gate electrode.     

Monolithic broadband GaAs f.e.t. amplifiers

A unique monolithic X-band f.e.t. amplifier is described. Wideband matching circuits, using lumped elements, are integrated with the transistor on semi-insulating gallium arsenide to produce an amplifier chip 1.8×1.2 mm. Gains in excess of 4.5 dB over 7.5 to 11.5 GHz have been measured. The chip has been installed into a low-parasitic package to produce a gain module suitable for the microwave engineer.     

Extending the low-frequency range of GaAs f.e.t. broadband microwave amplifiers using microstrip transmission lines

A new microwave circuit technique is introduced to extend the frequency range of high-frequency GaAs m.e.s.f.e.t.s into the neighbourhood of 2 GHz so that wide-band amplifiers may be developed. The negative-feedback technique reduces |s11| sufficiently yet allows the other s-parameters to remain approximately the same, permitting the design of high-performance wide-band amplifiers. One such design is discussed.     

GaAs f.e.t.s with silicon-implanted channels

Field-effect transistors with channel doping profiles fabricated by the implantation of silicon ions into high-resistivity vapour phase epitaxial GaAs have given noise figures of 2.9 dB with an associated gain of approximately 5 dB at 10 GHz. Similar measurements on F.E.T.S fabricated in an identical manner, except for the channel fabrication, where silicon ions were implanted directly into a Cr-doped semi-insulating GaAs substrate, have resulted in nose figures typically 1 dB higher.     

Performance of sulphur-ion-implanted GaAs f.e.t.s

GaAs f.e.t.s have been produced by sulphur-ion implantation that give optimum noise figures as low as 4.6 dB at 10 GHz and maximum available gains of greater than 10 dB at 10 GHz. A considerable degree of uniformity among the devices is observed.     

Tunable X band GaAs f.e.t. amplifier

The design of a frequency-tunable X band amplifier using GaAs Schottky field-effect transistors is described. By using a broadband input matching circuit and a frequency-tunable output matching circuit, the gain of 7±0.5 dB obtained from a single-stage amplifier may be varied from 8 to 10 GHz, with corresponding terminal v.s.w.r.s, over any 600 MHz band width, better than 2:1. A single-stage amplifier gives a noise figure of 4.7 dB with a gain of 5.8 dB, and a 2-stage amplifier a 6.0 dB noise figure with 12.5 dB power gain.     

Performance of selenium-ion-implanted GaAs f.e.t.s

Selenium-ion-implanted GaAs f.e.t.s have given minimum noise figures as low as 3·4 dB and maximum available gains of at least 10 dB at 10 GHz. The devices do not appear to suffer from short-term drift problems, and have greater device-characteristic uniformity and reproducibility than epitaxial f.e.t.s.     

Light-induced effects in GaAs f.e.t.s

It is shown theoretically and experimentally that the variations of the d.c. and dynamic properties in a GaAs f.e.t. when a light beam strikes the transistor's gate can be accounted for by an appropriate change in the gate-junction equivalent built-in voltage. A simple relationship connects this change with the variations of the light intensity.     

Ion-implanted GaAs X-band power f.e.t.s

Active layers for GaAs power f.e.t.s have been produced by Si implantation into Cr-doped substrates followed by a simple proximity-annealing technique. Devices fabricated on these layers have up to 1.05 W/mm gate width at 10 GHz. This performance is equal to that of epitaxial devices.     

Cryogenic 2?4 GHz f.e.t. amplifier

A cryogenic single-stage broadband f.e.t. amplifier with an average noise temperature of 34 K (0.5 dB) over a bandwidth of 2 GHz has been developed. The average gain is 12 dB. The best spot noise temperature is 17 K (0.25 dB) at 3.2 GHz, which is competitive with cryogenic parametric amplifiers.