Conversion gain of m.e.s.f.e.t. drain mixers

A theoretical analysis of the gain properties of m.e.s.f.e.t. drain mixers is presented. The m.e.s.f.e.t. model includes the nonlinearity of both the transconductance and the drain resistance. For a special case, a simple analytical expression for the gain is given. Numerical results for a typical example are briefly presented as an illustration.     

Two-dimensional electron gas m.e.s.f.e.t. structure

The first m.e.s.f.e.t. structure is reported in which the channel near pinch-off is occupied by a two-dimensional electron gas accumulated at the interface of a GaAs(N)-AlxGa1?xAs(N) heterojunction. Experimental data are in good agreement with theoretical calculations.     

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.     

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.     

Modelling the m.e.s.f.e.t. output nonlinearity

Conditions governing the modelling of transductance and drain-conductance nonlinearities from measured data are investigated. A simple representation for regions close to pinch-off, corresponding to mixer operation, is obtained. Results of the modelling are compared to measurements on a typical 1 ?m gate length m.e.s.f.e.t.     

Gain expansion and intermodulation in a m.e.s.f.e.t. amplifier

A simple way of biasing and tuning an X-band m.e.s.f.e.t. for gain expansion is presented. The measured gain and phase of an experimental amplifier make possible a prediction of the third-order intermodulation using a simple power series. The calculated and measured intermodulation are in agreement with each other.     

Modelling of Gunn-domain effects in GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t. [S22] values larger than unity have been measured from 1 to 10 GHz in the region where the ID/VD curves display a negative slope. An explanation of this phenomenon is proposed in terms of Gunn-domain formation. An equivalent-circuit model which includes this effect is presented and discussed.     

V-shaped-gate GaAs m.e.s.f.e.t. for improved high-frequency performance

The idea of gate shaping in f.e.t.s was implemented into the GaAs-m.e.s.f.e.t. structure. A m.e.s.f.e.t. with 2 ?m gate length was fabricated, the measured m.a.g. data of which allow an extrapolation to an fmax of about 45 GHz.     

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 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.     

Large signal GaAs m.e.s.f.e.t. model and distortion analysis

A simple large signal model, derived from small signal measurements over a range of bias points, is presented for a 2 ?m gate length GaAs m.e.s.f.e.t. Its accuracy is verified by comparing model-predicted second harmonic distortion via time domain and Volterra analyses, with measurements to input frequencies of 4.5 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.     

Micrometre-gate m.e.s.f.e.t.s on laser-annealed polysilicon

Schottky-barrier field-effect transistors (m.e.s.f.e.t.s) have been fabricated on uniformly doped laser-annealed polycrystalline silicon deposited on a silicon nitride insulator. The devices, which had aluminium Schottky-barrier gates and diffused n+ sources and drains but nonoptimised channel profiles, had about 65% the gm values of similar but optimised devices made on s.o.s. layers. Performance of these devices is considered adequate for certain innovative integrated-circuit technologies.     

Performance of self-oscillating GaAs m.e.s.f.e.t. mixers at X-band

A new mode of m.e.s.f.e.t. operation, the self-oscillating mixer is reported. Conversion gains of up to 2 dB at 10 GHz and noise figures as good as 15 dB have been demonstrated by using a simple circuit.     

Substrate conduction in GaAs m.e.s.f.e.t.s

Substrate currents in a gateless GaAs m.e.s.f.e.t. have been measured at d.c, 0.9 MHz and 2 GHz. The results are consistent with the assumption of substrate conduction at high frequencies and active-layer conduction alone at low frequencies.     

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.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.     

Optimised doping profiles for speed-up of GaAs m.e.s.f.e.t.s

Simulation of m.e.s.f.e.t. logic cell shows that discharging of the gate depletion is significantly slower than the charging process. The transient response with the charging/discharging is analytically connected to arbitrary doping profiles. Specific profiles with a doping peak near the substrate boundary can reduce this discharging delay remarkably.     

High-yield self-alignment method for submicrometre GaAs m.e.s.f.e.t.s

A high-yield self-alignment technique for submicrometer GaAs m.e.s.f.e.t.s is described. This method allows the production of submicrometre gate lengths and source-drain spacings by means of standard contact photolithography without requiring a particularly fine geometry on the masks. A 0.5 ?m long gate and a source-drain spacing of 2 ?m were obtained.     

100K uncooled GaAs m.e.s.f.e.t. amplifier as paramp replacement

The characterisation, design and realisation of a low noise GaAs m.e.s.f.e.t. amplifier to replace a narrow band parametric amplifier at 1.7 GHz is described. Special measurement and analytical techniques are necessary owing to the high reflection coefficients and conditional stability of the transistor, as well as the very low noise figures being measured. A single stage amplifier is realised with a noise figure of 1.25 dB and 13.5 dB associated gain at 1.7 GHz.