Circuit considerations in the design of wide-band tunable transferred electron oscillators

Studies of the effects of the encapsulation on Gunn device performance have been carried out. Results are compared with those of Howes [1], and certain apparent discrepancies are explained.     

Domain configurations in transferred-electron oscillators

An analysis is given of the field configuration of the drifting high-field domain in transferred-electron oscillators. It is shown that the field configuration is triangular in most samples used for microwave generation.     

Overlength modes of transferred-electron oscillators

Simulations of n+?n?n+ GaAs devices show three régimes where the operating frequency substantially exceeds the normal transit frequency. The efficiency/frequency characteristics and the effects of length and carrier density differ from predictions for an idealised I.s.a. mode.     

Push-pull operation of transferred-electron oscillators

Push-pull circuit configurations for GaAs transferred-electron oscillators are described. C.W. X band and pulsed L band devices have been operated in such circuits and have shown as much as 50% increase in output power compared with the sum of the powers obtained from the individual devices.     

Accumulation transit mode in transferred-electron oscillators

Computer simulations have been used to analyse device characteristics appropriate to an accumulation-layer transit mode. Data for GaAs, previously attributed to the limited-space-charge-accumulation mode, and for indium phosphide, are identified with accumulation transit oscillations.     

High-bias-voltage operation of GaAs transferred-electron oscillators

Pulsed operation of epitaxial GaAs transferred-electron oscillators at a bias voltage of ten times the threshold voltage is described. The operating frequency, 14.1 GHz, was close to the transit-time frequency of 13 GHz. A maximum power output of 800 mW at 10% efficiency was obtained at 1% duty cycle. The power output and efficiency decreased with increasing duty cycle, and this decrease is attributed to the decrease in the peak/valley ratio of GaAs with increasing lattice temperature.     

Operation of transferred-electron oscillators in the ridge-waveguide circuit

Operation of high-power X and K. band transferred-electron oscillators (t.e.o.s) in waveguide circuits is described. An increase in c.w. efficiency from 2.5 to 3.5% by decreasing the impedance of the waveguide circuit is reported. Output powers as high as 1.0 W at 10 GHz with 2.5% efficiency and 500 mW at 20 GHz with 3% efficiency were obtained in a ridge-waveguide circuit.     

Frequency-tuning characteristics of waveguide-mounted transferred-electron oscillators

It has been observed that there is an upper frequency limit to the mechanical tuning range of waveguide-mounted oscillators. This limit has been identified as being due to a transverse resonance of coaxial type along the diode mounting post. Reduction in waveguide height is shown to raise the transverse-resonance frequency to a limit determined by the encapsulation and diode parameters.     

Instabilities of InP 3-level transferred-electron oscillators

Experimental investigations of current instabilities in samples of bulk n type InP show an inherent domain-suppression mechanism in agreement with theoretical predictions of electron transfer between three sets of conduction-band valleys.     

Bias-dependent oscillations in 10 ?m-long transferred-electron oscillators

Computer simulations show that a transferred-electron oscillator sustaining X band circuit-controlled relaxation oscillations will, in the same circuit, but at higher bias levels, shift to a space-charge dominated oscillation, where the terminal voltage always exceeds threshold.     

Photoetching of InP mesas for production of mm-wave transferred-electron oscillators

A novel technique for fabricating small-diameter mesa-shaped structures on semiconducting substrates is described. The mesas, which are formed by etching and selective illumination of the substrate, show very little undercutting. The technique is suited for fabricating InP and GaAs transferred-electron oscillators, as well as impatt-diode structures for millimetre-wave sources.     

Determination of resonant frequency for 2nd-harmonic-mode millimetre-wave transferred-electron oscillators

Measurements performed on a 2nd-harmonic transferred-electron oscillator and a scale model are reported. A method is described for determining the resonant frequency of the oscillator once the diode parasitic reactances are defined.     

Electronical tunable millimeterwave oscillators in slotline technique

A new electronical tuning process is proposed for a millimeterwave oscillator in slotline-technique. The circuit used for the GaAs-FET oscillator is realized by a slotline coupler-structure in which the feedback between the resonator and the transistor drain is made by help of electromagnetical field.     

Optimum design of transferred-electron amplifier devices in GaAs

The paper concern the design of GaAs transferred electron amplifying diodes with a cathode doping notch. Simple analytical expressions for small signal impedance and noise factor are expressed in terms of the growth factor and transit phase angle for a constant electric field notch device. These are compared to experimental results, measured on such a device, and the agreement is remarkably good considering the simple model. A minimum measured noise figure of 10.5 dB was obtained. The gain saturation curves are given and briefly discussed. Although at higher frequencies, a small gain increase is encountered with increasing drive a properly controlled notch device does not show a marked gain jump at higher levels as is frequently encountered with Gunn amplifiers.     

Second-harmonic locking properties of l.s.a.-mode transferred-electron oscillators

Harmonic injection locking of an l.s.a.-mode oscillator has been studied by computer simulation. The results show that under certain circuit conditions the 2nd-harmonic frequency locking range may exceed that of the fundamemtal.     

Parametric interactions in optics and tunable light oscillators

The paper presents the review of the latest works at the University of Moscow in the field of pulsed parametric oscillators and the new application of parametric light interaction-nonlinear spectrograph. This spectrograph is based on the steep frequency dependence of phase-matched angles for nonlinear mixing processes. Two new types of oscillators are considered: one having a cavity without dielectric coatings, the other a travelling-wave oscillator that is really an amplifier of parametric superluminescence. The latter has a narrow spectrum of radiation (1-2 Å). The most possible applications of oscillators and their necessary characteristics are given.     

A contribution to the design of wideband tunable second harmonic mode millimeter-wave InP-TED oscillators above 110 GHz

Second harmonic InP-TED oscillators are investigated for frequencies above 110 GHz using different mounts and TED's. It is found that state of the art output powers, comparable to Schottky-varactor multipliers, of more than 2 mW can be generated above 190 GHz by reducing the capsule parasitics. Output power up to 216 GHz are observed. The tuning range above 110 GHz is found to be more than 40%. Using theoretical waveguide models the tuning behaviour of the oscillators is also investigated.     

Circuit characterisation of waveguide-mounted Gunn-effect oscillators

A lumped equivalent circuit is proposed to characterise the load impedance presented to a Gunn device mounted in a waveguide cavity. Using analytical expressions for the elements of the circuit, theoretical predictions for the properties of Gunn oscillators with and without a coupling iris are made, and are compared with experiments.