Source of f.m. noise in cavity-controlled Gunn-effect oscillators

The spectrum of Gunn-effect cavity-controlled oscillators has an f.m. noise power considerably greater than the a.m. noise power. A simple theory of a possible f.m. noise source peculiar to Gunn-effect oscillators is presented and compared with experimental data.     

Semiconductor-diode v.h.f. and u.h.f. noise sources

The v.h.f. and u.h.f. noise properties of silicon and gallium-arsenide diodes are discussed. A formula for calculating the noise output is given.     

Noise calibrator for v.h.f. and u.h.f. field-strength-measuring receivers

A simple noise generator, based on a semiconductor diode of the Zener type and suitable for use in the frequency range 30?900 MHz, can be used to check both absolute gain and noise performance of sensitive receivers.     

Encapsulant for buried u.h.f. antennas

Certain applications for above-ground communications require antennas placed below the ground surface. Under these conditions, reasonable antenna performance can be achieved if the antenna is encapsulated in a uniform low-loss dielectric having a relative permittivity near that of the surrounding earth. It is shown that, with special conditioning, refractory concrete is a suitable encapsulant. It is castable, extremely durable and has a relative permittivity of 6.5?7.0 and a loss tangent of 0.005?0.006 at 400 MHz. Resonator measurements have shown that the desired electrical properties can only be achieved, however, if the material is dried at a temperature of 125?150°C. Once dry, the concrete surface must be sealed to prevent water absorption.     

Acoustoelectric u.h.f. oscillator: frequency modulation

This letter describes some characteristics of an oscillator based upon the acoustoelectric interaction in piezoelectric semiconductors?the acoustoelectric oscillator. Particular reference is made to frequency modulation and to related-device applications.     

Field-diversity antenna for u.h.f. mobile radio

An antenna system using a vertical monopole and horizontal orthogonal slots is described. Impedance and radiation-pattern measurements have shown that the performance of the antenna is satisfactory, and tests in a multipath field have demonstrated its suitability for use in a predetection diversity combiner.     

Modulo-N counter technique for the u.h.f. band

A technique is described for implementing modulo-N counters with u.h.f. performance using commercially available e.c.l. components and a high-speed digital multiplexer. A modulo-5 counter is designed according to this technique and performance at 1.6 GHz is demonstrated.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.     

Measurement of field strength for mobile services at v.h.f. and u.h.f. for the city of Melbourne

A series of field-strength measurements at both v.h.f. and u.h.f. has been taken in Melbourne to assist in the introduction of mobile-radio-telephone services. These results have been analysed and the results are presented. A comparison is made with curves obtained from Okumura.     

GaAs varactor diode for u.h.f. t.v. tuners

The design and fabrication of a GaAs varactor diode for u.h.f. t.v. tuners were carried out using a GaAs double epitaxial layer. The capacitance ratio of diode. C3/C25, is 6.0 and the series resistance at 470 MHz is 0.24 ?. These characteristics are much better than those of an Si diode and well satisfy the requirements for t.v. tuners.     

Evaluation of a diversity system for u.h.f. mobile radio

A single-receiver diversity system for use in the lower u.h.f. mobile-radio band has been built. The results of field trials show the usefulness of such a system in reducing the effects of fading in builtup areas.     

Superposition and separation of a u.h.f. wave and a fast-risetime pulse

Arrangements using one or two 3 dB 90° coaxial hybrid couplers with bandwidths of one octave allow the superposition or separation of a u.h.f. wave and a fast-risetime pulse without disturbing the pulse risetime.     

Computer simulation of u.h.f.-transistor small-signal behaviour at high frequencies

High-frequency 2-port parameters of a u.h.f. transistor are presented, which have been derived from the numerical 1-dimensional solution of small-signal internal behaviour. Results shown include the ?locus and the determination of fT from hfe in the gigahertz region. The validity of the II equivalent circuit is discussed.     

Analogue model for the signal-and-noise equivalent circuit of u.h.f. transistors

The noise behaviour of microwave transistors is computed by an analogue model of the noise equivalent circuit. A specific example is used to verify the accuracy of the computation, by comparison with measured values up to 1500 MHz, for a transistor.     

V.H.F. f.e.t. preamplifier with 0.3 dB noise figure

Using a Plessey gallium-arsenide f.e.t., a preamplifier having a noise figure of 0.3 dB and a stage gain of 22 dB at 129 MHz has been constructed. A summary is given of the design, and the method of alignment, involving a simple inductive 4-port bridge, is also discussed.     

GaAs varactor diodes for u.h.f. TV tuners fabricated by ion implantation

Gallium-arsenide varactor diodes have been developed by using ion implantation techniques. Diode series resistance is around 0.25 ? and uniform among diodes. The standard deviation of resistance distribution is 11.6%. Capacitance variation ratio, C3/C25, is about 5.7.     

Thermally induced FM noise in Gunn oscillators and jitter in Gunn-effect digital devices

By considering the starting-time fluctuation of domain formation and the fluctuation of domain-formation time caused by thermal noise, the front-edge fluctuation of the output current pulse of a Gunn device is obtained. Taking the Fourier transform of the output current-pulse train with these front-edge fluctuations, we obtain the equivalent noise-current source due to the thermal noise of Gunn oscillators. Solving Kurokawa's oscillator equation including this equivalent noise-current source, an expression for thermally induced FM noise in Gunn oscillators is derived. The result is in good agreement with experimental data. These results are applied to estimate thermally induced jitter in Gunn-effect digital devices.     

Thermally induced FM noise in Gunn oscillators and jitter in Gunn-effect digital devices

By considering the fluctuation of the starting time of domain formation and that of domain formation time, an expression for thermally induced FM noise in Gunn oscillators is derived. The result is in good agreement with experimental data. These results are applied to estimate thermally induced jitter in Gunn-effect digital devices.     

Prediction of h.f. circuit availability

Simple empirical equations are presented which give circuit availability in terms of the upper-decile, median and lower-decile values of the maximum usable frequency. The equations are based on approximations to halves of two normal distributions.     

F.m. noise of low-level-operating IMPATT-diode oscillators

An analytical relationship for the output-spectrum width of a low-level-operating IMPATT-diode oscillator is verified experimentally by measuring relevant diode and circuit quantities as well as the oscillator noise. Good agreement between theory and experiment is found if the spectrum width is assumed to be predominantly due to f.m. noise.