摘要:

It has been shown theoretically that resonant azimuthal surface waves can be set up on a cylindrical-surface reactance sheet, and the special case of a line-source excitation has been studied by Cullen and by Wait and Conda.In the present paper the use of a dielectric tube to provide the necessary surface reactance is studied theoretically and experimentally. The main features of the theory are confirmed, but there are some discrepancies in detail which require further study.Possible applications are discussed, particularly in relation to the supergain-aerial problem.

DOI:10.1049/piee.1964.0035

出版商:IEE    

年代:1964

数据来源: IET

摘要:

A theoretical analysis of wave propagation in guiding structures with statistically varying parameters is given.The problem is treated as random cross-coupling among all the propagating modes of the structure, where the random functions describing the coupling coefficients are related to the inhomogeneities in the media or boundaries.It is shown that, in general, the solution is represented by a statistical quasimode which, in the mean, resembles the mode of the lowest attenuation, but that all the other coupled modes partake in a definite way in determining the nature of the mode. General formulas are derived which relate the properties of the solution to the statistical parameters. The use of the formulas is illustrated by application of the solution to a number of propagation problems.

DOI:10.1049/piee.1964.0036

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper considers a number of high-frequency applications of a technique, described by Midgley, which uses Hall effect in a semiconductor to increase the penetration of an externally applied magnetic field. High-mobility semiconductors, like the intermetallic indium compounds, giving large Hall effects, also have a high conductivity with a correspondingly small skin depth, so that it becomes difficult to utilise the body of the semiconductor effectively. Hall-effect reinforcement of the applied field is therefore particularly valuable at high frequencies, and methods by which this may be exploited to advantage in Hall-effect and magnetoresistance-effect linear mixers, power-measuring devices and mode transducers, are discussed. A new form of electrically controlled attenuator embodying the same principle is also proposed.

DOI:10.1049/piee.1964.0037

出版商:IEE    

年代:1964

数据来源: IET

摘要:

An untuned u.h.f. amplifier giving a mean gain of 25dB from 650 to 1000 Mc/s is described. Three discsealed triodes (type 416B) are cascaded in earthed-grid stages.Matching of interelectrode capacitances and the realisation of the broadband interstage transformers are obtained by simple transmission-line theory. The matching networks are constructed in slabline with a cylindrical inner conductor of a diameter suitable for axial mounting of the triodes. The noise figure varies from 7 to 10dB over the frequency band. Features of the design are the simplicity of the circuit configuration and the elimination of all tuning adjustments, with consequent ease of valve replacement.An extension of the circuit theory is briefly described, and it is shown that gain-bandwidth products in excess of the commonly accepted values can be achieved.

DOI:10.1049/piee.1964.0038

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Millimetre-wave radiometers suitable for making temperature measurements on plasmas are discussed. After a brief review of radiometer theory, special attention is paid to the design of the low-frequency radiometer circuits, the performance of mixer and harmonic-mixer crystals at short millimetre wavelengths, the local-oscillator power needed and the suppression of local-oscillator noise and spurious signals.An early 140-Gc/s radiometer, with second-harmonic mixing and an overall noise factor of 25dB, is mentioned, and a detailed description is then given of a recent 140Gc/s radiometer which contains: a fundamental local oscillator, VX3352 mixer crystals and a 408Mc/s i.f. amplifier commencing with an Adler tube. An overall noise factor of 19dB has been achieved with this equipment and its performance is fully discussed. Some typical recordings of the 2mm radiation from an argon noise tube and Zeta are included.Various ways of obtaining improved radiometer performance at millimetre wavelengths are mentioned. The appendixes are devoted to radiometer theory and an analysis of the halfwave commutator detector.

DOI:10.1049/piee.1964.0039

出版商:IEE    

年代:1964

数据来源: IET

摘要:

Crystal valves have undergone considerable development in recent years, and much improved silicon detectors and mixers are now available. The improvements stem partly from a fuller understanding of semiconductor phenomena, partly from more rigorous design techniques, but largely from advances in materials technology, particularly with regard to the production of silicon tailored to meet specific requirements.With detectors, operation with maximum sensitivity over greater bandwidths has been the principal requirement. Progress in design is illustrated by reference to a range of experimental broadband crystals intended to cover frequencies from the lower end of the microwave spectrum up to 40Gc/s. These experimental types are being superseded by a new range of high-sensitivity detectors which operate with a small positive d.c. bias and give better stability and resistance to burnout and, moreover, are far easier to manufacture. Performance data are presented in some detail.Mixers have been improved in overall noise factor, particularly at Xband, and tighter control of their r.f. properties has been achieved. Compared with other semiconductors, silicon-type mixers are relatively insensitive to variations in local-oscillator drive power and resistance of the d.c. circuit or to temperature changes. The use of silicon proves particularly advantageous for low-flicker noise mixers, which are required in c.w. radars.Significant improvements in the conversion loss of mixers and in the sensitivity of detectors are becoming possible through the reduction of series-spreading resistance with crystals which use silicon films deposited epitaxially on to more highly conducting substrates.

DOI:10.1049/piee.1964.0040

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper gives a derivation of the relation between the bandwidth and the gain of a single diode parametric amplifier using filter networks at both signal and idling frequencies. Approximate algebraic expressions are obtained and compared with computed characteristics. The effects of small variations in component values are computed in an attempt to estimate the probable permissible tolerances for diode parameters and circuit elements. The phase- and group-delay characteristics are also computed, and the latter is shown to be of the order of twice the inverse of 2π times the amplifier bandwidth.The noise contribution due to the parametric action is shown to be a function of the signal frequency gain and the signal/idling frequency ratio. Because this relationship is such that the noise contribution falls with decreasing gain, the effective bandwidth of a low-noise receiver using a parametric amplifier as the first stage may be substantially greater than the normal bandwidth defined by a reduction of 3dB in the gain.Reported practical results are briefly examined in the light of the theory.

DOI:10.1049/piee.1964.0041

出版商:IEE    

年代:1964

数据来源: IET

摘要:

A discussion is presented of the manner in which layer-type echoes may arise and be observed using a 10cm radar at vertical incidence; such echoes are due to variations in the gaseous refractive index and not to water droplets in clouds or precipitation. Specular reflection and scattering processes are compared and the conditions indicated when an echo may be due to one or the other process, although the applicability of the turbulence theories used to relatively thin layers needs to be established.The results of the analysis are discussed in relation to data obtained from simultaneous soundings of the troposphere by radar and airborne microwave refractometers. Some comments are made regarding further experimental and theoretical investigations of the fine structure of elevated layers.

DOI:10.1049/piee.1964.0042

出版商:IEE    

年代:1964

数据来源: IET

摘要:

In the first part of this paper the economic aspects of system reliability are explored. The concept of the ‘adequate system’ is introduced, which system is defined as the lowest total-cost system that will perform as required. The relation of component-part cost to failure-rate levels is investigated, and the reactions of component performance upon design of an adequate system are examined in terms of the economic factors involved. A typical system is used to illustrate the points developed. Further, the number of systems needed to perform a given mission are considered in terms of annual cost and reliability levels of an individual system.The second part of the paper is concerned with the appraisal of the reliability of a system. This appraisal begins as early as possible in system evolution and makes use of estimation procedures which draw upon prior knowledge. Various assumptions which enter into such estimation methods are examined. It is pointed out that reliability estimates derived analytically must be verified by suitable tests of models at appropriate stages in the development of the system. The value of failure data obtained during the course of system development, manufacture and use in establishing levels of system reliability is emphasised.The final part of the paper deals with the effects of operating environment upon system reliability. The necessity of knowing the environment, and of conducting tests on models to evaluate its effects, is stressed. Two examples are given to illustrate some of the factors associated with environmental testing. One relates to the electrical performance of nickel-cadmium cells under space-simulation conditions; the other to the mechanical response of a structure under missile-flight environment.Broadly, the point of view taken is that electronic-system reliability is a synthesis of many related and interacting factors. Throughout the evolution of system design these factors should be most carefully balanced so that the ultimate product will perform at a level of reliability which is the optimum for the time, effort and money expended.

DOI:10.1049/piee.1964.0043

出版商:IEE    

年代:1964

数据来源: IET

摘要:

The paper describes the characteristics and performance of the MAD-R shift register which uses multiapertures and connecting wire as the only components. In particular, it discusses the hold and prime operations and their effects on the performance of this shift register. A small modification adapts the basic shift register for bidirectional operation.

DOI:10.1049/piee.1964.0044

出版商:IEE    

年代:1964

数据来源: IET