DOI:10.1049/ree.1971.0081

出版商:IERE    

年代:1971

数据来源: IET

摘要:

Wide band gap II-VI compounds deposited epitaxially upon semiconducting substrates have possible applications as solid-state infra-red detectors and imaging devices. The Ge/ZnSe heterojunction has been prepared by vacuum evaporation of epitaxial layers of zinc selenide on to orientated, single crystal, p-type, germanium substrates. Measurements have been made of the electrical characteristics, capacitance properties and photoresponse of these junctions. From these measurements a realistic band model has emerged involving intrinsic and extrinsic defects present in the bulk and interfacial region of the zinc selenide. The data presented suggest that a Mott-type barrier rather than a Schottky barrier is present at the germanium-zinc selenide interface. Techniques are described for reducing the magnitude of this Mott barrier and the resulting change in the physical properties and band structure are discussed.

DOI:10.1049/ree.1971.0082

出版商:IERE    

年代:1971

数据来源: IET

摘要:

The circle criterion provides a convenient method of testing stability in nonlinear feedback systems. The need for computer computation of the relative stability conditions for the Nyquist plot can be avoided by using a logarithmic gain-phase plot on the Nichols chart. The results of this technique agree within about 1% with those obtained from a computer solution of the Nyquist plot.

DOI:10.1049/ree.1971.0083

出版商:IERE    

年代:1971

数据来源: IET

摘要:

The problem of the self- and mutual-impedances of two arbitrarily located parallel dipoles is solved by using the variational method and a two-term trial function for current distribution. The impedances are calculated for half-wave and full-wave dipoles in non-staggered, echelon and collinear arrangements. In all three cases the results are in excellent agreement with those obtained by the Chang-King five-term theory. In the non-staggered case agreement with experimental results is also very satisfactory.

DOI:10.1049/ree.1971.0084

出版商:IERE    

年代:1971

数据来源: IET

摘要:

The historical and technical background which lead to the development of 12 kHz channel spacing at u.h.f. is described. The advantages and disadvantages of the narrower channel spacing, including problems of achieving satisfactory adjacent channel protection and frequency stability, are discussed. A series of field tests within the London metropolitan area is reported which demonstrated that coverage and quality of reception is as good as with 25 kHz channel spacing.

DOI:10.1049/ree.1971.0085

出版商:IERE    

年代:1971

数据来源: IET

摘要:

The paper presents a new method for designing non-minimum phase rational approximants of the ideal delay function e−ssuitable for the applications where the frequency spectrum of the input signal occupies large bandwidth. It is shown by theoretical considerations that for this purpose the most suitable type of delay characteristic is the one approximating to a constant delay over a frequency range extending from zero to a frequency ω < ωcand having a relatively large delay peak at the end of the passband (ωc). The amplitude of the initial transient ringing (precursor) and the overshoot in the transient response of the filter mainly depend on the value of the peak in the delay characteristic. The polynomials with two variable parameters that exhibit this type of delay response are then introduced and shown that the precursor and overshoot can be adjusted to any prescribed value by varying the free parameters. Extensive tables are presented enabling direct determination of the fourth-order transfer function with three right-half-plane zeros for almost any practical prescribed values of the precursor and overshoot. The method can be extended to higher-order networks and as an example a table containing data on the sixth-order functions with five right-half-plane zeros is also included. A comparison of the transient responses reveals that the technique proposed yields an improvement over all other methods so far described.

DOI:10.1049/ree.1971.0086

出版商:IERE    

年代:1971

数据来源: IET

摘要:

A simple synchronous switch having a control circuit comprising integrated circuits and a triac switch is described. The synchronous switch is primarily designed to demonstrate the transient surge current taken by a transformer when its supply is applied but has many other applications.

DOI:10.1049/ree.1971.0087

出版商:IERE    

年代:1971

数据来源: IET

DOI:10.1049/ree.1971.0088

出版商:IERE    

年代:1971

数据来源: IET