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Radio and Electronic Engineer

Issue 2 • Date February 1966

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Displaying Results 1 - 8 of 8
  • International associations of engineers

    Page(s): 65 - 66
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (133 KB)  

    First Page of the Article
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  • Varactor diode measurements

    Page(s): 67 - 75
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    A comparison has been made of the `relative impedance¿ and `transmission¿ techniques of measuring the small-signal parameters of varactor diodes. Relative-impedance measurements have been made at u.h.f. and X-band and transmission measurements at X-band. It has been shown that losses associated with the matching circuit used in relative-impedance measurements can give rise to a degraded diode specification. Their effect is less if reduced-height waveguide is used at X-band. The transmission method leads to the most favourable specification for a diode. The measurements support the representation of the diode by a simple equivalent circuit to a first order View full abstract»

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  • Tunnel diodes integrated with microwave antenna systems

    Page(s): 76 - 80
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    The applications of tunnel diodes to antenna systems make use of devices as (1) negative conductances, (2) as pumped elements, and (3) as rectifiers View full abstract»

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  • A phase-switched radar system giving improved control of directional pattern

    Page(s): 81 - 92
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    This paper is a mathematical analysis of a new type of phaseswitched radar which uses four antennae, two for transmitting and two for receiving. By phase-switching the pulses of one of the transmitting antennae and by multiplicative detection of the outputs from the two receiving antennae one can obtain a two-way power pattern proportional to the product of the four directivity (field strength) patterns of the system's four antennae. Furthermore, by appropriate phase and amplitude switching of a single array's element currents it is possible to simulate four coincident arrays whose product pattern can be obtained. The greater flexibility of this system (four pattern functions instead of one) is demonstrated byexamples of improved pattern synthesis. Comparison is made with a conventional array of the same size whose pattern beam-width is the same as that of the phase-switched system; the phase-switched pattern has lower side-lobes and four times as many nulls. The effect of uncorrelated element noise and of a second target (either coherent or incoherent) is also considered. It is shown that for any degree of coherence one can synthesize a better pattern with the phase-switched system. View full abstract»

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  • Intrinsic frequency limitations for semiconductor microwave devices

    Page(s): 93 - 98
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (650 KB)  

    The upper frequency of operation for a semiconductor microwave device is usually considered in terms of the equivalent circuit parameters associated with the immediate neighbourhood of the active element, together with any stray reactances of the package. Whilst it is generally recognized that in the semiconductor contribution both the resistive and reactive terms may have a frequency dependence, the exact nature of this is difficult to determine experimentally and its importance is generally obscure. This paper seeks to give a brief survey of the various mechanisms which can conceivably introduce frequency-dependent effects and attempts to gauge which of them is likely to be important in devices of present interest¿crystal valves, varactors, tunnel/backward diodes and p-i-n switches. The mechanisms discussed include such items as skin effect, carrier/phonon collisions, dielectric relaxation, carrier lifetime, transit time, etc. View full abstract»

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  • Electromechanical switching devices: reliability, life and the relevance of circuit design

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    Electromechanical switching devices are grouped broadly into two classes: those which can be used to choose a specific set of contacts from a considerable number of selections, e.g. rotary switches, and those which when operated or released will establish or break the same set of contacts, e.g. relays. Both groups of devices are discussed in considerable detail from the point of view of reliability, and suggestions for maintenance organization are given. A variety of quenching techniques to minimize damage to the contacts are described. Some aspects affecting circuit design are also treated. View full abstract»

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  • The reliability of electronic systems

    Page(s): 110 - 116
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    Starting from the agreed definition of reliability the use of probability theory enables the design engineer to predict the reliability of a complex system as a function of the reliability of its component parts. The characteristics of series and parallel grouping are given, together with some applications of hammock networks. The exponential survival law is derived, and the conditions under which it may be applied are discussed. The use of redundancy to improve reliability is introduced, and examples are given of the effect of various schemes upon the reliability of a small electronic system, with and without maintenance. Some possible forms of passive redundancy are described, including block redundancy with majority voting, and quadded logic. View full abstract»

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  • A discussion of factors affecting the performance of microwave systems in certain plasma channels

    Page(s): 117 - 127
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    Principal factors affecting the performance of microwave systems in composite and transient plasma channels are reviewed. Only macroscopic aspects of the channel characterization are considered. These include such effects as absorption, refraction, dispersion and depolarization; also nonlinear and random effects. An effort is made to assess their importance to communication with and tracking of rocketborne systems. It is concluded that channels incorporating, for example, the re-entry plasma sheath or the rocket exhaust are inaccessible at the present time to a detailed characterization. Further research, especially of experimental nature and extending beyond the traditional study o absorption loss, is indicated View full abstract»

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