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Radio and Electronic Engineer

Issue 4 • Date April 1970

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Displaying Results 1 - 9 of 9
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  • The synthesis of asynchronous digital pattern generators

    Page(s): 179 - 184
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (699 KB)  

    The paper describes a method for designing circuits which generate predetermined digital waveforms when triggered by an input. To do this an asynchronous sequential machine is causedto move through a number of states under its own control. Individual portions of the waveform can be adjusted without interfering with the rest of the output sequence. The circuit can also be made to give different output sequences for different inputs. View full abstract»

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  • The design of broadband light modulators

    Page(s): 185 - 192
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1319 KB)  

    Curve sets are presented for the design of collinear travelling-wave light modulators using KDP, KDA, ADP(r63), ADP(r41), LiNbO3, LiTaO, as electro-optic materials. The transverse dimensions ratio, the characteristic impedance and the bandwidth-length product are plotted versus the velocity mismatch. The attenuation of modulating signal is plotted versus mismatch for the peak voltage and modulating power for different lengths of the electro-optic materials. Examples of the use of these curves are reported. View full abstract»

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  • An intermodulation phenomenon in the ring modulator

    Page(s): 193 - 197
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (465 KB)  

    Analysis of intermodulation distortion effects in diode modulators by `modulating function¿ techniqueshas, for some time, been recognized to be applicable where the diodes can be represented by a bi-linear d.c. characteristic in which the change of state from blocking to conduction takes place at zero bias. Experiments on ring modulators have shown, however, that predictions based on this diode model give unduly pessimistic results under some conditions. It is shown that theuse of a modified diode model incorporating a suitable offset voltage in the d.c. characteristic permits prediction of thehitherto anomalous results with greatly improved accuracy. View full abstract»

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  • The radiation field of the short backfire antenna

    Page(s): 198 - 200
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (538 KB)  

    The mathematical expressions for the far-field radiation pattern are derived for a short backfire antenna. By assuming that the plane conductors in the antenna are infinite in extent, a multiple image system is established as a first approximation in the derivation. Some calculated patterns are presented to illustrate the derived results and compare with the experimental E- and H- patterns given by Ehrenspeck in his work. View full abstract»

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  • Influence of reflecting surface characteristics on a laser rangefinder

    Page(s): 201 - 208
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (898 KB)  

    The laser rangefinder can enable the distance of remote objects, such as satellites, to be determined with an accuracy of 1.5 m up to a distance of 3000 km. This performance level accrues from three main factors: (i) the directivity of the laser light, which allows the emitted power to be concentrated in a very narrow cone; (ii) the high detection capability of up-to-date photomultipliers, which can generate a signal even in response to a mere hundred or so photons received; (iii) the directive reflexion properties of the retroreflective systems located on the object observed. The present paper investigates this last factor. It outlines the reflective photometric characteristics of various scattering and reflecting surfaces for comparison with those of retroreflectors, and describes several retroreflective systems. The comparison is made with a practical example, which corresponds to a rangefinder used for satellites. It is thereby demonstrated that a single 2 cm diameter retroreflector ensures a range 29 times that obtained on a 1 m2 diffusing surface and 6.7 times that achieved on a 1 m2 surface covered with glass balls. View full abstract»

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  • On the linearity of a thermistor thermometer

    Page(s): 209 - 214
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (545 KB)  

    A general approach to linearizing a thermistor thermometer over limited temperature ranges is developed. Theoretical and experimental results are presented for various typical operating modes. Effects of detector resistance, probe cableresistance and off-balance calibration on the linearity and sensitivity of the device are investigated. View full abstract»

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  • Determination of the parameters of an electrodynamic transducer

    Page(s): 215 - 223
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1051 KB)  

    One of the most interesting areas of contact between the studies of electrical and mechanical systems is that exemplified by the electrodynamic transducer. In such a device the electrical and mechanical aspects profoundly influence one another, so that in problems of performance and design it is frequently necessary to measure the parameters of the system. The electrodynamic transducer, whose mechanical system consists of mass, compliance and damping having a single degree of freedom and whose coil has inductance and resistance, is first treated in detail via its equivalent circuit. This therefore consists, over the working frequency range of the transducer, of five elements and it is to the measurement of these, and a sixth, the constant of transduction, that the bulk of the paper is devoted. Several methods of measurement of each of the mechanical parameters are described allowing the principle of intercomparisons of different determinations to be used. The methods described for measuring the electrical parameters, believed to be original, readily accommodate the frequency dependence, which due to eddy-current effects sometimes occurs in practice. Brief mention is made of some of the experimental techniques which have been successfully used for the measurements and some consideration is given to the factors which limit the accuracies attainable in practice. View full abstract»

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  • Potential integral theory for a log-periodic dipole array of n, parallel, non-staggered

    Page(s): 224 - 232
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (770 KB)  

    A new and more accurate theory for the log-periodic dipole array is presented which takes account of all mutual interaction effects between the elements of the array. The new theory is used to compute the performance of a 10-element log-periodic dipole array, which together with conventional theory is compared with experimental results for the array. The advantages of the new theory over the conventional analysis are discussed in detail View full abstract»

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