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Radio and Electronic Engineer

Issue 5 • Date May 1976

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Displaying Results 1 - 6 of 6
  • A Season of Exhibitions

    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (136 KB)  

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  • Second-order effects in acoustic surface-wave filters: design methods

    Page(s): 207 - 220
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    Second-order effects, which may be defined as those effects which prevent acoustic surface-wave filters from behaving as ideal transversal filters, are described systematically. Explicit exact and approximate formulas are given for the effect of acoustic multireflections and external matching circuits on both the main signal response and triple transit echoes. The effect of non-uniform tap coupling across the acoustic beam is described, and weighting methods thatprovide a more uniform coupling are presented. Other secondary effects like electrostatic or quasistatic end effects, beam diffraction, mass loading and bulk wave excitation are briefly described. A method for the correction of positioning errors or delay errors by experimental means is described. View full abstract»

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  • Engineering design and evaluation of s.a.w. pulse compression filters with low time sidelobes

    Page(s): 221 - 228
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (895 KB)  

    A linear f.m. pulse compression sub-system employing surface acoustic wave dispersive filters has been designed. When operated as a coherent pulse compression loop, this sub-system provides a compressed pulse with all time sidelobes suppressed by more than 40 dB. This demanding level of performance which is a significant improvement over previously reported sub-systems has been achieved by the development of a design procedure which permits compensations for the spectral ripples of the transmitted waveform to be incorporated in the design of the compression filter. Measurement of amplitude and phase characteristics of the compression filter indicates very good agreement with theoretical predictions. View full abstract»

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  • Examples of manufactured dispersive delay lines using acoustic surface waves

    Page(s): 229 - 236
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    Two kinds of dispersive delay lines operating in radars at the present time are described as examples of manufactured acoustic surface-wave components. These lines were designed some yearsago for a non-linear chirp impulse response and they are used as pulse expander and weighting matched pulse compressor. These dispersive delay lines consist of metallic interdigital transducers deposited on piezoelectric quartz substrates. The first kind of line, which was produced in quantity, (about 180 units) has a compression ratio equal to 23.5. The relative sidelobe level of the compressed pulse is ¿26 dB. The delay varies by 4 ¿s in a 7 MHz frequency range, the centre frequency being 30 MHz. A sampled transducer with variable finger pair spacing is used for the second kind of line in order to limit the number of fingers. The delay change is 25 ¿s for a 1 MHz frequency range centred at 30 MHz. The compression ratio and the relative sidelobe level of the compressed pulse are 19.2 and ¿24 dB respectively. View full abstract»

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  • Surface acoustic wave matched filters for communications systems

    Page(s): 237 - 246
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    The design, fabrication and performance of surface acoustic wave matched filters for particular communication systems are described. Applications are considered for synchronization acquisition by means of m-sequence phase shift keyed correlators, and for demodulation of data in (i) a four-level frequency-shift keyed system and (ii) a differentially coherent phase-shift keyed system. View full abstract»

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  • Sources of intermodulation in diode-ring mixers

    Page(s): 247 - 255
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    Intermodulation is known to arise in diode-ring mixers due to non-linearity in the diode switches, and also due to the interference by signal voltages with the local-oscillator switching function. This interference can be reduced by ensuring fast switching with a square-wave local-oscillator. In this paper the relationship between rise-time and intermodulation is investigated in connection with a practical mixer design for use at v.h.f. View full abstract»

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