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Radio and Electronic Engineer

Issue 10 • Date October 1977

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Displaying Results 1 - 9 of 9
  • 99 Gower Street

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    Freely Available from IEEE
  • The application of m.f.s.k. techniques to h.f. telegraphy

    Page(s): 435 - 444
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1135 KB)  

    The paper briefly describes the history and the principles of m.f.s.k. signalling as applied to h.f. telegraphy. It quotes mathematical relationships for the performance of such systems, and derives equations for the occupied bandwidth. These relationships, together with the results of measurements carried out on different experimental m.f.s.k. systems, and practical limitations suggested by experience, are used to suggest an approach to the selection of optimum parameters. Systems suitable for different telegraphy and telemetry applications are derived and discussed. Practical problems of synchronization and source stability are analysed, and methods of error coding for ARQ and FEC systems are described. It is concluded that for data links in the range of 20 to 200 bits per second, the use of m.f.s.k. techniques can give an improvement in performance equivalent to about 10 dB in signal-to-noise ratio, or a reduction in error rate of the order of 10/1 in the raw data (or more than 100/1 if an error coding system is used). View full abstract»

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  • RC active variable group-delay equalizers with independent Q and ¿ controls

    Page(s): 445 - 448
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The high-speed transmission of data over voice frequency telephone links creates the need for variable group-delay equalization networks. This paper describes two alternative group-delay sections, the characteristics of which may be continuously adjusted over the approximate bandwidth (300 to 3000 Hz). Both of the proposed networks provide for the desired degree of group-delay adjustment using only two resistive controls neither of which demand high precision components. View full abstract»

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  • Design of self-checking and fault-tolerant microprogrammed controllers

    Page(s): 449 - 454
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (649 KB)  

    A realization of a self-checking and fail-safe programmable controller which uses a new control memory organization to give a simple and elegant implementation is described. Using this self-checking controller as an example, a new approach to fault-tolerant design referred to as Dual-Fail-Safe (DFS) is presented which utilizes two self-checking modules. The resulting fault-tolerant system is shown to be less costly and significantly more reliable than a conventional Triple-Modular-Redundancy (TMR) system. View full abstract»

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  • Developing interactive systems for the small machine environment

    Page(s): 455 - 459
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (575 KB)  

    This paper describes the design methods, and tools, for developing interactive systems which will run in the small machine environment. The constraints of this environment are discussed, and it is shown that the requirements of users in this environment are rather stringent, but for systems with a well engineered interface rather than for high performance. The solution adopted is to provide realistic simulation early in the design process, and to provide mechanisms for divorcing the detailed screen layout design from program design. View full abstract»

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  • A method for the determination of the T-equivalent-circuit parameters of microwave structures

    Page(s): 460 - 464
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    A method is described for the measurement of the equivalent circuit parameters of waveguide-mounted structures, such as a post or an inductive iris. Experimental results for post structures centrally mounted in X-band waveguides are also given. The values obtained are found to agree closely with those predicted from theory and the estimated accuracy is about 5%. View full abstract»

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  • Automatic input attenuator for h.f. communication receivers

    Page(s): 465 - 469
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (439 KB)  

    The final selectivity of a communication receiver is generally determined by the bandwidth of the i.f. filters. When the a.g.c. of the receiver is determined only by the signals passing these filters, severe overloading of the relatively broadband h.f. gain stages may occur. Reducing this risk of overloading requires a broadband attenuator at the input of the receiver. The attenuation should be dependent on the signals passing the i.f. filters as on all other signals reaching the h.f. gain stages, but not the i.f. amplifiers. Such an automatic attenuator system is discussed, and its design philosophy presented. View full abstract»

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  • Recent trends in automative radar

    Page(s): 472 - 476
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    The possible advantages to be gained from the development of vehicle radar systems are outlined and the factors influencing the design of a suitable system are discussed. The various types of system which are commonly considered are introduced and their relative merits and associated problems are explained. Reference is made to typical experimental systems of each type. It is concluded that significant problems remain to be solved before practical automotive radar can become a reality for the general motoring public. View full abstract»

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