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Radio and Electronic Engineer

Issue 6 • Date June 1982

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Displaying Results 1 - 9 of 9
  • Molecular electronics

    Page(s): 259 - 260
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    Freely Available from IEEE
  • A survey of methods for digitally encoding speech signals

    Page(s): 267 - 276
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1477 KB)  

    Modern communications systems are increasingly using digital transmission, at various digit rates, for the many advantages thereby obtained. there are many methods that can be used for converting analogue speech signals to digital form. the aim is to produce very good speech quality using simple equipment at a low digit rate, but any application inevitably involves choosing the appropriate compromise between these three conflicting attributes. the paper reviews the most important of currently known methods, including systems already in widespread use and those still in the research stage. thel problem of assessing speech transmission performance is also discussed. View full abstract»

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  • Multi-transmitter data systems¿performance with stationary receivers

    Page(s): 277 - 282
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (965 KB)  

    A theory is developed, based on bench measurements with two quasi-synchronous data signals, which predicts the mean bit error rate (b.e.r.) and the mean 64-bit word failure rate experienced at stationary receivers in the overlap area of two quasi-synchronous transmitters. The signals from the transmitters suffer independent Rayleigh fading. The performance with a carrier frequency difference of a few hertz is shown to be 2 dB better, and with a larger difference (18 and 180 Hz) to be 5-10 dB worse, than with a single transmitter. View full abstract»

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  • Optical fibre transducers

    Page(s): 283 - 290
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1395 KB)  

    Light travelling in an optical fibre may be directly modulated by external parameters such as pressure, strain, temperature, etc. Thus the fibre may form the basis of a transducer involving neither moving parts nor electrical connections. Another class of transducers uses the fibre as a means of guiding light from a monitoring point to the measuring point where the light is externally modulated. This paper presents a review of the current status of optical fibre sensors and discusses their future potential. View full abstract»

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  • The impact of radio-data on broadcast receivers

    Page(s): 291 - 296
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1534 KB)  

    For some years the BBC and other European broadcasters have been investigating systems for broadcasting radiodata labels from v.h.f. radio-broadcast transmitters. These data signals are primarily intended to aid radio listeners in tuning their receivers to a desired station orprogramme. Other applications, such as the transmission of simple messages, are also envisaged. Although no firm specification for radio-data has yet been agreed by European broadcasters, recent international field-trials of various proposed radio-data systems were a significant milestone in the development of a standardized radio-data system. These field-trials also confirmed that reliable radio-data reception is possible with low-cost receiver/decoders even under very adverse reception conditions. View full abstract»

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  • Thin-wire antennas in the presence of a perfectly-conducting body of revolution

    Page(s): 297 - 303
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (736 KB)  

    A new numerical method for evaluating electromagnetic field, current distribution and input impedance of thin axial antennas in the presence of a perfectly conducting body of revolution is presented. Two particular cases, an axial dipole antenna near a conducting spheroid (prolate and oblate, including sphere) and near a solid truncated cone (including solid cylinder) are analysed. The actual body of revolution is replaced by an equivalent interior system of fictitious sources, axial arrays of Hertzian dipoles and magnetic ring currents. The moments of these sources are then adjusted to match boundary conditions on the surface of the body, while forthe current distributions on the antenna conductors Hallen's type integral equations are derived. The system of integral equations obtained is solved numerically by the point matching methodwith the polynomial approximation for distributions of antenna currents. The solution is numerically optimized due to the number and locations of fictitious sources. Some numerical results for antenna input impedance and cimomotore force (c.m.f.) are presented. View full abstract»

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  • A single-chip non-recursive digital processor

    Page(s): 304 - 308
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (469 KB)  

    A single-chip non-recursive digital processor is being made using a 5V ni-m.o.s. custom-l.s.i. approach. The processor will perform all the arithmetic required for a 48- tap non-recursive filter, with up to 30000 samples/s. The coefficient resolution is up to 10 bits. The processor uses a special coefficient coding to minimize the time required to perform the multiplications, and for this reason the maximum sampling rate depends on the coefficients and the coefficient resolution required. The design of the l.s.i. processor is given, and examples of filters which can be implemented using one l.s.i. processor, one 256×8 r.o.m. and two clock sources, are described. View full abstract»

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  • Economical filters for range sidelobe reduction with combined codes

    Page(s): 309 - 310
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (242 KB)  

    It is shown that approximate inverse filters for combined codes can be implemented using far fewer coefficients than required for direct implementation. This enhances the usefulness of recently reported work on the subject View full abstract»

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  • Book review: Antenna Theory and Design

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    Freely Available from IEEE