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1887

Radio and Electronic Engineer

Volume 42, Issue 10, October 1972

Volumes & issues:

Volume 42, Issue 10

October 1972

Assessing Profit
Magnetic bubbles and their applications
  • Author(s): R.D. Lock  and  J.M. Lucas
  • Source: Radio and Electronic Engineer, Volume 42, Issue 10, p. 435 –446
  • DOI:  10.1049/ree.1972.0075
  • Type: Article
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  • p. 435 –446 (12)
    Magnetic bubble domains may be formed in platelets of certain magnetic materials. They are the basis for an unusual new breed of devices in which bubbles are selectively created, propagated, interacted, detected and annihilated, so that both memory and logic functions may be performed in a single piece of material. Bubble devices are very compact and dissipate little energy. This paper describes the nature of magnetic bubbles, and the materials which support them. Various aspects of device technology are introduced, with discussion of all the functions required, including bubble interaction logic. Applications for bubble devices are indicated.
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Conduction and magnetic signalling in the sea a background review
Conduction signalling in the sea
  • Author(s): M.J. Tucker
  • Source: Radio and Electronic Engineer, Volume 42, Issue 10, p. 453 –456
  • DOI:  10.1049/ree.1972.0077
  • Type: Article
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  • p. 453 –456 (4)
    The concept of conduction signalling is that electric currents are injected into the sea by means of electrodes, producing resistive potential differences which are detected using another pair of electrodes at a distance. It is shown that even at low audio frequencies electromagnetic effects must be taken into account, and doing so leads to the conclusion,surprising at first sight, that the electrodes are largely incidental and that it is the wires connecting them which control the launching and detection of the signals.
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The performance of a magnetic loop transmitter-receiver system submerged in the sea
  • Author(s): R.M. Dunbar
  • Source: Radio and Electronic Engineer, Volume 42, Issue 10, p. 457 –462
  • DOI:  10.1049/ree.1972.0078
  • Type: Article
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  • p. 457 –462 (6)
    The theoretical predictions for an electromagnetic wave in both free-space and an infinite conducting medium are considered and an experimental technique is described which was used to measure the variation of signal strength with distance for a magnetic-loop transmitter-receiver system submerged in sea-water, at a mid-water depth (100 m) where boundary effects could be ignored safely.Underwater communication of audio-frequency signals in real time is normally carried out using acoustic techniques, but occasionally there are reports in the press of ‘magnetic carrier’ or ‘conduction field’ systems having ranges in the sea which apparently exceed those expected for a conventional electromagnetic wave.
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Meeting report: implantable cardiac pacemakers
Synchronous multiplexing of digital signals using a combination of time- and code- division multiplexing (T.D.M. and C.D.M.)
  • Author(s): A.P. Clark
  • Source: Radio and Electronic Engineer, Volume 42, Issue 10, p. 467 –475
  • DOI:  10.1049/ree.1972.0080
  • Type: Article
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  • p. 467 –475 (9)
    The paper describes some arrangements for multiplexing and demultiplexing digital signals in element synchronism. The multiplexed signals are transmitted over a common channel, from a single transmitter to a single receiver, and the demultiplexing of the signals is achieved in the detection process at the receiver. A combination of time division and code division multiplexing (t.d.m. and c.d.m.) is used, in which the t.d.m. signal-elements are orthogonal, as are the c.d.m. elements, but simultaneously transmitted t.d.m. and c.d.m. signalelements are not orthogonal. Arrangements using a linear combination of the two sets of orthogonal signals are studied, with various iterative detection processes, and their performances are compared with that of a system using a non-linear combination of the two orthogonal sets. It is shown that the latter system achieves a considerable advantage over the others and is particularly well suited to applications where the number of multiplexed signals is typically a little greater than the maximum number orthogonally multiplexed. Computer simulation has been used to measure the performances of the different systems.
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Letters: Sensitivity of radiation detectors

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