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Radio and Electronic Engineer

Issue 6 • Date December 1969

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Displaying Results 1 - 10 of 10
  • Communicating facts

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  • An investigation into the practicability of using an electromagnetic-acoustic probe to detect air turbulence

    Page(s): 315 - 325
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    This paper describes some theoretical and experimental investigations into the possible use of the reflexion of electromagnetic waves by an acoustic shock wave. Satisfactory detection of reflected microwave signals has been achieved in a number of experiments and the Doppler frequency shift of the signals has been shown to give a satisfactory indication of the wind velocity along the line of sight of the EMAC (ElectroMagnetic-ACoustic) probe arrangement. Remote indication of radial wind velocity has been achieved at ranges in excess of 450 m (1500 ft) and greater ranges should be obtained with improved experimental equipment. View full abstract»

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  • Paper transistors

    Page(s): 326 - 327
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  • Reply: Paper transistors

    Page(s): 327 - 328
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  • Signal processing and computation using pulse-rate techniques

    Page(s): 329 - 344
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    Pulse-rate signals are introduced and the influence of various conventional circuits on their behaviour is considered. An introduction to more complex systems is given by considering the behaviour of certain simple feedback circuits. A survey is then made of the major applications of pulse-rate signals, including regular and stochastic rates, sampled systems, and the digital-differential-analyser. The aim is to show the common features in the various systems, and to provide a common basis for analysing them. Pulse-rate systems can carry out the normal arithmetic and integral operations. They are characterized by relatively low speed, low accuracy in general, and low complexity. View full abstract»

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  • A high speed, high accuracy, digitally-set potentiometer

    Page(s): 345 - 351
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    A digitally-set potentiometer (d.s.p.) is required for any hybrid computing arrangement where iterative routines are used to establish the solution to dynamic systems. If computing accuracies of 0.1% at signal frequencies of 10 kHz are to be obtained special techniques in the design of a d.s.p. are necessary. A complete design for a 10-bit d.s.p. to fit this specification is presented, based on the use of a ladder network of low propagation delay. This in turn requires careful design of bipolar switches and a new form of switch is presented which uses f.e.t.s in the feed-back loop of monolithic d.c. amplifiers. The overall behaviour of the d.s.p. is illustrated and an estimation of errors made. View full abstract»

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  • High peak power from a CO2 laser system

    Page(s): 354 - 356
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    A CO2 laser oscillator/amplifier system which has produced peak output powers of 350 kW in 0.4 us long pulses is described. the output power achieved is shown to be in agreement with a theoretical equation. from these results and from the equation a new laser system has been designed, which it is hoped will produce more than 1 MW peak power. this new design is discussed. one problem associated with high gain amplifiers is their tendency to oscillate. an optical component has been designed which largely overcomes this problem. basically it consists of a moving tape, opaque to 10.6 ¿m radiation, which is perforated by the rising edge of the Q-switched pulse. View full abstract»

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  • Gain saturation in CO2 laser amplifiers

    Page(s): 357 - 360
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    Gain saturation in the CO2 laser system presents a limitation on the amplification of Q-switched pulses and this has been studied in some detail. With pulses of around 0.5 ¿s saturation effects are observed at power densities of order 104W cm¿2. The results of a theory of the time dependence of saturation are presented, together with supporting experimental data. This theory indicates that, at high power levels, the decrease in gain with time during the oscillator pulse can be described by the sum of two exponential decays. A value for the relaxation rate of the rotational sub-levels of the active vibrational states is obtained for various gas conditions. The implications of this relaxation rate on the design of high power oscillator/amplifier systems is discussed. View full abstract»

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  • A computer controlled train describer

    Page(s): 361 - 368
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    In modern railway signalling practice each train is allocated a code which describes its type, priority and route. the code is displayed on a schematic display diagram in the signal box and enables the signalman to set up the correct route for the train to follow. the description code on the diagram automatically follows the movements of the train, and in addition, is transmitted to the neighbouring signal box when the train enters the adjoining area. the equipment used to display and manipulate these codes is known as a train describer, and the paper describes the first computer-based system to be brought into operation. View full abstract»

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  • Design of a large read-only holographic memory

    Page(s): 369 - 375
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    Factors affecting the design of a read-only optical memory having a total capacity of the order of 108 bits with fast random access are discussed. Photographic information storage is used and random address selection is provided by a laser beam scanned across the photographic plate using non-mechanical beam deflection. `Page¿ organization of the memory involving parallel read-out of 104 bits from each of 104 beam addresses is used in order to achieve the large total storage capacity. the information array from each address is projected on to an array of 104 photodetectors and selection of the required bits from each `page¿ is done electronically. Information is stored at each address in the form of a small hologram, which offers the following advantages over the conventional method of storage: uncritical alignment of the photographic plate, reduced sensitivity of the plate to accidental damage by incorporating redundancy in the hologram, and the ease with which the reconstructions of each hologram may be superimposed at the output photodetectors. View full abstract»

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