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Radio and Electronic Engineer

Issue 3 • Date March 1970

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Displaying Results 1 - 10 of 10
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  • An experimental laser-photochromic display system

    Page(s): 123 - 129
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1517 KB)  

    A laser display system is described which can produce real-time television standard pictures, or alternatively reversible, stored images using photochromic film. The development of components for the modulation of laser beams is also described. The spatial modulators are acousto-optic diffraction cells, and the amplitude modulator uses the electro-optic effect in ADP. View full abstract»

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  • An optical fixed data store

    Page(s): 130 - 138
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1262 KB)  

    An optical fixed data storage system is described which is designed to hold 4 M bits of information on each exchangeable photographic plate. The store, intended as an integral part of a computing system, enables any of 65,536 69-bit words to be retrieved with a random access time of a few microseconds. Writing time for each data plate is approximately 1 hour. To record and retrieve the data, a spot is positioned on the face of a high resolution electrostatic cathode ray tube, and multi-imaged on to a photographic plate by means of a lens/square cross-section mirror tunnel/lens system. Word readout is achieved using one 11-stage photomultiplier as detector for each bit of the word. View full abstract»

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  • Six new delay functions and their realization using active rc networks

    Page(s): 139 - 144
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (773 KB)  

    Six new delay functions with three right-half s-plane zeros and four lefthalf s-plane poles are obtained from the application of Budak's technique to the Bessel and Chebyshev all-pole delay functions. These are compared with three well-known similar delay functions and three of them found to have some advantages over the existing ones. Active networks, which areuseful in the realization of the functions, are examined and experimental responses are given. View full abstract»

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  • Instantaneous and time-varying spectra¿an introduction

    Page(s): 145 - 152
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (894 KB)  

    Several definitions of `time-varying¿, `short-time¿ and `instantaneous¿ spectra exist. The paper relates these to the time-frequency energy distribution of a signal and to the time-varying power spectrum of a non-stationary random process. The treatment emphasizes physical interpretation, rather than mathematical rigour. View full abstract»

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  • A function generator using hybrid techniques

    Page(s): 153 - 160
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1467 KB)  

    The principle of operation of a novel function generator is outlined and some applications are reviewed. The basic function produced by the generator is a `box-car¿, or discrete, type function having fixed thresholds with respect to the input voltage, and output voltage levels that may be independently set in any segment. By using a sampling technique, linear interpolation may be applied across any of the discontinuities in the `boxcar¿ function to produce an `analogue¿, or continuous type function. This arrangement allows for the independent adjustment of the value of the function for input voltages midway between the threshold voltages. In the discrete mode, good accuracy is maintained for full amplitude input swing up to 80 kHz and in the continuous mode up to 5 kHz. View full abstract»

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  • Cyanide gas lasers for sub-millimetric wavelengths

    Page(s): 161 - 166
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (690 KB)  

    Progress is outlined in the design of c.w. and pulsed lasers, using methyl cyanide, dimethylamine and a mixture of methane and nitrogen, for use at wavelengths in the 337 ¿m region. Output stability is stated to be a function of cathode material, gas type and pressure and discharge current for any given laser design. Brass appears to be the best cathode material. With input power at 1 kW, outputs of 7 mW (c.w. laser) and 1 W (pulsed laser) were obtained, the gas used making no significant difference to these figures. An optimum working pressure of 0.55 torr was established using a mixture of 60% methane and 40% nitrogen. Tube life with all three gases is typically 100 hours. Initial investigations into transmission properties of various materials at sub-millimetric wavelengths show that p.t.f.e. and t.p.x. (polyolefin thermoplastic) make the best lenses and windows, and that black polythene makes the best attenuator. Investigations into atmospheric absorption at this wavelength indicate that, dependent on temperature and relative humidity, attenuations of between 36 dB/km and 204 dB/km can be expected. View full abstract»

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  • Semiconductor diodes as detectors and mixers at sub-millimetric wavelengths

    Page(s): 167 - 171
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (641 KB)  

    Reprinted from the Proceedings of the I.E.R.E. Conference on `Lasers and Opto-Electronics¿ held at the University of Southampton on 25th to 28th March 1969. View full abstract»

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  • The two-frequency m.t.i. system

    Page(s): 172 - 176
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (569 KB)  

    Clutter motion relative to the radar may seriously degrade the efficiency of moving target indication (m.t.i.) systems used in radio location. This problem arises in shipborne radar, airborne radar, or when the clutter is being carried by the wind. Although various methods have been devised to overcome the effect, the problem still exists because these have their inherent drawbacks. As another approach, the two-frequency m.t.i. system has been proposed occasionally in the past few years, but it seems that a more detailed consideration of this method is as yet not available in the literature. A basic theory of the two-frequency m.t.i. system, together with a discussion of its significant characteristics, is presented in this paper. View full abstract»

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