摘要:

The application of a very sensitive radar system to the observation of signals incoherently scattered in the ionosphere is briefly described. This technique can give more detailed information about height and time variations of bottom-side electron-density profiles than any other method, besides measuring several further parameters of the plasma. Electron-density profiles of the day-time lower Eregion, and of the whole of the night-time Eregion, allow much more reliable estimates than hitherto to be made of nondeviative h.f. absorption, and of the reflection heights of m.f. and l.f. waves. The morphology of the ‘valley’ in the profile between the E and Fregions can be investigated; also the ability to measure details of profile changes during ionospheric disturbances should allow the accompanying deterioration in h.f. propagation conditions to be understood. Incoherent-scatter measurements give unique opportunities of making independent calibrations of statellite instruments in orbit, and of measuring plasma movements induced by neutral aid winds. An empirical law relating the temperature and density of the electrons has been discovered; this will help in predicting the changes in density which should occur when additonal heat energy is deposited in the ionosphere during disturbances.

DOI:10.1049/piee.1971.0247

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Worldwide predictions of h.f. and m.f. radio propagation conditions require extensive data on the space and time variations of ionospheric parameters such asfoF2 andhmF2. Theoretical values of these parameters can be obtained by solving equations that represent the effects of various physical processes governing Flayer behaviour. The effects of winds, which are driven by the daily heating of the upper atmosphere, on the midlatitude F2layer are briefly described. Consideration is also given to the polar and the low-altitude F2layer and to problems of Flayer storms.

DOI:10.1049/piee.1971.0248

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A method of analysing cylindrical antennas with distributed impedance loading is presented. The loading is assumed to be an arbitrary but differentible function of position along the antenna. As an illustration, the most important class of such antennas in practice, the broadband cylindrical antennas with distributed resistive or capacitive loading, for which exprimental data are available, are analysed. The theoretica results are in satisfactory agreement with experiments.

DOI:10.1049/piee.1971.0249

出版商:IEE    

年代:1971

数据来源: IET

摘要:

The problem considered is that of clculating the angles of arrival of a multimoded signal at an antena array from simultaneous measurements of the amplitude and the phase of the signal in each element of the array. A general solution with wide application is described.

DOI:10.1049/piee.1971.0250

出版商:IEE    

年代:1971

数据来源: IET

摘要:

This paper describes a novel application of the field-gradient theory of plasma microwave harmonic generation, proposed by Krenz and Kino, to the case of a positive column placed through a rectangular waveguide. The distribution of 2nd-harmonic power between the TE01and TE11waveguide modes has been examined experimentally and found to be in agreement with qualitative predictions made from the gradient model. An inverse-cubic depence between the 2nd-harmonic-conversion efficiency and electron-collision frequency, predicted by Krens, has also been observed. A metal probe plaved against the column, with the intention of introducing severe microwave-field gradients in the plasma resonace at the fundamental frequency, a best overall conversion of about 25% was produced for an input power of 500mW at 2.42 GHz. At higher power levels, the plasma electron density appropriate for fundamental resonance could not be sustained, and the conversion effiency fell. Experiments using 9.6 and 35GHz fundamental signals gave best conversion efficiencies to the second harmonic of only 2.5 % and about 0.01%, respectively. It is concluded that the gradient model provides a satisfactory description of 2nd-harmonic generation in gaseous plasmas, but that devices based on this model do not operate efficiently at high power levels or at high microwave frequencies.

DOI:10.1049/piee.1971.0251

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A single-sideband suppressed-carrier ferrite modulator is used in aQband serrodyne phase bridge. By suitably processing the bridge-detector output, relative phase in the unknown bridge arm may be measured to within 1% of its true value, despite nonlinearities in both the static insertion-loss and phase-shift characteristics of the modulator. The modulator drive is not critical.

DOI:10.1049/piee.1971.0252

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Received v.l.f. signals during sunrise and sunset times over the propagation path are used to deduce information about the attenuation coefficients and phase velocities of the day and night waveguide modes, as well as the conversion factors between these modes at the day/night transition. Unlike any previous method used to obtain modal propagation constants, the present method does not need a mobile receiver, since it directly makes use of the moving secondary source formed by the mode conversion that takes place at the shadow line, or transition. A two-night-modes/two-day-modes model is discussed in detail. It is seen that it has a wider range of validity, with regard to both the path length and the frequency, than both the two-night-modes/one-day-mode model suggested by Crombie in 1964, and the one-night-mode/two-daymodes model used for the early part of the sunrise period by Kaiser.

DOI:10.1049/piee.1971.0253

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A simple time-tag data-compression scheme which uses a binary nonconsecutive one code is introduced to provide higher data compression ratios than similar schemes which have been suggested. This data-compression scheme should be very easy to implement. In addition, it does not requirea prioriknowledge of the information source.

DOI:10.1049/piee.1971.0254

出版商:IEE    

年代:1971

数据来源: IET

摘要:

Tests of the effect of time stress on human performance in the recognition situation were carried out using a standard television display with accompanying audio and noise sources, the student responding with a standard key punch. Reaction time and psychological moment measurements are reported and discussed.

DOI:10.1049/piee.1971.0255

出版商:IEE    

年代:1971

数据来源: IET

摘要:

A cathode-ray-tube graphical display system for use as a digital-computer output terminal has been developed The display employs analogue function-generation circuits to produce line drawings composed of straight-line and curved-line segments which are specified by parameters transferred from the computer in analogue form. To maintain a flicker-free image, while also imposing a minimal demand on the computer to which it is connected, the display incorporates an analogue memory composed of capacitors and field-effect-transistor switches. The displayed image may then be refreshed at the required rate by cyclically reading the line and curve control parameters from this memory. The computer need only access the memory to insert fresh data to be displayed or, infrequently, to refresh the stored information. The paper includes discussions of the specification of the overall display system, of the design of the analogue storage system and of two methods used to produce the required picture segments for display. Some results obtained with the display connected online to a small digital computer are shown.

DOI:10.1049/piee.1971.0256

出版商:IEE    

年代:1971

数据来源: IET