DOI:10.1049/pi-3.1951.0001

出版商:IEE    

年代:1951

数据来源: IET

DOI:10.1049/pi-3.1951.0002

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The servo-electric ionospheric recorder in use at the Radio Research Station, Slough, is described in relation to its general use for routine recording purposes. It contains five essential parts: (a) a pulse transmitter, (b) a pulse receiver, (c) a servo-electric control working through a discriminator to keep the receiver in tune with the transmitter, (d) a calibration unit and (e) a recording unit. This type of equipment has been in continuous use for over six years, producing hourly records of ionospheric conditions. The record consists of a graph of equivalent height of reflection of radio waves as a function of frequency. The height and frequency graticules are produced simultaneously with the echoes, and the date and time of the observations are recorded automatically.

DOI:10.1049/pi-3.1951.0003

出版商:IEE    

年代:1951

数据来源: IET

摘要:

A theory is given of the diversity effects produced in spaced aerials by incident waves having a distribution in direction of arrival. The general case of a continuous coplanar distribution of rays with random phase is considered, and when this distribution is narrow and symmetrical it is shown how its extent can be estimated from observations of either the amplitudes or the phase difference of the signals in the spaced aerials. The case of a strong steady signal superimposed on the centre of the continuous distribution is also analysed and the results are obtained in terms of a parameter which may be called the signal/noise ratio. It is shown how, by making measurements of the diversity effect in both amplitude and phase, both this ratio and the angular spread of the continuous distribution can be obtained.Some daytime measurements at nearly vertical incidence have been made on first-order ionospheric reflections at frequencies between 4 and 7 Mc/s, and it is found that the diversity effects observed are most satisfactorily explained in terms of a steady “signal” (or specularly reflected component) superimposed on a “noise” background (composed of the continuous angular distribution due to diffractive reflection). Values of signal/noise ratio of about two or three have been obtained, with a noise background which has an angular spread with standard deviation of about 1°.

DOI:10.1049/pi-3.1951.0004

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The absorption of electromagnetic waves in the atmospheric gases, and their absorption and scattering by various forms of precipitation, are discussed from the aspect of their effects on the performance of centimetre-wave radar equipment. Particular attention has been devoted to the phenomena to be expected at the wavelength of 3.2 cm, since this is the wavelength now used, and likely to be more widely used, for marine navigational radar.At a wavelength of 3.2 cm, absorption by the atmospheric gases is hardly significant, and absorption and scattering in rain are likely to cause most of the appreciable reductions in the range of detection. Whilst it is not possible to make a complete generalization, it appears that, at this wavelength, the deterioration in radar performance on targets having echoing areas greater than, say, 2 000 m2(e.g. ships of more than about 10 000 tons) arises mainly from attenuation produced in rain rather than as a result of masking by echoes from the precipitation itself. With smaller targets, however, this masking will often be the more serious factor. The heavy rates of rainfall common in tropical-equatorial regions will produce a much greater deterioration in radar performance than will the rainfall likely to occur at all frequently in temperate regions.Although very intense snow-storms can produce echoes sufficiently strong to be troublesome, the rate of precipitation required is such that its frequency of occurrence is unlikely to be great. Attenuation occurring in snowfalls is generally of little importance. In dense fogs reductions in detection range may be appreciable—especially in polar regions—when the optical visibility falls below about 25 m; in this case, attenuation is the significant factor.

DOI:10.1049/pi-3.1951.0005

出版商:IEE    

年代:1951

数据来源: IET

摘要:

Several types of aerial producing fan-beam radiation patterns with horizontal polarization are discussed from the aspect of side-lobe suppression in the horizontal plane—which is the plane of narrow beam-width. The theory of the primary feed requirements of cheese and half-cheese aerials is outlined, and the effect of the secondary radiator on the radiation pattern of the primary feed—and so on the distribution of energy across the aperture—is analysed.The factors contributing to side-lobe amplitude in the radiation pattern of the symmetrical cheese aerial are discussed in detail, and it is shown that this type of aerial has side lobes which are large compared with those of the half-cheese aerial and which cannot be reduced much more than 23 db below the main beam level.The design and performance of a half-cheese aerial having maximum side lobes some 30 db below the main beam level are described. The mechanical design and the matching of both cheese and half-cheese aerials are commented upon, and the factors influencing the choice between these two aerials are summarized.

DOI:10.1049/pi-3.1951.0006

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The paper deals with the theory of the propagation of microwaves, passing from a homogeneous and isotropic medium into a set of parallel metallic plates. The plane of separation between the set of plates and the homogeneous medium outside is assumed perpendicular to the plates. The incident wave is plane, and its direction of propagation is in the plane containing the perpendiculars to the plates and to the surface of separation. The electric field is parallel to the plates.The method is relatively simple. The study is based on Maxwell's equations and on periodicity and continuity considerations. An analytic method is introduced for the solution of the infinite set of linear equations with an infinity of unknowns, which arises from the continuity conditions at the boundary plane of the plate edges.Formulae are obtained giving the nature, direction, phase and amplitude of the reflected and transmitted waves. The reflected waves follow the usual laws found in the grating theory. In the case when only one non-evanescent plane wave is reflected, the transmission and reflection power coefficients are those obtained at the junction of two semi-infinite transmission lines corresponding to the free-space and the plate medium respectively. The analogy with transmission lines is more complex when two non-evanescent waves are reflected. For the usual angles of incidence and plate spacings the transmission power coefficient is high (maximum 99.5%), and the phase shift on transmission is small.

DOI:10.1049/pi-3.1951.0008

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The problem of calculating the electrostatic field in a single-grid radio valve is solved by placing systems of line charges at the centre of each grid wire and hence deriving a potential function which satisfies all the boundary conditions. This function is experessed in a series form, but it may readily be used to compute characteristics of the field to any required accuracy. Tabulated values of the more important characteristics are provided.

DOI:10.1049/pi-3.1951.0010

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The question of the extent to which field disturbances caused by the individual wires of a grid penetrate an adjacent grid is examined by considering inter-electrode capacitance relationships. By an experimental procedure, using an electrolytic tank, and also by computation, the magnitude and effect of these disturbances can be measured, and it is shown that the well-known ways of simplifying the problem of the multi-grid valve are justified in cases of greatest practical interest

DOI:10.1049/pi-3.1951.0011

出版商:IEE    

年代:1951

数据来源: IET

摘要:

The problem of determining the frequency spectrum of a sinusoidal carrier, frequency modulated by a modified rectangular wave, is considered and a general solution obtained. The modification of the rectangular wave consists in replacing the vertical sides by a non-instantaneous transition in the form of a half-cycle sine wave. It is shown that for the determination of bandwidth it is reasonable to use, instead of the spectrum proper, a function which forms an envelope to it; this function is simpler and, in particular, it is independent of the on/off ratio of the rectangular wave. curves are given for various values of the paramenters involved.

DOI:10.1049/pi-3.1951.0013

出版商:IEE    

年代:1951

数据来源: IET