摘要:

Measurements have been made of the extra-terrestrial noise picked up by an aerial on different bearings at different times of the day. This noise is expressed quantitatively by the equivalent temperature of the aerial radiation resistance. Temperatures between 1 800 and 10 000° K have been observed.

DOI:10.1049/ji-3a-1.1946.0252

出版商:IEE    

年代:1946

数据来源: IET

摘要:

An account is given of experiments leading to the design of 600-Mc/s radar aerials of Yagi type, suitable for mounting on naval gun-control directors. The basic array finally adopted had eight director rods, and a semi-circular cylindrical sheet reflector. Two such arrays, one for transmission and one for reception, were mounted with a separation of 1½ wavelengths on pom-pom directors; numbers of these arrays were fed in parallel as aerials for larger directors. The transmitting and receiving aerials on each director were later combined for common-aerial working, and beam-switching technique was applied by suitably phasing the currents in the dipoles. The performance characteristics of the above aerials are described.The experimental results show that when a number of Yagi arrays are fed in parallel with comparable powers and phases, the interaction between the arrays has only a small effect on the radiation pattern if the arrays are more than a wavelength apart. The overall radiation pattern is then given by the product of the radiation pattern of one of the arrays and a “group factor” calculated on the assumption of a point source of the necessary amplitude and phase at the centre of each array.

DOI:10.1049/ji-3a-1.1946.0253

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The development of microwave radar systems was started in 1940 largely because microwave aerial systems offered, particularly for airborne use, the definite advantages of narrow beams and high power-gains from practical aerial apertures. The principle was well known that to achieve these things it is necessary to spread out the power being radiated over as large an aperture as possible. One of the simplest forms of microwave aerial used to achieve this was the simple paraboloid. As radar in the centimetric field developed the characteristics demanded from the aerials systems increased in complexity.The paper starts with a very brief survey of some of the main features of paraboloid aerials and then outlines in rather more detail some of the work which has been done in recent years upon more complex microwave aerials to meet the new requirements.

DOI:10.1049/ji-3a-1.1946.0254

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The paper gives a short account of the technique of designing paraboloid and other forms of point-fed double-curvature aerials. The general properties of such aerials with their advantages and limitations are described; the requirements for the feed are discussed, and illustrated by reference to all the main types of feed that have been used. Some purely practical points such as reflector tolerances and the design of supporting members are dealt with. Special applications such as the provision of “split” feeds, and the production of shaped patterns for various purposes are also described. A bibliography of all the important British papers on the subject is appended.

DOI:10.1049/ji-3a-1.1946.0255

出版商:IEE    

年代:1946

数据来源: IET

摘要:

A study is made of the scattering of a plane wave incident obliquely upon an infinite plane grid of parallel equidistant circular wires. A simple means is described of picturing the mechanism by which side waves are produced as the angle of incidence is varied. Exact formulae and curves for the shunt reactance of the grid are given for the most useful case in which the spacing is less than a wavelength. Thus the reactance of the grid referred to the component of the wave impedance of the incident plane wave which is normal to the grid, viz. 376.5 sec θ ohms, isXg= 376.5d/λ[logε(d/2πa)+F(d/λ,θ)] ≃ 376.5d/λ[logε(d/2πa) fora≪b≪ λ,whered= spacing of wires,a= radius of each wire,θ= angle of incidence. The correction term is plotted in Fig. 6. The reflection coefficient isr= − 1/(1 + 2Xg/Zsec θ), Z0= 376.5 ohms

DOI:10.1049/ji-3a-1.1946.0256

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This paper describes the results of experiments carried out on horns having rectangular apertures one dimension of which is of the order of a quarter of a wavelength, the other being of the order of one wavelength or more. The polarization is parallel to the smaller dimension. The paper considers the radiation pattern in a plane normal to the aperture of the horn and perpendicular to the longer sides of the aperture. The results are shown in a graphical scheme which demonstrates the types of radiation pattern resulting when various symmetrical systems of metal flanges are attached to the long sides of the aperture. The scheme shows the effect of variation of two parameters defining the flange system. These parameters are the length of the flanges and the angle contained between their planes. In particular it is shown within what limits the form of the radiation pattern can be regulated by this means, and to what extent it is possible to get patterns of a rectangular shape. It is also shown how various special types of pattern can be generated: e.g. patterns having a pronounced “dip” in the forward direction.

DOI:10.1049/ji-3a-1.1946.0257

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The standing waves produced in a matched wave guide when it is placed at the focus of a paraboloid are analysed along the lines of classical diffraction theory. From the theory it is possible to deduce the size of a flat plate which, when fixed to the apex of the paraboloid, eliminates this source of reflection. The experimental results obtained with a paraboloid of aperture 20λ are in good agreement with the theory. The radiation pattern of the paraboloid is slightly affected by the plate, and the type of deterioration observed is consistent with an approximate theory of the effect.In the course of the investigation, a combination of flange and diaphragm was developed which matches the wave guide to free space over a wide band of wavelengths, and which can be used for radiating peak powers up to 750 kW.

DOI:10.1049/ji-3a-1.1946.0258

出版商:IEE    

年代:1946

数据来源: IET

DOI:10.1049/ji-3a-1.1946.0259

出版商:IEE    

年代:1946

数据来源: IET

摘要:

This series of experiments measures the radiation patterns of slot aerials associated with corner reflectors. The performances of slots in the faces of the corner reflectors and of slots in cavities in front of the reflectors are described. All the slots are cavity-fed.The effects on radiation patterns of variations in the corner angle and of displacements of a slotted cavity in front of the corner are also investigated.The final evolution of a reliable beam-approach aerial system is described and the results outlined of operational tests on this system.

DOI:10.1049/ji-3a-1.1946.0260

出版商:IEE    

年代:1946

数据来源: IET

摘要:

The functioning of linear arrays is explained in terms of familiar filter theory. Three basic types of array are considered, particular attention being paid to the non-resonant array, and the theory of each is investigated, first of all for an array consisting of radiators free from mutual interaction and then for a more general case. It is shown that the non-resonant array has a wide frequency band and that the design is in no way critical, but that the beam direction changes with frequency and that a truly broadside beam is unobtainable. Resonant arrays necessarily produce truly broadside radiation but their impedance characteristics limit their use to applications requiring only a very small frequency band. The leaky wave-guide type of array is only applicable when beams are required at comparatively large angles to the normal, and for this reason little work has been done on this kind of array. It is concluded that the non-resonant array is at present the most generally useful type, both on account of its inherent characteristics and the fact that most of the necessary experimental information has been acquired.

DOI:10.1049/ji-3a-1.1946.0261

出版商:IEE    

年代:1946

数据来源: IET