摘要:

Experiments are described, and their results analysed, of the reflection (at oblique incidence) of microwaves of 8 mm wavelength from a rippled water surface. The surface profile was, to a good approximation, randomly rough, and a series of roughness states, extending from ‘slightly rough’ to ‘very rough’ and whose statistical characteristics were known, were used. The time variation of the amplitude and phase of the reflected radiation was observed for the two principal polarizations of the incident radiation, as well as their covariation when the incident radiation was polarized in a direction at 45° to the plane of incidence. The results are discussed in terms of recently proposed theories, and some encouraging agreement is found.

DOI:10.1049/piee.1963.0270

出版商:IEE    

年代:1963

数据来源: IET

摘要:

An analysis of observations made over a period of a year shows that the phase changes of the signals from NBA as received in Lower Hutt, New Zealand, have a diurnal pattern but with considerable day-to-day and seasonal variations. It is concluded that, as recorded at present, the signal is not sufficiently stable to be used as a reference for standard frequency measurements. A suggestion is made for improving the the reception of the signals for frequency-comparison purposes.

DOI:10.1049/piee.1963.0271

出版商:IEE    

年代:1963

数据来源: IET

摘要:

The paper describes an investigation undertaken to derive data on which to base estimates of the telegraph performance to be expected over tropospheric-scatter radio links. H. B. Law has shown how the telegraph error rate depends on the signal/noise ratio at the input to the telegraph equipment for the case of a steady signal, and also for the case of one subject to Rayleigh fading.As the signal received over a tropospheric-scatter link has a short-term amplitude distribution following the Rayleigh law, it might be expected that Law's results could be applied directly. The problem is complicated, however, by the fact that most operational scatter links employ frequency modulation of the radio carrier, with the result that the receiver exhibits threshold effects. When the fading signal falls below the receiver threshold, which it may frequently do, the output signal/noise ratio is no longer linearly dependent on the input carrier/noise ratio. It is shown, however, that, if the output/input characteristic of the radio receiver is known, the telegraph error rate can still be calculated in terms of the mean carrier/noise ratio.An empirical law for the output/input characteristic of an f.m. radio receiver is proposed, and, using this law, the telegraph performance of circuits carried by tropospheric-scatter links is then calculated for the cases of non-diversity and dual and quadruple selector-type diversity receiving systems. It was considered desirable to make experimental checks, and an analogue method was employed in which the effects of the radio path were recorded and used to operate a fading machine, so as to reproduce, in the laboratory, the conditions which had existed over an actual radio path.A comparison is made of predicted values of telegraph error rate with experimental results obtained using the fading machine.

DOI:10.1049/piee.1963.0272

出版商:IEE    

年代:1963

数据来源: IET

摘要:

This paper considers the application of electronic scanning in the vertical plane to provide additional height information for surveillance radar systems. It is shown that, if the electronic scanning rate is made equal to the reciprocal of the pulse duration, this can result in the production of a 3-dimensional radar with a high data rate and several useful facilities for air-traffic surveillance. These include: slant-range correction, reduction of zenithal gap, individual aircraft height extraction and height-layering facilities.Consideration is also given to a technique of multiplicative signal processing which can provide increased height accuracy for very little additional equipment.A proposed scheme for such a radar is put forward using techniques which have already received some experimental study, and the scheme is compared briefly with stacked-beam radar systems. The proposed radar appears to possess most of the facilities of the stacked-beam radars, together with improved height-layering facilities and a high reliability.

DOI:10.1049/piee.1963.0273

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A method of separating the sections of a lumped-constant delay line by means of short-circuited coils has been proposed by V. A. Solov'ev. The paper shows that, using this principle and an improved method of construction, the size of a delay line may be very considerably reduced. The line considered follows conventional delay-line theory closely, but differs considerably in its construction. Small size is achieved partly by an economic use of ‘distributed constants’ within the sections and partly by the space-saving use of short-circuited coils. A practical method is given for the design of the delay line.

DOI:10.1049/piee.1963.0275

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A new concept, the null-return-difference matrix, is introduced. It is an extension of Tasny-Tschiassny's return-difference-matrix concept and Truxal's null-return-difference concept. In terms of the return-difference and null-return-difference matrices, two new theorems are formulated for multiple-loop feedback circuits. First, it is shown that in any such circuit the closed-loop gain is equal to the direct-signal transmission ratio multiplied by the ratio of the determinant of the null-return-difference matrix to the determinant of the return-difference matrix. Secondly, it is shown that the ratio of the driving-point impedance to the value it assumes when all the stages of a multiple-feedback circuit are put into their reference conditions is equal to the ratio of the determinant of the short-circuit return-difference matrix to the determinant of the open-circuit return-difference matrix.

DOI:10.1049/piee.1963.0276

出版商:IEE    

年代:1963

数据来源: IET

摘要:

It is shown in the paper that each paramount non-singular matrix of order 3, or alternatively its inverse, may always be ordered into the uniformly tapered form. The network-theory interpretation of this result shows that each resistive 3-port network may be realized by at least one (and sometimes both) of two minimal structures, one with just four vertices and the other one with three independent circuits only. Moreover, there exists a unique parent configuration, a completely connected graph with four vertices, which is applicable to each realizable 3-port. After choosing an arbitrary linear tree on this graph, one is able to obtain any realizable 3-port by one of two methods: by either describing the ports on, or inscribing them into, the edges of this tree and by suitably choosing the values of its elements.

DOI:10.1049/piee.1963.0277

出版商:IEE    

年代:1963

数据来源: IET

摘要:

A method is given for comparing binary codes and higher-order codes of the orthogonal type. By choosing codes which have the same message duration, utilise the same bandwidth, and have the same information content, a fair comparison of their performance for different signal/noise ratios can be obtained. An example of this concept is given for a trigonometric code of 32 equally probable messages.

DOI:10.1049/piee.1963.0278

出版商:IEE    

年代:1963

数据来源: IET

摘要:

After a brief historical introduction, the theory of the couple arising from angular momentum carried by a circularly polarized wave is discussed, with particular reference to waves in waveguides. The paper goes on to describe the design and construction of an absolute wattmeter based on this effect and operating in the millimetric waveband. A number of sources of error are then enumerated and discussed, and an estimate is made of the probable accuracy of the instrument.Careful comparisons with a dry-load calorimeter of the type described by Carlin and his collaborators shows that the two instruments agree to within the estimated errors.

DOI:10.1049/piee.1963.0279

出版商:IEE    

年代:1963

数据来源: IET

摘要:

Papers have been published recently giving measurements of the minimum perceptible diameter of test objects as a function of contrast at various specified X-ray doses. Some data are available for single-stage X-ray intensifiers observed visually and for intensifying systems in which a camera tube is used indirectly to view the output of an intensifier. The present paper reports comparative data for a television system in which a special camera tube is used to view the X-ray screen directly.

DOI:10.1049/piee.1963.0280

出版商:IEE    

年代:1963

数据来源: IET