摘要:

Four methods of determining the absolute power gain of microwave aerials are described, and some indication of their limitations and advantages is given. Two of them require no knowledge of the aerial geometry or polar diagram, and can therefore be used for finding the gain of any type of aerial. The other two, however, require a knowledge of the field across the aerial aperture, and can only readily be applied to horns of rectangular cross-section; even then several approximations have to be made. A method for comparing other aerials with the standard is also described.

DOI:10.1049/ji-3-2.1948.0042

出版商:IEE    

年代:1948

数据来源: IET

摘要:

The paper is concerned with the design and performance of inductive radiogoniometers for use in d.f. systems operating in the frequency band 3–100 Mc/s. The general principles of design are discussed, and it is shown that the main considerations are the coupling law, the electrical symmetry of the field coils and the coupling factor. The principal component of the instrumental error is the coupling error, and two methods of reducing it are described. One involves the use of a distributed search-coil winding, and the other the use of a compound-wound type of search coil. It is shown that, if the turns of the search-coil winding are wound on a cylindrical former so that they cover the surface completely, the coupling error is negligible, irrespective of the form of the field coils. Four h.f. instruments designed on this principle are described, and details of their performance are given.In the compound-wound search coil the winding is in two sections, the planes of which are set at an angle to each other. It is shown that the coupling error is dependent upon this angular separation and upon the configuration of the magnetic field. An investigation into the design of the field coils indicates how the most suitable field configurations may be obtained. The design and construction of a v.h.f. goniometer embodying these principles is described, and its measured performance provides confirmation of the theory of operation.The importance of electrical symmetry of the field coils is pointed out, and the ways in which it is affected by the design of the goniometer are discussed.Comparison between goniometers of the two types shows that, in general, for medium and high frequencies the distributed search-coil winding is the more suitable, and for v.h.f. operation that with the compound-wound search coil.In an appendix the operation of the inductive goniometer as a phase shifter is considered theoretically, and it is shown that it has the same instrumental error when used in this manner as when used as an amplitude comparator in a direction-finder.

DOI:10.1049/ji-3-2.1948.0043

出版商:IEE    

年代:1948

数据来源: IET

摘要:

A review of existing methods of measurement of the instrumental errors in inductive radiogoniometers is followed by detailed descriptions of three methods that have been used in the high- and very-high-frequency bands (3–100 Mc/s). The first, a field-coil interconnection method which requires no apparatus other than a signal generator and detector, has a limited application, but this disadvantage is offset by its simplicity. The second method makes use of a resistance potentiometer capable of a high order of accuracy at frequencies up to 30 Mc/s. In the third method two inductive piston attenuators are used. This apparatus has a very high order of accuracy, and may be used at the highest frequencies now employed for direction-finding purposes.The importance of the measurement of errors due to the electrical asymmetry of the field coils and search coil is emphasized, and methods that have been used at high and very high frequencies are described.The accuracy and limitations of the methods are discussed and their merits compared. Details of the construction of the measuring apparatus and of its calibration are given, and typical error measurements made on various goniometers are included.

DOI:10.1049/ji-3-2.1948.0044

出版商:IEE    

年代:1948

数据来源: IET

摘要:

An approximate analysis is made of the factors that influence the intrinsic accuracy of a heated filament used as a transfer device for measuring power at microwavelengths in terms of a low-frequency calibration. It is shown that instruments incorporating such filaments are usually subject to errors of significant magnitude if the filaments are longer than about one-tenth of a wavelength, and that the errors are usually smaller in resistance milliwattmeters than in thermocouple instruments used in similar conditions.Experiments are described which show that serious errors, due to the inefficiency of the transformer used to match the power source to the filament of the instrument, can occur in addition to those described in the analysis. It is concluded that filament instruments cannot, in the present state of development, be relied on as standard transfer instruments for measuring microwave power in terms of a low-frequency calibration.

DOI:10.1049/ji-3-2.1948.0045

出版商:IEE    

年代:1948

数据来源: IET

摘要:

The paper offers a theory of circle diagrams of impedance or admittance representing the relations between terminal impedances and input impedances for the general passive four-terminal network, including the cases of asymmetry and dissipation, so formulated that common transmission-line diagrams become special cases.After a review of earlier work on the subject, the relations between terminal and input impedances are expressed in terms of the iterative quantities of the network in a circle diagram. It is shown that this diagram is actually a graphical representation of the complex hyperbolic tangent function. Special circle diagrams are discussed corresponding to a non-dissipative network in the stop-band or pass-band, or at the cut-off frequency. These diagrams are studied by the application of projective geometry.An inversion of the ordinary circle diagram leads to the Smith diagram, which is described for both real and complex iterative impedances. It is pointed out that for a transmission line of less than ¼λ the error resulting from consideringZa pure resistance is of the same order of magnitude as that which would result from neglecting the damping.

DOI:10.1049/ji-3-2.1948.0048

出版商:IEE    

年代:1948

数据来源: IET

摘要:

The quality of service provided by a telephone concern is an essential factor in its financial economy. In this relation it is necessarily the overall quality as experienced by the subscribers. Division into different aspects such as traffic quality and transmission quality is arbitrary; each may be separately measured, but for economic balanced planning there is need of a combined measure of overall quality. The paper deals only with transmission quality. Planning has, in the past, been in terms of circuit attenuation and instrument efficiency, with the object of ensuring an adequate level of received speech, but this conception is no longer adequate or economical.The direct observation of the number of times a subscriber finds it necessary, in a unit time-interval, to repeat a word or a sentence is the best known indication of transmission quality in service; a complete rating system based upon such observations and other considerations has been put into operation by the American Telephone and Telegraph Co.In Europe, the repetition-rate criterion of service quality has been accepted, but application of the practice presents difficulties. Two plans are being investigated: (a) attempts are being made to find, under certain restricted conditions, a correlation between repetition rate in service and laboratory articulation tests; and (b) a provisional system of rating based on articulation tests (without reference to repetition rate) is being studied.Both plans are described, and possible correlation procedures are discussed. Reference is made to the economy aspect of rating on the broader basis of transmission quality, but the subject is too large to treat adequately in the present paper.Brief mention is made of foreign publications.Appendices include detailed descriptions of the experimental procedure to establish transmission service ratings.On account of the fluid condition of the subject of the paper, standardized terminology is not in existence and therefore definitions of the terms used are given as a final appendix.

DOI:10.1049/ji-3-2.1948.0049

出版商:IEE    

年代:1948

数据来源: IET

摘要:

The paper describes the methods and results of experiments made to map out the electromagnetic fields associated with a slot radiator. The radiator was a narrow slot about half a wavelength long cut in a large circular metal sheet of diameter about 9 wavelengths. The results include the relative magnitudes and phases of the electric vector over a quadrant of the metal sheet close to the slot, the relative magnitudes of the magnetic vector along the axes of the slot, and also some polar diagrams of radiation at relatively large distances from the slot, both on and off the sheet. The results obtained are correlated as well as possible with the theoretical expressions for the fields associated with a half-wave slot of infinitesimal width in a sheet of infinite extent. These theoretical expressions are derived from the usual formulae for the fields of a thin dipole by the use of an extension of Babinet's principle recently described by Booker.

DOI:10.1049/ji-3-2.1948.0057

出版商:IEE    

年代:1948

数据来源: IET

摘要:

Slot radiators of various widths were fed via balanced parallel-rod transmission lines connected near the centre points of opposite edges of the slots. Series components of impedance at the feed points were measured for each slot at a number of frequencies, including that at which the length of the slot was ½λ. In the first set of experiments the slot was free to radiate on both sides of the metal sheet in which it was cut. Further measurements are described in which the dimensions of the slot were kept constant whilst rectangular cavities of various dimensions were placed symmetrically behind the slot so as to prevent radiation from one face of the metal sheet.

DOI:10.1049/ji-3-2.1948.0058

出版商:IEE    

年代:1948

数据来源: IET

摘要:

In this paper the performance of klystron reflectors is studied in detail. The electrostatic potential distribution in the reflector space is calculated by means of relaxation methods for three typical reflector designs. The transit time for electrons moving along the tube axis is calculated as a function of the h.f. voltage picked up in the resonator gap. With the help of the transit-time curves the bunching is studied in detail. The advantage of this analysis as compared with the treatment by other authors is twofold: the analysis is not confined to small signals, and it is possible to attribute tube defects to features of reflector design. It is shown that the power output and the transit times as deduced from the theory are in good agreement with experimental determinations. Off-axis electron paths are then computed by means of a step-by-step method. A consideration of these paths shows that space-charge effects are not likely to play an essential part in the performance of the tubes studied. In conclusion, the effect of the spatial focusing by the reflector on the tube impedance is discussed.

DOI:10.1049/ji-3-2.1948.0059

出版商:IEE    

年代:1948

数据来源: IET

摘要:

A system of symbols is described, by which the various elements (contacts and operating coils) of a relay circuit can be represented. The symbols are then linked together by signs, the resultant algebraic expression corresponding to the circuit, and the operation of the circuit can be studied by considering the behaviour of the algebraic expression according to rules which are developed in the paper. Methods are described whereby complex circuits may be simplified by algebraic manipulation of the symbolic expressions; and design of relay circuits to perform given operations is discussed.

DOI:10.1049/ji-3-2.1948.0061

出版商:IEE    

年代:1948

数据来源: IET