摘要:

The paper presents, as far as possible in non-mathematical language, the concepts of modes currently in use.Some of the concepts are modified or generalized and a unified description is obtained. The term ‘proper-mode’ is reserved for a certain mathematical concept, which is usually concomitant with the concept of the eigen function, whereas the term ‘quasi-mode’ is reserved for a field configuration which can be supported by a physically realizable guiding structure.In the description given, the radiation field which must always accompany a guided wave is viewed in a slightly novel light, and a bridge is constructed between the concept of modes guided in closed waveguides and those guided by open structures.The paper concludes with a discussion on the existence of guided waves, and it is demonstrated that the existence or non-existence of a mode is entirely a matter of subjective opinion (implicit in the definitions). Nevertheless, it is shown that all quasi-modes are a physical reality and that they are useful in practical applications.

DOI:10.1049/pi-b-2.1960.0078

出版商:IEE    

年代:1960

数据来源: IET

DOI:10.1049/pi-b-2.1960.0079

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The need for a relatively high-speed analogue multiplier is discussed and the types of multiplier likely to meet this need at reasonable cost are investigated. It is concluded that the modulated square-wave type of multiplier using transistor modulators will be most suitable.The extension of the scope of the multiplier to operate with inputs of either sign is discussed. The causes of the various errors in the multiplier are examined and an overall accuracy of within ±2% is quoted. An explanation of the method used to ensure a good frequency response is given, and the transfer function of various parts of the circuit analysed. The experimental results are quoted as being similar in amplitude to a transfer of 1/(1 + 5 × 10−4jω), although the phase shift is considerably better than this.A number of circuits used to protect the transistors against damaging conditions are discussed. Special attention is given to a separate transistor circuit which disconnects all the power supplies in the event of an irregularity in any one of them.

DOI:10.1049/pi-b-2.1960.0082

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The theory of a parametric travelling-wave amplifier is developed, including the pumping wave explicitly.Particular reference is made to two characteristics of such amplifiers which theories assuming a constant pumping-wave amplitude fail to predict.The first arises from ohmic attenuation in the line, and limits the useful length of line to a length of the order of (α1α3)−1/2, where α1and α3are the signal- and pumping-wave attenuation coefficients. Further increase in length leads to a decrease in gain.The second characteristic is a saturation effect at high signal levels. This is found to be associated with a spatially periodic power transfer between signal and idling waves on the one hand and pumping wave on the other. The maximum power output at the signal frequency is obtainable from the input pump power and the input signal power through the Manley-Rowe relations.

DOI:10.1049/pi-b-2.1960.0085

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The paper gives a description of travelling-wave resonance in a waveguide ring fed through a directional coupler, and a resonance theory is developed which describes the behaviour of waves in the ring and the reflection and transmission in the feeder in the neighbourhood of resonance. The theory allows for equal propagation coefficients for the ring waves, or for a different propagation coefficient for one of the waves, and for a reflecting discontinuity in the ring. A method of investigating the ring resonance is described using a travelling probe, and experimental results are given for the case of equal ring-wave propagation coefficients, which substantiate the theory.

DOI:10.1049/pi-b-2.1960.0086

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The equations governing the voltage distribution along a parametric travelling-wave amplifier can, under certain conditions, be solved in terms of elliptic functions.The solution shows that there is a spatially periodic transfer of energy between the signal, idling and pumping waves. The maximum saturated power gain that can be achieved is1 + ω1/ω3pump input power/signal input powerwhere ω1and ω3are the angular frequencies of the signal and of the pump, respectively. The positions of these gain maxima can be calculated explicitly without invoking small-signal conditions.

DOI:10.1049/pi-b-2.1960.0087

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The parabolic-layer transmission equation of Appleton and Beynon has been solved for a wide range of its main parameters. A method of applying the equation to any long-distance circuit, in which the successive hop lengths of each transmitted ray are adjusted to accord with ionospheric variations along the path, is described. The only data required are directly obtainable from published ionospheric predictions. The results are displayed on mode plots, which comprise (a) a mode-angle plot, showing the angles of elevation of all rays and the modes in which they are propagated to all points along a great circle of any extent, and (b) a mode-delay plot, showing the time of travel of all rays instead of their angles of elevation. The effect on the mode plots of diurnal and longer-term changes in the ionosphere is discussed. Two long paths are examined experimentally and it is shown that the number of signal components observed, their relative time-delays, their angles of elevation and their response to varying ionospheric conditions, all agree well with those determined theoretically from the mode plots, provided that the effect of the tropical-Es layer is included. Mode-angle plots may also be used without modification to find both the angular spectrum of back-scatter patterns and the most probable paths taken by atmospheric noise energy arriving at a receiver. Mode-delay plots also provide direct backscatter patterns. The information on the plots may be used to improve aerial design and also to choose an optimum signalling frequency such that the number of active modes may be reduced, with a possible improvement in delay distortion of the signal. The choice of an optimum signal frequency is made possible by means of a mode-time plot, which shows the diurnal changes to be expected in propagation characteristics as determined by predicted changes in the ionosphere over the path.

DOI:10.1049/pi-b-2.1960.0090

出版商:IEE    

年代:1960

数据来源: IET

摘要:

A description is given of measurements made to compare the propagation of v.h.f. signals over paths in Cardigan Bay and the Irish Sea, some of which involve transmission over high mountain ridges. Comparisons are made, based on simple knife-edge diffraction theory used together with published propagation data, between the expected and measured field strengths at various distances beyond the Isle of Man mountain ridge. The results of the second series of experiments are applied to confirm that interference between co-channel television stations at Winter Hill, Lancashire and Black Mountain, Belfast should be at an acceptable level.

DOI:10.1049/pi-b-2.1960.0091

出版商:IEE    

年代:1960

数据来源: IET

摘要:

A null method has been devised for measuring changes in the amplitude and phase of the transmission characteristic of a network at any frequency in the range 41–1000 Mc/s. A commercial instrument, designed for admittance measurement, is used with only slight modification for this application. Its subsequent use as an admittance meter is unaffected.The measurement of phase can be made to within about ±3°, unless a large variation of amplitude is encountered, when reading accuracy limits the accuracy of phase measurement in the regions of small amplitude. If the error in a measurement is regarded as a vector, then, with any amplitude variation, the maximum value of the magnitude of this error vector is about 6% of the full-scale reading of the instrument.

DOI:10.1049/pi-b-2.1960.0092

出版商:IEE    

年代:1960

数据来源: IET

摘要:

The distortion of single-tone frequency modulation by passive networks whose amplitude and phase characteristics are non-linear with frequency is considered in some detail. A new approximate formula has been developed by extension of earlier methods, and its use, supplemented by the quasi-stationary approximation and by direct Fourier analysis, permits evaluation of distortion levels over ranges of parameters previously excluded. A number of examples are given, comparison being made where possible with results obtained by other methods. Particular attention is given to distortion of the amplitude and phase of the fundamental, this being of importance in connection with television baseband requirements. An attempt is made to clarify certain theoretical aspects, such as the validity of the ‘quasi-stationary’ solution, which have been the subject of controversy.

DOI:10.1049/pi-b-2.1960.0093

出版商:IEE    

年代:1960

数据来源: IET