摘要:

The paper aims at presenting a simple approach to developments in this field against the background of more conventional systems. Attention is drawn to some of the problems which have still to be solved, and a brief assessment is made of prospects for the future.

DOI:10.1049/pi-b-2.1959.0001

出版商:IEE    

年代:1959

数据来源: IET

摘要:

An analysis of electromagnetic wave propagation in mutually coupled parallel lines is carried out. The theory is then adapted to microwave propagation in waveguides capable of supporting simultaneously a large number of modes, and explicit solutions are obtained in the case of weak coupling.A detailed analysis of periodically coupled modes is developed and applied to a number of specific cases of practical interest. It is shown that, although very weakly coupled waveguides have negligible influence on signal distortion, periodic coupling results in considerable signal distortion. A waveguide with random irregularities is treated in some detail and explicit formulae for signal distortion are derived.The analysis is concluded with numerical examples illustrating signal distortion, increase in attenuation and echo distortion.

DOI:10.1049/pi-b-2.1959.0003

出版商:IEE    

年代:1959

数据来源: IET

摘要:

This paper records the results of a series of measurements carried out on waveguides and components of the type suitable for long-distance transmission.The description opens with a short discussion of methods of measurement, their applications and shortcomings. The reasons for choosing a pulse-testing method are explained, and the special equipment is briefly described. The measurement difficulties are discussed in detail, and some apparently conflicting results are explained. The problem of mode identification is tackled in a number of ways, and some experimental results are recorded. A number of components are studied and particular attention is paid to the feeds. Bends and corners are investigated in some detail, and it is claimed that, with suitably designed waveguides, these need not be a major design problem. In fact, using the techniques described, very satisfactory bends and corners can be made with relative ease.Some abridged results of numerous measurements carried out on plain metallic pipes under various conditions are recorded, and it is concluded that such waveguides are unsuitable for long-distance transmission. Performance figures of corrugated and helical Waveguides are quoted, and it is concluded that electrically satisfactory waveguides can be designed.

DOI:10.1049/pi-b-2.1959.0004

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Coupling to spurious modes at imperfections in a long circular waveguide may cause the TE01loss to increase and to fluctuate randomly with frequency. The statistical properties of the TE01loss/frequency curve can be expressed in terms of the statistical properties of the random geometric imperfections of the guide and therefore in terms of its mechanical tolerances. Such imperfections as poor joints and elliptical waveguide have negligible effect under reasonable tolerances. However, random deviations of the guide axis from a straight line may have very serious effects under certain conditions. The use of mode filters or of helix waveguide to increase the spurious-mode loss reduces the TE01loss fluctuations but leaves the average TE01loss due to mode conversion relatively unaffected.Experimental measurements of loss/frequency curves, of spurious-mode content and of mechanical tolerances which have been made on existing waveguides support these conclusions. Random straightness deviations introduced during manufacture of the waveguide are the primary cause of the observed transmission behaviour.

DOI:10.1049/pi-b-2.1959.0005

出版商:IEE    

年代:1959

数据来源: IET

摘要:

The phase delay and attenuation are found for a waveguide consisting of spaced discs with a central circular hole transmitting on circular modes.It is found that the attenuation is considerably less than that of a plain circular waveguide of internal diameter equal to that of the circular holes.

DOI:10.1049/pi-b-2.1959.0006

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Wave propagation in the H-guide is investigated theoretically and experimentally. Relationships are derived to describe the field distribution and to calculate the distribution constants of the single- and double-slab guide. Higher modes are studied. The height of the guide can be increased without introducing undamped higher modes. The attenuation coefficients are calculated and analysed for X-band and millimetre wavelengths. Conduction and dielectric losses are considered. Radiation losses and the corresponding attenuation are calculated. The radiation can be arbitrarily reduced by increasing the height of the guide. The maximum transmitted power at electric breakdown is calculated. Experiments are discussed which confirm the theoretically obtained results. The overall results suggest modifications of the original structure and permit the conclusion that the guide is particularly suitable for the frequency range above 20 Gc/s.

DOI:10.1049/pi-b-2.1959.0007

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Waveguides of varying cross-section are considered. An infinite system of ordinary differential equations is derived from the Maxwell equations and boundary conditions. The system of ordinary differential equations is converted into an infinite system of integral equations. The resulting formulae are particularly suitable for iteration.

DOI:10.1049/pi-b-2.1959.0008

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Resonant-cavity techniques provide a powerful method for evaluating circular-electric-mode waveguide performance, particularly attenuation, mode conversion and bend-loss characteristics. The waveguide to be tested forms the side wall of the resonator. Thus, a few samples of special waveguide may be sufficient to check design parameters.Cavity measuring equipment operating at frequencies between 50 and 60 Gc/s has been designed and used to study 7/16 in, 7/8 in and 2 in-inner-diameter copper, helix and dielectric-lined waveguide. Q-factors as high as 3.5×106have been measured for a 30 ft-long 2in-diameter copper cavity at room temperature.Attenuation characteristics are obtained by measuring several cavities of different lengths to obtain end-wall and coupling corrections.A pure-mode coupler is used to excite the cavity, allowing mode-conversion effects caused by power transferred from the circular electric to other modes generated by side-wall imperfections to be measured when both modes are resonant simultaneously.

DOI:10.1049/pi-b-2.1959.0011

出版商:IEE    

年代:1959

数据来源: IET

摘要:

A description is given of equipment and instruments suitable for the determination of the attenuation of circular waveguides of the type appropriate for long-distance transmission. Essentially the procedure consists of measuring the Q-factor of a resonator formed by the length of the waveguide to be tested (a few meters long), short-circuited at both ends, and deducing the attenuation figure therefrom. Some experimental results are quoted to illustrate the versatility of the equipment, its limitations and accuracy.

DOI:10.1049/pi-b-2.1959.0012

出版商:IEE    

年代:1959

数据来源: IET

摘要:

Some methods of measuring the attenuation in waveguides are discussed, and the particular difficulties involved in the determination of low attenuations are outlined. The measurement of the Q-factor of a resonant line appears to be the most satisfactory method for short specimen lengths of waveguide, and the paper deals chiefly with the special equipment required for the measurement of Q-factors of the order of 106. The frequency stability required for the measurement of the very small frequency changes involved is very considerable, and the apparatus described ensures that frequency instability of the oscillator will not affect this measurement. Frequency differences are measured by a frequency discriminator using a waveguide delay line, the output of the discriminator being capable of accurate absolute calibration.The effects of cavity losses other than wall losses are theoretically investigated, since their magnitude influences the minimum length of cavity that can be used.

DOI:10.1049/pi-b-2.1959.0013

出版商:IEE    

年代:1959

数据来源: IET