摘要:

An analysis is presented for rectangular waveguides with partial dielectric loading in theH-plane. Accurate results are given for attenuation and phase constant for lossy dielectric, using both exact and perturbation approaches. Particular attention is paid to the abnormal situation where attenuation can be greater for partial loading than for complete loading by the same lossy material. This abnormality was reported by Bui and Gagne but discounted by them as being mathematically spurious. By contrast, in this paper an exact theory has been used and the abnormality is shown to be genuine, and due to the hybrid mode redistribution of fields.

DOI:10.1049/ij-moa.1978.0001

出版商:IEE    

年代:1978

数据来源: IET

摘要:

A close lower bound is derived for the TE-transmission coefficient of a single-mode dielectric waveguide Y-junction. The input and output planar waveguides of the junction are of the same thickness and are connected by a tapered section. The transmission losses can be less than a few percent for sufficiently long tapers and moderately small junction angles.

DOI:10.1049/ij-moa.1978.0002

出版商:IEE    

年代:1978

数据来源: IET

摘要:

A laser Doppler anemometer is described in which an optical fibre is used to transmit the light to and from the measurement zone. An account is given of the various types of measurement that have been made with the instrument, particularly those involving Brownian motion. An analysis is made of backscattering into a fibre which shows that the back-scattered power is confined to a region extending only a few tens of core diameters from the fibre end.

DOI:10.1049/ij-moa.1978.0003

出版商:IEE    

年代:1978

数据来源: IET

摘要:

The combline directional coupler (c.d.c.) is a recently described planar device suitable for m.i.c. applications which couples power in a forward direction through controlled phase matching of the coupled waves. As a result high coupling levels (up to almost 0 dB) may be achieved at high frequencies (up to 20 GHz) without the need for close conductor spacings. The bandwidth of a basic c.d.c. is approximately 30%. We describe here two methods of broadbanding the c.d.c. which retain the advantages just mentioned and which enable operation over almost a decade to be achieved. Results for a 1.9–19 GHz, 3 dB power dividing coupler are presented. Both methods involve a spatial variation of the coupler parameters, and one of them, using the theory of warped modes, makes possible directional couplers which have a combination of frequency range and coupling level flexibility not at present obtainable by any other means. Particular attention is paid to practical details; design tables and methods are given which enable experimental couplers to be produced with any desired coupling level. We present experimental examples illustrating the various types of coupler design discussed and compare their performances. An indication is also given of the way in which the broadband design methods used for the c.d.c. may be applied to other types of planar forward directional coupler.

DOI:10.1049/ij-moa.1978.0004

出版商:IEE    

年代:1978

数据来源: IET

摘要:

It is shown that for a general asymmetric directional coupler formed by two electromagnetic transmission lines, resistive terminations can be chosen so that the normal modes of the coupled system are reflected without conversion from one to the other. With such ‘non-mode-converting’ terminations the scattering matrix assumes a particularly simple form which can readily be interpreted physically. Practical means of finding the value of non-mode-converting terminations are indicated and the behaviour of couplers with non-mode-converting terminations is predicted.

DOI:10.1049/ij-moa.1978.0006

出版商:IEE    

年代:1978

数据来源: IET