摘要:

The design problems associated with high-capacity digital microwave radio systems and their present status are reviewed. Nonmilitary systems having transmission capabilities of about 90 Mbit/s or greater per radio bearer have been considered, those known to be under development operating within the approximate frequency range 8–21 GHz. At the lower-frequency end, repeater spacings are limited by multipath effects to about 60 km, whereas at the higher-frequency end, spacings are dominated by rain attenuation and are limited to a few kilometres. The effects of both types of fading and the calculation of repeater spacings are considered. Bandwidth utilisation is very important for digital systems, and the design criteria for suitable filtering schemes are discussed leading to possible overall radio-frequency-channel arrangements. Constraints imposed by the system design are discussed, and the consideration of available components leads to outlines of possible repeater arrangements.

DOI:10.1049/ij-moa.1976.0001

出版商:IEE    

年代:1976

数据来源: IET

摘要:

A method is described for determining unambiguously, from the far-field pattern of single-mode fibres, the core diameter and the refractive-index difference between core and cladding. It involves measurements only of the half-power width of the main lobe and the width of the first minimum. Universal curves are presented that can be used with single-mode fibres or any fibre operating in the single-mode regime. Independent determinations of core diameter over the range 4–8μm by an etching technique are in excellent agreement with those obtained from the far-field pattern.

DOI:10.1049/ij-moa.1976.0002

出版商:IEE    

年代:1976

数据来源: IET

摘要:

The theory of junction circulators is either given in terms of a linear combination of the properties of single-port reactive eigennetworks or in terms of a single-port approximate equivalent circuit. The purpose of this paper is to present a unified theory of circulators using either approach in terms of ABCD matrices, ideal transformers, and resonator eigennetworks. It is found that all standard circulators can be conveniently described in the notation introduced in this text.

DOI:10.1049/ij-moa.1976.0003

出版商:IEE    

年代:1976

数据来源: IET

摘要:

Sandwich-ribbon-fibre waveguides are intended for directional coupling to and from thin-film optical integrated circuits. The propagation characteristics of a 3-dimensional ribbon fibre have been studied using the synchronous angles of a prism coupler, and by observing the near- and far-field patterns of the excited modes. Although the cross-section of the guiding region is not rectangular, it has been found that the modal characteristics can be adequately described using approximate solutions developed for rectangular waveguides.

DOI:10.1049/ij-moa.1976.0004

出版商:IEE    

年代:1976

数据来源: IET

摘要:

Explicit design formulas are given for the element values of symmetrical bandpass channel diplexers. Assuming that the element values in the independent doubly terminated filters are known, the element values are expanded as a power series in a well defined band-separation factor and the appropriate coefficients determined in a direct manner. This process involves the key factor that, at the zeros of the independent reflection coefficients, the interaction effects may readily be taken into account to retain the zero location in the diplexer up to a certain order of approximation. From the resulting prototype diplexer, which necessarily contains frequency-invariant reactances, designs for relatively narrow bandpass channel diplexers may readily be obtained. As an example, a waveguide direct-coupled cavity diplexer is designed in WG14. Finally, experimental results on this five-cavity-per-channel diplexer are cited showing excellent agreement with theory.

DOI:10.1049/ij-moa.1976.0005

出版商:IEE    

年代:1976

数据来源: IET