| 摘要 |
The invention provides a mode coupler arrangement comprising a main waveguide coupled via arrays of slots to two sets of subsidiary waveguides over a common length. One set of subsidiary waveguides is such as to support one mode of propagation and the other set another mode of propagation. In a preferred embodiment the slots in one set of subsidiary guides are staggered by (1 lambda /4) relative to the slots in the other set of subsidiary guides and the guides of one set are longer than the guides of the other set. For TE11 communications mode signals, the two sets of subsidiary guides are of different frequency, with each subsidiary guide arranged such that its variation of wavelength with frequency coincides with that of the main waveguide only in the frequency band for which that subsidiary guide is provided.
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