| 摘要 |
A tuneable microwave filter having a passband and stopband with a substantially constant passband bandwidth across a tuneable band, the filter comprising a plurality of resonators, each resonator having an equivalent circuit comprising a short circuited stub 16 in parallel with a capacitor 15, the resonators being electrically coupled together 17,18 such that each resonator is electrically coupled to at least one other resonator by an electrical coupling equivalent to a short circuited stub 19; each short circuited stub being dimensioned such that its electrical length θ varies between 2/9 and 13/36 or a portion of that range across the tuneable band. The tuneable microwave filter has a passband with a bandwidth which is substantially independent of frequency of the centre of the passband across the tuneable band. Accordingly, when changing the frequency of the centre of the passband there is no need to adjust the inter-resonator coupling. This makes adjustment of the filter much simpler and can now be achieved remotely. |
