| 摘要 |
The present invention relates to a microwave band-pass filter comprising a plurality of coupled resonators including at least one coaxial resonator ( 1 ). For suppression of higher order or spurious pass-bands the filter is characterised in that a central hole ( 9 ) extends from the upper end of the inner conductor ( 6 ) of said at least one coaxial resonator through at least part of the length of the inner conductor, the central hole ( 9 ) forming a wave guide section, the cut-off frequency of which being above the pass-band of the band-pass filter, and in that the wave guide section contains in an upper portion ( 11 ) thereof a low loss dielectric material with a dielectric constant sufficiently high so that the cut-off frequency of the wave guide section is below the first higher order response of the band-pass filter, and in that the lower end portion ( 10 ) of the central hole ( 9 ) contains a lossy material.
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