| 摘要 |
<p>1485505 Filters WESTERN ELECTRIC CO Inc 4 Nov 1974 [8 Nov 1973] 47668/74 Heading H1W A microwave filter comprises at least one dielectric resonator asymmetrically positioned with respect to a stripline in order to maximize the coupling between the stripline and the resonant TE 01 delta mode of the resonator. The resonators may be discs made of a barium titanate composition Ba 2 Ti 9 O 20 or of a lithium tantalate composition, these having desirable temperature coefficients of resonant frequency. The sign of this coefficient may be opposite to that of the dielectric substrate of the stripline or that of the filter housing, whereby temperature compensation is provided. In the multi-section filter of Figs. 4, 5, three resonant discs 41, 51, 61 rest on accurately-machined dielectric spacers 25 above a stripline conductor 44. The centres of the resonators are laterally displaced from the centre-line of the stripline. The resonators may be coupled, as shown, by striplines of length equal to an odd number of quarter-wavelengths at midband frequency. Alternatively, the stripline may be absent except at the input and output and the resonators directly coupled one to the next. The filter has a band rejection characteristic. A bandpass filter may be constructed by inserting the above-described filter in a waveguide dimensioned below cut-off for the operative frequency range. In such an arrangement, propagation is obtained only near the resonant frequency of the resonators.</p> |
