Band pass filter for decimetric and centimetric waves

摘要

731,498. Filters. STANDARD TELEPHONES & CABLES, Ltd. (Lorenz Akt.- Ges., C.). July 22, 1953, No. 20396/53. Class 40 (8). A band-pass filter comprises at least four hollow resonators arranged in cascade, adjacent resonators being inductively or capacitively coupled by apertures in the common partition walls. The oscillation resistances of the resonators and the impedances of the coupling apertures are such the group delay caused by the filter is constant over at least two thirds of the given pass band. The couplings of the cavities to one another and the dimensions of the cavities are so chosen that the attenuation in the centre of the pass-band width is zero. In one construction, Fig. 5, coaxial cylindrical resonators are coupled by apertures K. Probes E and A are provided for feeding and extracting waves. Each resonator is provided with a tuning screw VB. To enable the length of the resonators to be adjusted, they may be constructed of a number of rings separated by partitions. In a modification (Fig. 6, not shown), the rings may be secured together by clamping plates and bolts. In a further modification, Fig. 7, the resonators may have a central conductor extending partly across the inside. A compact filter, Fig. 8, may be formed by making the resonators in the form of sectors.