| 摘要 |
718,562. Ultra-high-frequency filtersRADIO CORPORATION OF AMERICA. July 22, 1952, No. 18549/52. Class 40 (8). [Also in Group XXXVI] A variable ultra-high-frequency filter comprises two resonant structures each comprising two capacitance members one of which can be varied by means of a movable tuning-member whilst the other remains constant, the capacitance members being connected to conductors representing inductances, whose free ends have a common connection. The structures are disposed adjacent to each other to provide electrostatic and electromagnetic coupling. As shown capacitance members of the structures 11, 12 consist of sleeves of copper or silver 13, 14; 27, 28 coated onto glass tubes 12, 26 within which are movable conductive tuning cores 20, 32. The position of the tapered ends of these cores determines the capacitance between the cores and the sleeves 13. 27, the capacitance between the cores and the sleeves 14, 28 remaining substantially constant. The sleeves are connected by conductors 15, 16; 30, 31 to a common conductive plate 17. The input is connected to an intermediate point 45 on the conductor 30 and the plate 17 which is earthed, whilst the output is connected to an intermediate point 47 on the conductor 16 and the plate 17. In the equivalent circuit of Fig. 2 the reference numerals of the various elements in the two structures are applied to the lumped inductances, capacfies &c., which represent them. The coupling between the two structures, represented in Fig. 2 by two coupled series resonant circuits, is preferably greater than the critical coupling in order to obtain a greater width of band-pass. The coupling and hence the band-pass may be varied by adjusting the angular setting of a metal' plate 55 which represents a short-circuited coil. The plate may be perforated, Fig. 10 (not shown), or may take the form of a circular, rectangular or oval annulus, Figs. 4, 5, 6, 7, 8, 9 (not shown).
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