GB809707A - Frequency rejection system for electro-mechanical filter - Google Patents

Abstract

809,707. Electromechanical filters. COLLINS RADIO CO. Oct. 17, 1956, No. 31639/56. Class 40 (8). An electromechanical filter comprises magneto-strictive input and output means and a mechanical resonant system comprising a series of coupled discs some of which are tuned to frequencies at the edge or edges of the passband of the filter in order to increase the steepness of these edges. Input and output coils 18 are housed within tubes 13, 14 which support a pair of inactive end discs 31, 32 joined by rods 33. A series of active discs 34 tuned to the mid frequency of the pass-band are supported by the rods 33 and are coupled to the input and output coils by magnetostrictive rods 30, 35 attached to the end members of the series. Between these end members and the inactive discs 31, 32 are situated one or more pairs of discs 36, 37 also supported by the rods 33. These may be tuned to frequencies # 1 , # 3 , Fig. 7, or, where there are two pairs, to frequencies # 1 , # 2 , # 3 , # 4 , Fig. 9, near the edges of the band pass. Alternatively, the discs 36, 37 may both be tuned to frequencies at one and the same edge of the band pass. A discussion of the electrical analogue of the resonant system is given in the Specification. Specifications 722,664 and 767,915 are referred to.