IE42756L - Electromechanical filters - Google Patents

Abstract

1531759 Electrochemical filters SIEMENS AG 6 Nov 1975 [8 Nov 1974] 45986/75 Heading H3U An electrochemical filter comprises parallel rodshaped resonators R1-R10 which are interconnected by at least one coupling wire LK, the input and output transducers EM being connected to resonators other than the end resonators, those resonators outside the signal path between the transducers providing attenuation poles in the transmission characteristic of the filter. The resonators are supported at nodal points by wires S welded thereto and mounted in grooves in base G, which is either of metal or synthetic resin. As shown, the resonators are bending oscillators and electrostrictive transducers are mounted on flat faces of resonators R2, R9; the other resonators also have flat faces by which they are coupled to wire LK. In a modification resonators R2, R9 each have a portion with a second flat face perpendicular to the first one and for coupling them to wire LK. Each transducer is connected to a respective coil, which together with the self-capacitance of the transducer forms a resonant circuit tuned to the centre of the filter pass band but with a greater band width. The position of the poles introduced by resonators such as Rl, R10 may be displaced by varying the masses of these resonators or the length or thickness of the adjacent part of wire LK. Further poles may be provided by coupling wires UK which bridge over one or more intermediate resonators. The resonators may be torsional oscillators in which case they may be supported by wires HD, Fig. 7, attached to projections A of base Gl; alternatively they may each be supported by a single respective wire connected between a node and the base (Fig. 5, not shown) or all the resonators may be supported by two common wires HD mounted in chips (SH, Fig. 6; not shown) extending from the base. In each case the resonators are coupled by a wire KD. [GB1531759A]