Improvements relating to electric filters

Abstract

Abstract 504,830. Impedance networks. ALLGEMEINE ELEKTRICITATS-GES.. Sept. 29, 1937, Nos. 26424 and 26425. Convention dates, Sept. 29, 1936 and Sept. 30. 1936. [Class 40 (iii)] A separating filter is formed by connecting the input terminals of two complementary symmetrical filters in series or parallel, and a constant input impedance is obtained by removing impedances present in the input, this being equivalent to adding a negative impedance. One of the constituent filters may be an antimetrical filter, i.e. a filter whose input and output impedances when multiplied together give a constant resistive impedance. The filters B, B<1> of Fig. 1, have their iriput connected in series, the impedances A, A<1>, being removed to give the separator of Fig. 2. Other examples are shown. In general, the separator is designed according to the Cauer methods. The hyperbolic cotangent of the propagation constant, coth g, for each of the component filters, and the image impedance R of the separator are chosen. The image impedance of filter B is then R /coth g<1> and the, image impedance of filter B<1> is then R /coth g, while the impedance to be removed is R/coth g.coth g<1>. Thus, the image impedance and coth g for each filter is determined and the filter can be designed to have the requisite impedance to be removed occurring in series or shunt, according as the filters are to be connected in series or parallel.

Inventors

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