GB410499A - Improvements in or relating to electrical resonant circuit arrangements - Google Patents

Abstract

410,499. Impedance networks. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, and RUST, N. M., 109, London Road, Chehnsford, Essex. Oct. 8, 1932, Nos. 28096 and 32055. [Classes 40 (iii) and 40 (v).] An unmatched filter particularly for use as an intervalve coupling in the intermediatefrequency circuit of a superheterodyne receiver comprises two or more series arms tuned to the desired frequency, the shunt arms (the inductance of which may be constituted by mutual inductance) being so tuned as to produce a sharp cut-off. Thus, the series arm comprising the condenser C3, Fig. 3 (Comp.), and the leakage inductance of the coils L1, L2, is tuned to the accepted frequency while the shunt arms, comprising the mutual inductances between the coils together with condensers Cl, C2, form acceptor arms tuned respectively to the two cut-off frequencies. Or there may be three tuned series arms (Fig. 3, Prov. 28096 /32, not shown). The input and output terminals may be connected across the condensers of the circuits which are tuned to the mean pass frequency, Fig. 9 (Comp.) and Fig. 5 (Comp., not shown;) or alternatively the two shunt arms, comprising mutual inductance and tuned to the two cut-off frequencies, may be located in separate stages of an amplifier, Fig. 8 (Comp., not shown). The shunt arms may be designed in relation to the ohmic resistance R, Fig. 3 (Prov. 32055/32) ; the impedance of each arm L2, C2, L3, C3 remains at or a little above the value of R throughout the pass range and falls off rapidly at a cut-off frequency ; or a rejector shunt arm L2, C2, Fig. 2 (Prov. 32055/32), may be tuned to the frequency at the middle of the pass band and have an impedance equal to or a little greater than R at that frequency. The shunt arms may have negative resistance as described in Specification 404,349. A circuit similar to that shown in Fig. 9 (Comp.) may be designed in relation to R in this manner, Fig. 4 (Prov. 32055/32, not shown).