Frequenzdemodulationsschaltung

942,894. Frequency discriminators. PHILIPS ELECTRICAL INDUSTRIES Ltd. Jan. 27, 1961 [Jan. 30, 1960], No. 3256/61. Heading H3A. In a modified Foster-Seeley discriminator, a series tuned LCR circuit 2 is fed by a current i such that quadrature components of magnitude Qi, together with the in-phase current i are fed to a push-pull rectifier arrangement with a push-pull output 10. In Fig. 5, the rectifiers are fed by a T network 12, 13, 14 and the circuit 2 includes two series-connected capacitors 25, 26 whose values are such that the impedances of the capacitor 25 and of the network 3 and 26 are equal at a chosen harmonic of the mean input frequency. In Fig. 7, the rectifiers are replaced by the emitters and bases of PNP transistors 17, 18, and the L/C arrangements of Fig. 5 are transposed to provide a biasing arrangement for a previous NPN driver transistor 35.