Fm demodulator

1,079,946. Frequency discriminators. FUJITSU Ltd. July 31, 1964, No. 30372/64. Heading H3A. FM input is applied to a quarter-wave line D terminated by a phase reversing transformer 13 of 1: 1 turns ratio. The output from the line D and from the phase reverser relative to the line input are both rectified by diodes 6, 7 and differentially combined to give a linear D.C. output at 3, 31 of magnitude and polarity indicating the instantaneous frequency deviation. The transformer may be replaced by a phase splitting valve or a transistor with collector and emitter outputs applied to the diodes. Further, the input to the other ends of the diodes may be applied through an emitter or cathode follower having an LF choke in the emitter or cathode circuit.