Multiplex demodulation circuit
AssigneePioneer Electronic Corporation
InventorsKohji Ishida, Tatsuo Numata
Life of this patent
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Abstract
A multiplex demodulation circuit in which no band elimination filter is required for eliminating beating between the mixed signals and odd harmonics of the 38 KHz switching signal derived from the 19 KHz pilot signal. The FM detection signal is logarithmicly converted as is the 38 KHz subcarrier signal. The two logarithmically converted signals are added and then inversely logarithmically converted. The inversely logarithmically converted signal is added to the FM detection signal to produce the left channel signal while the inversely logarithmically converted signal is phase inverted then added to the FM detection signal to provide the right channel signal.
Claims7
A multiplex demodulation circuit comprising:
- first logarithmic conversion means for subjecting an FM detection signal to logarithmic conversion;
- second logarithmic conversion means for subjecting to logarithmic conversion a subcarrier signal produced in response to a pilot signal component in said FM detection signal;
- addition means for adding an output of said first logarithmic conversion means to an output of said second logarithmic conversion means;
- inverse logarithmic conversion means for subjecting an output of said addition means to inverse logarithmic conversion;
- and
- means for separately adding normal-phase and inverted-phase outputs of said inverse logarithmic conversion means to said FM detection output to separate and provide right and left channels signals.
Dependencies are inferred from the claim text.