Quadrature multiplying four-channel demodulator

Details Quadrature multiplying four-channel demodulator Quadrature multiplying four-channel demodulator

1976-08-13

1977-12-06

Olms, Douglas W.

H04H 500

Patent

active

040618820

ABSTRACT:
A decoder is provided for a FM radio four-channel system having the usual 19 kHz pilot signal, a first subcarrier at 38 kHz, a second subcarrier in quadrature therewith, and another subcarrier at 76 kHz. The decoder of the present invention is a time division system wherein the 19 kHz pilot signal is doubled and the phase shifted 90.degree.. This produces sine and cosine 38 kHz signals to provide a first pair of outputs, and each of these signals is inverted to provide a second pair of outputs. By properly adding the four outputs thus derived, switching signals are provided to decode the four channel information.

REFERENCES:
patent: 3721766 (1973-03-01), Hilbert
patent: 3881063 (1975-04-01), Mawake et al.
patent: 3909539 (1975-09-01), Ohkubo et al.
patent: 3965302 (1976-06-01), Kurata
patent: 3967069 (1976-06-01), Dorren
patent: 3980832 (1976-09-01), Nakamura et al.
patent: 3985964 (1976-10-01), Ohkubo et al.

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