Demodulators – Amplitude modulation demodulator – Having specific distortion – noise or other interference...
Patent
1975-05-02
1977-04-19
Olms, Douglas W.
Demodulators
Amplitude modulation demodulator
Having specific distortion, noise or other interference...
325 36, 329132, 329135, H04H 500
Patent
active
040189945
ABSTRACT:
Compatible AM stereophonic receivers for reception of a radiant energy carrier wave modulated with two stereo related signals (L and R), each appearing as a respective first order single-sideband. Receivers embodying the invention in general improve an optimize output stereo signal quality by quadrature demodulation of the carrier to derive the stereo difference (L-R) signal, together with in-phase detection of the stereo summation (L+R) signal, the L+R and L-R signals thus derived being placed in phase and combined through sum and difference circuits to obtain the stereo related (L and R) outputs. Demodulation distortion may be minimized by inverse amplitude modulation of the carrier wave with a portion of at least the envelope fundamental (and preferably also one or more harmonics thereof). The carrier wave is preferably enhanced prior to quadrature demodulation and preferably is also modulated with an infrasonic frequency (e.g. 15 Hz) signal indicating stereo signal presence, with such infrasonic modulation either amplitude modulating or phase modulating the carrier wave. Such infrasonic modulation is utilized to automatically switch receiver output mode and to visually indicate stereo signal presence.
REFERENCES:
patent: 3068475 (1962-12-01), Avins
patent: 3076057 (1963-01-01), Baugh
patent: 3143600 (1964-08-01), De Vries
patent: 3218393 (1975-11-01), Kahn
patent: 3500217 (1970-03-01), Allen
"The Phase-Shift Method SSB Signal Reception" by Norgaard, Proceedings of the IRE, Dec. 1956 pp. 1735-1743.
LandOfFree
Compatible AM stereophonic receivers does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Compatible AM stereophonic receivers, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Compatible AM stereophonic receivers will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-104660