Multiple channel FM stereo system
US3944747A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Sep 28, 1973 |
| Grant date | Mar 16, 1976 |
| Priority date | — |
| Expiry date | Sep 28, 1993 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04H20/89
- WIPO fieldTelecommunications
- WIPO sectorElectrical engineering
Abstract
A transmitter or a receiver processes four-channel stereo frequency-modulation information. The information represents four audio signals A, B, C and D that correspond to sources respectively located at the left-front, right-front, left-rear and right-rear of a listening point. First and second sub-carrier signals .omega..sub.s and .omega..sub.s2 both have frequencies substantially higher than the highest audio signal component. In one disclosed embodiment all of the different signals are combined to develop a signal having a carrier signal frequency that is modulated by double-sideband amplitude-modulated suppressed-carrier sub-carrier signals as expressed by the modulation function EQU M(t) = K.sub.1 (A+B+C+D) + K.sub.2 (A-D) cos.omega..sub.s t + K.sub.3 (B-C) sin.omega..sub.s t + K.sub.4 [(A+D) - (B+C)] cos.omega..sub.s2 t where K.sub.1 to K.sub.4 are constants and t is time. An alternative system provides for single sideband transmission and reception of the sub-carrier .omega..sub.s2 and places an SCA channel at the location of the missing sideband.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.