FM Stereophonic system incorporating companding of difference signal
Patent 4485483 Issued on November 27, 1984. Estimated Expiration Date: 
March 18, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
March 18, 2003. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.Patent References 3067292 Compatible stereophonic receiver Compatible AM stereophonic system Signal compression and expansion system Patent #: 4376916 InventorsApplicationNo. 06/476738 filed on 03/18/1983US Classes:381/14, Having transmitter381/4AM subcarrierExaminersPrimary: Rubinson, Gene Z.Assistant: Brady, W. J. Attorney, Agent or FirmInternational ClassesH03G 7/00 (20060101)H04H 5/00 (20060101) H04B 1/64 (20060101) H04B 1/62 (20060101) AbstractAn FM stereophonic radio broadcasting system in which stereophonically related audio frequency source signals L and R are matrixed to obtain stereophonic sum and difference signals M and S, respectively. At the transmitter, the difference signal, is compressed, and the conventional difference signal and the compressed difference signal modulate respective quadrature-related sub-carriers of the same frequency to develop two double-sideband, suppressed-carrier signals, the frequency of the sub-carriers being sufficiently high as to assure a frequency gap between the lower sidebands of the modulated sub-carrier signals and the sum signal M. The M signal, the aforementioned suppressed-carrier signals, and a pilot signal having a frequency which lies within the frequency gap, are combined and frequency-modulated onto a high frequency carrier for the purpose of transmitting the same to one or more remote receivers. The receiver includes an expander for complementarily expanding the received compressed difference signal, and the expanded noise-reduced difference signal is combined with the received sum signal to reproduce the audio frequency source signals L and R. The system increases the broadcast coverage area over that of current biphonic service yet is compatible with existing monophonic and biphonic receivers.Other References
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