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Transmitting information with cut and flip spectrum
   
Document Number
US Patent 5142692
Issued Date
August 25, 1992
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Abstract
The present invention provides a technique and system for modifying the modulation of the 66.5 kHz subcarrier in such a way that its spectrum will not overlap that required by the 57 kHz subcarrier, while at the same time maintaining compatibility with existing subcarrier receivers. A special signal is created whose spectral shape is asymmetrical with respect to the 66.5 kHz subcarrier. In the frequency domain, the lowest frequency part of the symmetrical spectrum is cut off, flipped about the carrier frequency and then added to the highest frequency part of the spectrum. This technique and system takes advantage of the fact that the receiver, with which the system is designed to operate, uses a sampling process which products frequency aliasing. With the present invention, the spectral shape produced at the transmitter is such that the aliasing caused by sampling in the receiver results in the lower-than-carrier and higher-than-carrier portions of the spectrum being adding together, producing in the receiver a symmetrical spectrum.
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Transmitting information with cut and flip spectrum - US Patent 5142692 Drawing
Drawing from US Patent 5142692
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Number of Claims:
3
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Owner
Seiko Corp. (both of,JP)
Seiko Epson Corp. (both of,JP)
Published
August 25, 1992
Application Number
07/789,429
Filed
November 5, 1991
US Classification
455/48   375/240 455/45
Int'l Classification
H04B   1/16   (20060101)   H04H   5/00   (20060101)   H04H   1/00   (20060101)  
Examiner
Assistant Examiner
Attorney/Law Firm
Parent Case
This application is a continuation of application Ser. No. 07/367,532, filed Jun. 16, 1989, now abandoned.
USPTO Field of Search
455/42   455/45   455/48   455/110   455/113   455/118   455/47   381/2   381/3   381/4   381/5   381/6   381/7   381/14   381/30   381/31   375/26   375/60   375/122   340/825.44   333/165   333/167   332/119  
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