Transmitting information with cut and flip spectrum

Details Transmitting information with cut and flip spectrum Transmitting information with cut and flip spectrum

1991-11-05

1992-08-25

Kuntz, Curtis

Telecommunications

Transmitter and receiver at separate stations

Inverted sideband

455 45, 375122, H04B 102

Patent

active

051426927

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.

REFERENCES:
patent: 2898397 (1959-08-01), Richman
patent: 4379947 (1983-04-01), Warner
patent: 4594607 (1986-06-01), Lewis, Jr. et al.
patent: 4870480 (1989-09-01), Chao
patent: 4896152 (1990-01-01), Tiemann
patent: 5063610 (1991-11-01), Alwlapish

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