Title: Digital communications system with immunity to frequency selective fading

Abstract: A digital communications system with increased resistance to frequency selective fading. Digital signals to be transmitted are phase shift modulated upon a spectrum spreaded carrier. The carrier is generated by mixing the output of a band spread oscillator with a locally generated IF oscillator signal. The signal thus obtained is divided into transmission periods, each of which is longer than the maximum spreading time of the nonlinear transmission medium. The increased bandwidth occupancy thus obtained increases the immunity of the transmitted signals to frequency selective fades moving across the allocated bandwidth. The signals are received by a differentially adaptive receiver which automatically adjusts its response to the envelope of received signals.

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Inventors: Bickford, William J. (Weston, MA, US)

Application Number: 512654
Filing Date: 1974-10-07
Publication_date: 1976-09-14
Assignee: Raytheon Company (Lexington, MA)
Primary Class(es): 375/141 375/146, 375/147, 375/281, 375/284, 375/285
Other Classes:
US Patent Ref:

3478268	Nov, 1969	Coviello	325/65.
3665472	May, 1972	Kartchner et al.	325/65.
3714573	Jan, 1973	Grossman	325/32.
3794921	Feb, 1974	Unkauf	325/42.

Other Refs:
Primary Examiner: Safourek, Benedict V.
Assistant Examiner:
Attorney: Inge; John R., Pannone; Joseph D., Bartlett; Milton D.