PSK-FSK spread spectrum modulation/demodulation

• US 3,916,313 A
• Filed: 11/25/1974
• Issued: 10/28/1975
• Est. Priority Date: 11/25/1974
• Status: Expired due to Term

• Current Assignee: Ray B. Lowry
• Original Assignee: Ray B. Lowry
• Inventors: Lowry, Ray B.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US05/527,111
• Time in Patent Office: 337 Days
• Field of Search: 325/30,38R,39,42,43,44,65,163 343/7.6,17.2R,17.5 178/67
• US Class Current: 375/260
• CPC Class Codes: H04B 1/69 Spread spectrum techniques

Abstract

A spread spectrum link in which a transmitter section generates a different frequency signal for each unique data symbol accepted from the data source and phase shift modulates the frequency signals with a sequence of spread spectrum symbols, the frequency differences used being such that orthogonality is obtained over the receivers observation time of each spread spectrum symbol.

Claims

1. A communications system comprising:

a frequency synthesizer for outputting m different frequency signals having frequency spacings Delta f between adjacent frequency signals;

selector means for receiving m-ary data symbols and for selecting a different one of said m frequency signals for each unique data symbol of said m-ary data symbols that is received;

spread spectrum means for generating an n-ary sequence of symbols, the symbol period being TSS, and for modulating the selected frequency signals to produce n-ary phase shift modulated signals where the frequency spacings Delta f between adjacent n-ary phase shift modulated signals are equal, and

2. The system of claim 1 wherein said spread spectrum means comprises:

a binary sequence generator connected to said frequency synthesizer;

a binary to n-ary converter connected to said binary sequence generator;

an n-ary phase shift modulator connected to said binary to n-ary converter.

3. The system of claim 1 wherein said means for transmitting signals at carrier frequencies comprises:

an up-converter connected to said n-ary phase shift modulator; and

a transmitter amplifier connected to said up-converter.

4. The system of claim 1 wherein said receiver means comprises:

first means for converting said carrier frequency signals to receiver frequency signals having frequencies fr + k Delta f where 0 <

or = k <

or = (m-1); and

second means connected to said first means for determining which data symbols were transmitted.

5. The system of claim 4 wherein said second means comprises:

a plurality of filters connected to said first means;

a plurality of envelope detectors connected to said plurality of filters and;

decision means connected to said plurality of envelope detectors.

6. The system of claim 4 wherein said second means comprises:

a plurality of correlators connected to said first means;

a plurality of envelope detectors connected to said plurality of correlators; and

decision means connected to said plurality of correlators.

7. A method of spread spectrum communication comprising the steps of:

a. generating an n-ary sequence of signals, the signal period being TSS;

b. generating m different frequency signals having equal frequency spacings Delta f between adjacent frequency signals where

8. The method of spread spectrum communication of claim 7 further comprising the steps of:

receiving said signals at carrier frequencies; and

demodulating said signals at carrier frequencies to obtain the original data symbols.

9. A spread spectrum modulator comprising:

a frequency synthesizer for outputting m different frequency signals having frequency spacings Delta f between adjacent frequency signals;

selector means for accepting m-ary data symbols and for selecting a different one of said m frequency signals for each unique data symbol of said m-ary data symbols that is accepted;

spread spectrum means for generating an n-ary sequence of symbols, the symbol period being TSS, and for modulating the selected frequency signals to produce n-ary phase shift modulated signals, where the frequency spacings Delta f between adjacent n-ary phase shift modulated signals are equal, and