Impulse autocorrelation function communications system

• US 4,512,024 A
• Filed: 06/29/1983
• Issued: 04/16/1985
• Est. Priority Date: 06/29/1983
• Status: Expired due to Fees

• Current Assignee: United States Of America As Represented By The Secretary Of The Army (Government of the United States of America)
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Gutleber, Frank S.
• Primary Examiner(s): Safourek, Benedict V.
• Application Number:
  US06/508,791
• Time in Patent Office: 657 Days
• Field of Search: 370/18, 370/19, 370/21, 375/1, 375/25, 375/34, 375/38, 375/96, 455/60, 343/361, 343/378, 343/380, 364/728, 364/819, 364/820
• US Class Current: 375/254
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity
• CPC Class Codes: H04L 23/02 adapted for orthogonal signalling

Abstract

A pulse code modulation communications system employing orthogonally sepaed noise code mate pairs having autocorrelation functions which upon detection in a matched filter and addition compress to a lobeless impulse. A mate pair of bi-polar digital noise codes are impressed on respective RF carriers generated by the same frequency source with one code mate being transmitted separately as a vertically polarized wave while the other code mate is transmitted separately as a horizontally polarized wave. The polarized RF carrier signals containing the code mates are respectively received by horizontally and vertically polarized antennas coupled to radio receiver apparatus which provides respective received signals containing the code mates. The code mates are then detected by matched filters which operate to compress the code mates. The compressed code mates are then linearly added to provide an output signal comprising a lobeless impulse signal.

Claims

1. A bi-orthogonal pulse code modulation communication system, comprising:

means for generating first and second multi-bit digital noise codes;

means for generating first and second RF carrier signals;

means for modulating said first and second noise codes on said first and second RF carrier signals;

first transmitting antenna means having a first type polarization coupled to said first carrier signal for radiating a first polarized RF carrier wave modulated with said first noise code;

second transmitting antenna means having a second type polarization coupled to said second carrier signal for radiating a second polarized RF carrier wave modulated with said second noise code;

first receiving antenna means having said first type polarization and being receptive of said first polarized RF carrier wave;

second receiving antenna means having said second type polarization and being receptive of said second polarized RF carrier wave;

receiver means coupled to said first and second receiving antenna means for processing respective first and second received signals containing said noise codes from said first and second polarized RF carrier waves received by said antenna means;

means coupled to said receiver means for autocorrelation detecting said first and second received signals for detecting said first and second noise codes and providing thereby first and second compressed output signals; and

means for combining said first and second compressed output signals to provide a substantially lobeless impulse output signal.

2. The system of claim 1 wherein said first type of polarization comprises horizontal polarization and said second type of polarization comprises vertical polarization.

3. The system of claim 2 wherein said first and second noise codes comprise a pair of code mates which upon detection with a matched filter produces an impuse autocorrelation function.

4. The system of claim 3 wherein said means for autocorrelation detecting comprises first matched filter means for detecting the first of said pair of code mates and second matched filter means for detecting the second of said pair of code mates.

5. The system of claim 4 and wherein said combining means comprises linear adder means for providing said lobeless impulse output signal.

6. The system of claim 5 wherein said receiver means comprises first and second receiver apparatus respectively coupled to said first and second receiving antenna means, said first receiver apparatus being operable to provide said first code mate at an IF frequency and said second receiver apparatus being operable to provide said second code mate at said IF frequency.

7. The system of claim 5 wherein said first and second RF carrier signals comprise coherent signals derived from a common source and wherein said first and second received signals comprise IF signals.

8. The system of claim 7 and wherein said first matched filter means comprises a first matched filter coupled to one of said IF signals and wherein said second matched filter means comprises a second matched filter coupled to the other of said IF signals.

9. The system of claim 3 wherein said means for autocorrelation detecting comprises first and second mutually orthogonal signal detection channels coupled to said receiver means and being respectively responsive to said first and second received signals, each said channel including means for bi-polar video matched filter detecting said pair of code mates to provide a respective pair of compressed code mate signals,

and wherein said combining means comprises first and second means for linearly adding said pairs of compressed code mate signals provided by said first and second detection channels to provide said lobeless impulse output signal.

10. The system of claim 9 wherein said first and second received signals comprises first and second IF signals of said pair of code mates, and

wherein said means for bi-polar video matched filter detecting in each of said channels comprises:

means for providing a reference IF signal;

means for detecting the phase difference between said first and second IF signals and said reference IF signal in one of said channels to provide first and second video signals of said pair of code mates the amplitude and polarity of which are function of said phase difference, and first and second matched filters respectively coupled to said first and second video signals for providing a pair of compressed code mate signals for said first detection channel;

means for shifting the phase of said reference IF signal by 90°

;

means for detecting the phase difference between said first and second IF signals and said reference IF shifted in phase by 90°

in the other of said channels to provide third and fourth video signals of said pair of code mates whose amplitude and polarity are a function of said last recited phase difference, and third and fourth matched filters respectively coupled to said third and fourth video signals for providing a pair of compressed code mate signals for said second detection channel.

11. The system of claim 10 and additionally including respective positive and negative polarity threshold detector means coupled to said first and second means for linearly adding for identifying signal presence of said lobeless impulse output signal from either of said detection channels.

12. The system of claim 11 and additionally including means coupled to said threshold detector means for providing a common output of a lobless impulse output signal detected in said first and second detection channels.

13. The system of claim 12 wherein said means for providing a common output comprises an OR gate.

14. A method of communicating in a bi-orthogonal pulse code modulation communications system, comprising the steps of:

generating first and second multi-bit digital noise codes;

generating first and second RF carrier signals;

modulating said first and second noise codes on said first and second RF carrier signals;

radiating a first polarized RF carrier wave modulated with said first noise code from first transmitting antenna means, having a first type polarization, coupled to said first carrier signal;

radiating a second polarized RF carrier wave modulated with said second noise code from second transmitting antenna means, having a second type polarization, coupled to said second carrier signals;

receiving said first polarized RF carrier wave by a first receiving antenna means having said first type polarization;

receiving said second polarized RF carrier wave by a second receiving antenna means having said second type polarization;

providing respective first and second received signals containing said noise codes upon reception of said first and second polarized RF carrier waves by said first and second receiving antenna means;

autocorrelation detecting said first and second received signals for detecting said first and second noise codes and providing first and second compressed output signals; and

combining said first and second compressed output signals for providing a substantially lobeless impulse output signal.

15. The method of claim 14 wherein said first type of polarization comprises horizontal polarization and said second type of polarization comprises vertical polarization.

16. The method of claim 15 wherein said first and second noise codes comprise a pair of code mates and wherein said step of autocorrelation detecting comprises the step of detecting with a matched filter and producing thereby an impulse autocorrelation function.

17. The method of claim 16 and wherein said combining step comprises linearly adding said first and second compressed output signals for providing said lobeless impulse output signal.

18. The method of claim 17 wherein said step of generating said first and second carrier signals comprises generating RF carrier signals which are coherent and of the same frequency.