DISCRIMINATING SIGNALING SYSTEM

• US 3,755,811 A
• Filed: 06/10/1968
• Issued: 08/28/1973
• Est. Priority Date: 06/10/1968
• Status: Expired due to Term

• Current Assignee: Jack Breckman
• Original Assignee: Jack Breckman
• Inventors: Breckman, Jack
• Primary Examiner(s): Hubler, Malcolm F.
• Application Number:
  US04/735,716
• Time in Patent Office: 1,905 Days
• Field of Search: 343/6.5,6.8,112.4,6.5SS
• US Class Current: 342/30
• CPC Class Codes: G01S 13/79 Systems using random coded signals or random pulse repetition frequencies , e.g. "Separation and Control of Aircraft using Non synchronous Techniques" [SECANT]
• CPC Class Codes: G01S 13/933 of aircraft or spacecraft

Abstract

The disclosure is directed to a technique for discriminatingly extracting a subset of meaningful information signals from a babble of similar signals and then utilizing only the information contained in this subset. This technique is particularly suitable for use in an air collision avoidance system consisting of a plurality of essentially asynchronous interrogator-responder and transponder stations all of which utilize the same relatively long preselected pseudo-random code to provide the desired discrimination by correlation techniques.

Claims

1. A discriminating signaling system comprising a plurality of stations including at least one given type station a. said given type station including first means for generating a certain preselected binary code over an interval consisting of a predetermined plural number of successive bit periods each of which manifests either the binary value A or the binary value A in accordance with said code, second means coupled to said first means for transmitting a first signal only during each of those bit periods having the binary value A and for transmitting a second signal only during each of those bit periods having the binary value A, third means for receiving a third signal and a fourth signal, and fourth means coupled to said first and third means for deriving an output signal substantially in accordance with the following correlation function:

2. The system defined in claim 1, including a plurality of said given type stations all of which utilize the same certain preselected binary code.

3. The system defined in claim 2, wherein at least certain of said given type stations further include said transponder means.

4. The system defined in claim 1, wherein said plurality of stations include stations on moving craft.

5. The system defined in claim 1, wherein said interval includes at least several hundred pulse periods.

6. The system defined in claim 5, wherein said certain preselected binary code is a pseudo-random code.

7. The system defined in claim 1, wherein n is equal to at least the predetermined plural number of bit periods in said code interval.

8. The system defined in claim 7, wherein said first means repetitively generates said code, and wherein said fourth means includes fifth means for reading out said output signal therefrom after each successive set of n consecutive bit periods.

9. The system defined in claim 1, wherein each of said first, second, third and fourth signals is a modulated pulse having a pulse width which is insignificant with respect to the duration of a bit period, the modulation of the respective pulses comprising each of said first, second, third and fourth signals being different from each other.

10. The system defined in claim 9, wherein the duration of a bit period is in the order of one thousand times the width of a modulated pulse.

11. The system defined in claim 9, wherein said modulated pulse comprising said first, second, third and fourth signals, respectively, are bursts of electromagnetic waves occurring respectively at first, second, third and fourth predetermined frequencies all of which are different from each other.

12. The system defined in claim 1, wherein said correlation function applies at all times within a bit period, whereby said certain time is any given time after the beginning of each successive bit periods.

13. The system defined in claim 12, c. wherein said transponder means includes receiver means for receiving said first signal and said second signal, data code means coupled to said receiver means and actuated by each receipt of either said first signal or said second signal for supplying in order each time it is actuated the next individual bit of a data binary code, and transmitting means coupled to said receiving means and said data Code means for transmitting alternatively a fifth signal, a sixth signal, a seventh signal or an eighth signal, said fifth signal being transmitted only in response to the receipt of said first signal and said supplied bit manifesting a given binary value, said sixth signal being transmitted only in response to the receipt of said first signal and said supplied bit manifesting a binary value opposite to said given binary value, said seventh signal being transmitted only in response to the receipt of said second signal and said supplied bit manifesting a given binary value and said eighth signal being transmitted only in response to the receipt of said second signal and said supplied bit manifesting a binary value opposite to said given binary value, whereby said third signal is constituted of said fifth signal or said sixth signal and said fourth signal is constituted of said seventh signal or said eighth signal;

and d. wherein said given type station further includes fifth means responsive to the receipt of either said fifth signal or said seventh signal for reproducing a data code bit manifesting said given binary value and responsive to the receipt of either said sixth signal or said eighth signal for reproducing a data code bit manifesting a binary value opposite to said given binary value, and sixth means coupled to said fourth means and said fifth means for deriving the range from said given type station to a selected other station and reading out only the data code received from said selected other station.

14. The system defined in claim 13, wherein said given type station and said other stations are each on moving craft, and wherein said sixth means includes seventh means for automatically selecting a station in response to its range from said given type station becoming less than a given distance.

15. The system defined in claim 13, wherein said first, second, fifth, sixth, seventh and eighth signals, respectively, are bursts of electromagnetic waves occurring respectively at first, second, third, fourth, fifth and sixth predetermined frequencies, all of which are different from each other, the time duration of each burst being an insignificant portion of a bit period.

16. The system defined in claim 13, wherein said binary data code includes a given number of bits, wherein said data code means is cyclically operated to cause the repetitive transmission of said binary data code from said transponder means and wherein said sixth means includes cyclically-operated storage means for separately integrating each respective ordinal bit from a predetermined number of consecutive cycles of said binary data code received from said selected other station and thereafter reading out said integrated binary data code in the proper order from said storage means.

17. The system defined in claim 16, wherein said binary data code includes a unique fixed sync character code occupying predetermined ordinal bit positions in said binary data code, and wherein said storage means includes collating means responsive to said sync character code for controlling the reading out of said integrated binary data code from said storage means in the proper order.

18. A given type station adapted for use in a discriminating signaling system including a plurality of stations, said given type station comprising first means for generating a certain preselected binary code over an interval consisting of a predetermined plural number of successive bit periods each of which manifests either the binary value A or the binary value A in accordance with said code, second means coupled to said first means for transmitting a first signal only during each of those bit periods having the binary value A and for transmitting a second signal only during each of those bit periods having the binary value A, third means for receiving a third signal and a fourth signal, and fourth means coupled to said first and third means for deriving an output signal substantially in accordance with the following correlation function:

19. The station defined in claim 18, wherein said fourth means comprises a storage means for storing a signal proportional to the sum of a presently applied input signal and the signal which was stored therein an interval therebefore equal to one bit period, means including switch means coupled to said first and third means effective during each bit period manifesting the binary value A for applying said third signal with a certain phase and said fourth signal with a phase opposite to said certain phase as said input signal to said storage means and effective during each bit period manifesting the binary value A for applying said third signal with said phase opposite to said certain phase and said fourth signal with said certain phase as said input signal to said storage means, and means for effecting the readout of said storage means after n consecutive bit periods.

20. The station defined in claim 19, wherein said storage means is a recirculating delay line having a loop delay of one bit period.

21. The station defined in claim 18, wherein said fourth means comprises two separate storage means each of which store a signal proportional to the sum of a presently applied input signal thereto and the signal which was stored therein an interval therebefore equal to one bit period, means including switch means, coupled to said first and third means effective during each bit period manifesting the binary value A for applying said third signal as the input signal to one of said storage means and applying said fourth signal as the input signal to the other of said storage means and effective during each bit period manifesting the binary value A for applying said fourth signal as the input signal to said one of said storage means and said third signal as the input signal to said other of said storage means, means for effecting the readout of both said storage means after n consecutive bits, and means for producing an output signal equal to the difference in the respective outputs from said two storage means.

22. The station defined in claim 18 wherein said correlation function applies at all times within a bit period, whereby said certain time is any given time after the beginning of each successive bit period.

23. The station defined in claim 22, wherein said third means includes fifth means for receiving either a fifth signal or a sixth signal as said third signal for receiving either a seventh signal or an eighth signal as said fourth signal, and sixth means responsive to the receipt of either said fifth or said seventh signal for deriving a bit of a binary data code message manifesting a given binary value and the receipt of either said sixth or said eighth signal for deriving a bit of said binary data code message manifesting a binary value opposite to said given binary value, and wherein said given type station further includes seventh means coupled to said fourth means and said sixth means for deriving the range to a selected one of other stations which are transmitting messages in said binary data code, and for reading out only the data code received from said selected one of said other stations.

24. The station defined in claim 23, wherein said binary code message consists of a predetermined number of bits which are transmitted in order repeatedly, and wherein said seventh means includes eighth means for integrating the respective corresponding ordinal bits of a given number of consecutive repetitions of said message and ninth means for reading out the bits of said binary code message in the proper order in response to the completion of said given number of consecutive repetitions.