System and method for communicating low data rate information with a radar system

• US 7,769,105 B1
• Filed: 11/03/2006
• Issued: 08/03/2010
• Est. Priority Date: 11/03/2005
• Status: Active Grant

• Current Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: L-3 Communications Corporation (L3Harris Technologies, Inc.)
• Inventors: Boesch, James J., Robbins, David H., Thomson, Larry S., McIntire, William K.
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Perez; James M
• Application Number:
  US11/592,535
• Time in Patent Office: 1,369 Days
• Field of Search: 375/138, 375/140, 375/131, 375146-147, 375259-260, 375/295, 375/309, 375/316, 375/322, 375/324, 375/328, 375/338, 375/343, 375/346, 375/351, 342 62- 63, 342 52- 58, 342/60
• US Class Current: 375/309
• CPC Class Codes: G01S 13/90 using synthetic aperture techniques , e.g. synthetic aperture radar [SAR] techniques
• CPC Class Codes: G01S 7/006 using shared front-end circuitry, e.g. antennas G01S13/765, G01S13/825 take precedence

Abstract

A method for transmitting low data rate symbols from a burst radar transceiver is disclosed. The method includes dividing a symbol having a symbol period into a plurality of symbol sections. Each symbol section has a symbol section interval that is less than or equal to a burst interval of the radar transceiver. At least two symbol sections can be transmitted with the burst radar transceiver. Symbol energy can be accumulated from the at least two symbol sections at the communications terminal. Information in the received symbol sections can be identified based on characteristics of the accumulated symbol energy.

Claims

1. A method for transmitting low data rate symbols from a burst radar transceiver to a communications terminal, the symbols having information encoded therein, wherein the burst radar transceiver has a burst period including a burst interval and an inter-burst interval, the method comprising:

dividing a symbol having a symbol period into a plurality of symbol sections, wherein each of the symbol sections has a symbol section interval that is less than or equal to the burst interval;

modulating the symbol sections that occur during the burst interval onto a radar burst signal to form modulated radar bursts;

transmitting the modulated radar bursts;

discarding the symbol sections that occur during the inter-burst interval;

receiving the modulated radar bursts at the communications terminal;

accumulating symbol energy at the communications terminal from the modulated radar bursts to form an accumulated symbol energy; and

identifying the information in the symbol based on a characteristic of the accumulated symbol energy.

2. A method as in claim 1, wherein dividing the symbol further comprises dividing the symbol into a plurality of symbol sections prior to transmitting the symbol sections.

3. A method as in claim 1, wherein dividing the symbol further comprises dividing the symbol into a plurality of symbol sections using the radar transceiver, wherein the transceiver is configured to continuously accept the symbol and transmit sections of the symbol that occur during the burst period.

4. A method as in claim 1, further comprising blanking a communications terminal receiver in the communications terminal between reception of burst intervals to reduce noise in the communications terminal receiver due to at least one of interference between the communications terminal receiver and a communications terminal transmitter, thermal noise, and noise due to interference from other sources.

5. A method as in claim 4, further comprising blanking the communications terminal receiver using at least one of a physical switch, an electrical means, and a software means.

6. A method as in claim 1, wherein accumulating symbol energy further comprises accumulating symbol energy at the communications terminal for a plurality of burst radar transceiver burst periods using an integrator.

7. A method as in claim 6, further comprising freezing the integrator during the inter-burst interval to reduce noise received between the symbol sections.

8. A method as in claim 1, wherein accumulating symbol energy further comprises accumulating symbol energy at the communications terminal wherein the symbol sections that occur during the burst interval are coupled to a sequential burst radar transmission.

9. A method as in claim 1, wherein accumulating symbol energy further comprises accumulating symbol energy at the communications terminal wherein the symbol sections that occur during the burst interval are coupled to every Nth burst radar transmission, where N is a positive integer.

10. A method as in claim 1, wherein accumulating symbol energy further comprises accumulating symbol energy at the communications terminal wherein the symbol sections that occur during the burst interval are coupled to a burst radar transmission at irregular intervals.

11. A method as in claim 1, further comprising encoding the symbol with forward error correction prior to dividing the symbol into the plurality of symbol sections.

12. The method of claim 1, wherein the symbol timing is asynchronous relative to the burst interval and the inter-burst interval.

13. A means for transmitting low data rate data from a burst radar transceiver to a communications terminal, wherein the burst radar transceiver has a burst period including a burst interval and an inter-burst interval, comprising:

a means for dividing a symbol having a symbol period into a plurality of symbol sections, wherein each symbol section has a symbol section interval that is less than or equal to the burst interval;

a means for modulating the symbol sections that occur during the burst interval onto a radar burst signal to form modulated radar bursts;

a means for transmitting the modulated radar bursts, wherein symbol sections that occur during the inter-burst interval are discarded;

a means for receiving the modulated radar bursts at the communications terminal;

a means for accumulating symbol energy at the communications terminal from the received radar bursts; and

a means for identifying the information in the symbol based on a characteristic of the accumulated symbol energy.

14. A method for receiving at a receiver low data rate symbols transmitted from a burst radar transceiver, wherein the burst radar transceiver has a burst period including a burst interval and an inter-burst interval, the symbols having information encoded therein, the method comprising:

accepting modulated radar bursts at the receiver, wherein the modulated radar bursts encode a symbol, and the symbol has been divided into a plurality of symbol sections and each of the symbol sections that occur during the burst interval are modulated onto the radar burst and each of the symbol sections that occur during the inter-burst interval are discarded prior to transmission;

accumulating symbol energy of the symbol sections that occur during the burst interval over approximately a received symbol period of the low data rate symbols to form an accumulated symbol energy; and

identifying the encoded information based on a characteristic of the accumulated symbol energy.

15. A method as in claim 14, wherein the symbol sections have a symbol section interval less than the burst interval.

16. A method as in claim 14, wherein accumulating symbol energy further comprises accumulating symbol energy of the symbol sections at the receiver for approximately a received symbol period, wherein the received symbol period is approximately equal to P radar burst periods, where P is the number of symbol sections.

17. A method as in claim 14, wherein accumulating symbol energy further comprises accumulating symbol energy of the symbol sections for approximately the received symbol period, wherein the received symbol period is approximately equal to a transmitted symbol period.

18. The method of claim 14, wherein the receive symbol period is asynchronous relative to the inter-symbol section intervals.

19. A system for transmitting low data rate symbols from a burst radar transceiver to a communications terminal, the symbols having information encoded therein, wherein the burst radar transceiver has a burst period including a burst interval and an inter-burst interval, comprising:

a symbol divider configured to divide a symbol having a symbol period into a plurality of symbol sections, wherein each of the symbol sections has a symbol section interval that is less than or equal to the burst interval;

a modulator coupled to the burst radar transceiver, the modulator configured to modulate the symbol sections that occur during the burst interval onto a radar burst signal to form modulated radar burst signals and to discard the symbol sections that occur during the inter-burst interval;

wherein the burst radar transceiver is configured to transmit each of the modulated radar burst signals during the burst interval;

a communications terminal configured to receive the modulated radar burst signals from the burst radar transceiver; and

an integrator coupled to the communications terminal and configured to accumulate symbol energy from the plurality of symbol sections for approximately a received symbol period.

20. A system as in claim 19, wherein the communications terminal includes a transmitter and a receiver.

21. A system as in claim 20, further comprising a blanking device coupled to the communications terminal receiver, wherein the blanking device is configured to attenuate a signal to the receiver using at least one of a physical switch and an electronic switch.

22. A system as in claim 21, wherein the blanking device is configured to substantially eliminate digital data received at the communications terminal between burst intervals.

23. A system as in claim 20, wherein the receiver is further configured to identify information in the symbol based on a characteristic of the accumulated symbol energy.

24. A system as in claim 20, further comprising a phase memory configured to enable the receiver to ensure, at an end of a first burst period of the received signal, a correct phase at a beginning of a second burst period separated from the first burst period by the inter-burst interval.

25. A system as in claim 19, wherein the burst radar transceiver includes a transmitter and a receiver.

26. A system as in claim 19, wherein the received symbol period is approximately equal to P radar burst periods, where P is the number of symbol sections.

27. A system as in claim 19, wherein the received symbol period is approximately equal to the symbol period prior to being transmitted.

28. A system as in claim 19, wherein the symbol is divided into at least 2 symbol sections.

29. A method of communicating low data rate symbols with a burst radar transceiver, wherein the burst radar transceiver has a burst period comprising a burst interval and an inter-burst interval, the method comprising:

accepting symbols having a symbol period substantially greater than the burst period;

modulating portions of the symbols that occur during the burst-interval onto a radar burst signal to form modulated radar bursts;

discarding portions of the symbols that occur during the inter-burst interval; and

transmitting the modulated radar bursts.

30. The method of claim 29, wherein the symbol period is asynchronous relative to the burst period.