Communication-less bistatic ranging

Patent metadata

Field	Value
Publication number	US-11513218-B2
Application number	US-202016863055-A
Country	US
Kind code	B2
Filing date	Apr 30, 2020
Priority date	Apr 30, 2020
Publication date	Nov 29, 2022
Grant date	Nov 29, 2022

Abstract

A transmitter for communication-less bistatic ranging includes a photon emitter configured to emit a plurality of photons at particular times in a pointing direction, and a processor configured to identify a particular sub-code of a plurality of sub-codes based on a dynamic state of the transmitter, each one of the plurality of sub-codes including a portion of a long optimal ranging code, generate a plurality of encoded pulse timings by dithering pulse timings from a nominal repetition frequency based on the particular sub-code, and control the photon emitter to emit the plurality of photons at the plurality of encoded pulse timings.

First claim

What is claimed is:

1. A transmitter for communication-less bistatic ranging, the transmitter comprising:
a photon emitter configured to emit a plurality of photons at particular times in a pointing direction; and
a processor configured to:
identify a particular sub-code of a plurality of sub-codes based on a dynamic state of the transmitter, each one of the plurality of sub-codes comprising a portion of a long optimal ranging code;
generate a plurality of encoded pulse timings by dithering pulse timings from a nominal repetition frequency based on the particular sub-code; and
control the photon emitter to emit the plurality of photons at the plurality of encoded pulse timings.

2. The transmitter of claim 1 , wherein the long optimal ranging code has auto-correlation side lobes less than or equal to one.

3. The transmitter of claim 1 , wherein each one of the plurality of sub-codes comprises a portion of the long optimal ranging code and shares no more than one element from the long optimal ranging code.

4. The transmitter of claim 1 , wherein each one of the plurality of sub-codes is an optimal ranging code and is mutually orthogonal to other ones of the plurality of sub-codes under cross-correlation.

5. The transmitter of claim 1 , wherein each one of the plurality of sub-codes has auto-correlation side lobes less than or equal to a threshold, and cross-correlation side lobes of pairs of the plurality of sub-codes are less than or equal to the threshold.

6. The transmitter of claim 1 , wherein the plurality of sub-codes are pulse position modulated codes.

7. The transmitter of claim 1 , wherein the dynamic state of the transmitter comprises at least one of a transmitter location, the pointing direction, or a transmission time.

8. The transmitter of claim 1 , wherein, subsequent to controlling the photon emitter to emit the plurality of photons, the controller is configured to control the photon emitter to not transmit any pulses for a period of time corresponding to a length of a single sub-code of the plurality of sub-codes, prior to further emissions by the photon emitter.

9. The transmitter of claim 1 , wherein, subsequent to controlling the photon emitter to emit the plurality of photons, the controller is configured to control the photon emitter to not transmit any pulses for a period of time corresponding to an odd multiple of half of a length of a single sub-code of the plurality of sub-codes, prior to further emissions by the photon emitter.

10. The transmitter of claim 1 , wherein the processor is configured to encode the dynamic state of the transmitter into the pulse timings via a string of one or more sub-codes of the plurality of sub-codes.

11. A receiver for communication-less bistatic ranging, the receiver comprising:
a photodetector configured to receive, and record timing of, incoming photons; and
a processor configured to:
decode an encoded pulse timing of the incoming photons to generate a detected signal;
cross-correlate the detected signal with each one of a plurality of sub-codes to identify a sub-code of the plurality of sub-codes;
calculate a length of a path traversed by the incoming photons from a transmitter to a target and to the photodetector based on a cross-correlation of the detected signal and the identified sub-code;
identify a dynamic state of a transmitter based on the identified sub-code; and
calculate a location of the target based on the length of the path traversed by the incoming photons and the identified dynamic state of the transmitter.

12. The receiver of claim 11 , wherein the photodetector does not have any angular resolution.

13. The receiver of claim 11 , wherein a cross-correlation of the encoded pulse timing and the identified sub-code has a peak power greater than that of the cross-correlation of the encoded pulse timing and any other one of the plurality of sub-codes.

14. The receiver of claim 11 , wherein the dynamic state of the transmitter comprises a transmitter location and a pointing direction of the transmitter at a transmission time of the incoming photons.

15. The receiver of claim 11 , wherein the calculating of the length of the path traversed by the incoming photons comprises:
calculating a time lag associated with a peak of a cross-correlation of the detected signal and the identified sub-code; and
calculating the length of the path traversed by the incoming photons based on the time lag.

16. The receiver of claim 11 , wherein the plurality of sub-codes are common between the receiver and the transmitter.

17. The receiver of claim 11 , wherein each one of the plurality of sub-codes is an optimal ranging code and is mutually orthogonal to other ones of the plurality of sub-codes under cross-correlation.

18. The receiver of claim 11 , wherein each one of the plurality of sub-codes has auto-correlation side lobes less than or equal to a threshold, and cross-correlation side lobes of pairs of the plurality of sub-codes are less than or equal to the threshold.

19. A bistatic ranging system for identifying a location of a target, the bistatic ranging system comprising:
a transmitter comprising:
a photon emitter configured to emit a plurality of photons at particular times in a pointing direction; and
a first processor configured to:
identify a particular sub-code of a plurality of sub-codes based on a dynamic state of the transmitter;
generate a plurality of encoded pulse timings by dithering pulse timings from a nominal repetition frequency based on the particular sub-code; and
control the photon emitter to emit the plurality of photons at the plurality of encoded pulse timings; and

a receiver comprising:
a photodetector configured to receive, and record timing of, incoming photons; and
a second processor configured to:
decode an encoded pulse timing of the incoming photons to generate a detected signal;
cross-correlate the detected signal with each one of a plurality of sub-codes to identify a sub-code of the plurality of sub-codes; and
calculate a location of the target based on a cross-correlation of the detected signal and the identified sub-code.

20. The bistatic ranging system of claim 19 , wherein the transmitter and receiver are geographically separate from one another and have no means of direct communication.

Assignees

• Raytheon Co

Inventors

• Greenberg Adam Hodge
• Marcus Eran

Classifications

• G01S7/487

  Extracting wanted echo signals {, e.g. pulse detection} · CPC title

• G01S7/4811

  common to transmitter and receiver · CPC title

• G01S7/4865

  Time delay measurement, e.g. time-of-flight measurement, time of arrival measurement or determining the exact position of a peak (peak detection in noise, signal conditioning G01S7/487) · CPC title

• G01S17/003 Primary

  Bistatic lidar systems; Multistatic lidar systems · CPC title

• G01S7/4818

  using optical fibres · CPC title