System and method for calculating a binary cross-correlation

Patent metadata

Field	Value
Publication number	US-11480678-B2
Application number	US-202016863484-A
Country	US
Kind code	B2
Filing date	Apr 30, 2020
Priority date	Apr 30, 2020
Publication date	Oct 25, 2022
Grant date	Oct 25, 2022

Abstract

A method for operating a laser detection and ranging system. In some embodiments, the method includes transmitting a plurality of laser pulses, each at a respective one of a plurality of pulse transmission times; detecting a plurality of return pulses, each at a respective one of a plurality of return pulse times; forming a first time difference, the first time difference being the difference between a first return pulse time of the plurality of return pulse times and a first pulse transmission time of the plurality of pulse transmission times; and incrementing a first element of a first array, the first element of the first array having an index based on the first time difference.

First claim

What is claimed is:

1. A method for operating a laser detection and ranging system, the method comprising:
transmitting a plurality of laser pulses, each at a respective one of a plurality of pulse transmission times;
detecting a plurality of return pulses, each at a respective one of a plurality of return pulse times;
forming a first time difference, the first time difference being a difference between a first return pulse time of the plurality of return pulse times and a first pulse transmission time of the plurality of pulse transmission times;
forming a first element of a cross-correlation array based on the first time difference;
incrementing the first element of the cross-correlation array by n to form a second element of the cross-correlation array, where n is an integer based on a second time difference between a second pulse transmission time and a second return pulse time;
forming a first index to the first element of the cross-correlation array based on the first time difference;
forming a second index to the second element of the cross-correlation array based on the second time difference; and
estimating a range to a target based on the cross-correlation, the first index and the second index.

2. The method of claim 1 , wherein the first element of the cross-correlation array has a size of n memory words.

3. The method of claim 1 , further comprising calculating a plurality of time differences including the first time difference and the second time difference, the calculating of the plurality of time differences comprising calculating all time differences between a first subset of the pulse transmission times and a first subset of the return pulse times.

4. The method of claim 3 , further comprising calculating all time differences between a second subset of the pulse transmission times and a second subset of the return pulse times, wherein:
a pulse transmission time of the second subset of the pulse transmission times is greater than a pulse transmission time of the first subset of the pulse transmission times, and
a pulse transmission time of the second subset of the return pulse times is greater than a pulse transmission time of the first subset of the return pulse times.

5. The method of claim 1 , wherein:
the transmitting of the plurality of laser pulses comprises transmitting a first burst of laser pulses of the plurality of laser pulses, waiting during an inter-burst interval, and transmitting a second burst of laser pulses of the plurality of laser pulses;
each of the pulse transmission times of the first subset of the pulse transmission times is a pulse transmission time of a pulse of the first burst; and
each of the pulse transmission times of the second subset of the pulse transmission times is a pulse transmission time of a pulse of the second burst.

6. The method of claim 1 , further comprising allocating a region of memory for the cross-correlation array, the region of memory having a size based on the difference between:
the difference between an earliest return pulse time of the plurality of return pulse times and a latest pulse transmission time of the plurality of pulse transmission times; and
the difference between a latest return pulse time of the plurality of return pulse times and an earliest pulse transmission time of the plurality of pulse transmission times.

7. The method of claim 1 , further comprising:
estimating a range to a target, and
allocating a region of memory for the cross-correlation array, the region of memory having a size based on an uncertainty in the estimated range to the target.

8. The method of claim 7 , further comprising multiplying each element of the cross-correlation array by an attenuation factor, the attenuation factor being a positive number less than 1.

9. A laser detection and ranging system, comprising:
a laser transmitter;
a receiver; and
a processing circuit,
the processing circuit being configured to:
transmit, through the transmitter, a plurality of laser pulses, each at a respective one of a plurality of pulse transmission times;
detect, using the receiver, a plurality of return pulses, each at a respective one of a plurality of return pulse times;
form a first time difference, the first time difference being a difference between a first return pulse time of the plurality of return pulse times and a first pulse transmission time of the plurality of pulse transmission times;
form a first element of a cross-correlation array based on the first time difference;
increment the first element of the cross-correlation array by n to form a second element of the cross-correlation array, where n is an integer based on a second time difference between a second pulse transmission time and a second return pulse time;
form a first index to the first element of the cross-correlation array based on the first time difference;
form a second index to the second element of the cross-correlation array based on the second time difference; and
estimate a range to a target based on the cross-correlation, the first index and the second index.

10. The system of claim 9 , wherein the first element of the first array has a size of n memory words, and the index of the second element of the first array equals n times the second time difference plus the offset.

11. The system of claim 9 , wherein the processing circuit is further configured to calculate a plurality of time differences including the first time difference, the calculating of the plurality of time differences comprising calculating all time differences between a first subset of the pulse transmission times and a first subset of the return pulse times.

12. The system of claim 11 , wherein the processing circuit is further configured to calculate all time differences between a second subset of the pulse transmission times and a second subset of the return pulse times, wherein:
a pulse transmission time of the second subset of the pulse transmission times is greater than a pulse transmission time of the first subset of the pulse transmission times, and
a pulse transmission time of the second subset of the return pulse times is greater than a pulse transmission time of the first subset of the return pulse times.

13. The system of claim 12 , wherein:
the transmitting of the plurality of laser pulses comprises transmitting a first burst of laser pulses of the plurality of laser pulses, waiting during an inter-burst interval, and transmitting a second burst of laser pulses of the plurality of laser pulses;
each of the pulse transmission times of the first subset of the pulse transmission times is a pulse transmission time of a pulse of the first burst; and
each of the pulse transmission times of the second subset of the pulse transmission times is a pulse transmission time of a pulse of the second burst.

14. The system of claim 9 , wherein the processing circuit is further configured to allocate a region of memory for the first array, the region of memory having a size based on the difference between:
the difference between an earliest return pulse time of the plurality of return pulse times and a latest pulse transmission time of the plurality of pulse transmission times; and
the difference between a latest return pulse time of the plurality of return pulse times and an earliest pulse transmission time of the plurality of pulse transmission times.

15. The system of claim 9 , wherein the processing circuit is further configured to:
estimate a range to a target, and
allocate a region of memory for the first array, the region of memory having a size based on an uncertain

Assignees

• Raytheon Co

Inventors

• Greenberg Adam Hodge
• Marcus Eran

Classifications

• G01S17/10 Primary

  using transmission of interrupted, pulse-modulated waves (determination of distance by phase measurements G01S17/32) · CPC title

• G01S7/484

  Transmitters · CPC title

• G01S7/4865 Primary

  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

• G01S7/4861

  Circuits for detection, sampling, integration or read-out · CPC title

• G01S7/487

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