Constant false alarm rate detection in pulsed LiDAR systems

1. A light detection and ranging (LiDAR) system comprising:

a transmitter configured to transmit light pulses to a field of view of the LiDAR system; and

a receiver comprising a matched filter, the receiver configured to:

generate, in an operation condition of the LiDAR system,

a noise signal vector including noise data in the operation condition;

a transmitted signal vector corresponding to a light pulse transmitted by the transmitter; and

a returned signal vector corresponding to returned light received by the receiver;

determine a covariance matrix of the noise signal vector;

determine coefficients of the matched filter based on the transmitted signal vector and the covariance matrix of the noise signal vector;

filter, using the matched filter with the determined coefficients, the returned signal vector;

detect an object in the field of view of the LiDAR system based on identifying, in the returned signal vector filtered by the matched filter, a pulse having a peak higher than a threshold value;

determine a noise power of the noise data based on the noise signal vector;

determine a transmitted signal energy of the light pulse transmitted by the transmitter based on the transmitted signal vector; and

determine the threshold value based on a constant false alarm rate (CFAR), the noise power of the noise data, and the transmitted signal energy, wherein the receiver is configured to determine the threshold value by:

computing a square root of a product of the noise power of the noise data and the transmitted signal energy;

determining an inverse Q function of the CFAR; and

determining, as the threshold value, a product of the square root and the inverse Q function of the CFAR.

2. The LiDAR system of claim 1 , wherein the receiver is further configured to:

determine, based on a first time corresponding to a location of the identified pulse in the returned signal vector and a second time when the light pulse is transmitted by the LiDAR system, a distance between the LiDAR system and the detected object.

3. The LiDAR system of claim 1 , wherein the receiver is configured to determine the coefficients of the matched filter by:

determining an inverse matrix of the covariance matrix;

computing a product of the inverse matrix and the transmitted signal vector; and

assigning values in the product to the coefficients of the matched filter.

4. The LiDAR system of claim 1 , wherein the receiver is configured to determine the coefficients of the matched filter by:

determining a whitening matrix based on the covariance matrix;

calculating a product of the whitening matrix and the transmitted signal vector; and

assigning values in the product to the coefficients of the matched filter.

5. The LiDAR system of claim 1 , wherein the receiver is further configured to:

determine a bias of the noise data based on the noise signal vector; and

remove the bias from the returned signal vector,

wherein the receiver is configured to filter the returned signal vector by convolving the coefficients of the matched filter and the returned signal vector with the bias removed.

6. The LiDAR system of claim 1 , wherein the receiver is configured to generate the noise signal vector in a time window before receiving the returned light.

7. The LiDAR system of claim 1 , wherein the noise data includes interference data.

8. The LiDAR system of claim 1 , wherein the matched filter includes a discrete-time finite impulse response filter.

9. A method comprising:

generating, by a receiver of a light detection and ranging (LiDAR) system under an operation condition,

a noise signal vector including noise data under the operation condition;

a transmitted signal vector corresponding to a light pulse transmitted by the LiDAR system to a field of view of the LiDAR system; and

a returned signal vector corresponding to returned light detected by the LiDAR system;

determining a covariance matrix of the noise signal vector;

determining coefficients of a matched filter based on the transmitted signal vector and the covariance matrix of the noise signal vector;

filtering the returned signal vector using the matched filter with the determined coefficients; and

detecting an object in the field of view of the LiDAR system based on identifying, in the returned signal vector filtered by the matched filter, a pulse having a peak higher than a threshold value;

determining a noise power of the noise data based on the noise signal vector;

determining a transmitted signal energy of the light pulse transmitted by the transmitter based on the transmitted signal vector; and

determining the threshold value based on a constant false alarm rate (CFAR), the noise power of the noise data, and the transmitted signal energy, wherein the receiver is configured to determine the threshold value by:

computing a square root of a product of the noise power of the noise data and the transmitted signal energy;

determining an inverse Q function of the CFAR; and

determining, as the threshold value, a product of the square root and the inverse Q function of the CFAR.

10. The method of claim 9 , further comprising:

determining, based on a first time corresponding to a location of the identified pulse in the returned signal vector and a second time when the light pulse is transmitted by the LiDAR system, a distance between the LiDAR system and the detected object.

11. The method of claim 9 , wherein determining the coefficients of the matched filter comprises:

determining a whitening matrix based on the covariance matrix;

calculating a product of the whitening matrix and the transmitted signal vector; and

assigning values in the product to the coefficients of the matched filter.

12. A receiver for a light detection and ranging (LiDAR) system, the receiver comprising:

a noise parameter extraction unit configured to:

receive a noise signal vector including noise data in an operation condition of the LiDAR system; and

determine a covariance matrix of the noise signal vector;

a matched filter configured to:

receive a returned signal vector corresponding to returned light received by the LiDAR system; and

filter the returned signal vector;

a matched filter coefficient determination unit configured to:

receive a transmitted signal vector corresponding to a light pulse transmitted by the LiDAR system; and

determine coefficients of the matched filter based on the transmitted signal vector and the covariance matrix of the noise signal vector; and

an object detection unit configured to detect an object in a field of view of the LiDAR system based on identifying, in the returned signal vector filtered by the matched filter, a pulse having a peak higher than a threshold value.

13. The receiver of claim 12 , further comprising a threshold determination unit configured to:

determine a noise power of the noise data based on the noise signal vector;

determine a transmitted signal energy of the light pulse transmitted by the LiDAR system based on the transmitted signal vector; and

determine the threshold value based on a constant false alarm rate (CFAR), the noise power of the noise data, and the transmitted signal energy.

14. The receiver of claim 13 , wherein the threshold determination unit is configured to determine the threshold value by:

computing a square root of a product of the noise power of the noise data and the transmitted signal energy;

determining an inverse Q function of the CFAR; and

determining, as the threshold value, a product of the square root and the inverse Q function of the CFAR.

15. The receiver of claim 12 , wherein the matched filter coefficient determination unit is configured to determine the coefficients of the matched filter by:

determining a whitening matrix based on the covariance matrix;

calculating a product of the whitening matrix and the transmitted signal vector; and

assigning values in the product to the coefficients of the matched filter.

16. The receiver of claim 12 , wherein the object detection unit is further configured to:

determine, based on a first time corresponding to a location of the identified pulse in the returned signal vector and a second time when the light pulse is transmitted by the LiDAR system, a distance between the LiDAR system and the detected object.