Near-range interference mitigation for automotive radar system
A signal processing system and method includes a first input configured to receive an input signal range profile. The input signal range profile includes near-range interference signals. A second input is configured to receive a reference signal range profile; and a processor is configured to perform steps including: executing a recursive least squares operation to determine coefficient values of a finite impulse response (FIR) filter, wherein the coefficient values are selected to minimize a difference between the input signal range profile and the reference signal range profile when the reference signal range profile is filtered through the FIR filter to generate a filtered reference signal range profile, and subtracting the filtered reference signal range profile from the input signal range profile to remove the near-range interference signals from the input signal range profile.
1 . An automotive radar system, comprising:
at least one transmitter and at least one receiver, wherein the at least one transmitter and the at least one receiver are configured to transmit and receive radar signals, wherein the at least one transmitter and the at least one receiver are coupled to a vehicle; and
an automotive radar processor configured to:
receiving, from the at least one receiver, a received radar signal;
convert the received radar signal into an input signal range profile, wherein the input signal range profile includes near-range interference signals generated by reflections from a bumper of the vehicle and system component spill-over effects;
determine a reference signal;
convert the reference signal into a reference signal range profile by:
applying a tapering window to the reference signal to generate a tapered reference signal; and
applying a matched filter to the tapered reference signal to generate the reference signal range profile;
execute a recursive least squares operation to determine coefficient values of a finite impulse response (FIR) filter, wherein the coefficient values are selected to minimize an error between the input signal range profile and the reference signal range profile when the reference signal range profile is filtered through the FIR filter;
apply the FIR filter with the coefficient values to the reference signal range profile to determine a filtered reference signal range profile; and
subtract the filtered reference signal range profile from the input signal range profile to remove the near-range interference signals from the input signal range profile.
2 . The automotive radar system of claim 1 , wherein the reference signal has a predetermined value and the automotive radar processor is configured to perform the step of determining the reference signal by retrieving the reference signal from a memory system accessible to the automotive radar processor.
3 . The system of claim 1 , wherein the automotive radar processor is configured to perform the step of executing a fast-time matched filter to perform range compression on the received radar signal before converting the received radar signal into the input signal range profile.
4 . The system of claim 3 , wherein the automotive radar processor is configured to perform the step of executing a slow-time frequency Fourier transform to perform Doppler compression on the received radar signal before converting the received radar signal into the input signal range profile.
5 . The automotive radar system of claim 1 , wherein the tapering window is a Taylor tapering window or a Blackman tailoring window.
6 . The automotive radar system of claim 1 , wherein a number of coefficients n in the FIR filter is at least partially determined by a distance between at least one of the at least one transmitter and the at least one receiver and an edge of the bumper of the vehicle.
7 . The automotive radar system of claim 6 , wherein the number of coefficients n in the FIR filter is determined as a smallest integer that is larger than a ceiling of
N
=
R
e
δ
r
where N is a number of samples of the input signal range profile, R e is the distance, and δr is a range cell.
8 . The automotive radar system of claim 7 , wherein the number of coefficients n in the FIR filter is fewer than the number of samples of the input signal range profile N divided by
4
(
n
<
N
4
)
.
9 . The automotive radar system of claim 1 , wherein the automotive radar system is a frequency-modulated continuous-wave (FMCW) radar system.
10 . A signal processing system, comprising:
a first input configured to receive an input signal range profile, the input signal range profile including near-range interference signals;
a second input configured to receive a reference signal range profile; and
a processor configured to:
execute a recursive least squares operation to determine coefficient values of a finite impulse response (FIR) filter, wherein the coefficient values are selected to minimize a difference between the input signal range profile and the reference signal range profile when the reference signal range profile is filtered through the FIR filter to generate a filtered reference signal range profile; and
subtract the filtered reference signal range profile from the input signal range profile to remove the near-range interference signals from the input signal range profile.
11 . The signal processing system of claim 10 , wherein a number of coefficients n in the FIR filter at least partially determined by a distance between at least one a transmitter of a radar system and a receiver of the radar system and an edge of a bumper of a vehicle.
12 . The signal processing system of claim 11 , wherein the number of coefficients n in the FIR filter is determined as a smallest integer that is larger than a ceiling of
N
=
R
e
δ
r
where N is a number of samples of the input signal range profile, R e is the distance, and δr is a range cell.
13 . The signal processing system of claim 12 , wherein the number of coefficients n in the FIR filter in fewer than the number of samples of the input signal range profile N divided by
4
(
n
<
N
4
)
.
14 . A method, comprising:
converting a received radar signal into an input signal range profile;
applying a tapering window to a reference signal to generate a tapered reference signal;
applying a fast Fourier transform to the tapered reference signal to generate a reference signal range profile;
executing a recursive least squares operation to determine coefficient values of a finite impulse response (FIR) filter, wherein the coefficient values are selected to minimize a difference between the input signal range profile and the reference signal range profile when the reference signal range profile is filtered through the FIR filter to generate a filtered reference signal range profile; and
subtracting the filtered reference signal range profile from the input signal range profile to remove near-range interference signals from the input signal range profile.
15 . The method of claim 14 , wherein the reference signal has a predetermined value and further comprising retrieving the reference signal from a memory system.
16 . The method of claim 14 , further comprising executing a fast-time frequency Fourier transform to perform range compression on the received radar signal before converting the received radar signal into the input signal range profile.
17 . The method of claim 16 , further comprising executing a slow-time frequency Fourier transform to perform Doppler compression on the received radar signal before converting the received radar signal into the input signal range profile.
18 . The method of claim 14 , wherein the tapering window is a Taylor tapering window or a Blackman tailoring window.
19 . The method of claim 14 , further comprising determining a number of coefficients n in the FIR filter based upon a distance between at least one of a transmitter and a receiver and an edge of a bumper of a vehicle.
20 . The method of claim 19 , further comprising determining the number of coefficients n using a smallest integer that is larger than a ceiling of
N
=
R
e
δ
r
where N is a number of samples of the input signal range profile, R e is the distance, and δr is a range cell.