FMCW radar signal processing for distance estimation
A method and a Frequency-Modulated Continuous-Wave (FMCW) radar sensor are disclosed for estimating the distance to a target. The sensor comprises a transmitter, a receiver, and a signal processor. The receiver obtains a time-domain in-phase (I) signal and/or a quadrature-phase (Q) signal based on an echo of an emitted frequency-modulated wave. The signal processor is configured to isolate a segment of the time-domain signal, such as a signal peak between two local minima, and extract a waveform metric directly from the isolated segment. A predetermined function, such as a regression model, defines a mapping between a plurality of such waveform metrics and corresponding distance values. The processor inputs the extracted waveform metric into the predetermined function to receive a distance, thereby estimating the target's distance without requiring a frequency-domain transformation of the echo signal. The predetermined function may be generated by correlating waveform metrics acquired at known distances.
1 . A method for estimating a distance between a Frequency-Modulated Continuous-Wave (FMCW) radar sensor and a target, the FMCW radar sensor comprising a transmitter, a receiver and a signal processor, the method comprising:
emitting, by the transmitter, a radio wave, wherein the radio wave frequency is modulated over time;
obtaining, by the receiver, during said emitting of the radio wave, a time-domain in-phase signal and/or a time-domain quadrature-phase signal indicative of amplitude and phase information of an echo of the emitted radio wave;
selecting for processing, by the signal processor, the time-domain in-phase signal and/or the time-domain quadrature-phase signal;
isolating, by the signal processor, a segment of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal;
extracting, by the signal processor, a waveform metric from the isolated segment of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal;
obtaining, by the signal processor, a predetermined function defining a mapping between a plurality of waveform metrics and a corresponding plurality of distance values;
inputting, by the signal processer, the extracted waveform metric to the predetermined function; and
receiving, by the signal processor, a distance outputted by the predetermined function.
2 . The method according to claim 1 , wherein the isolated segment comprises a portion of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal located between a first local minimum and a second subsequent local minimum.
3 . The method according to claim 2 , wherein the isolated segment comprises a signal peak.
4 . The method according to claim 1 , wherein the at least one waveform metric comprises at least a peak center location from the isolated segment.
5 . The method according to claim 1 , wherein the predetermined function comprises a regression model.
6 . The method according to claim 1 , wherein the predetermined function comprises a polynomial regression-based function.
7 . The method according to claim 1 , wherein the method comprises:
selecting for processing, by the signal processor, the time-domain in-phase signal or time-domain the quadrature-phase signal.
8 . The method according to claim 1 , wherein the obtained predetermined function has been determined by:
acquiring, by the signal processer, a plurality of extracted waveform metrics and a plurality of known distance value corresponding to the plurality of extracted waveform metrics;
determining, by the signal processer, a predetermined function by correlating the plurality of acquired waveform metrics with the corresponding plurality of known distances.
9 . A method for calibrating a Frequency-Modulated Continuous-Wave (FMCW) radar sensor, the FMCW radar sensor comprising a transmitter, a receiver and a signal processor, the method comprises acquiring a plurality of waveform metrics corresponding to a plurality of known distances to a target, wherein the method comprises, for each distance among the plurality of known distances:
emitting, by the transmitter, a radio wave, wherein the radio wave frequency is modulated over time;
obtaining, by the receiver, during said emitting of the radio wave, a time-domain in-phase signal and/or a time-domain quadrature-phase signal indicative of amplitude and phase information of an echo of the emitted radio wave;
selecting for processing, by the signal processor, the time-domain in-phase signal and/or the time-domain quadrature-phase signal;
isolating, by the signal processor, a segment of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal;
extracting, by the signal processor, a waveform metric from the isolated segment of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal;
wherein the method further comprises:
determining, by the signal processer, a predetermined function by correlating the plurality of acquired waveform metrics with the corresponding plurality of known distances.
10 . The method according to claim 9 , wherein the isolated segment comprises a portion of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal located between a first local minimum and a second subsequent local minimum.
11 . The method according to claim 10 , wherein the isolated segment comprises a signal peak.
12 . The method according to claim 9 , wherein the at least one waveform metric comprises at least a peak center location from the isolated segment.
13 . The method according to claim 9 , wherein the predetermined function is a regression model.
14 . The method according to claim 9 , wherein the method comprises, for each distance among the plurality of known distances:
selecting for processing, by the signal processor, the time-domain in-phase signal or time-domain the quadrature-phase signal.
15 . The method according to claim 9 , wherein the isolated segment comprises a portion of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal located between a first local minimum and a second subsequent local minimum, and wherein the isolated segment comprises a signal peak.
16 . A Frequency-Modulated Continuous-Wave FMCW radar sensor, the sensor comprising:
a transmitter configured to emit a radio wave, wherein the radio wave frequency is modulated over time;
a receiver configured to obtain, while the transmitter emits the radio wave, a time-domain in-phase signal and/or the time-domain quadrature-phase signal that is indicative of the amplitude and phase information of an echo of the emitted radio wave; and,
a signal processor operatively connected to the receiver, the signal processor being configured to:
select for processing the time-domain in-phase signal and/or the time-domain quadrature-phase signal;
isolate a segment within the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal;
extract a waveform metric from the isolated segment of the selected time-domain in-phase signal and/or the time-domain quadrature-phase signal; and
obtaining, by the signal processor, a predetermined function defining a mapping between a plurality of waveform metrics and a corresponding plurality of distance values;
obtaining, by the signal processor, a predetermined function defining a mapping between a plurality of waveform metrics and a corresponding plurality of distance values;
inputting, by the signal processer, the extracted waveform metric to the predetermined function;
receiving, by the signal processor, a distance outputted by the predetermined function.
17 . The FMCW radar sensor according to claim 16 , wherein the at least one waveform metric comprises at least a peak center location from the isolated segment.
18 . The FMCW radar sensor according to claim 16 , wherein the predetermined function is a regression model.
19 . The FMCW radar sensor according to claim 16 , wherein the method comprises, for each distance among the plurality of known distances:
selecting for processing, by the signal processor, the time-domain in-phase signal or time-domain the quadrature-phase signal.
20 . The FMCW radar sensor according to claim 16 , wherein the obtained predetermined function has been determined by:
acquiring, by the signal processer, a plurality of extracted waveform metrics and a plurality of known distance value corresponding to the plurality of extracted waveform metrics;
determining, by the signal processer, a predetermined function by correlating the plurality of acquired waveform metrics with the corresponding plurality of known distances.