Measurement system, measurement method, and non-transitory computer-readable storage medium

Abstract

A measurement system that determines correspondence between distance and relative velocity with respect to a plurality of targets from a detection signal, includes: a first result acquisition unit (B1) that performs FFT processing on a signal generated based on both in-phase and quadrature components of received light, and acquires a peak frequency (fR) with respect to distance and a peak frequency (fd) with respect to relative velocity as first results; second result acquisition units (B2, B3) that acquire a peak frequency (f) as second results, the peak frequency (f; f1 to fn) being detected by performing FFT processing on at least one of the in-phase component signal and the quadrature component signal; and a combination determination unit (S108) that determines a combination of correspondence between distance and relative velocity based on both the first results and the second results as third results.

Description

Technical Field

[0001] This disclosure relates to measurement systems, measurement methods, and non-transitory computer-readable storage media. Background Technology

[0002] LiDAR (Light Detection and Ranging) is being developed for applications such as ambient light recognition sensors in automobiles and autonomous robots, as well as shape measurement in construction and civil engineering sites. Among LiDAR technologies, frequency-modulated continuous wave (FMCW) type LiDAR enables reduced peak power, expanded dynamic range, and excellent ranging resolution. Therefore, FMCW-based LiDAR is widely used in 3D imaging, weather observation, autonomous navigation, remote sensing, and autonomous driving. For example, phase diversity coherent detection allows for the simultaneous measurement of the intensity and phase of optical signals, thereby enhancing LiDAR performance.

[0003] However, in some applications (e.g., autonomous navigation), the Doppler shift effect is added to the range-related chirp frequency due to target movement; that is, this effect is superimposed on it. In FMCW-LiDAR, triangular waveform modulation is typically used, and attempts are made to measure range and velocity separately. However, in conventional FMCW-LiDAR, to separate range and velocity, both of the following are required: (i) the frequency obtained from the up-chirp modulated by the triangular waveform and (ii) the frequency obtained from the down-chirp modulated by the triangular waveform. Therefore, information about range and velocity cannot be obtained simultaneously at any given time.

[0004] The technology described in Non-Patent Document 1 proposes an FMCW LiDAR based on a phase diversity coherent optical receiver, which enables simultaneous measurement of range and velocity. This LiDAR employs an FMCW method using a subcarrier and generates beat signals to calculate range and velocity by chirping the frequency of the subcarrier and using partially performed heterodyne detection as a reference light. Furthermore, heterodyne detection is performed using coherent detection to separate range and velocity.

[0005] [Non-Patent Document 1] Zhang et al., “Frequency-modulated continuous-wave lidar using a phase-diversity coherent optical receiver for simultaneous ranging and velocimetry”, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL.31, NO.22, Nov 15, 1822 (2019).

[0006] When light reflected from each of a plurality of targets is received, a detection signal is generated for each of the distances to the targets. Since each detection signal corresponds to a single target, the distance to each of the targets can be measured.

[0007] However, since multiple detection signals are still generated based on velocity, it is impossible to determine the correspondence between one target (corresponding to a detection signal generated based on distance) and one detection signal generated based on velocity. A method could be considered to correlate the distance-based detection signals with the velocity-based detection signals based on the intensity of each detection signal. However, when the reflection intensity is substantially the same among the detection signals, this method cannot determine which target corresponds to which velocity detection signal.

[0008] Furthermore, in principle, no velocity peak is generated when the relative velocity with respect to the target is zero. Therefore, when the velocity peak is a specific value, although the relative velocities of some of the multiple targets can be determined, the situation cannot be determined in the following aspects: (i) which target has a relative velocity of zero, or (ii) all the multiple targets have the same velocity. Summary of the Invention

[0009] The purpose of this disclosure is to provide a measurement system, measurement method, and non-transitory computer-readable storage medium for determining the correspondence between distance detection signals and velocity detection signals of a plurality of targets.

[0010] According to an aspect of this disclosure, a measurement system is configured to: output emitted light including a subcarrier toward a target, wherein the frequency is changed by modulating the carrier of a single-frequency light source; and perform coherent detection on received light reflected from and received by the target to measure the distance to the target and the relative velocity of the target.

[0011] The measurement system includes: a first result acquisition unit configured to: perform FFT processing on a signal generated based on both the in-phase component and the quadrature component of the received light; and acquire the peak frequency with respect to distance and the peak frequency with respect to relative velocity as the first result.

[0012] The measurement system further includes a second result acquisition unit configured to acquire a peak frequency as a second result, the peak frequency being detected by performing FFT processing on at least one of the in-phase component signal and the quadrature component signal.

[0013] The measurement system also includes a combination determination unit configured to determine a corresponding combination between distance and relative speed as a third result based on both the first result and the second result.

[0014] According to one aspect of this disclosure, the combination determination unit enables the determination of a combination of the corresponding distance and relative velocity as a third result based on both the first result and the second result, thereby enabling the determination of the correspondence between distance detection signals and velocity detection signals of multiple targets. Attached Figure Description

[0015] The purpose, features, and advantages of this disclosure will become more apparent from the following detailed description with reference to the accompanying drawings, in which:

[0016] Figure 1 This is a functional block diagram illustrating the configuration according to the first embodiment;

[0017] Figure 2 This is a flowchart illustrating the processing flow.

[0018] Figure 3 This is a processing diagram of combined selections;

[0019] Figure 4 This is a flowchart illustrating the processing flow of the second embodiment;

[0020] Figure 5 This is a flowchart illustrating the processing flow of the second result acquisition unit in the third embodiment; and

[0021] Figure 6 This is a flowchart illustrating the processing flow of the fourth embodiment. Detailed Implementation

[0022] In the following description, several embodiments of the measurement system will be described with reference to the accompanying drawings. In the following embodiments, elements corresponding to those described in the preceding embodiments are indicated by the same reference numerals, and repeated descriptions may be omitted.

[0023] (First Embodiment)

[0024] refer to Figure 1-3 The first embodiment is described. The measurement system 1 is installed, for example, on a car and is used to detect other vehicles, pedestrians, etc., around the main vehicle (target A) to avoid collisions, thereby ensuring reliable and safe driving. Figure 1 As shown, the measurement system 1 includes a modulated light output unit 2, a scanner 3, and a measurement unit 4.

[0025] The modulation output unit 2 includes a laser 5 and an amplitude modulator 6. The measurement unit 4 includes a coherent detector 8, an A / D converter 9, and a DSP (digital signal processor) 10. The scanner 3 consists of a transmitting scanner and a receiving scanner. The scanner 3, including the transmitting scanner and the receiving scanner, may be composed of, for example, a mirror or prism having a mechanism for changing the angle, an optical phased array (OPA), etc.

[0026] Laser 5 consists of a DFB (distributed feedback) laser, a DBR (distributed Bragg reflector) laser, and an external resonant type laser. The output carrier of laser 5 serves as a single-frequency light source.

[0027] Amplitude modulator 6 generates a frequency-modulated subcarrier by using, for example, a Mach-Zehnder modulator. When oscillating light is input from laser 5, amplitude modulator 6 modulates the input oscillating light based on an externally input AC signal and DC bias. Amplitude modulator 6 modulates the carrier of the laser beam output from laser 5 to generate and output emitted light with a subcarrier.

[0028] The amplitude modulator 6 linearly changes the frequency of the subcarrier. The subcarrier frequency is changed linearly; however, it should be noted that it can be changed from a predetermined frequency to either uplink chirp or downlink chirp. The emitted light is split into two beams, one of which enters the coherent detector 8 as a reference beam, and the other beam passes through the optical circulator 11 and enters the scanner 3.

[0029] When the transmitting scanner 3 receives light through the optical circulator 11, the input light is output into space. When the output light strikes the target A and is reflected, the reflected light is incident on the receiving scanner 3 as incident light. The receiving scanner 3 outputs the received light to the coherent detector 8 through the optical circulator 11.

[0030] The coherent detector 8 is configured using a 90° optical mixer 8a and a balanced photodiode 8b. When the received light is input from the scanner 3 through the optical circulator 11, the coherent detector 8 detects the difference in amplitude and phase between the input received light and the reference light, and generates and outputs the in-phase component I and the quadrature component Q of the beat signal.

[0031] In this scenario, based on the round-trip time difference of the modulated light corresponding to the distance from measurement system 1 to target A, a frequency difference is generated between the reflected light and the reference light in the subcarrier frequency component. Furthermore, a frequency change occurs between the reflected light and the reference light as a Doppler shift in the carrier frequency component, corresponding to the relative velocity v between measurement system 1 and target A. These differences in frequency component changes are manifested in the beat signal.

[0032] The coherent detector 8 outputs the in-phase component I and quadrature component Q of the beat signal to the DSP 10 via the A / D converter 9. When the DSP 10 receives the digital signal of the beat signal, it performs various processes to obtain the distance R and relative velocity v.

[0033] For example, DSP 10 acquires the square root of the sum of the squares of the in-phase component I and the quadrature component Q detected by the balanced photodiode 8b of the coherent detector 8 as the amplitude component. Then, DSP 10 obtains the peak frequency fR of the peak by performing an FFT on the amplitude component. This corresponds to the first result of this embodiment. Furthermore, DSP 10 obtains the division value by dividing the in-phase component I by the quadrature component Q, acquires the arctangent of this division value as the phase component, and performs an FFT on the phase component. DSP 10 obtains the peak frequency fd by performing a digital FFT. This is also the first result of this embodiment. See also Figure 2 The first result acquisition unit B1 is shown in the figure. That is, the first result acquisition unit B1 outputs a peak frequency as a first result, which is obtained by performing FFT processing on the signal generated based on both the in-phase component I and the quadrature component Q of the received light.

[0034] Subsequently, DSP 10 calculates the distance R and relative velocity v based on these peak frequencies. The distance R can be calculated as a value dependent on the peak frequency fR. The relative velocity v can be calculated as a value dependent on the peak frequency fd. When a target A is present, the peak frequency fR and peak frequency fd corresponding to that target A are obtained. Therefore, the distance R and relative velocity v relative to that target A can be calculated.

[0035] The following describes the case of measuring multiple targets A. Here, the number of targets is specified as m. As described above, when reflected light is incident from multiple targets A, the distance R to each of the multiple targets A can be measured by detecting the corresponding peak frequencies. However, since multiple peak frequencies related to velocity are also detected, it is impossible to determine the correspondence between one target in the multiple targets A (which corresponds to one of the peaks detected based on distance) and one of the peaks detected based on velocity.

[0036] Therefore, in this embodiment, DSP 10 is configured according to... Figure 2 The process shown in the diagram performs the processing and calculates the distance R and relative velocity v for each of the m targets A. Details are described below. First, when the in-phase component I and the quadrature component Q are input, the DSP10 corrects the distortion generated in the in-phase component I and the quadrature component Q in S101i and S101q.

[0037] Next, in S102i, DSP 10 obtains the square root of the sum of the squares of the in-phase component I and the quadrature component Q as the amplitude component, and in S102q, it obtains the phase component as the arctangent by dividing the in-phase component I by the quadrature component Q. Next, in S103i and S103q, DSP 10 performs digital FFT processing separately on the processing results of S102i and S102q.

[0038] Next, in S103i, DSP 10 detects m peak frequencies fR related to distance based on the values ​​obtained in S102i, and in S103q, it detects m peak frequencies fd related to velocity based on the values ​​obtained in S102q. Thus far, the processing is the same as that of the first result acquisition unit B1 described above.

[0039] On the other hand, DSP 10 performs FFT processing on the spectra of the in-phase component I and the quadrature component Q in S105i and S105q, and adds the spectrum in S106. In this way, the in-phase component I and the quadrature component Q are averaged to remove noise, and the peak frequency f is detected in S107. This detected peak corresponds to the second result according to this embodiment. See also Figure 2 The second result acquisition unit B2 in the process. The peak frequency f corresponds to the frequency of the original signal of the beat signal.

[0040] In S108, DSP 10 calculates the peak combination fR±fd of the peak frequencies. This process is an operation of the combination determination unit according to this application. Here, when measuring m targets A, the combination (m fR)±(m fd) is calculated. In the following text, for convenience, the detected peak frequencies (of the m fR) are labeled as fR→fRx1, ..., fRxm, and the detected peak frequencies (of the m fd) are labeled as fd→fdx1, ..., fdxm. Then, for each of the multiple targets A, DSP 10 derives the correspondence between the peak frequency relative to distance R and the peak frequency relative to relative velocity v based on the peak frequency f of the original signal of the beat signal acquired in S107.

[0041] Figure 3An example of measuring target A with a quantity m=2 is shown. When the detected peak frequencies fRx1 and fRx2 are relative to distance and the detected peak frequencies fdx1 and fdx2 are relative to velocity, all combinations of frequencies acquired in S108 are fRx1±fdx1, fRx1±fdx2, fRx2±fdx1, and fRx2±fdx2, which are considered as combination candidates.

[0042] The peak value detected for each target in target A is, in principle, represented by the original signal (I). I I Q fR1±fd1 and fR2±fd2. See also Figure 3 The lower part. Therefore, by selecting from the combined candidates of the detected peak frequencies described above that satisfy the condition regarding the original signal (I) I I Q The combination of peaks of this principle can be used to derive the correspondence between the peak frequency with respect to distance R and the peak frequency with respect to relative velocity v.

[0043] For example, the peak frequency f of the original signal is used to determine whether there exists any combination of detected peaks near the detected peak frequencies fRx1 or fRx2 with respect to distance R; that is, whether there exists a separation condition that satisfies finding a pair of peaks with respect to the detected peak frequencies fRx1 or fRx2 that are equally separated by the amounts fdx1 and fdx2 of the detected peak frequencies with respect to relative velocity, and selecting the combination that satisfies this condition as the combination of detected peaks. By performing the above determination, a correspondence can be deterministically derived regarding which of the detected peak frequencies fRx1 and fRx2 with respect to distance R corresponds to which of the detected peak frequencies fdx1 and fdx2 with respect to relative velocity v.

[0044] Here, an example using two targets A as detection targets has been described. However, these relationships can be similarly determined even when there are three or more targets A to be detected.

[0045] In this way, it can be determined which target in target A (which corresponds to one of the peaks detected based on distance) corresponds to one of the peaks detected based on velocity. Therefore, a correspondence between the peak detected at distance R and the peak detected at relative velocity v can be determined for each of the multiple targets A.

[0046] When a combination of detected peak frequencies fRx1 and fRx2 with respect to distance R and detected peak frequencies fdx1 and fdx2 with respect to relative velocity v is selected, the relative velocity v can be calculated based on the frequency differences from the peak frequencies fRx1 and fRx2 with respect to the detected distance to the selected peak frequencies fdx1 and fdx2, respectively. In this way, the relative velocity v of each of the multiple targets A can be determined.

[0047] (Second Embodiment)

[0048] refer to Figure 4 The second embodiment is described. (As...) Figure 4 As shown, after executing processes S101i to S104i, S105i and S105q, and S106 and S107, DSP 10 calculates the frequency difference fΔ between the peak frequency f acquired in S107 and the peak frequency fR with respect to distance in S208. Meanwhile, DSP 10 executes processes S101q to S104q in parallel. Then, process S209 is executed.

[0049] In S209, DSP 10 verifies whether the following two items match: (i) the m peak frequencies fd with respect to relative velocity v obtained in S104q and (ii) the difference frequency fΔ obtained only from S104i and S107. When DSP 10 determines that they match, DSP 10 is able to determine the correspondence between peak frequencies fd and peak frequencies fR. These processes in S208 and S209 illustrate the processing as a combined determination unit.

[0050] Then, after calculating the relative velocity v of each target A based on the corresponding peak value determined for it, the sign (i.e., + or -) of the relative velocity v can be determined by comparing the following two items: (i) the peak frequency fΔ detected in S208 and (ii) the peak frequency fd detected in S104q. In this way, the travel direction of each target A can be determined.

[0051] In S210, DSP 10 outputs the correspondence between peak frequency fR and peak frequency fd, as well as the direction of relative velocity v. By determining whether they match, DSP 10 can determine the sign of relative velocity v by considering the phase component of relative velocity v, and can determine whether target A is moving away or approaching.

[0052] (Third Embodiment)

[0053] refer to Figure 5 The third embodiment is described. In the embodiments described above, in Figure 2 or Figure 4In the example of the second result acquisition unit B2, it is shown that the original signal is averaged by adding a spectrum after performing FFT processing on each of the in-phase component I and the quadrature component Q. In contrast, as Figure 5 As shown, the second result acquisition unit B3 may also be feasible, wherein the signals of the in-phase component I and the quadrature component Q are added in S305, then digital FFT processing is performed in S306, and peak values ​​are detected in S307. In this way, the same effect as the embodiment described above can be achieved.

[0054] (Fourth Embodiment)

[0055] refer to Figure 6 The fourth embodiment is described. A method for detecting m targets A is described. First, in Figure 6 In S401a, the peak frequencies with respect to distance R are labeled as fR1, fR2, ..., fRm. In S401b, the peak frequencies with respect to relative velocity v are labeled as fv1, fv2, ..., fvm. Then, in S402, the frequencies detected by the in-phase component I or the quadrature component Q are labeled as f1, f2, ..., fn.

[0056] These frequencies fR1, fR2, ..., fRm, fv1, fv2, ..., fvm and f1, f2, ..., fn can be detected by performing the same processing as the first result acquisition unit B1 and the second result acquisition units B2 and B3 described in the first to third embodiments.

[0057] Next, DSP 10 generates a frequency difference group Rx consisting of the differences between the following: (i) the frequencies f1, f2, ..., fn of the original signal detected by the in-phase component I and the quadrature component Q, and (ii) the peak frequencies fR1, fR2, ..., fRm with respect to distance. Figure 6 In steps S403 to S405, the frequency difference group Rx is generated by repeating the process n times with x as the variable. The results are as follows.

[0058] Group R1 f1-fR1, f1-fR2, f1-fRm

[0059] Group R2 f2-fR1, f2-fR2, f2-fRm

[0060] ...

[0061] Group Rn fn-fR1, fn-fR2, fn-fRm

[0062] Then, DSP 10 rearranges the absolute values ​​of all frequencies obtained through the calculation in S407 above in ascending or descending order. At this point, the n×m frequency differences obtained through sorting are defined as fΔ1, fΔ2, ..., fΔn×m.

[0063] Then, in S408, DSP 10 sets the initial value of variable k, and in S409, performs a search to find combinations in which frequency difference fΔi and frequency difference fΔi+1 match or are close to each other, that is, combinations with small absolute values ​​of the difference between frequency difference fΔi and frequency difference fΔi+1.

[0064] Then, in S410, it is determined whether all the searched frequency difference combinations (fΔi, fΔi+1) belong to group Rx. If they all belong to group Rx, then in S411, it is considered that the combination corresponds to the peak frequency fRx with respect to distance. Then, in S413, fΔi and fΔi+1 are excluded from the search targets, and in S414, the variable k is changed, and the process from S409 to S412 is repeated n times, so that the peak frequency combination with respect to distance R and relative velocity v is obtained for all targets A. The processing content of the combination determination unit as involved in this application is shown.

[0065] When there exists a group Rx that does not have a corresponding combination, i.e., the "yes" condition in S412 is determined, the relative velocity v of target A corresponding to the detected peak value of that distance R is considered zero in S415, i.e., target A is determined to be a stationary object. In this way, for all detected targets A, both distance R and relative velocity v are knowable.

[0066] (Other embodiments)

[0067] This disclosure should not be limited to the embodiments described above, and various modifications can be made without departing from the spirit of this disclosure. For example, the following modifications and extensions can be made.

[0068] In the embodiments described above, the in-phase component I and the quadrature component Q are averaged after FFT processing and addition, and then the peak value is detected. Furthermore, in the embodiments described above, the in-phase component I and the quadrature component Q are averaged by adding the waveform as is, and then the peak value is detected. However, this disclosure is not limited thereto.

[0069] The signal of either the in-phase component I or the quadrature component Q can be processed by FFT, and peak detection can be performed on the result of such processing to be used as a second result. That is, the peak value obtained by performing FFT processing on at least one of the signals of the in-phase component I and the quadrature component Q can be used as a second result.

[0070] The method of DSP 10 described in this disclosure can be implemented by a dedicated computer, which is provided by configuring a processor and memory programmed to perform one or more functions embodied by a computer program. Alternatively, the DSP 10 and its method described in this disclosure can be implemented by a dedicated computer, which is provided by configuring a processor having one or more dedicated hardware logic circuits. Alternatively, the DSP 10 and its method described in this disclosure can be implemented by one or more dedicated computers configured as a combination of a processor and memory programmed to perform one or more functions, and a processor composed of one or more hardware logic circuits. Furthermore, the computer program can also be stored on a computer-readable, non-transitory tangible recording medium as instructions executable by a computer.

[0071] The present disclosure has been described with reference to the embodiments described above. However, it should be understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and variations within the scope of equivalents. Additionally, various patterns / combinations, one or more elements added to or removed therefrom may also be considered as part of the present disclosure and understood as its technical ideas.

Claims

1. A measurement system configured to output transmitted light, including a subcarrier, toward a target, wherein, The frequency is changed by modulating the carrier wave of a single-frequency light source (5); and coherent detection is performed on the received light reflected from and received by the target to measure the distance to the target and the relative velocity of the target, the measurement system comprising: The first result acquisition unit (B1; S401a, S401b) is configured as follows: Perform FFT processing on the signal generated based on both the in-phase and quadrature components of the received light; and The peak frequencies (fR; fRx1 to fRxm) with respect to the distance and the peak frequencies (fd; fdx1 to fdxm) with respect to the relative velocity are obtained as a first result; The second result acquisition unit (B2, B3; S402) is configured to acquire peak frequencies (f; f1 to fn) as a second result, wherein the peak frequencies (f; f1 to fn) are detected by performing FFT processing on at least one of the in-phase component signals and the quadrature component signals; and The combination determination unit (S108; S208, S209; S403 to S414) is configured to determine a corresponding combination between the distance and the relative speed as a third result based on both the first result and the second result.

2. The measurement system according to claim 1 further includes: A modulator (6) is configured to generate the subcarrier by continuously changing the frequency while modulating the carrier.

3. The measurement system according to claim 2, wherein: The modulator is configured to linearly change the frequency of the subcarrier.

4. The measurement system according to claim 1, wherein: The combination determination unit is configured as follows: Determine whether the combination satisfies the following condition: wherein the peak frequency obtained as the second result and the peak frequency obtained as the first result with respect to the distance are equally separated by the peak frequency with respect to the speed; and Select the combination of detected peak frequencies that satisfy the conditions.

5. The measurement system according to claim 4, wherein: The combination determination unit is configured to calculate the relative speed based on the difference between the peak frequency with respect to the distance and the peak frequency obtained as the second result.

6. The measurement system according to claim 1, wherein: The combination determination unit is configured as follows: Calculate the frequency difference (fΔ) between the peak frequency obtained as the first result with respect to the distance and the peak frequency obtained as the second result. Determine whether the frequency difference matches the peak frequency of the relative velocity obtained as the first result, and Determine the corresponding combination of peak frequencies.

7. The measurement system according to claim 6, wherein: The relative velocity is calculated based on peak frequencies such that the corresponding combinations of these peak frequencies are determined by the combination determination unit, and The sign of the relative velocity is determined with reference to the peak frequency of the relative velocity obtained as the first result.

8. The measurement system according to claim 1, wherein: The second result is calculated by performing an FFT on the in-phase component and the quadrature component and by adding their spectra.

9. A measurement method for measuring the distance to a target and the relative velocity of the target by outputting emitted light including a subcarrier toward the target, wherein, The frequency is changed by modulating the carrier wave of the single-frequency light source (5); The measurement method includes performing coherent detection on the received light reflected from and received by the target, the measurement of which includes: The first result acquisition unit (B1) performs FFT processing on the signal generated based on both the in-phase component and the quadrature component of the received light, and obtains the peak value as the first result; The peak frequencies (f; f1 to fn) are acquired as a second result by the second result acquisition unit (B2, B3), wherein the peak frequencies (f; f1 to fn) are detected by performing FFT processing on at least one of the in-phase component signals and the quadrature component signals; and The combination determination unit (S108; S208, S209) determines a corresponding combination between the distance and the relative speed as a third result based on both the first result and the second result.

10. A non-transitory computer-readable storage medium comprising computer-executable instructions for a measurement system configured to measure distance to a target and relative velocity of the target by outputting emitted light including a subcarrier toward the target, wherein, The frequency is changed by modulating the carrier wave of the single-frequency light source (5); and coherent detection is performed on the received light reflected from and received by the target, the instructions causing at least one processor to perform the following operations: Perform FFT processing on the signal generated based on both the in-phase component and the quadrature component of the received light, and obtain the peak value as the first result; The peak frequencies (f; f1 to fn) are obtained as a second result, which are detected by performing FFT processing on at least one of the in-phase component signals and the quadrature component signals; as well as Based on both the first and second results, a corresponding combination between the distance and the relative speed is determined as a third result.

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