Distance measurement system

Abstract

The present invention relates to a distance measurement system, comprising: a source end generates a broadband incident wave, the broadband incident wave is transmitted to a target and reflected by the target to form a reflected wave; a feedback detector is used to detect the reflected wave to generate a detection signal; an operator is set to perform low-pass filtering on the detection signal with an adjustable filtering bandwidth to generate a filtered signal, and calculates the cross-correlation between a feedback signal derived from the filtered signal and a reference signal corresponding to the incident wave to generate a cross-correlation result; and a controller calculates the distance to the target according to the operation output derived from the cross-correlation result.

Description

Technical Field

[0001] The present invention relates to a distance measurement technology, and in particular to a distance measurement system. Background Art

[0002] A lidar system is a system that measures the distance from the lidar system to the target by illuminating the target with a laser and measuring the flight time required for the laser to return to the lidar system. The lidar system can detect the target when it is within the ranging dynamic range of the lidar system.

[0003] In a lidar system, a higher sampling frequency results in better ranging resolution; and the total number of samples is limited by a given power budget, so a higher sampling frequency results in a narrower ranging dynamic range. Therefore, given the power budget, the sampling frequency can be reduced to achieve a wider ranging dynamic range, trading off the ranging resolution for the ranging dynamic range, but this may result in missing the target (that is, the target is not detected). In addition, fine ranging resolution and wide ranging dynamic range cannot be achieved simultaneously without excessive power consumption. Summary of the invention

[0004] An object of the present invention is to provide a ranging system which can improve at least one disadvantage of the prior art when the adjustable parameters in the ranging system are properly set.

[0005] The ranging system of the present invention is suitable for measuring the distance from the ranging system to a target, and includes a source end, a feedback detector, an operator and a controller. The source end generates a broadband incident wave. The incident wave is transmitted to the target and reflected by the target to form a reflected wave. The feedback detector is used to detect the reflected wave to generate a detection signal. The operator is electrically connected to the feedback detector to receive the detection signal therefrom, and is set to perform low-pass filtering on the detection signal with an adjustable default filter bandwidth to generate a filtered signal, and calculates the cross-correlation between the feedback signal derived from the filtered signal and the reference signal corresponding to the incident wave to generate a cross-correlation result. The controller is electrically connected to the operator to receive the operation output from the cross-correlation result therefrom, and calculates the distance from the ranging system to the target based on the operation output.

[0006] Preferably, in the distance measuring system of the present invention, the operator calculates the cross-correlation corresponding to a plurality of delay times distributed in an adjustable default time zone.

[0007] Preferably, in the distance measurement system of the present invention, the operator is further used for sampling the first filtered signal at an adjustable default sampling frequency so as to generate the feedback signal; and the cross-correlation result is used as the operation output.

[0008] Preferably, in the distance measurement system of the present invention, the default sampling frequency is higher than the default filtering bandwidth.

[0009] Preferably, the distance measurement system of the present invention can be operated in a coarse mode and a fine mode, wherein:

[0010] In the coarse mode, the controller controls the operator in such a manner that the default filter bandwidth and the default sampling frequency are respectively equal to a first filter bandwidth and a first sampling frequency; and

[0011] In the fine mode, the controller controls the operator in such a way that the default filter bandwidth and the default sampling frequency are respectively equal to a second filter bandwidth and a second sampling frequency, wherein the second filter bandwidth is wider than the first filter bandwidth, and the second sampling frequency is higher than the first sampling frequency.

[0012] Preferably, the distance measurement system of the present invention, wherein:

[0013] The operator calculates the cross-correlations corresponding to a plurality of delay times distributed in an adjustable default time region;

[0014] In the rough mode, the controller controls the operator in such a way that the default time zone is equal to the first time zone, and obtains a rough delay time of the reflected wave corresponding to the incident wave in the ranging system according to the operation output; and

[0015] In the fine mode, the controller controls the operator in such a way that the default time zone is equal to the second time zone, and obtains a fine delay time of the reflected wave corresponding to the incident wave in the ranging system based on the operation output, and calculates the distance from the ranging system to the target based on the fine delay time, the second time zone is narrower than the first time zone and is the coarse delay time.

[0016] Preferably, the distance measuring system of the present invention further comprises a reference detector for detecting the incident wave to generate a second detection signal, wherein:

[0017] The operator is also electrically connected to the reference detector to receive a second detection signal from the reference detector, and is also used to

[0018] performing low pass filtering on the second detection signal with the default filtering bandwidth to generate a second filtered signal, and

[0019] The second filtered signal is sampled at the default sampling frequency to generate the reference signal.

[0020] Preferably, the distance measurement system of the present invention, wherein:

[0021] The source end is used to receive a source signal and generate the incident wave according to the source signal; and

[0022] The operator is also used to receive the source signal and to

[0023] performing low pass filtering on the source signal with the default filter bandwidth to generate a second filtered signal, and

[0024] The second filtered signal is sampled at the default sampling frequency to generate the reference signal.

[0025] Preferably, the distance measurement system of the present invention, wherein:

[0026] The source end is used to receive a source signal and generate the incident wave according to the source signal; and

[0027] The operator is also used to receive the source signal, and is also used to

[0028] performing low pass filtering on the source signal with the default filter bandwidth to generate a second filtered signal, and

[0029] The second filtered signal is downsampled to generate the reference signal corresponding to a sampling frequency equal to the default sampling frequency.

[0030] Preferably, the distance measurement system of the present invention, wherein:

[0031] The first filtered signal is used as the feedback signal; and

[0032] The operator is also configured to sample the cross-correlation result at an adjustable default sampling frequency to generate an operation output.

[0033] Preferably, the distance measuring system of the present invention further comprises:

[0034] a reference detector for detecting the incident wave to generate a second detection signal;

[0035] The operator is further electrically connected to the reference detector to receive the second detection signal from the reference detector to the reference detector, and is also configured to perform low-pass filtering on the second detection signal with the default filtering bandwidth to generate the reference signal.

[0036] Preferably, in the ranging system of the present invention, the source end is used to receive the source signal and generate the incident wave according to the source signal; and the operator is also used to receive the source signal and is also set to perform low-pass filtering on the source signal with the default filter bandwidth so as to generate the reference signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other features and effects of the present invention will be clearly presented in the embodiments with reference to the accompanying drawings, in which:

[0038] Figure 1 is a block diagram illustrating a first embodiment of a distance measurement system of the present invention;

[0039] Figure 2 is a diagram illustrating the simulated cross-correlation results of the first embodiment under different conditions with different default filter bandwidths;

[0040] Figure 3 is a diagram illustrating the cross-correlation results of the first embodiment under different conditions with different default sampling frequencies;

[0041] Figure 4 is a diagram illustrating the cross-correlation results of the first embodiment in a coarse mode and a fine mode;

[0042] Figure 5 is a block diagram illustrating a second embodiment of the distance measurement system according to the present invention;

[0043] Figure 6 is a block diagram illustrating a third embodiment of the distance measurement system according to the present invention;

[0044] Figure 7 is a block diagram illustrating a fourth embodiment of the distance measurement system according to the present invention;

[0045] Figure 8 is a block diagram illustrating a fifth embodiment of the distance measurement system according to the present invention; and

[0046] Fig. 9 is a block diagram illustrating a sixth embodiment of the distance measurement system according to the present invention. DETAILED DESCRIPTION

[0047] Before the present invention is described in detail, it should be noted that similar components are denoted by the same reference numerals in the following description.

[0048] See also Figure 1 A first embodiment of the ranging system 1 of the present invention is suitable for measuring a distance from the ranging system 1 to a target 2, and includes a source end 11, a feedback detector 12, a reference detector 13, an operator 14 and a controller 15.

[0049] The source 11 generates a broadband incident wave (eg, light, electromagnetic wave or sound), which may be modulated or unmodulated according to application requirements. The incident wave is transmitted to the target 2 and reflected by the target 2 to form a reflected wave.

[0050] The feedback detector 12 is used for detecting the reflected wave to generate a first detection signal.

[0051] The reference detector 13 is used to detect the incident wave to generate a second detection signal.

[0052] In the present embodiment, the source end 11 is a light source end (e.g., a laser) that generates light as the incident wave, and each of the feedback detector 12 and the reference detector 13 is a photoelectric converter (e.g., a photodiode) that converts a corresponding one of the reflected wave and the incident wave into an electrical signal as a corresponding one of the first detection signal and the second detection signal. However, the present invention is not limited to the above embodiment.

[0053] The operator 14 is electrically connected to the feedback detector 12 and the reference detector 13 to receive the first detection signal and the second detection signal from the feedback detector 12 and the reference detector 13 respectively, and is used to perform the following actions: perform low-pass filtering on the first detection signal and the second detection signal at an adjustable default filtering bandwidth to generate a first filtered signal and a second filtered signal respectively; sample the first filtered signal and the second filtered signal at an adjustable default sampling frequency to generate a feedback signal and a reference signal respectively derived from the first filtered signal and the second filtered signal and corresponding to the reflected wave and the incident wave respectively; and calculate the cross-correlation of the feedback signal and the reference signal corresponding to multiple delay times distributed in a default time zone to generate a cross-correlation result, wherein the default time zone is optionally adjustable.

[0054] The controller 15 is electrically connected to the operator 14, controls the adjustable parameters in the operator 14 (including the default filter bandwidth, the default sampling frequency and the default time zone), and is used to receive an operation output derived from the cross-correlation result from the operator 14, and calculate the distance from the ranging system 1 to the target 2 according to the operation output.

[0055] In this embodiment, the first detection signal and the second detection signal are both simulation signals; and the operator 14 includes a low-pass filter 141 , a sampler 142 and a cross-correlator 143 operating in the simulation domain, and also includes an analog-to-digital converter 144 .

[0056] The low-pass filter 141 has an adjustable filter bandwidth and is electrically connected to the controller 15, and is controlled by the controller 15 in such a manner that the adjustable filter bandwidth is set to the default filter bandwidth. The low-pass filter 141 is also electrically connected to the feedback detector 12 and the reference detector 13 to receive the first detection signal and the second detection signal from the feedback detector 12 and the reference detector 13, respectively, and performs low-pass filtering on the first detection signal and the second detection signal at the default filter bandwidth to generate the first filter signal and the second filter signal, respectively.

[0057] The sampler 142 has an adjustable sampling frequency and is electrically connected to the controller 15, and is controlled by the controller 15 in such a manner that the adjustable sampling frequency is set as the default sampling frequency. The sampler 142 is also electrically connected to the low-pass filter 141 to receive the first filter signal and the second filter signal from the low-pass filter 141, and samples the first filter signal and the second filter signal at the default sampling frequency to generate the feedback signal and the reference signal, respectively.

[0058] The cross-correlator 143 has an adjustable time zone, and is electrically connected to the controller 15, and is controlled by the controller 15 in a manner that the adjustable time zone is set as the default time zone. The cross-correlator 143 is also electrically connected to the sampler 142 to receive the feedback signal and the reference signal from the sampler 142, and calculates the cross-correlation of the feedback signal and the reference signal corresponding to the delay times distributed in the default time zone to generate the cross-correlation result as the operation output. Specifically, for each of the delay times, the cross-correlator 143 delays the reference signal by the delay time to generate a delayed signal, and calculates the dot product of the feedback signal and the delayed signal. The dot products corresponding to the delay times together constitute the cross-correlation result.

[0059] The analog-to-digital converter 144 is electrically connected to the cross-correlator 143 to receive the operation output from the cross-correlator 143, and is also electrically connected to the controller 15, and performs analog-to-digital conversion on the operation output to generate a digital representation of the operation output for reception by the controller 15. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the digital representation of the operation output.

[0060] In a first implementation of the present embodiment, the controller 15 controls the low-pass filter 141 and the sampler 142 so that the default filtering bandwidth is narrower than a signal bandwidth of the incident wave, and the default sampling frequency is higher than the default filtering bandwidth.

[0061] Figure 2 The simulation cross-correlation results of the present embodiment under various conditions are illustrated. Under all conditions, the signal bandwidth of the incident wave is 500 MHz and the default sampling frequency is 5 GHz, and the default filter bandwidth is infinity, 100 MHz, 50 MHz, 25 MHz and 10 MHz under various conditions. Under each condition, the delay time corresponding to the maximum dot product is the actual delay time of the reflected wave of the ranging system 1 corresponding to the incident wave. Figure 2 It can be reasonably determined that the lower the default filter bandwidth, the wider a pulse of the cross-correlation result containing the maximum dot product will be. Figure 3 As shown, when the default sampling frequency is higher than the default filtering bandwidth, the cross-correlation result (that is, the combination of solid dots and hollow dots) will not lose the above pulses, thus ensuring target detection (that is, target 2 has been detected); and when the default sampling frequency is lower than the default filtering bandwidth, the cross-correlation result (that is, the solid dots) may completely lose the above pulses that should have appeared, resulting in loss of the target (that is, target 2 is not detected). In a first implementation of this embodiment, by making the default filtering bandwidth lower than the default sampling frequency, even if the default sampling frequency is reduced in order to widen a ranging dynamic range of the ranging system 1, the target 2 will still be detected.

[0062] See also Figure 1 and Figure 4In a second implementation of the present embodiment, the ranging system 1 operates in the coarse mode and the fine mode in sequence. In the coarse mode, the controller 15 controls the low-pass filter 141, the sampler 142 and the cross-correlator 143 so that the default filter bandwidth, the default sampling frequency and the default time zone are respectively equal to a first filter bandwidth, a first sampling frequency and a first time zone, the first filter bandwidth is narrower than the signal bandwidth of the incident electromagnetic signal, and the first sampling frequency is higher than the first filter bandwidth. Furthermore, the controller 15 obtains a coarse delay time of the reflected wave of the ranging system 1 corresponding to the incident wave according to the operation output. In the fine mode, the controller 15 controls the low-pass filter 141, the sampler 142 and the cross-correlator 143 so that the default filter bandwidth, the default sampling frequency and the default time zone are respectively equal to a second filter bandwidth, a second sampling frequency and a second time zone. The second filter bandwidth is wider than the first filter bandwidth. The second sampling frequency is higher than the second filtering bandwidth and the first sampling frequency. Figure 4 As shown, the second time zone is narrower than the first time zone and is equal to the coarse delay time. Furthermore, the controller 15 obtains a fine delay time corresponding to the incident wave of the reflected wave of the ranging system 1 according to the calculation output, and calculates the distance from the ranging system 1 to the target 2 according to the fine delay time.

[0063] In the second implementation of the present embodiment, since the default sampling frequency in the fine mode is higher than the default sampling frequency in the coarse mode, and the default time range in the fine mode is narrower than the default time range in the coarse mode, the ranging system 1 has a wider dynamic range in the coarse mode and a better ranging resolution in the fine mode. In addition, the default sampling frequency and the default time range in both the coarse mode and the fine mode can make the total number of samples (that is, the dot products) included in the cross-correlation result not exceed the upper limit constituted by a predetermined power budget, so the ranging system 1 can have an overall fine ranging resolution within a wide ranging dynamic range without excessive power consumption.

[0064] See also Figure 5 A second embodiment of the ranging system 1 of the present invention is similar to the first embodiment, but differs from the first embodiment in that the correlator 143 operates in the digital domain.

[0065] In the second embodiment, the analog-to-digital converter 144 is electrically connected to the sampler 142 to receive the feedback signal and the reference signal from the sampler 142, and performs analog-to-digital conversion on the feedback signal and the reference signal to generate a digital representation of the feedback signal and a digital representation of the reference signal. The cross-correlator 143 is electrically connected to the analog-to-digital converter 144 to receive the digital representation of the feedback signal and the digital representation of the reference signal from the analog-to-digital converter 144, and is also electrically connected to the controller 15. The cross-correlator 143 calculates the cross-correlation of the digital representation of the feedback signal and the digital representation of the reference signal corresponding to the delay times distributed in the default time zone to generate the cross-correlation result as the operation output for reception by the controller 15. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the operation output.

[0066] See also Figure 6 A third embodiment of the distance measuring system 1 of the present invention is similar to the first embodiment, but differs from the first embodiment in that: (a) the reference detector 13 (see Figure 1 ); (b) the controller 15 also generates a source signal of a simulation signal; (c) the source end 11 is electrically connected to the controller 15 to receive the source signal from the controller 15, and generates the incident wave according to the source signal; and (d) the low-pass filter 141 is used to receive the source signal from the controller 15, and perform low-pass filtering on the source signal with the default filtering bandwidth to generate the second filtered signal.

[0067] See also Figure 7 A fourth embodiment of the distance measuring system 1 of the present invention is similar to the second embodiment, but differs from the second embodiment in that: (a) the reference detector 13 (see Figure 5 ); (b) the controller 15 also generates a digital source signal; (c) the source end 11 is electrically connected to the controller 15 to receive the source signal from the controller 15 and generate the incident wave according to the source signal; and (d) the operator 14 also includes another low-pass filter 145 and an extractor 146 operating in the digital domain.

[0068] In the fourth embodiment, the second filtered signal is generated by the low pass filter 145 instead of the low pass filter 141, and the reference signal is generated by the decimator 146 instead of the sampler 142. Specifically, the low pass filter 145 has an adjustable filter bandwidth, and is electrically connected to the controller 15 and controlled by the controller 15 so that the adjustable filter bandwidth is set to the default filter bandwidth. The low pass filter 145 is used to receive the source signal from the controller 15 and perform low pass filtering on the source signal with the default filter bandwidth to generate the second filtered signal. The decimator 146 has an adjustable sampling frequency, and is electrically connected to the controller 15 and controlled by the controller 15 so that the adjustable sampling frequency is set to the default sampling frequency. The decimator 146 is also electrically connected to the low-pass filter 145 and the cross-correlator 143, and is used to receive the second filtered signal from the low-pass filter 145, and downsample the second filtered signal to generate the reference signal having a sampling rate equal to the default sampling frequency, for reception by the cross-correlator 143. The cross-correlator 143 calculates the cross-correlation of the feedback signal and the digital representation of the reference signal corresponding to the delay times distributed in the default time region, to generate the cross-correlation result.

[0069] See also Figure 8 A fifth embodiment of the ranging system 1 of the present invention is similar to the first embodiment, but different from the first embodiment in that the operator 14 is used to perform the following actions: perform low-pass filtering on the first detection signal and the second detection signal with the default filtering bandwidth to generate the first filtered signal and the second filtered signal as the feedback signal and the reference signal respectively; calculate the cross-correlation of the feedback signal and the reference signal corresponding to the delay times distributed in the default time range to generate the cross-correlation result; and sample the cross-correlation result at the default sampling frequency to generate the operation output.

[0070] In the fifth embodiment, the cross-correlator 143 is electrically connected to the low-pass filter 141 to receive the feedback signal and the reference signal from the low-pass filter 141, and calculates the cross-correlation of the feedback signal and the reference signal corresponding to the delay times distributed in the default time region to generate the cross-correlation result. The sampler 142 is electrically connected to the cross-correlator 143 to receive the cross-correlation result from the cross-correlator 143, and samples the cross-correlation result at the default sampling frequency to generate the operation output. The analog-to-digital converter 144 is electrically connected to the sampler 142 to receive the operation output from the sampler 142, and performs analog-to-digital conversion on the operation output to generate a digital representation of the operation output for reception by the controller 15. The controller 15 calculates the distance from the ranging system 1 to the target 2 according to the digital representation of the operation output.

[0071] See also Fig. 9 A sixth embodiment of the distance measuring system 1 of the present invention is similar to the fifth embodiment, but differs from the fifth embodiment in that: (a) the reference detector 13 (see Figure 8 ); (b) the controller 15 also generates a source signal of a simulation signal; (c) the source end 11 is electrically connected to the controller 15 to receive the source signal from the controller 15, and generates the incident wave according to the source signal; and (d) the low-pass filter 141 is used to receive the source signal from the controller 15, and perform low-pass filtering on the source signal with the default filtering bandwidth to generate the reference signal.

[0072] In the above description, for the purpose of explanation, many specific details have been set forth in order to provide a thorough understanding of the embodiment. However, it is obvious to those skilled in the art that one or more other embodiments can be practiced without these specific details. It should be understood that throughout the specification, "one embodiment", "an embodiment", an embodiment with an ordinal number, etc., indicate that specific features, structures or characteristics may be included in the practice of the present invention. It should also be understood that in this specification, various features are sometimes combined in a single embodiment, figure or description thereof to simplify the present invention and help understand various inventive aspects, and one or more features or, where appropriate, in the practice of the present invention, the specific details of one embodiment can be practiced together with one or more features or specific details of another embodiment.

[0073] The above description is only a preferred embodiment of the present invention, but it is not intended to limit the scope of the present invention. Any person familiar with this technology can make further improvements and changes on this basis without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined by the claims of this application.

Claims

1. A distance measuring system, suitable for measuring the distance from the distance measuring system to a target, characterized in that: Include: A source end, for generating a broadband incident wave, the incident wave is transmitted to the target and is reflected by the target to form a reflected wave; A feedback detector, used for detecting the reflected wave to generate a first detection signal; an operator electrically connected to the feedback detector to receive the first detection signal from the feedback detector and to performing low pass filtering on the first detection signal with an adjustable default filter bandwidth to generate a first filtered signal, and calculating a cross-correlation between a feedback signal derived from the first filtered signal and a reference signal corresponding to the incident wave to produce a cross-correlation result; and a controller, configured to be electrically connected to the operator to receive an operation output from the operator derived from the cross-correlation result, and calculate the distance from the ranging system to the target according to the operation output, The operator is further used for sampling the first filtered signal at an adjustable default sampling frequency to generate the feedback signal; and The cross-correlation result is used as the operation output.

2. The distance measurement system according to claim 1, characterized in that: The operator calculates the cross-correlations corresponding to a plurality of delay times distributed in an adjustable default time region.

3. The distance measurement system according to claim 1, characterized in that: The default sampling frequency is higher than the default filtering bandwidth.

4. The distance measurement system according to claim 1, characterized in that: The ranging system is capable of operating in coarse mode and fine mode, In the coarse mode, the controller controls the operator in such a manner that the default filter bandwidth and the default sampling frequency are respectively equal to the first filter bandwidth and the first sampling frequency; and In the fine mode, the controller controls the operator in such a way that the default filter bandwidth and the default sampling frequency are respectively equal to the second filter bandwidth and the second sampling frequency, wherein the second filter bandwidth is wider than the first filter bandwidth, and the second sampling frequency is higher than the first sampling frequency.

5. The distance measurement system according to claim 4, characterized in that: The operator calculates the cross-correlations corresponding to a plurality of delay times distributed in an adjustable default time region; In the rough mode, the controller controls the operator in such a way that the default time zone is equal to the first time zone, and obtains a rough delay time of the reflected wave corresponding to the incident wave in the ranging system according to the operation output; and In the fine mode, the controller controls the operator in such a way that the default time zone is equal to the second time zone, and obtains a fine delay time of the reflected wave corresponding to the incident wave in the ranging system based on the operation output, and calculates the distance from the ranging system to the target based on the fine delay time, the second time zone is narrower than the first time zone and is the coarse delay time.

6. The distance measurement system according to claim 1, characterized in that: Also includes: a reference detector for detecting the incident wave to generate a second detection signal, The operator is also electrically connected to the reference detector to receive a second detection signal from the reference detector, and is also used to performing low pass filtering on the second detection signal with the default filtering bandwidth to generate a second filtered signal, and The second filtered signal is sampled at the default sampling frequency to generate the reference signal.

7. The distance measurement system according to claim 1, characterized in that: The source end is used to receive a source signal and generate the incident wave according to the source signal; and The operator is also used to receive the source signal and to performing low pass filtering on the source signal with the default filter bandwidth to generate a second filtered signal, and The second filtered signal is sampled at the default sampling frequency to generate the reference signal.

8. The distance measurement system according to claim 1, characterized in that: The source end is used to receive a source signal and generate the incident wave according to the source signal; and The operator is also used to receive the source signal, and is also used to performing low pass filtering on the source signal with the default filter bandwidth to generate a second filtered signal, and The second filtered signal is downsampled to generate the reference signal corresponding to a sampling frequency equal to the default sampling frequency.

9. The distance measurement system according to claim 1, characterized in that: The first filtered signal is used as the feedback signal; and The operator is also configured to sample the cross-correlation result at an adjustable default sampling frequency to generate an operation output.

10. The distance measurement system according to claim 9, characterized in that: Also includes: a reference detector for detecting the incident wave to generate a second detection signal; The operator is also electrically connected to the reference detector to receive the second detection signal from the reference detector, and is also configured to perform low-pass filtering on the second detection signal with the default filtering bandwidth to generate the reference signal.

11. The distance measurement system according to claim 9, characterized in that: The source end is used to receive a source signal and generate the incident wave according to the source signal; and The operator is further configured to receive the source signal and is further configured to perform low-pass filtering on the source signal with the default filtering bandwidth so as to generate the reference signal.

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