Focus positioning method and system based on focused sound field nonlinear effect

Abstract

The invention discloses a focus positioning method and system based on a focused sound field nonlinear effect, and the method comprises the steps: arranging a plurality of detection base stations outside a focused sound field focus region, and detecting and recording an original sound signal; calculating the frequency spectrum of the original sound signal detected by each detection base station, analyzing whether the detected original sound signal has a harmonic component or not, if not, judging that the focused sound field does not generate a nonlinear effect, and ending the process; if yes, judging that the focused sound field generates a nonlinear effect, designing a band-pass filter according to the harmonic frequency, filtering the original sound signal, analyzing the time-frequency characteristic of the filtered signal, calculating the time difference of the nonlinear harmonic signal reaching each detection base station, and calculating the time difference of the nonlinear harmonic signal reaching each detection base station according to the time difference of the harmonic signal reaching each detection base station. And calculating the position of the harmonic source based on the TDOA principle, namely the position coordinate of the focus. According to the invention, a plurality of base stations can be used for detecting sound signals, and the position of a harmonic source (sound field focus) is calculated by analyzing harmonic signals.

Description

Technical Field

[0001] The present invention belongs to the field of ultrasonic technology, and in particular relates to a focus positioning method and system based on the nonlinear effect of a focused acoustic field. Background Art

[0002] Ultrasound has the advantages of no ionizing radiation, low application cost, and clear physical effects, and is widely used in medical diagnosis and treatment. Focused ultrasound has a small action area and minimal collateral damage to surrounding normal tissues, reducing postoperative recovery time and complications. Focused ultrasound has important application value in the fields of tumor ablation, tissue damage, promotional therapy, neurological function regulation, and opening of the blood-brain barrier. The precise positioning and monitoring of focused ultrasound can reduce the adverse effects on normal tissues in non-target areas and improve the effectiveness and safety of treatment methods.

[0003] Currently, MRI-guided focused ultrasound systems have been approved by the FDA for clinical tissue ablation surgery. However, the high cost, low temporal resolution and compatibility issues of MRI and ultrasound equipment remain major challenges to their widespread clinical application. Ultrasound technology can monitor the focused sound field in tissues from multiple angles. Focused ultrasound navigation and monitoring based on ultrasound technology has the advantages of convenience, economy, high frame rate, and natural compatibility. Existing methods mainly include B-ultrasound monitoring of the physical and biological changes of focused ultrasound on tissues, passive detection of cavitation effects, and passive passive beam imaging to display ultrasound transmission paths. However, the above methods have the limitations of detection hysteresis, poor resolution and contrast. Summary of the invention

[0004] The purpose of the present invention is to provide a focus positioning method and system based on the nonlinear effect of the focused sound field to solve the problems existing in the prior art. The present invention can use multiple base stations to detect sound signals and calculate the position of the harmonic source (sound field focus) by analyzing the harmonic signals.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: A focus positioning method based on the nonlinear effect of a focused acoustic field comprises the following steps: Step 1: Arrange multiple detection base stations outside the focal area of ​​the focused sound field to detect and record the original sound signal; Step 2: Calculate the spectrum of the original sound signal detected by each detection base station, and analyze whether the original sound signal under test has harmonic components. If so, it is determined that the focused sound field produces nonlinear effects, and proceed to step 3; if not, it is determined that the focused sound field does not produce nonlinear effects, and the process ends; Step 3: Design a bandpass filter according to the harmonic frequency and filter the original sound signal; Step 4: Analyze the time-frequency characteristics of the filtered signal and calculate the time difference between the nonlinear harmonic signal and the arrival of each detection base station; Step 5: Using the time difference between the harmonic signals reaching each detection base station, the harmonic source position, that is, the position coordinates of the focus, is calculated based on the TDOA principle.

[0006] Furthermore, the detection base station in step 1 is a transducer for realizing acoustic signal detection, including an ultrasonic detection transducer, a needle hydrophone and an array transducer.

[0007] Furthermore, the step 1 of arranging a plurality of detection base stations outside the focal area of ​​the focused sound field is specifically as follows: When performing two-dimensional positioning, at least three non-colinear detection base stations are set; when performing three-dimensional positioning, at least four non-coplanar detection base stations are set.

[0008] Furthermore, in step 2, a Fourier transform or wavelet transform algorithm is used to calculate the frequency spectrum of the original sound signal detected by each detection base station.

[0009] Furthermore, in step 3, a bandpass filter is designed according to the harmonic frequency, and the original sound signal detected by each detection base station is subjected to bandpass filtering, so that only the nonlinear component is retained.

[0010] Furthermore, in step 4, the time-frequency characteristics of the filtered signal are analyzed using wavelet transform or short-time Fourier transform to obtain the time difference of the harmonic signal arriving at each base station.

[0011] Furthermore, in step 5, based on the TODA wave source position inversion algorithm, the position of the harmonic source is calculated using the time difference of the harmonic signal arriving at the base station, that is, the focus position is obtained.

[0012] A focus positioning system based on the nonlinear effect of a focused acoustic field, comprising: Detection base station: used to detect and record the original sound signal. There are multiple detection base stations, which are arranged outside the focal area of ​​the focused sound field; The first calculation module is used to calculate the spectrum of the original sound signal detected by each detection base station, and analyze whether the original sound signal under test has harmonic components. If so, it is determined that the focused sound field produces nonlinear effects and enters the filtering module; if not, it is determined that the focused sound field does not produce nonlinear effects and ends; Filter module: used to design a bandpass filter according to the harmonic frequency and filter the original sound signal; The second calculation module is used to analyze the time-frequency characteristics of the filtered signal and calculate the time difference of the nonlinear harmonic signal arriving at each detection base station; The third calculation module: uses the time difference of the harmonic signal arriving at each detection base station to calculate the harmonic source position, that is, the position coordinates of the focus based on the TDOA principle.

[0013] Furthermore, the arrangement of the detection base station is specifically as follows: When performing two-dimensional positioning, at least three non-colinear detection base stations are set; when performing three-dimensional positioning, at least four non-coplanar detection base stations are set.

[0014] Furthermore, in the third calculation module, based on the TODA wave source position inversion algorithm, the position of the harmonic source is calculated using the time difference of the harmonic signal arriving at the base station, that is, the focus position is obtained.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes to realize the focus positioning of the focused sound field by monitoring the nonlinear effect at the focal position of the focused sound field. Specifically, a sufficient number of detection transducers are arranged outside the focus, and the sound signals detected by the transducers are subjected to time-frequency analysis, and the time difference of the harmonic signal arriving at each monitoring base station is calculated to invert the harmonic source position. According to the local nonlinear effect of the focused sound field, the inverted harmonic source position is the focal position of the focused sound field. According to the nonlinear acoustic theory, the high-intensity sound field at the focal position of the focused sound field will produce a local nonlinear effect (that is, a high-order harmonic signal is generated at the focus), and the amplitude ratio of the harmonic component to the fundamental frequency reaches a maximum value at the focus, and the harmonic components generated in the areas before and after focusing cancel each other out due to opposite phases. Therefore, the focus of the focused sound field can be regarded as a nonlinear high-order harmonic source, and its position can be inverted by detecting and analyzing the harmonic signal.

[0016] The present invention proposes to treat the focus of the focused sound field as a nonlinear sound source, and to invert the focus position by locating the nonlinear sound source. The advantage is that it can be detected in real time, and since the harmonic source positioning signal frequency is higher, the focus positioning has high resolution and contrast, which is suitable for focused ultrasound related applications, especially for in-vivo real-time monitoring of the focus position in experiments and applications of focused ultrasound medical treatment / intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 This is a schematic diagram of the sound field focus positioning principle and solution proposed by the present invention; Figure 2 A schematic diagram of an experimental system and data processing flow designed based on the focus positioning method proposed in the present invention; Figure 3The harmonic source positioning result based on the TDOA algorithm of Example 2 (focusing transducer: PA1080, center frequency 1MHz), where (a) 1MHz sound field distribution, (b) 2MHz sound field distribution, base stations A, B, and C are selected to construct the TDOA algorithm, (c) time-frequency distribution diagram of base station A signal, (d) time-amplitude curves of 2MHz components of three base stations, (e) focus positioning based on the TDOA method (base stations A, B, and C); Figure 4 The harmonic source positioning results of Example 3 based on the TDOA method (focusing transducer: PA872, center frequency 2.5MHz), including: (a) 2.5MHz sound field distribution, (b) 5MHz sound field distribution, base stations D, E, and F are selected to construct the TDOA algorithm, (c) time-frequency distribution diagram of the harmonic signal of base station D, (d) time-amplitude curves of 5MHz components of three base stations, and (e) focus positioning based on the TDOA method (base stations D, E, and F). DETAILED DESCRIPTION

[0019] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0020] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0021] Embodiment 1 A focus positioning method based on the nonlinear effect of a focused acoustic field comprises the following steps: Step 1: Arrange multiple detection base stations outside the focal area of ​​the focused sound field to detect and record the original sound signal, wherein the detection base station is a transducer for realizing sound signal detection, including an ultrasonic detection transducer, a needle hydrophone and an array transducer. When two-dimensional positioning is performed, at least three non-colinear detection base stations are set; when three-dimensional positioning is performed, at least four non-coplanar detection base stations are set; Step 2: Use Fourier transform or wavelet transform algorithm to calculate the spectrum of the original sound signal detected by each detection base station, and analyze whether the original sound signal under test has harmonic components. If so, it is determined that the focused sound field produces nonlinear effects, and the base station is selected as the positioning base station, and the process proceeds to step 3; if not, it is determined that the focused sound field does not produce nonlinear effects, and the original sound signals monitored by other base stations are selected for analysis and judgment until the number of positioning base stations reaches the minimum requirement; Step 3: Design a bandpass filter according to the harmonic frequency, perform bandpass filtering on the original sound signal detected by each detection base station, and only retain the nonlinear component; Step 4: Analyze the time-frequency characteristics of the filtered signal and calculate the time difference of the nonlinear harmonic signal arriving at each detection base station; specifically, use wavelet transform or short-time Fourier transform to analyze the time-frequency characteristics of the harmonic signal and obtain the time difference of the harmonic component arriving at each detection base station; Step 5: Using the time difference between the harmonic signals arriving at each detection base station, the position coordinates of the focus (harmonic source) are calculated based on the TDOA principle.

[0022] Since the nonlinear effect at the focal position of the focused sound field will produce nonlinear harmonic signals, it can be regarded as a nonlinear harmonic source. By detecting the high-order harmonic signals generated by the nonlinear effect in the focused sound field and inverting the harmonic source position, the focus positioning of the sound field can be achieved.

[0023] Embodiment 2 A focus positioning method based on the nonlinear effect of a focused acoustic field comprises the following steps: Step 1: Design a focused ultrasound focal localization experimental system based on a needle hydrophone (NH 1000, PA, UK), e.g. Figure 2 As shown in the figure; the pulse signal (center frequency 1 MHz, 10 cycles) generated by the waveform generator (Teledyne, T3AFG120) excites the focused ultrasonic transducer (resonant frequency 1 MHz, focal length 75mm, PA1080, UK) to build a focused acoustic field in water; the C-scan system synchronously connected to the waveform generator is used to scan in a plane parallel to the transducer axis. The single-step step length of the ultrasonic C-scan system is set to 0.5mm, and the acoustic field area is 70mm*140mm. The ultrasonic signal of each point on the scanning path is obtained in the preset scanning range, and the fundamental frequency component of the focused ultrasonic sound field on the XY plane is obtained ( Figure 3 (a)) and harmonic components ( Figure 3 (b)) Amplitude distribution; Taking the scanning starting point when scanning the sound field as the coordinate origin, three detection positions A (33.50, 80.00), B (28.50, 75.00), C (40.00, 75.00) are selected in the scanning plane as base stations; Step 2: Use the Fourier algorithm to calculate the spectrum of the original signals detected by the three base stations A, B, and C; Step 3: Design a FIR bandpass filter with the harmonic frequency 2MHz as the center frequency, and filter the signal obtained in step 2; Step 4: In order to obtain the relative time when the harmonics arrive at the three base stations A, B, and C, the signal is transformed by continuous wavelet transform based on Morlet continuous wavelet transform to obtain the time-frequency diagram of the filtered signal ( Figure 3 (c)), take the time-frequency of three base station signals Figure 2 Amplitude-phase curve of MHz component ( Figure 3 (d)), the horizontal coordinate of the peak point is the relative time when the harmonic arrives at the base station; Step 5: Construct three sets of hyperbolas based on the location information of the three base stations in step 1 and the arrival time difference in step 4. The intersection point of the hyperbolas is the location of the harmonic source ( Figure 3 (e)); compare the harmonic source position obtained in step 5 with the sound field scanning result in step axis 2 ( Figure 3 (b)) were compared to verify the accuracy and effectiveness of the method in the present invention.

[0024] Embodiment 3 A focus positioning method based on the nonlinear effect of a focused acoustic field comprises the following steps: Step 1: Design a focused ultrasound focal localization experimental system based on a needle hydrophone (NH 1000, PA, UK), e.g. Figure 2 As shown in the figure; the pulse signal (center frequency 2.5 MHz, 10 cycles) generated by the waveform generator (Teledyne, T3AFG120) excites the focused ultrasonic transducer (resonant frequency 2.5 MHz, focal length 50mm, PA872, UK) to build a focused acoustic field in water; the C-scan system synchronously connected to the waveform generator is used to scan in a plane parallel to the transducer axis. The single-step step length of the ultrasonic C-scan system is set to 0.5mm, and the acoustic field area is 65mm*80.5mm. The ultrasonic signal at each point of the scanning path is obtained in the preset scanning range, and the fundamental frequency component of the focused ultrasonic sound field on the XY plane is obtained ( Figure 4 (a)) and harmonic components ( Figure 4(b)) Amplitude distribution; Taking the scanning starting point when scanning the sound field as the coordinate origin, three detection positions D (32.50, 73.50), E (27.50 68.50), and F (37.5, 68) are selected in the scanning plane as base stations; Step 2: Use the Fourier algorithm to calculate the spectrum of the original signals detected by the three base stations D, E, and F; Step 3: Design a FIR bandpass filter with the harmonic frequency of 5MHz as the center frequency, and filter the signal obtained in step 2; Step 4: In order to obtain the relative time when the harmonics arrive at the three base stations, the signal is transformed by continuous wavelet transform based on Morlet continuous wavelet transform to obtain the time-frequency diagram of the filtered signal ( Figure 4 (c)), take the amplitude and phase curves of the 5MHz component of the three base station signal time-frequency diagrams ( Figure 4 (d)), the horizontal coordinate of the peak point is the relative time when the harmonic arrives at the base station; Step 5: Construct three sets of hyperbolas based on the location information of the three base stations in step 1 and the arrival time difference in step 4. The intersection point of the hyperbolas is the location of the harmonic source ( Figure 4 (e)); compare the harmonic source position obtained in step 5 with the sound field scanning result in step axis 2 ( Figure 3 (b)) were compared to verify the accuracy and effectiveness of the method in the present invention.

[0025] The present invention proposes an ultrasonic focus detection principle based on nonlinear effects. According to the principle of local nonlinear effects of focused ultrasound, in the focused ultrasonic sound field, the focus is equivalent to a secondary sound source, and the harmonics are mainly distributed in the focus area. The focus is regarded as a nonlinear harmonic source, and the harmonic signal is detected in the area behind the focus. Based on the sound source localization method (TDOA), the position of the high-order harmonic source is determined, thereby inverting the focus position. Based on the above theory, two groups of experiments were designed respectively: Based on the central frequency of the needle hydrophone is 1MHz ( Figure 3 ) and 2.5MHz( Figure 4 ) focused transducer acoustic signal detection and sound source localization. In the acoustic signal detection and sound source localization based on the needle hydrophone, the C-scan system is used to visualize the focused ultrasonic sound field distribution, and three non-collinear positions are selected within the scanning range to receive the acoustic signal, such as Figure 2 Analyzing the received sound signal, in addition to the excited fundamental frequency signal (1MHz, 2.5MHz), there are also second and higher harmonic signals (2MHz, 5MHz) in its spectrum, indicating that the focused ultrasound has a nonlinear effect in the propagation process.

[0026] By processing the received sound signal, the time difference of the second harmonic signal arriving at each position is obtained, and the position of the harmonic source is calculated by combining the TDOA algorithm. According to the position information of the three points A (35.5, 85.5), B (30.5, 75.5), and C (37.5, 77.5) selected in the scanning space and the time difference of the second harmonic arriving at the receiving transducer, the position of the harmonic source is calculated to be (34.873, 49.154), as shown in Figure 3 As shown in (e), the focal spot constructed by the focused ultrasonic transducer obtained by acoustic field scanning is recorded as the focus point with the highest intensity. The focal coordinates are (35.50, 48.50) ( Figure 3 (a)). The difference between the harmonic source position and the focal position obtained by acoustic field scanning is (0.627, 0.654). The harmonic source position of the focused transducer with a center frequency of 2.5MHz calculated by the same method is (31.534, 39.156), as shown in Figure 4 (e) The focal position obtained by scanning the acoustic field is (32.50, 38.50) ( Figure 4 (a)), the difference between the harmonic source position and the focal position obtained by acoustic field scanning is (0.966, 0.656). The results show that the harmonic source position calculated based on high-order harmonics is consistent with the theoretical focus in both the horizontal and vertical directions. This shows that the method of calculating the harmonic source inversion focus through high-order harmonics can accurately calculate the focal position of focused ultrasound.

[0027] Embodiment 3 A focus positioning system based on the nonlinear effect of a focused acoustic field, comprising: Detection base station: used to detect and record the original sound signal. There are multiple detection base stations, which are arranged outside the focal area of ​​the focused sound field; The first calculation module is used to calculate the spectrum of the original sound signal detected by each detection base station, and analyze whether the original sound signal under test has harmonic components. If so, it is determined that the focused sound field produces nonlinear effects and enters the filtering module; if not, it is determined that the focused sound field does not produce nonlinear effects and ends; Filter module: used to design a bandpass filter according to the harmonic frequency and filter the original sound signal; The second calculation module is used to analyze the time-frequency characteristics of the filtered signal and calculate the time difference of the nonlinear harmonic signal arriving at each detection base station; The third calculation module: uses the time difference of the harmonic signal arriving at each detection base station to calculate the harmonic source position, that is, the position coordinates of the focus based on the TDOA principle.

[0028] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0029] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0030] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0031] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0032] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit its protection scope. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that after reading the present invention, those skilled in the art can still make various changes, modifications or equivalent substitutions to the specific implementation methods of the invention, but these changes, modifications or equivalent substitutions are all within the protection scope of the pending claims of the invention.

Claims

1. A focus positioning method based on the nonlinear effect of focused acoustic field, characterized in that: The following steps are involved: Step 1: Arrange multiple detection base stations outside the focal area of ​​the focused sound field to detect and record the original sound signal; Step 2: Calculate the spectrum of the original sound signal detected by each detection base station, analyze whether the original sound signal has harmonic components, and if so, determine whether the focused sound field produces nonlinear effects, and proceed to step 3; If not, it is determined that the focused sound field does not produce nonlinear effects, and the process ends; Step 3: Design a bandpass filter according to the harmonic frequency and filter the original sound signal; Step 4: Analyze the time-frequency characteristics of the filtered signal and calculate the time difference between the nonlinear harmonic signal and the arrival of each detection base station; Step 5: Using the time difference between the harmonic signals reaching each detection base station, the harmonic source position, that is, the position coordinates of the focus, is calculated based on the TDOA principle.

2. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: The detection base station in step 1 is a transducer for realizing acoustic signal detection, including an ultrasonic detection transducer, a needle hydrophone and an array transducer.

3. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: The step 1 of arranging multiple detection base stations outside the focal area of ​​the focused sound field is specifically as follows: When performing two-dimensional positioning, at least three non-colinear detection base stations are set; when performing three-dimensional positioning, at least four non-coplanar detection base stations are set.

4. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: In step 2, Fourier transform or wavelet transform algorithm is used to calculate the frequency spectrum of the original sound signal detected by each detection base station.

5. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: In step 3, a bandpass filter is designed according to the harmonic frequency, and the original sound signal detected by each detection base station is subjected to bandpass filtering, and only the nonlinear component is retained.

6. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: In step 4, wavelet transform or short-time Fourier transform is used to analyze the time-frequency characteristics of the filtered signal to obtain the time difference of the harmonic signal arriving at each base station.

7. The focus positioning method based on the nonlinear effect of the focused acoustic field according to claim 1, characterized in that: In step 5, based on the TODA source position inversion algorithm, the position of the harmonic source is calculated using the time difference of the harmonic signal arriving at the base station, that is, the focus position is obtained.

8. A focus positioning system based on the nonlinear effect of focused acoustic field, characterized in that: include: Detection base station: used to detect and record the original sound signal. There are multiple detection base stations, which are arranged outside the focal area of ​​the focused sound field; The first calculation module is used to calculate the spectrum of the original sound signal detected by each detection base station, analyze whether the original sound signal has harmonic components, and if so, determine whether the focused sound field produces nonlinear effects and enter the filtering module; If not, it is determined that the focused sound field does not produce nonlinear effects, and the process ends; Filter module: used to design a bandpass filter according to the harmonic frequency and filter the original sound signal; The second calculation module is used to analyze the time-frequency characteristics of the filtered signal and calculate the time difference of the nonlinear harmonic signal arriving at each detection base station; The third calculation module: uses the time difference of the harmonic signal arriving at each detection base station to calculate the harmonic source position, that is, the position coordinates of the focus based on the TDOA principle.

9. A focus positioning system based on the nonlinear effect of focused acoustic field according to claim 8, characterized in that: The arrangement of the detection base station is specifically as follows: When performing two-dimensional positioning, at least three non-colinear detection base stations are set; when performing three-dimensional positioning, at least four non-coplanar detection base stations are set.

10. The focus positioning system based on the nonlinear effect of the focused acoustic field according to claim 8, characterized in that: In the third calculation module, based on the TODA wave source position inversion algorithm, the position of the harmonic source is calculated using the time difference of the harmonic signal arriving at the base station, that is, the focus position is obtained.

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