Device for inhibiting grating lobes of acoustic transducer array by using band-pass driving signal

Abstract

The invention discloses a device for inhibiting grating lobes of an acoustic transducer array by using band-pass driving signals, which comprises an upper computer, an acoustic host and an acoustic transducer array which are connected in sequence, the acoustic host comprises a logic control circuit, N direct digital synthesis circuits connected with the logic control circuit, and N linear amplification circuits connected with the N direct digital synthesis circuits in a one-to-one correspondence manner, so that N channels are formed; and the acoustic transducer array is a linear regular arrangement array and comprises N transducer array elements connected with the N linear amplification circuits in a one-to-one correspondence manner, the width of each transducer array element is L, the spacing distance between the adjacent transducer array elements is dL, the resonance center frequency of each transducer array element is F, and the relative bandwidth is B. According to the invention, a good grating lobe suppression effect can be obtained with relatively low technical cost.

Description

Technical Field

[0001] The present invention relates to the technical field of acoustic applications, and particularly to a device for suppressing grating lobes of an acoustic transducer array by using a band-pass drive signal. Background Art

[0002] Acoustic transducer arrays are widely used in fields such as sonar, medical ultrasound imaging, and power ultrasound. In a sonar system, the array realizes underwater target detection and tracking through beamforming; medical ultrasound uses the array to transmit and receive sound waves to generate high-resolution human tissue images; in power ultrasound, sound energy is emitted to a specific position by controlling sound waves to achieve applications such as sonochemical reactions and microbial reactions. In addition, acoustic transducer array technology is also used in fields such as noise control, geological exploration, and consumer electronics, such as the beamforming speaker array of a smart speaker. With the development of MEMS and flexible electronics technologies, miniaturized arrays have further expanded the application potential in wearable devices and the Internet of Things. It can be said that the applications of acoustic transducer arrays almost cover all acoustic application fields.

[0003] When the element spacing of an acoustic transducer array exceeds half a wavelength, the transmitted signal will generate grating lobes in non-target directions, resulting in energy dispersion and interference. In sonar, grating lobes may cause false target detection; in medical ultrasound, it will reduce the imaging quality and generate artifacts. In addition, grating lobes may leak sensitive signals or interfere with adjacent frequency bands.

[0004] To suppress grating lobes, it is necessary to optimize the array design (such as sparse arrangement) or adopt amplitude weighting techniques (such as Gaussian distribution weighting). However, the currently commonly used grating lobe suppression methods often require sacrificing the beam width or signal gain, and sacrifices need to be made in terms of system performance or system technical complexity. For example, the Chinese invention patent "An Ultrasonic Transducer Linear Array with Random Element Spacing and Its Design Optimization Method" (202010993070.7) introduces a method of randomly arranging transducer elements to suppress grating lobes. However, manufacturing a transducer array with randomly arranged element positions has high technical difficulty. For example, the Chinese invention patent "Grating Lobe Suppression Method, System, Device, and Medium for MIMO Radar Images" (202310649187.7) introduces a method of suppressing array grating lobes through amplitude and phase weighting control, but such a method requires the array control system to have higher complexity and processing speed. Other related research results have similar problems, and it is always necessary to pay a price in some aspects of the system to obtain a better grating lobe suppression effect.

[0005] Therefore, finding a method to obtain a better grating lobe suppression effect at a lower cost has high scientific value and engineering value for various acoustic applications. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a device for suppressing grating lobes of an acoustic transducer array using a band-pass drive signal, which can achieve a good grating lobe suppression effect at a relatively low technical cost.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A device for suppressing grating lobes of an acoustic transducer array using a band-pass drive signal, comprising a host computer, an acoustic host, and an acoustic transducer array connected in sequence. The acoustic host includes 1 logic control circuit, N direct digital synthesis circuits all connected to the logic control circuit, and N linear amplification circuits respectively connected to the N direct digital synthesis circuits one by one, forming N channels; the acoustic transducer array is a linearly regular arrangement array, including N transducer array elements respectively connected to the N linear amplification circuits one by one. The width of each transducer array element is L, the interval distance between adjacent transducer array elements is dL, and the resonance center frequency of each transducer array element is F and the relative bandwidth is B, where

[0009] The host computer is configured to calculate the drive signal parameters of each channel and send them to the logic control circuit;

[0010] The logic control circuit is configured to receive the drive signal parameters of each channel sent by the host computer, convert them into specific circuit parameters, and then send them to the corresponding direct digital synthesis circuit; the direct digital synthesis circuit is configured to generate a drive signal with a waveform, amplitude, and phase meeting the requirements according to the circuit parameters; the linear amplification circuit is configured to amplify the power of the drive signal;

[0011] The drive acoustic transducer array is configured to generate different sound fields through different drive signals.

[0012] Preferably, the circuit structures and circuit parameters of the N direct digital synthesis circuits are all the same; the circuit structures and circuit parameters of the N linear amplification circuits are all the same.

[0013] Preferably, the logic control circuit is an FPGA or a CPLD.

[0014] Preferably, the host computer calculates the drive signal parameters of each channel, including the following steps:

[0015] Calculate the center distance P = L + dL between adjacent transducer array elements according to the width L of the transducer array element and the interval distance dL between transducer array elements of the acoustic transducer array;

[0016] Calculate the acoustic wave wavelength λ = C / F in the medium according to the resonance center frequency F of the transducer array element and the sound speed C in the medium of the sound wave to be emitted;

[0017] If P < λ / 2, then there is no need for grating lobe suppression; otherwise, grating lobe suppression is required. 1) Waveform, the formula is as follows:

[0018] sinc(B*T)*sin(2π*F*T) (1) where T is the time series required for a single emission, and sinc represents the sine cardinal function;

[0019] 2) Amplitude, the drive signals of N channels are all set to the same signal amplitude;

[0020] 3) Phase, if the acoustic transducer array is non-focusing emission, the drive signals of N channels are directly set to be in the same phase; if the acoustic transducer array is focusing emission, the phase calculation formula of the drive signal for each channel is:

[0021]

[0022] where D represents the vertical distance from the focal point to the acoustic transducer array; n represents the nth element; τ n represents the emission delay of the drive signal of the nth element.

[0023] Based on the above technical solutions, the beneficial effects of the present invention are as follows: When using a transducer array regularly arranged with a single-frequency drive signal, grating lobes will inevitably occur when the center distance between elements is greater than half the wavelength of the sound wave, especially for the case of a focused sound field. And the positions, amplitudes, etc. of the grating lobes can be calculated and known. If the frequency of the drive signal is changed, the positions and amplitudes of the grating lobes will change correspondingly. If the single-frequency drive signal is replaced with a drive signal containing many different frequency components and the energy is dispersed into different frequency components, there will be many different grating lobes, and the energy of these grating lobes is relatively small and the positions move slowly. Overall, there is no longer a single grating lobe with concentrated energy in the sound field, which is equivalent to suppressing the grating lobes in the sound field.

[0024] Since each transducer element has a certain resonant center frequency and relative bandwidth, only the drive signal with a frequency within this bandwidth can be effectively converted into a sound signal. Therefore, the drive signal must be a band-pass signal based on the bandwidth of the transducer element to normally drive the transducer element.

[0025] The acoustic transducer array used in the device for suppressing grating lobes of an acoustic transducer array by using a band-pass drive signal in the present invention is a regularly arranged array, which has relatively low manufacturing difficulty and cost. The logic control circuit is a conventional FPGA or CPLD, and the usage cost and development cost are also relatively low. The direct digital synthesis circuit (Direct Digital Synthesis, DDS) and the linear amplification circuit are also conventional circuits and do not require special design or processing. The direct digital synthesis circuit can generate waveforms of any shape according to formulas, and the linear amplification circuit can amplify signals of any waveform. The only control measures are the calculation of the drive waveform and parameter setting, which are slightly more complex than the single-frequency drive signal, achieving a relatively good grating lobe suppression effect with a relatively small system cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. is a schematic structural diagram of a device for suppressing grating lobes of an acoustic transducer array by using a band-pass drive signal in an embodiment;

[0027] Figure 2 FIG. is a schematic diagram for calculating the waveform parameters of the acoustic transducer array in an embodiment;

[0028] Figure 3 FIG. is a flowchart of the operation of a device for suppressing grating lobes of an acoustic transducer array by using a band-pass drive signal in an embodiment;

[0029] Figure 4 FIG. is a comparison diagram of the focal plane distributions of the sound fields generated by a single-frequency and a band-pass drive signal in an embodiment, where A is the focal plane distribution diagram of the sound field generated by a single frequency; B is the focal plane distribution diagram of the sound field generated by a band-pass drive signal;

[0030] Figure 5 FIG. is a comparison diagram of the full sound field distributions of the sound fields generated by a single-frequency and a band-pass drive signal in an embodiment, where A is the full sound field distribution diagram of the sound field generated by a single frequency; B is the full sound field distribution diagram of the sound field generated by a band-pass drive signal. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] As Figures 1 to 3As shown in the figure, this embodiment provides a device for suppressing grating lobes of an acoustic transducer array using a band - pass drive signal, which includes a host computer, an acoustic host, and an acoustic transducer array connected in sequence. The acoustic host includes 1 logic control circuit, N direct digital synthesis circuits all connected to the logic control circuit, and N linear amplification circuits connected to the N direct digital synthesis circuits one - to - one, forming N channels; the acoustic transducer array is a linearly regularly arranged array, including N transducer array elements connected to the N linear amplification circuits one - to - one. The width of each transducer array element is L, the interval distance between adjacent transducer array elements is dL, the resonant center frequency of each transducer array element is F, and the relative bandwidth is B. Among them,

[0033] The host computer is used to calculate the drive signal parameters of each channel according to the parameters of the acoustic device and the parameters of the medium of the acoustic wave to be transmitted, and send them to the logic control circuit;

[0034] The acoustic host is used to control the emission of acoustic waves, realize the control of the waveform, amplitude, and phase of the drive signal of each channel, so as to achieve good suppression of grating lobes in the sound field generated by the transducer array. Specifically, the logic control circuit is used to receive the drive signal parameters of each channel sent by the host computer, convert them into specific circuit parameters, and then send them to the corresponding direct digital synthesis circuit; the direct digital synthesis circuit is used to generate a drive signal with a waveform, amplitude, and phase meeting the requirements according to the circuit parameters; the linear amplification circuit is used to amplify the power of the drive signal;

[0035] The driven acoustic transducer array is used to generate different sound fields through different drive signals.

[0036] In a device for suppressing grating lobes of an acoustic transducer array using a band - pass drive signal in an embodiment, the acoustic host includes 1 logic control circuit, N direct digital synthesis circuits, and N linear amplification circuits. Its logic control circuit is connected to all the direct digital synthesis circuits and is connected to the host computer through a communication interface; the direct digital synthesis circuit is connected to the corresponding linear amplification circuit, and generates a drive signal with a waveform, amplitude, and phase meeting the requirements according to certain rules under the unified management of the logic control circuit; the said linear amplification circuit is connected to the corresponding transducer array element, linearly amplifies the power of the drive signal sent by the corresponding direct digital synthesis circuit, and then is used to drive the transducer array element to emit acoustic waves.

[0037] Among them, the direct digital synthesis circuit and the linear amplification circuit have exactly the same circuit structure and circuit parameters. The differences are that they are connected to different transducer array elements and generate different drive signals by receiving different instructions from the logic control circuit.

[0038] In a device for suppressing grating lobes of an acoustic transducer array using a band - pass drive signal according to an embodiment, the logic control circuit is generally an FPGA or CPLD. It receives the waveform, amplitude, and phase of the signal to be transmitted for each channel sent by the host computer, and parses and converts the instructions sent by the host computer into specific instruction contents executable by the direct digital synthesis circuit and the linear amplification circuit according to the parameter settings of the subsequent circuits, and sends them one by one to each circuit of these two parts, namely the direct digital synthesis circuit and the linear amplification circuit.

[0039] In a device for suppressing grating lobes of an acoustic transducer array using a band - pass drive signal according to an embodiment, a process of calculating the drive signal parameters for each channel by the host computer based on the parameters of the acoustic device and the parameters of the medium of the sound wave to be transmitted is provided. The process includes the following steps:

[0040] Calculate the center - to - center distance P = L + dL of adjacent transducer elements according to the transducer element width L and the transducer element interval distance dL of the acoustic transducer array;

[0041] Calculate the acoustic wavelength λ = C / F in the medium according to the resonant center frequency F of the transducer element and the speed of sound C in the medium of the sound wave to be transmitted;

[0042] If P < λ / 2, there is no need to suppress grating lobes; otherwise, grating lobe suppression is required. 1) Waveform, the calculation formula is:

[0043] sinc(B*T)*sin(2π*F*T) (1)

[0044] Among them, T is the time sequence required for a single emission, and sinc represents the sinus cardinalis function; 2) Amplitude, the drive signals of N channels are all set to the same signal amplitude;

[0045] 3) Phase, if the acoustic transducer array is non - focused emission, directly set the drive signals of N channels to be in the same phase; if the acoustic transducer array is focused emission, the phase calculation formula for the drive signal of each channel is:

[0046]

[0047] Among them, D represents the vertical distance from the focus to the acoustic transducer array; n represents the nth element; τ n represents the emission delay of the drive signal of the nth element.

[0048] Embodiment

[0049] Set one as Figure 2The acoustic transducer array shown has an element width L = 1.5 mm, an adjacent element spacing dL = 1.0 mm, the number of elements N = 64, the resonant center frequency of the elements is 1 MHz, the relative bandwidth is 40% (±0.2 MHz), and the perpendicular distance D from the sound field focus point to the transducer array is 100 mm. The transducer array is driven to emit sound waves using a single-frequency sine wave with a frequency of 1 MHz, and the sound field distribution at the focal plane and the full sound field distribution results are recorded. The transducer array is again driven to emit sound waves using a waveform with a center frequency of 1 MHz, a bandwidth of ±0.2 MHz, and calculated according to formula (1), and the sound field distribution at the focal plane and the full sound field distribution results are recorded.

[0050] Compare the sound field results at the focal plane as Figure 4 shown, Figure 4 A is the sound field result generated by the single-frequency drive signal, Figure 4 B is the sound field result generated by the band-pass drive signal. It is obvious that the absolute energy of the grating lobes in the sound field after being driven by the band-pass signal becomes smaller, but the distribution is relatively wider, and the energy at the grating lobes is dispersed to different spaces. Then observe the comparison of the full sound field results as Figure 5 shown, Figure 5 A is the sound field result generated by the single-frequency drive signal; Figure 5 B is the sound field result generated by the band-pass drive signal. It can be seen that the energy at the grating lobes after using the band-pass drive signal is effectively dispersed. Thus, through the change of the drive signal, the effective suppression of the grating lobes of the sound field generated by the regularly arranged transducer array is achieved.

[0051] The above is only the preferred embodiment of a device for suppressing the grating lobes of an acoustic transducer array using a band-pass drive signal disclosed in the present invention, and is not used to limit the protection scope of the embodiments of this specification. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of this specification shall be included within the protection scope of the embodiments of this specification.

[0052] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such a process, method, commodity or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, commodity or device including the said element.

Claims

1. An apparatus for suppressing grating lobes of an acoustic transducer array using a bandpass drive signal, characterized in that, It includes a host computer, an acoustic host, and an acoustic transducer array connected in sequence. The acoustic host includes 1 logic control circuit, N direct digital synthesis circuits all connected to the logic control circuit, and N linear amplification circuits respectively connected to the N direct digital synthesis circuits one by one, forming N channels; The acoustic transducer array is a linearly regularly arranged array, including N transducer array elements respectively connected to the N linear amplification circuits one by one. The width of each transducer array element is L, the interval distance between adjacent transducer array elements is dL, and the resonance center frequency of each transducer array element is F and the relative bandwidth is B. Among them, The host computer is used to calculate the driving signal parameters of each channel and send them to the logic control circuit; The logic control circuit is used to receive the driving signal parameters of each channel sent by the host computer, convert them into specific circuit parameters, and then send them to the corresponding direct digital synthesis circuit; the direct digital synthesis circuit is used to generate driving signals with waveforms, amplitudes, and phases meeting the requirements according to the circuit parameters; the linear amplification circuit is used to amplify the power of the driving signals; The driving acoustic transducer array is used to generate different sound fields through different driving signals.

2. The device for suppressing grating lobes of an acoustic transducer array by using a band-pass driving signal according to claim 1, wherein The circuit structures and circuit parameters of the N direct digital synthesis circuits are all the same; the circuit structures and circuit parameters of the N linear amplification circuits are all the same.

3. The device for suppressing grating lobes of an acoustic transducer array by using a band-pass drive signal according to claim 1, wherein The logic control circuit is an FPGA or a CPLD.

4. The device for suppressing grating lobes of an acoustic transducer array by using a band-pass driving signal according to claim 1, wherein The host computer calculates the driving signal parameters of each channel, including the following steps: Calculate the center distance P = L + dL between adjacent transducer array elements according to the width L of the transducer array element and the interval distance dL between transducer array elements of the acoustic transducer array; Calculate the acoustic wave wavelength λ = C / F in the medium according to the resonance center frequency F of the transducer array element and the sound speed C in the medium of the sound wave to be emitted; If P < λ / 2, there is no need to perform grating lobe suppression; otherwise, grating lobe suppression is required. 1) Waveform, the formula is as follows: sinc(B*T)*sin(2π*F*T) (1) where, T is the time sequence required for a single emission, and sinc represents the sine cardinal function; 2) Amplitude, the driving signals of the N channels are all set to the same signal amplitude; 3) Phase, if the acoustic transducer array is non-focusing emission, directly set the driving signals of the N channels to be in the same phase; if the acoustic transducer array is focusing emission, the phase calculation formula of the driving signal of each channel is: where D represents the vertical distance from the focal point to the acoustic transducer array; n represents the nth array element; τ n represents the transmission delay of the drive signal of the nth array element.

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