Impedance matching method of electret air coupling transducer

Abstract

The invention discloses an impedance matching method for an electret air-coupled transducer, and the method comprises the steps: determining the target working frequency of the electret air-coupled transducer, the target working frequency being the frequency enabling the electret air-coupled transducer to generate the highest energy conversion efficiency; constructing an equivalent circuit model of the electret air-coupled transducer, wherein the equivalent circuit model is used for simulating the electrical response of the electret air-coupled transducer at the target working frequency; and through a Smith chart tool, based on the acquired signal source impedance, the target working frequency and the equivalent circuit model, determining a target impedance matching network, so that the impedance of the electret air coupling transducer is matched with the impedance of the signal source. The impedance of the electret transducer can be reduced, and the electric energy transmission efficiency of the electret transducer can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of radio frequency impedance matching, and particularly relates to an impedance matching method of an electret air-coupled transducer. BACKGROUND

[0002] The piezoelectric electret not only has a relatively strong piezoelectric effect comparable to that of piezoelectric ceramics (such as PZT), but also has an extremely low acoustic impedance (about 0.03 MRayl), which can be well matched with the acoustic impedance of air. At present, such a material has gradually become an ideal piezoelectric material applied to an air-coupled ultrasonic transducer (also referred to as an air-coupled transducer).

[0003] However, the excessive electrical impedance and the phase close to-90° of the electret air-coupled transducer can cause a serious impedance mismatch between the electret air-coupled transducer and general electronic devices, thereby resulting in a low electrical energy transmission efficiency of the electret air-coupled transducer and limiting the practical application thereof.

[0004] Therefore, how to improve the electrical energy transmission efficiency of the electret air-coupled transducer is a technical problem to be solved at present. SUMMARY

[0005] In order to solve the problem of how to improve the electrical energy transmission efficiency of the electret air-coupled transducer, the application provides an impedance matching method of an electret air-coupled transducer. The technical problem to be solved by the application is achieved by the following technical scheme. The application provides an impedance matching method of an electret air-coupled transducer, comprising: determining a target working frequency of the electret air-coupled transducer, the target working frequency being a frequency at which the electret air-coupled transducer can generate the highest energy conversion efficiency; constructing an equivalent circuit model of the electret air-coupled transducer, the equivalent circuit model being used to simulate the electrical response of the electret air-coupled transducer at the target working frequency; determining a target impedance matching network based on the obtained signal source impedance, the target working frequency and the equivalent circuit model through a Smith chart tool, so that the impedance of the electret air-coupled transducer is matched with the signal source impedance.

[0006] In an embodiment of the application, the determination of the target working frequency of the electret air-coupled transducer comprises: obtaining an impedance phase spectrum of the electret air-coupled transducer; determining the frequency corresponding to the highest phase in the impedance phase spectrum as the target working frequency.

[0007] In an embodiment of the application, the determination of the target impedance matching network based on the obtained signal source impedance, the target working frequency and the equivalent circuit model through the Smith chart tool comprises: Input the impedance phase value corresponding to the target operating frequency into the Smith chart tool as the starting load point, and add a preset impedance matching network in the Smith chart tool to reduce the impedance of the electret air-coupled transducer. The load point is moved by increasing / decreasing the matching parameters of the preset impedance matching network by a preset step size. When the load point moves to the target area, the current matching parameters are determined as the matching parameters of the preset impedance matching network to obtain an updated impedance matching network. The target area is the area that enables the impedance matching between the electret air-coupled transducer and the signal source to meet the preset requirements. The updated impedance matching network is connected to the equivalent circuit model, and the power transfer efficiency of the electret air-coupled transducer is calculated. When the power transfer efficiency of the electret air-coupled transducer reaches the power transfer efficiency threshold, the updated impedance matching network is determined as the target impedance matching network.

[0008] In one embodiment of the present invention, calculating the power transfer efficiency of an electret air-coupled transducer includes: The power transfer efficiency of the electret air-coupled transducer is calculated based on the signal source impedance and the reduced impedance of the electret air-coupled transducer.

[0009] In one embodiment of the present invention, the expression for calculating the power transfer efficiency of the electret air-coupled transducer is as follows:

[0010] in, To improve the power transfer efficiency of electret air-coupled transducers and These are the real and imaginary parts of the signal source impedance, respectively. and These are the real and imaginary parts of the reduced impedance of the electret air-coupled transducer, respectively.

[0011] In one embodiment of the invention, the updated impedance matching network includes an inductor, and the matching parameters of the updated impedance matching network include the inductance value.

[0012] In one embodiment of the present invention, connecting the updated impedance matching network to the equivalent circuit model includes: Connect the inductor in series with the equivalent circuit model.

[0013] In one embodiment of the present invention, the method further includes: After determining the target impedance matching network, the corresponding physical matching circuit module is determined based on the target impedance matching network; Connect the physical matching circuit module to the electret air-coupled transducer so that the impedance of the electret air-coupled transducer is matched with the impedance of the signal source.

[0014] In one embodiment of the present invention, connecting the physical matching circuit module to the electret air-coupled transducer includes: The physical matching circuit module can be connected inside the electret air-coupled transducer, or connected outside the electret air-coupled transducer.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides an impedance matching method for electret air-coupled transducers. Through theoretical modeling and Smith chart tool-assisted design, efficient matching of electret air-coupled transducers at the target operating frequency is achieved, thereby improving the power transmission efficiency of electret transducers.

[0016] (2) The impedance matching method provided by this invention is based on the equivalent circuit model of the electret air-coupled transducer and the Smith chart simulation design. It relies entirely on theoretical analysis and software tools, avoiding the material loss and labor costs caused by repeatedly making physical matching circuits and conducting actual measurements and adjustments in the traditional trial-and-error method. The entire matching design process can be completed on a computer, which greatly reduces the R&D cost and time investment, and is particularly suitable for rapid prototyping and mass application.

[0017] (3) By establishing an equivalent circuit model of the electret air-coupled transducer, its complex impedance characteristics (including resistance and reactance components) at the target operating frequency can be accurately simulated. Combined with the Smith chart tool for visual matching path design, the accuracy of the determined target impedance matching network can be guaranteed. Compared with empirical matching, this method has higher matching accuracy and lower return loss.

[0018] (4) The impedance matching method provided by this invention does not depend on specific transducer physical structures or material parameters. As long as its equivalent circuit model can be established, it can be widely applied. This method can be used for impedance matching design of electret air-coupled transducers used in ultrasonic imaging, gas detection, or wireless power transmission, which means that this invention has high universality.

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0020] Figure 1 This is a flowchart of an impedance matching method for an electret air-coupled transducer provided in an embodiment of the present invention; Figure 2 The impedance phase spectrum of an electret air-coupled transducer without impedance matching is provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the equivalent circuit model of an electret air-coupled transducer provided in an embodiment of the present invention; Figure 4 This is a comparison diagram of the impedance phase of a simulated equivalent circuit model and the measured impedance phase of an electret air-coupled transducer provided in an embodiment of the present invention. Figure 5 This is a schematic diagram of a Smith chart tool for calculating matched inductance provided in an embodiment of the present invention; Figure 6 This is a schematic diagram of the equivalent circuit model of a 921μH inductor connected in series with an electret air-coupled transducer provided in an embodiment of the present invention; Figure 7 The impedance phase diagram is obtained by simulating the equivalent circuit model of a 921μH inductor and an electret air-coupled transducer provided in an embodiment of the present invention. Figure 8 This is an impedance phase diagram obtained by actual measurement after a physical circuit matching module and an electret air-coupled transducer are connected in series, as provided in an embodiment of the present invention. Figure 9 This is a comparison diagram of the signal amplitude of an electret air-coupled transducer measured in self-transmitting and self-receiving mode under conditions of no impedance matching and impedance matching, provided by an embodiment of the present invention. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following describes in detail an impedance matching method proposed according to the present invention, in conjunction with the accompanying drawings and specific embodiments.

[0022] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0023] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element.

[0024] This invention addresses the problem of improving the power transfer efficiency of electret air-coupled transducers by providing an impedance matching method for electret air-coupled transducers. Please refer to [link to relevant documentation]. Figure 1 The method includes the following steps: Step 1: Determine the target operating frequency of the electret air-coupled transducer.

[0025] The target operating frequency is the frequency at which the electret air-coupled transducer can produce the highest energy conversion efficiency. In other words, the resonant effect of the electret air-coupled transducer is strongest at the target operating frequency.

[0026] Specifically, the impedance phase spectrum of the electret air-coupled transducer can be measured, and the frequency corresponding to the highest phase in the impedance phase spectrum can be determined as the target operating frequency.

[0027] For example, the measured impedance phase spectrum of the electret air-coupled transducer can be specifically as follows: Figure 2 As shown, from Figure 1 It can be seen that the frequency corresponding to the highest phase in the impedance phase spectrum is 594 kHz, that is, the final determined target operating frequency is 594 kHz, and from... Figure 1 It can also be seen that the impedance of the electret air-coupled transducer at this frequency (594 kHz) is 3440Ω, the phase is -89.67°, and the power transfer efficiency T is 0.03%.

[0028] Step 2: Construct the equivalent circuit model of the electret air-coupled transducer.

[0029] The equivalent circuit model is used to simulate the electrical response of the electret air-coupled transducer at the target operating frequency.

[0030] It should be noted that the equivalent circuit model is used to simulate the electrical response of the electret air-coupled transducer at the target operating frequency. It can be understood as simulating the electrical behavior (e.g., impedance characteristics) of the electret air-coupled transducer at the actual target operating frequency through the equivalent circuit model, so that it can be analyzed and impedance matched in subsequent circuit design.

[0031] For example, the equivalent circuit model of the constructed electret air-coupled transducer can be found in [reference needed]. Figure 3 , Figure 3 This is a schematic diagram of the equivalent circuit model of an electret air-coupled transducer provided in an embodiment of the present invention, as shown below. Figure 3 As shown, the equivalent circuit model includes a resistor R, an inductor L1, a first capacitor C1, and a second capacitor C2. The resistor R has a resistance of 0.64 MΩ, the inductor L1 has an inductance of 0.68 H, the first capacitor C1 has a capacitance of 104.5 fF, and the second capacitor C2 has a capacitance of 77.85 fF.

[0032] Specifically, such as Figure 3 As shown, one end of resistor R is connected to one end of second capacitor C2, the other end of resistor R is connected to one end of inductor L1, the other end of inductor L1 is connected to one end of first capacitor C1, and the other end of first capacitor C1 is connected to the other end of second capacitor C2.

[0033] To verify the accuracy of the constructed equivalent circuit model, the impedance phase of the equivalent circuit model was simulated, and the impedance phase of the electret condenser transducer was measured. The simulated impedance phase was then compared with the measured impedance phase. Specifically, a comparison chart of the simulated impedance phase of the equivalent circuit model and the measured impedance phase of the electret condenser transducer can be found in [reference needed]. Figure 4 ,Depend on Figure 4 It can be seen that the simulated impedance curve and the measured impedance curve are in a state of overlap, and the frequency point corresponding to the highest phase in the simulation is also at the same point as the frequency point corresponding to the highest phase in the measurement. Therefore, it can be shown that the accuracy of the constructed equivalent circuit model meets the requirements.

[0034] Step 3: Using the Smith chart tool, based on the acquired signal source impedance, target operating frequency, and equivalent circuit model, determine the target impedance matching network to match the impedance of the electret air-coupled transducer with the signal source impedance.

[0035] It is understood that in the embodiments of the present invention, the signal source is an electronic device and the load is an electret air-coupled transducer, that is, in the embodiments of the present invention, the electret air-coupled transducer performs impedance matching to the electronic device.

[0036] In addition, in this embodiment of the invention, the impedance matching network includes an inductor, and the matching parameters of the impedance matching network include the inductance value.

[0037] In some embodiments, the target impedance matching network is determined using the Smith chart tool based on the acquired signal source impedance, target operating frequency, and equivalent circuit model, including: Step 3.1: Input the impedance phase value corresponding to the target operating frequency into the Smith chart tool as the starting load point, and add a preset impedance matching network in the Smith chart tool to reduce the impedance of the electret air-coupled transducer.

[0038] Step 3.2: Based on the preset step size, increase / decrease the preset impedance matching network matching parameters to move the load point. When the load point moves to the target area, determine the current matching parameters as the preset impedance matching network matching parameters to obtain an updated impedance matching network. The target area is the area that enables the impedance matching between the electret air-coupled transducer and the signal source to meet the preset requirements.

[0039] Specifically, after inputting the impedance phase value corresponding to the target operating frequency into the Smith chart tool, and adding the preset impedance matching network (i.e., the inductor with the preset inductance value) to the Smith chart tool, the inductance value can be increased / decreased based on a preset step size to move the load point (i.e., the impedance point) clockwise / counterclockwise until the load point moves to the region where the impedance matching between the electret air-coupled transducer and the signal source meets the preset requirements, i.e., the target region. Then, the currently modulated inductance value is determined as the matching parameter of the preset impedance matching network to obtain an updated impedance matching network.

[0040] For example, the target area can be represented on the Smith chart as a circular or elliptical region centered at point (1+j0) that meets specific matching criteria (such as return loss S11≤-10 dB).

[0041] For example, please see Figure 5 , Figure 5 This is a schematic diagram of a Smith chart tool for calculating matching inductance provided in an embodiment of the present invention. The blue arc represents the trajectory of the real part (i.e., the resistive component) of the impedance of the electret air-coupled transducer, and the red arc represents the trajectory of the imaginary part (i.e., the reactance component) of the impedance of the electret air-coupled transducer. Figure 5 It can be seen that the impedance corresponding to the initial load point is 3440Ω and the phase is -89.67°. As the inductance value of the inductor is continuously increased, after the load point moves clockwise to the target area, the impedance corresponding to the load point decreases to 19.5Ω and the phase is 0.25°. At this time, the inductance value of the inductor is 921μH.

[0042] Step 3.3: Connect the updated impedance matching network to the equivalent circuit model and calculate the power transfer efficiency of the electret air-coupled transducer.

[0043] Specifically, the updated impedance matching network (i.e., the inductor after modulation of the inductance value) is connected to the equivalent circuit model, and then the impedance matching results are simulated to calculate the power transfer efficiency of the electret air-coupled transducer.

[0044] In some embodiments, connecting the updated impedance matching network to the equivalent circuit model includes connecting the inductor in series with the equivalent circuit model.

[0045] Specifically, the inductor with an inductance value of 921μH is connected in series with the equivalent circuit model.

[0046] The schematic diagram of the equivalent circuit model after connecting a 921μH inductor L2 in series can be found in [reference needed]. Figure 6 .Depend on Figure 6It can be seen that the resistance of resistor R is 0.61MΩ, the inductance of inductor L1 is 0.68H, the capacitance of the first capacitor C1 is 104.5fF, and the capacitance of the second capacitor C2 is 77.85fF.

[0047] Specifically, such as Figure 6 As shown, one end of resistor R is connected to one end of second capacitor C2, the other end of resistor R is connected to one end of inductor L1, the other end of inductor L1 is connected to one end of first capacitor C1, the other end of first capacitor C1 and the other end of second capacitor C2 are connected together, and connected to one end of 921μH inductor L2, the other end of inductor L2 is grounded.

[0048] For example, an inductor with an inductance of 921μH is connected in series with the equivalent circuit model, and the impedance phase of the equivalent circuit model is simulated. The simulation results can be found in [reference needed]. Figure 7 , Figure 7 This is an impedance phase diagram obtained from simulation of an equivalent circuit model of a 921μH inductor and an electret air-coupled transducer provided in an embodiment of the present invention. Figure 7 It can be seen that at a frequency of 593kHz, the impedance of the equivalent circuit model is 19.5Ω, the phase is 0.25°, and the power transfer efficiency T is 81%.

[0049] In this context, power transfer efficiency refers to the percentage of electrical power transferred between the electret air-coupled transducer and the signal source (such as electronic equipment).

[0050] In some embodiments, calculating the power transfer efficiency of an electret air-coupled transducer includes: calculating the power transfer efficiency of the electret air-coupled transducer based on the signal source impedance and the reduced impedance of the electret air-coupled transducer.

[0051] Specifically, the expression for calculating the power transfer efficiency of an electret air-coupled transducer is:

[0052] in, To improve the power transfer efficiency of electret air-coupled transducers and These are the real and imaginary parts of the signal source impedance, respectively. and These are the real and imaginary parts of the reduced impedance of the electret air-coupled transducer, respectively.

[0053] Step 3.4: When the power transfer efficiency of the electret air-coupled transducer reaches the power transfer efficiency threshold, the updated impedance matching network is determined as the target impedance matching network.

[0054] Specifically, when the power transmission efficiency of the electret air-coupled transducer reaches the power transmission efficiency threshold, the inductor after modulation of the inductance value is determined as the target impedance matching network.

[0055] In some embodiments, after determining the target impedance matching network, a corresponding physical matching circuit module can be determined based on the target impedance matching network, and the physical matching circuit module can be connected to the electret air-coupled transducer so that the impedance of the electret air-coupled transducer is matched with the impedance of the signal source.

[0056] It should be noted that connecting this physical matching circuit module to the electret air-coupled transducer can eliminate the imaginary part of the electret air-coupled transducer impedance, so that the impedance of the electret air-coupled transducer is matched with the impedance of the signal source, thereby improving the power transmission efficiency of the electret air-coupled transducer.

[0057] It is understood that, in this embodiment of the invention, the physical matching circuit module is an inductor.

[0058] The physical matching circuit module is connected to the electret air-coupled transducer and includes: The physical matching circuit module can be connected inside the electret air-coupled transducer, or connected outside the electret air-coupled transducer.

[0059] Specifically, the physical matching circuit module (i.e., the inductor) can be directly integrated inside the electret air-coupled transducer. This reduces additional space requirements and signal loss caused by external wiring. Alternatively, the inductor can be used as an independent physical matching circuit module and connected to the electret air-coupled transducer via cables or other means. This approach allows for flexible adjustment of matching parameters based on specific application scenarios, adapting to different operating conditions.

[0060] It should be noted that the embodiments of the present invention do not specifically limit the connection method between the inductor and the electret air-coupled transducer, and the designer can choose according to specific needs and conditions.

[0061] In summary, the impedance matching method for an electret air-coupled transducer provided by this invention, through theoretical modeling and Smith chart-assisted design, achieves efficient matching of the electret air-coupled transducer at the target operating frequency, thereby improving the power transmission efficiency of the electret transducer.

[0062] Furthermore, the impedance matching method provided by this invention, based on the equivalent circuit model of an electret air-coupled transducer and Smith chart simulation design, relies entirely on theoretical analysis and software tools. This avoids the material waste and labor costs associated with repeatedly fabricating physical matching circuits and performing experimental adjustments in traditional trial-and-error methods. The entire matching design process can be completed on a computer, significantly reducing R&D costs and time investment, making it particularly suitable for rapid prototyping and mass application.

[0063] In addition, the impedance matching method provided by this invention, by establishing an equivalent circuit model of the electret empty-coupled transducer, can accurately simulate its complex impedance characteristics (including resistance and reactance components) at the target operating frequency. Combined with the Smith chart tool for visual matching path design, the accuracy of the determined target impedance matching network can be guaranteed. Compared with empirical matching, this method has higher matching accuracy and lower return loss. Moreover, the impedance matching method provided by this invention does not depend on specific transducer physical structures or material parameters; as long as its equivalent circuit model can be established, it can be widely applied. Whether used for electret empty-coupled transducers in ultrasonic imaging, gas detection, or wireless power transmission, this method can be used for impedance matching design, meaning this invention has high versatility.

[0064] To verify the technical effect of the impedance matching method provided by this invention, after connecting an inductor with an inductance of 921 μH to an electret air-coupled transducer, the impedance phase of the electret air-coupled transducer was measured. The results of this measurement can be found in [reference needed]. Figure 8 , Figure 8 This is an impedance phase diagram obtained by actual measurement after a physical circuit matching module (i.e., a 921μH inductor) and an electret air-coupled transducer are connected in series, as provided in an embodiment of the present invention. Figure 8 It can be seen that at a frequency of 629kHz, the impedance of the electret air-coupled transducer is 201Ω, the phase is -1.7°, and the power transfer efficiency T is 75%.

[0065] It should be noted that the simulation is based on an ideal situation (i.e., the inductance value remains constant at 921μH). However, the inductance value of the inductor actually connected in series with the electret air-coupled transducer may have a tolerance of 5% to 10% due to manufacturing or signal loss. Therefore, the frequency will deviate during the actual measurement. At the same time, the inductor used also has parasitic resistance at this frequency, which will also cause the measured impedance (201Ω) to differ from the simulated impedance (19.5Ω).

[0066] In addition, it is understandable that the frequency deviation after impedance matching within ±50 kHz will not affect the reliability of the matching compared to the target operating frequency before impedance matching, because this frequency range is still within the -6dB bandwidth of the electret air-coupled transducer, that is, the impact on the output of the electret air-coupled transducer is small and can be ignored.

[0067] Furthermore, after impedance matching of the electret air-coupled transducer, the signal amplitude of the electret air-coupled transducer can be measured and compared in both self-transmit / self-receive and single-transmit / single-receive modes, with and without impedance matching. The comparison results can be found in [reference needed]. Figure 9 , Figure 9 This is a comparison chart of signal amplitude measurements taken from an electret air-coupled transducer in a self-transmitting and self-receiving mode without impedance matching, provided by an embodiment of the present invention. Figure 9 It can be seen that the signal amplitude of the received signal without impedance matching is Vp-p=1.2mV, while the signal amplitude of the received signal with impedance matching is Vp-p=125mV. This indicates that after impedance matching of the electret air-coupled transducer, the energy reflection caused by impedance mismatch of the electret air-coupled transducer is eliminated, the power transmission efficiency of the electret air-coupled transducer is improved, and thus the signal amplitude of the received signal is greatly improved.

[0068] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An impedance matching method for an electret air-coupled transducer, characterized in that, include: Determine the target operating frequency of the electret air-coupled transducer, wherein the target operating frequency is the frequency at which the electret air-coupled transducer can produce the highest energy conversion efficiency. An equivalent circuit model of an electret air-coupled transducer is constructed, and the equivalent circuit model is used to simulate the electrical response of the electret air-coupled transducer at the target operating frequency. Using the Smith chart tool, based on the acquired signal source impedance, the target operating frequency, and the equivalent circuit model, a target impedance matching network is determined to match the impedance of the electret air-coupled transducer with the signal source impedance.

2. The impedance matching method according to claim 1, characterized in that, Determining the target operating frequency of the electret air-coupled transducer includes: Obtain the impedance phase spectrum of the electret air-coupled transducer; The frequency corresponding to the highest phase in the impedance phase spectrum is determined as the target operating frequency.

3. The impedance matching method according to claim 1, characterized in that, The step of determining the target impedance matching network using the Smith chart tool, based on the acquired signal source impedance, the target operating frequency, and the equivalent circuit model, includes: The impedance phase value corresponding to the target operating frequency is input into the Smith chart tool as the starting load point, and a preset impedance matching network is added to the Smith chart tool to reduce the impedance of the electret air-coupled transducer. The load point is moved by increasing / decreasing the matching parameters of the preset impedance matching network based on a preset step size. When the load point moves to the target area, the current matching parameters are determined as the matching parameters of the preset impedance matching network to obtain an updated impedance matching network. The target area is the area that enables the impedance matching between the electret air-coupled transducer and the signal source to meet the preset requirements. Connect the updated impedance matching network to the equivalent circuit model and calculate the power transfer efficiency of the electret air-coupled transducer. When the power transfer efficiency of the electret air-coupled transducer reaches the power transfer efficiency threshold, the updated impedance matching network is determined as the target impedance matching network.

4. The impedance matching method according to claim 3, characterized in that, The calculation of the power transfer efficiency of the electret air-coupled transducer includes: The power transfer efficiency of the electret air-coupled transducer is calculated based on the impedance of the signal source and the reduced impedance of the electret air-coupled transducer.

5. The impedance matching method according to claim 4, characterized in that, The expression for calculating the power transfer efficiency of the electret air-coupled transducer is as follows: in, The power transfer efficiency of the electret air-coupled transducer is given. and These are the real and imaginary parts of the impedance of the signal source, respectively. and These are the real and imaginary parts of the reduced impedance of the electret air-coupled transducer, respectively.

6. The impedance matching method according to claim 3, characterized in that, The updated impedance matching network includes an inductor, and the matching parameters of the updated impedance matching network include the inductance value.

7. The impedance matching method according to claim 6, characterized in that, Connecting the updated impedance matching network to the equivalent circuit model includes: The inductor is connected in series with the equivalent circuit model.

8. The impedance matching method according to claim 1, characterized in that, The method further includes: After determining the target impedance matching network, the corresponding physical matching circuit module is determined based on the target impedance matching network; The physical matching circuit module is connected to the electret air-coupled transducer so that the impedance of the electret air-coupled transducer is matched with the impedance of the signal source.

9. The impedance matching method according to claim 8, characterized in that, Connecting the physical matching circuit module to the electret air-coupled transducer includes: The physical matching circuit module can be connected inside the electret air-coupled transducer, or the physical matching circuit module can be connected outside the electret air-coupled transducer.

Images