Electroacoustic transducer and method, system for controlling the same

Abstract

The application discloses an electro-acoustic transducer and a control method and system thereof. The electro-acoustic transducer comprises a power amplifier coupled with an impedance matching network through a transformer; the impedance matching network is connected with a transducer; the transducer is in communication with a receiving end; the impedance matching network comprises a first inductor, a second inductor and a third capacitor connected in series; one end of the first inductor is connected with one end of the transformer secondary side; the third capacitor is connected with the transducer; one end of a first capacitor is connected in parallel between the first inductor and the second inductor, and the other end of the first capacitor is connected with the other end of the transformer secondary side; one end of a second capacitor is connected in parallel between the second inductor and the third capacitor, and the other end of the second capacitor is connected with the other end of the transformer secondary side. The application can effectively realize impedance matching of the electro-acoustic transducer, so that the transducer is free from the frequency limitation.

Description

Technical Field

[0001] The present invention relates to electroacoustic transducer design technology, in particular to an electroacoustic transducer and a control method and system thereof. Background Art

[0002] As mechanical waves, sound waves transmit information through mechanical vibrations. During underwater transmission, sound waves have the characteristics of low signal attenuation and low energy loss, making them suitable for underwater communications. The generation of sound waves relies on a transducer device, which converts electrical energy into an acoustic signal, which is then received by the receiver. In the past, underwater acoustic communication was limited by technical issues, and single-frequency carrier transmission was usually used for communication. However, with the continuous development of science and technology, the use of multi-carrier communication transmission methods has also become possible. Current problems with underwater acoustic communication include:

[0003] (1) The operation of the electroacoustic transducer requires a high-intensity excitation circuit, so a large amount of reactive power is consumed during operation, resulting in limited output power of the transducer and limiting the intensity of the emitted sound waves.

[0004] (2) Due to its own characteristics, the intensity of the emitted sound waves of the electroacoustic transducer is greatly attenuated as the frequency increases. Therefore, it is difficult to control the sound source level intensity of the signal when the transducer switches the operating frequency point.

[0005] (3) The intensity of the sound source transmitting the sound wave exhibits a Rayleigh distribution in the frequency domain. The varying intensity of the sound source causes excessive amplification of the noise when the signal is used for channel estimation in the frequency domain, seriously affecting the accuracy of the channel estimation. The signal needs to be calibrated for the sound source.

[0006] (4) The nonlinear effects generated during multi-carrier transmission cause interactions between the carrier signals, resulting in large fluctuations in the transmission power. This not only requires the front-end amplifier to have a wide range of variation, but also requires the back-end demodulator to adopt more processing methods for the signal.

[0007] In the existing technology, the method of switching capacitors is used to meet the demand for wide bandwidth. However, the method of switching capacitors requires a large number of switching devices to be switched, which not only easily causes instantaneous current shocks to the main circuit, but also requires the addition of additional control algorithms to control the switching devices, which brings very high instability to the operation of the system.

[0008] Existing impedance matching methods based on active impedance matching primarily leverage the controllability of the inverter to accurately compensate for reactive power in the circuit. Reactive current in the circuit is detected using instantaneous reactive power theory. While active impedance matching methods can achieve excellent impedance matching over a wide bandwidth, the addition of active components makes the overall system costly. Furthermore, active components require a controller, which also introduces significant instability into the overall system's operation. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide an electroacoustic transducer and its control method and system in response to the shortcomings of the existing technology, which ensures that the circuit maintains a high power factor within a wide bandwidth without adding active components, and reduces the requirements of the electroacoustic transducer for the power amplifier end capacity.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is: an electroacoustic transducer, including a power amplifier, the power amplifier is coupled to an impedance matching network through a transformer; the impedance matching network is connected to the transducer; the transducer communicates with a receiving end; the impedance matching network includes a first inductor, a second inductor and a third capacitor connected in series; one end of the first inductor is connected to one end of the secondary side of the transformer; the third capacitor is connected to the transducer; one end of the first capacitor is connected in parallel between the first inductor and the second inductor, and the other end of the first capacitor is connected to the other end of the secondary side of the transformer; one end of the second capacitor is connected in parallel between the second inductor and the third capacitor, and the other end of the second capacitor is connected to the other end of the secondary side of the transformer; wherein the objective function F1 of the impedance matching network is as follows:

[0011]

[0012] Wherein, L1 and L2 are the first inductance and second inductance of the impedance matching network, C1, C2, and C3 are the first capacitance, second capacitance, and third capacitance of the impedance matching network, respectively; α and β are the set upper limits; n is the number of data groups involved in the optimization process; Z in (s) is the transfer function of the total input impedance of the impedance matching network in the complex frequency domain, real(Z in )、imag(Z in ) represent the transfer function Z in The real and imaginary parts of a0~a5, b0~b6 are all constant coefficients, and s is a complex variable.

[0013] After constructing the impedance matching network using the above method, the improvements to the underwater acoustic system are as follows:

[0014] 1) The circuit maintains a high power factor within a certain wide bandwidth, reducing the requirements for the power amplifier end capacity;

[0015] 2) Due to the presence of capacitance in the matching network, the circuit can boost the voltage of the transducer to a certain extent, thereby increasing the intensity of the sound wave output by the transducer;

[0016] 3) After matching, the input impedance Z in Always keep it within a certain size range, and the transducer can maintain high power operation within the frequency band.

[0017] The objective function calculation process includes:

[0018] 1) Randomly generate multiple parameter groups, each parameter group includes inductance value and capacitance value;

[0019] 2) Determine whether the parameters in each parameter group meet the constraints of the objective function. If so, substitute each parameter group into the impedance matching network to obtain multiple power factors λ; otherwise, return to step 1);

[0020] 3) calculating the value of the objective function using the power factor, and saving the parameter group corresponding to the minimum objective function value;

[0021] 4) Substitute the parameter group obtained in step 3) into the chaotic mapping formula to generate a new parameter group, and return to step 1) until the set maximum number of cycles is reached; wherein, the chaotic mapping formula expression is: X k represents the parameter group obtained in step 3), X k+1 Indicates a new parameter group.

[0022] The objective function contains many unknowns and contains many non-differentiable points. Using conventional gradient descent or particle swarm optimization algorithms can easily lead to local minima during the optimization process. The chaotic mapping method of the present invention allows the objective function to traverse all possibilities during the optimization process, allowing the optimal point to be found over a wide range.

[0023] As an inventive concept, the present invention also provides a control method for the above-mentioned electroacoustic transducer, which comprises the following steps:

[0024] S1. Sampling an underwater acoustic signal received by a receiving end, demodulating and restoring the underwater acoustic signal, and using the restored signal as input to a software equalizer to obtain an equalized signal;

[0025] S2 modulates the equalized signal to generate a switching signal to drive the switch of the power amplifier and adjust the amplitude of the transmitted signal;

[0026] The software equalizer is an FIR filter, and the transfer function G(z) of the FIR filter is expressed as:

[0027] G(z)=a1z -1 +a2z-2 +a3z -3 ...+a m z -m ;

[0028] Among them, a1, a2, ..., a m are the coefficients of the FIR filter.

[0029] The advantages of adopting the above control method are:

[0030] 1) It solves the problem of inconsistent output sound wave source level intensity caused by the impedance matching circuit, bringing convenience to underwater acoustic communication.

[0031] 2) Automatically adjust the power amplifier without having to worry about the size of the output signal at the power amplifier end.

[0032] 3) It can output any mixed-frequency wave, providing conditions for mixed-frequency wave communication.

[0033] In the present invention, the coefficient calculation process of the FIR filter includes:

[0034] A) determining a signal with the largest amplitude among the restored signals;

[0035] B) normalizing the remaining restored signals using the signal determined in step A), taking the inverse of the normalized value to obtain the amplitude-frequency characteristic γ of the ideal filter;

[0036] C) Take k groups of frequency points to construct the filter function, and use the following formula to construct the error function E(z) of the filter:

[0037] Where G(z x ) is at a specific frequency f x The value of the transfer function G(z);

[0038] D) changing the coefficients of the FIR filter until the error function value is less than a set value, obtaining the final coefficients of the FIR filter, and using the FIR filter at this time as a software equalizer.

[0039] The advantages of the FIR filter coefficient calculation process are:

[0040] 1) Given the frequency response characteristics and order, the target performance of the filter is fixed and the calculation is convenient.

[0041] 2) Ability to quickly design filters.

[0042] In the above step A), the bubble sorting method is used to obtain the signal with the largest amplitude in the restored signals.

[0043] As an inventive concept, the present invention also provides a control system for an electroacoustic transducer, which includes:

[0044] one or more processors;

[0045] A memory having one or more programs stored thereon, which, when executed by the one or more processors, enables the one or more processors to implement the steps of the above method of the present invention.

[0046] As an inventive concept, the present invention further provides a computer-readable storage medium storing a computer program, which implements the steps of the above-described method of the present invention when executed by a processor.

[0047] Compared with existing technologies, the present invention offers the following advantages: it effectively achieves impedance matching for electroacoustic transducers, freeing the transducers from frequency limitations and enabling broadband sound wave transmission. Furthermore, a software equalization algorithm is used to perform sound source calibration on the matched sound waves, transforming a series of sound waves into signals of consistent intensity, facilitating subsequent signal processing. This invention facilitates high-power operation, broadband operation, and mixed-frequency communication of the transducers. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a schematic diagram of the design principle of the electroacoustic transducer according to an embodiment of the present invention;

[0049] Figure 2 The calculation process of the passive matching circuit according to the embodiment of the present invention;

[0050] Figure 3 The calculation process of the software equalizer according to the embodiment of the present invention;

[0051] Figure 4 is a comparison curve between different topologies in the embodiment of the present invention;

[0052] FIG5(a) and FIG5(b) are comparisons of voltage and current waveforms on the power amplifier side before and after matching under the same conditions in an embodiment of the present invention;

[0053] FIG6(a) and FIG6(b) are comparisons of active power and reactive power output by the power amplifier side before and after matching under the same conditions in an embodiment of the present invention;

[0054] FIG7( a ) and FIG7 ( b ) are comparisons of the effects of 300 Hz and 400 Hz signal mixing waves before and after matching according to an embodiment of the present invention;

[0055] Figures 8(a) to 8(c)Figure 8(a) is a diagram showing the effect of software filtering according to an embodiment of the present invention; Figure 8(b) is the ideal signal given by the power amplifier; Figure 8(c) is the signal received by the hydrophone after passing through the hardware matching circuit; and Figure 8(c) is the signal received by the hydrophone after passing through the software equalizer and returning to the power amplifier for adjustment. DETAILED DESCRIPTION

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying 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 making creative efforts shall fall within the scope of protection of the present invention.

[0057] Figure 1 This is a simplified diagram of the entire device. It uses an H-bridge power amplifier topology and consists of four switching devices: S1, S2, S3, and S4. A transformer is used to convert the output voltage U o The signal is then transmitted to the matching network on the secondary side. The matching network consists of inductors L1 and L2, and capacitors C1, C2, and C3. The transducer converts the electrical signal from the matching circuit into an acoustic wave for output, which is received by a hydrophone. A sampling circuit then demodulates and restores the received signal above water. This restored signal is then fed into a software equalizer to produce an equalized signal. This equalized signal is modulated and generates a switching signal that drives switches S1-S4, which are fed back to the power amplifier to adjust the amplitude of the transmitted signal.

[0058] The impedance matching circuit of the embodiment of the present invention is designed as follows.

[0059] The impedance characteristics of the transducer are relatively complex, and its impedance characteristic curve can be divided into a linear part and a nonlinear part. Considering the needs of underwater acoustic communication, it is usually only used in the frequency band with linear characteristics. Therefore, the embodiment of the present invention can give the equivalent impedance of the transducer as:

[0060] Z L =R+jX L =R+j(2πf)L (1)

[0061] Since the impedance characteristics of the transducer are inductive, the impedance matching method of a single capacitor in series effectively improves the operating characteristics of the transducer. Assuming that the inductance of the capacitor in series is C, the capacitor and the transducer together form an LC series circuit, then the total impedance of the circuit is Z L The expression is:

[0062]

[0063] After impedance matching, the complex impedance of the circuit is significantly reduced, and the reactive power consumed during the operation of the transducer is also greatly reduced. However, this LC series matching circuit can only achieve good matching results near the resonant frequency point and cannot meet the requirements of broadband impedance matching.

[0064] The embodiment of the present invention uses a high-order passive impedance matching topology as the best choice. The high-order impedance matching topology is more complex, but its phase-frequency characteristics change slowly and can meet the needs of broadband impedance matching. Traditional high-order matching topologies have T-type or π-type matching circuits, but this third-order impedance matching topology still cannot meet the impedance matching requirements of the transducer. Therefore, the embodiment of the present invention provides a higher-order LCLCC impedance matching model, whose topology is shown in the attached figure. Figure 1 shown.

[0065] After using the LCLCC network to perform impedance matching on the transducer, the total impedance transfer function Z of the loop in the complex frequency domain is obtained by Laplace transform. in The expression for (s) is as follows:

[0066]

[0067] Where a0-a5 and b0-b6 are constant coefficients. The effect of the matching topology is completely determined by the parameters within the topology components, so the selection of parameters is very important.

[0068] The design goal of passive impedance matching is to pursue the transfer function Z in The phase-frequency characteristic of (s) is kept near 0 degrees within a certain frequency band, thus achieving the purpose of impedance matching. For the design target λ, the following formula can be given:

[0069]

[0070] The closer the value of λ is to 1, the better the matching effect is, which reflects that the reactive current component in the circuit is smaller.

[0071] For the solution of matching network parameters, it is the best choice to use iterative algorithm for optimization. Set the objective function to λ and give constraints that are in line with the reality. After inputting the required objective function and constraints, the problem to be solved is transformed into a constrained optimization problem. For the objective function and variable constraints in the optimization problem, combining formula (3) and formula (4) and the attached Figure 1 , the specific details of the optimization problem are shown in formula (5):

[0072]

[0073] Among them, F1 is the target fitness function, L and C represent the parameters of the inductor and capacitor in the impedance matching circuit, α and β are the set upper limits, which are 0.01 and 10 respectively.

[0074] The specific process for solving the matching circuit parameters is as follows: Figure 2 As shown:

[0075] 1. Randomly generate 10,000 sets of parameter sets X for inductors and capacitors L1, L2, C1, C2, and C3 k , where k is the group number of the parameter group. And use the constraints in formula (5) to determine whether the generated parameters meet the constraints. If the constraints are not met, re-generate the parameters randomly;

[0076] 2. Substitute the parameters of each parameter group into the circuit and use the total impedance Z in (s) Calculate the power factor λ and the value of the fitness function F1. Under the premise of satisfying the constraints, find the minimum value of the function F1 from 10,000 groups of parameter groups, and save the corresponding parameters into an array, and prepare to look for a better solution again.

[0077] 4. Input the parameter group obtained in step 2 into the chaotic mapping formula and generate a new parameter group X k+1 , repeat the above steps until the set maximum number of cycles is reached. The chaotic mapping formula is shown in formula (6).

[0078]

[0079] 5. Find the optimal solution from the saved data set. Under the premise of satisfying the constraints, the parameter set corresponding to the minimum F1 function is the optimal solution to be searched.

[0080] After the design is completed, the designed impedance matching circuit is calculated using formula (4) to verify the topology effect, and the matching effect of the LCCLC impedance matching topology is compared with the single capacitor type and T-type circuits. The results are shown in the attached figure. Figure 4 express.

[0081] It can be observed that the impedance matching topology proposed in the example of the present invention has a better matching effect than the traditional matching circuit, and can achieve a high power factor matching effect within a very wide frequency band.

[0082] At the same time, the output current of the power supply is analyzed using the instantaneous reactive power. The instantaneous reactive power formula is as follows:

[0083]

[0084] Where D represents the signal phase shift of 90 degrees, V s , Is Represent the voltage and current at the power supply end, P s , Q s Represents active power and reactive power respectively.

[0085] The effect can be viewed through simulation software. After impedance matching, the voltage and current waveforms at the power amplifier end, as well as the active and reactive power output by the power supply, are shown in Figures 5(a), 5(b), 6(a), and 6(b). It can be seen that the phase difference between the voltage and current at the power supply end is significantly reduced after matching. In addition, the active power output by the power amplifier end is significantly increased, which improves the active output of the transducer. It can also be seen that under the same conditions, the output power of the transducer is amplified after impedance matching. This also leads to huge differences in the sound source level intensity of the output sound waves when transmitting signals in different frequency bands, which will cause problems for subsequent signal processing. Therefore, while performing impedance matching in hardware, a software equalizer is also required to equalize the output sound source.

[0086] For the transmission of the mixing wave, the phase angle correction implemented by the impedance matching circuit reduces the phase angle difference between the signal at the transducer output and the given command signal. This not only avoids the problem of peak overlap between the currents and reduces power fluctuations, but also facilitates the subsequent modulation of the mixing wave, making the transmission of the mixing wave feasible from a hardware perspective. The matching effect of the mixing wave is shown in Figures 7(a) and 7(b). As can be seen, the matching effect for the mixing wave is good, and the phase angle error between the signal and the current is reduced.

[0087] The software filter of the embodiment of the present invention is designed as follows.

[0088] After impedance matching, the transducer's output power is enhanced across different frequency bands, but this also exacerbates the differences in acoustic signal intensity between these bands, creating challenges for data processing during underwater acoustic communication. Therefore, a software algorithm is needed to automatically adjust the output sound waves.

[0089] The FIR filter based on finite impulse response is a typical software filter. The FIR filter has the function of smoothing the time domain waveform and is very suitable for use as a software equalizer. For the FIR filter, its Z-domain transfer function expression is mainly:

[0090] G(z)=a1z -1 +a2z -2 +a3z -3 ...+a n z -n (8)

[0091] where a n These are the coefficients of the FIR filter.

[0092] After the sound wave signal is multiplied with the FIR filter in the frequency domain, i.e. convolution in the time domain, the obtained sound wave signal can maintain high consistency in sound source intensity.

[0093] For the design of the equalization algorithm, the key lies in the solution of the coefficients and the order in the FIR expression. For the solution of the filter coefficients, the computer iteration is also used. The TLS least square method is selected, the frequency domain response of the desired filter is taken as the objective function, and the least square method is used for fitting, so that the desired digital filter is obtained. The order of the filter is selected as 7000. For the solution problem of the software equalizer, the specific process is shown in the attached Figure 3

[0094] 1. The demodulated carrier signal is restored, and the receiving is stopped after a certain time length;

[0095] 2. For the received signal group, the bubble sort method is used to find the signal with the largest amplitude;

[0096] 3. The maximum amplitude signal is used to normalize other signals, and the obtained normalized value is inverted to obtain the amplitude-frequency characteristic γ of the ideal filter;

[0097] 4. The amplitude-frequency characteristic γ of the ideal filter is taken as the design target of the filter, and the gain of the filter is given as 7000. Combined with formula (9), the error function E(z) of the filter is constructed as:

[0098]

[0099] Based on the principle of least square method, the coefficients in formula (8) are continuously changed to reduce the error function E(z).

[0100] 5. When the error function E(z) is less than the specified value, the expression of the filter is obtained, and it is used as a software equalizer.

[0101] The software equalizer is simulated by using simulation software. After the signal is processed by the digital filter, it can be seen that the originally inconsistent underwater acoustic signals are converted into signals with the same amplitude after the FIR filter. The signal is fed back to the power amplifier, so that the amplitudes of all frequency bands can remain consistent, which will bring convenience for subsequent signal processing.

[0102] ​The entire setup was verified using simulation software. The power amplifier was fed with an ideal signal, as shown in Figure 8(a). After passing through the hardware matching circuit, the signal received by the hydrophone is shown in Figure 8(b). It can be clearly seen that after matching, the strength of the transmitted signal in different frequency bands changes, affecting subsequent signal processing. After passing through the software equalizer and returning to the power amplifier for adjustment, the signal received by the hydrophone is shown in Figure 8(c). After adjustment by the software equalizer, the amplitude strength of the signal across all frequency bands is normalized, facilitating subsequent signal processing.

[0103] The simulation results above verify that the method of the embodiment of the present invention can effectively achieve impedance matching for electroacoustic transducers, freeing the transducer from frequency limitations and enabling broadband sound wave transmission. Simultaneously, a software equalization algorithm is used to perform sound source calibration on the matched sound waves, transforming a series of sound waves into signals of consistent intensity, facilitating subsequent signal processing. This complete hardware and software impedance matching method facilitates high-power operation, broadband operation, and mixed-frequency wave communication for the transducer.

Claims

1. An electroacoustic transducer, characterized in that: The device comprises a power amplifier coupled to an impedance matching network via a transformer; the impedance matching network is connected to a transducer; the transducer communicates with a receiving end; the impedance matching network comprises a first inductor, a second inductor, and a third capacitor connected in series; One end of the first inductor is connected to one end of the secondary side of the transformer; the third capacitor is connected to the transducer; one end of the first capacitor is connected in parallel between the first inductor and the second inductor, and the other end of the first capacitor is connected to the other end of the secondary side of the transformer; One end of the second capacitor is connected in parallel between the second inductor and the third capacitor, and the other end of the second capacitor is connected to the other end of the secondary side of the transformer. The objective function F1 of the impedance matching network is as follows: Wherein, L1 and L2 are the first inductance and second inductance of the impedance matching network, C1, C2, and C3 are the first capacitance, second capacitance, and third capacitance of the impedance matching network, respectively; α and β are the set upper limits; n is the number of data groups involved in the optimization process; Z in (s) is the transfer function of the total input impedance of the impedance matching network in the complex frequency domain, real(Z in )、imag(Z in ) represent the transfer function Z in The real and imaginary parts of (s), a0~a5, b0~b6 are all constant coefficients, and s is a complex variable.

2. The electroacoustic transducer according to claim 1, characterized in that The objective function calculation process includes: 1) Randomly generate multiple parameter groups, each parameter group includes inductance value and capacitance value; 2) Determine whether the parameters in each parameter group meet the constraints of the objective function. If so, substitute each parameter group into the impedance matching network and obtain multiple groups of power factor λ calculation results; Otherwise, return to step 1); 3) calculating the value of the objective function using the power factor, and saving the parameter group corresponding to the minimum objective function value; 4) Substitute the parameter group obtained in step 3) into the chaotic mapping formula to generate a new parameter group, and return to step 1) until the set maximum number of cycles is reached; wherein, the chaotic mapping formula expression is: X k represents the parameter group obtained in step 3), X k+1 Indicates a new parameter group.

3. A control method for the electroacoustic transducer according to claim 1 or 2, characterized in that: The following steps are involved: S1. Sampling an underwater acoustic signal received by a receiving end, demodulating and restoring the underwater acoustic signal, and using the restored signal as input to a software equalizer to obtain an equalized signal; S2 modulates the equalized signal to generate a switching signal to drive the switch of the power amplifier and adjust the amplitude of the transmitted signal; The software equalizer is an FIR filter, and the transfer function G(z) of the FIR filter is expressed as: G(z)=a1z -1 +a2z -2 +a3z -3 ...+a m z -m ; Among them, a1, a2, ..., a m are the coefficients of the FIR filter.

4. The control method of the electroacoustic transducer according to claim 3, characterized in that: The coefficient calculation process of the FIR filter includes: A) determining a signal with the largest amplitude among the restored signals; B) normalizing the remaining restored signals using the signal determined in step A), taking the reciprocal of the normalized value to obtain the amplitude-frequency characteristic γ of the ideal filter; C) Use the following formula to construct the error function E(z) of the filter: Where G(z x ) is at a specific frequency f x The value of the transfer function G(z); k is the number of frequency data points involved in the filter construction; D) changing the coefficients of the FIR filter until the error function value is less than a set value, obtaining the final coefficients of the FIR filter, and using the FIR filter at this time as a software equalizer.

5. The control method of the electroacoustic transducer according to claim 4, characterized in that: In step A), a bubble sorting method is used to obtain a signal with the largest amplitude in the restored signals.

6. A control system for an electroacoustic transducer, characterized in that: include: one or more processors; A memory having one or more programs stored thereon, which, when executed by the one or more processors, enables the one or more processors to implement the steps of the method according to any one of claims 3 to 5.

7. A computer-readable storage medium, characterized in that It stores a computer program, which implements the steps of the method according to any one of claims 3 to 5 when executed by a processor.

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