CN109365250B - Frequency locking implementation method for high-frequency ultrasonic transducer - Google Patents
Frequency locking implementation method for high-frequency ultrasonic transducer Download PDFInfo
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- CN109365250B CN109365250B CN201811257569.0A CN201811257569A CN109365250B CN 109365250 B CN109365250 B CN 109365250B CN 201811257569 A CN201811257569 A CN 201811257569A CN 109365250 B CN109365250 B CN 109365250B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
- B06B1/0207—Driving circuits
- B06B1/0223—Driving circuits for generating signals continuous in time
- B06B1/0269—Driving circuits for generating signals continuous in time for generating multiple frequencies
- B06B1/0276—Driving circuits for generating signals continuous in time for generating multiple frequencies with simultaneous generation, e.g. with modulation, harmonics
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Abstract
The invention provides a frequency locking method for a high-frequency ultrasonic transducer, which solves the problems of slow frequency tracking, low precision and dependence on a high-performance processor of the conventional high-frequency ultrasonic imaging transducer. According to voltage and current signals at two ends of a load of an acquisition transducer, the signals are mixed by a multiplier, high-frequency components are filtered by a low-pass filter, the direct-current components are sampled by an ADC (analog to digital converter) and a median average filtering method, the magnitude of the direct-current components reflects the magnitude of phase difference, and finally, a large step size searching method is used for controlling frequency output to lock frequency. The invention can control DDS to generate continuous wave to quickly and accurately track and lock the resonance frequency of the high-frequency ultrasonic transducer through the common performance processor.
Description
Technical Field
The invention relates to an ultrasonic imaging transducer, in particular to a frequency tracking and locking method for a high-frequency ultrasonic transducer.
Background
Ultrasonic transducers are an important component of ultrasonic equipment, and particularly, high-frequency ultrasonic imaging transducers play an indispensable role in medical ultrasonic imaging systems and detection ultrasonic imaging systems. The ultrasonic imaging transducer has the highest electromechanical conversion efficiency only when working at a resonance frequency. However, in the use process of the ultrasonic imaging transducer, due to changes of external environmental factors such as changes of temperature and changes of parameters of the ultrasonic imaging transducer after long use, the resonant frequency point of the ultrasonic imaging transducer changes, once the ultrasonic imaging transducer works at a non-resonant frequency point, the output power of the ultrasonic imaging transducer is greatly reduced, so that an ultrasonic signal emitted by the transducer is weak, an echo signal is weak, and the imaging requirements of high precision and high quality are difficult to meet. It is therefore desirable for the excitation circuitry of an ultrasonic imaging transducer to have the ability to track and lock on to its frequency.
The existing ultrasonic transducer frequency tracking methods are various, but the problems that the frequency tracking is slow, the high-frequency ultrasonic imaging transducer cannot be accurately tracked, or a high-performance processor is needed for tracking the high-frequency ultrasonic imaging transducer exist.
The patent publication number CNIO1468347A, the patent name is automatic frequency tracking method and system of ultrasonic transducer, the patent is that a direct digital synthesizer generates sine wave signal with adjustable frequency, after the sine wave signal is amplified by a power amplifier, the matching network drives the ultrasonic transducer, a sampling loop collects a group of voltage and current feedback signals of the ultrasonic transducer from the power output end of the ultrasonic transducer, the group of signals are respectively sent to a phase comparison circuit through a filter shaping circuit and sent to a main control singlechip through an amplitude adjusting circuit, the main control singlechip controls the trigger signal and frequency word of a DDS controller according to the working frequency range of the transducer, and sends a continuous frequency scanning instruction to the DDS controller, so that the DDS controller outputs sine wave with continuously changing frequency; meanwhile, the master control single chip microcomputer also monitors the amplitude of a sampling current feedback signal of the transducer in real time, and when the amplitude of the current feedback signal is larger than half of the current amplitude of the transducer during resonance, the master controller enables the DDS controller to stop sweeping the frequency and sends an automatic tracking instruction to the DDS controller; the phase comparison circuit carries out phase comparison on the voltage and current feedback signals processed by the filtering and shaping circuit, then the phase difference signals are input to the phase difference accumulation circuit to generate frequency words of the DDS chip, and the DDS controller can transmit the frequency words to the DDS chip according to a fixed time sequence to automatically change the frequency of output signals of the DDS chip, so that the ultrasonic transducer always works near a resonance point, and automatic frequency tracking is realized. The automatic frequency locking method of the ultrasonic generator in the prior art has the following defects:
the tracking speed is slow, when the main control single chip monitors that the amplitude of the current feedback signal is larger than half of the current amplitude when the transducer resonates, the main controller enables the DDS controller to stop sweeping the frequency and send out an automatic tracking instruction, when the amplitude of the current feedback signal is larger than half of the current amplitude when the transducer resonates, the frequency needs to be continuously scanned in the period, meanwhile, the sampling current is continuously compared and analyzed, the period does not really enter a frequency locking process, and the preparation time is long.
The invention is difficult to accurately track the high-frequency transducer, the invention compares the phases of the voltage and current feedback signals processed by the filter shaping circuit, and inputs the phase difference signals to the phase difference accumulation circuit to generate the frequency words of the DDS chip, because the high-frequency signals have high requirements on the shaping circuit, and the phase of the shaped waveform can be shifted, so that the tracking to a non-resonance point is caused, and simultaneously, a trigger is utilized to give the time difference of arrival of the rising edge signals of the I _ ph and V _ ph input signals to the sensitive characteristics of the rising edge signals of the trigger to judge the phase difference, which needs to rely on a high-performance processor to capture the rising edge signals of the trigger, the higher the resonance frequency of the transducer is, the higher the performance of the required processor is, in addition, because the transducer has the gradual change characteristic, the frequency current output at the non-resonance point is not zero, and the interference is caused to the result.
The patent publication CNIO6140592A, entitled digital ultrasonic generator and automatic frequency locking method thereof, is characterized in that a transducer is driven by a driving circuit through a high-frequency inverter circuit, current and voltage signals are sampled and sent to a multiplier, a high-frequency signal is filtered through low-pass filtering, then the direct current signal is subjected to cosine inversion processing to obtain a phase difference signal, and finally the phase difference signal is controlled by a processor to track the frequency to a resonance point. According to the method, a high-voltage signal passing through a high-frequency inverter circuit can generate spike pulses, the spike pulses cannot be completely eliminated after passing through a filter circuit, and in addition, a sampling circuit needs to pass through a voltage-current isolation circuit, so that original waveform information of the sampling signal is difficult to keep unchanged, interference can be caused on subsequent sampling, and the resonant frequency of the high-frequency ultrasonic imaging transducer is difficult to accurately lock.
Disclosure of Invention
The invention aims to provide a method for quickly and accurately tracking and locking the resonant frequency of a high-frequency ultrasonic transducer by using a common performance processor, and solves the problems that the conventional ultrasonic imaging transducer is slow in frequency tracking, low in precision, dependent on the high-performance processor for processing and difficult to track the high-frequency transducer.
The invention provides a method for realizing frequency locking of a high-frequency ultrasonic transducer, which comprises the following steps:
(1) and the processor module is used for driving the DDS signal generation module to generate a high-frequency continuous sine wave signal with variable frequency.
(2) And the adjustable power amplification module is used for carrying out adjustable power amplification on the high-frequency sine wave signal.
(3) The high-frequency continuous sine wave signal after power amplification drives the high-frequency ultrasonic transducer to work in a continuous wave mode.
(4) The voltage and current sampling and I/V conversion module is used for collecting voltage and current signals output by the transducer load, the voltage signals are subjected to partial pressure collection processing, and the current signals are converted into voltage signals through I/V for collection.
(5) And sending the acquired voltage and current signals to a multiplier module for frequency mixing processing.
(6) And sending the output mixed frequency signal to a low-pass filter module, filtering the high-frequency component signal, and leaving the low-frequency direct-current component.
(7) And sending the low-frequency direct current component into an ADC (analog-to-digital converter) sampling module for AD conversion, wherein ADC sampling data processing adopts a median average filtering method, and the value of the digitized low-frequency direct current component reflecting the phase difference is output.
(8) And sending the AD converted value to a processor module for judgment processing, determining the phase difference according to the sampling value by judging the ADC sampling direct current component, tracking and locking the frequency by using a large and small step size searching method, and finally outputting the locked resonance frequency.
(9) And finally, outputting and displaying the locked resonant frequency result to an LCD (liquid crystal display) screen.
As an improvement of the method, an LC low-pass passive filter network is added behind the DDS signal generation module, so that the sine wave signal generated by the DDS signal generation module is effectively filtered after passing through the low-pass filter network, and the signal-to-noise ratio of the signal is improved.
As a further improvement of the above method, the I/V conversion module feedback resistor RfAdopts a precise adjustable rheostat with the range of 0-5K omega, RfThe gain of the transimpedance operational amplifier circuit is influenced, the output current of the transducer changes along with the frequency change, the output current is the largest at a resonant frequency point, in order to enable the voltage and current amplitudes to be better matched and ensure the frequency locking precision, the precise adjustable rheostat is adopted to facilitate the adjustment of the gain of the transimpedance operational amplifier circuit, and meanwhile, the precise adjustable rheostat can adapt to the gain adjustment of replacing transducers with different frequencies.
As a further improvement of the above method, the cutoff frequency of the low-pass filter module is adjusted to 10KHz, since the ADC sampling signal is a dc component and the sampling time is related to the signal frequency, the higher the signal frequency is, the shorter the period of sampling the complete signal is, and the shorter the required time is, in order to quickly sample and calculate the signal, the higher the cutoff frequency of the filter is properly increased, which is beneficial to shortening the sampling time while ensuring the sampling precision.
Compared with the prior art, the method for realizing the frequency locking of the high-frequency ultrasonic transducer has the advantages that:
(1) the DDS is adopted to generate high-frequency continuous sine waves, the transducers are excited to work in a continuous wave mode after power amplification, frequency tracking and locking are carried out on the transducers, the transducers are not required to be driven by a high-frequency inverter circuit, spike pulses cannot be generated, an isolation circuit is not required, the integrity and undistortion of output waveforms are guaranteed to the maximum extent, and precision guarantee is provided for subsequent frequency locking.
(2) The effective current and voltage of the high-frequency ultrasonic transducer are sampled and then are subjected to frequency mixing through a high-bandwidth multiplier, high-frequency components are filtered through a five-order low-pass filter, low-frequency components are sampled through a high-precision ADC, the phase difference is directly reflected by the size of the ADC sampling result, the series of processes can be finished without depending on a high-performance processor, the ADC sampling result can be processed only by a common-performance processor, and therefore frequency locking of the high-frequency ultrasonic imaging transducer can be easily achieved.
(3) The ADC sampling utilizes a median average filtering method, so that a very large minimum value generated by unstable factors of a circuit can be effectively filtered, the sampling precision of the ADC is further ensured, and compared with a conventional frequency scanning and frequency locking method, a frequency locking algorithm adopts a large step length method, so that the frequency locking frequency scanning range can be greatly reduced, and the frequency can be quickly locked on the premise of ensuring the precision.
The method is verified to be capable of locking the resonant frequency of the high-frequency ultrasonic transducer quickly and accurately.
Drawings
FIG. 1 is an overall block diagram of the present invention.
Fig. 2 is a schematic diagram of a DDS signal generating module circuit of the present invention.
Fig. 3 is a circuit schematic of the I/V conversion module of the present invention.
Fig. 4 is a schematic circuit diagram of a fifth-order low-pass filter module according to the present invention.
FIG. 5 is a flowchart of the mean filtering method for bit values according to the present invention.
Fig. 6 is a flowchart of the size step search method of the present invention.
Fig. 7 is a process diagram of the size step search method of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings and the detailed description.
As shown in fig. 1, the method for implementing frequency locking of a high-frequency ultrasonic transducer according to the present invention comprises a processor module 1, a DDS signal generating module 2, an adjustable power amplifying module 3, a current sampling and I/V converting module 4, a voltage sampling module 5, a multiplier module 6, a low-pass filter module 7, an ADC sampling module 8, a display module 9, and a high-frequency ultrasonic transducer 10.
The processor module 1 is connected with the DDS signal generating module 2, the ADC sampling module 8, and the display module 9, the DDS signal generating module 2 is connected with the adjustable power amplifying module 3, the adjustable power amplifying module 3 is connected with the high-frequency ultrasonic transducer 10, the high-frequency ultrasonic transducer 10 is connected with the voltage sampling module 5 and the current sampling and I/V conversion module 4, the voltage sampling module 5 and the current sampling and I/V conversion module 4 are connected with the multiplier module 6, the multiplier module 6 is connected with the low-pass filter module 7, and the low-pass filter module 7 is connected with the ADC sampling module 8.
The detailed implementation method comprises the following steps:
(1) as shown in fig. 2, a processor module 1 is used for driving a DDS signal generating module 2 to generate a high-frequency continuous sine wave signal with variable frequency, when a rising edge of a W _ CLK signal arrives, one bit of data information is input into a chip through a D7 pin, when transmission of 40 bits of control information is finished, a pulse is generated through an FQ _ UD pin to update the output frequency and phase, and a frequency-adjustable sine wave signal is generated and is output after being filtered through an LC passive low-pass filter network.
(2) And the adjustable power amplification module 3 is used for carrying out adjustable power amplification on the high-frequency sine wave signal. The high-frequency continuous sine wave signal after power amplification drives the high-frequency ultrasonic transducer to work in a continuous wave mode.
(3) The voltage sampling module 5 and the current sampling and I/V conversion module 4 are used for collecting voltage and current signals output by the load of the energy converter, the voltage signals are subjected to partial pressure collection processing, the current signals are converted into voltage signals through I/V, and the voltage signals are collected, and the I/V conversion module is shown in figure 3.
(4) And sending the acquired voltage and current signals to a multiplier module 6 for frequency mixing processing.
(5) The output mixed signal is sent to the low pass filter module 7, as shown in fig. 4, which filters the high frequency component signal and leaves the low frequency dc component.
(6) Sending the low-frequency direct current component into an ADC sampling module 8 for AD conversion, wherein the ADC sampling data processing adopts a median average filtering method, as shown in FIG. 5, removing m1 minimum values and m2 maximum values from the acquired N data, and averaging the intermediate N-m1-m2 values to output the value of the digitized low-frequency direct current component reflecting the phase difference.
(7) The value after AD conversion is sent to the processor module 1 for judgment processing, and the value after AD conversion is sent to the processor module 1 for judgment processing, because the output power of the ultrasonic transducer meets the requirement
Using integrated sum and difference conversion
Wherein
Is a high frequency component, and
is a low frequency component which
For the voltage and current phase difference, the ADC sampling direct current component is judged, the phase difference is determined according to the size of the sampling value, and the frequency is tracked and locked by using a large step length searching method, as shown in fig. 6 and 7, the large step length searching method is firstly according to a large step length (m)1-m2)/N1In a set frequency range m1-m2Internally scanning frequency, and feeding back the ADC output result to the processor for judgment to reduce the range to s1-s2Internally performing a frequency sweep with a step size of(s)1-s2)/N2And repeating the steps until judging whether the frequency point with the maximum corresponding ADC value meets the precision requirement, wherein the searching step length is (k)1-k2)/NnThe frequency f meeting the accuracy requirement falls within n1-n2Within the range, the locked resonance frequency f is finally output.
(8) And finally, outputting and displaying the result of the locked resonant frequency to a display module 9.
While the foregoing is directed to embodiments of the present invention, various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.
Claims (7)
1. A method for realizing frequency locking of a high-frequency ultrasonic transducer is characterized by comprising the following steps: comprises a processor module, a DDS signal generation module, an adjustable power amplification module, a voltage and current sampling and I/V conversion module, a multiplier module, a low-pass filter module, an ADC sampling module, a display module and a high-frequency ultrasonic transducer,
the DDS signal generation module is driven by the processor module to generate a high-frequency continuous sine wave signal with variable frequency; the adjustable power amplification module is used for carrying out adjustable power amplification on the high-frequency sine wave signal; the high-frequency continuous sine wave signal subjected to power amplification drives a high-frequency ultrasonic transducer to work in a continuous wave mode; collecting voltage and current signals output by a load of the transducer by using a voltage and current sampling and I/V conversion module, carrying out partial pressure collection processing on the voltage signals, and converting the current signals into voltage signals through I/V for collection; sending the collected voltage and current signals to a multiplier module for frequency mixing processing; sending the output mixed frequency signal into a low-pass filter module, filtering the high-frequency component signal, and leaving a low-frequency direct-current component; sending the low-frequency direct current component into an ADC (analog-to-digital converter) sampling module for AD conversion, wherein ADC sampling data processing adopts a median average filtering method, and the value of the digitized low-frequency direct current component reflecting the phase difference is output; sending the value after AD conversion into a processor module for judgment processing, determining the phase difference according to the size of a sampling value by judging the ADC sampling direct current component, tracking and locking the frequency by using a large and small step size searching method, and finally outputting the locked resonance frequency; finally, the result of the locked resonant frequency is output and displayed on a display module;
the low-pass filter module has the order of five orders and the cut-off frequency of 10 Hz.
2. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1, wherein: the processor is used as a master control center, controls the DDS signal generation module to generate a sine wave with variable high frequency, simultaneously processes the sampling data of the ADC sampling module and drives the display module to perform subsequent programming processing and result display.
3. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1 or 2, wherein: the processor controls the DDS signal generation module to output continuous high-frequency sine waves, one bit of data information is input into the chip through the bit control pin when the rising edge of the clock signal arrives, and when the transmission of the bit control information is finished, a pulse is generated through the frequency control pin to update the output frequency and the phase.
4. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1, wherein: the adjustable power amplification module realizes adjustable power amplification of the continuous sine wave signal generated by the DDS signal generation module.
5. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1, wherein: the I/V conversion module in the voltage and current sampling and I/V conversion module adopts a transimpedance operational amplifier circuit, the input bias current of the transimpedance operational amplifier circuit is 2pA, and the input offset voltage is +/-250 muV.
6. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1, wherein: the bandwidth of the multiplier module is 250MHz, and the bandwidth requirement required by the high-frequency ultrasonic signal is met.
7. The method for realizing frequency locking of the high-frequency ultrasonic transducer according to claim 1, wherein: the ADC sampling module adopts a chip with 24-bit high precision and 10-muV voltage resolution.
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| CN109445353A (en) * | 2018-12-12 | 2019-03-08 | 江苏集萃微纳自动化系统与装备技术研究所有限公司 | Digital ultrasound power driving circuit |
| CN110441613B (en) * | 2019-08-14 | 2022-04-19 | 中电科思仪科技股份有限公司 | Coaxial resonant cavity testing method and system based on scalar network analyzer |
| CN111658207A (en) * | 2020-06-08 | 2020-09-15 | 桂林市啄木鸟医疗器械有限公司 | Dental treatment system |
| CN111658210A (en) * | 2020-06-09 | 2020-09-15 | 桂林市啄木鸟医疗器械有限公司 | Small-sized hand-held comfortable dental scaler |
| CN113014115B (en) * | 2021-03-15 | 2022-06-21 | 科益展智能装备有限公司 | Ultrasonic power supply and power supply method thereof |
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| CN101024216A (en) * | 2005-12-29 | 2007-08-29 | 杜凯恩公司 | Systems for providing power to ultrasonic welding probes |
| CN101204699A (en) * | 2006-12-20 | 2008-06-25 | 先宁电子科技股份有限公司 | Ultrasonic transducer and frequency-stabilizing method |
| CN203409422U (en) * | 2013-06-28 | 2014-01-29 | 东莞华中科技大学制造工程研究院 | Ultrasonic drive system |
| CN106140592A (en) * | 2016-07-29 | 2016-11-23 | 宁波中物东方光电技术有限公司 | Digital ultrasonic generator and auto frequency locking method thereof |
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| EP0430072A2 (en) * | 1989-11-22 | 1991-06-05 | Mdt Corporation | Improved ultrasonic cleaner |
| CN101024216A (en) * | 2005-12-29 | 2007-08-29 | 杜凯恩公司 | Systems for providing power to ultrasonic welding probes |
| CN101204699A (en) * | 2006-12-20 | 2008-06-25 | 先宁电子科技股份有限公司 | Ultrasonic transducer and frequency-stabilizing method |
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