CN113945608B - Magnetic induction phase shift measurement system based on magneto-electric sensor - Google Patents

Abstract

The present invention discloses a magnetic induction phase shift measurement system based on a magnetoelectric sensor, which overcomes the problem that the prior art cannot accurately determine whether the biological tissue is abnormal when using the magnetic induction phase shift technology to detect biological tissues such as liver tissue, breast tissue, and bladder tissue. The system includes a signal source module, an amplification excitation module, a magnetoelectric sensor, and a signal processing module. The output end of the signal source module is respectively connected to the input end of the amplification excitation module and the reference signal end of the signal processing module. The output end of the amplification excitation module is connected to the magnetoelectric sensor, and the output end is connected to the input end of the signal processing module. The magnetoelectric sensor is used to detect a magnetic field of the order of 10 ^‑13 T at a resonant frequency of kHz, so that the induced magnetic field can be better detected, the sensitivity of the entire system to changes in the conductivity of biological tissues is improved, and a more internal detection of biological tissues is achieved.

Description

A magnetic induction phase shift measurement system based on magnetoelectric sensor

Technical Field

The invention relates to the technical field of biomedical equipment, and in particular to a magnetic induction phase shift measurement system based on a magnetoelectric sensor.

Background Art

Magnetic Induction Phase Shift (MIPS) technology uses the principle of magnetic induction to place biological tissue between an excitation coil and a detection magnetic field sensor. When the excitation coil with alternating current generates an alternating excitation magnetic field B that passes through the biological tissue, an induced current is generated in the biological tissue, which in turn generates an induced magnetic field ΔB, which can be detected by the detection magnetic field sensor. When the conductivity σ of the biological tissue changes, it will affect the intensity and distribution of the induced current. The measured ΔB can reflect the change in conductivity. From the vector relationship between B and ΔB, the phase shift θ between the excitation magnetic field and the induced magnetic field can be deduced. By detecting the phase shift θ, the change in conductivity can be reflected. Therefore, the change in phase difference can be used to determine whether the biological tissue is abnormal.

Biological tissues, such as the human head, will only show obvious phase differences under the action of an excitation magnetic field at a megahertz frequency, and coils or antennas have outstanding performance in detecting magnetic fields at megahertz and above, so they are often used as sensors for detecting induced magnetic fields in this frequency band. On July 20, 2021, the China Patent Office disclosed an invention entitled a real-time monitoring system for blood flow in biological tissues and an analog monitoring system based on magnetic induction phase shift, with a publication number of CN113133753A. The invention includes a signal source, an excitation coil unit, a receiving coil unit, a digitizer, and a host computer PC; the signal source outputs two sinusoidal signals with the same frequency and phase, which are respectively connected to the excitation coil unit and the digitizer, and the receiving coil unit is connected to the digitizer to collect the output signal emitted by the excitation coil unit and generated in the receiving coil unit after passing through the part to be detected, and transmit it to the host computer for analysis and processing to obtain the real-time status of the part to be detected. The system provided by the invention uses magnetic induction phase shift to monitor the pulsation of cerebral blood flow. By combining the theory of arterial hemodynamics with the principle of magnetic induction phase shift detection, the changes in cerebral blood flow pulsation are continuously and effectively monitored. The system has the advantages of being non-invasive, safe, non-contact, small in size, and highly penetrating. However, the system uses a coil as a magnetic field sensor, which is limited by the insufficient sensitivity of the coil, and the excitation frequency is often between 1 and 100 MHz. Due to the skin effect, the detection depth is insufficient. Different biological tissues have different characteristics. For example, liver tissue, breast tissue, bladder tissue, etc., show obvious phase differences under the excitation magnetic field of kilohertz frequencies, but the performance of the coil or antenna at kilohertz frequencies is not very outstanding.

Magnetoelectric sensors have attracted extensive attention due to their convenient operation and high sensitivity at room temperature, especially their outstanding performance at the resonant frequency of kilohertz. Depending on the materials and sizes of the magnetoelectric sensors, the resonant frequency of the magnetoelectric sensors can be in the range of zero to kilohertz. In addition, the output response of the magnetoelectric sensor depends on the piezomagnetic coefficient, which first increases and then decreases with the DC bias magnetic field. Under a certain DC bias magnetic field, the piezomagnetic coefficient will reach its maximum. The DC bias magnetic field at this time is the optimal DC bias magnetic field. Under this DC magnetic field, the performance of the sensor can be improved by dozens or even thousands of times. At present, using the magnetostrictive material Metglas and the piezoelectric material lithium niobate, an AC magnetic field of 200 fT can be detected at a resonant frequency of 6.862 kHz under the optimal DC bias magnetic field of 5 Oe.

Summary of the invention

The purpose of the present invention is to overcome the problem in the prior art that when using magnetic induction phase shift technology to detect biological tissues such as liver tissue, breast tissue, bladder tissue, etc., it is impossible to accurately determine whether the biological tissue is abnormal. A magnetic induction phase shift measurement system based on a magnetoelectric sensor is provided. The performance of the magnetoelectric sensor that can detect a magnetic field of the order of ^10-13 T at a resonant frequency of kHz is utilized, and the induced magnetic field can be better detected, thereby improving the sensitivity of the entire system to changes in the conductivity of biological tissues and realizing a more internal detection of biological tissues.

In order to achieve the above object, the present invention adopts the following technical solutions: including:

Signal source module: outputs two AC signals with the same frequency and phase, one of which is transmitted to the amplification and excitation module to generate an excitation signal, and the other is transmitted to the signal processing module to generate a reference signal;

Amplification excitation module: amplifies the signal provided by the signal source module and generates AC excitation magnetic field and DC bias magnetic field at the same time;

Magnetoelectric sensor: detects the excitation magnetic field generated by the amplifying excitation module and the induced magnetic field generated by the biological tissue at the same time, and generates an output signal to the signal processing module;

Signal processing module: processes the output signal of the magnetoelectric sensor and the reference signal provided by the signal source module to obtain the phase difference, and determines whether the measured tissue has abnormalities according to the change of the phase difference.

The output end of the signal source module is respectively connected to the input end of the amplifying excitation module and the reference signal end of the signal processing module, the output end of the amplifying excitation module is connected to the magnetoelectric sensor, and the output end is connected to the input end of the signal processing module. There is no less than one magnetoelectric sensor. Under the action of the AC excitation magnetic field, the biological tissue generates an induced magnetic field due to the eddy current effect, wherein there is a phase difference between the induced magnetic field and the excitation magnetic field. The magnetoelectric sensor simultaneously detects the excitation magnetic field and the induced magnetic field generated by the biological tissue, and the output signal of the magnetoelectric sensor is processed by the signal processing module and the reference signal provided by the signal source module to obtain the phase difference, and the change in the phase difference is used to determine whether the intracranial pressure has changed.

The present invention utilizes a kHz excitation magnetic field. According to the skin effect, the lower the excitation magnetic field frequency, the deeper the detection depth. Compared with the existing MHz or even GHz excitation magnetic field, the depth that the system can detect is greatly improved. Therefore, the kHz excitation magnetic field can realize the detection of the inner part of the biological tissue, rather than just the surface. The common high-precision magnetic field sensors currently include fluxgate meters, superconducting quantum interference devices, and optical pump magnetometers, but fluxgate meters can only realize the detection of magnetic fields of the order of ^10-9 T and are relatively expensive; superconducting quantum interference devices can only measure the magnetic field size within a very small range, the cost is too high and cannot work at room temperature, liquid helium refrigeration is required to make the SQUID work normally, the volume is large and not easy to carry; optical pump magnetometers can only detect the magnetic field size within ±5× ^10-9 T, the bandwidth is low, the cost is high, and the shielding performance requirements for the surrounding environment are high. Therefore, the present invention uses a magnetoelectric sensor with excellent performance under frequency and optimal bias magnetic field to detect the induced magnetic field generated by biological tissues such as liver tissue, breast tissue, bladder tissue, etc. under the action of an excitation magnetic field, and performs signal processing on the output signal of the magnetoelectric sensor to obtain the phase difference between the induced magnetic field and the excitation magnetic field, and judges whether the biological tissue is abnormal by the change of the phase difference. The magnetoelectric sensor has extremely excellent performance at the resonant frequency point of kHz, and can detect magnetic fields of the order of ^10-13 T, and the excitation magnetic field frequency only requires one frequency point, so it can better detect the induced magnetic field, thereby improving the sensitivity of the entire system to changes in the conductivity of biological tissues, and the magnetoelectric sensor is low in cost, can work at room temperature, is small in size, and is easy to carry.

Preferably, the frequency of the AC signal generated by the signal source module is the same as the resonant frequency of the magnetoelectric sensor. At this frequency, the magnetoelectric sensor has the best performance.

Preferably, the amplification and excitation module comprises:

Current amplifier: amplifies the signal generated by the signal source module;

DC bias module: generates DC bias current, performs DC bias on the signal amplified by the current amplifier, and applies the amplified signal to the excitation coil;

Excitation coil: generates AC excitation magnetic field and DC bias magnetic field simultaneously.

The input end of the current amplifier is connected to the output end of the signal source module, the output end of the current amplifier is connected to the input end of the DC bias module, and the output end of the DC bias module is connected to the excitation coil. The signal source module generates an AC signal with the same frequency as the resonant frequency of the magnetoelectric sensor. The signal amplified by the current amplifier is then DC biased by the DC bias module. The final output signal acts on the excitation coil, and the excitation coil simultaneously generates an AC excitation magnetic field and a DC bias magnetic field.

Preferably, the excitation coil is a solenoid wound on the magnetoelectric sensor, the two ends of the solenoid are respectively connected to the output end of the DC bias module, and the measured tissue is arranged on the right side of the solenoid. The excitation coil is wound on the magnetoelectric sensor, which can reduce the volume and facilitate operation.

Preferably, the excitation coil is a Helmholtz coil, and the Helmholtz coil includes a left Helmholtz coil and a right Helmholtz coil, the magnetoelectric sensor is arranged between the left Helmholtz coil and the right Helmholtz coil, and the measured tissue is arranged between the magnetoelectric sensor and the right Helmholtz coil. The Helmholtz coil is a device for producing a uniform magnetic field in a small area, and has an open nature, and other instruments can be easily placed in or removed. The left Helmholtz coil and the right Helmholtz coil generate a uniform field in a large range, and the uniform field includes an AC excitation magnetic field and a DC bias magnetic field, and the magnetoelectric sensor and the measured tissue are in this uniform field.

Preferably, the left Helmholtz coil and the right Helmholtz coil can be perpendicular to the magnetoelectric sensor or at an angle. The horizontal line where the magnetoelectric sensor is located can be perpendicular to the plane where the left Helmholtz coil and the right Helmholtz coil are located or at an angle. The left Helmholtz coil and the right Helmholtz coil generate a uniform field over a large range, and the uniform field includes an AC excitation magnetic field and a DC bias magnetic field. The direction of the uniform field is at a certain angle to the sensitive direction of the magnetoelectric sensor, so the response of the magnetoelectric sensor to the excitation magnetic field will be weakened, but it will hardly affect the magnetoelectric sensor's detection of the induced magnetic field generated by the object being measured, thereby improving the magnetoelectric sensor's ability to distinguish the induced magnetic field.

Preferably, the magnitude of the DC bias magnetic field generated by the DC bias module is the optimal DC bias magnetic field magnitude of the magnetoelectric sensor. By adjusting the DC bias module to make the magnitude of the DC bias magnetic field equal to the optimal DC bias magnetic field magnitude of the magnetoelectric sensor, the DC bias magnetic field at this magnitude can maximize the performance of the magnetoelectric sensor.

Preferably, the signal processing module comprises:

Preamplifier module: amplifies the output signal of the magnetoelectric sensor;

Filter: Filter the amplified output signal;

Phase detection module: The reference signal of the signal source module and the output signal of the magnetoelectric sensor after amplification and filtering are processed and analyzed to obtain the phase difference.

The input end of the preamplifier module is connected to the output end of the magnetoelectric sensor, the input end of the filter is connected to the output end of the preamplifier module, and the input end of the phase detector module is simultaneously connected to the output end of the filter and the reference signal output end of the signal source module. The phase detector module processes the test signal and the output signal to obtain a phase difference. Once the conductivity or volume of the measured tissue changes, the phase of the final output will change. The change in phase can be used to infer that the measured tissue is abnormal.

Preferably, the filter can be a hardware circuit or a software program. The filter is a common instrument, and its hardware circuit is mainly composed of capacitors, inductors and resistors. It can effectively filter out a specific frequency point in the power line or frequencies other than the frequency point to obtain a power signal with a specific frequency, or eliminate a power signal with a specific frequency.

Preferably, the phase detection module can be a hardware circuit or a software program. The phase detection module is also available in the prior art.

Therefore, the present invention has the following beneficial effects: 1. It can effectively detect the induced magnetic field generated by biological tissues such as liver tissue, breast tissue, bladder tissue, etc. under the action of the excitation magnetic field of kilohertz frequency; 2. It can work at room temperature, real-time dynamic, simple in structure, easy to operate and low in cost; 3. By using a magnetoelectric sensor as a detection sensor, a magnetic field of the order of ^10-13 T can be detected at the resonant frequency of kHz, so that the induced magnetic field can be better detected, thereby improving the sensitivity of the entire system to changes in the conductivity of biological tissues, and realizing a more internal detection of biological tissues.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of the excitation coil of the present invention as a solenoid;

FIG2 is a schematic diagram of a structure in which the excitation coil of the present invention is a Helmholtz coil;

FIG3 is another schematic diagram of the structure of the excitation coil of the present invention being a Helmholtz coil;

FIG4 is a graph showing the test results of the present invention;

FIG5 is a schematic diagram of the structure of two magnetoelectric sensors of the present invention;

FIG6 is a schematic diagram of the structure of the magnetoelectric sensor of the present invention having two signal output ports;

In the figure: 1. phase detection module; 2. filter; 3. preamplifier module; 4. solenoid; 5. magnetoelectric sensor; 6. measured tissue; 7. signal source module; 8. current amplifier; 9. DC bias module; 10. left Helmholtz coil; 11. right Helmholtz coil; 12. acquisition module; 13. phase detector; 14. first magnetoelectric sensor; 15 second magnetoelectric sensor; 16. magnetostrictive material; 17. first piezoelectric material; 18. second piezoelectric material; 19. charge amplifier; 20. differential amplifier.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

The present embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein the excitation coil is a solenoid, and its structure is shown in FIG1 , including a phase detector module 1, a filter 2, a preamplifier module 3, a solenoid 4, a magnetoelectric sensor 5, a signal source module 7, a current amplifier 8, and a DC bias module 9. The output end of the signal source module is respectively connected to the input end of the current amplifier and the reference signal end of the phase detector module, the output end of the current amplifier is connected to the input end of the DC bias module, the output end of the DC bias module is connected to the solenoid, the measured tissue 6 is located on the right side of the solenoid, the solenoid generates an AC excitation magnetic field and a DC bias magnetic field at the same time, the magnetoelectric sensor detects the excitation magnetic field and the induced magnetic field generated by the biological tissue, and its output end is connected to the preamplifier module, and the output end of the preamplifier module is connected to the phase detector module through the filter 2.

When working, the signal source module generates an AC signal with the same frequency as the resonant frequency of the magnetoelectric sensor. The signal amplified by the current amplifier is then DC biased by the DC bias module. The final output signal acts on the excitation coil, which simultaneously generates an AC excitation magnetic field and a DC bias magnetic field. The DC bias module is adjusted to make the size of the DC bias magnetic field equal to the optimal DC bias magnetic field size of the magnetoelectric sensor. After detecting the excitation magnetic field and the induced magnetic field, the magnetoelectric sensor performs phase analysis with the reference signal in the phase detector module after preamplification and filtering, and obtains the phase difference.

This embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein the excitation coil is a Helmholtz coil, and its structure is shown in FIG2 . The output end of the signal source module 7 is respectively connected to the input end of the current amplifier 8 and the input end of the phase detector 13, providing an excitation signal to the current amplifier and a reference signal to the phase detector. The output end of the current amplifier is connected to the input end of the DC bias module 9, and the two output ends of the DC bias module are respectively connected to the left Helmholtz coil 10 and the right Helmholtz coil 11. The magnetoelectric sensor 5 and the measured tissue 6 are placed in sequence between the left Helmholtz coil and the right Helmholtz coil, and the magnetoelectric sensor and the biological tissue are on the same straight line, which is perpendicular to the plane where the left Helmholtz coil and the right Helmholtz coil are located. The output end of the magnetoelectric sensor is connected to the input end of the preamplifier module, the output end of the preamplifier module is connected to the input end of the filter, the output end of the filter is connected to the input end of the phase detector, and the output end of the phase detector is connected to the acquisition module.

When working, the signal source module is connected to the left Helmholtz coil 10 and the right Helmholtz coil 11 through the current amplifier and the DC bias module. Here, the DC bias module is a voltage bias adjustment circuit. The left Helmholtz coil and the right Helmholtz coil generate a large-scale uniform field, which includes an AC excitation magnetic field and a DC bias magnetic field. The AC excitation magnetic field frequency is the resonant frequency of the magnetoelectric sensor. The DC bias magnetic field size generated by the DC bias module is the optimal bias magnetic field size of the magnetoelectric sensor. The magnetoelectric sensor and the measured tissue 6 are in this uniform field. At this time, the excitation magnetic field direction is the same as the sensitive direction of the magnetoelectric sensor. The magnetoelectric sensor detects the induced magnetic field generated by the excitation magnetic field and the measured tissue, and the output of the magnetoelectric sensor is connected to the preamplifier module, where the preamplifier module is a charge preamplifier. The charge preamplifier is connected to the phase detector module through a filter. Here, the phase detector module includes a phase detector and an acquisition module. At the same time, the reference signal of the signal source module is connected to the phase detector. The acquisition module 12 acquires the magnitude of the DC quantity output by the phase detector, and obtains the phase through the relationship between the DC quantity and the phase of the phase detector itself. Once the conductivity or volume of the tissue being measured changes, the phase of the final output will change. The change in phase can be used to infer that an abnormality has occurred in the object being measured.

This embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein the excitation coil is a Helmholtz coil, and its structure is shown in FIG3 . The output end of the signal source module 7 is respectively connected to the input end of the current amplifier 8 and the input end of the phase detector 13, providing an excitation signal to the current amplifier and a reference signal to the phase detector. The output end of the current amplifier is connected to the input end of the DC bias module 9, and the two output ends of the DC bias module are respectively connected to the left Helmholtz coil 10 and the right Helmholtz coil 11. The magnetoelectric sensor 5 and the measured tissue 6 are placed in sequence between the left Helmholtz coil and the right Helmholtz coil, and the magnetoelectric sensor and the biological tissue are on the same straight line, and the straight line is at an angle to the plane where the left Helmholtz coil and the right Helmholtz coil are located. The output end of the magnetoelectric sensor is connected to the input end of the preamplifier module, the output end of the preamplifier module is connected to the input end of the filter, the output end of the filter is connected to the input end of the phase detector, and the output end of the phase detector is connected to the acquisition module.

When working, the signal source module is connected to the left Helmholtz coil 10 and the right Helmholtz coil 11 through the current amplifier and the DC bias module, wherein the DC bias module is a voltage bias adjustment circuit, and the left Helmholtz coil and the right Helmholtz coil generate a large-scale uniform field, wherein the uniform field includes an AC excitation magnetic field and a DC bias magnetic field, wherein the AC excitation magnetic field frequency is the resonant frequency of the magnetoelectric sensor, and the DC bias magnetic field magnitude generated by the DC bias module is the optimal bias magnetic field magnitude of the magnetoelectric sensor, and the magnetoelectric sensor and the measured tissue 6 are in this uniform field. At this time, the uniform field direction is at a certain angle to the sensitive direction of the magnetoelectric sensor, so the magnetoelectric sensor's response to the excitation magnetic field will be weakened, but it will hardly affect the magnetoelectric sensor's detection of the induced magnetic field generated by the measured tissue, thereby improving the magnetoelectric sensor's ability to distinguish the induced magnetic field. The magnetoelectric sensor detects the excitation magnetic field and the induced magnetic field generated by the measured tissue, and the magnetoelectric sensor output is connected to the preamplifier module, wherein the preamplifier module is a charge preamplifier. The charge preamplifier is connected to the phase detector module through a filter, and the phase detector module includes an AD8302 phase detector and an acquisition module. At the same time, the reference signal of the signal source module is connected to the phase detector. The acquisition module 12 collects the DC magnitude output by the AD8302 phase detector, and obtains the phase through the relationship between the DC magnitude and the phase of the phase detector itself. Once the conductivity or volume of the measured tissue changes, the final output phase will change. The change in phase can be used to infer that the measured object has an abnormality.

This structure was used to test the magnetoelectric sensor based on Metglas (magnetostrictive material)/PZT (piezoelectric material). The resonant frequency of this magnetoelectric sensor was 19.8kHz, and the optimal bias magnetic field was 9.6Oe. Therefore, the excitation magnetic field frequency was selected to be 19.8kHz, and the voltage bias adjustment circuit adjusted the DC magnetic field to 9.6Oe. In order to test the feasibility of the system, brass balls and 20% concentration of salt water were used as the tested tissues for the test, and the results are shown in Figure 4. It can be seen from the figure that as the volume of the brass ball or salt water increases, the phase of the system output gradually increases, which can reflect the feasibility of the system when testing objects of the same conductivity and different volumes.

This embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein the excitation coil is a Helmholtz coil, there are two magnetoelectric sensors, and its structure is shown in FIG5 , at this time, the preamplifier module includes two identical charge amplifiers 19 and a differential amplifier 20, the phase detector module includes a phase detector and an acquisition module, and the phase detector is preferably an AD8302 phase detector, and there are two magnetoelectric sensors, including a first magnetoelectric sensor and a second magnetoelectric sensor. The output end of the signal source module 7 is respectively connected to the input end of the current amplifier 8 and the input end of the phase detector 13, providing an excitation signal to the current amplifier and a reference signal to the phase detector, the output end of the current amplifier is connected to the input end of the DC bias module 9, and the two output ends of the DC bias module are respectively connected to the left Helmholtz coil 10 and the right Helmholtz coil 11. The magnetoelectric sensor and the measured tissue 6 are placed in sequence between the left Helmholtz coil and the right Helmholtz coil. The first magnetoelectric sensor 14 and the second magnetoelectric sensor 15 are placed in parallel up and down. The first magnetoelectric sensor and the biological tissue are on the same horizontal straight line, and the straight line forms an angle with the plane where the left Helmholtz coil and the right Helmholtz coil are located. The output ends of the two magnetoelectric sensors are connected to the input ends of a charge amplifier respectively, and the output ends of the two charge amplifiers are connected to the input ends of the differential amplifier, the output end of the differential amplifier is connected to the input end of the filter, the output end of the filter is connected to the input end of the phase detector, and the output end of the phase detector is connected to the acquisition module.

When working, the signal source module is connected to the left Helmholtz coil 10 and the right Helmholtz coil 11 through the current amplifier and the DC bias module. Here, the DC bias module is a voltage bias adjustment circuit. The left Helmholtz coil and the right Helmholtz coil generate a large-scale uniform field, which includes an AC excitation magnetic field and a DC bias magnetic field. The AC excitation magnetic field frequency is the resonant frequency of the magnetoelectric sensor, and the DC bias magnetic field generated by the DC bias module has an optimal bias magnetic field size of the magnetoelectric sensor. The two magnetoelectric sensors and the measured tissue 6 are in this uniform field.

At this time, the uniform field direction is at a certain angle to the sensitive directions of the two sensors, so the response of the magnetoelectric sensor to the excitation magnetic field will be weakened. In addition, the two magnetoelectric sensors are exactly the same. The first magnetoelectric sensor 14 is the main sensor, and the second magnetoelectric sensor 15 is the reference sensor. The main sensor is close to the measured tissue, so it can detect both the excitation magnetic field and the induced magnetic field, while the reference sensor is far from the measured tissue, and the induced magnetic field decreases with the increase of the distance, so the reference sensor mainly detects the excitation magnetic field. The outputs of the two magnetoelectric sensors are connected to the differential amplifier through the same charge amplifier, and after differential amplification, the signal output is the voltage signal generated by the detection of the induced magnetic field. The differential amplifier is connected to the phase detector through the filter. At the same time, the reference signal of the signal source module is connected to the phase detector. The phase detector collects the DC output of the AD8302 phase detector through the acquisition module, and the phase is obtained through the relationship between the DC output and the phase of the phase detector. Once the conductivity or volume of the measured tissue changes, the final output phase will change. The change in phase can be used to infer that the measured object has an abnormality.

This embodiment is a magnetic induction phase shift measurement system based on a magnetoelectric sensor, wherein the excitation coil is a Helmholtz coil, and the magnetoelectric inductor is a magnetoelectric inductor assembled by itself and including two signal output ports, and its structure is shown in FIG6 , wherein the magnetoelectric inductor includes a magnetostrictive material 16, a first piezoelectric material 17 and a second piezoelectric material 18, and the preamplifier module includes two identical charge amplifiers 19 and a differential amplifier 20, and the phase detector module includes a phase detector and an acquisition module, and the phase detector is preferably an AD8302 phase detector. The output end of the signal source module 7 is respectively connected to the input end of the current amplifier 8 and the input end of the phase detector 13, providing an excitation signal to the current amplifier and a reference signal to the phase detector, and the output end of the current amplifier is connected to the input end of the DC bias module 9, and the two output ends of the DC bias module are respectively connected to the left Helmholtz coil 10 and the right Helmholtz coil 11. A magnetoelectric sensor and a measured tissue 6 are placed in sequence between the left Helmholtz coil and the right Helmholtz coil. The first piezoelectric material 17 and the second piezoelectric material 18 are sleeved on the magnetostrictive material 16. The first piezoelectric material and the second piezoelectric material are placed in parallel up and down. The first piezoelectric material and the biological tissue are on the same horizontal straight line, and the straight line forms an angle with the plane where the left Helmholtz coil and the right Helmholtz coil are located. The first piezoelectric material and the second piezoelectric material are used as two output ends of the magnetoelectric sensor, and are respectively connected to a charge amplifier. The output ends of the two charge amplifiers are both connected to the input end of the differential amplifier, the output end of the differential amplifier is connected to the input end of the filter, the output end of the filter is connected to the input end of the phase detector, and the output end of the phase detector is connected to the acquisition module.

When working, the signal source module is connected to the left Helmholtz coil and the right Helmholtz coil through the current amplifier and the DC bias module. Here, the DC bias module is a voltage bias adjustment circuit. The left Helmholtz coil and the right Helmholtz coil generate a large-scale uniform field, which includes an AC excitation magnetic field and a DC bias magnetic field.

The magnetostrictive material, the first piezoelectric material and the second piezoelectric material form a magnetoelectric sensor with two signal output ports, wherein the first piezoelectric material is exactly the same as the second piezoelectric material, serving as the two signal output ports A and B of the magnetoelectric sensor, and the first piezoelectric material and the second piezoelectric material are sleeved on the magnetostrictive material and are symmetrical about the center of the magnetostrictive material. In the uniform field generated by the Helmholtz coil, the frequency of the AC excitation magnetic field is the resonant frequency of the magnetoelectric sensor, and the magnitude of the DC bias magnetic field generated by the DC bias module is the optimal bias magnetic field magnitude of the magnetoelectric sensor, and the two magnetoelectric sensors and the measured tissue 6 are in this uniform field. At this time, the direction of the uniform field is at a certain angle to the sensitive direction of the sensor, so the response of the magnetoelectric sensor to the excitation magnetic field will be weakened. In addition, the signal output port A of the magnetoelectric sensor is used as the main output port, and the signal output port B is used as the reference output port. The main output port is close to the measured tissue, so the output signal includes the signal generated after the excitation magnetic field and the induced magnetic field are detected, while the reference output port is far from the measured tissue, and the induced magnetic field decreases with the increase of the distance, so the output signal is only the signal generated after the excitation magnetic field is detected. The outputs of the two signal output ports are connected to the differential amplifier through the same charge amplifier, and after differential amplification, the output signal is the voltage signal generated by the detection of the induced magnetic field. The differential amplifier is connected to the phase detector through the filter. At the same time, the reference signal of the signal source module is connected to the phase detector. The phase detector collects the DC output of the phase detector through the acquisition module, and the phase is obtained through the relationship between the DC output and the phase of the phase detector itself. Once the conductivity or volume of the measured tissue changes, the final output phase will change. The change in phase can be used to infer that the measured object has an abnormality.

The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims (10)

1. A magneto-inductive phase shift measurement system based on a magneto-electric sensor, comprising:

Signal source module (7): outputting two alternating current signals with the same frequency and phase, wherein one signal is transmitted to an amplifying excitation module to generate an excitation signal, and the other signal is transmitted to a signal processing module to generate a reference signal;

amplifying and exciting module: amplifying the signal provided by the signal source module and simultaneously generating an alternating current excitation magnetic field and a direct current bias magnetic field;

Magneto-electric sensor (5): simultaneously detecting an excitation magnetic field generated by the amplification excitation module and an induction magnetic field generated by biological tissues, and generating an output signal to the signal processing module; the uniform field direction is angled to the direction of sensitivity of the magneto-electric sensor;

And a signal processing module: processing an output signal of the magneto-electric sensor (5) and a reference signal provided by a signal source module to obtain a phase difference, and judging whether the tested tissue is abnormal or not through the change of the phase difference;

If the two magneto-electric sensors are arranged, the main output port which is close to the tissue to be detected is the reference output port which is far away from the tissue to be detected, the main output port outputs signals generated after the excitation magnetic field and the induction magnetic field are detected, the reference output port outputs signals generated after the excitation magnetic field is detected, the two output signals are respectively amplified by the identical charge amplifier and the differential amplifier to obtain voltage signals generated by the induction magnetic field, the differential amplifier is connected with the phase discriminator, and the phase is obtained through the relation characteristic of the direct current capacity and the phase of the phase discriminator.

2. The magneto-inductive phase shift measurement system based on the magneto-sensor according to claim 1, wherein the frequency of the alternating current signal generated by the signal source module is the same as the resonance frequency of the magneto-sensor (5).

3. The magneto-inductive phase shift measurement system of claim 1, wherein the amplifying excitation module comprises:

current amplifier (8): amplifying the signal generated by the signal source module (7);

direct current bias module (9): generating a direct current bias current, carrying out direct current bias on the signal amplified by the current amplifier (8), and applying the amplified signal to the exciting coil;

An exciting coil: and simultaneously generates an alternating current excitation magnetic field and a direct current bias magnetic field.

4. A magneto-inductive phase shift measurement system based on a magneto-inductive sensor according to claim 3, wherein the exciting coil is a solenoid (4) wound on the magneto-inductive sensor, two ends of the solenoid (4) are respectively connected with the output end of the dc bias module (9), and the tissue to be measured is arranged on the right side of the solenoid (4).

5. A magneto-inductive phase shift measurement system based on a magneto-sensor according to claim 3, characterized in that the excitation coil is a helm-hertz coil comprising a left helm-hertz coil (10) and a right helm-hertz coil (11), the magneto-sensor being arranged between the left helm-hertz coil (10) and the right helm-hertz coil (11), the tissue to be measured being arranged between the magneto-sensor (5) and the right helm-hertz coil (11).

6. The magneto-inductive phase shift measurement system based on a magneto-sensor according to claim 5, wherein the left (10) and right (11) helm hertz coils are perpendicular to the magneto-sensor (5) or are at an angle.

7. A magneto-inductive phase shift measurement system based on magneto-inductive sensors according to claim 3 or 4 or 5 or 6, characterized in that the dc bias magnetic field generated by the dc bias module (9) has a dc bias magnetic field that is optimal for the magneto-inductive sensor (5).

8. The magneto-inductive phase shift measurement system of claim 1, wherein the signal processing module comprises:

Pre-amplification module (3): amplifying the output signal of the magneto-electric sensor (5);

filter (2): filtering the amplified output signal;

Phase discrimination module (1): and processing and analyzing the reference signal of the signal source module (7) and the amplified and filtered output signal of the magneto-electric sensor (5) to obtain a phase difference.

9. A magneto-inductive phase shift measurement system based on magneto-electric sensors according to claim 8, characterized in that the filter (2) is either a hardware circuit or a software program.

10. A magneto-inductive phase shift measurement system based on magneto-electric sensors according to claim 8 or 9, characterized in that the phase discrimination module (1) is either a hardware circuit or a software program.