TWI467167B - Electromagnetic coupling measurement device of self-excited oscillation type - Google Patents

Description

Self-oscillating electromagnetic coupling measuring device

The present invention relates to a non-contact measuring device, and more particularly to a self-oscillating electromagnetic coupling measuring device.

The use of roll to roll (R2R) processes to make electronic products is growing, such as flexible printed circuit boards, conductive films, and the like. Among them, a conductive film is deposited on the substrate, and the impedance of the conductive film formed after deposition is measured. The device for measuring the conductive film can be divided into various types, wherein the non-contact measuring device can detect the characteristics and defects of the sample to be tested without damaging the sample to be tested, and thus is widely used in today's industry.

Non-contact measuring devices have been proposed in the prior art, for example, U.S. Patent No. 5,559,428, U.S. Patent No. 5,731,697, and U.S. Patent No. 4,000,458. Among them, U.S. Patent Nos. 5,559,428, 5,731,697 and 5,731,697 mainly use LCR for frequency scanning, and then perform characteristic analysis of frequency and complex impedance to thereby measure the characteristic change of the sample to be tested. However, the above methods often require a frequency sweep operation. The non-linearity of the measurement results is related to the reliability of the measurement.

Furthermore, in U.S. Patent No. 4,000,458, the sensing module is used as a resonant element of the oscillating circuit to oscillate the driving voltage by self-returning resonance. The sensing module is a resonant component of the oscillating circuit. A device for measuring different samples to be tested is proposed below.

The invention provides a self-oscillating electromagnetic coupling measuring device, which uses an adjustable frequency oscillator to adjust the phase of the driving voltage so that the sensing module continuously operates at the resonant frequency and maintains the amplitude of the driving voltage constant. Thereby, the power loss generated at the resonant frequency will be reflected in the drive current provided by the power amplifier. In this way, it will help to improve the measurement range of the sensing module and the speed and linearity of the measurement.

The invention provides a self-oscillating electromagnetic coupling measuring device, which comprises a first sensing module, an adjustable frequency oscillator, an amplitude control unit, a power amplifier and a current sensor. The first sensing module uses the driving voltage to emit an alternating magnetic field to sense the sample to be tested, and generates a feedback signal according to the change of the equivalent impedance. The adjustable frequency oscillator generates an oscillating voltage and causes the oscillating voltage to have a frequency equal to the resonant frequency of the first sensing module. The amplitude control unit generates control information according to the driving voltage feedback. The power amplifier amplifies the oscillating voltage according to a gain value to generate a driving voltage. In addition, the power amplifier adjusts the gain value based on the control information so that the amplitude of the driving voltage is maintained constant. The current sensor detects the drive current generated by the power amplifier and generates a detection signal related to the characteristics of the sample to be tested.

In an embodiment of the invention, the adjustable frequency oscillator is constructed by a phase locked loop. The phase locked loop includes a voltage controlled oscillator, a phase comparator, and a low pass filter. The voltage controlled oscillator generates an oscillating voltage. The phase comparator compares the phase difference between the oscillating voltage and the feedback signal and generates a phase error signal accordingly. The low pass filter filters out high frequency components in the phase error signal and generates an adjusted voltage accordingly. The voltage controlled oscillator re-oscillates according to the adjusted voltage to adjust the frequency of the oscillating voltage.

In an embodiment of the invention, the amplitude control unit includes a voltage generator and a voltage gain controller. Wherein, the voltage generator generates a reference voltage. The voltage gain controller converts the drive voltage to a sense voltage. In addition, the voltage gain controller compares the detected voltage with the reference voltage and generates control information based on the comparison result.

In an embodiment of the invention, the first sensing module includes a driving coil and a capacitor, and the driving coil and the capacitor are electrically connected in parallel with each other.

In an embodiment of the invention, the first sensing module includes a first winding, and the self-oscillating electromagnetic coupling measuring device further includes a second sensing module. The second sensing module includes a second winding. In addition, the first winding is electrically connected to the second winding to form a driving coil for generating an alternating magnetic field.

In an embodiment of the present invention, the first sensing module and the second sensing module are disposed together with the sample to be tested, or the first sensing module and the second sensing module. Set on the upper and lower sides of the sample to be tested.

In an embodiment of the invention, the self-oscillating electromagnetic coupling measuring device further includes a magnetic sensing component. The magnetic sensing component is disposed on the path of the alternating magnetic field and senses a change of the alternating magnetic field to feedback the second feedback signal from the first sensing module to the amplitude control unit.

In an embodiment of the invention, the magnetic sensing component and the first sensing module are disposed on the same side of the sample to be tested, or the magnetic sensing component and the first sensing module are respectively disposed on the sample to be tested. On both sides.

In an embodiment of the invention, the sample to be tested is a film, and the film is composed of a non-magnetic material. Further, the self-excited oscillation electromagnetic coupling measuring device described above discriminates the sheet resistance value of the film based on the detection signal.

The above described features and advantages of the present invention will be more apparent from the following description.

1 is a schematic diagram of a self-excited oscillation electromagnetic coupling measuring device according to an embodiment of the present invention. As shown in FIG. 1 , the self-excited oscillation electromagnetic coupling measuring device 100 includes a sensing module 110 , a power amplifier 120 , an adjustable frequency oscillator 130 , an amplitude control unit 140 , and a current sensor 150 . In operation, the power amplifier 120 provides a driving voltage V _D to the sensing module 110. The sensing module 110 will generate an alternating magnetic field using the driving voltage V _D .

When the alternating magnetic field passes through the sample 101 to be tested, an eddy current will be induced on the sample 101 to be tested, and the magnitude of the eddy current will be the same as the characteristics of the sample 101 to be tested, such as conductivity, permeability, thickness, defect, and distance. ...and so on. In addition, the eddy current induced by the sample 101 to be tested radiates a secondary magnetic field to resist the change of the alternating magnetic field (ie, the primary magnetic field) generated by the sensing module 110. In other words, the sensing module 110 receives a change in the secondary magnetic field, that is, a coupling effect between the sensing module 110 and the sample 101 to be tested. Thereby, the sensing module 110 achieves energy transfer between the sample 101 and the sample 101 to be tested by coupling the magnetic field. In addition, during the coupling process, the relevant information of the sample 101 to be tested will also be coupled to the self-oscillating electromagnetic coupling measuring device 100 in a non-contact manner.

In order to make the present inventors have a better understanding of the present embodiment, the coupling effect between the sensing module 110 and the sample 101 to be tested will be described below.

2 is a schematic diagram of a coupling model of eddy currents in accordance with an embodiment of the present invention. Referring to FIG. 2, can simply be coupled to the model transformer model do approximation, wherein the primary winding of the transformer T ₂ corresponds to the driving coil L ₁ of the sensing module 110, the current I ₁ is generated by the power amplifier 120 is equivalent to Drive current. Furthermore, the eddy current generated by the sample 101 to be tested, that is, the current I ₂ , is equivalent to that generated by the secondary coil L _{2 of} the transformer T ₂ , and R _L is the impedance of the sample 101 to be tested. Wherein, the middle of the transformer T ₂ is separated by air, so there is a coupling coefficient K. In addition, the coupling coefficient K is between 0 and 1, and is related to the distance between the sensing module 110 and the sample 101 to be tested, the shape of the medium and the sensing module 110.

Referring to the coupling model of Fig. 2, the characteristic matrix of equation (1) can be used to represent the voltage-current relationship at the input/output terminals of the double-turn transformer.

Where M is the mutual inductance of the two coils, and M = . In addition, using the characteristic matrix of equation (1) and the relationship between voltage and current, the equivalent impedance Z=X+jY of the sensing module 110 can be solved and can be represented by the equivalent circuit of FIG. 3 is an equivalent circuit diagram of a sensing module according to an embodiment of the present invention, and the real part X and the imaginary part Y of the equivalent impedance Z are as shown in equations (2) and (3):

According to the formulas (2) and (3), the change of the equivalent impedance of the sensing module 110 includes the change of the impedance R _L of the sample 101 to be tested and the coupling coefficient K. In addition, if the distance between the sensing module 110 and the sample 101 to be tested is fixed, the coupling coefficient K will be a fixed value. Thereby, the equivalent impedance of the sensing module 110 will change correspondingly with the impedance R _{L of} the sample 101 to be tested, thereby achieving the purpose of sensing the sample 101 to be tested.

On the other hand, in terms of the impedance R _{L of} the sample 101 to be tested, the transmission impedance of the electromagnetic wave is approximated by the transmission line theorem, and the transmission impedance of the electromagnetic wave can be approximated by the transmission reflection of the interface. The phase is equal to the ratio of the electric field to the magnetic field. Accordingly, assuming that the sample to be tested 101 is a film of a non-magnetic material, the impedance R _{L of} the sample 101 to be tested will be expressed as:

Where Z _P is the interface impedance, γ is the reflection coefficient, μ ₀ is the permeability coefficient, σ is the electrical conductivity of the material, and t is the material thickness. When penetrating the medium, the electromagnetic waves are depleted and decelerated at an exponential rate. Among them, when the attenuation of the electromagnetic wave reaches 37%, the depth of the penetrating material will be defined as the penetration depth of the material. Further, as shown in the formula (5), the penetration depth of the material will be related to the frequency and the conductivity σ of the material.

Compared with the penetration depth, if the thickness of the sample to be tested 101 is a relatively thin film, according to the formula (4), it can be calculated that the impedance R _L of the sample 101 to be tested approximates the sheet resistance value of the film. And as shown in equation (6):

In other words, when the sample to be tested 101 is a thin film of a non-magnetic material, the sheet resistance value of the sample 101 to be tested will be regarded as a resistance and coupled to the sensing module 110 through the magnetic field. Accordingly, the impedance characteristics of the sensing module 110 will produce corresponding changes. The effect of the resistance of the sample 101 to be tested on the impedance of the sensing module 110 will be described below in terms of a second-order circuit system.

In the present embodiment, the sensing module 110 is an element having an LC characteristic, that is, the sensing module 110 includes a driving coil and a capacitor, and the driving coil and the capacitor are electrically connected in parallel with each other. In addition, the driving coil may be combined by more than one winding, and the capacitor is mainly used to match the resonant frequency of the sensing module 110. Accordingly, the equivalent circuit of the sensing module 110 will be as shown in FIG. 4, wherein FIG. 4 is an equivalent circuit diagram of the sensing module according to another embodiment of the present invention.

Referring to FIG. 4, the equivalent circuit of the sensing module 110 includes a capacitor C, an inductor L and a load R _P , and the controllable current source is equivalent to the driving current I _D provided by the power amplifier 120. Furthermore, looking at the two ends of the controllable current source, the equivalent impedance Z(jω) of the sensing module 110 will be as shown in equation (7):

Z ( jω )= H ( jω )‧ R _P (7)

Where H(jω) is a transfer function that drives the equivalent impedance Z(jω) and the load R _P , and the transfer function H(jω) has a resonant frequency ω ₀ =1/ . Further, the transfer function H(jω) can be represented by a quality factor Q. Accordingly, by plotting the transfer function on the excitation frequency, the frequency response as shown in FIG. 5 can be obtained. Referring to Figure 5, at the resonant frequency ω ₀ , the equivalent impedance of the transfer function H(jω) will be maximized. This means that the amplitude of the voltage oscillation is maximum at this time, and then a small current wide-band noise can be amplified and output. Furthermore, at the resonant frequency ω ₀ , the drive voltage V _D and the drive current I _D will reach zero phase. For example, in terms of component characteristics, at the resonant frequency ω ₀ , the loss caused by the phase will not exist. That is, the energy stored in the inductor L will be the same as the energy stored in the capacitor C.

In other words, at the resonant frequency ω ₀ , the magnitude of the drive voltage V _D is maximized, and the drive current I _D provided by the controllable current source will all flow through the purely resistive load R _P . Therefore, if the sensing module 110 can be stabilized at the resonant frequency ω ₀ , the power loss of the load R _P will also be maximized. Moreover, in terms of the energy loss of the sensing module 110, if the driving voltage V _D and the driving current I _D provided by the controllable current source are respectively a sine wave signal, the average power will be as shown in equation (8). :

Wherein, V _m and I _m are amplitudes of the driving voltage V _D and the driving current I _D , respectively. Accordingly, FIG. 6 is a schematic diagram illustrating waveforms of a sensing module according to an embodiment of the present invention, wherein curves 610-640 are voltage, current, power, and average power of load R _P at a resonant frequency ω ₀ , respectively. . As shown in Figure 6, the drive current I _D provided by the controllable current source will all be supplied to the load R _P to compensate for the energy loss, thereby maintaining oscillation.

In accordance with the above concept, the embodiment of Fig. 1 is reversed. Here, when the sample 101 to be tested passes through the alternating magnetic field generated by the sensing module 110, the resistance of the sample 101 to be tested will be coupled to the sensing module 110 through the magnetic field. At this time, taking FIG. 4 as an example, the load R _P and the inductance L in the equivalent impedance of the sensing module 110 will be correspondingly changed, thereby causing the phase of the driving current I _D flowing into the sensing module 110 and The resonant frequency ω _{0 of the} sensing module 110 produces a corresponding change. Furthermore, in an embodiment circuit, the metal wiring carrying the drive current I _D contributes a corresponding impedance, such as resistor R' in FIG. Therefore, in design, the voltage at the node N4 can be utilized as the feedback signal S _F , and thereby the phase change of the drive current I _D is reflected by the feedback signal S _F . In other words, the sensing module 110 generates a feedback signal S _F related to the driving current I _D in response to a change in its equivalent impedance 401. It is worth mentioning that the feedback signal S _{F is} mainly used to reflect the phase change of the driving current I _D . Therefore, in practical applications, those skilled in the art can arbitrarily change the setting position of the node N4 according to the circuit structure of the sensing module 110. In other words, the location of the node N4 illustrated in FIG. 4 is only a specific embodiment and is not intended to limit the present invention.

In order to cause the sensing module 110 to continuously operate at the resonant frequency ω ₀ , the feedback signal S _F will be transmitted to the adjustable frequency oscillator 130 . Thereby, the adjustable frequency oscillator 130 generates an oscillating voltage V _O and adjusts the phase and frequency of the oscillating voltage V _O by using the feedback signal S _F such that the phase and frequency of the oscillating voltage V _O and the feedback signal S _{F are obtained} . All are equal. It is known that the frequency of the feedback signal S _F is the resonant frequency ω _{0 of the} sensing module 110. In other words, the adjustable frequency oscillator 130 adjusts the frequency of the oscillating voltage V _O to the resonant frequency ω _{0 of the} sensing module 110 by using the feedback signal S _F .

For example, in a preferred embodiment, the adjustable frequency oscillator 130 can be constructed of a phase locked loop. 7 is a block diagram of a phase locked loop in accordance with an embodiment of the present invention. Referring to FIG. 7, the phase locked loop 700 includes a phase comparator 710, a low pass filter 720, and a voltage controlled oscillator 730. The voltage controlled oscillator 730 is configured to generate the oscillating voltage V _O and return the oscillating voltage V _O to the phase comparator 710. The phase comparator 710 compares the phase difference between the feedback signal S _F and the oscillating voltage V _O and generates a phase error signal accordingly. The low pass filter 720 will filter out the high frequency components in the phase error signal and accordingly generate corresponding adjustment voltages. The voltage controlled oscillator 730 will re-oscillate according to the adjusted voltage to adjust the frequency of the oscillating voltage V _O . In this way, the phase-locked loop 700 will continuously adjust the frequency of the oscillating voltage V _O until the phase difference between the feedback signal S _F and the oscillating voltage V _O approaches 0, and then enters the locked state.

In other words, the adjustable frequency oscillator 130 itself can oscillate the oscillating voltage V _O . In addition, the adjustable frequency oscillator 130 also tracks the phase change of the feedback signal S _F such that the frequency of the oscillating voltage V _O is equal to the resonant frequency ω _{0 of the} sensing module 110. Frequency other hand, since the power amplifier 120 is based on the oscillating voltage to generate the driving voltage V _O V _D, so as to adjust the adjustable frequency oscillator oscillating voltage V _O 130 pairs, the amplifier 120 provides the driving voltage of V _D It will also be equal to the resonant frequency ω _{0 of the} sensing module 110, thereby ensuring that the sensing module 110 can continuously operate at the resonant frequency ω ₀ .

Furthermore, the power amplifier 120 amplifies the oscillating voltage V _O according to a gain value, and accordingly generates a driving voltage V _D . In addition, the amplitude control unit 140 generates a control information DT according to the driving voltage V _D . In a preferred embodiment, the amplitude control unit 140 includes a voltage gain controller 141 and a voltage generator 142. The voltage gain controller 141 receives the driving voltage V _D . In addition, in practical applications, the driving voltage V _D is transmitted through a clamper and a low-pass filter in the voltage gain controller 141 to be converted into a detection voltage. In addition, voltage generator 142 provides a reference voltage V _R to voltage gain controller 141. Thereby, the voltage gain controller 141 compares the detection voltage with the reference voltage V _R to generate control information DT according to the comparison result.

Thereby, the power amplifier 120 will adjust its gain value in accordance with the control information DT so that the amplitude of the driving voltage V _D is fixed. Since the loss energy of the load R _P will be reflected on the output power of the power amplifier 120, and the amplitude of the driving voltage V _D provided by the power amplifier 120 is fixed again, the driving current I _D provided by the power amplifier 120 will vary. The change in the load R _P in the test module 110 produces a corresponding change. Therefore, the current sensor 150 is configured to detect the driving current I _D provided by the power amplifier 120 and generate a detection signal SD to reflect the characteristics of the sample 101 to be tested.

For example, according to the formulas (2) and (3), when the impedance R _{L of} the sample 101 to be tested is decreased, the imaginary part impedance Y of the sensing module 110 is reduced, and the sensing module 110 is The impedance X will increase. In addition, a decrease in the imaginary impedance Y will cause the resonant frequency of the sensing module 110 to rise, resulting in an increase in the average power loss of the pure resistive load. In other words, when the impedance R _L of the sample 101 to be tested is decreased, that is, when the sheet resistance of the sample 101 to be tested is larger, energy loss is increased. That is to say, the energy consumed will appear to be strictly increasing or decreasing with the sheet resistance of the sample 101 to be tested, and has no phase-induced loss.

Further, according to the formula (2), the impedance R _{L of} the sample 101 to be tested is coupled to the sensing module 110 through the transfer function A as shown in the equation (9). Assuming that the sample 101 to be tested is a film, and the coupling coefficient K and the secondary coil L ₂ are fixed, the imaginary impedance Y of the sensing module 110 will increase as the impedance R _L of the sample 101 to be tested increases. . In addition, an increase in the imaginary impedance Y will cause the resonant frequency of the sensing module 110 to increase by a squared change in proximity to the inductive reactance. Thereby, the variation in the conversion function A / ω ² L ₂ will be able to close to the offset, causing the transfer function A to remain unchanged. Therefore, when the sensing module 110 operates at the resonant frequency and the amplitude of the driving voltage V _D of the sensing module 110 is fixed, the method of reacting the sample 101 to be tested by the driving current I _D can improve the measurement. Linearity and improved nonlinearity in traditional measurements.

In addition, in the embodiment, the adjustable frequency oscillator 130 is an active circuit and can oscillate by itself to generate an oscillating voltage V _O . In contrast, the power amplifier 120 is used to isolate the adjustable frequency oscillator 130 and the sensing module 110. In other words, the adjustable frequency oscillator 130 is not affected by the sensing module 110, thereby helping to increase the measurement range of the sensing module 110. Furthermore, in this embodiment, the sensing module 110 is continuously operated at the resonance frequency ω ₀ , so that the frequency scanning operation is not required, and the measurement speed of the self-excited oscillation electromagnetic coupling measuring device 100 is further improved.

In addition, in the system architecture, the sensing module 110 in the embodiment of FIG. 1 is disposed above the sample 101 to be tested. Although the embodiment of FIG. 1 exemplifies the configuration of the sensing module 110 and the sample 101 to be tested, it is not intended to limit the present invention. Those skilled in the art can change the number and arrangement position of the sensing module 110 according to the needs of the device, or add corresponding magnetic sensing components to detect the sample 101 to be tested for special needs. For example, FIG. 8 to FIG. 12 are schematic diagrams of a self-excited oscillation electromagnetic coupling measuring device according to another embodiment of the present invention.

In the embodiment of FIG. 8 and FIG. 9 , the self-oscillating electromagnetic coupling measuring device 100 further includes a sensing module 810 . The sensing module 110 includes a first winding, and the sensing module 810 includes a second winding, and the first winding is electrically connected to the second winding to form a driving coil. In other words, the sensing module 110 and the sensing module 810 are composed of the same driving coil, and the alternating magnetic field is generated by driving the coil. In addition, in the embodiment of FIG. 8 , the sensing module 110 and the sensing module 810 are disposed together above the sample 101 to be tested. In the embodiment of FIG. 9 , the sensing module 110 and the sensing module 810 are respectively disposed on the upper and lower sides of the sample 101 to be tested. Accordingly, the self-oscillating electromagnetic coupling measuring device 100 can form an alternating magnetic field of different magnetic circuits through the sensing module 110 and the sensing module 810, and then detect the sample 101 to be tested for special needs. For example, the surface of the sample to be tested 101 may be a plane, a cylindrical surface or an arbitrary curved surface. Furthermore, in the embodiment of FIGS. 8 and 9, the amplitude control unit 140 generates the control information DT based on the feedback signal S _F . That is, the voltage gain controller 141 at this time converts the feedback signal S _F into a detection voltage, and generates a control voltage DT according to the comparison result with the reference voltage V _R . In other words, under the embodiment of Figure 1 as compared with, in addition to the amplitude control unit 140 may generate control information other than the DT, the feedback signal may also be utilized to generate the control information S _F DT by the driving voltage V _D.

In the embodiment of FIGS. 10 and 11, the self-oscillating electromagnetic coupling measuring device 100 further includes a magnetic sensing element 1010. Wherein, the magnetic sensing element 1010 is disposed on the path of the alternating magnetic field. Thereby, the magnetic sensing component 1010 senses the change of the alternating magnetic field, and then returns the second feedback signal S _F2 from the sensing module 110 to the amplitude control unit 140. At this time, the amplitude control unit 140 will generate the control information DT by using the second feedback signal S _F2 . That is, the voltage gain controller 141 at this time converts the second feedback signal S _F2 into a detection voltage, and generates the control voltage DT according to the comparison result by the detection voltage and the reference voltage V _R . In other words, in comparison with the embodiment of FIG. 1, FIG. 8 and FIG. 9, the amplitude control unit 140 can use the second feedback function in addition to the driving voltage V _D or the feedback signal S _F to generate the control information DT. Signal S _{F2 is} used to generate control information DT. In addition, the magnetic sensing element 1010 may be composed of other elements that can induce magnetic fields, such as a coil, a Hall sensor, a giant magnetoresistance (GMR), and the like. Furthermore, in the embodiment of FIG. 10, the magnetic sensing component 1010 and the sensing module 110 are disposed together above the sample 101 to be tested. In the embodiment of FIG. 11 , the sensing module 110 and the magnetic sensing component 1010 are respectively disposed on the upper and lower sides of the sample 101 to be tested.

The embodiment of Figure 12 is another embodiment extending from the embodiment of Figures 8-11. In the embodiment of FIG. 12 , the self-oscillating electromagnetic coupling measuring device 100 further includes a sensing module 1210 , a magnetic sensing component 1220 and a magnetic sensing component 1230 . The sensing module 110 and the sensing module 1220 are composed of the same driving coil. In addition, the sensing module 110 and the sensing module 1220 are respectively disposed on upper and lower sides of the sample 101 to be tested. Furthermore, the magnetic sensing element 1220 and the magnetic sensing element 1230 are disposed on the path of the alternating magnetic field, and are respectively disposed on the upper and lower sides of the sample 101 to be tested. The detailed description of the components of the components in the embodiment of Fig. 12 is included in the above embodiments, and therefore will not be described herein.

In summary, the present invention utilizes an adjustable frequency oscillator to track the phase change of the driving voltage so that the sensing module can still operate at the resonant frequency after sensing the sample to be tested. In addition, the present invention further utilizes the amplitude control unit to feedback the amplitude of the control driving voltage so that the amplitude of the driving voltage is maintained constant. Thereby, the power loss generated at the resonant frequency will be reflected in the driving current provided by the power amplifier, so the present invention can obtain the relevant information of the sample to be tested by detecting the driving current. In addition, since the present invention utilizes the adjustable frequency oscillator to self-oscillate the oscillating voltage, the measurement range of the sensing module can be improved. Furthermore, since the present invention can measure the characteristics of the sample to be tested without performing frequency scanning, the speed and linearity of the measurement can be improved.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

100. . . Self-oscillating electromagnetic coupling measuring device

110, 810, 1210. . . Sensing module

120. . . Power amplifier

130. . . Adjustable frequency oscillator

140. . . Amplitude control unit

141. . . Voltage gain controller

142. . . Voltage generator

150. . . Current sensor

101. . . Sample to be tested

V _R . . . Reference voltage

V _O . . . Oscillating voltage

V _D . . . Driving voltage

S _F . . . Feedback signal

S _F2 . . . Second feedback signal

DT. . . Control information

SD. . . Checkout signal

T ₂ . . . transformer

L ₁ . . . Main coil

L ₂ . . . Secondary coil

I ₁ , I ₂ . . . Current

V ₁ , V ₂ . . . Voltage

R _S , R _L . . . impedance

R _eq . . . Equivalent resistance

L _eq . . . Equivalent inductance

C. . . capacitance

L. . . inductance

R _P . . . load

R’. . . resistance

I _D . . . Drive current

N4. . . node

401. . . Equivalent impedance

610~640. . . curve

700. . . Phase-locked loop

710. . . Phase comparator

720. . . Low pass filter

730. . . Voltage controlled oscillator

1010, 1220, 1230. . . Magnetic sensing component

1 is a schematic diagram of a self-excited oscillation electromagnetic coupling measuring device according to an embodiment of the present invention.

2 is a schematic diagram of a coupling model of eddy currents in accordance with an embodiment of the present invention.

3 is an equivalent circuit diagram of a sensing module in accordance with an embodiment of the present invention.

4 is an equivalent circuit diagram of a sensing module in accordance with another embodiment of the present invention.

Figure 5 is a schematic diagram of the frequency response of a transfer function in accordance with an embodiment of the present invention.

FIG. 6 is a schematic diagram showing waveforms of a sensing module according to an embodiment of the invention.

7 is a block diagram of a phase locked loop in accordance with an embodiment of the present invention.

8 to 12 are schematic views of a self-excited oscillation electromagnetic coupling measuring device according to another embodiment of the present invention.

100. . . Self-oscillating electromagnetic coupling measuring device

110. . . Sensing module

120. . . Power amplifier

130. . . Adjustable frequency oscillator

140. . . Amplitude control unit

141. . . Voltage gain controller

142. . . Voltage generator

150. . . Current sensor

101. . . Sample to be tested

V _R . . . Reference voltage

V _O . . . Oscillating voltage

V _D . . . Driving voltage

S _F . . . Feedback signal

DT. . . Control information

SD. . . Checkout signal

Claims (17)

A self-oscillating electromagnetic coupling measuring device comprises: a first sensing module, which uses an driving voltage to emit an alternating magnetic field to sense a sample to be tested, and generates a response according to a change in its equivalent impedance An adjustable frequency oscillator generates an oscillating voltage and causes the oscillating voltage to have a frequency equal to a resonant frequency of the first sensing module; an amplitude control unit generates a control information according to the driving voltage; a power amplifier amplifying the oscillating voltage according to a gain value to generate the driving voltage, and adjusting the gain value according to the control information to maintain a constant amplitude of the driving voltage; and a current sensor detecting the power amplifier The generated drive current generates a detection signal related to the characteristics of the sample to be tested. The self-oscillating electromagnetic coupling measuring device according to claim 1, wherein the adjustable frequency oscillator is constituted by a phase locked loop. The self-excited oscillation electromagnetic coupling measuring device according to claim 2, wherein the phase locked loop comprises: a voltage controlled oscillator to generate the oscillating voltage; and a phase comparator for comparing the oscillating voltage with the feedback a phase difference between the signals, and according to which a phase error signal is generated; and a low pass filter that filters out high frequency components in the phase error signal and generates an adjusted voltage, wherein the voltage controlled oscillator Re-oscillation according to the adjustment voltage to adjust the frequency and phase of the oscillating voltage. The self-excited oscillation electromagnetic coupling measuring device according to claim 1, wherein the amplitude control unit comprises: a voltage generator that generates a reference voltage; and a voltage gain controller that converts the driving voltage into one The voltage is detected, and the voltage gain controller compares the detected voltage with the reference voltage, and generates the control information according to the comparison result. The self-oscillating electromagnetic coupling measuring device according to the first aspect of the invention, wherein the first sensing module comprises a driving coil and a capacitor, and the driving coil and the capacitor are electrically connected in parallel with each other. The self-oscillating electromagnetic coupling measuring device of the first sensing module includes a first winding, and the self-oscillating electromagnetic coupling measuring device further comprises: a second The sensing module includes a second winding, wherein the first winding is electrically connected to the second winding to form a driving coil for generating the alternating magnetic field. The self-oscillating electromagnetic coupling measuring device according to the sixth aspect of the invention, wherein the first sensing module and the second sensing module are disposed above the sample to be tested. The self-oscillating electromagnetic coupling measuring device according to the sixth aspect of the invention, wherein the first sensing module and the second sensing module are respectively disposed on upper and lower sides of the sample to be tested. The self-oscillating electromagnetic coupling measuring device according to claim 1, further comprising: a magnetic sensing component disposed on the path of the alternating magnetic field and sensing a change of the alternating magnetic field to be derived from A second feedback signal of the first sensing module is fed back to the amplitude control unit. The self-oscillating electromagnetic coupling measuring device according to claim 9, wherein the magnetic sensing component is composed of a coil, a Hall sensor or a giant magnetoresistance. The self-excited oscillation electromagnetic coupling measuring device according to claim 9, wherein the magnetic sensing component and the first sensing module are disposed on the same side of the sample to be tested. The self-oscillating electromagnetic coupling measuring device according to claim 11, wherein the magnetic sensing component is disposed above the sample to be tested together with the first sensing module. The self-excited oscillation electromagnetic coupling measuring device according to claim 9, wherein the magnetic sensing component and the first sensing module are respectively disposed on two sides of the sample to be tested. The self-oscillating electromagnetic coupling measuring device according to claim 1, wherein the sample to be tested is a film, and the film is composed of a non-magnetic material. The self-oscillating electromagnetic coupling measuring device according to claim 14, wherein the self-oscillating electromagnetic coupling measuring device determines the sheet resistance value of the film according to the detection signal. The self-oscillating electromagnetic coupling measuring device according to the first aspect of the invention, wherein the equivalent impedance of the first sensing module causes a phase of a driving current flowing into the first sensing module and the first The resonant frequency of the sensing module produces a corresponding change. The self-oscillating electromagnetic coupling measuring device according to claim 16, wherein the driving current flows through a node of the first sensing module, and a voltage at the node is used as the feedback a signal, and the first sensing module uses the feedback signal to reflect a phase change of the driving current.