TWI546553B - System and method of detecting ultra weak magnetic field - Google Patents

Description

System and method for detecting ultra-weak magnetic fields

The present disclosure is directed to a system and method for detecting a magnetic field.

Recently, a technique suitable for detecting geomagnetism has reached a need to detect a very weak magnetic field with high sensitivity and high precision to expand the range of applications. Magnetic Impedance (MI) components of this type of magnetic field detecting component have attracted attention. A method of using a known MI element for magnetic field detection by applying a high frequency current to a magnetic element and detecting a voltage signal generated by a detecting coil wound or disposed in the vicinity of the magnetic element.

The first figure illustrates a basic circuit diagram of the prior art for detecting a magnetic field. Referring to the first figure, the oscillation circuit 11 surrounded by a broken line generates a pulse oscillation, and current is flown to the MI element 14 via the inverter 12 and the current adjustment resistor 13. Then, the change in the magnetic flux caused by the MI element 14 is taken out to cause a change in the voltage in the detection coil 15 around the MI device 14. One end of the detecting coil 15 is connected to the ground terminal, and the other end is connected to a waveform detecting circuit 16 formed of a peak detecting diode and an RC circuit so that an amplitude modulated magnetic field signal can be taken out from the waveform detecting circuit 16. In contrast, the magnetic field signal can be detected synchronously in synchronization with the rising and falling of the oscillation of the oscillation circuit 11 of an analog switch and a holding capacitor. Then a voltage Vso of a zero external magnetic field characteristic and a reference voltage matching the voltage Vso The voltage is selected, which is via an amplifier 17 and a variable resistor 18 inserted between the supply voltage and the ground terminal. Therefore, the output voltage is manually adjusted at the output of the amplifier.

However, Vso often changes due to changes in the surrounding environment. In this case, it is difficult to manually adjust the output voltage. If the signal on the sense coil is a sharp peak top, the sample jitter of the peak detection will also result in a high signal change. If the magnetic field is not smooth or the magnetic field changes significantly, even if a nonlinear effect is added, it cannot optimize the detection of the signal. Therefore, such a magnetic field detecting circuit for detecting a magnetic field cannot detect a very weak magnetic field, particularly for detecting a secondary mG (milli Gauss) magnetic field or a noisy magnetic field. For modern applications, especially in the case of aerial mice, gyroscopes, etc., such detection techniques will result in large errors.

For some cases, the above-mentioned existing detection magnetic field technology has the disadvantages that cannot be handled, especially the inherent noise of the component of the oscillation circuit, the noise of the peak voltage change caused by the sampling jitter, the coil loading effect that affects the characteristics of the non-external magnetic field, and the weak magnetic field, etc. Happening. Therefore, it is necessary to design a magnetic field detecting technique with high flexibility and reliability.

The disclosed embodiments provide a technique for detecting a magnetic field that uses a magnetic impedance element to detect the intensity of an external magnetic field, wherein the impedance of the magnetic impedance element varies according to changes in the external magnetic field. More specifically, the present invention relates to a highly sensitive and highly accurate detection technique for generating a very weak magnetic field from a geomagnetic or very weak current.

One disclosed embodiment relates to a system for detecting a magnetic field. The system comprises: a magnetic impedance component surrounded by a detection coil, a source unit for generating a pulse signal of programmable rise/fall time to drive the magnetic impedance component, and a signal detection module The signal detecting module comprises: a buffer unit having an adjustable bandwidth shape to shape an output signal of the detecting coil, and a signal amplifying unit amplifying the buffer signal output by the buffer unit, a signal The processing unit applies a selectable algorithm to the signal amplified by the signal amplifying unit to output the detection result, and a control unit is connected to the signal processing unit to generate control parameters of the source unit, the buffer unit, the signal amplifying unit and the signal processing unit. .

Another embodiment disclosed is directed to a method of detecting a magnetic field. The method includes: generating a voltage of a programmable rise/fall time to drive a detection coil surrounding a magnetic impedance element; shaping an output signal of the detection coil via a buffer unit having an adjustable bandwidth; by using a sampling sum A hold circuit and a chopper programmable gain amplifier amplify the buffered signal output by the buffer unit; process the amplified signal through a selectable algorithm to output the detection result; and check the detection result to control the generated voltage, buffer unit, sample And hold circuits, chopper programmable gain amplifiers, and algorithms.

The above and other advantages of the present disclosure will be described in detail below with reference to the following drawings, detailed description of the embodiments, and claims.

11‧‧‧Oscillation circuit

12‧‧‧Connected interface inverter

13‧‧‧current adjustment resistor

14‧‧‧MI components

14‧‧‧Data Communication Module

15‧‧‧Control Module

16‧‧‧ Waveform detection circuit

17‧‧‧Amplifier

18‧‧‧Variable resistor

220‧‧‧Detection coil

230‧‧‧Source unit

240‧‧‧Signal Detection Module

241‧‧‧buffer unit

242‧‧‧Signal amplification unit

245‧‧‧Signal Processing Unit

246‧‧‧Control unit

610‧‧‧Sampling and holding circuit

611, 612‧‧ ‧ sampling switch

613, 614‧‧ ‧ holding capacitor

620‧‧‧Chopper programmable gain amplifier

621, 622, 623, 624‧‧ ‧ switch

625, 626, 627, 628‧‧ ‧ switch

710‧‧‧ Analog/Digital Converter

720‧‧‧Digital Signal Processor

901‧‧‧ pumping Gaussian magnetic field

902‧‧‧System covering magnetic shielding box to detect magnetic field

903‧‧‧A system that does not cover the magnetic shield box to detect the magnetic field

910‧‧‧Scan standard magnetic field

920‧‧‧Sampling full signal waveforms

930‧‧‧Confirm that the scanning environment is complete

940‧‧‧ Looking for a new sampling edge

950‧‧‧Comparing the top and bottom values of the crest

960‧‧‧Adjust the delay circuit in the control unit

970‧‧‧Change the source slew rate in the source unit

980‧‧‧Change the bandwidth of the buffer in the buffer unit

990‧‧‧Select digital signal processing (DSP) filtering in the signal processing unit

1010‧‧‧ Generates a programmable rise/fall time voltage to drive a sense coil around a magnetic impedance element

1020‧‧‧Integrated output signal of the detection coil via a buffer unit with adjustable bandwidth

1030‧‧Amplify the buffered signal output from the buffer unit by using a sample and hold circuit and a chopper programmable gain amplifier

1040‧‧‧Processing the amplified signal via an optional algorithm to output the test result

1050‧‧‧Check the test results to control the generated voltage, buffer unit, sample and hold circuit, chopper programmable gain amplifier, and algorithm

The first figure illustrates a basic circuit diagram of the prior art for detecting a magnetic field.

The second figure is a schematic view consistent with an embodiment of the disclosure, illustrating a system for detecting a magnetic field.

The third figure is a schematic diagram consistent with an embodiment of the disclosure, illustrating the source unit of the system for detecting a magnetic field in the second figure.

The fourth a-fourth diagram is a schematic diagram consistent with an disclosed embodiment, illustrating The signal generated by the source unit of the programmable rise/fall time of the system that detects the magnetic field in the three figures.

The fifth figure is a schematic view consistent with an embodiment of the disclosure, illustrating the input and output signals of the buffer unit of the system for detecting magnetic fields in the second figure.

The sixth drawing is a schematic view consistent with an embodiment of the disclosure, illustrating a signal amplifying unit of the system for detecting a magnetic field in the second figure.

The seventh figure is a schematic view consistent with an embodiment of the disclosure, illustrating the processing unit of the system for detecting magnetic fields in the second figure.

The eighth figure is a schematic view consistent with an embodiment of the disclosure, illustrating the adjustable bandwidth of the processing unit of the system for detecting magnetic fields in the second figure.

The ninth a-ninth b-figure is a schematic diagram consistent with an embodiment of the disclosure, illustrating a flow chart for establishing a system for detecting a magnetic field and optimizing control parameters of the control unit.

The tenth figure is a schematic view consistent with an embodiment of the disclosure, illustrating a method of detecting a magnetic field.

The disclosed embodiments provide a technique for detecting a magnetic field that uses a magnetic impedance element to detect the intensity of an external magnetic field, wherein the impedance of the magnetic impedance element varies according to changes in the external magnetic field. More specifically, the present invention relates to a highly sensitive and highly accurate detection technique for generating a very weak magnetic field from a geomagnetic or very weak current.

One disclosed embodiment relates to a system for detecting a magnetic field. The second figure is a schematic view consistent with an embodiment of the disclosure, illustrating a system for detecting a magnetic field. Referring to the second figure, the system includes a magnetic impedance element 210 surrounded by a detection coil 220. A source unit 230 generates a programmable rise/fall time voltage signal to drive the magnetic impedance element 210, and a signal detection module. 240 detects the output of the detection coil 220 The signal detection module 240 includes a buffer unit 241 having an adjustable bandwidth to shape the output signal of the detection coil 220, and a signal amplification unit 242 amplifies the buffer signal output by the buffer unit 241, and a signal processing unit 245 passes A signal that is amplified by the amplifying unit 242 is subjected to signal processing to output a detection result, and a control unit 246 is connected to the signal processing unit 245 to generate the source unit 230, the buffer unit 241, the signal amplifying unit 242, and signal processing. Control parameters of unit 245.

Referring to the second figure, the impedance of the magnetic impedance element 210 varies according to changes in the external magnetic field. The source unit 230 generates a signal of programmable rise/fall time to drive the magnetic impedance element 210. The signal generated by the source unit 230 can be implemented by the circuit diagram shown in the third figure. As shown in the third figure, two voltages V1 and V2 are applied to the circuits in which the two switches S1 and S2 are coupled to the two parallel RC circuits R1C1 and R2C2 to connect the two end points of the magnetic impedance element 210 to drive the magnetic Impedance element 210.

Therefore, in the third figure, the switches S1 and S2 switch the timings Φ1 and Φ2, and the parallel RC circuits R1C1 and R2C2 via the two voltages V1 and V2, and the signal VI of the two end points of the magnetic impedance element 210 is as shown in the fourth figure. Show. In the fourth a diagram, the two voltages V1 and V2 are two different DC voltages, and the switching timings Φ1 and Φ2 of the switches S1 and S2 are the same. In the fourth b-picture, the two voltages V1 and V2 are two different DC voltages, and the switching timings Φ1 and Φ2 of the switches S1 and S2 are different clock timings. In the fourth c-picture, the two voltages V1 and V2 are two different voltages, that is, V1 is a DC voltage, V2 is a two-stage voltage, and the switching timings Φ1 and Φ2 of the switches S1 and S2 are two different clocks. time. As shown in the fourth d-d, the two voltages V1 and V2 are two different DC voltages, the switching timings Φ1 and Φ2 of the switches S1 and S2 are two opposite clock timings, and the component values of R1C1 and R2C2 are different. . The different voltage values of the above two voltages V1 and V2, the switching timings Φ1 and Φ2 of the switches S1 and S2, and the component values of the parallel RC circuits R1C1 and R2C2 are programmable, and the control list Element 246 is controlled by generating corresponding control parameters. Therefore, the signal generated by the source unit 230 is a programmable rise/fall time signal.

In the above, the signal generated by the source unit 230 is applied to both end points of the magnetic impedance element 210, and a current is generated through the magnetic impedance element 210 according to the impedance thereof. The detecting coil 220 is wound around, for example, wound on the magnetic impedance element 210, thereby inducing a voltage signal at both ends of the detecting coil, wherein the voltage signal is proportional to the magnetic field according to the current.

After the detection coil 220 outputs a voltage signal, the signal detection module 240 detects the signal on the detection coil. The buffer unit 241 of the signal detection module 240 has an adjustable bandwidth, and the shape of the detection coil output signal can be shaped to reduce the signal variation of the sampling point near the peak. The fifth figure is a schematic view consistent with an embodiment of the disclosure, illustrating the input and output signals of the buffer unit of the system for detecting magnetic fields in the second figure. The buffer unit provides a frequency of the selected bandwidth in response to the detection coil to reduce variations in the signal due to peak sample jitter. As shown in the fifth figure, for the same sampling jitter Δt, the output signal change ΔV of the buffer unit is reduced. According to an embodiment, the adjustable bandwidth is adjustable and is controlled by control unit 246 by generating corresponding control parameters.

According to an embodiment, signal amplification unit 242 is coupled to buffer unit 241 to provide an amplification function for further processing. The sixth drawing is a schematic view consistent with an embodiment of the disclosure, illustrating a signal amplifying unit of the system for detecting a magnetic field in the second figure. As shown in the sixth diagram, the signal amplifying unit 242 includes a sample and hold circuit 610 and a Chopping Programmable Gain Amplifier (PGA) 620 to amplify the buffered signal from the buffer unit. The sample and hold circuit 610 includes sampling switches 611 and 612, and holding capacitors 613 and 614 to maintain peaks of the buffer voltage output from the two terminals of the buffer unit. Chopper programmable gain amplifier (PGA) 620 includes switches 621, 622, 623, and 624 for chopping the hold signals Vip and Vim input to the two terminals of the sample and hold circuit 610, a programmable gain amplifier (PGA) for amplification, and a switch 625, 626, 627, and 628 are used to transmit the output signals Vop and Vom to the signal processing unit 245. An advantage of the amplification unit 242 is to reduce flicker noise and noise due to unbalanced signal mismatch. The switching times of the sampling switches 611 and 612, the switching times of the switches 621-628 and the amplification of the programmable gain amplifier (PGA) are programmable and controlled by the control unit 246 by generating corresponding control parameters. Therefore, the amplified signal of the signal amplifying unit 242 is a programmable amplified signal.

As shown in the second figure, signal processing unit 245 is coupled to amplifier 242, which processes the amplified signal by applying a selectable algorithm to output a detection result. The seventh figure is a schematic view consistent with an embodiment of the disclosure, illustrating the processing unit of the system for detecting magnetic fields in the second figure. Referring to the seventh diagram, the signal processing unit includes an analog/digital converter (ADC) 710 and a digital signal processor 720. Wherein, the analog/digital converter 710 converts the analog signal output by the amplifying unit into digital data, and the digital signal processor 720 performs different signal processing algorithms, such as digital signal filtering, to reduce out-of-band noise for different applications. As shown in the eighth figure, which is consistent with an embodiment of the disclosed embodiment, the adjustable bandwidth for signal processing is implemented by the digital signal processor of the seventh figure. The adjustable bandwidth for signal processing is adjustable and controlled by control unit 246 to generate corresponding control parameters.

According to an embodiment, the control unit 246 is coupled to the signal processing unit 245 to generate control parameters for the source unit, the buffer unit, the signal amplifying unit, and the signal processing unit. The control unit is connected to the processing unit to generate control parameters such as switching timing and voltage values of the switches in the source unit, bandwidth parameters of the buffer unit, switching timing of the signal amplifying unit, and filtering parameters in the signal processing unit. Control unit can include timing delay The circuit adjusts the switching timing of the switch. Additionally, control unit 246 can further include a memory for storing updated control parameters.

In view of the above, the ninth a-9th diagram is a schematic diagram consistent with an embodiment of the disclosure, illustrating a method of establishing a system for detecting a magnetic field and optimizing a control parameter of the control unit. Referring to Figure 9a, the system is established in a two-step system using a pumping Gaussian scanning magnetic field 901 to detect the magnetic field, wherein the first step is to cover the magnetic shield box to the system 902 for detecting the magnetic field, and the second step is A system 903 that covers the magnetic shield box to detect the magnetic field. The flow chart for optimizing the control parameters of the control unit is shown in Figure IXb. In Figure 9b, the system first scans the standard magnetic field (step 910) and then uses the delay circuit in the control unit to generate a timing to sample the full signal waveform (step 920) to confirm that the scanning environment is complete (step 930). Then, if necessary, by comparing the top and bottom values of the peaks (step 950), the system looks for a new sampling edge (step 940) and adjusts the delay circuit in the control unit (step 960). Finally, the system changes the bandwidth of the buffer in the buffer unit by changing the source slew rate (rise/fall time) in the source unit (step 970) (step 980), and selecting the digital signal processing (DSP) in the signal processing unit. Filtering (step 990) to optimize system performance for better detection results.

Another embodiment relates to a method of detecting a magnetic field. The tenth figure is a schematic view consistent with an embodiment of the disclosure, illustrating a method of detecting a magnetic field. The method for detecting a magnetic field includes: generating a voltage of a programmable rise/fall time to drive a detection coil surrounding a magnetic impedance element (step 1010); and shaping an output signal of the detection coil via a buffer unit having an adjustable bandwidth (Step 1020): amplifying the buffered signal output by the buffer unit by using a sample and hold circuit and a chopper programmable gain amplifier (step 1030); processing the amplified signal via a selectable algorithm to output the detection result ( Step 1040); and checking the detection results to control the generated voltage, buffer unit, sample and hold circuit, chopper programmable gain amplifier, and algorithm (step 1050).

In view of the above, according to an embodiment, the control in step 1050 can include using a memory for storing the updated control state. An alternative algorithm for processing the amplified signal may for example be signal filtering.

This embodiment provides a magnetic field detection technique using a signal generator having an adjustable slew rate, a buffer for signal shaping to reduce the effects of sample jitter, a sample and hold circuit and a chopping PGA as a differential signal The amplification is to reduce the effects of signal imbalance, and a digital signal processing is filtered as a different application to reduce out-of-band noise. This magnetic field detection technology is flexible and reliable, providing a highly sensitive and highly accurate detection for generating very weak magnetic fields from geomagnetic or very weak currents.

The above descriptions are only examples of the disclosure, and the disclosure is not limited thereto. range. The equal changes and modifications made by the scope of the patent application of the present invention should belong to this The scope of the invention patent covers.

210‧‧‧Magnetic impedance components

220‧‧‧Detection coil

230‧‧‧Source unit

240‧‧‧Signal Detection Module

241‧‧‧buffer unit

242‧‧‧Signal amplification unit

245‧‧‧Signal Processing Unit

246‧‧‧Control unit

Claims (13)

A system for detecting an ultra-weak magnetic field, the system comprising: a magnetic impedance element surrounded by a detection coil; a source unit for generating a pulse signal of programmable rise/fall time to drive the magnetic impedance element; and a signal detection The module is configured to detect a signal on the detecting coil, wherein the signal detecting module comprises: a buffer unit having an adjustable bandwidth shape to shape an output signal of the detecting coil; and a signal amplifying unit buffering the output of the buffer unit Signal amplification; a signal processing unit applies a selectable algorithm to the signal amplified by the signal amplification unit to output a detection result; and a control unit is coupled to the signal processing unit to generate the source unit, the buffer unit, and the Signal amplification unit and control parameters of the signal processing unit. The system of claim 1, wherein the source unit comprises two voltages applied to the two switches coupled to the two parallel RC circuits. The system of claim 1, wherein the buffer unit provides a frequency of the selected bandwidth in response to the detection coil to reduce variations in the signal due to peak sample jitter. The system of claim 1, wherein the signal amplifying unit comprises a sample and hold circuit and a chopper programmable gain amplifier. The system of claim 1, wherein the signal processing unit comprises an analog/digital converter and a digital signal processor. The system of claim 1, wherein the algorithm is a signal filtering. The system of claim 1, wherein the control unit includes a memory for storing updated control parameters. The system of claim 1, wherein the control parameter is a switching timing, a voltage value, a bandwidth parameter, and a filtering parameter of the switch. A buffer unit adapted to detect a system of an ultra-weak magnetic field, the buffer unit having an adjustable bandwidth, providing a frequency of a frequency response to an output signal of a detection coil to reduce a change in a signal due to peak sampling jitter, wherein The output signal of the detection coil is induced by the detection coil surrounding a magnetic impedance element. A source unit adapted to detect a system of ultra-weak magnetic fields, the source unit generating a programmable rise/fall time signal to drive a magnetic impedance element, wherein the signal is coupled by two voltages applied to the two switches Formed by parallel RC circuits. A method of detecting an ultra-weak magnetic field, the method comprising: generating a programmable rise/fall time voltage to drive a detection coil surrounding a magnetic impedance element; outputting the detection coil via a buffer unit having an adjustable bandwidth Integral; amplifying the buffered signal output by the buffer unit by using a sample and hold circuit and a chopper programmable gain amplifier; processing the amplified signal via a selectable algorithm to output the detection result; The detection result is checked to control the generated voltage, the buffer unit, the sample and hold circuit, the chopper programmable gain amplifier, and the algorithm. The method of claim 11, wherein the algorithm is a signal filtering. The method of claim 11, wherein the controlling comprises using a memory to store the updated control state.