CN103512592B - Wireless and passive LC resonant transducer testing circuit and corresponding information getting method - Google Patents

Abstract

The invention discloses a kind of wireless and passive LC resonant transducer information detection, this circuit comprises: master controller, Direct Digital Frequency Synthesizers, high-speed AD converter and differential driving symmetric detection circuit, main controller controls signal source exports swept-frequency signal, sampled by main controller controls after differential driving symmetric detection circuit, master controller calculates the phase spectrum of network by DFT, and final master controller completes the calibration of phase spectrum and the detection of resonance frequency.The invention also discloses a kind of wireless and passive LC resonant transducer information getting method, in the method, first the phase spectrum without system during sensor itself is obtained, by subtracting each other with the phase spectrum of system own the phase spectrum calibrated and obtain at every turn, by the harmonic peak frequency detecting LC resonant transducer after the phase spectrum filtering after calibrating.The present invention effectively improves the sensitivity of detection, eliminates the impact of system and the phase spectrum of read coil own, improves the stability of detection and the portability of system simultaneously.

Description

Wireless and passive LC resonant transducer testing circuit and corresponding information getting method

Technical field

The present invention relates to sensor detection field, particularly relate to a kind of wireless and passive LC resonant transducer testing circuit and corresponding information getting method.

Background technology

The sensing system that wireless and passive LC resonant transducer is made up of read coil and inductance, capacitor resonance loop, Fig. 1 (a) is the structural representation of wireless and passive LC resonant transducer conventional in prior art, wherein variable inductance or variable capacitance are as sensing unit impression measured (such as: pressure, temperature, chemical quantity), and resonant tank is by the measured resonance frequency being converted to resonant tank; Fig. 1 (b) is the simplified model of described wireless and passive LC resonant transducer, wherein the principle of read coil acquisition resonant tank resonance frequency is the coupling due to inductance in read coil and resonant tank, cause read coil impedance phase to be composed and occur little depression at resonant tank resonance frequency place, the position of depression is moved along with the change of resonance frequency, obtain the resonance frequency of resonant tank by detecting recessed position, thus realize measured detection.

Because the sensing unit of wireless and passive LC resonant transducer adopts passive device--inductance and electric capacity composition, make it have structure simple, be easy to miniaturization, advantage that manufacturing cost is lower, simultaneously because sourceless characteristic makes it be particularly suitable for For Long-term Monitoring Systems, such as, monitoring under inside of human body pressure monitoring, industrial high temperature environment and the detection etc. of closed system.

According to the principle of work of wireless and passive LC resonant transducer, high-precision network analyzer is usually used to measure the impedance phase spectrum of read coil in an experiment, the position of resonance frequency is detected from impedance phase spectrum, but the volume of network analyzer is large, equipment is heavy, cost is high, and the restriction that there are the aspects such as above-mentioned volume, cost due to network analyzer makes it be difficult to be applied in actual detection.The people such as MichelNowak propose to use closed loop circuit to detect resonance frequency, and the mode of its closed loop circuit is phase method, and the position being zero by locking read coil impedance phase realizes closed loop.Because the phase place of read coil own is 90 °, therefore need read coil and the stronger coupling coefficient of inductance to make phase place back variation be greater than 90 °, thus limit the detecting distance of this circuit.The people such as J.Coosemans adopt read coil to construct voltage controlled oscillator device (VCO), exported by Control of Voltage VCO frequency sweep, in this process, the voltage at read coil two ends changes due to the existence of LC resonant transducer, the resonance frequency of the position that change in voltage is maximum and LC resonant transducer, this testing circuit same needs stronger coupling coefficient, the people such as J.Coosemans adopt this circuit only to achieve detection that coupling distance is the wireless and passive LC resonant transducer of 7.5mm.

For low coupling coefficient, at a distance wireless and passive LC resonance sensor systems, detection difficult is caused because the change of read coil phase place is little, the present invention proposes a kind of information getting method and testing circuit of wireless and passive LC resonant transducer, improve sensitivity and the convenience of the detection of wireless and passive LC resonant transducer.

Summary of the invention

In order to solve above-mentioned problems of the prior art, the present invention proposes a kind of wireless and passive LC resonant transducer testing circuit and corresponding information getting method, object is to be provided in the effective information detection of wireless and passive LC resonant transducer and acquisition methods in lower coupling coefficient situation, and described information detection and acquisition methods are equally applicable to the detection of wireless and passive LC resonant transducer under high coupling coefficient.

According to an aspect of the present invention, propose a kind of information detection of wireless and passive LC resonant transducer, this circuit comprises: master controller, Direct Digital Frequency Synthesizers DDS, high-speed AD converter ADC, differential driving symmetric detection circuit wherein:

Described DDS is connected with described master controller and differential driving symmetric detection circuit, control signal for receiving described master controller also produces the swept-frequency signal determined by described control signal, and the swept-frequency signal that described DDS produces exports described differential driving symmetric detection circuit to;

Described differential driving symmetric detection circuit is connected with described DDS and ADC, for receiving the swept-frequency signal that described DDS exports, to extract and the phase place of amplifying its read coil impedance changes, and phase place is changed feedback signal and export described ADC to;

Described ADC is connected with described differential driving symmetric detection circuit and described master controller, phase place change feedback signal for exporting for described differential driving symmetric detection circuit carries out analog-to-digital conversion process, and exports the feedback signal obtained after process to described master controller;

Described master controller is connected with described DDS, high-speed AD converter ADC, for carrying out the harmonic peak frequency controlling also to process to determine current LC resonant transducer to the received signal to described DDS and ADC.

According to a further aspect in the invention, propose a kind of information getting method of wireless and passive LC resonant transducer, the method comprises the following steps:

Step 1, main controller controls Direct Digital Frequency Synthesizers DDS completes a frequency sweep and exports, differential driving symmetric detection circuit is extracted and is amplified the phase place change of its read coil impedance, described main controller controls high-speed AD converter ADC to the sampling of phase place change feedback signal, and reads the phase place change feedback signal through ADC process;

Step 2, the DSP in master controller processes according to described step 1 the phase place change feedback signal obtained to obtain this frequency sweep phase spectrum according to DFT algorithm;

Step 3, the phase spectrum utilizing described step 2 to obtain upgrades system phase spectrum;

Step 4, is positioned over LC resonant transducer to be detected in the read coil in differential driving symmetric detection circuit, and repeating said steps 1-2;

Step 5, the system phase that the phase spectrum utilizing described step 4 to obtain and described step 3 obtain is composed and is carried out phase spectrum calibration;

Step 6, the phase spectrum after calibrating for described step 5 carries out filtering;

Step 7, based on filtered phase spectrum, adopts peak detection algorithm to obtain the harmonic peak frequency of described LC resonant transducer.

Information getting method and the testing circuit of above-mentioned a kind of wireless and passive LC resonant transducer disclosed in this invention have the following advantages:

The symmetrical Sampling network of a, differential driving has the function of the phase place change of amplifying read coil impedance, effectively improves the sensitivity of detection;

The calibration of b, system phase spectrum eliminates the impact of system and the phase spectrum of read coil own;

C, the noise had in limit for length's unit impulse response (FIR) digital filter elimination phase spectrum, improve the stability of detection;

The embedded system that d, DSP and FPGA realize improves the portability of system.

Accompanying drawing explanation

Fig. 1 is the structural representation of wireless and passive LC resonant transducer of the prior art;

Fig. 2 is the structural representation of the wireless and passive LC resonant transducer testing circuit that the present invention proposes;

Fig. 3 is differential driving symmetric detection circuit network topology structure figure of the present invention;

Fig. 4 is the wireless and passive LC resonant transducer information getting method process flow diagram that the present invention proposes;

Fig. 5 is the frequency sweep phase spectrum comparison diagram of frequency sweep phase spectrum of the present invention (before comprising FIR filtering and after filtering) and AgilentE5061B network analyzer.

Embodiment

For making the object, technical solutions and advantages of the present invention clearly understand, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.

The present invention proposes a kind of information getting method and testing circuit of wireless and passive LC resonant transducer, object is to be provided in the effective information getting method of wireless and passive LC resonant transducer and testing circuit in lower coupling coefficient situation, and described information getting method and testing circuit are equally applicable to the detection of wireless and passive LC resonant transducer under high coupling coefficient.

From the principle of work of wireless and passive LC resonant transducer, the frequency of harmonic peak can be detected by the change of measuring read coil impedance phase.Therefore, the present invention uses the symmetrical Sampling network of differential driving to realize the amplification of read coil impedance phase change.

Fig. 2 is the structural representation of the wireless and passive LC resonant transducer testing circuit that the present invention proposes, as shown in Figure 2, described testing circuit comprises: master controller, Direct Digital Frequency Synthesizers (DDS), high-speed AD converter (ADC), differential driving symmetric detection circuit and display, wherein:

Described Direct Digital Frequency Synthesizers (DDS) is connected with described master controller and differential driving symmetric detection circuit, control signal for receiving described master controller also produces the swept-frequency signal determined by described control signal, the swept-frequency signal that described DDS produces exports described differential driving symmetric detection circuit to, wherein, described swept-frequency signal is two paths of differential signals, be expressed as A (W) and-A (W), the frequency range of described swept-frequency signal is 10kHz ~ 20MHz;

Described differential driving symmetric detection circuit is connected with described Direct Digital Frequency Synthesizers (DDS) and high-speed AD converter (ADC), for receiving the swept-frequency signal that described Direct Digital Frequency Synthesizers (DDS) exports, extracting and amplifying its read coil L _readthe phase place change of impedance, and phase place is changed feedback signal and export described high-speed AD converter (ADC) to;

Described differential driving symmetric detection circuit adopts the symmetrical Sampling network topological structure of differential driving as shown in Figure 3, the symmetrical Sampling network of described differential driving is by the symmetrical structure formed with reference to inductance and read coil, driven by differential signal, tie point with reference to inductance and read coil is the output terminal of Sampling network, particularly, described differential driving symmetric detection circuit comprises further with reference to inductance L _ref, read coil L _read, the first circuit for amplifying differential signal A1, the second circuit for amplifying differential signal A2, output signal amplification circuit A3, wherein:

The input end of described first circuit for amplifying differential signal A1, the second circuit for amplifying differential signal A2 connects the two-way swept-frequency signal A (W) ,-A (W) that are exported by described DDS respectively, and its output terminal connects described with reference to inductance L respectively _ref, read coil L _readone end; Described with reference to inductance L _ref, read coil L _readthe other end be interconnected, tie point is as the input end of described output signal amplification circuit A3, and the output terminal of described output signal amplification circuit A3 is connected to the input end of described ADC, is sent to described ADC will output signal B (W).

In the structure shown here, when the frequency of operation of this network is the resonance frequency of LC resonant transducer: with reference to inductance L _refimpedance be Z _ref=R _ref+ jwL _ref, wherein wL _ref>>R _ref, R _reffor described with reference to inductance L _refdead resistance, w is the resonance frequency of LC resonant transducer; Read coil L _readin when there is no a LC resonant transducer, read coil L _readimpedance be Z _read=R _read+ jwL _read, wherein wL _read>>R _read, R _readfor described read coil L _readdead resistance; Read coil L _readin when there is LC resonant transducer, read coil L _readimpedance be Z _read'=R _read+ Δ R+jwL _read, wherein Δ R is that the equivalence of LC loop is to the equivalent resistance in read coil.Owing to there is similarity with reference to inductance and read coil, therefore Z can be supposed _ref=α Z _read, α is the inductance value ratio with reference to inductance and read coil, 0.4< α <2.5.

The system function of the symmetrical Sampling network of described differential driving is:

$F\left(w\right)=2\frac{Z_{\mathrm{read}}}{Z_{\mathrm{read}}+Z_{\mathrm{ref}}}-1---\left(1\right)$

When LC resonant transducer adds after in read coil, the phase differential of this network is:

$\mathrm{\&Delta;\&theta;}\left(w\right)=\arctan \left(\frac{(1-\mathrm{\&alpha;})w{L}_{\mathrm{read}}}{(1-\mathrm{\&alpha;})R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)-\arctan \left(\frac{(1+\mathrm{\&alpha;})w{L}_{\mathrm{read}}}{(1+\mathrm{\&alpha;})R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)---\left(2\right)$

The phase differential of read coil self is:

$\mathrm{\&Delta;}{\mathrm{\&theta;}}_0\left(w\right)=\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)-\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}}\right)---\left(3\right)$

As ratio cc ≈ 1 with reference to inductance and read coil impedance, there is following relation:

$\arctan \left(\frac{(1-\mathrm{\&alpha;})w{L}_{\mathrm{read}}}{(1-\mathrm{\&alpha;})R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)<<\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)<\arctan \left(\frac{(1+\mathrm{\&alpha;})w{L}_{\mathrm{read}}}{(1+\mathrm{\&alpha;})R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)<\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}}\right)$

（4）

$\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)\&ap;\arctan \left(\frac{(1+\mathrm{\&alpha;})w{L}_{\mathrm{read}}}{(1+\mathrm{\&alpha;})R_{\mathrm{read}}+\mathrm{\&Delta;R}}\right)\&ap;\arctan \left(\frac{w{L}_{\mathrm{read}}}{R_{\mathrm{read}}}\right)---\left(5\right)$

Δ θ (w) > Δ θ can be obtained according to formula (4), (5) ₀w (), this illustrates that the phase differential of the symmetrical Sampling network of differential driving is greater than the phase differential of read coil self, and adopt numerical analysis method to demonstrate when described Sampling network symmetry is higher in addition, the enlargement factor of this system phase difference is higher.

Described high-speed AD converter (ADC) is connected with described differential driving symmetric detection circuit and described master controller, phase place change feedback signal for exporting for described differential driving symmetric detection circuit carries out analog-to-digital conversion process, and exports the feedback signal obtained after process to described master controller;

Described master controller is connected with described Direct Digital Frequency Synthesizers (DDS), high-speed AD converter (ADC) and display, for carrying out the harmonic peak frequency controlling also to process to determine current LC resonant transducer to the received signal to described DDS and ADC, it comprises digital signal processor (DSP) and field programmable device (FPGA) further, wherein, described FPGA is controlled described DDS and ADC respectively by control signal, to realize the synchronized sampling of swept-frequency signal and feedback signal; The phase place change feedback signal that described DSP exports based on described ADC is determined to be specially the harmonic peak frequency of current LC resonant transducer: the phase place change feedback signal that first described DSP exports based on described ADC calculates the phase spectrum of described differential driving symmetric detection circuit by DFT algorithm; Then by the phase spectrum calculated and the calibration realizing phase spectrum without system phase spectrum subtraction during LC resonant transducer; Then the phase spectrum convolution after adopting the Serial No. of FIR filter design and calibrating completes digital filtering; Value in filtered phase spectrum is searched to determine the harmonic peak frequency of current LC resonant transducer finally by peak detection algorithm.

Described display is connected with described master controller, for receiving the control signal of described master controller to show related data, the running status of such as described master controller, the resonance frequency of current LC resonant transducer and the resonance frequency change curve etc. of LC resonant transducer.

Fig. 4 is the process flow diagram of the wireless and passive LC resonant transducer information getting method that the present invention proposes, and as shown in Figure 4, said method comprising the steps of:

Step 1, main controller controls DDS completes a frequency sweep and exports, and differential driving symmetric detection circuit is extracted and amplified its read coil L _readthe phase place change of impedance, described main controller controls ADC to the sampling of phase place change feedback signal, and reads the phase place change feedback signal through ADC process;

Step 2, the DSP in master controller processes according to described step 1 the phase place change feedback signal obtained to obtain this frequency sweep phase spectrum according to DFT algorithm;

Step 3, the phase spectrum utilizing described step 2 to obtain upgrades system phase spectrum;

Step 4, is positioned over LC resonant transducer to be detected in the read coil in differential driving symmetric detection circuit, and repeating said steps 1-2;

Step 5, the system phase that the phase spectrum utilizing described step 4 to obtain and described step 3 obtain is composed and is carried out phase spectrum calibration, and the phase spectrum that described calibration adopts described step 4 to obtain and the system phase that described step 3 obtains compose the mode of carrying out subtracting each other;

Step 6, the phase spectrum after calibrating for described step 5 carries out filtering, to eliminate the impact of high frequency noise, in an embodiment of the present invention, adopts Finite Impulse Response filter to carry out filtering;

Step 7, based on filtered phase spectrum, adopt peak detection algorithm to obtain the harmonic peak frequency of described LC resonant transducer, namely the position of the harmonic peak of described LC resonant transducer is the position of maximal value in filtered phase spectrum.

Described step 1-3 belongs to system calibration part, described step 4-7 belongs to sensor measurement part, the object of system calibration obtains the phase spectrum without system during sensor itself, when measuring sensor, the phase spectrum that described information getting method obtains at every turn all uses the phase spectrum of system itself to calibrate, phase spectrum after calibration adopts Finite Impulse Response filter to eliminate high frequency noise, adopt peak detection algorithm to find out the harmonic peak frequency of LC resonant transducer, thus realize the function reading heat transfer agent.

Information getting method and the testing circuit of above-mentioned a kind of wireless and passive LC resonant transducer disclosed in this invention have the following advantages:

The symmetrical Sampling network of a, differential driving has the function of the phase place change of amplifying read coil impedance, effectively improves the sensitivity of detection.

The calibration of b, system phase spectrum eliminates the impact of system and the phase spectrum of read coil own.

C, the noise had in limit for length's unit impulse response (FIR) digital filter elimination phase spectrum, improve the stability of detection.

The embedded system that d, DSP and FPGA realize improves the portability of system.

Fig. 5 is for same wireless and passive stomach pressure sensor, phase spectrum curve after the calibration adopting AgilentE5061B network analyzer and described information getting method and testing circuit to record respectively, and phase spectrum curve after FIR filtering.Very clearly can find out by figure, adopt described information getting method and testing circuit to significantly improve detection sensitivity, the noise in phase spectrum can be significantly reduced, improve the combination property detected.

Above-described specific embodiment; object of the present invention, technical scheme and beneficial effect are further described; be understood that; the foregoing is only specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any amendment made, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.

Claims (9)

1. an information detection for wireless and passive LC resonant transducer, is characterized in that, this circuit comprises: master controller, Direct Digital Frequency Synthesizers DDS, high-speed AD converter ADC and differential driving symmetric detection circuit, wherein:

Described DDS is connected with described master controller and differential driving symmetric detection circuit, control signal for receiving described master controller also produces the swept-frequency signal determined by described control signal, and the swept-frequency signal that described DDS produces exports described differential driving symmetric detection circuit to;

Described differential driving symmetric detection circuit is connected with described DDS and ADC, for receiving the swept-frequency signal that described DDS exports, to extract and the phase place of amplifying its read coil impedance changes, and phase place is changed feedback signal and export described ADC to;

Described ADC is connected with described differential driving symmetric detection circuit and described master controller, phase place change feedback signal for exporting for described differential driving symmetric detection circuit carries out analog-to-digital conversion process, and exports the phase place obtained after process change feedback signal to described master controller;

Described master controller is connected with described DDS, high-speed AD converter ADC, for carrying out the harmonic peak frequency controlling also to process to determine current LC resonant transducer to the received signal to described DDS and ADC;

Described differential driving symmetric detection circuit comprises with reference to inductance L _ref, read coil L _read, the first circuit for amplifying differential signal A1, the second circuit for amplifying differential signal A2, output signal amplification circuit A3, wherein:

The input end of described first circuit for amplifying differential signal A1, the second circuit for amplifying differential signal A2 connects the two-way swept-frequency signal A (W) ,-A (W) that are exported by described DDS respectively, and its output terminal connects described with reference to inductance L respectively _ref, read coil L _readone end;

Described with reference to inductance L _ref, read coil L _readthe other end be interconnected, tie point is as the input end of described output signal amplification circuit A3, and the output terminal of described output signal amplification circuit A3 is connected to the input end of described ADC, is sent to described ADC will output signal B (W).

2. circuit according to claim 1, is characterized in that, described swept-frequency signal is two paths of differential signals.

3. circuit according to claim 1, is characterized in that, described differential driving symmetric detection circuit adopts the symmetrical Sampling network topological structure of differential driving.

4. circuit according to claim 1, is characterized in that, described master controller comprises digital signal processor DSP and on-site programmable device FPGA, wherein:

Described FPGA is controlled described DDS and ADC respectively by control signal, to realize the synchronized sampling of swept-frequency signal and phase place change feedback signal;

Described DSP determines the harmonic peak frequency of current LC resonant transducer based on the phase place change feedback signal that described ADC exports.

5. circuit according to claim 4, it is characterized in that, when described DSP determines the harmonic peak frequency of current LC resonant transducer, the phase place first exported based on described ADC changes feedback signal calculates described differential driving symmetric detection circuit phase spectrum by DFT algorithm; Then by the phase spectrum calculated and the calibration realizing phase spectrum without system phase spectrum subtraction during LC resonant transducer; Then the phase spectrum convolution after adopting the Serial No. of FIR filter design and calibrating completes digital filtering; Value in filtered phase spectrum is searched to determine the harmonic peak frequency of current LC resonant transducer finally by peak detection algorithm.

6. circuit according to claim 1, is characterized in that, also comprises display, and described display is connected with described master controller, for receiving the control signal of described master controller to show related data.

7. circuit according to claim 6, is characterized in that, described data comprise the running status of described master controller, the resonance frequency of current LC resonant transducer and the resonance frequency change curve of LC resonant transducer.

8. an information getting method for wireless and passive LC resonant transducer, is characterized in that, the method comprises:

Step 1, main controller controls Direct Digital Frequency Synthesizers DDS completes a frequency sweep and exports, differential driving symmetric detection circuit is extracted and is amplified the phase place change of its read coil impedance, described main controller controls high-speed AD converter ADC to the sampling of phase place change feedback signal, and reads the phase place change feedback signal through ADC process;

Step 2, the DSP in master controller processes according to described step 1 the phase place change feedback signal obtained to obtain this frequency sweep phase spectrum according to DFT algorithm;

Step 3, the phase spectrum utilizing described step 2 to obtain upgrades system phase spectrum;

Step 4, is positioned over LC resonant transducer to be detected in the read coil in differential driving symmetric detection circuit, and repeating said steps 1-2;

Step 5, the system phase that the phase spectrum utilizing described step 4 to obtain and described step 3 obtain is composed and is carried out phase spectrum calibration;

Step 6, the phase spectrum after calibrating for described step 5 carries out filtering;

Step 7, based on filtered phase spectrum, adopts peak detection algorithm to obtain the harmonic peak frequency of described LC resonant transducer.

9. method according to claim 8, is characterized in that, the phase spectrum that the phase spectrum calibration in described step 5 adopts described step 4 to obtain and the system phase that described step 3 obtains compose the mode of carrying out subtracting each other.