阅读说明：本技术 一种基于pt对称的lc无源无线双参数传感系统 (PT symmetry-based LC passive wireless dual-parameter sensing system ) 是由 董蕾 戴鹏 王立峰 于 2021-09-03 设计创作，主要内容包括：本发明提供一种基于PT对称的LC无源无线双参数传感装置,该传感装置包括：LC双参数传感器(2)与读出电路(1)两部分,其中LC双参数传感器(2)与读出电路(1)通过电感耦合进行能量耦合和信号传输；控制电路(3)控制读出电路(1)。所述控制电路中单片机能够检测电压幅度和频率是否满足PT对称状态,即电压幅度是否达到最大,频率是否出现分频现象,并通过步进调节可调电容,直到系统达到PT对称状态,再通过检测系统频率值和负电阻值来检测被测参数。本发明结构简单,能检测双参数,从而节省空间,降低成本。(The invention provides a PT symmetry-based LC passive wireless dual-parameter sensing device, which comprises: the device comprises an LC double-parameter sensor (2) and a reading circuit (1), wherein the LC double-parameter sensor (2) and the reading circuit (1) are in energy coupling and signal transmission through inductive coupling; a control circuit (3) controls the readout circuit (1). The single chip microcomputer in the control circuit can detect whether the voltage amplitude and the frequency meet the PT symmetrical state, namely whether the voltage amplitude reaches the maximum or not and whether the frequency division phenomenon occurs or not, and the adjustable capacitor is adjusted in a stepping mode until the system reaches the PT symmetrical state, and then the detected parameters are detected by detecting the system frequency value and the negative resistance value. The invention has simple structure and can detect double parameters, thereby saving space and reducing cost.)

1. A PT symmetry-based LC passive wireless dual-parameter sensing device is characterized by comprising: the device comprises an LC double-parameter sensor (2) and a reading circuit (1), wherein the LC double-parameter sensor (2) and the reading circuit (1) are in energy coupling and signal transmission through inductive coupling; a control circuit (3) controls the readout circuit (1).

2. The PT-symmetry-based LC passive wireless dual-parameter sensing device according to claim 1, wherein the readout circuit (1) is formed by connecting a signal analyzer (11), an adjustable capacitor (12), an inductance coil secondary (13), a negative resistance circuit (4) and a control circuit (3) in parallel.

3. The PT-symmetry-based LC passive wireless dual-parameter sensing device according to claim 1, wherein the LC dual-parameter sensor (2) is formed by connecting an inductance coil source side (21), a sensitive capacitor (22) and a sensitive resistor (23) in parallel; the sensitive capacitance value changes with the change of one measured parameter in the double-parameter sensing device, and the sensitive resistance value changes with the change of the other measured parameter in the double-parameter sensing device; the measured parameter varies according to the types of the sensitive capacitor and the sensitive resistor.

4. The PT-symmetry-based LC passive wireless dual-parameter sensing device according to claim 1, wherein the control circuit (3) is composed of an operational amplifier (31), an envelope detection circuit (32), a frequency division circuit (33) and a single-chip MCU (34); the two input ends of the operational amplifier (31) are respectively connected with the two ends of the reading circuit (1), the output end of the operational amplifier (31) is respectively connected with the input ends of the envelope detection circuit (32) and the frequency dividing circuit (33), the output ends of the envelope detection circuit (32) and the frequency dividing circuit (33) are respectively connected with the input end of the single-chip microcomputer MCU (34), and the output end of the single-chip microcomputer MCU (34) is connected with the control end of the adjustable capacitor (12).

5. The PT-symmetry-based LC passive wireless dual-parameter sensing device of claim 2, wherein the negative resistance circuit (4) is formed by cross-coupling emitters of a first NMOS tube (41) and a second NMOS tube (42) and connecting a constant current source (43) in series.

6. The PT symmetry based LC passive wireless dual-parameter sensing device according to claim 4, wherein the MCU (34) detects whether the voltage amplitude and frequency satisfy PT symmetry conditions through an envelope detection circuit (32) and a frequency division circuit (33), and makes the system satisfy the PT symmetry conditions by adjusting the adjustable capacitor (12) in a stepping manner.

7. The dual-parameter detection method of the PT-symmetry-based LC passive wireless dual-parameter sensing device according to claim 1, characterized in that by the PT-symmetry principle, when the dual-parameter sensing device works in a PT-symmetry region, the magnitudes of the sensitive resistor and the sensitive capacitor in the dual-parameter sensing device can be calculated by only measuring and reading the impedance value and the frequency value of the dual-parameter sensing device, and then the magnitudes of the two measured parameters are calculated, thereby realizing dual-parameter detection.

8. The dual-parameter detection method of the PT-symmetry-based LC passive wireless dual-parameter sensing device according to claim 7, wherein the specific detection method is as follows:

step 1, when two measured parameters change, a sensitive capacitor and a sensitive resistor of a sensing device change along with the change of the measured parameters, so that the resonance frequency of an LC resonance circuit changes;

step 2, the reading circuit performs signal transmission through inductive coupling of the reading coil and the sensor coil;

and 3, after the control circuit buffers and converts the single end of the signal, envelope detection and frequency division are respectively carried out, so that voltage amplitude measurement and frequency measurement are realized. Detecting whether the voltage amplitude and the frequency meet the PT symmetrical state or not through the single chip microcomputer, namely whether the voltage amplitude reaches the maximum or not and whether the frequency has a frequency division phenomenon or not; if not, the capacitance value is adjusted in a stepping mode until the system reaches a PT symmetrical state;

step 4, measuring two frequencies of the double-parameter sensing device to obtain the change condition of the sensitive capacitor, thereby obtaining the parameter to be measured related to the sensitive capacitor;

and 5, when the double-parameter sensing device PT is symmetrical, automatically matching the negative resistance working in the nonlinear region with the sensitive resistance of the sensing device, and measuring the size of the nonlinear resistance to obtain the parameter to be measured related to the sensitive resistance.

Technical Field

The invention relates to an LC (inductance-capacitance) passive wireless dual-parameter sensing system based on PT (space inversion transformation-time inversion transformation) symmetry, belonging to the technical field of measurement and testing.

Background

LC passive wireless sensors have been widely used in various applications, such as the detection of pressure, temperature, humidity, rotational speed, gases, etc., since they were first proposed in 1967. The traditional LC sensor is generally formed by connecting a sensitive capacitor and a spiral inductor in series, and the working principle is simple: the sensing capacitance of the LC sensor changes along with the change of the measured parameter, so that the resonant frequency of the LC resonant circuit changes, a reading coil is arranged on the outer side of the sensor, the reading coil is coupled with the inductance of the sensor, the resonant frequency of the LC sensor is measured by analyzing the input impedance of the reading coil or analyzing the input return loss of the reading coil, and the specific numerical value of the measured parameter can be calculated.

The traditional quantum mechanics theory considers that the condition of a certain quantum system having a real solution (observable solution) is that the Hamiltonian H of the system must have Hermitian property. The bender c.m. teaching of washington university, usa, proposed in 1998 a PT symmetric hamilton that does not have hermitian but has a real solution as well. The existing LC system based on PT symmetry theory focuses on the aspects of improving the sensing distance of the sensor, the strength of detected signals, the sensitivity of the sensor and the like; while LC multi-parameter sensors based on PT symmetry have not been reported.

In the existing multi-parameter monitoring scheme, detected signals (frequency and real impedance part values) are influenced by coupling distances, different detection distances generate inconsistent frequency values and real impedance part values, and problems are brought to accurate detection in practical application.

In addition, the parameters of the sensitive elements of the LC sensor change along with the change of the environment to be measured during operation, so that the corresponding elements of the readout circuit also change in real time to maintain PT symmetry. When multiple sensitive parameters are involved in simultaneous changes, a simplified automatic matching system is needed to complete real-time PT symmetric matching of the LC sensing system.

Disclosure of Invention

The technical problem is as follows: the invention aims to overcome the defects of the prior art and provides a PT-symmetry-based LC passive wireless dual-parameter sensing system, which realizes LC dual-parameter measurement by utilizing a PT symmetry principle, realizes automatic real-time PT symmetric matching of dual-parameter detection, improves the reading distance and sensitivity of LC dual-parameter measurement, and solves the problems of single measurement parameter, complex reading system and signal detection distance change of the traditional passive wireless LC sensor.

The technical scheme is as follows: the invention discloses a PT symmetry-based LC passive wireless dual-parameter sensing device, which adopts the following structure:

the sensing device includes: the device comprises an LC double-parameter sensor and a reading circuit, wherein the LC double-parameter sensor and the reading circuit are coupled through inductance to perform energy coupling and signal transmission; the control circuit controls the readout circuit.

The reading circuit is formed by connecting a signal analyzer, an adjustable capacitor, an inductance coil pair, a negative resistance circuit and a control circuit in parallel.

The LC double-parameter sensor is formed by connecting an inductance coil source side, a sensitive capacitor and a sensitive resistor in parallel; the sensitive capacitance value changes with the change of one measured parameter in the double-parameter sensing device, and the sensitive resistance value changes with the change of the other measured parameter in the double-parameter sensing device; the measured parameter varies according to the types of the sensitive capacitor and the sensitive resistor.

The control circuit consists of an operational amplifier, an envelope detection circuit, a frequency division circuit and a single chip Microcomputer (MCU); the two input ends of the operational amplifier are respectively connected with the two ends of the reading circuit, the output end of the operational amplifier is respectively connected with the input ends of the envelope detection circuit and the frequency dividing circuit, the output ends of the envelope detection circuit and the frequency dividing circuit are respectively connected with the input end of the single-chip microcomputer MCU, and the output end of the single-chip microcomputer MCU is connected with the control end of the adjustable capacitor.

The negative resistance circuit is formed by connecting emitters of a first NMOS tube and a second NMOS tube which are cross-coupled in series with a constant current source.

The MCU detects whether the voltage amplitude and the frequency meet PT symmetrical conditions or not through the envelope detection circuit and the frequency division circuit, and enables the system to meet the PT symmetrical conditions through step-by-step adjustment of the adjustable capacitor.

According to the double-parameter detection method of the PT-symmetry-based LC passive wireless double-parameter sensing device, by virtue of the PT symmetry principle, when the double-parameter sensing device works in a PT symmetric region, the sizes of a sensitive resistor and a sensitive capacitor in the double-parameter sensing device can be calculated by only measuring and reading the impedance value and the frequency value of the double-parameter sensing device, and then the sizes of two measured parameters are calculated, so that double-parameter detection is realized.

The specific detection method comprises the following steps:

step 1, when two measured parameters change, a sensitive capacitor and a sensitive resistor of a sensing device change along with the change of the measured parameters, so that the resonance frequency of an LC resonance circuit changes;

step 2, the reading circuit performs signal transmission through inductive coupling of the reading coil and the sensor coil;

and 3, after the control circuit buffers and converts the single end of the signal, envelope detection and frequency division are respectively carried out, so that voltage amplitude measurement and frequency measurement are realized. Detecting whether the voltage amplitude and the frequency meet the PT symmetrical state or not through the single chip microcomputer, namely whether the voltage amplitude reaches the maximum or not and whether the frequency has a frequency division phenomenon or not; if not, the capacitance value is adjusted in a stepping mode until the system reaches a PT symmetrical state;

step 4, measuring two frequencies of the double-parameter sensing device to obtain the change condition of the sensitive capacitor, thereby obtaining the parameter to be measured related to the sensitive capacitor;

and 5, when the double-parameter sensing device PT is symmetrical, automatically matching the negative resistance working in the nonlinear region with the sensitive resistance of the sensing device, and measuring the size of the nonlinear resistance to obtain the parameter to be measured related to the sensitive resistance.

Has the advantages that: by adopting the technical scheme, the invention has the following advantages:

(1) the PT symmetry-based LC passive wireless dual-parameter sensing system provided by the invention is additionally provided with dual-parameter measurement on the basis of the traditional LC passive wireless sensor.

(2) The PT symmetry principle is utilized to simplify a reading system, realize real-time measurement and improve the measurement precision.

(3) The negative resistance formed by the cross-coupled MOS tube can realize automatic matching PT symmetry, so that the real part value of the impedance is irrelevant to the coupling coefficient k, and the accurate measurement of the parameter to be measured is realized.

(4) Whether the system meets the PT symmetrical state or not is judged by detecting the voltage amplitude and the frequency, and the adjustable capacitor is adjusted by stepping of the single chip microcomputer, so that the system works in the PT symmetrical area.

(5) The monitoring mode that the reading circuit is in zero contact with the object to be detected can be realized by utilizing a passive wireless technology, and inconvenience caused by wired connection of lead wires and the like is avoided.

Drawings

FIG. 1 is an equivalent circuit diagram of a PT-symmetry-based LC passive wireless dual-parameter sensing system of the present invention.

Fig. 2 is an equivalent circuit diagram of a negative resistance circuit in the readout circuit shown in fig. 1.

The figure shows that:

the device comprises a reading system 1, a signal analyzer 11, an adjustable capacitor 12 and an inductance coil secondary side 13;

the sensor comprises an LC double-parameter sensor 2, an inductance coil source 21, a sensitive capacitor 22 and a sensitive resistor 23;

the control circuit 3, the operational amplifier 31, the envelope detection circuit 32, the frequency division circuit 33, and the MCU 34;

the negative resistance circuit 4, the first NMOS transistor 41, the second NMOS transistor 42, and the constant current source 43.

Detailed Description

The technical scheme of the invention is explained in detail in the following with reference to the attached drawings.

As shown in fig. 1 and fig. 2, the LC sensor based on the negative resistance circuit disclosed by the present invention includes a readout system 1, an LC dual-parameter sensor 2, a control circuit 3 and a negative resistance circuit 4; the reading system 1 is formed by connecting a signal analyzer 11, a negative resistance circuit 4, a control circuit 3, an adjustable capacitor 12 and an inductance coil secondary side 13 in parallel; the LC double-parameter sensor 2 is formed by connecting an inductance coil source 21, a sensitive capacitor 22 and a sensitive resistor 23 in parallel; the control circuit consists of an operational amplifier 31, an envelope detection circuit 32, a frequency division circuit 33 and an MCU 34; the negative resistance circuit is formed by cross-coupling a first NMOS transistor 41 and a second NMOS transistor 42, and connecting a constant current source 43 in series.

And the signal transmission is carried out between the reading coil and the sensor coil through inductive coupling. The single chip microcomputer in the control circuit can detect whether the voltage amplitude and the frequency meet the PT symmetrical state (namely whether the voltage amplitude reaches the maximum or not, whether the frequency has a frequency division phenomenon or not and the like), and detect the detected parameters by regulating the adjustable capacitor in a stepping mode until the system reaches the PT symmetrical state and detecting and reading out the frequency value and the impedance value of the circuit.

To form a symmetric structure of PT, L is required to be satisfied_r＝L_s、C_r＝C_s、R_r＝-R_sWhile ensuring (1) ω_r＝ω_s；(2)g_r＝γ_s。

The Hamiltonian of the system can be written asSatisfy [ PT, H]The condition of 0, so the system is in PT symmetry.

Wherein L is_r、L_sInductance values of the coils in the readout circuit and the LC sensor, respectively; c_r、C_sCapacitance values of the readout circuit and the LC sensor, respectively; r_r、R_sImpedance values of the readout circuit and the LC sensor, respectively;is the resonant frequency of the LC sensor;the gain coefficient of the reading circuit and the loss coefficient of the LC sensor are respectively; k is the inductive coupling coefficient of the sense coil and the sensor coil. H is the Hamiltonian of the system.

The specific working process is as follows:

(1) when two measured parameters change, the sensitive capacitance and the sensitive resistance of the sensor change along with the change of the measured parameters, so that the resonant frequency of the LC resonant circuit changes;

(2) the reading circuit performs signal transmission through inductive coupling of the reading coil and the sensor coil;

(3) the control circuit carries out envelope detection and frequency division after buffering and single-ended conversion of the signal, and voltage amplitude measurement and frequency measurement are achieved. Detecting whether the voltage amplitude and the frequency meet the PT symmetrical state (namely whether the voltage amplitude reaches the maximum or not, whether the frequency has a frequency division phenomenon or not) through the single chip microcomputer, and if not, adjusting the capacitance value step by step until the system reaches the PT symmetrical state;

(4) measuring two frequencies of the system according to the formula

The change condition of the sensitive capacitor can be obtained, so that the to-be-measured parameter related to the sensitive capacitor can be measured;

(5) when the system PT is symmetrical, the negative resistance working in the nonlinear area is automatically matched with the sensitive resistance of the sensor, and the to-be-measured parameter related to the sensitive resistance is measured by measuring the size of the nonlinear resistance.

When the measured parameters are changed, the capacitance value of the sensitive capacitor 22 and the resistance value of the sensitive resistor 23 are changed, so that the resonant frequency of the LC dual-parameter sensor is changed, the readout system 1 performs signal transmission through mutual inductance coupling between the inductance coil secondary side 13 and the inductance coil source side 21, and the signals are processed by the operational amplifier 31 and then respectively pass through the envelope detection circuit 32 and the frequency division circuit 33, so that voltage amplitude measurement and frequency measurement are realized. Whether the voltage amplitude and the frequency meet the PT symmetrical state (namely whether the voltage amplitude reaches the maximum or not, whether the frequency division phenomenon occurs or not and the like) is detected through the MCU34, and if not, the capacitance value of the adjustable capacitor 12 is adjusted in a stepping mode until the system reaches the PT symmetrical state.

The signal analyzer 11 measures the maximum and minimum frequencies of the system, so that the change condition of the sensitive capacitor 22 can be obtained, and the to-be-measured parameters related to the sensitive capacitor can be measured;

the negative resistance circuit 4 working in the nonlinear region is automatically matched with the sensor sensitive resistor 23, and the resistance value R of the real part of the circuit impedance is measured by a signal analyzer_realDue to the size of R_real＝R_SThereby measuring the parameter to be measured related to the sensitive resistor 23.

The measured parameter can vary according to the type of the sensitive capacitor and the sensitive resistor. For example, humidity is measured with a sensitive capacitor and temperature is measured with a sensitive resistor.