阅读说明：本技术 一种基于负阻电路的无源无线lc中性传感器 (Passive wireless LC neutral sensor based on negative resistance circuit ) 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负阻电路的无源无线LC中性传感器,属于测量、测试的技术领域。该无源无线LC中性传感器包括读出系统和传感器节点；所述读出系统由读出电路和一个读出线圈串联而成；所述传感器节点由敏感电容、初级电感线圈和负阻电路串联而成；所述负阻电路由运算放大器构成的负电阻和无线供电模块所构成；所述无线供电模块由电感线圈、可选变频电容、整流电路、滤波电路和稳压电路构成,作用是给运算放大器无线供电；所述读出系统与传感器节点通过电感耦合进行信号传输,从而检测被测参数。本发明结构简单,能有效降低寄生电阻的能量损耗,提高系统的工作效率。(The invention provides a passive wireless LC neutral sensor based on a negative resistance circuit, and belongs to the technical field of measurement and testing. The passive wireless LC neutral sensor comprises a reading system and a sensor node; the reading system is formed by connecting a reading circuit and a reading coil in series; the sensor node is formed by connecting a sensitive capacitor, a primary inductance coil and a negative resistance circuit in series; the negative resistance circuit consists of a negative resistance formed by an operational amplifier and a wireless power supply module; the wireless power supply module consists of an inductance coil, a selectable variable frequency capacitor, a rectifying circuit, a filter circuit and a voltage stabilizing circuit and is used for wirelessly supplying power to the operational amplifier; and the reading system and the sensor node carry out signal transmission through inductive coupling so as to detect the measured parameter. The invention has simple structure, can effectively reduce the energy loss of the parasitic resistance and improve the working efficiency of the system.)

1. A passive wireless LC neutral sensor based on a negative resistance circuit is characterized by comprising a reading system (1) and a sensor node (2), wherein the reading system (1) and the sensor node (2) are in energy coupling and signal transmission through inductive coupling;

the sensor node (2) is formed by connecting a negative resistance circuit (3), a primary inductance coil (21) and a sensitive capacitor (22) in series;

the inductance coil (21) is formed by connecting an equivalent inductance and a coil parasitic resistance (23) in series;

the value of the sensitive capacitor (22) changes along with the change of the measured parameter, so that the resonant frequency of the sensor node (2) changes, and a frequency signal is transmitted to the reading circuit (11) through inductive coupling, so that the value of the measured parameter is read.

2. The passive wireless LC neutral sensor based on a negative resistance circuit according to claim 1, characterized in that the readout system (1) is composed of a readout circuit (11) and a readout coil (12);

the sensing circuit (11) sends out a frequency sweeping electromagnetic excitation signal, so that on one hand, the resonant frequency of the sensor node is detected, and on the other hand, the circuit of the sensor node (2) is provided with energy in a wireless charging mode.

3. The passive wireless LC neutral sensor based on the negative resistance circuit is characterized in that the negative resistance circuit (3) is composed of a negative resistance and a wireless power supply module, and the negative resistance is powered by the wireless power supply module.

4. The passive wireless LC neutral sensor based on the negative resistance circuit is characterized in that the wireless power supply module comprises a secondary inductance coil (31), a selectable variable frequency capacitor (32), a rectifying circuit (33), a filter circuit (34) and a voltage stabilizing circuit (35).

5. The passive wireless LC neutral sensor based on negative resistance circuit of claim 4, characterized in that said negative resistance is composed of an operational amplifier (36), a first resistor (37), a second resistor (38), a third resistor (39); the resistance value of the negative resistance circuit (3) isWherein R is₁Is a first resistor (37), R₂Is a second resistor (38), R₃Is a third resistor (39).

6. The passive wireless LC neutral sensor based on negative resistance circuit of claim 4, characterized in that said negative resistance is a negative resistance (4) of cross-coupled MOS tubes.

7. The passive wireless LC neutral sensor based on the negative resistance circuit is characterized in that the negative resistance (4) formed by the cross-coupled MOS tubes comprises a first NMOS tube (41), a second NMOS tube (42) and a constant current source (43).

Technical Field

The invention belongs to the field of LC (inductance-capacitance) sensors, and particularly relates to a passive wireless LC neutral sensor based on a negative resistance circuit.

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 LC sensor is usually 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 LC passive wireless sensor does not need power supply or electrical connection, and has small volume, low power consumption and low cost, so that the LC passive wireless sensor has incomparable advantages in certain special application environments, such as closed environments, mechanical rotating structures and the like.

Due to parasitic effect, parasitic resistance in the LC sensor causes the LC sensor to be in a loss state, the strength of a detection signal is influenced, and the distance and the accuracy of wireless detection are limited.

Disclosure of Invention

The invention aims to provide a passive wireless LC neutral sensor based on a negative resistance circuit, and aims to solve the technical problems of large energy loss, low transmission efficiency and short wireless measurement distance of the traditional passive wireless LC sensor.

In order to solve the technical problems, the specific technical scheme of the invention is as follows:

a passive wireless LC neutral sensor based on a negative resistance circuit comprises a reading system and a sensor node, wherein the reading system and the sensor node are in energy coupling and signal transmission through inductive coupling;

the sensor node is formed by connecting a negative resistance circuit, a primary inductance coil and a sensitive capacitor in series;

the inductance coil is formed by connecting an equivalent inductance and a coil parasitic resistance in series;

the sensitive capacitance value changes along with the change of the measured parameter, so that the resonant frequency of the sensor node changes, and the frequency signal is transmitted to the reading circuit through inductive coupling, so that the value of the measured parameter is read.

Further, the readout system is composed of a readout circuit and a readout coil;

the sensing circuit sends out a frequency sweeping electromagnetic excitation signal, so that on one hand, the resonant frequency of the sensor node is detected, and on the other hand, the sensor node circuit is provided with energy in a wireless charging mode.

Furthermore, the negative resistance circuit is composed of a negative resistance and a wireless power supply module, and the negative resistance is powered by the wireless power supply module.

Furthermore, the wireless power supply module comprises a secondary inductance coil, a selectable variable frequency capacitor, a rectification circuit, a filter circuit and a voltage stabilizing circuit.

Further, the negative resistance is composed of an operational amplifier, a first resistor, a second resistor and a third resistor; the negative resistance circuit has a resistance value ofWherein R is₁Is a first resistance, R₂Is a second resistance, R₃Is a third resistor.

Further, the negative resistance is formed by cross-coupled MOS tubes.

Furthermore, the negative resistance formed by the cross-coupled MOS tube comprises a first NOMS tube, a second NMOS tube and a constant current source.

The passive wireless LC neutral sensor based on the negative resistance circuit has the following advantages:

(1) according to the passive wireless LC neutral sensor based on the negative resistance circuit, the negative resistance circuit is added on the basis of the traditional LC passive wireless sensor, so that the loss of parasitic resistance to circuit energy is reduced, and the working efficiency of the sensor is improved.

(2) The negative resistance circuit is applied to the sensor node and is charged in a wireless coupling mode, so that inconvenience caused by battery replacement is avoided.

Drawings

Fig. 1 is an equivalent circuit diagram of a passive wireless LC neutral sensor based on a negative resistance circuit of the present invention;

FIG. 2 is an equivalent circuit diagram of the negative resistance circuit in the LC neutral sensor of the present invention;

FIG. 3 is a circuit diagram of another implementation of the negative resistance circuit of the present invention using cross-coupled mos transistors;

the notation in the figure is: 1. a readout system; 2. a sensor node; 3. a negative resistance circuit; 4. a negative resistance formed by cross-coupled MOS tubes; 11. a readout circuit; 12. a readout coil; 21. a primary inductor coil; 22. a sensitive capacitance; 23. a parasitic resistance; 3. a negative resistance circuit; 31. a secondary inductor coil; 32. a variable frequency capacitor is selectable; 33. a rectifying circuit; 34. a filter circuit; 35. a voltage stabilizing circuit; 36. an operational amplifier; 37. a first resistor; 38. a second resistor; 39. a third resistor; 41. a first NOMS tube; 42. a second NMOS transistor; 43. and a constant current source.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, a passive wireless LC neutral sensor based on a negative resistance circuit of the present invention is described in further detail below with reference to the accompanying drawings.

As shown in fig. 1 and fig. 2, the passive wireless LC neutral sensor based on the negative resistance circuit disclosed by the invention comprises a readout system 1, a sensor node 2 and a negative resistance circuit 3; the readout system 1 is formed by serially connecting a readout circuit 11 and a readout coil 12; the sensor node 2 is formed by connecting a primary inductance coil 21, a sensitive capacitor 22 and a negative resistance circuit 3 in series, wherein the primary inductance coil 21 is formed by connecting an equivalent inductance and a parasitic resistance 23 of the coil in series.

The negative resistance circuit 3 is composed of a negative resistance and a wireless power supply module. The negative resistance is powered by the wireless power supply module.

The wireless power supply module comprises a secondary inductance coil 31, a selectable variable frequency capacitor 32, a rectifying circuit 33, a filter circuit 34 and a voltage stabilizing circuit 35.

The first embodiment of the negative resistor is composed of an operational amplifier 36, a first resistor 37, a second resistor 38, and a third resistor 39.

As shown in fig. 1, the sensing circuit 11 emits a sinusoidal ac signal at a frequency that couples the excitation signal to the sensor node 2 through mutual inductance coupling of the sensing coil 12 to the primary inductor 21 of the sensor node 2. Meanwhile, a coupling voltage is generated through mutual inductance coupling of the sensing coil 12 and the secondary inductance coil 31, a constant voltage is output through the rectifying circuit 33, the filter circuit 34 and the voltage stabilizing circuit 35, a power supply is provided for the operational amplifier 36, the operational amplifier 36 normally works in a linear region, and the whole circuit externally has a negative resistance characteristic, so that energy loss caused by a parasitic resistor 23 in the sensor node 2 is reduced.

When the measured parameter changes, the capacitance value of the sensitive capacitor 22 changes, so that the resonant frequency of the sensor node 2 changes, and the readout circuit 11 measures the resonant frequency through inductive coupling, so as to measure the measured parameter.

The sensing coil 12 and the secondary inductor 31 may form a transformer circuit, and the coupling coefficient between the two inductors is k. In order to increase the coupling efficiency, a variable frequency-selecting capacitor 32 is connected in parallel with the secondary inductor 31 to form a resonant circuit. According to the coupling theory, the voltage coupled to the secondary inductor 31 can be written as:

whereinFor inductance coil mutual inductance, L₁For reading out the coils 12, L₃Is the secondary inductance coil 31; z₁＝iωL₁，Z₂＝iωL₃+1/iωC₂Equivalent impedance of the two-stage coupling coil; c₂Is a variable frequency-selective capacitor 32. ω is the coupling frequency whenThe coupling voltage reaches an optimum value. The coupling voltage may be supplied to the operational amplifier 36 after passing through a rectifying, voltage-stabilizing filter circuit.

The negative resistance circuit 3 including the operational amplifier 36 has a resistance value ofWherein R is₁Is a first resistor 37, R₂Is a second resistor 38, R₃As the third resistor 39, the resistance values of R1, R2, and R3 are adjusted so that the negative resistance value is equal to the parasitic resistance 23 of the inductor.

The working principle is as follows:

(1) when the measured parameter changes, the sensitive capacitor 22 of the sensor node 2 changes along with the change of the measured parameter, so that the resonant frequency of the LC resonant circuit changes;

(2) the reading circuit 11 outputs a sine excitation current signal to the reading coil 12, forms a coupling voltage at two ends of the secondary inductance coil 31 through inductive coupling, and provides a voltage for the operational amplifier 36 through the rectification voltage-stabilizing filter circuit, so that the operational amplifier 36 normally works in a linear region, and the whole circuit presents a negative resistance characteristic; the negative resistance is made equal to the parasitic resistance 23 of the inductance coil by adjusting the resistance values of R1, R2, and R3;

(3) coupling the excitation signal to the sensor node 2 by mutual inductance coupling of the sense coil 12 to the inductor coil in the sensor node 2;

(4) the specific value of the measured parameter can be calculated by analyzing the input impedance of the readout coil 12 or analyzing the input return loss thereof to measure the resonant frequency of the LC sensor.

As shown in fig. 3, the second embodiment of the negative resistance of the present invention is composed of a first NOMS tube 41, a second NOMS tube 42, and a constant current source 43.

After the secondary inductance coil 31 obtains energy through inductive coupling, stable voltage is provided for the circuit through the selectable variable frequency capacitor 32, the rectifying circuit 33, the filter circuit 34 and the voltage stabilizing circuit 35, so that the first NOMS tube 41 and the second NOMS tube 42 work in a nonlinear region, the circuit has a negative resistance characteristic to the outside, and the negative resistance of the circuit can be calculated to be the negative resistance according to a small signal model of the circuitWherein g is_mIs the ratio of current to voltage in the circuit. In this case, a part of the parasitic resistance loss to energy can be offset.

It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.