CN218120997U

CN218120997U - Readout circuit of LC wireless passive sensor

Info

Publication number: CN218120997U
Application number: CN202222346271.5U
Authority: CN
Inventors: 张文斌; 缪谨柒; 丁镓骏; 赵子瑞; 耿圆; 徐欣筑; 张彬辉; 姚飞; 黄俊晟; 赵辉东; 王世杰
Original assignee: China Jiliang University
Current assignee: China Jiliang University
Priority date: 2022-09-05
Filing date: 2022-09-05
Publication date: 2022-12-23
Anticipated expiration: 2032-09-05

Abstract

The utility model discloses a readout circuit of wireless passive sensor of LC, this readout circuit include single chip microcomputer control module, DDS sweep frequency signal generation module, L type matching circuit module, buffering amplifier module, button module and display module. The L-shaped matching circuit module is composed of a variable resistor, a variable inductor, a frequency-selecting capacitor, a variable capacitance diode, a first decoupling capacitor, a second decoupling capacitor and a reading coil. The reading coil and the LC wireless passive sensor perform strong coupling magnetic resonance, so that the signal strength is improved. The utility model discloses a reading circuit simple structure easily realizes, can carry out wireless measurement to the resonant frequency of the wireless passive sensor of LC, can improve the several times that does not have the matching with reading the distance to can restrain the noise.

Description

Readout circuit of LC wireless passive sensor

The technical field is as follows:

the utility model belongs to the technical field of the sensor, a readout circuit of wireless passive sensor of LC is related to.

Background art:

the measurement parameters of the sensor need to be obtained through a wireless reading mode, so that the selection of a reading method and the design of a reading circuit are crucial to the measurement performance of the sensing system. The design of the readout circuit is to detect the sensor changes accurately, sensitively and quickly, so there are certain requirements on the readout accuracy, sensitivity, resolution and detection time, where accuracy is a primary issue. In the actual reading process, the reading position between the reading coil and the sensor has an influence on most signals measured by the reading circuit, so that the reading detection method and the circuit design need to be optimized, and the influence of the reading position on the reading signals needs to be reduced as much as possible.

The reading distance of the LC passive wireless sensing is shorter than that of the RFID passive sensing because the reading distance is limited by the nature of inductive near-field coupling, but the definition of the near field is lambda/2 pi, while the reading distance of a general LC passive wireless sensing system can only be in the diameter range of an inductive coil and far cannot reach the range defined by the near field, which indicates that the near-field coupling has a large distance which can be expanded. The improvement of the LC passive wireless sensing reading distance is characterized in that on one hand, the LC wireless passive sensor is designed, and the larger the quality factor of the LC wireless passive sensor is, the better the reading performance is; another aspect is the optimization of the readout circuitry. When the LC wireless passive sensor is applied to the environment with limited size and loss, the improvement of the quality factor of the sensor is very limited, the circuit size of a reading circuit is not limited, and more design space can be provided for improving the reading performance of the sensor.

The utility model has the following contents:

the utility model aims to solve the technical problem that: aiming at an LC wireless passive sensor, a reading circuit is provided, and the effect of reading signal enhancement or reading distance enhancement is realized.

The utility model provides a readout circuit of wireless passive sensor of LC, this circuit include single chip microcomputer control module, DDS sweep frequency signal generation module, L type matching circuit module, buffering amplifier module, button module and display module. The DDS frequency sweeping signal generating module, the L-shaped matching circuit module, the buffering amplifying module, the key module and the display module are respectively connected with the single-chip microcomputer control module; and the L-shaped matching circuit module is connected with the buffer amplification module.

The L-shaped matching circuit module consists of a variable resistor, a variable inductor, a frequency-selecting capacitor, a variable capacitance diode, a first decoupling capacitor, a second decoupling capacitor and a reading coil; the reading coil and the LC wireless passive sensor perform strong coupling magnetic resonance, so that the signal strength is improved.

The first decoupling capacitor, the variable capacitance diode and the second decoupling capacitor are sequentially connected in series.

The frequency-selecting capacitor is connected in parallel with a series circuit formed by the first decoupling capacitor, the second decoupling capacitor and the variable capacitance diode.

The readout coil is connected in parallel with a series circuit formed by the first decoupling capacitor, the second decoupling capacitor and the varactor.

One end of the variable resistor is connected with the DDS frequency sweeping signal generating module, and the other end of the variable resistor is connected with the first decoupling capacitor in series.

One end of the variable inductor is connected with the buffer amplification module, and the other end of the variable inductor is connected with the frequency-selecting capacitor in series.

In order to realize that the inductance value is adjustable according to the required size, preferably, the variable inductor is adopted as a series inductor element in the L-shaped matching circuit.

In order to realize that the capacitance value can be adjusted according to the requirement, preferably, the varactor diode is adopted by the L-shaped matching circuit as a parallel capacitor for scanning change.

The readout circuit of the LC wireless passive sensor keeps the series inductance at an optimal value, and the capacitance of a variable capacitance diode in the readout circuit is controlled and scanned by direct-current voltage. When the varactor diode reaches the optimal matching, an S11 signal of the L-shaped matching circuit is obviously reduced, and the frequency corresponding to the reduced point is the resonance frequency of the LC wireless passive sensor. The L-shaped matching network only has a reactive element, and the reactive element is a lossless element and does not lose energy of the system. When the impedance matching condition is that the load impedance is equal to the internal impedance of the signal source, the energy can be transmitted without reflection, the S11 signal strength reaches the maximum, the reading of the resonant frequency of the LC wireless passive sensor is not influenced, and the reading distance of the LC wireless passive sensor is prolonged.

The LC wireless passive sensor reading circuit has the following advantages: (1) The circuit has simple structure, small volume and easy realization, and is suitable for field use; (2) The circuit readout distance is further compared with other readout circuits; (3) The circuit signal noise is significantly reduced compared to other readout circuits. Based on the advantages, the sensor can improve the distance to be several times of that without matching, and can suppress noise.

Description of the drawings:

fig. 1 is a circuit diagram of the readout circuit of the present invention.

Fig. 2 is a circuit diagram of the L-shaped matching circuit module in the readout circuit of the present invention.

The specific implementation mode is as follows:

to further explain the technical solutions adopted by the present invention to achieve the intended purpose of the invention, the following detailed description is made with reference to the accompanying drawings and preferred embodiments:

fig. 1 is a circuit diagram of a readout circuit according to the present invention. The utility model provides a readout circuit of wireless passive sensor of LC, this circuit include single chip microcomputer control module 1, DDS sweep frequency signal generation module 2, L type matching circuit module 3, buffering amplifier module 4, button module 5 and display module 6. The DDS frequency sweeping signal generation module 2, the L-shaped matching circuit module 3, the buffering amplification module 4, the key module 5 and the display module 6 are respectively connected with the single-chip microcomputer control module 1, and the L-shaped matching circuit module 3 is connected with the buffering amplification module 4.

Fig. 2 is a circuit diagram of the L-type matching circuit module 3 in the readout circuit of the present invention. The L-shaped matching circuit module 3 is composed of a variable resistor 33, a variable inductor 34, a frequency-selecting capacitor 35, a varactor diode 37, a first decoupling capacitor 32, a second decoupling capacitor 36, and a readout coil 31. The readout coil 31 and the LC wireless passive sensor perform strong coupling magnetic resonance, thereby improving the signal strength.

The first decoupling capacitor 32, the varactor diode 37 and the second decoupling capacitor 36 are connected in series in sequence.

The frequency-selecting capacitor 35 is connected in parallel with a series circuit formed by the first decoupling capacitor 32, the varactor diode 37 and the second decoupling capacitor 36.

The readout coil 31 is connected in parallel with the series circuit formed by the first decoupling capacitor 32, the varactor diode 37 and the second decoupling capacitor 36.

One end of the variable resistor 33 is connected to the DDS frequency sweeping signal generating module 2, and the other end is connected in series to the first decoupling capacitor 32.

One end of the variable inductor 34 is connected to the buffer amplifying module 4, and the other end is connected to the frequency-selecting capacitor 35 in series.

The key module 5 is connected with the singlechip control module 1 through an I/O interface.

The buffer amplification module 4 is connected with the singlechip control module 1 through an A/D interface.

The L-type matching circuit module uses the variable inductor 34 as a series inductor element and the varactor 37 as a parallel capacitor for scan variation; the variable resistor 33 and the frequency-selecting capacitor 35 are used for setting the central frequency range of the LC wireless passive sensor loop; the first decoupling capacitor 32 and the second decoupling capacitor 36 are used to reduce the influence of the dc voltage source noise on the circuit.

The singlechip control module 1 controls the DDS signal generation module 2 to generate direct current voltage to set the optimal matching inductance of the variable inductance 34. The readout coil 31 is close to the LC wireless passive sensor, and the readout coil 31 and the LC wireless passive sensor generate strong coupling magnetic resonance. The start frequency, step frequency and cut-off frequency of the frequency sweep required are entered by the keyboard 5 and the measurement is started. The single chip microcomputer control module 1 controls the DDS signal generation module 2 to generate signals with certain frequency and amplitude, and the signals are sent to the L-shaped matching circuit module 3, and are sent to the single chip microcomputer control module 1 after passing through the buffering amplification module 4. The single chip microcomputer control module 1 sends a control signal to the signal generation module 2 again, so that the measurement frequency is increased progressively, and the process is repeated until the set cut-off frequency is reached. The resonant frequency of the reading circuit can cover the variation range of the LC wireless passive sensor, and the frequency and the signal strength of the S11 minimum value point under the scanning voltage are extracted to obtain the resonant frequency of the LC wireless passive sensor.

Claims

1. A readout circuit of an LC wireless passive sensor, characterized by: the reading circuit comprises a singlechip control module, a DDS frequency sweeping signal generation module, an L-shaped matching circuit module, a buffering amplification module, a key module and a display module; the DDS frequency sweeping signal generating module, the L-shaped matching circuit module, the buffering amplifying module, the key module and the display module are respectively connected with the single-chip microcomputer control module; the L-shaped matching circuit module is connected with the buffer amplification module; the L-shaped matching circuit module consists of a variable resistor, a variable inductor, a frequency-selecting capacitor, a variable capacitance diode, a first decoupling capacitor, a second decoupling capacitor and a reading coil; the first decoupling capacitor, the variable capacitance diode and the second decoupling capacitor are sequentially connected in series.

2. A readout circuit for an LC wireless passive sensor according to claim 1, wherein: the frequency-selecting capacitor is connected in parallel with a series circuit formed by the first decoupling capacitor, the variable capacitance diode and the second decoupling capacitor.

3. A readout circuit for an LC wireless passive sensor according to claim 1, wherein: the readout coil is connected in parallel with a series circuit formed by the first decoupling capacitor, the varactor and the second decoupling capacitor.

4. A readout circuit for an LC wireless passive sensor according to claim 1, wherein: one end of the variable resistor is connected with the DDS frequency sweeping signal generating module, and the other end of the variable resistor is connected with the first decoupling capacitor in series.

5. A readout circuit for an LC wireless passive sensor according to claim 1, wherein: one end of the variable inductor is connected with the buffering amplification module, and the other end of the variable inductor is connected with the frequency-selecting capacitor in series.

6. A readout circuit for an LC wireless passive sensor according to claim 1, wherein: the type of the variable capacitance diode is BB910, and the capacitance range is 2-20pF.