Wireless passive temperature measurement system and temperature measurement method based on MEMS resonator

Abstract

The present invention provides a wireless passive temperature measurement system and method based on a MEMS resonator, wherein the system includes a MEMS oscillator, a MEMS resonator, and a corresponding interface circuit, for generating a reference frequency signal; a phase-locked loop (PLL) for generating a high-frequency signal; a passive frequency multiplier for multiplying the high-frequency frequency output by the PLL; a coupler for dividing the multiplied high-frequency signal into two harmonic signals; a tunable filter for selecting a target harmonic signal; a dual-polarized antenna for transmitting the target harmonic signal to a terminal and receiving an electromagnetic wave signal emitted by the terminal; a rectifier module for converting the electromagnetic wave signal and the harmonic signal reflected by the coupler into direct current (DC); and an energy management module for storing and stabilizing the DC power output to supply energy to the MEMS oscillator and the PLL. The present invention can achieve long-distance transmission of passive wireless temperature detection while ensuring measurement accuracy and resolution.

Description

Technical Field

[0001] The present invention belongs to the technical field of temperature monitoring, and in particular relates to a wireless passive temperature measurement system based on a MEMS resonator. Background Art

[0002] With the advancement of industrial automation and intelligentization, real-time monitoring of equipment operating status has become increasingly important. As a key indicator of equipment operating status, accurate temperature measurement is crucial for preventing equipment failures and ensuring production safety. While widely used, traditional temperature measurement methods, such as thermocouples and thermistors, are limited in certain environments, such as high temperature, high pressure, and corrosive environments, or for inaccessible equipment.

[0003] In recent years, wireless passive temperature measurement technology has become a research hotspot in the temperature monitoring field due to its advantages such as easy installation, low maintenance costs, and freedom from environmental restrictions. Wireless passive temperature measurement uses wireless signals to transmit temperature information without the need for an external power supply, making it suitable for a variety of applications such as manufacturing, logistics and warehousing, and power systems.

[0004] As a new sensor technology, MEMS (microelectromechanical system) resonators have shown great potential for application in wireless passive temperature measurement systems due to their small size, light weight, high integration, and low cost. MEMS resonators sense temperature changes by detecting changes in resonant frequency and have the characteristics of wide temperature coverage, high Q value, high sensitivity, high linearity, and high resolution.

[0005] However, existing wireless passive temperature measurement systems based on MEMS resonators still face several technical challenges. Conventional MEMS resonator-based circuit designs consume high power, making long-distance wireless transmission difficult, limiting their application in remote monitoring. Furthermore, in passive systems, it is difficult to effectively isolate the energy harvesting and energy transmission circuits to prevent mutual interference. Furthermore, achieving long-distance transmission of passive wireless temperature measurement while maintaining measurement accuracy and resolution is challenging under low power consumption conditions. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a wireless passive temperature measurement system and a temperature measurement method based on a MEMS resonator.

[0007] In a first aspect, the present invention provides a wireless passive temperature measurement system based on a MEMS resonator, comprising a MEMS oscillator formed with the MEMS resonator and a corresponding interface circuit, for generating a reference frequency signal;

[0008] a phase-locked loop, electrically connected to an output end of the MEMS oscillator, for generating a high-frequency signal;

[0009] a passive frequency multiplier, electrically connected to an output terminal of the phase-locked loop, and configured to multiply the high frequency output by the phase-locked loop;

[0010] a coupler electrically connected to the output end of the passive frequency multiplier and configured to split the frequency-multiplied high-frequency signal into two harmonic signals;

[0011] a tunable filter, electrically connected to an output end of the coupler, for selecting a target harmonic signal;

[0012] a dual-polarized antenna, electrically connected to an output end of the tunable filter, for transmitting a target harmonic signal to a terminal and receiving an electromagnetic wave signal transmitted by the terminal;

[0013] a rectifier module, electrically connected to the dual-polarized antenna and the coupler, respectively, for converting the electromagnetic wave signal and the harmonic signal reflected by the coupler into direct current;

[0014] The energy management module is electrically connected to the phase-locked loop and the MEMS resonator, and is used to store and output DC power at a regulated voltage to supply energy to the MEMS oscillator and the phase-locked loop.

[0015] Optionally, the temperature resolution ΔT after frequency doubling is:

[0016]

[0017] Where Δf is the frequency measurement resolution; N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; and TCF is the temperature coefficient of the MEMS resonator.

[0018] Optionally, the antenna of the terminal is a dual-polarized antenna, and the dual-polarized antenna on the terminal side and the dual-polarized antenna on the MEMS resonator side are in a ±45° polarization form.

[0019] Optionally, the operating bandwidth of the dual-polarized antenna satisfies a frequency offset within a temperature variation range, and the operating bandwidth of the dual-polarized antenna is greater than or equal to the frequency offset after frequency multiplication.

[0020] Optionally, the frequency offset f3 after frequency multiplication is calculated according to the following formula:

[0021] f3 = N × f1 × TCF × (T2 - T1);

[0022] Where N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; TCF is the temperature coefficient of the MEMS resonator; T1 is the minimum value of the measured temperature; and T2 is the maximum value of the measured temperature.

[0023] Optionally, the terminal includes a bandpass filter, a low-noise amplifier and a spectrum detection circuit; the transmission signal of the dual-polarized antenna on the MEMS resonator side is received by the dual-polarized antenna on the terminal side, and is transmitted to the spectrum detection circuit through the bandpass filter and the low-noise amplifier. The spectrum detection circuit detects the maximum power and corresponding frequency of the spectrum under the current working bandwidth, and determines the current test temperature based on the correlation between frequency and temperature.

[0024] Optionally, the output of the passive frequency multiplier includes multiple harmonics, and the tunable filter is used to select the harmonic components of the target output power to characterize the temperature information.

[0025] In a second aspect, the present invention provides a temperature measurement method of a wireless passive temperature measurement system based on a MEMS resonator as described in the first aspect, comprising:

[0026] Using a dual-polarized antenna to receive electromagnetic wave signals transmitted by the terminal;

[0027] The rectifier module converts the received electromagnetic wave signal into direct current to supply power to the MEMS oscillator and phase-locked loop;

[0028] A MEMS oscillator is used to generate a reference frequency signal, which is then multiplied by a phase-locked loop and a passive frequency multiplier.

[0029] The target harmonic signal in the frequency-multiplied high-frequency signal is selected by an adjustable filter and sent to the terminal through a dual-polarized antenna;

[0030] The terminal receives the target harmonic signal and determines the current test temperature based on the correlation between the frequency corresponding to the target harmonic signal and the temperature.

[0031] The present invention provides a wireless passive temperature measurement system based on a MEMS resonator and a temperature measurement method thereof, wherein the system includes a MEMS oscillator composed of a MEMS resonator and a corresponding interface circuit, for generating a reference frequency signal; a phase-locked loop, electrically connected to the output end of the MEMS oscillator, for generating a high-frequency signal; a passive frequency multiplier, electrically connected to the output end of the phase-locked loop, for multiplying the high-frequency frequency output by the phase-locked loop; a coupler, electrically connected to the output end of the passive frequency multiplier, for dividing the multiplied high-frequency signal into two harmonic signals; a tunable filter, electrically connected to the output end of the coupler, for selecting a target harmonic signal; a dual-polarization antenna, electrically connected to the output end of the tunable filter, for sending the target harmonic signal to a terminal and receiving an electromagnetic wave signal emitted by the terminal; a rectifier module, electrically connected to the dual-polarization antenna and the coupler, respectively, for converting the electromagnetic wave signal and the harmonic signal reflected by the coupler into direct current; and an energy management module, electrically connected to the phase-locked loop and the MEMS resonator, respectively, for storing and outputting the direct current in a regulated voltage to supply energy to the MEMS oscillator and the phase-locked loop. The present invention can realize long-distance wireless transmission and effectively isolate energy collection and energy transmission circuits to avoid mutual interference. Under the condition of low power consumption, it can realize long-distance transmission of passive wireless temperature detection while ensuring measurement accuracy and resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 A schematic structural diagram of a wireless passive temperature measurement system based on a MEMS resonator provided in an embodiment of the present invention;

[0034] Figure 2 A spectrum diagram of a frequency doubling circuit constructed based on a MEMS resonator according to an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of an electromagnetic energy harvesting circuit provided by an embodiment of the present invention;

[0036] Figure 4 A schematic diagram of signal link isolation based on dual-polarized transceiver provided in an embodiment of the present invention;

[0037] Figure 5 A schematic diagram of a signal chain of a frequency multiplication circuit using specific devices according to an embodiment of the present invention;

[0038] Figure 6A test spectrum diagram of an oscillator provided in an embodiment of the present invention;

[0039] Figure 7 A test spectrum diagram of a phase-locked loop provided in an embodiment of the present invention;

[0040] Figure 8 A test spectrum diagram of the passive frequency multiplier provided in an embodiment of the present invention;

[0041] Figure 9 A flow chart of a temperature measurement method provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0042] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment provides a wireless passive temperature measurement system based on a MEMS resonator, comprising:

[0045] A MEMS oscillator formed with a MEMS resonator and corresponding interface circuit is used to generate a reference frequency signal;

[0046] a phase-locked loop, electrically connected to an output end of the MEMS oscillator, for generating a high-frequency signal;

[0047] a passive frequency multiplier, electrically connected to an output terminal of the phase-locked loop, and configured to multiply the high frequency output by the phase-locked loop;

[0048] a coupler electrically connected to the output end of the passive frequency multiplier and configured to split the frequency-multiplied high-frequency signal into two harmonic signals;

[0049] a tunable filter, electrically connected to an output end of the coupler, for selecting a target harmonic signal;

[0050] a dual-polarized antenna, electrically connected to an output end of the tunable filter, for transmitting a target harmonic signal to a terminal and receiving an electromagnetic wave signal transmitted by the terminal;

[0051] a rectifier module, electrically connected to the dual-polarized antenna and the coupler, respectively, for converting the electromagnetic wave signal and the harmonic signal reflected by the coupler into direct current;

[0052] The energy management module is electrically connected to the phase-locked loop and the MEMS resonator, and is used to store and output DC power at a regulated voltage to supply energy to the MEMS oscillator and the phase-locked loop.

[0053] For a temperature sensor based on a MEMS resonator, its resolution can be calculated using the resonator's temperature coefficient of frequency (TCF, in ppm / °C).

[0054] In order to effectively improve the resolution of temperature measurement, the reference frequency can be multiplied to a high frequency through devices such as a phase-locked loop and a passive frequency multiplier. The temperature resolution △T after multiplication can be expressed as:

[0055]

[0056] Where Δf is the frequency measurement resolution; N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; and TCF is the temperature coefficient of the MEMS resonator.

[0057] like Figure 1 As shown, a MEMS resonator combined with an interface circuit forms an oscillator that generates a signal with a reference frequency of f1. A phase-locked loop (output frequency f2) combined with a passive frequency multiplier generates a high-frequency signal (M×N×f2, where M is the multiplication factor of the frequency multiplier and N is the multiplication coefficient). A tunable filter allows only certain harmonics to pass through the filter and be transmitted to the terminal via an antenna. Other harmonics are reflected by a coupler to a rectifier module for further energy conversion.

[0058] In this embodiment, two fixed-multiple phase-locked loops and a passive frequency multiplier are used to achieve a higher frequency multiplication factor. Testing has found that the harmonic power of the passive frequency multiplier is also high, so harmonics are selected to further increase the frequency multiplication factor, thereby improving temperature resolution.

[0059] In this embodiment, electromagnetic waves are actively transmitted through the terminal, and the wireless passive temperature sensor receives the electromagnetic wave signal, which is converted into direct current through the rectifier module and then stabilized to drive the MEMS resonator and the phase-locked loop. The rectifier module contains two types of RF signals, one is the electromagnetic wave signal actively transmitted by the external (terminal), and the other is the fundamental and harmonic signals of the frequency multiplier. The introduction of two RF signal streams improves the efficiency of the rectifier module, reduces the charging time, and improves the response speed of the temperature sensor. The rectifier module needs to perform RF-DC conversion in multiple frequency bands based on the externally transmitted RF signal and the signal reflected by the coupler to achieve high-efficiency rectification.

[0060] In this embodiment, both the terminal antenna and the temperature sensor antenna utilize dual-polarization antennas, such as ±45-degree polarization. If the terminal transmits signals to the temperature sensing node at +45°, the temperature sensing node transmits signals to the terminal at -45°. These different polarizations effectively avoid electromagnetic coupling between transmission and reception, achieving effective isolation from the perspective of polarization orthogonality. This allows for uninterrupted transmission and reception between the terminal and the temperature sensor, enabling a temperature measurement system with uninterrupted temperature detection or a configurable refresh rate.

[0061] like Figure 2 Figure 1 shows a spectrum diagram of a frequency multiplication circuit built based on a MEMS resonator. The goal is to maximize the frequency multiplication factor while taking into account system power consumption, ultimately improving the resolution of temperature measurement. The output frequency f1 of the MEMS resonator itself has a linear relationship with temperature and has a certain TCF. The signal of the MEMS resonator is multiplied to f2 through a phase-locked loop. Furthermore, the frequency multiplication factor is increased by a passive frequency multiplier, and the output of the passive frequency multiplier contains multiple harmonics (M×N×f2). Through a coupler and a bandpass filter, high-order harmonics can be reasonably selected and wirelessly transmitted to the terminal via an antenna, but it is necessary to consider whether the output power of the harmonics meets the wireless coverage distance of the temperature sensing node. Other filtered harmonics are reflected to the rectifier module through the coupler to achieve more efficient energy collection.

[0062] like Figure 3 Figure 2 shows a schematic diagram of the electromagnetic energy harvesting circuit. The rectifier module's RF signal sources include two types: one is an externally transmitted RF signal, which is received by one end of a dual-polarized antenna and then fed into the rectifier circuit; the other is a harmonic signal filtered by a reflective filter and reflected, which is then transmitted to the rectifier circuit through the other end of a coupler. This enables multi-band RF-DC conversion and more efficient energy harvesting. Following the rectifier circuit, the energy management circuit achieves DC-DC conversion, storage, and regulated output, ultimately supplying energy to the MEMS oscillator and phase-locked loop.

[0063] like Figure 4The figure shows a transmit-receive link isolation solution based on a dual-polarized antenna. The terminal generates a fixed-frequency signal through an RF signal source, which is amplified by an amplifier and then radiated. The radiated electromagnetic wave has a +45° linear polarization. This polarized electromagnetic wave is received by the temperature sensor node's dual-polarized antenna and transmitted to a rectifier circuit for rectification. Note that to comply with national standards for transmit power, the terminal's transmit frequency is designed to be within the RFID band, with the corresponding transmit power + transmit antenna gain ≤ 36dBm, or EIRP (Effective Isotropic Radiated Power) ≤ 36dBm. The output signal of the frequency multiplier is wirelessly transmitted through a dual-polarized antenna, with a -45° polarization. This transmitted signal is received by the terminal's dual-polarized antenna (which includes a bandpass filter, a low-noise amplifier, and a spectrum detection circuit) and transmitted through the bandpass filter and low-noise amplifier (LNA) to the spectrum detection circuit. The detection circuit detects the maximum power and corresponding frequency in the spectrum within the current bandwidth and determines the current test temperature based on the correlation between frequency and temperature. In this solution, there is a high degree of isolation between the transmitting link and the receiving link of the terminal, and there is also a high degree of isolation between the transmitting link and the receiving link in the sensor node. Based on this, the transmission of external electromagnetic energy can work continuously or intermittently to achieve uninterrupted or periodic wireless passive temperature measurement with a high degree of freedom. In this embodiment, the working bandwidth of the dual-polarized antenna needs to meet the frequency offset under the temperature variation range. In the case of the current TCF of the MEMS resonator, the measurement temperature range (T1~T2℃) is considered to determine the frequency offset after frequency doubling. The working bandwidth of the dual-polarized antenna needs to be greater than or equal to this frequency offset; wherein, the frequency offset f3 after frequency doubling is calculated according to the following formula:

[0064] f3 = N × f1 × TCF × (T2 - T1);

[0065] Where N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; TCF is the temperature coefficient of the MEMS resonator; T1 is the minimum value of the measured temperature; and T2 is the maximum value of the measured temperature.

[0066] It should be pointed out that Figure 1 In the circuit, any MEMS resonator with stable TCF can be used to achieve high-precision temperature detection function. Taking the MEMS oscillator model LTC1799 as an example, the following is built: Figure 5In the frequency multiplication circuit shown, the MEMS oscillator generates a reference signal of ~10MHz, which is multiplied by two phase-locked loops. The frequency multiplication coefficients of the two phase-locked loops are 3.33 and 6 respectively. The final output frequency of the phase-locked loop is ~200MHz, and the signal power is about 17dBm. Furthermore, after the passive frequency multiplier MK-5-14, the output signal frequency is increased to ~1GHz, and its power is -5dBm. Higher frequency harmonic signals (such as 1.2GHz, 1.4GHz and other harmonics) can also be selected to characterize temperature information, but it is necessary to consider that the output power of higher harmonic signals is low, and it is difficult to achieve long-distance coverage. The total frequency multiplication coefficient of this scheme is 99.8, which verifies Figure 1 The feasibility of the circuit architecture shown in the figure can achieve effective frequency multiplication while considering the system power consumption through the frequency multiplication scheme, and further improve the resolution of temperature sensing.

[0067] like Figure 6 、 Figure 7 and Figure 8 The following are test spectra of the oscillator, phase-locked loop, and passive frequency multiplication circuit. The test results show that the phase noise of the MEMS oscillator and phase-locked loop is ~-61dBc / Hz@1kHz. This phase noise is limited by the selected MEMS oscillator model. A MEMS oscillator with a higher Q value can be selected to reduce system phase noise and achieve higher-precision temperature measurement. The output spectrum of the passive frequency multiplier shows that, although calibrated to a fixed multiplication factor, the output spectrum of the frequency multiplier exhibits harmonic characteristics. This can be used to characterize temperature information by selecting harmonic components with higher output power and higher frequencies.

[0068] In summary, this embodiment provides a wireless passive temperature measurement system based on MEMS resonators, which can realize long-distance wireless transmission and effectively isolate the energy collection and energy transmission circuits to avoid mutual interference. Under low power consumption conditions, it can realize long-distance transmission of passive wireless temperature detection while ensuring measurement accuracy and resolution.

[0069] Example 2

[0070] like Figure 9 As shown, this embodiment provides a temperature measurement method of a wireless passive temperature measurement system based on a MEMS resonator as described in Example 1, comprising:

[0071] Step 101: Receive electromagnetic wave signals transmitted by a terminal using a dual-polarized antenna.

[0072] Step 102: Utilize a rectifier module to convert the received electromagnetic wave signal into direct current, and supply power to the MEMS oscillator and the phase-locked loop.

[0073] Step 103: Generate a reference frequency signal using a MEMS oscillator, and multiply the frequency using a phase-locked loop and a passive frequency multiplier.

[0074] Step 104 : Select the target harmonic signal in the frequency-multiplied high-frequency signal using an adjustable filter, and send the target harmonic signal to the terminal through a dual-polarized antenna.

[0075] Step 105 : Utilize the terminal to receive the target harmonic signal, and determine the current test temperature based on the correlation between the frequency corresponding to the target harmonic signal and the temperature.

[0076] The present invention has been described in detail above with reference to specific embodiments and exemplary examples. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art will appreciate that various equivalent substitutions, modifications, or improvements may be made to the technical solutions and implementations of the present invention without departing from the spirit and scope of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A wireless passive temperature measurement system based on MEMS resonator, characterized in that: include: A MEMS oscillator formed with a MEMS resonator and corresponding interface circuit is used to generate a reference frequency signal; a phase-locked loop, electrically connected to an output end of the MEMS oscillator, for generating a high-frequency signal; a passive frequency multiplier, electrically connected to an output terminal of the phase-locked loop, and configured to multiply the high frequency output by the phase-locked loop; a coupler electrically connected to the output end of the passive frequency multiplier and configured to split the frequency-multiplied high-frequency signal into two harmonic signals; a tunable filter, electrically connected to an output end of the coupler, for selecting a target harmonic signal; a dual-polarized antenna, electrically connected to an output end of the tunable filter, for transmitting a target harmonic signal to a terminal and receiving an electromagnetic wave signal transmitted by the terminal; a rectifier module, electrically connected to the dual-polarized antenna and the coupler, respectively, for converting the electromagnetic wave signal and the harmonic signal reflected by the coupler into direct current; The energy management module is electrically connected to the phase-locked loop and the MEMS resonator, and is used to store and output DC power at a regulated voltage to supply energy to the MEMS oscillator and the phase-locked loop.

2. The wireless passive temperature measurement system based on MEMS resonator according to claim 1, characterized in that: The temperature resolution △T after frequency doubling is: Where Δf is the frequency measurement resolution; N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; and TCF is the temperature coefficient of the MEMS resonator.

3. The wireless passive temperature measurement system based on MEMS resonator according to claim 1, characterized in that: The antenna of the terminal is a dual-polarized antenna, and the dual-polarized antenna on the terminal side and the dual-polarized antenna on the MEMS resonator side are in a ±45° polarization form.

4. The wireless passive temperature measurement system based on MEMS resonator according to claim 1, characterized in that: The operating bandwidth of the dual-polarized antenna satisfies the frequency offset within a temperature variation range, and the operating bandwidth of the dual-polarized antenna is greater than or equal to the frequency offset after frequency multiplication.

5. The wireless passive temperature measurement system based on MEMS resonator according to claim 4, characterized in that: The frequency offset f3 after frequency multiplication is calculated according to the following formula: f3 = N × f1 × TCF × (T2 - T1); Where N is the frequency multiplication factor; f1 is the reference frequency of the MEMS resonator; TCF is the temperature coefficient of the MEMS resonator; T1 is the minimum value of the measured temperature; and T2 is the maximum value of the measured temperature.

6. The wireless passive temperature measurement system based on MEMS resonator according to claim 3, characterized in that: The terminal includes a bandpass filter, a low-noise amplifier, and a spectrum detection circuit. The transmission signal of the dual-polarized antenna on the MEMS resonator side is received by the dual-polarized antenna on the terminal side and transmitted to the spectrum detection circuit through the bandpass filter and the low-noise amplifier. The spectrum detection circuit detects the maximum power and corresponding frequency of the spectrum within the current working bandwidth, and determines the current test temperature based on the correlation between frequency and temperature.

7. The wireless passive temperature measurement system based on MEMS resonator according to claim 1, characterized in that: The output of the passive frequency multiplier includes multiple harmonics, and the tunable filter is used to select the harmonic components of the target output power to characterize the temperature information.

8. A temperature measurement method for a wireless passive temperature measurement system based on a MEMS resonator according to any one of claims 1 to 7, characterized in that: include: Using a dual-polarized antenna to receive electromagnetic wave signals transmitted by the terminal; The rectifier module converts the received electromagnetic wave signal into direct current to supply power to the MEMS oscillator and phase-locked loop; A MEMS oscillator is used to generate a reference frequency signal, which is then multiplied by a phase-locked loop and a passive frequency multiplier. The target harmonic signal in the frequency-multiplied high-frequency signal is selected by an adjustable filter and sent to the terminal through a dual-polarized antenna; The terminal receives the target harmonic signal and determines the current test temperature based on the correlation between the frequency corresponding to the target harmonic signal and the temperature.

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