Temperature detection device based on surface acoustic wave temperature sensor

Abstract

The present invention provides a temperature detection device based on a surface acoustic wave temperature sensor, comprising: a signal source, a power amplifier, a radio frequency switch, a low-noise amplifier circuit, a mixer, a filter, an analog-to-digital converter, a fast Fourier converter and a processor. The present invention converts an unknown input signal with a large dynamic range into an intermediate frequency signal with a small dynamic range by introducing a mixer down-conversion process, which makes it easier to perform subsequent operations such as amplification and filtering, thereby solving the problem of uneven sensitivity of the surface acoustic wave temperature reader in receiving signals at different frequencies. The temperature detection device of the present invention can analyze subsequent intermediate frequency signals more specifically. Compared with the current "sweeping frequency" solution, the present invention can make the receiving effect of the entire temperature detection device more consistent on the overall frequency band, obtain a receiving signal with better sensitivity, and finally obtain a more accurate temperature measurement effect.

Description

Technical Field

[0001] The invention belongs to the field of surface acoustic wave monitoring technology and applications, and in particular relates to a temperature detection device based on a surface acoustic wave temperature measurement sensor. Background Art

[0002] In recent years, my country has vigorously promoted "Industrial Electrical Automation" and "Ubiquitous Power Internet of Things". According to statistics from the National Fire Protection Center, electrical fires are the main factor causing 70% of fire accidents.

[0003] In power plants and substations, the numerous high-voltage electrical connection points of switchgear are the weakest links in power transmission. After long-term operation, these links are reflected in the heating of contacts (contact points). As the load increases, the connection points heat up and form a vicious cycle: temperature rise, expansion, contraction, oxidation, increased resistance, and temperature rise again. Implementing "online temperature monitoring" of switchgear is an important means to ensure the safe operation of power equipment. Hidden dangers can be discovered and dealt with as soon as they occur, eliminating disgusting accidents and improving operation and maintenance efficiency.

[0004] In order to meet the temperature measurement requirements of power equipment (such as power switch cabinets, cable joints, etc.), passive wireless temperature sensing technology is adopted: surface acoustic wave (SAW) temperature sensing technology. Its sensor has the advantages of being completely passive (no battery required) and wirelessly readable, which effectively solves the problems of high insulation level, high temperature resistance, and easy maintenance required for temperature measurement of power equipment.

[0005] Surface acoustic waves are elastic waves that propagate along the surface of an object. When the transducer on the piezoelectric crystal substrate converts the wireless signal from the reader into an acoustic signal through the inverse piezoelectric effect, it is reflected by the two periodic gratings on the left and right to form a resonance. The resonant frequency of the resonator is related to the temperature, and the change of the resonator frequency is linear with the change of temperature within a certain range. The transducer then converts the acoustic signal into a wireless signal and returns it to the reader. Since there is a one-to-one correspondence between temperature and signal frequency, the reader can obtain the accurate measured temperature through the signal frequency, such as Figure 1 shown.

[0006] The resonator frequency of the surface acoustic wave sensor will change with temperature, so how to detect the frequency of the echo signal of the surface acoustic wave sensor is very critical. Since the current temperature and the change of the surface acoustic wave sensor with temperature are not known in advance, the current common practice is to use the resonator frequency of the surface acoustic wave sensor in the initial state. After transmitting the wireless signal of this frequency, the echo is detected by "sweeping frequency" around this frequency with this frequency as the center. When strong energy is found on a certain frequency, it is considered to be the echo signal of the surface acoustic wave sensor, and the corresponding temperature value is found according to the frequency of the echo signal to complete a temperature measurement process.

[0007] The disadvantage of this approach is that since the frequency of the echo signal is variable, the detection system has very high requirements for the design of the filter and amplifier of the echo signal in the receiving part of the reader, and it is difficult to make the receiver's receiving sensitivity uniform across the entire band, which makes the temperature measurement effect less accurate. Especially in actual applications, a reader often needs to connect to multiple surface acoustic wave sensors, and their resonator frequencies are different, for example, ranging from 425MHz to 442MHz. The receiver's amplification performance in the high and low segments of the receiving frequency band is different, which will lead to poor consistency among multiple temperature sensors. Summary of the invention

[0008] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a temperature detection device based on a surface acoustic wave temperature sensor, so as to solve the problem of low temperature measurement accuracy of the temperature detection device based on a surface acoustic wave temperature sensor in the prior art.

[0009] To achieve the above-mentioned purpose and other related purposes, the present invention provides a temperature detection device based on a surface acoustic wave temperature sensor, the detection device comprising: a signal source, used to generate a local oscillator frequency signal corresponding to the surface acoustic wave temperature sensor; a power amplifier, connected to the signal source, used to amplify the local oscillator frequency signal; a radio frequency switch, connected to the power amplifier, used to send the amplified local oscillator frequency signal to the surface acoustic wave temperature sensor to generate an echo signal, and receive the echo signal through the radio frequency switch; a low-noise amplifier circuit, connected to the radio frequency switch, used to amplify the echo signal. A mixer is connected to the low noise amplifier and is used to perform down-conversion processing on the echo signal based on the local oscillator frequency signal to obtain an intermediate frequency signal; a filter is connected to the mixer and is used to filter the intermediate frequency signal; an analog-to-digital converter is connected to the filter and is used to sample the intermediate frequency signal and convert it into a digital signal; a fast Fourier transformer is connected to the digital-to-analog converter and is used to perform fast Fourier transform on the digital signal to obtain the frequency of the intermediate frequency signal; a processor is connected to the fast Fourier transformer and is used to obtain a corresponding temperature value according to the frequency of the intermediate frequency signal.

[0010] Optionally, the signal source includes a phase-locked loop, a unidirectional switch and a bandpass filter, the phase-locked loop is used to generate a local oscillation frequency signal, the unidirectional switch is used to output the local oscillation frequency signal, and the bandpass filter is used to filter the local oscillation frequency signal.

[0011] Optionally, the local oscillation frequency signal is between 420 MHz and 450 MHz.

[0012] Optionally, the surface acoustic wave temperature sensor includes a piezoelectric substrate, an interdigital transducer located on the piezoelectric substrate, and two groups of reflection gratings symmetrically distributed on both sides of the interdigital transducer, and the interdigital transducer and the reflection gratings form a resonant cavity, so that the surface acoustic wave temperature sensor only responds to radio frequency signals of a specific frequency.

[0013] Optionally, when the radio frequency switch sends the local oscillator frequency signal to the surface wave temperature sensor, the local oscillator frequency signal is transmitted to the surface acoustic wave temperature sensor through the antenna, and the surface acoustic wave temperature sensor converts electrical energy into mechanical energy under the action of the inverse piezoelectric effect, and excites surface acoustic waves on the piezoelectric substrate through the interdigital transducer; then, the surface acoustic wave temperature sensor converts mechanical energy into electrical energy under the action of the piezoelectric effect, and excites an echo signal with the same frequency as the surface acoustic wave through the interdigital transducer.

[0014] Optionally, the radio frequency switch is a single-pole double-throw switch.

[0015] Optionally, the mixer is a down-conversion mixer, configured to obtain the intermediate frequency signal by acquiring a difference between the local oscillation frequency signal and the echo signal.

[0016] Optionally, the low-noise amplifier circuit includes two low-noise amplifiers and a VGA signal amplifier connected in series.

[0017] Optionally, the frequency of the intermediate frequency signal is less than or equal to 2 MHz, and the sampling frequency of the analog-to-digital converter is greater than or equal to 5 MHz.

[0018] Optionally, the processor obtains the final temperature value by querying a frequency-temperature curve or a frequency-temperature table according to the frequency of the intermediate frequency signal.

[0019] As described above, the temperature detection device based on the surface acoustic wave temperature sensor of the present invention has the following beneficial effects:

[0020] The present invention converts an unknown input signal with a large dynamic range into an intermediate frequency signal with a small dynamic range by introducing a mixer down-conversion process, which makes it easier to perform subsequent operations such as amplification and filtering, thereby solving the problem of uneven sensitivity of the surface acoustic wave temperature reader in receiving signals at different frequencies. The temperature detection device of the present invention can analyze subsequent intermediate frequency signals more specifically, and compared with the current "sweeping frequency" solution, the receiving effect of the entire temperature detection device on the overall frequency band is more consistent, and a receiving signal with better sensitivity can be obtained, and finally a more accurate temperature measurement effect is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1Shown is a schematic structural diagram of a surface acoustic wave temperature measurement sensor according to an embodiment of the present invention.

[0022] Figure 2 Shown is a schematic structural diagram of a temperature detection device based on a surface acoustic wave temperature measurement sensor according to an embodiment of the present invention.

[0023] Figure 3 It is a schematic diagram showing the structure of a signal sending end of a temperature detection device based on a surface acoustic wave temperature measurement sensor according to an embodiment of the present invention.

[0024] Figure 4 It is a schematic diagram showing the structure of a signal receiving end of a temperature detection device based on a surface acoustic wave temperature measurement sensor according to an embodiment of the present invention.

[0025] Figure 5 It is a schematic diagram showing a signal waveform of an intermediate frequency signal (Output) obtained by the difference between a local oscillation frequency signal (LO) and an echo signal (Input) in a temperature detection device based on a surface acoustic wave temperature sensor according to an embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram showing a frequency-temperature curve of a temperature detection device based on a surface acoustic wave temperature sensor according to this embodiment of the present invention.

[0027] Component number description

[0028] 10 Signal Source

[0029] 101 Phase-Locked Loop

[0030] 102 One-way switch

[0031] 103 Bandpass filter

[0032] 11 Power Amplifier

[0033] 111 ADL5324 Power Amplifier

[0034] 12 RF switch

[0035] 121 SPDT switch

[0036] 13 Surface Acoustic Wave Temperature Sensor

[0037] 14 Low noise amplifier circuit

[0038] 141 First Low Noise Amplifier

[0039] 142 Second Low Noise Amplifier

[0040] 143 VGA signal amplifier

[0041] 15 Mixer

[0042] 16 Filter

[0043] 17 Analog-to-digital converter

[0044] 18 Fast Fourier Transformer

[0045] 19 Processor DETAILED DESCRIPTION

[0046] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0047] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0048] For ease of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0049] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0050] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0051] like Figure 2 to Figure 6As shown, this embodiment provides a temperature detection device based on a surface acoustic wave temperature sensor 13, and the detection device includes: a signal source 10, a power amplifier 11, a radio frequency switch 12, a low-noise amplifier circuit 14, a mixer 15, a filter 16, an analog-to-digital converter 17, a fast Fourier transformer 18 and a processor 19.

[0052] The signal source 10 is used to generate a local oscillation frequency signal corresponding to the surface acoustic wave temperature sensor 13. In this embodiment, Figure 3 As shown, the signal source 10 includes a phase-locked loop 101, a unidirectional switch 102 and a bandpass filter 103. The phase-locked loop 101 is used to generate a local oscillation frequency signal, the unidirectional switch 102 is used to output the local oscillation frequency signal, and the bandpass filter 103 is used to filter the local oscillation frequency signal based on a bandpass filtering method. In this embodiment, the phase-locked loop 101 is an ADF4360-7 phase-locked loop, and the unidirectional switch 102 is an ADG901 unidirectional switch. For example, the local oscillation frequency signal is between 420MHz and 450MHz. In a specific embodiment, the local oscillation frequency signal is 433MHz.

[0053] like Figure 2 and Figure 3 As shown, the power amplifier 11 is connected to the signal source 10 and is used to amplify the local oscillation frequency signal. In this embodiment, the power amplifier 11 is an ADL5324 power amplifier 111.

[0054] like Figure 2 and Figure 3 As shown, the RF switch 12 is connected to the power amplifier, and is used to send the amplified local oscillation frequency signal to the surface wave temperature measurement sensor to generate an echo signal, and receive the echo signal through the RF switch 12.

[0055] The surface acoustic wave temperature sensor 13 includes a piezoelectric substrate, an interdigital transducer located on the piezoelectric substrate, and two groups of reflection gratings symmetrically distributed on both sides of the interdigital transducer. The interdigital transducer and the reflection grating form a resonant cavity, so that the surface acoustic wave temperature sensor 13 only responds to radio frequency signals of a specific frequency.

[0056] As an example, the RF switch 12 is a single-pole double-throw switch 121. For example, in a specific implementation process, the RF switch 12 is an ADG918 single-pole double-throw switch. When the RF switch 12 sends the local oscillation frequency signal to the surface wave temperature sensor, that is, when the RF switch 12 connects the power amplifier and the surface acoustic wave temperature sensor 13, the RF switch 12 turns off the surface acoustic wave temperature sensor 13 and the low-noise amplifier circuit 14, and the local oscillation frequency signal is transmitted to the surface acoustic wave temperature sensor 13 through the antenna. The surface acoustic wave temperature sensor 13 converts electrical energy into mechanical energy under the action of the inverse piezoelectric effect, and excites surface acoustic waves on the piezoelectric substrate through the interdigital transducer; then, when the RF switch 12 connects the surface acoustic wave temperature sensor 13 and the low-noise amplifier circuit 14, the RF switch 12 turns off the power amplifier and the surface acoustic wave temperature sensor 13, and the surface acoustic wave temperature sensor 13 converts mechanical energy into electrical energy under the action of the piezoelectric effect, and excites an echo signal with the same frequency as the surface acoustic wave through the interdigital transducer.

[0057] like Figure 2 and Figure 4 As shown, the low-noise amplifier circuit 14 is connected to the RF switch 12, and is used to amplify the echo signal. In this embodiment, the low-noise amplifier circuit 14 includes a first low-noise amplifier 141, a second low-noise amplifier 142 and a VGA signal amplifier 143 connected in series. The present invention amplifies the echo signal by two low-noise amplifiers connected in series and a VGA signal amplifier, which can ensure that the echo signal is effectively amplified while having lower noise and improving the accuracy of the signal.

[0058] like Figure 2 and Figure 4 As shown, the mixer 15 is connected to the low noise amplifier and is used to perform down-conversion processing on the echo signal based on the local oscillation frequency signal to obtain an intermediate frequency signal.

[0059] In this embodiment, the mixer 15 is a down-conversion mixer, which is used to obtain the intermediate frequency signal by acquiring the difference between the local oscillation frequency signal and the echo signal. Figure 5 A schematic diagram showing a signal waveform of an intermediate frequency signal (Output) obtained by the difference between the local oscillator frequency signal (LO) and the echo signal (Input).

[0060] As an example, the frequency of the intermediate frequency signal is less than or equal to 2MHz. Specifically, in the present embodiment, the frequency of the intermediate frequency signal is 1 to 2MHz. Since the frequency of the above-mentioned echo signal will change with the change of parameters such as temperature, and since its frequency is relatively high, the dynamic range of the frequency is too large, resulting in the traditional detection system having very high requirements on the design of the filter and amplifier of the echo signal in the receiving part of the reader, and it is difficult to make the receiving sensitivity of the receiving end uniform in the entire band, which makes the temperature measurement effect less accurate. The present invention introduces a mixer down-conversion process to convert an unknown input signal with a large dynamic range into an intermediate frequency signal with a small dynamic range, which makes it easier to perform subsequent operations such as amplification and filtering, thereby effectively solving the problem of uneven sensitivity of the surface acoustic wave temperature reader in receiving signals of different frequencies.

[0061] like Figure 2 and Figure 4 As shown, the filter 16 is connected to the mixer 15 and is used to filter the intermediate frequency signal. As an example, the filter 16 is a low-pass filter.

[0062] like Figure 2 and Figure 4 As shown, the analog-to-digital converter 17 is connected to the filter 16 and is used to sample the intermediate frequency signal and convert it into a digital signal.

[0063] The sampling frequency of the analog-to-digital converter 17 is greater than or equal to 5 MHz, and further, the sampling frequency of the analog-to-digital converter 17 can be about 5 MHz. The signal sampling rate of the analog-to-digital converter 17 of the present invention only needs to cover the entire bandwidth range for the intermediate frequency signal, and can realize the signal reception of the surface acoustic wave temperature sensor 13 of multiple frequencies without frequency scanning, thereby greatly simplifying the circuit design.

[0064] like Figure 2 As shown, the fast Fourier transformer 18 is connected to the digital-to-analog converter and is used to perform fast Fourier transform on the digital signal to obtain the frequency of the intermediate frequency signal.

[0065] like Figure 2 As shown, the processor 19 is connected to the fast Fourier transformer 18 and is used to obtain a corresponding temperature value according to the frequency of the intermediate frequency signal.

[0066] As an example, the processor 19 obtains the final temperature value by querying a frequency-temperature curve or a frequency-temperature table according to the frequency of the intermediate frequency signal. Figure 6The frequency-temperature curve diagram of this embodiment is shown. From the curve, it can be seen that after obtaining the frequency of the intermediate frequency signal, it is only necessary to directly substitute it into the curve to obtain the temperature value corresponding to the frequency of the intermediate frequency signal.

[0067] As described above, the temperature detection device based on the surface acoustic wave temperature sensor of the present invention has the following beneficial effects:

[0068] The present invention converts an unknown input signal with a large dynamic range into an intermediate frequency signal with a small dynamic range by introducing a mixer down-conversion process, which makes it easier to perform subsequent operations such as amplification and filtering, and solves the problem of uneven sensitivity of the surface acoustic wave temperature reader in receiving signals at different frequencies. The temperature detection device of the present invention can analyze the subsequent intermediate frequency signal more specifically, and compared with the current "sweep frequency" solution, the receiving effect of the entire temperature detection device on the overall frequency band is more consistent, and a receiving signal with better sensitivity can be obtained, and finally a more accurate temperature measurement effect is obtained.

[0069] Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0070] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A temperature detection device based on a surface acoustic wave temperature sensor, characterized in that: The detection device comprises: A signal source, used for generating a local oscillation frequency signal corresponding to the surface acoustic wave temperature measurement sensor; A power amplifier, connected to the signal source, for amplifying the local oscillation frequency signal; A radio frequency switch, connected to the power amplifier, for sending the amplified local oscillation frequency signal to the surface wave temperature sensor to generate an echo signal, and receiving the echo signal through the radio frequency switch; A low-noise amplifier circuit, connected to the radio frequency switch, for amplifying the echo signal; A mixer, connected to the low-noise amplifier circuit, for performing down-conversion processing on the echo signal based on the local oscillation frequency signal to obtain an intermediate frequency signal; A filter, connected to the mixer, for filtering the intermediate frequency signal; An analog-to-digital converter, connected to the filter, for sampling the intermediate frequency signal and converting it into a digital signal; A fast Fourier transformer, connected to the analog-to-digital converter, for performing a fast Fourier transform on the digital signal to obtain the frequency of the intermediate frequency signal; A processor, connected to the fast Fourier transformer, for obtaining a corresponding temperature value according to the frequency of the intermediate frequency signal; The signal source includes a phase-locked loop, a one-way switch and a band-pass filter, wherein the phase-locked loop is used to generate a local oscillation frequency signal, the one-way switch is used to output the local oscillation frequency signal, and the band-pass filter is used to filter the local oscillation frequency signal; The local oscillator frequency signal is between 420MHz and 450MHz; The surface acoustic wave temperature sensor comprises a piezoelectric substrate, an interdigital transducer located on the piezoelectric substrate, and two sets of reflection gratings symmetrically distributed on both sides of the interdigital transducer, wherein the interdigital transducer and the reflection grating form a resonant cavity, so that the surface acoustic wave temperature sensor only responds to a radio frequency signal of a specific frequency; When the radio frequency switch sends the local oscillation frequency signal to the surface wave temperature measurement sensor, the local oscillation frequency signal is transmitted to the surface acoustic wave temperature measurement sensor through the antenna, and the surface acoustic wave temperature measurement sensor converts electrical energy into mechanical energy under the action of the inverse piezoelectric effect, and excites surface acoustic waves on the piezoelectric substrate through the interdigital transducer; then, the surface acoustic wave temperature measurement sensor converts mechanical energy into electrical energy under the action of the piezoelectric effect, and excites an echo signal with the same frequency as the surface acoustic wave through the interdigital transducer; The radio frequency switch is a single-pole double-throw switch; The mixer is a down-conversion mixer, which is used to obtain the intermediate frequency signal by acquiring the difference between the local oscillation frequency signal and the echo signal; The low noise amplifier circuit comprises two low noise amplifiers and a VGA signal amplifier connected in series in sequence; The frequency of the intermediate frequency signal is less than or equal to 2 MHz, and the sampling frequency of the analog-to-digital converter is greater than or equal to 5 MHz; The processor obtains a final temperature value by querying a frequency-temperature curve or a frequency-temperature table according to the frequency of the intermediate frequency signal.

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