Microwave temperature measurement system and microwave temperature measurement method

Abstract

The present application discloses a microwave temperature measurement system and a microwave temperature measurement method thereof. The microwave temperature measurement system includes: a controller, a microwave cavity calibration unit, a temperature sensor connected in sequence, a multi-channel switch, a signal amplification unit, a signal processing unit, and a signal acquisition unit. The temperature sensor for generating and outputting microwave signals is placed in the same test environment as the system to be measured, and the temperature sensor includes multiple microwave resonant cavities with different resonant frequencies. The multi-channel switch is placed in a preset temperature environment. The microwave cavity calibration unit is electrically connected to the multi-channel switch and is used to perform calibration processing to obtain resonant cavity parameters and system gain coefficients. The controller is electrically connected to the microwave cavity calibration unit and the signal acquisition unit, respectively, and is configured to determine a first absolute temperature value based on power, resonant cavity parameters, and system gain coefficients, wherein the first absolute temperature value is the absolute temperature value of the test environment in which the system to be measured is located. The solution of the present application can achieve accurate temperature measurement in extreme environments.

Description

Technical Field

[0001] The present application relates to the field of quantum precision measurement technology, and in particular to a microwave temperature measurement system and a microwave temperature measurement method thereof. Background Art

[0002] With the development and advancement of science and technology, more and more scientific research requires precise measurement of experimental environment temperature, and there is a desire to establish low-temperature standards to measure extremely low temperatures. Many scientific research activities are conducted in extreme environments, often facing harsh conditions such as strong magnetic and electric fields, confined spaces for temperature measurement, and extremely low temperatures that are sensitive to noise. Measuring temperature in these extreme environments is of paramount importance.

[0003] In the related art, based on the resistance-temperature characteristics exhibited by different resistor materials, a small excitation current is applied to the resistor to measure the resistance value, thereby calibrating the corresponding temperature value. When using a resistance sensor, the use of an additional excitation current will cause thermal excitation, resulting in temperature measurement errors; and the resistance sensor must be compared and calibrated with a calibrated calibration source before it can be put into use, and its measurement accuracy depends on the calibration source; and the sensitivity of the resistance sensor working in different temperature zones is inconsistent, and there is an optimal temperature measurement range. In addition, based on the adaptability of different materials and the difference in temperature zone curves, in a large temperature range from high temperature to extremely low temperature, or in special environments such as magnetic fields and electric fields, it is usually necessary to replace different resistance sensors to meet the requirements. However, in extremely low temperature environments with magnetic fields, there is currently no effective and feasible temperature measurement system. Summary of the Invention

[0004] The embodiments of the present application provide a microwave temperature measurement system and a microwave temperature measurement method thereof, which can achieve accurate temperature measurement in extreme environments.

[0005] In a first aspect, an embodiment of the present application provides a microwave temperature measurement system, comprising:

[0006] A temperature sensor placed in the same test environment as the system to be tested; the temperature sensor includes a plurality of microwave resonant cavities with different resonant frequencies; the temperature sensor is used to generate and output microwave signals;

[0007] a multi-channel switch, which is in a preset temperature environment and is electrically connected to the temperature sensor, and is used to select different microwave resonant cavities;

[0008] a signal amplifying unit, wherein an input end of the signal amplifying unit is electrically connected to the multi-channel switch; the signal amplifying unit is used to amplify the microwave signal;

[0009] a signal processing unit, wherein the input end of the signal processing unit is connected to the output end of the signal amplifying unit; the signal processing unit is used to perform signal processing on the amplified microwave signal;

[0010] A signal acquisition unit, wherein the input end of the signal acquisition unit is connected to the output end of the signal processing unit; the signal acquisition unit is used to measure the power of the microwave signal after amplification and signal processing;

[0011] a microwave cavity calibration unit, electrically connected to the multi-channel switch; the microwave cavity calibration unit is used to perform a first calibration process to obtain the cavity parameters of the microwave cavity, and to perform a second calibration process to obtain the system gain coefficient of the microwave temperature measurement system;

[0012] A controller is electrically connected to the microwave cavity calibration unit and the signal acquisition unit, respectively; the controller is configured to perform signal temperature conversion processing and differential differentiation processing according to the power, the resonant cavity parameters, and the system gain coefficient to determine a first absolute temperature value, wherein the first absolute temperature value is the absolute temperature value of the environment to be measured in which the system to be measured is located.

[0013] According to some embodiments of the present application, the microwave temperature measurement system further includes: a microwave circulator; a first end of the microwave circulator is connected to the multi-channel switch, a second end of the microwave circulator is connected to the input end of the signal amplification unit, and a third end of the microwave circulator is connected to the microwave cavity calibration unit; the microwave circulator is used to conduct the line between the multi-channel switch and the signal amplification unit in a first working state, and to conduct the line between the multi-channel switch and the microwave cavity calibration unit in a second working state.

[0014] According to some embodiments of the present application, the microwave cavity calibration unit includes: a first microwave signal source, a first switch and a microwave analyzer; the first switch is connected between the output end of the first microwave signal source and the microwave circulator; the input end of the microwave analyzer is connected to the microwave circulator, and the output end of the microwave analyzer is electrically connected to the controller.

[0015] According to some embodiments of the present application, the signal amplification unit includes: a low-temperature low-noise amplifier group in a preset temperature environment, and a room-temperature low-noise amplifier group in a room-temperature environment;

[0016] The input end of the low-temperature low-noise amplifier group is electrically connected to the microwave circulator;

[0017] The output end of the low-temperature low-noise amplifier group is electrically connected to the input end of the room-temperature low-noise amplifier group;

[0018] The output end of the room temperature low noise amplifier group is electrically connected to the input end of the signal processing unit.

[0019] According to some embodiments of the present application, the signal processing unit includes: a signal down-conversion unit and a signal noise reduction filtering unit connected in sequence.

[0020] According to some embodiments of the present application, the signal down-conversion unit includes: a mixer and a second microwave signal source; the first input end of the mixer is connected to the output end of the signal amplification unit, the second input end of the mixer is connected to the output end of the second microwave signal source, and the output end of the mixer is connected to the input end of the signal noise reduction filtering unit.

[0021] According to some embodiments of the present application, the signal noise reduction filtering unit includes: a low-pass filter, a low-frequency band low-noise amplifier, a first band-pass filter, and a high-pass filter connected in sequence.

[0022] In a second aspect, an embodiment of the present application provides a microwave temperature measurement method for a microwave temperature measurement system, which is applied to the microwave temperature measurement system as described in the first aspect. The method includes:

[0023] After the microwave resonant cavity of the temperature sensor is selected by the multi-channel switch, the temperature sensor is made to output the generated microwave signal; after passing through the multi-channel switch, the signal amplification unit, and the signal processing unit, the power of the microwave signal is collected by the signal collection unit;

[0024] The controller performs signal-temperature conversion processing based on the power of the microwave signal and a preset signal-temperature conversion formula to obtain a signal power-temperature curve of the microwave resonant cavity; wherein the signal-temperature conversion formula includes resonant cavity parameters and a system gain coefficient; the resonant cavity parameters and the system gain coefficient are obtained after a first calibration process and a second calibration process of the microwave cavity calibration unit, respectively;

[0025] After selecting different microwave resonant cavities by the multi-channel switch, a signal power-temperature curve of each microwave resonant cavity in the temperature sensor is obtained;

[0026] Converting the signal power-temperature curve to obtain a cavity mode signal-temperature curve;

[0027] arbitrarily selecting a first curve, a second curve, a third curve, and a fourth curve from the plurality of cavity mode signal-temperature curves;

[0028] Performing differential processing on the first curve and the second curve to determine a first absolute temperature value; performing differential processing on the third curve and the fourth curve to determine a second absolute temperature value;

[0029] Obtain a first error value between the first absolute temperature value and the second absolute temperature value. When the first error value is less than or equal to a preset threshold, determine that the first absolute temperature value and the second absolute temperature value are equal, and the first absolute temperature value is the absolute temperature value of the test environment in which the system to be tested is located.

[0030] According to some embodiments of the present application, performing differential processing on the first curve and the second curve to obtain a first differential curve includes:

[0031] performing a difference operation on the first curve and the second curve to obtain a first difference curve;

[0032] performing a differential operation on the first differential curve to obtain a first differential curve;

[0033] A first temperature marker point is determined according to a first maximum value of the first differential curve, and the corresponding first absolute temperature value is determined according to the first temperature marker point.

[0034] According to some embodiments of the present application, after obtaining the error value between the first absolute temperature value and the second absolute temperature value, the microwave temperature measurement method further includes:

[0035] When the first error value is greater than a preset threshold, reselecting the fifth curve, the sixth curve, the seventh curve, and the eighth curve from the plurality of signal power-temperature curves;

[0036] performing differential processing on the fifth curve and the sixth curve to determine a third absolute temperature value; performing differential processing on the seventh curve and the eighth curve to determine a fourth absolute temperature value;

[0037] Obtain a second error value between the third absolute temperature value and the fourth absolute temperature value. When the second error value is less than or equal to a preset threshold, determine that the third absolute temperature value is equal to the fourth absolute temperature value and that the third absolute temperature value is the absolute temperature value of the test environment in which the system to be tested is located.

[0038] According to some embodiments of the present application, the first calibration process performed by the microwave cavity calibration unit includes:

[0039] closing the first switch to connect the output end of the first microwave signal source to the microwave circulator;

[0040] Selecting a microwave resonant cavity by the multi-channel switch;

[0041] generating and outputting a second test signal by the first microwave signal source, wherein the second test signal passes through the microwave circulator and the multi-channel switch and then enters the selected microwave resonant cavity;

[0042] A reflected signal of the second test signal is obtained through reflection by the microwave resonant cavity, and the reflected signal is collected by the microwave analyzer after passing through the microwave circulator and the multi-channel switch;

[0043] The collected reflection signal is analyzed by a microwave analyzer to obtain resonance cavity parameters, and the resonance cavity parameters are output to the controller; the resonance cavity parameters include: resonance frequency, loaded quality factor value, and external quality factor value.

[0044] According to some embodiments of the present application, the method further includes: performing the second calibration process on the microwave temperature measurement system by the microwave cavity calibration unit to obtain a system gain coefficient of the microwave temperature measurement system.

[0045] The embodiment of the present application includes: a microwave temperature measurement system including: a controller, a microwave cavity calibration unit, a temperature sensor connected in sequence, a multi-channel switch, a signal amplification unit, a signal processing unit, and a signal acquisition unit; the temperature sensor includes multiple microwave resonant cavities with different resonant frequencies; the multi-channel switch is in a preset temperature environment and is electrically connected to the temperature sensor; the microwave cavity calibration unit is electrically connected to the multi-channel switch. When the microwave temperature measurement system is in operation, after the microwave resonant cavity of the temperature sensor is selected by the multi-channel switch, the temperature sensor outputs the generated microwave signal; the microwave signal is transmitted through the multi-channel switch and enters the signal amplification unit, and is amplified and processed by the signal amplification unit to obtain an amplified microwave signal; the amplified microwave signal is output to the signal processing unit, and the signal processing unit outputs the amplified and signal-processed microwave signal to the signal acquisition unit; the signal acquisition unit collects the power of the amplified and signal-processed microwave signal. Based on the Bose-Einstein distribution principle, the microwave resonator in the temperature sensor is excited to generate a microwave signal. When under the same temperature environment, the power of the microwave signal generated by the microwave resonant cavity with different resonant frequencies is also different; and for the same microwave resonator, the power of the microwave signal it generates reflects the relative temperature of the environment to be measured; the greater the power of the microwave signal generated, the higher the relative temperature of the environment to be measured, and conversely, the smaller the power of the microwave signal generated, the lower the relative temperature of the environment to be measured. When determining the absolute temperature of the environment to be measured, in addition to collecting the power of the microwave signal, it is also necessary to perform a first calibration process through the microwave cavity calibration unit to obtain the resonant cavity parameters of the microwave resonant cavity, and perform a second calibration process to obtain the system gain coefficient of the microwave temperature measurement system. Among them, the resonant cavity parameters reflect the physical properties of the microwave resonant cavity, which will affect the power of the generated microwave signal. The resonant cavity parameters of the microwave resonant cavity will not be affected by external factors such as magnetic fields and low temperatures. Therefore, the microwave temperature measurement system of the present application can operate under extreme environmental conditions such as strong magnetic fields and extremely low temperatures. In addition, the system gain coefficient reflects the amplification performance of the constructed microwave temperature measurement system, and this amplification performance will affect the power of the collected microwave signal. The controller is configured to perform signal temperature conversion processing and differential differentiation processing based on the power, resonant cavity parameters, and system gain coefficient to determine the first absolute temperature value of the environment to be measured. The first absolute temperature value is the absolute temperature value of the environment to be measured in which the system to be measured is located. In summary, in the embodiment of the present application, no excitation current is applied to the temperature measurement environment during the entire microwave temperature measurement process, and the temperature of the environment to be measured is not affected; accurate temperature measurement is achieved in extreme environments. Therefore, the embodiment of the present application can achieve accurate temperature measurement in extreme environments without introducing an excitation current and without relying on a calibration source.

[0046] Other features and advantages of the invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained through the structures particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a schematic diagram of the system architecture of a temperature measurement system provided by an embodiment of the present application;

[0048] Figure 2 This is a schematic diagram of the specific structure of a temperature measurement system provided by an embodiment of the present application;

[0049] Figure 3 This is a schematic diagram of the specific structure of a temperature measurement system when the signal processing unit provided by another embodiment of the present application is a heterodyne measurement loop;

[0050] Figure 4 This is a schematic diagram of the specific structure of a temperature sensor provided by an embodiment of the present application;

[0051] Figure 5 This is a flow chart of a microwave temperature measurement method provided by an embodiment of the present application;

[0052] Figure 6 is a schematic diagram of a cavity mode signal-temperature curve provided by an embodiment of the present application;

[0053] Figure 7 is a schematic diagram of a differential curve after differential processing provided by an embodiment of the present application;

[0054] Figure 8 This is a schematic diagram of the overall process of a microwave temperature measurement method provided by an embodiment of the present application;

[0055] Figure 9 Schematic diagram of a system sensitivity curve of a microwave temperature measurement system provided in one embodiment of the present application. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solutions and advantages of this application more clear, this application is further described in detail below with reference to the accompanying drawings and embodiments.

[0057] It should be noted that although a logical order is shown in the flowchart in the description of this application, in some cases, the steps shown or described may be performed in an order different from that in the flowchart. In the description of this application, "several" means one or more, and "more" means two or more. The description of "first" and "second" is only used to distinguish technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein are for the purpose of describing the embodiments of this application only and are not intended to limit this application.

[0059] With the development and advancement of science and technology, more and more scientific research requires precise measurement of experimental environment temperature, and there is a desire to establish low-temperature standards to measure extremely low temperatures. Many scientific research activities are conducted in extreme environments, often facing harsh conditions such as strong magnetic and electric fields, confined spaces for temperature measurement, and extremely low temperatures that are sensitive to noise. Measuring temperature in these extreme environments is of paramount importance.

[0060] In related technologies, based on the resistance-temperature characteristics exhibited by different resistor materials, a small excitation current is applied to the resistor to measure the resistance value and thus calibrate the corresponding temperature value. Ruthenium oxide and germanium thermometers are the only temperature sensors that can be used below 100mK, while the lowest temperature measurement value of platinum thermometers is 14K, the lowest temperature measurement value of gallium aluminum arsenide diode thermometers is 1.4K, and the lowest temperature measurement value of silicon diode thermometers is 3K. Using an additional excitation current when using a resistance sensor introduces thermal noise, which can cause errors. Furthermore, the resistance sensor must be calibrated with a calibrated calibration source before use, and its measurement accuracy depends on the calibration source. Furthermore, the sensitivity of the resistance sensor varies across different temperature zones, resulting in an optimal temperature measurement range. Furthermore, due to the different adaptability of different materials and their different temperature zone curves, different resistance sensors are often required to adapt to wide temperature ranges, from high to very low temperatures, or in special environments such as those with magnetic and electric fields. Currently, there is no effective and feasible temperature measurement system for very low temperatures (less than 100mK) in the presence of magnetic fields.

[0061] Based on this, the present application provides a microwave temperature measurement system and a microwave temperature measurement method thereof, the microwave temperature measurement system comprising: a controller, a microwave cavity calibration unit, a temperature sensor connected in sequence, a multi-channel switch, a signal amplification unit, a signal processing unit, and a signal acquisition unit; the temperature sensor for generating and outputting a microwave signal is placed in the same test environment as the system to be measured, and the temperature sensor includes multiple microwave resonant cavities with different resonant frequencies; the multi-channel switch is in a preset temperature environment; the microwave cavity calibration unit is electrically connected to the multi-channel switch and is used to perform calibration processing to obtain resonant cavity parameters and system gain coefficients; the controller is electrically connected to the microwave cavity calibration unit and the signal acquisition unit, respectively, and is configured to determine a first absolute temperature value based on power, resonant cavity parameters, and system gain coefficients, wherein the first absolute temperature value is the absolute temperature value of the test environment in which the system to be measured is located. The solution of the present application can achieve accurate temperature measurement in extreme environments.

[0062] The embodiments of the present application are further described below with reference to the accompanying drawings.

[0063] like Figure 1 As shown, in the first aspect, an embodiment of the present application provides a microwave temperature measurement system 100, including: a controller 170, a microwave cavity calibration unit 130, a temperature sensor 110 connected in sequence, a multi-channel switch K0, a signal amplification unit 140, a signal processing unit 150, and a signal acquisition unit 160; wherein, the temperature sensor 110 includes multiple microwave resonant cavities and is placed in the same test environment as the system to be measured; the multi-channel switch K0 is in a preset temperature environment; the microwave cavity calibration unit 130 is connected to the multi-channel switch K0; and the controller 170 is electrically connected to the microwave cavity calibration unit 130 and the signal acquisition unit 160, respectively.

[0064] The temperature sensor 110 and the system to be measured are placed in the same environment to be measured; the temperature sensor 110 includes a plurality of microwave resonant cavities with different resonance frequencies; and the temperature sensor 110 is used to generate and output microwave signals.

[0065] The multi-channel switch K0 is in a preset temperature environment and is electrically connected to the temperature sensor 110 ; the multi-channel switch K0 is used to select different microwave resonant cavities.

[0066] The signal amplifying unit 140 has an input end electrically connected to the multi-channel switch K0 ; the signal amplifying unit 140 is used to amplify the microwave signal.

[0067] The signal processing unit 150 has an input end connected to the output end of the signal amplifying unit 140 ; ​​the signal processing unit 150 is used to perform signal processing on the amplified microwave signal.

[0068] The signal acquisition unit 160 has an input end connected to the output end of the signal amplification unit 140 ; ​​the signal acquisition unit 160 is used to measure the power of the amplified microwave signal.

[0069] The microwave cavity calibration unit 130 is electrically connected to the multi-channel switch K0 and is used to perform a first calibration process to obtain the cavity parameters of the microwave cavity and to perform a second calibration process to obtain the system gain coefficient of the microwave temperature measurement system 100 .

[0070] Controller 170 is electrically connected to microwave cavity calibration unit 130 and signal acquisition unit 160. Controller 170 is configured to perform signal-to-temperature conversion and differential processing based on power, resonant cavity parameters, and system gain coefficients to determine a first absolute temperature value, where the first absolute temperature value is the absolute temperature value of the environment under test in which the system under test is located.

[0071] Combine Figure 2 According to some embodiments of the present application, the microwave temperature measurement system 100 further includes a microwave circulator 120. A first end of the microwave circulator 120 is connected to the multi-channel switch K0, a second end of the microwave circulator 120 is connected to the input end of the signal amplification unit 140, and a third end of the microwave circulator 120 is connected to the microwave cavity calibration unit 130. Microwave circulator 120 is configured to conduct a circuit between the multi-channel switch K0 and the signal amplification unit 140 in a first operating state and to conduct a circuit between the multi-channel switch K0 and the microwave cavity calibration unit 130 in a second operating state.

[0072] It should be noted that by providing the microwave circulator 120 before the low-temperature low-noise amplifier group 141 of the signal amplifying unit 140 , noise can be reduced and the pre-low-noise amplifier can be protected.

[0073] It should be noted that temperature sensor 110 is a measuring probe. It has a microwave resonant cavity structure, or a microcavity structure in a small space. Temperature sensor 110 includes multiple microwave resonant cavities with different resonant frequencies. Signals from different microwave resonant cavities can be selectively routed to other components via a microwave switch.

[0074] When the microwave cavity is made of suitable materials, such as oxygen-free copper, its resonant frequency and quality factor will not be affected by the external magnetic field. Therefore, the microwave temperature measurement system 100 can operate in a strong magnetic field environment. Similarly, the microwave temperature measurement system 100 can also operate in other extreme environments.

[0075] It should be noted that the microwave resonant cavity can be a three-dimensional cavity, an on-chip microstrip cavity, etc.; therefore, the present application does not impose any specific restrictions on the form of the microwave resonant cavity.

[0076] It should be noted that when building the microwave temperature measurement system 100, the existing small microstrip cavity can be used to obtain a deterministic resonant frequency value, and then the back-end connected microwave isolator, low-noise amplifier, and low-pass, band-pass, and high-pass microwave filter devices containing the resonant frequency value can be built according to the determined resonant frequency value.

[0077] For example, Figure 4 As shown, a microstrip cavity in a micro cavity is taken as an example as a schematic diagram of the temperature sensor 110. Figure 4 In the microcavity structure shown, each vertical stripe is a microcavity, while the horizontal stripe is a waveguide antenna for signal coupling. A microcavity is a miniature microwave resonant cavity, typically a planar cavity structure with dimensions ranging from micrometers to millimeters. Using smaller microcavity structures facilitates measurement in confined spaces, expanding temperature measurement applications.

[0078] It should be noted that the multi-channel switch K0 is located in a preset temperature environment. The lower the ambient temperature of the multi-channel switch K0, the greater the noise introduced into the temperature measurement system and the more likely it is to cause temperature changes in the temperature measurement system itself. Therefore, in practice, the multi-channel switch K0 is placed in a relatively low-temperature environment that is thermally isolated from the temperature measurement environment. Specifically, the preset temperature environment is a low-temperature environment in the 4K range, and its thermal conductivity must be fully considered during installation. The multi-channel switch K0 is used to select the microwave resonant cavity and collect the microwave signals generated by the microwave resonators in the multiple temperature measurement sensors 110 one by one.

[0079] In some embodiments, the signal acquisition unit 160 includes one of the following: a spectrum analyzer, an AC signal acquisition card, and a logarithmic detector. Therefore, this application does not impose any specific restrictions on the implementation of the signal acquisition unit 160.

[0080] In the microwave temperature measurement system 100 provided by the embodiment of the present invention, when the microwave temperature measurement system 100 is in operation, the microwave resonant cavity of the temperature sensor 110 is selected via the multi-channel switch K0, and the temperature sensor 110 outputs a generated microwave signal. The microwave signal then passes through the multi-channel switch K0 and enters the signal amplification unit 140, where it undergoes amplification processing to produce an amplified microwave signal. The amplified microwave signal is then output to the signal processing unit 150, which then outputs the amplified and processed microwave signal to the signal acquisition unit 160. The signal acquisition unit 160 collects the power of the amplified and processed microwave signal. Based on the Bose-Einstein distribution principle, the microwave resonator in the temperature sensor 110 is excited to generate a microwave signal. Under the same temperature environment, microwave resonant cavities with different resonant frequencies generate microwave signals with different powers. For the same microwave resonator, the power of the microwave signal reflects the relative humidity of the environment being measured. The greater the power of the generated microwave signal, the higher the relative humidity of the environment being measured. Conversely, the smaller the power of the generated microwave signal, the lower the relative humidity of the environment being measured. To determine the absolute temperature of the measured environment, in addition to collecting the power of the microwave signal, the microwave cavity calibration unit 130 must also perform a first calibration process to obtain the cavity parameters of the microwave resonant cavity and a second calibration process to obtain the system gain coefficient of the microwave temperature measurement system. The cavity parameters reflect the physical properties of the microwave resonant cavity, which affect the power of the generated microwave signal. The cavity parameters of the microwave resonant cavity are not affected by external factors such as magnetic fields and low temperatures. Therefore, the microwave temperature measurement system 100 of the present application can operate in extreme environmental conditions such as strong magnetic fields and extremely low temperatures. Furthermore, the system gain coefficient reflects the amplification performance of the microwave temperature measurement system 100, which affects the power of the collected microwave signal. The controller 170 is configured to perform signal-to-temperature conversion and differential processing based on the power, cavity parameters, and system gain coefficient to determine the first absolute temperature value of the measured environment. The first absolute temperature value is the absolute temperature value of the measured environment in which the measured system is located. In summary, the embodiments of the present application do not apply an excitation current to the temperature measurement environment during the entire microwave temperature measurement process, thus not affecting the temperature of the measured environment. Accurate temperature measurement is achieved in extreme environments. Therefore, the embodiments of the present application can achieve accurate temperature measurement in extreme environments without introducing an excitation current and without relying on a calibration source.

[0081] Combine Figure 1 and Figure 2According to some embodiments of the present application, signal amplification unit 140 includes: a low-temperature low-noise amplifier group 141 in a 4K environment; and a room-temperature low-noise amplifier group 142 in a room-temperature environment. The input of low-temperature low-noise amplifier group 141 is electrically connected to microwave circulator 120; the output of low-temperature low-noise amplifier group 141 is electrically connected to the input of room-temperature low-noise amplifier group 142; and the output of room-temperature low-noise amplifier group 142 is electrically connected to the input of a signal processing unit. Signal amplification unit 140, including low-temperature low-noise amplifier group 141 and room-temperature low-noise amplifier group 142, can amplify the final detection signal and improve its signal-to-noise ratio.

[0082] In some embodiments, the low-temperature low-noise amplifier group 141 is in a preset temperature environment together with the multi-channel switch K0. Specifically, the preset temperature environment is a low-temperature environment in the 4K range. In a low-temperature environment in the 4K range. When installing the low-temperature low-noise amplifier group 141, its thermal conductivity needs to be fully considered. Therefore, installing a microwave circulator 120 after the temperature sensor 110 and before the low-temperature low-noise amplifier group 141 can reduce noise and protect the pre-low noise amplifier. Since the low-temperature low-noise amplifier group 141 can be placed outside the temperature system to be measured, this measurement method will not increase the heat load on the temperature system to be measured.

[0083] Specifically, if Figure 3 As shown, the room temperature low noise amplifier group 142 includes: an isolator group, two two-stage cascaded high gain low noise amplifiers, and a high frequency band pass filter connected in sequence; wherein the isolator group includes two microwave isolators.

[0084] It should be noted that the low-noise amplifier is used to amplify the cavity mode signal, the microwave signal, the isolator group is used to suppress noise, and the high-frequency bandpass filter is used for filtering. The room-temperature low-noise amplifier group 142 can amplify the microwave field signal of the microwave resonant cavity and improve the signal-to-noise ratio before down-conversion.

[0085] In some embodiments, the microwave isolator may be a microwave aperture or a microwave circulator; therefore, the present application does not impose any specific limitation on the type of microwave isolator used.

[0086] like Figure 2 As shown, according to some embodiments of the present application, the microwave temperature measurement system 100 further includes: a direct measurement loop 152 ; a high-bandwidth measurement instrument 1521 is provided on the direct measurement loop 152 .

[0087] It can be understood that after the signal amplification unit 140 amplifies the input microwave signal, it outputs the amplified microwave signal to the direct measurement circuit 152, and directly measures the bandwidth of the output signal of the signal amplification unit 140 (i.e., the amplified microwave signal) through the high-bandwidth measuring instrument 1521.

[0088] According to some embodiments of the present application, Figure 2 As shown, the signal processing unit 150 includes: a signal down-conversion unit 1511 and a signal noise reduction filtering unit 1512 connected in sequence.

[0089] It can be understood that a heterodyne measurement circuit 151 is formed by the signal down-conversion unit 1511 and the signal noise reduction filter unit 1512; by utilizing the heterodyne measurement circuit 151 including the signal down-conversion unit 1511 and the signal noise reduction filter unit 1512, the microwave signal frequency obtained by heterodyne down-conversion detection can be used to reduce the system construction cost and further amplify and reduce the noise of the low-frequency signal.

[0090] In some embodiments, as Figure 3 As shown, the signal down-conversion unit 1511 includes: a mixer 1511B and a second microwave signal source 1511A; the first input end of the mixer 1511B is connected to the output end of the signal amplification unit 140, the second input end of the mixer 1511B is connected to the output end of the second microwave signal source 1511A, and the output end of the mixer 1511B is connected to the input end of the signal noise reduction filter unit 1512.

[0091] It can be understood that in the signal down-conversion unit 1511, the high-frequency signal of the temperature sensor 110 is down-converted to a signal frequency within the detector bandwidth by utilizing a mixer 1511B with a suitable frequency range and a second microwave signal source 1511A that can provide adjustable frequency and power.

[0092] Specifically, the mixer 1511B is an IQ mixer. The first input terminal is the RF terminal of the IQ mixer, and the second input terminal is the LO terminal of the IQ mixer. The output terminals of the mixer 1511B include an I terminal and a Q terminal.

[0093] Specifically, the RF end of the mixer 1511B is connected to the output end of the room temperature low noise amplifier group 142 of the signal amplification unit 140, the LO end of the mixer 1511B is connected to the output end of the second microwave signal source 1511A, and the I end and Q end of the mixer 1511B are respectively connected to the input end of the signal noise reduction filter unit 1512 through a coaxial cable.

[0094] In some embodiments, the amplified high-frequency signal output by the signal amplification unit 140 is input to the mixer 1511B through the RF terminal; the second microwave signal source 1511A, which can provide adjustable frequency and power, outputs a signal to be mixed whose frequency is the sum of the high-frequency signal frequency and the down-conversion frequency, and is input to the mixer 1511B through the LO terminal; after the mixer 1511B mixes the input high-frequency signal and the signal to be mixed, it outputs a first down-conversion signal from the I terminal of the mixer 1511B and outputs a second down-conversion signal from the Q terminal; wherein, the second down-conversion signal output from the Q terminal and the first down-conversion signal output from the I terminal have a signal phase difference of 90 degrees.

[0095] like Figure 3 As shown, signal noise reduction filter unit 1512 includes: a low-pass filter, a low-frequency low-noise amplifier, a first band-pass filter, and a high-pass filter, connected in sequence. In this application, signal noise reduction filter unit 1512 specifically refers to the low-noise amplifier and low-pass filter components for the down-converted signal. The noise reduction filtering processing performed by signal noise reduction filter unit 1512 can improve the signal-to-noise ratio of the down-converted signal.

[0096] In some embodiments, the signal acquisition unit 160 further includes a second bandpass filter having an intermediate frequency (IF) as the down-conversion frequency and a passband corresponding to the 3dB bandwidth of the down-converted signal; the output of the second bandpass filter is connected to the input of a signal acquisition instrument, such as an AC signal acquisition card with logarithmic detection.

[0097] It can be understood that, in the heterodyne measurement loop 151 , the signal down-conversion unit 1511 , the signal noise reduction filter unit 1512 and the signal acquisition unit 160 are equivalent to a small signal receiver system.

[0098] like Figure 2 As shown, in some embodiments, a direct measurement circuit 152 and a heterodyne measurement circuit 151 can be simultaneously provided in a microwave temperature measurement system 100, with the direct measurement circuit 152 and the heterodyne measurement circuit 151 connected in parallel. A second switch K2 is provided between the direct measurement circuit 152 and the signal amplification unit 140, and a third switch K3 is provided between the heterodyne measurement circuit 151 and the signal amplification unit 140. Both the second switch K2 and the third switch K3 are connected to a controller 170. The second switch K2 is configured to be closed or opened under the control of the controller 170, thereby controlling the access to the direct measurement circuit 152. The third switch K3 is configured to be closed or opened under the control of the controller 170, thereby controlling the access to the heterodyne measurement circuit 151. By controlling the on / off of the second switch K2 and the third switch K3, either the direct measurement circuit 152 or the heterodyne measurement circuit 151 can be selected for microwave temperature measurement. The measurement circuit can be flexibly selected and switched according to actual measurement requirements, thereby improving the flexibility of the microwave temperature measurement system 100.

[0099] For example, when the direct measurement loop 152 needs to be selected to participate in microwave temperature measurement, the second switch K2 is controlled to be closed and the third switch K3 is controlled to be open, so that the signal amplification unit 140 is connected to the direct measurement loop 152 .

[0100] For example, when the heterodyne measurement circuit 151 is required to participate in microwave temperature measurement, the third switch K3 is controlled to be closed and the second switch K2 is controlled to be open, so that the signal amplification unit 140 is connected to the heterodyne measurement circuit 151 .

[0101] It should be emphasized that for strong signals, a heterodyne measurement circuit 151 can be selected and measured using a small signal receiver system; for weak signals at the quantum level, a microwave single photon detector can be used for measurement.

[0102] It is understandable that, in one embodiment, in a microwave temperature measurement system 100 , the direct measurement circuit 152 may be used alone for measurement without additionally providing a heterodyne measurement circuit 151 .

[0103] In another embodiment, a microwave temperature measurement system 100 can be configured to use a single heterodyne measurement circuit 151 for measurement without providing an additional direct measurement circuit 152. After passing through the signal amplification unit 140, the microwave signal is input into the heterodyne measurement circuit 151. The high-frequency signal is converted into a low-frequency signal by the mixer 1511B, and the bandwidth of the low-frequency signal is then measured using a low-bandwidth measurement instrument.

[0104] It should be noted that, no matter whether the direct measurement circuit 152 or the heterodyne measurement circuit 151 is used, the output signals of these two measurement circuits can be collected by a signal acquisition card, and the power of the microwave signal to be measured can be obtained through data analysis.

[0105] According to some embodiments of the present application, the microwave cavity calibration unit 130 includes: a first microwave signal source 131, a first switch K1 and a microwave analyzer 132; the first switch K1 is connected between the output end of the first microwave signal source 131 and the microwave circulator 120; the input end of the microwave analyzer 132 is connected to the microwave circulator 120, and the output end of the microwave analyzer 132 is electrically connected to the controller 170.

[0106] Specifically, if Figure 2 As shown, the first switch K1 includes an active end, a first selected end and a second selected end, wherein the active end is connected to the microwave circulator 120, the first selected end is connected to the first microwave signal source 131, and the second selected end is connected to the load in the system under test.

[0107] In one embodiment, when performing the first calibration process using the microwave cavity calibration unit 130, the active end of the first switch K1 is connected to the first selected end, thereby accessing the first microwave signal source 131. A microwave signal is output by the first microwave signal source 131. After passing through the first switch K1, the microwave circulator 120, and the multi-channel switch K0, the microwave signal is input into the microwave resonant cavity selected by the multi-channel switch K0. The microwave resonant cavity reflects the input microwave signal to produce a reflected signal. After passing through the multi-channel switch K0 and the microwave circulator 120, the reflected signal enters the microwave analyzer 132. The microwave analyzer 132 analyzes and processes the reflected signal to obtain the resonant cavity parameters of the selected microwave resonant cavity. Specifically, the resonant cavity parameters include the resonant frequency and quality factor of the microwave resonant cavity. By repeating the above steps to select different microwave resonant cavities using the multi-channel switch K0, the resonant cavity parameters of each microwave resonant cavity can be obtained. It is understood that the microwave cavity calibration unit 130 can be used to obtain the parameters necessary for subsequent signal-to-temperature conversion, laying the data foundation for subsequent microwave temperature measurement.

[0108] In one embodiment, when the microwave cavity calibration unit 130 is used to perform the second calibration process, the active end of the first switch K1 is connected to the first selected end and connected to the first microwave signal source 131; a third test signal with known input power and frequency is output by the first microwave signal source 131; after the third test signal passes through the microwave circulator 120, the signal amplification unit 140 and the signal processing unit 150, the output power of the third test signal is collected by the signal acquisition unit 160; based on the output power and input power, the system gain coefficient of the microwave temperature measurement system 100 for signals of different frequencies can be obtained.

[0109] In one embodiment, the microwave temperature measurement system 100 provided in the embodiment of the present application, in addition to the microwave components and the microwave temperature measurement sensor 110, may also include cables connecting the components and a microwave attenuator (not shown) to reduce thermal noise. The microwave attenuator may be configured as needed, and the present application does not impose any specific restrictions on the specific configuration of the microwave attenuator.

[0110] In order to achieve accurate temperature measurement of a very low temperature system in extreme environments such as strong magnetic fields, strong electric fields, and small spaces, an embodiment of the present application provides a miniaturized, very low temperature, and anti-interference microwave temperature measurement system 100. The microwave temperature measurement system 100 includes: a controller 170, a microwave cavity calibration unit 130, a temperature sensor 110 connected in sequence, a multi-channel switch K0, a microwave circulator 120, a signal amplification unit 140, a signal processing unit 150, and a signal acquisition unit 160; the microwave cavity calibration unit 130 is connected to the microwave circulator 120, and the controller 170 is electrically connected to the microwave cavity calibration unit 130 and the signal acquisition unit 160 respectively.

[0111] Take an example, combined with Figure 1 、 Figure 2 and Figure 3 , the complete workflow of the hardware system of the microwave temperature measurement system 100 is described.

[0112] In an extremely low-temperature environment with or without magnetic or electric fields or in a confined space, microwave temperature sensor 110 must first be installed in the low-temperature environment to be measured, preferably on or near the sample surface. This must be connected to a high-temperature environment above 4K via a low-temperature CuNi or NbTi cable, and then to a multi-channel microwave switch. The multi-channel microwave switch is connected to microwave circulator 120, and the output of microwave circulator 120 is connected to a low-temperature, low-noise amplifier device group in a low-temperature environment within the 4K range with good heat exchange. In other words, temperature sensor 110 should be placed in the environment to be measured, multi-channel switch K0 and low-temperature, low-noise amplifier group 141 of signal amplification unit 140 should be placed in a preset temperature environment, and the small-signal receiver system should be connected via a coaxial cable and placed outside the environment to be measured.

[0113] A microwave signal is generated inside the temperature sensor 110. After passing through the multi-channel switch K0 and the signal amplification unit 140, the microwave signal is transmitted to the small signal receiver system (i.e., including: a signal down-conversion unit 1511, a signal noise reduction filter unit 1512, and a signal acquisition unit 160). The signal power detected by the small signal receiver system is used to sense the sample space temperature. Among them, the signal amplification unit 140 is used to amplify the final detection signal and improve the signal-to-noise ratio of the final detection signal. The heterodyne measurement circuit 151 mainly includes a small signal receiver system, whose main function is to use the heterodyne method to down-convert the detection signal frequency, reduce the system construction cost, and further amplify and reduce the noise of the low-frequency signal.

[0114] Specifically, the microwave signal passes through the multi-channel switch K0 and is input into the signal amplification unit 140; after passing through the low-temperature low-noise amplifier group and the room-temperature low-noise amplifier group 142 in the signal amplification unit 140, according to different optional measurement methods, the microwave signal can be input into the heterodyne measurement circuit 151 including the small-signal receiver system, or into the direct measurement circuit 152 including the high-bandwidth measuring instrument 1521.

[0115] When connected to the heterodyne measurement circuit 151, which includes a small-signal receiver system, the input signal first passes through the signal downconversion unit 1511 of the small-signal receiver system. In this unit, the amplified high-frequency signal is connected to the RF terminal of a mixer 1511B. A second microwave signal source 1511A, which provides adjustable frequency and power, outputs a signal to be mixed. The frequency of this signal is the sum of the high-frequency signal and the downconversion frequency. This signal is then fed into mixer 1511B via the LO terminal. The first downconverted signal is output from the I terminal of mixer 1511B, while the second downconverted signal, with a 90-degree phase difference from the I terminal, is output from the Q terminal. These signals are then fed via coaxial cables to the signal noise reduction filter unit 1512 of the small-signal receiver system. Within this unit, the signal noise reduction filter unit 1512 filters the signal through a low-pass filter, a low-band low-noise amplifier, a first bandpass filter, and a high-pass filter to improve the signal-to-noise ratio of the downconverted signal. Finally, the down-converted signal output by the high-pass filter is input to the signal acquisition unit 160 of the receiver.

[0116] In the signal acquisition unit 160, the power of the final microwave signal is first collected through a bandpass filter with an intermediate frequency as the down-conversion frequency and a passband of 3dB bandwidth of the down-conversion signal, and then through an AC signal acquisition card with logarithmic detection.

[0117] After the controller 170 receives the power of the microwave signal, the resonant cavity parameters, and the system gain coefficient, the microwave temperature measurement is realized through the signal temperature conversion algorithm function and the absolute temperature difference calibration algorithm function integrated in the controller 170 .

[0118] The microwave temperature measurement system 100 provided in the embodiments of the present application can achieve high sensitivity across the entire range from ultra-low temperatures to room temperature, has a high sampling rate greater than kHz, can operate in extreme environments such as strong magnetic fields and high voltages, does not introduce heat loads at the measurement location due to the excitation current, and can perform absolute temperature self-calibration without relying on a calibration source. The microwave temperature measurement system 100 provided in the embodiments of the present application can fill the gap in temperature measurement systems for extremely low temperature (less than 100 mK) magnetic field environments.

[0119] Those skilled in the art will understand that the system structure shown in the figure does not constitute a limitation on the embodiments of the present application, and may include more or fewer components than shown in the figure, or a combination of certain components, or a different arrangement of components.

[0120] The system embodiment described above is merely illustrative. The units described as separate components may or may not be physically separate, i.e., they may be located in one place or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of this embodiment.

[0121] Those skilled in the art will understand that the system architecture and application scenarios described in the embodiments of the present application are intended to more clearly illustrate the technical solutions of the embodiments of the present application, and do not constitute a limitation on the technical solutions provided in the embodiments of the present application. Those skilled in the art will know that with the evolution of the system architecture and the emergence of new application scenarios, the technical solutions provided in the embodiments of the present application are also applicable to similar technical problems.

[0122] Based on the above system structure, various embodiments of the microwave temperature measurement method of the present application are proposed below.

[0123] Second, as Figure 5 As shown, the microwave temperature measurement method can be applied to Figure 1 In the illustrated system framework, the microwave temperature measurement system includes: a controller, a microwave cavity calibration unit, a temperature sensor connected in sequence, a multi-channel switch, a signal amplification unit, a signal processing unit, and a signal acquisition unit. The temperature sensor includes multiple microwave resonant cavities and is placed in the same test environment as the system under test. The multi-channel switch is in a preset temperature environment. The microwave cavity calibration unit is connected to the multi-channel switch, and the controller is electrically connected to the microwave cavity calibration unit and the signal acquisition unit. The microwave temperature measurement method may include, but is not limited to, steps S110 to S170.

[0124] Step S110: After the microwave resonant cavity of the temperature sensor is selected through the multi-channel switch, the temperature sensor outputs the generated microwave signal; after passing through the multi-channel switch, the signal amplification unit, and the signal processing unit, the power of the microwave signal is collected by the signal collection unit.

[0125] Step S120: The controller performs signal-temperature conversion processing based on the power of the microwave signal and a preset signal-temperature conversion formula to obtain a signal power-temperature curve of the microwave resonant cavity; wherein the signal-temperature conversion formula includes resonant cavity parameters and system gain coefficient; the resonant cavity parameters and system gain coefficient are obtained after the first calibration processing and the second calibration processing of the microwave cavity calibration unit, respectively.

[0126] Step S130: After selecting different microwave resonant cavities through the multi-channel switch, a signal power-temperature curve of each microwave resonant cavity in the temperature sensor is obtained.

[0127] Step S140: converting the signal power-temperature curve and the Bose-Einstein distribution to obtain a cavity mode signal-temperature curve.

[0128] Step S150 : arbitrarily selecting a first curve, a second curve, a third curve, and a fourth curve from a plurality of cavity mode signal-temperature curves.

[0129] Step S160: performing differential processing on the first curve and the second curve to determine a first absolute temperature value; performing differential processing on the third curve and the fourth curve to determine a second absolute temperature value.

[0130] Step S170: Obtain a first error value between the first absolute temperature value and the second absolute temperature value. When the first error value is less than or equal to a preset threshold, determine that the first absolute temperature value and the second absolute temperature value are equal, and the first absolute temperature value is the absolute temperature value of the test environment in which the test system is located.

[0131] For step S170, since the hardware system may introduce a certain error, a preset threshold is set to determine the first error value between the first absolute temperature value and the second absolute temperature value; when the first error value is less than or equal to the preset threshold, the extremely small first error value can be ignored, and the first absolute temperature value and the second absolute temperature value are considered to be equal; thereby determining that the first absolute temperature value is the absolute temperature value of the test environment in which the test system is located.

[0132] Through steps S110 to S170, when the microwave temperature measurement system is working, after the microwave resonant cavity of the temperature measurement sensor is selected through the multi-channel switch, the temperature measurement sensor outputs the generated microwave signal; after passing through the multi-channel switch, the signal amplification unit, and the signal processing unit, the power of the microwave signal is collected by the signal acquisition unit; the controller performs signal temperature conversion processing based on the power of the microwave signal and a preset signal-temperature conversion formula to obtain a signal power-temperature curve of the microwave resonant cavity; wherein the resonant cavity parameters and the system gain coefficient are obtained after the first calibration processing and the second calibration processing of the microwave cavity calibration unit respectively; that is, the system can be self-calibrated and does not rely on the calibration source; after different microwave resonant cavities are selected through the multi-channel switch, the signal power of the microwave signal is obtained. The temperature sensor comprises a signal power-temperature curve for each microwave resonant cavity; a cavity mode signal-temperature curve is converted based on the signal power-temperature curve and the Bose-Einstein distribution; a first curve, a second curve, a third curve, and a fourth curve are arbitrarily selected from the plurality of cavity mode signal-temperature curves; a differential processing is performed on the first curve and the second curve to determine a first absolute temperature value; a differential processing is performed on the third curve and the fourth curve to determine a second absolute temperature value; a first error value between the first absolute temperature value and the second absolute temperature value is obtained; when the first error value is less than or equal to a preset threshold, the first absolute temperature value and the second absolute temperature value are determined to be equal, and the first absolute temperature value is determined to be the absolute temperature value of the environment to be measured in which the system to be measured is located. The resonant cavity parameters of the microwave resonant cavity are not affected by external factors such as magnetic fields and low temperatures. Therefore, the microwave temperature measurement system 100 of the present application can operate under extreme environmental conditions such as strong magnetic fields and extremely low temperatures. During the entire microwave temperature measurement process, no excitation current is applied to the temperature measurement environment, which does not affect the temperature of the temperature measurement environment; thus, accurate temperature measurement is achieved in extreme environments. Therefore, the embodiments of the present application can achieve accurate temperature measurement in extreme environments without introducing an excitation current and without relying on a calibration source.

[0133] Before step 110, a first calibration process and a second calibration process are performed. Figures 1 to 3 , the first calibration process and the second calibration process are further explained respectively.

[0134] According to some embodiments of the present application, the first calibration process includes but is not limited to the following steps S210 to S250.

[0135] Step S210: Close the first switch to connect the output end of the first microwave signal source to the microwave circulator.

[0136] Step S220: Select a microwave resonant cavity through a multi-channel switch.

[0137] Step S230: Generate and output a second test signal through the first microwave signal source. The second test signal passes through the microwave circulator and the multi-channel switch and then enters the selected microwave resonant cavity.

[0138] Step S240: After reflection from the microwave resonant cavity, a reflected signal of the second test signal is obtained. The reflected signal passes through the microwave circulator and the multi-channel switch and is then collected by the microwave analyzer.

[0139] Step S250: performing data analysis on the collected reflection signal by a microwave analyzer to obtain the resonant cavity parameters, and outputting the resonant cavity parameters to the controller; the resonant cavity parameters include: resonant frequency, loaded quality factor value, and external quality factor value.

[0140] Through steps S210 to S250, the sensor quality factor calibration function is implemented. The resonant cavity parameters, including the resonant frequency, loaded quality factor, and external quality factor, can be obtained at low temperatures. The resonant cavity parameters are used as a parameter in the principle formula of the signal-to-temperature conversion algorithm. Substituting them into the principle formula for analysis allows for temperature measurement. Therefore, measuring the resonant cavity parameters lays the data foundation for implementing the signal-to-temperature conversion algorithm.

[0141] According to some embodiments of the present application, the microwave temperature measurement method further includes: performing a second calibration process on the microwave temperature measurement system by a microwave cavity calibration unit to obtain a system gain coefficient of the microwave temperature measurement system.

[0142] The system gain coefficient is a parameter in the principle formula of the signal-to-temperature conversion algorithm. The system gain coefficient obtained through calibration lays the data foundation for implementing the signal-to-temperature conversion algorithm.

[0143] In one embodiment, when the microwave cavity calibration unit is used to perform the second calibration process, the active end of the first switch is connected to the first selected end and connected to the first microwave signal source; a third test signal with known input power and frequency is output by the first microwave signal source; after the third test signal passes through the microwave circulator, the signal amplification unit and the signal processing unit, the output power of the third test signal is collected by the signal acquisition unit; based on the output power and the input power, the system gain coefficient of the microwave temperature measurement system for signals of different frequencies can be obtained.

[0144] The measurement principle adopted in steps S110 to S140 and the signal temperature conversion algorithm function implemented are further explained.

[0145] In step S110 , the temperature measurement principle of the temperature sensor used is: utilizing the microwave radiation energy at the resonant frequency in the microwave cavity to satisfy the Bose-Einstein distribution, and determining the temperature of the sample environment by measuring the intensity of the microwave radiation.

[0146] The principle of Bose-Einstein distribution states that, under thermal equilibrium, the distribution of a large number of bosons in various states follows a Bose-Einstein distribution. The relationship between the number of cavity-mode photons in a microwave cavity and temperature follows a Bose-Einstein distribution, resulting in a unique, deterministic relationship between cavity-mode signal intensity and temperature.

[0147] Specifically, the formula for the Bose-Einstein distribution is: in, is the number of microwave photons corresponding to the resonant frequency in the microwave cavity, h is Planck's constant, k B is the Boltzmann constant, f is the resonant frequency of the microwave cavity, and T is the ambient temperature of the microwave cavity.

[0148] Specifically in the embodiment of the present application, when the temperature sensor and the system to be measured are placed in the same environment to be measured, and the temperature of the environment to be measured is T; the microwave resonant cavity of the temperature sensor is selected by the multi-channel switch, and the resonant frequency of the selected microwave resonant cavity is f1, according to the Bose-Einstein distribution, the number of microwave photons generated in the microwave resonant cavity corresponding to the resonant frequency is:

[0149] n(f1,T)=[exphf1 / k B T-1] -1 ; where h is Planck's constant, k B is the Boltzmann constant, and f is the resonant frequency of the microwave cavity.

[0150] It can be understood that the temperature sensor outputs a microwave signal in the form of microwave photons. After passing through a multi-channel switch, microwave circulator, signal amplification unit, and signal processing unit, the signal acquisition unit collects the power P of the microwave signal. A second calibration process is performed in advance using the microwave cavity calibration unit to obtain the system gain coefficient G(f, T) of the microwave temperature measurement system for signals of different frequencies. The power P measured and collected by the microwave temperature measurement system is then: P = p(f, T, G) = G(f, T)n(f, T).

[0151] Specifically in the embodiment of the present application, when the resonant frequency of the selected microwave resonant cavity is f1, the power P measured and collected by the microwave temperature measurement system is P = p(f1, T, G1) = G1(f1, T)n(f1, T).

[0152] The signal temperature conversion algorithm function is further explained.

[0153] The signal-to-temperature conversion algorithm primarily utilizes the physical principle that microwave signals conform to the Bose-Einstein distribution. The conversion formula incorporates the noise temperature of the pre-stage, low-noise amplifier (LNA) used in the microwave temperature measurement system, the system gain coefficient, and harmonic cavity parameters. Based on these parameters, the signal strength is resolved into a uniquely corresponding temperature value. In some embodiments, the signal-to-temperature conversion algorithm can be integrated into the software, appearing as a "Power to Temperature Conversion" button.

[0154] In step S120, the preset signal temperature conversion formula is:

[0155]

[0156] Among them, the first ratio The second ratio k=Q l / Q e .

[0157] Wherein, P is the microwave signal intensity collected by the signal acquisition unit in the microwave temperature measurement system, P0 is the microwave signal intensity collected by the signal acquisition unit at room temperature (290K), T LNA is the noise temperature of the pre-placed low-temperature low-noise amplifier group; when the temperature sensor is placed in the test environment, it corresponds to the temperature value T mode , as the temperature of the measured environment changes, the temperature value T mode The temperature corresponding to the temperature sensor will also change. The initial temperature of the temperature sensor is room temperature (290K), and T0 represents the room temperature (290K) in the atmospheric environment. In the preset signal temperature conversion formula, It has a different meaning from T0, but the value is the same, both are room temperature. f is the resonant frequency of the microwave resonant cavity of the temperature sensor in the temperature measurement range measured using the sensor quality factor calibration function, Q l is the loaded quality factor value, Q e is the external quality factor value. f, Q l , Q e All are obtained after the first calibration process by the microwave cavity calibration unit.

[0158] It should be noted that when the signal acquisition unit adopts a logarithmic detector, the value output by the logarithmic detector is ΔP (dB).

[0159] By executing step S130, after selecting microwave resonant cavities with different resonant frequencies through the multi-channel switch, the signal power-temperature curve of each microwave resonant cavity in the temperature sensor is obtained, laying a data foundation for the subsequent implementation of the absolute temperature difference calibration algorithm function.

[0160] Further explanation of step S140, according to the Bose-Einstein distribution The specific process of converting the signal power-temperature curve.

[0161] First, the signal power-temperature curve:

[0162] Converts to:

[0163]

[0164] Secondly, according to the Bose-Einstein distribution and T mode The cavity mode signal-temperature curve is obtained by converting the expression:

[0165] in,

[0166] It can be understood that the cavity mode signal-temperature curve is used to represent the relationship between the number of photons generated by the microwave resonant cavity and the temperature of the environment to be measured. Specifically, the cavity mode signal-temperature curve is plotted as follows: Figure 6 shown.

[0167] It should be noted that the cavity mode signal-temperature curve obtained lays the data foundation for the subsequent realization of the absolute temperature difference calibration algorithm function.

[0168] It should be noted that the absolute temperature differential calibration algorithm performs absolute temperature calibration by performing differential processing on the microwave radiation energy of multiple microwave resonant cavities within the temperature sensor, using the energy-temperature landmarks where the curves are stable. In a practical microwave temperature measurement system, n microwave resonant cavities can be used to measure n signal power-temperature curves and n cavity mode signal-temperature curves. Pairwise differential processing of these n cavity mode signal-temperature curves yields n*(n-1) / 2 differential curves, each containing an energy differential signal inflection point at the same temperature as a landmark. Absolute temperature calibration is then performed using the corresponding temperature value determined by this landmark.

[0169] Taking an example, the steps of absolute temperature calibration processing are further explained.

[0170] First, the microwave cavity resonant frequency is measured: different microwave cavities are selected through a multi-channel switch, and then the resonant frequencies of different microwave cavities are measured using microwave cavity calibration. For example, there are two microwave cavities with different resonant frequencies, whose resonant frequencies are f1 and f2 respectively, and the temperatures corresponding to these two resonant frequencies are T1 and T2 respectively.

[0171] Next, the temperature of the system under test is changed. Temperature measurements are used to obtain the output signals of the two microwave resonant cavities at different temperatures. Two signal power-temperature curves are plotted, and after conversion, two cavity mode signal-temperature curves are obtained. The difference between the two cavity output signals is then calculated as a function of temperature. A maximum value is obtained near T1. Numerical calculations can be used to determine the absolute temperature corresponding to the maximum value. The calculation formula is as follows:

[0172] Difference curve: g(f1,f2,T) = G1(f1,T)n(f1,T) - G2(f2,T)n(f2,T); where G1(f1,T) is the system gain coefficient of the microwave temperature measurement system for a frequency signal of frequency f1; G2(f2,T) is the system gain coefficient of the microwave temperature measurement system for a frequency signal of frequency f2. n(f1,T) is the number of photons generated by the microwave resonant cavity with a resonant frequency of f1; n(f2,T) is the number of photons generated by the microwave resonant cavity with a resonant frequency of f2. n(f1,T) and n(f2,T) can also be understood as cavity mode signal-temperature curves.

[0173] Differentiation curve:

[0174] According to the expression of the differential curve, we can draw the following Figure 7 Schematic diagram of the differential curve shown.

[0175] When implementing the absolute temperature difference calibration algorithm, the calibration curve is obtained by performing differential differentiation using two microwave resonant cavities with different resonant frequencies. Figure 7 The mid-absolute temperature mark point (inflection point) does not change with changes in the temperature measurement system, and the temperature of the system to be measured can be calibrated for absolute temperature.

[0176] In one embodiment, before performing step S150, the process further includes: determining whether the cavity mode signal-temperature curve is valid. Within the measurable range of the microwave temperature measurement system provided in the embodiment of the present application, if the cavity mode signal-temperature curve undergoes a linear transformation, the cavity mode signal-temperature curve is determined to be valid; if the cavity mode signal-temperature curve undergoes a nonlinear transformation, the cavity mode signal-temperature curve is determined to be invalid. If the cavity mode signal-temperature curve is determined to be valid, the absolute temperature calibration process shown in steps S150 to S170 is continued based on the cavity mode signal-temperature curve. If the cavity mode signal-temperature curve is determined to be invalid, the microwave signal is re-collected.

[0177] According to some embodiments of the present application, step S160 is further described. The step S160 of "performing differential processing on the first curve and the second curve to determine the first absolute temperature value" includes but is not limited to steps S161 to S163.

[0178] Step S161: performing a differential operation on the first curve and the second curve to obtain a first differential curve.

[0179] Step S162: performing a differential operation on the first differential curve to obtain a first differential curve.

[0180] Step S163: determining a first temperature marker point according to the first maximum value of the first differential curve, and determining a corresponding first absolute temperature value according to the first temperature marker point.

[0181] Through steps S161 to S163 , a difference operation and a differential operation are performed based on the first curve and the second curve to determine the first absolute temperature value.

[0182] According to some embodiments of the present application, step S160 is further described. The step S160 of "performing differential processing on the third curve and the fourth curve to determine the second absolute temperature value" includes but is not limited to steps S164 to S166.

[0183] Step S164: performing a differential operation on the third curve and the fourth curve to obtain a second differential curve.

[0184] Step S165: performing a differential operation on the second differential curve to obtain a second differential curve.

[0185] Step S166: determining a second temperature marker point according to the second maximum value of the second differential curve, and determining a corresponding second absolute temperature value according to the second temperature marker point.

[0186] Through steps S164 to S166 , a difference operation and a differential operation are performed based on the third curve and the fourth curve to determine the second absolute temperature value.

[0187] According to some embodiments of the present application, after obtaining the error value between the first absolute temperature value and the second absolute temperature value, the microwave temperature measurement method further includes but is not limited to steps S310 to S330.

[0188] Step S310: When the first error value is greater than a preset threshold, randomly selecting the fifth curve, the sixth curve, the seventh curve, and the eighth curve from the plurality of signal power-temperature curves;

[0189] Step S320: performing differential processing on the fifth curve and the sixth curve to determine the third absolute temperature value; performing differential processing on the seventh curve and the eighth curve to determine the fourth absolute temperature value;

[0190] Step S330: Obtain a second error value between the third absolute temperature value and the fourth absolute temperature value. When the second error value is less than or equal to a preset threshold, determine that the third absolute temperature value and the fourth absolute temperature value are equal, and the third absolute temperature value is the absolute temperature value of the test environment in which the test system is located.

[0191] Through steps S310 to S330, when the first error value is greater than the preset threshold, the absolute temperature value of the environment to be measured cannot be determined; therefore, it is necessary to re-select the fifth and sixth curves, and the seventh and eighth curves from the multiple signal power-temperature curves, and perform differential processing based on the re-selected fifth and sixth curves, and differential processing on the seventh and eighth curves. When the second error value between the third absolute temperature value and the fourth absolute temperature value obtained is less than or equal to the preset threshold, the absolute temperature value of the environment to be measured is determined to be the third absolute temperature value. When the second error value is greater than the preset threshold, steps S210 to S230 are repeated until the absolute temperature value of the environment to be measured is obtained.

[0192] Take an example, combined with Figure 8 , the overall process of microwave temperature measurement method is briefly described.

[0193] Step S401: receiving a microwave signal output by a microwave resonant cavity.

[0194] Step S402: performing signal power-temperature conversion processing based on the microwave signal, and drawing a signal power-temperature curve.

[0195] Step S403: deriving a cavity mode signal-temperature curve based on the signal power-temperature curve.

[0196] Step S404: determine whether all obtained cavity mode signal-temperature curves are valid; if so, jump to step S405; if not, jump to S401 and re-collect valid cavity mode signal-temperature curves.

[0197] Step S405 : Select any two cavity mode signal-temperature curves from the plurality of valid cavity mode signal-temperature curves and perform differential processing to obtain a first differential curve.

[0198] Step S406: determining a first temperature marker point from the first differential curve.

[0199] Step S407 : Selecting another two cavity mode signal-temperature curves from the multiple valid cavity mode signal-temperature curves and performing differential processing to obtain a second differential curve.

[0200] Step S408: Determine a second temperature marker point from the second differential curve.

[0201] Step S409: Based on the first temperature mark point and the second temperature mark point, determine whether the error value between the first absolute temperature value and the second absolute temperature value is less than or equal to a preset threshold; if so, jump to step S410; if not, jump to step S405 to re-perform absolute temperature calibration.

[0202] Step S410: Outputting a first absolute temperature value as the absolute temperature value of the system to be measured.

[0203] In summary, the microwave temperature measurement system and microwave temperature measurement method of the embodiment of the present application utilize the microwave temperature measurement principle and a microcavity structure to greatly reduce the size of the temperature sensor, making the microwave temperature measurement system suitable for extreme environments in small spaces. Moreover, due to the good functional relationship between the microwave cavity signal and the temperature, the microwave signal power can be collected by a signal acquisition unit outside the environment to be measured in the microwave temperature measurement system without the need for an excitation current to introduce additional ambient noise temperature. After the signal power-temperature conversion, the temperature of the environment to be measured is obtained, and after absolute temperature calibration, the absolute temperature of the system to be measured is obtained. Moreover, the microwave temperature measurement system of the embodiment of the present application does not need to rely on a calibration source for calibration. In addition, since the microwave signal has good low electromagnetic sensitivity, the microwave temperature measurement system of the embodiment of the present application can also accurately measure temperature in an environment with a magnetic field or an electric field.

[0204] The microwave temperature measurement system of the embodiment of the present application is theoretically verified. The signal power-temperature curve of a microwave resonant cavity is obtained arbitrarily, and the signal power-temperature curve is directly differentiated to obtain the following: Figure 9 The system sensitivity curve is used to characterize the corresponding relationship between system sensitivity and temperature change. Figure 9 It can be seen that the temperature sensitivity of the microwave temperature measurement system in the embodiment of the present application is constant above the resonance frequency, which means that it can operate in a wide range.

[0205] The above is a specific description of the preferred implementation of the present application, but the present application is not limited to the above implementation mode. Technical personnel familiar with the field can also make various equivalent modifications or substitutions without violating the spirit of the present application. These equivalent modifications or substitutions are all included in the scope defined by the present application.

Claims

1. A microwave temperature measurement system, characterized in that: include: A temperature sensor placed in the same test environment as the system to be tested; the temperature sensor includes a plurality of microwave resonant cavities with different resonant frequencies; The temperature sensor is used to generate and output a microwave signal; wherein the resonant cavity parameters of the microwave resonant cavity are not affected by the magnetic field; a multi-channel switch, which is in a preset temperature environment and is electrically connected to the temperature sensor, and is used to select different microwave resonant cavities; a signal amplifying unit, wherein an input end of the signal amplifying unit is electrically connected to the multi-channel switch; the signal amplifying unit is used to amplify the microwave signal; a signal processing unit, wherein the input end of the signal processing unit is connected to the output end of the signal amplifying unit; the signal processing unit is used to perform signal processing on the amplified microwave signal; A signal acquisition unit, wherein the input end of the signal acquisition unit is connected to the output end of the signal processing unit; the signal acquisition unit is used to measure the power of the microwave signal after amplification and signal processing; a microwave cavity calibration unit, electrically connected to the multi-channel switch; the microwave cavity calibration unit is used to perform a first calibration process to obtain the cavity parameters of the microwave cavity, and to perform a second calibration process to obtain the system gain coefficient of the microwave temperature measurement system; A controller is electrically connected to the microwave cavity calibration unit and the signal acquisition unit, respectively; the controller is configured to perform signal temperature conversion processing and differential differentiation processing according to the power, the resonant cavity parameters, and the system gain coefficient to determine a first absolute temperature value, wherein the first absolute temperature value is the absolute temperature value of the environment to be measured in which the system to be measured is located.

2. The microwave temperature measurement system according to claim 1, characterized in that: The microwave temperature measurement system also includes: a microwave circulator; a first end of the microwave circulator is connected to the multi-channel switch, a second end of the microwave circulator is connected to the input end of the signal amplification unit, and a third end of the microwave circulator is connected to the microwave cavity calibration unit; the microwave circulator is used to conduct the line between the multi-channel switch and the signal amplification unit in a first working state, and to conduct the line between the multi-channel switch and the microwave cavity calibration unit in a second working state.

3. The microwave temperature measurement system according to claim 2, characterized in that: The microwave cavity calibration unit includes: a first microwave signal source, a first switch and a microwave analyzer; the first switch is connected between the output end of the first microwave signal source and the microwave circulator; the input end of the microwave analyzer is connected to the microwave circulator, and the output end of the microwave analyzer is electrically connected to the controller.

4. The microwave temperature measurement system according to claim 2, characterized in that: The signal amplification unit includes: a low-temperature low-noise amplifier group in a preset temperature environment, and a room-temperature low-noise amplifier group in a room-temperature environment; The input end of the low-temperature low-noise amplifier group is electrically connected to the microwave circulator; The output end of the low-temperature low-noise amplifier group is electrically connected to the input end of the room-temperature low-noise amplifier group; The output end of the room temperature low noise amplifier group is electrically connected to the input end of the signal processing unit.

5. The microwave temperature measurement system according to claim 1, characterized in that: The signal processing unit includes: a signal down-conversion unit and a signal noise reduction filtering unit which are connected in sequence.

6. A microwave temperature measurement method of a microwave temperature measurement system, characterized in that: Applied to the microwave temperature measurement system according to any one of claims 1 to 5, the method comprises: After the microwave resonant cavity of the temperature sensor is selected by the multi-channel switch, the temperature sensor is made to output the generated microwave signal; after passing through the multi-channel switch, the signal amplification unit, and the signal processing unit, the power of the microwave signal is collected by the signal collection unit; The controller performs signal-temperature conversion processing based on the power of the microwave signal and a preset signal-temperature conversion formula to obtain a signal power-temperature curve of the microwave resonant cavity; wherein the signal-temperature conversion formula includes resonant cavity parameters and a system gain coefficient; the resonant cavity parameters and the system gain coefficient are obtained after a first calibration process and a second calibration process of the microwave cavity calibration unit, respectively; After selecting different microwave resonant cavities by the multi-channel switch, a signal power-temperature curve of each microwave resonant cavity in the temperature sensor is obtained; Converting the signal power-temperature curve to obtain a cavity mode signal-temperature curve; arbitrarily selecting a first curve, a second curve, a third curve, and a fourth curve from the plurality of cavity mode signal-temperature curves; Performing differential processing on the first curve and the second curve to determine a first absolute temperature value; performing differential processing on the third curve and the fourth curve to determine a second absolute temperature value; Obtain a first error value between the first absolute temperature value and the second absolute temperature value. When the first error value is less than or equal to a preset threshold, determine that the first absolute temperature value and the second absolute temperature value are equal, and the first absolute temperature value is the absolute temperature value of the test environment in which the system to be tested is located.

7. The microwave temperature measurement method according to claim 6, characterized in that: The performing differential processing on the first curve and the second curve to obtain a first differential curve includes: performing a difference operation on the first curve and the second curve to obtain a first difference curve; performing a differential operation on the first differential curve to obtain a first differential curve; A first temperature marker point is determined according to a first maximum value of the first differential curve, and the corresponding first absolute temperature value is determined according to the first temperature marker point.

8. The microwave temperature measurement method according to claim 6, characterized in that: After obtaining the error value between the first absolute temperature value and the second absolute temperature value, the microwave temperature measurement method further includes: When the first error value is greater than a preset threshold, reselecting the fifth curve, the sixth curve, the seventh curve, and the eighth curve from the plurality of signal power-temperature curves; performing differential processing on the fifth curve and the sixth curve to determine a third absolute temperature value; performing differential processing on the seventh curve and the eighth curve to determine a fourth absolute temperature value; Obtain a second error value between the third absolute temperature value and the fourth absolute temperature value. When the second error value is less than or equal to a preset threshold, determine that the third absolute temperature value is equal to the fourth absolute temperature value and that the third absolute temperature value is the absolute temperature value of the test environment in which the system to be tested is located.

9. The microwave temperature measurement method according to claim 6, characterized in that: The first calibration process performed by the microwave cavity calibration unit includes: closing the first switch to connect the output end of the first microwave signal source to the microwave circulator; Selecting a microwave resonant cavity by the multi-channel switch; generating and outputting a second test signal by the first microwave signal source, wherein the second test signal passes through the microwave circulator and the multi-channel switch and then enters the selected microwave resonant cavity; A reflected signal of the second test signal is obtained through reflection by the microwave resonant cavity, and the reflected signal is collected by a microwave analyzer after passing through the microwave circulator and the multi-channel switch; The collected reflection signal is analyzed by a microwave analyzer to obtain resonance cavity parameters, and the resonance cavity parameters are output to the controller; the resonance cavity parameters include: resonance frequency, loaded quality factor value, and external quality factor value.

10. The microwave temperature measurement method according to claim 6, characterized in that: The method further includes: performing the second calibration process on the microwave temperature measurement system by the microwave cavity calibration unit to obtain a system gain coefficient of the microwave temperature measurement system.

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