Wireless passive tunable temperature sensor in harsh environments

Abstract

The present application belongs to the field of microwave sensors, and particularly relates to a wireless passive tunable temperature sensor in harsh environment. The wireless passive temperature sensor is optimized in adjustment adaptability in harsh environment, so as to improve the measurement accuracy. The temperature sensor comprises an upper metal structure, an alumina substrate, a lower metal structure and a photosensitive structure; the upper metal structure is arranged on one side surface of the alumina substrate, the lower metal structure and the photosensitive structure are arranged on the surface of the other side of the alumina substrate; the surface of the lower metal structure and the photosensitive structure away from the upper metal structure is covered with a transparent alumina film structure; the photosensitive structure is a doped silicon material, which is configured to adjust the dielectric constant of the equivalent LC circuit of the temperature sensor under the condition of receiving near-infrared light pumping with different powers, so as to produce controllable changes in the resonant frequency and amplitude.

Description

Technical Field

[0001] This invention relates to the field of microwave sensors, and more particularly to a wireless passive tunable temperature sensor for harsh environments. Background Technology

[0002] Temperature monitoring in harsh environments is crucial in fields such as industrial pipelines, hazardous materials storage, mining safety, and aerospace. Abnormal temperatures in industrial pipelines can lead to ruptures, and real-time temperature monitoring is a core safety guarantee in hazardous materials storage and mining operations. Temperature changes in components such as turbine blades in aero-engines under ultra-high temperatures and strong vibrations directly affect equipment performance and lifespan; these scenarios place stringent demands on sensors' ability to withstand extreme environments.

[0003] Traditional wired active temperature measurement technology has significant shortcomings in high-temperature environments: problems such as performance degradation of matching circuits, solder joint failure, and difficulty in maintaining continuous power supply are prominent. Wireless passive sensing technology, because it does not require leads or external power supplies, fundamentally solves problems such as lead aging and contact failure, making it the preferred solution for monitoring harsh environments. Mainstream technologies include LC resonance, surface acoustic wave, and microwave scattering technology.

[0004] However, existing wireless passive sensors have the following limitations: their structural parameters are fixed, they can only passively respond to changes in ambient temperature, they have weak adaptability and are easily affected by vibration, humidity and other interference; their measurement range and sensitivity are limited by the fixed design, and their stability and accuracy drop significantly in ultra-high temperature environments above 800℃, making it difficult to meet the wide temperature range and high precision monitoring requirements of complex scenarios. Summary of the Invention

[0005] The purpose of this invention is to provide a wireless passive tunable temperature sensor for harsh environments, aiming to optimize the adaptability of the wireless passive temperature sensor in harsh environments, thereby improving measurement accuracy.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a wireless passive tunable temperature sensor for harsh environments. The temperature sensor includes an upper metal structure, an alumina substrate, a lower metal structure, a photosensitive structure, and a transparent alumina thin film structure. The upper metal structure is disposed on one side of the alumina substrate, and the lower metal structure and the photosensitive structure are disposed on the other side of the alumina substrate. The surfaces of the lower metal structure and the photosensitive structure away from the upper metal structure are covered with the transparent alumina thin film structure. The photosensitive structure is made of silicon-doped material and is configured to adjust the dielectric constant of the equivalent LC circuit of the temperature sensor when receiving near-infrared light pumps of different powers, so as to produce controllable changes in the resonant frequency and amplitude.

[0007] The upper metal structure includes multiple fan-shaped first sub-metal structures, which are distributed around the center of the alumina substrate and have a first interval between them; the lower metal structure includes multiple fan-shaped second sub-metal structures, and the projections of the multiple first sub-metal structures on the alumina substrate coincide with the projections of the multiple second sub-metal structures on the alumina substrate; the photosensitive structure is arranged in a cross shape in the interval area formed between the multiple second sub-metal structures, and the thickness of the photosensitive structure is the same as the thickness of the second sub-metal structures; each first sub-metal structure and each second sub-metal structure has a concave cutout.

[0008] The wireless passive tunable temperature sensor for harsh environments also includes a polling antenna, located on the side of the upper metal structure away from the alumina substrate. This antenna receives the resonant frequency signal output by the temperature sensor and feeds it back to the external resolution module. The polling antenna uses TEM wave transmission mode, and its S11 parameter is less than 10dB within the operating range of 7.45GHz-11.96GHz.

[0009] The interrogation antenna includes a dielectric substrate, and a ground plane, a microstrip transmission line, and a rectangular radiating patch integrated on the surface of the dielectric substrate away from the alumina substrate; the ground plane is symmetrically distributed on both sides of the microstrip transmission line, and one end of the microstrip transmission line is connected to the rectangular radiating patch; the operating frequency range of the interrogation antenna is adapted to the resonant frequency range of the temperature sensor.

[0010] The upper and lower metal structures are made of platinum and have a thickness of 0.5 μm; the alumina substrate has a thickness of 1.1 mm and is made of HTCC ceramic; the photosensitive structure has a thickness of 0.5 μm; and the transparent alumina film structure has a thickness of 1 μm.

[0011] The transparent alumina thin film structure is a γ-Al2O3 crystal structure formed by thermal oxidation and annealing of aluminum thin film. The thickness and refractive index of the single layer of the transparent alumina thin film structure satisfy 2ne=(k+1 / 2)λ; where k is a natural number and λ is the wavelength of near-infrared pump light.

[0012] The wavelength of the near-infrared light pump is 808 nm. The power variation of the near-infrared light pump causes the carrier concentration of the photosensitive structure to vary in the range of 0-80 S / m, so as to achieve a controllable shift of the resonant frequency around 11 GHz.

[0013] The dielectric constant of the alumina substrate changes linearly with temperature; the temperature sensor is configured to measure the temperature by acquiring the resonant frequency shift caused by the change in the dielectric constant of the alumina substrate; the temperature sensitivity is greater than or equal to 819 kHz / ℃.

[0014] The dielectric substrate measures 15.5mm × 93.1mm × 0.7mm, the rectangular radiating patch measures 5mm × 6mm, the microstrip transmission line measures 1.1mm × 78.1mm, the distance between the ground plane and the microstrip transmission line is 0.8mm, and the distance between the ground plane and the rectangular radiating patch is 1.1mm.

[0015] The ground plane, microstrip transmission line, and rectangular radiating patch are made of platinum with a thickness of 20 μm.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The temperature sensor provided in this application embodiment receives 808nm near-infrared light pumping through a doped silicon photosensitive structure. By varying the near-infrared light power, the carrier concentration of silicon in the photosensitive structure is affected, thereby influencing the dielectric constant in the equivalent LC circuit of the temperature sensor, causing changes in the equivalent inductance and equivalent capacitance values, ultimately resulting in changes in the resonant frequency and amplitude of the temperature sensor. Because the optical pump actively compensates for environmental interference, it can significantly improve measurement stability and achieve a controllable shift in the resonant frequency near 11GHz.

[0017] 2. Utilizing an HTCC alumina substrate, platinum metal structure, and a γ-Al2O3 thin film protective layer, a high-temperature resistant and oxidation-resistant material system is formed. Compared to ordinary ceramic and aluminum metal materials used in traditional temperature sensors, this system is less prone to failure at high temperatures, significantly expanding the temperature measurement range and enabling long-term stable operation in ultra-high temperature environments (such as aero-engines and industrial furnaces). The γ-Al2O3 thin film combines optical anti-reflection and physical protection functions, and its protective layer further optimizes the photoresponse efficiency and long-term stability of the photosensitive structure. Furthermore, the interrogation antenna employs specific dimensions and materials, with its operating frequency precisely matched to the sensor's resonant frequency, achieving efficient signal reception. Attached Figure Description

[0018] Figure 1 A schematic diagram of a wireless passive tunable temperature sensor for use in harsh environments is provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the interrogation antenna in an embodiment of the present invention; Figure 3 The following are simulation diagrams and three-dimensional radiation patterns of the interrogation antenna S11 in this embodiment of the invention; Figure 4 This is a schematic diagram illustrating the interaction between the temperature sensor and the interrogation antenna in an embodiment of the present invention. Figure 5 This is a schematic diagram of the resonant frequency tuning of the present invention under different optical pump excitation doped silicon with different carrier concentrations at room temperature. Figure 6 This is a schematic diagram showing the temperature test data of the present invention at different temperatures. Figure 7 This is a fitting graph showing the relationship between the resonant frequency and temperature of the present invention at different temperatures; Figure 8 This is a schematic diagram of temperature test data at different temperatures after tuning according to the present invention; Figure 9 This is a fitting graph showing the relationship between the resonant frequency and temperature after tuning according to the present invention at different temperatures.

[0019] Among them, 1 is the upper metal structure, 11 is the first sub-metal structure, 2 is the alumina substrate, 3 is the lower metal structure, 31 is the second sub-metal structure, 4 is the photosensitive structure, 5 is the transparent alumina thin film structure, 6 is the interrogation antenna, 61 is the dielectric substrate, 62 is the ground plane, 63 is the microstrip transmission line, and 64 is the rectangular radiating patch. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] For example, such as Figures 1-4 As shown in the embodiment of this application, a wireless passive tunable temperature sensor for harsh environments is provided by the present invention. The temperature sensor includes an upper metal structure 1, an alumina substrate 2, a lower metal structure 3, a photosensitive structure 4, and a transparent alumina thin film structure. The upper metal structure 1 is disposed on one side of the alumina substrate 2, and the lower metal structure 3 and the photosensitive structure 4 are disposed on the other side of the alumina substrate 2. The surface of the lower metal structure 3 and the photosensitive structure 4 away from the upper metal structure 1 is covered with a transparent alumina thin film structure 5. The photosensitive structure 4 is made of silicon-doped material and is configured to adjust the dielectric constant of the equivalent LC circuit of the temperature sensor when receiving near-infrared light pumps of different powers, so as to controllably change the resonant frequency and amplitude.

[0022] More specifically, the temperature sensor receives 808nm near-infrared light pump through a silicon-doped photosensitive structure 4. By varying the near-infrared light power, the carrier concentration of silicon in the photosensitive structure 4 is affected, which in turn affects the dielectric constant in the equivalent LC circuit of the temperature sensor, causing changes in the equivalent inductance and equivalent capacitance values, and ultimately causing changes in the resonant frequency and amplitude of the temperature sensor.

[0023] The wireless passive tunable temperature sensor for harsh environments also includes a polling antenna 6, which is located on the side of the upper metal structure 1 away from the alumina substrate 2. The polling antenna 6 receives the resonant frequency signal output by the temperature sensor and feeds it back to the external analysis module. Specifically, the external analysis module is a radio frequency device network analysis system, i.e., a vector network analyzer.

[0024] The interrogation antenna 6 includes a dielectric substrate 61, and a ground plane 62, a microstrip transmission line 63, and a rectangular radiating patch 64 integrated on the surface of the dielectric substrate 61 away from the alumina substrate 2. The ground plane 62 is symmetrically distributed on both sides of the microstrip transmission line 63, and one end of the microstrip transmission line 63 is connected to the rectangular radiating patch 64. The operating frequency range of the interrogation antenna 6 is adapted to the resonant frequency range of the temperature sensor.

[0025] In some embodiments, the upper metal structure 1 and the lower metal structure 3 are made of platinum and have a thickness of 0.5 μm; the alumina substrate 2 is made of HTCC ceramic and has a thickness of 1.1 mm with a dielectric constant of 9.8 at room temperature; the photosensitive structure 4 is made of N-type doped silicon and has a thickness of 0.5 μm; the transparent alumina thin film structure 5 has a thickness of 1 μm. As a possible implementation, in this embodiment, the temperature-sensitive unit is a dielectric substrate, and the tuning photosensitive unit is doped silicon.

[0026] Furthermore, the transparent alumina thin film structure 5 is a γ-Al2O3 crystal structure formed by thermal oxidation and annealing of aluminum thin film. The single-layer film thickness and refractive index of the transparent alumina thin film structure 5 satisfy 2ne=(k+1 / 2)λ, where k is a natural number and λ is the wavelength of near-infrared pump light.

[0027] The near-infrared light pumping wavelength is 808 nm. Variations in the near-infrared light pumping power cause changes in the carrier concentration of photosensitive structure 4 within the range of 0-80 S / m, achieving a controllable shift of the resonant frequency around 11 GHz. For example, ... Figure 5 As shown, Figure 5 This is a schematic diagram illustrating the resonant frequency tuning of the present invention at room temperature under different optical pumping excitations of doped silicon with different carrier concentrations. According to... Figure 5 It can be seen that the tunability test started with a silicon carrier concentration of 0 S / m, and then gradually increased the silicon carrier concentration until it reached 80 S / m. The resonant frequency and amplitude of the sensor changed with the change in the carrier concentration of the photosensitive unit. The resonant frequency shifted around 11 GHz, while the resonant amplitude S11 increased from 20.75 dB to 24.78 dB.

[0028] Figure 5The resonant frequency shifts around 11 GHz with changes in carrier concentration, and the resonant amplitude S11 increases from 20.75 dB to 24.78 dB. This indicates that the doped silicon photosensitive structure can respond to changes in the power of near-infrared light pumping. This response can be translated into a controllable change in the equivalent LC circuit parameters (dielectric constant) of the sensor, ultimately achieving active adjustment of the resonant frequency and amplitude. Furthermore, when the carrier concentration varies within the range of 0-80 S / m, the resonant frequency exhibits a continuous and repeatable shift trend, indicating that the tuning process is linearly controllable rather than exhibiting random fluctuations. These quantitative results provide a concrete basis for the sensor to preset tuning parameters through optical power in practical scenarios (such as compensating for environmental interference and extending the temperature measurement range).

[0029] The dielectric constant of the alumina substrate 2 changes linearly with temperature; the temperature sensor is configured to measure the temperature by acquiring the resonant frequency shift caused by the change in the dielectric constant of the alumina substrate 2; the temperature sensitivity is greater than or equal to 819 kHz / ℃.

[0030] The dielectric substrate 61 has dimensions of 15.5mm × 93.1mm × 0.7mm, the rectangular radiating patch 64 has dimensions of 5mm × 6mm, the microstrip transmission line 63 has dimensions of 1.1mm × 78.1mm, the distance between the ground plane 62 and the microstrip transmission line 64 is 0.8mm, and the distance between the ground plane 62 and the rectangular radiating patch 64 is 1.1mm.

[0031] The ground plane 62, microstrip transmission line 63 and rectangular radiating patch 64 are made of platinum with a thickness of 20 μm.

[0032] The interrogation antenna 6 uses TEM wave transmission mode, and the S11 parameter is less than 10dB in the operating range of 7.45GHz-11.96GHz.

[0033] This application also provides a method for fabricating a temperature sensor. First, the green ceramic sheets of the alumina substrate 2 and the dielectric substrate 61 are drilled, positioned, and vacuum-sealed. Then, they are placed in a warm water isostatic press and laminated at 70°C and 20MPa to achieve densification of the alumina particles.

[0034] Next, a ceramic cutter is used to cut the alumina green ceramic to the preset size. The cut alumina green ceramic is placed in a muffle furnace and heated to 1500°C according to the set heating curve to completely remove the chemical binder in the HTCC green ceramic belt, thus forming the HTCC substrate.

[0035] In a vacuum environment, using an RF sputtering power source, the upper and lower surfaces of the alumina substrate 2 were masked with a 0.1 mm thick 304 stainless steel metal mask to complete the magnetron sputtering deposition of platinum and silicon, achieving a deposition thickness of 0.5 μm. To prevent oxidation of the doped silicon at high temperatures while ensuring effective transmission of pump light to the doped silicon surface, an aluminum thin film was deposited on its surface. The sample was then placed in an alumina crucible for isothermal oxidation, held at that temperature for 9 hours, and then annealed before natural cooling. During this process, the aluminum thin film oxidized to form a smooth and dense γ-Al₂O₃ crystalline thin film structure with a thickness of 1 μm, completing the fabrication of the temperature sensor.

[0036] A 20 μm thick platinum paste was printed onto the surface of a dielectric substrate 61 using screen printing to form a metallic structure. The printed antenna was then dried in a muffle furnace at 100°C for 20 minutes, and then heated to 900°C at a rate of 10°C / min, and sintered at this temperature for 30 minutes to complete the fabrication of the coplanar waveguide antenna.

[0037] For example, refer to Figure 6 , Figure 6 This is a schematic diagram illustrating temperature testing data at different temperatures according to the present invention. Using a high-temperature heating experimental platform built based on a muffle furnace, the temperature was gradually increased from room temperature (25°C), with a 10-minute holding period at 150°C to ensure temperature stability before data storage. This process was repeated every 150°C until reaching 1050°C. Figure 6 As can be seen, with increasing temperature, the resonant frequencies of many S11 curves in the graph shift towards lower frequencies, meaning the S11 curve of the temperature sensor continuously exhibits a redshift. For example, the resonant frequency is relatively high at 25℃, but as the temperature rises to 1050℃, the curve shifts to the left (lower frequencies). This is because the increased temperature leads to an increase in the dielectric constant of the substrate, resulting in an increase in the equivalent capacitance in the equivalent LC circuit of the temperature sensor, which in turn causes a decrease in the resonant frequency.

[0038] Throughout the entire temperature range from 25℃ to 1050℃, the S11 curve consistently maintains a clear resonance peak without any random fluctuations or signal loss. This demonstrates that the high-temperature resistant system composed of the HTCC substrate, platinum metal structure, and γ-Al2O3 thin film used in the sensor can operate stably in ultra-high temperature environments, overcoming the limitations of existing technologies (performance degradation above 800℃) and making it suitable for harsh high-temperature environments.

[0039] Extract the trough resonant frequency points of the sensor at different temperatures and perform curve fitting on the extracted points, such as... Figure 7 As shown, the temperature transmission curve of the sensor is approximately a linear function, and the calculated temperature sensitivity of the sensor is 819.51 kHz / ℃. Its expression is: Where a = -7.920E-4, b = 11.186, y represents the temperature value (°C), and x represents the resonant frequency (GHz).

[0040] To verify the temperature characteristics of the tuned temperature sensor, an AI-708 / 708P temperature control box based on an external ceramic heating element was used to rapidly heat the sensor, and near-infrared light with a wavelength of 808nm was used for optical excitation. During the experiment, the heating element was fixed to the sensor with high-temperature resistant iron wire, and the sensor temperature was monitored in real time using a K-type or S-type thermocouple provided with the temperature control box. Starting from room temperature of 25℃, the temperature was gradually increased, maintained at 150℃ for 10 minutes at intervals, and the data was saved until 1050℃ was reached. To prevent the influence of ambient temperature fluctuations on the sensor's measurement accuracy, the external surface was coated with mullite (3Al2O3·2SiO2) ceramic material to enhance thermal stability and reduce temperature drift.

[0041] In existing technologies, most wireless passive sensors experience increased measurement errors at high temperatures due to material nonlinearity, such as distortion in the dielectric constant-temperature curve. This causes the frequency-temperature relationship to deviate from linearity. Figure 7 The linear fitting results prove that the HTCC alumina substrate provided by the present invention maintains stable linear variation characteristics of dielectric constant in the range of 25-1050℃, which solves the problem of poor linearity at high temperature. Even at a high temperature of 1050℃, it still maintains a high sensitivity of 819.51KHz / ℃, breaking through the contradiction between the upper limit of temperature and sensitivity.

[0042] Reference Figure 8 and Figure 9 , Figure 8 These are test results of the temperature sensor after active tuning via near-infrared light pumping. For example, a temperature-controlled chamber with an external ceramic heating element is used for heating (from 25℃ to 1050℃, with a 10-minute hold at 150℃ intervals), and tuning is achieved by exciting the photosensitive structure with 808nm near-infrared light. The core objective is to verify the optimization effect of the active tuning mechanism on temperature measurement performance. Figure 9 Yes Figure 8 Curve fitting was performed after extracting the resonant frequency troughs at various temperatures.

[0043] Will Figure 8 and Figure 6The comparison shows that after tuning, the S11 curve still exhibits a regular redshift with increasing temperature, but the curve shape is more stable and the resonant peak is sharper. For example, the resonant frequency is approximately 11.198 GHz at 25℃, decreasing to 10.350 GHz at 1050℃, with a continuous shift trend and no abnormal fluctuations. This means that near-infrared light pumping affects the carrier concentration of silicon in the photosensitive structure, thereby affecting the dielectric constant in the equivalent LC circuit of the temperature sensor, causing changes in the equivalent inductance and equivalent capacitance values, ultimately altering the resonant frequency and amplitude of the temperature sensor. This cancels out any minor interference that might exist in the untuned state, making the curve more regular.

[0044] The tuned fitting curve is closer to the ideal linear function, and the linear correlation is higher than that of the original function. Figure 7 The untuned linear correlation implies that the active tuning mechanism corrects for potential nonlinear deviations, such as small fluctuations in the material's dielectric constant, making the temperature-resonance frequency conversion relationship more reliable. Figure 8 During testing, as the temperature increased, the sensor's resonant frequency shifted from 11.198 GHz to 10.350 GHz. By extracting the resonant point and performing curve fitting, the sensor's sensitivity was calculated to be 827.32 kHz / ℃. Its expression is: Where a = -8.214E-4, b = 11.150, y represents the temperature value (°C), and x represents the resonant frequency (GHz).

[0045] The above data shows that the temperature sensor provided by the present invention is adjustable, can achieve temperature measurement within the range of 25℃ to 1050℃, has good linearity characteristics, and has higher sensitivity, thus expanding the application of wireless passive temperature sensors in harsh environments.

[0046] In summary, this invention provides a wireless, passive, tunable temperature sensor for harsh environments. Through precise optimization of the sensor size and integration of photosensitive materials, it ensures excellent sensitivity and tunability. The temperature sensor provided in this application employs microwave scattering technology for signal interrogation and reception, solving the problem of high-temperature damage to traditional wired sensors; and utilizes high-temperature resistant ceramics to achieve temperature measurement within the range of 25℃ to 1050℃.

[0047] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0048] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A wireless passive tunable temperature sensor for use in harsh environments, characterized in that: The system includes an upper metal structure (1), an alumina substrate (2), a lower metal structure (3), a photosensitive structure (4), and a transparent alumina thin film structure (5). The upper metal structure (1) is disposed on one side of the alumina substrate (2), and the lower metal structure (3) and the photosensitive structure (4) are disposed on the other side of the alumina substrate (2). The lower metal structure (3) and the photosensitive structure (4) are covered with a transparent alumina thin film structure (5) on the side away from the upper metal structure (1). The photosensitive structure (4) is an N-type doped silicon material. The transparent alumina thin film structure (5) is a γ-Al2O3 crystal structure formed by thermal oxidation and annealing of an aluminum thin film. The photosensitive structure (4) is configured to: when pumped by near-infrared light with a wavelength of 808 nm, adjust the carrier concentration in the range of 0-80 S / m by varying the pump power, thereby adjusting the equivalent LC of the temperature sensor. The dielectric constant of the circuit is adjusted to allow a controllable shift in the resonant frequency around 11 GHz, while simultaneously achieving adjustable changes in the resonant amplitude; the upper metal structure (1) includes multiple fan-shaped first sub-metal structures (11), which are distributed around the center of the alumina substrate (2), and there is a first interval between the multiple first sub-metal structures (11); the lower metal structure (3) includes multiple fan-shaped second sub-metal structures (31), the projections of the multiple first sub-metal structures (11) on the alumina substrate (2) and the projections of the multiple second sub-metal structures (31) on the alumina substrate (2) are... The projections on the first sub-metal structure (11) and the second sub-metal structure (31) are aligned; the photosensitive structure (4) is arranged in a cross shape in the spacer region formed between the multiple second sub-metal structures (31), and the thickness of the photosensitive structure (4) is the same as the thickness of the second sub-metal structure (31); each first sub-metal structure (11) and each second sub-metal structure (31) has a concave cutout; the dielectric constant of the alumina substrate (2) changes linearly with temperature; the temperature sensor is configured to: obtain the resonant frequency offset caused by the change in dielectric constant of the alumina substrate (2) to achieve temperature measurement; the temperature sensitivity is greater than or equal to 819KHz / ℃.

2. The wireless passive tunable temperature sensor for harsh environments according to claim 1, characterized in that: It also includes an interrogation antenna (6), which is located on the side of the upper metal structure (1) away from the alumina substrate (2) and is used to receive the resonant frequency signal output by the temperature sensor and feed it back to the external analysis module; the interrogation antenna (6) adopts the TEM wave transmission mode and the S11 parameter is less than 10dB in the working range of 7.45GHz-11.96GHz.

3. The wireless passive tunable temperature sensor for harsh environments according to claim 2, characterized in that: The interrogation antenna (6) includes a dielectric substrate (61), and a ground plane (62), a microstrip transmission line (63), and a rectangular radiating patch (64) integrated on the surface of the dielectric substrate (61) away from the alumina substrate (2); the ground plane (62) is symmetrically distributed on both sides of the microstrip transmission line (63), and one end of the microstrip transmission line (63) is connected to the rectangular radiating patch (64); the operating frequency range of the interrogation antenna (6) is adapted to the resonant frequency range of the temperature sensor.

4. The wireless passive tunable temperature sensor for harsh environments according to claim 1, characterized in that: The upper metal structure (1) and the lower metal structure (3) are made of platinum and have a thickness of 0.5 μm; the alumina substrate (2) has a thickness of 1.1 mm and is made of HTCC ceramic; the photosensitive structure (4) has a thickness of 0.5 μm. The thickness of the transparent alumina film structure (5) is 1 μm.

5. The wireless passive tunable temperature sensor for harsh environments according to claim 1, characterized in that: The thickness n of the single layer of the transparent alumina thin film structure (5) and the refractive index e satisfy 2ne=(k+1 / 2)λ; where k is a natural number and λ is the wavelength of the near-infrared pump light.

6. The wireless passive tunable temperature sensor for harsh environments according to claim 3, characterized in that: The dielectric substrate (61) has dimensions of 15.5mm × 93.1mm × 0.7mm, the rectangular radiating patch (64) has dimensions of 5mm × 6mm, the microstrip transmission line (63) has dimensions of 1.1mm × 78.1mm, the distance between the ground plane (62) and the microstrip transmission line (63) is 0.8mm, and the distance between the ground plane (62) and the rectangular radiating patch (64) is 1.1mm.

7. The wireless passive tunable temperature sensor for harsh environments according to claim 3, characterized in that: The ground plane (62), microstrip transmission line (63) and rectangular radiating patch (64) are made of platinum and have a thickness of 20 μm.

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