A non-contact microwave humidity sensor based on dielectric material whispering gallery mode

Abstract

The application relates to the technical field of non-contact humidity sensors, and discloses a non-contact microwave humidity sensor based on a dielectric material whispering gallery mode, which comprises a resonant cavity base and a top cover connected to the top of the resonant cavity base, and the resonant cavity base and the top cover jointly form an electromagnetic shielding chamber; further comprising a ring resonator made of low-loss dielectric material, a support frame supported in the ring resonator and connected to the bottom wall of the resonant cavity base; the sensor combines the mature high-Q value WGM principle of the optical wave band with the sensing application of the microwave wave band, creatively utilizes the intrinsic advantages and evanescent field sensing mechanism of the low-loss dielectric material, realizes millisecond-level ultrafast response, eliminates the risk of performance attenuation or failure of the sensitive coating, can effectively identify slight loss disturbance, and improves the detection precision.

Description

Technical Field

[0001] This invention relates to the field of non-contact humidity sensor technology, specifically to a non-contact microwave humidity sensor based on the whispering gallery mode of a dielectric material. Background Technology

[0002] Modern precision manufacturing, aerospace, healthcare, and food processing industries have placed stringent demands on real-time, stable, and high-precision monitoring of environmental humidity. Microwave sensing technology based on the principle of electromagnetic disturbance, with its advantages of non-contact measurement, strong anti-interference capability, and good stability, has become a research hotspot in the field of precision sensing. In terms of physical mechanisms, whispering-gallery mode resonators utilize the principle of total internal reflection to highly confine energy within the medium, enabling strong interaction with the measured material. Optical dielectric resonators based on this mode have been widely used in recent years in sensor applications such as temperature, pressure, and electromagnetic fields due to their high Q-factor, extremely high sensitivity, and small mode volume.

[0003] Among related technologies, although WGM (Whispering Gallery Mode) technology is highly mature in the field of optical precision measurement, its application in microwave sensing is still relatively limited. Traditional adsorption-based humidity sensors mainly rely on the physical or chemical adsorption of water molecules by functional humidity-sensitive materials to change electrical performance parameters. This mechanism leads to severe response hysteresis in the sensors, and the humidity-sensitive coating is prone to aging or poisoning by chemical contaminants during long-term use, making it difficult to meet the high stability and fast response monitoring requirements of harsh industrial environments. Acoustic humidity sensors detect humidity based on the principle that the speed of sound propagation in a medium is affected by humidity. These sensors are highly susceptible to external environmental noise interference, resulting in large random errors in the signal. Their detection accuracy and long-term working stability in complex dynamic environments are relatively limited. High-reliability precision monitoring is difficult to achieve. Optical humidity sensors utilize optical microcavities or fiber optic structures to sense fluctuations in light propagation characteristics caused by changes in humidity. The fabrication process of these optical microcavities is extremely complex, and the sensing system requires sophisticated light sources and spectral analysis equipment, resulting in extremely high system integration costs and large size. Furthermore, the optical path system exhibits extremely high sensitivity to dust contamination and light interference, severely limiting sensitivity and reliability. Moreover, existing microwave metal resonant cavity humidity sensors achieve sensing based on frequency shifts caused by disturbances in the dielectric properties of the air. Because the metal resonant cavity uses low-Q, low-order modes (such as TE modes), the detection accuracy of water molecules is low. In addition, the thermal expansion and contraction of the metal cavity due to ambient temperature can cause frequency drift, interfering with humidity sensing.

[0004] Therefore, there is an urgent need for a non-contact microwave humidity sensor based on the whispering gala mode of dielectric materials. This sensor utilizes the low dielectric loss characteristics of low-loss dielectric materials to excite a high Q value, ensuring the sensitivity of the resonance peak to environmental disturbances. The WGM sensing mechanism of low-loss dielectric materials enables cross-frequency applications from the optical to the microwave field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a non-contact microwave humidity sensor based on the whispering-gallery mode of dielectric materials. The non-contact microwave humidity sensor based on the whispering-gallery mode of dielectric materials is easy to excite a high Q value, ensuring the sensitivity of the resonance peak to environmental disturbances, and realizing cross-frequency application from the optical to the microwave field by utilizing the low-loss dielectric material WGM sensing mechanism.

[0006] To solve the above problems, the present invention adopts the following technical solution:

[0007] A non-contact microwave humidity sensor based on the whispering-gallery mode of a dielectric material, comprising:

[0008] The resonant cavity base and the top cover connected to the top of the resonant cavity base together form an electromagnetic shielding chamber;

[0009] A plurality of first air guide holes are uniformly arranged along the side wall and bottom wall of the resonant cavity base, and a plurality of second air guide holes corresponding to the plurality of first air guide holes are provided on the top cover;

[0010] A positioning post and a support frame sleeved outside the positioning post are provided at the geometric center of the resonant cavity base; the positioning post is connected to the top cover.

[0011] It also includes a ring resonator made of low-loss dielectric material, wherein the support frame is supported inside the ring resonator and connected to the bottom wall of the resonant cavity base;

[0012] Two sets of coaxial connectors are symmetrically arranged along the top of the top cover. The inner conductor ends of the two sets of coaxial connectors are respectively provided with metal probes, and the ends of the metal probes extend into the electromagnetic shielding cavity.

[0013] Preferably, a plurality of first threaded holes are provided along the top circumference of the resonant cavity base, a second threaded hole is provided on the top of the positioning post, and a through hole corresponding to the first threaded holes and the second threaded holes is provided on the top cover. A screw is provided in the through hole, and the top cover is threadedly connected to the resonant cavity base and the positioning post respectively by the screw.

[0014] Preferably, a plurality of the first air guide holes on the sidewall and bottom wall of the resonant cavity base, together with a plurality of the second air guide holes on the top cover, form an airflow exchange network.

[0015] Preferably, the diameter of the plurality of first air guide holes and the plurality of second air guide holes ranges from 1.8 mm to 2.2 mm.

[0016] Preferably, the support frame includes a first support block arranged in a stepped manner and a second support block coaxially arranged on top of the first support block, wherein the diameter of the first support block is larger than the diameter of the second support block.

[0017] Preferably, the first support block and the second support block are coaxially provided with through holes, and the first support block and the second support block are sleeved on the positioning post through the through holes, and the bottom of the first support block is connected to the bottom wall of the resonant cavity base.

[0018] Preferably, the first support block and the second support block are polygonal structures respectively arranged accordingly, and the first support block and the second support block each include a plurality of support feet. The plurality of support feet of the first support block are supported on the bottom of the ring resonator, and the plurality of support feet of the second support block are supported on the inner wall of the ring resonator.

[0019] Preferably, the number of support legs of the first support block is greater than or equal to the number of support legs of the second support block.

[0020] Preferably, the coaxial connector includes a flange, and bolts for connecting to the top cover are provided on both sides of the flange. The metal probe is disposed on the flange and located in the middle of the bolts on both sides.

[0021] Preferably, the ring resonator is made of one of the following materials: single-crystal sapphire, quartz glass, silicon, or silicon oxide, which are low-loss dielectric materials.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] (1) In this invention, a ring resonator made of low-loss dielectric material is used, especially a ring resonator made of low-loss dielectric single crystal sapphire. The evanescent field outside the ring resonator interacts instantaneously with water molecules in the humid air passing through the ring resonator cavity. Since the resonator cavity base and top cover together form an electromagnetic shielding cavity, there is no water molecule penetration and adsorption process. The sensor's response to humidity changes mainly depends on the airflow displacement speed and signal transmission speed, thus achieving a millisecond-level ultrafast response. This makes the sensor suitable for scenarios with extremely high time resolution requirements, such as human respiratory diagnosis and industrial gas monitoring. By combining the mature high-Q WGM principle of the optical band with the sensing application of the microwave band, the intrinsic advantages of low-loss dielectric material and the evanescent field sensing mechanism are creatively utilized, achieving effective breakthroughs in multiple dimensions such as response speed, sensitivity, stability, anti-interference ability and applicability.

[0024] (2) In this invention, compared with the traditional adsorption-type resistive humidity sensor or capacitive humidity sensor, the sensitive coating is prone to aging or contaminant poisoning, and the optical humidity sensor has poor resistance to environmental interference, and the system is complex and expensive, the sensing element of this invention is a chemically stable and corrosion-resistant low-loss medium material, and there is no functional material coating on the surface, which eliminates the risk of performance degradation or failure of the sensitive coating, and still has strong resistance to environmental interference; at the same time, since there is no sensitive material that will degrade, the sensor does not need to frequently replace the sensing element or perform periodic calibration during long-term use, which greatly reduces maintenance costs.

[0025] (3) This invention utilizes the low dielectric loss characteristic of the ring resonator, when the loss tangent tanδ < 10 -5 In this case, the Q value of the higher-order whispering galvanic modes excited in the microwave frequency band can reach 10. 5 The above results in an extremely narrow linewidth for the resonance peak, which can effectively identify minute loss disturbances, thereby clearly distinguishing frequency shifts or resonance peak deformations and significantly improving detection accuracy.

[0026] (4) Compared with the solid structure, the ring resonator of this invention introduces an additional inner boundary. While increasing the sensing area, the geometric boundary constraint realizes the radial compression of electromagnetic field energy, causing more energy to concentrate at the medium interface. This allows a higher proportion of energy to be pushed to the medium under the same material volume and resonance mode, thereby significantly enhancing the intensity of the surface evanescent field. At the same time, the measured humid air flowing through the inside of the ring channel and surrounding the outside can interact with the evanescent field, increasing the probability and total amount of water molecules captured, and effectively improving the response sensitivity of the evanescent field to water molecules.

[0027] (5) Traditional microwave sensors mainly rely on the drift of the resonant frequency to detect humidity. However, this invention uses the change of Q value of the resonant peak to infer humidity, effectively distinguishing humidity changes from other interferences, clearly identifying sensor contamination or abnormal conditions, and significantly improving the reliability of measurement and the ability to diagnose faults. Attached Figure Description

[0028] Figure 1 This is a three-dimensional exploded view of the non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials in Embodiment 1 of the present invention.

[0029] In the figure: 1-Resonant cavity base; 101-First vent hole; 102-First threaded hole; 2-Top cover; 201-Second vent hole; 202-Screw; 3-Positioning post; 301-Second threaded hole; 4-Support frame; 401-First support block; 402-Second support block; 5-Ring resonator; 6-Coaxial connector; 601-Flange; 602-Bolt; 7-Metal probe. Detailed Implementation

[0030] The technical solutions of the invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without creative effort are within the scope of the invention.

[0031] In the description of this invention, it should be noted that the terms "above" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience and simplification of the description and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection," "setting," "installation," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0034] like Figure 1As shown, this embodiment discloses a non-contact microwave humidity sensor based on a dielectric material whispering-gallery mode, comprising: a resonant cavity base 1 and a top cover 2 connected to the top of the resonant cavity base 1, wherein the resonant cavity base 1 and the top cover 2 together form an electromagnetic shielding chamber; the resonant cavity base 1 and the top cover 2 are made of highly conductive materials such as oxygen-free copper or aluminum alloy, and a plurality of first air guide holes 101 are uniformly arranged along the side wall and bottom wall of the resonant cavity base 1, and a plurality of second air guide holes corresponding to the plurality of first air guide holes 101 are arranged on the top cover 2. A vent 201 is included; a positioning post 3 and a support frame 4 sleeved around the positioning post 3 are located at the geometric center within the resonant cavity base 1, with the positioning post 3 connected to the top cover 2; a ring resonator 5 is also included, preferably sapphire (α-Al2O3) made of low-loss dielectric single crystal material, with the support frame 4 supported within the ring resonator 5 and connected to the bottom wall of the resonant cavity base 1; two sets of coaxial connectors 6 are symmetrically arranged along the top of the top cover 2, both sets of coaxial connectors 6 being SMA coaxial connectors with a standard 50 ohms microwave interface, establishing a microwave transmission link and measuring S... 21 The transmission parameters are used to provide feedback on humidity information; the inner conductor ends of the two sets of coaxial connectors 6 are respectively provided with metal probes 7, and the ends of the metal probes 7 extend into the electromagnetic shielding cavity.

[0035] Specifically, by using a ring resonator 5 made of low-loss dielectric material, especially a ring resonator 5 made of low-loss dielectric single-crystal sapphire, the instantaneous electromagnetic interaction between the evanescent field outside the ring resonator 5 and water molecules in the humid air passing through the ring resonant cavity is directly utilized. Since the resonant cavity base 1 and top cover 2 together form an electromagnetic shielding chamber, there is no water molecule penetration or adsorption process. The sensor's response to humidity changes mainly depends on the airflow displacement speed and signal transmission speed, thus achieving a millisecond-level ultrafast response. This makes the sensor suitable for scenarios with extremely high time resolution requirements, such as human respiratory diagnosis and industrial gas monitoring. By combining the mature high-Q WGM principle in the optical band with the sensing application in the microwave band, the intrinsic advantages of low-loss dielectric materials and the evanescent field sensing mechanism are creatively utilized, achieving effective breakthroughs in multiple dimensions such as response speed, sensitivity, stability, anti-interference ability, and applicability.

[0036] Compared to traditional adsorption-type resistive humidity sensors or capacitive humidity sensors, which are prone to aging or contaminant poisoning of their sensitive coatings, and optical humidity sensors, which have poor resistance to environmental interference and are complex and expensive, the sensing element of this invention is a chemically stable and corrosion-resistant low-loss dielectric material with no functional material coating on its surface. This eliminates the risk of performance degradation or failure of the sensitive coating and still maintains strong resistance to environmental interference. At the same time, since there is no degradable sensitive material, the sensor does not require frequent replacement of the sensing element or periodic calibration during long-term use, significantly reducing maintenance costs.

[0037] Furthermore, this invention utilizes the low dielectric loss characteristics of the ring resonator 5, especially the low-loss dielectric of single-crystal sapphire, whose loss tangent tanδ < 10°. -5 This allows the Q value of higher-order whispering gallery modes excited in the microwave frequency band to reach 10. 5 The above results in an extremely narrow linewidth for the resonance peak, which can effectively identify minute loss disturbances, thereby clearly distinguishing frequency shifts or resonance peak deformations and significantly improving detection accuracy.

[0038] Meanwhile, compared to a solid structure, the ring resonator 5 of this invention introduces an additional inner boundary. While increasing the sensing area, the geometric boundary constraint achieves radial compression of electromagnetic field energy, causing more energy to concentrate at the medium interface. This allows a higher proportion of energy to be pushed towards the medium under the same material volume and resonance mode, thereby significantly enhancing the intensity of the surface evanescent field. At the same time, it enables the measured humid air flowing through the inside of the ring channel and surrounding the outside to interact with the evanescent field, increasing the probability and total amount of water molecules captured, and effectively improving the response sensitivity of the evanescent field to water molecules.

[0039] In addition, traditional microwave sensors mainly rely on the drift of the resonant frequency to detect humidity, while this invention uses the change of the Q value of the resonant peak to infer humidity, effectively distinguishing humidity changes from other interferences, clearly identifying sensor contamination or abnormal conditions, and significantly improving the reliability of measurement and the ability to diagnose faults.

[0040] Furthermore, such as Figure 1 As shown, a plurality of first threaded holes 102 are provided along the top circumference of the resonant cavity base 1, and a second threaded hole 301 is provided on the top of the positioning post 3. The top cover 2 is provided with through holes corresponding to the first threaded holes 102 and the second threaded holes, and screws 202 are provided in the through holes. The top cover 2 is threadedly connected to the resonant cavity base 1 and the positioning post 3 by the screws 202 respectively.

[0041] Specifically, a number of first threaded holes 102 are provided around the top of the resonant cavity base 1, a second threaded hole 301 is provided on the top of the positioning post 3, and a through hole corresponding to the first threaded hole 102 and the second threaded hole is provided on the top cover 2. A screw 202 is provided in the through hole, and the top cover 2 is threadedly connected to the resonant cavity base 1 and the positioning post 3 by the screw 202 respectively. The top cover encloses the resonant cavity base 1, forming an electromagnetic shielding chamber together with the resonant cavity base 1. This minimizes the leakage of external electromagnetic interference and suppresses the leakage of internal high-frequency signals, providing a pure and stable electromagnetic environment for high-Q resonance. Simultaneously, the top cover 2 connects to the positioning column 3, applying pressure to lock the longitudinal direction of the positioning column 3 to maintain structural stability. This allows the positioning column 3 to radially position and axially fix the support frame 4, ensuring that the support frame 4 remains centered within the electromagnetic shielding chamber. This guarantees that the ring resonator 5 it supports is at the absolute geometric center of the electromagnetic shielding chamber, effectively preventing disturbances in the electromagnetic field distribution caused by slight eccentricity of the ring resonator 5, and eliminating resonant frequency drift, Q-value decrease, and mode distortion.

[0042] According to embodiments of the present invention, such as Figure 1 As shown, a number of first air guide holes 101 on the sidewall and bottom wall of the resonant cavity base 1 and a number of second air guide holes 201 on the top cover 2 together form an airflow exchange network.

[0043] Specifically, since the first air guide holes 101 on the side wall and bottom wall of the resonant cavity base 1 and the second air guide holes 201 on the top cover 2 together form an airflow exchange network, a three-dimensional, low-resistance channel is provided for the effective passage of airflow. This can guide the humid air to form a more uniform and stable flow field in the electromagnetic shielding cavity, avoiding the airflow dead zone, eddies or laminar unevenness that may be formed by air intake in one direction. This ensures that the humidity environment of the entire sensing surface of the ring resonator is consistent, thereby improving the spatial uniformity and instantaneous accuracy of the measurement.

[0044] Furthermore, the diameter of the plurality of first air guide holes 101 and the plurality of second air guide holes 201 ranges from 1.8mm to 2.2mm.

[0045] Specifically, since the aperture range of the first air guide holes 101 and the second air guide holes 201 is 1.8mm-2.2mm, and preferably the aperture of the first air guide holes 101 and the second air guide holes 201 is 2mm, it ensures that moisture flows inside and outside the electromagnetic shielding cavity while preventing the leakage of electromagnetic energy inside the electromagnetic shielding cavity. At this aperture, microwaves in the working frequency band cannot pass through the air guide holes in the propagation mode, and their energy will be severely attenuated, effectively preventing the leakage of high Q value resonant energy inside the electromagnetic shielding cavity, and also blocking the intrusion of external interference signals, ensuring that the ring resonator 5 maintains high Q value resonant energy, thereby ensuring the sensitivity and resolution of the sensor.

[0046] According to embodiments of the present invention, such as Figure 1 As shown, the support frame 4 is preferably made of a low dielectric loss material such as polytetrafluoroethylene or quartz, and includes a first support block 401 arranged in a stepped manner and a second support block 402 coaxially arranged on the top of the first support block 401. The diameter of the first support block 401 is larger than the diameter of the second support block 402. The first support block 401 and the second support block 402 are coaxially provided with through holes. The first support block 401 and the second support block 402 are sleeved on the positioning post 3 through the through holes. The bottom of the first support block 401 is connected to the bottom wall of the resonant cavity base 1.

[0047] Specifically, by setting the support frame 4 as a stepped type, and using the through hole coaxially arranged in the first support block 401 and the second support block 402, the support frame 4 is sleeved on the outside of the positioning post 3, and the bottom of the first support block 401 is connected to the bottom wall of the resonant cavity base 1, which ensures the radial positioning and axial fixation of the support frame 4, providing a stable and reliable support structure for the ring resonator 5, and ensuring the positional accuracy of the ring resonator 5 during installation.

[0048] Furthermore, the first support block 401 and the second support block 402 are respectively arranged as polygonal structures, and the first support block 401 and the second support block 402 each include a number of support feet. The number of support feet of the first support block 401 are supported on the bottom of the ring resonator 5, and the number of support feet of the second support block 402 are supported on the inner wall of the ring resonator 5.

[0049] Specifically, since the first support block 401 and the second support block 402 are respectively arranged as polygonal structures, and each of the first support block 401 and the second support block 402 includes a number of support feet, the support feet of the first support block 401 support the bottom of the ring resonator 5, and the support feet of the second support block 402 support the inner wall of the ring resonator 5. The support feet of the first support block 401 form an outer edge step to support the bottom of the ring resonator 5, and the support feet of the second support block 402 abut against the inner wall of the ring resonator 5 for precise positioning. At the same time, the shape design of the support frame 4 can minimize the contact area with the ring resonator 5, effectively reduce the Q value degradation caused by mechanical clamping due to excessive contact area, and greatly reduce the intrusion and disturbance of the highly concentrated WGM electromagnetic field inside the ring resonator by the support frame 4, thereby maximizing the maintenance of the inherent high Q value of the resonator.

[0050] Furthermore, the number of support legs of the first support block 401 is greater than or equal to the number of support legs of the second support block 402.

[0051] Specifically, since the number of support feet of the first support block 401 is greater than or equal to the number of support feet of the second support block 402, the first support block 401 has more contact points with the resonant cavity base 1, which can ensure a wider and more stable support base and outer edge steps, and can always provide effective support for the second support block 402. It also enhances the support area for the bottom of the ring resonator 5, preventing excessive suspension or insufficient support at the bottom of the ring resonator 5. At the same time, when the sensor is subjected to external vibration or impact, the vibration energy can be dispersed and transferred to the resonant cavity base 1 through the multiple support feet of the first support block 401, reducing local stress concentration, reducing the direct impact of vibration on the precision ring resonator 5, and ensuring the stability of the ultra-high Q value resonance.

[0052] In this invention, such as Figure 1 As shown, the coaxial connector 6 includes a flange 601, with bolts 602 on both sides of the flange 601 for connecting to the top cover 2, and a metal probe 7 is disposed on the flange 601 and located in the middle of the bolts 602 on both sides.

[0053] Specifically, the coaxial connector 6 includes a flange 601 with bolts 602 on both sides for connecting to the top cover 2. The metal probe 7 is located on the flange 601 and in the middle of the bolts 602 on both sides. After the coaxial connector 6 is fixed to the top cover 2, the end of the metal probe 7 is located in the electromagnetic shielding cavity and excites the ring resonator 5 in the sounding-gallery mode. By precisely controlling the insertion depth of the metal probe 7 and the distance between it and the ring resonator 5, the coupling strength is set in the undercoupled region. In the undercoupled state, the loading effect of the external circuit on the resonator is minimal, and the resonance peak is the sharpest. When water molecules cause slight losses, the Q value change of the resonance peak width is the most obvious and sensitive, ensuring that the system operates in the undercoupled state, so that the output signal truly reflects the Q value loss caused by water molecules, thereby achieving high detection sensitivity for humidity.

[0054] In addition, the ring resonator 5 is made of one of the following materials: single-crystal sapphire, quartz glass, silicon, or silicon oxide, which are low-loss dielectrics.

[0055] Specifically, the ring resonator 5 can be fabricated using one of the following low-loss dielectric materials, such as single-crystal sapphire, quartz glass, silicon, or silicon oxide, with single-crystal sapphire (α-Al2O3) being the preferred low-loss dielectric material. The ring resonator 5 fabricated using this low-loss dielectric material achieves a sensing mechanism where the evanescent field generated by the whispering-gallery mode directly couples to the dielectric loss of water molecules, thus resolving the signal delay caused by physical and chemical adsorption processes and achieving millisecond-level ultrafast response. This meets the needs of high-dynamic scenarios such as respiratory analysis, engine exhaust monitoring, and rapid industrial process control. In particular, single-crystal sapphire, with its extremely low dielectric loss in the microwave band (loss tangent tanδ < 10°), is particularly advantageous. -5 This allows the Q value of higher-order whispering gallery modes excited in the microwave frequency band to reach 10. 5 The above makes its resonance peak extremely sensitive to environmental disturbances. By utilizing the sapphire WGM sensing mechanism, it has achieved cross-frequency application from the optical to the microwave field, breaking the deadlock of insufficient accuracy of traditional microwave sensors and excessively expensive optical sensors.

[0056] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A non-contact microwave humidity sensor based on the whispering-gallery mode of a dielectric material, characterized in that, include: The resonant cavity base and the top cover connected to the top of the resonant cavity base together form an electromagnetic shielding chamber; A plurality of first air guide holes are uniformly arranged along the side wall and bottom wall of the resonant cavity base, and a plurality of second air guide holes corresponding to the plurality of first air guide holes are provided on the top cover; A positioning post and a support frame sleeved outside the positioning post are provided at the geometric center of the resonant cavity base; the positioning post is connected to the top cover. It also includes a ring resonator made of low-loss dielectric material, wherein the support frame is supported inside the ring resonator and connected to the bottom wall of the resonant cavity base; Two sets of coaxial connectors are symmetrically arranged along the top of the top cover. The inner conductor ends of the two sets of coaxial connectors are respectively provided with metal probes, and the ends of the metal probes extend into the electromagnetic shielding cavity.

2. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 1, characterized in that, A plurality of first threaded holes are provided along the top circumference of the resonant cavity base, and a second threaded hole is provided on the top of the positioning post. The top cover is provided with through holes corresponding to the first threaded holes and the second threaded holes, and screws are provided in the through holes. The top cover is threadedly connected to the resonant cavity base and the positioning post respectively by the screws.

3. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 1, characterized in that, The first air guide holes on the sidewall and bottom wall of the resonant cavity base, together with the second air guide holes on the top cover, form an airflow exchange network.

4. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 3, characterized in that, The diameter of the first air guide holes and the second air guide holes ranges from 1.8 mm to 2.2 mm.

5. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 1, characterized in that, The support frame includes a first support block arranged in a stepped manner and a second support block coaxially arranged on top of the first support block, wherein the diameter of the first support block is larger than the diameter of the second support block.

6. The non-contact microwave humidity sensor based on the whispering gallery mode of a dielectric material according to claim 5, characterized in that, The first support block and the second support block are coaxially provided with through holes. The first support block and the second support block are sleeved on the positioning post through the through holes. The bottom of the first support block is connected to the bottom wall of the resonant cavity base.

7. The non-contact microwave humidity sensor based on the whispering-gallery mode of a dielectric material according to claim 6, characterized in that, The first support block and the second support block are polygonal structures respectively, and the first support block and the second support block each include a plurality of support feet. The plurality of support feet of the first support block are supported on the bottom of the ring resonator, and the plurality of support feet of the second support block are supported on the inner wall of the ring resonator.

8. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 7, characterized in that, The number of support legs of the first support block is greater than or equal to the number of support legs of the second support block.

9. The non-contact microwave humidity sensor based on the whispering gallery mode of dielectric materials according to claim 1, characterized in that, The coaxial connector includes a flange with bolts on both sides for connecting to the top cover, and a metal probe is disposed on the flange and located in the middle of the bolts on both sides.

10. The non-contact microwave humidity sensor based on the whispering-gallery mode of a dielectric material according to any one of claims 1 to 9, characterized in that, The ring resonator is made of one of the following materials: single-crystal sapphire, quartz glass, silicon, or silicon oxide, which are low-loss dielectric materials.

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