Frequency-reconfigurable high-sensitivity differential sensor

Abstract

The invention discloses a frequency-reconfigurable high-sensitivity differential sensor, relates to the field of differential sensors, and aims to solve the problems of system complexity, sensing performance reduction and fixed and non-tunable working frequency in the prior art. According to the technical scheme, a reference group and a test group are in a mirror symmetry structure, a bonding pad is arranged on a through hole, and the bonding pad is connected with the reference group and the test group; the bonding pad is covered with a thin film; and two groups of CSRR structures are etched on the upper layer. By covering the pad area with the film, the state of the pad area can be changed when the temperature changes, so that communication and segmentation of the resonant cavity body are changed, and frequency reconfiguration is realized; by arranging the CSRR structure in the sensing area, strong electric field concentration can be formed in the sensing area, and the sensitivity of the sensor to dielectric constant change is remarkably improved. And the reference group and the test group of the differential sensor are combined, so that the environmental interference is eliminated, and the multi-frequency-point measurement is combined, so that the measurement precision is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of differential sensor technology, specifically to a frequency-reconfigurable high-sensitivity differential sensor. Background Technology

[0002] Differential microwave sensors have attracted much attention in recent years to suppress common-mode interference from environmental temperature, humidity, and air pressure. Differential sensors based on surface plasmon polaritons (SSPPs) use a T-shaped power divider to distribute the signal to two SSPP microstrip lines, one as a reference branch and the other as a test branch. The dielectric constant of the measured quantity is extracted by comparing the resonant frequency offsets of the two branches. While this design achieves environmental self-calibration, the three-port network increases the complexity of the measurement system. Existing technologies apply traditional power divider-combiner structures to differential microstrip sensors, loading open-loop resonators (SRRs) at the ends of the two branches to form a two-port network, simplifying the connection method. However, the power divider and combiner occupy a large area, and the isolation is limited by the microstrip coupling effect. To address this issue, existing technologies further insert a metal via array at the center of the sensor to construct an electromagnetic bandgap to improve port isolation, but this results in poor sensor sensitivity. Therefore, existing differential schemes, while suppressing interference, often come with limitations such as increased system complexity, decreased sensing performance, and a fixed, non-tunable operating frequency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the existing defects and provide a frequency reconfigurable high-sensitivity differential sensor, which can effectively solve the problems in the background art.

[0004] To achieve the above objectives, this invention discloses a frequency-reconfigurable high-sensitivity differential sensor. The technical solution includes a reference group and a test group, both with identical structures; it includes a dielectric layer, with an upper layer above the dielectric layer and a ground layer below it, connected by vias. The upper layer, ground layer, and vias are all made of conductive material; both the reference group and the test group have pads on their upper layers, which are located on the vias. A cover layer is placed on the pads, and the cover layer includes a sapphire polymer substrate. The sapphire polymer substrate has... The thin film; both the reference group and the test group are equipped with a first port and a second port. Utilizing... The metal-insulator phase transition characteristics allow for frequency reconfiguration through temperature control:

[0005] - At low temperature (25℃), In an insulating state, a complete quarter-mode SIW (QMSIW) resonant cavity is formed;

[0006] - At high temperatures (80℃), Metallization to form an HMSIW-QMSIW composite resonant cavity

[0007] As a preferred embodiment of the present invention, complementary open-circuit resonator (CSRR) rings are provided on both the reference group and the test group. The CSRR structure forms a strong electric field concentration in the sensing region, which significantly improves the sensor's sensitivity to changes in dielectric constant.

[0008] In a preferred embodiment of the present invention, two sets of complementary split-ring resonators are provided on both the reference group and the test group, namely a first complementary split-ring resonator and a second complementary split-ring resonator, wherein the size of the first complementary split-ring resonator is larger than the size of the second complementary split-ring resonator. The pads, cover layer, and first port are all located between the first and second complementary split-ring resonators.

[0009] By optimizing the structure and location of the CSRR, the electric field concentration effect can be further enhanced, significantly improving the sensor's sensitivity. The optimized CSRR structure can generate a stronger electric field concentration in a smaller area, making the sensor more sensitive to changes in dielectric constant. Simultaneously, the CSRR's capacitive-like characteristics shift the resonant frequency to lower frequencies, achieving a lower operating frequency without changing the structural dimensions, providing a new approach for device miniaturization.

[0010] As a preferred technical solution of the present invention The thin film is bonded to the upper layer of the area where the solder pads are located. The film can completely cover the solder pads.

[0011] As a preferred technical solution of the present invention The thin film was deposited on a sapphire polymer substrate by pulsed laser deposition or sputtering and chemical vapor deposition, and then annealed in an oxygen atmosphere to improve its crystallinity and MIT properties.

[0012] As a preferred technical solution of the present invention The thin film was deposited on a sapphire polymer substrate using pulsed laser deposition.

[0013] Compared with the prior art, the beneficial effects of the present invention are: the present invention covers the pad area Thin film, utilizing The metal-insulator phase transition characteristics were modulated, and the sensor generated an operating mode (f1 = 3.1 GHz) by exciting a single QMSIW resonant cavity at low temperature (25°C) and at high temperature (80°C). Metallization forms an HMSIW-QMSIW composite cavity, generating two operating modes with resonant frequencies of 4.78 GHz (f2) and 5.33 GHz (f3). By incorporating a CSRR structure in the sensing region, a strong electric field concentration is achieved, significantly improving the sensor's sensitivity to changes in dielectric constant, achieving high sensitivity of 4.84%, 8.84%, and 10.52%. Furthermore, the mirror-image combination of the reference and test groups within the differential sensor significantly suppresses environmental interference, ensuring measurement stability. Combined with multi-frequency measurements, the absolute error is less than 1.5%, significantly improving measurement accuracy. Through the synergistic effect of these features, the differential sensor achieves its goals of compact structure, strong environmental adaptability, high sensitivity, strong anti-interference, multi-frequency reconfigurability, and high-precision measurement. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the planar structure of the present invention;

[0015] Figure 2 This is a three-dimensional structural diagram of the present invention;

[0016] Figure 3 This is a schematic diagram of the three-dimensional structure of the present invention without the covering layer;

[0017] Figure 4 This is the planar structure of the complete QMSIW resonant cavity in the disconnected state of this invention;

[0018] Figure 5 The graph shows the S-parameters and frequency variations of the complete QMSIW resonant cavity in the disconnected state of this invention.

[0019] Figure 6 This is the planar structure of the HMSIW-QMSIW composite resonant cavity in the connected state of the present invention;

[0020] Figure 7 The diagram shows the S-parameters and frequency variations of the HMSIW-QMSIW composite resonant cavity in the connected state of this invention.

[0021] Figure 8 This is an electric field distribution diagram of the complete QMSIW resonant cavity in the disconnected state of this invention;

[0022] Figure 9 This is an electric field distribution diagram of the HMSIW-QMSIW composite resonant cavity in the connected state of the present invention;

[0023] Figure 10 This is a graph showing the sensitivity variation of the second complementary open-ended resonant ring of the present invention at different distances from the first port;

[0024] Figure 11 This is a graph showing the relationship between the width and sensitivity of the first complementary open-loop resonator of the present invention.

[0025] Figure 12 This is a graph showing the relationship between the length of the first complementary open-loop resonator and its sensitivity in this invention.

[0026] Figure 13 This is a graph showing the relationship between the length of the second complementary open-loop resonator and its sensitivity in this invention.

[0027] Figure 14 This is a graph showing the relationship between the width and sensitivity of the second complementary open-loop resonator of the present invention.

[0028] Figure 15 This is a comparison of the curves of relative permittivity-resonant frequency offset obtained from HFSS simulation and fitting function under Mode 1 of this invention;

[0029] Figure 16 This is a comparison of the curves of relative permittivity-resonant frequency offset obtained from HFSS simulation and fitting function under Mode 2 of this invention;

[0030] Figure 17 This is a comparison of the curves of relative permittivity-resonant frequency offset obtained from HFSS simulation and fitting function under Mode 3 of this invention;

[0031] Figure 18 The graph shows the variation of sensitivity with relative permittivity under the three modes of this invention;

[0032] Figure 19 This is a schematic diagram of the dimension markings of the present invention.

[0033] In the diagram: 1. Dielectric layer; 2. Upper layer; 3. Ground layer; 4. Reference group; 5. Test group; 6. First via; 7. Pad; 8. Cover layer; 9. First complementary open-circuit resonator; 10. Second complementary open-circuit resonator; 11. First port; 12. Second port; 13. Second via; 14. Test object; 15. QMSIW resonant cavity; 16. HMSIW resonant cavity. Detailed Implementation

[0034] 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] Example 1

[0036] like Figures 1 to 3As shown, this invention discloses a frequency-reconfigurable high-sensitivity differential sensor. The technical solution adopted includes a dielectric layer 1, which is a rectangular block of Taconic RF-35 material, with a length of 47.6 mm, a width of 24.5 mm, and a thickness of 1.524 mm, and a relative permittivity of [missing information]. =3.5, the bottom surface of dielectric layer 1 has a copper ground layer 3 with a thickness of 1 oz (referring to the thickness achieved when 1 oz of copper is evenly laid flat on an area of ​​1 square foot), and the top surface has a copper upper layer 2 with a thickness of 1 oz. Dielectric layer 1, upper layer 2, and ground layer 3 together form an SIW (substrate integrated waveguide) structure. Upper layer 2 is connected to a copper first via 6. The first via 6 has a radius of 0.325 mm and a center-axis spacing of 1 mm. The first via 6 passes through dielectric layer 1 and connects to ground layer 3. There are multiple first via 6, which are distributed in a T-shape. The first via 6 extending along the width direction of dielectric layer 1 divides the sensor into a reference group 4 and a test group 5. The reference group 4 and test group 5 have the same structure and are arranged in a mirror symmetrical layout. The sensing area of ​​the sensor is 18.26 mm long and 14.33 mm wide.

[0037] Taking reference group 4 as an example, the upper layer 2 of reference group 4 is provided with a first port 11 and a second port 12. The first port 11 is located on the side of the upper layer 2 extending along the long side of the dielectric layer 1, and the second port is located on the side of the upper layer 2 extending along the wide side of the dielectric layer 1. Figure 1 As shown for directional reference, a second complementary open-circuit resonator 10 is etched on the upper left layer 2 of the first port 11, and a first complementary open-circuit resonator 9 is etched on the upper right layer 2. The first complementary open-circuit resonator 9 is 4.6 mm long and 3.5 mm wide, and is 1 mm away from the first port 11. The second complementary open-circuit resonator 10 is 4.36 mm long and 3.4 mm wide. Between the first port 11 and the second complementary open-circuit resonator 10, there is a row of second vias 13 extending along the width direction of the dielectric layer 1. The axial spacing of the second vias 13 is... The second via 13 has a diameter of 0.85 mm and a width of 0.1 mm, with a hole radius of 0.45 mm. This annular pad 7 reduces surface current disturbance in the OFF state. The second complementary open-ring resonator 10 is 0.463 mm away from the pad 7. A capping layer 8 is bonded to the upper layer 2 of the area containing the pad 7 using adhesive. The capping layer 8 completely covers the row of pads 7. The capping layer 8 uses sapphire polymer as a substrate and is deposited on the substrate using pulsed laser deposition with a thickness of 200 nm. The thin film, whose thickness can be precisely controlled during deposition, significantly affects the performance of the switching components. After deposition, annealing in an oxygen atmosphere improves its crystallinity and MIT (metal-insulator transition) properties. Pad 7 and the upper layer 2 together form the temperature-controlled switching unit.

[0038] Vanadium dioxide is a unique functional material that undergoes a reversible metal-insulator transition (MIT) around 68°C, during which its conductivity jumps from a low-temperature insulating state (<10 S / m) to a high-temperature metallic state (>10^5 S / m). This dramatic change, occurring up to three orders of magnitude above and below the transition temperature, makes it an ideal candidate material for switching devices and frequency reconfigurable switching components. The MIT (mitochondrial transition) of vanadium crystals is not only temperature-controlled, but can also be triggered by external stimuli such as light, electric fields, and pressure. Among these, temperature-induced transitions are widely used due to their ease of operation and compatibility with various device structures. This transition mechanism is related to the structural phase transition of the crystal from a monoclinic (M1) to a rutile (R) crystal system during heating, which leads to vanadium-oxygen bond rearrangement and thus changes the electronic band structure and conductivity.

[0039] Based on the principle of symmetrical design, the left and right structures of the sensor are mirror-symmetrical. Taking one side of the test group as an example, the frequency reconfigurable mechanism is to... The thin film is integrated on the upper layer 2 of SIW. The thin film, pad 7, second via 13, and ground plane 3 together constitute the tunable unit. It is controlled by an external heat source. The insulator-metal phase transition allows the unit to dynamically switch the electrical connection state (on / off) of the second via 13, thereby changing the electromagnetic boundary conditions of the QMSIW resonant cavity 15 and achieving reconfigurable control of the resonant frequency. SIW is a waveguide structure compatible with PCB technology, combining the low loss and high power handling capabilities of traditional waveguides with the convenience of planar integration. Its dominant mode is... Module. By optimizing the dimensions, the SIW design of this model can cover the 2.3–5.4 GHz operating frequency band, and its resonant frequency satisfies:

[0040]

[0041] In the formula, and For the equivalent waveguide size, For the effective dielectric constant, The speed of light in a vacuum, In mode and All are 1. Controlled by using an external heat source. The phase transition enables the sensor to operate in three modes: when the temperature is below... At the metal-insulator phase transition temperature (68℃), it is in an insulating state (tunable unit off), and the QMSIW forms a complete resonant cavity, corresponding to a single resonant frequency f1 (mode 1); when the temperature rises above the phase transition temperature, When the resonant cavity is switched to the conductive state (tunable unit on state), it is divided into two independent cavities: QMSIW resonant cavity 15 and HMSIW resonant cavity 16 (half-mode substrate integrated waveguide resonant cavity), at which point two resonant frequencies f2 and f3 (mode 2 and mode 3) are generated.

[0042] a. Off state (25°C):

[0043] At room temperature, The thin film is in an insulating state (high resistance state), which means The second via 13 in the region is not connected to the metal of the upper layer 2, and the via is ineffective. This "disconnected" state allows electromagnetic waves to propagate unimpeded from the first port 11 to the second port 12 within the QMSIW resonant cavity 15, and the impedance effect of the induction post on the QMSIW is negligible. At this time, the QMSIW resonant cavity 15 structure is complete, as shown... Figure 4 As shown, it includes a first via 6, a first complementary open-circuit resonator 9 and a second complementary open-circuit resonator 10 etched on the upper layer 2, and a pad 7. The cavity of the QMSIW resonant cavity 15 and the complementary open-circuit resonator work together to generate strong electromagnetic resonance. The results are as follows: Figure 5 As shown, at 3.11 GHz, S 21 Approaching 0dB, S 11 and S 22 The deep indentation (below -10 dB) indicates that the energy reflected from the input port is extremely low, and most of the energy is received by the sensor and transmitted from the first port 11 to the second port 12, proving that the transmission path is unobstructed. At this time, a single resonant frequency f1 of 3.11 GHz is generated.

[0044] b. On state (80°C):

[0045] Conversely, when the temperature is above 68°C (on state), The transition to a metallic state means that the second via 13 is connected to the metal of the upper layer 2, and the pad 7 becomes ineffective. The metallization makes its rectangular array equivalent to a short-circuit wall, dividing the original QMSIW resonant cavity 15 into two independent cavities, forming an HMSIW-QMSIW composite structure, such as... Figure 6 As shown. The first complementary open-circuit resonator 9 and the second complementary open-circuit resonator 10 are respectively loaded at the points where the electric fields of the two resonators are strongest. The second via 13 connects the conductors of the upper layer 2 and the ground layer 3 to form an ideal electric wall, generating a strong electromagnetic isolation effect between the first port 11 and the second port 12, resulting in the efficient reflection of the incident electromagnetic wave. Figure 7 The S-parameter test results clearly verify that the transmission coefficient S 21 The full-band voltage is below -15dB, indicating that inter-port energy transfer is significantly suppressed (isolation >15dB). Meanwhile, the reflection coefficient S... 22A deep resonance valley (-11.2 dB) is observed at 4.78 GHz, corresponding to the resonant frequency f2 of the 16-cavity HMSIW resonator on the left, while S 33 An independent resonance valley (-14.1 dB) appears at 5.33 GHz, corresponding to the resonant frequency f3 of cavity 15 of the QMSIW resonator on the right.

[0046] Therefore, based on The phase change component has thermal regulation characteristics. The sensor achieves two working states, OFF-state and ON-state, through temperature switching. It realizes three reconfigurable resonant modes (mode 1, mode 2, mode 3) with three frequencies (f1, f2, f3) in a single structure.

[0047] To improve sensor sensitivity, a first complementary open-circuit resonator 9 and a second complementary open-circuit resonator 10 are etched onto the upper metal surface of the SIW structure, significantly enhancing the electric field concentration in the sensing region. Based on TE 101 The master mode analysis shows the electric field distribution in the on or off states, as follows: Figure 8 , Figure 9 As shown, the sensing region where the complementary split-ring resonators are located exhibits a significantly high electric field intensity. This is because the complementary split-ring resonators force the current to flow along a curved path, promoting the concentrated storage of electromagnetic energy. This high electric field region is the optimal placement position for the sample, maximizing the sensor's frequency response. The highest sensitivity is achieved by adjusting the structure and position of the first complementary split-ring resonator 9 and the second complementary split-ring resonator 10. Taking the position of the first complementary split-ring resonator 9 as an example, because it has a significant impact on the sensor's sensitivity, simulation results... Figures 10 to 14 It can be seen that the first complementary split-ring resonator 9 is located at y=1mm. Similarly, the CSRRs structure is optimized with dimensions of W=3.5mm, Z=4.6mm, S=4.36mm, and U=3.4mm. In addition, the capacitor-like characteristics of the complementary split-ring resonator shift the resonant frequencies of the three modes to lower frequencies, achieving a reduction in operating frequency without changing the structural dimensions, thus providing a new approach for device miniaturization.

[0048] The test object 14 is placed on a SIW-based frequency reconfigurable differential sensor, and its dielectric properties significantly affect the sensor's resonant frequency. The difference in resonant frequencies between reference group 4 and test group 5 is then compared. This allows for high-precision extraction of the relative permittivity characteristics of the sample. Specifically, different permittivity values ​​of the analyte 14 result in different resonant frequency shifts. Based on this, the resonant frequency shift ( ) and relative permittivity ( A fitting relationship can be established between them, and then the relative permittivity value of the test object 14 can be retrieved. ), and to analyze the sensor sensitivity (S).

[0049] To achieve maximum sensitivity, the test object 14 was mounted on top of the complementary open-loop resonator structure, with dimensions of 18.26 × 14.33 × 1.524 mm. 3 To completely cover the measurement area, simulation tests were conducted on different materials with dielectric constants ranging from 1 to 9 using HFSS electromagnetic simulation software, with a step size of 1. The simulation results show that, as... Figure 10 As shown, S 11 S 22 S 33 resonant frequency offset ( , All of these vary with the relative permittivity ( Significant changes occur due to the increase of ). Figures 15 to 17 The simulation data (HFSS) for sensor modes 1, 2, and 3 are displayed, along with the high-fitting fitting function. Based on polynomial fitting techniques, the resonant frequency shift ( , ) and relative permittivity ( The mathematical expression for ) is as follows:

[0050] Mode 1:

[0051] Mode 2:

[0052] Mode 3:

[0053] in It is the relative permittivity of the object under test, 14. , It represents the resonant frequency offset of mode i (i = 1, 2, 3).

[0054] The formula for calculating the sensitivity of a sensor is:

[0055]

[0056] in This represents the relative permittivity of the measured material compared to the permittivity of air. The difference between ) It is the resonant frequency of the sensor in its reference state (without the object being measured). Resonant frequency of the object under test The frequency difference. For example... Figure 18The figure shows the fitting curves between the sensitivity and relative permittivity of the sensor's three modes (mode 1, mode 2, and mode 3). Under high-temperature conditions (on-state), modes 2 and 3, with the CSRR applied, exhibit higher sensitivity. This is because, during the design phase, the CSRR loading position was optimized to make the electric field distribution of the two modes more concentrated in the on-state. This optimized design avoids [further issues related to the sensor's sensitivity]. The phase transition characteristics significantly improve the sensitivity of modes 2 and 3. The average sensitivity of the frequency reconfigurable differential sensor in the three modes is 4.84%, 8.84%, and 10.52%.

[0057] To verify Example 1, as Figure 19 As shown, the optimized layout parameters for the manufactured circuit are: a=37.6mm, b=14.5mm, h=1.524mm, y=1mm, y b =0.463mm, Rvia=0.45mm, v=1.9mm, d=0.325mm, p=1mm, W=3.5mm, Z=4.6mm, S=4.36mm, U=3.4mm.

[0058] To improve measurement reliability, a vector network analyzer (VNA) was used to measure three samples, with each sample being measured 10 times and the average value taken. The analyte 14 used in the three samples was: Teflon (…). =2.1, =0.0005), RF35 substrate ( =3.5, =0.0007), FR4 substrate ( =4.4, =0.02). The vector network analyzer simultaneously acquires the resonant frequencies of the reference and test ends, and calculates the frequency difference between the two. Substituting the resonant frequency offset into the mathematical expression for the relative permittivity, the relative permittivity of the test object 14 is obtained by inversion. Subsequently, the sensor accuracy was evaluated based on the error formula. Measurement results ( The display shows the relative permittivity ( ) compared to the actual permittivity ( ) The smallest deviation indicates the highest measurement accuracy. The error formula is as follows:

[0059]

[0060] After repeated experiments, the average errors of the three modes of the reconfigurable sensor are approximately 1.2%, 1.45%, and 1.42%.

[0061] Comparing Example 1 with the comparative example:

[0062] Comparative Example 1: The sensor disclosed in S. Jiang, G. Liu, M. Wang et al., “Design of High-Sensitivity Microfluidic Sensor Based on CSRR With Interdigital Structure,” IEEE Sensors J., vol. 23, no. 16, pp. 17901-17909, Aug. 2023;

[0063] Comparative Example 2: The sensor disclosed in P. Mohammadi, H. Teimouri, A. Mohammadi et al., “Dual Band, Miniaturized Permittivity Measurement Sensor With Negative-Order SIWResonator,” Ieee Sensors Journal, vol. 21, no. 20, pp. 22695-22702, Oct 15, 2021;

[0064] Comparative Example 3: The sensor disclosed in T. Qi, G. Liu, J. Yu et al., “A Quarter-Mode SubstrateIntegrated Waveguide Microwave Sensor Loaded With CCRR for Solid Material Measurement,” IEEE Sensors J., vol. 23, no. 18, pp. 21105-21112, Sept. 2023.

[0065] Comparative Example 4: The sensor disclosed in P. Mohammadi, A. Mohammadi, and A. Kara, “Enhanced Half-ModeSIW Loaded With Interdigital Capacitor for Permittivity Measurements,” IEEE Trans. Instrum. Meas., vol. 72, pp. 1-8, Apr. 2023;

[0066] Comparative Example 5: The sensor disclosed in Y. Gong, G. Liu, S. Jiang et al., “A DGS-CPW Microwave Sensor Loaded With SRR for Solid Material Measurement,” IEEE Transactions on Instrumentation and Measurement, vol. 73, pp. 1-8, 2024;

[0067] Table 1 Comparison of Example 1 with other similar sensors

[0068]

[0069] As can be seen from the above comparison, Example 1, by employing a phase change thin film, can achieve reconstruction through temperature changes, enabling measurements in three modes. Its frequency detection range is also significantly higher than that of the comparative examples, and it possesses comparable performance to the comparative examples. The detection range was improved, and higher sensitivity was achieved by loading the CSRR structure. The combination of the reference group and the test group resulted in lower error.

[0070] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A frequency-reconfigurable high-sensitivity differential sensor, comprising a reference group (4) and a test group (5), both having identical structures; characterized in that: The dielectric layer (1) includes an upper layer (2) above the dielectric layer (1) and a ground layer (3) below it. The upper layer (2) and the ground layer (3) are connected by vias. The upper layer (2), the ground layer (3), and the vias are all made of conductive materials. The upper layer (2) of both the reference group (4) and the test group (5) has pads (7) on the vias. The pads (7) have a cover layer (8) on them. The cover layer (8) includes a sapphire polymer substrate. The sapphire polymer substrate has The thin film; a first port (11) and a second port (12) are provided on both the reference group (4) and the test group (5).

2. The frequency-reconfigurable high-sensitivity differential sensor according to claim 1, characterized in that: Both the reference group (4) and the test group (5) are equipped with complementary open resonant rings.

3. The frequency-reconfigurable high-sensitivity differential sensor according to claim 2, characterized in that: The reference group (4) and the test group (5) each have two sets of complementary open-ring resonators, namely the first complementary open-ring resonator (9) and the second complementary open-ring resonator (10). The size of the first complementary open-ring resonator (9) is larger than the size of the second complementary open-ring resonator (10).

4. The frequency-reconfigurable high-sensitivity differential sensor according to claim 3, characterized in that: The pad (7), cover layer (8), and first port (11) are all located between the first complementary open-circuit resonator (9) and the second complementary open-circuit resonator (10).

5. The frequency-reconfigurable high-sensitivity differential sensor according to claim 1, characterized in that: The The thin film is bonded to the upper layer (2) of the area where the pad (7) is located. The film can completely cover the pads (7).

6. The frequency-reconfigurable high-sensitivity differential sensor according to claim 5, characterized in that: The thin film was deposited on a sapphire polymer substrate by pulsed laser deposition or sputtering and chemical vapor deposition, and then annealed in an oxygen atmosphere.

7. The frequency-reconfigurable high-sensitivity differential sensor according to claim 6, characterized in that: The The thin film was deposited on a sapphire polymer substrate using pulsed laser deposition.

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