A dielectric constant measurement sensor based on ltcc technology

Abstract

The application discloses a dielectric constant measurement sensor based on an LTCC process and relates to the technical field of dielectric constant measurement.The application comprises an upper metal layer, an LTCC dielectric substrate layer and a ground metal plate layer which are sequentially stacked from top to bottom; two L-shaped coupling feed grooves are symmetrically etched in the upper metal layer, the L-shaped coupling feed grooves are electrically connected with an input port, and are used for introducing microwave signals of the input port and generating electromagnetic coupling with a lower H-shaped slot line structure through the LTCC dielectric substrate layer; a copper edge wall is arranged on three side edges of the LTCC dielectric substrate layer, and a metal via array is arranged on a signal port side of the LTCC dielectric substrate layer, and the copper edge wall and the metal via array jointly form an enclosed electromagnetic shielding boundary.The application generates a strong electric field concentration effect through the H-shaped slot line structure, directly contacts with a solid sample to be measured to realize dielectric constant measurement, has the advantages of high measurement precision, good sensitivity, easy integration and the like, and is suitable for the measurement of the relative dielectric constant of a solid substance.

Description

Technical Field

[0001] This invention relates to the field of dielectric constant measurement technology, specifically to a dielectric constant measurement sensor based on LTCC technology. Background Technology

[0002] The dielectric constant is a core parameter characterizing the electromagnetic properties of a material, and its accurate measurement plays an irreplaceable role in many fields such as materials science, electronic communications, aerospace, and biomedicine. For example, in the field of microwave communications, the dielectric constant stability of the substrate directly determines the performance indicators of devices such as antennas and filters; in biological detection scenarios, early diagnosis of lesions can be achieved by measuring changes in the dielectric constant of biological tissues. Therefore, developing high-precision and high-reliability dielectric constant measurement technologies and equipment has always been a key research direction in the industry.

[0003] Existing dielectric constant measurement sensors based on the resonance principle mostly employ structures such as microstrip lines, coplanar waveguides, or cavity resonators, and rely on traditional printed circuit board (PCB) processes for fabrication. However, PCB processes have significant technical limitations: on the one hand, the dielectric constant stability of PCB substrates is poor, and high-frequency signal transmission losses are high, making the sensor's resonant characteristics susceptible to environmental interference and hindering further improvements in measurement accuracy; on the other hand, PCB processes have weak multi-layer integration capabilities. When sensors need to achieve complex electromagnetic shielding, multi-port signal transmission, or other functions, multiple substrates must be spliced ​​together, which not only increases the sensor's size and weight but also reduces structural consistency and reliability, making it difficult to meet the miniaturization and integration requirements of applications.

[0004] To address these issues, the industry has begun exploring the application of low-temperature co-fired ceramic (LTCC) technology in sensor fabrication. LTCC technology, through the co-firing of multiple layers of green ceramic strips, achieves integrated metal structures and ceramic media, effectively improving sensor measurement accuracy and miniaturization. However, existing LTCC-based sensors still utilize traditional microstrip resonant ring or open-ring structures in their sensing element design, limiting their electromagnetic field energy confinement and sensitivity enhancement. Furthermore, existing structures have poor adaptability to direct contact measurements with solid samples, typically requiring additional sample support or fixation devices.

[0005] Therefore, this invention proposes a dielectric constant measurement sensor based on LTCC technology. Summary of the Invention

[0006] The purpose of this invention is to provide a dielectric constant measurement sensor based on LTCC technology to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a dielectric constant measurement sensor based on LTCC technology, comprising an upper metal layer, an LTCC dielectric substrate layer, and a ground metal plate layer stacked sequentially from top to bottom; Two L-shaped coupling feed slots are symmetrically etched in the upper metal layer. The L-shaped coupling feed slots are electrically connected to the input port and are used to introduce the microwave signal of the input port and generate electromagnetic coupling with the lower H-shaped slot line structure through the LTCC dielectric substrate layer. The LTCC dielectric substrate layer has copper cladding walls on three sides, and a metal via array is arranged on the signal port side. The copper cladding walls and the metal via array together form an enclosed electromagnetic shielding boundary. The central region of the grounding metal plate layer is etched to form an H-shaped groove structure, and the region where the H-shaped groove structure is located serves as the core sensing region of the sensor. The L-shaped coupling feed groove of the upper metal layer and the H-shaped groove line structure of the ground metal plate layer form electromagnetic coupling through the LTCC dielectric substrate layer. The sensor directly contacts the solid sample under test through the sensing surface of the H-shaped groove line structure, and the dielectric constant is measured based on the change of the resonant characteristics of the electromagnetic coupling.

[0008] Furthermore, the L-shaped coupling feed slot includes a horizontal section and a vertical section that are perpendicularly connected to each other; the two L-shaped coupling feed slots are mirror-distributed with the center line on the signal port side as the axis of symmetry; the horizontal section is parallel to the horizontal etching groove direction of the H-shaped slot line structure, and the vertical section is parallel to the vertical etching groove direction of the H-shaped slot line structure.

[0009] Furthermore, the L-shaped coupling feed groove has a transverse section length of 1.5–2.2 mm, a longitudinal section length of 3.5–4.8 mm, and a groove width of 0.2–0.3 mm.

[0010] Furthermore, both the upper metal layer and the grounding metal plate layer are made of silver paste, formed by LTCC thick film printing process, and co-fired with the LTCC dielectric substrate layer at high temperature to form an integral structure. The L-shaped coupling feed groove and H-shaped groove line structure are obtained by patterning etching of the printed metal layer.

[0011] Furthermore, the LTCC dielectric substrate layer uses low-temperature co-fired ceramic green ceramic tape as the substrate material, which is formed by multi-layer lamination and high-temperature co-firing process. The dielectric constant of the ceramic green ceramic tape in the 3GHz microwave band is 7.0~8.5, the dielectric loss tangent is not greater than 0.008, and the bending strength is not less than 280MPa.

[0012] Furthermore, the LTCC dielectric substrate layer is composed of multiple layers of green ceramic tapes stacked together, with 5 to 20 layers and a single layer thickness of 80 to 250 μm.

[0013] Furthermore, the cross-sectional shape of the metal through-holes in the metal through-hole array is circular or square. When the metal through-hole is circular, its diameter is 0.13 to 0.2 mm; when the metal through-hole is square, its side length is not less than 0.61 mm; the center-to-center distance between adjacent through-holes is 3 times the diameter or side length of the through-hole.

[0014] Furthermore, the metal through-hole is prepared using the LTCC through-hole metallization process, which involves punching, filling with silver paste, and high-temperature co-firing.

[0015] Furthermore, the H-shaped groove structure includes two parallel transverse etching grooves and a vertical etching groove connecting the two transverse etching grooves. Two parallel transverse etching grooves are symmetrically distributed on both sides of the transverse centerline of the ground metal plate layer. Their electrical length matches one-quarter of the waveguide wavelength of the sensor's operating frequency band. The vertical etching groove is located at the midpoint of the ground metal plate layer. Its groove width is the same as that of the transverse etching grooves, and its electrical length is less than one-quarter of the waveguide wavelength. It is used as a coupling connection structure to realize electromagnetic coupling between the two transverse etching grooves.

[0016] Furthermore, the length L1 of the horizontal etching groove is 9.5–12 mm, and the groove width W1 is 0.2–0.3 mm; the length L2 of the vertical etching groove is 2.8–4.2 mm.

[0017] This invention has at least the following beneficial effects: 1. This invention utilizes the LTCC process to form an integrated structure by co-firing the upper metal layer and feed line structure, the middle dielectric substrate, and the bottom ground metal plate at high temperature. This eliminates the need for splicing multiple substrates or additional assembly steps in traditional PCB processes, significantly improving the structural consistency and reliability of the sensor. The overall size is greatly reduced, which is beneficial for embedding more complex microwave modules or realizing system-level packaging. At the same time, it reduces manufacturing costs and is suitable for mass production.

[0018] 2. This invention uses LTCC ceramic material as the dielectric substrate, which has stable dielectric properties and extremely low high-frequency dielectric loss. Combined with the enclosed electromagnetic shielding boundary formed by the copper cladding and the metal through-hole array on the port side, it can effectively block external electromagnetic interference and strictly confine the internal microwave energy to the resonant region, thereby obtaining pure and stable resonant characteristics and ensuring high repeatability and accuracy of sensor measurement results under mass production and different environmental conditions.

[0019] 3. The H-shaped groove structure designed in this invention can excite the fundamental mode and higher-order modes by reasonably configuring the electrical length ratio of the horizontal etching groove and the vertical etching groove, thereby forming two stable measurement frequency bands in a wide operating frequency band, expanding the sensor's measurement range of dielectric constant at different frequencies, and enhancing its flexibility and adaptability in application scenarios.

[0020] 4. This invention etches an H-shaped groove in the central region of the bottom ground metal plate as the core sensing area. This structure can highly concentrate electromagnetic energy around the groove, generating a strong electric field concentration effect. When the solid sample under test is directly attached to the sensing surface of the bottom H-shaped groove, even a small change in the sample's dielectric constant can cause a significant change in the resonant frequency and quality factor, thereby endowing the sensor with excellent sensitivity and meeting different needs from conventional to high-precision dielectric constant measurement.

[0021] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a three-dimensional schematic diagram of the overall structure of the present invention; Figure 2 This is a top view of the overall structure of the invention; Figure 3 This is a simulated resonance response curve of the sensor described in this invention.

[0024] Figure label: 1. Input port; 2. Metal via array; 3. Upper metal layer; 4. Vertical etching trench; 5. Horizontal etching trench; 6. LTCC dielectric substrate layer; 7. Embossing copper wall; 8. Grounding metal plate layer. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] Please see Figure 1 and Figure 2The present invention provides a technical solution: a dielectric constant measurement sensor based on LTCC process, comprising an upper metal layer, an LTCC dielectric substrate layer 6 and a ground metal plate layer 8 stacked sequentially from top to bottom; Two L-shaped coupling feed grooves 3 are symmetrically etched in the upper metal layer. The L-shaped coupling feed grooves 3 are electrically connected to the input port and are used to introduce the microwave signal of the input port and generate electromagnetic coupling with the lower H-shaped groove line structure. The LTCC dielectric substrate has stable dielectric properties and extremely low high-frequency loss, which makes the signal have low transmission loss in the microwave band, which helps to maintain the stability of the sensor resonance characteristics. Furthermore, the upper metal layer and the LTCC dielectric substrate are formed by thick film printing process and co-fired at high temperature, eliminating the interface gaps or adhesive layers between traditional multilayer boards, avoiding additional losses and reflections caused by poor delamination or bonding, and significantly improving the consistency and reliability of the structure. The LTCC dielectric substrate layer 6 has copper walls 7 on three sides, and metal via array 2 is arranged on the signal port side. The copper walls 7 and the metal via array 2 together form an enclosed electromagnetic shielding boundary. The continuous conductive boundary formed by the copper walls 7 and the metal via array 2 can effectively confine electromagnetic energy within the area defined by the dielectric substrate, preventing microwave signals from radiating outward from the side of the substrate or the port edge, thereby reducing transmission loss and improving the quality factor. The central region of the grounding metal plate layer 8 is etched to form an H-shaped groove structure. The area where the H-shaped groove structure is located serves as the core sensing area of ​​the sensor. The H-shaped groove structure can confine electromagnetic energy to a small area around the groove, forming a strong electric field concentration area. When the solid sample under test is in direct contact with this area, a small change in the dielectric constant of the sample can cause a significant change in the resonance characteristics, thereby improving the sensor's response sensitivity to changes in dielectric constant. The L-shaped coupling feed groove 3 of the upper metal layer and the H-shaped groove line structure of the lower ground metal plate layer 8 form electromagnetic coupling through the LTCC dielectric substrate layer 6. The sensor directly contacts the solid sample under test through the sensing surface of the H-shaped groove line structure, and the dielectric constant is measured based on the change of the resonant characteristics of the electromagnetic coupling.

[0027] Regarding the technical solution of this embodiment, the L-shaped coupling feed slot 3 includes a horizontal segment and a vertical segment that are perpendicularly connected to each other. The two L-shaped coupling feed slots 3 are mirror-distributed with the center line on the signal port side as the axis of symmetry. The horizontal segment is parallel to the direction of the horizontal etching groove 5 of the H-shaped slot line structure, and the vertical segment is parallel to the direction of the vertical etching groove 4 of the H-shaped slot line structure. This symmetrical double L-shaped layout achieves electromagnetic coupling between the input port and the lower H-shaped slot resonant unit through reasonable design of geometric parameters. The symmetrical distribution of the two L-shaped slots helps to reduce the parasitic effects caused by the asymmetrical structure and is beneficial to improving the consistency of the sensor response.

[0028] In this embodiment, both the upper metal layer and the grounding metal plate layer 8 are made of silver paste. After being integrally printed using LTCC thick film printing technology, the printed metal layers are patterned and etched to obtain two symmetrical L-shaped coupling feed slots 3 on the upper layer and an H-shaped slot line structure on the lower layer. The upper metal layer, the grounding metal plate layer 8, and the LTCC dielectric substrate layer 6 are co-fired at high temperature to form an integrated structure. The high conductivity of silver paste can effectively reduce the conductor loss of the metal layer, ensuring that the amplitude attenuation and phase distortion of the microwave signal during transmission are at a low level, thereby improving the quality factor and measurement resolution of the sensor. Furthermore, the silver paste and the LTCC ceramic green ceramic tape shrink and densify synchronously during high-temperature co-firing, forming a tight bond without gaps or voids. This eliminates the interface gaps or delamination risks that may exist in traditional lamination or bonding processes, significantly improving the continuity and stability of signal transmission.

[0029] The LTCC dielectric substrate layer 6 uses DuPont 951PT series ceramic green ceramic tape as the substrate material, which is formed by multi-layer lamination and high-temperature co-firing at 900℃. The dielectric constant of the ceramic green ceramic tape in the 3GHz microwave band is 7.0~8.5, the dielectric loss tangent is not greater than 0.008, and the bending strength is not less than 280MPa. For the technical solution of this embodiment, the dielectric constant of the ceramic green ceramic tape in the 3GHz microwave band is 7.8, the dielectric loss tangent is 0.006, and the bending strength is 320MPa. The high bending strength gives the dielectric substrate good rigidity and resistance to deformation. It is not easy to bend, crack or delaminate when in direct contact with solid samples, subjected to assembly pressure or external impact, ensuring the structural integrity of the sensor and the flatness of the measurement contact surface during long-term use.

[0030] Furthermore, the LTCC dielectric substrate layer 6 has 5 to 20 layers, with a single layer thickness of 80 to 250 μm. In the technical solution of this embodiment, a total of 10 layers of ceramic green ceramic tape are stacked, with a single layer thickness of 97 μm and an overall thickness of 970 μm. The thickness of each layer of green ceramic tape is uniform, which allows for precise control of the total thickness. This ensures that the key electrical parameters such as the characteristic impedance, effective dielectric constant, and waveguide wavelength of the resonant unit of the upper metal layer strictly meet the design expectations, improving the consistency and reproducibility of sensor performance. Moreover, through the stacking and co-firing of multiple thin green ceramic tapes, the dielectric substrate formed has sufficient rigidity to support the upper microstrip line and the bottom ground metal plate, making it less prone to bending or deformation when in direct contact with solid samples. It also maintains the thin and light characteristics of the overall thickness, making it easy to embed into miniaturized microwave modules or system-in-package.

[0031] Regarding the technical solution of this embodiment, the cross-sectional shape of the metal through-holes in the metal through-hole array 2 is circular or square. When the metal through-hole is circular, its diameter is 0.13 to 0.2 mm; when the metal through-hole is square, its side length is not less than 0.61 mm. The center-to-center distance between adjacent through-holes is 3 times the diameter or side length of the through-hole. Square through-holes and circular through-holes have comparable electromagnetic shielding performance. The specific shape can be selected according to the actual processing technology and layout density requirements. Specifically, a dense array of metal vias 2 is used on the signal input port 1 side, which together with the continuous metal surfaces on both sides of the L-shaped coupling feed groove 3 in the upper metal layer constitutes a shielding structure at the port. This can effectively suppress higher-order modes and edge radiation, improve the impedance matching of the port, reduce signal reflection, and ensure that the input energy is efficiently coupled to the sensing area. The copper wall 7 is a continuous metal layer, which, together with the periodically arranged metal vias on the port side, eliminates dead corners or weak points in the shielding boundary, making the electric field suppression effect around the entire substrate more uniform and avoiding resonant frequency drift or mode distortion caused by uneven shielding.

[0032] Regarding the technical solution of this embodiment, the metal through hole is prepared by LTCC through hole metallization process, which involves punching, filling with silver paste and high-temperature co-firing to achieve reliable electrical connection between the silver conductor in the hole and the upper metal layer and the bottom grounding metal plate 8, forming an enclosed equivalent electromagnetic shielding boundary with the copper walls 7 on the other three sides. The through-hole metallization and co-firing of the dielectric substrate are completed simultaneously. The silver conductor and the ceramic substrate maintain coordinated deformation during the shrinkage and densification process. There are no gaps or voids between the hole wall and the dielectric, which avoids the thermal stress mismatch or peeling problems that may occur in the later metallization of traditional processes, and significantly enhances the long-term reliability.

[0033] Regarding the technical solution of this embodiment, the H-shaped groove structure includes two parallel horizontal etching grooves 5 and a vertical etching groove 4 connecting the two horizontal etching grooves 5. Two parallel transverse etching grooves 5 are symmetrically distributed on both sides of the transverse centerline of the ground metal plate layer 8. Their electrical length matches the quarter-waveguide wavelength of the sensor's operating frequency band, so that each transverse etching groove 5 can independently generate a strong and stable resonant mode, providing the sensor with a clear and sharp resonant peak, which is beneficial to improving the resolution of dielectric constant measurement. The vertical etched groove 4 is located at the midpoint of the grounded metal plate layer 8 and has a vertically penetrating middle section (not shown in the figure). Its groove width is the same as that of the horizontal etched groove 5, and its electrical length is less than one-quarter of the waveguide wavelength. It is used as a coupling connection structure to realize electromagnetic coupling between the two horizontal etched grooves 5. This facilitates the effective connection of the electromagnetic energy of the two horizontal grooves with appropriate coupling strength, which not only ensures the uniformity of the resonant mode, but also avoids mode splitting or bandwidth distortion caused by over-coupling. Furthermore, the introduction of the vertical etched groove 4 into the vertical middle section makes the energy exchange between the two horizontal etched grooves 5 smoother. This moderately widens the working bandwidth while maintaining a high quality factor, reduces frequency jitter caused by slight offset of the sample contact position or environmental disturbance, and enhances the repeatability and anti-interference ability of the measurement. Furthermore, the length L1 of the transverse etching groove is 9.5–12 mm, and the groove width W1 is 0.2–0.3 mm; the length L2 of the vertical etching groove is 2.8–4.2 mm. The rationally designed ratio of the transverse groove length to the vertical groove length enables the H-shaped groove structure to excite the fundamental mode and higher-order modes, thereby forming two usable measurement frequency bands in a wider frequency band, expanding the sensor's measurement range of dielectric constant at different frequency bands, and enhancing the flexibility of applicable scenarios.

[0034] Regarding the technical solution of this embodiment, the sensing surface is the exposed surface of the bottom ground metal plate 8 after etching the H-shaped groove structure. The electric field distribution formed by the H-shaped groove is strictly confined to the periphery and vertical middle section of the groove. In particular, after the groove width is optimized, the electric field intensity reaches a high concentration at the edge of the groove. When the solid sample is directly attached to the surface of the bottom ground metal plate, the change in the dielectric constant of the sample can more strongly disturb the electric field, thereby significantly improving the sensor's response sensitivity to changes in dielectric constant.

[0035] The technical solution of this embodiment will be further elaborated below with reference to specific simulation experiments: In this embodiment, the LTCC dielectric substrate layer 6 is formed by stacking 10 layers of DuPont 951PT series (Al2O3-SiO2-ZnO system) ceramic green ceramic tapes. The thickness of a single green ceramic tape is 97μm, and the total thickness is 0.97mm. It is co-fired at 900℃. The ceramic material has a dielectric constant of 7.8, a dielectric loss tangent of 0.006, and a bending strength of 320MPa in the 3GHz microwave band.

[0036] Both the upper metal layer and the ground metal plate layer 8 are made of silver paste and formed by LTCC thick film printing process, and are co-fired with the dielectric substrate layer 6. Two L-shaped coupling feed slots 3 are symmetrically etched in the upper metal layer. The horizontal length of the L-shaped coupling feed slot 3 is 1.81 mm, the vertical length is 4.18 mm, and the slot width is 0.23 mm. The two L-shaped coupling feed slots 3 are mirrored with the center line of the signal port side as the axis of symmetry. By optimizing the geometric parameters of this symmetrical double L-shaped slot structure, the microwave signal of the input port 1 is electromagnetically coupled to the lower H-shaped slot line resonant unit through the L-shaped coupling feed slots 3.

[0037] The LTCC dielectric substrate layer 6 has copper walls 7 on three sides, and a metal via array 2 is provided on the signal port side. The via diameter is 0.13mm and the via spacing is 0.39mm, forming an enclosed electromagnetic shielding boundary with the copper walls 7 on the three sides.

[0038] The two transverse etched grooves 5 of the H-shaped groove structure have a length L1 = 10.71 mm and a groove width W1 = 0.23 mm. Their electrical length is approximately one-quarter of the waveguide wavelength, serving as the core electromagnetic resonant unit of the sensor and providing the basic resonant response. The vertical etched groove 4 has a length L2 = 3.4 mm and acts as a coupling connection structure. Its electrical length is less than one-quarter of the waveguide wavelength, enabling efficient electromagnetic coupling between the two transverse etched grooves 5 and optimizing the bandwidth and stability of the resonant frequency band.

[0039] Based on the above structural parameters, the electromagnetic characteristics of the sensor were optimized using the electromagnetic simulation software HFSS. First, the initial physical dimensions of each slot structure were determined according to the electric length theory. Then, a three-dimensional electromagnetic model was established in HFSS, and the optimal physical dimensions of the L-shaped coupled feed slot 3 and the H-shaped slot were calculated using HFSS. Electromagnetic simulation and debugging were then performed on the overall physical structure.

[0040] like Figure 3 The figure shows the simulated resonant response curve of the sensor in this embodiment. Simulation results show that the sensor has stable resonant characteristics in the 3.5GHz~5.5GHz frequency band, realizing dual-band measurement, and the measurement error for solid materials with dielectric constants of 2~8 is ≤2.5%; the overall size of the sensor is 20mm×20mm×1mm, realizing a miniaturized design.

[0041] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0042] The foregoing has shown and described the basic principles, main features, and advantages of this application. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of the claims of this application.

Claims

1. A dielectric constant measurement sensor based on LTCC technology, characterized in that, It includes an upper metal layer, an LTCC dielectric substrate layer (6), and a ground metal plate layer (8) stacked sequentially from top to bottom; Two L-shaped coupling feed trenches (3) are symmetrically etched in the upper metal layer. The L-shaped coupling feed trenches (3) are electrically connected to the input port and are used to introduce the microwave signal of the input port and generate electromagnetic coupling with the lower H-shaped groove line structure through the LTCC dielectric substrate layer (6). The LTCC dielectric substrate layer (6) has copper cladding walls (7) on three sides, and a metal via array (2) is arranged on its signal port side. The copper cladding walls (7) and the metal via array (2) together form an enclosed electromagnetic shielding boundary. The central region of the grounding metal plate layer (8) is etched to form an H-shaped groove structure, and the region where the H-shaped groove structure is located serves as the core sensing region of the sensor. The L-shaped coupling feed groove (3) of the upper metal layer and the H-shaped groove line structure of the ground metal plate layer (8) form electromagnetic coupling through the LTCC dielectric substrate layer (6). The sensor directly contacts the solid sample under test through the sensing surface of the H-shaped groove line structure, and the dielectric constant is measured based on the change of the resonance characteristics of the electromagnetic coupling.

2. The dielectric constant measurement sensor based on LTCC technology according to claim 1, characterized in that: The L-shaped coupling feed groove (3) includes a horizontal section and a vertical section that are perpendicularly connected to each other; the two L-shaped coupling feed grooves (3) are mirror-distributed with the center line on the signal port side as the axis of symmetry; the horizontal section is parallel to the horizontal etching groove direction of the H-shaped groove line structure, and the vertical section is parallel to the vertical etching groove direction of the H-shaped groove line structure.

3. The dielectric constant measurement sensor based on LTCC technology according to claim 2, characterized in that: The L-shaped coupling feeder (3) has a transverse section length of 1.5 to 2.2 mm, a longitudinal section length of 3.5 to 4.8 mm, and a groove width of 0.2 to 0.3 mm.

4. The dielectric constant measurement sensor based on LTCC technology according to claim 1, characterized in that: The upper metal layer and the ground metal plate layer (8) are both made of silver paste and formed by LTCC thick film printing process. They are then co-fired with the LTCC dielectric substrate layer (6) at high temperature to form an integral structure. The L-shaped coupling feed groove (3) and the H-shaped groove line structure are obtained by patterning the printed metal layer.

5. A dielectric constant measurement sensor based on LTCC technology according to claim 1, characterized in that: The LTCC dielectric substrate layer (6) uses low-temperature co-fired ceramic green ceramic tape as the substrate material, and is formed by multi-layer lamination and high-temperature co-firing process. The dielectric constant of the ceramic green ceramic tape in the 3GHz microwave band is 7.0~8.5, the dielectric loss tangent is not greater than 0.008, and the bending strength is not less than 280MPa.

6. A dielectric constant measurement sensor based on LTCC technology according to claim 5, characterized in that: The LTCC dielectric substrate layer (6) is composed of multiple layers of ceramic green ceramic tape, with 5 to 20 layers and a single layer thickness of 80 to 250 μm.

7. A dielectric constant measurement sensor based on LTCC technology according to claim 1, characterized in that: The cross-sectional shape of the metal through holes in the metal through hole array (2) is circular or square. When the metal through hole is a circular hole, its diameter is 0.13 to 0.2 mm; when the metal through hole is a square hole, its side length is not less than 0.61 mm; the center distance between adjacent through holes is 3 times the diameter or side length of the through hole.

8. A dielectric constant measurement sensor based on LTCC technology according to claim 7, characterized in that: The metal through-holes are prepared using the LTCC through-hole metallization process, which involves punching, filling with silver paste, and co-firing at high temperature.

9. A dielectric constant measurement sensor based on LTCC technology according to claim 1, characterized in that: The H-shaped groove structure includes two parallel transverse etching grooves (5) and a vertical etching groove (4) connecting the two transverse etching grooves (5); Two parallel transverse etching grooves (5) are symmetrically distributed on both sides of the transverse centerline of the ground metal plate layer (8). Their electrical length matches the quarter-waveguide wavelength of the sensor's operating frequency band. The vertical etching groove (4) is located at the midpoint of the ground metal plate layer (8) and has a vertically penetrating middle section. Its groove width is consistent with that of the transverse etching groove (5), and its electrical length is less than the quarter-waveguide wavelength. It is used as a coupling connection structure to realize electromagnetic coupling between the two transverse etching grooves (5).

10. A dielectric constant measurement sensor based on LTCC technology according to claim 9, characterized in that: The length L1 of the horizontal etching groove (5) is 9.5-12 mm, and the groove width W1 is 0.2-0.3 mm; the length L2 of the vertical etching groove (4) is 2.8-4.2 mm.

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