Electromagnetic multi-functional high-resolution sensor based on microwave negative resistance circuit compensation technology

Abstract

The application discloses a kind of electromagnetic multifunctional high-resolution sensors based on microwave negative resistance circuit compensation technology, and it relates to the field of sensor technology.The sensor of the present application comprises a passive resonant cavity, a first ring-shaped microfluidic chip embedded in the passive resonant cavity, a second ring-shaped microfluidic chip and a negative resistance compensation circuit.The passive resonant cavity is composed of an upper dielectric substrate and a lower dielectric substrate vertically superimposed.The present application connects the adjacent two layers of dielectric substrate around the hollow metal cylinder through the ring-shaped bottom metal layer, forms an equivalent inductor column in the center of the resonant cavity, and serves as the inner conductor of the short-circuit coaxial line.The cylindrical area around the inner conductor has a strong magnetic field, which serves as the magnetic permeability sensing area.The upper and lower second metal through holes are connected through the ring-shaped metal layer between the two polar plates, which is equivalent to a ring-shaped parallel-plate capacitor, forming the outer conductor of the short-circuit coaxial line.There is a strong electric field between the ring-shaped parallel-plate capacitor, which serves as the dielectric sensing area.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology, and in particular relates to an electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology. Background Technology

[0002] With the development of microwave technology in many fields (military, medical, food, metallurgy, etc.), various high-frequency devices have been developed and applied, and a variety of new magnetic media materials have emerged in various industries. The demand for measuring the magnetoelectric properties of materials is constantly increasing. In military and civilian technological applications such as radar, microwave communication, and electronic countermeasures, materials that can absorb microwaves are needed.

[0003] Ferrite magnetic materials are excellent microwave absorbing materials with a wide absorption range. Incorporating ferrite and chromium alloy nanoparticles into coatings enhances their microwave absorption and infrared absorption / dissipation properties. Therefore, accurately determining the basic magnetoelectric properties of ferrite and nanoparticles is of high practical significance. Furthermore, nanomagnetic liquid materials are stable colloidal substances formed by uniformly dispersing magnetic nanoparticles coated with an organic surfactant in a base liquid. Because magnetic liquids can be guided by external magnetic fields, and some magnetic substances are non-toxic, nanomagnetic liquids are also widely used in biomedical engineering, such as in magnetothermal therapy. Magnetothermal therapy involves injecting nanomagnetic liquid... When inserted into a tumor, the nanomagnetic particles are confined to the tumor area using an external magnetic field. Then, an alternating electromagnetic field is applied to heat the nanomagnetic particles, raising the tumor area to 41–46°C. Because tumor cells are more sensitive to temperature than healthy cells, this method can conveniently and effectively destroy diseased cells. This method provides localized heating without toxic side effects and is considered one of the main methods for future cancer treatment. When heating the nanomagnetic particles using an alternating electromagnetic field, the complex permeability of the nanomagnetic particles determines the heating efficiency. To achieve a suitable heating efficiency, the permeability of the nanomagnetic liquid needs to be accurately measured. Therefore, studying the basic magnetoelectric properties of various magnetic liquids has high practical significance for biomedical engineering.

[0004] Existing methods for measuring complex permittivity and complex permeability can be mainly divided into resonance methods, free-space transmission methods, and coaxial transmission line methods. Microwave transmission line methods can measure the complex permittivity and complex permeability of materials over a wide frequency band, which is beneficial for studying the dispersion characteristics of materials at different frequencies. Compared to other methods, resonance methods have been widely used due to their unique advantages such as high quality factor and high precision. Microwave resonance methods can more accurately characterize the material properties of the analyte at specific frequencies, but many microwave sensors can only detect permittivity or permeability separately. In recent years, researchers have proposed multifunctional sensors with a single structure that can simultaneously characterize magnetoelectric properties, which have advantages such as low cost, compact structure, high design flexibility, and ease of integration into radio frequency detection systems. However, currently reported multifunctional sensors still suffer from poor separation of electric and magnetic fields, and the measurement of the permittivity of magnetic materials is affected by their high magnetic loss, resulting in significant errors.

[0005] To address this, an electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology is designed. By employing a sensing scheme with a short-circuited coaxial line embedded in the resonant cavity, and utilizing its excellent electromagnetic separation characteristics to characterize the basic electromagnetic properties of the material, a technical solution is provided. Summary of the Invention

[0006] The purpose of this invention is to provide an electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology to solve the problems mentioned in the background art.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution:

[0008] This invention relates to an electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology. The sensor comprises a passive resonant cavity, a first annular microfluidic chip, a second annular microfluidic chip, and a negative resistance compensation circuit embedded in the passive resonant cavity. The passive resonant cavity is composed of an upper dielectric substrate and a lower dielectric substrate stacked longitudinally.

[0009] Both the upper and lower dielectric substrates have annular stepped grooves at their centers. The upper dielectric substrate has a four-layer structure consisting of a top metal layer, a middle dielectric layer, a bottom metal layer, and an annular metal layer at the bottom of the stepped groove.

[0010] The lower dielectric substrate has a three-layer structure consisting of a top metal layer, a middle dielectric layer, and a bottom metal layer.

[0011] The resonant cavity of the passive resonant cavity is surrounded by a ring of first metal through holes, which are etched at the same positions on the upper dielectric substrate and the lower dielectric substrate.

[0012] A metallized via is formed at the center of the upper dielectric substrate, and a fourth metallized via is formed at the center of the lower dielectric substrate. The two metallized vias overlap longitudinally and are joined together by the annular bottom metal at the bottom of the metallized via of the upper dielectric substrate and the annular top metal at the top of the metallized via of the lower dielectric substrate.

[0013] The bottom metal layer of the upper dielectric substrate is etched to the middle dielectric layer to form a first annular stepped groove. The outer diameter edge of the first annular stepped groove is close to the first metal via, and the inner diameter edge is close to the metallized via. The first annular stepped groove is etched upward to part of the middle dielectric layer to form an annular microfluidic chip embedding groove, into which the first annular microfluidic chip is embedded.

[0014] The top metal layer of the lower dielectric substrate is etched down to the middle dielectric layer to form a second annular stepped groove. The inner edge of the second annular stepped groove is close to the fourth metal via. The second annular stepped groove is etched down to a portion of the middle dielectric layer to form an annular microfluidic chip embedding groove, into which the second annular microfluidic chip is embedded.

[0015] The upper and lower dielectric substrates have two rings of second and third metal vias distributed along the central axis of the cavity. The second and third metal vias overlap longitudinally to form an upper capacitor pillar and a lower capacitor pillar. According to the concentric ring area formed by the two rings of second and third metal vias, the bottom of the annular stepped groove of the upper dielectric substrate and the upper surface of the lower dielectric substrate are provided with an annular metal layer that overlaps longitudinally.

[0016] Furthermore, the first annular microfluidic chip has a unidirectional microfluidic channel;

[0017] The second ring-shaped microfluidic chip has a unidirectional microfluidic channel.

[0018] Furthermore, the upper dielectric substrate has two metallized open first vias distributed between two rings of second metal vias, extending downwards from the top metal layer, which communicate with the microfluidic channels of the first annular microfluidic chip and serve as inlet and outlet holes for the microfluidic channels; the upper dielectric substrate also has a non-metallized open second via distributed in the center of the metallized via, which communicates with the microfluidic channels of the second annular microfluidic chip and serves as the inlet for the second microfluidic channels.

[0019] The lower dielectric substrate has a non-metallized open third through-hole distributed in the center of the fourth metal through-hole, which is connected to the microfluidic channel of the second annular microfluidic chip and serves as the liquid outlet of the second microfluidic channel.

[0020] Furthermore, the upper and lower regions of the top metal layer of the upper dielectric substrate have two first coplanar waveguide feed lines that are symmetrical about the horizontal axis; the negative resistance compensation circuit is connected to the passive resonant cavity through the second coplanar waveguide feed line.

[0021] Furthermore, the first annular microfluidic chip uses polytetrafluoroethylene (PTFE) as the material; the second annular microfluidic chip uses PTFE as the material.

[0022] Furthermore, the centers of the first annular microfluidic chip, the second annular microfluidic chip, the first annular stepped groove, the second annular stepped groove, the annular metal layer, the annular bottom metal, the annular top metal, and the metallized via at the center position, as well as the center of the fourth metal via, are all on the same vertical straight line.

[0023] Furthermore, a rectangular notch is etched on the lower dielectric substrate at the position corresponding to the first coplanar waveguide feed line.

[0024] Furthermore, a tapered microstrip line is connected to the second coplanar waveguide feed line and then to the negative resistance compensation circuit.

[0025] Furthermore, the intermediate dielectric layer material of the two dielectric substrates is Rogers 4350B, with a relative permittivity of 3.48, a relative permeability of 1, and a loss tangent of 0.0037.

[0026] Furthermore, the negative resistance compensation circuit includes a resistor, a capacitor, an inductor, a transistor, and a varactor diode; one end of inductor L1 is connected to the base (b) of transistor BFP420, and the other end of inductor L1 is directly grounded; the collector (c) of transistor BFP420 is connected to the cathode of varactor diode, and one end of inductor L2 is connected; the cathode of varactor diode SMV1405 is connected to one end of inductor L4 and one end of capacitor C1; the other end of inductor L4 is connected to the positive terminal of voltage source VBIas; the negative terminal of voltage source VBIas is connected to... Ground; the other end of capacitor C1 serves as the output terminal of the negative resistance circuit; one end of resistor R2 is connected to the other end of inductor L2, and the other end of resistor R2 is connected to the positive terminal of voltage source V1; the negative terminal of voltage source V1 is directly grounded; the emitter e of transistor BFP420 is connected to one end of inductor L3 and one end of capacitor C2 respectively; one end of resistor R3 is connected to the other end of inductor L3, and the other end of resistor R3 is connected to the negative terminal of voltage source V2; the positive terminal of voltage source V2 is directly grounded; one end of resistor R1 is connected to the other end of capacitor C2, and the other end of resistor R1 is directly grounded.

[0027] The present invention has the following beneficial effects:

[0028] 1. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology proposed in this invention has a closed structure. The electromagnetic energy is confined inside the resonant cavity and cannot be radiated into free space, thereby ensuring the high quality factor characteristics of the passive resonant cavity.

[0029] 2. This invention combines a short-circuit coaxial line structure with a resonant cavity to obtain an electromagnetic multifunctional sensor for simultaneously measuring the dielectric constant and magnetic permeability of a liquid medium.

[0030] 3. In this invention, the inner conductor of the short-circuited coaxial line is formed by the longitudinal overlap of metallized vias at the center of the upper and lower dielectric substrates. The magnetic field is strongest and the electric field is weakest around the inner conductor of the coaxial line. By setting the permeability sensing area in the cylindrical region surrounding the inner conductor, the magnetic field and electric field in the permeability measurement area are separated.

[0031] 4. In this invention, two rings of metal vias distributed along the central axis of the cavity on the upper and lower dielectric substrates overlap longitudinally to form an upper capacitor column and a lower capacitor column. In the concentric ring region enclosed by the two rings of metal vias, the bottom of the annular stepped groove of the upper dielectric substrate and the upper surface of the lower dielectric substrate are provided with an annular metal layer that overlaps longitudinally, forming the upper and lower plates of the annular capacitor. The two annular capacitor columns connected by parallel plate capacitors form the outer conductor of the short-circuit coaxial line in the cavity. The electric field is strongest and the magnetic field is weakest in the annular gap region between the upper and lower annular capacitor plates. The dielectric sensing area is set in this annular gap region to achieve the separation of the magnetic field and electric field in the dielectric constant measurement area.

[0032] 5. This invention integrates two annular microfluidic chips in a longitudinal nested manner, so that the microfluidic channels of the two annular microfluidic chips are located in the gap region with the greatest electric field strength and the cylindrical region with the greatest magnetic field strength in the resonant cavity, respectively. This makes full use of the electric field region and magnetic field region of the short-circuited coaxial line in the resonant cavity, thereby improving the measurement sensitivity.

[0033] 6. This invention utilizes negative resistance circuit compensation technology to design a negative resistance circuit that matches the impedance of the passive resonator. It adds a negative resistance resistor connected in parallel with the internal impedance of the passive resonator to compensate for the heat loss power consumed by the inherent resistance inside the passive resonator, thereby improving the quality factor of the tag sensor and achieving high-resolution measurement of the basic electromagnetic properties of liquid media materials. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1This is a cross-sectional schematic diagram of the sensor-loaded microfluidic chip of the present invention;

[0036] Figure 2 The interface of the sensor loading microfluidic chip of the present invention is not shown in the schematic diagram;

[0037] Figure 3 This is a schematic diagram of the equivalent circuit model of the microwave negative resistance circuit of the present invention;

[0038] Figure 4 This is a schematic diagram of the assembly of the various components of the multifunctional sensor of the present invention;

[0039] Figure 5 This is a front view of the upper dielectric substrate of the present invention;

[0040] Figure 6 A schematic diagram of the back side of the upper dielectric substrate of the present invention;

[0041] Figure 7 This is a front view of the lower dielectric substrate of the present invention;

[0042] Figure 8 This is an enlarged schematic diagram of the first coplanar waveguide feed line of the present invention;

[0043] Figure 9 This is an enlarged schematic diagram of the second coplanar waveguide feed line of the present invention;

[0044] Figure 10 This is a three-dimensional schematic diagram of the first annular microfluidic chip of the present invention;

[0045] Figure 11 This is a three-dimensional schematic diagram of the second annular microfluidic chip of the present invention;

[0046] Figure 12 This is a transmission response curve of a sample with a real part of different dielectric constants simulated in the dielectric constant sensing region of the multifunctional sensor of the present invention.

[0047] Figure 13 This is a transmission response curve of a sample with a real part of different magnetic permeability in the magnetic permeability sensing area of ​​the multifunctional sensor of the present invention.

[0048] Figure 14 This is a transmission response curve of a sample with a real part of different magnetic permeability in the dielectric constant sensing region of the multifunctional sensor of the present invention.

[0049] Figure 15 This is a transmission response curve of a sample with a real part of different dielectric constants simulated in the permeability sensing region of the multifunctional sensor of the present invention.

[0050] Figure 16 This is a transfer response curve of the multifunctional device of the present invention under different transistor and diode bias voltages;

[0051] Figure 17 This is a schematic diagram showing the relationship between the transmission curves of the multifunctional sensor of the present invention in active and passive modes and the dielectric constant of the sample under test.

[0052] Figure 18 This is a schematic diagram showing the relationship between the transmission curves of the multifunctional sensor of the present invention under active and passive conditions and the magnetic permeability of the sample under test.

[0053] The attached diagram lists the components represented by each number as follows:

[0054] 1. Passive resonant cavity; 11. Upper dielectric substrate; 111. First metal via; 112. Second metal via; 113. First annular stepped groove; 114. Metallized via; 115. Annular bottom metal; 116. Metallized open first via; 117. Non-metallized open second via; 118. First coplanar waveguide feed line; 119. Second coplanar waveguide feed line; 1110. Annular metal layer; 1111. Tapered microstrip line; 12. Lower dielectric substrate; 121. Third metal via; 122. Second annular stepped groove; 123. Fourth metal via; 124. Non-metallized open third via; 125. Annular top metal; 126. Rectangular notch; 2. First annular microfluidic chip; 21. First insulating adhesive; 22. First microfluidic channel; 3. Second annular microfluidic chip; 31. Second insulating adhesive; 32. Second microfluidic channel. Detailed Implementation

[0055] 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.

[0056] Please see Figure 1-11 As shown, the present invention is an electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology.

[0057] The electromagnetic multi-functional high-resolution sensor consists of a passive resonant cavity 1 and a negative resistance compensation circuit.

[0058] The passive resonant cavity 1 is composed of an upper dielectric substrate 11 and a lower dielectric substrate 12 stacked longitudinally. Each dielectric substrate has an annular stepped groove at its center. The upper dielectric substrate 11 has a four-layer structure: a top metal layer, a middle dielectric layer, a bottom metal layer, and an annular metal layer at the bottom of the stepped groove. The lower dielectric substrate 12 has a three-layer structure: a top metal layer, a middle dielectric layer, and a bottom metal layer.

[0059] The bottom metal layer of the upper dielectric substrate 11 is etched down to the intermediate dielectric layer to form a first annular stepped groove 113. The outer edge of the first annular stepped groove 113 is close to the first metal via 111, and the inner edge is close to the metallized via 114. The first annular stepped groove 113 is etched upwards to a portion of the intermediate dielectric layer to form an annular microfluidic chip embedding groove. The area of ​​the first annular stepped groove 113 is the same as the area of ​​the first annular microfluidic chip 2, and the depth of the stepped groove is the same as the thickness of the first annular microfluidic chip 2. The first annular microfluidic chip 2 is embedded in the annular groove with its front side facing upwards, and the front side of the chip is bonded to the groove of the upper dielectric substrate 11 with the first insulating adhesive 21. The purpose of this is to seal the microchannel and thus prevent leakage of the liquid to be tested.

[0060] The top metal layer of the lower dielectric substrate 12 is etched down to the intermediate dielectric layer to form a second annular stepped groove 122. The inner edge of the second annular stepped groove 122 is close to the fourth metal via 123. The second annular stepped groove 122 is etched downwards to a portion of the intermediate dielectric layer to form an embedding groove for the second annular microfluidic chip 3. The area of ​​the second annular stepped groove 122 is the same as the area of ​​the second annular microfluidic chip 3, and the depth of the stepped groove is the difference between the thickness of the second annular microfluidic chip 3 and the first annular microfluidic chip 2. The second annular microfluidic chip 3 is embedded in the annular groove with its front side facing upwards. The front side of the chip is bonded to the groove of the upper dielectric substrate 11 with the first insulating adhesive 21, and the back side of the chip is bonded to the annular stepped groove 122 of the lower dielectric substrate 12 with the second insulating adhesive 31. The purpose of this is to seal the microchannel and prevent leakage of the liquid to be tested. The two annular microfluidic chips are concentric and nested together, with their front sides on the same plane.

[0061] In this embodiment, preferably, the first annular stepped groove 113 corresponding to the upper dielectric substrate 11 has a depth of 0.885 mm, an outer diameter of 24.5 mm, and an inner diameter of 5.5 mm. The second annular stepped groove 122 corresponding to the lower dielectric substrate 12 has a depth of 1.05 mm, an outer diameter of 5.5 mm, and an inner diameter of 2.8 mm.

[0062] In the actual structure, the two dielectric substrates mentioned above are fixed with screws with a radius of 1 mm. The screws are located outside the resonant cavity and do not affect the resonant characteristics of the resonant cavity.

[0063] In this embodiment, the intermediate dielectric layer material of both dielectric substrates is Rogers 4350B, which has a relative permittivity of 3.48, a relative permeability of 1, and a loss tangent of 0.0037.

[0064] The upper dielectric substrate 11, used to house the negative resistance compensation circuit, has a length of 95 mm and a width of 65 mm. The lower dielectric substrate 12 has the same length and width, preferably both being 65 mm, and each dielectric substrate has a thickness of 1.524 mm.

[0065] The intermediate dielectric layer of the two dielectric substrates described above has a periodically arrayed array of first metal vias 111 near the edge of the resonant cavity. The first metal vias 111 overlap longitudinally, forming an equivalent metal wall of the resonant cavity. In this embodiment, preferably, the radius of the metallized via is 0.5 mm, and the distance between the centers of two adjacent metallized vias is 1.52 mm.

[0066] Both the upper dielectric substrate 11 and the lower dielectric substrate 12 have metallized vias 114 and 123 at their center positions. These two metallized vias overlap longitudinally and are joined together by an annular bottom metal 115 at the bottom of the metallized via in the upper dielectric substrate 11 and an annular top metal 125 at the top of the metallized via in the lower dielectric substrate 12, forming a central inductor pillar or an inner conductor of a short-circuited coaxial line. The cylindrical region surrounding the inductor pillar is a permeability sensing area. In this embodiment, preferably, the radii of the metallized vias 114 and 123 are 2.4 mm, and the inner diameters of the annular bottom metal 115 and top metal 125 are 2.4 mm and 2.8 mm, respectively.

[0067] The upper dielectric substrate 11 and the lower dielectric substrate 12 have two rings of second metal vias 112 and third metal vias 121 distributed annularly along the central axis of the cavity. The second metal vias 112 and third metal vias 121 on the upper and lower dielectric substrates overlap longitudinally to form an upper capacitor pillar and a lower capacitor pillar. A ring-shaped metal layer 1110, longitudinally overlapping with the bottom of the annular stepped groove of the upper dielectric substrate 11 and the upper surface of the lower dielectric substrate 12, forms the upper and lower plates of the annular capacitor. Together, they form the outer conductor of the short-circuit coaxial line. The annular gap region between the upper and lower annular capacitor plates is the dielectric constant sensing region. In this embodiment, preferably, the inner ring of the two rings of second metal through holes 112 and third metal through holes 121 has a radius of 0.4 mm, adjacent inner ring metal through holes have a radius of 1.5 mm, and the inner ring radius is 11 mm; the outer ring of the metal through holes has a radius of 0.4 mm, adjacent outer ring metal through holes have a radius of 0.5 mm, and the outer ring radius is 14 mm; the inner diameter of the annular metal layer 1110 is 10.6 mm, and the outer diameter is 15.2 mm.

[0068] See Figure 8The first coplanar waveguide feed line 118 is located on the top metal layer of the upper dielectric substrate 11. A rectangular notch 126 is etched on the lower dielectric substrate 12 at the position corresponding to the coplanar waveguide feed line 118, serving as a placement location for mounting a solderless terminal connector. This is to excite the resonant cavity. The feed line adopts a tapered gradient structure and appropriately reduces the feed depth. Preferably, its total length is 11mm, its inner width is 3mm, its outer width is 1mm, and the width of the gaps on both sides of the feed line is 0.25mm. Simultaneously, to accommodate the use of the solderless terminal connector, two symmetrical screw holes with a radius of 1mm are etched, and the center distance between the two holes is 9.53mm.

[0069] The first coplanar waveguide feeder has a tapered, gradually changing structure. The tapered feeder has a total length of 11 mm, a width of 3 mm, and a feed port width of 1 mm. The gaps on both sides of the feeder are 0.25 mm wide, and the gap at the end is 8 mm long.

[0070] See Figure 9 The second coplanar waveguide feed line 119 on the dielectric substrate 11 is directly connected to the tapered microstrip line 1111 for connecting the negative resistance compensation circuit 4. Preferably, the total length of the coplanar waveguide is 8 mm, the width is 3.5 mm, and the gap width on both sides of the feed line is 0.25 mm; the microstrip line directly connected to the coplanar waveguide has a length of 2 mm, a width of 3.5 mm, a tapered width of 1 mm, and a total length of 4.5 mm.

[0071] The thickness of the first annular microfluidic chip 2 is 0.8 mm; the depth of the first microfluidic channel 22 is 0.45 mm. The inlet and outlet ports of the first microfluidic channel 22 are connected to two metallized open first through-holes 116 of the upper dielectric substrate 11.

[0072] The second annular microfluidic chip 3 has a thickness of 1.8 mm; the first microfluidic channel 22 has a depth of 1.3 mm. The liquid inlet of the second microfluidic channel 32 is connected to the non-metallized open second via 117 of the upper dielectric substrate 11. The liquid outlet of the second microfluidic channel 32 is connected to the non-metallized open third via 124 of the lower dielectric substrate 12.

[0073] The first annular stepped groove 113 of the upper dielectric substrate 11 has an outer diameter of 49 mm, an inner diameter of 5.6 mm, and a depth of 0.885 mm. The second annular stepped groove 122 of the lower dielectric substrate 12 has an outer diameter of 11 mm, an inner diameter of 5.6 mm, and a depth of 1.05 mm.

[0074] The bottom of the annular stepped groove of the upper dielectric substrate 11 and the upper surface of the lower dielectric substrate 12 are provided with an annular metal layer 1110 that overlaps longitudinally; the outer diameter of the annulus is 15.2 mm and the inner diameter is 10.6 mm.

[0075] The negative resistance compensation circuit 4 is connected to the passive resonant cavity 1 via a coplanar waveguide-to-microstrip line. The negative resistance circuit includes resistors, capacitors, inductors, transistors, and varactor diodes; one end of inductor L1 is connected to the base (b) of transistor BFP420, and the other end of inductor L1 is directly grounded; the collector (c) of transistor BFP420 is connected to the cathode of the varactor diode, and one end of inductor L2 is connected; the cathode of varactor diode SMV1405 is connected to one end of inductor L4 and one end of capacitor C1; the other end of inductor L4 is connected to the positive terminal of voltage source VBIas; The negative terminal of voltage source VBIas is grounded; the other end of capacitor C1 serves as the output terminal of the negative resistance circuit; one end of resistor R2 is connected to the other end of inductor L2, and the other end of resistor R2 is connected to the positive terminal of voltage source V1; the negative terminal of voltage source V1 is directly grounded; the emitter e of transistor BFP420 is connected to one end of inductor L3 and one end of capacitor C2 respectively; one end of resistor R3 is connected to the other end of inductor L3, and the other end of resistor R3 is connected to the negative terminal of voltage source V2; the positive terminal of voltage source V2 is directly grounded; one end of resistor R1 is connected to the other end of capacitor C2, and the other end of resistor R1 is directly grounded.

[0076] When measuring the dielectric constant of a medium, to facilitate the introduction and export of the liquid being measured, the upper dielectric substrate 11 has two metallized open first vias 116 distributed between two rings of second metal vias 112, extending downwards from the top metal layer, which communicate with the first microfluidic channel 22 of the microfluidic chip 2, serving as the inlet and outlet of the first microfluidic channel 22. In this embodiment, preferably, the radius of the two open vias is 0.9 mm. When measuring the magnetic permeability of a medium, to facilitate the introduction and export of the liquid being measured, the upper dielectric substrate 11 has a non-metallized open second via 117 distributed in the center of the metallized via 114, extending downwards from the top metal layer, which communicates with the microfluidic channel of the second annular microfluidic chip 3, serving as the inlet of the second microfluidic channel 32. The lower dielectric substrate 12 has a non-metallized third via 124 distributed in the center of the fourth metal via 123, extending upwards from the bottom metal layer, which communicates with the microfluidic channel of the second annular microfluidic chip 3, serving as the outlet of the second microfluidic channel 32. Preferably, the radius of the two open through holes is 0.6 mm.

[0077] See Figure 10 A unidirectional microfluidic channel 22 is etched on the front side of the first annular microfluidic chip 2. The start and end points of the microfluidic channel are both circular, and the center of the circle is on the same vertical line as the center of the open via, with a corresponding radius of 0.8 mm. In this embodiment, the material of the first annular microfluidic chip 2 is polytetrafluoroethylene, with a dielectric constant of 2.035 and a loss tangent of 0.0015.

[0078] See Figure 11A unidirectional microfluidic channel 32 is etched on the front side of the second annular microfluidic chip 3. The microfluidic channel starts at a sloping guide port and ends at a circular outlet below. In this embodiment, the material of the second annular microfluidic chip 3 is resin, with a dielectric constant of 3.3 and a loss tangent of 0.003.

[0079] Figure 12 The transmission response curves of samples with different real parts of dielectric constants are shown in the dielectric constant sensing region. Figure 13 The transmission response curves of simulated samples with different real parts of magnetic permeability are shown in the magnetic permeability sensing region. Figure 14 The transmission response curves are shown for samples with different permeability in the dielectric constant sensing region. Figure 15 The above simulation results show the transmission response curves of samples with different dielectric constants in the permeability sensing region. The simulation results illustrate that the influence of sample permeability in the dielectric constant sensing region and the influence of sample dielectric constant in the permeability sensing region are extremely small; compared to the sensitivity of the sensor test, the mutual influence between dielectric constant and permeability is negligible.

[0080] Figure 16 This diagram shows the transmission response curves of the multifunctional sensor proposed in this invention under different transistor and diode bias voltages. By adjusting different combinations of transistor and diode bias voltages, the quality factor of the resonant cavity at the corresponding resonant frequency S21 can be improved.

[0081] Figure 17 and Figure 18 The figures show the S21 response curves of the multifunctional sensor proposed in this invention when the dielectric constant or magnetic permeability of the sample changes in the dielectric sensing region and the magnetic sensing region, respectively. The passive resonator has a very low quality factor, making it difficult to determine its corresponding resonant frequency. However, connecting the negative resistance compensation circuit does not affect the sensitivity of the sensor. At the same time, the negative resistance circuit can greatly improve the quality factor and resolution of the resonant cavity by compensating for energy in the resonant cavity.

[0082] In the description of this specification, 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 the invention. In this specification, 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.

[0083] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. An electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology, characterized in that, The sensor includes a passive resonant cavity (1), a first annular microfluidic chip (2) embedded in the passive resonant cavity (1), a second annular microfluidic chip (3) and a negative resistance compensation circuit (4); the passive resonant cavity (1) is composed of an upper dielectric substrate (11) and a lower dielectric substrate (12) stacked longitudinally. The upper dielectric substrate (11) and the lower dielectric substrate (12) both have annular stepped grooves in their centers. The upper dielectric substrate (11) has a four-layer structure consisting of a top metal layer, a middle dielectric layer, a bottom metal layer, and an annular metal layer at the bottom of the stepped groove. The lower dielectric substrate (12) has a three-layer structure consisting of a top metal layer, an intermediate dielectric layer, and a bottom metal layer. The resonant cavity of the passive resonant cavity (1) is surrounded by a ring of first metal through holes (111), which are etched at the same position on the upper dielectric substrate (11) and the lower dielectric substrate (12). The upper dielectric substrate (11) has a metallized via at its center and the lower dielectric substrate (12) has a fourth metallized via at its center. The two metallized vias overlap longitudinally and are joined together by the annular bottom metal at the bottom of the metallized via of the upper dielectric substrate (11) and the annular top metal at the top of the metallized via of the lower dielectric substrate (12). The bottom metal layer of the upper dielectric substrate (11) is etched to the middle dielectric layer to form a first annular stepped groove (113). The outer diameter edge of the first annular stepped groove (113) is close to the first metal through hole, and the inner diameter edge is close to the metallized through hole. The first annular stepped groove (113) is etched upward to part of the middle dielectric layer to form an annular microfluidic chip embedding groove, into which the first annular microfluidic chip (2) is embedded. The top metal layer of the lower dielectric substrate (12) is etched to the middle dielectric layer to form a second annular stepped groove (122). The inner diameter edge of the second annular stepped groove (122) is close to the fourth metal through hole. The second annular stepped groove (122) is etched downward to part of the middle dielectric layer to form an annular microfluidic chip embedding groove, into which the second annular microfluidic chip (3) is embedded. The upper dielectric substrate (11) has two rings of second metal through holes (112) distributed in a ring along the central axis of the cavity, and the lower dielectric substrate (12) has two rings of third metal through holes (121) distributed in a ring along the central axis of the cavity. The second metal through holes and the third metal through holes (121) overlap longitudinally to form an upper capacitor pillar and a lower capacitor pillar. According to the concentric ring area formed by the two rings of second metal through holes and the third metal through holes (121), the bottom of the annular stepped groove of the upper dielectric substrate (11) and the upper surface of the lower dielectric substrate (12) are provided with an annular metal layer (1110) that overlaps longitudinally.

2. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 1, characterized in that, The first annular microfluidic chip (2) has a unidirectional microfluidic channel; The second ring-shaped microfluidic chip (3) has a unidirectional microfluidic channel.

3. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 2, characterized in that, The upper dielectric substrate (11) has two metallized open first through-holes (116) distributed between two rings of second metal through-holes (112) from the top metal layer downwards, which are connected to the microfluidic channels of the first annular microfluidic chip (2) and serve as the liquid inlet and outlet holes of the microfluidic channel (22); the upper dielectric substrate (11) has a non-metallized open second through-hole (117) distributed in the center of the metallized through-hole (114) from the top metal layer downwards, which are connected to the microfluidic channels of the second annular microfluidic chip (3) and serve as the liquid inlet of the second microfluidic channel (32); The lower dielectric substrate (12) has a non-metallized open third through hole (124) distributed in the center of the fourth metal through hole (123) from the bottom metal upwards, which is connected to the microfluidic channel of the second annular microfluidic chip (3) and serves as the liquid outlet hole of the second microfluidic channel (32).

4. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 3, characterized in that, The upper and lower regions of the top metal layer of the upper dielectric substrate (11) have two first coplanar waveguide feed lines that are symmetrical about the horizontal axis; the negative resistance compensation circuit (4) is connected to the passive resonant cavity (1) through the second coplanar waveguide feed line.

5. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 4, characterized in that, The first annular microfluidic chip (2) is made of polytetrafluoroethylene (PTFE); the second annular microfluidic chip (3) is made of PTFE.

6. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 5, characterized in that, The first annular microfluidic chip (2), the second annular microfluidic chip (3), the first annular stepped groove (113), the second annular stepped groove (122), the annular metal layer (1110), the annular bottom metal, the annular top metal, and the metallized through hole at the center position and the center of the fourth metal through hole (123) are all on the same vertical straight line.

7. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 4, characterized in that, The lower dielectric substrate (12) has a rectangular notch etched at the position corresponding to the first coplanar waveguide feed line.

8. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 4, characterized in that, A tapered microstrip line is connected to the second coplanar waveguide feed line and then to the negative resistance compensation circuit (4).

9. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 4, characterized in that, The intermediate dielectric layer material of both dielectric substrates is Rogers 4350B, with a relative permittivity of 3.48, a relative permeability of 1, and a loss tangent of 0.0037.

10. The electromagnetic multifunctional high-resolution sensor based on microwave negative resistance circuit compensation technology according to claim 1, characterized in that, The negative resistance compensation circuit (4) includes a resistor, a capacitor, an inductor, a transistor, and a varactor diode; one end of inductor L1 is connected to the base b of transistor BFP420, and the other end of inductor L1 is directly grounded; the collector c of transistor BFP420 is connected to the cathode of varactor diode, and one end of inductor L2 is connected; the cathode of varactor diode SMV1405 is connected to one end of inductor L4 and one end of capacitor C1; the other end of inductor L4 is connected to the positive terminal of voltage source VBIas; the negative terminal of voltage source VBIas is grounded. The other end of capacitor C1 serves as the output terminal of the negative resistance circuit; one end of resistor R2 is connected to the other end of inductor L2, and the other end of resistor R2 is connected to the positive terminal of voltage source V1; the negative terminal of voltage source V1 is directly grounded; the emitter e of transistor BFP420 is connected to one end of inductor L3 and one end of capacitor C2 respectively; one end of resistor R3 is connected to the other end of inductor L3, and the other end of resistor R3 is connected to the negative terminal of voltage source V2; the positive terminal of voltage source V2 is directly grounded; one end of resistor R1 is connected to the other end of capacitor C2, and the other end of resistor R1 is directly grounded.

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