Electromagnetic sensor for detecting rotation angle and pressure of finger and detection method

Abstract

The invention discloses an electromagnetic sensor for detecting the rotation angle and pressure of a finger and a detection method. The electromagnetic sensor comprises a metal microstrip transmission line on the upper layer, a medium substrate on the middle layer and a grounding layer on the lower layer, the metal micro-strip transmission line is composed of a micro-strip double-branch coupler with an open-circuit port and a plurality of interdigital capacitors connected with the micro-strip double-branch coupler. The grounding layer is provided with a plurality of complementary split resonant rings with the same number as the interdigital capacitors, and one complementary split resonant ring corresponds to one interdigital capacitor; the dielectric substrate has electromagnetic wave propagation performance and is arranged between the metal microstrip transmission line and the grounding layer; when the fingertip of the finger is close to any interdigital capacitor, the contact area is a local electric field concentration area of the electromagnetic sensor, small changes of electromagnetic characteristics of a transmission line can be accurately sensed when the finger rotates and applies pressure, and then accurate measurement of the rotation angle of the finger and the change of the pressure of the finger is provided.

Description

Technical Field

[0001] The present invention relates to an electromagnetic sensor for detecting the rotation angle and pressure of a finger, specifically, an electromagnetic sensor combining a traditional microstrip double-branch coupler structure with a co-digital capacitor and a complementary split resonant ring (CSRR) structure, and is used to detect the rotation angle and pressure change of a fingertip, belonging to the field of electromagnetic sensors. Background Art

[0002] With the rapid development of smart wearable devices, virtual reality, medical health monitoring and other fields, accurate finger rotation angle and pressure detection technology has received widespread attention. Existing pressure and angle sensors mostly use optical, capacitive, mechanical and other principles, but these technologies often face problems such as insufficient sensitivity, poor stability or complex multi-sensor systems. Especially when it is required to detect rotation angle and pressure changes at the same time, the existing technology usually requires the use of multiple independent sensors in combination, which not only increases the complexity of the system, but also increases the cost and maintenance difficulty. Therefore, how to design a sensor with a simple structure, high sensitivity and the ability to simultaneously detect finger rotation angle and pressure has become a technical problem that needs to be solved urgently.

[0003] In the field of electromagnetic sensors, existing electromagnetic sensors have been less studied in finger rotation angle and pressure detection, while double-branch couplers, as a classic microwave component, are widely used in signal distribution, filtering, power monitoring, etc. The traditional double-branch coupler structure usually contains four ports, among which the input port, output port, coupling port and isolation port are connected by microstrip transmission lines. The coupling port couples part of the input signal to the output port, and the isolation port avoids mutual interference of signals through electromagnetic isolation technology. This structure can efficiently distribute electromagnetic energy, so it has been widely used in many wireless communication systems. However, since the output and coupling ends of the traditional coupler structure are not optimized, they are easily affected by the external environment, resulting in unstable measurement results. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention opens the output end and the coupling end of the traditional double-branch coupler, adds a matching load at the open circuit, and further improves it through a cross-toe capacitor and a complementary split resonant ring (CSRR) structure, thereby designing a new electromagnetic sensor that can efficiently and accurately detect the changes in the rotation angle and pressure of the finger.

[0005] The present invention is implemented according to the following technical solutions:

[0006] In a first aspect, the present invention provides an electromagnetic sensor for detecting a rotation angle and pressure of a finger, comprising:

[0007] The metal microstrip transmission line on the upper layer is composed of a microstrip double-branch coupler with an open port and a plurality of cross-toed capacitors connected thereto;

[0008] A lower grounding layer, on which a plurality of complementary split resonant rings having the same number as the co-digital capacitors are arranged, and one complementary split resonant ring corresponds to one of the co-digital capacitors;

[0009] The dielectric substrate of the middle layer has electromagnetic wave propagation performance and is arranged between the metal microstrip transmission line and the ground layer;

[0010] When the fingertip is close to any cross-digital capacitor, this contact area becomes the local electric field concentration area of ​​the electromagnetic sensor, which can accurately sense the slight changes in the electromagnetic characteristics of its transmission line when the finger rotates and applies pressure, thereby providing accurate measurement of the finger rotation angle and finger pressure changes.

[0011] In some embodiments, the microstrip double-branch coupler includes four ports, namely an input port, an output port, a coupling port and an isolation port; the output port and the coupling port of the microstrip double-branch coupler are open-circuited, and matching loads are added at the open ports respectively; the input port and the isolation port of the microstrip double-branch coupler are respectively set as transmission lines with fixed resistance values, the input port inputs the signal, and the isolation port outputs the signal; a connecting line is provided between two adjacent ports, and the length of each connecting line is one-quarter wavelength; the middle part of each connecting line is disconnected, and the cross-toe capacitor is arranged at the disconnected part.

[0012] In some embodiments, the upper connecting line between the input terminal and the output terminal, the upper side co-digital capacitor and the lower connecting line between the coupling terminal and the isolation terminal, the lower side co-digital capacitor are symmetrical to each other; the left connecting line between the input terminal and the isolation terminal, the left side co-digital capacitor and the right connecting line between the output terminal and the coupling terminal, the right side co-digital capacitor are symmetrical to each other; wherein, the upper connecting line and the protruding parts of the transmission lines at the ports on both sides thereof are each provided with a cut angle, and the lower connecting line and the protruding parts of the transmission lines at the ports on both sides thereof are each provided with a cut angle.

[0013] In some embodiments, the upper interdigital capacitor has the same structure as the lower interdigital capacitor, and both are composed of multiple interdigital pole pieces of the same size, which are staggered in pairs and do not touch each other; the left interdigital capacitor has the same structure as the right interdigital capacitor, and both are composed of multiple interdigital pole pieces of the same size, which are staggered in pairs and do not touch each other.

[0014] In some embodiments, the upper side co-digital capacitor is composed of an upper co-digital pole piece, a middle co-digital pole piece and a lower co-digital pole piece located on the input end side, and an upper co-digital pole piece and a lower co-digital pole piece located on the output end side; wherein, the upper co-digital pole piece on the output end side is inserted between the upper co-digital pole piece and the middle co-digital pole piece on the input end side, and the lower co-digital pole piece on the output end side is inserted between the middle co-digital pole piece and the lower co-digital pole piece on the input end side; the gap distance between two adjacent co-digital pole pieces is the same, and the gap distance at the side where the top of each co-digital pole piece is disconnected from the metal microstrip transmission line is the same.

[0015] In some embodiments, the left-side interdigital capacitor is composed of a left interdigital pole piece, a right interdigital pole piece and a middle interdigital pole piece located on the input end side; wherein, the middle interdigital pole piece on the isolation end side is inserted between the left interdigital pole piece and the right interdigital pole piece on the input end side; the gap distance between two adjacent interdigital pole pieces is the same, and the gap distance at the side where the top of each interdigital pole piece is disconnected from the metal microstrip transmission line is the same.

[0016] In some embodiments, the number of the complementary split resonant rings is four, and the four complementary split resonant rings are symmetrical in structure left-right and top-bottom, and the center of each complementary split resonant ring corresponds to the center of a co-digital capacitor; wherein the radii of the left complementary split resonant ring and the right complementary split resonant ring are both R1, and the radii of the upper complementary split resonant ring and the lower complementary split resonant ring are both R2, and R1 is greater than R2.

[0017] In some embodiments, the complementary split resonant ring is composed of a cylinder and a ring cylinder formed by a large ring and a small ring arranged concentrically etched on a ground layer; the small ring in each complementary split resonant ring is provided with an opening 180 degrees apart from the large ring; the width of the large ring is the same as that of the small ring; the openings of the large rings in the upper and lower complementary split rings are both facing the input end, and the openings of the small rings are both facing the output end; the opening of the large ring in the left complementary split ring is facing the isolation end, and the opening of the small ring is facing the input end; the opening of the large ring in the right complementary split ring is facing the output end, and the opening of the small ring is facing the coupling end.

[0018] In some embodiments, the input end and the isolation end of the microstrip double-branch coupler are respectively welded to the female connector of the RF coaxial connector through connector pins, and the ground end of the RF coaxial connector is welded to the lower ground layer.

[0019] In a second aspect, the present invention provides a detection method based on the above electromagnetic sensor, comprising the following steps:

[0020] Step 1: Connect the RF coaxial connectors welded on the input and isolation ends of the electromagnetic sensor to the interface feeder corresponding to the vector network analyzer, so that the microwave signal is transmitted through the upper metal transmission line of the electromagnetic sensor; by debugging the vector network analyzer, measure and record the return loss curve of the electromagnetic sensor under no-load conditions, and obtain its resonant frequency point and corresponding amplitude;

[0021] The electromagnetic sensor can be equivalent to a parallel or series resonant circuit composed of inductance L and capacitance C. The resonant frequency f0 of its equivalent resonant circuit is expressed as:

[0022]

[0023] Where L is the inductance and C is the capacitance;

[0024] Step 2: Place the fingertip at any cross-digital capacitor in the metal transmission line on the upper layer of the electromagnetic sensor, and record the change in return loss when the finger touches at different finger rotation angles and different pressures, paying special attention to the shift of the resonant frequency;

[0025] When the electromagnetic sensor measures the rotation angle and finger pressure of the finger, the capacitance of the interdigital capacitance part will change as the finger approaches. The size of the changed capacitance ΔC is expressed as:

[0026]

[0027] Where ε0 is the dielectric constant of vacuum, ε r is the relative dielectric constant of the tissue between the fingers, A is the effective area of ​​the interdigital capacitor electrode, and d is the distance between the interdigital capacitor electrode pieces;

[0028] Step 3: When the finger touches or applies pressure, the capacitance value changes, causing the resonant frequency to change; at this time, the new resonant frequency f′0 is calculated by the following formula:

[0029]

[0030] Where L is the inductance and C is the capacitance.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The electromagnetic sensor of this invention has a novel structure. The traditional double-branch coupler is improved by opening its output end and coupling end, and adding a matching load at the open circuit to ensure the stability of the signal. The present invention also uniquely combines the cross-toe capacitor and complementary split resonant ring (CSRR) structure. This combination enhances the electromagnetic performance of the sensor.

[0033] 2. By opening the output and coupling ends of the double-branch coupler and adding a matching load, and combining the cross-digital capacitor and complementary split resonant ring (CSRR) structure, the signal reflection and noise interference problems are effectively reduced, the signal stability is ensured, and the sensor can respond to physical changes (finger rotation and pressure changes) in two different frequency bands at the same time, realizing dual-frequency characteristics. Through this dual-frequency response characteristic, the electromagnetic sensor can greatly improve the measurement accuracy and response speed, and enhance its frequency selectivity and sensitivity.

[0034] 3. The method for measuring the finger rotation angle and the pressure applied by the finger is novel. The present invention adopts a combination of cross-digital capacitance and complementary split resonant ring, which can effectively detect the changes in the finger rotation angle and pressure. By analyzing the changes in the return loss curve, the resonant frequency changes of the electromagnetic wave can be extracted, and there is a close relationship between the capacitance value and the resonant frequency. Therefore, the electromagnetic sensor can not only measure the rotation angle, but also measure the pressure applied by the finger. This feature makes the application of electromagnetic sensors more diversified and adapts to the detection needs of various physical quantities.

[0035] 4. Simple structure and easy integration. Compared with the traditional multi-sensor system, the electromagnetic sensor of the present invention has a simple structure and high integration, and can realize multiple detection functions of finger rotation angle and applied pressure in one sensor. Since the electromagnetic sensor has a low manufacturing cost, its maintenance and maintenance work is also greatly simplified, which is suitable for wide promotion in practical applications.

[0036] The electromagnetic sensor of the present invention is not only suitable for detecting finger rotation angle and pressure change, but also has a wide range of application prospects. Its dual-frequency response characteristics enable the sensor to work stably in complex environments and has strong anti-interference ability, especially in the fields of smart wearable devices, virtual reality, medical health monitoring, and robot control, which has huge market application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are part of the present invention and are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the accompanying drawings described below are only some embodiments. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0038] In the attached picture:

[0039] Figure 1 It is a schematic diagram of the three-layer structure of an electromagnetic sensor provided by the present invention, and shows that the input and output sides of the transmission line are respectively welded through the female connectors of the coaxial connector.

[0040] Figure 2 A schematic diagram of the structure of a metal microstrip transmission line containing four cross-toe capacitors in the electromagnetic sensor provided by the present invention;

[0041] Figure 3 This is a schematic diagram of the ground layer structure containing four complementary split resonant ring structures in the electromagnetic sensor provided by the present invention.

[0042] Figure 4 It is an enlarged schematic diagram of the upper side cross-digital capacitor structure contained in the upper metal microstrip transmission line in the electromagnetic sensor of the present invention.

[0043] Figure 5 It is an enlarged schematic diagram of the left cross-digital capacitor structure contained in the upper metal microstrip transmission line in the electromagnetic sensor of the present invention.

[0044] Figure 6 It is an enlarged schematic diagram of a complementary split resonant ring structure obtained by etching the upper side of the lower ground layer in the electromagnetic sensor of the present invention.

[0045] Figure 7 It is an enlarged schematic diagram of a complementary split resonant ring structure obtained by etching the left side of the lower ground layer in the electromagnetic sensor of the present invention.

[0046] Figure 8 This is a device connection diagram for the use of the electromagnetic sensor of the present invention.

[0047] Fig. 9 It is a simulated S11 return loss curve of the electromagnetic sensor of the present invention when it is unloaded.

[0048] Fig.10 It is a curve diagram of the S21 transmission coefficient simulated when the electromagnetic sensor of the present invention is unloaded.

[0049] Fig.11 This is a simulated S11 return loss curve of the electromagnetic sensor of the present invention when the fingertip is rotated 60°.

[0050] Fig.12 This is a simulated S11 return loss curve of the electromagnetic sensor of the present invention when the fingertip is rotated 120°.

[0051] Fig.13 This is a simulated S11 return loss curve of the electromagnetic sensor of the present invention when the fingertip is rotated 240°.

[0052] Fig.14 This is a graph of the S11 return loss simulated when the finger tip of the electromagnetic sensor of the present invention applies normal pressure to the sensor.

[0053] Fig.15This is a graph of the S11 return loss simulated when the finger tip of the electromagnetic sensor of the present invention applies increased pressure to the sensor.

[0054] Fig.16 This is a graph of the S11 return loss simulated when the finger tip applies a second increased pressure to the electromagnetic sensor of the present invention.

[0055] Figure numerals: 1-metal microstrip transmission line, 2-dielectric substrate, 3-ground layer, 4-input end, 5-output end, 6-coupling end, 7-isolation end, 8-main transmission line (upper connecting line), 9-coupling line (right connecting line), 10-coupling isolation line (lower connecting line), 11-input isolation line (left connecting line), 12-upper side co-digital capacitor, 13-right side co-digital capacitor, 14-lower side co-digital capacitor, 15-left side co-digital capacitor, 16-input side RF coaxial connector; 17-output side RF coaxial connector; 18-upper side complementary split resonant ring, 19-right side complementary split resonant ring, 20-lower side complementary split resonant ring, 21-left side complementary split Resonant ring, 22-upper co-digital pole piece, 23-middle co-digital pole piece; 24-lower co-digital pole piece, 25-upper co-digital pole piece, 26-lower co-digital pole piece, 27-gap, 28-gap, 29-left co-digital pole piece, 30-right co-digital pole piece, 31-middle co-digital pole piece, 32-large circular ring, 33-small circular ring, 34-circular ring width, 35-large circular ring opening, 36-small circular ring opening, 37-circular ring cylinder, 38-cylinder, 39-large circular ring diameter, 40-small circular ring, 41-circular ring width, 42-large circular ring opening, 43-small circular ring opening, 44-circular ring cylinder, 45-cylinder, 46-co-digital capacitor, 47-complementary split resonant ring, 48-cut angle.

[0056] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0058] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0059] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] like Figure 1 , Figure 2 , Figure 3 As shown, in order to solve the defects of the prior art and the latest needs in the industry, the present invention provides an electromagnetic sensor for detecting the rotation angle and pressure of a finger, by improving the structure of the traditional microstrip double-branch coupler structure, and adding a cross-toe capacitor and a complementary split resonant ring (CSRR) structure. The specific structure is as follows: the electromagnetic sensor is a three-layer structure, namely, the metal microstrip transmission line 1 of the upper layer, the dielectric substrate 2 of the middle layer and the grounding layer 3 of the lower layer; the metal microstrip transmission line 1 of the upper layer is improved based on the traditional microstrip double-branch coupler, and is composed of a microstrip double-branch coupler with an open port and a plurality of co-digital capacitors 46 connected thereto; the grounding layer 3 of the lower layer is provided with a plurality of complementary split resonant rings 47 having the same number as the co-digital capacitors 46, and one complementary split resonant ring 47 corresponds to one co-digital capacitor 46; the dielectric substrate 2 of the middle layer has electromagnetic wave propagation performance, and is arranged between the metal microstrip transmission line 1 and the grounding layer 3; the input end and the isolation end of the microstrip double-branch coupler are respectively welded to the female connectors of the RF coaxial connectors 16 and 17 through connector pins (that is, the input side RF coaxial connector 16 with a characteristic impedance of 50 ohms and the output side RF coaxial connector 17 with a characteristic impedance of 50 ohms in the attached figure), and the grounding ends of the RF coaxial connectors 16 and 17 are welded to the grounding layer 3 of the lower layer. When the finger tip is close to any interdigital capacitor 46, this contact area is the local electric field concentration area of ​​the electromagnetic sensor, which can accurately sense the slight changes in the electromagnetic characteristics of its transmission line when the finger rotates and applies pressure, thereby providing accurate measurement of the finger rotation angle and finger pressure changes.

[0061] The specific structure of the above-mentioned dielectric substrate is further described below.

[0062] like Figure 1As shown, the dielectric substrate 2 has a total length of 52.47 mm, a total width of 43.65 mm, and a thickness of 0.813 mm. It is made of Rogers Ro4003c model plate, and has a relative dielectric constant of 3.38 and a dielectric loss tangent of 0.0027. This material not only provides good electromagnetic wave propagation performance, low loss, high stability, and the advantages of adapting to high-frequency applications, but also improves the measurement accuracy, sensitivity, and reliability of the sensor.

[0063] The specific structure of the above-mentioned microstrip double-branch coupler is further described below.

[0064] like Figure 2 As shown, the microstrip double-branch coupler includes four ports, namely an input terminal 4, an output terminal 5, a coupling terminal 6 and an isolation terminal 7; the output terminal 5 and the coupling terminal 6 of the microstrip double-branch coupler are open-circuited, and matching loads are added at the open ports (that is, the output terminal 5 is a matching load transmission line and the coupling terminal 6 is a matching load transmission line); the input terminal 4 and the isolation terminal 7 of the microstrip double-branch coupler are respectively set as 50-ohm transmission lines, which are 14 mm long, 1.86 mm wide and 18 um high; the input terminal 4 inputs signals (that is, the input terminal 4 is a 50-ohm transmission line), and the isolation terminal 7 outputs signals (that is, the isolation terminal 7 is a 50-ohm transmission line).

[0065] Further solutions, such as Figure 1 , Figure 2 As shown, in the input end 4, output end 5, coupling end 6 and isolation end 7 of the upper metal microstrip transmission line 1, a connecting line is provided between each of the two adjacent ports, namely, the upper connecting line between the input end 4 and the output end 5 (i.e. Figure 2 The main transmission line 8 in the output terminal 5 and the right connecting line of the coupling terminal 6 (i.e. Figure 2 The coupling line 9 in the coupling end 6 and the left connecting line of the isolation end 7 (i.e. Figure 2 The coupling isolation line 10 in the isolation terminal 7 and the lower connection line of the input terminal 4 (ie Figure 2 The length of each connecting line is one quarter wavelength λ0:

[0066]

[0067] Where c is the speed of light (about 3×10 8 m / s), f is the operating frequency.

[0068] Further solutions, such as Figure 1 , Figure 2As shown, the middle part of each connecting line is disconnected, and a co-digital capacitor 46 is arranged at the disconnected part. The upper connecting line (i.e., the main transmission line 8) between the input terminal 4 and the output terminal 5, the upper co-digital capacitor 12, the lower connecting line (i.e., the coupling isolation line 10) between the coupling terminal 6 and the isolation terminal 7, and the lower co-digital capacitor 14 are symmetrical to each other; the left connecting line (i.e., the input isolation line 11) between the input terminal 4 and the isolation terminal 7, the left co-digital capacitor 15, the right connecting line (i.e., the coupling line 9) between the output terminal 5 and the coupling terminal 6, and the right co-digital capacitor 13 are symmetrical to each other; wherein, the main transmission line 8 and the protruding part of the transmission line at the ports on both sides thereof are each provided with a cut corner 48, and the coupling isolation line 10 and the protruding part of the transmission line at the ports on both sides thereof are each provided with a cut corner 48. It should be noted that the depths of the four cut corners 48 are the same, all of which are 1.86 mm.

[0069] As can be seen from the above, the present invention effectively reduces the signal reflection and noise interference problems and ensures the stability of the signal by opening the output end 5 and the coupling end 6 of the traditional double-branch coupler and adding a matching load at the open circuit. The matching load can adjust the impedance of the port so that the system achieves the best signal transmission effect.

[0070] The specific structure of the above-mentioned cross-toe capacitor is further described below.

[0071] Figure 4 , Figure 5 This is a diagram showing the enlarged structure of the upper interdigital capacitor 12 and the left interdigital capacitor 15 among the four interdigital capacitors 46. Because the upper connecting lines and the lower connecting lines of the four interdigital capacitors 46 are symmetrical with each other, namely the main transmission line 8 between the input terminal 4 and the output terminal 5 and the coupling isolation line 10 between the coupling terminal 6 and the isolation terminal 7; and the left connecting line and the right connecting line are symmetrical with each other, namely the coupling line 9 between the output terminal 5 and the coupling terminal 6 and the input isolation line 11 between the isolation terminal 7 and the input terminal 4, only one of the symmetrical ones, namely the upper interdigital capacitor 12 and the left interdigital capacitor 15, is described here.

[0072] like Figure 4 As shown, the upper interdigital capacitor 12 is composed of a plurality of interdigital pole pieces of the same size, staggered in pairs and not in contact with each other. Specifically, the upper interdigital capacitor 12 is composed of an upper interdigital pole piece 22, a middle interdigital pole piece 23 and a lower interdigital pole piece 24 located on the input end side, and an upper interdigital pole piece 25 and a lower interdigital pole piece 26 located on the output end side; wherein, the upper interdigital pole piece 25 on the output end side is inserted between the upper interdigital pole piece 22 and the middle interdigital pole piece 23 on the input end side, and the lower interdigital pole piece 26 on the output end side is inserted between the middle interdigital pole piece 23 and the lower interdigital pole piece 24 on the input end side.

[0073] Further solutions, such as Figure 4As shown, the upper interdigital pole piece 22, the middle interdigital pole piece 23, the lower interdigital pole piece 24 on the input end side and the upper interdigital pole piece 25 and the lower interdigital pole piece 26 on the output end side are staggered in pairs, but not in contact. The length, width and height of these five interdigital pole pieces are the same, which are 7.3mm long, 0.5mm wide and 18um high respectively, and the gap 27 between the staggered pole pieces is the same everywhere, which is 0.1mm, and the gap 28 at the side where the top of each interdigital pole piece is disconnected from the metal microstrip transmission line is also the same everywhere, which is 0.2mm.

[0074] like Figure 5 As shown, the left-side interdigital capacitor 15 is composed of a plurality of interdigital pole pieces of the same size, staggered in pairs and not in contact with each other. Specifically, the left-side interdigital capacitor 15 is composed of a left interdigital pole piece 29 located on the input end side, a right interdigital pole piece 30 and a middle interdigital pole piece 31 located on the isolation end side; wherein the middle interdigital pole piece 31 on the isolation end side is inserted between the left interdigital pole piece 29 and the right interdigital pole piece 30 on the input end side.

[0075] Further solutions, such as Figure 5 As shown, the left interdigital pole piece 29, the right interdigital pole piece 30 on the input end side and the middle interdigital pole piece 31 on the isolation end side are also staggered in pairs and have no contact. The length, width and height of these three interdigital pole pieces are the same, which are 7.38mm long, 0.54mm wide and 18um high respectively. The gap 27 between the staggered pole pieces is the same everywhere, which is 0.12mm, and the gap 28 at the side where the top of each interdigital pole piece is disconnected from the metal microstrip transmission line is also the same everywhere, which is 0.12mm.

[0076] The specific structure of the complementary split resonant ring is further described below.

[0077] Figure 3The bottom of the dielectric substrate 2 of the middle layer is provided with a grounding layer 3 containing four complementary split resonant rings 47. The centers of the four complementary split resonant rings 47 correspond to the centers of the interdigital capacitors 46 on the four transmission lines on the metal microstrip transmission line 1 of the upper layer, respectively. The four complementary split resonant rings 47 are symmetrical in pairs, that is, the upper complementary split resonant ring 18 and the lower complementary split resonant ring 20 are symmetrical to each other, that is, the upper complementary split resonant ring 18 under the interdigital capacitor on the main transmission line 8 between the input end 4 and the output end 5 and the interdigital capacitor on the coupling isolation line 10 between the coupling end 6 and the isolation end 7 are symmetrical to each other. The lower complementary split resonant ring 20 under the toe capacitor is symmetrical; and the left complementary split ring 21 and the right complementary split ring 19 are symmetrical with each other, that is, the right complementary split resonant ring 19 under the toe capacitor of the coupling line 9 between the output end 5 and the coupling end 6 and the left complementary split resonant ring 21 under the toe capacitor of the input isolation line 11 between the isolation end 7 and the input end 4 are symmetrical, wherein the left complementary split resonant ring structure 21 and the right complementary split resonant ring structure 19 have larger radii than the upper complementary split resonant ring structure 18 and the lower complementary split resonant ring structure 20.

[0078] Further solutions, such as Figure 3 As shown, the four complementary split resonant rings 47 are respectively formed by a cylinder and a ring cylinder by etching a large ring and a small ring arranged concentrically on the ground layer 3, wherein the etched small ring and the large ring both have openings, and the opening directions of the large ring and the small ring in the four etched rings are opposite.

[0079] Figure 6 , Figure 7 It is an enlarged structural diagram of the upper complementary split resonant ring 18 and the left complementary split resonant ring 21 among the four complementary split resonant rings 47 etched in the ground layer; because the centers of the four complementary split resonant rings 47 correspond to the centers of the four transmission line co-indentation capacitors 46 on the upper metal microstrip transmission line 1, and the four port connecting lines in the upper transmission line 1 are symmetrical in the upper and lower directions and in the left and right directions, the four complementary split resonant rings corresponding to the co-indentation capacitor structure on the connecting lines will also be symmetrical in the upper and lower directions and in the left and right directions, so only one of the symmetrical ones will be described here, namely, the upper complementary split resonant ring 18 and the left complementary split resonant ring 21.

[0080] Continue to refer to Figure 6As shown, the upper complementary split ring structure 18 is etched from two open and concentric rings 32 and 33. The two open rings are respectively a large ring 32 and a small ring 33, and the outer radii of the two rings are 7mm and 6.25mm respectively. The ring widths 34 are both 0.25mm. The large ring opening 35 is located at the input port side and has a width of 0.5mm; the small ring opening 36 is located at the output port side and has a width of 0.5mm. After etching, the grounding layer 3 obtains a ring cylinder 37 and a cylinder 38. The outer radius of the ring cylinder 37 is 6.75mm, the ring width is 0.5mm, and the radius of the cylinder 38 is 6mm. The upper complementary split ring 18 is symmetrical and identical to the lower complementary split ring 20.

[0081] Continue to refer to Figure 7 As shown, the left complementary split ring 21 is also etched from two open and concentric rings 39 and 40. The two open rings are a large ring 39 and a small ring 40, but they are different in size from the upper complementary split ring 18 and the lower complementary split ring 20. The radii of their outer circles are 7.35mm and 6.6mm respectively, and the ring width 41 is 0.25mm. The large ring opening 42 is on the isolation port side and has a width of 0.5mm; the small ring opening 43 is on the input port side and has a width of 0.5mm. After etching, the grounding layer 3 obtains a ring cylinder 44 and a cylinder 45. The outer radius of the ring cylinder 44 is 7.1mm, the ring width is 0.5mm, and the radius of the cylinder 45 is 6.35mm. The left complementary split ring 21 is symmetrical and identical to the right complementary split ring 19.

[0082] Figure 8 An operational demonstration diagram for measuring the finger rotation angle and the finger pressing pressure is given. The input end and the isolation end of the electromagnetic sensor are respectively welded to the female connector of the RF coaxial connector through the connector pin, and then they are respectively connected to the ports of the vector network analyzer (VNA). Then, the fingertip is placed on one of the four coaxial capacitors. When the finger rotates and presses, the S11 return loss changes. At this time, we collect the changed data for analysis to obtain the changing rules of the finger rotation and finger pressing. After that, we can use this electromagnetic sensor to measure the finger rotation angle and finger pressing pressure.

[0083] The present invention also provides a detection method of an electromagnetic sensor for measuring finger rotation angle and pressure, which specifically includes the following steps:

[0084] Step 1: Connect the RF coaxial connectors welded on the input and isolation ends of the electromagnetic sensor to the interface feeder corresponding to the vector network analyzer (VNA), so that the microwave signal is transmitted through the upper metal transmission line. In this process, by debugging the vector network analyzer, measure and record the return loss (reflection coefficient) curve of the electromagnetic sensor under no-load conditions, and obtain its resonant frequency point and corresponding amplitude. When the electromagnetic sensor measures the finger rotation angle and pressure, the changes in the resonant frequency and amplitude of the curve can be tracked through the measurement values ​​of the vector network analyzer (VNA).

[0085] The electromagnetic sensor can be equivalent to a parallel or series resonant circuit composed of inductance L and capacitance C. The resonant frequency f0 of its equivalent resonant circuit can be expressed as:

[0086]

[0087] Where L is the inductance and C is the capacitance.

[0088] Step 2: Place the tip of your index finger on any of the four interdigital capacitors in the upper metal transmission line of the electromagnetic sensor, and select the interdigital capacitor with the strongest electric field concentration for measurement. Record the change in return loss when the finger touches at different rotation angles and pressures, paying special attention to the shift in the resonant frequency. When the finger touches, the capacitance changes because the dielectric constant of the finger is much greater than that of air. The change in capacitance will cause changes in the local electric field distribution, thereby affecting the propagation characteristics of the electromagnetic wave, and then causing changes in return loss, which manifests as a shift in the resonant frequency.

[0089] When the electromagnetic sensor measures the rotation angle and finger pressure of the finger, the capacitance of the interdigital capacitance part will change as the finger approaches. The size of the changed capacitance ΔC is expressed as:

[0090]

[0091] Among them; ε0 is the dielectric constant of vacuum, ε r is the relative dielectric constant of the tissue between fingers, A is the effective area of ​​the interdigital capacitor electrode, and d is the distance between the interdigital capacitor electrode pieces.

[0092] When the finger applies pressure, the inter-digital capacitor's pole piece spacing d is affected, causing the capacitance to change. At this time, as the pressure increases, the capacitance value increases or decreases, depending on the pressure distribution of the finger and the area of ​​contact with the electromagnetic sensor. The change in capacitance affects the shift of the resonant frequency.

[0093] When the finger rotates and is placed on the upper end of the cross-digital capacitor, the different tissues of the finger cause its dielectric constant to be much different from that of the air, which will cause the capacitance of the sensor to change, thereby changing the electric field distribution and the capacitance value, which in turn affects the transmission characteristics of the electromagnetic wave and changes the resonant frequency of the return loss.

[0094] Step 3: When the finger touches or applies pressure, the capacitance value changes, causing the resonant frequency to change. At this time, the new resonant frequency f'0 can be calculated by the following formula:

[0095]

[0096] Where L is the inductance and C is the capacitance.

[0097] Fig. 9 , Fig.10 The S11 return loss and S21 transmission coefficient curves obtained by simulation when the electromagnetic sensor of the present invention is unloaded, that is, when no finger is placed on the electromagnetic sensor, in this state, the S11 return loss curve shows a dual-frequency characteristic, which is 5.35GHz and 4.15GHz, and the corresponding return losses are -22.63dB and -22.64dB, which shows the stable reflection characteristics of this electromagnetic sensor, indicating that the electromagnetic characteristics of the sensor are very stable under the unloaded state; for the S21 transmission coefficient curve, it shows a single-frequency characteristic under unloaded conditions, with a resonant frequency of 3.35GHz and a corresponding return loss of -37.58dB. This shows that although the S21 transmission coefficient is transmitted, the signal transmission is very weak, most of the signal is reflected, and it has a lower transmission coefficient of -38.8dB near the 3.35GHz frequency.

[0098] Fig.11 , Fig.12 and Fig.13 These are the S11 return loss curves for 60°, 120°, and 240° rotations when a finger is placed on a co-digital capacitor.

[0099] Fig.11 When the finger rotates 60°, the resonant frequencies of the S11 return loss curve are 4.6 GHz and 5.25 GHz, and the corresponding return losses are -27.3 dB and -34.8 dB, respectively.

[0100] The above data show that when the finger rotates 60°, the change in rotation angle of the fingertip on the cross-toe capacitor and complementary split resonant ring (CSRR) structure causes a change in the electric field distribution, thereby causing a significant change in the S11 return loss.

[0101] Fig.12When the finger is rotated 120°, the resonant frequencies of S11 return loss are 4.7GHz and 5.25GHz, and the return loss is -24.5dB and -29.6dB.

[0102] At this time, the rotation angle is further increased, the frequency of the S11 return loss changes, and the return loss amplitude changes, showing a more sensitive response.

[0103] Fig.13 When the finger rotates 240°, the resonant frequencies of the S11 return loss curve are 4.7 GHz and 5.25 GHz, and the return losses are -23.78 dB and -24.3 dB.

[0104] When the rotation continues, the resonance frequency of the S11 return loss shifts slightly, but the amplitude of the return loss changes greatly, indicating that the sensor has good responsiveness to changes in the finger rotation angle.

[0105] The change in the finger rotation angle causes the geometry and electric field distribution of the cross-digital capacitance to change, which directly affects the frequency response of the S11 return loss. When the finger rotates, the frequency of the S11 return loss shifts, proving that the sensor can accurately capture the change in angle, which is sufficient to prove that this invention can measure different rotation angles of the fingertip.

[0106] Fig.14 , Fig.15 and Fig.16 This is the curve change of S11 return loss obtained when the finger tip applies pressure to the sensor.

[0107] Fig.14 When the finger applies normal pressure to the electromagnetic sensor, the resonant frequencies of the S11 return loss curve are 4.6 GHz and 5.25 GHz, and the return losses are -25.082 dB and -26.878 dB, respectively.

[0108] At this time, the contact area between the finger and the sensor is small, but it also causes the change of S11 return loss to change greatly compared with the stable S11 return loss when no load is applied.

[0109] Fig.15 The resonant frequencies of the simulated S11 return loss curve when the finger tip applies increased pressure to the sensor are 4.6 GHz and 5.25 GHz, and the return losses are -18.16 dB and -27.55 dB.

[0110] As the pressure increases, the soft tissue of the finger is compressed, the contact area increases, and the capacitance changes significantly, causing the resonance point of the S11 return loss curve to change significantly in amplitude compared to when it is unloaded and under normal pressure. This indicates that the sensor has good responsiveness to changes in pressure detection when the fingertip applies pressure to the sensor.

[0111] Fig.16 When the finger tip applies a second increased pressure to the sensor, when the pressure is further increased, the resonant frequency of the S11 return loss curve is 4.55 GHz and 5.25 GHz, and the return loss is -17.91 dB and -40.02 dB.

[0112] At this time, the contact area between the finger and the sensor continues to increase, and the frequency response of the S11 return loss changes more dramatically, showing a stronger sensitivity.

[0113] When the finger applies pressure, the position of the finger tip in local contact with the sensor increases, which causes the capacitance value to change, resulting in a significant change in the electromagnetic wave propagation characteristics, which in turn causes the frequency and amplitude of the S11 return loss to change. This proves that the sensor can accurately reflect the pressure applied by the finger.

[0114] In summary, when unloaded, the electromagnetic sensor has a stable dual-frequency S11 return loss and a single-frequency S21 transmission coefficient. When the finger applies a rotation angle or pressure, the frequency and amplitude of the S11 return loss change significantly, showing a high sensitivity to the rotation and pressure detection of the finger.

[0115] The present invention adds a cross-digital capacitor at the center of the transmission line and etches a complementary split resonant ring (CSRR) on the ground layer. The combination of the cross-digital capacitor and the complementary split resonant ring (CSRR) structure is used to detect changes in electromagnetic waves when the finger rotates and applies pressure. The combination of these two structures enables the sensor to respond to physical changes in two different frequency bands at the same time, thereby achieving dual-frequency characteristics and greatly improving the accuracy and response speed of the system. Not only does it improve the frequency selectivity of the system, but it also enhances the sensitivity of the sensor to changes in rotation angle and pressure.

[0116] There is a close relationship between the capacitance value of the electromagnetic sensor of the present invention and the resonant frequency of the return loss. When a finger approaches or touches a cross-capacitor where the electric field of the electromagnetic sensor is relatively concentrated, the contact of the finger will cause the capacitance value of the cross-capacitor to change because the dielectric constant of the finger is significantly different from that of the air. This change will directly affect the distribution of the electromagnetic field, causing the electric field characteristics of the sensor to change and affecting the propagation characteristics of the electromagnetic wave. The pressure effect of the finger pressure and the change in the rotation angle of the finger will significantly affect the electromagnetic performance of the sensor.

[0117] When the rotation angle of the finger changes, the geometry, size and electric field distribution of the cross-digital capacitor will adjust with the change of the rotation angle. These changes will directly affect the propagation path and propagation characteristics of the electromagnetic wave in the sensor, causing the electromagnetic characteristics of the sensor to change, which is specifically manifested as the shift of the resonant frequency of the S11 return loss curve.

[0118] When the finger applies different degrees of pressure, the capacitance value of the cross-digital capacitor will also change accordingly. This change will also affect the propagation characteristics of the electromagnetic wave and manifest as a change in frequency response in the S11 return loss. Therefore, by monitoring the change in the S11 return loss, not only can the information of the finger rotation angle be obtained, but also the pressure applied by the finger can be inferred.

[0119] Among them, S11 return loss (reflection coefficient) is an important indicator to measure the reflection characteristics of electromagnetic waves in the sensor, reflecting the amplitude ratio between the input signal and the reflected signal. Generally, the shape and position of the S11 return loss curve can reflect the propagation characteristics of electromagnetic waves. When the finger rotates or applies pressure, the electric field distribution of the cross-toe capacitance will change, thereby changing the propagation characteristics of the electromagnetic wave, causing the S11 return loss curve to shift.

[0120] This invention can extract the change of the resonant frequency of the electromagnetic wave through the precise analysis of the S11 return loss curve, and further calculate the rotation angle and applied pressure of the finger according to the relationship between the capacitance value and the resonant frequency. Specifically, the corresponding frequency offset can be extracted by performing frequency domain analysis on the S11 return loss curve, and converted into the rotation angle of the finger or the applied pressure value.

[0121] In summary, the electromagnetic sensor for detecting finger rotation angle and pressure provided by the present invention has the following advantages:

[0122] 1. The electromagnetic sensor of this invention has a novel structure. The traditional double-branch coupler is improved by opening its output end and coupling end, and adding a matching load at the open circuit to ensure the stability of the signal. The present invention also uniquely combines the cross-toe capacitor and complementary split resonant ring (CSRR) structure. This combination enhances the electromagnetic performance of the sensor.

[0123] 2. By opening the output and coupling ends of the double-branch coupler and adding a matching load, and combining the cross-digital capacitor and complementary split resonant ring (CSRR) structure, the signal reflection and noise interference problems are effectively reduced, the signal stability is ensured, and the sensor can respond to physical changes (finger rotation and pressure changes) in two different frequency bands at the same time, realizing dual-frequency characteristics. Through this dual-frequency response characteristic, the electromagnetic sensor can greatly improve the measurement accuracy and response speed, and enhance its frequency selectivity and sensitivity.

[0124] 3. The method for measuring the finger rotation angle and the pressure applied by the finger is novel. The present invention adopts a combination of cross-digital capacitance and complementary split resonant ring, which can effectively detect the changes in the finger rotation angle and pressure. By analyzing the changes in the return loss curve, the resonant frequency changes of the electromagnetic wave can be extracted, and there is a close relationship between the capacitance value and the resonant frequency. Therefore, the electromagnetic sensor can not only measure the rotation angle, but also measure the pressure applied by the finger. This feature makes the application of electromagnetic sensors more diversified and adapts to the detection needs of various physical quantities.

[0125] 4. Simple structure and easy integration. Compared with the traditional multi-sensor system, the electromagnetic sensor of the present invention has a simple structure and high integration, and can realize multiple detection functions of finger rotation angle and applied pressure in one sensor. Since the electromagnetic sensor has a low manufacturing cost, its maintenance and maintenance work is also greatly simplified, which is suitable for wide promotion in practical applications.

[0126] The electromagnetic sensor of the present invention is not only suitable for detecting finger rotation angle and pressure change, but also has a wide range of application prospects. Its dual-frequency response characteristics enable the sensor to work stably in complex environments and has strong anti-interference ability, especially in the fields of smart wearable devices, virtual reality, medical health monitoring, and robot control, which has huge market application value.

[0127] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. In some instances, well-known methods, structures and techniques are not shown in detail so as not to obscure the understanding of this description.

[0128] In addition, those skilled in the art will understand that, although some embodiments described herein include certain features included in other embodiments but not other features, the combination of features of different embodiments also means being within the scope of protection of the present invention and forming different embodiments. For example, in the above embodiments, those skilled in the art can use them in combination according to the known technical solutions and the technical problems to be solved by this application.

[0129] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. An electromagnetic sensor for detecting finger rotation angle and pressure, characterized in that: include: The metal microstrip transmission line on the upper layer is composed of a microstrip double-branch coupler with an open port and a plurality of cross-toed capacitors connected thereto; A lower grounding layer, on which a plurality of complementary split resonant rings having the same number as the co-digital capacitors are arranged, and one complementary split resonant ring corresponds to one of the co-digital capacitors; The dielectric substrate of the middle layer has electromagnetic wave propagation performance and is arranged between the metal microstrip transmission line and the ground layer; When the fingertip is close to any cross-digital capacitor, this contact area becomes the local electric field concentration area of ​​the electromagnetic sensor, which can accurately sense the slight changes in the electromagnetic characteristics of its transmission line when the finger rotates and applies pressure, thereby providing accurate measurement of the finger rotation angle and finger pressure changes.

2. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 1, characterized in that: The microstrip double-branch coupler comprises four ports, namely an input port, an output port, a coupling port and an isolation port; The output end and the coupling end of the microstrip double-branch coupler are open-circuited, and matching loads are added at the open-circuited ports respectively; The input end and the isolation end of the microstrip double-branch coupler are respectively set as transmission lines with fixed resistance values, the input end is used for inputting signals, and the isolation end is used for outputting signals; A connecting line is provided between two adjacent ports, and the length of each connecting line is a quarter wavelength; The middle part of each connecting line is disconnected, and the cross-toe capacitor is arranged at the disconnected part.

3. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 2, characterized in that: The upper connecting line between the input end and the output end, the upper interdigital capacitor, and the lower connecting line between the coupling end and the isolation end, and the lower interdigital capacitor are symmetrical to each other; the left connecting line between the input end and the isolation end, the left interdigital capacitor, and the right connecting line between the output end and the coupling end, and the right interdigital capacitor are symmetrical to each other; The upper connecting line and the protruding parts of the transmission lines of the ports on both sides thereof are each provided with a cut corner, and the lower connecting line and the protruding parts of the transmission lines of the ports on both sides thereof are each provided with a cut corner.

4. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 3, characterized in that: The upper interdigital capacitor has the same structure as the lower interdigital capacitor, and is composed of a plurality of interdigital pole pieces of the same size, which are staggered in pairs and do not contact each other; The left-side interdigital capacitor has the same structure as the right-side interdigital capacitor, and both are composed of a plurality of interdigital pole pieces of the same size, which are staggered in pairs and do not contact each other.

5. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 4, characterized in that: The upper side interdigital capacitor is composed of an upper interdigital pole piece, a middle interdigital pole piece and a lower interdigital pole piece located on the input end side, and an upper interdigital pole piece and a lower interdigital pole piece located on the output end side; The upper interdigital pole piece on the output end side is inserted between the upper interdigital pole piece and the middle interdigital pole piece on the input end side, and the lower interdigital pole piece on the output end side is inserted between the middle interdigital pole piece and the lower interdigital pole piece on the input end side; The gap distances between two adjacent interdigital pole pieces are the same, and the gap distances between the top of each interdigital pole piece and the side where the metal microstrip transmission line is disconnected are the same.

6. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 4, characterized in that: The left-side interdigital capacitor is composed of a left interdigital pole piece located at the input end side, a right interdigital pole piece and a middle interdigital pole piece located at the isolation end side; Wherein, a middle interdigital pole piece on the isolation end side is inserted between the left interdigital pole piece and the right interdigital pole piece on the input end side; The gap distances between two adjacent interdigital pole pieces are the same, and the gap distances between the top of each interdigital pole piece and the side where the metal microstrip transmission line is disconnected are the same.

7. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 2, characterized in that: The number of the complementary split resonant rings is four, and the four complementary split resonant rings are symmetrical in left-right and top-bottom structures, and the center of each complementary split resonant ring corresponds to the center of a cross-toe capacitor; The radii of the left complementary split resonant ring and the right complementary split resonant ring are both R1, and the radii of the upper complementary split resonant ring and the lower complementary split resonant ring are both R2, and R1 is greater than R2.

8. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 7, characterized in that: The complementary split resonant ring is composed of a cylinder and a ring cylinder formed by a large ring and a small ring arranged concentrically etched on a ground layer; the small ring and the large ring in each complementary split resonant ring are provided with an opening 180 degrees apart; the width of the large ring is the same as that of the small ring; The openings of the large circular rings in the upper and lower complementary split rings are both oriented toward the input end, and the openings of the small circular rings are both oriented toward the output end; The opening of the large circular ring in the left complementary split ring faces the isolation end, and the opening of the small circular ring faces the input end; the opening of the large circular ring in the right complementary split ring faces the output end, and the opening of the small circular ring faces the coupling end.

9. The electromagnetic sensor for detecting finger rotation angle and pressure according to claim 2, characterized in that: The input end and the isolation end of the microstrip double-branch coupler are respectively welded to the female connector of the radio frequency coaxial connector through connector pins, and the grounding end of the radio frequency coaxial connector is welded to the lower grounding layer.

10. A detection method based on the electromagnetic sensor according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1: Connect the RF coaxial connectors welded on the input and isolation ends of the electromagnetic sensor to the interface feeder corresponding to the vector network analyzer, so that the microwave signal is transmitted through the upper metal transmission line of the electromagnetic sensor; by debugging the vector network analyzer, measure and record the return loss curve of the electromagnetic sensor under no-load conditions, and obtain its resonant frequency point and corresponding amplitude; The electromagnetic sensor can be equivalent to a parallel or series resonant circuit composed of inductance L and capacitance C. The resonant frequency f0 of its equivalent resonant circuit is expressed as: Where L is the inductance and C is the capacitance; Step 2: Place the fingertip at any cross-digital capacitor in the metal transmission line on the upper layer of the electromagnetic sensor, and record the change in return loss when the finger touches at different finger rotation angles and different pressures, paying special attention to the shift of the resonant frequency; When the electromagnetic sensor measures the rotation angle and finger pressure of the finger, the capacitance of the interdigital capacitance part will change as the finger approaches. The size of the changed capacitance ΔC is expressed as: Where ε0 is the dielectric constant of vacuum, ε r is the relative dielectric constant of the tissue between the fingers, A is the effective area of ​​the interdigital capacitor electrode, and d is the distance between the interdigital capacitor electrode pieces; Step 3: When the finger touches or applies pressure, the capacitance value changes, causing the resonant frequency to change; at this time, the new resonant frequency f′0 is calculated by the following formula: Where L is the inductance and C is the capacitance.

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