Electromagnetic tag and health monitoring system

Abstract

The embodiment of the invention provides an electromagnetic tag and a health monitoring system, the electromagnetic tag can be worn on a target body area of a target object, the electromagnetic tag comprises a plurality of modulation units which are arranged in a two-dimensional period, and the electromagnetic tag corresponds to a target working frequency band. When incident electromagnetic waves emitted by detection equipment irradiate a reflection interface of the electromagnetic tag at a target incident angle, the plurality of modulation units perform reflection phase modulation on a target electromagnetic wave component corresponding to the target working frequency band in the incident electromagnetic waves; the target electromagnetic wave component is subjected to reverse reflection on a reflection interface, reflected electromagnetic waves are generated, and the reflected electromagnetic waves are received by the detection equipment and used for determining vital sign indexes corresponding to the target object. Therefore, the electromagnetic tag can be matched with the detection equipment to realize non-contact health monitoring, the convenience and comfort of health monitoring can be improved, and the precision of health monitoring can also be improved.

Description

Technical Field

[0001] The embodiments of this specification relate to the field of electromagnetic technology, and in particular, to an electromagnetic tag and a health monitoring system. Background Art

[0002] With the aggravation of population aging and people's concern about their own health conditions, more and more users expect to conveniently monitor their own health conditions on a daily basis. Therefore, health monitoring systems based on 5G and Internet of Things (IoT) technologies are increasingly favored.

[0003] Vital sign signals such as respiration and heartbeat can directly reflect the health condition of the human body. Real-time and accurate monitoring of these signals has very important practical value in clinical disease diagnosis, health monitoring, etc. At present, contact monitoring methods are mainly used to extract vital sign signals. For example, a contact detection device is attached to the surface of the human skin to extract the vital sign signals of the human body. However, this contact monitoring method will affect the human experience and quality of life, and there is a problem of user compliance, which limits its application to a certain extent.

[0004] The content in the background art section is only the information known to the inventor personally, and does not represent that the above information has entered the public domain before the filing date of this disclosure, nor does it represent that it can become the prior art of this disclosure. Summary of the Invention

[0005] This specification provides an electromagnetic tag and a health monitoring system, which realize non-contact health monitoring, can improve the convenience and comfort of health monitoring, and can also improve the accuracy of health monitoring.

[0006] In a first aspect, this specification provides an electromagnetic tag that can be worn on a target body area of a target object. The electromagnetic tag includes a plurality of modulation units arranged in a two-dimensional periodic pattern. Among them, the electromagnetic tag corresponds to a target operating frequency band. When the incident electromagnetic wave emitted by the detection device irradiates the reflection interface of the electromagnetic tag at a target incident angle, the plurality of modulation units perform reflection phase modulation on the target electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic wave, so that the target electromagnetic wave component undergoes retroreflection on the reflection interface and generates a reflected electromagnetic wave. The reflected electromagnetic wave is received by the detection device and is used to determine the vital sign index corresponding to the target object.

[0007] In some embodiments, for any adjacent first modulation unit and second modulation unit in the target direction among the plurality of modulation units: the first modulation unit modulates the target electromagnetic wave component to obtain a first reflection phase, the second modulation unit modulates the target electromagnetic wave component to obtain a second reflection phase, and there is a preset phase difference between the second reflection phase and the first reflection phase.

[0008] In some embodiments, the arrangement period of the modulation units is related to at least one of the target incident angle, the target operating frequency band, and the preset phase difference.

[0009] In some embodiments, the modulation unit includes: a dielectric substrate, a metal bottom plate, and a metal pattern. Wherein, the dielectric substrate has opposite first and second surfaces, the metal bottom plate is located on the first surface for grounding, and the metal pattern is formed by at least one metal piece located on the second surface. When the incident electromagnetic wave irradiates the metal pattern, the incident electromagnetic wave couples with the metal pattern to generate an electromagnetic field and generate resonance inside the modulation unit to change the reflection phase of the incident electromagnetic wave.

[0010] In some embodiments, the metal pattern satisfies a preset condition such that the incident electromagnetic wave couples with the metal pattern to generate an electromagnetic field and generate Fano resonance inside the modulation unit.

[0011] In some embodiments, the metal pattern is asymmetric with respect to the polarization direction of the incident electromagnetic wave.

[0012] In some embodiments, the metal pattern includes any one of the following: a metal ring with at least one notch, a metal rectangular ring with at least one notch, and a metal semi-ring with at least one notch.

[0013] In some embodiments, the metal pattern includes a first pattern and a second pattern, where the first pattern and the second pattern are arranged in sequence on the second surface, or the first pattern is nested inside the second pattern.

[0014] In some embodiments, the first pattern and the second pattern are respectively any one of the following: a metal ring with at least one notch, a metal rectangular ring with at least one notch, and a metal semi-ring with at least one notch.

[0015] In some embodiments, for any adjacent first modulation unit and second modulation unit among the multiple modulation units along the target direction: the metal pattern corresponding to the first modulation unit is different from the metal pattern corresponding to the second modulation unit, so that there is a preset phase difference between the reflection phase generated by the first modulation unit and the reflection phase generated by the second modulation unit.

[0016] In some embodiments, the pattern styles of the metal pattern corresponding to the first modulation unit and the metal pattern corresponding to the second modulation unit are the same, but the pattern sizes are different.

[0017] In some embodiments, when the incident electromagnetic wave irradiates the reflection interface at the target incident angle, the multiple modulation units perform specular reflection on the electromagnetic wave components corresponding to other frequency bands in the incident electromagnetic wave, where the other frequency bands are the frequency bands in the frequency band covered by the incident electromagnetic wave except the target working frequency band.

[0018] In some embodiments, the electromagnetic tag is a flexible tag to adapt to the surface contour of the target body area.

[0019] In some embodiments, the electromagnetic tag is a metasurface formed by two-dimensional metamaterials.

[0020] In a second aspect, this specification also provides a health monitoring system, including: an electromagnetic tag, a detection device, and a computing device. Among them, the electromagnetic tag is the electromagnetic tag according to any one of the first aspect, can be worn on the target body area of the target object, and corresponds to a target working frequency band; when the detection device is configured to operate: it emits an incident electromagnetic wave and makes the incident electromagnetic wave irradiate the reflection interface of the electromagnetic tag at a target incident angle, where the incident electromagnetic wave includes a target electromagnetic wave component corresponding to the target working frequency band, and receives the reflected electromagnetic wave generated by the retroreflection of the target electromagnetic wave component on the reflection interface; the computing device is communicatively connected to the detection device and is configured to operate: based on the incident electromagnetic wave and the reflected electromagnetic wave, determine the life characteristic index corresponding to the target object.

[0021] In some embodiments, the detection device includes a millimeter-wave radar.

[0022] In some embodiments, the target body area includes a thoracic region, and the life characteristic index includes at least one of a respiration characteristic index and a heartbeat characteristic index.

[0023] In a third aspect, this specification also provides a health monitoring system, including: a first electromagnetic tag, a second electromagnetic tag, a detection device, and a computing device. Among them, the first electromagnetic tag and the second electromagnetic tag are both electromagnetic tags as described in any item of the first aspect. The first electromagnetic tag can be worn on a first body area of a first object and corresponds to a first operating frequency band. The second electromagnetic tag can be worn on a second body area of a second object and corresponds to a second operating frequency band, and the second operating frequency band is different from the first operating frequency band. When the detection device is configured to operate: it emits an incident electromagnetic wave and causes the incident electromagnetic wave to irradiate the first reflection interface of the first electromagnetic tag and the second reflection interface of the second electromagnetic tag at a target incident angle. Among them, the incident electromagnetic wave includes a first electromagnetic wave component corresponding to the first operating frequency band and a second electromagnetic wave component corresponding to the second operating frequency band, and receives a first reflected electromagnetic wave generated by the reverse reflection of the first electromagnetic wave component on the first reflection interface, and receives a second reflected electromagnetic wave generated by the reverse reflection of the second electromagnetic wave component on the second reflection interface. The computing device is communicatively connected to the detection device and is configured to operate: based on the incident electromagnetic wave and the first reflected electromagnetic wave, determine a vital sign index corresponding to the first object, and based on the incident electromagnetic wave and the second reflected electromagnetic wave, determine a vital sign index corresponding to the second object.

[0024] In some embodiments, the detection device includes a millimeter-wave radar.

[0025] In some embodiments, the first body area includes the chest area of the first object, and the second body area includes the chest area of the second object; and the vital sign index includes at least one of a respiration feature index and a heart rate feature index.

[0026] As can be seen from the above technical solutions, the electromagnetic tag and the health monitoring system provided in this specification can realize non-contact health monitoring of a target object by wearing an electromagnetic tag on a target body area of the target object and performing reverse reflection on the electromagnetic wave emitted by the detection device through the electromagnetic tag, thereby improving the convenience and comfort of health monitoring. Further, since the electromagnetic tag can perform reverse reflection on the electromagnetic wave, the detection device can more accurately locate the position of the electromagnetic tag and improve the signal-to-noise ratio corresponding to the reflected electromagnetic wave received by the detection device, thereby improving the accuracy of health monitoring. In addition, when performing health monitoring, frequency diversity can also be performed on the operating frequency band of the detection device by using multiple electromagnetic tags corresponding to different operating frequency bands, so as to realize simultaneous health monitoring of two objects by using the same detection device and improve the health monitoring efficiency of multiple objects.

[0027] Other functions of the electromagnetic tag and the health monitoring system provided in this specification will be partially listed in the following description. The creative aspects of the electromagnetic tag and the health monitoring system provided in this specification can be fully explained by practicing or using the methods, devices, and combinations described in the detailed examples below. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] To more clearly illustrate the technical solutions in the embodiments of this specification, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of this specification. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1A FIG. shows a schematic diagram of the application scenario of the health monitoring system provided according to an embodiment of this specification;

[0030] Figure 1B FIG. shows a schematic diagram of the application scenario of the health monitoring system provided according to an embodiment of this specification;

[0031] Figure 2 FIG. shows a schematic diagram of the electromagnetic tag provided according to an embodiment of this specification;

[0032] Figure 3A FIG. shows Figure 2 a three-dimensional structural schematic diagram of each modulation unit in;

[0033] Figure 3B FIG. shows Figure 2 a top view of each modulation unit in;

[0034] Figure 4 FIG. shows Figure 3A and Figure 3B a schematic diagram of the reflection coefficient curve corresponding to the modulation unit in;

[0035] Figure 5 FIG. shows Figure 3A and Figure 3B a schematic diagram of the reflection phase generated by the modulation unit varying with the radius of the ring;

[0036] Figure 6 FIG. shows Figure 2 a schematic diagram of one super unit in;

[0037] Figure 7A FIG. shows a schematic diagram of the change curve of the reflection phase corresponding to the first electromagnetic tag with the radius of the ring;

[0038] Figure 7B FIG. shows a schematic diagram of the change curve of the reflection phase corresponding to the second electromagnetic tag with the radius of the ring;

[0039] Figure 8A Shows a schematic diagram of the scattering characteristics corresponding to the first electromagnetic tag;

[0040] Figure 8B Shows a schematic diagram of the scattering characteristics corresponding to the second electromagnetic tag; and

[0041] Figures 9A to 9G Schematically shows several possible metal patterns respectively. Detailed implementation manners

[0042] The following description provides specific application scenarios and requirements of this specification, aiming to enable those skilled in the art to manufacture and use the content in this specification. For those skilled in the art, various local modifications to the disclosed embodiments are obvious, and without departing from the spirit and scope of this specification, the general principles defined here can be applied to other embodiments and applications. Therefore, this specification is not limited to the shown embodiments, but has the broadest scope consistent with the claims.

[0043] The terms used here are only for the purpose of describing specific example embodiments and are not restrictive. For example, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used here may also include the plural forms. When used in this specification, the terms "comprise", "include" and / or "contain" mean that the associated integers, steps, operations, elements and / or components exist, but do not exclude the existence of one or more other features, integers, steps, operations, elements, components and / or groups, or the addition of other features, integers, steps, operations, elements, components and / or groups in the system / method.

[0044] Considering the following description, these features of this specification and other features, as well as the operations and functions of the related elements of the structure, and the combination and manufacturing economy of the components can be significantly improved. Referring to the accompanying drawings, all of these form a part of this specification. However, it should be clearly understood that the drawings are only for the purpose of illustration and description and are not intended to limit the scope of this specification. It should also be understood that the drawings are not drawn to scale.

[0045] The flowcharts used in this specification show the operations implemented by the system according to some embodiments in this specification. It should be clearly understood that the operations in the flowchart may not be implemented in sequence. On the contrary, the operations may be implemented in reverse order or simultaneously. In addition, one or more other operations may be added to the flowchart. One or more operations may be removed from the flowchart.

[0046] For the convenience of description, this specification first explains the terms that will appear later as follows.

[0047] Metasurface: A metasurface refers to an artificial layered material with a thickness of sub - wavelength. A metasurface is a two - dimensional metamaterial. Metasurfaces have the ability to flexibly control multiple degrees of freedom of electromagnetic waves (including polarization, amplitude, phase, polarization direction, propagation mode, etc.), and have received extensive attention in the past decade or so, and have great application potential in information communication, radar sensing, etc.

[0048] Phase Gradient Metasurface (PGMS): It is a special metasurface. Based on the generalized Snell's law, the phase gradient metasurface can modulate the direction of refracted / reflected waves and has attracted much attention in electromagnetic wave beam control.

[0049] Fano Resonance: It can also be called Fano resonance. In physics, Fano resonance is a scattering resonance phenomenon that produces an asymmetric line shape.

[0050] Quality Factor value: It can also be called the Q - value, which is an important parameter of the resonance peak. It is defined as the center frequency of the resonance peak divided by the resonance peak width. A higher Q - value indicates that the resonance peak width of a resonance peak is narrower, which is of great practical significance. It has very important significance in application fields such as ultra - high - sensitivity sensors and ultra - narrow - band filters. Currently, the design of metasurface resonance peaks is limited to surface modes, such as dipole resonance, LC resonance and other resonance peaks. Due to the influence of metal ohmic loss and radiation loss, it is very difficult to improve their Q - values.

[0051] Reflection coefficient: The reflection coefficient is a parameter that describes how much electromagnetic wave is reflected due to impedance discontinuity in the transmission medium. It is equal to the amplitude ratio of the reflected wave to the incident wave.

[0052] As mentioned above, currently, contact - type monitoring methods are usually adopted in the field of health monitoring. This contact - type monitoring method will affect the human experience and quality of life, and there are problems with user compliance, which limits its application to a certain extent. This specification provides a non - contact monitoring method. Compared with the contact - type monitoring method, the non - contact monitoring method does not need to contact the human body, can complete health monitoring in a comfortable and convenient situation, does not affect the user's quality of life, and helps health monitoring devices integrate into people's daily lives.

[0053] Before describing the specific embodiments of this specification in detail, the application scenarios of this specification are introduced as follows.

[0054] The technical solution provided in this specification can be used in the health monitoring scenario and realizes the monitoring of the vital sign indicators of the target object. In some scenarios, the above-mentioned vital sign indicators may include respiratory characteristic indicators. In some scenarios, the above-mentioned vital sign indicators may include heartbeat characteristic indicators. In some scenarios, the above-mentioned vital sign indicators may include respiratory characteristic indicators and heartbeat characteristic indicators. In some scenarios, the above-mentioned vital sign indicators may include other indicators. It should be noted that the above-mentioned health monitoring scenario may be a self-health monitoring scenario at home or a medical health monitoring scenario in medical institutions (such as hospitals, nursing homes, rehabilitation centers, etc.). This specification does not limit this.

[0055] The following combines Figure 1A and Figure 1B to give an example of the application scenario of the health monitoring system.

[0056] Figure 1A FIG. shows a schematic diagram of the application scenario of the health monitoring system 001 provided according to an embodiment of this specification. Refer to Figure 1A , the health monitoring system 001 can monitor the vital sign indicators of the target object 100. Among them, the target object 100 can be any object with vital signs. For example, it can be a human user or an animal, etc. The target object 100 can be a healthy object or a non-healthy object.

[0057] As Figure 1A shown, the health monitoring system 001 may include: an electromagnetic tag 200, a detection device 500, and a computing device 600.

[0058] Among them, the electromagnetic tag 200 can also be called an electromagnetic reflector, which is a device capable of reflecting electromagnetic waves. In this specification, the electromagnetic tag 200 corresponds to a target operating frequency band and has the ability to retro-reflect electromagnetic waves within the target operating frequency band. That is to say, when the incident electromagnetic wave irradiates the reflection interface of the electromagnetic tag 200 at the target incident angle, the reflection interface retro-reflects the target electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic wave, while specular reflection or diffuse reflection may occur for the electromagnetic wave components corresponding to other frequency bands in the incident electromagnetic wave. It should be noted that the specific structure of the electromagnetic tag 200 can be referred to the relevant description later and will not be elaborated here.

[0059] Assume that the electromagnetic wave irradiating the reflection interface of the electromagnetic tag 200 is called the incident electromagnetic wave, and the electromagnetic wave reflected by the electromagnetic tag 200 is called the reflected electromagnetic wave. In this specification, retro-reflection refers to a reflection in which the reflected electromagnetic wave returns from a direction close to the opposite direction of the incident electromagnetic wave. The direction of the reflected electromagnetic wave after retro-reflection coincides or is close to coinciding with the opposite direction of the incident electromagnetic wave. Retro-reflection can also be called retro-reflection or reverse reflection.

[0060] Continue to refer to Figure 1A , the electromagnetic tag 200 can be worn on a certain body area of the target object 100. It should be noted that this specification does not limit which specific body area the electromagnetic tag 200 is worn on, and the electromagnetic tag 200 can be worn in a suitable area according to actual monitoring requirements. For example, when at least one of the respiratory characteristic index and the heartbeat characteristic index needs to be monitored, the electromagnetic tag 200 can be worn on the chest area of the target object 100. Another example is that when other indexes need to be monitored, the electromagnetic tag 200 can be worn on other body areas of the target object 100. Figure 1A Taking being worn on the chest area as an example for illustration.

[0061] It should be noted that this specification does not limit the wearing method of the electromagnetic tag 200 on the body area of the target object 100. For example, in some embodiments, a pasting part can be provided on the electromagnetic tag 200, so that the electromagnetic tag 200 can be fixedly pasted on the body area of the target object 100. In some embodiments, a strap can be provided on the electromagnetic tag 200, so that the electromagnetic tag 200 can be fixed on the body area of the target object 100 through the strap. In some embodiments, an adsorbing part can be provided on the electromagnetic tag 200, so that the electromagnetic tag 200 can be adsorbed and fixed on the body area of the target object 100.

[0062] The detection device 500 is an electronic device that detects a target by emitting electromagnetic waves. In this specification, the detection device 500 can emit electromagnetic waves and monitor the life characteristic indexes of the target object 100 through the electromagnetic waves. The following combines Figure 1A , taking the monitoring of the respiratory characteristic index and the heartbeat characteristic index as an example, to illustrate the monitoring principle by way of example.

[0063] In Figure 1AIn the application scenario shown, the target object 100 lies in bed, and an electromagnetic tag 200 is worn on the chest region of the target object 100. The heartbeat and breathing of the target object 100 drive the chest to move up and down. Correspondingly, the electromagnetic tag 200 also moves up and down with the chest. The detection device 500 emits incident electromagnetic waves, and the incident electromagnetic waves irradiate the reflection interface of the electromagnetic tag 200 at the target incident angle. Since the electromagnetic tag 200 has the ability to retro-reflect electromagnetic waves within the target operating frequency band, therefore, the electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic waves undergoes retro-reflection on the reflection interface and generates reflected electromagnetic waves. The detection device 500 receives the reflected electromagnetic waves. Since the reflected electromagnetic waves are reflected by the electromagnetic tag 200, and the electromagnetic tag 200 moves up and down with the chest, the reflected electromagnetic waves received by the detection device 500 carry a heartbeat vibration signal and a breathing vibration signal. Thus, it can be seen that the reflected electromagnetic waves can be used to determine the heartbeat characteristic index and the breathing characteristic index of the target object 100.

[0064] In some embodiments, the detection device 500 can be a radar device. Radar can detect, locate, track, image, and identify a target by using the reflection or scattering phenomenon of the target to electromagnetic waves. It should be noted that the type of the radar device is not limited in this specification. For example, the above-mentioned radar device can be a lidar, a millimeter-wave radar, an ultrasonic radar, or other radars, etc. Electromagnetic waves with a wavelength of 1 to 10 millimeters are called millimeter waves, which are located in the wavelength range where microwaves and far-infrared waves overlap, and thus have the characteristics of both spectra. According to the wave propagation theory, the higher the frequency, the shorter the wavelength, the higher the resolution, and the stronger the penetration ability, but the loss during propagation is also greater and the transmission distance is shorter; relatively, the lower the frequency, the longer the wavelength, the stronger the diffraction ability, and the farther the transmission distance. Therefore, compared with microwaves, millimeter waves have high resolution, good directivity, strong anti-interference ability, and good detection performance. Compared with infrared, millimeter waves have less atmospheric attenuation, better penetration to smoke and dust, and are less affected by the weather. Therefore, when the detection device 500 uses a millimeter-wave radar, the detection accuracy of the vital sign index can be improved.

[0065] The computing device 600 can be an electronic device with certain computing capabilities. The computing device 600 can obtain the incident electromagnetic waves it emits and the received reflected electromagnetic waves from the detection device 500, and perform certain analysis and calculations based on the incident electromagnetic waves and the reflected electromagnetic waves, so as to determine the vital sign index corresponding to the target object 100 (such as the breathing characteristic index and the heartbeat characteristic index). For example, the computing device 600 can obtain the vital sign index by using the frequency difference and phase difference between the incident electromagnetic waves and the reflected electromagnetic waves.

[0066] It should be noted that in practical applications, there can be various deployment forms between the detection device 500 and the computing device 600, which are not limited in this specification. For example, in some embodiments, the computing device 600 and the detection device 500 can be independent physical devices, and they can be communicatively connected by wired or wireless means. In this case, the computing device 600 can obtain the incident electromagnetic wave and the reflected electromagnetic wave from the detection device 500 through the above communication connection. In some embodiments, the computing device 600 and the detection device 500 can be integrated into the same physical device. For example, the detection device 500 can correspond to the transceiver module of a radar device, and the computing device 600 can correspond to the computing module in the radar device, and they can be connected by a communication bus inside the radar device. In this case, the computing device 600 can obtain the incident electromagnetic wave and the reflected electromagnetic wave from the detection device 500 through the communication bus.

[0067] In some embodiments, the computing device 600 may further include a display screen, or the computing device 600 can be communicatively connected to an external display device. After the computing device 600 obtains the vital sign indicators corresponding to the target object 100, the vital sign indicators can be displayed through the display screen or the display device. In some embodiments, the computing device 600 can also evaluate the health status, sleep status, etc. of the target object 100 based on the vital sign indicators to obtain an evaluation result. Further, the computing device 600 can also formulate a reasonable health improvement plan for the target object 100 based on the above evaluation result.

[0068] In Figure 1A In the health monitoring scenario shown, by wearing the electromagnetic tag 200 on the target body area of the target object 100 and reversely reflecting the electromagnetic wave emitted by the detection device 500 through the electromagnetic tag 200, non-contact health monitoring of the target object 100 can be realized using the detection device 500. In addition, those skilled in the art can understand that reverse reflection can significantly enhance the backscattering ability of the electromagnetic tag 200, thereby enhancing the echo signal and increasing the radar cross section (RCS). Therefore, compared with some health monitoring methods that do not use the electromagnetic tag 200 (directly using the skin tissue of the target body area of the target object 100 to diffusely reflect the incident electromagnetic wave), or compared with some health monitoring methods that use electromagnetic reflectors with specular reflection ability, the health monitoring method based on the reverse reflection of the electromagnetic tag 200 provided in this specification can more accurately locate the position of the electromagnetic tag 200, and can enhance the reflected electromagnetic wave, improve the signal-to-noise ratio corresponding to the reflected electromagnetic wave received by the detection device 500, thereby improving the accuracy of health monitoring.

[0069] Figure 1A The health monitoring scenario shown can achieve health monitoring of a single object (i.e., the target object 100). In practical applications, in some scenarios (such as the intelligent hospital bed scenario), there may also be a need to simultaneously monitor the health of multiple objects. The following will be described in detail in conjunction with Figure 1B this.

[0070] Figure 1B FIG. shows a schematic diagram of an application scenario of a health monitoring system 002 provided according to an embodiment of the present specification. The health monitoring system 002 can simultaneously monitor the vital sign indicators of the first object 100-A and the second object 100-B. It should be noted that the relevant descriptions of Figure 1A above also apply to Figure 1B this, and the repeated content will not be elaborated here.

[0071] As Figure 1B shown, the health monitoring system 002 may include: a first electromagnetic tag 200-A, a second electromagnetic tag 200-B, a detection device 500, and a computing device 600. Among them, the first electromagnetic tag 200-A corresponds to a first operating frequency band and has the ability to retro-reflect electromagnetic waves within the first operating frequency band. The second electromagnetic tag 200-B corresponds to a second operating frequency band and has the ability to retro-reflect electromagnetic waves within the second operating frequency band. The first operating frequency band and the second operating frequency band are different. For example, assuming that the detection device 500 uses a millimeter-wave radar, the frequency range of the millimeter-wave radar includes 60 GHz - 64 GHz. The first operating frequency band corresponding to the first electromagnetic tag 200-A may be 60 GHz - 61 GHz, with a center frequency of 60.5 GHz, and the second operating frequency band corresponding to the second electromagnetic tag 200-B may be 62.5 GHz - 63.5 GHz, with a center frequency of 63 GHz.

[0072] In Figure 1BIn the application scenario shown, both the first object 100-A and the second object 100-B are lying in bed, and a first electromagnetic tag 200-A is worn on the chest area of the first object 100-A, and a second electromagnetic tag 200-B is worn on the chest area of the second object 100-B. The detection device 500 emits incident electromagnetic waves, and the incident electromagnetic waves are respectively irradiated onto the first reflection interface of the first electromagnetic tag 200-A and the second reflection interface of the second electromagnetic tag 200-B at a target incident angle. The incident electromagnetic waves include a first electromagnetic wave component corresponding to a first operating frequency band and a second electromagnetic wave component corresponding to a second operating frequency band. Since the first electromagnetic tag 200-A has the ability to retro-reflect electromagnetic waves within the first operating frequency band, the first electromagnetic wave component undergoes retro-reflection on the reflection interface of the first electromagnetic tag 100-A and generates a first reflected electromagnetic wave. Since the second electromagnetic tag 200-B has the ability to retro-reflect electromagnetic waves within the second operating frequency band, the second electromagnetic wave component undergoes retro-reflection on the reflection interface of the second electromagnetic tag 200-B and generates a second reflected electromagnetic wave. The detection device 500 receives the first reflected electromagnetic wave and the second reflected electromagnetic wave.

[0073] Since the first reflected electromagnetic wave carries the heartbeat vibration signal and the breathing vibration signal of the first object 100-A, the computing device 600 can determine the heartbeat characteristic index and the breathing characteristic index of the first object 100-A based on the incident electromagnetic wave and the first reflected electromagnetic wave. Since the second reflected electromagnetic wave carries the heartbeat vibration signal and the breathing vibration signal of the second object 100-B, the computing device 600 can determine the heartbeat characteristic index and the breathing characteristic index of the second object 100-B based on the incident electromagnetic wave and the second reflected electromagnetic wave.

[0074] In Figure 1BIn the application scenario shown, the first object 100-A wears the first electromagnetic tag 200-A, and the second object 100-B wears the second electromagnetic tag 200-B. The first electromagnetic tag 200-A and the second electromagnetic tag 200-B correspond to different operating frequency bands, so that the first electromagnetic tag 200-A and the second electromagnetic tag 200-B can retro-reflect different frequency band components of the incident electromagnetic wave. Thus, the first reflected electromagnetic wave generated by the retro-reflection of the first electromagnetic tag 200-A carries the life characteristic signal of the first object 100-A, and the second reflected electromagnetic wave generated by the retro-reflection of the second electromagnetic tag 200-B carries the life characteristic signal of the second object 200-B. It can be seen that the health monitoring system 002 provided in this specification realizes the simultaneous health monitoring of two objects 100-A and 100-B by using two electromagnetic tags 200-A and 200-B and performing frequency diversity on the operating frequency band of the detection device 500. Further, since the life characteristic signals of the two objects 100-A and 100-B are carried in the reflected electromagnetic waves of different frequency bands, the life characteristic signals corresponding to the two objects 100-A and 100-B are easy to distinguish, and the monitoring accuracy can be improved.

[0075] Those skilled in the art can understand that Figure 1B the simultaneous health monitoring of two objects is taken as an example for illustration. By adopting a similar monitoring principle, it is also possible to realize the simultaneous health monitoring of more objects, and this specification does not give examples one by one.

[0076] In Figure 1A and Figure 1B the application scenario shown, the detection device 500 can adopt a millimeter-wave frequency-modulated continuous wave (FMCW) radar. In this case, the detection device 500 can emit a continuous wave and obtain an incident electromagnetic wave corresponding to the operating frequency band of the electromagnetic tag by performing frequency modulation on the continuous wave. Thus, the detection device 500 can flexibly adapt to electromagnetic tags of multiple operating frequency bands, facilitating the realization of the simultaneous health monitoring of multiple objects.

[0077] As can be seen from the above, both the health monitoring systems 001 and 002 provided in this specification realize non-contact health monitoring. The detection device 500 does not need to directly contact the human body, enabling the object to complete health monitoring in a comfortable and convenient manner without affecting the quality of life of the object, making the application of health monitoring more flexible and convenient.

[0078] It should be noted that Figure 1A and Figure 1BThey are all illustrated by taking the monitoring of respiratory characteristic indicators and heartbeat characteristic indicators as examples. Those skilled in the art can understand that the health monitoring system provided in this specification can also be used to monitor other vital characteristic indicators, and the monitoring principle is similar to that described above. This specification does not give examples one by one. In addition, this specification does not limit the posture adopted when monitoring the target object. Figure 1A and Figure 1B both take the lying posture as an example for illustration. In actual applications, the target object can also adopt other postures, such as sitting posture, standing posture, etc.

[0079] The embodiment of this specification also provides an electromagnetic tag, which has the ability to retro-reflect electromagnetic waves. This electromagnetic tag can be used in health monitoring scenarios such as Figure 1A or Figure 1B shown (for example, as the electromagnetic tag 200 in Figure 1A , or as the first electromagnetic tag 200-A in Figure 1B , or as the second electromagnetic tag 200-B in Figure 1B ).

[0080] The following will combine the attached Figure 2 to describe the electromagnetic tag provided in this specification in detail. It should be noted that when referring to the coordinate system / coordinate axis in the following description, unless otherwise specified, it generally refers to the XYZ coordinate system, where the X-axis corresponds to the length direction of the electromagnetic tag, the Y-axis corresponds to the width direction of the electromagnetic tag, and the Z-axis corresponds to the thickness direction of the electromagnetic tag.

[0081] Figure 2 shows a schematic diagram of the electromagnetic tag 200 provided according to the embodiment of this specification. It should be understood that the electromagnetic tag 200 is a three-dimensional structure. Figure 2 shows the top view of the electromagnetic tag 200, that is, the thickness information of the electromagnetic tag 200 along the Z-axis direction is not shown in Figure 2 .

[0082] As Figure 2 shown, the electromagnetic tag 200 may include a plurality of modulation units 210 arranged in a two-dimensional period. Figure 2 takes the example that the electromagnetic tag 200 contains 15*15 modulation units 210 for illustration.

[0083] The electromagnetic tag 200 corresponds to a target operating frequency band, and the electromagnetic tag 200 can perform retro-reflection on electromagnetic waves within the target operating frequency band. Specifically, when the incident electromagnetic wave emitted by the detection device 500 irradiates the reflection interface of the electromagnetic tag 200 at a target incident angle, the plurality of modulation units 210 perform reflection phase modulation on the target electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic wave, so that the target electromagnetic wave component undergoes retro-reflection on the reflection interface and generates a reflected electromagnetic wave. If the frequency band covered by the incident electromagnetic wave includes other frequency bands in addition to the target operating frequency band, the plurality of modulation units 210 perform specular reflection on the electromagnetic wave components corresponding to the other frequency bands in the incident electromagnetic wave.

[0084] Those skilled in the art can understand that when the incident electromagnetic wave irradiates the reflection interface of the electromagnetic tag 200, each modulation unit 210 in the electromagnetic tag 200 respectively modulates the reflection phase of the target electromagnetic wave component, and the modulation results of all the modulation units 210 interfere with each other, and finally form a reflected electromagnetic wave in the opposite direction to the incident electromagnetic wave direction. That is to say, through the comprehensive modulation effect of all the modulation units 210 in the electromagnetic tag 200 on the reflection phase of the target electromagnetic wave component, the retro-reflection is realized.

[0085] In this specification, the retro-reflection ability of the electromagnetic tag 200 to electromagnetic waves can be used for non-contact health monitoring, such as monitoring the vital sign indicators (such as respiration characteristic indicators and heartbeat characteristic indicators) of the target object 100. The specific monitoring principle is as follows: Combined with Figure 1A In the application scenario shown, the electromagnetic tag 200 is worn on the chest area of the target object 100. The detection device 500 emits an incident electromagnetic wave, and the incident electromagnetic wave irradiates the reflection interface of the electromagnetic tag 200 at a target incident angle. Since the electromagnetic tag 200 has the ability to perform retro-reflection on electromagnetic waves within the target operating frequency band, the target electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic wave undergoes retro-reflection on the reflection interface and generates a reflected electromagnetic wave. Since the electromagnetic tag 200 will move up and down with the chest of the target object 100, the reflected electromagnetic wave generated by the retro-reflection of the electromagnetic tag 200 carries the respiration vibration signal and the heartbeat vibration signal of the target object 100. Therefore, the reflected electromagnetic wave can be used to determine the heartbeat characteristic indicators and respiration characteristic indicators corresponding to the target object 100.

[0086] It can be seen that the electromagnetic tag 200 provided in this specification cooperates with the detection device 500 to achieve non-contact health monitoring of the target object 100. In the non-contact health monitoring mode, the detection device 500 does not need to directly contact the human body, so that the object can complete health monitoring in a comfortable and convenient manner without affecting the object's quality of life, making the application of health monitoring more flexible and convenient.

[0087] Furthermore, those skilled in the art can understand that retroreflection can significantly enhance the backscattering ability of the electromagnetic tag 200, thereby enhancing the echo signal and increasing the radar cross section (RCS). Therefore, by wearing the electromagnetic tag 200 with retroreflective effect on the target body area of the target object 100, on the one hand, the detection device 500 can more accurately locate the position of the electromagnetic tag 200, and on the other hand, the electromagnetic tag 200 can significantly enhance the reflected electromagnetic wave and increase the signal-to-noise ratio corresponding to the reflected electromagnetic wave, thereby improving the detection accuracy of the detection device 500 and further improving the accuracy of health monitoring.

[0088] The electromagnetic tag 200 provided in this specification can be a retroreflector based on metasurface. That is to say, the electromagnetic tag 200 can be a metasurface formed by two-dimensional metamaterials. Compared with devices such as corner reflectors and Luneburg lenses used to achieve retroreflection, the retroreflector based on metasurface has a simple structure, lower manufacturing difficulty, is easy to conform to a planar surface, and can be conveniently worn on the body area of the target object, thus better adapting to the health monitoring scenario. Further, in order to achieve retroreflection, the electromagnetic tag 200 can be designed as a phase gradient metasurface (PGMS), and the phase gradient metasurface can cause a phase mutation of the incident electromagnetic wave on the metasurface, generating a phase gradient in the target direction of the metasurface. Phase is an important factor affecting the direction of electromagnetic waves. The phase gradient metasurface can control the direction of the reflected electromagnetic wave through the generation of the phase gradient, thereby achieving retroreflection of the electromagnetic wave.

[0089] That is to say, in order to achieve retroreflection, when the incident electromagnetic wave emitted by the detection device 500 irradiates the reflection interface of the electromagnetic tag 200 at the target incident angle, the electromagnetic tag 200 needs to meet the following two conditions.

[0090] Condition A: Each modulation unit 210 can modulate the reflection phase of the incident electromagnetic wave, that is, each modulation unit 210 can change the reflection phase of the incident electromagnetic wave.

[0091] Condition B: Different modulation units 210 in the electromagnetic tag 200 generate a phase gradient in the target direction along the reflection interface. The target direction may be the length direction or the width direction of the electromagnetic tag, or in other words, the target direction may be the X-axis direction or the Y-axis direction.

[0092] Specifically, the above Condition B can also be expressed as follows: for any adjacent first modulation unit and second modulation unit among the multiple modulation units 210 in the target direction: the first modulation unit modulates the target electromagnetic wave component to obtain a first reflection phase, and the second modulation unit modulates the target electromagnetic wave component to obtain a second reflection phase, and there is a preset phase difference between the second reflection phase and the first reflection phase. Combined with Figure 2 For example, among the 15 modulation units 210 in each row along the X-axis direction, there is a preset phase difference between the reflection phases modulated by any two adjacent modulation units 210. For example, assume The reflection phase modulated by the 1st modulation unit 210 is 0°, the reflection phase modulated by the 2nd modulation unit 210 is 120°, the reflection phase modulated by the 3rd modulation unit 210 is 240°, the reflection phase modulated by the 4th modulation unit 210 is 0°, and so on.

[0093] Next, a specific example is used to illustrate in detail how to design the modulation unit 210 so that the electromagnetic tag 200 satisfies the above Condition A and Condition B.

[0094] Figure 3A Shows Figure 2 A three-dimensional structural schematic diagram of each modulation unit 210 in Figure 3B Shows Figure 2 A top view of each modulation unit 210 in Figure 3A As shown in

[0095] Among them, the dielectric substrate 211 may be a substrate formed of a dielectric material having a certain relative dielectric constant. In some embodiments, the relative dielectric constant ε of the dielectric substrate 211 r = 3, the loss tangent tanδ of the dielectric substrate 211 = 0.001, and the thickness (i.e., the height in the Z-axis direction) h of the dielectric substrate 211 = 0.508 mm. It should be noted that this specification does not limit the values of the relative dielectric constant ε r 、loss tangent tanδ, and thickness h of the dielectric substrate 211, and the above-listed values are only used as a possible example.

[0096] See Figure 3A , the dielectric substrate 211 has opposite first and second surfaces. For example, in Figure 3A , the lower surface of the dielectric substrate 211 in the thickness direction (i.e., the Z-axis direction) can be the first surface, and the upper surface can be the second surface.

[0097] The metal bottom plate 212 is attached to the first surface of the dielectric substrate 211 for grounding.

[0098] The metal pattern 213 can be located on the second surface of the dielectric substrate 211. The metal pattern 213 can be a pattern formed by at least one metal piece located on the second surface of the dielectric substrate 211. For example, at least one metal piece is etched on the second surface of the dielectric substrate 211 to form the metal pattern 213. When the incident electromagnetic wave irradiates the metal pattern 213, the incident electromagnetic wave is coupled with the metal pattern 213 to generate an electromagnetic field and generate resonance inside the modulation unit 210 to change the reflection phase of the incident electromagnetic wave, so that the modulation unit 210 has the reflection phase modulation ability. Thus, Figure 3A and Figure 3B the modulation unit 210 shown can meet the above condition A.

[0099] In some embodiments, the metal pattern 213 can be a pattern that meets a preset condition through specific design, so that the incident electromagnetic wave is coupled with the metal pattern 213 to generate an electromagnetic field and generate Fano resonance inside the modulation unit 210. Those skilled in the art can understand that when Fano resonance occurs inside the modulation unit 210, the sensitivity of the reflection phase of the incident electromagnetic wave to frequency change is greater than a preset sensitivity, that is, the sensitivity of the reflection phase of the incident electromagnetic wave to frequency change is higher. When the reflection phase of the incident electromagnetic wave changes more sensitively with frequency, it means that the modulation unit 210 has strong dispersion characteristics and a high Q (quality factor) value.

[0100] For example, in order to achieve Fano resonance inside the modulation unit 210, the metal pattern 213 can be designed to be asymmetric with respect to the polarization direction of the incident electromagnetic wave. See Figure 3A and Figure 3B, the metal pattern can be a metal ring with two notches. Specifically, the metal pattern 213 can be formed by a first arc-shaped metal piece 2131 and a second arc-shaped metal piece 2132. Among them, the central angle corresponding to the first arc-shaped metal piece 2131 is α, and the radius is r; the central angle corresponding to the second arc-shaped metal piece is β, and the radius is r. The widths of the first arc-shaped metal piece 2131 and the second arc-shaped metal piece 2132 are both w, and the thicknesses are both t. Assuming that the polarization direction of the incident electromagnetic wave is the Y-axis direction, the first arc-shaped metal piece 2131 and the second metal piece 2132 can be arranged concentrically, so that they form a metal ring with two notches and a radius of r, and the metal ring is asymmetric about the Y-axis direction.

[0101] When the metal pattern 213 adopts a symmetric design, the super-radiant (bright) mode of dipole resonance will cause radiation loss, resulting in a low Q value of the modulation unit 210. When the metal pattern 213 is asymmetric about the polarization direction of the incident electromagnetic wave, the introduction of this asymmetry causes symmetry breaking, thus exciting a sub-radiant (dark) mode. Among them, the sub-radiant (dark) mode refers to an electromagnetic mode that is weakly coupled to space. The interaction and coupling between the super-radiant (bright) mode and the sub-radiant (dark) mode inside the modulation unit 210 form a Fano resonance. The excitation of the sub-radiant (dark) mode will reduce the radiation loss of the modulation unit 210, thereby increasing the Q value of the modulation unit 210.

[0102] Figure 3A and Figure 3B The modulation unit 210 shown changes the reflection phase of the electromagnetic wave by forming a Fano resonance through an asymmetric metal split ring. Therefore, the above modulation unit 210 can also be called an Asymmetric Split Ring Resonator (ASRR).

[0103] Figure 4 shows Figure 3A and Figure 3B a schematic diagram of the reflection coefficient curve corresponding to the modulation unit 210 in Figure 4 The reflection coefficient curve shown is obtained by simulating the modulation unit 210 using electromagnetic simulation software. When simulating, periodic boundary conditions are adopted, assuming that the target incident angle is set to 30°, and the polarization direction of the incident electromagnetic wave is along the Y-axis direction. When the modulation unit 210 generates a Fano resonance at 62 GHz, its corresponding reflection coefficient curve is as shown by the dashed line in Figure 4 From this reflection coefficient curve, it can be seen that the modulation unit 210 has a very steep reflection phase curve in the frequency band of 60 GHz - 64 GHz. That is to say, the reflection phase is sensitive to frequency changes, indicating that the modulation unit 210 has strong dispersion characteristics and a high Q value.

[0104] Those skilled in the art can understand that when the modulation unit 210 has strong dispersion characteristics and a high Q value, the electromagnetic tag 200 formed by multiple modulation units 210 can achieve retroreflection within a relatively narrow frequency band. That is to say, the target operating frequency band corresponding to the electromagnetic tag 200 can be relatively narrow. In this way, it helps to perform frequency diversity on the operating frequency band range of the detection device 500, that is, divide the operating frequency band range of the detection device 500 into multiple sub-frequency band ranges, and design an electromagnetic tag 200 for each sub-frequency band range respectively. Thus, the same detection device 500 can cooperate with multiple electromagnetic tags 200 with different operating frequency bands simultaneously to realize the simultaneous health monitoring of multiple objects.

[0105] In Figure 3A and Figure 3B Based on the structure of the modulation unit 210 shown, the following will explain how to generate a phase gradient between different modulation units 210, that is, how to meet condition B.

[0106] Those skilled in the art can understand that any parameter (including but not limited to: α, β, r, w, t, etc.) of the metal pattern 213 in the modulation unit 210 will affect the dispersion characteristics of the modulation unit 210 and affect the Q value of the modulation unit 210. Therefore, when designing the electromagnetic tag 200, for any two adjacent modulation units 210 along the target direction, the metal patterns 213 of these two modulation units 210 can be made different, that is, the parameters (such as α, β, r, w, t, etc.) of the metal patterns 213 of these two modulation units 210 are made different. In this way, a phase gradient can be generated between two adjacent modulation units.

[0107] In other words, for any adjacent first modulation unit and second modulation unit along the target direction, the metal pattern 213 corresponding to the first modulation unit is different from the metal pattern 213 corresponding to the second modulation unit, so that there is a preset phase difference between the reflection phase modulated by the first modulation unit and the reflection phase modulated by the second modulation unit Such a design enables the electromagnetic tag 200 to meet the above-mentioned condition B.

[0108] For the convenience of description, assume that the metal pattern corresponding to the first modulation unit is pattern 1, and the metal pattern corresponding to the second modulation unit is pattern 2. It should be noted that pattern 1 and pattern 2 being different can include at least one of the following situations:

[0109] (1) The circular ring radius r of pattern 1 is different from the circular ring radius r of pattern 2;

[0110] (2) The central angle α of pattern 1 is different from the central angle α of pattern 2;

[0111] (3) The central angle β of Pattern 1 is different from the central angle β of Pattern 2;

[0112] (4) The ring width w of Pattern 1 is different from the ring width w of Pattern 2;

[0113] (5) The ring thickness t of Pattern 1 is different from the ring thickness t of Pattern 2.

[0114] In the specific implementation process, in order to simplify the design, some parameters of Pattern 1 and Pattern 2 can be made the same, and Pattern 1 and Pattern 2 can be made different by changing some other parameters.

[0115] For example, since it is found in the simulation process that the reflection phase of the modulation unit 210 is relatively sensitive to the change of the ring radius r. Figure 5 shows Figure 3A and Figure 3B a schematic diagram of the change of the reflection phase generated by the modulation unit 210 in Figure 5 As shown, when the ring radius r of the modulation unit 210 changes, the reflection phase modulated by the modulation unit 210 changes accordingly. Thus, in order to make the electromagnetic tag 200 generate a phase gradient along the target direction, for any adjacent first modulation unit and second modulation unit of the electromagnetic tag 200 along the target direction, the following design can be adopted: the central angle α corresponding to the first modulation unit is the same as that corresponding to the second modulation unit, the central angle β corresponding to the first modulation unit is the same as that corresponding to the second modulation unit, the ring width w corresponding to the first modulation unit is the same as that corresponding to the second modulation unit, the ring thickness t corresponding to the first modulation unit is the same as that corresponding to the second modulation unit, while the ring radius r corresponding to the first modulation unit is different from that corresponding to the second modulation unit, so that there is a preset phase difference between the reflection phase modulated by the first modulation unit and the reflection phase modulated by the second modulation unit

[0116] Based on the above analysis, we can change the ring radius r so that the reflection phases modulated by N modulation units 210 along the target direction cover a phase period (i.e., 360°). Wherein, N is an integer greater than 1. For the convenience of description, in this specification, N adjacent modulation units 210 whose modulated reflection phases cover 360° are referred to as a super unit 220.

[0117] Figure 6 shows Figure 2 a schematic diagram of a super unit 220 in Figure 6As shown, taking N = 3 as an example, the supercell 220 includes 3 modulation units 210. The pattern styles of the metal patterns 213 corresponding to these 3 modulation units 210 are the same, that is, the metal patterns of these 3 modulation units 210 are all metal rings with two notches. However, the pattern sizes of the metal patterns 213 corresponding to these 3 modulation units 210 are different. Specifically, the central angles α, β, the ring width w, and the ring thickness t corresponding to the metal patterns of the 3 modulation units 210 are the same. However, the ring radius corresponding to the metal pattern of the first modulation unit 210 is r 1 , the ring radius corresponding to the metal pattern of the second modulation unit 210 is r 2 , the ring radius corresponding to the metal pattern of the third modulation unit 210 is r 3 , r 1 ≠r 2 ≠r 3 . Among the above 3 modulation units 210, there is a phase difference of 120° between the reflection phases generated by any two adjacent modulation units 210. That is, the phase difference between the second modulation unit 210 and the first modulation unit 210 is 120°, and the phase difference between the third modulation unit 210 and the second modulation unit 210 is 120°.

[0118] The above describes how to design the modulation unit 210. The following specifically describes how to design the complete electromagnetic tag 200 based on the modulation unit 210.

[0119] Those skilled in the art can understand that for a reflective metasurface, the reflection characteristics of the metasurface can be controlled by designing a sub-wavelength periodic structure, so as to achieve an anomalous reflection (such as retroreflection) phenomenon. Therefore, we can design the periodicity of the modulation unit 210 (i.e., the length d of the modulation unit 210 along the target direction) to obtain an electromagnetic tag 200 with retroreflective ability. In some embodiments, the arrangement period of the modulation unit 210 (i.e., the length d of the modulation unit 210 along the target direction) is related to at least one of the target incident angle, the target operating frequency band, and the preset phase difference. That is, the arrangement period of the modulation unit 210 can be calculated from at least one of the target incident angle, the target operating frequency band, and the preset phase difference.

[0120] The following reasons and explains the design principle of the periodicity of the modulation unit 210 (i.e., the length d of the modulation unit 210 along the target direction).

[0121] According to the generalized Snell's law, Equation (1) can be obtained.

[0122]

[0123] Where θr is the reflection angle, θ i is the incident angle, n i is the refractive index of free space is the phase gradient along the target direction (taking the X-axis direction as an example) of the reflection interface. Retroreflection requires that the direction of the reflected wave is parallel to the direction of the incident wave, so θ r = -θ i , and at the same time n i = 1. Substituting it into equation (1), equation (2) can be obtained.

[0124]

[0125] Among them, is the incident wave vector in free space. It can be seen from equation (2) that the phase difference between the reflected phases modulated by two adjacent modulation units 210 along the target direction can be expressed as equation (3).

[0126]

[0127] In the formula, d is the length of the modulation unit 210 along the X-axis direction, which characterizes the periodicity of the electromagnetic tag 200 along the X-axis direction. From equation (3), it can be obtained that:

[0128]

[0129] It can be seen from equation (4) that the arrangement period of the modulation units 210 in the electromagnetic tag 200 (i.e., the length of each modulation unit 210 along the x-axis direction) can be calculated through the target incident angle θ i , the target operating frequency band (which has a corresponding relationship with λ), and the preset phase difference is calculated.

[0130] Furthermore, assuming that a super unit 220 includes N modulation units 210, that is, the reflected phases modulated by N adjacent modulation units 210 cover a phase period (i.e., 360°), then the preset phase difference can be expressed as equation (5).

[0131]

[0132] Substituting equation (5) into equation (4) can obtain equation (6).

[0133]

[0134] It can be seen from equation (6) that the arrangement period of the modulation units 210 in the electromagnetic tag 200 (i.e., the length of each modulation unit 210 along the x-axis direction) can also be obtained through the target incident angle θ iare calculated based on the target operating frequency band (which has a corresponding relationship with λ), and N.

[0135] Continue to refer to Figure 2 , taking N = 3 as an example, each row of the electromagnetic tag 200 in the X-axis direction can be obtained by periodically arranging a plurality of supercells 220. Further, in the Y-axis direction, each row is periodically arranged to obtain the electromagnetic tag 200. In some embodiments, the reflection interface corresponding to the modulation unit 210 can be designed as a square, that is, the length of the modulation unit 210 in the X-axis direction is equal to the length in the Y-axis direction. In this way, the length of the electromagnetic tag 200 in the X-axis direction is equal to the length in the Y-axis direction, that is to say, the reflection interface of the electromagnetic tag 200 is a square.

[0136] It should be noted that the number of modulation units 210 included in the electromagnetic tag 200 is not limited in this specification. Figure 2 Only 15 * 15 modulation units 210 are taken as an example for illustration. Those skilled in the art can understand that the number of modulation units 210 will affect the physical size of the electromagnetic tag 200. Therefore, the number of modulation units 210 included can be reasonably determined according to the application scenario of the electromagnetic tag 200 (such as the size of the body area to be covered).

[0137] In addition, it should also be noted that although in the description of this specification, the electromagnetic tag 200 is divided into a plurality of modulation units 210, and each modulation unit 210 includes a dielectric substrate 211, a metal bottom plate 212, and a metal pattern 213 respectively. However, those skilled in the art should understand that in the physical structure of the electromagnetic tag 200, the dielectric substrates 211 corresponding to the respective modulation units 210 can be an integral dielectric substrate, and the metal bottom plates 212 in the respective modulation units 210 can also be an integral metal bottom plate. That is to say, the electromagnetic tag 200 can include a dielectric substrate, a metal bottom plate located on the bottom surface of the dielectric substrate, and a plurality of metal patterns periodically arranged on the top surface of the dielectric substrate.

[0138] The electromagnetic tag 200 can also be a flexible tag. For example, the dielectric substrate in the electromagnetic tag 200 can use a flexible substrate. In this way, the electromagnetic tag 200 is more easily fitted to the surface contour of the target body area, which helps to collect more accurate vital sign signals and improve the wearing comfort of the object.

[0139] Next, taking the Figure 1B shown application scenario as an example, specifically illustrate how to design the first electromagnetic tag 200 - A and the second electromagnetic tag 200 - B based on the Figure 3A and Figure 3B shown modulation unit 210.

[0140] Taking the detection device 500 using a millimeter-wave radar as an example, the operating frequency band range of the millimeter-wave radar is 60 GHz - 64 GHz. In Figure 1B In the application scenario shown, assuming that it is necessary to simultaneously monitor the health of two objects 100, we can adopt the idea of frequency diversity for the operating frequency band range of the millimeter-wave radar to design and obtain the first electromagnetic tag 200-A and the second electromagnetic tag 200-B. Among them, the first operating frequency band corresponding to the first electromagnetic tag 200-A is 60 GHz - 61 GHz, and its center frequency is 60.5 GHz; the second operating frequency band corresponding to the second electromagnetic tag 200-B is 62.5 GHz - 63.5 GHz, and its center frequency is 63 GHz.

[0141] Assume that the incident angle of the incident electromagnetic wave emitted by the detection device 500 is 30°. And assume that N = 3, that is, a super unit includes 3 detection units.

[0142] For the first electromagnetic tag 200-A, based on its corresponding center frequency 60.5 GHz, the value of N, and the incident angle 30°, according to the derivation of the foregoing formulas (1)-(3), the curve of the reflection phase corresponding to the first electromagnetic tag 200-A changing with the ring radius r can be obtained. Figure 7A The schematic diagram of the curve of the reflection phase corresponding to the first electromagnetic tag 200-A changing with the ring radius r is shown. As Figure 7A shown, based on this curve, we can select the following 3 values of the ring radius r: 0.5547 mm, 0.562 mm, 0.579 mm. That is to say, in the same super unit 220 of the first electromagnetic tag 200-A, the ring radii r corresponding to the 3 detection units 210 are 0.5547 mm, 0.562 mm, and 0.579 mm respectively. Correspondingly, the reflection phases (the reflection phases normalized by the first detection unit) corresponding to these 3 detection units 210 are: 0°, -120°, -240°. The values of the remaining parameters can be: α = 148°, β = 172°, w = 0.1 mm, t = 0.035 mm.

[0143] After determining the super unit 220, the above super unit 220 is periodically arranged to obtain the first electromagnetic tag 200-A. Those skilled in the art can understand that the structure of the first electromagnetic tag 200-A can be as Figure 2 shown. Assume that the first electromagnetic tag 200-A includes 15 * 15 detection units. In this case, the physical size of the first electromagnetic tag 200-A is 24.75 mm × 24.75 mm.

[0144] For the second electromagnetic tag 200-B, based on its corresponding central frequency of 63 GHz, the value of N, and the incident angle of 30°, according to the derivation of the aforementioned formulas (1)-(3), the curve of the reflection phase corresponding to the second electromagnetic tag 200-B varying with the ring radius r can be obtained. Figure 7B It shows a schematic diagram of the curve of the reflection phase corresponding to the second electromagnetic tag 200-B varying with the ring radius r. As Figure 7B shown, based on this curve, we can select the following 3 values of the ring radius r: 0.5306 mm, 0.537 mm, 0.554 mm. That is to say, in the same supercell 220 of the second electromagnetic tag 200-B, the ring radii r corresponding to the 3 detection units 210 are 0.5306 mm, 0.537 mm, and 0.554 mm respectively. Correspondingly, the reflection phases (the reflection phases normalized by the first detection unit) corresponding to these 3 detection units 210 are 0°, -120°, and -240° respectively. The values of the remaining parameters can be: α = 148°, β = 172°, w = 0.1 mm, t = 0.035 mm.

[0145] After determining the supercell 220, the above supercell 220 is periodically arranged to obtain the second electromagnetic tag 200-B. Those skilled in the art can understand that the structure of the second electromagnetic tag 200-B can be as Figure 2 shown. Assuming that the second electromagnetic tag 200-B contains 15*15 detection units, in this case, the physical size of the second electromagnetic tag 200-B is 23.85 mm × 23.85 mm.

[0146] Next, the test results of the scattering characteristics of the first electromagnetic tag 200-A and the second electromagnetic tag 200-B are described.

[0147] Figure 8A It shows a schematic diagram of the scattering characteristics corresponding to the first electromagnetic tag 200-A. Among them, the following test conditions are adopted: full-wave simulation is carried out on the first electromagnetic tag 200-A, plane wave excitation is used, the polarization direction of the incident electromagnetic wave is along the Y-axis direction, and the incident angle of the incident electromagnetic wave is -30°. In addition, for the convenience of comparison, a comparative test is carried out on the first electromagnetic tag 200-A and a metal plate of the same size. That is to say, the above incident electromagnetic wave is irradiated onto the first electromagnetic tag 200-A and the metal plate respectively at the above incident angle of -30° to obtain the schematic diagram of the scattering characteristics as Figure 8A shown. See Figure 8A, the solid line represents the scattering characteristic curve corresponding to the first electromagnetic tag 200-A, and the dashed line represents the scattering characteristic curve corresponding to the metal plate. In the frequency band of 60 GHz - 61 GHz, the angle of the reflected electromagnetic wave generated by the first electromagnetic tag 200-A is -30°, that is, along the reverse direction of the incident electromagnetic wave; while the angle of the reflected electromagnetic wave generated by the metal plate is 30°. In the frequency band of 62.5 GHz - 63.5 GHz, the angle of the reflected electromagnetic wave generated by the first electromagnetic tag 200-A is 30°, and the angle of the reflected electromagnetic wave generated by the metal plate is 30°. Thus, it can be seen that the first electromagnetic tag can achieve retroreflection in the frequency band of 60 GHz - 61 GHz, while in the frequency band of 62.5 GHz - 63.5 GHz, it is specular reflection that conforms to the classical Snell's law.

[0148] Figure 8B shows the schematic diagram of the scattering characteristics corresponding to the second electromagnetic tag 200-B. Among them, the test conditions adopted are as follows: full-wave simulation is carried out on the second electromagnetic tag 200-B, plane wave excitation is used, the polarization direction of the incident electromagnetic wave is along the Y-axis direction, and the incident angle of the incident electromagnetic wave is -30°. In addition, for the convenience of comparison, a comparative test is carried out on the second electromagnetic tag 200-B and a metal plate of the same size. That is to say, the above incident electromagnetic wave is irradiated onto the second electromagnetic tag 200-B and the metal plate respectively at the above incident angle of -30°, and the schematic diagram of the scattering characteristics as shown in Figure 8B is obtained. See Figure 8B , the solid line represents the scattering characteristic curve corresponding to the second electromagnetic tag 200-B, and the dashed line represents the scattering characteristic curve corresponding to the metal plate. In the frequency band of 60 GHz - 61 GHz, the angle of the reflected electromagnetic wave generated by the second electromagnetic tag 200-B is 30°, and the angle of the reflected electromagnetic wave generated by the metal plate is 30°. In the frequency band of 62.5 GHz - 63.5 GHz, the angle of the reflected electromagnetic wave generated by the second electromagnetic tag 200-B is -30°, that is, along the reverse direction of the incident electromagnetic wave; while the angle of the reflected electromagnetic wave generated by the metal plate is 30°. Thus, it can be seen that the second electromagnetic tag is specular reflection that conforms to the classical Snell's law in the frequency band of 60 GHz - 61 GHz, while it achieves retroreflection in the frequency band of 62.5 GHz - 63.5 GHz.

[0149] Thus, it can be seen that the above-mentioned first electromagnetic tag 200-A and second electromagnetic tag 200-B can respectively achieve retroreflection of electromagnetic waves in different frequency bands emitted by the millimeter-wave radar, which helps the millimeter-wave radar distinguish the reflected signals of different objects calibrated by different electromagnetic tags, so that it can use the same millimeter-wave radar to simultaneously monitor the health of multiple objects and effectively improve the accuracy of the millimeter-wave radar for multi-object monitoring.

[0150] In the above description, the metal pattern 213 in the modulation unit 210 is illustrated by taking a "metal ring with two notches" as an example. It should be noted that the metal pattern 213 in the modulation unit 210 can also be replaced with other styles of metal patterns. Figures 9A to 9G Schematic diagrams of several possible metal patterns 213 are respectively shown. The following Figures 9A to 9G will be illustrated by examples.

[0151] As Figure 9A shown, the metal pattern 213 can be a metal ring with one notch. Taking the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction) as the reference axis, the position of the notch is set at a position to the left or to the right, so that the metal ring is asymmetric with respect to the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction).

[0152] As Figure 9B shown, the metal pattern 213 can be a metal rectangular ring with one notch. Taking the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction) as the reference axis, the position of the notch is set at a position to the left or to the right, so that the metal rectangular ring is asymmetric with respect to the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction).

[0153] As Figure 9C shown, the metal pattern 213 can be a metal rectangular ring with two notches. Taking the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction) as the reference axis, the positions of the two notches are both at a position to the left, so that the metal rectangular ring is asymmetric with respect to the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction). Similarly, the positions of the two notches can also be both set at a position to the right, or one to the left and the other to the right (as long as the metal rectangular ring is asymmetric with respect to the Y-axis).

[0154] As Figure 9D shown, the metal pattern 213 can be a metal semi-ring with one or more notches. The positions of the one or more notches make the metal semi-ring asymmetric with respect to the polarization direction of the incident electromagnetic wave (i.e., the Y-axis direction).

[0155] In some embodiments, the metal pattern 213 can include a first pattern and a second pattern. Among them, the first pattern and the second pattern are arranged in sequence on the second surface of the modulation unit 210. Or, the first pattern is nested inside the second pattern. Among them, both the first pattern and the second pattern can be any one of the following: a metal ring with at least one notch (such as Figure 3B and Figure 9A shown), a metal rectangular ring with at least one notch (as Figure 9B and 9C shown), a metal semi-ring with at least one notch (as Figure 9D shown).

[0156] Those skilled in the art can understand that there can be various forms of the metal pattern 213 formed by the combination of the first pattern and the second pattern, and this specification does not limit this. Figures 9E to 9G Only several possible examples are given for reference.

[0157] The above describes specific embodiments of this specification. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve the desired result. Additionally, the processes depicted in the drawings do not necessarily require a specific order or a sequential order to achieve the desired result. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0158] In summary, after reading this detailed disclosure, those skilled in the art can understand that the foregoing detailed disclosure can be presented only by way of example and may not be restrictive. Although not explicitly stated herein, those skilled in the art can understand that this specification is intended to encompass various reasonable changes, improvements, and modifications to the embodiments. These changes, improvements, and modifications are intended to be proposed by this specification and are within the spirit and scope of the exemplary embodiments of this specification.

[0159] In addition, certain terms in this specification have been used to describe the embodiments of this specification. For example, "one embodiment", "an embodiment", and / or "some embodiments" mean that the specific features, structures, or characteristics described in connection with the embodiment can be included in at least one embodiment of this specification. Therefore, it should be emphasized and understood that two or more references to "an embodiment" or "one embodiment" or "alternative embodiments" in various parts of this specification do not necessarily all refer to the same embodiment. Additionally, the specific features, structures, or characteristics can be appropriately combined in one or more embodiments of this specification.

[0160] It should be understood that in the foregoing description of the embodiments of this specification, for the purpose of helping to understand a feature, and for the purpose of simplifying this specification, this specification combines various features in a single embodiment, drawing, or its description. However, this does not mean that the combination of these features is necessary. Those skilled in the art are fully likely to mark out some of the devices as separate embodiments for understanding when reading this specification. That is to say, the embodiments in this specification can also be understood as the integration of multiple sub - embodiments. And the content of each sub - embodiment is also valid when it has fewer features than all the features of a single foregoing disclosed embodiment.

[0161] Each patent, patent application, publication of patent application, and other materials cited herein, such as articles, books, specifications, publications, documents, items, etc., except those that are inconsistent with or conflict with this document, or those that have a limiting effect on the broadest scope of the claims, may be incorporated herein by reference and used for all purposes now or hereafter associated with this document. In addition, in the event of any inconsistency or conflict between the description, definition, and / or use of relevant terms in any material and the description, definition, and / or use of relevant terms in this document, the terms in this document shall prevail.

[0162] Finally, it should be understood that the embodiments of the application disclosed herein are illustrative of the principles of the embodiments of this specification. Other modified embodiments are also within the scope of this specification. Therefore, the embodiments disclosed in this specification are merely examples and not limitations. Those skilled in the art can adopt alternative configurations based on the embodiments in this specification to implement the application in this specification. Therefore, the embodiments of this specification are not limited to the embodiments precisely described in the application.

Claims

1. An electromagnetic tag, characterized in that, it can be worn on a target body area of a target object, and the electromagnetic tag includes a plurality of modulation units arranged in a two-dimensional periodic pattern, wherein, the electromagnetic tag corresponds to a target operating frequency band. When an incident electromagnetic wave emitted by a detection device irradiates a reflection interface of the electromagnetic tag at a target incident angle, the plurality of modulation units perform a reflection phase modulation on a target electromagnetic wave component corresponding to the target operating frequency band in the incident electromagnetic wave, so that the target electromagnetic wave component undergoes retroreflection on the reflection interface and generates a reflected electromagnetic wave. The reflected electromagnetic wave is received by the detection device and is used to determine a vital sign index corresponding to the target object.

2. The electromagnetic tag according to claim 1, characterized in that, for any adjacent first modulation unit and second modulation unit in a target direction among the plurality of modulation units: the first modulation unit modulates the target electromagnetic wave component to obtain a first reflection phase, the second modulation unit modulates the target electromagnetic wave component to obtain a second reflection phase, and there is a preset phase difference between the second reflection phase and the first reflection phase.

3. The electromagnetic tag according to claim 2, characterized in that, the arrangement period of the modulation unit is related to at least one of the target incident angle, the target operating frequency band, and the preset phase difference.

4. The electromagnetic tag according to claim 1, characterized in that, the modulation unit includes: a dielectric substrate having opposite first and second surfaces; a metal bottom plate located on the first surface for grounding; and a metal pattern formed by at least one metal piece located on the second surface. When the incident electromagnetic wave irradiates the metal pattern, the incident electromagnetic wave couples with the metal pattern to generate an electromagnetic field and resonates inside the modulation unit to change the reflection phase of the incident electromagnetic wave.

5. The electromagnetic tag according to claim 4, characterized in that, the metal pattern satisfies a preset condition, so that the incident electromagnetic wave couples with the metal pattern to generate an electromagnetic field and generates a Fano resonance inside the modulation unit.

6. The electromagnetic tag according to claim 4, characterized in that, the metal pattern is asymmetric with respect to the polarization direction of the incident electromagnetic wave.

7. The electromagnetic tag according to claim 6, characterized in that, the metal pattern includes any one of the following: a metal ring having at least one notch, a metal rectangular ring having at least one notch, and a metal semi-ring having at least one notch.

8. The electromagnetic tag according to claim 6, characterized in that, the metal pattern includes a first pattern and a second pattern, wherein, the first pattern and the second pattern are arranged in sequence on the second surface, or the first pattern is nested inside the second pattern.

9. The electromagnetic tag according to claim 8, characterized in that, the first pattern and the second pattern are respectively any one of the following: a metal ring having at least one notch, a metal rectangular ring having at least one notch, and A metal semi-circular ring with at least one notch.

10. The electromagnetic tag according to claim 4, wherein, for any adjacent first modulation unit and second modulation unit in the target direction among the plurality of modulation units: the metal pattern corresponding to the first modulation unit is different from the metal pattern corresponding to the second modulation unit, so that there is a preset phase difference between the reflection phase generated by modulating the first modulation unit and the reflection phase generated by modulating the second modulation unit.

11. The electromagnetic tag according to claim 10, wherein, the metal pattern corresponding to the first modulation unit and the metal pattern corresponding to the second modulation unit have the same pattern style but different pattern sizes.

12. The electromagnetic tag according to claim 1, wherein, when the incident electromagnetic wave irradiates the reflection interface at the target incident angle, the plurality of modulation units perform specular reflection on the electromagnetic wave components corresponding to other frequency bands in the incident electromagnetic wave, where the other frequency bands are the frequency bands in the frequency band covered by the incident electromagnetic wave except the target working frequency band.

13. The electromagnetic tag according to claim 1, wherein, the electromagnetic tag is a flexible tag to adapt to the surface contour of the target body area.

14. The electromagnetic tag according to claim 1, wherein, the electromagnetic tag is a metasurface formed by two-dimensional metamaterials.

15. A health monitoring system, wherein, comprising: the electromagnetic tag according to any one of claims 1 to 14, worn on a target body area of a target object and corresponding to a target working frequency band; a detection device configured to, when operating: transmit an incident electromagnetic wave and cause the incident electromagnetic wave to irradiate the reflection interface of the electromagnetic tag at a target incident angle, where the incident electromagnetic wave includes a target electromagnetic wave component corresponding to the target working frequency band, and receive the reflected electromagnetic wave generated by the retroreflection of the target electromagnetic wave component on the reflection interface; and a computing device communicatively connected to the detection device and configured to, when operating: determine the life characteristic index corresponding to the target object based on the incident electromagnetic wave and the reflected electromagnetic wave.

16. The system according to claim 15, wherein, the detection device includes a millimeter-wave radar.

17. The system according to claim 15, wherein, the target body area includes a chest area, and the life characteristic index includes at least one of a breathing characteristic index and a heartbeat characteristic index.

18. A health monitoring system, wherein, comprising: a first electromagnetic tag, which is the electromagnetic tag according to any one of claims 1 - 14, wearable on a first body area of a first object and corresponding to a first working frequency band; a second electromagnetic tag, which is the electromagnetic tag according to any one of claims 1 - 14, wearable on a second body area of a second object and corresponding to a second working frequency band, and the second working frequency band is different from the first working frequency band; a detection device configured to, when operating: Transmit incident electromagnetic waves and cause the incident electromagnetic waves to irradiate the first reflection interface of the first electromagnetic tag and the second reflection interface of the second electromagnetic tag at a target incident angle, wherein the incident electromagnetic waves include a first electromagnetic wave component corresponding to the first operating frequency band and a second electromagnetic wave component corresponding to the second operating frequency band, and Receive a first reflected electromagnetic wave generated by retroreflection of the first electromagnetic wave component on the first reflection interface, and receive a second reflected electromagnetic wave generated by retroreflection of the second electromagnetic wave component on the second reflection interface; And A computing device, communicatively connected to the detection device and configured to, when operating: Based on the incident electromagnetic wave and the first reflected electromagnetic wave, determine a vital sign index corresponding to the first object, and Based on the incident electromagnetic wave and the second reflected electromagnetic wave, determine a vital sign index corresponding to the second object.

19. The system according to claim 18, wherein, The detection device includes a millimeter-wave radar.

20. The system according to claim 18, wherein, The first body area includes the chest area of the first object, and the second body area includes the chest area of the second object; And The vital sign index includes at least one of a breathing feature index and a heartbeat feature index.

Images