A passive room division monitoring tag and passive room division monitoring system

Abstract

The application provides a passive room division monitoring label and a passive room division monitoring system. The passive room division monitoring label is arranged on the shell of a room division antenna of the passive room division monitoring system. The passive room division monitoring label comprises a label antenna and a passive room division monitoring label chip. The label antenna is configured to generate resonant current in a direction substantially perpendicular to the metal ground plane of the room division antenna in a resonant state. The passive room division monitoring label controls the resonant current generated by the label antenna in the resonant state in a direction substantially perpendicular to the metal ground plane of the room division antenna based on the characteristics of the current distribution of the room division antenna, reduces the mutual coupling of the resonant current in the label antenna and the current of the room division antenna, thereby reducing the negative influence on the resonant characteristics of the room division antenna, and further ensuring that the standing wave ratio of the room division antenna is not affected.

Description

Technical Field

[0001] This invention relates to the field of passive indoor distribution monitoring tag communication technology, specifically to a passive indoor distribution monitoring tag and a passive indoor distribution monitoring system. Background Technology

[0002] A passive indoor distributed antenna system (DAS) refers to a system that connects an RFID gateway to a passive indoor distributed antenna system via a dedicated multi-frequency combiner. Passive radio frequency tags are installed on the antennas of the passive indoor distributed antenna system. The system automatically traverses and detects each radio frequency link by transmitting radio frequency identification signals through the RFID gateway. The system reads and analyzes the received signal strength indication value of the signals returned by the passive radio frequency tags to achieve high-range detection of link loss.

[0003] The operating bandwidth of existing passive RFID tags is usually maintained at 860–960 MHz. Since this frequency band overlaps with the operating frequency band of indoor distributed antennas provided by telecommunications operators, when passive RFID tags are placed on the housing of indoor distributed antennas, the electromagnetic waves radiated by the indoor distributed antennas will excite the passive RFID tags to resonate. The resonant current generated by the passive RFID tags in the resonant state will interfere with the original current distribution on the surface of the indoor distributed antennas, resulting in impedance mismatch and deterioration of the VSWR of the indoor distributed antennas.

[0004] In addition, the following technical problems exist in the actual deployment of the aforementioned monitoring tags on indoor distributed antennas: Firstly, excessively strong signals in the operating frequency bands of authorized operators can also intrude into the backscatter communication channels of passive tags, causing communication blockage.

[0005] Secondly, parasitic capacitance will form between the radiator of the monitoring tag and the metal ground plane of the indoor antenna, causing the impedance of the tag antenna to shift and mismatch with the impedance of the passive indoor monitoring tag chip, thereby affecting the reading distance and wake-up sensitivity of the monitoring tag.

[0006] Third, after the monitoring tag is placed on the surface of the indoor distributed antenna, some of the electromagnetic energy of the radiator of the indoor distributed antenna will be absorbed or reflected by the metal structure of the monitoring tag (antenna radiator, chip circuit, etc.), resulting in a decrease in the effective radiation power of the indoor distributed antenna and affecting the original coverage distance and signal quality of the indoor distributed antenna. Summary of the Invention

[0007] Purpose of the invention: The embodiments in this specification aim to provide a passive indoor monitoring tag and a passive indoor monitoring system to at least partially solve the above-mentioned technical problems.

[0008] Summary of the Invention: To achieve the above objectives, the embodiments of this specification propose the following technical solutions: In a first aspect, a passive indoor distribution monitoring tag is provided, wherein the passive indoor distribution monitoring tag is disposed on the housing of the indoor distribution antenna of the passive indoor distribution monitoring system; the passive indoor distribution monitoring tag includes a tag antenna and a passive indoor distribution monitoring tag chip; The tag antenna is configured such that the direction of the resonant current generated in the resonant state is substantially perpendicular to the metal ground plane of the indoor antenna.

[0009] Optionally, the angle between the direction of the resonant current generated by the tag antenna in the resonant state and the metal ground plane of the indoor antenna. satisfy: .

[0010] Optionally, the radiator of the tag antenna has at least one bent segment or patch segment, such that the direction of the resonant current on the radiator is substantially perpendicular to the metal ground plane of the indoor distributed antenna.

[0011] Optionally, the tag antenna can be any one of a dual-segment stepped bent antenna, a single-segment stepped bent antenna, or a microstrip patch antenna.

[0012] Optionally, the operating frequency band of the tag antenna covers at least the effective frequency band and the intermodulation interference frequency band; the passive indoor monitoring tag further includes a filter, which is used to acquire the radio frequency signal received by the tag antenna, filter the radio frequency signal of the intermodulation interference frequency band from the radio frequency signal, and transmit the radio frequency signal of the effective frequency band to the passive indoor monitoring tag chip.

[0013] Optionally, the operating frequency band of the tag antenna is 920-960 MHz, the effective frequency band is 920–925 MHz, which is the operating frequency band of the passive indoor monitoring tag chip, and the intermodulation interference frequency band is 934-960 MHz, which is the intermodulation interference frequency band of mobile communication signals.

[0014] Optionally, the tag antenna further includes a resonant ring coupled to the radiator of the tag antenna to introduce two resonant points in the operating frequency band of the tag antenna, forming a smooth frequency band covering the 920–960 MHz band between the two resonant points.

[0015] Optionally, a tag metal ground layer is provided on the back side of the radiator of the tag antenna, near the indoor distributed antenna, and the tag metal ground layer is used to eliminate the parasitic capacitance between the metal ground plane of the indoor distributed antenna and the radiator of the tag antenna.

[0016] Optionally, a tag metal ground layer is provided on the front side of the radiator of the tag antenna, away from the indoor distributed antenna. The tag metal ground layer is used as a reflector to enhance the radiation intensity of the indoor distributed antenna.

[0017] Secondly, a passive indoor distribution monitoring system is provided, including: a passive indoor distribution system, an RFID gateway, a multi-frequency combiner, and the aforementioned monitoring tags; The monitoring tag is mounted on the indoor distributed antenna of the passive indoor distribution system; The RFID gateway, as an independent signal source, is connected to the antenna feeder system of the passive indoor distributed antenna system. By sending radio frequency signals to the monitoring tags on each indoor distributed antenna and receiving the received signal strength indication value returned by the monitoring tags, the link loss of the indoor distributed antenna is monitored.

[0018] Beneficial effects: Compared with the prior art, the passive indoor monitoring tag and passive indoor monitoring system proposed in this application have the following beneficial effects: In passive indoor distributed antenna monitoring systems, the current of the indoor antenna is usually distributed on the metal ground plane of the indoor antenna. The passive indoor distributed antenna monitoring tag described in this application is based on the current distribution characteristics of the indoor antenna. It controls the direction of the resonant current generated by the tag antenna in the resonant state to be basically perpendicular to the metal ground plane of the indoor antenna, thereby reducing the mutual coupling between the resonant current in the tag antenna and the current of the indoor antenna, thereby reducing the negative impact on the resonant characteristics of the indoor antenna, and thus ensuring that the standing wave ratio of the indoor antenna is not affected.

[0019] Furthermore, in this embodiment, a filter is used to filter radio frequency signals in the intermodulation interference band to prevent authorized operators' operating frequency bands from intruding into the RFID chip's operating frequency band, thereby eliminating the communication blockage phenomenon of passive indoor monitoring tags.

[0020] Furthermore, the passive indoor distributed antenna monitoring tag described in this application eliminates the parasitic capacitance between the metal ground plane of the indoor distributed antenna and the radiator of the tag antenna by setting a tag metal ground layer on the back of the tag antenna radiator, so that the impedance of the tag antenna remains constant after it is attached to the indoor distributed antenna, thus ensuring the reading distance and wake-up sensitivity of the monitoring tag.

[0021] Furthermore, the passive indoor distributed antenna monitoring tag described in this application embodiment sets a tag metal ground layer on the front side of the tag antenna radiator, away from the metal ground plane of the indoor distributed antenna, to reflect the electromagnetic waves radiated by the indoor distributed antenna in a direction away from the monitoring tag, thereby reducing the absorption and reflection loss of the energy radiated by the indoor distributed antenna by the monitoring tag, thereby enhancing the effective radiation power of the indoor distributed antenna and ensuring that the coverage performance of the indoor distributed antenna is not affected by the attachment of the monitoring tag. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the architecture of a prior art passive indoor distribution monitoring system involved in an embodiment.

[0023] Figure 2 This is a schematic diagram of the structure of a passive indoor monitoring tag involved in an embodiment.

[0024] Figure 3 The image shows the physical diagram of the indoor distributed antenna involved in the embodiment and its electromagnetic simulation model of current distribution.

[0025] Figure 4 This is a schematic diagram of the bent dipole antenna structure involved in the embodiment.

[0026] Figure 5 This is a schematic diagram showing the relative position of the bent dipole antenna to the metal ground plane of the indoor antenna when it is installed in the outer shell of the indoor antenna according to the embodiment.

[0027] Figure 6 This is a schematic diagram of a dipole antenna structure with an added resonant ring, as described in the embodiment.

[0028] Figure 7 This is a schematic diagram of a single-segment stepped bent antenna structure involved in the embodiment.

[0029] Figure 8 This is a schematic diagram of the microstrip patch antenna structure involved in the embodiment. Detailed Implementation

[0030] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments. However, it should be understood that the present invention can be implemented in various forms. The exemplary and non-limiting embodiments shown in the drawings and described below are not intended to limit the invention to the specific embodiments illustrated.

[0031] It should be understood that, where technically feasible, the technical features listed above for different embodiments can be combined with each other to form other embodiments within the scope of this invention. Furthermore, the specific examples and embodiments described in this invention are non-limiting, and corresponding modifications can be made to the structures, steps, and order described above without departing from the protection scope of this invention.

[0032] This application aims to provide a passive indoor distributed antenna monitoring tag and a passive indoor distributed antenna monitoring system. The passive indoor distributed antenna monitoring tag is applied to the passive indoor distributed antenna monitoring system. Specifically, the passive indoor distributed antenna monitoring tag is set on the outer shell of the indoor distributed antenna of the passive indoor distributed antenna monitoring system during use.

[0033] Before introducing the passive indoor distribution monitoring tag described in the embodiments of this application, we will first introduce the application scenario of the passive indoor distribution monitoring tag described in the embodiments of this application, namely the passive indoor distribution monitoring system.

[0034] Please refer to Figure 1 , Figure 1 The architecture diagram of a current passive indoor distribution monitoring system is shown. Figure 1 As shown, the passive indoor distribution monitoring system includes a passive indoor distribution system, an RFID gateway, a multi-frequency combiner, and monitoring tags.

[0035] The passive indoor distributed antenna system (DAS) combines multiple signals from external sources (including 2G, 3G, 4G, and 5G mobile communication sources) into a single antenna feeder system via a multi-frequency combiner. This allows the signal to be evenly distributed throughout the room via the DAS antenna, solving the problems of signal blind spots and weak coverage. The passive indoor DAS monitoring system adds an RFID gateway and monitoring tags (passive RFID tags) to the passive DAS system. The RFID gateway acts as an independent signal source, connected to the antenna feeder system via the multi-frequency combiner. The monitoring tags are mounted on the DAS antenna. The system automatically traverses and detects each RF link by transmitting RFID signals from the RFID gateway. By reading and analyzing the received signal strength indication value returned by the passive RFID tags, the system achieves high-range detection of link loss.

[0036] However, the operating bandwidth of existing passive RFID tags is usually maintained at 860–960 MHz. According to the 5G NR band specifications formulated by the international telecommunications standards organization 3GPP and China's current spectrum allocation framework, the Band 8 band (880-960 MHz) has been fully allocated by multiple operators such as China Mobile, China Unicom, and China Telecom, leaving only a 5 MHz of idle spectrum in the 920-925 MHz range.

[0037] Because the operating frequency band of passive RFID tags overlaps with that of indoor distributed antennas provided by mobile communication operators, when passive RFID tags are placed on the housing of indoor distributed antennas, the electromagnetic waves radiated by the indoor distributed antennas will excite the passive RFID tags to resonate. The resonant current of the passive RFID tags will interfere with the original current distribution on the surface of the indoor distributed antennas, resulting in impedance mismatch of the indoor distributed antennas and a deterioration of the standing wave ratio.

[0038] In view of this, embodiments of this specification provide a passive indoor monitoring tag and a passive indoor monitoring system to at least partially solve the above-mentioned technical problems existing in the prior art.

[0039] Please refer to Figure 2 , Figure 2 A schematic diagram of the structure of a passive indoor monitoring tag is shown. For example... Figure 2 As shown in the embodiment of this application, the passive indoor distribution monitoring tag includes: a tag antenna and a passive indoor distribution monitoring tag chip; wherein, the tag antenna is configured such that the direction of the resonant current generated in the resonant state is substantially perpendicular to the metal ground plane of the indoor distribution antenna.

[0040] In the aforementioned passive indoor monitoring tag, the direction of the resonant current of the tag antenna in the resonant state is controlled to suppress the deteriorating effect of the resonant current on the VSWR of the indoor antenna. The principle is as follows: Please refer to Figure 3 , Figure 3 This shows a physical diagram of the indoor distributed antenna and its electromagnetic simulation model of current distribution, which is composed of... Figure 3 Simulation results show that the current of an indoor distributed antenna is usually distributed on the metal ground plane of the indoor distributed antenna.

[0041] When a passive indoor distributed antenna (DDA) monitoring tag is attached to the DDA antenna housing, the tag is very close to the antenna's metal ground plane (a few millimeters to a few centimeters). At this point, the tag antenna is in the near-field region of the DDA antenna, and there is strong electromagnetic coupling between them. When the tag antenna resonates in its operating frequency band, the resonant current on it generates an alternating electromagnetic field. This abrupt electromagnetic field excites an induced current on the antenna's metal ground plane. This induced current, superimposed on the original current distribution, changes the equivalent current amplitude and phase on the ground plane, thereby altering the DDA antenna's input impedance, causing it to deviate from its design value, and ultimately leading to a deterioration in the DDA antenna's standing wave ratio (VSWR).

[0042] Based on the reasons for the deterioration of the VSWR of the indoor distributed antenna mentioned above, the resonant current of the tag antenna is decomposed into horizontal current components and vertical current components.

[0043] The horizontal current component generates a vertical time-varying magnetic field near the metal ground plane of the indoor distributed antenna. This vertical time-varying magnetic field induces closed eddy currents within the metal ground plane. These eddy currents superimpose with the original horizontal surface current on the metal ground plane of the indoor distributed antenna in the same or opposite direction, directly disturbing the original current distribution, causing a significant drift in input impedance and a significant deterioration in the standing wave ratio.

[0044] The magnetic field generated by the vertical current component directly above the metal ground plane of the indoor distributed antenna is horizontal. This horizontal magnetic field does not pass through the ground plane and produce a net change in magnetic flux, so it does not induce obvious closed-loop eddy currents in the ground plane.

[0045] Meanwhile, the electric field generated by the vertical current component is vertical. For an ideal conducting plane (the metal ground plane of the indoor antenna), the vertically incident electric field will induce surface charges on the surface of the metal ground plane of the indoor antenna, but will not drive its horizontal surface current. In actual operation, although the metal ground plane of the indoor antenna is not an ideal conductor, this effect still greatly weakens the excitation of the horizontal current on the metal ground plane of the indoor antenna.

[0046] Based on the above principle, the embodiments of this application control the direction of the resonant current generated in the resonant state of the tag antenna, so that the direction of the resonant current is basically perpendicular to the metal ground plane of the indoor antenna, so that the magnetic field component generated by the resonant current perpendicular to the metal ground plane of the indoor antenna is minimized, thereby suppressing the induced current on the metal ground plane of the indoor antenna as much as possible, controlling the original current distribution on the metal ground plane of the indoor antenna to remain as unchanged as possible, thereby controlling the input impedance of the indoor antenna to remain unchanged, and ultimately preventing the standing wave ratio of the indoor antenna from deteriorating.

[0047] It should be noted that the aforementioned "basic verticality" refers to the basic verticality in engineering practice, allowing for a certain degree of error during the manufacturing and installation of passive indoor monitoring tags. Specifically, it refers to the angle between the direction of the resonant current generated by the tag antenna in its resonant state and the metal ground plane of the indoor antenna. The specified threshold range is met so that the resonant current generated by the tag antenna in the resonant state has a negligible or acceptable impact on the VSWR of the indoor distributed antenna. Of course, the impact on the VSWR of the indoor distributed antenna is minimized when the direction of the resonant current generated by the tag antenna in the resonant state is perpendicular to the metal ground plane of the indoor distributed antenna.

[0048] In one embodiment, the angle between the direction of the resonant current generated by the tag antenna in the resonant state and the metallic ground plane of the indoor antenna is... satisfy: .

[0049] In one embodiment, to ensure that the direction of the resonant current generated by the tag antenna in the resonant state is substantially perpendicular to the metal ground plane of the indoor distributed antenna, the structure of the tag antenna can be designed. Specifically, the radiator of the tag antenna can be designed to have at least one bent segment or patch segment, so that the direction of the resonant current on the radiator is substantially perpendicular to the metal ground plane of the indoor distributed antenna.

[0050] by Figure 4 Taking the bent dipole antenna as an example, the radiator of the bent dipole antenna can be designed in a stepped shape so that most of the radiators are basically perpendicular to the metal ground plane of the indoor antenna, and thus the direction of the resonant current flowing through most of these radiators is perpendicular to the metal ground plane of the indoor antenna.

[0051] It should be noted that, Figure 4 The basic verticality shown refers to the basic verticality in engineering, meaning that a certain degree of error is allowed during the manufacturing and installation of passive indoor monitoring tags. For example... Figure 5 As shown, during the installation / manufacturing process, the passive indoor monitoring tag allows for a certain angle between the direction of the resonant current generated by the tag antenna in the resonant state and the metal ground plane of the indoor antenna. The requirement is that the resonant current generated by the tag antenna in its resonant state has a negligible or acceptable impact on the deterioration of the standing wave ratio (SWR) of the indoor distributed antenna. In practical operation, Generally, the following conditions are met: .

[0052] It should be noted that the structure of the tag antenna described above is not limited to a bent dipole antenna, but may also include a two-segment stepped bent antenna (e.g., Figure 4 (as shown in the bent dipole antenna) Figure 7 The single-segment stepped bent antenna shown or as Figure 8 The microstrip patch antenna shown can also include other antenna structures that can achieve the same function.

[0053] In one implementation, the tag antenna operates in a frequency band that covers at least the effective frequency band and the intermodulation interference band. Please continue to refer to... Figure 2 The passive indoor monitoring tag also includes a filter, which is used to acquire the radio frequency signal received by the tag antenna and filter out the radio frequency signal in the intermodulation interference band from the radio frequency signal, while transmitting the radio frequency signal in the effective band to the passive indoor monitoring tag chip.

[0054] Specifically, the operating frequency band of the aforementioned tag antenna is 920-960 MHz, with an effective frequency band of 920–925 MHz, which is the operating frequency band of the passive indoor monitoring tag chip. The intermodulation interference frequency band is 934-960 MHz, which is prone to intermodulation interference because it includes licensed frequency bands from multiple mobile communication operators.

[0055] By filtering radio frequency signals in intermodulation interference bands, it is possible to effectively prevent authorized operators' operating frequency bands from encroaching on the RFID chip's operating frequency band, thereby eliminating communication blockage in passive indoor monitoring tags. The principle behind solving this technical problem is as follows: As mentioned above, the operating bandwidth of existing passive RFID tags is typically maintained at 860–960 MHz, and most of the frequency bands in this bandwidth have been licensed to mobile communication operators, with only a 5 MHz vacant spectrum segment in the 920–925 MHz range.

[0056] To prevent authorized operators' operating frequency bands from encroaching on the RFID chip's operating frequency band, one solution is to directly design the operating frequency band of the passive indoor distributed antenna monitoring tag to be 920-925 MHz. However, this approach is not practically feasible for the following reasons: 1. The precision machining process required to achieve narrowband resonance will significantly increase manufacturing costs, making it difficult to meet the economic requirements for large-scale deployment.

[0057] 2. The antenna of a passive RFID tag is a typical electrically small antenna (its size is much smaller than the operating wavelength). Due to size limitations, passive RFID tags must expand their bandwidth to achieve high sensitivity. This means that the overall operating bandwidth of passive RFID tags is usually maintained in a relatively wide range of about 920-960 MHz.

[0058] 3. Narrow-bandwidth tags are susceptible to frequency shifts due to environmental factors (such as temperature changes and material deformation) during actual deployment, causing the tags to deviate from the preset operating frequency band and become ineffective.

[0059] Based on the above factors, in practical operation, it is difficult to achieve isolation of intermodulation interference frequency band radio frequency signals at the receiving end (tag antenna end) of the passive RFID tag. Therefore, this application embodiment adopts the idea of ​​filter filtering. After the radio frequency signals covering the effective frequency band and the intermodulation interference frequency band enter the internal transmission channel of the passive indoor monitoring tag, the intermodulation interference frequency band is filtered. The radio frequency signals of the remaining effective frequency band after filtering are provided to the RFID chip for processing. The radio frequency signals of the effective frequency band are only 920-925MHz. This frequency band does not belong to the frequency band authorized by the operator. Therefore, it ensures that the passive monitoring tags operating in this frequency band form an effective backscatter communication channel and avoid communication blockage problems.

[0060] In one embodiment, a resonant loop can also be incorporated into the tag antenna, coupled to the radiator of the tag antenna, to introduce two resonant points within the operating frequency band of the tag antenna. These two resonant points form a smooth frequency band covering the 920–960 MHz band. Please refer to [reference needed]. Figure 6 , Figure 6 The diagram schematically illustrates a dipole antenna structure with an added resonant ring. It should be noted that this embodiment does not limit the specific tag antenna structure; other antenna structures that can achieve the corresponding functions of the tag antenna in this embodiment should also be included within the scope of protection of this application.

[0061] The resonant ring design is used to broaden the operating frequency band of the tag antenna. Ordinary RFID tags typically operate in the 920-940MHz range. However, in this embodiment, the tag antenna's operating frequency band is designed to be 920-960MHz. This is because the 934-960MHz band includes licensed frequency bands from multiple mobile communication operators. When the tag antenna is placed on an indoor distributed antenna system, it will inevitably be exposed to signals in this frequency band. If the tag antenna's operating frequency band does not fully encompass 934-960MHz, then communication signals in the 941-960MHz band will be reflected back to the indoor distributed system when they reach the tag antenna. The N-order intermodulation products generated by this reflection intrude into the feeder network of the indoor distributed system, interacting with other frequency components within the system, causing severe intermodulation interference and exacerbating the communication blockage of the passive indoor distributed monitoring tags. In this embodiment, the operating frequency band of the tag antenna is designed to cover the intermodulation band and the effective frequency band of 920-960 MHz. This ensures that all communication signals in the intermodulation band can be received by the tag antenna and then fully filtered through a filter during transmission, rather than being reflected back to the indoor distribution system at the tag antenna end. This eliminates the intrusive impact of the N-order intermodulation products excited by the reflected signal on the indoor distribution system from the root cause, and can effectively solve the communication blocking problem of passive indoor distribution monitoring tags caused by insufficient tag bandwidth in the prior art.

[0062] In one embodiment, a tag metal ground layer can also be provided on the back side of the tag antenna radiator, near the indoor distributed antenna. This tag metal ground layer is used to eliminate parasitic capacitance between the metal ground plane of the indoor distributed antenna and the radiator of the tag antenna. The specific principle is as follows: When a standard dipole tag antenna is directly attached to the metal ground plane of an indoor distributed antenna, a parallel-plate capacitor structure is formed between them: the radiator of the tag antenna forms one plate of the capacitor, the metal ground plane of the indoor distributed antenna forms the other plate, and the dielectric between them (such as the antenna substrate, air layer, or plastic shell) forms the capacitor's dielectric. This structure introduces a parasitic capacitance. The tag antenna's originally designed impedance (e.g., 50 ohms or the conjugate matching value required by the chip) is "pulled off" by this parasitic capacitance, resulting in impedance mismatch. The chip cannot obtain enough power to start, the reading distance drops sharply, or it may even become unable to read.

[0063] A metal ground layer is inserted on the back of the tag antenna, which serves as an electrostatic shield.

[0064] According to the principles of electromagnetism, metal is an equipotential body. When the tag's metal ground layer is present on the back, the electric field lines generated by the tag antenna radiator will terminate at this metal ground layer on the back, instead of extending through the medium to the indoor distributed antenna metal ground plane below. In other words, the indoor distributed antenna metal ground plane is "blocked" by this metal ground plane.

[0065] Therefore, parasitic capacitance no longer exists between the tag antenna radiator and the indoor distributed antenna's metal ground plane. Instead, there is a fixed capacitance between the tag antenna's own radiator and the tag's metal ground layer on the back. Since this tag metal ground layer is part of the tag antenna design, this capacitance can be fixed and compensated for during the design phase, thus ensuring that the tag antenna's impedance remains constant before and after being attached to the indoor distributed antenna, guaranteeing the consistency and reliability of the monitoring tag's performance.

[0066] In one embodiment, a tag metal ground layer can be provided on the front side of the tag antenna's radiator, away from the indoor distributed antenna. This tag metal ground layer serves as a reflector to enhance the radiation intensity of the indoor distributed antenna. The specific principle is as follows: The metal ground layer of the tag is used as a reflector to reflect the electromagnetic waves radiated backward by the tag antenna (i.e., the radiation component facing away from the RFID gateway) to the front, so that they are superimposed in phase with the forward radiation component. This realizes the secondary utilization of the energy radiated backward by the tag antenna, which significantly improves the radiation gain and receiving sensitivity of the tag antenna in the forward direction, thereby effectively extending the effective reading distance of the RFID gateway for passive monitoring tags.

[0067] In one embodiment, the monitoring tag can be designed as a flexible tag so that it can be easily attached to the housing of an indoor distributed antenna with a certain curvature.

[0068] Corresponding to the aforementioned passive indoor distribution monitoring tag, this application embodiment also provides a passive indoor distribution monitoring system, which includes: a passive indoor distribution system, an RFID gateway, a multi-frequency combiner, and the aforementioned passive indoor distribution monitoring tag; the passive indoor distribution monitoring tag is disposed on the housing of the indoor distribution antenna of the passive indoor distribution system; the RFID gateway is connected to the antenna feeder system of the passive indoor distribution system as an independent signal source, and monitors the link loss of the indoor distribution antenna by sending radio frequency signals to the passive indoor distribution monitoring tag on each indoor distribution antenna and receiving the received signal strength indication value returned by the passive indoor distribution monitoring tag.

[0069] The design principle of the passive indoor distribution monitoring tag in this passive indoor distribution monitoring system can be referred to the above introduction on passive indoor distribution monitoring tags, and will not be repeated here in this embodiment.

[0070] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0071] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A passive indoor distribution monitoring tag, characterized in that, The passive indoor distributed antenna monitoring tag is mounted on the housing of the indoor distributed antenna of the passive indoor distributed antenna monitoring system; the passive indoor distributed antenna monitoring tag includes a tag antenna and a passive indoor distributed antenna monitoring tag chip; The tag antenna is configured such that the direction of the resonant current generated in the resonant state is substantially perpendicular to the metal ground plane of the indoor antenna.

2. The passive indoor monitoring tag according to claim 1, characterized in that, The angle between the direction of the resonant current generated by the tag antenna in the resonant state and the metal ground plane of the indoor antenna. satisfy: .

3. The passive indoor monitoring tag according to claim 1, characterized in that, The radiator of the tag antenna has at least one bent or attached segment, such that the direction of the resonant current on the radiator is substantially perpendicular to the metal ground plane of the indoor distributed antenna.

4. The passive indoor distribution monitoring tag according to claim 3, characterized in that, The tag antenna is any one of a dual-segment stepped bent antenna, a single-segment stepped bent antenna, or a microstrip patch antenna.

5. The passive indoor monitoring tag according to claim 1, characterized in that, The operating frequency band of the tag antenna covers at least the effective frequency band and the intermodulation interference frequency band; the passive indoor monitoring tag also includes a filter, which is used to acquire the radio frequency signal received by the tag antenna, filter the radio frequency signal of the intermodulation interference frequency band from the radio frequency signal, and transmit the radio frequency signal of the effective frequency band to the passive indoor monitoring tag chip.

6. The passive indoor distribution monitoring tag according to claim 5, characterized in that, The tag antenna operates in the 920-960 MHz frequency band, and the effective frequency band is 920–925 MHz, which is the operating frequency band of the passive indoor monitoring tag chip. The intermodulation interference frequency band is 934-960 MHz, which is the intermodulation interference frequency band of mobile communication signals.

7. The passive indoor monitoring tag according to claim 5, characterized in that, The tag antenna also includes a resonant ring, which is coupled to the radiator of the tag antenna to introduce two resonant points in the operating frequency band of the tag antenna, forming a smooth frequency band covering the 920–960 MHz band between the two resonant points.

8. The passive indoor distribution monitoring tag according to claim 1, characterized in that, A tag metal ground layer is provided on the back of the radiator of the tag antenna, on the side close to the indoor distributed antenna. The tag metal ground layer is used to eliminate the parasitic capacitance between the metal ground plane of the indoor distributed antenna and the radiator of the tag antenna.

9. The passive indoor distribution monitoring tag according to claim 1, characterized in that, A tag metal ground layer is provided on the front side of the radiator of the tag antenna, away from the indoor distributed antenna. The tag metal ground layer is used as a reflector to enhance the radiation intensity of the indoor distributed antenna.

10. A passive indoor distribution monitoring system, characterized in that, include: Passive indoor distribution system, RFID gateway, multi-frequency combiner and monitoring tag as described in any one of claims 1 to 9; The monitoring tag is mounted on the indoor distributed antenna of the passive indoor distribution system; The RFID gateway, as an independent signal source, is connected to the antenna feeder system of the passive indoor distributed antenna system. By sending radio frequency signals to the monitoring tags on each indoor distributed antenna and receiving the received signal strength indication value returned by the monitoring tags, the link loss of the indoor distributed antenna is monitored.

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