A radio frequency tag
By designing the impedance matching network and radiator structure of the RFID tag to make its polarization direction vertical, the problem of low performance of RFID tags in stacked environments was solved, and efficient reading in lossy media environments was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG CAINIAO SUPPLY CHAIN MANAGEMENT CO LTD
- Filing Date
- 2022-08-03
- Publication Date
- 2026-06-30
AI Technical Summary
Radio frequency tags (RFID tags) do not perform well in stacked environments, especially in the presence of lossy media, where electromagnetic wave energy attenuation is severe and polarization loss is significant.
Design an RFID tag in which the antenna body includes an impedance matching network and a radiator, formed by parallel impedance matching units. The radiator has a hollow design and the polarization direction is vertical. It is suitable for stacked items and can be installed in the gaps between items.
By reversing the polarization direction by 90°, polarization loss is reduced and the performance of RFID tags is improved, especially in lossy media environments where reading performance is significantly improved.
Smart Images
Figure CN117559113B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of radio frequency identification technology, and in particular to an radio frequency tag. Background Technology
[0002] Radio Frequency Identification (RFID) technology is a communication technology that can identify specific targets and read / write related data via radio signals without requiring mechanical or optical contact between the identification system and the target. RFID tags, as a crucial component of an RFID system, significantly impact the overall system performance. Key factors affecting RFID tag performance include chip sensitivity, antenna size, operating frequency band, impedance, antenna polarization, and gain.
[0003] In RFID systems, radio frequency tags are typically attached to items, and RFID readers monitor the item's status by reading the tags. However, the environment in which items are placed may contain lossy media, and items are often stacked together, causing significant energy attenuation of electromagnetic waves as they pass through the medium. Furthermore, the radiation pattern of the RFID tag's antenna is distorted, and the polarization effect of the lossy medium causes changes in the electric field direction at gaps, often resulting in polarization losses. Therefore, the performance of RFID tags faces significant challenges. Summary of the Invention
[0004] This application provides an RFID tag method to address the problem of low performance of RFID tags.
[0005] To address the aforementioned problems, this application discloses an RFID tag, which includes:
[0006] RF chip and antenna body;
[0007] The antenna body includes an impedance matching network and a radiator, and the radio frequency chip is connected to the impedance matching network.
[0008] The impedance matching network is formed by parallel impedance matching units. The impedance matching network is connected to the radiator, which has a hollow design. Based on the parallel impedance matching network and the gap between the impedance matching network and the radiator, the polarization direction of the RFID tag is vertical.
[0009] Optionally, the impedance matching network includes a first impedance matching unit and a second impedance matching unit, wherein the first impedance matching unit and the second impedance matching unit are connected in parallel through the radio frequency chip.
[0010] Optionally, the first impedance matching unit and the second impedance matching unit are inductive impedance matching units with a T-type structure.
[0011] Optionally, the gap between the impedance matching network and the radiator forms a capacitive load, creating a vertical electric field direction on the radiator. Combined with the vertical current direction of the impedance matching network, a mirror current is formed on the radiator, making the polarization direction of the RFID tag vertical.
[0012] Optionally, the radio frequency chip is a single-port radio frequency chip.
[0013] Optionally, the RFID tag is suitable for scenarios involving stacked items.
[0014] Optionally, the RFID tag is installed on the item and located in the gap between the items when the items are stacked.
[0015] Optionally, when the circularly polarized electromagnetic waves radiated by the radio frequency reader / writer pass through the article, they are affected by the polarization effect of the article, and the electric field direction of the electromagnetic waves becomes perpendicular to the gap between the articles, which is the same as the polarization direction of the radio frequency tag installed on the article.
[0016] Optionally, the article contains a consumable medium.
[0017] Optionally, the RFID tag is located in the gap between the lossy media of the article.
[0018] This application also discloses a product packaging that includes the aforementioned radio frequency tag.
[0019] Compared with the prior art, the embodiments of this application have the following advantages:
[0020] In this embodiment, the RFID tag includes an RFID chip and an antenna body. The antenna body includes an impedance matching network and a radiator. The RFID chip is connected to the impedance matching network, which is formed by parallel impedance matching units. The impedance matching network and the radiator are connected, and the radiator has a hollow design. Based on the parallel impedance matching network and the gap between the impedance matching network and the radiator, the polarization direction of the RFID tag is vertical. This embodiment of the RFID tag, by changing the structure of the antenna, achieves a vertical polarization direction, a 90° reversal of the polarization direction compared to a conventional dipole antenna, thus improving the performance of the RFID tag. Attached Figure Description
[0021] Figure 1 This is one of the structural schematic diagrams of an RFID tag according to an embodiment of this application;
[0022] Figure 2 This is a second schematic diagram of the structure of an RFID tag according to an embodiment of this application;
[0023] Figure 3 This is a schematic diagram of an article stacking according to an embodiment of this application.
[0024] Figure label:
[0025] 1. Radio frequency chip; 2. Antenna body; 21. GND of radiator; 22. Radiator; 231. First impedance matching unit; 232. Second impedance matching unit; 241. Capacitive loading; 242. Capacitive loading; 3. Radio frequency tag; 4. Lossy dielectric. Detailed Implementation
[0026] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0027] Reference Figure 1 This is a schematic diagram of the structure of an RFID tag according to an embodiment of this application. The RFID tag may include: an RFID chip 1 and an antenna body 2; the antenna body 2 includes an impedance matching network and a radiator, and the RFID chip 1 is connected to the impedance matching network; the impedance matching network is formed by parallel impedance matching units, and the impedance matching network and the radiator are connected. The radiator has a hollow design. Based on the parallel impedance matching network and the gap between the impedance matching network and the radiator, the polarization direction of the RFID tag is vertical.
[0028] In RFID tags, the polarization direction of the antenna refers to the direction of the electric field. Electromagnetic waves are transmitted in space by the mutual conversion between electric and magnetic fields. For example, horizontal polarization means that the direction of the electric field is horizontal with the ground, while vertical polarization means that the direction of the electric field is perpendicular to the ground. It can be understood that the polarization of the antenna will be different depending on the placement of the antenna of the same RFID tag.
[0029] In a specific implementation, the polarization direction of a conventional dipole antenna is horizontal. However, the RFID tag in this application changes the structure of the antenna in the RFID tag so that the polarization direction of the RFID tag antenna is vertical, achieving a 90° reversal of the polarization direction compared to the conventional dipole antenna.
[0030] The RFID chip in the RFID tag can be a single-port RFID chip, which refers to a chip with only one set of ports. The RFID tag in this embodiment uses a single-port RFID chip. Since single-port RFID chips are less expensive and their antenna size is smaller compared to dual-port RFID chips, the cost is also lower.
[0031] Reference Figure 2 The impedance matching network may include a first impedance matching unit 231 and a second impedance matching unit 232. Specifically, the first impedance matching unit 231 and the second impedance matching unit 232 are connected in parallel by connecting to the ports of the RF chip, respectively. Optionally, the first impedance matching unit 231 and the second impedance matching unit 232 may both be T-shaped inductive impedance matching units. Of course, the first impedance matching unit 231 and the second impedance matching unit 232 may also be T-shaped, multi-segment bent, I-shaped, or other shapes, and this embodiment of the application does not impose any limitations on this.
[0032] In this embodiment, the gap between the impedance matching network and the radiator forms a capacitive load. Specifically, refer to... Figure 2 Capacitive loading refers to the gaps 214 and 242 between the impedance matching network and the end of the radiator (only the two gaps on the upper half of the radiator are shown in the figure). Capacitive loading can adjust the input impedance and electrical length of the antenna body, which can reduce the size of the antenna body of the RFID tag.
[0033] In the embodiments of this application, the gap between the impedance matching network and the radiator forms a capacitive load, creating a vertical electric field direction on the radiator. Combined with the vertical current direction of the impedance matching network, a mirror current is formed on the radiator, making the polarization direction of the RFID tag vertical. Specifically, refer to... Figure 2 ,by Figure 2 The dashed line in the diagram is the dividing line. The left side of the radiator can be regarded as the GND of the radiator, and the right side of the radiator can be regarded as the radiator. There is a gap between the right end of the radiator and the inductive impedance matching network. Based on this gap, a capacitive load is formed, and a vertical electric field direction is formed on the radiator. Combined with the vertical current direction at the feed point of the parallel inductive impedance matching network, a mirror current is formed at the left GND. Compared with the horizontal direction of a conventional dipole antenna, the polarization direction of the RFID tag in this embodiment of the application is a 90° flip of the polarization direction based on the polarization direction of a conventional dipole antenna. That is, the polarization direction of the RFID tag in this embodiment of the application changes from the direction parallel to the RFID tag to the direction perpendicular to the RFID tag.
[0034] The RFID tags with a vertical polarization direction in this application embodiment are particularly suitable for scenarios involving stacked items. Specifically, item stacking refers to piling up items or arranging items in a regular pattern to form a stack. When using the RFID tags of this application embodiment, the tags can be installed on each item, and when the items are stacked, the RFID tags will be located in the gaps between the items. As an example, the items on which the RFID tags of this application embodiment are installed can be items containing a lossy medium. A lossy medium is a medium that affects the direction of the electric field of the electromagnetic waves radiated by the RFID reader / writer, such as ice cream.
[0035] Specifically, when the circularly polarized electromagnetic waves radiated by the RFID reader pass through an object, they are affected by the polarization effect of the lossy medium in the object. The electric field direction of the electromagnetic waves from the RFID reader will become perpendicular to the gap between the objects. It can be seen that if a conventional RFID tag with a horizontal polarization direction is used, the polarization loss will be extremely large, which will greatly affect the performance of the RFID tag.
[0036] As a concrete example, refer to Figure 3 This is a schematic diagram of an article stacking according to an embodiment of this application. During article stacking, the RFID tag of this embodiment is installed on the side edge of the top cover of two paper packaging barrels containing a built-in lossy medium 3 (such as ice cream). The RFID tag will be located in the gap between the lossy medium 3. At this time, if radio frequency identification is performed, the circularly polarized wave radiated by the antenna of the RFID reader / writer will, after passing through the gap, have its electric field direction become approximately perpendicular to the gap due to the polarization effect of the lossy medium 3. Furthermore, the electromagnetic wave of the RFID reader / writer will experience significant attenuation after passing through the lossy medium 3. Therefore, this embodiment requires that after the articles are stacked, the radiator of the RFID tag be located in the gap between the lossy medium 3. If the RFID tag installed on the article is a conventional RFID tag (e.g., an RFID tag using a dipole antenna), its polarization direction is horizontal, perpendicular to the electric field direction at the gap, resulting in significant polarization loss. However, if the RFID tag installed on the article is the RFID tag of this embodiment, whose polarization direction is vertical, the polarization loss can be significantly reduced.
[0037] Impedance is a crucial parameter of an antenna, determined by its shape, material, size, and operating environment. Antenna impedance matching is the process of tuning to match the antenna impedance to the transmitter impedance. When an antenna is operating, high-frequency signals are fed back to it. Most of the energy is radiated away, while the remaining energy is reflected back to the transmitter, creating a standing wave on the transmission line. When the antenna impedance equals the transmitter impedance (i.e., impedance matching), reflection is minimized, and the loss rate is also minimized. In other words, impedance matching between the antenna and the transmitter not only increases the operating range but also helps reduce power consumption. The RFID tag in this embodiment uses a parallel T-shaped inductive impedance matching unit. Because the parallel T-shaped inductive impedance matching unit is less affected by the parasitic capacitance between the RFID tag and the lossy dielectric, the impedance matching of the RFID tag is less affected by the height and dielectric properties of the lossy dielectric inside the paper packaging drum, further improving the performance of the RFID tag.
[0038] In summary, the RFID tag in this embodiment is implemented based on a single-port RFID chip. Single-port RFID chips have lower costs, and their antenna size is smaller and less expensive compared to dual-port RFID chips. Furthermore, the polarization direction of the RFID tag in this embodiment is flipped by 90° compared to conventional RFID tags, resulting in a vertical polarization direction. Therefore, in scenarios involving stacked items, the polarization direction of the RFID tag can be approximately the same as the electric field direction at the gap between the lossy media, significantly reducing polarization loss. While effectively reducing polarization loss, the radiator of the RFID tag is located in a region with higher electric field strength at the gap between the lossy media, improving the reading performance of the RFID reader / writer.
[0039] This application also provides a product packaging that includes the aforementioned RFID tag. Specifically, the product packaging refers to the general term for the decorations attached to a product using containers, materials, and auxiliary materials according to certain technical methods during the product transportation, storage, and sales processes, in order to protect the product, facilitate storage, and promote sales. In this application embodiment, the RFID tag can be attached to the product packaging using methods such as pasting, embedding, or hooking, enabling the tracking and location of the product containing the packaging. Furthermore, since the RFID tag in this application embodiment is small in size, it does not increase the cost during the product transportation, storage, and sales processes.
[0040] Other embodiments of this specification will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This specification is intended to cover any variations, uses, or adaptations that follow the general principles of this specification and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this specification are indicated by the following claims.
[0041] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0042] The above description is merely a preferred embodiment of this specification and is not intended to limit this specification. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this specification should be included within the scope of protection of this specification.
[0043] The above provides a detailed description of an RFID tag provided in this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.
Claims
1. A radio frequency tag, characterized by The radio frequency tag includes: RF chip and antenna body; The antenna body includes an impedance matching network and a radiator, and the radio frequency chip is connected to the impedance matching network. The impedance matching network is formed by parallel impedance matching units. The impedance matching network is connected to the radiator, which has a hollow design. Based on the parallel impedance matching network and the gap between the impedance matching network and the radiator, the polarization direction of the RFID tag is vertical. The impedance matching network includes a first impedance matching unit and a second impedance matching unit, which are connected in parallel through the radio frequency chip. The gap between the impedance matching network and the radiator forms a capacitive load, creating a vertical electric field direction on the radiator. Combined with the vertical current direction of the impedance matching network, a mirror current is formed on the radiator, making the polarization direction of the RFID tag vertical.
2. The radio frequency tag of claim 1, wherein, The first impedance matching unit and the second impedance matching unit are inductive impedance matching units with a T-type structure.
3. The radio frequency tag of claim 1, wherein, The radio frequency chip is a single-port radio frequency chip.
4. The radio frequency tag of claim 1, wherein, The RFID tag is suitable for use in scenarios involving stacked items.
5. The radio frequency tag according to claim 4, characterized in that, The RFID tag is installed on the item and is located in the gap between the items when the items are stacked.
6. The radio frequency tag according to claim 5, characterized in that, When the circularly polarized electromagnetic waves radiated by the radio frequency reader / writer pass through the article, they are affected by the polarization effect of the article. The electric field direction of the electromagnetic waves becomes perpendicular to the gap between the articles, and is the same as the polarization direction of the radio frequency tag installed on the article.
7. The radio frequency tag according to claim 5, characterized in that, The item contains a consumable medium.
8. The radio frequency tag according to claim 7, characterized in that, The RFID tag is located in the gap between the lossy media of the article.
9. A product packaging, characterized in that, The product packaging includes the radio frequency tag as described in any one of claims 1 to 8.