A small-sized printed circuit board RFID tag antenna resistant to metal interference

Abstract

This invention discloses a small-sized printed circuit board radio frequency identification (RFID) tag antenna with anti-metal interference, comprising three metal layers from top to bottom. The top layer is a radiating layer with a "U"-shaped antenna of zigzag structure on its surface. The middle layer is an impedance matching layer with a non-resonant loop structure on its surface. The bottom layer is a grounding shielding layer. An FR-4 dielectric substrate is placed between the top radiating layer and the impedance matching layer, and similarly, an FR-4 dielectric substrate of the same thickness is placed between the impedance matching layer and the grounding shielding layer. Furthermore, short-circuit walls connecting the three metal layers are provided on both sides of the edges. This invention utilizes mature printed circuit board (PCB) processing technology, enabling efficient and low-cost manufacturing of the tag antenna. The stability and consistency of PCB processing technology ensure product quality while supporting large-scale mass production, suitable for industrial applications. Combined with the multi-layer antenna design of this invention, the precise processing of complex electromagnetic structures is achieved through standardized processes, simplifying the production process and significantly reducing manufacturing costs. Compared with traditional ceramic antenna designs that require precise material preparation, molding and sintering steps, this invention is not only easier to process, but also more cost-effective and easier to promote and apply.

Description

Technical Field

[0001] The utility model belongs to the technical field of antennas, and particularly relates to a small-sized printed circuit board RFID tag antenna with anti-metal interference. Background Technique

[0002] Existing RFID tag antennas with anti-metal interference ability are usually designed as single-layer structures and often use flexible materials (such as polyimide film, PI film) as tag substrates. Although this design has certain flexibility and lightweight characteristics, there are significant challenges in size control, and the tag area is often large. In addition, when such tags are attached to the surface of metal or liquid, their electromagnetic characteristics will change significantly, resulting in a significant reduction in the reading and writing sensitivity of the tags, and even complete failure in extreme cases, thus limiting their reliability and functionality in practical application scenarios.

[0003] In contrast, some RFID tag antennas with anti-metal design choose ceramic materials as substrates. The antennas designed in this way have excellent anti-interference performance in a metal environment and can significantly reduce the influence of the metal surface on the antenna resonance frequency and impedance matching. However, the high cost of ceramic materials poses a severe challenge to the economy of the overall system and limits its promotion in large-scale low-cost applications. Content of the Utility Model

[0004] The purpose of the utility model is to provide a small-sized printed circuit board RFID tag antenna with anti-metal interference for the defects of the existing technology.

[0005] To achieve the above purpose, the utility model adopts the following technical scheme: A small-sized printed circuit board RFID tag antenna with anti-metal interference, including three metal layers from top to bottom. The topmost layer of the metal layer is the radiation layer, and the metal layer is an antenna with a folded line structure. There is a position reserved for installing the RFID chip in the middle of the antenna;

[0006] The middle layer is the impedance matching layer, which is in a non-resonant - annular structure, and the bottom layer is the grounding shielding layer;

[0007] Dielectric board substrates are arranged between the topmost layer and the middle layer and between the middle layer and the bottom layer. The radiation layer and the grounding shielding layer are connected through short-circuit walls on both sides of the edges of the dielectric board substrates.

[0008] Further, the folded line structure of the radiation layer antenna is in a "Ji" shape. Symmetrical folded line structures with the same number are arranged on both sides of the RFID chip. The number of "Ji" shaped folded line structures is between 1 and 3. The "Ji" shaped folded line structures are connected to the short-circuit walls located at the edges of the dielectric board substrates through rectangular blocks.

[0009] Further, the non-resonant - annular structure of the impedance matching layer is in a rectangular ring shape.

[0010] Furthermore, the substrate of the dielectric substrate is FR-4 dielectric substrate, and the thickness of the two dielectric substrate layers is the same.

[0011] Furthermore, the grounding shielding layer is a single sheet of metal, with the same dimensions as the substrate of the dielectric board.

[0012] Furthermore, the metal layers are all made of copper.

[0013] This invention utilizes mature printed circuit board (PCB) processing technology, enabling efficient and low-cost manufacturing of tag antennas. The stability and consistency of PCB processing technology ensure product quality while supporting large-scale mass production, making it suitable for industrial applications. Combined with the multi-layer antenna design of this invention, standardized processes enable precise fabrication of complex electromagnetic structures, simplifying the production process and significantly reducing manufacturing costs. Compared to traditional ceramic antenna designs that require precise material preparation, molding, and sintering steps, this invention is not only simpler to manufacture but also more cost-effective, facilitating widespread application.

[0014] This utility model's RFID tag achieves a significant reduction in size through optimized antenna structure; the current example finished product measures only 30*18*1.3mm. 3 The finished tag occupies a small area and is designed with ease of installation in mind, allowing it to be easily attached to various substrate surfaces (including flat and curved metal objects). Compared to traditional, larger antenna designs, the optimized tag size of this invention makes it more suitable for space-constrained scenarios, such as small metal containers and complex equipment surfaces. Furthermore, its lightweight and flexible characteristics further enhance the flexibility of installation and use, eliminating the need for additional complex fixing processes and providing great convenience for practical deployment.

[0015] This invention fundamentally solves the problem of significant performance degradation of traditional tags on metal surfaces by designing a grounding layer (GND layer) on the back of the antenna and introducing a non-resonant ring structure. The grounding layer effectively shields against metal interference, significantly enhancing the antenna's stability and enabling it to maintain excellent read / write performance in both metallic and liquid environments. Experiments show that the antenna's resonant frequency is unaffected by changes in the size and shape of the metal substrate, demonstrating strong environmental adaptability. This resistance to metal interference significantly improves the reliability of RFID tags in complex application scenarios, solving the problem of traditional tags failing due to interference. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the tag antenna structure in an embodiment.

[0017] Figure 2 This is a schematic diagram of the structure of the tag antenna radiating layer in an embodiment.

[0018] Figure 3 This is a schematic diagram of the impedance matching layer of the tag antenna in the embodiment.

[0019] Figure 4 This is a schematic diagram of the structure of the tag antenna grounding shield layer in the embodiment.

[0020] Figure 5 This is a specific implementation of the non-resonant-ring structure of the impedance matching layer in the embodiment to reduce the antenna resonant frequency. Detailed Implementation

[0021] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of the present application.

[0022] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification, claims and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product or device.

[0023] 1. The proposed tag antenna, fabricated using a multilayer printed circuit board, consists of three metal layers.

[0024] To address the limitations of traditional single-layer antennas in terms of performance and stability, the proposed RFID tag antenna employs a multi-layer printed circuit board (PCB) manufacturing process, achieving an innovative design structure composed of three metal layers.

[0025] like Figure 1 As shown, the topmost layer of the metal layer is the radiating layer 1, and the metal layer is the antenna 2 with a zigzag structure. The middle of the antenna has a reserved position for installing an RFID chip. The middle layer is the impedance matching layer 3, which has a non-resonant ring structure, and the bottom layer is the grounding shielding layer 4.

[0026] A dielectric substrate is provided between the top layer and the middle layer, as well as between the middle layer and the bottom layer. The radiation layer and the grounding shielding layer are connected by short-circuit walls 5 on both sides of the dielectric substrate.

[0027] This multi-layered metal structure, through the rational arrangement of electromagnetic components between different layers, allows the antenna to fully utilize vertical space distribution, increasing the overall design freedom of the antenna. While ensuring a compact structure, this design significantly improves the antenna's electromagnetic performance, enabling it to better meet the read / write requirements in metallic environments.

[0028] 2. The top antenna structure of the tag adopts a zigzag structure design, which enables miniaturization of the tag antenna.

[0029] At the top layer, such as Figure 2 As shown, the antenna adopts a zigzag structure design with the following dimensions (width): a: 3mm, b: 5.4mm, c: 3mm.

[0030] This design effectively reduces the antenna's resonant frequency by extending the current path, allowing it to meet the resonance requirements of VHF RFID tags while maintaining a miniaturized physical size. Compared to traditional linear structures, the polygonal design significantly reduces the antenna's physical footprint and avoids compromising its electromagnetic performance, thus achieving a balance between high performance and miniaturization. This structure makes the antenna more suitable for space-constrained applications, such as the surface of metal containers or complex curved surfaces.

[0031] In practical implementation, for very high frequency (UHF) RFID operating frequency bands (e.g., 920 MHz), the number of "U"-shaped structures is symmetrical, one on each side. Similarly, when RFID tags need to operate in other frequency bands, such as 433 MHz, 860 MHz, and 2400 MHz, the target operating frequency can be adjusted by increasing or decreasing the number of "U"-shaped structures. In this example, the dimensions (width) of the "U"-shaped structure for 920 MHz are as follows: d: 13 mm, e: 19 mm. At the end of the "U"-shaped structure, a rectangular block 6 of a certain size extends to the edge of the FR-4 dielectric substrate, and then, through a short-circuit wall structure, is electrically connected to the grounding shield layer at the bottom of the tag. Figure 4 The dimensions (length) are as follows: f: 18mm, g: 30mm. See the detailed diagram below. Figure 1 Side view and Figure 2 As shown in the top view.

[0032] 3. The tag's middle layer has a non-resonant ring structure, which can effectively adjust the input impedance of the tag antenna and achieve conjugate matching with the RFID chip in the specified VHF band.

[0033] The intermediate layer incorporates a meticulously designed non-resonant ring structure. Its primary function is to precisely adjust the input impedance of the tag antenna by applying specific capacitors and inductors, enabling it to achieve conjugate matching with the RFID chip in the UHF band. This ring structure not only makes efficient use of the antenna's intermediate layer in terms of space but also achieves precise control of the input impedance through flexible adjustment of its geometric parameters (such as the ring width and diameter). This ensures that the antenna's power transmission efficiency is consistently above 80%, maintaining stable read / write performance even in different operating environments.

[0034] In practical implementation, the non-resonant ring structure is used for fine-tuning the operating frequency to a target frequency, such as 920 MHz in this example. The dimensional parameters of the actual non-resonant ring structure are as follows: Figure 1 As shown.

[0035] like Figure 5 Simulations show that when the non-resonant ring structure is not loaded into the overall structure, the antenna operates at 2 GHz (shown by the red line). When according to... Figure 1 As shown, after adding this non-resonant-loop structure to the middle layer of the tag, the antenna's operating frequency is... Figure 5 The frequency drops from 2 GHz to 920 MHz as indicated by the arrow (shown by the black line). This addition does not require increasing the antenna area and, combined with the fine tuning of the "U-shaped structure," forms a coordinated frequency regulation mechanism.

[0036] 4. The back of the tag has a metal grounding shield (GND layer) to effectively shield against metal interference.

[0037] A dedicated GND layer is designed on the back of the tag antenna to serve as the primary barrier against metal interference. This GND layer eliminates resonant frequency drift caused by electromagnetic interference by blocking electromagnetic field coupling induced by the metal surface. Regardless of the metal surface to which the antenna is attached, its resonant characteristics remain stable, ensuring the antenna's reliability and consistency in complex environments. This design effectively solves the problem of traditional RFID tag antennas being susceptible to interference in metallic environments, making its installation and use on metal surfaces feasible. The specific dimensions of the rectangular grounding shield are as follows: Figure 4 As shown.

[0038] The above description is merely a preferred embodiment of this utility model and is not intended to limit the utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A small-sized printed circuit board RFID tag antenna with anti-metal interference, characterized in that: It includes three metal layers from top to bottom. The topmost metal layer is the radiation layer. The metal layer is an antenna with a zigzag structure, and there is a reserved position for installing an RFID chip in the middle of the antenna; The middle layer is the impedance matching layer, which has a non-resonant - annular structure, and the bottom layer is the ground shielding layer; Dielectric substrates are provided between the topmost layer and the middle layer and between the middle layer and the bottom layer. The radiation layer and the ground shielding layer are connected through short - circuit walls on both edges of the dielectric substrates.

2. The anti-metal interference small-size printed circuit board RFID tag antenna according to claim 1, characterized in that: The zigzag structure of the radiation layer antenna is in a "ji" shape. Symmetric zigzag structures with the same number are respectively arranged on both sides of the RFID chip. The number of "ji" - shaped zigzag structures is between 1 and 3, and the "ji" - shaped zigzag structures are connected to the short - circuit walls located at the edge of the dielectric substrate through rectangular blocks.

3. The anti-metal interference small-size printed circuit board RFID tag antenna according to claim 1, characterized in that: The non - resonant - annular structure of the impedance matching layer is in a rectangular ring shape.

4. The anti-metal interference small-size printed circuit board RFID tag antenna according to claim 1, characterized in that: The dielectric substrate is an FR - 4 dielectric substrate, and the thicknesses of the two dielectric substrates are the same.

5. The anti-metal interference small-size printed circuit board RFID tag antenna according to claim 1, characterized in that: The ground shielding layer is a whole - piece metal layer, and its size is the same as that of the dielectric substrate.

6. The anti-metal interference small-size printed circuit board RFID tag antenna according to claim 1, characterized in that: All the metal layers are made of copper metal.

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