A tunable miniaturized RFID tag antenna

Abstract

The application discloses a tunable and miniaturized RFID tag antenna, which comprises a dielectric substrate, a tag chip and a radiation unit arranged on the dielectric substrate. The radiation unit comprises a rectangular ring, a first bending arm, a second bending arm, a first multi-stage stepped gradient network and a second multi-stage stepped gradient network arranged in a left-right symmetrical interval along a central axis, and the tag chip is arranged between the first multi-stage stepped gradient network and the second multi-stage stepped gradient network. The transverse arms of the first bending arm and the second bending arm jointly form a interdigital metal strip. The rectangular ring, the first multi-stage stepped gradient network, the second multi-stage stepped gradient network, and the vertical arms of the first bending arm and the second bending arm jointly form a closed loop to adapt to an ultra-high frequency working frequency band, and the peak reading distance in a darkroom is up to 4.6 m, so that the RFID tag antenna has the advantages of miniaturization and tunability.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a tunable miniaturized RFID tag antenna. Background Technology

[0002] Radio Frequency Identification (RFID), as a contactless automatic identification and communication technology, has been widely applied in key industries such as logistics warehousing, intelligent manufacturing, and medical traceability due to its advantages such as fast identification speed, large data storage capacity, and long-distance communication. It is one of the core technologies of the Internet of Things (IoT) sensing layer. The tag antenna plays a crucial role in receiving radio frequency energy and transmitting signals via backscattering. The performance of its antenna structure directly determines the tag's wake-up sensitivity and effective reading distance, making it a key component that restricts the overall application effectiveness of RFID devices.

[0003] To meet the needs of different application scenarios, RFID tags need to be attached to the surface of objects made of different materials, and the tag antennas are gradually becoming smaller. However, when RFID tags are attached to high dielectric carriers, problems such as the resonant frequency shifting to lower frequencies and impedance mismatch are likely to occur, and in severe cases, they may deviate from the ultra-high frequency operating band. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a tunable miniaturized RFID tag antenna. It features a single-sided structure, allows for flexible tuning of the resonant frequency, and also boasts excellent long-distance identification performance and structural adaptability. Therefore, it is suitable for various application scenarios where the size of the RFID tag is limited and long-distance radio frequency communication is required.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows: This invention provides a tunable miniaturized RFID tag antenna, comprising a dielectric substrate and a tag chip and a radiating unit disposed on the dielectric substrate. The radiating unit includes a rectangular ring, a bent arm group, and a gradient network group. The gradient network group includes a first multi-level stepped gradient network and a second multi-level stepped gradient network arranged symmetrically at left and right intervals along the central axis of the radiating unit, and the tag chip is disposed between the first multi-level stepped gradient network and the second multi-level stepped gradient network. The bent arm group includes a first bent arm and a second bent arm arranged opposite to each other. The lateral arms of the first bent arm and the second bent arm are respectively located above the gradient network group and together form an interdigitated metal strip. The rectangular ring is located below the gradient network group. The first multi-level stepped gradient network is connected to the left end of the rectangular ring through the vertical arm of the first bent arm, and the second multi-level stepped gradient network is connected to the right end of the rectangular ring through the vertical arm of the second bent arm.

[0006] Furthermore, both the first and second multi-level stepped gradient networks include connected upper gentle step segments and lower steep step segments; the upper gentle step segments of the first and second multi-level stepped gradient networks are respectively connected to the interdigitated metal strips to form a ring structure; the lower steep step segments of the first and second multi-level stepped gradient networks are respectively connected to the rectangular ring through the vertical arms of the first and second bent arms, and combined to form a closed loop.

[0007] Furthermore, the rectangular ring is a single-loop, flat, long, closed structure extending laterally to the left and right, and it has bent branches inside.

[0008] Furthermore, the rectangular ring includes two horizontal sides arranged at the top and bottom, and two vertical sides arranged at the left and right; the two horizontal sides and the vertical sides are connected end to end to form a closed loop.

[0009] Furthermore, the rectangular ring and the bent branch are integrally formed structures, and the bent branch is connected to the inner wall of one side of the rectangular ring in the left and right directions.

[0010] Furthermore, the bent branch is a single L-shaped stepped bend structure, including a horizontal main branch segment and a secondary horizontal branch segment parallel to the horizontal side, and an upwardly bent short branch segment connecting the horizontal main branch segment and the secondary horizontal branch segment; the upwardly bent short branch segment is parallel to the side vertical side; one end of the horizontal main branch segment away from the upwardly bent short branch segment is connected to the lower part of the first inner sidewall of the rectangular ring in the left and right directions; the rectangular ring has a second inner sidewall opposite to the first inner sidewall; the end of the secondary horizontal branch segment away from the upwardly bent short branch segment is suspended and forms a coupling gap with the second inner sidewall.

[0011] Furthermore, the bent branch is arranged on one side of the inner cavity of the rectangular ring to form an asymmetrical single-branch bent structure.

[0012] Furthermore, the first bent arm is an F-shaped bent arm, including a first vertical branch segment and two first and second horizontal branches arranged at an upward and downward distance, the first and second horizontal branches being connected to the first vertical branch segment respectively, and the length of the first horizontal branch segment being greater than the length of the second horizontal branch segment; the second bent arm is an L-shaped bent arm, including a second vertical branch segment and a third horizontal branch segment connected together; the third horizontal branch segment is inserted at a distance between the first and second horizontal branch segments, and together they form an interdigitated metal strip for interdigital coupling; the first and second horizontal branch segments are the two transverse arms of the first bent arm; the third horizontal branch segment is the transverse arm of the second bent arm; the first vertical branch segment is the vertical arm of the first bent arm; the second vertical branch segment is the vertical arm of the second bent arm.

[0013] Furthermore, the dielectric substrate is a flexible polymer film; the radiating unit is an etched structure on the dielectric substrate.

[0014] Furthermore, the rectangular ring, the bent arm group, and the gradient network group are respectively etched aluminum wires.

[0015] The technical solution provided by this invention has the following beneficial effects: 1. This invention changes the resonant frequency of the tag antenna by adjusting the size of each multi-level stepped gradient network in the gradient network group, thereby adapting to the ultra-high frequency operating band. At the same time, it can reduce the overall size of the tag antenna and take into account long-distance identification and structural adaptability. Therefore, it is suitable for the surface of objects of various shapes and sizes.

[0016] 2. The present invention achieves fine-tuning of the resonant frequency of the tag antenna by adjusting the dimensions of the first bent arm and the second bent arm, that is, by adjusting the dimensions of the interdigitated metal strip accordingly.

[0017] 3. The present invention achieves impedance matching between the tag chip and the radiating unit by setting a bent branch within the rectangular ring, thereby achieving conjugate matching between the tag chip and the radiating unit.

[0018] 4. The overall size of the tag antenna in this invention can be set to 20.2×10.95×0.05mm. When the tag antenna is attached to the surface of a high-dielectric carrier (such as foam), the optimal resonance range is 865~925MHz, the lowest positive activation threshold power can reach -9.8dBm, and the measured peak reading distance in an anechoic chamber can reach 4.6m. Attached Figure Description

[0019] Figure 1The diagram shown is a structural schematic of the tunable miniaturized RFID tag antenna in the embodiment. Figure 2 The figure shown is a comparison curve of the sensitivity and measured reading distance of the tunable miniaturized RFID tag antenna in the embodiment. Detailed Implementation

[0020] To further illustrate the various embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention and are mainly used to illustrate the embodiments, and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these drawings, those skilled in the art should be able to understand other possible implementations and the advantages of the present invention. Components in the drawings are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0021] The present invention will now be further described in conjunction with the accompanying drawings and specific embodiments.

[0022] Reference Figure 1 and Figure 2 This embodiment provides a tunable miniaturized RFID tag antenna (hereinafter referred to as tag antenna) to ensure that it has miniaturized, bendable and tunable characteristics, and when it is attached to the surface of a high dielectric carrier (such as foam), it can meet the usage requirements for normal operation in the ultra-high frequency band.

[0023] like Figure 1 As shown, the tag antenna of this embodiment includes a dielectric substrate 7 and a tag chip 6 and a radiating unit 100 disposed on one side of the dielectric substrate 7. The radiating unit 100 includes a rectangular ring 1, a bent arm group 10 and a gradient network group 3. The dielectric substrate 7 is a flexible polymer film (such as a polyimide film or a polyethylene terephthalate film), and the radiating unit 100 is an etched structure on the dielectric substrate 7.

[0024] In this embodiment, the gradient network group 3 includes a first multi-level stepped gradient network 31 and a second multi-level stepped gradient network 32 arranged with left and right symmetrical spacing along the central axis I of the radiation unit 100, and the tag chip 6 is disposed at the center between the first multi-level stepped gradient network 31 and the second multi-level stepped gradient network 32.

[0025] The bending arm assembly 10 includes a first bending arm 4 and a second bending arm 5 arranged opposite to each other. The lateral arms of the first bending arm 4 and the second bending arm 5 are respectively located above the gradient network assembly 3, and the rectangular ring 1 is located below the gradient network assembly 3. The lateral arms of the first bending arm 4 and the second bending arm 5 together constitute the interdigitated metal strip 8.

[0026] The first multi-level stepped gradient network 31 is connected to the left end of the rectangular ring 1 through the vertical arm of the first bent arm 4, and the second multi-level stepped gradient network 32 is connected to the right end of the rectangular ring 1 through the vertical arm of the second bent arm 5.

[0027] More specifically, such as Figure 1 As shown, both the first multi-level stepped gradient network 31 and the second multi-level stepped gradient network 32 include an upper gentle step segment 311 and a lower steep step segment 312 arranged vertically and connected to each other. The upper gentle step segment 311 of the first multi-level stepped gradient network 31 and the second multi-level stepped gradient network 32 are respectively connected to the interdigitated metal strip 8 to form a ring structure. The lower steep step segment 312 of the first multi-level stepped gradient network 31 and the second multi-level stepped gradient network 32 are respectively connected to the rectangular ring 1 through the vertical arms of the first bending arm 4 and the second bending arm 5, and combined to form a closed loop.

[0028] The resonant frequency of the tag antenna can be changed by adjusting the size of each multi-level stepped gradient network in gradient network group 3.

[0029] Furthermore, by adjusting the dimensions of the first bent arm 4 and the second bent arm 5, that is, by adjusting the dimensions of the interdigitated metal strip 8 accordingly, the resonant frequency of the tag antenna can be finely adjusted.

[0030] In summary, this embodiment achieves coarse adjustment of the tag antenna's resonant frequency by changing the size of the gradient network group 3, and fine adjustment of the tag antenna's resonant frequency by adjusting the size of the first bent arm 4 and the second bent arm 5, thereby adapting to the ultra-high frequency operating band. At the same time, it can reduce the overall size of the tag antenna and take into account long-distance identification and structural adaptability. Therefore, it is suitable for object surfaces of various shapes and sizes.

[0031] Further preferred, such as Figure 1 As shown, the rectangular ring 1 is a single-ring flat and long closed structure extending laterally to the left and right, and the left inner sidewall 13 inside the rectangular ring 1 is connected to a bent branch 2 (i.e., set on one side), so that the bent branch 2 forms an asymmetrical single bent structure.

[0032] In this specific embodiment, the rectangular ring 1 and the bent branch 2 are integrally formed structures.

[0033] like Figure 1 As shown, the rectangular ring 1 includes two horizontal sides 11 arranged at the top and bottom, and two vertical sides 12 arranged at the left and right. The two horizontal sides 11 and the vertical sides 12 are connected end to end to form a closed loop. Of course, the line width, line spacing, vertical side height, horizontal side length, and other dimensions of the rectangular ring 1 can be set according to actual performance requirements, and the corresponding dimensional parameter values ​​can be the same or different.

[0034] The bent branch 2 is a single L-shaped stepped bend structure, including a horizontal main branch segment 21 and a secondary horizontal branch segment 23 parallel to each horizontal side 11, and an upwardly bent short branch segment 22 connecting the horizontal main branch segment 21 and the secondary horizontal branch segment 23. The upwardly bent short branch segment 22 is perpendicular to the horizontal main branch segment 21 and the secondary horizontal branch segment 23, and is parallel to each side vertical side 12.

[0035] The left end of the horizontal main branch 21, which is away from the upwardly bent short branch 22, is connected to the lower part of the left inner wall 13 of the rectangular ring 1, forming a single-point support.

[0036] The rectangular ring 1 has a right inner wall 14 opposite to the left inner wall 13, and the right end of the secondary horizontal branch 23 is suspended away from the upwardly bent short branch 22, forming a coupling gap with the right inner wall 14. This can generate capacitive coupling, so as to flexibly change the overall equivalent electrical length of the antenna and improve the degree of freedom of antenna impedance adjustment, thereby facilitating the conjugate matching between the tag chip 6 and the radiating unit 100.

[0037] By setting a bent branch 2 inside the rectangular ring 1, impedance matching between the tag chip 6 and the radiation unit 100 can be achieved, thereby realizing conjugate matching between the tag chip 6 and the radiation unit 100.

[0038] Further preferred, such as Figure 1 As shown, the first bent arm 4 is an F-shaped bent arm, and includes a first vertical branch 43 and two first horizontal branches 41 and second horizontal branches 42 arranged at an upper and lower distance. The left ends of the first horizontal branches 41 and the second horizontal branches 42 are respectively connected to the upper part of the first vertical branch 43, and the length of the first horizontal branch 41 is greater than the length of the second horizontal branch 42.

[0039] The second bent arm 5 is an L-shaped bent arm and includes a second vertical branch 52 and a third horizontal branch 51 connected to each other. The third horizontal branch 51 is inserted at intervals between the first horizontal branch 41 and the second horizontal branch 42, and together they form an interdigitated metal strip 8 for interdigital coupling. Specifically, the two horizontal branches of the first bent arm 4 and the single horizontal branch of the second bent arm 5 interweave with each other without contacting each other. Therefore, the three cooperate to form the interdigitated metal strip 8. At this time, the first horizontal branch 41 and the second horizontal branch 42 are the two horizontal arms of the first bent arm 4, the third horizontal branch 51 is the horizontal arm of the second bent arm 5, the first vertical branch 43 is the vertical arm of the first bent arm 4, and the second vertical branch 52 is the vertical arm of the second bent arm 5.

[0040] The F-shaped and L-shaped bent arms together form an interdigital structure (i.e., interdigital metal strip 8). The first horizontal branch 41 forms the outer contour of the interdigital structure, and the second horizontal branch 42 is an overlapping interdigital branch. The surrounding electric field distribution of the two horizontal branches is significantly different. Furthermore, adjusting the structural parameters of the first horizontal branch 41 and the second horizontal branch 42 can have a differentiated effect on the equivalent coupling capacitance of the interdigital structure, thereby achieving multi-gradient and different precision tuning control of the antenna resonant frequency.

[0041] In practice, the cross-section of the tag antenna is rectangular, with dimensions of 20.2 × 10.95 × 0.05 mm. The rectangular ring 1, the bent branch 2, the first bent arm 4, the second bent arm 5, the first multi-level stepped gradient network 31, and the second multi-level stepped gradient network 32 are all made of aluminum (i.e., etched aluminum wires), and the radiating unit 100 is etched onto the dielectric substrate 7 using an etching process.

[0042] like Figure 2 As shown, when the tag antenna is attached to the surface of a high-dielectric carrier (such as foam) and tested in an anechoic chamber, its optimal resonance range is 865~925MHz, the lowest positive activation threshold power can reach -9.8dBm, and the measured peak reading distance in the anechoic chamber can reach 4.6m. Therefore, the tag antenna of this embodiment can exhibit good performance.

[0043] Therefore, the tag antenna of this embodiment can be coordinated and tuned to the first multi-level stepped gradient network 31, the second multi-level stepped gradient network 32, the rectangular ring 1 with bent branches 2, and the F / L-shaped interdigitated metal strip 8, so as to ensure that it has the advantages of miniaturization, bendability, and tunability at the same time, and its comprehensive performance can meet the usage requirements of special application scenarios such as being attached to a high dielectric carrier.

[0044] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art will understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A tunable miniaturized RFID tag antenna, comprising a dielectric substrate and a tag chip and a radiating unit disposed on the dielectric substrate, characterized in that: The radiating element includes a rectangular ring, a bent arm group, and a gradient network group; The gradient network group includes a first multi-level stepped gradient network and a second multi-level stepped gradient network arranged symmetrically on the left and right sides along the central axis of the radiation unit, and the tag chip is disposed between the first multi-level stepped gradient network and the second multi-level stepped gradient network. The bending arm assembly includes a first bending arm and a second bending arm arranged opposite to each other; the lateral arms of the first bending arm and the second bending arm are respectively located above the gradient network assembly and together form an interdigitated metal strip; the rectangular ring is located below the gradient network assembly; The first multi-level stepped gradient network is connected to the left end of the rectangular ring through the vertical arm of the first bent arm, and the second multi-level stepped gradient network is connected to the right end of the rectangular ring through the vertical arm of the second bent arm.

2. The tunable miniaturized RFID tag antenna according to claim 1, characterized in that: Both the first and second multi-level stepped gradient networks include connected upper gentle step segments and lower steep step segments; the upper gentle step segments of the first and second multi-level stepped gradient networks are respectively connected to the interdigitated metal strips to form a ring structure; the lower steep step segments of the first and second multi-level stepped gradient networks are respectively connected to the rectangular ring through the vertical arms of the first and second bent arms, and combined to form a closed loop.

3. The tunable miniaturized RFID tag antenna according to claim 1 or 2, characterized in that: The rectangular ring is a single-loop, flat, long, closed structure extending laterally to the left and right, and it has bent branches inside.

4. The tunable miniaturized RFID tag antenna according to claim 3, characterized in that: The rectangular ring includes two horizontal sides arranged at the top and bottom, and two vertical sides arranged at the left and right; the two horizontal sides and the vertical sides are connected end to end to form a closed loop.

5. The tunable miniaturized RFID tag antenna according to claim 4, characterized in that: The rectangular ring and the bent branch are integrally formed, and the bent branch is connected to the inner wall of one side of the rectangular ring in the left and right directions.

6. The tunable miniaturized RFID tag antenna according to claim 5, characterized in that: The bent branch is a single L-shaped stepped bend structure, including a horizontal main branch segment and a secondary horizontal branch segment parallel to the horizontal side, as well as an upwardly bent short branch segment connecting the horizontal main branch segment and the secondary horizontal branch segment; the upwardly bent short branch segment is parallel to the side vertical side; The end of the horizontal main branch that is away from the upwardly bent short branch is connected to the lower part of the first inner wall of the rectangular ring in the left and right directions; the rectangular ring has a second inner wall opposite to the first inner wall; the end of the secondary horizontal branch that is away from the upwardly bent short branch is suspended and forms a coupling gap with the second inner wall.

7. The tunable miniaturized RFID tag antenna according to claim 6, characterized in that: The bent branch is arranged on one side of the inner cavity of the rectangular ring to form an asymmetrical single-branch bent structure.

8. The tunable miniaturized RFID tag antenna according to claim 1 or 2, characterized in that: The first bent arm is an F-shaped bent arm, including a first vertical branch and two horizontal branches, a first horizontal branch and a second horizontal branch, spaced vertically. The first horizontal branch and the second horizontal branch are respectively connected to the first vertical branch, and the length of the first horizontal branch is greater than the length of the second horizontal branch. The second bent arm is an L-shaped bent arm, including a second vertical branch and a third horizontal branch connected to each other. The third horizontal branch is inserted between the first horizontal branch and the second horizontal branch at intervals, and together they form an interdigitated metal strip for interdigital coupling. The first horizontal branch and the second horizontal branch are the two horizontal arms of the first bent arm. The third horizontal branch is the horizontal arm of the second bent arm. The first vertical branch is the vertical arm of the first bent arm. The second vertical branch is the vertical arm of the second bent arm.

9. The tunable miniaturized RFID tag antenna according to claim 1 or 2, characterized in that: The dielectric substrate is a flexible polymer film; the radiating unit is an etched structure on the dielectric substrate.

10. The tunable miniaturized RFID tag antenna according to claim 1 or 2, characterized in that: The rectangular ring, the bent arm group, and the gradient network group are respectively etched aluminum wires.

Images