An antenna for a radio frequency identification tag

Abstract

The utility model discloses an antenna of radio frequency identification label, contain inside loop, outer loop, first radiator and second radiator. Inside loop contains common part and opposite two open ends. Outer loop extends from common part, and surround inside loop. First radiator contains first connecting line, first radiating sheet, first extension line and second extension line. First connecting line extends from outer loop or common part outward. The end of first connecting line is connected with first radiating sheet. First extension line and second extension line extend from first radiating sheet. Second radiator contains second connecting line, second radiating sheet, third extension line and fourth extension line. Second connecting line extends from outer loop or common part outward. The end of second connecting line is connected with second radiating sheet. Third extension line and fourth extension line extend from second radiating sheet. This antenna of radio frequency identification label can be applied to the high dielectric constant substrate such as glass and rubber, and has excellent performance.

Description

Technical Field

[0001] This utility model relates to the field of product identification, specifically to an antenna for a radio frequency identification tag. Background Technology

[0002] Radio frequency identification (RFID) tags are widely used in logistics management, access control, asset tracking, and supply chain monitoring. Passive RFID tags are the most common in commercial applications due to their simple structure, low cost, and long lifespan. However, the application of passive RFID tags in specific environments still faces technical challenges, especially when the tags need to be attached to surfaces with high dielectric constant materials such as glass, where antenna performance is often significantly affected. High dielectric materials alter the propagation characteristics of electromagnetic waves, leading to problems such as antenna resonant frequency shift, impedance mismatch, and reduced radiation efficiency, ultimately resulting in shortened reading distance or even failure to be read. Therefore, designing an RFID tag that can be effectively applied to high dielectric constant substrates is currently an important technical issue. Utility Model Content

[0003] One objective of this invention is to provide an antenna for a radio frequency identification (RFID) tag, which can be applied to substrates with high dielectric constants, such as glass and rubber, and has excellent performance.

[0004] In some embodiments, an antenna for a radio frequency identification tag includes:

[0005] The inner loop includes a common portion and a first clamp and a second clamp extending from opposite ends of the common portion, wherein the ends of the first clamp and the ends of the second clamp are opposite to each other and spaced apart by a gap;

[0006] The outer loop extends from the opposite ends of the common portion and surrounds the inner loop;

[0007] The first radiator includes:

[0008] The first connecting line extends outward from the outer loop or the common portion;

[0009] The first radiating plate is connected to the end of the first connecting line;

[0010] A first extension line extends from the first radiating plate; and

[0011] The second extension line extends from the first radiating plate; and

[0012] The second radiator includes:

[0013] The second connecting line extends outward from the outer loop or the common part;

[0014] The second radiating plate is connected to the end of the second connecting line;

[0015] The third extension line extends from the second radiating plate; and

[0016] The fourth extension line extends from the second radiating plate.

[0017] In some embodiments, the first clamp includes an inner connecting line and a recess, the inner connecting line extending from one of the opposite two ends, the recess extending from one end of the inner connecting line toward the interior of the inner loop and then folding back, and forming a notch at the outer edge of the inner loop.

[0018] In some embodiments, the total length of the inner loop and the outer loop is 65 mm to 135 mm.

[0019] In some embodiments, the minimum distance between the inner loop and the outer loop is 0.5 mm to 2.5 mm.

[0020] In some implementations, the common portion is substantially a straight line.

[0021] In some embodiments, the first connecting line extends from the outer loop and includes a first main line segment and a first auxiliary line segment. The first main line segment is directly connected to the outer loop, and the first auxiliary line segment is directly connected to the first radiating plate. The first main line segment is not parallel to the first auxiliary line segment.

[0022] In some implementations, the first auxiliary line segment is substantially perpendicular to the first main line segment, and the first main line segment is substantially parallel to the common portion.

[0023] In some implementations, the second extension line is substantially parallel to the first main line segment.

[0024] In some embodiments, the first radiating sheet and the second radiating sheet are polygonal, circular, or elliptical.

[0025] In some embodiments, the area of ​​each of the first radiating sheet and the second radiating sheet is 70 mm². 2 Up to 130mm 2 .

[0026] In some embodiments, the first extension line is located between the first radiating sheet and the first main line segment.

[0027] In some embodiments, the first extension line includes a first long segment and a first short segment, the first short segment being directly connected to the first radiating sheet, the first long segment being connected to the first radiating sheet via the first short segment, and the first long segment not being parallel to the first short segment.

[0028] In some embodiments, the first long segment is substantially perpendicular to the first short segment, and the first long segment is substantially parallel to the first main line segment.

[0029] In some implementations, the second extension line is substantially parallel to the first long segment.

[0030] In some embodiments, the second extension line and the first extension line extend from different positions on one side of the first radiating sheet adjacent to the outer loop.

[0031] In some embodiments, the first radiator has a characteristic length defined as the perimeter of the first radiator minus the width of the first connecting line contacting the outer loop or the common portion, the characteristic length being 100 mm to 130 mm.

[0032] In some embodiments, the first radiator and the second radiator are mirror images of each other.

[0033] In some implementations, the outer loop and the common portion together form a closed loop. Attached Figure Description

[0034] Figure 1 This is a top view schematic diagram of the antenna of a radio frequency identification tag according to certain embodiments of the present invention.

[0035] Figure 2 This is a top view schematic diagram of the antenna of a radio frequency identification tag according to other embodiments of the present invention.

[0036] Figure 3 This is a partial top view of the antenna of a radio frequency identification tag according to certain embodiments of the present invention.

[0037] Figure 4 The diagram shows the simulation results of the current density of the antenna in one embodiment of the present invention and Comparative Example 1.

[0038] Figure 5 The diagram shows the impedance simulation results of the antennas of one embodiment and Comparative Example 2 of this utility model.

[0039] Figure 6 The diagram shows the impedance simulation results of several embodiments of this utility model.

[0040] Figure 7The diagram shows the impedance simulation results of several embodiments of this utility model.

[0041] Figure 8 This is a top view of the antenna of the radio frequency identification tag of Comparative Example 3 of this utility model.

[0042] Figure 9 Impedance simulation results of the antenna in one embodiment and Comparative Example 3 of this invention are shown in the figure.

[0043] Figure 10 The diagram shows the impedance simulation results of several embodiments of this utility model.

[0044] Figure 11 The figure shows the measurement results of the readable distance of an antenna according to an embodiment of the present invention when it is attached to a glass substrate and in free space (not attached to a glass substrate).

[0045] Explanation of key figure labels:

[0046] 10: Antenna for Radio Frequency Identification (RFID) Tags

[0047] 100: Inner Loop

[0048] 110: Common areas

[0049] 111, 112: End

[0050] 130: First clamp

[0051] 131: End

[0052] 133: Internal connection

[0053] 134: End

[0054] 137: Depression

[0055] 140: Second clamp

[0056] 142: End

[0057] 147: Depression

[0058] 150: Notch

[0059] 200: Outer loop

[0060] 300: First radiator

[0061] 310: First connecting line

[0062] 310: First connecting line

[0063] 312: First Main Segment

[0064] 314: First auxiliary line segment

[0065] 316: End

[0066] 320: First Radiation Plate

[0067] 330: First extension line

[0068] 332: The First Long Section

[0069] 334: First short paragraph

[0070] 340: Second extension line

[0071] 400: Second radiator

[0072] 410: Second connecting line

[0073] 420: Second Radiation Plate

[0074] 430: Third extension line

[0075] 440: Fourth extension line

[0076] 500: Chip

[0077] A, B: Location

[0078] D: Distance

[0079] L: Length

[0080] S: Spacing

[0081] W: Width Detailed Implementation

[0082] Figure 1 This is a top view schematic diagram of the antenna 10 of a radio frequency identification (RFID) tag in some embodiments of the present invention. The antenna 10 of the RFID tag includes an inner loop 100, an outer loop 200, a first radiator 300, and a second radiator 400.

[0083] The inner loop 100 includes a common portion 110 and a first clamp 130 and a second clamp 140 extending from opposite ends 111 and 112 of the common portion 110, respectively. The ends 131 and 142 of the first clamp 130 and the second clamp 140 are open ends, facing each other and spaced apart by a gap. The ends 131 and 142 of the first clamp 130 and the second clamp 140 are used to connect to the chip 500, and the chip 500 and the inner loop 100 form a closed loop. In this document, the terms "first," "second," etc., are used to describe various components; these terms are used only to distinguish one component from another. A first component can also be called a second component; similarly, a second component can also be called a first component.

[0084] In some embodiments, the first clamp 130 includes an inner interconnect 133 and a recess 137. The inner interconnect 133 extends from the end 111 of the common portion 110, and the recess 137 extends from the other end 134 of the inner interconnect 133 in an inward direction of the inner loop 100 and then folds back, thus forming a notch 150 at the outer edge of the inner loop 100. By adjusting the distance the recess 137 extends inward, the length of the inner loop 100 can be adjusted, thereby adjusting the sum of the lengths of the inner loop 100 and the outer loop 200. In some embodiments, the sum of the lengths of the inner loop 100 and the outer loop 200 affects the performance of the antenna 10, as will be described in more detail below.

[0085] In some embodiments, the second clamping portion 140 has structural features similar to the first clamping portion 130 described above. For example, the second clamping portion 140 also includes a recess 147, which is similar to the recess 137 described above. In some embodiments, the second clamping portion 140 is mirror-symmetrical to the first clamping portion 130, but in other embodiments, the second clamping portion 140 is not mirror-symmetrical to the first clamping portion 130; for example, the size of the recess 147 in the second clamping portion 140 is different from that in the first clamping portion 130. In still other embodiments, the second clamping portion 140 does not include any recess.

[0086] In some embodiments, the common portion 110 is essentially a straight line segment. However, in other embodiments, the common portion 110 may have a recess, the structural features of which are similar to the recess 137 described above with respect to the first clamp portion 130. In this document, the terms "line" or "segment" refer to a "line" or "segment" having a certain width, and not to a "line" or "segment" that has no width in a mathematical sense.

[0087] The outer loop 200 extends from the two ends 111, 112 of the common portion 110 and surrounds the inner loop 100. Furthermore, the outer loop 200 and the common portion 110 together form a closed loop. The total length of the inner loop 100 and the outer loop 200 affects the overall reactance matching between the antenna 10 and the chip in the US and European frequency ranges. In some embodiments, the total length of the inner loop 100 and the outer loop 200 is approximately 65 mm to approximately 135 mm, for example, approximately 65 mm, approximately 75 mm, approximately 85 mm, approximately 95 mm, approximately 105 mm, approximately 115 mm, approximately 125 mm, or approximately 135 mm. However, in other embodiments, such as when using chips of drastically different specifications or significantly altering the shape and / or size of the first radiator 300 and the second radiator 400, the total length of the inner loop 100 and the outer loop 200 may not fall within the aforementioned ranges. By adjusting the total length of the inner loop 100 and the outer loop 200, the antenna 10 can be matched to the impedance of various chips. In this article, the "total length of the inner loop and the outer loop" refers to the sum of the lengths of the central axes of the wires that make up the inner loop and the outer loop.

[0088] In some embodiments, the spacing between the inner loop 100 and the outer loop 200 affects the impedance matching between the overall antenna 10 and the chip within the US and European standard frequency ranges. In some embodiments, the minimum spacing S between the inner loop 100 and the outer loop 200 is approximately 0.5 mm to approximately 2.5 mm, for example, approximately 0.5 mm, approximately 1.0 mm, approximately 1.5 mm, approximately 2.0 mm, or approximately 2.5 mm. However, in other embodiments, such as when the specifications of the chip used or the shape and size of other parts of the antenna are significantly changed, the minimum spacing S between the inner loop 100 and the outer loop 200 may not be within the above-mentioned range. By changing the minimum spacing S between the inner loop 100 and the outer loop 200, the antenna 10 can be matched to the impedance of various chips.

[0089] Figure 1 The approximate extent of the first radiator 300 is shown in the dashed box. The first radiator 300 includes a first connecting line 310, a first radiating plate 320, a first extension line 330, and a second extension line 340.

[0090] The first connecting line 310 extends outward from the outer loop 200 or the common portion 110 and connects to the first radiating plate 320. In some embodiments, such as Figure 1As shown, the first connecting line 310 extends from the outer loop 200. In some embodiments, the first connecting line 310 includes a first main line segment 312 and a first auxiliary line segment 314, the first main line segment 312 being non-parallel to the first auxiliary line segment 314, the first main line segment 312 being directly connected to the outer loop 200, and the first auxiliary line segment 314 being directly connected to the first radiating plate 320. In still other embodiments, the first auxiliary line segment 314 is substantially perpendicular to the first main line segment 312. In other embodiments, the first main line segment 312 is substantially parallel to the common portion 110. In still other embodiments, the length of the first main line segment 312 is greater than the length of the first auxiliary line segment 314. In this document, when an element is referred to as "connected" to another element, it may be directly connected to the other element or there may be an intermediary element. Conversely, when an element is referred to as "directly connected" to another element, there is no intermediary element.

[0091] In other embodiments, the first connecting line 310 extends outward from the common portion 110, for example, the first connecting line 310 extends from... Figure 1 The marked position A extends upwards a short distance and then to the right, connecting to the first radiating plate 320. In some other embodiments, such as... Figure 2 As shown, when the position of the outer loop 200 connected to the inner loop 100 changes, the range of the common part 110 also changes. Figure 2 The general extent of the common portion 110 is shown in the dashed box, so that the first connecting line 310 can extend outward from the common portion 110.

[0092] Please see Figure 1 The first radiating element 320 connects to the end 316 of the first connecting line 310. In some embodiments, the first radiating element 320 has a polygonal, circular, elliptical, or other shaped outline. In still other embodiments, the first radiating element 320 has a relatively large area design, which is beneficial to improving the radiation efficiency of the antenna. For example, the area of ​​the first radiating element 320 is greater than the sum of the areas of the first connecting line 310, the first extension line 330, and the second extension line 340. In some embodiments, the area of ​​the first radiating element 320 is approximately 70 mm². 2 Approximately 130mm 2 For example, approximately 70mm 2 Approximately 80mm 2 Approximately 90mm 2 Approximately 100mm 2 Approximately 110mm 2 Approximately 120mm 2 or approximately 130mm 2 However, in other embodiments, the area of ​​the first radiating sheet 320 is not within the above-mentioned numerical range.

[0093] A first extension line 330 extends from a first radiating sheet 320. In some embodiments, the first extension line 330 is located between the first radiating sheet 320 and the first connecting line 310. In some embodiments, the first extension line 330 is located between the first radiating sheet 320 and the first main line segment 312. In other embodiments, the first extension line 330 includes a first long segment 332 and a first short segment 334, the first long segment 332 being non-parallel to the first short segment 334, the first short segment 334 being directly connected to the first radiating sheet 320, and the first long segment 332 being connected to the first radiating sheet 320 via the first short segment 334. In some embodiments, the first long segment 332 is substantially perpendicular to the first short segment 334. In still other embodiments, the first long segment 332 is substantially parallel to the first main line segment 312. In still other embodiments, the length of the first long segment 332 is greater than the length of the first short segment 334.

[0094] The second extension line 340 extends from the first radiating sheet 320. In some embodiments, the second extension line 340 and the first extension line 330 extend from different positions on the side of the first radiating sheet 320 adjacent to the outer loop 200.

[0095] In some other embodiments, the second extension line 340 is substantially parallel to the first main line segment 312. In other embodiments, the second extension line 340 is substantially parallel to the first long segment 332.

[0096] Figure 3 This is a partial top view of the antenna 10 of the radio frequency identification tag in some embodiments of the present invention. The first radiator 300 has a characteristic length. Figure 3 The path of the characteristic length is indicated by an arrow (→). The characteristic length is defined as the perimeter of the first radiator 300, minus the width W of the first connecting line 310 contacting the outer loop 200 (or common portion 110). In some embodiments, the characteristic length of the first radiator 300 affects the impedance matching between the overall antenna 10 and the chip in the US and European frequency ranges. In some embodiments, the characteristic length is approximately 100 mm to approximately 130 mm, for example, approximately 100 mm, approximately 105 mm, approximately 110 mm, approximately 115 mm, approximately 120 mm, approximately 125 mm, or approximately 130 mm. However, in other embodiments, such as when the specifications of the chip used change significantly, the characteristic length of the first radiator 300 is not within the above-mentioned range. Furthermore, the antenna 10 can be matched to the impedance of various chips by adjusting the characteristic length of the first radiator 300.

[0097] Please see Figure 1The second radiator 400 has structural features similar to the first radiator 300, and any of the embodiments, examples, and features described above regarding the first radiator 300 can be applied to the second radiator 400. In short, the second radiator 400 includes a second connecting line 410, a second radiating plate 420, a third extension line 430, and a fourth extension line 440. The second connecting line 410 extends outward from the outer loop 200 or the common portion 110. The second radiating plate 420 connects to one end of the second connecting line 410. The third extension line 430 and the fourth extension line 440 extend from different positions of the second radiating plate 420. In some embodiments, the first radiator 300 and the second radiator 400 are mirror-symmetrical. In still other embodiments, the area of ​​the second radiating plate 420 is approximately 70 mm². 2 Approximately 130mm 2 .

[0098] The simulation results of various embodiments and comparative examples of this utility model will be described in detail below. Unless otherwise specified, the simulation environment is with the antenna mounted on a glass substrate, and the simulation software used is "Ansys HFSS".

[0099] Figure 4 The graph shows the simulation results of the current density of the antenna in one embodiment of this utility model and Comparative Example 1. Figure 4 The upper part is similar Figure 1 The embodiment of the antenna shown is as follows. Figure 4 The lower half is Comparative Example 1. The difference between the embodiment and Comparative Example 1 is that Comparative Example 1 does not have an outer loop, but both have the same first radiator 300 and second radiator 400. Figure 4 The results show that the first extension line 330 and the second extension line 340 of the embodiment exhibit high current densities in red or yellow, and the upper half of the first radiating sheet 320 also exhibits high current densities in red or yellow. Conversely, the current densities in the first and second extension lines of Comparative Example 1 are significantly lower, and the current density in the upper half of the first radiating sheet 320 is also significantly lower. This result shows that although the first radiator 300 and the second radiator 400 of the embodiment and Comparative Example 1 are exactly the same, the different loop structures cause the first radiator 300 and the second radiator 400 to produce drastically different current densities.

[0100] Figure 5 The diagram shows the impedance simulation results of the antennas of one embodiment of the present invention and Comparative Example 2. Comparative Example 2 and... Figure 5 The difference in the embodiments is that, in Comparative Example 2, the chip is designed on an outer loop 200 with two open ends (i.e., Figure 1Position B is indicated in the diagram. Inner loop 100 is a closed loop. Conversely, in this embodiment, the chip is configured on the two open ends of inner loop 100, while outer loop 200 is a closed loop. Figure 5 The simulation results show that the resistance and reactance curves of the antenna in this embodiment change gently, and the reactance of the antenna in this embodiment matches the reactance of the chip well. Conversely, the resistance and reactance curves of Comparative Example 2 change drastically and cannot match the impedance of the chip at all. Figure 5 The results show that whether the chip is placed in the inner or outer loop has a crucial impact.

[0101] Figure 6 These are impedance simulation results for several embodiments of this utility model, wherein changes... Figure 1 The distance D (indicated in the inner loop 100) extending inward from the recesses 137 and 147 is respectively shown. Figure 1 The sizes are 2mm, 3mm, 4mm, 5mm, and 6mm. Figure 6 The results show that distance D has a significant impact on reactance (imaginary impedance), with the reactance curve generally shifting upwards as distance D increases. When distance D changes, the length of the inner loop 100 also changes, consequently altering the total length of the inner loop 100 and the outer loop 200. Therefore, as mentioned earlier, according to some embodiments, the total length of the inner loop 100 and the outer loop 200 is approximately 65 mm to approximately 135 mm, providing certain technical advantages.

[0102] Figure 7 These are impedance simulation results for several embodiments of this utility model, wherein changes... Figure 1 The minimum distance S between the inner loop 100 and the outer loop 200 shown is indicated in Figure 1 The thicknesses are 0.5mm, 1.0mm, 1.5mm, 2.0mm, and 2.5mm. Figure 7 The results show that when the minimum pitch S is between 0.5mm and 2.0mm, the applicable frequency range of the antenna is generally still close to the European and / or American standard frequency ranges. When the minimum pitch S is 2.5mm, the applicable frequency range of the antenna exceeds the European and American standard frequency ranges. The above information is about... Figure 7 The various embodiments are results obtained under specific simulation conditions. If the specifications of the chip used or the shape and size of other parts of the antenna change significantly, a minimum spacing S of 2.5 mm is still feasible.

[0103] Figure 8 This is a top view schematic diagram of the antenna of the radio frequency identification tag in Comparative Example 3 of this utility model, which is similar to... Figure 1 The difference between the illustrated antenna 10 and the antenna in Comparative Example 3 is that the antenna in Comparative Example 3 does not have... Figure 1The first extension line 330 and the third extension line 430 are shown. Figure 9 The diagram shows the impedance simulation results of the antenna of one embodiment of the present invention and Comparative Example 3. Figure 9 The results showed that the resonant frequency of the antenna in Comparative Example 3 was significantly higher than the frequency range of the US standard. The antenna in the embodiment, because it was designed with a first extension line 330 and / or a third extension line 430, effectively adjusted the resonant frequency of the antenna to a lower frequency.

[0104] Figure 10 These are impedance simulation results for several embodiments of this utility model, wherein changes... Figure 1 The lengths L of the second extension line 340 and the fourth extension line 440 shown are indicated in (in the diagram). Figure 1 The thicknesses are 12.8mm, 13.2mm, 13.6mm, 14.0mm, and 14.4mm. Figure 10 The results show that when the length L of the second extension line 340 and / or the fourth extension line 440 increases, the resonant frequency of the antenna shifts towards lower frequencies.

[0105] According to the previous text about Figure 9 and Figure 10 The simulation results of the various embodiments described above can summarize the key characteristics of the first radiator (and the second radiator) of the antenna. According to some embodiments, the characteristic length of the first radiator (and / or the second radiator) can be defined as "the perimeter of the first radiator minus the width of the first connecting line contacting the outer loop or common portion". (As mentioned above...) Figure 3 The length of this feature is, for example, about 100 mm to about 130 mm.

[0106] Figure 11 For use of products manufactured by "Voyantic" The measurement results of the antenna of an embodiment of this utility model are shown in the figure, which are readable distances when the antenna is attached to a glass substrate and in free space (without being attached to a glass substrate). Figure 11 The results show that when the antenna of the embodiment is in free space (not attached to the glass substrate), the readable distance in the frequency range of 860MHz to 940MHz is less than about 3 meters. However, when the antenna is attached to the glass substrate, the readable distance in the same frequency range is greater than 10 meters. The above measurement results confirm that the antenna of the RFID tag of various embodiments and examples of this utility model can indeed be applied to substrates with high dielectric constants, such as glass and rubber, and has excellent performance.

[0107] The foregoing discloses multiple embodiments (or examples) of this utility model and their related technical effects. Different embodiments or examples may have different or the same technical effects. Therefore, any embodiment (or example) of this utility model or the scope of the patent application need not achieve all the purposes, advantages, or features disclosed in this utility model. Furthermore, the content disclosed above is only a part of the many embodiments of this utility model and is not intended to limit this utility model. Any simple equivalent changes and modifications made to the content of the scope of the patent application of this utility model are within the scope of this utility model patent. In addition, the abstract and the name of the utility model are only used to assist in patent document retrieval and are not intended to limit the scope of the rights of this utility model.

Claims

1. An antenna for a radio frequency identification tag, characterized in that: Include: The inner loop includes a common portion and a first clamp and a second clamp extending from opposite ends of the common portion, wherein the ends of the first clamp and the ends of the second clamp are opposite to each other and spaced apart by a gap; The outer loop extends from the opposite ends of the common portion and surrounds the inner loop; The first radiator includes: The first connecting line extends outward from the outer loop or the common portion; The first radiating plate is connected to the end of the first connecting line; The first extension line extends from the first radiating sheet; as well as The second extension line extends from the first radiating sheet; as well as The second radiator includes: The second connecting line extends outward from the outer loop or the common part; The second radiating plate is connected to the end of the second connecting line; The third extension line extends from the second radiating plate; as well as The fourth extension line extends from the second radiating plate.

2. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The first clamp portion includes an inner connecting line and a recessed portion. The inner connecting line extends from one of the opposite two ends. The recessed portion extends from one end of the inner connecting line toward the interior of the inner loop and then folds back, forming a notch at the outer edge of the inner loop.

3. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The total length of the inner loop and the outer loop is 65mm to 135mm.

4. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The minimum distance between the inner loop and the outer loop is 0.5 mm to 2.5 mm.

5. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The common portion therein is essentially a straight line.

6. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The first connecting line extends from the outer loop and includes a first main line segment and a first auxiliary line segment. The first main line segment is directly connected to the outer loop, and the first auxiliary line segment is directly connected to the first radiating plate. The first main line segment is not parallel to the first auxiliary line segment.

7. The antenna for a radio frequency identification tag as described in claim 6, characterized in that: The first auxiliary line segment is substantially perpendicular to the first main line segment, and the first main line segment is substantially parallel to the shared portion.

8. The antenna for a radio frequency identification tag as described in claim 6, characterized in that: The second extension line is substantially parallel to the first main line segment.

9. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The first radiating sheet and the second radiating sheet are polygonal, circular, or elliptical.

10. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The area of ​​each of the first and second radiating plates is 70 mm². 2 Up to 130mm 2 .

11. The antenna for a radio frequency identification tag as described in claim 6, characterized in that: The first extension line is located between the first radiating sheet and the first main line segment.

12. The antenna for a radio frequency identification tag as described in claim 11, characterized in that: The first extension line includes a first long segment and a first short segment. The first short segment is directly connected to the first radiating plate, and the first long segment is connected to the first radiating plate via the first short segment. The first long segment is not parallel to the first short segment.

13. The antenna for a radio frequency identification tag as described in claim 12, characterized in that: The first long segment is substantially perpendicular to the first short segment, and the first long segment is substantially parallel to the first main line segment.

14. The antenna for a radio frequency identification tag as described in claim 12, characterized in that: The second extension line is substantially parallel to the first long segment.

15. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The second extension line and the first extension line extend from different positions on the side of the first radiating plate adjacent to the outer loop, respectively.

16. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The first radiator has a characteristic length, which is defined as the perimeter of the first radiator minus the width of the first connecting line contacting the outer loop or the common part, and the characteristic length is 100mm to 130mm.

17. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The first radiator and the second radiator are mirror images of each other.

18. The antenna for a radio frequency identification tag as described in claim 1, characterized in that: The outer loop and the shared portion together form a closed loop.

Images