CN103227361A - Small shape-adjustable double ring-shaped ultrahigh frequency RFID tag antenna - Google Patents

Abstract

The invention discloses an adjustable-shape double-ring UHF RFID tag antenna, which belongs to the technical field of radio frequency identification. The tag antenna processes two conductor loops on one side of the substrate as an antenna structure, wherein the inner loop is a closed conductor loop connected to the chip, and the outer loop is a conductor loop with an inverted Z-shaped gap, and the shape of the loop can be circular , rectangle and other shapes with little change in performance. The tag antenna can be applied to frequency bands such as UHF or microwave, and the center frequency is 915MHz, and the chip adopts Monza4 as an example. The size of the tag antenna adopting the structure of the present invention is only 32*32*0.8mm ³ (0.1*0.1*0.002 λ ³ ), with high efficiency, omnidirectionality and wide applicability, it can be applied to other chips and operating frequencies with a simple adjustment. The invention provides a method for solving the problem of further miniaturization of the tag antenna, and is especially suitable for application in fields that require tag antenna miniaturization, omnidirectionality and special requirements on tag shape.

Description

A Small, Adjustable Shape Dual Loop UHF RFID Tag Antenna

technical field

The invention relates to a radio frequency identification electronic tag, especially a miniaturized, omnidirectional, and adjustable-shaped electronic tag. the

Background technique

Radio Frequency Identification (RFID) technology is a technology that conducts non-contact two-way data communication through radio frequency to identify targets. An RFID system usually consists of a reader and an electronic tag. The electronic tag is composed of a tag chip and a tag antenna. It exchanges data with the reader through electromagnetic waves, and has functions such as intelligent reading and writing and encrypted communication. The tag antenna is a vital part of the RFID system. The RFID system transmits and receives electromagnetic waves through the tag antenna, thereby realizing the identification of the electronic tag by the reader. the

RFID systems mainly work in low frequency, high frequency, ultra high frequency and microwave frequency bands. Among them, the radio frequency identification system working in the ultra-high frequency (UHF) frequency band has attracted extensive attention and research because of its advantages such as small size, long reading distance, and high data transmission rate. At present, most UHF tag antennas use a single-sided bent dipole structure, and optimize the bent shape by different methods to achieve the goals of reducing volume and improving performance. However, this tag antenna based on the bent dipole structure The volume is still large, and the performance is not good enough, and other principles and structures need to be adopted for further improvement. the

Contents of the invention

The purpose of the present invention is to introduce a near-field resonant parasitic structure derived from MNG (Mu-Negative) material—a split ring into the design of UHF tag antennas, and to design a design that is different from traditional bent dipole antennas. A new tag antenna structure, so as to achieve the goal of further miniaturizing the tag antenna and having higher performance. The tag antenna adopting the structure of the present invention is ultra-small in size, has high efficiency, omnidirectionality and wide applicability, and can be applied to other tag chips and operating frequencies only by simple adjustment, and can be used according to different application environments , to adjust the shape of the label, for example: circle, rectangle, ellipse, etc. The invention provides a method for solving the problem of further miniaturization of the tag antenna, and is especially suitable for application in fields that require tag antenna miniaturization, omnidirectionality and special requirements on tag shape. the

Technical scheme of the present invention is:

A small, adjustable-shaped double-ring UHF RFID tag antenna, characterized in that the tag antenna includes: a double-ring conductor structure, a substrate, and an RFID tag chip;

The RFID tag chip is connected to the inner ring in the double ring conductor structure. the

The antenna adopts a double loop conductor structure, and the inner loop and the outer loop can be located on the same side or the front and back sides of the substrate. the

The inner ring of the double ring conductor structure is connected with the RFID tag chip to form a closed ring. the

The outer ring of the double-ring conductor structure surrounds the inner ring, and there is an inverted Z-shaped or Z-shaped notch on the outer ring. the

The inner ring and the outer ring of the double ring conductor structure may be in the form of a rectangle, a circle or the like. the

The position of the closed ring formed by the RFID tag chip and the inner ring on the substrate can be adjusted. the

The beneficial effects of the present invention are:

By introducing a split ring structure derived from MNG material near the patch magnetic dipole that is much smaller than the working wavelength, a small, adjustable shape double-loop UHF RFID tag antenna structure is proposed, so that the total volume of the tag antenna can be obtained. If it is further reduced, it not only has better performance, but also can adjust the shape of the label according to different needs. There is no direct electrical connection between the inner ring and the outer ring of the double ring structure, and the current is transmitted through coupling. By adjusting the length and line width of each side of the small patch magnetic dipole, that is, the inner ring and outer ring structure, and the inverted Z-shaped Or the size of each side of the Z-shaped notch can adjust the real and imaginary parts of the input impedance of the tag antenna to achieve conjugate matching with the tag chip. Taking the Monza4 chip as an example, the required input impedance of the tag antenna is 11 +j143Ω. the

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. the

Fig. 1 is a three-dimensional structural schematic diagram of a preferred embodiment (rectangular ring) of the present invention when it works at 915 MHz. the

Fig. 2 is a schematic diagram of a double-ring structure of a preferred embodiment (rectangular ring) of the present invention working at 915MHz. the

Fig. 3 is a simulation diagram of the S11 parameter of the preferred embodiment (rectangular ring) of the present invention when it works at 915MHz. the

Fig. 4 is a simulation diagram of the input impedance (ideally lossless) of the preferred embodiment (rectangular ring) of the present invention when it works at 915MHz. the

Fig. 5 is a simulation diagram of the input impedance (copper) of the preferred embodiment (rectangular ring) of the present invention when it works at 915MHz. the

Fig. 6 is a simulation diagram of the gain (ideal lossless) of the preferred embodiment (rectangular ring) of the present invention working at 915MHz. the

Fig. 7 is a three-dimensional schematic diagram of the preferred embodiment (circular ring) of the present invention when it works at 915MHz. the

Fig. 8 is a schematic diagram of a double-ring structure of a preferred embodiment (circular ring) of the present invention working at 915 MHz. the

Fig. 9 is a simulation diagram of S11 parameters of the preferred embodiment (circular ring) of the present invention when it works at 915MHz. the

Fig. 10 is a simulation diagram of the input impedance (ideally lossless) of the preferred embodiment (circular ring) of the present invention working at 915MHz. the

Fig. 11 is a simulation diagram of the input impedance (copper) of the preferred embodiment (circular ring) of the present invention when it works at 915MHz. the

Fig. 12 is a simulation diagram of the gain (ideally lossless) of the preferred embodiment (circular ring) of the present invention when it works at 915MHz. the

Fig. 13 is the profile comparison diagram of a preferred embodiment of a rectangular ring form and a preferred embodiment of a circular ring form when the present invention works at 915MHz

In the figure, 1. inner ring, 2. outer ring with inverted Z-shaped notch, 3. substrate, 4. RFID tag chip. the

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. the

It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. the

As shown in Figures 1 and 2, it is a schematic structural diagram of a preferred embodiment in the form of a rectangular loop of a small, adjustable shape dual-loop UHF RFID tag antenna of the present invention. This embodiment includes a rectangular substrate 3 (ε _r =4.4, μ _r =1), an RFID tag chip 4 (a Monza4 chip is used in this embodiment, and its impedance is 11-j143Ω when the operating frequency is 915MHz), and an inner ring 1 , the outer ring 2 with an inverted Z-shaped notch, by adjusting the dielectric constant and thickness of the substrate 3, the inner ring 1, the outer ring 2 and the size of the notch, the input impedance and operating frequency of the tag antenna can be changed to meet the required parameters, the tag antenna in this embodiment is a small cube of 32*32*0.8mm ³ (0.1*0.1*0.002λ ³ ).

As shown in Figure 3, it is the S11 parameter simulation figure of the preferred embodiment of a kind of rectangular ring form of the present invention, has provided the S11 parameter when adopting ideal conductor and copper as antenna material in the figure, as seen from the figure, adopts copper as Compared with the ideal conductor, the S11 parameter of the material is slightly lower in resonance frequency, but the overall performance is basically the same, and the -10dB bandwidth is about 5MHz, which meets the standards of China, Japan and other countries and regions. the

As shown in Figure 4, it is an input impedance (ideal lossless) simulation diagram of a preferred embodiment of a rectangular ring form of the present invention. It can be seen from the figure that the input impedance of the tag antenna at the designed 915MHz frequency is 10.9+143.5 Ω, forming a good conjugate match with the 11-143Ω of the tag chip. the

As shown in Figure 5, it is an input impedance (copper) simulation diagram of a preferred embodiment of a rectangular ring form of the present invention. It can be seen from the figure that the input impedance of the tag antenna at the designed 915MHz frequency is 14.3+145.6Ω, The result is slightly higher than the ideal lossless case but the difference is not significant. the

As shown in Figure 6, it is a gain (ideal lossless) simulation diagram of a preferred embodiment of a rectangular ring form of the present invention. The XOZ plane and the XOY plane are shown in Figure 2, as can be seen from the figure, which is different from the traditional dipole The sub-type tag antenna, the radiation of the tag antenna in the present invention has good omnidirectionality, and the difference between the maximum gain and the minimum gain is only 4dB. the

As shown in Figures 7 and 8, it is a structural schematic diagram of a preferred embodiment of a circular ring form of a small, adjustable shape dual-ring UHF RFID tag antenna of the present invention. This embodiment includes a circular substrate 3 (ε _r =4.4, μ _r =1), an RFID tag chip 4 (a Monza4 chip is used in this embodiment, and its impedance is 11-j143Ω when the operating frequency is 915MHz), an inner ring 1. The outer ring 2 has an inverted Z-shaped notch. By adjusting the dielectric constant and thickness of the substrate 3, the inner ring 1, the outer ring 2 and the size of the gap, the input impedance and operating frequency of the tag antenna can be changed to meet the required parameters, the tag antenna in this embodiment is a small cylinder with a diameter of 36mm (0.1λ) and a thickness of 0.8mm (0.002λ).

As shown in Figure 9, it is the S11 parameter simulation figure of the preferred embodiment of a kind of circular ring form of the present invention, has provided the S11 parameter when adopting ideal conductor and copper as antenna material in the figure, as seen from the figure, adopts copper Compared with the ideal conductor, the S11 parameter of the material is slightly lower than that of the ideal conductor, but the overall performance is basically the same. The -10dB bandwidth is about 5MHz, which meets the standards of China, Japan and other countries and regions. the

As shown in Figure 10, it is an input impedance (ideal lossless) simulation diagram of a preferred embodiment of a circular ring form of the present invention. It can be seen from the figure that the input impedance of the tag antenna at the designed 915MHz frequency is 10.3+ 144.2Ω, forming a good conjugate match with the 11-143Ω of the tag chip. the

As shown in Figure 11, it is an input impedance (copper) simulation diagram of a preferred embodiment of a circular ring form of the present invention. It can be seen from the figure that the input impedance of the tag antenna at the designed frequency of 915MHz is 14.8+150.4Ω , which is slightly higher than the result of the ideal lossless case but the difference is not significant. the

As shown in Figure 12, it is a gain (ideal lossless) simulation diagram of a preferred embodiment of a circular ring form of the present invention. The XOZ plane and the XOY plane are shown in Figure 8, as can be seen from the figure, which is different from the traditional couple For the pole-type tag antenna, the radiation of the tag antenna in the present invention has good omnidirectionality, the difference between the maximum value and the minimum value of the gain is only 4.9dB, and the overall radiation characteristics are basically the same as those of the preferred embodiment in the form of a rectangular ring. the

As shown in Figure 13, it is a comparison of the appearance of a preferred embodiment of a rectangular ring form and a preferred embodiment of a circular ring form of the present invention. As can be seen from the figure, the preferred embodiment of the circular ring form and the rectangular ring form The size of the preferred embodiment is not much different, and the performance is basically the same, which shows that the shape of the tag antenna according to the present invention can be adjusted conveniently according to different application environments, such as rectangle, circle, and ellipse, with little change in performance. wait. the

The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent transformation made using the content of the present invention, or the direct/indirect application of the present invention to specific equipment or other related technical fields shall be accepted. included in the scope of patent protection of the present invention. the

Claims (6)

1. the Crossed Circle ultra-high frequency RFID label antenna of small-sized a, adjustable shape is characterized in that described label antenna comprises: Crossed Circle conductor structure, substrate, RFID label chip;

Described RFID label chip links to each other with interior ring in the described Crossed Circle conductor structure.

2. label antenna according to claim 1 is characterized in that, described antenna adopts the Crossed Circle conductor structure, and interior ring and outer shroud can be positioned at described substrate with one side or coplanar not.

3. label antenna according to claim 1 and 2 is characterized in that, the interior ring of described Crossed Circle conductor structure links to each other with described RFID label chip, constitutes a closed hoop.

4. label antenna according to claim 1 and 2 is characterized in that, ring in the outer shroud of described Crossed Circle conductor structure surrounds has down Z-shaped or Z-shaped breach on the outer shroud.

5. label antenna according to claim 1 and 2 is characterized in that, the interior ring of described Crossed Circle conductor structure and outer shroud can be annular form such as rectangle, circle.

6. label antenna according to claim 1 is characterized in that, the position of closed hoop on described substrate that described RFID label chip and interior ring are constituted can be adjusted.

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