CN112151935A - A liquid-insensitive UHF RFID flexible tag antenna - Google Patents

Abstract

Translated fromChinese

本发明涉及一种液体不敏感超高频RFID柔性标签天线，其包括折叠偶极子臂、多环路匹配结构、射频识别芯片以及柔性介质基板。所述折叠偶极子臂与多环路匹配结构通过机械雕刻覆铜的柔性介质基板形成，在中心放置射频识别芯片。由于多环路匹配结构的阻抗调节作用，使得标签天线在空气中与射频芯片的阻抗匹配良好，并且在液体表面上工作时阻抗失配的程度也大大减小。此外，调节偶极子臂可以显著的提升标签天线具有较高的增益，使得其阅读距离在空气中以及液体表面分别可以达到8米和5.6米。本发明专利成本低、易于制造，解决了传统RFID标签天线不能工作于液体表面的难题。同时，柔性介质基板可以使标签天线与任意瓶体或者罐体进行共形，使其能够方便的与被识别物体进行配套。

The invention relates to a liquid-insensitive ultra-high frequency RFID flexible label antenna, which comprises a folded dipole arm, a multi-loop matching structure, a radio frequency identification chip and a flexible medium substrate. The folded dipole arm and the multi-loop matching structure are formed by mechanically engraving a copper-clad flexible dielectric substrate, and a radio frequency identification chip is placed in the center. Due to the impedance adjustment effect of the multi-loop matching structure, the impedance matching between the tag antenna and the radio frequency chip is good in the air, and the degree of impedance mismatch is also greatly reduced when working on the liquid surface. In addition, adjusting the dipole arm can significantly improve the gain of the tag antenna, so that its reading distance in air and liquid surface can reach 8 meters and 5.6 meters, respectively. The invention has low patent cost and is easy to manufacture, and solves the problem that the traditional RFID tag antenna cannot work on the liquid surface. At the same time, the flexible medium substrate can make the label antenna conform to any bottle or tank, so that it can be easily matched with the identified object.

Description

Translated fromChinese

一种液体不敏感超高频RFID柔性标签天线A liquid-insensitive UHF RFID flexible tag antenna

技术领域technical field

本发明涉及无线射频识别技术领域，具体地说，涉及一种液体不敏感超高频RFID柔性标签天线。The invention relates to the technical field of radio frequency identification, in particular to a liquid-insensitive ultra-high frequency RFID flexible label antenna.

背景技术Background technique

射频识别即RFID（Radio Frequency Identification）技术是一种通过无线电讯号对特定物体内的存储芯片进行读写，而无需在识别系统与特定物体中建立机械或者光学接触的技术。由于RFID系统在读写的过程中具有穿透性强、可多次读写、数据的记忆容量大，无源标签成本低，体积小，使用方便，可靠性和寿命高等优点，在仓储，物流等方面获得了广泛的应用。常见的无源RFID频段有高频（HF:13.56MHz）以及超高频（UHF:860-960MHz）,由于超高频的RFID识别系统具有更远的阅读距离，因此超高频是目前RFID技术使用的主流频段。RFID (Radio Frequency Identification) technology is a technology that uses radio signals to read and write memory chips in a specific object without establishing mechanical or optical contact between the identification system and the specific object. Because the RFID system has the advantages of strong penetrability, multiple reading and writing, large data memory capacity, low cost of passive tags, small size, convenient use, high reliability and longevity in the process of reading and writing, it is widely used in warehousing, logistics, etc. etc. have been widely used. Common passive RFID frequency bands include high frequency (HF: 13.56MHz) and ultra-high frequency (UHF: 860-960MHz). Because the ultra-high frequency RFID identification system has a longer reading distance, ultra-high frequency is the current RFID technology. Mainstream frequency used.

RFID标签天线作为射频识别系统中重要的组件，其性能的好坏决定着整个识别系统的阅读能力。然而，随着RFID应用环境的多样化，其自身也暴露出一定短板。诸如当RFID标签天线在贴附于装有液体的瓶体外，由于液体的作用会使标签天线自身的阻抗值发生改变，从而使其与射频芯片的阻抗值不匹配。通常，标签天线在设计过程中需要将阻抗值与射频芯片的阻抗值达到共轭匹配，以实现能量传输的最大化。而当标签天线与射频芯片的阻抗发生失配的情况时，标签天线辐射的能量过低甚至天线本身根本无法谐振，即发生了标签天线无法被系统读取的情况。因此，设计一款能够同时在液体环境中与空气环境中工作良好的超高频RIFD标签天线一直是RFID系统中重点研究的问题。The RFID tag antenna is an important component in the radio frequency identification system, and its performance determines the reading ability of the entire identification system. However, with the diversification of RFID application environment, it also exposes certain shortcomings. For example, when the RFID tag antenna is attached to the outside of the bottle containing liquid, the impedance value of the tag antenna itself will change due to the action of the liquid, so that it does not match the impedance value of the radio frequency chip. Usually, the impedance value of the tag antenna needs to be conjugated with the impedance value of the RF chip during the design process to maximize energy transmission. When the impedance of the tag antenna and the RF chip is mismatched, the energy radiated by the tag antenna is too low or even the antenna itself cannot resonate at all, that is, the tag antenna cannot be read by the system. Therefore, designing a UHF RIFD tag antenna that can work well in both liquid and air environments has always been a key research problem in RFID systems.

发明内容SUMMARY OF THE INVENTION

本发明解决的技术问题是如何使超高频RFID标签天线同时在液体表面与空气中保持良好的工作性能。The technical problem solved by the present invention is how to make the ultra-high frequency RFID tag antenna maintain good working performance on the liquid surface and in the air at the same time.

为了解决上述技术问题，本发明提供了一种工作于超高频频段，在空气与液体表面均工作良好的RFID柔性标签天线。所采用的技术方案是：一种偶极子标签天线，包括折叠偶极子臂、多环路匹配结构、柔性介质基板、射频识别芯片。折叠偶极子臂与多环路匹配结构均为铜质导体相互连接，其覆于柔性介质基板上方，中心连接射频识别芯片。In order to solve the above technical problems, the present invention provides an RFID flexible tag antenna that works in the ultra-high frequency band and works well on both air and liquid surfaces. The adopted technical scheme is: a dipole tag antenna, comprising a folded dipole arm, a multi-loop matching structure, a flexible medium substrate, and a radio frequency identification chip. Both the folded dipole arm and the multi-loop matching structure are connected with each other by copper conductors, which are covered above the flexible dielectric substrate, and the center is connected to the radio frequency identification chip.

所述的折叠偶极子臂应分为左折叠偶极子臂和右折叠偶极子，且左右折叠偶极子臂的长度相同。The folded dipole arm should be divided into a left folded dipole arm and a right folded dipole arm, and the left and right folded dipole arms have the same length.

所述的折叠偶极子臂的长度总和应为工作频段所对应的频率的四分之一。The sum of the lengths of the folded dipole arms should be a quarter of the frequency corresponding to the working frequency band.

所述的多环路匹配结构每一环的线宽由内到外应依次递增，以第一环路为最宽。The line width of each loop of the multi-loop matching structure should increase sequentially from the inside to the outside, with the first loop being the widest.

优选的，所述的多环路匹配结构至少应有两个，以三环路匹配结构为最佳。Preferably, there should be at least two multi-loop matching structures, and a three-loop matching structure is the best.

优选的，所述的柔性介质基板可由其他类型的柔性基板所替代，以聚酰亚胺材质的柔性介质基板为最优。Preferably, the flexible dielectric substrate can be replaced by other types of flexible substrates, and a flexible dielectric substrate made of polyimide material is the best.

本发明的有益效果：本发明采用了多环路匹配结构使标签天线对外界的环境改变而引起的阻抗值的变化程度大大减小，可以在空气以及液体表面工作良好。Beneficial effects of the present invention: The present invention adopts a multi-loop matching structure to greatly reduce the change of the impedance value of the tag antenna caused by the change of the external environment, and can work well on air and liquid surfaces.

本发明采用折叠偶极子臂作为标签天线的辐射体，在显著减小了标签天线尺寸的同时保持了较高的增益，可以使其在915MHz频率下在空气和液体表面的最大读取距离分别为8m和5.6m。The invention adopts the folded dipole arm as the radiator of the tag antenna, which significantly reduces the size of the tag antenna while maintaining a high gain, so that the maximum reading distances on the air and liquid surfaces at the frequency of 915MHz can be respectively 8m and 5.6m.

附图说明Description of drawings

图1是本发明的结构及工作示意图；Fig. 1 is the structure and working schematic diagram of the present invention;

图2是本发明的阻抗带宽图；Fig. 2 is the impedance bandwidth diagram of the present invention;

图3是本发明在915MHz时工作于液体表面上的增益方向图；Fig. 3 is the gain pattern that the present invention works on the liquid surface when 915MHz;

图4是本发明在915MHz时工作于空气中的增益方向图；Fig. 4 is the gain pattern that the present invention works in the air when 915MHz;

图1至图4中的附图标记说明：1-折叠偶极子臂；11-左折叠偶极子臂；12-右折叠偶极子臂；2-多环路匹配结构；21-第一环路匹配结构；22-第二环路匹配结构；23-第三环路匹配结构；3-射频识别芯片；4-柔性介质基板。Explanation of reference numerals in Figures 1 to 4: 1-folded dipole arm; 11-left folded dipole arm; 12-right folded dipole arm; 2-multi-loop matching structure; 21-first loop matching structure; 22-second loop matching structure; 23-third loop matching structure; 3-radio frequency identification chip; 4-flexible dielectric substrate.

具体实施方式Detailed ways

下面结合附图，具体实施方式对本发明做进一步的详细说明，并不是把本发明的实施范围限制于此。The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of implementation of the present invention is not limited thereto.

如图1所示，本发明公开了一种液体不敏感超高频RFID柔性标签天线，包括：1-折叠偶极子臂；11-左折叠偶极子臂；12-右折叠偶极子臂；2-多环路匹配结构；21-第一环路匹配结构；22-第二环路匹配结构；23-第三环路匹配结构；3-射频识别芯片；4-柔性介质基板。标签天线顶层由机械雕刻覆铜介质基板形成折叠偶极子臂以及多环路匹配结构，折叠偶极子臂为标签天线提供辐射体，折叠偶极子臂为标签天线与射频识别芯片提供匹配电路。射频识别芯片通过熔融焊锡将引脚与标签天线连接，用以读写数据。标签天线底层为柔性聚酰亚胺介质基板，此处统称为柔性介质基板或介质基板，本领域技术人员应可理解，制造商可能会将同一组件不加以区分。As shown in Figure 1, the present invention discloses a liquid-insensitive UHF RFID flexible tag antenna, comprising: 1-folded dipole arm; 11-left folded dipole arm; 12-right folded dipole arm 2-Multi-loop matching structure; 21-First loop matching structure; 22-Second loop matching structure; 23-Third loop matching structure; 3-Radio frequency identification chip; 4-Flexible dielectric substrate. The top layer of the tag antenna is made of a mechanically engraved copper-clad dielectric substrate to form a folded dipole arm and a multi-loop matching structure. The folded dipole arm provides a radiator for the tag antenna, and the folded dipole arm provides a matching circuit for the tag antenna and the RFID chip. . The RFID chip connects the pins to the tag antenna through molten solder to read and write data. The bottom layer of the tag antenna is a flexible polyimide dielectric substrate, which is collectively referred to as a flexible dielectric substrate or a dielectric substrate. Those skilled in the art should understand that the same component may not be distinguished by the manufacturer.

进一步的，为了提升标签天线的阻抗带宽以及减小外界环境对标签天线阻抗值的影响，可以通过增加匹配环路方式实现此目的。由于越靠近外层的匹配环路具有更大的电长度即电感量，因而越靠近外侧的匹配环路具有更窄的线宽即更小的电容量。为了保证加工时有一定的加工余量并且减小标签天线的尺寸，匹配环路的个数以三组为最优，同时其线宽值应控制在0.2mm~0.5mm内。Further, in order to increase the impedance bandwidth of the tag antenna and reduce the influence of the external environment on the impedance value of the tag antenna, this purpose can be achieved by adding a matching loop. Since the matching loop closer to the outer layer has a larger electrical length, that is, inductance, the matching loop closer to the outer layer has a narrower line width, that is, a smaller capacitance. In order to ensure a certain machining allowance during processing and reduce the size of the tag antenna, the number of matching loops is optimal in three groups, and the line width value should be controlled within 0.2mm~0.5mm.

进一步的，折叠偶极子臂的总长度应约为22mm，为了保证标签天线的增益同时减小其体积，相邻弯折的臂之间的距离应在2mm以上。Further, the total length of the folded dipole arms should be about 22mm. In order to ensure the gain of the tag antenna and reduce its volume, the distance between adjacent folded arms should be more than 2mm.

图2为本发明功率反射系数

图。标签天线的工作带宽可以等同的表示为功率波反射系数小于-6 dB部分的带宽。在已知射频识别芯片的输入阻抗值

以及标签天线的输入阻抗值

，可以通过公式计算出功率反射系数的值，其中

代表标签天线输入阻抗值的共轭。计算公式如下：Fig. 2 is the power reflection coefficient of the present invention

picture. The working bandwidth of the tag antenna can be equivalently expressed as the bandwidth of the part where the reflection coefficient of the power wave is less than -6 dB. The input impedance value of the known RFID chip

and the input impedance value of the tag antenna

, the value of the power reflection coefficient can be calculated by the formula, where

Represents the conjugate of the tag antenna input impedance value. Calculated as follows:

通过数值计算，实施例所能工作的带宽为863 MHz至963 MHz，覆盖了超高频射频识别的工作频段。Through numerical calculation, the working bandwidth of the embodiment is 863 MHz to 963 MHz, covering the working frequency band of ultra-high frequency radio frequency identification.

图3为本发明的增益方向图。通过仿真实验，标签天线在

以及

，即在正对标签天线的方向上的实际增益值可以达到-5.6 dBi。FIG. 3 is a gain pattern diagram of the present invention. Through simulation experiments, the tag antenna is

as well as

, that is, the actual gain value in the direction facing the tag antenna can reach -5.6 dBi.

在RFID系统中，在已知阅读器天线与标签天线之间的极化失配因子

，标签天线的实际增益

，标签天线的等效全向辐射功率EIPR，射频识别芯片的唤醒功率

以及标签天线在工作频率时所对应的波长，便可计算出标签天线所能被读取到的最大距离

。其中假定没有出现极化失配的情况，即极化失配因子为1，等效全向辐射功率在中国地区被标定为4 W, 射频识别芯片的唤醒功率为-20 dBm。计算公式如下：In an RFID system, the polarization mismatch factor between the reader antenna and the tag antenna is known

, the actual gain of the tag antenna

, the equivalent isotropic radiation power EIPR of the tag antenna, the wake-up power of the RFID chip

And the wavelength corresponding to the tag antenna at the operating frequency, the maximum distance that the tag antenna can read can be calculated

. It is assumed that there is no polarization mismatch, that is, the polarization mismatch factor is 1, the equivalent isotropic radiation power is calibrated to 4 W in China, and the wake-up power of the RFID chip is -20 dBm. Calculated as follows:

本发明经过测试，在915MHz工作频率下，本实施例的阅读距离可以在含有液体的瓶体表面达到5.6m，在空气环境中达到8m以上，均符合理论预期。The present invention has been tested and found that under the working frequency of 915MHz, the reading distance of this embodiment can reach 5.6m on the surface of the bottle body containing liquid, and more than 8m in the air environment, which are all in line with theoretical expectations.

以上所述的具体实施例，对本发明的目的、技术方案和有益效果进行了进一步的详细说明，所应理解的是，以上所说仅为本发明的具体实施例而已，并不用于限制本发明，所做的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. , any modification, equivalent replacement, improvement, etc. made shall be included within the protection scope of the present invention.

Claims (5)

1. A liquid insensitive ultrahigh frequency RFID flexible tag antenna comprises a folded dipole arm, a multi-loop matching structure, a radio frequency identification chip and a flexible medium substrate; the folded dipole arm and the multi-loop matching structure are mutually connected copper conductors, cover the upper part of the flexible medium substrate, and are provided with a radio frequency identification chip in the center;

the multi-loop matching structure at least comprises a matching loop, and the resonant frequency of the loop is the same as the working frequency of the tag antenna;

the flexible medium substrate needs to use a single-sided metal coating, and other metal materials except the radiation metal sheet cannot exist;

the flexible media substrate addresses its properties, such as: the thickness, dielectric constant and tangent loss angle are strictly controlled.

2. The liquid UHF RFID flexible insensitive tag antenna of claim 1, wherein: the working frequency Band of the tag antenna is located in ultra high frequency (UHF Band), namely 860-960 MHz.

3. The liquid UHF RFID flexible insensitive tag antenna of claim 1, wherein: the total length of the folded dipole arms should be one quarter of the wavelength corresponding to the operating frequency.

4. The liquid UHF RFID flexible insensitive tag antenna of claim 1, wherein: the resonant frequency of each loop of the multi-loop matching structure is the same as the working frequency of the tag antenna.

5. The liquid UHF RFID flexible insensitive tag antenna of claim 1, wherein: the radio frequency identification chip is a two-port device, and the distance between ports is larger than 1 mm.

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