TWI521442B - Electromagnetic bandgap structured radio frequency identification tags - Google Patents

Description

Radio frequency tag with electromagnetic energy gap structure

The invention relates to a radio frequency tag, in particular to a metal object by using a periodic electromagnetic energy gap structure to effectively shield a metal material and improve a reading distance and a reading rate.

According to Radio Frequency Identification (FRID), a communication technology that automatically identifies a target through wireless signals and reads and writes data related to the target without establishing a mechanical or optical contact between the system and a specific target. The RFID tag is the key to the current RFID technology. It can store a certain amount of information and has information processing functions. The read/write device can exchange information with the tag at a certain data transmission rate through radio signals. Because RFID tags have unique electronic codes, small size, long life, low price and data portability, they are now widely used in animal wafers, building access control, product security and anti-counterfeiting.

The radio frequency identification tag can be divided into low frequency (LF), intermediate frequency (MF), high frequency (HF), ultra high frequency (VHF), ultra high frequency (UHF) and microwave (SHF) according to the frequency domain of electromagnetic waves, among which Ultra-High Frequency (UHF) transmission distance can reach more than 5 meters, and the speed is fast and can overcome the limitation of high frequency (HF) reader and reading distance in the past, so it is more in line with market demand. It is widely used.

However, the material quality, stacking method, and surrounding environment of the UHF RFID tag may reduce the reading distance, especially when the antenna is in contact with the metal object, because the incident wave is incident on the metal surface, the phase of the reflected wave is due to the metal. The surface is changed by 180°, which seriously affects the antenna gain and the radiation frequency, so that the directivity, the front wave and the return wave ratio and the radiation field shape are affected. To solve the above situation, the industry is also actively developing a labeling technology that can resist metal interference.

At present, the RFID tags for metal objects are mostly covered by inverted-F antennas, thickened antennas and metal objects, or special materials to shield metal objects, such as the Republic of China Announcement No. I310160 An RFID tag is disclosed, which is formed on a film to form a planar inverted F-type antenna, and is adhered to the radiation element, the jumper, and the power supply portion of the inverted-F antenna by a metal protruding state. Radio frequency identification tags can be placed close to metal objects for wireless communication. However, although the above structure can solve the problem of metal interference, the production steps are complicated and unfavorable for mass production.

The distance between the thickened antenna and the metal object tends to increase the volume and thickness of the RFID tag, so it cannot cope with the trend of light, thin, short and small development of the current product. In addition, the use of absorbing materials to reduce electromagnetic noise or reflect electromagnetic waves to block the outside of the system to maintain normal operation of the system is also another countermeasure to solve metal interference, such as the Republic of China Public Publication No. 200949710, which discloses a UHF RF tag. The absorbing material is mainly composed of a polymer material foam layer and a composite material magnetic layer, and is disposed between the label and the metal layer and the non-metal layer, so that the RF tag can be better read when it is close to the metal object. The distance is taken, but in order to reduce the size of the radio frequency tag and reduce the weight, the absorbing material is made of a conductive polymer composite material, so that the cost is greatly increased.

The reason is that the inventors have the determination to use the expensive absorbing materials or the complicated antenna structure in the conventional use of radio frequency identification tags, which cause difficulties in production and cost reduction, and the determination to improve the germination and to solve the problem. After many years of research and design experience and knowledge in related fields, we have conducted various discussions. After several trials and improvements, we have developed a radio frequency identification tag for metal objects.

The object of the present invention is to suppress the surface wave by attaching an antenna to an electromagnetic energy gap substrate having a periodic planar structure, thereby effectively shielding metal object interference, and combining the metal layer to directly apply the radio frequency tag. For metal objects, and maintain the required transmission power, so that the recognition distance is increased.

Another object of the present invention is to make the fabricated radio frequency tag flexible, and to reduce the manufacturing cost and improve the industrial applicability by using a simple structure and a process.

In order to achieve the foregoing, the present invention provides a radio frequency tag having an electromagnetic energy gap structure, the structure comprising: a first substrate, the first substrate is composed of a soft dielectric material, and forms an electromagnetic energy gap surface (Electromagnetic Bandgap, EBG) and a Perfect Electric Conductor (PEC), the electromagnetic energy gap surface is formed on the first substrate to form a plurality of planar periodic arrangement structures for controlling electromagnetic waves by a bandgap phenomenon; a metal layer, The metal layer is combined with the complete electrical conductor surface of the first substrate; at least one antenna is attached to the electromagnetic energy gap surface of the first substrate; and a second substrate is formed of a soft dielectric material and placed on the first Between a substrate and an antenna; and a wireless identification transceiver chip, the wireless identification transceiver chip is connected to the antenna and can be used for writing and reading information by the wireless signal.

In a preferred embodiment of the invention, the flexible dielectric material is a polyester (Polyethylene Terephthalate, PET) copper foil.

In a preferred embodiment of the invention, the first substrate has a thickness of 1.6 mm.

In a preferred embodiment of the invention, the antenna is an ultra high frequency band (UHF) antenna.

Thereby, an electromagnetic energy gap absorbing material with a periodic planar structure is placed on the first substrate, and the first substrate has a bottom surface of the complete electrical conductor, and then the antenna is attached to the electromagnetic energy gap surface and is disposed between the two a second substrate, the antenna is fed with electromagnetic waves to the electromagnetic energy gap of the periodic planar structure, and the individual planar structures are combined with the metal layer to form an Artificial Magnetic Conductor (AMC), and the broadband is provided in the UHF band. The characteristic of the stop band is to achieve the backscattering electromagnetic wave effect, and the electromagnetic wave reflection can be used to transmit the data of the radio frequency tag and the reader, and the artificial magnetic conductor formed by the electromagnetic energy gap shields the influence of the metal object on the radio frequency tag.

In order to make the reviewers aware of the techniques, means and effects of the present invention in order to achieve the objectives, a preferred embodiment will be described in detail with reference to the drawings.

First, referring to FIG. 1 and in conjunction with FIG. 2, the radio frequency tag 1 includes a first substrate 11 which is made of a soft dielectric material. In the preferred embodiment of the present invention, the softness The dielectric material is a polyester (Polyethylene Terephthalate, PET) copper foil and has a thickness of 1.6 mm, and forms a plurality of electromagnetic energy gaps 12 (EBG) having a planar periodic arrangement and a complete electrical conductor surface 13 (Perfect Electric Conductor, PEC); a metal layer 14 bonded to the complete electrical conductor face 13 of the first substrate 11; at least one antenna 15, which in the present embodiment is a UHF band ( An antenna of 868 MHz to 950 MHz is etched or printed on the electromagnetic energy gap surface 12 of the first substrate 11; a second substrate 16 is formed of a flexible dielectric material. In a preferred embodiment of the present invention, The flexible dielectric material is Polyethylene Terephthalate (PET) and is placed between the antenna 15 and the electromagnetic energy gap surface 12; Identifying line transceiver chip 17, the RFID transceiver 17 is connected to the wafer end 15 of the antenna feed, the antenna 15 can receive the electromagnetic wave transmission, and a wireless signal to write and read information.

Since the radio frequency tag 1 is attached to the metal object, the incident wave is incident on the surface of the metal object, and the phase of the reflected wave is affected by the change of the metal surface, so that the gain and the radiation frequency of the antenna 15 of the radio frequency tag 1 are affected, and the full electric conductor surface is affected. 13 is a reflective material, and the reflected wave has a phase change of 180° with respect to the incident wave. Therefore, the present invention utilizes the characteristic of the electromagnetic energy gap with a stop band, so that the phase change of the reflected wave exhibits a continuous change of -180° to 180°. The phase change of the reflected wave of 915 MHz is set between 90 ° ± 45 ° to reduce the reflection loss.

Next, please refer to FIG. 2 and in conjunction with FIG. 3, the present invention adopts an electromagnetic energy gap absorbing material with a periodic planar structure, and is placed on the first substrate 11, and the bottom surface of the first substrate 11 is formed. A complete electrical conductor surface 13, and then a second substrate 16 is placed on the electromagnetic energy gap surface 12, and the antenna 15 and the wireless identification transceiver chip 17 are attached, so that the antenna 15 feeds electromagnetic waves to the electromagnetic energy gap surface of the periodic planar structure. 12, and the individual planar structures are combined with the metal layer 14 to form an Artificial Magnetic Conductor (AMC), and the UHF frequency band is provided with a wide-band stop band characteristic to achieve backscattering effect, and electromagnetic waves can be utilized. The reflection transmits data of the radio frequency tag 1 and the reader (not shown), and the artificial magnetic conductor formed by the electromagnetic energy gap 12 shields the influence of the metal object on the radio frequency tag 1.

Next, please refer to FIG. 4, which is a transmission power coefficient graph of the present invention. The radio frequency tag 1 attaches the antenna 15 to the electromagnetic energy gap surface 13 having a periodic planar structure (refer to FIG. 3). After the measurement, it is found that the antenna 15 has the best transmission power coefficient frequency close to 915 MHz, and when the radio frequency tag 1 is placed on the surface of the metal object, the wireless identification transceiver chip 17 and the reader (not shown) are effectively read. The distance is 5.0m, and the result shows that the radio frequency tag 1 can greatly improve the reading distance and achieve the purpose of resisting metal objects, so that the developed radio frequency tag 1 can be widely used in any metal (such as bicycle) or non- Metal objects (refer to Figure 5) to facilitate long-distance tracking and inspection of goods, and further collect information to control the movement of goods. Therefore, the radio frequency tag 1 of the present invention obviously has the following advantages: 1. The present invention A substrate 11 is provided with a periodic planar structure electromagnetic energy gap surface 12, and the bottom surface of the first substrate 11 is formed into a complete electrical conductor surface. 13, a metal layer 14 is combined to form an artificial magnetic conductor, thereby achieving the function of backscattering electromagnetic waves, and effectively shielding the influence of the metal object on the radio frequency tag 1, and the radio frequency tag 1 is combined with a metal layer 14, The metal layer 14 can be attached to the surface of the product of any material, so that the radio frequency tag 1 does not have to worry about the interference of the metal object. 2. The present invention uses a soft dielectric material to form the first substrate 11, and forms an electromagnetic energy gap surface 12 on the first substrate 11 to shield metal interference without thickening the distance between the antenna 15 and the metal object or adding special materials to shield The metal object allows the radio frequency tag 1 to be flexible, and can be applied to various materials and shapes to increase industrial applicability. 3. The radio frequency tag 1 of the radio frequency tag 1 of the present invention can be fabricated by etching or printing technology, and can simultaneously complete the fabrication of the antenna 15, and has the advantages of simple process and reduced manufacturing cost.

In summary, the present invention attaches the antenna to the electromagnetic energy gap surface of the periodic planar structure, and can effectively shield the metal material, improve the reading distance and the reading rate, and is more progressive and practical than the conventional wireless radio frequency tag. The invention is in accordance with the requirements of the invention patent, and the patent application is filed according to the law, but the above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and the changes are not deviated from the spirit of the present invention. Modifications are covered by the scope of the invention.

this invention︰
1‧‧‧ Radio Frequency Label 11‧‧‧ First Substrate 12‧‧‧ Electromagnetic Energy Gap 13‧‧‧Complete Electrical Conductor Surface 14‧‧‧Metal Layer 15‧‧‧Antenna 16‧‧‧Second Substrate 17‧‧ ‧Wireless identification transceiver chip

Figure 1 is a perspective exploded view of the present invention. Figure 2 is a cross-sectional view of the present invention. Figure 3 is a perspective view of the present invention. Fig. 4 is a graph showing the transmission power coefficient of the present invention. Fig. 5 is a schematic view showing the state of use of the present invention.

1‧‧‧RF tags

11‧‧‧First substrate

12‧‧‧Electromagnetic energy gap

13‧‧‧Complete electrical conductor surface

14‧‧‧metal layer

15‧‧‧Antenna

16‧‧‧second substrate

17‧‧‧Wireless identification transceiver chip

Claims (4)

A radio frequency tag having an electromagnetic energy gap structure, comprising: a first substrate, the first substrate is made of a soft dielectric material, and comprises an electromagnetic energy gap surface (EBG) and a complete electric conductor surface (Perfect Electric Conductor) a metal layer bonded to the complete electrical conductor surface of the first substrate; at least one antenna attached to the electromagnetic energy gap surface of the first substrate; a second substrate, the second substrate being a soft dielectric The material is formed between the first substrate and the antenna; and a wireless identification transceiver chip for writing and reading information to and from the wireless signal. A radio frequency tag having an electromagnetic energy gap structure according to claim 1, wherein the flexible dielectric material is a polyester (Polyethylene Terephthalate, PET) copper foil. A radio frequency tag having an electromagnetic energy gap structure according to claim 1, wherein the first substrate has a thickness of 1.6 mm. A radio frequency tag having an electromagnetic energy gap structure according to claim 1, wherein the antenna is an ultra high frequency band antenna (UHF).