TWI497817B - A UHF RFID tag antenna that can be attached to a metal surface - Google Patents

Description

UHF RFID tag antenna that can be attached to a metal surface

The present invention relates to a tag antenna, and more particularly to a UHF RFID tag antenna attachable to a metal surface.

RFID is the abbreviation of "Radio Frequency Identification", which is called "Radio Frequency Identification System" in Chinese (hereinafter referred to as Radio Frequency Identification System for RFID). In recent years, RFID has gradually set off a wave in various fields, such as procurement and distribution of goods, commercial trade, manufacturing and logistics, and even in some European and American highways, RFID is used to charge. RFID mainly provides information about individuals and animals. , goods and goods information. The tag itself does not need to provide additional power, but also has a high anti-fouling property. It can read and write and store a large amount of data (64 bits~2K bits or more), while a reader (Reader) can read every second. More than ten RFID tags (Tag), the reading speed is quite fast, the RFID operating principle is that there is a reader coupled with an RFID tag, and a radio wave emitted from the Reader is induced by the RFID tag to generate an induced current. The resulting current is sufficient to operate the wafer within the RFID tag and pass the signal back to the reader. In terms of power supply, it can be divided into active (active) and passive (Passive). The sensor that installs the independent power supply on the sensor is called active tag, and the sensor that supplies energy through the antenna is called passive tag. RFID has brought many applications to our lives, making our lives more convenient, and will gradually replace bar code functions in a few years, bringing revolutionary changes to the retail, logistics and global supply chains. And the shape of the antenna inside the RFID tag is dazzling, according to Different environments or requirements begin to have RFID tags with different antenna shapes.

However, the shape has a considerable influence on the characteristics of the antenna. At the same time, the frequency bands opened by each region and country are different. At present, the design of the antenna in the RFID tag is not only large in size but also narrow in bandwidth, so it cannot be applied to various countries, and the reflection of the RFID tag antenna The loss varies with the metal surface attached to different areas, making the RFID tag less directional. Accordingly, the inventors believe that such an RFID tag has a need for improvement.

In order to solve the deficiencies of the prior art, the inventors propose a UHF RFID tag antenna that can be attached to a metal surface, comprising: a substrate: a top surface of the substrate is provided with a first radiating metal surface and a wafer, and a bottom surface is provided with a A second radiating metal surface for attaching the metal surface, one metal piece is connected to the first radiating metal surface at one end, and the other end is connected to the second radiating metal surface.

The first radiating metal surface includes: two first radiating metal segments: each of the first radiating metal segments is disposed on a top surface of the substrate, and the first ends of the first radiating metal segments are respectively connected to the wafer.

a second radiant metal segment: each second radiant metal segment is disposed on a top surface of the substrate, and a root portion of each of the second radiant metal segments is respectively connected to a second end of the first radiant metal segment, and the second radiant metal segment and the second The second radiant metal segments collectively enclose a space, and the second radiant metal segments have a spacing between the second ends.

Two third radiating metal segments: each third radiating metal segment is disposed on the top surface of the substrate and located in the space, and the second third radiation The first ends of the metal segments are respectively connected to the second ends of the two first radiating metal segments or the root portions of the second second radiating metal segments.

By the configuration between the components of the present invention, the disadvantage of excessive size of the three-dimensional structure can be improved, and by the connection relationship between the two first to third radiating metal segments, the tag antenna can generate a double resonance frequency during operation, and By adjusting the lengths of the two first to third radiating metal segments, the dual resonant frequency is controlled to cover the UHF global frequency band, and the bandwidth is preferably about 112 MHz, so that the tag antenna can be applied to the frequency bands of various countries and their frequencies. Wide specification; and connecting the first radiating metal surface and the second radiating metal surface respectively by the metal piece to reduce the input impedance of the tag antenna and reducing the first radiating metal surface and the second radiating metal surface The capacitive effect between the two antennas is increased by the tag antenna. The return loss is greater than or equal to 3dB. The bandwidth ranges from 850 to 962MHz (112MHz) and covers the entire UHF band. The arrangement of the second radiating metal surface gives the tag antenna a good directional read range and a read range of 5.2 meters.

(A)‧‧‧ tag antenna

(1) ‧‧‧Substrate

(2) ‧‧‧first radiation metal surface

(21) ‧‧‧First radiant metal segment

(211) ‧‧‧ Space

(212) ‧‧‧First bend

(22) ‧‧‧second radiant metal segment

(221) ‧‧‧ spacing

(222)‧‧‧Second bend

(223)‧‧‧The first paragraph

(224)‧‧‧The second paragraph

(23) ‧‧‧third radiant metal segment

(231) ‧‧‧ Third bend

(232) ‧‧ Section III

(233) ‧ ‧ Section IV

(234) ‧ ‧ Section 5

(235)‧‧‧Section 6

(24)‧‧‧U-shaped radiant metal segments

(3) ‧‧‧second radiating metal surface

(4)‧‧‧metal pieces

(5) ‧‧‧ wafer

The first A diagram is a schematic diagram (I) of the components of the present invention.

The first B diagram is a schematic diagram of the components of the present invention (2).

The second picture A shows the result of measuring the return loss of the tag antenna under the condition that the tag antenna is provided with the U-shaped radiant metal segment.

The second B is a schematic diagram showing the result of measuring the resistance of the tag antenna under the condition that the tag antenna is provided with a U-shaped radiant metal segment.

The second C picture is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the tag antenna is provided with a U-shaped radiant metal segment.

The third A picture shows the tag antenna under the condition that there is no metal piece. Schematic diagram of the results of the resistance.

The third B is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the tag antenna is provided with or without a metal piece.

The fourth A diagram is a diagram showing the result of measuring the return loss of the tag antenna under the condition that the length value of the sixth segment is changed.

The fourth B is a diagram showing the result of measuring the resistance of the tag antenna under the condition that the length value of the sixth segment is changed.

The fourth C diagram is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the length value of the sixth segment is changed.

The fifth A is a schematic diagram showing the result of measuring the return loss of the tag antenna under the condition that the tag antenna changes the length value of the second segment.

Fig. 5B is a diagram showing the result of measuring the resistance of the tag antenna under the condition that the length value of the second segment is changed.

The fifth C diagram is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the length value of the second segment is changed.

Fig. 6A is a diagram showing the result of measuring the return loss to the tag antenna under the condition that the width value of the first segment is changed.

The sixth B diagram is a schematic diagram showing the result of measuring the resistance of the tag antenna under the condition that the width value of the first segment is changed.

The sixth C diagram is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the width value of the first segment is changed.

Fig. 7A is a diagram showing the result of measuring the return loss to the tag antenna under the condition that the width value of the second segment is changed.

The seventh B diagram is a diagram showing the result of measuring the resistance of the tag antenna under the condition that the width value of the second segment is changed.

The seventh C diagram is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition that the width value of the second segment is changed.

Figure 8A is a diagram showing the result of measuring the resistance of the tag antenna under the condition of changing the distance between the first radiating metal surface and the second radiating metal surface.

The eighth B is a schematic diagram showing the result of measuring the reactance of the tag antenna under the condition of changing the distance between the first radiating metal surface and the second radiating metal surface.

The ninth A is a schematic diagram showing the result of measuring the return loss of the tag antenna under the condition that the tag antenna is attached to the metal copper plate of different areas.

The ninth B-picture is a schematic diagram showing the result of measuring the resistance of the tag antenna under the condition that the tag antenna is attached to the metal copper plate of different areas.

The ninth C-picture tag antenna is attached to a metal copper plate of different areas, and the result of measuring the reactance of the tag antenna is shown.

The tenth figure is a schematic diagram of the result of the tag antenna operating at 900 MHz to measure the read range type.

The construction, features and embodiments of the present invention are illustrated by the accompanying drawings, which will be further understood by the review.

Referring to the first figure and the second figure, the present invention relates to a UHF RFID tag antenna attachable to a metal surface, the tag antenna (A) comprising: a substrate (1): the substrate (1) The top surface is provided with a first radiating metal surface (2) and a wafer (5), and the bottom surface is provided with a second radiating metal surface (3), and the second radiating metal surface (3) is attached to the surface of the metal object, The metal piece (4) is connected to the first radiating metal surface (2) at one end and to the second radiating metal surface (3) at the other end. Wherein the substrate (1) is preferably FR4 glass fiber The substrate is made to have the advantages of good insulation, high heat resistance, excellent corrosion resistance, and high mechanical strength.

And the first radiating metal surface (2) comprises: two first radiating metal segments (21): each of the first radiating metal segments (21) is respectively disposed on a top surface of the substrate (1), and each of the first radiating metal segments ( The first end of each of the first radiating metal segments (21) is preferably provided with two first bent portions (212) to reduce the first radiating metal surface (2). The area of the tag antenna (A) is further reduced. And the first radiant metal segment (21) is preferably implemented by: further forming a U-shaped radiant metal segment (24), the U-shaped radiant metal segment (24) spanning the two first radiant metal segments (21) The first end is to reduce the input impedance of the tag antenna (A).

a second radiant metal segment (22): each of the second radiant metal segments (22) is respectively disposed on a top surface of the substrate (1), and the root portions of each of the second radiant metal segments (22) are respectively connected to the first radiant metal segments The second end of (21), the two first radiating metal segments (21) and the two second radiating metal segments (22) collectively enclose a space (211), and the second radiating metal segments (22) are free ends. There is a spacing (221) between them. When the tag antenna (A) is in operation, the first radiating metal segment (21) and the second radiating metal segment (22) together generate a first resonant frequency.

The second radiant metal segment (22) may further be implemented such that the second radiant metal segment (22) has a second bent portion (222) and the second radiant metal segment (22) is directed from the root toward the free portion. The first segment (223) and the second segment (224) are sequentially defined, and the second segment (224) has a width ≧ the width of the first segment (223) to enable the tag antenna ( A) During operation, the distribution of the current generated by the second segment (224) can be made uniform, and the variation of the value of the first resonant frequency is small.

Two third radiating metal segments (23): Each of the third radiant metal segments (23) is respectively disposed on the top surface of the substrate (1) and located in the space (211), and the root portions of the second radiant metal segments (23) are respectively connected to the two first radiant metal segments (21) The second end or the root of the second second radiating metal segment (22). Therefore, when the tag antenna (A) is in operation, the first radiating metal segment (21) and the third radiating metal segment (23) together generate a second resonant frequency, and the first resonant frequency and the second The resonant frequency is collectively referred to as the dual resonant frequency.

The third radiant metal segment (23) can further be implemented such that the third radiant metal segment (23) is provided with three third bending portions (231), and the third radiant metal segment (23) is oriented from the root to the free portion. The third segment to the sixth segment (232-235) are sequentially defined, and the sixth segment (235) is adjacent to the second segment (224) and is parallel to the second segment (224). The free end of the sixth segment (235) is adjacent to the first segment (223), thereby reducing the area of the first radiating metal surface (2), and the volume of the tag antenna (A) can be further reduced.

By the configuration between the above components, the volume of the tag antenna (A) can be reduced, and the arrangement relationship between the first to third radiating metal segments (21, 22, 23) allows the tag antenna (A) The double resonance frequency is generated during operation, and the value of the double resonance frequency can be controlled by adjusting the lengths of the first to third radiation metal segments (21, 22, 23) to cover the UHF global frequency band. Preferably, the bandwidth of the first radiating metal segment (21) and the second radiating metal segment (22) is 103.5 (1±5%) mm, and may cooperate with the first When the length of the three-radiation metal segment (23) is preferably 105.5 (1±5%) mm, the tag antenna (A) has a better effect covering the UHF global frequency band, so that the tag antenna (A) can be applied to Frequency bands and their bandwidth specifications for each country.

The tag antenna (A) is further configured to reduce the input impedance of the tag antenna (A) and reduce the first radiating metal surface (2) and the second radiation by the configuration of the metal piece (4). The capacitance effect between the metal faces (3), the value of the double resonance frequency is increased, and the return loss value is 3 dB or more as a standard specification, and the bandwidth is in the range of 850 to 962 MHz (112 MHz), which covers the entire UHF band, and the The metal piece (4) is preferably disposed at the second end of the first radiant metal segment (21) such that the metal piece (4) is adjacent to the first to third radiant metal segments (21~23) and can be lifted The effect of the metal sheet (4); the label antenna (A) is further matched with the configuration of the second radiating metal surface (3) to obtain a good directivity read field type, and the reading distance is 5.2 meters.

The advantages of the tag antenna (A) will be further explained below by means of the experimental results.

Referring to Figure 2A, the result of measuring the return loss of the tag antenna (A) under the condition that the tag antenna (A) is provided with the U-shaped radiating metal segment (24), wherein the vertical axis represents the return. Loss (dB), the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the tag antenna (A) can be excited into a dual resonance mode with a return loss value of 3 dB or more as a standard, and its operating frequency band can meet the bandwidth requirement of the UHF global frequency band (860 to 960 MHz).

Referring to FIG. 2B and FIG. 2C again, the tag antenna (A) is measured for the resistance of the tag antenna (A) with or without the U-shaped radiant metal segment (24). A schematic diagram of the results of the reactance, wherein the vertical axis represents ohms (Ω), the horizontal axis represents the operating frequency (MHz), and the resistance of the wafer (5) is 17 Ω and the reactance is j 120 Ω. As can be seen from the figure, the U-shaped radiant metal segment (24) can reduce the input impedance of the dual resonance mode, and achieve a conjugate matching with the wafer (5), and the measurement is quite close to the simulation result.

Please refer to the third and third B diagrams for the tag antenna (A) to measure the resistance and reactance of the tag antenna (A) with or without the metal piece (4). The axis represents ohms (Ω), and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the metal piece (4) can reduce the input impedance of the tag antenna (A) and reduce the first radiating metal surface (2) and The capacitive effect between the second radiating metal face (3) causes the target The double resonance frequency excited by the tag antenna (A) is increased, and by the metal piece (4), the second resonance frequency generated by the third radiation metal segment (23) can be controlled.

Referring to FIG. 4A, the result of measuring the return loss of the tag antenna (A) under the condition that the length value of the sixth segment (235) is changed, wherein the vertical axis represents the return loss (dB). The horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the second resonant frequency is affected by the length of the sixth segment (235). Referring to FIG. 4B and FIG. 4C again, the result of measuring the resistance and reactance of the tag antenna (A) under the condition that the length value of the sixth segment (235) is changed, wherein The vertical axis represents ohms (Ω), and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the second resonant frequency is inversely affected by the length value of the sixth segment (235), but the first A resonance frequency is less affected, and as shown in the figure, the length of the sixth segment (235) is preferably 25 (1 ± 5%) mm.

Referring to FIG. 5A, the tag antenna (A) is a state in which the return loss of the tag antenna (A) is measured in a state in which the length value of the second segment (224) is changed, wherein the vertical axis The return loss (dB) is shown, and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the first resonant frequency is affected by the length value of the second segment (224). Referring to FIG. 5B and FIG. 5C again, the result of measuring the resistance and reactance of the tag antenna (A) under the condition that the length value of the second segment (224) is changed, Wherein, the vertical axis represents ohms (Ω), and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the first resonant frequency is inversely proportional to the length value of the second segment (224), and the second resonant frequency It is less affected by the change in the length value of the second segment (224), and as shown by the figure, the length of the second segment (224) is preferably 31 (1 ± 5%) mm.

Referring to FIG. 6A, the result of measuring the return loss of the tag antenna (A) under the condition that the width value of the first segment (223) is changed, wherein the vertical axis table The return loss (dB) is shown, and the horizontal axis represents the operating frequency (MHz). From this figure, the first resonant frequency generated by the tag antenna (A) during operation is affected by the width of the first segment (223). influences. Referring to FIG. 6B and FIG. 6C again, the result of measuring the resistance and reactance of the tag antenna (A) under the condition that the width value of the first segment (223) is changed, wherein The vertical axis represents ohms (Ω), and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the first resonant frequency is proportional to the width of the first segment (223), and the second resonant frequency is less. Affected by the width value of the first segment (223), it can be seen from the figure that the width of the first segment (223) is preferably 2 (1 ± 5%) mm.

Referring to FIG. 7A, the result of measuring the return loss of the tag antenna (A) after changing the width value of the second segment (224), wherein the vertical axis represents the return loss (dB), the horizontal axis. The operating frequency (MHz) is shown. From this figure, the double resonant frequency generated by the tag antenna (A) during operation is affected by the width of the second segment (224). Referring to FIG. 7B and FIG. 7C again, the result of measuring the resistance and reactance of the tag antenna (A) under the condition that the width value of the second segment (224) is changed, wherein The vertical axis represents ohms (Ω), and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the double resonant frequency is inversely proportional to the width value of the second segment (224), and is illustrated by the figure. The width of the second segment (224) is preferably 2 (1 ± 5%) mm.

Referring to FIGS. 8A and 8B, the tag antenna (A) is measured under the condition that the distance between the first radiating metal surface (2) and the second radiating metal surface (3) is changed. A schematic diagram of the results of resistance and reactance, wherein the vertical axis represents ohms (Ω) and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the dual resonant frequencies are proportional to the distance, which is due to the increase in the distance. The capacitance between the first radiating metal surface (2) and the second radiating metal surface (3) is reduced, and it is known from the figure that the distance is preferably 5 (1 ± 5%) mm.

Refer to Figure 9A for the measurement of the return loss of the tag antenna (A) under the condition that the tag antenna (A) is attached to a metal copper plate of different area, wherein the vertical axis represents the return loss (dB). The horizontal axis represents the operating frequency (MHz). As can be seen from the figure, when the tag antenna (A) is attached to a metal surface of a different area, the change in return loss is less affected, and it can be seen that the antenna of the present invention can be applied to different antennas. Dimensional metal copper plate. Please refer to the ninth B and ninth C diagrams, showing the results of measuring the resistance and reactance of the tag antenna (A) under the condition that the tag antenna (A) is attached to a metal copper plate of different area. The axis represents ohms (Ω) and the horizontal axis represents the operating frequency (MHz). As can be seen from the figure, the double resonant frequency is not affected by the size of the metal copper plate.

Please refer to the tenth figure for the result of the tag antenna (A) operating at 900 MHz to measure the read range type. As can be seen from the figure, by the configuration of the second radiating metal surface (3), the tag antenna (A) has a typical directivity radiation field in both XY Plane and XZ Plane, and the reading distance thereof is Up to 5.2 meters.

In summary, the present invention is indeed in line with industrial utilization, and is not found in publications or publicly used before application, nor is it known to the public, and has non-obvious knowledge, conforms to patentable requirements, and patents are filed according to law. .

However, the above description is a preferred embodiment of the invention in the industry, and all the equivalent changes made according to the scope of the patent application of the present invention belong to the scope of the claim.

(A)‧‧‧ tag antenna

(21) ‧‧‧First radiant metal segment

(211) ‧‧‧ Space

(212) ‧‧‧First bend

(22) ‧‧‧second radiant metal segment

(221) ‧‧‧ spacing

(222)‧‧‧Second bend

(223)‧‧‧The first paragraph

(224)‧‧‧The second paragraph

(23) ‧‧‧third radiant metal segment

(231) ‧‧‧ Third bend

(232) ‧‧ Section III

(233) ‧ ‧ Section IV

(234) ‧ ‧ Section 5

(235)‧‧‧Section 6

(24)‧‧‧U-shaped radiant metal segments

(4)‧‧‧metal pieces

(5) ‧‧‧ wafer

Claims (10)

A UHF RFID tag antenna attachable to a metal surface includes: a substrate: a top surface is provided with a first radiating metal surface and a wafer, and a bottom surface is provided with a second radiating metal surface for attaching a metal surface, and a metal piece end Connecting the first radiating metal surface, the other end is connected to the second radiating metal surface, and the first radiating metal surface comprises: two first radiating metal segments: disposed on the top surface of the substrate, and each of the first radiating metal segments One end of each of the signals is connected to the wafer; two second radiating metal segments are disposed on the top surface of the substrate, and the root portions of each of the second radiating metal segments are respectively connected to the second ends of the two first radiating metal segments, and the first radiating metal segments And the second radiant metal segments together form a space, and the second radiant metal segments have a spacing between the second ends; the second radiant metal segments are disposed on the top surface of the substrate and located in the space, The first ends of the third radiating metal segments are respectively connected to the second ends of the two first radiating metal segments or the roots of the second second radiating metal segments. The UHF RFID tag antenna attachable to a metal surface according to claim 1, wherein the first radiating metal surface comprises a U-shaped radiating metal segment, and the U-shaped radiating metal segment is disposed across the first radiation. The first end of the metal segment. The UHF RFID tag antenna attachable to a metal surface according to claim 1, wherein the second radiating metal segment has a first bent portion, and the second radiating metal segment is directed from the root toward the free end. The sequence defines a first segment and a second segment, and the second segment has a width ≧ the first segment width. A UHF RFID tag antenna attachable to a metal surface as described in claim 3, wherein the first segment has a width of 2 (1±5%) mm and the second segment has a width of 2 (1). ±5%) mm. A UHF RFID tag antenna attachable to a metal surface according to claim 3, wherein the third radiating metal segment is provided with three second bending portions, and the third radiating metal segment is directed from the root toward the free end. The sixth segment of the third segment is defined adjacent to the second segment and is parallel to the second segment, and the free end of the sixth segment is adjacent to the first segment. A UHF RFID tag antenna attachable to a metal surface as described in claim 5, wherein the length of the second segment is 31 (1±5%) mm, and the length of the sixth segment is 25 (1) ±5%) mm. A UHF RFID tag antenna attachable to a metal surface as described in claim 5, wherein each of the first radiating metal segments is provided with two bent portions. A UHF RFID tag antenna attachable to a metal surface according to claim 1, wherein the length of the first radiating metal segment and the second radiating metal segment is 103.5 (1±5%) mm. A UHF RFID tag antenna attachable to a metal surface as described in claim 1 wherein the third radiant metal segment has a length of 105.5 (1 ± 5%) mm. A UHF RFID tag antenna attachable to a metal surface according to claim 1, wherein a distance between the first radiating metal surface and the second radiating metal surface is 5 (1 ± 5%) mm.