CN110247179B - UHF near field RFID reader antenna capable of identifying randomly placed tags - Google Patents
UHF near field RFID reader antenna capable of identifying randomly placed tags Download PDFInfo
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- CN110247179B CN110247179B CN201910536372.9A CN201910536372A CN110247179B CN 110247179 B CN110247179 B CN 110247179B CN 201910536372 A CN201910536372 A CN 201910536372A CN 110247179 B CN110247179 B CN 110247179B
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- 238000005452 bending Methods 0.000 claims description 16
- 238000009826 distribution Methods 0.000 description 16
- 238000010586 diagram Methods 0.000 description 7
- 238000013461 design Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011160 research Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 238000012938 design process Methods 0.000 description 1
- 230000005672 electromagnetic field Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/12—Supports; Mounting means
- H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
- H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
- H01Q1/2216—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in interrogator/reader equipment
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
- H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
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Abstract
The invention provides a UHF near field RFID reader antenna capable of identifying any placed label, which comprises a dielectric plate, wherein a metal layer is arranged on the dielectric plate, the metal layer comprises two dipoles which are perpendicular to each other and have different lengths, and the two arms of any one of the two dipoles have equal length and are parallel and non-collinear in position. A first dipole comprising a first arm and a second arm, and a second dipole comprising a third arm and a fourth arm; the first dipole and the second dipole are perpendicular to each other but have different lengths; the first arm and the second arm are equal in length, parallel and non-collinear with each other, and the third arm and the fourth arm are equal in length, parallel and non-collinear with each other.
Description
Technical Field
The invention relates to the technical field of electromagnetic fields and microwaves, in particular to a UHF near-field RFID reader antenna capable of identifying any placed tag.
Background
The UHF near field RFID system has been widely applied to the fields of modern intelligent logistics, warehouse management, industrial sensing and the like due to the advantages of high transmission rate, high read-write rate, long-distance identification and the like. The performance of the reader antenna, which is the most critical one, often determines the quality of the system performance. In the design process of the reader antenna, only the intensity of the magnetic field component in the direction perpendicular to the antenna surface is generally considered, because the surface of the near field tag and the surface of the reader antenna are generally required to be parallel to each other. However, in practical applications, the placement position of the near field tag is arbitrary and random, which will cause the identification rate of the conventional reader antenna to be low, and there is a dead zone of identification. To cope with this demand, a reader antenna is required to generate a sufficiently strong and uniform magnetic field in three dimensions in its near field region, which is a research hotspot in recent years.
For the conventional loop antenna, the component strength of the near field magnetic field in the direction perpendicular to the antenna surface is strong and uniform, but the component parallel to the antenna surface has an extremely weak area, which makes the loop antenna unable to identify the tag placed perpendicular to the antenna surface, resulting in the generation of an identification blind area. At present, most reader antennas in UHF frequency range have the problem, or the research on the magnetic field distribution in the direction parallel to the surface of the antenna is omitted.
Disclosure of Invention
The invention aims to: aiming at the defects of the prior art, the invention provides the UHF near field RFID reader antenna capable of identifying any placed tag.
In order to solve the technical problem, the UHF near field RFID reader antenna capable of identifying any placed label comprises a dielectric plate, wherein a metal layer is arranged on the dielectric plate, the metal layer comprises two dipoles which are perpendicular to each other and have different lengths, and the two arms of any one of the two dipoles are equal in length, parallel in position and non-collinear.
The invention comprises a first dipole and a second dipole, wherein the first dipole comprises a first arm and a second arm, and the second dipole comprises a third arm and a fourth arm;
The first dipole and the second dipole are perpendicular to each other but have different lengths;
The first arm and the second arm are equal in length, parallel and non-collinear with each other, and the third arm and the fourth arm are equal in length, parallel and non-collinear with each other.
In the invention, the distance between the parallel lines of the first arm and the second arm is different from the distance between the parallel lines of the third arm and the fourth arm.
In the present invention, the first arm is connected to the third arm, and the second arm is connected to the fourth arm.
In the invention, the length of any dipole is slightly shorter than one half wavelength, the UHF frequency band is 860-960 MHz, and the wavelength is 915 MHz.
In the invention, when the distance between the parallel lines of the first arm and the second arm is larger than the distance between the parallel lines of the third arm and the fourth arm, the length of the first dipole is smaller than that of the second dipole.
In the invention, when the distance between the parallel lines of the first arm and the second arm is smaller than the distance between the parallel lines of the third arm and the fourth arm, the length of the first dipole is longer than that of the second dipole.
In the invention, one side of the dielectric plate, which is far away from the metal layer, is provided with the feed terminal, and the feed terminal is respectively connected to the connection part of the first arm and the third arm and the connection part of the second arm and the fourth arm, so that the test is convenient.
In the invention, the first bending angle is arranged at the joint of the first arm and the third arm, and the second bending angle is arranged at the joint of the second arm and the fourth arm, so that the near-field magnetic field intensity of the reader antenna is enhanced, and the generation of the recognition blind area is reduced.
The beneficial effects are that: the antenna breaks through the limitation that the tag antenna can only be placed parallel to the surface of the reader antenna; the structure is simple and compact, and the impedance matching performance is good.
Drawings
The foregoing and other advantages of the invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings and detailed description.
FIG. 1a is a three-dimensional schematic diagram of an ultra wideband cross reader antenna for UHF near field RFID;
FIG. 1b is a design parameter label;
fig. 2 is a diagram of simulation results of return loss of a reader antenna according to the present invention;
FIG. 3 is a graph showing the distribution of the magnetic field x component |H x | along the y-axis at 50mm directly above the reader antenna according to the present invention;
FIG. 4 is a graph showing the y-axis distribution of the y-component H y of the magnetic field at 50mm directly above the reader antenna according to the present invention;
fig. 5 is a graph showing the distribution of the z-component of the magnetic field, |h z |, along the line y=x, 50mm directly above the reader antenna according to the present invention;
FIG. 6a is a schematic diagram of an embodiment;
fig. 6b is a schematic view of the first bending portion and the second bending portion.
FIG. 7a is a schematic view of an antenna with a bent angle structure;
FIG. 7b is a schematic diagram of an antenna in a right angle configuration;
FIG. 8 is a graph of reflectance versus time;
FIG. 9a is a schematic diagram showing the distribution of the x component |H x | along the y-axis;
FIG. 9b is a schematic diagram showing the distribution of the y component |H y | along the y-axis;
fig. 10 is a schematic diagram showing the distribution of the magnetic field component |h z | along the line y=x.
Detailed Description
The present invention will be described in detail with reference to the accompanying drawings.
Example 1:
An ultra wideband cross reader antenna for UHF near field RFID designed in this embodiment is shown in FIG. 1a, and comprises a dielectric plate 1 and a metal layer 2 on the top surface of the dielectric plate. The first dipole 2 comprises a first arm 2a and a second arm 2b, and the second dipole 3 comprises a third arm 3a and a fourth arm 3b;
the first dipole 2 and the second dipole 3 are perpendicular to each other but have different lengths;
The first arm 2a and the second arm 2b are equal in length, parallel and non-collinear with each other, and the third arm 3a and the fourth arm 3b are equal in length, parallel and non-collinear with each other.
The distance between the parallel lines of the first arm 2a and the second arm 2b is not equal to the distance between the parallel lines of the third arm 3a and the fourth arm 3 b.
The distance between the parallel lines of the first arm 2a and the second arm 2b is smaller than the distance between the parallel lines of the third arm 3a and the fourth arm 3b, and the length of the first dipole is larger than the length of the second dipole.
As shown in fig. 1b, the length and width of the dielectric plate are L, the thickness is h, the dipole single arm length along the y-axis is L 1, the dipole single arm length along the x-axis is L 2, and the line widths of the two dipoles are w.
The ultra-wideband crisscross reader antenna with the working frequency of 920MHz has the dielectric constant of 4.4, the length and the width of the dielectric substrate of L=80 mm, the thickness of h=1.6 mm, the lengths of two large single dipole arms of L 1 =62 mm and L 2 =54 mm respectively, and the line widths of w=3 mm.
Fig. 2 is a graph of simulation results using commercially available full wave simulation software HFSS for reader antenna reflection coefficients having the dimensions described above. As can be seen from FIG. 2, the operating frequency bandwidth of-10 dB of the reader antenna is about 180MHz, and the relative bandwidth is about 19.3% greater than that of a common line antenna from 840MHz to 1020 MHz. This bandwidth covers the specification of the worldwide UHF near field RFID band (860 MHz-960 MHz).
To verify the near field magnetic field performance of this embodiment, fig. 3 and 4 are graphs showing the distribution of near field x and y direction components (|h x | and |h y |) along the y axis, and fig. 5 shows the distribution of near field z direction component (|h z |) along the line y=x. If the magnetic field strength is taken as a limit of-30 dBA/m, H x is stronger than the value within the range of-160 mm < x < 160mm, H y is slightly smaller than the limit value (about-140 mm < x < 140 mm), and H z is larger than-30 dBA/m within the whole range (-200 mm < y=x < 200 mm). The reader antenna of the embodiment can generate strong and uniform magnetic field distribution in the three-dimensional direction in a larger near field area, is favorable for identifying labels placed at any position, and provides a new design idea for UHF near field RFID reader antennas.
The antenna utilizes the characteristic that dipoles placed along the x axis only generate magnetic field components in the y and z directions in the near field region, and can provide a strong and uniform magnetic field in the three-dimensional direction in a large area of the near field region by means of placing the two dipoles in mutually perpendicular mode.
The total length of the dipole determines the working frequency and bandwidth of the antenna, and the working bandwidth of the antenna can be flexibly adjusted by changing the total length of the dipole, and meanwhile, the distribution of the near-field magnetic field in the three-dimensional direction is controlled.
As shown in fig. 6a, in this embodiment, the distance s1=4mm between the center parallel lines where the first arm 2a and the second arm 2b are located is smaller than the distance s2=8mm between the center parallel lines where the third arm 3a and the fourth arm 3b are located, the length of the first dipole is greater than the length of the second dipole, the lengths of the first arm 2a and the second arm 2b are both 62mm, and the lengths of the third arm 3a and the fourth arm 3b are both 54mm.
The connection of the first arm 2a and the third arm 3a is provided with a first bending angle 4a, the connection of the second arm 2b and the fourth arm 3b is provided with a second bending angle 4b, and for practical machining, a certain space needs to be reserved for the feed terminal, as in fig. 6b, the space is fed=1 mm long and w 1 =3 mm wide, d=3 mm, and α is 45 °, wherein the side lengths of the bending angles are d=3 mm and w=3 mm, respectively. The second bending angle 4b is symmetrical with the first bending angle 4a as a center.
Fig. 7a shows an antenna with a bending angle according to the present embodiment, and fig. 7b shows a right angle form.
The arm lengths, i.e., 2a, 2b, 3a and 3b, were kept equal in both cases while the line widths were kept consistent, so that performance comparison analysis was performed.
Fig. 8 is a graph comparing the reflection coefficients, from which it can be seen that the-10 dB bandwidth is substantially uniform and relatively wide in both cases. Since the present embodiment is mainly developed around the UHF band (860 MHz to 960 MHz), the bandwidth of the present embodiment covers the band from 840MHz to 1020MHz, whereas the band cannot be completely covered from 890MHz to 1100MHz in a right angle form. In addition, from the point of view of the frequency corresponding to the minimum value of the reflection coefficient, the structure according to the present embodiment corresponds to the frequency of about 920MHz, and the right angle form is 970MHz. Therefore, the performance of the antenna reflection coefficient with the bending angle structure provided by the embodiment is better than that of an antenna in a right angle form, and the antenna reflection coefficient with the bending angle structure can be better suitable for a UHF near field RFID system.
Fig. 9a and 9b show the distribution of the magnetic field component along the y-axis, which is (a) the x-component |hx| and (b) the y-component |hy|;
Fig. 9a, 9b and 9 are distribution of magnetic field components in the near field region of the reader antenna. Wherein fig. 9a and 9b are distributions of the x component |hx| and the y component |hy| along the y axis. From this, the distribution trends of the two forms are substantially the same, but the proposed structure of the present embodiment has a magnetic field strength at the central region (in the range of about-50 mm to 50 mm) that is at least 3dB greater than that of the right angle form, which means that the reader antenna of the right angle form may generate a dead zone at its central region under the same power input. In addition, fig. 10 shows the distribution of the z component |hz| of the magnetic field along the diagonal y=x, and it is obvious from the figure that the structure proposed by the present embodiment can effectively enhance the near field magnetic field strength.
Conclusion: in summary, the antenna with the bent angle structure provided by the embodiment can effectively adjust the reflection coefficient and the bandwidth of the reader antenna, so that the antenna is applied to a UHF frequency band near field RFID system; meanwhile, the near field magnetic field intensity of the reader antenna is enhanced, so that the generation of a recognition blind area is avoided.
Example 2:
in this embodiment, the distance between the center parallel lines of the first arm 2a and the second arm 2b is greater than the distance between the center parallel lines of the third arm 3a and the fourth arm 3b, and the length of the first dipole is smaller than the length of the second dipole. Specifically, the distance between the center parallel lines where the first arm 2a and the second arm 2b are located is 8nm, the distance between the center parallel lines where the third arm 3a and the fourth arm 3b are located is 4nm, the lengths of the first arm 2a and the second arm 2b are 54mm, and the lengths of the third arm 3a and the fourth arm 3b are 62mm.
The invention provides a UHF near field RFID reader antenna capable of identifying any placed tag, and the method and the way for realizing the technical scheme are numerous, the above description is only a preferred embodiment of the invention, and it should be noted that, for a person skilled in the art, a plurality of improvements and modifications can be made without departing from the principle of the invention, and the improvements and modifications are also considered as the protection scope of the invention. The components not explicitly described in this embodiment can be implemented by using the prior art.
Claims (4)
1. The UHF near field RFID reader antenna capable of identifying any placed label is characterized by comprising a dielectric plate, wherein a metal layer is arranged on the dielectric plate, the metal layer comprises two dipoles which are perpendicular to each other and have different lengths, and two arms of any one of the two dipoles are equal in length, parallel in position and non-collinear;
The two dipoles comprise a first dipole (2) and a second dipole (3), the first dipole (2) comprises a first arm (2 a) and a second arm (2 b), and the second dipole (3) comprises a third arm (3 a) and a fourth arm (3 b);
The first dipole (2) and the second dipole (3) are perpendicular to each other but have different lengths;
The first arm (2 a) and the second arm (2 b) are equal in length, parallel and non-collinear, and the third arm (3 a) and the fourth arm (3 b) are equal in length, parallel and non-collinear;
The first arm (2 a) is connected with the third arm (3 a), and the second arm (2 b) is connected with the fourth arm (3 b); the distance between parallel lines of the first arm (2 a) and the second arm (2 b) is different from the distance between parallel lines of the third arm (3 a) and the fourth arm (3 b);
A first bending angle (4 a) is arranged at the joint of the first arm (2 a) and the third arm (3 a), a second bending angle (4 b) is arranged at the joint of the second arm (2 b) and the fourth arm (3 b), and the second bending angle (4 b) is symmetrical with the first bending angle (4 a) as a center;
a feed terminal is arranged on one side of the dielectric plate, which is away from the metal layer, and is respectively connected to the connection part of the first arm and the third arm and the connection part of the second arm and the fourth arm;
When feeding, the UHF near field RFID reader antenna can provide a strong enough and uniform magnetic field in the three-dimensional direction in a larger area of the near field region.
2. The UHF near field RFID reader antenna of claim 1, wherein the length of any one dipole is slightly shorter than one-half wavelength.
3. A UHF near field RFID reader antenna capable of identifying arbitrarily placed tags according to claim 1, wherein the first dipole length is smaller than the second dipole length when the distance between the parallel lines of the first arm (2 a) and the second arm (2 b) is greater than the distance between the parallel lines of the third arm (3 a) and the fourth arm (3 b).
4. A UHF near field RFID reader antenna capable of identifying arbitrarily placed tags according to claim 1, wherein the first dipole length is greater than the second dipole length when the distance between the parallel lines of the first arm (2 a) and the second arm (2 b) is less than the distance between the parallel lines of the third arm (3 a) and the fourth arm (3 b).
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| CN201910536372.9A CN110247179B (en) | 2019-06-20 | 2019-06-20 | UHF near field RFID reader antenna capable of identifying randomly placed tags |
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| CN201910536372.9A CN110247179B (en) | 2019-06-20 | 2019-06-20 | UHF near field RFID reader antenna capable of identifying randomly placed tags |
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| CN110247179B true CN110247179B (en) | 2024-05-03 |
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| CN111900541B (en) * | 2020-07-02 | 2022-07-29 | 江苏电子信息职业学院 | UHF near field RFID reader antenna with reconfigurable identification area |
| CN113570766B (en) * | 2021-07-27 | 2022-04-19 | 广州安的电子科技有限公司 | Non-inductive channel intelligent networking identification system |
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| CN102956967A (en) * | 2012-10-24 | 2013-03-06 | 深圳大学 | Circularly polarized RFID (Radio Frequency Identification Device) tag antenna |
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| CN209747721U (en) * | 2019-06-20 | 2019-12-06 | 南京师范大学 | UHF near field RFID reader antenna capable of identifying randomly placed tags |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20170149145A1 (en) * | 2009-08-03 | 2017-05-25 | Venti Group Llc | Cross-Dipole Antenna Configurations |
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| CN102956967A (en) * | 2012-10-24 | 2013-03-06 | 深圳大学 | Circularly polarized RFID (Radio Frequency Identification Device) tag antenna |
| CN107275765A (en) * | 2017-05-18 | 2017-10-20 | 广东顺德中山大学卡内基梅隆大学国际联合研究院 | It is a kind of from the broadband circle polarized cross dipole antenna of phase shift |
| CN107369921A (en) * | 2017-07-13 | 2017-11-21 | 江苏智周万物科技有限公司 | Nearly far-field R FID read write lines switchable antenna and its design method |
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