A small UHF tag antenna with easily adjustable impedance

Abstract

The present invention discloses a small ultra-high frequency tag antenna with easily adjustable impedance, comprising a dielectric substrate and an antenna pattern arranged on the surface of the dielectric substrate; the antenna pattern comprises a special-shaped open conductor resonant ring, an impedance-adjusting conductor belt inside the ring and a double conductor belt; the impedance-adjusting conductor belt inside the ring is loaded inside the special-shaped open conductor resonant ring, and the opening of the special-shaped open conductor resonant ring is used to connect a chip; one of the conductor belts in the double conductor belt runs through the special-shaped open conductor resonant ring, and a metal surface is loaded at the end of the double conductor belt. The small ultra-high frequency tag antenna with easily adjustable impedance of the present invention realizes easy adjustment of the imaginary impedance of the ultra-high frequency tag antenna by designing that the impedance-adjusting conductor belt inside the ring is loaded inside the special-shaped open conductor resonant ring, so that it is easy to match the impedance of different electronic tag chips; the antenna has a simple structure, is easy to install, has a low production cost, a small size, and is easy to mass produce.

Description

Technical Field

[0001] The invention relates to the field of electronic tags in radio frequency identification technology, and in particular to a small ultra-high frequency tag antenna with easily adjustable impedance. Background Art

[0002] Radio frequency identification (RFID) technology is a technology that uses radio frequency signals to automatically identify objects. It has been widely used in the field of the Internet of Things. RFID systems are generally composed of electronic tags (including chips and tag antennas), readers and writers, and computers. At present, the commonly used working frequencies of radio frequency identification include low frequency bands (125KHz, 134KHz), high frequency bands (13.56MHz), ultra-high frequency (UHF) bands (840-960MHz) and microwave bands above 2.45GHz. The ultra-high frequency band and microwave band have the advantages of long operating distance, batch reading, and small size.

[0003] At present, the chip impedance of UHF electronic tags at home and abroad generally has a smaller real part and a larger imaginary part. The difference in chip impedance of UHF electronic tags from different companies is mainly reflected in the difference in the imaginary part of the chip impedance. Therefore, a miniaturized UHF tag antenna that is easy to adjust the imaginary impedance of the antenna is needed to facilitate matching with the impedance of different electronic tag chips. Summary of the invention

[0004] The purpose of the present invention is to provide a small ultra-high frequency tag antenna with easily adjustable impedance, so as to solve the problem of impedance matching with different electronic tag chips.

[0005] The present invention adopts the following technical solutions to achieve the above-mentioned invention objectives:

[0006] The present invention provides a small ultra-high frequency tag antenna with easily adjustable impedance, comprising a dielectric substrate and an antenna pattern arranged on the surface of the dielectric substrate;

[0007] The antenna pattern includes a special-shaped open conductor resonant ring, an impedance adjustment conductor strip in the ring, and a double conductor strip;

[0008] The impedance adjustment conductor belt in the ring is loaded inside the special-shaped open conductor resonant ring, and the opening of the special-shaped open conductor resonant ring is used to connect the chip;

[0009] One of the dual conductor strips passes through the special-shaped open conductor resonant ring, and a metal surface is loaded at the end of the dual conductor strip.

[0010] Furthermore, the outer curve shape of the special-shaped open resonant ring is a crescent shape, the inner curve shape of the special-shaped open resonant ring is a diamond shape, and the impedance adjustment conductor belt in the ring is connected to the inner curve of the special-shaped open conductor resonant ring.

[0011] Furthermore, the outer straight line edges of the special-shaped open conductor resonant ring are respectively parallel to the impedance adjustment conductor strip and the dual conductor strip within the ring.

[0012] Furthermore, a break is provided along the center line of the outer straight line edge of the special-shaped open conductor resonant ring for connecting the chip.

[0013] Furthermore, the intra-ring impedance adjustment conductor strip is inside the special-shaped open conductor resonant ring and is located between the outer straight edge of the special-shaped open conductor resonant ring and the dual conductor strip.

[0014] Furthermore, the dual conductor strip includes two mutually parallel first conductor strips and second conductor strips, the first conductor strip passes through the special-shaped open conductor resonant ring, the second conductor strip is located on the side of the first conductor strip away from the impedance adjustment conductor strip in the ring, and the ends of the first conductor strip and the second conductor strip are respectively connected to the metal surface.

[0015] Furthermore, the metal surface is in a semi-elliptical shape.

[0016] Furthermore, the major axis of the semi-elliptical metal surface is perpendicular to the dual conductor strip, and the major axis of the ellipse ranges from 3 to 16 times the minor axis of the ellipse.

[0017] Furthermore, the dielectric substrate is a PET substrate.

[0018] The beneficial effects of the present invention are as follows:

[0019] The small-sized UHF tag antenna with easily adjustable impedance of the present invention realizes easy adjustment of the imaginary impedance of the UHF tag antenna by loading an impedance-adjusting conductor strip in a special-shaped open conductor resonant ring, thereby facilitating impedance matching with different electronic tag chips; the antenna has a simple structure, is easy to install, has a low production cost, a small size, and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of an electronic tag obtained after a tag antenna is connected to a chip according to an embodiment of the present invention;

[0021] Figure 2 is a frequency characteristic curve of the input impedance of the tag antenna according to an embodiment of the present invention;

[0022] Figure 3 is a gain pattern of a tag antenna in the xoy plane according to an embodiment of the present invention;

[0023] Figure 4 FIG. 4 is a gain pattern of a tag antenna on the xoz plane according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so as to describe the embodiments of the present invention described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0026] In the present invention, the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the directions or positional relationships shown in the drawings. These terms are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific direction, or to be constructed and operated in a specific direction.

[0027] In addition, some of the above terms may be used to express other meanings in addition to indicating orientation or positional relationship. For example, the term "on" may also be used to express a certain dependency or connection relationship in some cases. For those skilled in the art, the specific meanings of these terms in the present invention can be understood according to specific circumstances.

[0028] In addition, the terms "installed", "set", "provided with", "connected", "connected", and "socketed" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection, or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be an internal connection between two devices, elements, or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] like Figure 1As shown, a small ultra-high frequency tag antenna with easy impedance adjustment is formed by printing an antenna pattern on a thin dielectric substrate with a conductive material, and an electronic tag is obtained after connecting a chip. The tag antenna includes a dielectric substrate, an antenna pattern printed on the surface of the dielectric substrate, and the antenna pattern includes a special-shaped open conductor resonant ring 1, an impedance adjustment conductor belt 2 in the ring, and a double conductor belt 3 loaded at the end; the outer curve shape of the special-shaped open resonant ring 1 is a crescent shape, and the inner curve shape is a diamond shape (one end is a cone and the other end is a trapezoid), and the opening is connected to a chip 4; the impedance adjustment conductor belt 2 in the ring is connected to the inner circle of the special-shaped open conductor resonant 1; the left and right ends of the double conductor belt 3 loaded at the end are respectively loaded with semi-elliptical metal surfaces.

[0030] The tag antenna of the invention is printed on an insulating dielectric substrate, which adopts a PET substrate with a thickness of 0.102 mm (relative dielectric constant εr=3.5). The optimized antenna size is as follows: the distance from the opening of the special-shaped open conductor resonant ring to the corner is L4=9.25 mm, the distance from the straight edge of the special-shaped open resonant ring to the end-loaded dual conductor belt is L5=5.5 mm, the distance from the straight edge of the special-shaped open resonant ring to the impedance adjustment conductor belt inside the ring is L6=4.4 mm, and the distance from the lower conductor belt in the end-loaded dual conductor belt to the bottom of the special-shaped open resonant ring is L9=1.8 mm; the impedance adjustment conductor belt inside the ring is connected to the inner periphery of the special-shaped open conductor resonant ring, and the ring The inner length L7 is 7.41mm, and the width is 1mm; the distance between the impedance-adjusting conductor strip inside the ring and the end-loaded dual conductor strip is 0.1mm; the end-loaded dual conductor strip includes a first conductor strip and a second conductor strip, and the distance between the two conductor strips is S=3.3mm. The width of the first conductor strip located at the top is 1mm, the inner length L8 is 4.63mm, and the length across the special-shaped open resonant ring is L2=4.16mm. The width of the second conductor strip located at the bottom is 0.8mm, and the overall length L3=26mm. Semi-elliptical metal surfaces are loaded on the left and right ends respectively, the eccentricity of the ellipse is 0.13, the overall length L1=12.6mm, and the length of the minor axis of the ellipse is 1.62mm.

[0031] The RI-UHF-STRAP-08 tag chip of Ti Company is connected to the center line break of the outer straight edge of the special-shaped open conductor resonant ring. The tag antenna and the tag chip together form a radio frequency electronic tag. The overall size of the electronic tag is 27mm×13mm, which is smaller than most UHF electronic tags.

[0032] Figure 2The real and imaginary parts of the input impedance of the tag antenna of the present invention are obtained by simulation, and the impedance at 915MHz is 0.02+j61.95 ohms. The input impedance of the tag antenna of the present invention and the impedance of the RI-UHF-STRAP-08 tag chip used are basically conjugate matched (the impedance of the chip at 915MHz is 9.9-j60.53 ohms), thereby meeting the impedance characteristic requirements of the RFID electronic tag antenna.

[0033] Table 1 shows the antenna parameters of the tag antenna at 915MHz when the distance L6 from the straight edge of the special-shaped open resonant ring to the impedance adjustment conductor strip inside the ring has different values. It can be seen that by only changing the value of L6, the imaginary part of the antenna input impedance is quickly adjusted, while the real part does not change significantly. It has the advantages of easy adjustment of the antenna input impedance and small changes in other performances.

[0034] Table 1 Antenna parameters of the tag antenna when adjusting parameter L6

[0035]

[0036] Figure 3 and Figure 4 The simulation results of the antenna gain pattern when L6=4.4mm are given. Figure 3 It shows that the tag antenna of the present invention radiates approximately omnidirectionally on the xoy plane, which can meet the requirement of being able to read the electronic tag information from all directions in practical applications; Figure 4 The simulation results show that the tag antenna of the present invention exhibits an inverted 8-shaped radiation characteristic on the xoz plane.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A small UHF tag antenna with easily adjustable impedance, characterized in that: It includes a dielectric substrate and an antenna pattern arranged on the surface of the dielectric substrate; The antenna pattern includes a special-shaped open conductor resonant ring, an impedance adjustment conductor strip in the ring, and a double conductor strip; The impedance adjustment conductor belt in the ring is loaded inside the special-shaped open conductor resonant ring, and the opening of the special-shaped open conductor resonant ring is used to connect the chip; One of the dual conductor strips passes through the special-shaped open conductor resonant ring, and the end of the dual conductor strip is loaded with a metal surface; The dual conductor strip comprises two mutually parallel first conductor strips and second conductor strips, the first conductor strip passes through the special-shaped open conductor resonant ring, the second conductor strip is located on the side of the first conductor strip away from the impedance adjustment conductor strip in the ring, and the ends of the first conductor strip and the second conductor strip are respectively connected to the metal surface; The metal surface is in a semi-elliptical shape; The outer curve shape of the special-shaped open conductor resonant ring is a crescent shape, the inner curve shape of the special-shaped open conductor resonant ring is a diamond shape, and the impedance adjustment conductor belt in the ring is connected to the inner curve of the special-shaped open conductor resonant ring.

2. The small UHF tag antenna with easily adjustable impedance according to claim 1, characterized in that: The outer straight line edges of the special-shaped open conductor resonant ring are respectively parallel to the impedance adjustment conductor strip and the double conductor strip in the ring.

3. A small UHF tag antenna with easily adjustable impedance according to claim 1 or 2, characterized in that: A break is provided along the center line of the outer straight line edge of the special-shaped open conductor resonant ring for connecting the chip.

4. The small-sized UHF tag antenna with easily adjustable impedance according to claim 2, characterized in that: The in-ring impedance adjustment conductor strip is located inside the special-shaped open conductor resonant ring and between the outer straight edge of the special-shaped open conductor resonant ring and the double conductor strip.

5. The small-sized UHF tag antenna with easily adjustable impedance according to claim 1, characterized in that: The major axis of the semi-elliptical metal surface is perpendicular to the dual conductor strip, and the value range of the major axis of the ellipse is 3 to 16 times of the minor axis of the ellipse.

6. The small-sized UHF tag antenna with easily adjustable impedance according to claim 1, characterized in that: The medium substrate is a PET substrate.

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