TWI757966B - Antenna structure - Google Patents

Abstract

An antenna structure includes a plurality of radiating portions and a plurality of extension portions. The radiating portions are separated from each other and arranged in a circle. The extension portions are connected to the radiating portions and extend to a center of the circle. A first gap between two top ends of two adjacent radiating portions is equal to a second gap between two bottom ends of two adjacent radiating portions.

Description

Antenna structure

The present invention relates to an antenna structure, and more particularly, to an antenna structure used in short-range wireless communication.

Radio Frequency Identification (RFID) technology uses an RFID reader with an antenna to generate an electromagnetic field or transmit electromagnetic waves to an RFID tag. A responsive electromagnetic field or electromagnetic wave is generated for identification by an RFID reader. Wireless identification through radio frequency identification technology has been widely used in automated production equipment, warehouse management, electronic toll collection and other purposes.

The antenna is an important component of the RFID reader, and the design of the antenna greatly affects the efficiency of wireless identification. Existing antennas are divided into Far Field Antenna and Near Field Antenna according to the transmission distance. The far field antenna is used to transmit or receive far field electromagnetic waves, so it focuses more on the gain; Field antennas are mostly used in RFID readers, which use electromagnetic coupling to read the memory data of the object to be tested. Therefore, near-field antennas pay more attention to the strength of the electromagnetic field.

The present invention provides an antenna structure, which can provide a uniformly distributed short-range magnetic field, and has high induction sensitivity and induction accuracy.

The antenna structure of the present invention includes a plurality of radiating parts and a plurality of extending parts. The radiation parts are separated from each other and arranged in a circle. The extension part is connected to the radiation part and extends toward a center of the circle. A first gap between two top ends of two adjacent radiating parts is equal to a second gap between two bottom ends of two adjacent extending parts.

In an embodiment of the present invention, the first gap ranges from 0.5 mm to 4 mm.

In an embodiment of the present invention, the above-mentioned radiating portion and the extending portion are integrally formed.

In an embodiment of the present invention, each of the above-mentioned radiating portions has a first arc-shaped edge and a second arc-shaped edge opposite to each other. The length of the first arcuate edge is greater than the length of the second arcuate edge. The extension parts are respectively connected to opposite sides of the second arc-shaped edge.

In an embodiment of the present invention, a shortest distance from the first arc-shaped edge to the second arc-shaped edge is between 34 mm and 40 mm.

In an embodiment of the present invention, the shape of each radiating portion is a fan shape.

In an embodiment of the present invention, an included angle between the extending direction of the two adjacent first gaps and the center of the circle is 90 degrees.

In an embodiment of the present invention, one of the above-mentioned radiating parts has an opening to divide the radiating part into a first radiating part and a second radiating part. The aperture of the opening is equal to the first gap.

In an embodiment of the present invention, each of the above-mentioned extension portions includes a first extension portion and a second extension portion, and the first extension portion is vertically connected to the second extension portion.

In an embodiment of the present invention, the length of the first extension portion is between 29 mm and 32 mm.

In an embodiment of the present invention, the length of the second extension portion is between 8 mm and 15 mm.

In an embodiment of the present invention, the shape of each of the above-mentioned extending portions is an L-shape.

In an embodiment of the present invention, the L-shapes of each of the above-mentioned extending portions are separated by a second gap, and have a left-right reversed structure back-to-back.

In an embodiment of the present invention, the thickness of each radiating portion and the thickness of each extending portion are between 0.018 mm and 0.07 mm.

In an embodiment of the present invention, the above-mentioned first radiating part and the second radiating part are connected by a transmission line as a feeding line.

In an embodiment of the present invention, the above-mentioned transmission line is a SAM connector, an N-type connector or a TNC connector.

In an embodiment of the present invention, the above-mentioned antenna structure further includes a carrier, and the radiation portion and the extension portion are disposed on the carrier.

In an embodiment of the present invention, the shape of the above-mentioned carrier includes a square or a circle.

In an embodiment of the present invention, the side length or diameter of the carrier is between 160 mm and 180 mm.

In an embodiment of the present invention, the thickness of the above-mentioned carrier ranges from 1.5 mm to 2.5 mm.

In an embodiment of the present invention, the material of the carrier includes paper material, ceramics, epoxy glass fiberboard, polyimide, polyester, polyurethane, polycarbonate, polyethylene or polypropylene .

In an embodiment of the present invention, the material of the radiation portion and the material of the extension portion include copper, silver or conductive ink.

Based on the above, in the design of the antenna structure of the present invention, the radiating parts of the antenna structure are separated from each other and arranged in a circle, which can achieve the effect of mutual resonance and generate a short-range magnetic field above the antenna structure. In addition, the extension part of the antenna structure is connected to the radiation part and extends toward the center of the circle, so that the magnetic field can be uniformly distributed. In short, the antenna structure of the present invention can provide a uniformly distributed short-range magnetic field, and has high induction sensitivity and induction accuracy.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

FIG. 1 is a schematic top view of an antenna structure according to an embodiment of the present invention. Please refer to FIG. 1 , in this embodiment, the antenna structure 100 includes a plurality of radiating parts (four radiating parts 110 a , 110 b , 110 c and 110 d are schematically shown) and a plurality of extending parts (eight extending parts are schematically shown) 120). The radiation parts 110a, 110b, 110c, 110d are separated from each other and arranged in a circle. The extension portion 120 is connected to the radiation portions 110a, 110b, 110c, and 110d and extends toward a center C of the circle. The first gap G1 between the top ends 110a and 110b of the two adjacent radiating parts is equal to the second gap G2 between the two bottom ends of the two adjacent extending parts 120 . Preferably, the range of the first gap G1 is, for example, between 0.5 mm and 4 mm.

In detail, in this embodiment, each radiating portion (eg, the radiating portion 110 a ) has a first arc-shaped edge 112 and a second arc-shaped edge 114 opposite to each other. The length of the first arc-shaped edge 112 is greater than the length of the second arc-shaped edge 114 , wherein the first arc-shaped edge 112 and the second arc-shaped edge 114 are disposed in a concentric manner. Preferably, a shortest distance L from the first arc-shaped edge 112 to the second arc-shaped edge 114 is, for example, between 34 mm and 40 mm. As shown in FIG. 1 , the shape of each radiating portion 110a, 110b, 110c, and 110d in this embodiment is, for example, a sector, and the outer diameter of each sector (ie, the distance from the first arc edge 112 to the center C) is the same, And the inner diameter (ie, the distance from the second arc edge 114 to the center C) is also the same.

Furthermore, the radiating portion 110c of this embodiment has an opening 113 to divide the radiating portion 110c into a first radiating portion 115 and a second radiating portion 117, which are used for feeding circuit connection. Preferably, the diameter D of the opening 113 is equal to the first gap G1, which means that the diameter D of the opening 113 ranges from 0.5 mm to 4 mm, for example. As shown in FIG. 1 , the transmission line 10 can be connected to the first radiating part 115 and the second radiating part 117 , wherein the transmission line 10 can be a SAM connector, an N-type connector or a TNC connector, which is not limited thereto.

In particular, in this embodiment, the first gap G1 between the two adjacent radiating parts 110a, 110b, 110c, 110d can be used as a gap where the radiating parts 110a, 110b, 110c, 110d are coupled to each other, and can achieve mutual resonance , and a short-range magnetic field is generated above the antenna structure 100 . Here, an included angle A between the extending direction of the two adjacent first gaps G1 and the center C is, for example, 90 degrees, which means that the included angles between the four sector-shaped (ie, the radiating portions 110a, 110b, 110c, 110d) gaps and the center of the circle are respectively 90 degrees.

Referring to FIG. 1 again, the extending portions 120 of this embodiment are respectively connected to opposite sides of the second arc-shaped edge 114 , that is, each radiating portion 110 a , 110 b , 110 c , 110 d is connected to two extending portions 120 . Each extension portion 120 includes a first extension portion 122 and a second extension portion 124 , wherein the first extension portion 122 is vertically connected to the second extension portion 124 . That is, the shape of each extending portion 120 is, for example, an L-shape, and the L-shapes of each extending portion are separated by the second gap G2 and have a left-right inverted structure back-to-back. Preferably, the length L1 of the first extending portion 122 is between 29 mm and 32 mm, and the length L2 of the second extending portion 124 is between 8 mm and 15 mm. The L-shaped extension portion 120 is located inside the circle formed by the radiating portions 110a, 110b, 110c, and 110d, so that the overall antenna structure 100 can have ideal impedance adjustment and uniform magnetic field distribution.

In this embodiment, the radiation parts 110a, 110b, 110c, 110d and the extension part 120 are preferably integrally formed structures, wherein the radiation parts 110a, 110b, 110c, 110d and the extension part 120 are formed by etching or printing, for example . The material of the radiation parts 110a, 110b, 110c, 110d and the material of the extension part 120 are, for example, copper, silver or conductive ink, but not limited thereto. The thickness of each radiating portion 110a, 110b, 110c, 110d and the thickness of each extending portion 120 are, for example, between 0.018 mm and 0.07 mm.

In addition, please refer to FIG. 1 again, the antenna structure 100 of this embodiment further includes a carrier 130 , wherein the radiating portions 110 a , 110 b , 110 c , 110 d and the extension portion 120 are disposed on the carrier 130 . The material of the carrier 130 is, for example, paper material, ceramics, epoxy glass fiberboard, polyimide (PI), polyester (PET), polyurethane (PU), polycarbonate (PC), polyethylene (PE) or polypropylene (PP), but not limited thereto. Here, the shape of the carrier 130 is, for example, a square. Preferably, the side length T of the carrier 130 is, for example, between 160 mm and 180 mm. Of course, in other non-illustrated embodiments, the shape of the carrier can also be a circle, and the diameter of the carrier is, for example, between 160 mm and 180 mm. In addition, the thickness of the carrier 130 is, for example, between 1.5 mm and 2.5 mm, which means that the antenna structure 100 of this embodiment has the advantage of being small in size. During fixing, holes can be made on the carrier 130 and related parts can be used to fix the device, or an adhesive layer can be applied on the back of the carrier 130 (ie, the opposite side of the antenna) to be fixed on the device, which is not limited.

In short, in this embodiment, four fan-shaped radiating portions 110a, 110b, 110c, and 110d are used as antenna conductors, and the first gap G1 between each sector can be used as a mutual coupling gap, and can Resonate with each other and generate a short-range magnetic field above the antenna structure 100 . In addition, the extension portion 120 of the antenna structure 100 is connected to the radiation portions 110a, 110b, 110c, and 110d and extends toward the center C of the circle, so that the magnetic field can be uniformly distributed. Therefore, the antenna structure 100 of the present embodiment can provide a uniformly distributed short-range magnetic field, and has high sensing sensitivity and sensing accuracy.

In application, the receiving range of the antenna structure 100 of this embodiment is less than 30 cm, and can be applied to unmanned stores or vending machines. If the product is placed on the shelf, each product can have its own near-field antenna; if it is not placed on the shelf, the product can be placed on it at checkout for checkout, but the size or number of the product increases the antenna quantity. Furthermore, the antenna structure 100 of this embodiment can be applied to a smart shelf, and read by near-field sensing, so that customers or employees can take out the products on the shelf as long as they swipe the identification card on the sensing device, and cooperate with the back end. The big data can deduct the payment and compile the details of the transaction.

FIG. 2 is a graph of frequency and impedance value of the HFSS computer-simulated antenna structure test of FIG. 1 . Theoretically, in the 902 MHz to 928 MHz frequency band, the impedance approaching 50±10Ω is ideal. In the impedance test of the HFSS computer simulated antenna structure shown in Figure 2, three frequencies (marked as 1, 2, and 3) in the frequency range of 902MHz to 928MHz were taken out, and the corresponding impedance values were measured as shown in Table 1. It can be seen that the impedance values are all close to 50±10Ω and meet the ideal value range.

Table I HFSS computer simulation antenna structure test Frequency (GHz) Impedance value (Ω) mark 1 0.90 41.26 Mark 2 0.91 42.41 mark 3 0.92 43.68

FIG. 3 is a graph of frequency and loss values of the HFSS computer-simulated antenna structure test of FIG. 1 . Theoretically, in the frequency band from 902MHz to 928MHz, it is ideal that the loss value (that is, the signal feedback loss value) should be lower than -12dB, which means that the lower the loss value, the more completely the energy sent by the reader to the antenna can be transmitted. In the loss test of the HFSS computer simulated antenna structure, three frequencies (marked as 4, 5, and 6) in the frequency range of 902MHz to 928MHz were taken out, and their corresponding loss values (ie, signal feedback loss values) were measured as shown in Table 2. And from the test results, it can be seen that the loss values are all lower than -12dB and meet the ideal value range.

Table II HFSS computer simulation antenna structure test Frequency (GHz) Loss value (dB) Mark 4 0.90 -20.09 Mark 5 0.91 -21.67 mark 6 0.92 -23.36

On the other hand, the physical test of the network instrument is carried out for the actual antenna structure, and three frequencies (marked as 7, 8, and 9) in the frequency range of 902MHz to 928MHz are also taken out. The test results are shown in Table 3, and it can be seen from the test results. The corresponding impedance values are all close to 50±10Ω, and the corresponding loss values are all lower than -12dB, so they all meet the ideal value range.

Table 3 Network instrument entity test Frequency (GHz) Impedance value (Ω) Loss value (dB) mark 7 0.902 56.971 -17.089 mark 8 0.915 57.108 -19.957 mark 9 0.928 55.228 -20.443

On the whole, the ideal standard for antenna matching value is that the impedance value is close to 50±10Ω and the loss value is lower than -12dB, which means that the magnetic field distribution in the short distance of the antenna structure is uniform, and it has high induction sensitivity and induction accuracy. Please refer to Figure 2, Figure 3 and Table 4 below at the same time, through the HFSS computer simulation antenna structure test and the actual antenna network instrument physical test comparison results, the impedance value is close to 50 ± 10 Ω, and the loss The values are all lower than -12dB, so they are all within the ideal standard range, which means that the magnetic field distribution in the short distance of the antenna structure is uniform, and it has high induction sensitivity and induction accuracy.

Table 4 HFSS computer simulation antenna structure test Network instrument entity test Frequency (GHz) 0.90 0.91 0.902 0.902 0.915 0.928 Impedance value (Ω) 41.28 42.41 43.68 56.971 57.108 55.228 Loss value (dB) -20.09 -21.67 -23.38 -17.08 -19.95 -20.44

To sum up, in the design of the antenna structure of the present invention, the radiating parts of the antenna structure are separated from each other and arranged in a circle, which can achieve the effect of mutual resonance and generate a short-range magnetic field above the antenna structure. In addition, the extension part of the antenna structure is connected to the radiation part and extends toward the center of the circle, so that the magnetic field can be uniformly distributed. In short, the antenna structure of the present invention can provide a uniformly distributed short-range magnetic field, and has high induction sensitivity and induction accuracy.

Although the present invention has been disclosed as above with examples, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The protection scope of the present invention shall be determined by the scope of the appended patent application.

10: Transmission line 100: Antenna structure 110a, 110b, 110c, 110d: Radiation part 112: First arc edge 114: Second arc edge 113: Opening 115: First Radiation Department 117: Second Radiation Department 120: Extensions 122: The first extension 124: Second extension 130: Carrier A: Included angle C: center of circle D: Diameter L: shortest distance L1, L2: length G1: first gap G2: Second Gap T: side length

FIG. 1 is a schematic top view of an antenna structure according to an embodiment of the present invention. FIG. 2 is a graph of frequency and impedance value of the HFSS computer-simulated antenna structure test of FIG. 1 . FIG. 3 is a graph of frequency and loss values of the HFSS computer-simulated antenna structure test of FIG. 1 .

10: Transmission line

100: Antenna structure

110a, 110b, 110c, 110d: Radiation part

112: First arc edge

114: Second arc edge

113: Opening

115: First Radiation Department

117: Second Radiation Department

120: Extensions

122: The first extension

124: Second extension

130: Carrier

A: Included angle

C: center of circle

D: Diameter

L: shortest distance

L1, L2: length

G1: first gap

G2: Second Gap

T: side length

Claims (19)

An antenna structure, comprising: a plurality of radiating parts, separated from each other and arranged in a circle; a plurality of extending parts, connecting the radiating parts and extending toward a center of the circle, wherein two of the two adjacent radiating parts A first gap between the top ends is equal to a second gap between two adjacent bottom ends of the extending portions, and a first radiating portion and a second radiating portion of the radiating portions are fed by a transmission line. The electrical circuit is connected, each of the extension parts includes a first extension part and a second extension part, and the first extension part is vertically connected to the second extension part; and a carrier, the radiating parts and the extension parts are arranged on the on the carrier, and the first radiating part and the second radiating part are located on the same plane. The antenna structure of claim 1, wherein the first gap ranges from 0.5 mm to 4 mm. The antenna structure of claim 1, wherein the radiating portions and the extending portions are integrally formed. The antenna structure of claim 1, wherein each of the radiating portions has a first arc-shaped edge and a second arc-shaped edge opposite to each other, and the length of the first arc-shaped edge is greater than the length of the second arc-shaped edge , and the extending portions are respectively connected to opposite sides of the second arc-shaped edge. The antenna structure of claim 4, wherein a shortest distance from the first arc-shaped edge to the second arc-shaped edge is between 34 mm and 40 mm. The antenna structure according to claim 1 or 4, wherein the shape of each radiating portion is a sector. The antenna structure of claim 1, wherein an included angle between the extending direction of the two adjacent first gaps and the center of the circle is 90 degrees. The antenna structure of claim 1, wherein one of the radiating portions has an opening to divide the radiating portion into the first radiating portion and the second radiating portion, and the aperture of the opening is equal to the first radiating portion gap. The antenna structure of claim 1, wherein the transmission line is a SAM connector, an N-type connector or a TNC connector. The antenna structure of claim 1, wherein the length of the first extension portion is between 29 mm and 32 mm. The antenna structure of claim 10, wherein the length of the second extension portion is between 8 mm and 15 mm. The antenna structure of claim 11, wherein the shape of each of the extending portions is an L-shape. The antenna structure as claimed in claim 12, wherein the L-shapes of each of the extending portions are separated by the second gap, and have a left-right inverted structure back-to-back. The antenna structure of claim 1, wherein the thickness of each of the radiation portions and the thickness of each of the extension portions is between 0.018 mm and 0.07 mm. The antenna structure of claim 1, wherein the shape of the carrier includes a square or a circle. The antenna structure of claim 15, wherein the side length or diameter of the carrier is between 160 mm and 180 mm. The antenna structure of claim 1, wherein the thickness of the carrier is between 1.5 mm and 2.5 mm. The antenna structure according to claim 1, wherein the material of the carrier comprises paper material, ceramics, epoxy glass fiber board, polyimide, polyester, polyurethane, polycarbonate, polyethylene or polyethylene acrylic. The antenna structure of claim 1, wherein the materials of the radiating parts and the materials of the extending parts comprise copper, silver or conductive ink.

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