CN104183913B - Broadband circle polarized RFID handheld readers antenna - Google Patents

Abstract

The invention discloses a kind of broadband circle polarized RFID handheld readers antenna, including FR4 substrates, loop antenna, high-pass filter, low pass filter, Wilkinson power divider and metal；FR4 base upper portions peripheral edge is provided with loop antenna；High-pass filter, low pass filter and Wilkinson power divider are provided with the inside of loop antenna；The output end of Wilkinson power divider connects the midpoint for connecting another adjacent inner wall of loop antenna after the midpoint for connecting the inwall of loop antenna one after low pass filter by the first feeder line, another road connection high-pass filter of output end of Wilkinson power divider by the second feeder line all the way；FR4 base lower portions are with being provided with metal.Inventive antenna has wide impedance bandwidth, wide axial ratio bandwidth, and its working frequency range can cover China, the working frequency range of the RFID prescribed by standard of US and European；Antenna has big circular polarisation main lobe width, and the main lobe width of its left-hand circular polarization directional diagram is 55 °.

Description

Broadband Circular Polarization RFID Handheld Reader Antenna

technical field

The invention belongs to the field of antenna technology and wireless communication, and relates to a broadband circularly polarized RFID handheld reader antenna.

Background technique

Radio Frequency Identification (RFID) technology is a non-contact communication technology that can identify specific targets and read and write data through wireless communication. The widely used UHF RFID frequency band standards in the world include Chinese standards (840-844.5MHz and 920.5-924.5MHz), American standards (902-928MHz) and European standards (866-869MHz).

As an important part of the RFID system, the RFID reader antenna's performance will greatly affect the efficiency and quality of the entire RFID system. The main factors affecting the RFID reader antenna include the size of the antenna, operating frequency band, impedance, gain and polarization.

The operating frequency bands of most existing circularly polarized UHF RFID reader antennas can only meet one of the Chinese standards, American standards, and European standards, and cannot cover all standard operating frequency bands at the same time.

Contents of the invention

The object of the present invention is to provide a broadband circularly polarized RFID handheld reader antenna for the deficiencies of the prior art.

The purpose of the present invention is achieved by the following technical solutions: a broadband circularly polarized RFID handheld reader antenna, including FR4 substrate, loop antenna, high-pass filter, low-pass filter, Wilkinson power divider and metal ground ; Wherein, the FR4 substrate is a square, and a loop antenna is provided on the upper peripheral edge; the loop antenna is a square loop structure, and a high-pass filter, a low-pass filter and a Wilkinson power divider are provided on the inner side; the Will The output end of the Kingson power divider is connected to the low-pass filter through the first feeder and connected to the midpoint of the inner wall of the loop antenna, and the other output end of the Wilkinson power divider is connected to the high-pass filter through the second feeder to connect the ring At the midpoint of the other adjacent inner wall of the antenna; the input end of the Wilkinson power divider is externally connected to the RF front-end through the through hole of the SMA connector; a metal ground is provided at the lower part of the FR4 substrate.

Further, the Wilkinson power divider includes a copper-clad split ring and a chip resistor, and the chip resistor is bridged to the opening of the copper-clad split ring.

Further, the high-pass filter includes a first chip capacitor, a second chip capacitor, a first chip inductor, a first copper-clad area, a second copper-clad area, a fourth copper-clad area and a fifth copper-clad area ; One end of the fourth copper clad area is connected to the second feeder, the other end is connected to one end of the fifth copper clad area through the first chip inductor, and the other end of the fifth copper clad area is connected to the Wilkinson power divider; A first chip capacitor is provided on the copper area, and the first chip capacitor is connected to the first copper-clad area, and is connected to the metal ground through a ground via hole; a second chip capacitor is provided on the fifth copper-clad area, and the second chip capacitor The chip capacitor is connected to the second copper pour area, and is connected to the metal ground through the ground via hole.

Further, the low-pass filter includes a third chip capacitor, a fourth chip capacitor, a second chip inductor, a third copper clad area, a sixth copper clad area and a seventh copper clad area; the seventh copper clad area One end of the area is connected to the Wilkinson power divider, the other end is connected to the sixth copper-clad area through the third chip capacitor, and the other end of the sixth copper-clad area is connected to the first feeder through the fourth chip capacitor; in the seventh A second chip inductor is provided on the copper-clad area, and the second chip inductor is connected to the third copper-clad area and connected to the metal ground through the ground via hole.

The beneficial effect of the present invention is that the size of the RFID antenna of the present invention is only 95mm×95mm×1.6mm, and it can be integrated into a hand-held reader. The antenna has a wide impedance bandwidth, and its -10dB impedance bandwidth is 710-1150MHz. The antenna has a wide axial ratio bandwidth, and the 3dB axial ratio bandwidth of the maximum gain direction is 800-940MHz, which can cover the working frequency bands of China, the United States and Europe. The antenna has a large circular polarization main lobe width, and the main lobe width of its left-handed circular polarization pattern is 55°.

Description of drawings

Figure 1 is a top view of the overall structure of the antenna;

Figure 2 is a bottom view of the overall structure of the antenna;

Fig. 3 is the impedance bandwidth test chart of antenna;

Figure 4 is a test diagram of the axial ratio bandwidth in the direction of the maximum gain of the antenna;

Fig. 5 is a left-handed circular polarization pattern perpendicular to the base direction when the antenna works at 910MHz.

detailed description

The present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in Figures 1 and 2, a broadband circularly polarized RFID handheld reader antenna of the present invention includes an FR4 substrate 5, a loop antenna 1, a high-pass filter, a low-pass filter, a Wilkinson power divider and a metal ground 17 ; Wherein, the FR4 base 5 is a square, and the upper peripheral edge is provided with a loop antenna 1; the loop antenna 1 is a square loop structure, and the inner side is provided with a high-pass filter, a low-pass filter and a Wilkinson power splitter; The output of the Wilkinson power divider is connected to the low-pass filter through the first feeder 2 and connected to the midpoint of the inner wall of the loop antenna 1, and the output of the Wilkinson power divider is connected to the high-pass filter through the other way. The second feeder 3 is connected to the midpoint of another adjacent inner wall of the loop antenna 1; the input end of the Wilkinson power divider is externally connected to the RF front end through the SMA connector through hole 16; a metal ground 17 is provided at the bottom of the FR4 substrate 5 .

The Wilkinson power divider includes a copper clad split ring 4 and a chip resistor 12 , and the chip resistor 12 is bridged at the opening of the copper clad split ring 4 .

The high-pass filter includes a first chip capacitor 6, a second chip capacitor 7, a first chip inductor 8, a first copper clad area 13, a second copper clad area 14, a fourth copper clad area 18 and a fifth Copper-clad area 19; one end of the fifth copper-clad area 19 is connected to the second feeder 3, the other end is connected to one end of the fourth copper-clad area 18 through the first chip inductor 8, and the other end of the fourth copper-clad area 18 is connected to Will Jinsen power divider; the first patch capacitor 6 is arranged on the fifth copper clad area 19, the first chip capacitor 6 is connected to the first copper clad area 13, and is connected to the metal ground 17 through the ground via hole; A second chip capacitor 7 is provided on the copper area 18 , and the second chip capacitor 7 is connected to the second copper-clad area 14 and connected to the metal ground 17 through a ground via hole.

The low-pass filter includes a third chip capacitor 9, a fourth chip capacitor 10, a second chip inductor 11, a third copper clad area 15, a sixth copper clad area 20 and a seventh copper clad area 21; One end of the seventh copper clad area 21 is connected to the Wilkinson power divider, the other end is connected to the sixth copper clad area 20 through the third chip capacitor 9, and the other end of the sixth copper clad area 20 is connected to the sixth copper clad area 20 through the fourth chip capacitor 10. The first feeder 2 is connected; the second chip inductor 11 is provided on the sixth copper-clad area 20, and the second chip inductor 11 is connected to the third copper-clad area 15, and is connected to the metal ground 17 through a ground via hole.

Among them, the size of the FR4 substrate 5 is 95mm×95mm×1.6mm, using FR4 material, and the dielectric constant is 4.4; the chip resistor 12 is a 100Ω chip resistor with a model of 1206; the first chip capacitor 6 and the second chip resistor The capacitance 7 is 1.4pF, the third chip capacitor 9 and the fourth chip capacitor 10 are both 8.5pF; the first chip inductor 8 is 6.2nH, the second chip inductor 11 is 12nH; the first chip capacitor 6 , the second chip capacitor 7, the third chip capacitor 9, the fourth chip capacitor 10, the first chip inductor 8 and the second chip inductor 11 all adopt the chip component of model 0603; the first feeder 2 and The width of the second feeder 3 is 3 mm and the same length; the inner diameter of the copper-clad split ring 4 is 13.7 mm and the outer diameter is 15.3 mm; the material of the metal ground 17 is copper, and the side length is 64 mm; the outer side length of the loop antenna 1 is 95 mm , The inner side length is 76mm.

The test input impedance of the antenna is shown in Figure 3, and the measured impedance matches well with the 50Ω impedance transmission line at 710-1150MHz. The axial ratio bandwidth test results of the antenna in the direction of maximum gain are shown in Figure 4, and the axial ratios are all less than 3dB at 800-940MHz. The left-hand circular polarization pattern of the antenna perpendicular to the base at 910MHz is shown in Figure 5. The maximum gain can reach 1.3dBic, and the 3dB power beamwidth can reach 55°.

The working process of the present invention is as follows: the radio frequency signal is fed to the Wilkinson power divider through the SMA connector through hole 16, and after the power is evenly distributed by the Wilkinson power divider, all the way is fed to the loop antenna through the high-pass filter and the second feeder 3 1. The other path is fed to the loop antenna 1 through a low-pass filter and the first feeder 2. The two signals generate a wideband 90° phase shift, so that the loop antenna 1 excites a circularly polarized signal operating at 800-940MHz for use in Broadband circular polarized RFID handheld reader.

Advantages of the RFID reader antenna of the present invention include:

(1) Low cost and relatively small size. The antenna only uses FR4 and copper as the most basic materials for antenna processing and commonly used patch components. And the size of the whole antenna is only 95mm×95mm×1.6mm, which is smaller than other circularly polarized antennas.

(2) The working frequency band can meet the Chinese standard, American standard and European standard of UHF frequency band RFID at the same time.

(3) The 800-940MHz frequency band works well. The reflection coefficients are all less than -10dB, the axial ratio bandwidth in the maximum gain direction is all less than 3dB, and the gain at 910MHz can reach 1.3dBic.

(4) The main lobe width of the circular polarization pattern is wide. When the operating frequency is 910MHz, the left-hand circular polarization 3dB power beam width can reach 55°.

The above-mentioned embodiments are provided for those of ordinary skill in the art to implement or use the present invention. Those of ordinary skill in the art can make various modifications or changes to the above-mentioned embodiments without departing from the inventive idea of the present invention. Therefore, the present invention The scope of protection of the invention is not limited by the above-mentioned embodiments, but should be the maximum scope consistent with the innovative features mentioned in the claims.

Claims (2)

1. a broadband circular polarization RFID handheld reader antenna is characterized in that, comprises FR4 substrate (5), loop antenna (1), high-pass filter, low-pass filter, Wilkinson power divider and metal ground ( 17); wherein, the FR4 substrate (5) is a square, and the upper peripheral edge is provided with a loop antenna (1); the loop antenna (1) is a square loop structure, and the inner side is provided with a high-pass filter, a low-pass filter and Wilkinson power divider; the output end of the Wilkinson power divider is connected to the low-pass filter through the first feeder (2) and connected to the midpoint of the inner wall of the loop antenna (1), and the Wilkinson power divider The other way of the output end of the power splitter is connected to the high-pass filter and then connected to the midpoint of the other adjacent inner wall of the loop antenna (1) through the second feeder (3); the input end of the Wilkinson power divider is through the through hole of the SMA connector (16 ) is externally connected to the RF front end; the bottom of the FR4 substrate (5) is provided with a metal ground (17); the high-pass filter includes a first chip capacitor (6), a second chip capacitor (7), a first chip inductor (8), the first copper clad area (13), the second copper clad area (14), the fourth copper clad area (18) and the fifth copper clad area (19); one end of the fifth copper clad area (19) Connect the second feeder (3), the other end is connected to one end of the fourth copper-clad area (18) through the first chip inductor (8), and the other end of the fourth copper-clad area (18) is connected to the Wilkinson power divider; A first chip capacitor (6) is provided on the fifth copper-clad area (19), and the first chip capacitor (6) is connected to the first copper-clad area (13), and is connected to the metal ground (17) through a ground via hole ; A second chip capacitor (7) is provided on the fourth copper-clad area (18), and the second chip capacitor (7) is connected to the second copper-clad area (14), and is connected to the metal ground (17) through a ground via hole connected; the low-pass filter includes a third chip capacitor (9), a fourth chip capacitor (10), a second chip inductor (11), a third copper-clad area (15), and a sixth copper-clad area (20) and the seventh copper-clad area (21); one end of the seventh copper-clad area (21) is connected to the Wilkinson power divider, and the other end passes through the third chip capacitor (9) and the sixth copper-clad area (20 ), the other end of the sixth copper-clad area (20) is connected to the first feeder (2) through the fourth chip capacitor (10); a second chip inductor ( 11), the second chip inductor (11) is connected to the third copper-clad area (15), and connected to the metal ground (17) through the ground via hole; the radio frequency signal is fed to the Wilkinson power divider through the SMA connector via hole (16) After the power is evenly distributed by the Wilkinson power divider, one path is fed to the loop antenna (1) through the high-pass filter and the second feeder (3), and the other path is fed to the loop antenna (1) through the low-pass filter and the first feeder (2). In the loop antenna (1), the two-way signals generate a broadband 90° phase shift, so that the loop antenna (1) is excited to generate a circularly polarized signal working at 800-940MHz. 2. a kind of broadband circularly polarized RFID handheld reader antenna according to claim 1, is characterized in that, described Wilkinson power divider comprises copper-clad split ring (4) and chip resistance (12), and chip The resistor (12) is bridged at the opening of the copper clad split ring (4).