Ternary linear phased-array antenna and ceiling type ultrahigh frequency RFID access control system

Abstract

The utility model discloses a ternary linear phased array antenna and ceiling type ultrahigh frequency RFID access control system, including power distribution network, phase shift circuit and ternary linear array antenna, the power distribution network includes two 3dB Wilkinson microstrip power divider, the input port of power distribution network is connected with signal source, the output end is equipped with three ports, the three ports are connected with the phase shift circuit, the phase shift circuit is connected with the 3dB Wilkinson microstrip power divider. The three ports are respectively connected with the three phase shift circuits, and the power ratio of output of the three ports is 2: 1: 1. According to the utility model, three non-overlapped sector wave beams are formed through the ternary linear phased-array antenna, and the width of the sector reaches 100 degrees, thereby ensuring that the three wave beams in the channel direction are not subjected to serial reading, and ensuring that the reading area is large enough in the direction perpendicular to the channel direction; and meanwhile, the size and the cost of the product are greatly reduced by only using three array elements, a fixed power distribution ratio and reflective circuit phase shift.

Description

Technical Field

[0001] The utility model relates to the technical field of ultra-high frequency RFID and antennas, and in particular to a three-element linear phased array antenna and a ceiling-mounted ultra-high frequency RFID access control system based on the three-element linear phased array antenna. Background Art

[0002] UHF RFID access control systems are currently widely used in shopping malls, library reading rooms, warehouses and other fields. The most common is the vertical access control system, which mainly uses infrared plus directional antennas to determine the entry and exit of people by the order in which multiple pairs of infrared sensors are blocked. The antenna field is limited to the range of the access control to identify the RFID tags entering the area.

[0003] The vertical access control system has three disadvantages. First, it occupies a relatively large area. Second, when multiple tags enter the antenna area at the same time, it is impossible to determine which one enters and which one exits. Third, due to the directionality of the directional antenna, it is easy to misread RFID tags outside the access control range.

[0004] In order to realize the scanning of the antenna beam of the access control system, the existing technology currently uses multiple antenna array elements, and realizes amplitude and phase control by switching unequal power division networks and microstrip lines of different electrical lengths.

[0005] In order to obtain multiple antenna beams with a certain accuracy, multiple antenna array elements, multiple unequal power division networks and multiple microstrip lines of different electrical lengths are required. The switching circuit will be very complicated and the circuit size will be very large, which cannot meet the needs of product miniaturization and low cost. Summary of the invention

[0006] In order to solve the above problems, the utility model proposes a three-element linear phased array antenna, including a power distribution network, a phase shift circuit and a three-element linear array antenna. The phase shift circuit switches three phase states so that three antenna elements have three different phase combinations to form fan beams in three directions.

[0007] Specifically, the utility model adopts the following technical solutions to achieve: a three-element linear phased array antenna, including a power distribution network, a phase shift circuit and a three-element linear array antenna.

[0008] The power distribution network includes two 3dB Wilkinson microstrip power dividers. The input port of the power distribution network is connected to the signal source. The output end is provided with three ports, which are respectively connected to three phase shift circuits. The power ratio of the three ports output is 2:1:1.

[0009] The phase shift circuit is based on the reflective phase shift principle and includes a 3dB hybrid coupler, two single-pole four-throw radio frequency switches, two capacitors and two inductors. The two single-pole four-throw switches synchronously switch three load states: capacitor, inductor and open circuit. The three load states correspond to the output phase of the phase shift circuit of -135°, 135° and 0° respectively.

[0010] The three-element linear array antenna includes a dielectric substrate and three microstrip patch antenna elements located on the dielectric substrate. The resonant frequencies of the three antenna elements are all 915 MHz. The three antenna elements are evenly arranged along a straight line, and the interval between the elements is half the air wavelength of 915 MHz.

[0011] The array element at the middle position is connected to the output port of the power distribution network with a power ratio of 2, and the two array elements at both sides of the array element at the middle position are respectively connected to the output ports of the two power distribution networks with a power ratio of 1.

[0012] Furthermore, the three antenna array elements have three different phase combinations to form fan beams in three directions, namely a left beam, a lower beam and a right beam.

[0013] When the phases of the three antenna elements are all 0°, the beam formed by the three-element linear array antenna points directly downward, which is the down beam.

[0014] When the phase of the left element is -135°, the phase of the middle element is 0°, and the phase of the right element is 135°, the beam formed by the three-element linear array antenna is oriented to the left, which is the left beam.

[0015] When the phase of the left element is 135°, the phase of the middle element is 0°, and the phase of the right element is -135°, the beam formed by the three-element linear array antenna is directed to the right, which is the right beam.

[0016] Furthermore, through simulation tests, the inclination angles of the left beam and the right beam are both 45°, the beam bandwidths of the left beam, the lower beam and the right beam along the array element direction are 45°, and the beam bandwidths perpendicular to the array element direction are 100°.

[0017] Furthermore, the lengths of the three microstrip lines in the power distribution network from the input port to the three phase shift circuits are equal. This ensures that the electromagnetic waves remain in phase when they reach the input ports of the three phase shift circuits, i.e., ensure that the excitation phases of the three antenna elements are only controlled by the three phase shift circuits. Based on the above-mentioned three-element linear phased array antenna, a ceiling-mounted ultra-high frequency RFID access control system is proposed, including a ceiling-mounted ultra-high frequency RFID access control, a display alarm system and a server.

[0018] The UHF RFID access control system includes an UHF RFID reader and a three-element linear phased array antenna. The UHF RFID reader inputs the inventory signal into the three-element linear phased array antenna, and controls the phase switching of the phase shift circuit through the IO port in the UHF RFID reader. After the UHF RFID reader obtains the tag information, it uploads the tag information to the server through the second network port, and the second network port is set in the UHF RFID reader.

[0019] The three-element linear phased array antenna comprises a power distribution network, a phase shift circuit and a three-element linear array antenna.

[0020] The power distribution network includes two 3dB Wilkinson microstrip power dividers. The input port of the power distribution network is connected to the UHF RFID reader. The output end is provided with three ports, which are respectively connected to three phase shift circuits. The power ratio of the three ports output is 2:1:1.

[0021] The phase shift circuit is based on the reflective phase shift principle and includes a 3dB hybrid coupler, two single-pole four-throw radio frequency switches, two capacitors and two inductors. The two single-pole four-throw switches synchronously switch three load states: capacitor, inductor and open circuit. The three load states correspond to the output phase of the phase shift circuit of -135°, 135° and 0° respectively.

[0022] The three-element linear array antenna includes a dielectric substrate and three microstrip patch antenna elements located on the dielectric substrate. The resonant frequencies of the three antenna elements are all 915 MHz. The three antenna elements are evenly arranged along a straight line, and the interval between the elements is half the air wavelength of 915 MHz.

[0023] The array element at the middle position is connected to the output port of the power distribution network with a power ratio of 2, and the two array elements at both sides of the array element at the middle position are respectively connected to the output ports of the two power distribution networks with a power ratio of 1.

[0024] Furthermore, the three antenna array elements have three different phase combinations to form fan beams in three directions, namely a left beam, a lower beam and a right beam.

[0025] When the phases of the three antenna elements are all 0°, the beam formed by the three-element linear array antenna points directly downward, which is the down beam.

[0026] When the phase of the left element is -135°, the phase of the middle element is 0°, and the phase of the right element is 135°, the beam formed by the three-element linear array antenna is oriented to the left, which is the left beam.

[0027] When the phase of the left element is 135°, the phase of the middle element is 0°, and the phase of the right element is -135°, the beam formed by the three-element linear array antenna is directed to the right, which is the right beam.

[0028] The display alarm system includes a main control unit, a display screen, an audible and visual alarm unit and a first network port. The main control unit receives data information sent by the server through the network port, the display screen is used to display information of illegal tags, and the audible and visual alarm unit is used to prompt illegal tags to enter or leave.

[0029] The ceiling-mounted ultra-high frequency RFID access control system scans the RFID tags entering the access control area through the left beam, the lower beam and the right beam, obtains the movement trajectory of the tag through the order in which the three beams scan the tag, and uploads the data to the server. The server determines whether there is a tag illegally entering or leaving the access control area based on the system information. If the tag illegally enters or leaves the access control area, the tag information is sent to the display alarm system. The display alarm system issues an alarm through the sound and light alarm unit, and displays the tag information of the illegal entry or exit on the display screen.

[0030] The beneficial effect of the utility model lies in that three non-overlapping sector beams are formed by a three-element linear phased array antenna, and the sector width is 100°, which not only ensures that the three beams along the channel direction will not be read in series, but also ensures that there is a sufficiently large reading area perpendicular to the channel direction; at the same time, by using only three array elements, a fixed power allocation ratio and a reflective phase shifting circuit, the size and cost of the product are greatly reduced.

[0031] The above description is only an overview of the technical solution of the utility model. In order to more clearly understand the technical means of the utility model, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites a preferred embodiment and describes it in detail with the accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 This is a schematic diagram of the ceiling-mounted UHF RFID access control system;

[0034] Figure 2 This is the internal architecture diagram of the ceiling-mounted UHF RFID access control system;

[0035] Figure 3is the block diagram of the phase shift circuit;

[0036] Figure 4 This is the arrangement diagram of the three-element linear array antenna;

[0037] Figure 5 To show the internal block diagram of the alarm system;

[0038] Figure 6 This is the 3D simulation diagram of the left beam;

[0039] Figure 7 This is the simulation diagram of the 3dB bandwidth of the left beam along the directional beam arrangement of the array elements;

[0040] Figure 8 This is the simulation diagram of the 3dB bandwidth of the left beam along the direction perpendicular to the array element arrangement;

[0041] In the figure: 100, server; 200, ceiling-mounted UHF RFID access control; 210, UHF RFID reader; 220, second network port; 230, 3dB Wilkinson microstrip power divider; 240, phase shift circuit; 241, 3dB hybrid coupler; 242, single-pole four-throw switch; 243, chip inductor; 244, chip capacitor; 245, open-circuit total reflection load; 250, three-element linear array antenna; 251, dielectric substrate; 252, chip array unit; 300, display alarm system; 310, main control unit; 320, display screen; 330, sound and light alarm unit; 340, first network port. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects solved by the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0043] The utility model is further described in conjunction with the accompanying drawings.

[0044] like Figure 1 The figure shows a schematic diagram of a ceiling-mounted UHF RFID access control system based on a three-element linear phased array antenna. The ceiling-mounted UHF RFID access control system includes a server 100, a ceiling-mounted UHF RFID access control system 200 and a display alarm system 300.

[0045] The ceiling-mounted UHF RFID access control 200 can form three fan-shaped beams, including a left beam that can scan area 1, a lower beam that can scan area 2, and a right beam that can scan area 3. When a tag enters from area 1, passes through area 2, and then leaves the access control scanning area from area 33, it will be scanned by the three fan-shaped beams in turn, and the ceiling-mounted UHF RFID access control 200 will report the information of the tag to the server 100.

[0046] After system search, if the server 100 finds that the tag has not been unlocked by the system, it will be deemed as an illegal operation and the information of the tag will be sent to the display alarm system 300.

[0047] like Figure 5 The figure shows an internal block diagram of the display alarm system 300, which includes a main control unit 310, a display screen 320, an audio and video alarm unit 330 and a first network port 340. The first network port 340 is responsible for receiving data from the server 100. After receiving the tag data of illegal operation, the main control unit 310 controls the audio and video alarm unit 330 to issue an audio and video alarm prompt, and displays the information of the tag on the display screen 320.

[0048] like Figure 2 The figure shows the internal architecture block diagram of the ceiling-mounted UHF RFID access control 200, including an UHF RFID reader / writer 210, a second network port 220, a 3dB Wilkinson microstrip power divider 230, a phase shift circuit 240 and a three-element linear array antenna 250. The UHF RFID reader / writer 210 inputs the inventory signal into the power distribution network, and at the same time controls the phase shift circuit 240 to perform phase switching through the IO port in the UHF RFID reader / writer 210, and collects the tag information through the UHF RFID reader / writer, and then uploads the tag information to the server 100 through the second network port 220.

[0049] The three-element linear phased array antenna includes the above-mentioned power distribution network, phase shift circuit 240 and three-element linear array antenna 250. The power distribution network includes two 3dB Wilkinson microstrip power dividers 230. The input port of the power distribution network is connected to the ultra-high frequency RFID reader 210. The output end includes three ports, which are respectively connected to three phase shift circuits 240. The power ratios of the three ports output are 2:1:1.

[0050] The Wilkinson microstrip power divider 230 includes a Wilkinson power divider 1 and a Wilkinson power divider 2, the phase shift circuit 240 includes a phase shift circuit 1, a phase shift circuit 2 and a phase shift circuit 3, and the three-element linear array antenna 250 includes an antenna 1, an antenna 2 and an antenna 3.

[0051] The input power first passes through Wilkinson power divider 1 and is divided into two paths, one path is input to phase shift circuit 1 and then fed into antenna 1, and the other path is input to Wilkinson power divider 2 and then divided into two paths, one path is input to phase shift circuit 2 and then fed into antenna 2, and the other path is input to phase shift circuit 3 and then fed into antenna 3. In order to ensure that the phases of antenna 1, antenna 2 and antenna 3 are only controlled by phase shift circuit 240, the lengths of the microstrip lines of Wilkinson power divider 1 and Wilkinson power divider 2 need to be adjusted so that the phases of the electromagnetic waves reaching the three input ports of phase shift circuit 1, phase shift circuit 2 and phase shift circuit 3 are the same.

[0052] like Figure 3 The circuit block diagram of the phase shift circuit 240 is shown, including a 3dB hybrid coupler 241, a single-pole four-throw switch 242, a chip inductor 243 and a chip capacitor 244, P1 is the input port of the 3dB hybrid coupler 241, P2 is the output port of the 3dB hybrid coupler 241, the load modes of the circuit include a reactive total reflection load and an open circuit total reflection load 245, the chip inductor 243 and the chip capacitor 244 are both reactive total reflection loads, and the single-pole four-throw switch 242 realizes phase switching by switching different load modes.

[0053] Assume the load impedance QUOTE , QUOTE , the reflection coefficient is QUOTE , phase shift angle QUOTE It can be determined by the following formula: QUOTE And QUOTE By selecting appropriate inductance and capacitance values, the single-pole four-throw switch 242 can switch the load mode. When switching to the open-circuit total reflection load 245, the phase shift is 0°, when switching to the chip inductor 243, the phase shift is 135°, and when switching to the chip capacitor 244, the phase shift is -135°.

[0054] like Figure 4 As shown, the three-element linear array antenna 250 includes a dielectric substrate 251 and a patch array unit 252, and the patch array unit 252 is composed of antenna 1, antenna 2 and antenna 3, wherein antenna 1 is connected to phase shift circuit 1 and is located in the middle of the array, antenna 2 is connected to phase shift circuit 2 and is located on the left side of the array, and antenna 3 is connected to phase shift circuit 2 and is located on the right side of the array.

[0055] The patch array unit 252 is a microstrip metal patch with a resonant frequency of 915 MHz. The distance between the center position of antenna 1 and antenna 2 and the center position of antenna 3 is 1 / 2 of the 915 MHz air wavelength.

[0056] When the phases of antenna 1, antenna 2, and antenna 3 are all 0°, the beam formed by the three-element linear array antenna 250 points directly downward, which is the lower beam, and its scanning area is Figure 1 Region 2 in

[0057] When the phase of antenna 1 is 0°, the phase of antenna 2 is -135°, and the phase of antenna 3 is 135°, the beam formed by the three-element linear array antenna 250 is oriented to the left, which is the left beam, and its scanning area is Figure 1 Region 1 in

[0058] When the phase of antenna 1 is 0°, the phase of antenna 2 is 135°, and the phase of antenna 3 is -135°, the beam formed by the three-element linear array antenna 250 is oriented to the right, which is the right beam, and its scanning area is Figure 1 Area 3 in.

[0059] like Figure 6 The figure shows a 3D simulation diagram of the left beam, which has a fan-shaped shape.

[0060] like Figure 7 As shown, the inclination angle of the left beam is 90°-m1, which is about 45°, along the direction of the array element arrangement ( Figure 6 The beam width (m2-m3, x-axis) is approximately 45°.

[0061] like Figure 8 As shown, the left beam is along the direction perpendicular to the array element arrangement ( Figure 6 The beam width (m6-m5, center y-axis) is approximately 100°.

[0062] The utility model discloses a ceiling-mounted ultra-high frequency RFID access control system based on a three-element linear phased array antenna, which can form three beams that do not overlap in the channel direction, thereby reducing the probability of cross-reading in the three beam directions.

[0063] In the direction perpendicular to the channel, the fan of each beam is 100°, which improves the reading range and success rate at each beam location.

[0064] What is described above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes within the technical scope disclosed by the present invention according to the technical scheme and the utility model concept of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A three-element linear phased array antenna, comprising a power distribution network, a phase shifting circuit and a three-element linear array antenna, The power distribution network includes two 3dB Wilkinson microstrip power dividers, the input port of the power distribution network is connected to the signal source, and the output end is provided with three ports, which are respectively connected to three phase shift circuits, and the power ratio of the three ports output is 2:1:1; The phase shift circuit is based on the reflective phase shift principle and includes a 3dB hybrid coupler, two single-pole four-throw radio frequency switches, two capacitors and two inductors; the two single-pole four-throw switches synchronously switch three load states of capacitor, inductor and open circuit, and the three load states correspond to the output phase of the phase shift circuit of -135°, 135° and 0° respectively; The three-element linear array antenna comprises a dielectric substrate and three microstrip patch antenna elements located on the dielectric substrate, the resonant frequencies of the three antenna elements are all 915 MHz, the three antenna elements are evenly arranged along a straight line, and the interval between the elements is half the air wavelength of 915 MHz; The array element at the middle position is connected to the output port of the power distribution network with a power ratio of 2, and the two array elements at both sides of the array element at the middle position are respectively connected to the output ports of the two power distribution networks with a power ratio of 1; The three antenna array elements have three different phase combinations, forming fan beams in three directions, namely the left beam, the down beam and the right beam.

2. The three-element linear phased array antenna according to claim 1, characterized in that: When the phases of the three antenna elements are all 0°, the beam formed by the three-element linear array antenna points directly downward, which is the down beam. When the phase of the left element is -135°, the phase of the middle element is 0°, and the phase of the right element is 135°, the beam formed by the three-element linear array antenna is oriented to the left, which is the left beam. When the phase of the left element is 135°, the phase of the middle element is 0°, and the phase of the right element is -135°, the beam formed by the three-element linear array antenna is directed to the right, which is the right beam.

3. The three-element linear phased array antenna according to claim 1, characterized in that: The inclination angles of the left beam and the right beam are both 45°, the beam bandwidths of the left beam, the lower beam and the right beam along the array element direction are 45°, and the beam bandwidths perpendicular to the array element direction are 100°.

4. The three-element linear phased array antenna according to claim 1, characterized in that: The three microstrip lines in the power distribution network extending from the input port to the three phase shifting circuits are equal in length.

5. Based on the above three-element linear phased array antenna, a ceiling-mounted ultra-high frequency RFID access control system is proposed, including a ceiling-mounted ultra-high frequency RFID access control, a display alarm system and a server, characterized in that: The UHF RFID access control system includes an UHF RFID reader and a three-element linear phased array antenna. The UHF RFID reader is in signal communication with the three-element linear phased array antenna. The UHF RFID reader is provided with an IO port capable of controlling the phase switching of a phase shift circuit. The UHF RFID reader is provided with a second network port, and is connected to the server through the second network port. The three-element linear phased array antenna comprises a power distribution network, a phase shift circuit and a three-element linear array antenna. The power distribution network includes two 3dB Wilkinson microstrip power dividers. The input port of the power distribution network is connected to the UHF RFID reader. The output end is provided with three ports, which are respectively connected to three phase shift circuits. The power ratio of the three ports output is 2:1:

1. The phase shift circuit is based on the reflective phase shift principle and includes a 3dB hybrid coupler, two single-pole four-throw radio frequency switches, two capacitors and two inductors. The two single-pole four-throw switches synchronously switch three load states: capacitor, inductor and open circuit. The three load states correspond to the output phase of the phase shift circuit of -135°, 135° and 0° respectively. The three-element linear array antenna comprises a dielectric substrate and three microstrip patch antenna elements on the dielectric substrate. The resonant frequencies of the three antenna elements are all 915 MHz. The three antenna elements are evenly arranged along a straight line, and the interval between the elements is half the air wavelength of 915 MHz. The array element at the middle position is connected to the output port of the power distribution network with a power ratio of 2, and the two array elements at both sides of the array element at the middle position are respectively connected to the output ports of the two power distribution networks with a power ratio of 1; The three antenna array elements have three different phase combinations to form fan beams in three directions, namely a left beam, a lower beam and a right beam.

6. According to claim 5, a ceiling-mounted ultra-high frequency RFID access control system is characterized in that: When the phases of the three antenna elements are all 0°, the beam formed by the three-element linear array antenna points directly downward, which is the down beam. When the phase of the left element is -135°, the phase of the middle element is 0°, and the phase of the right element is 135°, the beam formed by the three-element linear array antenna is oriented to the left, which is the left beam. When the phase of the left element is 135°, the phase of the middle element is 0°, and the phase of the right element is -135°, the beam formed by the three-element linear array antenna is directed to the right, which is the right beam.

7. According to claim 5, a ceiling-mounted UHF RFID access control system is characterized in that: The display alarm system includes a main control unit, a display screen capable of displaying illegal tag information, an audible and visual alarm unit capable of prompting illegal tags to enter or leave a scanning area, and a first network port, and the main control unit is connected to the server via the first network port.

8. According to claim 5, a ceiling-mounted UHF RFID access control system is characterized in that: The inclination angles of the left beam and the right beam are both 45°, the beam bandwidths of the left beam, the lower beam and the right beam along the array element direction are 45°, and the beam bandwidths perpendicular to the array element direction are 100°.

9. The ceiling-mounted UHF RFID access control system according to claim 5, characterized in that: The three microstrip lines in the power distribution network extending from the input port to the three phase shifting circuits are equal in length.

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