CN110247158B - UHF RFID reader antenna and switching method - Google Patents
UHF RFID reader antenna and switching method Download PDFInfo
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- CN110247158B CN110247158B CN201910449749.7A CN201910449749A CN110247158B CN 110247158 B CN110247158 B CN 110247158B CN 201910449749 A CN201910449749 A CN 201910449749A CN 110247158 B CN110247158 B CN 110247158B
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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
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/0006—Particular feeding systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q21/00—Antenna arrays or systems
- H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
- H01Q21/20—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path
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Abstract
The embodiment of the invention provides an UHF RFID reader antenna and a switching method. The antenna includes: n same antenna elements, N equal power dividers, phase extension lines, phase compensation lines and radio frequency switches are uniformly distributed on a printed circuit board, the N antenna elements, the N equal power dividers and the phase extension lines form a first group of N-arm feed networks with the same amplitude and the phase difference of 360 degrees/N, the N antenna elements, the N equal power dividers, the phase extension lines and the phase compensation lines form a second group of N-arm feed networks with the same amplitude and the same phase, and the radio frequency switches control the switching antennas to enter a first group of N-arm feed network mode or a second group of N-arm feed network mode. The feed network mode is switched to form switching of a far-field antenna mode and a near-field antenna mode, so that the characteristic of a far UHF RFID reading distance is kept, and the reading coverage area and the near-field intensity of a near-field area are increased under the condition of not increasing the cost and the system complexity.
Description
Technical Field
The embodiment of the invention relates to the technical field of antennas, in particular to a UHF RFID (ultra high frequency radio frequency identification) reader antenna and a switching method.
Background
Radio Frequency Identification (RFID) is an automatic Identification technology that automatically identifies a target object by a Radio Frequency signal, and rapidly performs item tracking and data exchange. The RFID technology does not need manual intervention, can work in various severe environments, can simultaneously identify a plurality of labels, is quick and convenient to operate, and is widely applied to the fields of warehouse logistics, book management, industrial production, traffic, clothing and the like.
Fig. 1 is a schematic structural diagram of an RFID system in the prior art, and as shown in fig. 1, the RFID system mainly comprises three parts: the Reader comprises a Reader (Reader), a Tag (Tag) and a data processing system (Processor), wherein the Reader comprises a control module, a radio frequency module and a Reader Antenna (Reader Antenna); the tag includes a tag antenna and a tag chip.
Currently, there are four operating frequency bands for RFID, which are: low frequency (LF: 135 KHz-134 KHz), high frequency (HF: 13.56MHz), ultra high frequency (UHF: 860-960 MHz), and microwave bands (2.4GHz and 5.8 GHz). The UHF RFID technology has the characteristics of simultaneous reading of a plurality of tags, repeated reading and writing, large data capacity, low tag cost, small volume, convenient use, high reliability, long service life and the like, and is widely applied.
The tag antenna of the UHF band mostly adopts a dipole antenna form, the polarization direction is linear polarization, and in order to read the tags of each polarization direction, the conventional UHF reader antenna generally adopts a circular polarization antenna, such as a quadrifilar helix circular polarization antenna, a microstrip circular polarization antenna and the like, and has the characteristics of high gain, long reading distance and the like, and the reading distance can reach 10 meters generally. However, the energy distribution of the UHF radio frequency identification device is concentrated or uneven in a near field area (within 30 cm), so that the reading coverage area is small or a reading blind area exists, and the UHF radio frequency identification device is limited in the RFID application of scenes where the near field or the near field and the far field exist.
Disclosure of Invention
Aiming at the defects in the prior art, the embodiment of the invention provides an UHF RFID reader antenna and a switching method.
In a first aspect, an embodiment of the present invention provides an UHF RFID reader antenna, including: n arm feed network and N-1 radio frequency switches;
the N-arm feed network comprises N antenna oscillators and a power division phase shift network which are identical and uniformly distributed on the front surface of the printed circuit board, wherein N is an integer greater than 1;
the power distribution phase shift network comprises N equal power distribution devices, N phase extension lines and N-1 phase compensation lines, wherein each N equal power distribution device comprises 1 input port and N output ports, the input ports are connected with a radio frequency module of a UHF RFID reader, and the N output ports are respectively connected with one ends of the N phase extension lines and used for providing N feeds with the same amplitude and the phase difference of 360 DEG/N;
the other end of the first phase extension line in the N phase extension lines is connected with the feed end of one antenna element in the N-arm feed network;
the other ends of the rest N-1 phase extension lines in the N phase extension lines are respectively connected with one ends of the N-1 radio frequency switches, the other ends of the N-1 radio frequency switches are respectively connected with one ends of the N-1 phase compensation lines and a control module of a UHF RFID reader, and the other ends of the N-1 phase compensation lines are respectively connected with the feed ends of the rest N-1 antenna oscillators in the N-arm feed network;
the grounding ends of the N antenna oscillators are connected with a reference grounding end on the front side of the printed circuit board;
when the control module controls the N-1 radio frequency switches to be switched off, a first group of N-arm feed networks with the same amplitude and the same phase difference of 360 degrees/N are formed, and when the control module controls the N-1 radio frequency switches to be switched on, a second group of N-arm feed networks with the same amplitude and the same phase are formed.
As the antenna, optionally, each of the N-1 rf switches includes: the radio frequency input port, two radio frequency output ports and two direct current input ports;
the radio frequency input port is connected with the feed end of the corresponding antenna oscillator;
a first radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase extension line;
the second radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase compensation line;
the two direct current input ports are respectively connected with a direct current power supply of the reader and a control module of the UHF RFID reader, and the two direct current input ports switch the UHF RFID reader antenna to a first group of N-arm feed networks or a second group of N-arm feed networks through direct current signals under the control of the control module.
As for the antenna, optionally, when a first dc input port of the two dc input ports of each of the N-1 rf switches supplies power and a second dc input port of the two dc input ports is powered off, the first group of N-arm feed networks is connected;
and when each first direct current input port in the N-1 radio frequency switches is powered off and each second direct current input port is powered on, the second group of N arm feed networks are communicated.
As the above antenna, optionally, the N-division power divider, the phase extension line, and the phase compensation line are formed by a microstrip transmission line.
As for the above antenna, optionally, the forming the N-division power divider by a microstrip transmission line includes:
n-1 halved Wilkinson power dividers are formed through microstrip transmission lines, each halved Wilkinson power divider comprises two output ports and an input port, and the N-1 halved Wilkinson power dividers are connected to form the N halved power dividers.
As the above antenna, optionally, the forming the phase extension line and the phase compensation line by a microstrip transmission line includes:
according to the working wavelength lambda of the microstrip transmission line0Dielectric constant ∈rAnd calculating the waveguide wavelength lambda of the microstrip transmission line according to the height-to-width ratio h/Wg；
Calculating lambdagThe length of the phase extension line and the phase compensation line is determined by/N.
As for the antenna, optionally, N is 2M, M is an integer greater than 1, and the N antenna elements are arranged in a circle on the front surface of the printed circuit board.
As with the antenna described above, optionally N-4.
In a second aspect, an embodiment of the present invention provides a UHF RFID reader antenna switching method, which is applied to the UHF RFID reader antenna described above, and includes:
when the data of the tag antenna needs to be read, the radio frequency switch is switched to be connected to the first group of N-arm feed networks or the second group of N-arm feed networks according to a preset frequency so as to read the data of the tag antenna.
The method as described above, optionally, further includes:
and if all the data of the tag antenna are read, stopping switching.
The method as described above, optionally, further includes:
if the distance between the tag antenna and the UHF RFID reader antenna is smaller than a first preset length, switching the radio frequency switch to be connected to a second group of N-arm feed networks with the same amplitude and phase to read data of the tag antenna;
and if the distance between the tag antenna and the UHF RFID reader antenna is judged to be larger than a second preset length, the radio frequency switch is switched to be connected to a first group of N arm feed networks with the same amplitude and phase difference of 360 DEG/N so as to read the data of the tag antenna.
The UHF RFID reader antenna provided by the embodiment of the invention adopts the technical scheme that N identical antenna elements are uniformly distributed on the front side of a printed circuit board, an N equal power divider, a phase extension line and a phase compensation line are arranged on the front side or the back side of a PCB, a radio frequency switch is arranged on the front side or the back side of the PCB, the N antenna elements, the N equal power divider and the phase extension line form a first group of N-arm feed networks with identical amplitude and 360 DEG/N phase difference, the N antenna elements, the N equal power divider, the phase extension line and the phase compensation line form a second group of N-arm feed networks with identical amplitude and identical phase, and the radio frequency switch controls the switching antenna to enter a first group of N-arm feed network mode or a second group of N-arm feed network mode. Because one group of the two groups of feed networks has high near field intensity and the other group has high far field intensity, the feed network mode is switched to form the switching of a far field antenna mode and a near field antenna mode, and the reading coverage area and the near field intensity of a near field area are increased under the condition of keeping the characteristic of long reading distance of UHF RFID without increasing the cost and the system complexity.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a prior art RFID system;
FIG. 2 is a schematic diagram of an antenna structure of a UHF RFID reader according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a quartering power divider of an antenna of a UHF RFID reader according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a near-field electric field distribution of a first group of four-arm feed networks according to an embodiment of the present invention;
fig. 5 is a schematic diagram of a near-field electric field distribution of a second group of four-arm feed networks according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to improve the near field coverage area of the UHF RFID reader antenna, N identical antenna elements are uniformly distributed on the front surface (Top) of a Printed Circuit Board (PCB), an N equal power divider, a phase extension line and a phase compensation line are arranged on the front surface or the back surface (Bot) of the PCB, a radio frequency switch is arranged on the front surface or the back surface of the PCB, the N antenna elements, the N equal power divider and the phase extension line form a first group of N arm feed networks with identical amplitude and phase difference of 360 DEG/N, the N antenna elements, the N equal power divider, the phase extension line and the phase compensation line form a second group of N arm feed networks with identical amplitude and phase difference, and the radio frequency switch controls the switching antenna to enter a first group of N arm feed network mode or a second group of N arm feed network mode. Because one group of the two groups of feed networks has high near field intensity and the other group has high far field intensity, the feed network mode is switched to form the switching of a far field antenna mode and a near field antenna mode, and the reading coverage area and the near field intensity of a near field area are increased under the condition of keeping the characteristic of long reading distance of UHF RFID without increasing the cost and the system complexity.
The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.
Fig. 2 is a schematic view of an antenna structure of a UHF RFID reader according to an embodiment of the present invention, as shown in fig. 2, including: n arm feed network and N-1 radio frequency switches;
the N-arm feed network comprises N antenna oscillators and a power division phase shift network which are identical and uniformly distributed on the front surface of the printed circuit board, wherein N is an integer greater than 1;
the power distribution phase shift network comprises N equal power distribution devices, N phase extension lines and N-1 phase compensation lines, wherein each N equal power distribution device comprises 1 input port and N output ports, the input ports are connected with a radio frequency module of a UHF RFID reader, and the N output ports are respectively connected with one ends of the N phase extension lines and used for providing N feeds with the same amplitude and the phase difference of 360 DEG/N;
the other end of the first phase extension line in the N phase extension lines is connected with the feed end of one antenna element in the N-arm feed network;
the other ends of the rest N-1 phase extension lines in the N phase extension lines are respectively connected with one ends of the N-1 radio frequency switches, the other ends of the N-1 radio frequency switches are respectively connected with one ends of the N-1 phase compensation lines and a control module of a UHF RFID reader, and the other ends of the N-1 phase compensation lines are respectively connected with the feed ends of the rest N-1 antenna oscillators in the N-arm feed network;
the grounding ends of the N antenna oscillators are connected with a reference grounding end on the front side of the printed circuit board;
when the control module controls the N-1 radio frequency switches to be switched off, a first group of N-arm feed networks with the same amplitude and the same phase difference of 360 degrees/N are formed, and when the control module controls the N-1 radio frequency switches to be switched on, a second group of N-arm feed networks with the same amplitude and the same phase are formed.
Specifically, as shown in fig. 2, N identical antenna elements are uniformly distributed on the front surface of the PCB, where N may be singular or even, and these antenna elements may be one or more of monopole (monopole), dipole (dipole), loop (loop), inverted f (ifa), planar inverted f (pifa), and microstrip patch (patch). The antenna oscillators comprise a feed end and a grounding end, the grounding end of the antenna oscillator is connected with a reference grounding end of the Top surface, and the reference grounding end can be realized by covering copper on the Top surface of the PCB. An N-division power divider is further disposed on the Top surface or the Bot surface of the PCB (fig. 2 takes the Top surface as an example), the N-division power divider is for implementing N feeding with the same amplitude, the N-division power divider includes 1 input port and N output ports, the input port is connected to a radio frequency module (shown in fig. 1) of the reader, the N output ports are respectively connected to N phase extension lines (shown by thin lines in fig. 2), the purpose of the phase extension lines is for implementing N feeding with a phase difference of 360 °/N, for example, N is 8, if the antenna array and the phase extension line are not on the same plane of the PCB, the feeding end of the antenna element passes through the PCB and is connected with the phase extension line on the other plane. The other ends of the other N-1 phase extension lines are connected to one ends of the N-1 radio frequency switches, the other ends of the radio frequency switches are connected to one ends of the N-1 phase compensation lines (shown by thick lines in fig. 2) and a control module (shown in fig. 1) of the reader, the control module is used for controlling the radio frequency switches to be disconnected or connected, and the other ends of the phase compensation lines are connected to the feed ends of the other N-1 antenna oscillators. When the control module controls the N-1 radio frequency switches to be connected, the phase compensation line is connected to the phase compensation line to compensate the phase, and a second group of N-arm feed networks with the same amplitude and the same phase are formed.
In the embodiment of the present invention, the switching between the first group of N-arm feed networks and the second group of N-arm feed networks is controlled by the radio frequency switch, and the radio frequency switch may be disposed on the front side or the back side of the PCB. When the radio frequency switch is communicated with the first group of N-arm feed network, the reader antenna is in a first group of N-arm feed network mode, when the radio frequency switch is communicated with the second group of N-arm feed network, the reader antenna is in a second group of N-arm feed network mode, because one group of the two groups of feed networks (same amplitude and same phase) has high near field intensity and the other group (same amplitude and same phase with 360 degrees/N) has high far field intensity, switching between a far field antenna mode and a near field antenna mode is formed by switching the feed network modes, and the reading coverage area and the near field intensity of a near field area are increased without increasing the cost and the system complexity while the characteristic of far UHF RFID reading distance is maintained.
On the basis of the above embodiment, further, each of the N-1 rf switches includes: the radio frequency input port, two radio frequency output ports and two direct current input ports;
the radio frequency input port is connected with the feed end of the corresponding antenna oscillator;
a first radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase extension line;
the second radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase compensation line;
the two direct current input ports are respectively connected with a direct current power supply of the reader and a control module of the UHF RFID reader, and the two direct current input ports switch the UHF RFID reader antenna to a first group of N-arm feed networks or a second group of N-arm feed networks through direct current signals under the control of the control module.
When a first direct current input port of the two direct current input ports of each radio frequency switch of the N-1 radio frequency switches supplies power and a second direct current input port of the two direct current input ports is powered off, the first group of N-arm feed networks are communicated;
and when each first direct current input port in the N-1 radio frequency switches is powered off and each second direct current input port is powered on, the second group of N arm feed networks are communicated.
Specifically, each radio frequency switch includes: 1 radio frequency input port connected to the feed end of the antenna oscillator corresponding to the radio frequency switch through a microstrip transmission line; 2 radio frequency output ports, wherein one radio frequency output port RF1 is connected with the phase extension line corresponding to the radio frequency switch, and the other radio frequency output port RF2 is connected with the phase compensation line corresponding to the radio frequency switch; 2 direct current input ports V1 and V2 are respectively connected with a direct current power supply of the reader and a control module of the reader, and the control module provides direct current signals and simultaneously controls the switching of the states of the N-1 radio frequency switches. When a first direct current input port V1 of two direct current input ports of each radio frequency switch in the N-1 radio frequency switches supplies power and a second direct current input port V2 is powered off, the first group of N arm feed networks are connected; when each first direct current input port V1 in the N-1 radio frequency switches is powered off and each second direct current input port V2 is powered on, the second group of N arm feed networks are connected.
For example, when N is 4, there are 3 rf switches, and 6 dc input ports of the 3 rf switches may form two switch modes, i.e., mode 1((1,0), (1,0)) and mode 2((0,1), (0,1)), and when the rf switches are in mode 1((1,0), (1,0)), the feeding network is not directly connected to 4 antenna elements through phase compensation lines, and 4 feeding lines with the same amplitude and 90 degrees of phase are provided to form a far-field antenna mode; when the radio frequency switch is in a mode 2((0,1), (0,1)), the feed network is connected with 4 antenna elements through phase compensation lines, 4 feeds with the same amplitude and the same phase are provided, and a near-field antenna mode is formed.
In addition to the above embodiments, the N-division power divider, the phase extension line, and the phase compensation line are formed by microstrip transmission lines.
The forming of the N-division power divider by a microstrip transmission line includes:
n-1 halved Wilkinson power dividers are formed through microstrip transmission lines, each halved Wilkinson power divider comprises two output ports and an input port, and the N-1 halved Wilkinson power dividers are connected to form the N halved power dividers.
The forming of the phase extension line and the phase compensation line by a microstrip transmission line includes:
according to the microstrip transmission lineAs wavelength lambda0Dielectric constant ∈rAnd calculating the waveguide wavelength lambda of the microstrip transmission line according to the height-to-width ratio h/Wg；
Calculating lambdagThe length of the phase extension line and the phase compensation line is determined by/N.
Specifically, the N-level power divider, the phase extension line, and the phase compensation line may be formed by a microstrip transmission line, which is a microwave transmission line composed of a single conductor strip supported on a dielectric substrate. Firstly, manufacturing N-1 halved Wilkinson power dividers by using microstrip transmission lines, wherein the method for manufacturing the Wilkinson power dividers is the prior art, the embodiment of the invention is not repeated, each halved Wilkinson power divider comprises 1 input port and two output ports, and the N halved Wilkinson power dividers are connected to form the N halved power dividers. For example, fig. 3 is a schematic structural diagram of a quartering power divider of an antenna of a UHF RFID reader according to an embodiment of the present invention, as shown in fig. 3, an input port of a first halving power divider is used as an input port of the whole quartering power divider, two output ports are respectively connected to an input port of a second halving power divider and an input port of a third halving power divider, and two output ports of the second halving power divider and two output ports of the third halving power divider form 4 output ports of the quartering power divider.
Phase extension and phase compensation can also be realized by using the length of the microstrip transmission line, and the working wavelength lambda of the used microstrip transmission line is firstly determined0Dielectric constant ∈rAnd an aspect ratio h/W, (h is height, W is width) and then the waveguide wavelength lambda of the microstrip transmission line is calculated according to the following formulag：
The length L of the phase extension is then calculated according to the following formula:
for example, if N is 4, the calculated L is an extension length whose phase is different by 90 °. For example, if the length of the extension lines with 90 ° phase difference is calculated to be 12.96mm, the length of one phase extension line can be fixed, and the length of the phase extension line can be sequentially added to 12.96mm to form a second phase extension line, added to 2 × 12.96mm to form a third phase extension line, and added to 3 × 12.96mm to form a third phase extension line, so that the 90 ° phase difference can be realized. Similarly, phase compensation may be performed according to the calculated value, for example, if the length of the extension lines with a phase difference of 90 ° is calculated to be 12.96mm, the length of one of the phase extension lines may be fixed, for example, the longest phase extension line is fixed, 3 × 12.96mm is sequentially added from short to long to form the second phase extension line, 2 × 12.96mm is added to form the third phase extension line, and 12.96mm is added to form the third phase extension line, so that a phase difference of 90 ° may be compensated to form the same phase.
In addition to the above embodiments, N is 2M, M is an integer greater than 1, and the N antenna elements are arranged in a circle on the front surface of the printed circuit board, and preferably N is 4.
Specifically, in order to increase the near field coverage area of the UHF RFID reader antenna, 2M antenna elements may be provided, and arranged in a circular shape on the front surface of the PCB to form a circular polarized antenna, for example, N is set to 4, so that a four-arm spiral circular polarized antenna is formed on the front surface or the back surface of the PCB using 4 identical antenna elements, which can significantly increase the near field coverage area of the UHF RFID reader antenna. Fig. 4 is a schematic diagram of a near-field electric field distribution of a first set of four-arm feed networks (far-field mode) according to an embodiment of the present invention; fig. 5 is a schematic diagram of the near-field electric field distribution of the second group of four-arm feed networks (near-field mode), as shown in fig. 4 and 5, the deeper the gray scale, the stronger the electric field, and it can be seen intuitively that the near-field intensities of the first group of four-arm feed networks and the second group of four-arm feed networks are different from each other, and the reading coverage area and the near-field intensity in the near-field area are increased without increasing the cost and the system complexity while maintaining the characteristic of the UHF RFID reading distance.
Based on the above UHF RFID reader antenna, an embodiment of the present invention further provides a UHF RFID reader antenna switching method, including:
when the data of the tag antenna needs to be read, the radio frequency switch is switched to be connected to the first group of N-arm feed networks or the second group of N-arm feed networks according to a preset frequency so as to read the data of the tag antenna.
And if all the data of the tag antenna are read, stopping switching.
Specifically, the UHF RFID reader antenna has two sets of N-arm feed networks, so when data of the tag antenna needs to be read, the radio frequency switch can be controlled by the control module to switch different N-arm feed networks to enter a working state, for example, the radio frequency switch can be switched according to a preset frequency so that the first set of N-arm feed networks and the second set of N-arm feed networks are switched according to the preset frequency, and when all data of the tag antenna has been read, the switching is stopped. The method for switching the first group of N-arm feed networks and the second group of N-arm feed networks has already been described in the above device embodiments, and is not described herein again. According to the UHF RFID reader antenna switching method provided by the embodiment of the invention, through switching the N-arm feed network, the reading coverage area of a near field area is increased under the condition of not increasing the cost and the system complexity while the characteristic of long reading distance of the UHF RFID is kept.
On the basis of the above embodiment, further, the method further includes:
if the distance between the tag antenna and the UHF RFID reader antenna is smaller than a first preset length, switching the radio frequency switch to be connected to a second group of N-arm feed networks with the same amplitude and phase to read data of the tag antenna;
and if the distance between the tag antenna and the UHF RFID reader antenna is judged to be larger than a second preset length, the radio frequency switch is switched to be connected to a first group of N arm feed networks with the same amplitude and phase difference of 360 DEG/N so as to read the data of the tag antenna.
Specifically, because the first group of N-arm feed networks is in a far mode and the second group of N-arm feed networks is in a near field mode, the distance between the tag antenna and the reader antenna can be determined first, and if the distance is smaller than a first preset length, for example, smaller than 30cm, the control module can be connected to the second group of N-arm feed networks with the same amplitude and the same phase by controlling the radio frequency switch, so that the reader antenna enters the near field mode, and if the distance is larger than a second preset length, for example, larger than 10m, the control module can be connected to the first group of N-arm feed networks with the same amplitude and the same phase difference of 360 °/N by controlling the radio frequency switch, so that the reader antenna enters the far field mode, and the reading coverage area of the near field area is increased without increasing the cost and the system complexity while maintaining the characteristic of the far UHF RFID reading distance.
According to the UHF RFID reader antenna switching method provided by the embodiment of the invention, switching between a far field antenna mode and a near field antenna mode is formed by switching the feed network mode, and the reading coverage area and the near field intensity of a near field area are increased without increasing the cost and the system complexity while the characteristic of a far reading distance of the UHF RFID is kept.
Those of ordinary skill in the art will understand that: all or part of the steps for realizing the method embodiments can be completed by hardware related to program instructions, the program can be stored in a computer readable storage medium, and the program executes the steps comprising the method embodiments when executed; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
The above-described embodiments of the apparatuses and the like are merely illustrative, wherein the units described as separate parts may or may not be physically separate, and the parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Finally, it should be noted that: the above embodiments are only used for illustrating the technical solutions of the embodiments of the present invention, and are not limited thereto; although embodiments of the present invention have been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (11)
1. A UHF RFID reader antenna, comprising: n arm feed network and N-1 radio frequency switches;
the N-arm feed network comprises N antenna oscillators and a power division phase shift network which are identical and uniformly distributed on the front surface of the printed circuit board, wherein N is an integer greater than 1;
the power distribution phase shift network comprises N equal power distribution devices, N phase extension lines and N-1 phase compensation lines, wherein each N equal power distribution device comprises 1 input port and N output ports, the input ports are connected with a radio frequency module of a UHF RFID reader, and the N output ports are respectively connected with one ends of the N phase extension lines and used for providing N feeds with the same amplitude and the phase difference of 360 DEG/N;
the other end of the first phase extension line in the N phase extension lines is connected with the feed end of one antenna element in the N-arm feed network;
the other ends of the rest N-1 phase extension lines in the N phase extension lines are respectively connected with one ends of the N-1 radio frequency switches, the other ends of the N-1 radio frequency switches are respectively connected with one ends of the N-1 phase compensation lines and a control module of a UHF RFID reader, and the other ends of the N-1 phase compensation lines are respectively connected with the feed ends of the rest N-1 antenna oscillators in the N-arm feed network;
the grounding ends of the N antenna oscillators are connected with a reference grounding end on the front side of the printed circuit board;
when the control module controls the N-1 radio frequency switches to be switched off, a first group of N-arm feed networks with the same amplitude and phase difference of 360 DEG/N are formed, and when the control module controls the N-1 radio frequency switches to be switched on, a second group of N-arm feed networks with the same amplitude and phase difference are formed;
wherein each of the N-1 radio frequency switches comprises: the radio frequency input port, two radio frequency output ports and two direct current input ports;
the radio frequency input port is connected with the feed end of the corresponding antenna oscillator;
a first radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase extension line;
the second radio frequency output port of the two radio frequency output ports is connected with the other end of the corresponding phase compensation line;
the two direct current input ports are respectively connected with a direct current power supply of the reader and a control module of the UHF RFID reader;
when the control module controls the N-1 radio frequency switches to be connected, the phase compensation line is connected to the phase compensation line to compensate the phase, and a second group of N-arm feed networks with the same amplitude and the same phase are formed.
2. The antenna of claim 1, wherein the two dc input ports switch the UHF RFID reader antenna to either the first set of N-arm feed networks or the second set of N-arm feed networks by a dc signal under the control of the control module.
3. The antenna of claim 2, wherein the first set of N-arm feed networks is connected when a first dc input port of the two dc input ports of each of the N-1 rf switches is powered and a second dc input port of the two dc input ports is powered down;
and when each first direct current input port in the N-1 radio frequency switches is powered off and each second direct current input port is powered on, the second group of N arm feed networks are communicated.
4. An antenna according to any of claims 1-3, wherein said N-divider, said phase extension and said phase compensation line are formed by microstrip transmission lines.
5. The antenna of claim 4, wherein the N-tap splitter formed by a microstrip transmission line comprises:
n-1 halved Wilkinson power dividers are formed through microstrip transmission lines, each halved Wilkinson power divider comprises two output ports and an input port, and the N-1 halved Wilkinson power dividers are connected to form the N halved power dividers.
6. The antenna of claim 4, wherein the phase extension line and the phase compensation line are formed by microstrip transmission lines, comprising:
according to the working wavelength lambda of the microstrip transmission line0Dielectric constant ∈rAnd calculating the waveguide wavelength lambda of the microstrip transmission line according to the height-to-width ratio h/Wg；
Calculating lambdagThe length of the phase extension line and the phase compensation line is determined by/N.
7. The antenna of claim 4, wherein N is 2M, M is an integer greater than 1, and the N antenna elements are arranged in a circle on the front side of the printed circuit board.
8. The antenna of claim 7, wherein N-4.
9. A UHF RFID reader antenna switching method, applied to the UHF RFID reader antenna of any one of claims 1 to 8, comprising:
when the data of the tag antenna needs to be read, the radio frequency switch is switched to be connected to the first group of N-arm feed networks or the second group of N-arm feed networks according to a preset frequency so as to read the data of the tag antenna.
10. The method of claim 9, further comprising:
and if all the data of the tag antenna are read, stopping switching.
11. The method of claim 9, further comprising:
if the distance between the tag antenna and the UHF RFID reader antenna is smaller than a first preset length, switching the radio frequency switch to be connected to a second group of N-arm feed networks with the same amplitude and phase to read data of the tag antenna;
and if the distance between the tag antenna and the UHF RFID reader antenna is judged to be larger than a second preset length, the radio frequency switch is switched to be connected to a first group of N arm feed networks with the same amplitude and phase difference of 360 DEG/N so as to read the data of the tag antenna.
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| JP2006060352A (en) * | 2004-08-18 | 2006-03-02 | Matsushita Electric Ind Co Ltd | Variable resonator |
| CN101989676A (en) * | 2009-08-07 | 2011-03-23 | 西门子公司 | Antenna used for radio frequency identification device system and configuration method thereof, and radio frequency identification reader-writer |
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| KR100750850B1 (en) * | 2006-04-21 | 2007-08-22 | (주)에이스안테나 | Compact size high gain circularly polarized antenna for rfid reader and attach clamp there of |
| KR101689891B1 (en) * | 2008-01-30 | 2016-12-26 | 프란웰, 아이엔씨. | Array antenna system and algorithm applicable to rfid readers |
| WO2010106396A1 (en) * | 2009-03-16 | 2010-09-23 | Sabanci Universitesi | A microstrip phased array antenna |
| CN204189948U (en) * | 2014-10-29 | 2015-03-04 | 南京师范大学 | A kind of far and near field RFID read-write antenna for uhf band |
| CN204834892U (en) * | 2015-06-26 | 2015-12-02 | 无锡德鑫泉物联网科技有限公司 | Dull and stereotyped phased array antenna device |
| 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 |
| CN108321491B (en) * | 2018-01-04 | 2019-12-20 | 苏州大学 | Switchable near-far field radio frequency identification antenna |
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| JP2006060352A (en) * | 2004-08-18 | 2006-03-02 | Matsushita Electric Ind Co Ltd | Variable resonator |
| CN101989676A (en) * | 2009-08-07 | 2011-03-23 | 西门子公司 | Antenna used for radio frequency identification device system and configuration method thereof, and radio frequency identification reader-writer |
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