CN112864605A

CN112864605A - Miniaturized quadrifilar helix antenna for portable UHF RFID device

Info

Publication number: CN112864605A
Application number: CN202110334189.8A
Authority: CN
Inventors: 戴海军; 刘奕彬; 李忠心; 严清夏
Original assignee: Shenzhen Haidemen Electronics Co ltd; Shanghai Deman Electronics Technology Co Ltd
Current assignee: Shenzhen Haidemen Electronics Co ltd; Shanghai Deman Electronics Technology Co Ltd
Priority date: 2021-03-29
Filing date: 2021-03-29
Publication date: 2021-05-28
Anticipated expiration: 2041-03-29

Abstract

A miniaturized four-armed helical antenna for portable UHF RFID devices, comprising a dielectric cylinder, four sets of helical arms and a four-part feeding network, the four sets of helical arms are wound around an axis on the outer surface of the dielectric cylinder, and one-part The four-feed network has two layers of dielectric substrates, the upper surface of the upper layer of the dielectric substrate and the lower surface of the lower layer of the dielectric substrate are respectively provided with a two-to-two feeder network, a grounding line is arranged between the two layers of the dielectric substrate, and the spiral arm includes an L-shaped radiation Branches and a short-circuit branch, in which the L-shaped radiating branches of the two sets of helical arms are connected to the upper one-to-two feed network, and the L-shaped radiating branches of the other two sets of helical arms are connected to the lower one-to-two feed network, and the short-circuit branches Connected to the ground line, a one-point four-feed network provides four sets of helical arms with phase differences of 0, ‑90, ‑180, and ‑270 degrees in sequence, resulting in circular polarization. The miniaturized quadrifilar helix antenna has the advantages of miniaturization, high gain and wide beam.

Description

Miniaturized quadrifilar helix antenna for portable UHF RFID device

Technical Field

The invention relates to the technical field of antennas, in particular to a miniaturized quadrifilar helix antenna for portable UHF RFID equipment.

Background

In recent years, due to the rapid development of the internet of things, the Radio Frequency Identification (RFID) technology is receiving more and more attention. RFID systems generally include two parts, an RFID reader and a tag, and the RFID reader antenna has a large influence on the performance of the RFID system. In the UHF band (860) and 960MHz), the RFID system has a larger transmission range and a faster transmission rate. The quadrifilar helix antenna is suitable for being used in a UHF RFID system due to the advantages of circular polarization, a heart-shaped directional diagram, excellent front-to-back ratio and the like. At present, the rise of handheld RFID read-write equipment has necessitated providing an antenna with the characteristics of miniaturization, high gain and wide beam.

It is to be noted that the information disclosed in the above background section is only for understanding the background of the present application and thus may include information that does not constitute prior art known to a person of ordinary skill in the art.

Disclosure of Invention

The invention mainly aims to provide a quadrifilar helix antenna for portable UHF RFID equipment, which overcomes the defects of miniaturization, high gain and wide beam of the traditional antenna.

In order to achieve the purpose, the invention adopts the following technical scheme:

a miniaturized quadrifilar helix antenna for portable UHF RFID equipment comprises a dielectric cylinder, four groups of helix arms and a one-to-four feed network, wherein the four groups of helix arms are wound on the outer surface of the dielectric cylinder around an axis, the one-to-four feed network is provided with two layers of dielectric substrates, the upper surface of an upper layer dielectric substrate and the lower surface of a lower layer dielectric substrate in the two layers of dielectric substrates are respectively provided with a one-to-two feed network, a grounding circuit is arranged between the two layers of dielectric substrates, the helix arms comprise an L-shaped radiation branch and a short circuit branch, wherein the L-shaped radiation branch of 2 groups of helix arms is connected with the upper layer one-to-two feed network, the L-shaped radiation branch of the other 2 groups of helix arms is connected with the lower layer one-to-two feed network, the short circuit branch is connected with the grounding circuit, and the one-to-four feed network sequentially, -90, -180 and-270 degrees phase difference, thereby forming a circular polarization.

Further:

the medium cylinder is made of alumina ceramics.

The short-circuit branches of the four groups of spiral arms are connected with the metal floor through short-circuit probes, the L-shaped radiation branches of the 2 groups of spiral arms are directly connected with the upper one-to-two feed network, and the L-shaped radiation branches of the 2 groups of spiral arms are connected with the lower one-to-two feed network through the short-circuit probes.

The one-to-four feed network feeds power through a coaxial line, an inner core of the coaxial line is connected with the upper-layer one-to-two feed network, and an outer conductor of the coaxial line is connected with the lower-layer one-to-two feed network.

The one-in-two feed network comprises three sections of microstrip lines and a patch type bridge, the patch type bridge is provided with 6 pins, wherein 3 pins are respectively connected with the three sections of microstrip lines, 2 pins are connected with the grounding circuit through a short-circuit probe, one section of microstrip line of the upper layer one-in-two feed network is also connected with an inner core of the coaxial line, and one section of microstrip line of the lower layer one-in-two feed network is also connected with an outer conductor of the coaxial line.

The three microstrip lines are three 50 ohm microstrip lines.

The patch type bridge is a patch type 3dB bridge.

The dielectric substrate is FR4 dielectric substrate.

The grounding circuit is a metal floor.

The medium cylinder is a medium cylinder.

The invention has the following beneficial effects:

the invention provides a miniaturized quadrifilar helix antenna which has the advantages of miniaturization, high gain and wide beam, the quadrifilar helix antenna has higher gain while effectively meeting the miniaturization requirement, can ensure that an RFID system keeps a longer reading distance, has wider beam width and can ensure that the RFID system can accurately read in a larger angle range, and the four-filar helix antenna is particularly suitable for being used in portable UHF RFID equipment.

Drawings

Fig. 1 is a side view of a quadrifilar helix antenna according to an embodiment of the present invention;

fig. 2 is a planar expanded view of a quadrifilar helix antenna according to an embodiment of the present invention;

fig. 3 is a top view of a one-to-four feeding network according to an embodiment of the present invention;

fig. 4 is a return loss curve diagram of the quadrifilar helix antenna according to the embodiment of the present invention;

FIG. 5 is a graph of axial ratio and gain for a quadrifilar helix antenna according to an embodiment of the present invention;

FIG. 6 is a graph of axial ratio and gain at a frequency of 915MHz for a quadrifilar helix antenna provided in accordance with an embodiment of the present invention;

FIG. 7 is a gain radiation pattern at a frequency of 915MHz for a quadrifilar helix antenna provided in accordance with an embodiment of the present invention;

description of reference numerals: 1. a media column; 2. four groups of spiral arms; 2A, radiation branches; 2B, short circuit branch knots; 3. a one-to-four feed network; 4. a dielectric substrate; 5. the upper layer is a one-to-two feed network; 6. the lower layer is a one-to-two feed network; 7. a metal floor; 8. a shorting probe; 9. a coaxial line; 10. a patch bridge; 11. a plastic screw; 12. three microstrip lines.

Detailed Description

The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary in nature and is not intended to limit the scope of the invention or its application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element. In addition, the connection may be for either a fixed or coupled or communicating function.

It is to be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like are used in an orientation or positional relationship indicated in the drawings for convenience in describing the embodiments of the present invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be in any way limiting of the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.

Referring to fig. 1 to 3, an embodiment of the present invention provides a miniaturized quadrifilar helix antenna for a portable UHF RFID device, including a dielectric cylinder 1, four sets of helix arms 2, and a one-to-four feed network 3, where the dielectric cylinder 1 is preferably a dielectric cylinder, the four sets of helix arms 2 are wound around an axis on an outer surface of the dielectric cylinder 1, the one-to-four feed network 3 has two layers of dielectric substrates 4, a one-to-two feed network is respectively disposed on an upper surface of an upper layer dielectric substrate 4 and a lower surface of a lower layer dielectric substrate 4 of the two layers of dielectric substrates 4, a ground line (such as a metal floor 7) is disposed between the two layers of dielectric substrates 4, the helix arm 2 includes an L-shaped radiation branch 2A and a short-circuit branch 2B, where the L-shaped radiation branch 2A of the 2 sets of helix arms 2 is connected to the upper layer-to, in addition, the L-shaped radiation branches 2A of the 2 groups of spiral arms 2 are connected with the lower one-to-two feed network 6, the short circuit branches 2B are connected with the grounding circuit, and the one-to-four feed network 3 sequentially provides phase differences of 0 degree, -90 degrees, -180 degrees and-270 degrees for the four groups of spiral arms 2, so that circular polarization is formed.

The quadrifilar helix antenna of the embodiment of the invention has the advantages of miniaturization, high gain and wide beam, and the quadrifilar helix antenna effectively meets the miniaturization requirement, and simultaneously has higher gain, can keep a longer reading distance of an RFID system, has wider beam width and can accurately read the RFID system in a larger angle range according to the test data shown in figures 4 to 7, so that the quadrifilar helix antenna is particularly suitable for being used in portable UHF RFID equipment.

In a preferred embodiment, the dielectric cylinder 1 is made of alumina ceramic, which is beneficial to realizing miniaturization of the antenna.

Referring to fig. 1 to 2, in a preferred embodiment, the short-circuit branches 2B of the four sets of spiral arms 2 are connected to the metal floor through short-circuit probes 8, wherein the L-shaped radiation branches 2A of the 2 sets of spiral arms 2 are directly connected to the upper one-to-two feeding network 5, and the L-shaped radiation branches 2A of the 2 sets of spiral arms 2 are connected to the lower one-to-two feeding network 6 through short-circuit probes 8.

Referring to fig. 1 to 2, in a preferred embodiment, the one-in-four feeding network 3 feeds through a coaxial line 9, an inner core of the coaxial line 9 is connected with an upper layer one-in-two feeding network 5, and an outer conductor of the coaxial line 9 is connected with a lower layer one-in-two feeding network 6.

Referring to fig. 3, in a preferred embodiment, the one-to-two feeding network includes three microstrip lines 12 and a patch bridge 10, the patch bridge 10 has 6 pins, wherein 3 pins are respectively connected to the three

microstrip lines

12, 2 pins are connected to the ground line through a short-circuit probe 8, a section of the microstrip line of the upper one-to-two feeding network 5 is further connected to an inner core of the coaxial line 9, and a section of the microstrip line of the lower one-to-two feeding network 6 is further connected to an outer conductor of the coaxial line 9.

In some embodiments, the three pieces of microstrip line 12 are preferably three pieces of 50 ohm microstrip lines. The patch type bridge 10 is preferably a patch type 3dB bridge, and serves as a patch type 3dB power divider.

In some embodiments, the dielectric substrate 4 may be an FR4 dielectric substrate.

In a preferred embodiment, the ground line may employ a metal floor 7.

Specific embodiments of the present invention are further described below.

As shown in fig. 1 to 3, the embodiment provides a miniaturized quadrifilar helix antenna applied to a portable UHF RFID device, which includes a dielectric cylinder 1 made of alumina ceramic material, four sets of helix arms 2, and a one-to-four feeding network 3 under the dielectric cylinder 1. The four groups of spiral arms 2 are wound on the outer surface of the medium column body 1 made of the alumina ceramic material around an axis, and each group of spiral arms 2 comprises an L-shaped radiation branch 2A and a short-circuit branch 2B; the one-to-four feed network comprises two layers of dielectric substrates 4, preferably FR4 dielectric substrates, one-to-two

feed networks

5 and 6 are printed on the upper and lower surfaces of the two layers of dielectric substrates 4, and a metal floor 7 is printed on the middle layer; the one-to-two

feed networks

5 and 6 comprise three microstrip lines 12 and a patch type bridge 10, and preferably adopt three microstrip lines of 50 ohms and a patch type 3dB bridge; in addition, the short-circuit branch 2B is connected with the metal floor 7 through a short-circuit probe 8, and the two groups of L-shaped radiation branches 2A are connected with the lower one-to-two feed network 6 through the short-circuit probe 8; a one-to-four feed network 3 provides phase differences of 0, -90, -180 and-270 degrees for the four groups of spiral arms in sequence, thereby forming circular polarization.

In this embodiment, the dielectric cylinder 1 is made of alumina ceramic with a high dielectric constant, which is advantageous for miniaturization. The spiral arm 2 comprises a radiating L-shaped branch 2A and a short-circuit branch 2B, wherein the purpose of bending the radiating branch into an L shape is to reduce the axial length, and the function of increasing the short-circuit branch is to improve impedance matching. A one-to-two

feed network

5 or 6 comprises a patch type 3dB bridge with 6 pins and three sections of 50 ohm microstrip lines 12. Pins at two ends of the patch type bridge 10 are connected with three microstrip lines 12, and the pin in the middle is connected with the metal floor 7. The one-to-four feeding network 3 adopts a coaxial line 9 for feeding, an inner core of the coaxial line 9 is connected with the upper one-to-two feeding network 5, and an outer conductor of the coaxial line 9 is connected with the lower one-to-two feeding network 6. The one-to-four feed network 3 is used for realizing the phase difference of 90 degrees of the four output ports and the power with the same amplitude, thereby realizing circular polarization. In addition, output ports A and B of the upper layer one-to-two feed network 5 are directly connected with two groups of spiral arms 2, and output ports C and D of the lower layer one-to-two feed network 6 are connected with the other two groups of spiral arms 2 through short-circuit probes. Finally, a one-to-four feed network is reinforced by plastic screws 11. Referring to fig. 4 to 7, the quadrifilar helix antenna of the embodiment has the advantages of large gain, small size, wide beam, heart-shaped directional diagram, excellent front-to-back ratio and the like.

As shown in FIG. 4, the return loss of the antenna in the frequency band of 0.8-1GHz is less than-10 dB; as shown in fig. 5, the average gain of the antenna in the UHF RFID band is 4.5dB, and the axial ratio is less than 0.08; as shown in fig. 6, the 3dB gain beamwidth of the antenna at the 915MHz frequency is 120 degrees, and the 3dB axial ratio beamwidth is 184 degrees; as shown in fig. 7, the radiation pattern of the antenna at 915MHz has a front-to-back ratio of 22dB and has a cardioid pattern.

The background of the present invention may contain background information related to the problem or environment of the present invention and does not necessarily describe the prior art. Accordingly, the inclusion in the background section is not an admission of prior art by the applicant.

The foregoing is a more detailed description of the invention in connection with specific/preferred embodiments and is not intended to limit the practice of the invention to those descriptions. It will be apparent to those skilled in the art that various substitutions and modifications can be made to the described embodiments without departing from the spirit of the invention, and these substitutions and modifications should be considered to fall within the scope of the invention. In the description herein, references to the description of the term "one embodiment," "some embodiments," "preferred embodiments," "an example," "a specific example," or "some examples" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the claims.

Claims

1. A miniaturized four-armed helical antenna for portable UHF RFID equipment, characterized in that it comprises a dielectric cylinder, four groups of helical arms, and a four-point feed network, wherein the four groups of helical arms are wound around the axis in all the The outer surface of the dielectric cylinder, the one-to-four feed network has two layers of dielectric substrates, and the upper surface of the upper dielectric substrate and the lower surface of the lower dielectric substrate of the two-layer dielectric substrate are respectively provided with one-to-two feeds network, a grounding line is arranged between the two layers of dielectric substrates, the spiral arm includes an L-shaped radiating branch and a short-circuit branch, wherein the L-shaped radiating branch of the two sets of helical arms is connected to the upper-layer one-to-two feed network , the L-shaped radiating branches of the other two groups of helical arms are connected to the lower one-to-two feeder network, the short-circuit branch is connected to the grounding line, and the one-to-four feeder network is the sequence of the four groups of helical arms. Phase differences of 0, -90, -180 and -270 degrees are provided, resulting in circular polarization.

2 . The miniaturized quadruple helix antenna according to claim 1 , wherein the material of the dielectric cylinder is alumina ceramics. 3 .

3. The miniaturized four-armed helical antenna according to claim 1, wherein the short-circuit branches of the four groups of helical arms are connected to the metal floor through short-circuit probes, wherein the L-shaped radiation branches of the two groups of helical arms are connected to the upper layer. The one-to-two feed network is directly connected, and the L-shaped radiating branches of the other two groups of helical arms are connected to the lower one-to-two feed network through short-circuit probes.

4 . The miniaturized quadruple helix antenna according to claim 1 , wherein the one-to-four feed network is fed through a coaxial line, and the inner core of the coaxial line is connected to the upper layer of one-to-two feeds. 5 . network, the outer conductor of the coaxial line is connected to the lower layer one-to-two feeding network.

5. The miniaturized quadruple helix antenna according to claim 1, wherein the one-to-two feed network comprises three sections of microstrip lines and a patch-type electric bridge, and the patch-type electric bridge has 6 3 pins are connected to the three sections of the microstrip line respectively, and 2 pins are connected to the grounding line through short-circuit probes, wherein a section of the microstrip line of the upper-layer one-to-two feeder network is also connected to the ground line. The inner core of the coaxial line is connected, and a section of the microstrip line of the lower layer one-to-two feeding network is also connected to the outer conductor of the coaxial line.

6 . The miniaturized quadrifilar helix antenna according to claim 5 , wherein the three sections of microstrip line are three sections of 50 ohm microstrip line. 7 .

7 . The miniaturized quadrifilar helix antenna according to claim 5 , wherein the patch-type electric bridge is a patch-type 3dB electric bridge. 8 .

8 . The miniaturized quadrifilar helix antenna according to claim 1 , wherein the dielectric substrate is an FR4 dielectric substrate. 9 .

9 . The miniaturized quadrifilar helix antenna according to claim 1 , wherein the ground line is a metal floor. 10 .

10 . The miniaturized quadrifilar helix antenna according to claim 1 , wherein the dielectric cylinder is a dielectric cylinder. 11 .