CN116933815A - Miniaturized reader-writer antenna capable of realizing space three-dimensional field uniformity and method - Google Patents
Miniaturized reader-writer antenna capable of realizing space three-dimensional field uniformity and method Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
- G06K7/10316—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves using at least one antenna particularly designed for interrogating the wireless record carriers
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
- G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
- G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
- G06K7/10297—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves arrangements for handling protocols designed for non-contact record carriers such as RFIDs NFCs, e.g. ISO/IEC 14443 and 18092
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Abstract
The application discloses a miniaturized reader-writer antenna and a method capable of realizing uniform spatial three-dimensional field, wherein the miniaturized reader-writer antenna comprises a first dielectric substrate, a second dielectric substrate and a third dielectric substrate which are arranged in a three-layer lamination manner, the first dielectric substrate is provided with a first microstrip structure for realizing uniform planar two-dimensional field parallel to the surface of the reader-writer antenna, a second microstrip structure is arranged between the first dielectric substrate and the second dielectric substrate, a third microstrip structure is arranged between the second dielectric substrate and the third dielectric substrate, electric fields generated by the second microstrip structure and the third microstrip structure in the vertical direction of the reader-writer antenna are mutually overlapped, the electric field intensity in the vertical direction above the reader-writer antenna is enhanced, the indiscriminate identification of an electronic tag in the vertical direction is realized, the three-dimensional field uniformity is realized in a limited space above the reader-writer antenna, and the electronic tag can be effectively identified no matter how.
Description
Technical Field
The application relates to the field of radio frequency identification, in particular to a miniaturized reader-writer antenna and a method capable of realizing space three-dimensional field uniformity.
Background
In recent years, rapid development of radio frequency identification technology enables the concept of the internet of things to be forcefully implemented and advanced, and the purpose of the internet of things is to construct a network and a channel for communicating between physical objects, fortunately, the radio frequency identification technology can achieve the goal almost perfectly. In a radio frequency identification system, a reader antenna exchanges information with an electronic tag in a non-contact manner by generating an electromagnetic field in a radio frequency mode so as to achieve the purpose of identification. In view of miniaturization, mass production and cost control, the electronic tag antenna adopts a linear polarization mode in most applications, and the mode can be identified when the included angle between the polarization of the electronic tag antenna and the polarization direction of an electric field emitted by the reader-writer antenna is smaller than a certain range, and is missed to be read beyond the certain range, namely the identification of the electronic tag has a relative relationship with the orientation and placement of the electronic tag. In practical application, the placement of articles is seriously affected by the electronic tag attached to the articles, so that the freedom of the radio frequency identification system in working is greatly limited, and the concept of the Internet of things is weakened. Meanwhile, the intelligent requirement of the 'Internet of things' is that articles (attached with electronic tags) outside the identification area are not misread, namely, each reader unit is only responsible for reading articles inside a specific area, so that management confusion is avoided, and the working efficiency of the whole system is improved. The traditional reader-writer antenna not only has difficulty in meeting the freedom of the orientation of the electronic tag in the horizontal plane, but also has more difficulty in identifying the electronic tag in the vertical orientation, and even the electronic tag outside the identification area can be misread on the basis. Therefore, it is very significant and valuable to design a reader-writer antenna that can completely read an electronic tag placed arbitrarily in a specified area, and this effect is equivalent to achieving uniform electric field distribution in a specified space above the reader-writer antenna.
Disclosure of Invention
In order to overcome the above-mentioned drawbacks and disadvantages of the prior art, the present application is directed to a miniaturized reader antenna and method for realizing spatial three-dimensional field uniformity.
The aim of the application is achieved by the following technical scheme:
the miniaturized reader-writer antenna capable of realizing space three-dimensional field uniformity comprises three layers of dielectric substrates, wherein the three layers of dielectric substrates are arranged in a stacked manner, and each three layers of dielectric substrates comprises a first dielectric substrate, a second dielectric substrate and a third dielectric substrate;
a first microstrip structure is arranged on the first surface of the first medium substrate and is used for generating a multi-polarization electric field of a near field by the reader-writer antenna, so that the planar two-dimensional field parallel to the surface of the reader-writer antenna is uniform, and the electronic tag in the plane is identified indiscriminately;
a second microstrip structure is arranged between the first dielectric substrate and the second dielectric substrate, a third microstrip structure is arranged between the second dielectric substrate and the third dielectric substrate, and electric fields generated by the second microstrip structure and the third microstrip structure in the vertical direction of the reader antenna are mutually overlapped, so that the electric field intensity in the vertical direction above the reader antenna is enhanced, and the indiscriminate identification of the electronic tag in the vertical direction is realized;
the first microstrip structure, the second microstrip structure and the third microstrip structure are fed by a first feed port, a second feed port and a third feed port respectively;
and the second surface of the third dielectric substrate is provided with a grounding plate.
Further, the first microstrip structure comprises a one-to-two power divider, a connecting microstrip line for providing 90-degree phase shift and a first radiation unit, wherein the first radiation unit is in mirror symmetry with respect to an incident end of the one-to-two power divider;
the first radiating unit comprises a radiating microstrip line and an S-shaped microstrip line, the radiating microstrip line comprises a horizontal microstrip line and a vertical microstrip line, the S-shaped microstrip line enables a current node to appear on the S-shaped microstrip line, a current antinode appears on the horizontal microstrip line and the vertical microstrip line which are connected with two ends of the S-shaped microstrip line, the horizontal microstrip line is used for generating an X-direction electric field, and the vertical microstrip line is used for generating a Y-direction electric field.
Further, the first radiating unit comprises eight S-shaped microstrip lines and twelve radiating microstrip lines, wherein every four S-shaped microstrip lines and six radiating microstrip lines are in one group, the two groups of the S-shaped microstrip lines and the six radiating microstrip lines have the same structure, the six microstrip lines comprise three vertical microstrip lines and three horizontal microstrip lines, and two ends of the S-shaped microstrip lines are connected with the radiating microstrip lines.
Further, the second microstrip structure and the third microstrip structure are identical in structure, and the third microstrip structure is embedded in the second microstrip structure in the vertical direction.
Further, the second microstrip structure and the third microstrip structure each comprise a split-two power divider, a near-field electric field distribution balancer and a second radiation unit, the second radiation unit is in a hollowed-out cross shape, each hollowed-out cross shape comprises two branches, each branch is composed of two radiation elements, and the included angle between every two adjacent radiation elements is 90 degrees.
Further, each of the radiating elements includes two mutually parallel microstrip lines and an S-type microstrip line, the two mutually parallel microstrip lines being connected with both ends of the S-type microstrip line, respectively.
Further, an included angle between the radiating units of the second microstrip structure and the third microstrip structure and the first radiating unit of the first microstrip structure is 45 degrees.
Further, the second feeding port and the third feeding port are located on the same side of the reader-writer antenna, and the first feeding port and the second feeding port are located on different sides of the reader-writer antenna.
Further, the first microstrip structure, the second microstrip structure and the third microstrip structure all adopt leaky wave radiation.
The method for realizing the miniaturized reader-writer antenna comprises the steps of controlling the alternate feeding operation of a first feeding port, a second feeding port and a third feeding port to realize two modes of the operation of the reader-writer antenna;
mode one: when the first feed port works, the polarization direction of the generated near-field electric field can rotate anticlockwise by 360 degrees;
mode two: when the second feed port and the third feed port work simultaneously, the second microstrip structure and the third microstrip structure respectively form a hollowed cross, the hollowed cross is formed by two branches, one branch comprises two radiation elements, the directions of currents generated by two opposite radiation units in position are opposite, the currents are the same, so that transverse leaky waves cancel each other, and longitudinal filtering is reserved;
the longitudinal leaky waves generated by the two branches at the same time are mutually overlapped, so that an electric field in the vertical direction of the reader antenna is increased;
the two modes are combined to realize the uniformity of the three-dimensional field in the limited space above the antenna of the reader-writer.
Compared with the prior art, the application has the following advantages and beneficial effects:
(1) The reader-writer antenna adopts an S-shaped microstrip structure, reduces the size of the whole antenna, realizes miniaturization, and can build a radio frequency identification system without occupying a large space.
(2) On the basis of miniaturization, the designed first microstrip structure can realize two-dimensional field uniformity in a plane parallel to the surface of the antenna, and the electronic tag in the plane can be identified indiscriminately.
(3) According to the application, through the second and third microstrip structures, the electric field intensity in the vertical direction above the reader antenna is enhanced, and the electronic tag in the vertical orientation in the limited space can be identified indiscriminately.
(4) The application utilizes the characteristics of electric fields radiated by three different microstrip structures, and constructs the effect of uniform three-dimensional field in a limited space above an antenna of a reader-writer under the condition of maximally reducing the mutual influence of radiation during working.
(5) The radiation mode of the application is mainly wave leakage, so that the reader antenna can not misread the electronic tag outside the limited area, and the intelligence of the 'Internet of things' concept is enhanced.
Drawings
FIG. 1 is a schematic diagram of a miniaturized reader antenna according to the present application;
FIG. 2 is a schematic plan view of the structure of FIG. 1;
fig. 3 is a schematic structural view of a first microstrip structure;
fig. 4 is a schematic structural diagram of a second microstrip structure;
fig. 5 is a schematic diagram illustrating a radiation unit arrangement of a second microstrip structure and a third microstrip structure according to the present application;
fig. 6 is a schematic structural diagram of an S-shaped microstrip line of the present application;
FIG. 7 is a schematic diagram of the antenna S parameters and gain of the reader/writer according to the present application;
fig. 8 is a schematic diagram of the principle of miniaturization of the S-shaped microstrip line of the present application;
FIG. 9 is a schematic diagram of the first microstrip structure of the present application for achieving planar multi-polarized electric field and field uniformity;
fig. 10 (a) to 10 (d) are schematic diagrams showing field uniformity effects of the planar multi-polarized electric field achieved by the first microstrip structure of the present application, and fig. 10 (a) to 10 (d) are field uniformity effects of the planar multi-polarized electric field with feed phases of 0 degrees, 90 degrees, 180 degrees and 270 degrees, respectively;
FIG. 11 is a schematic diagram of the present application for generating a Z-reversed electric field component;
FIG. 12 is a schematic diagram of the principle of the present application for enhancing the Z-direction electric field component;
FIG. 13 is a schematic diagram showing the distribution of the electric field component in the X direction of the reader antenna according to the present application;
FIG. 14 is a schematic diagram showing the distribution of the Y-direction electric field component of the reader antenna according to the present application;
fig. 15 is a schematic diagram showing the distribution of the Z-direction electric field component of the reader antenna according to the present application.
Detailed Description
In order to make the object of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application, and it is obvious that the described embodiments are only some embodiments of the present application, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
In the description of the embodiments of the present application, it should be understood that the terms "vertical," "upper," "lower," "width," "length," "tail," and the like indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, and are merely for convenience of description, and do not indicate or imply that the devices or elements being referred to must have a specific position, be configured and operated in a specific orientation, and thus should not be construed as limiting the embodiments of the present application.
Furthermore, unless explicitly specified and limited otherwise, the terms "open", "connected", "bent", "positioned" and the like are to be construed broadly, and may be, for example, mechanically or electrically connected; either directly or indirectly, through intermediaries, or both, may be in communication with each other or in interaction with each other, unless expressly defined otherwise. The specific meaning of the above terms in the embodiments of the present application will be understood by those of ordinary skill in the art according to specific circumstances.
In the present embodiments, the terms "first," "second," and "second" are used for descriptive purposes only and not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated unless otherwise explicitly specified and defined. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include at least one such feature. In the description of the embodiments of the present application, the meaning of "plurality" is at least two, for example, two, three, etc.
As shown in fig. 1 and 2, a miniaturized reader-writer antenna capable of realizing uniform spatial three-dimensional field includes three layers of dielectric substrates stacked, wherein the three layers of dielectric substrates include a first dielectric substrate 2, a second dielectric substrate 4 and a third dielectric substrate 6, and in this embodiment, the first dielectric substrate, the second dielectric substrate and the third dielectric substrate all adopt FR4 with a dielectric constant of 4.4 and a loss tangent angle of 0.02.
The first surface of the first medium substrate is provided with a first microstrip structure 1, a second microstrip structure 3 is arranged between the first medium substrate and the second medium substrate, a third microstrip structure 5 is arranged between the second medium substrate and the third medium substrate, and the second surface of the third medium substrate is provided with a grounding plate 7. The dielectric substrates and the microstrip structures in the embodiment are in seamless fit according to the arrangement sequence of the Z direction.
The first microstrip structure 1, the second microstrip structure 3 and the third microstrip structure 5 are respectively fed by a first feed port 8, a second feed port 9 and a third feed port 10; the first feed port 8 and the third feed port 10 are located on the same side but are intersecting. The second feeding port 9 is located at the other side of the antenna, and two working modes of the antenna are realized by alternately feeding the first feeding port 8, the second feeding port 9 and the third feeding port 10, and the two working modes are combined to enable a specific area above the antenna of the reader-writer to form a uniform electric field. The radiation mode of the microstrip standing wave antenna is mainly leaky, so that the radiation gain of the microstrip standing wave antenna is smaller, and the electronic tag outside a specific area cannot be misread.
In this embodiment, the length of the reader antenna is 215mm, the width of the reader antenna is 140mm, and the total height of the reader antenna is 4mm, wherein the height of the first dielectric substrate is 2mm, the heights of the second dielectric substrate and the third dielectric substrate are 1mm, and the lengths and the widths of the three-layer dielectric substrate and the grounding plate are the same.
In this embodiment, the first surface is an upper surface, and the second surface is a lower surface.
As shown in fig. 3, further, the first microstrip structure 1 is specifically disposed on the upper surface of the first dielectric substrate 2. The first microstrip structure comprises a one-to-two power divider 11, a connecting microstrip line 12 providing 90-degree phase shift, and a first radiating unit, wherein the first radiating unit is divided into two parts, and the two parts are in mirror symmetry about an incident end of the one-to-two power divider.
The connection mode is as follows: one end of the one-to-two power divider is connected with the 90-degree phase shift connection microstrip line, the other end of the connection microstrip line is connected with one part of the first radiation unit, and the other end of the one-to-two power divider is connected with the other part of the first radiation unit.
In this embodiment, the 90-degree phase-shifted connection microstrip line 12 is in a shape of a Chinese character 'ji', and has an upward opening, and two ends of the opening are respectively connected with the one-to-two power divider and the first radiating element.
Specifically: the first radiating unit comprises eight S-shaped microstrip lines and twelve radiating microstrip lines for radiating a near-field uniform electric field, each part comprises four S-shaped microstrip lines and six radiating microstrip lines, each six radiating microstrip lines comprises three vertical microstrip lines and three horizontal microstrip lines, each horizontal microstrip line is used for generating an X-direction electric field, and each vertical microstrip line is used for generating a Y-direction electric field. The S-shaped microstrip line causes a current node to appear on the S-shaped microstrip line, and a current antinode appears on the microstrip line connected to both ends of the S-shaped microstrip line.
Preferred linkages are: taking the part for realizing the electric field in the Y axis and X axis directions as an example:
the three vertical microstrip lines comprise a vertical microstrip line A, a vertical microstrip line B and a vertical microstrip line C, the three horizontal microstrip lines comprise a horizontal microstrip line D, a horizontal microstrip line E and a horizontal microstrip line F, an S-shaped microstrip line is arranged between the vertical microstrip line A and the vertical microstrip line B, the vertical microstrip line B is connected with the vertical microstrip line C through an elongated microstrip line, the other end of the vertical microstrip line C is connected with the horizontal microstrip line D through an S-shaped microstrip line, the other end of the horizontal microstrip line D is connected with the horizontal microstrip line E through an S-shaped microstrip line, and the horizontal microstrip line E is connected with the horizontal microstrip line F through an S-shaped microstrip line.
The three vertical microstrip lines realize the Y-axis direction electric field, and the three horizontal microstrip lines realize the X-axis direction electric field.
Based on the first microstrip line structure design, the first microstrip structure can provide a near-field multi-polarization electric field, so that the indiscriminate identification of the electronic tag in the plane parallel to the antenna surface in a limited space above the reader-writer antenna is realized.
As shown in fig. 4 and 5, further, the second microstrip structure 3 is tightly attached between the lower surface of the first dielectric substrate 2 and the upper surface of the second dielectric substrate 4, and includes a one-to-two power divider, a near field electric field distribution balancer 13 and a second radiating unit, where the second radiating unit is in a hollowed cross shape, the hollowed cross shape includes two branches, each branch includes two radiating elements, the two branches are crisscross, the four radiating elements have the same structural size, each radiating element includes an S-type microstrip line and two mutually parallel microstrip lines, and two ends of the S-type microstrip line are respectively connected with the two flat microstrip lines to form a radiating element. Adjacent radiating elements are connected through slender horizontal microstrip lines, two radiating elements form an included angle of 90 degrees with each other and are connected between the microstrip power divider and a near-field electric field distribution balancer, and four radiating elements are in mirror symmetry with respect to the incident end of the microstrip power divider in pairs and form a hollowed "+" shape as a whole.
Specifically, four S-shaped microstrip lines are positioned at four vertex angle ends of the hollowed-out cross shape.
Based on such a structural design, the second microstrip structure may provide a relatively weak uniform electric field perpendicular to the antenna surface.
The half-divided microstrip power divider also has radiation to generate a near field electric field, and the generated electric field belongs to interference items, so that the whole electric field is offset, and the main working area of the antenna is not right above the antenna, and therefore, a near field electric field distribution balancer is introduced to balance the interference electric field, and the main working area of the antenna is right above the whole antenna.
Further, the third microstrip structure is seamlessly attached between the second dielectric substrate and the third dielectric substrate, the structure is similar to the second microstrip structure, the size is smaller than that of the second microstrip structure, and the third microstrip structure is embedded in the second microstrip structure when seen from the vertical direction. For a specific structure, reference is made to the specific description of the second microstrip structure.
Moreover, the included angle between the cross shape of the second microstrip line structure and the vertical microstrip line of the first microstrip line structure is 45 degrees, so that the effect is to avoid the induction current generated by the second microstrip line structure and the third microstrip line structure to each other when the second microstrip line structure and the third microstrip line structure work to the greatest extent, and the original current of the second microstrip line structure and the third microstrip line structure is weakened, so that the realization effect of the final field uniformity is affected.
The electric fields generated by the third microstrip structure and the second microstrip structure in the vertical direction can be mutually overlapped, so that a relatively weak uniform electric field perpendicular to the surface of the antenna is enhanced, and indiscriminate identification of the vertical orientation electronic tag in a limited space above the reader-writer antenna is realized.
As shown in fig. 6, the S-type microstrip line mentioned in the present embodiment is constituted by nine microstrip lines vertically connected in order.
The principle how the application utilizes the S-shaped microstrip line to realize the miniaturization of the antenna of the reader-writer is shown in fig. 8, and as is well known, when the tail end of the microstrip line is open, the current on the line can show standing wave distribution, namely, a current node appears every half-wavelength length, and the antinode appears on two adjacent current units with half-wavelength lengths and the current directions are opposite, wherein the current node is the minimum point of a current value, and the antinode is the maximum point of the current value. When the current node appears on the non-central axis of the radiating element, it means that the current antinode is not bilateral symmetry, which can make the near field electric field radiated by the radiating element not appear right above it, but have offset, such irregularity is unfavorable for the construction and design of the near field multi-polarization electric field, and the current antinode is asymmetric, which also means that the near field electric field excited by the current on the left and right sides cannot be superimposed in the same direction, which is unfavorable for enhancing the field uniformity effect of the near field. When the current nodes can appear on the central axis of the radiating element, the current antinodes are bilaterally symmetrical, the design of a near-field electric field is most facilitated by such current distribution, the current distribution is obtained, the size of the whole radiating element is inevitably increased under the condition that an S-shaped microstrip line is not introduced, and when the length of the radiating element is increased from 51.2mm to 62.2mm, the current nodes and the antinodes appear at expected positions as can be seen from fig. 8. After the S-shaped microstrip line is introduced, current nodes can be continuously locked on the central axis of the whole radiating unit under the condition that the size of the radiating unit is not increased, so that current effective values are symmetrically distributed on the left side and the right side, the regularity of current distribution is still ensured on the premise that each radiating unit is reduced, and effective guarantee is provided for the design of a subsequent near-field electric field. Therefore, the introduction of the S-shaped microstrip line reduces the size of each radiating element while ensuring the design feasibility of the whole antenna, thereby reducing the plane size of the whole antenna.
In summary, the multi-polarized electric field parallel to the antenna surface generated by the first microstrip structure and the uniform electric field perpendicular to the antenna surface generated by the second and third microstrip structures are overlapped to generate an electric field uniformly distributed in a limited space above the antenna of the reader-writer, thereby realizing the indiscriminate identification of the electronic tag in the space.
In this embodiment, the principle description of realizing planar multi-polarization electric field and field uniformity by the first microstrip structure is as follows:
as shown in fig. 9, when the feed phase of the first feed port is 350 degrees, the directions of currents on the vertical microstrip line a, the vertical microstrip line B and the vertical microstrip line C are opposite to those on the vertical microstrip line a, the vertical microstrip line B and the vertical microstrip line C, so that the currents cancel each other out, and the directions of currents on the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F are opposite to those of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, but the current intensities of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F are obviously greater than those of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, so that the near field only maintains an overall leftward electric field generated by the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, and the corresponding electric field vector diagram is shown in fig. 10 (a) and the feed phase is 0 degrees.
When the feed source phase of the first feed port is 80 degrees, the directions of currents on the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F are opposite to those of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, so that the currents cancel each other, the directions of currents on the vertical microstrip line A, the vertical microstrip line B and the vertical microstrip line C are the same as those of the vertical microstrip line a, the vertical microstrip line B and the vertical microstrip line C, the current magnitude is not larger than that of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F when the feed source phase is 350 degrees, but six microstrip lines with the same current directions are overlapped to generate an overall downward electric field, the strength of the electric field can be basically ensured, and a corresponding electric field vector diagram is shown in the condition that the feed source phase of fig. 10 (B) is 90 degrees.
When the feed source phase of the first feed port is 170 degrees, the vertical microstrip line A, the vertical microstrip line B and the vertical microstrip line C are opposite to the current direction on the vertical microstrip line a, the vertical microstrip line B and the vertical microstrip line C, and the current directions on the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F are opposite to the directions of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, but the current intensity of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F is obviously larger than that of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, so that the near field only maintains the electric field to the right as a whole generated by the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, and the corresponding electric field vector diagram is shown in the condition that the feed source phase of fig. 10 (C) is 180 degrees.
When the feed source phase of the first feed port is 260 degrees, the directions of currents on the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F are opposite to those of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F, so that the currents on the vertical microstrip line A, the vertical microstrip line B and the vertical microstrip line C are mutually counteracted, the directions of the currents on the vertical microstrip line A, the vertical microstrip line B and the vertical microstrip line C are the same as those of the vertical microstrip line a, the vertical microstrip line B and the vertical microstrip line C, the currents are different from those of the horizontal microstrip line D, the horizontal microstrip line E and the horizontal microstrip line F when the feed source phase is 170 degrees, but six microstrip lines with the same current directions are overlapped, so that the intensity of the generated overall upward electric field can be ensured most basically, and a corresponding electric field vector diagram is shown when the feed source phase is 270 degrees as shown in fig. 10 (D).
As can be seen from the above analysis, the near field electric field generated by the reader antenna of the present application realizes multiple polarizations, and when the first feed port works, the polarization direction of the near field electric field rotates counterclockwise by 360 degrees, and repeats. The greatest advantage of this is that the electronic tag in the plane can be effectively identified no matter what direction, and the effect is equivalent to realizing two-dimensional electric field distribution uniformity in the plane.
In this embodiment, the principle of the second microstrip structure and the third microstrip structure generating the Z-direction electric field structure is described:
as shown in fig. 11, when the second and third feeding ports work simultaneously, on one line (the area shown by the square frame in the figure) of the hollowed "+" character pattern, the directions of the currents generated by the area a and the area B are opposite, and the sizes are the same, so that the transverse leaky waves cancel each other, only the longitudinal leaky waves, namely the electric field in the z direction, are reserved, and the other line is the same, so that the longitudinal leaky waves generated simultaneously on the two lines are overlapped with each other, and the effect of enhancing the electric field in the z direction is achieved. As shown in fig. 12, if only the third microstrip structure is adopted, the electric field strength in the z direction is weaker, and in order to further enhance the Ez component and minimize the influence on the third microstrip structure, a second microstrip structure with a similar shape but a slightly larger size is adopted, so that the third microstrip structure is enclosed inside the second microstrip structure in the plane, if two identical shapes are adopted, induced currents with opposite directions are generated at the I and II positions in the figure, and the electric field strength in the z direction is weakened instead, so that the design is practical and creative in application. The structural design strengthens the electric field distribution in the dimension of the z direction, and is uniformly combined with the two-dimensional electric field distribution generated by the first microstrip structure, and the three-dimensional field uniformity in the limited space above the antenna is realized by the synergistic effect due to the principle of leaky wave radiation.
The distribution diagrams of Ex, ey and Ez field intensity components generated above the antenna by the reader antenna of the present application are shown in FIG. 13, FIG. 14 and FIG. 15. It can be seen that the Ex, ey and Ez field intensity components are greater than the minimum activation electric field intensity of 0.3v/m of a common electronic tag in the planes with the cross section size of 400mm x 400mm at the heights of 50mm, 100mm, 150mm, 200mm, 250mm and 300mm above the antenna, and the electric field is a vector, so that the electric field can be decomposed into vector superposition of components in the x, y and z directions, and when each component can achieve the same effect, the electric field distribution at the moment can be considered to be uniform, namely the electronic tag can be effectively identified in any way in the space with the cross section size of 400mm x 300mm above the antenna, and the initial design target is completed.
In fig. 13, 14 and 15, the three panels of the first row are from left to right the heights of the Ex, ey and Ez field intensity components 50mm, 100mm, 150mm above the antenna, respectively, and the three panels of the second row are from left to right the heights of the Ex, ey and Ez field intensity components 200mm, 250mm, 300mm above the antenna, respectively.
Fig. 7 is a schematic diagram of S parameters and gain of the reader-writer antenna according to the present application, where the S parameters of the first, second and third microstrip structures are all lower than-10 dB within the frequency band of the rfid in china 920mhz to 925mhz, which conforms to the matching principle of the antenna design, and the gain of the antenna is lower than-6 dB in two working modes of the antenna within the frequency band, which indicates that the antenna cannot misread electronic tags outside the limited area, and meets the original design objective and requirement.
The embodiments described above are preferred embodiments of the present application, but the embodiments of the present application are not limited to the embodiments described above, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principles of the present application should be made in the equivalent manner, and are included in the scope of the present application.
Claims (10)
1. The miniaturized reader-writer antenna capable of realizing space three-dimensional field uniformity is characterized by comprising three layers of dielectric substrates, wherein the three layers of dielectric substrates are arranged in a stacked manner, and each three layers of dielectric substrates comprises a first dielectric substrate, a second dielectric substrate and a third dielectric substrate;
a first microstrip structure is arranged on a first surface of the first dielectric substrate and is used for generating a multi-polarization electric field of a reader antenna near field so as to realize indiscriminate identification of an electronic tag in a planar two-dimensional field, and the planar two-dimensional field is parallel to the surface of the reader antenna;
a second microstrip structure is arranged between the first dielectric substrate and the second dielectric substrate, a third microstrip structure is arranged between the second dielectric substrate and the third dielectric substrate, and electric fields generated by the second microstrip structure and the third microstrip structure in the vertical direction of the reader antenna are mutually overlapped, so that the electric field intensity in the vertical direction above the reader antenna is enhanced, and the indiscriminate identification of the electronic tag in the vertical direction is realized;
the first microstrip structure, the second microstrip structure and the third microstrip structure are fed by a first feed port, a second feed port and a third feed port respectively;
and the second surface of the third dielectric substrate is provided with a grounding plate.
2. The miniaturized reader/writer antenna of claim 1 wherein the first microstrip structure comprises a split-two power divider, a connecting microstrip line for providing a 90 degree phase shift, and a first radiating element that is mirror symmetric about an incident end of the split-two power divider;
the first radiation unit comprises a radiation microstrip line and an S-shaped microstrip line, and the radiation microstrip line comprises a horizontal microstrip line and a vertical microstrip line;
the S-shaped microstrip line enables a current node to appear on the S-shaped microstrip line, and a current antinode appears on a horizontal microstrip line or a vertical microstrip line connected with two ends of the S-shaped microstrip line;
the horizontal microstrip line is used for generating an X-direction electric field, and the vertical microstrip line is used for generating a Y-direction electric field.
3. The miniaturized reader/writer antenna of claim 2 wherein the first radiating element comprises eight S-type microstrip lines and twelve radiating microstrip lines, wherein each four S-type microstrip lines and six radiating microstrip lines are in a group, two groups are identical in structure, and the six radiating microstrip lines comprise three vertical microstrip lines and three horizontal microstrip lines.
4. The miniaturized reader/writer antenna of claim 1 wherein,
the second microstrip structure and the third microstrip structure are identical in structure, and the third microstrip structure is embedded in the second microstrip structure in the vertical direction.
5. The miniaturized reader/writer antenna of claim 4 wherein the second and third microstrip structures each comprise a split-two power divider, a near field electric field distribution balancer, and a second radiating element, the second radiating element being a hollowed cross comprising two branches, each branch being made up of two radiating elements, adjacent radiating elements having an included angle of 90 degrees.
6. The miniaturized reader/writer antenna of claim 5 wherein each of the radiating elements comprises two mutually parallel microstrip lines and an S-type microstrip line, the two mutually parallel microstrip lines being connected to two ends of the S-type microstrip line, respectively.
7. The miniaturized reader/writer antenna of any of claims 4-6, wherein the angle between the second radiating element and the first radiating element is 45 degrees.
8. The miniaturized reader/writer antenna of claim 1 wherein the second and third feed ports are on the same side of the reader/writer antenna and the first and second feed ports are on different sides of the reader/writer antenna.
9. The miniaturized reader/writer antenna of claim 1 wherein the first, second and third microstrip structures each employ leaky wave radiation.
10. A method based on a miniaturized reader-writer antenna according to any of claims 1-9, characterized in that two modes of operation of the reader-writer antenna are achieved by controlling the alternating feeding operation of the first feeding port, the second feeding port and the third feeding port;
mode one: when the first feed port works, the polarization direction of the generated near-field electric field can rotate anticlockwise by 360 degrees;
mode two: when the second feed port and the third feed port work simultaneously, the second microstrip structure and the third microstrip structure respectively form a hollowed cross, the hollowed cross is formed by two branches, one branch comprises two radiation elements, the generated currents are opposite in direction and same in size, so that transverse leakage waves are mutually offset, and longitudinal filtering is reserved;
the longitudinal leaky waves generated by the two branches at the same time are mutually overlapped, so that an electric field in the vertical direction of the reader antenna is increased;
the two modes are combined to realize the uniformity of the three-dimensional field in the space above the antenna of the reader-writer.
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