A miniaturized, stable, high-gain circularly polarized mobile phone detection antenna

Abstract

This invention belongs to the field of radio frequency identification (RFID) technology and discloses a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna. It includes an antenna radiating layer and a feeding network layer. The antenna radiating layer comprises a dielectric substrate and radiating elements printed on the substrate. The feeding network layer has two dielectric substrates: an upper feeding network dielectric substrate and a lower feeding network dielectric substrate, and 90-degree phase-shifted microstrip Wilkinson feeding networks printed on both sides of the dielectric substrates. A reflector is fixed in the middle of the feeding network layer. The antenna is fed via a coaxial line. The reflector is a metal plate with a circular hole in the center, which serves as the antenna reference ground. This invention solves the problems of low axial ratio bandwidth and poor axial ratio performance of UHF band RFID antennas, ensuring that while miniaturizing the antenna, the gain in the UHF band remains relatively stable, consistently above 0dB, with a maximum value reaching 2.8dB.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency identification technology, and in particular relates to a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna. Background Technology

[0002] The UHF band is primarily used for radio frequency identification (RFID) and broadcast television, especially as a second-generation communication band for mobile communication. With advancements in technology and the deepening development of communication technologies, 5G technology has gradually matured and entered people's lives. However, for some economically underdeveloped areas with lagging communication technology, 5G technology is too expensive, and 2G, 3G, and 4G communication methods remain dominant. Therefore, research on facilities and equipment within traditional communication bands cannot be ignored, especially in remote mountainous areas. 2G signals have a longer wavelength, possessing a higher ability to diffract through mountains and avoid obstacles. In the event of natural disasters disrupting communication, using 2G mobile phone signals to locate the injured for search and rescue operations is an excellent option. Since antennas are the terminals for signal transmission and reception, the design of 2G mobile phone signal detection and positioning antennas also places certain demands on their design. To further improve the search and rescue range and positioning accuracy, antennas should primarily adopt circular polarization design to reduce polarization imbalance with the targeted mobile phone, while also possessing a wide beamwidth and stable high gain throughout the entire 2G band. However, for mobile phone signal detection and positioning antennas used in mountainous areas, portability is a crucial parameter for evaluating the design quality. Antenna theory reveals a trade-off between antenna gain, bandwidth, and size reduction; each comes at a cost. Therefore, developing a miniaturized, stable, high-gain, circularly polarized mobile phone detection antenna is of significant importance. The 2G signal bands of my country's three major operators primarily fall within the UHF band; therefore, research on antenna design within the UHF band is sufficient. In recent years, research on UHF band antennas has become increasingly in-depth. The following section compares some typical literature to demonstrate the design of this antenna.

[0003] The existing technology "A miniaturized high-gain RFID reader antenna" (CN 216436122 U) designs an antenna with a symmetrical hourglass-shaped structure composed of trapezoids and rectangles. Although the designed antenna has a high gain, with an actual gain of 6.7dB, its bandwidth is narrow, with a -10dB operating bandwidth of 907MHz-922MHz. It cannot achieve full coverage of the 2G frequency band signals of the three major operators. In addition, the antenna profile is relatively high, and the overall size reaches 100mm*100mm*25mm.

[0004] In the literature "Design of UHF RFID Dual Circular Polarized Antenna Based on Miniaturized Branch Line Coupler", although the antenna has a low profile and a total size of 80mm*80mm*1.6mm, its overall gain is low in the 2G band, almost all below 0dB, with the highest gain being only 0.89dB. It is difficult to achieve long-distance mobile phone signal detection and positioning in the entire 2G band.

[0005] The paper “Lerkbangplad C, Namahoot A, Akkaraekthalin P, et al. A compact wideband circularly polarized quadrifilar antenna with PIFA elements for UHF RFID readers[J]. International Journal of Microwave and Wireless Technologies, 2020, 12(10):1020-1028” describes a rotating quadrifilar antenna with a Wilkinson feed network that splits one channel into four. Its circular polarization gain is 3.32 dBic. Although the profile is low, the antenna area is relatively large (120mm*120mm), which is not conducive to miniaturization and integration.

[0006] Mobile phone signal detection antennas primarily achieve three-point positioning by assembling designed antenna elements. Therefore, designing a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna element and performing array-based detection and positioning remains an extremely challenging task. This section mainly studies the element structure of this antenna.

[0007] Based on the above analysis, the problems and defects of the existing technology are as follows: the antenna bandwidth of the existing device is relatively narrow and cannot achieve full coverage of the 2G signal frequency bands of the three major operators. At the same time, the existing device is large in size, which is not conducive to miniaturization and integration. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna, and particularly relates to a miniaturized, stable, high-gain circularly polarized reader antenna for UHF band RFID.

[0009] This invention is implemented as follows: a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna element includes: The antenna radiating layer comprises a dielectric substrate and radiating elements printed on the dielectric substrate.

[0010] The feed network layer consists of two dielectric substrates: an upper feed network dielectric substrate and a lower feed network dielectric substrate. Both sides of each substrate are printed with a 90-degree phase-shifted microstrip Wilkinson feed network. A reflector is fixed in the middle of the feed network layer. The antenna is fed via a coaxial cable.

[0011] Furthermore, the reflector is a metal plate, and a circular slot is formed in the middle of the metal plate to serve as the antenna reference ground.

[0012] Furthermore, the upper feed network dielectric substrate, the reference ground, and the lower feed network dielectric substrate are sequentially laminated to form a feed network layer. The upper feed network is printed on the upper surface of the upper feed network dielectric substrate, the lower feed network is printed on the lower surface of the lower feed network dielectric substrate, and the reference ground is sandwiched between the upper feed network dielectric substrate and the lower feed network dielectric substrate.

[0013] Furthermore, there are two 90-degree phase-shifted microstrip Wilkinson feed networks, fixedly connected in an upper and lower structure. The lower 90-degree phase-shifted microstrip Wilkinson feed network is rotated 180 degrees relative to the upper feed network around the z-axis. The antenna uses a differential feeding method.

[0014] Furthermore, the 90-degree phase-shifted microstrip Wilkinson feed network has two forms: loaded microstrip open-circuit stubs and short-circuit stubs. The end of the short-circuit stub is connected to the reference ground through a small metal post, which can realize the broadband of the antenna and the high-performance circular polarization characteristics with an axial ratio of less than 1dB, while also having low port insertion loss.

[0015] Furthermore, the coaxial cable adopts a 50Ω coaxial power supply. The input port of the lower power supply network is connected to the outer core shielding layer of the coaxial cable, while the inner core of the coaxial cable is connected to the upper power supply network input port through a hole drilled in the middle reference ground without contacting it.

[0016] Furthermore, the antenna radiating layer is separated from the feed network layer by a certain distance to reduce the Q value (Q value is called the quality factor in an antenna, which mainly characterizes the resonant characteristics of the antenna and is inversely proportional to the bandwidth of the antenna) and increase the bandwidth. The four output ports of the upper and lower feed networks are fed to the input terminals of the radiating dipole on the antenna radiating plate substrate through metal pillars.

[0017] Furthermore, the radiating element consists of four rotationally symmetric, slender, bent microstrip patches printed on the surface of the antenna radiating layer dielectric substrate. Taking one unit as an example, a λ / 2 wavelength bend is made from the input end of the radiating element patch, and then short-circuited to the reference ground via a vertical microstrip metal sheet. Simultaneously, an inverted L-shaped stub is added to the bent section of the radiating element to improve radiation gain. The other three units can be obtained by rotating them 90°, 180°, and 270° around the z-axis, respectively.

[0018] Another objective of this invention is to provide a method for designing a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna unit. The design method includes: during operation, the radiating element is four rotationally symmetrical, slender, bent microstrip patches printed on the surface of an upper feed network dielectric substrate.

[0019] Furthermore, after bending λ / 2 wavelength from the input end of the radiating oscillator patch, it is shorted to the reference ground through a vertical microstrip metal sheet. An inverted L-shaped stub is added to the bent straight section of the radiating oscillator, and the remaining three units are rotated 90°, 180° and 270° around the z-axis, respectively.

[0020] Furthermore, two cross patches are added in the middle of the antenna to enhance the gain of the low-frequency and high-frequency components, respectively.

[0021] Furthermore, the antenna elements are arrayed, such as in a linear array, a circular array, or a square array, to form the final mobile phone signal detection and positioning antenna.

[0022] Another object of the present invention is to provide a radio frequency identification (RFID) device, wherein the RFID device is equipped with the miniaturized, stable, high-gain circularly polarized mobile phone detection and positioning antenna.

[0023] Another objective of this invention is to provide a smart terminal equipped with the aforementioned miniaturized, stable, high-gain circularly polarized mobile phone positioning and detection antenna.

[0024] Based on the above technical solutions and the technical problems solved, please analyze the advantages and positive effects of the technical solution to be protected by this invention from the following aspects: First, addressing the technical problems existing in the prior art and the difficulty in solving them, this paper closely analyzes, in conjunction with the technical solution to be protected by this invention and the results and data obtained during the research and development process, how the technical solution of this invention solves the technical problems, and the inventive technical effects brought about by solving these problems. The specific description is as follows: The embodiments of the present invention solve the problems of low axial ratio bandwidth and poor axial ratio performance of mobile phone signal detection and positioning antennas, greatly reducing the polarization mismatch rate. While ensuring miniaturization, the gain in the UHF band is relatively stable, all above 0dB, with a maximum value of 2.8dB.

[0025] Second, considering the technical solution as a whole or from a product perspective, the technical effects and advantages of the technical solution to be protected by this invention are specifically described as follows: The embodiments of the present invention have a simple structure and obvious effects, with excellent structural characteristics. The structure is simple, easy to process and install, and the antenna meets |S11|<-10dB in the 800MHz-960MHz frequency band, the axial ratio meets AR<0.8dB, and the circular polarization performance is good.

[0026] A miniaturized, stable, high-gain circularly polarized mobile phone detection antenna has an overall physical size of 80mm*80mm*12mm and a total size of only 0.25λ*0.25λ*0.035λ (wavelength at 880MHz).

[0027] Third, as supplementary evidence of the inventive step of the claims of this invention, it is also reflected in the following important aspects: The technical solution of this invention overcomes technical bias: it bypasses the traditional UHF band antenna vibrator—the planar inverted F structure. Gain is primarily increased by folding the radiating vibrator at approximately a quarter wavelength and adding stubs to the long side. Furthermore, the gain in the high-frequency and low-frequency bands is adjusted separately by adding inner and outer cross-shaped patches for coupling. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the miniaturized, stable, high-gain circularly polarized mobile phone detection antenna unit provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the coaxial cable structure provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the antenna radiating layer structure provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of a 90-degree phase-shifted microstrip Wilkinson feeder network provided in an embodiment of the present invention; Figure 5 The S of the antenna provided in the embodiment of the present invention 11 Curve and axis ratio curve; Figure 6 This is a polarization gain curve of the antenna provided in an embodiment of the present invention; In the diagram: 1. Antenna radiating layer; 2. Reference ground; 3. Antenna radiating element dielectric substrate; 4. Feed network layer; 5. Coaxial line; 6. Antenna radiating element. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0030] I. Explanatory and Illustrative Embodiments. To enable those skilled in the art to fully understand how the present invention is specifically implemented, this section provides an explanatory and illustrative description of the embodiments described in the claims.

[0031] like Figures 1-6As shown, the miniaturized, stable, high-gain circularly polarized mobile phone detection antenna unit provided in this embodiment of the invention includes: an antenna radiating layer 1, a reference ground 2, an antenna radiating element dielectric substrate 3, a feed network layer 4, a coaxial line 5, and an antenna radiating element 6.

[0032] Antenna radiating layer 1, comprising a dielectric substrate and a radiating element 6 printed on the dielectric substrate.

[0033] The feed network layer 4 consists of two dielectric substrates: an upper feed network dielectric substrate and a lower feed network dielectric substrate. Both sides of each substrate are printed with a 90-degree phase-shifted microstrip Wilkinson feed network. A reflector is fixed in the middle of the feed network layer 4. The antenna is fed via a coaxial cable 3.

[0034] The reflector is a metal plate, and a circular slot is opened in the middle of the metal plate to serve as the antenna reference ground 2.

[0035] The upper feed network dielectric substrate, the reference ground, and the lower feed network dielectric substrate are sequentially laminated to form a feed network layer. The upper feed network is printed on the upper surface of the upper feed network dielectric substrate, and the lower feed network is printed on the lower surface of the lower feed network dielectric substrate. The reference ground 2 is sandwiched between the upper feed network dielectric substrate and the lower feed network dielectric substrate.

[0036] There are two 90-degree phase-shifted microstrip Wilkinson feed networks, fixedly connected in an upper and lower structure. The lower 90-degree phase-shifted microstrip Wilkinson feed network is rotated 180 degrees relative to the upper feed network around the z-axis. The antenna uses a differential feeding method.

[0037] The 90-degree phase-shifted microstrip Wilkinson feed network has two forms: loaded microstrip open-circuit stubs and short-circuit stubs. The end of the short-circuit stub is connected to the reference ground through a small metal post, which can realize the broadband of the antenna and the high-performance circular polarization characteristics with an axial ratio of less than 1dB, while also having low port insertion loss.

[0038] The coaxial cable uses a 50Ω coaxial power supply. The input port of the lower power supply network is connected to the outer core shielding layer of the coaxial cable. The inner core of the coaxial cable is connected to the upper power supply network input port through a hole drilled in the middle reference ground without contacting it.

[0039] The antenna radiating layer is separated from the feed network layer by a certain distance to reduce the Q value and increase the bandwidth. The four output ports of the upper and lower feed networks are fed to the input terminals of the radiating oscillator on the antenna radiating plate substrate through metal pillars.

[0040] In this invention, the radiating element is composed of four rotationally symmetrical, elongated, bent microstrip patches printed on the upper surface of the antenna radiating layer 3. Taking one unit as an example, a λ / 2 wavelength bend is made from the input end of the radiating element patch 6 and then shorted to the reference ground via a vertical microstrip metal sheet. Simultaneously, a reverse stub is added to the bent section of the radiating element to improve radiation gain. The other three units can be obtained by rotating them around the z-axis by 90°, 180°, and 270° respectively. Furthermore, two intersecting patches are added in the middle of the antenna to enhance the low-frequency and high-frequency gain respectively. like Figure 5 This is a graph showing the S11 curve and axial ratio curve of the antenna in an embodiment of the present invention. Figure 6 This is a polarization gain curve of the antenna in an embodiment of the present invention.

[0041] II. Application Examples. To demonstrate the inventiveness and technical value of the technical solution of this invention, this section provides application examples of the technical solution of the claims on specific products or related technologies.

[0042] The embodiments of the present invention are applied in radio frequency identification technology.

[0043] III. Evidence of the Relevant Effects of the Embodiments. The embodiments of the present invention have achieved some positive effects during research and development or use, and indeed possess significant advantages compared to existing technologies. The following description, in conjunction with data, charts, and other materials from the experimental process, illustrates these advantages.

[0044] Simulation results show that the antenna satisfies |S11| < -10dB and axial ratio AR < 0.8dB in the 800MHz-960MHz frequency band, exhibiting excellent circular polarization performance. Furthermore, the simulated actual gain values ​​within the frequency band are all above 0dB, with a peak gain reaching 2.8dB. In the description of this invention, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0045] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A miniaturized, stable, high-gain circularly polarized mobile phone detection antenna, characterized in that, The miniaturized, stable, high-gain circularly polarized mobile phone detection antenna includes: The antenna radiating layer includes a dielectric substrate and a radiating element printed on the dielectric substrate. The feed network layer consists of two dielectric substrates: an upper feed network dielectric substrate and a lower feed network dielectric substrate. Both sides of the dielectric substrates are printed with 90-degree phase-shifted microstrip Wilkinson feed networks. A reflector is fixed in the middle of the feed network layer, and the antenna is fed through a coaxial line. The reflector is a metal plate, and a circular slot is opened in the middle of the metal plate to serve as the antenna reference ground. The upper feed network dielectric substrate, the reference ground, and the lower feed network dielectric substrate are sequentially laminated to form a feed network layer. The upper feed network is printed on the upper surface of the upper feed network dielectric substrate, the lower feed network is printed on the lower surface of the lower feed network dielectric substrate, and the reference ground is sandwiched between the upper feed network dielectric substrate and the lower feed network dielectric substrate. The radiating oscillator consists of four rotationally symmetrical, slender, bent microstrip line patches printed on the surface of the radiating layer dielectric substrate. The input end of the radiating oscillator patch is bent at λ / 2 wavelength and then short-circuited to the reference ground through a vertical microstrip metal sheet. An inverted L-shaped stub is added to the bent straight section of the radiating oscillator, and the other three units are obtained by rotating them around the z-axis by 90°, 180° and 270° respectively. There are two 90-degree phase-shifted microstrip Wilkinson feed networks, which are fixedly connected in an upper and lower structure. The lower 90-degree phase-shifted microstrip Wilkinson feed network is rotated 180 degrees around the z-axis relative to the upper feed network. The antenna adopts a differential feeding method. The 90-degree phase-shifted microstrip Wilkinson feed network has two forms: loaded microstrip open-circuit stubs and short-circuit stubs. The end of the short-circuit stub is connected to the reference ground through a small metal post, realizing the broadband of the antenna and high-performance circular polarization characteristics with an axial ratio of less than 1dB.

2. The miniaturized, stable, high-gain circularly polarized mobile phone detection antenna as described in claim 1, characterized in that, The coaxial cable is fed by a 50Ω coaxial power supply. The input port of the lower power supply network is connected to the outer core shielding layer of the coaxial cable. The inner core of the coaxial cable is connected to the upper power supply network input port through a hole drilled in the middle reference ground and does not contact it. The antenna radiating layer is separated from the feed network layer by a certain distance to reduce the Q value and increase the bandwidth. The four output ports of the upper and lower feed networks are fed to the input end of the radiating oscillator on the antenna radiating plate substrate through metal pillars. The radiating element consists of four rotationally symmetrical, slender, bent microstrip patch pieces printed on the surface of the antenna radiating element substrate.

3. A design method for a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna as described in any one of claims 1 to 2, characterized in that, The design method includes: during operation, the radiating oscillator consists of four rotationally symmetrical, slender, bent microstrip patches printed on the surface of the upper feed network dielectric substrate.

4. The design method as described in claim 3, characterized in that, The design method involves bending a λ / 2 wavelength section from the input end of the radiating oscillator patch and then short-circuiting it to the reference ground via a vertical microstrip metal sheet. An inverted L-shaped stub is added to the bent straight section of the radiating oscillator, and the remaining three units are rotated 90°, 180° and 270° around the z-axis, respectively. Two cross patches, one inside and one outside, are added in the middle of the antenna to enhance the gain of the low-frequency and high-frequency components, respectively. The final mobile phone signal detection and positioning antenna is formed by arranging antenna elements into arrays, such as linear arrays, circular arrays, and square arrays.

5. A radio frequency identification device, characterized in that, The radio frequency identification device is equipped with the miniaturized, stable, high-gain circularly polarized mobile phone detection antenna as described in any one of claims 1 to 2.

6. A smart terminal, wherein the smart terminal is equipped with a miniaturized, stable, high-gain circularly polarized mobile phone detection antenna as described in any one of claims 1 to 2.

Images