Miniaturized low-profile dual-polarized microstrip antenna, antenna assembly and PDA device

Abstract

The application provides a miniaturized low-profile dual-polarized microstrip antenna, an antenna assembly and a PDA device, the microstrip antenna comprising at least one guiding layer, a ground layer and a radiation layer arranged in parallel and spaced apart from top to bottom, the radiation layer adopting a coaxial transmission line direct feeding structure, the advantage of the direct feeding structure being that the coaxial line feeding is directly used to save the complicated power division and phase shift structure, the radiation efficiency can be improved and the loss can be reduced; wherein the guiding layer is a first metal floor, the ground layer is a second metal floor, and the radiation layer comprises four dipole units in a cross distribution at a central position, the antenna structure enables the microstrip antenna to use air as a propagation medium, the speed of electric signal propagation is inversely proportional to the square root of the dielectric constant, when the dielectric constant is lower, the signal transmission speed is faster, therefore, the application uses air medium to transmit signals, the signal transmission speed can be accelerated, and the label reading efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of ultra-high frequency radio frequency identification technology, and in particular to a miniaturized low-profile dual-polarized microstrip antenna, antenna assembly and PDA device. Background Technology

[0002] Ultra-high frequency radio frequency identification (UHF RFID) technology boasts significant advantages such as long reading distance, high recognition rate, and high transmission speed. It is currently widely used in a range of scenarios including animal microchips, automotive microchip anti-theft devices, access control, warehousing and logistics, production line automation, and material management. In specific applications requiring even longer reading distances and higher recognition rates, the antenna of the device must possess higher gain and better directivity. Therefore, developing antennas with low cost, simple structure, and high gain is crucial to addressing the shortcomings of current industry equipment.

[0003] Currently, most devices using UHF RFID in the industry employ circularly polarized antennas. Circularly polarized antennas are highly versatile when reading both linearly polarized and circularly polarized tags, and generally have two implementation methods. The first method uses a ceramic microstrip antenna, which achieves circular polarization using a 1-to-2 power divider network. Its advantages are low profile and low cost, but its disadvantages include narrow antenna bandwidth and low gain, resulting in a short reading distance. The second method uses a four-arm antenna combination, employing Wilkinson power divider technology to impart equal power to each element and a 90-degree phase delay rotation on the phase of each element to achieve circular polarization. This method offers improved antenna gain and bandwidth compared to ceramic antennas, but its disadvantages include significant gain loss due to the power divider structure and higher production costs.

[0004] Furthermore, there are some single-line polarized antennas in the industry. These antennas have extremely high gain and directivity and are suitable for most scenarios. However, when the linearly polarized tag is completely isolated from the antenna, there will be situations where the tag cannot be read. This type of scenario is the pain point of linearly polarized antennas.

[0005] Furthermore, dual-polarized antennas offer significant advantages over circularly polarized antennas of the same gain in scenarios involving reading mostly linearly polarized tags. However, existing dual-polarized antennas, due to their linear polarization characteristics, are bulky and have a high profile, hindering their widespread application in PDA devices. For example, in patent CN 114628912 A, the antenna dimensions are as large as 280mm*280mm*48mm, making integration into a PDA device impossible.

[0006] In summary, the main pain points of UHF RFID device antennas in the industry at present are low antenna gain and poor directionality, with significant room for improvement in long-distance card finding and linear polarized tag reading speed; single-line polarized antennas have blind spots that cannot be read at all; and dual-line polarized antennas are not easy to integrate into handheld terminals due to their large size. Summary of the Invention

[0007] The purpose of this application is to at least solve one of the above-mentioned technical defects, especially the low gain and poor directivity of the antenna in the prior art, which leaves considerable room for improvement in long-distance card finding and linearly polarized tag reading speed; the existence of a blind zone where single-line polarized antennas cannot be read at all; and the technical defects of dual-line polarized antennas, which are difficult to integrate into handheld terminals due to their large size.

[0008] This application provides a miniaturized low-profile dual-polarized microstrip antenna, the microstrip antenna comprising: at least one guide layer, a ground layer and a radiating layer arranged in parallel from top to bottom;

[0009] The guiding layer includes a first metal floor;

[0010] The grounding layer includes a second metal floor;

[0011] The radiating layer includes four dipole units arranged in a cross shape at the center. Each dipole unit includes a dipole oscillator, a grounding through hole through the middle of the dipole oscillator, and an open-circuit capacitor loaded at the end of the dipole oscillator. The portion of the open-circuit capacitor that extends beyond the edge of the second metal floor is bent vertically upward.

[0012] Each pair of oppositely arranged dipole units forms a group. The front ends of the two dipole oscillators in one group are connected by a first microstrip line, while the front ends of the two dipole oscillators in the other group are connected by a power feed via.

[0013] The radiating layer and the second metal floor are fixedly connected by an equivalent capacitance passing through the grounding via.

[0014] Optionally, the size of the first metal floor is smaller than the size of the second metal floor.

[0015] Optionally, the height between the first metal floor and the second metal floor is less than the height between the radiant layer and the second metal floor.

[0016] Optionally, the height between the first metal floor and the radiating layer is less than half a wavelength.

[0017] Optionally, the height between the first metal floor and the radiating layer is one-quarter wavelength.

[0018] Optionally, when the guiding layer is a multi-layer structure, each guiding layer is arranged in parallel at intervals.

[0019] The dimensions of the other guide layers are smaller than the dimensions of the guide layer closest to the radiation layer, and the spacing between each guide layer is smaller than the height between the guide layer closest to the radiation layer and the radiation layer.

[0020] Optionally, the equivalent capacitance is a metal pillar and / or a second microstrip line.

[0021] Optionally, the open-circuit capacitor includes a first metal patch and a second metal patch;

[0022] Wherein, the front end of the first metal patch is connected to the end of the dipole oscillator, and the end of the first metal patch extends to be aligned with the edge of the second metal ground plate;

[0023] The second metal patch is loaded at the end of the first metal patch and extends upward perpendicular to the extension direction of the first metal patch.

[0024] Optionally, the first metal patch has a triangular structure, and the second metal patch has a square structure;

[0025] Wherein, the vertex of the first metal patch is the front end, and the bottom edge of the first metal patch is the end end.

[0026] Optionally, the equivalent electrical length of each dipole unit is one-quarter of a wavelength.

[0027] Optionally, the profile height of the microstrip antenna is less than 0.1λ.

[0028] This application also provides a dual-polarized microstrip antenna assembly, the dual-polarized microstrip antenna assembly including an antenna housing and a miniaturized low-profile dual-polarized microstrip antenna as described in any of the above embodiments, installed inside the cavity of the antenna housing.

[0029] Optionally, the dual-polarized microstrip antenna assembly further includes a radio frequency switch and a radio frequency module, and the antenna housing includes a front antenna housing and a rear antenna housing;

[0030] The guiding layer is close to or attached to the inner wall of the antenna front shell, and the radio frequency switch and the radio frequency module are disposed between the radiating layer and the inner wall of the antenna rear shell;

[0031] The front shell of the antenna and the rear shell of the antenna are detachably connected.

[0032] Optionally, the two sets of dipole units are respectively connected to the two input terminals of the radio frequency switch via coaxial lines;

[0033] The output terminal of the RF switch is connected to the RF module.

[0034] Optionally, the inner wall of the antenna front shell and / or the inner surface of the antenna rear shell are covered with a microwave absorbing material.

[0035] Optionally, the length of the absorbing material covering the inner wall of the antenna front shell along the radiation direction may exceed or not exceed the guiding layer.

[0036] Optionally, the microwave absorbing material is a composite oxide with iron oxide and other iron group or rare earth group oxides as the main components.

[0037] Optionally, the radio frequency module is used to control the start and stop of the miniaturized low-profile dual-polarized microstrip antenna in two polarization directions based on the number of tags in the field and the tag reading rate.

[0038] This application also provides a PDA device, which includes a complete unit and a dual-polarized microstrip antenna assembly as described in any of the above embodiments connected to the complete unit.

[0039] Optionally, the radio frequency module in the dual-polarized microstrip antenna assembly is connected to the main unit via an FPC.

[0040] As can be seen from the above technical solutions, the embodiments of this application have the following advantages:

[0041] This application provides a miniaturized, low-profile, dual-polarized microstrip antenna, antenna assembly, and PDA device. The microstrip antenna includes at least one director layer, a ground layer, and a radiating layer arranged in parallel from top to bottom. The radiating layer employs a direct-feed structure via a coaxial transmission line. The advantage of this direct-feed structure is that it eliminates the need for a complex power divider / phase shifter structure, thereby improving radiation efficiency and reducing losses. The director layer is a first metal ground plane, the ground layer is a second metal ground plane, and the radiating layer includes four dipole elements arranged in a cross shape at the center. This antenna structure allows the microstrip antenna of this application to use air as the propagation medium. Since the speed of electrical signal propagation is inversely proportional to the square root of the dielectric constant, when the dielectric constant... The lower the constant, the faster the signal transmission speed. Therefore, this application uses air as the medium to transmit signals, which can accelerate the signal transmission speed and improve the tag reading efficiency. Furthermore, the guiding layer of this application can also be regarded as a new radiating patch, which gathers the electromagnetic waves from the ground layer and the radiating layer and then further emits them forward, thereby effectively improving the front-to-back ratio and gain. Next, each dipole unit in this application includes a dipole oscillator. Every two oppositely arranged dipole units form a group. The front ends of the two dipole oscillators in one group of dipole units are connected by a first microstrip line, and the front ends of the two dipole oscillators in the other group of dipole units are connected by a feed via. This allows the signal to pass through the first microstrip line and the feed via. The through-hole connects the dipole element to the circuit, thereby feeding the dual-polarized antenna through the circuit. This allows the dual-polarized antenna to change between two polarization directions, effectively avoiding the drawback of not being able to read the tag when the polarization directions are completely isolated. Furthermore, each dipole element in this application also includes an open-circuit capacitor loaded at the end of the dipole element. The portion of the open-circuit capacitor extending beyond the edge of the second metal ground plane is bent vertically upwards. This open-circuit capacitor design can bend the original capacitor structure into two parts, thereby reducing the volume of the overall capacitor on the horizontal plane and utilizing the remaining space for capacitor loading. This allows for both adjustment of the resonant frequency and reduction of the antenna size. Each dipole element also includes a through-hole... The grounding via in the middle of the dipole element allows the second metal ground plane to be fixedly connected to the radiating layer via an equivalent capacitance passing through the grounding via. This equivalent capacitance can be considered as a series short-circuit structure of a resistor and capacitor. This can further reduce the return loss of the antenna while also expanding the impedance bandwidth. Furthermore, since the equivalent capacitance is located between the radiating layer and the ground layer, if the equivalent capacitance is set as a metal rod in this application, it is equivalent to adding four metal rods in a rectangular cavity. Using the perturbation method, it can be seen that inserting tiny metal rods in areas with strong electric fields will shift the resonant frequency to a lower frequency. Therefore, this structure can be used to further fine-tune the resonant frequency, thereby further reducing the antenna size.This antenna structure allows for easy integration into PDA devices, solving the industry's pain point of being unable to use dual-polarized antennas. Furthermore, final physical testing results show that the overall gain of the microstrip antenna is approximately 3 dB higher than that of a circularly polarized antenna of the same volume, and approximately 2 dB higher than that of a linearly polarized antenna of the same structure. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A schematic diagram of a miniaturized low-profile dual-polarized microstrip antenna provided in this application embodiment;

[0044] Figure 2 This is a schematic diagram of the structure of the radiation layer provided in an embodiment of this application;

[0045] Figure 3 A side view of the guide layer, ground layer and radiating layer provided in an embodiment of this application;

[0046] Figure 4 This is a schematic diagram of the structure of a dual-polarized microstrip antenna assembly provided in an embodiment of this application;

[0047] Figure 5 A schematic diagram of the structure for controlling the start-up and shutdown of a dual-polarized microstrip antenna in two polarization directions by a radio frequency module provided in an embodiment of this application;

[0048] Figure 6 This is a schematic diagram of the structure of a PDA device provided in an embodiment of this application.

[0049] The above-mentioned figures include a guide layer 10, a ground layer 20, a radiating layer 30, a dipole vibrator 31, a grounding via 32, an open-circuit capacitor 33, an equivalent capacitor 40, a complete unit 50, an antenna housing 51, an antenna front housing 511, an antenna rear housing 510, an RF switch 52, and an RF module 53. Detailed Implementation

[0050] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] The main pain points of UHF RFID device antennas currently used in the industry are low antenna gain and poor directivity, leaving significant room for improvement in areas such as long-distance card finding and reading speed of linearly polarized tags. Single-line polarized antennas also suffer from completely unreadable blind spots, while dual-line polarized antennas are bulky and difficult to integrate into handheld terminals. Based on these issues, this application proposes the following technical solution, as detailed below:

[0052] In one embodiment, such as Figure 1 As shown, Figure 1 This is a schematic diagram of the structure of a miniaturized low-profile dual-polarized microstrip antenna provided in an embodiment of this application. This application provides a miniaturized low-profile dual-polarized microstrip antenna, which includes at least one guide layer 10, a ground layer 20, and a radiating layer 30 arranged in parallel from top to bottom.

[0053] The guiding layer 10 includes a first metal floor.

[0054] The grounding layer 20 includes a second metal floor.

[0055] The radiating layer 30 includes four dipole units arranged in a cross shape at the center. Each dipole unit includes a dipole oscillator 31, a grounding through-hole 32 passing through the middle of the dipole oscillator 31, and an open-circuit capacitor 33 loaded at the end of the dipole oscillator 31. The portion of the open-circuit capacitor 33 extending beyond the edge of the second metal floor is bent vertically upward.

[0056] Each pair of oppositely arranged dipole units forms a group. The front ends of the two dipole oscillators 31 in one group of dipole units are connected by a first microstrip line, while the front ends of the two dipole oscillators 31 in the other group of dipole units are connected by a power supply via.

[0057] The radiating layer 30 is fixedly connected to the second metal floor by an equivalent capacitance 40 passing through the grounding through hole 32.

[0058] In this embodiment, as Figure 1As shown, the dual-polarized antenna mainly consists of three layers: a guide layer 10, a ground layer 20, and a radiating layer 30, arranged in parallel and spaced intervals from top to bottom. The upper guide layer 10 has at least one layer, primarily composed of a first metal ground plane. This first metal ground plane can be connected to the inner surface of the housing supporting the dual-polarized antenna, or it can be fixed by screws or a snap-fit ​​structure; no limitation is made here. Furthermore, this application places the ground layer 20 between the guide layer 10 and the radiating layer 30. This makes the height between the guide layer 10 and the radiating layer 30 greater than the height between the ground layer 20 and the radiating layer 30. Compared to a structure with the upper layer being the guide layer 10, the middle layer being the radiating layer 30, and the lower layer being the ground layer 20, this improves the antenna's aspect ratio and gain while further reducing its size.

[0059] Furthermore, both the guiding layer 10 and the ground layer 20 in this application are metal ground planes. This allows the ground layer 20 to be viewed as a guiding layer 10, concentrating the electromagnetic waves from the radiating layer 30 for forward transmission, improving the front-to-back ratio and gain. Alternatively, the guiding layer 10 can be viewed as a new radiating patch, concentrating the electromagnetic waves from the ground layer 20 and the radiating layer 30 for further forward transmission, thereby further improving the front-to-back ratio and gain. Additionally, the antenna structure of this application allows the dual-polarized microstrip antenna to use air as the propagation medium when receiving or transmitting electromagnetic signals, enabling rapid signal transmission. It is understood that the speed of electrical signal propagation is inversely proportional to the square root of the dielectric constant. The lower the dielectric constant, the faster the signal transmission speed (a high dielectric constant can reduce field leakage and cross-coupling effects). Commonly used PCB dielectrics are FR4 materials, with a dielectric constant of 4.2-4.7 relative to air (air's dielectric constant is 1). Therefore, using air as the medium for signal propagation can effectively improve the signal propagation speed.

[0060] Immediately afterwards, such as Figure 2 , 3 As shown, Figure 2 This is a schematic diagram of the structure of the radiation layer provided in an embodiment of this application. Figure 3 This is a side view of the guide layer, ground layer, and radiating layer provided in an embodiment of this application; the radiating layer 30 of the dual-polarized antenna in this application is mainly composed of four dipole units arranged in a cross shape at the center. For example, Figure 1 and Figure 2As shown, each dipole unit contains a dipole oscillator 31. Two oppositely positioned dipole units form a group. The front ends of the two dipole oscillators 31 in one group are connected via a first microstrip line, while the front ends of the two dipole oscillators 31 in the other group are connected via a feed via. This allows the two groups of dipole units to be directly fed via coaxial lines, effectively improving radiation efficiency and reducing losses. Furthermore, the use of a two-group dipole unit structure allows for the reception and transmission of electromagnetic waves in both vertical and horizontal polarization directions, effectively avoiding the drawback of not being able to read the tag when the polarization directions are completely isolated. Additionally, as... Figure 1 , 3 As shown, each dipole unit in this application is also loaded with an open-circuit capacitor 33 at the end of the dipole oscillator 31, and the part of the open-circuit capacitor 33 that extends beyond the edge of the second metal ground plane is bent vertically upward. This structure can bend the original capacitor structure into two parts, thereby reducing the volume of the overall capacitor on the horizontal plane and using the spare space for capacitor loading. This can be used to adjust the resonant frequency and further reduce the size of the antenna.

[0061] It should be noted that the shape of the open-circuit capacitor 33 in this application can be set arbitrarily, such as a combination design of semi-circle + semi-circle, semi-circle + triangle, triangle + square, etc. In this combination design, the open-circuit capacitor located on the side of the second dielectric substrate is in a floating state.

[0062] Furthermore, such as Figure 1 , Figure 2 As shown, the dipole oscillator 31 of this application also has a grounding through-hole 32 for fixing the equivalent capacitance 40 through its middle part. In this way, the second metal ground plane and the radiating layer 30 can be fixedly connected through the equivalent capacitance 40 passing through the grounding through-hole 32. In addition, the equivalent capacitance 40 of this application can be a metal structure or an equivalent structure in the form of radio frequency traces. Placing it between the radiating layer 30 and the ground layer 20 can further reduce the return loss of the antenna and expand the impedance bandwidth. At the same time, since the equivalent capacitance 40 is located between the radiating layer 30 and the ground layer 20, it is equivalent to adding four small metal rods in a rectangular cavity. Using the perturbation method, it can be seen that inserting tiny metal rods in a place with a strong electric field will shift the resonant frequency to a lower frequency. This structure can fine-tune the resonant frequency, thereby further reducing the size.

[0063] Understandably, based on the relationship between antenna Q-value and bandwidth, increasing bandwidth is achieved by decreasing Q-value. Therefore, connecting the radiating layer 30 and ground layer 20 via an equivalent capacitance 40 in the form of a metal structure or RF trace increases distributed capacitance and decreases distributed inductance, thereby increasing antenna bandwidth. Furthermore, placing the equivalent capacitance 40 between the radiating layer 30 and ground layer 20 halves the length of the dipole element in the radiating layer 30, thus reducing antenna size. Additionally, the width of the equivalent capacitance 40 significantly affects the resonant frequency; the resonant frequency increases with the width of the equivalent capacitance 40. In other words, for the same resonant frequency, a narrower equivalent capacitance 40 results in a smaller dipole element area, allowing for further reduction in antenna size by decreasing the width of the equivalent capacitance 40. Of course, the length of the equivalent capacitance 40 also affects the resonant frequency; changing the aspect ratio of the equivalent capacitance 40 can also alter the resonant frequency. This can be determined through simulation and debugging results, and will not be elaborated upon here.

[0064] The relationship between the resonant frequency and the equivalent capacitance and inductance of this application can be proven by the following formula:

[0065]

[0066] Wherein, L and C are the equivalent capacitance and inductance of the equivalent capacitance 40 or the open-circuit capacitance 33 mentioned above. As can be seen from the above formula, when the equivalent capacitance 40 or the open-circuit capacitance 33 in the circuit of this application is increased, the resonant frequency can be reduced to a certain extent.

[0067] In the above embodiments, the microstrip antenna includes at least one director layer, a ground layer, and a radiating layer arranged in parallel from top to bottom. The radiating layer adopts a direct-feed structure using a coaxial transmission line. The advantage of the direct-feed structure is that it eliminates the need for a complex power divider / phase shifter structure by directly feeding through a coaxial line, thereby improving radiation efficiency and reducing losses. The director layer is a first metal ground plane, the ground layer is a second metal ground plane, and the radiating layer includes four dipole elements arranged in a cross shape at the center. This antenna structure allows the microstrip antenna of this application to use air as the propagation medium. Since the speed of electrical signal propagation is inversely proportional to the square root of the dielectric constant, the lower the dielectric constant, the faster the signal transmission speed. This application uses air as the medium to transmit signals, which can accelerate signal transmission speed and improve tag reading efficiency. Furthermore, the guiding layer of this application can also be considered a new radiating patch, which gathers the electromagnetic waves from the ground layer and the radiating layer and then further emits them forward, thereby effectively improving the front-to-back ratio and gain. Next, each dipole unit in this application includes a dipole oscillator. Every two oppositely arranged dipole units form a group. The front ends of the two dipole oscillators in one group are connected by a first microstrip line, and the front ends of the two dipole oscillators in the other group are connected by a feed via. This allows the dipole oscillators to be connected to the electrical circuit via the first microstrip line and the feed via. In the circuit, the dual-polarized antenna is fed through a circuit to enable the dual-polarized antenna to change between two polarization directions, effectively avoiding the drawback of not being able to read the tag when the polarization directions are completely isolated; furthermore, each dipole unit in this application also includes an open-circuit capacitor loaded at the end of the dipole element. The part of the open-circuit capacitor that extends beyond the edge of the second metal ground plane is bent vertically upward. The design of the open-circuit capacitor can bend the original capacitor structure into two parts, thereby reducing the volume of the original overall capacitor on the horizontal plane, and using the spare space for capacitor loading. This can both adjust the resonant frequency and reduce the size of the antenna; each dipole unit also includes a circuit penetrating the dipole element. The grounding via in the middle allows the second metal ground plane and the radiating layer to be fixedly connected through the equivalent capacitance passing through the grounding via. This equivalent capacitance can be regarded as a resistor-capacitor series short-circuit structure, which can further reduce the return loss of the antenna while expanding the impedance bandwidth. Furthermore, since the equivalent capacitance is located between the radiating layer and the ground layer, if the equivalent capacitance is set as a metal rod in this application, it is equivalent to adding four metal rods in a rectangular cavity. According to the perturbation method, inserting a small metal rod in a place with a strong electric field will shift the resonant frequency to a lower frequency. Therefore, this structure can further fine-tune the resonant frequency, thereby further reducing the size of the antenna.This antenna structure allows for easy integration into PDA devices, solving the industry's pain point of being unable to use dual-polarized antennas. Furthermore, final physical testing results show that the overall gain of the microstrip antenna is approximately 3 dB higher than that of a circularly polarized antenna of the same volume, and approximately 2 dB higher than that of a linearly polarized antenna of the same structure.

[0068] In one embodiment, the size of the first metal floor is smaller than the size of the second metal floor.

[0069] In this embodiment, the size of the first metal ground plane is smaller than the size of the second metal ground plane, while the size of the second metal ground plane is the same as the size of the radiating layer 30. The size of the radiating layer 30 is determined based on the overall requirements of the device. Given a limited size, the size of the radiating layer 30 can be indirectly controlled by adjusting the dipole elements, thereby controlling the overall size of the antenna.

[0070] In one embodiment, the height between the first metal floor and the second metal floor is less than the height between the radiant layer 30 and the second metal floor.

[0071] In this embodiment, the ground layer 20 is disposed between the guide layer 10 and the radiating layer 30, so that the height between the guide layer 20 and the radiating layer 30 is less than the height between the ground layer 20 and the radiating layer 30. Furthermore, this application can set the height between the first metal ground plane and the second metal ground plane to be less than the height between the radiating layer 30 and the second metal ground plane, which can further improve the front-to-back ratio and gain of the antenna while further reducing the size of the antenna.

[0072] In one embodiment, the height between the first metal floor and the radiating layer 30 is less than half a wavelength.

[0073] In this embodiment, the height between the first metal ground plane and the radiating layer 30 is less than half a wavelength. When the distance is less than half a wavelength, the farther the first metal ground plane is from the radiator in the radiating layer 30, the higher the gain. Of course, in actual design and use, the antenna volume limitation needs to be considered, which will not be elaborated here.

[0074] In one embodiment, the height between the first metal floor and the radiating layer 30 is one-quarter wavelength.

[0075] In this embodiment, the height between the first metal ground plane and the radiating layer 30 is generally set to be less than half a wavelength, specifically a quarter wavelength. This can further improve the front-to-back ratio and gain of the antenna. In addition, the addition of the first metal ground plane can completely reverse the maximum radiation direction of the antenna, so that the overall gain of the antenna is about 3 dB higher than that of a circularly polarized antenna of the same volume, and the front-to-back ratio is about 2 dB higher than that of a linearly polarized antenna of the same structure.

[0076] In one embodiment, when the guiding layer 10 has a multi-layer structure, each guiding layer 10 is arranged in parallel at intervals.

[0077] The dimensions of the other guiding layers 10 are smaller than the dimensions of the guiding layer closest to the radiation layer 30, and the spacing between each guiding layer 10 is smaller than the height between the guiding layer 10 closest to the radiation layer 30 and the radiation layer 30.

[0078] In this embodiment, the guiding layer 10 can also be regarded as a new radiating patch, which gathers the electromagnetic waves from the ground layer 20 and the radiating layer 30 and then emits them forward, thereby improving the front-to-back ratio and gain of the antenna. The guiding layer 10 of this application can be configured as a multi-layer structure, in which each layer is arranged in parallel and spaced apart. The size of the first guiding layer 10 closest to the radiating layer 30 is larger than the size of the other guiding layers 10, and the spacing between the other guiding layers 10 is smaller than the spacing between the first guiding layer 10 and the radiating layer 30. Each guiding layer 10 can be fixed with screws or with a housing snap-fit ​​structure.

[0079] In one embodiment, the equivalent capacitance 40 is a metal pillar and / or a second microstrip line.

[0080] In this embodiment, the equivalent capacitor 40 can theoretically be equivalent to a grounding capacitor. Therefore, the structure of the equivalent capacitor can be a metal structure, such as a metal pillar, or it can be a microstrip line, that is, a radio frequency trace structure, such as a second microstrip line.

[0081] In one embodiment, the open-circuit capacitor 33 may include a first metal patch and a second metal patch.

[0082] The front end of the first metal patch is connected to the end of the dipole oscillator 31, and the end of the first metal patch extends to be aligned with the edge of the second metal floor.

[0083] The second metal patch is loaded at the end of the first metal patch and extends upward perpendicular to the extension direction of the first metal patch.

[0084] In this embodiment, the open-circuit capacitor 33 can be composed of two irregularly shaped metal structures, specifically a first metal patch and a second metal patch. The front end of the first metal patch is connected to the end of the dipole oscillator 31, and its end extends to be aligned with the edge of the second metal ground plane and connected to the front end of the second metal patch. The second metal patch is loaded at the end of the first metal patch and extends upward perpendicular to the extension direction of the first metal patch. This not only allows the original capacitor structure to be folded in space, but also further reduces the size of the antenna.

[0085] The first and second metal patches of this application may have the same or different shapes. They may be semi-circular, elliptical, triangular, square, rectangular or other polygonal structures, etc., and there are no restrictions on them.

[0086] In one embodiment, the first metal patch has a triangular structure, and the second metal patch has a square structure.

[0087] Wherein, the vertex of the first metal patch is the front end, and the bottom edge of the first metal patch is the end end.

[0088] In this embodiment, as Figure 1 , Figure 3 As shown, the first metal patch of this application can be a triangular structure, and the second metal patch can be a square structure. When the first metal patch is a triangular structure, the vertex of the triangular structure is the front end and is connected to the dipole oscillator 31, and the base of the triangular structure is the end end and is connected to the square structure of the second metal patch.

[0089] In one embodiment, the equivalent electrical length of each dipole unit is one-quarter of a wavelength.

[0090] In this embodiment, the equivalent electrical length of each dipole unit is a quarter wavelength. That is to say, the functions of the dipole oscillator 31, grounding via 32, open-circuit capacitor 33, and equivalent capacitor 40 between the radiating layer 30 and the grounding layer 20 in each dipole unit can be combined to form a dipole antenna with a size of a quarter wavelength, and realize the reception and transmission of electromagnetic waves in two polarization directions.

[0091] In one embodiment, the profile height of the microstrip antenna is less than 0.1λ.

[0092] In this embodiment, the microstrip antenna is designed as a low-profile antenna, with a profile height less than 0.1λ. This microstrip antenna structure allows for easy integration into PDA devices, thus solving the industry's pain point of being unable to use microstrip antennas. Furthermore, final physical measurement results show that the overall gain of the microstrip antenna in this application is approximately 3dB higher than that of a circularly polarized antenna of the same volume, and approximately 2dB higher than that of a linearly polarized antenna of the same structure.

[0093] In one embodiment, such as Figure 4 As shown, Figure 4 This is a schematic diagram of the structure of a dual-polarized microstrip antenna assembly provided in an embodiment of this application; this application also provides a dual-polarized microstrip antenna assembly, which includes an antenna housing 51 and a miniaturized low-profile dual-polarized microstrip antenna as described in any of the above embodiments, installed inside the antenna housing 51.

[0094] In this embodiment, as Figure 4 As shown, Figure 4 In this application, the miniaturized low-profile dual-polarized microstrip antenna described in the above embodiments can be installed in the inner cavity of the antenna housing 51. This not only protects the antenna structure but also makes it easy to install in a handheld device for daily use.

[0095] In one embodiment, the dual-polarized microstrip antenna assembly may further include an RF switch 52 and an RF module 53, and the antenna housing 51 includes an antenna front housing 511 and an antenna rear housing 510.

[0096] The guiding layer 10 is close to or attached to the inner wall of the antenna front shell 511, and the radio frequency switch 52 and the radio frequency module 53 are disposed between the radiating layer 30 and the inner wall of the antenna rear shell 510.

[0097] The front housing 511 of the antenna and the rear housing 510 of the antenna are detachably connected.

[0098] In this embodiment, as Figure 4 As shown, Figure 4 In this application, the antenna housing 51 may include an antenna front housing 511 and an antenna rear housing 510 detachably connected to the antenna front housing 511. The dual-polarized antenna assembly may also include an RF switch 52 and an RF module 53. The RF switch 52 and the RF module 53 are both disposed between the radiating layer 30 of the miniaturized low-profile dual-polarized microstrip antenna and the inner wall of the antenna rear housing 510, and are fixedly connected to the inner wall of the antenna rear housing 510. The guiding layer 10 of the miniaturized low-profile dual-polarized antenna is opposite to the inner wall of the antenna front housing 511. It can be attached to the inner wall of the antenna front housing 511 or fixed by screws or housing snap-fit ​​structure.

[0099] In one embodiment, the two sets of dipole units are respectively connected to the two input terminals of the RF switch 52 via coaxial lines; the output terminal of the RF switch 52 is connected to the RF module 53.

[0100] In this embodiment, since the dual-polarized antenna of this application is composed of two sets of dipole units, and the front end of the dipole vibrator of each set of dipole units is connected through a first microstrip line or a feed via, when implementing the transmission and reception functions of the dual-polarized antenna, the positive and negative poles of the two sets of dipole units can be connected to the inner core and outer sheath of two coaxial lines respectively, and the two coaxial lines can be connected to the two input terminals of the RF switch 52 respectively. The output terminal of the RF switch 52 can be connected to the RF module 53. In this way, not only can the transmission and reception of the dual-polarized antenna be controlled by the RF module 53, but the start and stop of the dual-polarized antenna in the two polarization directions can also be controlled by setting a control algorithm inside the RF module 53.

[0101] In one embodiment, the inner wall of the antenna front shell 511 and / or the inner surface of the antenna rear shell 510 are covered with a microwave absorbing material.

[0102] In this embodiment, in order to further improve the front-to-back ratio and gain of the dual-polarized microstrip antenna, a wave-absorbing material can be covered on the inner sidewall of the antenna front shell 511 and / or the inner surface of the antenna rear shell 510. The wave-absorbing material can be a ferrite wave-absorbing material, a dielectric ceramic wave-absorbing material, a polycrystalline iron fiber wave-absorbing material, a conductive polymer wave-absorbing material, or a nano wave-absorbing material, etc., and there are no restrictions here.

[0103] Understandably, due to its high permeability, the absorbing material located on the inner wall of the antenna front shell 511 can be equivalent to an open-circuit inductor, which can shift the frequency point to a lower frequency. If the frequency point is to be adjusted back to the operating frequency band, the size of the original antenna must be reduced. Therefore, by adding absorbing material, the size of the dual-polarized antenna can be further reduced. The absorbing material located on the inner surface of the antenna rear shell 510, due to its high permeability, can also play a shielding role, so that the metal behind the antenna will not affect the antenna performance. In addition, the absorbing materials located on the sides and bottom have a large imaginary part of permeability, so they can absorb diffracted waves and back waves, and can also focus the beam to a certain extent, thereby effectively improving the gain and front-to-back ratio. Furthermore, due to the addition of absorbing material, the overall profile of the antenna can be significantly reduced without changing the performance.

[0104] In one embodiment, the length of the absorbing material covering the inner wall of the antenna front shell 511 along the radiation direction exceeds or does not exceed the guiding layer 10.

[0105] In this embodiment, the length of the absorbing material covering the inner wall of the antenna front shell 511 along the radiation direction can exceed the guiding layer 10 or not exceed the guiding layer 10. Specifically, it can be set according to the distance between the guiding layer 10 and the inner wall of the antenna front shell 511, and there is no limitation here.

[0106] In one embodiment, the microwave absorbing material is a composite oxide with iron oxide and other iron group or rare earth group oxides as the main components.

[0107] In this embodiment, the absorbing material covering the inner wall of the antenna front shell 511 and / or the inner surface of the antenna rear shell 510 can be ferrite, which is a composite oxide with iron oxide and other iron group or rare earth group oxides as the main components. This type of material refers to a composite oxide magnetic material composed of iron ions, oxygen ions and other metal ions, and a few magnetic oxides do not contain iron.

[0108] It is understandable that ferrites are mostly semiconductors with a resistivity much greater than that of general metallic magnetic materials. They have the advantage of low eddy current loss and have been widely used in high-frequency and microwave technology fields, such as radar technology, communication technology, space technology, and electronic computers.

[0109] In one embodiment, such as Figure 5 As shown, Figure 5 This is a schematic diagram of the structure of the radio frequency module controlling the dual-polarized microstrip antenna to start and stop in two polarization directions according to the number of tags in the field and the tag reading rate.

[0110] In this embodiment, as Figure 5 As shown, the two polarization directions of the dual-polarized microstrip antenna are connected to the two interfaces of the RF switch 52, respectively. The output of the RF switch 52 is connected to the RF module 53, which is connected to the main unit. At the software level, a dual-polarization control algorithm is implemented within the RF module 53. This algorithm can automatically switch the activation and deactivation of the two polarization directions of the antenna based on the number of tags in the field and the reading rate of each tag. This design combines the advantages of linearly polarized microstrip antennas in reading linearly polarized tags with the use of dual polarization to avoid the drawback of not being able to read tags when the polarization directions are completely isolated. Overall, its performance is superior to that of circularly polarized schemes.

[0111] Specifically, when the radio frequency module 53 controls the start and stop of the dual-polarized microstrip antenna in two polarization directions, it can first determine whether the number of tags read by the dual-polarized microstrip antenna in one polarization direction within a certain time is less than a certain number. If it is less, it will automatically switch to the other polarization direction for reading. Of course, this application can also add gyroscope judgment and tag reading rate to comprehensively determine which polarization direction is easier to read tags. This can improve the tag reading rate and avoid the disadvantage of not being able to read tags when the polarization directions are completely isolated.

[0112] In one embodiment, such as Figure 6 As shown, Figure 6 This is a schematic diagram of the structure of a PDA device provided in an embodiment of this application; this application also provides a PDA device, which includes a complete unit 50 and a dual-polarized microstrip antenna assembly as described in any of the above embodiments connected to the complete unit.

[0113] In one embodiment, the radio frequency module 53 in the dual-polarized microstrip antenna assembly is connected to the main unit 50 via an FPC.

[0114] In this embodiment, the radio frequency module 53 in the dual-polarized antenna assembly can be connected to the main unit 50 via an FPC connector. FPC, also known as a flexible printed circuit board, is simply a PCB made of soft materials (materials that can be folded and bent). FPC connectors are mainly used in various digital communication products, portable electronic products, computer peripherals, measuring instruments, automotive electronics, etc., such as PDA devices, mobile phones, digital cameras, laptops, MIDs, MP3 / 4 / 5 players, handheld game consoles, and audio systems.

[0115] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0116] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A miniaturized, low-profile, dual-polarized microstrip antenna, characterized in that, The microstrip antenna includes at least one guide layer, a ground layer, and a radiating layer arranged in parallel from top to bottom; The guiding layer includes a first metal floor; The grounding layer includes a second metal floor; The radiating layer includes four dipole units arranged in a cross shape at the center. Each dipole unit includes a dipole oscillator, a grounding through hole through the middle of the dipole oscillator, and an open-circuit capacitor loaded at the end of the dipole oscillator. The portion of the open-circuit capacitor that extends beyond the edge of the second metal floor is bent vertically upward. Each pair of oppositely arranged dipole units forms a group. The front ends of the two dipole oscillators in one group are connected by a first microstrip line, and the front ends of the two dipole oscillators in the other group are connected by a power feed via. The radiating layer and the second metal floor are fixedly connected by an equivalent capacitance passing through the grounding via.

2. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The size of the first metal floor is smaller than the size of the second metal floor.

3. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The height between the first metal floor and the second metal floor is less than the height between the radiant layer and the second metal floor.

4. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The height between the first metal floor and the radiating layer is less than half a wavelength.

5. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The height between the first metal floor and the radiating layer is one-quarter wavelength.

6. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, When the guiding layer is a multi-layer structure, each guiding layer is arranged in parallel with a spacing between them; The dimensions of the other guide layers are smaller than the dimensions of the guide layer closest to the radiation layer, and the spacing between each guide layer is smaller than the height between the guide layer closest to the radiation layer and the radiation layer.

7. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The equivalent capacitance is a metal pillar and / or a second microstrip line.

8. The miniaturized low-profile dual-polarized microstrip antenna according to claim 1, characterized in that, The open-circuit capacitor includes a first metal patch and a second metal patch; Wherein, the front end of the first metal patch is connected to the end of the dipole oscillator, and the end of the first metal patch extends to be aligned with the edge of the second metal ground plate; The second metal patch is loaded at the end of the first metal patch and extends upward perpendicular to the extension direction of the first metal patch.

9. The miniaturized low-profile dual-polarized microstrip antenna according to claim 8, characterized in that, The first metal patch has a triangular structure, and the second metal patch has a square structure; Wherein, the vertex of the first metal patch is the front end, and the bottom edge of the first metal patch is the end end.

10. The miniaturized low-profile dual-polarized microstrip antenna according to any one of claims 1-9, characterized in that, The equivalent electrical length of each dipole unit is one-quarter of a wavelength.

11. The miniaturized low-profile dual-polarized microstrip antenna according to any one of claims 1-9, characterized in that, The profile height of the microstrip antenna is less than 0.1λ.

12. A dual-polarized microstrip antenna assembly, characterized in that, The dual-polarized microstrip antenna assembly includes an antenna housing and a miniaturized low-profile dual-polarized microstrip antenna as described in any one of claims 1-11, mounted inside the antenna housing.

13. The dual-polarized microstrip antenna assembly according to claim 12, characterized in that, The dual-polarized microstrip antenna assembly also includes a radio frequency switch and a radio frequency module, and the antenna housing includes a front antenna housing and a rear antenna housing. The guiding layer is close to or attached to the inner wall of the antenna front shell, and the radio frequency switch and the radio frequency module are disposed between the radiating layer and the inner wall of the antenna rear shell; The front shell of the antenna and the rear shell of the antenna are detachably connected.

14. The dual-polarized microstrip antenna assembly according to claim 13, characterized in that, The miniaturized low-profile dual-polarized microstrip antenna includes a radiating layer, which includes four dipole elements arranged in a cross shape at the center. Each pair of opposite dipole elements forms a group, and the two groups of dipole elements are respectively connected to the two input terminals of the radio frequency switch via coaxial lines. The output terminal of the RF switch is connected to the RF module.

15. The dual-polarized microstrip antenna assembly according to claim 13, characterized in that, The inner wall of the antenna front shell and / or the inner surface of the antenna rear shell are covered with a microwave absorbing material.

16. The dual-polarized microstrip antenna assembly according to claim 13, characterized in that, The length of the absorbing material covering the inner wall of the antenna front shell along the radiation direction exceeds or does not exceed the guiding layer.

17. The dual-polarized microstrip antenna assembly according to claim 15 or 16, characterized in that, The microwave absorbing material is a composite oxide with iron oxide and other iron group or rare earth group oxides as the main components.

18. The dual-polarized microstrip antenna assembly according to claim 13, characterized in that, The radio frequency module is used to control the start and stop of the miniaturized low-profile dual-polarized microstrip antenna in two polarization directions based on the number of tags in the field and the tag reading rate.

19. A PDA device, characterized in that, The PDA device includes a complete unit and a dual-polarized microstrip antenna assembly as described in any one of claims 12-18 connected to the complete unit.

20. The PDA device according to claim 19, characterized in that, The radio frequency module in the dual-polarized microstrip antenna assembly is connected to the main unit via an FPC.

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