L-band broadband circularly polarized microstrip antenna assembly

Abstract

The utility model provides an L-band broadband circularly polarized microstrip antenna assembly, which comprises a multi-feed-point feed circularly polarized microstrip antenna and a feed network, the circularly polarized microstrip antenna comprises a grounding plate and a radiation patch which is separated from the grounding plate and is provided with a plurality of feed ports, and the feed network adopts a coupler to realize power division. According to the L-band broadband circularly polarized microstrip antenna assembly of the utility model, the wide bandwidth can be realized by adjusting the interval between the radiation patch of the circularly polarized microstrip antenna with multi-feed-point feed and the grounding plate, and the impedance matching can be realized by adjusting the position of the feed port; meanwhile, the feed network of the L-band broadband circularly polarized microstrip antenna assembly realizes power division through the coupler, and the isolation performance is improved on the basis of keeping the miniaturization of the antenna structure.

Description

Technical Field

[0001] The utility model relates to the technical field of antennas, in particular to an L-band broadband circularly polarized microstrip antenna assembly. Background Art

[0002] With the continuous transformation of the information age, the development of communication technology is very rapid. Compared with the previous large-volume machines and devices, people are increasingly pursuing the miniaturization and functionality of devices. As a key part of a wireless communication system, the performance of an antenna directly affects the working performance of the entire communication system. The reduction of the antenna size will inevitably lead to a decrease in the efficiency and gain of the antenna, and the working bandwidth will also become narrower. Therefore, designing an antenna with a small structure, high gain, and wide bandwidth will surely become the trend of future antenna design.

[0003] The wavelength range of the L-band is 1565nm to 1625nm. Among them, the L-band has a wide range of applications in the field of communication, especially in satellite communication. For example, the design of a spaceborne L-band broadband high-gain circularly polarized microstrip antenna is aimed at the requirements of a satellite L-band communication transponder system, and a specific design is adopted to achieve a wide frequency band and high gain, meet the requirements of circular polarization, and improve the communication quality and efficiency.

[0004] Circular polarization means that when the angle between the polarization plane of a radio wave and the normal plane of the earth changes periodically from 0 to 360°, that is, the magnitude of the electric field remains unchanged and the direction changes with time, and the trajectory of the end of the electric field vector projected on a plane perpendicular to the propagation direction is a circle, it is called circular polarization. Due to the strong anti-interference ability and strong adaptability of circularly polarized antennas, they have been widely used in satellite communication, mobile communication, and radar systems.

[0005] At present, microstrip lines can be used as circularly polarized antennas. However, the polarization method of traditional microstrip antennas is single, the impedance bandwidth is narrow, and its axial ratio bandwidth is also limited. The antenna has a narrow working bandwidth, low antenna efficiency and gain, and a large volume, making it difficult to be applied to portable and small devices. Summary of the Utility Model

[0006] The purpose of the utility model is to provide an L-band broadband circularly polarized microstrip antenna assembly to improve the antenna bandwidth and reduce the volume.

[0007] To achieve the above purpose, the utility model provides an L-band broadband circularly polarized microstrip antenna assembly, which includes a circularly polarized microstrip antenna with multi-feedpoint feeding and a feeding network. The circularly polarized microstrip antenna includes a ground plane and a radiation patch spaced apart from the ground plane and having a plurality of feeding ports. The feeding network uses a coupler to achieve power division.

[0008] Preferably, the feeding network includes a microstrip double-branch directional coupler as the first stage of the four-way power divider, and two output ports of the microstrip double-branch directional coupler are connected to two bisected T-type power dividers as the second stage of the four-way power divider.

[0009] Preferably, the microstrip double-branch directional coupler is used to achieve equal power splitting of the transmitted signal and a 90° phase difference; the input end of each T-type power divider as the second stage is connected to the first stage of the four-way power divider, and two output ends are each connected to a microstrip line. The lengths of the microstrip lines connected to the two output ends of each T-type power divider enable the two output signals of the T-type power divider to achieve a 180° phase difference; and / or

[0010] A voltage-stabilizing microstrip line and a grounding filter component are provided between each T-type power divider as the second stage and the microstrip double-branch directional coupler.

[0011] Preferably, a plurality of feeding ports are symmetrically arranged at the center of the radiation patch.

[0012] Preferably, the shape of the radiation patch is circular or square.

[0013] Preferably, the shapes of the ground plane and the radiation patch are both square, and the side length of the radiation patch is smaller than that of the ground plane; 4 feeding ports are symmetrically arranged on the radiation patch, and the 4 feeding ports are all located on the perpendicular bisectors of the two pairs of opposite sides of the radiation patch.

[0014] Preferably, the position of the feeding port of the radiation patch when the input impedance is 50Ω is estimated by the following formula:

[0015]

[0016] In the formula,

[0017]

[0018] where d is the spacing between adjacent feeding ports, L is the actual length of the radiation element, which is related to the width of the radiation patch, ε re is the effective dielectric constant, ε r is the relative dielectric constant, and h is the dielectric thickness between the ground plane and the radiation patch.

[0019] Preferably, the width of the radiation patch is:

[0020]

[0021] In the formula, c is the speed of light, ε r is the relative dielectric constant, and f is the operating frequency.

[0022] Preferably, the grounding plate and the radiation patch are both made of metal, and an insulating dielectric substrate or an air dielectric is provided between the grounding plate and the radiation patch.

[0023] Preferably, a plurality of coaxial lines for feeding the feeding port are provided between the grounding plate and the radiation patch, and capacitive coupling patches are provided on the coaxial lines. Thus, the best antenna axial ratio performance can be achieved.

[0024] The L-band broadband circularly polarized microstrip antenna assembly of the present invention can achieve a wide bandwidth by adjusting the interval between the circularly polarized microstrip antenna radiation patch fed by multiple feeding points and the grounding plate, and achieve impedance matching through the positions of multiple feeding ports; at the same time, the feeding network of the L-band broadband circularly polarized microstrip antenna assembly of the present invention realizes power division through a coupler, improving the isolation performance on the basis of maintaining the miniaturization of the antenna structure. In addition, the L-band broadband circularly polarized microstrip antenna assembly specifically includes a microstrip double-branch directional coupler as the first stage of a four-way power divider, and a bisected T-shaped power divider as the second stage of the four-way power divider, which can stably achieve that the feeding phases of the four ports are 0°, 90°, 180°, and 270° respectively, avoiding external interference, and thus improving the ideal degree of the circularly polarized signal emitted by the antenna. Furthermore, the shape of the feeding network is adjusted according to the position of the feeding port of the radiation patch to realize the miniaturization of the antenna structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural block diagram of an L-band broadband circularly polarized microstrip antenna assembly according to an embodiment of the present invention.

[0026] Figure 2 as Figure 1 shown, it is a schematic structural diagram of a circularly polarized microstrip antenna with multi-feed-point feeding of the L-band broadband circularly polarized microstrip antenna assembly.

[0027] Figure 3 as Figure 1 shown, it is a circuit diagram of a feeding network with coupler power division of the L-band broadband circularly polarized microstrip antenna assembly. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this specification will be clearly and completely described below in conjunction with specific embodiments of this specification and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this specification, rather than all the embodiments. Based on the embodiments in this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this specification.

[0029] as Figure 1As shown in the figure, the present utility model provides an L-band broadband circularly polarized microstrip antenna assembly, which is composed of a circularly polarized microstrip antenna 100 fed by multiple feeding points and a feeding network 200 with coupler power splitting. As Figure 2 shown, the circularly polarized microstrip antenna fed by multiple feeding points includes a ground plane 10, a radiation patch 20 spaced apart from the ground plane 10 and having multiple feeding ports 21, and multiple coaxial cables (not shown in the figure) connected between the ground plane 10 and the radiation patch 20 to feed the multiple feeding ports 21. In this embodiment, the number of the feeding ports 21 is 4.

[0030] The maximum radiation direction of this type of circularly polarized microstrip antenna is generally in the +Z axis direction, that is, the direction perpendicular to the ground plane 10 and upward. The most important thing to achieve circularly polarized radiation is to select a suitable feeding method. We know that for two linearly polarized waves, as long as they satisfy orthogonality in space, equal amplitude, and a 90° phase difference, a circularly polarized wave can be radiated.

[0031] In the present utility model, the feeding phase parameters corresponding to the multiple feeding ports 21 are configured to meet the circular polarization conditions of the antenna. Therefore, in this embodiment, when feeding the 4 feeding ports 21, the feeding phases corresponding to the 4 feeding ports 21 are 0°, 90°, 180°, and 270° respectively, so as to achieve the phase difference of the 4 feeding ports 21, and further achieve the circular polarization of the antenna.

[0032] The position of the feeding port 21 is designed as follows:

[0033] For a microstrip patch antenna fed by a coaxial cable, the most important thing is to determine the position of the feeding port 21, because the position of the feeding port 21 will have a certain influence on the input impedance of the antenna. Given the size of the radiation patch 20, the feeding port position of the radiation patch with an input impedance of 50Ω can be roughly estimated by the following formula:

[0034]

[0035] In the formula,

[0036]

[0037] where d is the spacing between adjacent feeding ports, L is the actual length of the radiation element, which is related to the width W of the radiation patch, ε re is the effective dielectric constant, ε r is the relative dielectric constant, and h is the dielectric thickness between the ground plane and the radiation patch.

[0038] This is only the roughly calculated position of the feeding port, and the optimal position still needs to be determined according to the input impedance during the design process.

[0039] The size of the microstrip patch antenna is designed as follows:

[0040] The common radiation patch 20 is rectangular or circular. The size of the conductor patch determines the operating frequency of the antenna. That is to say, the size of the radiation patch can adjust the center frequency.

[0041] In this embodiment, the shapes of the ground plane 10 and the radiation patch 20 are both square, and the side length of the radiation patch 20 is less than that of the ground plane 10. In this embodiment, the size of the ground plane is 100 mm. At the same time, the radiation patch 20 has 4 feeding ports 21, and the 4 feeding ports 21 are symmetrically arranged on the radiation patch 20, and the 4 feeding ports 21 are all located on the perpendicular bisectors of the two groups of opposite sides of the radiation patch 20.

[0042] Therefore, for the radiation patch 20 with an operating frequency of f, the width W of the radiation patch 20 is:

[0043]

[0044] In the formula, c is the speed of light, ε r is the relative permittivity, ε r = 4.4, and f is the operating frequency.

[0045] The width W of the radiation patch 20 is generally taken as λ e / 2, where λ e is the guided wavelength in the medium, that is:

[0046]

[0047] In the formula, ε e is the effective permittivity, and the calculation formula of the effective permittivity ε e is:

[0048]

[0049] In actual design, due to the edge shortening effect, the actual length L of the radiation element is:

[0050]

[0051] In the formula, c is the speed of light, f is the operating frequency, ε e is the effective permittivity, ΔL is the equivalent radiation slot length, and the calculation formula of the equivalent radiation slot length ΔL is:

[0052]

[0053] Among them, W is the width of the radiation patch, h is the dielectric thickness between the ground plane and the radiation patch, and ε e is the effective permittivity.

[0054] The materials of the ground plane 10 and the radiation patch 20 are both metals. In this embodiment, an insulating dielectric substrate is provided between the ground plane 10 and the radiation patch 20. The thickness of the dielectric substrate, the relative dielectric constant of the dielectric substrate, the loss tangent, as well as the length and width of the dielectric substrate will affect the performance and parameters of the antenna. Among them, coaxial feeding is also called backfeeding. A coaxial socket is installed on the ground plane 10. The inner conductor of the coaxial line passes through the dielectric substrate and is connected to the radiation patch 20, and the outer conductor of the coaxial line is connected to the ground plane 10.

[0055] In another embodiment, a layer of air dielectric can also be provided between the ground plane 10 and the radiation patch 20 to replace the dielectric substrate to adjust the performance of the antenna, and the working bandwidth is changed by adjusting the thickness of the air dielectric layer.

[0056] The power divider feeding network 200 of the coupler in this embodiment is arranged below the ground plane 10, and its specific structure is as Figure 3 shown, where MLIN represents a microstrip line, MTEE represents a microstrip line T-junction, MLSC all represent stubs short-circuited from the terminal to the ground, T1 and T2 represent two input ports for connecting an external power supply, and T3 - T6 respectively represent the first to fourth output ports for connecting coaxial sockets through feeding probes and then connecting 4 coaxial lines.

[0057] The power divider feeding network 200 of the coupler includes a microstrip two-branch directional coupler 201 as the first stage of the four-way power divider. Two output ports of the microstrip two-branch directional coupler 201 are connected to two bisected T-type power dividers 202, and the bisected T-type power dividers 202 serve as the second stage of the four-way power divider. The microstrip two-branch directional coupler 201 as the first stage is used to achieve the two-way equal power division of the transmitted signal and a 90° phase difference; the input end of each T-type power divider 202 as the second stage is connected to the first stage of the four-way power divider, and the two output ends are each connected to a microstrip line (i.e., MLIN5 - MLIN8). The lengths of the microstrip lines connected to the two output ends of each T-type power divider enable the two-way output signals of the T-type power divider to achieve a 180° phase difference, and the four ports sequentially achieve a 90° phase difference, thus laying a foundation for realizing the circular polarization of the antenna.

[0058] In addition, a voltage-stabilizing microstrip line (i.e., MLIN9 - MLIN10) and a grounding filter component are provided between each T-type power divider 202 as the second stage and the microstrip two-branch directional coupler 201. The grounding filter component is a T-type power divider grounded at one end (i.e., MTEE7, MTEE8, and the two are connected through MLSC1, MLSC2).

[0059] In this embodiment, the microstrip dual-branch directional coupler 201 includes first to fourth microstrip line T-junctions MTEE1 - MTEE4 that are connected in series in sequence to form a loop, and branch microstrip lines MLIN1 - MLIN4 that are connected in series between every two adjacent ones of the first to fourth microstrip line T-junctions.

[0060] The microstrip dual-branch directional coupler 201 is a four-port network device, having four ports corresponding to the first to fourth microstrip line T-junctions MTEE1 - MTEE4 respectively and having functions such as input, through, coupling, and isolation. The length of each section of the branch microstrip line between the four ports is one-quarter of a wavelength. When a signal is input at the port where the first microstrip line T-junction MTEE1 is located, there are two paths for the signal to enter the port where the fourth microstrip line T-junction MTEE4 is located. The first path is MTEE1→MTEE2→MTEE3→MTEE4, with a transmission distance of three-quarters of a wavelength and a phase difference of 180° between the two ports. The second path is MTEE1→MTEE4, with a transmission distance of one-quarter of a wavelength. There are also two paths for the signal to enter the port where the second microstrip line T-junction MTEE2 is located. The first path is MTEE1→MTEE2, with a transmission distance of one-quarter of a wavelength. The second path is MTEE1→MTEE4)→MTEE3→MTEE2, with a transmission distance of three-quarters of a wavelength and a phase difference of 90° between the two ports. There are also two paths for the signal to enter the port where the third microstrip line T-junction MTEE3 is located. The first path is MTEE1→MTEE2→MTEE3, with a transmission distance of half a wavelength. The second path is MTEE1→MTEE4→MTEE3, with a transmission distance of also half a wavelength. The amplitudes of the signals transmitted by these two paths are the same. After superposition, they are output at the port where the third microstrip line T-junction MTEE3 is located. The phase at the port where the third microstrip line T-junction MTEE3 is located lags behind the port where the first microstrip line T-junction MTEE1 is located by 180°. Therefore, as the first stage, the microstrip dual-branch directional coupler 201 can achieve equal power splitting of the transmitted signal and a 90° phase difference. In summary, the feeding network of the L-band broadband circularly polarized microstrip antenna assembly of the present utility model realizes power splitting through a coupler, on the one hand, keeping the antenna structure relatively small, and on the other hand, improving the isolation performance on the basis of the miniaturization of the antenna structure. In addition, the L-band broadband circularly polarized microstrip antenna assembly specifically includes a microstrip dual-branch directional coupler 201 as the first stage of a four-way power divider, and includes a two-way T-type power divider 202 as the second stage of the four-way power divider, which can stably achieve that the feeding phases of the four ports are 0°, 90°, 180°, and 270° respectively, avoiding external interference, and thus can improve the ideal degree of circular polarization emitted by the antenna.

[0061] In other embodiments, the number of feeding ports 21 in the L-band broadband circularly polarized microstrip antenna assembly is not limited to 4, and can be any number, so as to obtain a circularly polarized microstrip antenna with multi-feedpoint feeding.

[0062] The L-band broadband circularly polarized microstrip antenna assembly of the present invention can achieve a wide bandwidth by adjusting the interval between the microstrip antenna radiation patch 20 and the ground plane 10. However, blindly increasing the dielectric thickness between the radiation patch 20 and the ground plane 10 will increase the loss of the antenna, cause impedance mismatch, and the performance of the antenna cannot be guaranteed. Therefore, in the present invention, the position of the feeding port 21 of the radiation patch is configured to meet the impedance matching condition, so as to achieve impedance matching by adjusting the position of the feeding port 21. However, the position of the feeding port 21 has a greater impact on the real part of the impedance, and the imaginary part of the impedance still exists. For this, a capacitive coupling patch (not shown in the figure) can be added to the coaxial line of the antenna to balance the imaginary part of the impedance. The capacitive coupling patch is configured such that the axial ratio of the antenna is less than an axial ratio threshold, so as to achieve the best axial ratio performance of the antenna.

[0063] Among them, the principle of the capacitive coupling patch is to add a matching device between the load and the transmission line to achieve matching between the two. The principle of realizing the impedance matching network also utilizes the transmission of waves, which is equivalent to introducing a brand-new wave that is equal in amplitude and opposite in phase to the reflected wave caused by the load in the original circuit to cancel each other out and achieve the traveling wave working state of transmission.

[0064] After ensuring the axial ratio performance of the circularly polarized microstrip antenna with multi-feedpoint feeding, it can be determined that the position of the feeding port 21 can be adjusted, and the shape of the feeding network 200 can be determined according to the position of the feeding port 21 of the radiation patch, so as to reduce the area occupied by the feeding network 200 itself. Finally, the feeding network 200 and the upper-layer circularly polarized microstrip antenna 100 are docked through feeding probes and coaxial lines. Therefore, in the present invention, the position of the feeding port 21 of the radiation patch 20 is configured to meet the impedance matching condition; and the shape of the feeding network 200 is determined according to the position of the feeding port 21 of the radiation patch 20 to achieve miniaturization of the antenna structure.

[0065] In addition to using four-feedpoint feeding, the circularly polarized microstrip antenna of the present invention can also use 2 feeding ports, three feeding ports, six feeding ports, etc. The number of feeding ports is any number, as long as they are centrosymmetric with each other. For example, when the radiation patch is circular, the feeding ports can be evenly distributed along the circumference at 3 o'clock, 6 o'clock, etc. to achieve centrosymmetric setting.

[0066] It should also be noted that the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, commodity or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, commodity or device. Without further limitation, an element defined by the phrase "comprising an …" does not exclude the presence of additional identical elements in the process, method, commodity or device comprising said element.

[0067] The various embodiments in this specification are described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other. Each embodiment focuses on the differences from other embodiments. In particular, for the system embodiments, since they are basically similar to the method embodiments, the description is relatively simple, and for the relevant parts, reference can be made to the description of the method embodiments.

[0068] The above description is only for the embodiments of this specification and is not intended to limit this specification. For those skilled in the art, various modifications and changes can be made to this specification. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this specification shall be included within the scope of the claims of this specification.

Claims

1. An L-band broadband circularly polarized microstrip antenna assembly, characterized in that, It includes a circularly polarized microstrip antenna fed by multiple feed points and a feeding network. The circularly polarized microstrip antenna includes a ground plane and a radiation patch spaced apart from the ground plane and having multiple feed ports. The feeding network uses a coupler to achieve power division.

2. The L-band broadband circularly polarized microstrip antenna assembly according to claim 1, wherein The feeding network includes a microstrip two-branch directional coupler as the first stage of a four-way power divider. Two output ports of the microstrip two-branch directional coupler are connected to two bisected T-shaped power dividers as the second stage of the four-way power divider.

3. The L-band broadband circularly polarized microstrip antenna assembly according to claim 2, wherein The microstrip two-branch directional coupler is used to achieve equal power division of the transmitted signal and a 90° phase difference; the input end of each T-shaped power divider as the second stage is connected to the first stage of the four-way power divider, and two output ends are each connected to a microstrip line. The lengths of the microstrip lines connected to the two output ends of each T-shaped power divider cause the two output signals of the T-shaped power divider to have a 180° phase difference; and / or A voltage-stabilizing microstrip line and a grounding filter component are provided between each T-shaped power divider as the second stage and the microstrip two-branch directional coupler.

4. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1-3, characterized in that Multiple feed ports are symmetrically arranged at the center of the radiation patch.

5. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1-3, characterized in that, The shape of the radiation patch is circular or square.

6. The L-band broadband circularly polarized microstrip antenna assembly according to claim 5, characterized in that, The shapes of the ground plane and the radiation patch are both square, and the side length of the radiation patch is less than that of the ground plane; the number of feed ports is 4, and the 4 feed ports are all located on the perpendicular bisectors of the two pairs of sides of the radiation patch.

7. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1-3, characterized in that, The positions of the feed ports of the radiation patch when the input impedance is 50Ω are estimated by the following formula: In the formula, Among them, d is the spacing between adjacent feeding ports, L is the actual length of the radiation element, which is related to the width of the radiation patch, ε re is the effective dielectric constant, ε r is the relative dielectric constant, and h is the dielectric thickness between the ground plane and the radiation patch.

8. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1-3, characterized in that The width of the radiation patch is: where c is the speed of light, ε r is the relative permittivity, and f is the operating frequency.

9. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1 to 3, characterized in that, The materials of the ground plane and the radiation patch are both metal, and an insulating dielectric substrate or an air dielectric is provided between the ground plane and the radiation patch.

10. The L-band broadband circularly polarized microstrip antenna assembly according to any one of claims 1-3, characterized in that, Multiple coaxial lines for feeding the feed ports are provided between the ground plane and the radiation patch, and capacitive coupling patches are provided on the coaxial lines.

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