A compact circularly polarized filter patch antenna

Abstract

The present invention discloses a compact circularly polarized filter patch antenna, comprising upper and lower dielectric substrates. The upper dielectric substrate is printed with a main radiating patch at a positive 45° angle, a pair of oblique rectangular parasitic patches placed parallel to the main radiating patch at a positive 45° angle, and a pair of L-shaped parasitic patches placed diagonally at a positive 45° angle. The lower surface of the upper dielectric substrate is printed with a pair of vertical rectangular parasitic patches placed diagonally at a negative 45° angle. The upper surface of the lower dielectric substrate is printed with a floor, with a central rectangular groove etched in the lower middle portion and four edge rectangular grooves etched on the edges. The lower dielectric substrate is printed with a microstrip feeder and branches. Signals enter from a port, are coupled to the main radiating patch via the microstrip feeder through the central rectangular groove in the floor, and are then coupled by the main radiating patch to the surrounding parasitic patches. The compact circularly polarized filter patch antenna provided by the present invention achieves circularly polarized radiation performance with a compact structure and good bandpass filtering response.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency communications, and in particular to a compact circularly polarized filtering patch antenna. Background Art

[0002] Antennas are an integral part of wireless communication systems. As devices that transmit and receive electromagnetic waves, they play a crucial role in wireless communications. With the rapid development of mobile communication technology and various wireless systems, compact circularly polarized filter patch antennas, which can significantly improve communication quality, have attracted widespread attention. Patch antennas are widely used due to their low profile, miniaturization, and low cost.

[0003] With the advancement of drone and aerospace technology, the required range of antennas has expanded. Linearly polarized antennas are no longer able to meet these requirements. Circularly polarized antennas offer numerous advantages. Currently, linear polarization is commonly used in wireless communications, but a single polarization scheme is no longer sufficient for positioning and navigation. Circularly polarized antennas, in particular, offer advantages such as rain and fog resistance, multipath interference immunity, and high reception efficiency, leading to their widespread adoption in satellite navigation systems. Furthermore, antennas and filters are two of the most important components in RF front-end circuits, and their size and performance are crucial to overall system quality. Traditional design methods separate the antenna and filter, resulting in losses due to incomplete matching when cascaded. Integrating the antenna and filter into a filtered antenna not only combines both radiation and filtering characteristics, but also significantly reduces overall circuit size and unnecessary energy loss between components. Consequently, filtered circularly polarized antennas have become a hot topic of research for scholars both domestically and internationally.

[0004] Amidst the rapidly evolving communications technology landscape, researchers have proposed numerous approaches to integrating filter antennas with circularly polarized antennas, such as adding filter circuits to patch antennas. However, these approaches suffer from significant drawbacks, most notably severe gain degradation and narrow bandwidth, making them difficult to meet the practical application requirements of communications systems. Therefore, it is necessary to design a new, compact circularly polarized filter patch antenna to address these issues. Summary of the Invention

[0005] The present invention aims to provide a compact circularly polarized filtering patch antenna to solve at least one technical problem existing in the above-mentioned prior art.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A compact circularly polarized filter patch antenna comprises an upper dielectric substrate and a lower dielectric substrate, with an air gap between the upper and lower dielectric substrates. The upper surface of the upper dielectric substrate is printed with a main radiating patch at a positive 45° angle, a pair of oblique rectangular parasitic patches parallel to the main radiating patch and placed along a positive 45° direction of the upper dielectric substrate, a pair of L-shaped parasitic patches placed diagonally along a positive 45° direction of the upper dielectric substrate, and a pair of vertical rectangular parasitic patches placed diagonally at a negative 45° angle are printed on the lower surface of the upper dielectric substrate.

[0008] The lower dielectric substrate is located below the upper dielectric substrate. A floor is printed on the upper surface of the lower dielectric substrate. A middle rectangular groove in the y direction is etched in the middle and lower part of the floor. Four edge rectangular grooves in the y direction are etched on the edge of the floor. A microstrip feeder and branches are printed on the lower surface of the lower dielectric substrate. A signal enters from a port, is coupled to the main radiation patch through the microstrip feeder and the middle rectangular groove on the floor, and is then coupled and excited to the surrounding parasitic patches by the main radiation patch.

[0009] As a preferred embodiment of the present invention, the main radiation patch of the present invention is a slotted patch rotated 45°, the main part of the main radiation patch is a square patch, and two slots are etched along the edge of the main radiation patch in the negative 45° direction, namely the first main radiation patch slot and the second main radiation patch slot. The first main radiation patch slot and the second main radiation patch slot are located in the middle of the edge of the square patch. The signal enters from the port, passes through the microstrip feed line and the middle rectangular slot on the floor to be coupled to the slotted main radiation patch, generating the first circularly polarized radiation frequency point.

[0010] As a preferred embodiment of the present invention, the shape of the oblique rectangular parasitic patch of the present invention is rectangular, and the number of the oblique rectangular parasitic patches is two. The two oblique rectangular parasitic patches are respectively located between the main radiation patch and the L-shaped parasitic patch and between the main radiation patch and the rectangular parasitic patch. The slotted main radiation patch is coupled to the oblique rectangular parasitic patch parallel to it to generate a second circularly polarized radiation frequency point.

[0011] As a preferred embodiment of the present invention, the L-shaped parasitic patch of the present invention is L-shaped, and there are two of them, which are placed along the diagonal line of the positive 45° direction of the upper dielectric substrate. The first L-shaped parasitic patch includes a first rectangular patch component and a first L-shaped patch component. The first rectangular patch component is placed adjacent to the first L-shaped patch component for adjusting impedance matching. The second L-shaped parasitic patch includes a second rectangular patch component and a second L-shaped patch component. The second rectangular patch component is placed adjacent to the second L-shaped patch component for adjusting impedance matching. The lengths of the first rectangular patch component and the second rectangular patch component are less than the lengths of the first L-shaped patch component and the second L-shaped patch component. The first rectangular patch component and the second rectangular patch component as well as the first L-shaped patch component and the second L-shaped patch component are all made of metal.

[0012] As a preferred embodiment of the present invention, the rectangular parasitic patch of the present invention is rectangular in shape, and there are two of them, which are placed along the negative 45° diagonal of the upper dielectric substrate. The first rectangular parasitic patch includes a first rectangular parasitic patch component and a second rectangular parasitic patch component. The second rectangular parasitic patch component is placed adjacent to the first rectangular parasitic patch component for adjusting impedance matching. The second rectangular parasitic patch includes a third rectangular parasitic patch component and a fourth rectangular parasitic patch component. The third rectangular parasitic patch component is placed adjacent to the fourth rectangular parasitic patch component for adjusting impedance matching. The lengths of the second rectangular parasitic patch component and the fourth rectangular parasitic patch component are shorter than the lengths of the first rectangular parasitic patch component and the third rectangular parasitic patch component. The first rectangular parasitic patch component, the second rectangular parasitic patch component, the third rectangular parasitic patch component, and the fourth rectangular parasitic patch component have the same width and are all made of metal.

[0013] At the same time, a pair of L-shaped parasitic patches and a pair of rectangular parasitic patches are loaded around the main radiation patch to generate a third circularly polarized radiation frequency point.

[0014] As a preferred embodiment of the present invention, the edge rectangular grooves of the present invention include an upper left rectangular groove, an upper right rectangular groove, a lower left rectangular groove, and a lower right rectangular groove. The upper left rectangular groove, the upper right rectangular groove, the lower left rectangular groove, and the lower right rectangular groove are of equal length and size. The etching positions of the upper left rectangular groove, the upper right rectangular groove, the lower left rectangular groove, and the lower right rectangular groove are symmetrical about the center of the floor. A controllable radiation zero point is generated at a low frequency by the upper left rectangular groove, the upper right rectangular groove, the lower left rectangular groove, and the lower right rectangular groove etched on the edge of the floor.

[0015] As a preferred embodiment of the present invention, the microstrip feeder of the present invention includes a first microstrip, a second microstrip and a parallel branch for adjusting impedance matching. The width of the first microstrip is greater than the width of the second microstrip. The first microstrip is located at the starting end of the microstrip feeder, and the end is connected to one end of the second microstrip. The other end of the second microstrip is connected to the parallel branch. The parallel branch is located directly below the rectangular groove etched on the floor. The branch is located directly above the open end of the microstrip feeder, generating a controllable radiation zero point at high frequency.

[0016] As a preferred embodiment of the present invention, the branches of the present invention are in an inverted U-shape.

[0017] Compared with the prior art, the compact circularly polarized filter patch antenna provided by the present invention has the following advantages:

[0018] 1. The antenna designed in the present invention can generate three circularly polarized radiation frequencies by etching a main radiating patch with two slots in the negative 45° direction and loading a pair of oblique rectangular parasitic patches parallel to the main radiating patch, as well as loading parasitic patches on all sides. This achieves a wider circularly polarized bandwidth without increasing the antenna cross-sectional height, maintaining a compact antenna structure.

[0019] 2. The antenna designed in this invention etches four rectangular slots along the edge of the floor. This allows a pair of vertical rectangular parasitic patches placed at a negative 45° diagonal angle on the upper dielectric substrate to flow currents in opposite directions with the main radiating patch, thereby creating a radiation null. By adjusting the length of the rectangular slots, the position of the radiation point can be flexibly controlled without affecting antenna performance.

[0020] 3. The antenna designed in the present invention can form a reverse current in the x-direction of the main radiation patch by loading an inverted U-shaped microstrip branch at the open end of the microstrip feeder, thereby generating a radiation zero point. By adjusting the length of the inverted U-shaped branch in the x-direction, the position of the radiation point can be flexibly controlled with little impact on the performance of the antenna.

[0021] 4. The antenna designed by the present invention adjusts the length of the four edge rectangular slots to produce a radiation zero point at low frequency, and then adjusts the length of the inverted U-shaped branch in the x direction to produce a radiation zero point at high frequency. Ultimately, the antenna achieves circularly polarized radiation performance with a compact structure and good bandpass filtering response.

[0022] Compared with other antennas, the antenna designed in the present invention has a more compact antenna structure, and does not require the addition of a filtering network or the superposition of structures in the vertical direction to generate a radiation zero point, thereby achieving a bandpass filtering response and having a stable gain pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the antenna structure of the present invention;

[0024] Figure 2 is a side view of the antenna structure of the present invention;

[0025] Figure 3 is a top view of the upper dielectric substrate;

[0026] Figure 4 is a bottom view of the upper dielectric substrate;

[0027] Figure 5 is a top view of the lower dielectric substrate;

[0028] Figure 6 is a bottom view of the lower dielectric substrate;

[0029] Figure 7 1 is a diagram showing the simulation results of the S parameters and main polarization gain of the compact circularly polarized filter patch antenna of this embodiment;

[0030] Figure 8 1 is a diagram showing the simulation results of the axial ratio of the compact circularly polarized filter patch antenna of this embodiment;

[0031] Figure 9 1 is a simulation result diagram showing the variation of the main polarization and cross-polarization gains of the compact circularly polarized filter patch antenna with frequency;

[0032] Figure 10 2. FIG. 4 is a simulation result diagram of the XOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.77 GHz;

[0033] Figure 11 2. FIG. 4 is a simulation result diagram of the YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.77 GHz;

[0034] Figure 12 2. FIG. 4 is a simulation result diagram of the XOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.88 GHz;

[0035] Figure 13 2. FIG. 1 is a simulation result diagram of the YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.88 GHz;

[0036] Figure 14 3.02 GHz is a simulation result diagram of the XOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment;

[0037] Figure 15 3. This is a simulation result diagram of the YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 3.02 GHz;

[0038] In the figure: 1. main radiation patch; 1a. square patch; 1b. first main radiation patch slot; 1c. second main radiation patch slot; 2. oblique rectangular parasitic patch; 3. L-shaped parasitic patch; 3a. first L-shaped patch assembly; 3b. first rectangular patch assembly; 3c. second L-shaped patch assembly; 3d. second rectangular patch assembly; 4. vertical rectangular parasitic patch; 4a. first rectangular parasitic patch assembly; 4b. second rectangular parasitic patch assembly; 4c. third rectangular parasitic patch assembly; 4d. fourth rectangular parasitic patch assembly; 5. upper dielectric substrate; 6. floor; 7. edge rectangular slot; 7a. upper left rectangular slot; 7b. upper right rectangular slot; 7c. lower left rectangular slot; 7d. lower right rectangular slot; 8. middle rectangular slot; 9. branch; 10. microstrip feed line; 11. lower dielectric substrate; 20. port. DETAILED DESCRIPTION

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0040] In the description of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0041] Please see the attached Figure 1-6 As shown, this embodiment provides a compact circularly polarized filter patch antenna including an upper dielectric substrate 5 and a lower dielectric substrate 11. An air gap is provided between the upper dielectric substrate 5 and the lower dielectric substrate 11. The upper surface of the upper dielectric substrate 5 is printed with a main radiating patch 1 at a positive 45° angle, a pair of oblique rectangular parasitic patches 2 placed along the positive 45° direction of the upper dielectric substrate 5 and parallel to the main radiating patch 1, a pair of L-shaped parasitic patches 3 placed diagonally along the positive 45° direction of the upper dielectric substrate 5, and a pair of vertical rectangular parasitic patches 4 placed diagonally at a negative 45° angle are printed on the lower surface of the upper dielectric substrate 5.

[0042] The lower dielectric substrate 11 is located below the upper dielectric substrate 5. A floor 6 is printed on the upper surface of the lower dielectric substrate 11. A middle rectangular groove 8 in the y direction is etched in the middle and lower part of the floor 6. Four edge rectangular grooves 7 in the y direction are etched on the edge of the floor 6. A microstrip feed line 10 and branches 9 are printed on the lower surface of the lower dielectric substrate 11. The signal enters from the port 20, is coupled to the main radiation patch 1 through the microstrip feed line 10 and the middle rectangular groove 8 on the floor 6, and then is coupled by the main radiation patch 1 to the surrounding parasitic patches.

[0043] In this embodiment, three circularly polarized radiation frequencies can be generated by etching a main radiation patch 1 with two slots in the negative 45° direction and loading a pair of oblique rectangular parasitic patches 2 parallel to the main radiation patch 1, as well as loading parasitic patches on all sides, thereby achieving a wider circular polarization bandwidth without increasing the antenna cross-sectional height, maintaining a compact antenna structure, and by etching four edge rectangular slots 7 on the edge of the floor and loading an inverted U-shaped branch 9 at the open end of the microstrip feed line 10, a controllable radiation zero point is generated at low frequency and high frequency respectively, thereby achieving a bandpass filtering response, while the existing technology rarely involves the integrated design of compact antenna structure characteristics, circular polarization characteristics and filtering characteristics.

[0044] In a specific embodiment, Figure 1-6 As shown, the main radiation patch 1 is a slotted patch rotated 45°, and the main part of the main radiation patch 1 is a square patch 1a. Two slots are etched on the edge of the main radiation patch 1 in the negative 45° direction, namely the first main radiation patch slot 1b and the second main radiation patch slot 1c. The first main radiation patch slot 1b and the second main radiation patch slot 1c are located in the middle of the edge of the square patch 1a. The signal enters from the port 20, passes through the microstrip feed line 10 and is coupled to the slotted main radiation patch 1 through the rectangular slot 8 on the floor 6, generating the first circularly polarized radiation frequency point.

[0045] In this embodiment, a main radiation patch 1 rotated at a positive angle of 45° is printed on the upper surface of the upper dielectric substrate 5. Two slots are etched on the edge of the main radiation patch 1 along the negative angle of 45°. The signal enters from the port 20, passes through the microstrip feed line 10 and couples to the slotted main radiation patch 1 through the middle rectangular slot 8 on the floor 6, thereby generating the first circularly polarized radiation frequency point (3.02 GHz).

[0046] In a specific embodiment, Figure 1-4As shown, the shape of the oblique rectangular parasitic patch 2 is rectangular, and the number of the oblique rectangular parasitic patches 2 is two. The two oblique rectangular parasitic patches 2 are respectively located between the main radiation patch 1 and the L-shaped parasitic patch 3 and between the main radiation patch 1 and the vertical rectangular parasitic patch 4. The slotted main radiation patch 1 is coupled to the oblique rectangular parasitic patch 2 parallel to it to generate a second circularly polarized radiation frequency point.

[0047] In this embodiment, a pair of oblique rectangular parasitic patches 2 are printed on the upper surface of the upper dielectric substrate 5 and are placed at a positive 45° angle and parallel to the main radiation patch 1. The patches are located between the main radiation patch 1 and the L-shaped parasitic patch 3, respectively. The slotted main radiation patch 1 is coupled to the oblique rectangular parasitic patch 2 parallel to the main radiation patch 1, thereby generating a second circularly polarized radiation frequency (2.88 GHz).

[0048] In a specific embodiment, Figure 1-3 As shown, the L-shaped parasitic patch 3 is L-shaped, and there are two of them, which are placed along the positive 45° direction diagonal of the upper dielectric substrate 5. The first L-shaped parasitic patch 3 includes a first rectangular patch component 3b and a first L-shaped patch component 3a. The first rectangular patch component 3b is placed adjacent to the first L-shaped patch component 3a for adjusting impedance matching. The second L-shaped parasitic patch 3 includes a second rectangular patch component 3d and a second L-shaped patch component 3c. The second rectangular patch component 3d is placed adjacent to the second L-shaped patch component 3c for adjusting impedance matching. The lengths of the first rectangular patch component 3b and the second rectangular patch component 3d are less than the lengths of the first L-shaped patch component 3a and the second L-shaped patch component 3c. The first rectangular patch component 3b and the second rectangular patch component 3d as well as the first L-shaped patch component 3a and the second L-shaped patch component 3c are all made of metal.

[0049] In this embodiment, a pair of L-shaped parasitic patches 3 are printed on the upper surface of the upper dielectric substrate 5 and are placed along the positive 45° diagonal line of the upper dielectric substrate. The pair of L-shaped parasitic patches 3 are composed of a shorter rectangular metal patch and a longer L-shaped metal patch. The shorter rectangular metal patch is placed adjacent to the long side of the L-shaped metal patch to adjust impedance matching.

[0050] In a specific embodiment, Figure 1-4As shown, the vertical rectangular parasitic patch 4 is rectangular in shape, and there are two of them. They are placed along the negative 45° diagonal of the upper dielectric substrate 5. The first vertical rectangular parasitic patch 4 includes a first rectangular parasitic patch component 4a and a second rectangular parasitic patch component 4b. The second rectangular parasitic patch component 4b is placed adjacent to the first rectangular parasitic patch component 4a for adjusting impedance matching. The second vertical rectangular parasitic patch 4 includes a third rectangular parasitic patch component 4c and a fourth rectangular parasitic patch component 4d. The third rectangular parasitic patch component 4c is placed adjacent to the fourth rectangular parasitic patch component 4d for adjusting impedance matching. The lengths of the second rectangular parasitic patch component 4b and the fourth rectangular parasitic patch component 4d are shorter than those of the first rectangular parasitic patch component 4a and the third rectangular parasitic patch component 4c. The first rectangular parasitic patch component 4a, the second rectangular parasitic patch component 4b, the third rectangular parasitic patch component 4c and the fourth rectangular parasitic patch component 4d are all of the same width and are all made of metal.

[0051] At the same time, a pair of L-shaped parasitic patches 3 and a pair of vertical rectangular parasitic patches 4 are loaded around the main radiation patch 1 to generate a third circularly polarized radiation frequency point.

[0052] In this embodiment, a pair of vertical rectangular parasitic patches 4 are printed on the lower surface of the upper dielectric substrate 5, placed along the negative 45° diagonal of the upper dielectric substrate. These patches 4 consist of a shorter rectangular metal patch and a longer rectangular metal patch of equal width, with the shorter patch placed adjacent to the longer one to adjust impedance matching. A pair of L-shaped and rectangular parasitic patches, placed around the main radiating patch, generate a third circularly polarized radiation frequency (2.77 GHz), thereby achieving a wide circularly polarized bandwidth without increasing the antenna's profile, maintaining a compact antenna structure.

[0053] In a specific embodiment, Figure 1-6 As shown, the edge rectangular grooves 7 include an upper left rectangular groove 7a, an upper right rectangular groove 7b, a lower left rectangular groove 7c, and a lower right rectangular groove 7d. The upper left rectangular groove 7a, the upper right rectangular groove 7b, the lower left rectangular groove 7c, and the lower right rectangular groove 7d are of equal length and size. The etching positions of the upper left rectangular groove 7a, the upper right rectangular groove 7b, the lower left rectangular groove 7c, and the lower right rectangular groove 7d are symmetrical about the center of the floor 6. A controllable radiation null point is generated at a low frequency by the upper left rectangular groove 7a, the upper right rectangular groove 7b, the lower left rectangular groove 7c, and the lower right rectangular groove 7d etched on the edge of the floor 6.

[0054] In this embodiment, a floor panel 6 is printed on the upper surface of the lower dielectric substrate 11. A central rectangular groove 8 in the y-direction is etched in the lower center of the floor panel 6. Four edge rectangular grooves 7 of equal length and size in the y-direction are etched on the edges of the floor panel 6. The four edge rectangular grooves are etched symmetrically about the center of the floor panel 6. The four edge rectangular grooves 7 etched on the edges of the floor panel 6 enable a pair of vertical rectangular parasitic patches 4 placed at a negative 45° diagonal on the upper dielectric substrate 5 to generate opposite currents with the main radiating patch 1, thereby generating a radiation null. By adjusting the lengths of the upper left rectangular groove 7a, the upper right rectangular groove 7b, the lower left rectangular groove 7c, and the lower right rectangular groove 7d, the null point is located at a low frequency, with minimal impact on antenna performance.

[0055] In a specific embodiment, Figure 1-6 As shown, the microstrip feed line 10 includes a first microstrip 10a, a second microstrip 10b and a parallel branch 10c, which are used to adjust impedance matching. The width of the first microstrip 10a is greater than the width of the second microstrip 10b. The first microstrip 10a is located at the starting end of the microstrip feed line 10, and the end is connected to one end of the second microstrip 10b. The other end of the second microstrip 10b is connected to the parallel branch 10c. The parallel branch 10c is located directly below the middle rectangular groove 8 etched on the floor 6. The branch 9 is located directly above the open end of the microstrip feed line 10, generating a controllable radiation zero point at high frequencies; the branch 9 is shaped like an inverted U.

[0056] In this embodiment, a microstrip feed line 10 and an inverted U-shaped branch 9 are printed on the lower surface of the lower dielectric substrate 11. The microstrip feed line 10 consists of a parallel branch 10c and two microstrips of different widths and lengths, which are used to adjust impedance matching. The wider first microstrip 10a is located at the starting end of the microstrip feed line 10, and is then connected to the narrower second microstrip 10b. The parallel branch 10c is directly below the middle rectangular slot 8 etched on the floor 6; by loading the inverted U-shaped branch 9 at the open end of the microstrip feed line 10, a reverse current can be formed in the x direction of the main radiation patch 1, generating a radiation zero point. By adjusting the length of the inverted U-shaped branch 9 in the x direction, the radiation zero point is located at a high frequency, thereby achieving circularly polarized radiation performance with a compact structure and good bandpass filtering response.

[0057] Figure 7This is a simulation result diagram of the S parameters and main polarization gain of the compact circularly polarized filter patch antenna of this embodiment. The frequency band where the S parameter is lower than -10dB is 2.64-3.42GHz (25.74%), a radiation zero point in the low-frequency stop band is 2.41GHz, and a radiation zero point in the high-frequency stop band is 3.71GHz, which makes the low frequency from 2.25GHz above have a good out-of-band suppression effect, and the high frequency from 3.75GHz above also has a good out-of-band suppression effect, and obtains a good bandpass filtering response.

[0058] Figure 8 This is a diagram of the axial ratio simulation results of the compact circularly polarized filter patch antenna of this embodiment. The axial ratio bandwidth below -3dB is 2.75GHz-3.04GHz (10.02%), and the three axial ratio frequencies are 2.77GHz, 2.88GHz and 3.02GHz respectively. The 2.77GHz is generated by a pair of "L"-shaped parasitic patches and a pair of rectangular parasitic patches loaded around the main radiation patch, the 2.88GHz is generated by a pair of rectangular parasitic patches placed parallel to the main radiation patch, and the 3.02GHz is generated by the main radiation patch with two grooves etched in the negative 45° direction.

[0059] Figure 9 3 is a simulation result diagram showing the variation of the main polarization and cross-polarization gains of the compact circularly polarized filter patch antenna of this embodiment with frequency. It can be seen that there is good cross-polarization within the axial ratio bandwidth.

[0060] Figure 10-11 2. This is a simulation result diagram of the XOZ plane and YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.77 GHz. It can be seen that the circular polarization direction at this frequency point is right-hand circular polarization (RHCP);

[0061] Figure 12-13 2. This is a simulation result diagram of the XOZ plane and YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment at a frequency of 2.88 GHz. It can be seen that the circular polarization direction at this frequency point is right-hand circular polarization (RHCP);

[0062] Figure 14-15 3.02 GHz frequency is the simulation result of the XOZ plane and YOZ plane radiation pattern of the compact circularly polarized filter patch antenna of this embodiment. It can be seen that the circular polarization direction of this frequency point is right-hand circular polarization (RHCP).

[0063] In summary, by etching a main radiation patch 1 with two slots in the negative 45° direction and loading a pair of oblique rectangular parasitic patches 2 parallel to the main radiation patch 1, as well as loading parasitic patches on all sides, three circularly polarized radiation frequencies can be generated, thereby achieving a wider circular polarization bandwidth without increasing the antenna cross-sectional height, maintaining a compact antenna structure, and by etching four edge rectangular slots 7 on the edge of the floor 6 and loading an inverted U-shaped microstrip branch 9 at the open end of the microstrip feed line 10, a controllable radiation zero point is generated at low and high frequencies, respectively, thereby achieving a bandpass filtering response and solving the problems of gain reduction and large size caused by the introduction of the filtering circuit.

[0064] Compared with other antennas, the antenna designed in the present invention has a more compact antenna structure, and does not require the addition of a filtering network or the superposition of structures in the vertical direction to generate a radiation zero point, thereby achieving a bandpass filtering response and having a stable gain pattern.

[0065] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A compact circularly polarized filter patch antenna, characterized by: The invention comprises an upper dielectric substrate (5) and a lower dielectric substrate (11), wherein an air gap exists between the upper dielectric substrate (5) and the lower dielectric substrate (11), and the upper surface of the upper dielectric substrate (5) is printed with a main radiation patch (1) at a positive angle of 45°, a pair of oblique rectangular parasitic patches (2) placed along the positive angle of 45° of the upper dielectric substrate (5) and parallel to the main radiation patch (1), a pair of L-shaped parasitic patches (3) placed along the diagonal line of the positive angle of 45° of the upper dielectric substrate (5), and a pair of vertical rectangular parasitic patches (4) placed along the negative angle of 45° of the lower surface of the upper dielectric substrate (5); The main radiation patch (1) is a slotted patch rotated 45 degrees. The main part of the main radiation patch (1) is a square patch (1a). The main radiation patch (1) is etched with a slot along the edge in the negative 45-degree direction, which are respectively a first main radiation patch slot (1b) and a second main radiation patch slot (1c). The first main radiation patch slot (1b) and the second main radiation patch slot (1c) are located in the middle of the edge of the square patch (1a). The signal enters from the port (20), is coupled to the slotted main radiation patch (1) through the microstrip feed line (10) and the middle rectangular slot (8) on the floor (6), and generates a first circularly polarized radiation frequency point. The lower dielectric substrate (11) is located below the upper dielectric substrate (5), and a floor (6) is printed on the upper surface of the lower dielectric substrate (11). The edge of the floor (6) is etched with an edge rectangular groove (7); The edge rectangular groove (7) includes an upper left rectangular groove (7a), an upper right rectangular groove (7b), a lower left rectangular groove (7c) and a lower right rectangular groove (7d); the upper left rectangular groove (7a), the upper right rectangular groove (7b), the lower left rectangular groove (7c) and the lower right rectangular groove (7d) are of equal length and size; the etching positions of the upper left rectangular groove (7a), the upper right rectangular groove (7b), the lower left rectangular groove (7c) and the lower right rectangular groove (7d) are symmetrical about the center of the floor (6); a radiation zero point is generated at a low frequency by the upper left rectangular groove (7a), the upper right rectangular groove (7b), the lower left rectangular groove (7c) and the lower right rectangular groove (7d) etched on the edge of the floor (6); The connection direction between the upper left rectangular groove (7a) and the upper right rectangular groove (7b) is the y-axis direction; A middle rectangular groove (8) in the y-axis direction is etched in the lower middle of the floor (6). The length extension direction of the edge rectangular slot (7) is the y-axis direction. The lower surface of the lower dielectric substrate (11) is printed with a microstrip feed line (10) and a branch (9). The signal enters from the port (20), is coupled to the main radiation patch (1) through the microstrip feed line (10) and the middle rectangular slot (8) on the floor (6), and is then coupled and excited by the main radiation patch (1) to the surrounding parasitic patches. The microstrip feed line (10) includes a first microstrip (10a), a second microstrip (10b) and a parallel branch (10c), which are used to adjust impedance matching. The width of the first microstrip (10a) is greater than the width of the second microstrip (10b). The first microstrip (10a) is located at the starting end of the microstrip feed line (10), and the end is connected to one end of the second microstrip (10b). The other end of the second microstrip (10b) is connected to the parallel branch (10c). The parallel branch (10c) is located directly below the middle rectangular groove (8) etched on the floor (6). The branch (9) is located directly above the open end of the microstrip feed line (10), generating a radiation zero point at high frequencies.

2. The compact circularly polarized filter patch antenna according to claim 1, characterized in that: The oblique rectangular parasitic patch (2) is rectangular in shape, and there are two oblique rectangular parasitic patches (2). The two oblique rectangular parasitic patches (2) are respectively located between the main radiation patch (1) and the L-shaped parasitic patch (3) and between the main radiation patch (1) and the vertical rectangular parasitic patch (4). The slotted main radiation patch (1) is coupled to the oblique rectangular parasitic patch (2) parallel to the main radiation patch (1) to generate a second circularly polarized radiation frequency point.

3. The compact circularly polarized filter patch antenna according to claim 1, wherein: The L-shaped parasitic patch (3) is L-shaped, and there are two of them. They are placed along the diagonal line of the upper dielectric substrate (5) in the positive 45° direction. The first L-shaped parasitic patch (3) includes a first rectangular patch component (3b) and a first L-shaped patch component (3a). The first rectangular patch component (3b) is placed adjacent to the first L-shaped patch component (3a) and is used to adjust impedance matching. The second L-shaped parasitic patch (3) includes a second rectangular patch component (3d) and a second L-shaped patch component (3c). The second rectangular patch component (3d) is placed adjacent to the second L-shaped patch component (3c) and is used to adjust impedance matching. The lengths of the first rectangular patch component (3b) and the second rectangular patch component (3d) are shorter than the lengths of the first L-shaped patch component (3a) and the second L-shaped patch component (3c). The first rectangular patch component (3b) and the second rectangular patch component (3d) as well as the first L-shaped patch component (3a) and the second L-shaped patch component (3c) are all made of metal.

4. The compact circularly polarized filter patch antenna according to claim 1, wherein: The vertical rectangular parasitic patches (4) are rectangular in shape and are two in number. They are placed along the negative 45° diagonal line of the upper dielectric substrate (5). The first vertical rectangular parasitic patch (4) includes a first rectangular parasitic patch component (4a) and a second rectangular parasitic patch component (4b). The second rectangular parasitic patch component (4b) is placed adjacent to the first rectangular parasitic patch component (4a) for adjusting impedance matching. The second vertical rectangular parasitic patch (4) includes a third rectangular parasitic patch component (4c) and a fourth rectangular parasitic patch component (4d). The third rectangular parasitic patch component (4c) is placed adjacent to the fourth rectangular parasitic patch component (4d) for adjusting impedance matching; the lengths of the second rectangular parasitic patch component (4b) and the fourth rectangular parasitic patch component (4d) are shorter than the lengths of the first rectangular parasitic patch component (4a) and the third rectangular parasitic patch component (4c); the first rectangular parasitic patch component (4a), the second rectangular parasitic patch component (4b), the third rectangular parasitic patch component (4c) and the fourth rectangular parasitic patch component (4d) are all of the same width and are all made of metal; At the same time, a pair of L-shaped parasitic patches (3) and a pair of vertical rectangular parasitic patches (4) are loaded around the main radiation patch (1) to generate a third circularly polarized radiation frequency point.

5. The compact circularly polarized filter patch antenna according to claim 1, characterized in that: The branch (9) is in an inverted U-shape.

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