A single-fed broadband circularly polarized patch antenna for navigation

Abstract

A single-feed broadband circularly polarized patch antenna for navigation provided by the present invention comprises a first dielectric plate, a second dielectric plate, a third dielectric plate, a metal shielding box and a coaxial cable; an antenna radiator is printed on the first dielectric plate, a coplanar waveguide structure is printed on the second dielectric plate, and a feeding structure is printed on the third dielectric plate; the coaxial cable feeds power to the coplanar waveguide structure on the second dielectric plate through the feeding structure on the third dielectric plate; and the coplanar waveguide structure on the second dielectric plate couples and feeds power to the antenna radiator on the first dielectric plate. The present invention combines a coplanar waveguide structure with a patch antenna, and through a coplanar waveguide coupling feeding technique, successfully improves the axial ratio bandwidth of the single-feed circularly polarized antenna, doubles the maximum operating bandwidth of the single-feed circularly polarized antenna, solves the problem that it is difficult to apply the single-feed circularly polarized antenna with a narrow bandwidth to satellite navigation, and has extremely high applicability and flexibility in the satellite navigation applications of multiple systems and multiple frequency bands.

Description

Technical Field

[0001] The present invention relates to the field of patch antennas, and particularly to a single-fed broadband circularly polarized patch antenna for navigation. Background Art

[0002] Due to its advantages of miniaturization, light weight, good directivity, easy realization of circular polarization and multi-band or broadband functions, and easy integration and low cost, the patch antenna plays an indispensable role in satellite navigation systems. Traditional satellite navigation antennas usually adopt a stacked structure, using multiple radiators to meet the multi-frequency requirements, and signal distribution is achieved through a power divider and a phase shifter, which increases the circuit complexity and occupies more space. In contrast, single-fed circularly polarized antennas simplify the design and reduce costs because they do not require these additional components. However, for the need to cover a relatively wide frequency band, the existing single-fed circularly polarized antennas in the past often only provide a limited bandwidth (usually not exceeding 20%), which limits their use in certain application scenarios, especially in satellite navigation systems.

[0003] Therefore, how to expand the effective operating frequency band of the single-fed circularly polarized patch antenna to better meet the application requirements of satellite navigation systems has become an urgent problem to be solved currently. Summary of the Invention

[0004] The purpose of the present invention is to provide a single-fed broadband circularly polarized patch antenna for navigation, aiming at the problems existing in the prior art, and expanding the effective operating frequency band of the single-fed circularly polarized patch antenna through a simple structure to better meet the application requirements of satellite navigation systems.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A single-fed broadband circularly polarized patch antenna for navigation, comprising a first dielectric plate, a second dielectric plate, a third dielectric plate, a metal shielding box and a coaxial cable;

[0007] The first dielectric plate is arranged parallel to the upper side of the second dielectric plate, and the two are fixedly connected by a plurality of insulating support columns; the metal shielding box covers the lower surface of the second dielectric plate to form a hollow metal cavity below the second dielectric plate; the third dielectric plate is arranged in the hollow metal cavity and is vertically connected between the bottom surface of the metal shielding box and the second dielectric plate;

[0008] An antenna radiator is printed on the first dielectric plate, a coplanar waveguide structure is printed on the second dielectric plate, and a feeding structure is printed on the third dielectric plate; the coaxial cable feeds power to the coplanar waveguide structure on the second dielectric plate through the feeding structure on the third dielectric plate; the coplanar waveguide structure on the second dielectric plate feeds power to the antenna radiator on the first dielectric plate by coupling; the metal shielding box is used to reduce the back lobe of the antenna radiation pattern and make the antenna gain stable;

[0009] The antenna radiator includes a first metal patch printed on the upper surface of the first dielectric plate and a second metal patch printed on the lower surface of the first dielectric plate; wherein, the first metal patch is circular, the second metal patch is annular, and the centers of both are located at the center of the first dielectric plate;

[0010] A circular slot, a cross slot and four elliptical hollow slots are etched on the first metal patch; the circular slot is arranged in the middle of the first metal patch, so that the first metal patch is divided into a circular patch at the center and an annular patch surrounding the circular patch; the cross slot is composed of two linear slots vertically intersecting at the center of the circular patch, and the two linear slots penetrate the circular patch and the annular patch along the diameter direction respectively, so that the circular patch is divided into four identical sector patches, and the annular patch is also divided into four identical sector-annular patches; the four elliptical hollow slots are respectively arranged in the middle of the four sector-annular patches, and the major axis of the elliptical hollow slot is arranged along the diameter direction of the first metal patch; one end of each elliptical hollow slot close to the center is connected to the circular slot through a slot respectively, so that the elliptical hollow slot and the circular slot together form a T-shaped slot structure, which is used to make the axial ratio resonate at high frequencies to expand the high-frequency axial ratio bandwidth of the antenna;

[0011] The second metal patch has a slot corresponding to the cross slot, so that the second metal patch is divided into four identical sector-annular regions; the second metal patch is used to maintain the low-frequency gain of the antenna and also used to adjust the high-frequency axial ratio of the antenna by changing its diameter;

[0012] The coplanar waveguide structure includes an annular metal ground and a rectangular metal patch printed on the upper surface of the second dielectric substrate; the annular metal ground is in the shape of a hollow rectangular frame, the rectangular metal patch is arranged in the middle of the annular metal ground, and the annular metal ground and the rectangular metal patch are separated by a rectangular slot, and the rectangular slot is used to improve the low-frequency gain of the antenna; a C-shaped slot is etched in the middle of the rectangular metal patch, and a resistor is arranged in the C-shaped slot; the C-shaped slot is arranged directly below the antenna radiator and is in the shape of a non-closed circular ring with an opening as a whole; the resistor is arranged in the C-shaped slot along the diameter direction to connect the metal patches inside and outside the C-shaped slot, and is used to absorb the standing wave on the C-shaped slot to maintain the amplitude and phase difference of the orthogonal excitation, so as to provide broadband circular polarization coupling feeding for the antenna radiator.

[0013] Further, in the first metal patch, a plurality of rectangular bumps are uniformly arranged on the outer arc edges of each sector-shaped annular patch for improving the gain of the antenna.

[0014] Further, a feeding connection slot is etched in the rectangular metal patch on the second dielectric substrate, the feeding connection slot is arranged at the outer edge of the C-shaped slot and is communicated with the C-shaped slot, and a feeding connection jack penetrating the second dielectric substrate in the vertical direction is arranged in the feeding connection slot; a feeding metal branch is connected to the inner edge of the C-shaped slot, and the feeding metal branch extends along the diameter direction to the side of the feeding connection jack in the feeding connection slot;

[0015] An upwardly protruding upper connection plug is arranged at the upper end of the third dielectric substrate, the upper connection plug is matched with the feeding connection jack on the second dielectric substrate, and the second dielectric substrate and the third dielectric substrate are mutually plugged and fixed through the upper connection plug and the feeding connection jack;

[0016] The feeding structure includes a feeding microstrip line and a grounding microstrip line printed on the front and back surfaces of the third dielectric substrate respectively; the feeding microstrip line and the grounding microstrip line are arranged in parallel with each other to form a parallel two-wire structure; one ends of the feeding microstrip line and the grounding microstrip line are electrically connected to the inner conductor and the outer conductor of the coaxial cable respectively, and the other ends of the feeding microstrip line and the grounding microstrip line extend to the upper connection plug at the upper end of the third dielectric substrate; after passing through the second dielectric substrate along with the upper connection plug, the other end of the feeding microstrip line is welded to the feeding metal branch, and then electrically connected to the part of the rectangular metal patch inside the C-shaped slot for transmitting the excitation signal of the coaxial cable to the coplanar waveguide structure; the other end of the grounding microstrip line is welded to the part of the rectangular metal patch outside the C-shaped slot for realizing the grounding of the coplanar waveguide structure.

[0017] Further, a coaxial cable jack is provided at the center of the bottom surface of the metal shielding box. The coaxial cable is introduced from below the metal shielding box. The outer conductor of the coaxial cable is welded to the metal shielding box at the coaxial cable jack. The inner conductor of the coaxial cable passes through the coaxial cable jack and is welded to one end of the feeding microstrip line.

[0018] A downwardly protruding lower connection plug board is provided at the lower end of the third dielectric plate. A matching mounting jack is provided on the bottom surface of the metal shielding box. The third dielectric plate and the metal shielding box are mutually plugged and fixed through the lower connection plug board and the mounting jack. One end of the grounding microstrip line extends to the lower connection plug board at the lower end of the third dielectric plate, and the grounding microstrip line is welded to the metal shielding box to be connected to the outer conductor of the coaxial cable through the metal shielding box, thereby realizing grounding.

[0019] Further, a plurality of upwardly protruding grounding plug boards are evenly provided at the opening edge of the upper end of the metal shielding box. After the grounding plug boards penetrate the second dielectric plate in the vertical direction, they are welded to the annular metal ground on the second dielectric plate for grounding the annular metal ground and simultaneously realizing the fixation of the metal shielding box and the second dielectric plate.

[0020] Further, two mounting jacks are provided on the bottom surface of the metal shielding box, and the two mounting jacks are symmetrically distributed on the opposite sides of the coaxial cable jack. Two lower connection plates are provided at the lower end of the third dielectric plate, and the two lower connection plates are respectively inserted and connected into the two mounting jacks. One end of the grounding microstrip line is divided into two paths, which are respectively distributed on the two lower connection plates and are both welded to the metal shielding box.

[0021] Further, the dielectric constants of the first dielectric plate, the second dielectric plate and the third dielectric plate are 4.6, the thicknesses of the first dielectric plate and the third dielectric plate are 1 mm, and the thickness of the second dielectric plate is 1.6 mm.

[0022] Further, the circular slot on the first metal patch is arranged within the coverage area of the second metal patch.

[0023] Further, in the coplanar waveguide structure, the resistor and the feeding metal stub are respectively arranged on the opposite sides of the C-shaped slot, and the distances from both of them to the opening of the C-shaped slot are equal.

[0024] The present invention innovatively combines the coplanar waveguide structure with the patch antenna. By adopting the coplanar waveguide coupling feeding technology, the axial ratio bandwidth of the single-fed circularly polarized antenna is successfully improved, and the maximum operating bandwidth of the single-fed circularly polarized antenna is increased by more than one time, solving the problem that the bandwidth of the past single-fed circularly polarized antenna is narrow and difficult to be applied to satellite navigation.

[0025] A single-feed broadband circularly polarized patch antenna for navigation provided by the present invention has an operating frequency band of 1.11 GHz - 1.84 GHz, a matching and axial ratio cross bandwidth of 48.6%, and can comprehensively cover multiple navigation systems such as the Chinese Beidou satellite navigation system, the US GPS positioning system, the Russian GLONASS satellite navigation system, and the EU Galileo satellite navigation system. It has extremely high applicability and flexibility in satellite navigation applications with multiple systems and multiple frequency bands; not only overcomes the limitations existing in the prior art, but also further enhances the application potential of this type of antenna.

[0026] At the same time, the gain of the present invention within the navigation frequency band is 5.14 - 6 dBic, and it has the advantages of high gain, stable radiation pattern, and stable gain. Compared with traditional satellite navigation antennas, the present invention also has the advantages of fewer required dielectric substrates, simple installation, and easy production. Brief Description of the Drawings

[0027] Figure 1 is an exploded view of the structure of a single-feed broadband circularly polarized patch antenna for navigation provided by an embodiment of the present invention.

[0028] Figure 2 is a schematic structural diagram of the first dielectric plate and the antenna radiator in an embodiment of the present invention.

[0029] Figure 3 is a schematic structural diagram of the second dielectric plate and the coplanar waveguide structure in an embodiment of the present invention.

[0030] Figure 4 is a schematic structural diagram of the third dielectric plate and the feeding structure in an embodiment of the present invention.

[0031] Figure 5 is a schematic structural diagram of the metal shielding box and the coaxial cable in an embodiment of the present invention.

[0032] Figure 6 is a comparison diagram of the S-parameter curves in an embodiment of the present invention.

[0033] Figure 7 is a comparison diagram of the axial ratio curves in an embodiment of the present invention.

[0034] Figure 8 is a gain curve diagram in an embodiment of the present invention.

[0035] Figure 9 is the radiation pattern in an embodiment of the present invention.

[0036] Figure 10 is a comparison of the radiation patterns before and after installing the metal shielding box in an embodiment of the present invention. Detailed Embodiment

[0037] The technical solution of the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0038] As Figure 1 shown, a single-feed broadband circularly polarized patch antenna for navigation provided by an embodiment of the present invention includes a first dielectric plate 11, a second dielectric plate 12, a third dielectric plate 13, a metal shielding box 2, and a coaxial cable 3.

[0039] Among them, the first dielectric plate 11 is disposed parallel above the second dielectric plate 12, and the two are fixedly connected by a plurality of insulating support columns; the metal shielding box 2 covers the lower surface of the second dielectric plate 12 to form a hollow metal cavity below the second dielectric plate 12; the third dielectric plate 13 is disposed in the hollow metal cavity and is vertically connected between the bottom surface of the metal shielding box 2 and the second dielectric plate 12. In this embodiment, the dielectric constants of the first dielectric plate 11, the second dielectric plate 12, and the third dielectric plate 13 are 4.6, the thickness of the first dielectric plate 11 and the third dielectric plate 13 is 1 mm, and the thickness of the second dielectric plate 12 is 1.6 mm.

[0040] An antenna radiator 4 is printed on the first dielectric plate 11, a coplanar waveguide structure 5 is printed on the second dielectric plate 12, and a feeding structure 6 is printed on the third dielectric plate 13; the coaxial cable 3 feeds power to the coplanar waveguide structure 5 on the second dielectric plate 12 through the feeding structure 6 on the third dielectric plate 13; the coplanar waveguide structure 5 on the second dielectric plate 12 couples and feeds power to the antenna radiator 4 on the first dielectric plate 11. The metal shielding box 2 is used to reduce the back lobe of the antenna radiation pattern and make the antenna gain stable.

[0041] Specifically, in combination with Figure 2 shown, the antenna radiator 4 includes a first metal patch 41 printed on the upper surface of the first dielectric plate 11 and a second metal patch 42 printed on the lower surface of the first dielectric plate 11; wherein, the first metal patch 41 is circular, the second metal patch 42 is annular, and the centers of both are located at the center of the first dielectric plate 11;

[0042] A circular slot 43, a cross slot 44 and four elliptical hollow slots 45 are etched on the first metal patch 41; the circular slot 43 is arranged in the middle of the first metal patch 41, so that the first metal patch 41 is divided into a circular patch at the center and an annular patch surrounding the circular patch; the cross slot 44 is composed of two linear slots vertically intersecting at the center of the circular patch, and the two linear slots penetrate the circular patch and the annular patch along the diameter direction respectively, so that the circular patch is divided into four identical sector patches, and the annular patch is also divided into four identical sector-annular patches. A plurality of rectangular bumps are uniformly arranged on the outer arc edge of each sector-annular patch to improve the gain of the antenna. The four elliptical hollow slots 45 are respectively arranged in the middle of the four sector-annular patches, and the long axis of the elliptical hollow slot 45 is arranged along the diameter direction of the first metal patch 41; one end of each elliptical hollow slot 45 close to the center of the circle is connected to the circular slot 43 through a slot 46 respectively, so that the elliptical hollow slot 45 and the circular slot 43 together form a T-shaped slot structure, which is used to resonate the axial ratio of the antenna at high frequencies to expand the high-frequency axial ratio bandwidth of the antenna.

[0043] The second metal patch 42 is arranged below the circular slot 43, so that the circular slot 43 is located within the coverage area of the second metal patch 42. The second metal patch 42 has a slot corresponding to the cross slot 44, so that the second metal patch 42 is divided into four identical sector-annular regions; the second metal patch 42 is used to maintain the low-frequency gain of the antenna, and the high-frequency axial ratio of the antenna can be adjusted by adjusting the diameter of the second metal patch 42. The second metal patch 42 is a necessary structure to enhance the internal and external coupling effects of the first metal patch 41. After the first metal patch 41 is divided into an internal circular patch and an external annular patch by the circular slot 43, the second metal patch 42 must be arranged below the circular slot 43, otherwise the input impedance of the antenna will lose matching and circular polarization cannot be formed.

[0044] Combined with Figure 3As shown, the coplanar waveguide structure 5 includes an annular metal ground 51 printed on the upper surface of the second dielectric plate 12 and a rectangular metal patch 52; the annular metal ground 51 is in the shape of a hollow rectangular frame, the rectangular metal patch 52 is arranged in the middle of the annular metal ground 51, and the annular metal ground 51 and the rectangular metal patch 52 are separated by a rectangular slot 50, and the rectangular slot 50 is used to improve the low-frequency gain of the antenna. A C-shaped slot 53 is etched in the middle of the rectangular metal patch 52, and a resistor 54 is arranged in the C-shaped slot 53; the C-shaped slot 53 is arranged directly below the antenna radiator 4 and is in the shape of an open non-closed circular ring as a whole; the resistor 54 is arranged in the C-shaped slot 53 along the diameter direction to connect the metal patches on the inner side and the outer side of the C-shaped slot 53, and is used to absorb the standing wave on the C-shaped slot 53 to maintain the amplitude and phase difference of the orthogonal excitation, so as to provide broadband circular polarization coupling feeding for the antenna radiator 4.

[0045] In this embodiment, the resistor 54 and the feeding metal branch 56 in the coplanar waveguide structure 5 are respectively arranged on opposite sides of the C-shaped slot 53, and the distances from both of them to the opening of the C-shaped slot 53 are equal, that is, there is a 90° phase difference between the feeding metal branch 56 and the opening of the C-shaped slot 53, and there is also a 90° phase difference between the resistor 54 and the opening of the C-shaped slot 53, and there is a 180° phase difference between the feeding metal branch 56 and the resistor 54. To achieve circular polarization, sequential phase shift needs to be realized through a certain structure. In the present invention, a resistor 54 is loaded on the C-shaped slot 53, so that the components of the electric field in the X-axis and Y-axis maintain equal amplitudes and a 90° phase difference, thereby realizing the orthogonal excitation with a 90° phase difference of equivalent three feeding points on the C-shaped slot 53.

[0046] Furthermore, a feeding connection slot 55 is etched in the rectangular metal patch 52 on the second dielectric plate 12, the feeding connection slot 55 is arranged at the outer edge of the C-shaped slot 53 and is communicated with the C-shaped slot 53, and a feeding connection jack 50 penetrating the second dielectric plate 12 in the vertical direction is arranged in the feeding connection slot 55; a feeding metal branch 56 is connected to the inner edge of the C-shaped slot 53, and the feeding metal branch 56 extends along the diameter direction to the side of the feeding connection jack 50 in the feeding connection slot 55.

[0047] Combined with Figure 4 As shown, an upward protruding upper connection plug 131 is provided at the upper end of the third dielectric plate 13, the upper connection plug 131 is matched with the feeding connection jack 50 on the second dielectric plate 12, and the second dielectric plate 12 and the third dielectric plate 13 are mutually plugged and fixed through the upper connection plug 131 and the feeding connection jack 50.

[0048] Further, the feeding structure 6 includes a feeding microstrip line 61 and a grounding microstrip line 62 printed on the front and back sides of the third dielectric plate 13 respectively; the feeding microstrip line 61 and the grounding microstrip line 62 are arranged in parallel with each other to form a parallel two-wire structure; one ends of the feeding microstrip line 61 and the grounding microstrip line 62 are electrically connected to the inner conductor and the outer conductor of the coaxial cable 3 respectively, and the other ends of the feeding microstrip line 61 and the grounding microstrip line 62 extend to the upper connection plug 131 at the upper end of the third dielectric plate 13; after passing through the second dielectric plate 12 with the upper connection plug 131, the other end of the feeding microstrip line 61 is welded to the feeding metal branch 56, and then electrically connected to the part of the rectangular metal patch 52 inside the C-shaped groove 53, for transmitting the excitation signal of the coaxial cable 3 to the coplanar waveguide structure 5; the other end of the grounding microstrip line 62 is welded to the part of the rectangular metal patch 52 outside the C-shaped groove 53, for realizing the grounding of the coplanar waveguide structure 5.

[0049] As shown in Figure 5 FIG. 5, a coaxial jack 22 is provided at the center of the bottom surface of the metal shielding box 2, the coaxial cable 3 is introduced from below the metal shielding box 2, the outer conductor of the coaxial cable 3 is welded to the metal shielding box 2 at the coaxial jack 22, and the inner conductor of the coaxial cable 3 passes through the coaxial jack 22 and is welded to one end of the feeding microstrip line 61.

[0050] As shown in Figure 4 and Figure 5 FIG. 6, a downwardly protruding lower connection plug 132 is provided at the lower end of the third dielectric plate 13, and a matching mounting jack 23 is provided on the bottom surface of the metal shielding box 2; the third dielectric plate 13 and the metal shielding box 2 are fixedly plugged to each other through the lower connection plug 132 and the mounting jack 23; one end of the grounding microstrip line 62 extends to the lower connection plug 132 at the lower end of the third dielectric plate 13, and the grounding microstrip line 62 is welded to the metal shielding box 2 to be connected to the outer conductor of the coaxial cable 3 through the metal shielding box 2, thereby realizing grounding.

[0051] In this embodiment, two mounting jacks 23 are provided on the bottom surface of the metal shielding box 2, and the two mounting jacks 23 are symmetrically distributed on opposite sides of the coaxial jack 22; two lower connection plates 132 are provided at the lower end of the third dielectric plate 13, and the two lower connection plates 132 are respectively inserted and connected into the two mounting jacks 23, one end of the grounding microstrip line 62 is divided into two paths, which are respectively distributed on the two lower connection plates 132 and are both welded to the metal shielding box 2.

[0052] Furthermore, a plurality of upwardly protruding grounding plug plates 21 are evenly arranged at the upper opening edge of the metal shielding box 2; after the grounding plug plates 21 penetrate the second dielectric plate 12 in the vertical direction, they are welded to the annular metal ground 51 on the second dielectric plate 12 to ground the annular metal ground 51 and at the same time fix the metal shielding box 2 to the second dielectric plate 12.

[0053] When the embodiment of the present invention works, the inner conductor of the coaxial cable 3 transmits the excitation signal to the coplanar waveguide structure 5 through the feeding microstrip line 61, and the coplanar waveguide structure 5 is connected to the outer conductor of the coaxial cable 3 through the grounding microstrip line 52 and the metal shielding box 2 to achieve grounding. In the coplanar waveguide structure 5, after the feeding microstrip line 61 transmits the excitation signal to the feeding metal stub 56, together with the opening of the C-shaped slot 53, it makes the electric field propagate in the counterclockwise direction, and at the same time couples to the patch during the forward process, thereby forming an orthogonal excitation with a 90° phase difference. The resistor 54 is used to absorb the standing wave on the C-shaped slot 53, so that the orthogonal excitation maintains the same amplitude and stable phase, thereby providing broadband circular polarization coupling feeding for the antenna radiator 4. At the same time, the low-profile metal shielding box 2 installed below the coplanar waveguide structure 5 can effectively reduce the back lobe of the antenna radiation pattern and make the antenna gain stable.

[0054] In the antenna radiator 4, the cross slit groove 44, the elliptical hollow groove 45 and the T-shaped groove structure are the core improvements of the present invention, which are used to achieve low-frequency broadband impedance matching and improve the 3dB axial ratio bandwidth of the antenna at low and high frequencies. Among them, the T-shaped groove structure can make the axial ratio resonate at high frequencies to expand the high-frequency axial ratio bandwidth of the antenna. In the antenna radiator 4, the second metal patch 42 located below the first dielectric plate 11 is used to maintain the low-frequency gain of the antenna; by adjusting the diameter of the second metal patch 42 (that is, the distance of the second metal patch 42 relative to the center of the first dielectric plate 11), the high-frequency axial ratio of the antenna can also be adjusted.

[0055] Please refer to Figure 6 , which is a comparison diagram of the S-parameter curves of the embodiment of the present invention. The solid line in the figure is the S-parameter curve of the embodiment of the present invention; the dotted line is the S-parameter curve when there is no slot in the antenna radiator 4 under a similar structure. The results show that the cross slit groove 44, the elliptical hollow groove 45 and the T-shaped groove structure on the antenna radiator 4 play an important role in low-frequency impedance matching. Under the combined action of various slot structures, the antenna of the present invention realizes impedance matching in the frequency band of 1.07 GHz - 1.95 GHz, and the relative matching bandwidth is 58.27%.

[0056] Please refer to Figure 7, which is the comparison diagram of the axial ratio curves of the embodiments of the present invention. The solid line in the figure is the axial ratio curve of the embodiments of the present invention; the dashed line is the axial ratio curve when the resistor 54 is not loaded in the C-shaped groove 53 under a similar structure. The results show that the resistor 54 for absorbing standing waves on the coplanar waveguide structure 5 greatly affects the amplitude and phase difference of orthogonal excitation, which is crucial for the axial ratio bandwidth of the present invention and is the core feature of the present invention. After loading the resistor 54, the axial ratio of the antenna of the present invention is lower than 3 dB in the frequency band of 1.11 GHz - 1.84 GHz, and the relative axial ratio bandwidth is 48.6%, having a wide axial ratio bandwidth.

[0057] Combined with Figure 6 and Figure 7 It can be seen that the antenna of the present invention achieves impedance matching in the frequency band of 1.07 GHz - 1.95 GHz, and the relative matching bandwidth is 58.27%. At the same time, the axial ratio of the antenna of the present invention is lower than 3 dB in the frequency band of 1.11 GHz - 1.84 GHz, and the relative axial ratio bandwidth is 48.6%, having a wide axial ratio bandwidth. Therefore, the present invention can comprehensively cover all relevant frequency bands of major satellite navigation systems including B1 (1561.098 MHz), B2 (1207.140 MHz), and B3 (1268.520 MHz) of the Chinese Beidou satellite navigation system, L1 (1575.42 MHz), L2 (1227.60 MHz), and L5 (1176.45 MHz) of the US GPS positioning system, L1 (1602 MHz - 1615 MHz) and L2 (1246 MHz - 1256 MHz) of the Russian GLONASS satellite navigation system, and E1 (1575.42 MHz), E5 (1191.795 MHz), E5a (1176.45 MHz), E5b (1207.14 MHz), and E6 (1278.75 MHz) of the EU Galileo satellite navigation system. This wide coverage makes the antenna of the present invention have extremely high applicability and flexibility in satellite navigation applications of multiple systems and multiple frequency bands.

[0058] Please refer to Figure 8 , which is the gain curve diagram of the embodiments of the present invention. The results show that the embodiments of the present invention are high-gain patch antennas, the peak gain reaches 6.17 dBic, and the lowest gain in the navigation antenna frequency band is 5.14 dBic. At the same time, the gain of the embodiments of the present invention is stable, and the 1-dB bandwidth is 38.84%.

[0059] Please refer to Figure 9 , which is the radiation pattern of the embodiments of the present invention. Among them, Figure 9 in (a) is the radiation pattern when the center frequency is 1.2 GHz and Phi is 0°; Figure 9 in (b) is the radiation pattern when the center frequency is 1.6 GHz and Phi is 0°.Figure 9 Among them, (c) is the radiation pattern when the center frequency is 1.2 GHz and Phi is 90°; Figure 9 Among them, (d) is the radiation pattern when the center frequency is 1.6 GHz and Phi is 90°. The results show that the radiation pattern of the embodiment of the present invention is stable, the cross-polarization ratio is greater than 16.7 dB, and it has good radiation characteristics.

[0060] Please refer to Figure 10 , which is the comparison of the radiation patterns before and after installing the metal shielding box in the embodiment of the present invention. Among them, Figure 10 Among them, (a) and (c) are the radiation patterns when Phi is 0° and 90° respectively under the condition of installing the metal shielding box; Figure 10 Among them, (b) and (d) are the radiation patterns when Phi is 0° and 90° respectively under the condition of not installing the metal shielding box. The results show that by installing the metal shielding box, the backward radiation of the embodiment of the present invention can be effectively reduced, and the back lobe of the antenna radiation pattern becomes smaller.

[0061] The present invention innovatively combines the coplanar waveguide structure with the patch antenna. By adopting the coplanar waveguide coupling feeding technology, the axial ratio bandwidth of the single-fed circularly polarized antenna is successfully improved, and the maximum operating bandwidth of the single-fed circularly polarized antenna is increased by more than one time, solving the problem that the bandwidth of the past single-fed circularly polarized antenna is narrow and difficult to be applied to satellite navigation.

[0062] A single-fed broadband circularly polarized patch antenna for navigation provided by the present invention has a working frequency band of 1.11 GHz - 1.84 GHz, a matching and axial ratio cross bandwidth of 48.6%, and can comprehensively cover multiple navigation systems such as the Chinese Beidou satellite navigation system, the American GPS positioning system, the Russian GLONASS satellite navigation system, and the European Union Galileo satellite navigation system. It has extremely high applicability and flexibility in satellite navigation applications of multiple systems and multiple frequency bands; it not only overcomes the limitations existing in the prior art, but also further enhances the application potential of this type of antenna.

[0063] At the same time, the gain of the present invention in the navigation frequency band is 5.14 - 6 dBic, and it has the advantages of high gain, stable radiation pattern, and stable gain. Compared with the traditional satellite navigation antenna, the present invention also has the advantages of fewer required dielectric substrates, simple installation, and easy production.

[0064] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be subject to the appended claims.

Claims

1. A single-fed broadband circularly polarized patch antenna for navigation, characterized in that, It includes a first dielectric plate, a second dielectric plate, a third dielectric plate, a metal shielding box, and a coaxial cable; The first dielectric plate is arranged parallel to the upper side of the second dielectric plate, and the two are fixedly connected by a plurality of insulating support columns; the metal shielding box covers the lower surface of the second dielectric plate to form a hollow metal cavity below the second dielectric plate; the third dielectric plate is arranged in the hollow metal cavity and is vertically connected between the bottom surface of the metal shielding box and the second dielectric plate; An antenna radiator is printed on the first dielectric plate, a coplanar waveguide structure is printed on the second dielectric plate, and a feeding structure is printed on the third dielectric plate; the coaxial cable feeds power to the coplanar waveguide structure on the second dielectric plate through the feeding structure on the third dielectric plate; the coplanar waveguide structure on the second dielectric plate couples and feeds power to the antenna radiator on the first dielectric plate; the metal shielding box is used to reduce the back lobe of the antenna radiation pattern and make the antenna gain stable; The antenna radiator includes a first metal patch printed on the upper surface of the first dielectric plate and a second metal patch printed on the lower surface of the first dielectric plate; wherein, the first metal patch is circular, the second metal patch is annular, and the centers of both are located at the center of the first dielectric plate; A circular slot, a cross slot, and four elliptical hollow slots are etched on the first metal patch; the circular slot is arranged in the middle of the first metal patch, so that the first metal patch is divided into a circular patch at the center and an annular patch surrounding the circular patch; the cross slot is composed of two linear slots vertically intersecting at the center of the circular patch, and the two linear slots respectively penetrate the circular patch and the annular patch along the diameter direction, so that the circular patch is divided into four sector patches with the same shape, and the annular patch is also divided into four sector-annular patches with the same shape; the four elliptical hollow slots are respectively arranged in the middle of the four sector-annular patches, and the long axis of the elliptical hollow slot is arranged along the diameter direction of the first metal patch; one end of each elliptical hollow slot close to the center is respectively connected to the circular slot through a slot, so that the elliptical hollow slot and the circular slot together form a T-shaped slot structure, which is used to make the axial ratio resonate at high frequencies to expand the high-frequency axial ratio bandwidth of the antenna; The second metal patch has a slot corresponding to the cross slot, so that the second metal patch is divided into four sector-annular regions with the same shape; the second metal patch is used to maintain the low-frequency gain of the antenna and is also used to adjust the high-frequency axial ratio of the antenna by changing its diameter; The coplanar waveguide structure includes an annular metal ground and a rectangular metal patch printed on the upper surface of the second dielectric plate; the annular metal ground is in the shape of a hollow rectangular frame, the rectangular metal patch is arranged in the middle of the annular metal ground, and the annular metal ground and the rectangular metal patch are separated by a rectangular slot, and the rectangular slot is used to improve the low-frequency gain of the antenna; a C-shaped slot is etched in the middle of the rectangular metal patch, and a resistor is arranged in the C-shaped slot; the C-shaped slot is arranged directly below the antenna radiator and is in the shape of an open non-closed circular ring as a whole; the resistor is arranged in the C-shaped slot along the diameter direction to connect the metal patches on the inner and outer sides of the C-shaped slot, and is used to absorb the standing wave on the C-shaped slot to maintain the amplitude and phase difference of the orthogonal excitation, so as to provide broadband circular polarization coupling feeding for the antenna radiator.

2. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, characterized in that On the first metal patch, a plurality of rectangular bumps are evenly arranged on the outer arc edges of each fan-shaped annular patch, which are used to improve the gain of the antenna.

3. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, wherein A feeding connection slot is etched in the rectangular metal patch on the second dielectric plate, the feeding connection slot is arranged at the outer edge of the C-shaped slot and is communicated with the C-shaped slot, and a feeding connection jack penetrating the second dielectric plate in the vertical direction is arranged in the feeding connection slot; a feeding metal branch is connected to the inner edge of the C-shaped slot, and the feeding metal branch extends along the diameter direction to the side of the feeding connection jack in the feeding connection slot; An upward protruding upper connection plug is arranged at the upper end of the third dielectric plate, the upper connection plug is matched with the feeding connection jack on the second dielectric plate, and the second dielectric plate and the third dielectric plate are mutually plugged and fixed through the upper connection plug and the feeding connection jack; The feeding structure includes a feeding microstrip line and a grounding microstrip line respectively printed on the front and back sides of the third dielectric plate; the feeding microstrip line and the grounding microstrip line are arranged parallel to each other to form a parallel two-wire structure; one ends of the feeding microstrip line and the grounding microstrip line are electrically connected to the inner conductor and the outer conductor of the coaxial cable respectively, and the other ends of the feeding microstrip line and the grounding microstrip line respectively extend to the upper connection plug at the upper end of the third dielectric plate; after passing through the second dielectric plate along with the upper connection plug, the other end of the feeding microstrip line is welded to the feeding metal branch, and then electrically connected to the part of the rectangular metal patch inside the C-shaped slot, which is used to transmit the excitation signal of the coaxial cable to the coplanar waveguide structure; the other end of the grounding microstrip line is welded to the part of the rectangular metal patch outside the C-shaped slot, which is used to realize the grounding of the coplanar waveguide structure.

4. The single-fed broadband circularly polarized patch antenna for navigation according to claim 3, characterized in that, A coaxial line jack is arranged at the center of the bottom surface of the metal shielding box, the coaxial cable is introduced from below the metal shielding box, the outer conductor of the coaxial cable is welded to the metal shielding box at the coaxial line jack, and the inner conductor of the coaxial cable passes through the coaxial line jack and is welded to one end of the feeding microstrip line; A downwardly protruding lower connection plug is provided at the lower end of the third dielectric plate, and a matching mounting jack is provided on the bottom surface of the metal shielding box; the third dielectric plate and the metal shielding box are fixedly connected to each other by inserting the lower connection plug into the mounting jack; one end of the grounding microstrip line extends to the lower connection plug at the lower end of the third dielectric plate, and the grounding microstrip line is welded to the metal shielding box to be connected to the outer conductor of the coaxial cable through the metal shielding box, thereby achieving grounding.

5. The single-fed broadband circularly polarized patch antenna for navigation according to claim 4, wherein A plurality of upwardly protruding grounding plugs are evenly provided at the opening edge of the upper end of the metal shielding box; after the grounding plugs penetrate the second dielectric plate in the vertical direction, they are welded to the annular metal ground on the second dielectric plate to ground the annular metal ground and at the same time fix the metal shielding box to the second dielectric plate.

6. The single-fed broadband circularly polarized patch antenna for navigation according to claim 4, characterized in that, Two mounting jacks are provided on the bottom surface of the metal shielding box, and the two mounting jacks are symmetrically distributed on the opposite sides of the coaxial line jack; two lower connecting plates are provided at the lower end of the third dielectric plate, and the two lower connecting plates are respectively inserted and connected into the two mounting jacks, and one end of the grounding microstrip line is divided into two paths and is respectively distributed on the two lower connecting plates and is welded to the metal shielding box.

7. The single-feed broadband circularly polarized patch antenna for navigation according to claim 1, wherein The dielectric constants of the first dielectric plate, the second dielectric plate and the third dielectric plate are 4.6, the thicknesses of the first dielectric plate and the third dielectric plate are 1 mm, and the thickness of the second dielectric plate is 1.6 mm.

8. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, wherein The circular slot on the first metal patch is provided within the coverage area of the second metal patch.

9. The single-fed broadband circularly polarized patch antenna for navigation according to claim 3, wherein In the coplanar waveguide structure, the resistor and the feeding metal stub are respectively provided on the opposite sides of the C-shaped slot, and the distances from both of them to the opening of the C-shaped slot are equal; that is, there is a 90° phase difference between the feeding metal stub 56 and the opening of the C-shaped slot 53, and there is also a 90° phase difference between the resistor 54 and the opening of the C-shaped slot 53, and there is a 180° phase difference between the feeding metal stub 56 and the resistor 54.

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