Single-feed broadband circularly polarized patch antenna for navigation

Abstract

The invention provides a single-feed broadband circularly polarized patch antenna for navigation. The single-feed broadband circularly polarized patch antenna 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 feed 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 feed structure on the third dielectric plate; and the coplanar waveguide structure on the second dielectric plate feeds the antenna radiator on the first dielectric plate in a coupling manner. The coplanar waveguide structure and the patch antenna are combined, the axial ratio bandwidth of the single-feed circularly polarized antenna is successfully improved through the coplanar waveguide coupling feed technology, the maximum working bandwidth of the single-feed circularly polarized antenna is improved by more than one time, and the problem that the single-feed circularly polarized antenna is narrow in bandwidth and difficult to apply to satellite navigation is solved. And the method has extremely high applicability and flexibility in multi-system and multi-band satellite navigation application.

Description

Technical Field

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

[0002] Patch antennas play an indispensable role in satellite navigation systems because of their miniaturization, light weight, good directivity, easy realization of circular polarization and multi-band or broadband functions, and easy integration and low cost. Traditional satellite navigation antennas usually adopt a stacked structure, using multiple radiators to meet multi-frequency requirements, and use power dividers and phase shifters to achieve signal distribution, which increases circuit complexity and takes up more space. In contrast, single-fed circularly polarized antennas do not require these additional components, thus simplifying the design and reducing costs. However, for the needs of covering a wider frequency band, the existing single-fed circularly polarized antennas in the past can only provide limited bandwidth (usually no more than 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 the satellite navigation system has become a problem that needs to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to provide a single-fed broadband circularly polarized patch antenna for navigation in response to the problems existing in the prior art, and to expand the effective working 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 object, the present invention adopts the following technical solutions:

[0006] A single-feed 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 second dielectric plate, and the two are fixedly connected by a plurality of insulating support columns; the metal shielding box is covered on the lower surface of the second dielectric plate to form a hollow metal cavity under the second dielectric plate; the third dielectric plate is arranged in the hollow metal cavity and vertically connected between the bottom surface of the metal shielding box and the second dielectric plate;

[0008] The first dielectric plate is printed with an antenna radiator, the second dielectric plate is printed with a coplanar waveguide structure, and the third dielectric plate is printed with a feeding structure; the coaxial cable feeds 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 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 stabilize the antenna gain;

[0009] The antenna radiator comprises 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 and the second metal patch is annular, and the centers of both circles 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 located in the center and an annular patch surrounding the circular patch; the cross slot is composed of two straight slots perpendicularly crossing the center of the circular patch, and the two straight slots respectively penetrate the circular patch and the annular patch in the diameter direction, so that the circular patch is divided into four fan-shaped patches of the same shape, and the annular patch is divided into four fan-shaped patches of the same shape; the four elliptical hollow slots are respectively arranged in the middle of the four fan-shaped 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 of the circle is connected to the circular slot slot through a slot, so that the elliptical hollow slot and the circular slot slot together form a T-slot structure, which is used to make the axial ratio resonate at high frequency to expand the high-frequency axial ratio bandwidth of the antenna;

[0011] The second metal patch has a gap corresponding to the cross-slot groove, so that the second metal patch is divided into four fan-shaped annular areas of the same shape; the second metal patch is used to maintain the low-frequency gain of the antenna and 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 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, 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 the whole is in the shape of a non-closed circular ring with an opening; the resistor is arranged in the C-shaped slot along the diameter direction, connecting the metal patches located on the inner and outer sides of the C-shaped slot, and is used to absorb standing waves on the C-shaped slot to maintain the amplitude and phase difference of orthogonal excitation, thereby providing broadband circularly polarized coupled feeding for the antenna radiator.

[0013] Furthermore, in the first metal patch, a plurality of rectangular protrusions are evenly arranged on the outer arc edge of each sector ring patch to improve the gain of the antenna.

[0014] Further, a feed connection groove is etched in the rectangular metal patch on the second dielectric plate, the feed connection groove is arranged at the outer edge of the C-shaped groove and is connected to the C-shaped groove, and a feed connection jack is provided in the feed connection groove and penetrates the second dielectric plate in the vertical direction; a feed metal branch is connected to the inner edge of the C-shaped groove, and the feed metal branch extends in the diameter direction to the side of the feed connection jack in the feed connection groove;

[0015] The upper end of the third dielectric plate is provided with an upper connecting plug plate protruding upwards, the upper connecting plug plate matches the feeding connecting jack on the second dielectric plate, and the second dielectric plate and the third dielectric plate are plugged and fixed to each other through the upper connecting plug plate and the feeding connecting jack;

[0016] The feeding structure comprises a feeding microstrip line and a grounding microstrip line respectively printed on the front and back surfaces of the third dielectric plate; the feeding microstrip line and the grounding microstrip line are arranged in parallel to each other to form a parallel double-line structure; one end of the feeding microstrip line and the grounding microstrip line are respectively electrically connected to the inner conductor and the outer conductor of the coaxial cable, and the other ends of the feeding microstrip line and the grounding microstrip line are respectively extended to the upper connecting plug plate at the upper end of the third dielectric plate; after the upper connecting plug plate passes through the second dielectric plate, 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 located on the inner side of the C-shaped groove, so as 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 located on the outer side of the C-shaped groove, so as to realize the grounding of the coplanar waveguide structure.

[0017] Furthermore, a coaxial cable jack is provided at the center of the bottom surface of the metal shielding box, the coaxial cable is introduced from the bottom of the metal shielding box, the outer conductor of the coaxial cable is welded to the metal shielding box at the coaxial cable jack, and 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 lower connecting plate protruding downward is provided at the lower end of the third dielectric plate, and a matching mounting socket is provided on the bottom surface of the metal shielding box; the third dielectric plate and the metal shielding box are plugged and fixed to each other through the lower connecting plate and the mounting socket; one end of the grounding microstrip line extends to the lower connecting plate 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.

[0019] Furthermore, a plurality of upwardly protruding grounding plugs are evenly arranged at the edge of the upper opening 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 fix the metal shielding box and the second dielectric plate at the same time.

[0020] Furthermore, the bottom surface of the metal shielding box is provided with two mounting holes, and the two mounting holes are symmetrically distributed on opposite sides of the coaxial cable hole; the lower end of the third dielectric plate is provided with two lower connecting plates, and the two lower connecting plates are respectively inserted and connected to the two mounting holes, and one end of the grounding microstrip line is divided into two paths, which are respectively distributed on the two lower connecting plates, and are both welded to the metal shielding box.

[0021] Furthermore, 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] Furthermore, the circular slot on the first metal patch is arranged within the coverage area of ​​the second metal patch.

[0023] Furthermore, in the coplanar waveguide structure, the resistor and the feeding metal branch are respectively arranged on two opposite sides of the C-shaped slot, and the distances between the resistor and the opening of the C-shaped slot are equal.

[0024] The present invention innovatively combines a coplanar waveguide structure with a patch antenna and successfully improves the axial ratio bandwidth of a single-fed circularly polarized antenna by adopting coplanar waveguide coupled feeding technology, thereby more than doubling the maximum operating bandwidth of the single-fed circularly polarized antenna, thus solving the problem that the single-fed circularly polarized antenna had a narrow bandwidth and was difficult to apply to satellite navigation in the past.

[0025] The present invention provides a single-fed broadband circularly polarized patch antenna for navigation, which has an operating frequency band of 1.11 GHz-1.84 GHz and a matching and axial ratio cross-bandwidth of 48.6%. It can fully cover multiple navigation systems such as China's Beidou satellite navigation system, the United States' GPS positioning system, Russia's GLONASS satellite navigation system, and the European Union's Galileo satellite navigation system, and has extremely high applicability and flexibility in multi-system and multi-band satellite navigation applications; it not only overcomes the limitations of 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 in the navigation frequency band is 5.14-6dBic, and has the advantages of high gain, stable directional pattern and stable gain. Compared with the traditional satellite navigation antenna, the present invention also has the advantages of less required dielectric substrates, simple installation and easy production. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

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

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

[0032] Figure 6 4 is a comparison diagram of S parameter curves of embodiments of the present invention.

[0033] Figure 7 2 is a comparison diagram of axis ratio curves of embodiments of the present invention.

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

[0035] Fig. 9 is a radiation pattern of an embodiment of the present invention.

[0036] Fig.10 1 is a comparison of radiation patterns before and after the metal shielding box is installed in the embodiment of the present invention. DETAILED DESCRIPTION

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

[0038] like Figure 1 As shown, a single-fed 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] The first dielectric plate 11 is arranged parallel to 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 arranged in the hollow metal cavity and 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 thicknesses of the first dielectric plate 11 and the third dielectric plate 13 are 1 mm, and the thickness of the second dielectric plate 12 is 1.6 mm.

[0040] The first dielectric plate 11 is printed with an antenna radiator 4, the second dielectric plate 12 is printed with a coplanar waveguide structure 5, and the third dielectric plate 13 is printed with a feeding structure 6; the coaxial cable 3 feeds 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 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 stabilize the antenna gain.

[0041] Specifically, combined Figure 2 As 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, and the second metal patch 42 is annular, and the centers of both circles are located at the center of the first dielectric plate 11;

[0042] The first metal patch 41 is etched with a circular slot 43, a cross slot 44 and four elliptical hollow slots 45; 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 located in the center and an annular patch surrounding the circular patch; the cross slot 44 is composed of two straight slots perpendicularly crossing the center of the circular patch, and the two straight slots respectively penetrate the circular patch and the annular patch in the diameter direction, so that the circular patch is divided into four fan-shaped patches of the same shape, and the annular patch is divided into four fan-shaped annular patches of the same shape. A number of rectangular bumps are evenly arranged on the outer arc edge of each fan-shaped annular patch to improve the gain of the antenna. The four elliptical hollow grooves 45 are respectively arranged in the middle of the four fan-shaped patches, and the long axis of the elliptical hollow groove 45 is arranged along the diameter direction of the first metal patch 41; one end of each elliptical hollow groove 45 close to the center of the circle is connected to the circular slot groove 43 through a slot 46, so that the elliptical hollow groove 45 and the circular slot groove 43 together form a T-slot structure, which is used to make the antenna axial ratio resonate at high frequency 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 fan-shaped ring areas of the same shape; 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 effect of the first metal patch 41. After the first metal patch 41 is divided into a circular patch located inside and a ring patch located outside 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] Combination Figure 3As shown, the coplanar waveguide structure 5 includes an annular metal ground 51 and a rectangular metal patch 52 printed on the upper surface of the second dielectric plate 12; 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 groove 53 is etched in the middle of the rectangular metal patch 52, and a resistor 54 is arranged in the C-shaped groove 53; the C-shaped groove 53 is arranged directly below the antenna radiator 4, and is in the shape of a non-closed circular ring with an opening as a whole; the resistor 54 is arranged in the C-shaped groove 53 along the diameter direction, connecting the metal patches located inside and outside the C-shaped groove 53, and is used to absorb the standing wave on the C-shaped groove 53 to maintain the amplitude and phase difference of orthogonal excitation, thereby providing broadband circularly polarized coupled 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 the two 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, 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 realize circular polarization, a certain structure is required to realize sequential phase shift. The present invention loads the resistor 54 on the C-shaped slot 53, so that the components of the electric field on the X-axis and the Y-axis maintain equal amplitudes and a 90° phase difference, thereby realizing orthogonal excitation of 90° phase difference of equivalent three feeding points on the C-shaped slot 53.

[0046] Furthermore, a feeding connection groove 55 is etched in the rectangular metal patch 52 on the second dielectric plate 12, and the feeding connection groove 55 is arranged at the outer edge of the C-shaped groove 53 and is connected to the C-shaped groove 53. A feeding connection jack 50 is provided in the feeding connection groove 55 and penetrates the second dielectric plate 12 in the vertical direction; a feeding metal branch 56 is connected to the inner edge of the C-shaped groove 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 groove 55.

[0047] Combination Figure 4 As shown, the upper end of the third dielectric plate 13 is provided with an upwardly protruding upper connecting plug plate 131, and the upper connecting plug plate 131 matches the feeding connecting jack 50 on the second dielectric plate 12, and the second dielectric plate 12 and the third dielectric plate 13 are plugged and fixed to each other through the upper connecting plug plate 131 and the feeding connecting jack 50.

[0048] Furthermore, the feeding structure 6 includes a feeding microstrip line 61 and a grounding microstrip line 62 respectively printed on the front and back surfaces of the third dielectric plate 13; the feeding microstrip line 61 and the grounding microstrip line 62 are arranged in parallel to each other to form a parallel double-line structure; one end of the feeding microstrip line 61 and the grounding microstrip line 62 are respectively electrically connected to the inner conductor and the outer conductor of the coaxial cable 3, and the other ends of the feeding microstrip line 61 and the grounding microstrip line 62 are respectively extended to the upper connecting plug plate 131 at the upper end of the third dielectric plate 13; after the upper connecting plug plate 131 passes through the second dielectric plate 12, 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 located on the inner side of the C-shaped groove 53, which is used to transmit 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 located on the outer side of the C-shaped groove 53, which is used to realize the grounding of the coplanar waveguide structure 5.

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

[0050] Combination Figure 4 and Figure 5 As shown, the lower end of the third dielectric plate 13 is provided with a downwardly protruding lower connecting plate 132, and the bottom surface of the metal shielding box 2 is provided with a matching mounting hole 23; the third dielectric plate 13 and the metal shielding box 2 are plugged and fixed to each other through the lower connecting plate 132 and the mounting hole 23; one end of the grounding microstrip line 62 extends to the lower connecting plate 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 achieving grounding.

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

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

[0053] When the embodiment of the present invention is working, 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 branch 56, it makes the electric field propagate in the counterclockwise direction together with the opening of the C-shaped slot 53, 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 circularly polarized coupled 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 stabilize the antenna gain.

[0054] In the antenna radiator 4, the cross slot 44, the elliptical hollow slot 45 and the T-slot structure are the core improvements of the present invention, which are used to achieve broadband impedance matching at low frequencies and improve the 3dB axial ratio bandwidth of the antenna at low and high frequencies. Among them, the T-slot 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 embodiments 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 no slots are set in the antenna radiator 4 under similar structure. The results show that the cross slot 44, the elliptical hollow slot 45 and the T-slot structure on the antenna radiator 4 play an important role in low-frequency impedance matching. Under the joint action of various slot structures, the antenna of the present invention achieves impedance matching in the 1.07GHz-1.95GHz frequency band, and the relative matching bandwidth is 58.27%.

[0056] Please refer to Figure 7, which is a 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 embodiment of the present invention; the dotted line is the axial ratio curve when the resistor 54 is not loaded in the C-shaped slot 53 under a similar structure. The results show that the resistor 54 used to absorb standing waves on the coplanar waveguide structure 5 greatly affects the amplitude and phase difference of the orthogonal excitation, which is crucial to 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 in the frequency band of 1.11GHz-1.84GHz is less than 3dB, and the relative axial ratio bandwidth is 48.6%, which has a wide axial ratio bandwidth.

[0057] Combination Figure 6 and Figure 7 It can be seen that the antenna of the present invention achieves impedance matching in the 1.07GHz-1.95GHz frequency band, and the relative matching bandwidth is 58.27%. At the same time, the axial ratio of the antenna of the present invention in the 1.11GHz-1.84GHz frequency band is less than 3dB, and the relative axial ratio bandwidth is 48.6%, which has a wide axial ratio bandwidth. Therefore, the present invention can comprehensively cover all relevant frequency bands of major satellite navigation systems including the B1 (1561.098 MHz), B2 (1207.140 MHz) and B3 (1268.520 MHz) frequency bands of China's Beidou satellite navigation system, the L1 (1575.42 MHz), L2 (1227.60 MHz) and L5 (1176.45 MHz) frequency bands of the U.S. GPS positioning system, the L1 (1602 MHz-1615 MHz) and L2 (1246 MHz-1256 MHz) frequency bands of the Russian GLONASS satellite navigation system, and the E1 (1575.42 MHz), E5 (1191.795 MHz), E5a (1176.45 MHz), E5b (1207.14 MHz) and E6 (1278.75 MHz) frequency bands of the European Union Galileo satellite navigation system. This wide coverage makes the antenna of the present invention extremely applicable and flexible in multi-system and multi-band satellite navigation applications.

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

[0059] Please refer to Fig. 9 , is the radiation pattern of an embodiment of the present invention. Among them, Fig. 9 (a) is the radiation pattern when the center frequency is 1.2 GHz and Phi is 0°; Fig. 9 (b) is the radiation pattern when the center frequency is 1.6 GHz and Phi is 0°; Fig. 9 (c) is the radiation pattern when the center frequency is 1.2GHz and Phi is 90°; Fig. 9 (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 Fig.10 , is a comparison of the radiation patterns before and after the metal shielding box is installed in the embodiment of the present invention. Among them, Fig.10 (a) and (c) are the radiation patterns when Phi is 0° and 90° respectively when a metal shielding box is installed; Fig.10 (b) and (d) are the radiation patterns when Phi is 0° and 90° without 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, making the rear lobe of the antenna radiation pattern smaller.

[0061] The present invention innovatively combines a coplanar waveguide structure with a patch antenna and successfully improves the axial ratio bandwidth of a single-fed circularly polarized antenna by adopting coplanar waveguide coupled feeding technology, thereby more than doubling the maximum operating bandwidth of the single-fed circularly polarized antenna, thus solving the problem that the single-fed circularly polarized antenna had a narrow bandwidth and was difficult to apply to satellite navigation in the past.

[0062] The present invention provides a single-fed broadband circularly polarized patch antenna for navigation, which has an operating frequency band of 1.11 GHz-1.84 GHz and a matching and axial ratio cross-bandwidth of 48.6%. It can fully cover multiple navigation systems such as China's Beidou satellite navigation system, the United States' GPS positioning system, Russia's GLONASS satellite navigation system, and the European Union's Galileo satellite navigation system, and has extremely high applicability and flexibility in multi-system and multi-band satellite navigation applications; it not only overcomes the limitations of 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 5.14-6dBic, and has the advantages of high gain, stable directional pattern and stable gain. Compared with the traditional satellite navigation antenna, the present invention also has the advantages of less required dielectric substrates, simple installation and easy production.

[0064] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A single-feed 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 second dielectric plate, and the two are fixedly connected by a plurality of insulating support columns; the metal shielding box is covered on the lower surface of the second dielectric plate to form a hollow metal cavity under the second dielectric plate; the third dielectric plate is arranged in the hollow metal cavity and vertically connected between the bottom surface of the metal shielding box and the second dielectric plate; The first dielectric plate is printed with an antenna radiator, the second dielectric plate is printed with a coplanar waveguide structure, and the third dielectric plate is printed with a feeding structure; the coaxial cable feeds 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 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 stabilize the antenna gain; The antenna radiator comprises 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 and the second metal patch is annular, and the centers of both circles 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 located in the center and an annular patch surrounding the circular patch; the cross slot is composed of two straight slots perpendicularly crossing the center of the circular patch, and the two straight slots respectively penetrate the circular patch and the annular patch in the diameter direction, so that the circular patch is divided into four fan-shaped patches of the same shape, and the annular patch is divided into four fan-shaped patches of the same shape; the four elliptical hollow slots are respectively arranged in the middle of the four fan-shaped 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 of the circle is connected to the circular slot slot through a slot, so that the elliptical hollow slot and the circular slot slot together form a T-slot structure, which is used to make the axial ratio resonate at high frequency to expand the high-frequency axial ratio bandwidth of the antenna; The second metal patch has a gap corresponding to the cross-slot groove, so that the second metal patch is divided into four fan-shaped annular areas of the same shape; the second metal patch is used to maintain the low-frequency gain of the antenna and 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, 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 the whole is in the shape of a non-closed circular ring with an opening; the resistor is arranged in the C-shaped slot along the diameter direction, connecting the metal patches located on the inner and outer sides of the C-shaped slot, and is used to absorb standing waves on the C-shaped slot to maintain the amplitude and phase difference of orthogonal excitation, thereby providing broadband circularly polarized coupled feeding for the antenna radiator.

2. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, characterized in that: In the first metal patch, a plurality of rectangular protrusions are evenly arranged on the outer arc edge of each sector ring patch to improve the gain of the antenna.

3. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, characterized in that: A feed connection groove is etched in the rectangular metal patch on the second dielectric plate, the feed connection groove is arranged at the outer edge of the C-shaped groove and is connected to the C-shaped groove, and a feed connection jack is arranged in the feed connection groove and passes through the second dielectric plate in the vertical direction; a feed metal branch is connected to the inner edge of the C-shaped groove, and the feed metal branch extends in the diameter direction to the side of the feed connection jack in the feed connection groove; The upper end of the third dielectric plate is provided with an upper connecting plug plate protruding upwards, the upper connecting plug plate matches the feeding connecting jack on the second dielectric plate, and the second dielectric plate and the third dielectric plate are plugged and fixed to each other through the upper connecting plug plate and the feeding connecting jack; The feeding structure comprises a feeding microstrip line and a grounding microstrip line respectively printed on the front and back surfaces of the third dielectric plate; the feeding microstrip line and the grounding microstrip line are arranged in parallel to each other to form a parallel double-line structure; one end of the feeding microstrip line and the grounding microstrip line are respectively electrically connected to the inner conductor and the outer conductor of the coaxial cable, and the other ends of the feeding microstrip line and the grounding microstrip line are respectively extended to the upper connecting plug plate at the upper end of the third dielectric plate; after the upper connecting plug plate passes through the second dielectric plate, 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 located on the inner side of the C-shaped groove, so as 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 located on the outer side of the C-shaped groove, so as 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 cable jack is provided at the center of the bottom surface of the metal shielding box, the coaxial cable is introduced from the bottom of the metal shielding box, the outer conductor of the coaxial cable is welded to the metal shielding box at the coaxial cable jack, and the inner conductor of the coaxial cable passes through the coaxial cable jack and is welded to one end of the feeding microstrip line; A lower connecting plate protruding downward is provided at the lower end of the third dielectric plate, and a matching mounting socket is provided on the bottom surface of the metal shielding box; the third dielectric plate and the metal shielding box are plugged and fixed to each other through the lower connecting plate and the mounting socket; one end of the grounding microstrip line extends to the lower connecting plate 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-feed broadband circularly polarized patch antenna for navigation according to claim 4, characterized in that: A plurality of upwardly protruding grounding plugs are evenly arranged at the edge of the upper opening 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 fix the metal shielding box to the second dielectric plate.

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

7. The single-fed broadband circularly polarized patch antenna for navigation according to claim 1, characterized in that: 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-feed broadband circularly polarized patch antenna for navigation according to claim 1, characterized in that: The circular slot on the first metal patch is arranged in the coverage area of ​​the second metal patch.

9. The single-feed broadband circularly polarized patch antenna for navigation according to claim 3, characterized in that: In the coplanar waveguide structure, the resistor and the feeding metal branch are respectively arranged on opposite sides of the C-shaped slot, and the distances between the two and the opening of the C-shaped slot 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, 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.

Images