A low profile circularly polarized end-fire antenna

Abstract

A low-profile circularly polarized end-fire antenna includes an integrated waveguide part and a microstrip metal antenna part. A metal via is arranged on the edge of the integrated waveguide part corresponding to the substrate, and a coaxial cable is arranged in the middle; the microstrip metal antenna part includes a metal microstrip line and a dipole symmetrically arranged on the upper and lower surfaces of the substrate; a radiation enhancement unit is also arranged on the outside of the dipole, and the length of the metal microstrip line is adjustable to change the phase difference of the waveform. The present invention arranges a resonant column in the integrated waveguide to effectively solve the problem of antenna resonance misalignment and impedance matching with a 50-ohm coaxial feeder; adjusts the length of the metal microstrip connecting line to achieve different circularly polarized waveforms in the end-fire direction; increases the number of parasitic radiation patches to effectively improve the antenna end-fire gain, and selects a suitable number of patches to avoid antenna resonant frequency deviation.

Description

Technical Field

[0001] The present invention relates to the field of radar, and in particular to a low-profile circularly polarized end-fire antenna with a simple structure. Background Art

[0002] In wireless communication systems, alignment errors between receivers and transmitters are difficult to avoid. If linearly polarized antennas are used as transceiver antennas, polarization mismatch between the transceiver antennas and deterioration of the received signal-to-noise ratio will occur. Circularly polarized antennas are widely used to solve the above problems due to their resistance to multipath fading and low sensitivity to antenna azimuth attitude. According to the maximum radiation direction of the antenna, circularly polarized antennas can be divided into sidefire and endfire. Since the maximum radiation direction of the endfire circularly polarized antenna is parallel to the array axis, it is more suitable for certain airborne reconnaissance equipment application scenarios. Compared with sidefire antennas, endfire antennas can deal with radar "blind spot" problems in radar systems with their unique radiation pattern characteristics.

[0003] Most circularly polarized and planar antennas radiate in the direction of the antenna's sidefire. When designing a circularly polarized endfire antenna, the above principle usually introduces a large size or a complex periodic structure. Therefore, to obtain an endfire beam, it is necessary to retain the low profile and easy-to-carry characteristics of the traditional endfire antenna while achieving a circularly polarized beam.

[0004] One solution in the prior art is to use a metal waveguide process to achieve broadband end-fire circular polarization, but this solution has a bulky structure, a high antenna profile, a high processing cost, and is difficult to integrate with a planar circuit; another solution is to use a metal floor and a substrate integrated waveguide to connect vertically to form a T-shaped 3D structure, but this solution has problems such as a high profile and is not easy to conformally install for airborne communication equipment; another solution is a focused feeding mode, for example, a dual-fed microstrip quasi-end-fire circularly polarized Yagi antenna is used to achieve orthogonal electric fields to generate circular polarization, but this solution has a complex feeding network and is naturally limited by the floor with obvious beam upwarping problems.

[0005] Therefore, how to simplify the design of circularly polarized antennas and reduce the size of the antennas while maintaining the antenna operating parameters, thereby reducing the wind resistance when installed on platforms such as drones and ships, has become a technical problem that urgently needs to be solved in existing technologies. Summary of the invention

[0006] The purpose of the present invention is to propose a simple low-profile circularly polarized end-fire antenna, which gets rid of the problems of multiple feeding ports and high complexity of the feeding network in the traditional circularly polarized antenna design, and has the advantages of high gain, low profile, light weight, wide beam, etc. It is suitable for conformal installation on attitude jitter platforms such as drones, and the antenna gain can be improved by simply increasing the number of arrays.

[0007] To achieve this object, the present invention adopts the following technical solutions:

[0008] A low-profile circularly polarized end-fire antenna comprises a substrate on which an integrated waveguide portion and a microstrip metal antenna portion are formed,

[0009] wherein the integrated waveguide portion is at one end of the substrate, and the microstrip metal antenna portion is at the other end of the substrate, and both extend in the lateral direction of the substrate;

[0010] The substrate is provided with an upper metal surface and a lower metal bottom surface on the upper and lower surfaces of the integrated waveguide part, that is, a metal surface part is formed, a metal via is provided on the edge of the integrated waveguide part corresponding to the substrate, and a coaxial cable is provided in the middle;

[0011] The microstrip metal antenna part includes a metal microstrip line and a dipole symmetrically arranged on the upper and lower surfaces of the substrate;

[0012] One end of the metal microstrip line is connected to the metal surface portion, and the other end is connected to the dipole.

[0013] The microstrip metal antenna part is further provided with a radiation enhancement unit on the outside of the dipole, that is, in the radiation direction, and the radiation enhancement unit is a dipole parasitic radiation patch;

[0014] The length of the metal microstrip line is adjustable, specifically, it is extended to both sides during the connection, so as to adjust the length of the microstrip transmission line to change the phase difference of the waveform.

[0015] Optionally, the dipole is connected to the center of the integrated waveguide part through a metal microstrip line, and extends to both sides perpendicular to the extension direction of the connection line during the connection to form a bent structure, thereby adjusting the length of the metal microstrip line.

[0016] Optionally, the waveform phase difference is adjusted by setting the length of the microstrip transmission line to generate a 270° or 90° phase difference in free space, ultimately forming an end-fired right-handed or left-handed circularly polarized waveform in the far field.

[0017] Optionally, the total length of the metal microstrip line is 30.3 mm, and a right-hand circularly polarized wave is realized in the end-fire reverse direction, or the total length of the metal microstrip line is 17.1 mm, and a right-hand circularly polarized wave is realized in the end-fire reverse direction.

[0018] Optionally, the metal vias are provided on the edge of the integrated waveguide portion corresponding to the substrate: the metal vias include two rows of transverse metal vias and one row of longitudinal metal vias on the substrate.

[0019] Optionally, the coaxial cable of the integrated waveguide part is a 50-ohm coaxial line feeder, and two metal resonant columns that are laterally symmetrical along the substrate are arranged in the substrate integrated waveguide.

[0020] Optionally, the number of the radiation patches is 2-5, which are arranged in parallel with the dipole and spaced apart, and are located on one or both sides of the bottom and the top of the substrate.

[0021] Optionally, there are two radiation patches, which are located on the top of the substrate.

[0022] Optionally, the substrate is made of a microwave composite medium with a thickness of h 2mm, dielectric constant ε=2.6, lateral length L 25mm, vertical length W The lateral length of the integrated waveguide is 33 mm. =11.5mm, longitudinal length is 33mm;

[0023] The distance between the coaxial cable and the longitudinal edge of the substrate d f 3.2 mm, centered in the longitudinal direction;

[0024] The distance between the metal resonant column and the lateral edge of the substrate W side 7.5mm, the distance from the longitudinal edge of the substrate L side It is 15mm.

[0025] Optionally, the dipole extends in the longitudinal direction of the substrate W p 10mm, the width of the substrate in the horizontal direction L p =0.5mm;

[0026] The lengths of the two radiation patches in the longitudinal direction of the substrate are W p1 、W p2 12mm, 6mm, the horizontal width of the substrate L p1 、 L p2 is 0.5 mm, and the spacing between the two radiation patches and the dipole is equal, that is, the axial distance L d1 、L d2 is 2mm.

[0027] The present invention has the following advantages:

[0028] 1. In terms of antenna feeding, by setting a resonant column in the integrated waveguide, the problem of antenna resonance misalignment and impedance matching with the 50 ohm coaxial feeder is effectively solved;

[0029] 2. By adjusting the length of the metal microstrip connection line between the substrate integrated waveguide and the printed dipole, different circularly polarized waveforms can be achieved in the end-fire direction;

[0030] 3. In terms of antenna gain, the antenna end-fire gain can be effectively improved by increasing the number of parasitic radiation patches, and the appropriate number of patches can be selected to avoid antenna resonant frequency deviation. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a three-dimensional view of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0032] Figure 2 is a physical processing diagram of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0033] Figure 3 is a top view of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0034] Figure 4 is a bottom view of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0035] Figure 5 is a dimensional diagram of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0036] Figure 6 is a schematic diagram of a radiation patch of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0037] Figure 7 is a relationship diagram between the number of radiating patches and gain of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0038] Figure 8 1 is a schematic diagram of antenna return loss measurement and simulation of a circularly polarized end-fire antenna according to a specific embodiment of the present invention;

[0039] Fig. 9 is a schematic diagram of comparison between measurement and simulation of the axial ratio of the circularly polarized end-fire antenna in the end-fire direction according to a specific embodiment of the present invention;

[0040] Fig.10 It is a schematic diagram of measurement and simulation of a 3dB axial ratio beam of a circularly polarized end-fire antenna in the azimuth plane according to a specific embodiment of the present invention;

[0041] Fig.11 It is a schematic diagram of measurement and simulation of a 3dB axial ratio beam of a circularly polarized end-fire antenna in a pitch plane according to a specific embodiment of the present invention;

[0042] Fig.12 is a radiation pattern of a circularly polarized end-fire antenna in an azimuth plane of 7 GHz according to a specific embodiment of the present invention;

[0043] Fig.13 3 is the radiation pattern of the circularly polarized end-fire antenna in the elevation plane at 7 GHz according to a specific embodiment of the present invention.

[0044] The technical features indicated by the reference numerals in the figure are:

[0045] 1. Integrated waveguide part; 2. Metal via; 3. Coaxial cable; 4. Resonant column; 5. Metal microstrip line; 6. Substrate; 7. Dipole; 8. Radiation enhancement unit. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0047] In the present invention, the lateral direction of the substrate refers to the direction extending from the integrated waveguide part to the microstrip metal antenna part, that is, Figure 1 in the Y direction.

[0048] The longitudinal direction of the substrate refers to the direction perpendicular to the extension direction of the integrated waveguide part to the microstrip metal antenna part, that is, Figure 1 The X direction in .

[0049] The present invention mainly comprises: a substrate integrated waveguide is superimposed with a dipole patch to construct a substrate integrated waveguide structure SIW, a feeding port is connected to the substrate integrated waveguide from top to bottom through a coaxial line to feed the antenna, and a resonant column is arranged in the integrated waveguide to solve the antenna resonance misalignment and impedance matching with a 50-ohm coaxial feed line; the length of the microstrip connecting line is adjustable, so as to realize different circular polarization waveforms in the end-fire direction; a dipole parasitic radiation patch is arranged in the radiation direction of the dipole, and the number of the radiation patches is adjusted to improve the gain of the antenna of the present invention and reduce the antenna resonance frequency offset.

[0050] See also Figure 1-Figure 5 , shows a schematic diagram of a circularly polarized end-fire antenna according to a specific embodiment of the present invention, and a physical processing diagram.

[0051] A low-profile circularly polarized end-fire antenna comprises a substrate 6 on which an integrated waveguide portion 1 and a microstrip metal antenna portion are formed.

[0052] The integrated waveguide part 1 is at one end of the substrate 6, and the microstrip metal antenna part is at the other end of the substrate 6, and both extend in the lateral direction of the substrate 6;

[0053] The substrate 6 is provided with an upper metal surface and a lower metal bottom surface on the upper and lower surfaces of the integrated waveguide part, that is, a metal surface part is formed, a metal via 2 is provided on the edge of the integrated waveguide part corresponding to the substrate 6, and a coaxial cable 3 is provided in the middle;

[0054] The microstrip metal antenna part includes a metal microstrip line 5 and a dipole 7 symmetrically arranged on the upper and lower surfaces of a substrate 6;

[0055] One end of the metal microstrip line 5 is connected to the metal surface portion, and the other end is connected to the dipole 7.

[0056] The microstrip metal antenna part is further provided with a radiation enhancement unit 8 on the outside of the dipole 7, i.e. in the radiation direction. The radiation enhancement unit 8 is a dipole parasitic radiation patch to enhance the far-field radiation gain. In an optional embodiment, the radiation patch is made of copper clad.

[0057] The length of the metal microstrip line 5 is adjustable, specifically, it is extended to both sides during the connection, so as to adjust the length of the microstrip transmission line to change the phase difference of the waveform.

[0058] Therefore, in the present invention, the integrated waveguide part generates a vertically polarized wave, and the microstrip metal antenna part generates a horizontally polarized wave. The two are superimposed on each other in the end-fire direction (y-axis). Under the condition of ensuring that the amplitudes of the two are the same, the waveform phase difference is adjusted by setting the length of the microstrip transmission line, thereby generating a 270° or 90° phase difference in free space, and finally forming an end-fire right-handed or left-handed circularly polarized waveform in the far field.

[0059] Specifically, the dipole 7 is connected to the center of the integrated waveguide part through the metal microstrip line 5, symmetrically along the y-axis, and extends up and down along the x-axis during the connection, that is, extends to both sides perpendicular to the extension direction of the connecting line, forming a bent structure, thereby adjusting the length of the metal microstrip line 5.

[0060] In a specific embodiment, the metal microstrip line 5 is led out from the integrated waveguide and has a width of Wm = 0.2mm, and extends upward and downward once in the longitudinal direction, so its total length includes the total transverse length and the total longitudinal length. Its total transverse length is Lm+Lg +2 Wm +gg=0.5+3.8+2*0.5+0.2=5.5mm, the total longitudinal length is W =6.2mm, the total longitudinal length is 4 W=4*6.2mm=24.8mm. At this time, the total length of the metal microstrip line 5 is 30.3mm. At this time, the phase difference between the integrated waveguide part and the microstrip metal antenna part in the far field is 270°, and the right-hand circular polarization wave can be realized in the end-fire reverse direction; when W =2.9mm, the total longitudinal length is 4 W =4*2.9mm=11.6mm, the total length of the metal microstrip line 5 is 17.1mm, at this time, the phase difference between the waveforms of the integrated waveguide part and the microstrip metal antenna part in the far field is 90°, and right-hand circularly polarized waves can be realized in the end-fire reverse direction.

[0061] In this embodiment, the metal microstrip line 5 only extends upward and downward once in the longitudinal direction, but the present invention is not limited to this. It can be bent up and down multiple times, so as to change the length of the metal microstrip line 5 without changing the position of the dipole 7, so as to maintain the overall size of the end-fire antenna or reduce the size of the end-fire antenna as much as possible.

[0062] Specifically, the metal vias 2 are provided on the edge of the integrated waveguide portion corresponding to the substrate 6 : the metal vias 2 include two rows of transverse metal vias and one row of longitudinal metal vias on the substrate 6 .

[0063] The coaxial cable 3 of the integrated waveguide part 1 is fed by a 50-ohm coaxial line. Therefore, the connection between the coaxial line probe and the substrate integrated waveguide will introduce an inductive impedance component, which will lead to mismatching of the antenna impedance and fail to effectively radiate energy at the designed frequency. The present invention sets two metal resonant columns 4 that are symmetrical along the y-axis, i.e., the substrate 6, in the substrate integrated waveguide, thereby introducing capacitive impedance to tune the antenna impedance.

[0064] In a specific embodiment, the material of the substrate 6 is a microwave composite medium with a thickness of h 2mm, dielectric constant ε=2.6, lateral length L 25mm, vertical length W 33mm, the lateral length of the integrated waveguide part, that is, the metal surface part =11.5mm, the longitudinal length is 33mm, the metal via 2 is on the side of the metal surface part of the substrate 6, the diameter R The spacing of metal vias 2 is 1 mm. s The distance between the coaxial cable 3 and the longitudinal edge of the substrate 6 is 1.5 mm. d f It is 3.2mm and is centered in the longitudinal direction.

[0065] The distance between the metal resonant column 4 and the lateral edge of the substrate 6 is W side 7.5 mm, the distance from the longitudinal edge of the substrate 6L side It is 15mm.

[0066] The radiation patch is located on one or both of the bottom and the top of the substrate, preferably located on the top of the substrate.

[0067] See also Figure 6 , Figure 7 The number of the radiation patches is 2-5, which are arranged in parallel with the dipole 7 and spaced apart. Arranging multiple radiation patches can improve the gain of the antenna of the present invention, and by increasing the number of the directing arrays, the energy concentration in the end-fire direction is improved, thereby improving the antenna gain.

[0068] However, as the number of radiating patches increases, the equivalent size of the antenna increases, causing the antenna resonant frequency to shift and drop below 7 GHz. For example, when the number of patches N=5, it can reach 4.8 dB, but frequency deviation will occur. In order to ensure that the radiation pattern does not shift, the number of radiating patches is preferably 2. At this time, the antenna gain effect is the best, the gain can reach 4.7 dB and avoid antenna frequency deviation.

[0069] In a specific embodiment, the extension length of the dipole 7 in the longitudinal direction (x-axis direction) is W p The width in the horizontal direction (y-axis direction) is 10 mm. L p = 0.5mm; the lengths of the radiation patch in the longitudinal direction (x-axis direction) are W p1 、W p2 12mm, 6mm, in the horizontal (y-axis direction) width L p1 、L p2 is 0.5mm, and the spacing between multiple radiation patches and dipoles is equal, that is, the axial distance L d1 、L d2 The antenna gain is 4.7dB, and the 3dB axial ratio bandwidth covers 6.74~7.32GHz.

[0070] In the present invention, the metal is mainly copper-clad, but is not limited thereto and may also be other commonly used materials in metal substrates and manufactured using a common process.

[0071] See also Figure 8-Figure 13 The antenna impedance bandwidth of the present invention is 6.73 GHz to 7.32 GHz ( Figure 8 ), 3dB axial ratio bandwidth covers 6.71~7.33GHz and the relative bandwidth is 8.86% ( Fig. 9), the beam width in the elevation plane exceeds 160°, and the 3dB axis ratio beam width in the azimuth plane exceeds 130° ( Fig.10 , 11 ), the gain can reach 4.7dB. The beam width of the antenna with 3dB gain can reach 70° and 160° in azimuth and elevation planes ( Fig.12 , Fig.13 ). Through theoretical analysis, parameter simulation and comparison with actual measurement, the antenna designed in the present invention realizes the circular polarization function under end-fire conditions, and has a wider beam.

[0072] The present invention has the following advantages:

[0073] 1. In terms of antenna feeding, by setting a resonant column in the integrated waveguide, the problem of antenna resonance misalignment and impedance matching with the 50 ohm coaxial feeder is effectively solved;

[0074] 2. By adjusting the length of the microstrip connection line between the substrate integrated waveguide and the printed dipole, different circularly polarized waveforms can be achieved in the end-fire direction;

[0075] 3. In terms of antenna gain, the antenna end-fire gain can be effectively improved by increasing the number of parasitic radiation patches, and selecting the appropriate number of patches can avoid antenna resonant frequency deviation.

[0076] Therefore, the present invention uses the combination of printed dipole + substrate integrated waveguide antennas to design a circularly polarized end-fire microstrip antenna that works in the C band, has a gain of 4.7dB, and a beam width of more than 120°. The antenna has the advantages of low profile, light weight, and wide beam, and is suitable for conformal installation on attitude jitter platforms such as drones. It gets rid of the problems of multiple feeding ports and high complexity of the feeding network in traditional circularly polarized antenna designs. For attitude jitter platforms such as drones and ships, it also has the advantages of small caliber size and low wind resistance (thickness is only 2mm), and the antenna gain can be improved by simply increasing the number of arrays.

[0077] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention determined by the submitted claims.

Claims

1. A low-profile circularly polarized end-fire antenna, characterized in that: comprising a substrate on which an integrated waveguide portion and a microstrip metal antenna portion are formed, wherein the integrated waveguide portion is at one end of the substrate, and the microstrip metal antenna portion is at the other end of the substrate, and both extend in the lateral direction of the substrate; The substrate is provided with an upper metal surface and a lower metal bottom surface on the upper and lower surfaces of the integrated waveguide part, that is, a metal surface part is formed, a metal via is provided on the edge of the integrated waveguide part corresponding to the substrate, and a coaxial cable is provided in the middle; The microstrip metal antenna part includes a metal microstrip line and a dipole symmetrically arranged on the upper and lower surfaces of the substrate; One end of the metal microstrip line is connected to the metal surface portion, and the other end is connected to the dipole. The microstrip metal antenna part is further provided with a radiation enhancement unit on the outside of the dipole, that is, in the radiation direction, and the radiation enhancement unit is a dipole parasitic radiation patch; The length of the metal microstrip line is adjustable, specifically, it is extended to both sides during the connection, thereby adjusting the length of the microstrip transmission line to change the phase difference of the waveform; The dipole is connected to the center of the integrated waveguide part through a metal microstrip line, and extends to both sides perpendicular to the extension direction of the connection line during the connection to form a bent structure, thereby adjusting the length of the metal microstrip line; The waveform phase difference is adjusted by setting the length of the microstrip transmission line, generating a 270° or 90° phase difference in free space, and ultimately forming an end-fire right-handed or left-handed circularly polarized waveform in the far field; The coaxial cable of the integrated waveguide part is fed by a 50-ohm coaxial line, and two metal resonant columns are arranged in the substrate integrated waveguide and are symmetrical along the substrate. The distance W between each of the metal resonant columns and the lateral edge of the substrate is side The distance L from the longitudinal edge of the substrate is 7.5 mm. side 15mm to solve the problem of antenna resonance detuning and impedance matching with 50 ohm coaxial feed line; The radiation patches are 2 to 5 pieces, which are arranged in parallel with the dipoles and spaced apart, and are located on one or both sides of the bottom and the top of the substrate.

2. The circularly polarized end-fire antenna according to claim 1, characterized in that: The total length of the metal microstrip line is 30.3 mm, and a right-hand circularly polarized wave is realized in the end-fire direction, or the total length of the metal microstrip line is 17.1 mm, and a left-hand circularly polarized wave is realized in the end-fire direction.

3. The circularly polarized end-fire antenna according to claim 1, characterized in that: The metal vias are arranged on the edge of the integrated waveguide portion corresponding to the substrate: the metal vias include two rows of transverse metal vias and one row of longitudinal metal vias on the substrate.

4. The circularly polarized end-fire antenna according to claim 1, characterized in that: There are two radiation patches, which are located on the top of the substrate.

5. The circularly polarized end-fire antenna according to claim 1, characterized in that: The substrate is made of microwave composite dielectric with a thickness h of 2 mm, a dielectric constant ε=2.6, a lateral length L of 25 mm, a longitudinal length W of 33 mm, and a lateral length L of the integrated waveguide part. l =11.5mm, longitudinal length is 33mm; The distance d between the coaxial cable and the longitudinal edge of the substrate f It is 3.2mm and is centered in the longitudinal direction.

6. The circularly polarized end-fire antenna according to claim 4, characterized in that: The dipole's extension length W in the longitudinal direction of the substrate p The width L of the substrate is 10 mm. p =0.5mm; The lengths of the two radiation patches in the longitudinal direction of the substrate are W p1 , W p2 12mm, 6mm, the lateral width L of the substrate p1 , L p2 is 0.5 mm, and the spacing between the two radiation patches and the dipole is equal, that is, the axial distance L d1 , L d2 is 2mm.

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