Ka-band low-profile broadband circularly polarized wide-angle scanning antenna

Abstract

The application provides a Ka-band low-profile wideband circularly polarized wide-angle scanning antenna, which comprises an open metal ring, a first dielectric layer loaded with air cavities, a bonding layer, a circularly polarized radiation unit, a second dielectric layer, a feeding probe and a metal ground; the open metal ring is composed of a circular slot with a center circle dug out and has two symmetrical rectangular notches opened along the axial direction; the first dielectric layer loaded with air cavities contains three sizes of air cavities, and the open metal ring and the first dielectric layer jointly widen the working bandwidth of the antenna; the circularly polarized radiation unit is a circular microstrip patch with an etched C-shaped slot, and the phase difference of degenerate modes is adjusted to realize circularly polarized radiation by controlling the opening angle of the C-shaped slot and the size of the two side rectangular perturbation patches; the feeding point of the antenna unit is located at the geometric center position, the axial ratio bandwidth of the antenna is improved by suppressing cross polarization, and the wide-angle circularly polarized scanning capability is improved jointly with the open metal ring.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of antennas, in particular to a Ka-band low-profile wideband circularly polarized wide-angle scanning antenna. BACKGROUND

[0002] The wide-angle circularly polarized scanning antenna has important significance in the fields of satellite navigation and positioning, satellite communication, radar and electronic countermeasure, etc. In the implementation form of the circularly polarized antenna, the microstrip antenna and the cross-dipole antenna are the most commonly used two antenna forms. The cross-dipole antenna has high performance, but the antenna longitudinal size is large. Compared with the cross-dipole antenna, the longitudinal size of the microstrip array antenna is small, so the research on the low-profile microstrip array antenna has important significance for the development of the communication system.

[0003] In recent years, researchers have never stopped researching the low-profile wideband circularly polarized wide-angle scanning array antenna. For example, microstrip patch antennas, spiral antennas and planar cross-dipole antennas. The spiral antenna has a wide operating frequency band, but the unit gain is low. The planar cross-dipole antenna has excellent circularly polarized performance, but the antenna profile is high, which is not conducive to the integration of the phased array field. The traditional single-layer microstrip patch antenna has a narrow operating frequency band, and the relative bandwidth of the antenna is usually about 7%. At the same time, when scanning to 60°, the axial ratio is greater than 5dB. Scholars have also proposed some methods to widen the antenna bandwidth and improve the circularly polarized scanning, such as using stacked antennas to increase the resonance point, super surface technology and increasing the air layer, etc. However, at the Ka frequency band, due to the short wavelength, these methods increase the difficulty of antenna processing, and the profile of the antenna is increased, which is not conducive to the system integration. SUMMARY

[0004] The purpose of the application is to provide a Ka-band low-profile wideband circularly polarized wide-angle scanning antenna, which has the characteristics of wide bandwidth and excellent wide-angle scanning circularly polarized performance, can be used in large space communication and system integration field, and has strong practicability and application prospect.

[0005] In order to achieve the above purpose, the application realizes the following technical scheme:

[0006] A Ka-band low-profile wideband circularly polarized wide-angle scanning antenna, comprising an open metal ring, a first dielectric layer loaded with an air cavity, an adhesive layer, a circularly polarized radiation unit, a second dielectric layer, a feed probe and a metal ground;

[0007] The open metal ring is located on the upper surface of the first dielectric layer, the lower surface of the first dielectric layer is connected to the upper surface of the second dielectric layer through the adhesive layer, the circularly polarized radiation unit is further arranged between the upper surface of the second dielectric layer and the adhesive layer, the lower surface of the second dielectric layer is connected to the metal ground, and the feed probe is connected to the feed point of the circularly polarized radiation unit.

[0008] The open metal ring is provided with a circular patch slot in the middle region and two symmetrical rectangular notches in the edge along the diameter direction;

[0009] The first dielectric layer is provided with three specifications of air cavities;

[0010] The circular polarization radiation unit is a circular microstrip patch with a middle-etched C-shaped slot and is provided with two symmetrical rectangular perturbation patches along the diameter direction.

[0011] Optionally, the diameter of the circular patch slot in the middle region of the open metal ring is greater than 2.0 times the thickness of the first dielectric layer.

[0012] Optionally, the length and width of the two rectangular notches in the edge of the open metal ring along the diameter direction are both less than λ0 / 10, wherein λ0 is the free space wavelength corresponding to the working center frequency.

[0013] Optionally, the three specifications of air cavities provided by the first dielectric layer are respectively: eight first air cavities with the same radius located around, a second air cavity formed in the middle region of the upper surface and a third air cavity formed in the middle region of the lower surface.

[0014] Optionally, the diameter of the second air cavity is the same as that of the circular patch slot in the middle region of the open metal ring.

[0015] Optionally, the diameter ratio of the second air cavity to the third air cavity is 1:1.5.

[0016] Optionally, in the circular polarization radiation unit, the opening direction of the C-shaped slot is rotated by 45° relative to the rectangular perturbation patch.

[0017] Optionally, the feed point of the circular polarization radiation unit is located at the geometric center of the antenna unit.

[0018] Optionally, the relative impedance bandwidth of the circular polarization radiation unit is 20%, and the circular polarization axial ratio is less than 3dB during the scanning process of the antenna beam from 0° to 60°.

[0019] Optionally, the profile height of the antenna is less than 0.08λ0, and λ0 is the free space wavelength corresponding to the working center frequency.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] The open metal ring is composed of a circular groove with a center circle dug out and two symmetrical rectangular notches opened in the axial direction, and the open metal ring is isotropic to electromagnetic waves incident in each direction, ensuring that the antenna beam scanning to a large angle has good circular polarization axial ratio characteristics; the first dielectric layer loaded with air cavities contains three sizes of air cavities, and the open metal ring and the first dielectric layer jointly widen the antenna operating bandwidth; the circularly polarized radiation unit is a circular microstrip patch with a C-shaped groove, and the phase difference of degenerate modes is adjusted by controlling the opening angle of the C-shaped groove and the size of the two side rectangular perturbation patches to realize circularly polarized radiation, and the feed point of the antenna unit is located at the geometric center position, and the cross-polarization is suppressed to improve the axial ratio bandwidth of the antenna, and the open metal ring and the first dielectric layer jointly improve the large-angle circularly polarized scanning capability. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the description will be briefly introduced as follows. Obviously, the drawings in the following description are one embodiment of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings:

[0023] Figure 1 The antenna unit appearance schematic diagram of the present application is shown in the figure;

[0024] Figure 2 The antenna unit structure composition diagram of the present application is shown in the figure;

[0025] Figure 3 The open metal ring schematic diagram of the present application is shown in the figure;

[0026] Figure 4 The first dielectric layer loaded with air cavities of the present application is shown in the figure;

[0027] Figure 5 The circularly polarized radiation unit schematic diagram of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] The scheme proposed by the present application will be further described in detail in combination with the drawings and specific embodiments. According to the following description, the advantages and characteristics of the present application will be more clear. It should be noted that the drawings are greatly simplified and all use non-precise proportions, only to facilitate and clearly assist the purpose of explaining the embodiments of the present application.

[0029] Please refer to Figures 1 to 5 The present application provides a Ka-band low-profile wideband circularly polarized large-angle scanning antenna, which comprises an open metal ring 1, a first dielectric layer 2 loaded with air cavities, an adhesive layer 3, a circularly polarized radiation unit 4, a second dielectric layer 5, a feed probe 6 and a metal ground 7.

[0030] The open metal ring 1 is located on the upper surface of the first dielectric layer 2, the lower surface of the first dielectric layer 2 is connected with the upper surface of the second dielectric layer 5 through the adhesive layer 3, the circular polarization radiation unit 4 is further arranged between the upper surface of the second dielectric layer 5 and the adhesive layer 3, and the lower surface of the second dielectric layer 5 is connected with the metal ground 7, and the feeding probe 6 is connected with the feeding point 15 of the circular polarization radiation unit;

[0031] The open metal ring 1 is provided with a circular patch slot 16 in the middle region, and two symmetrical rectangular notches 8 are arranged in the edge along the diameter direction, the open metal ring 1 is isotropic to the electromagnetic waves incident in each direction, and the antenna beam scanning to a large angle has good circular polarization axial ratio characteristics, the first dielectric layer 2 is provided with three specifications of air cavities, and the open metal ring 1 and the first dielectric layer 2 jointly widen the antenna working bandwidth, the circular polarization radiation unit 4 is a circular microstrip patch 13 with a middle etched C-shaped slot 12, and two symmetrical rectangular perturbation patches 14 are arranged along the diameter direction, and the antenna feeding impedance matching is realized by etching the C-shaped slot 12 to change the patch surface current distribution. By controlling the opening angle of the C-shaped slot 12 and the size of the two rectangular perturbation patches 14 on the sides, the phase difference of the degenerate mode can be adjusted to realize circular polarization radiation.

[0032] In the embodiment, as shown in Figure 3 The diameter of the circular patch slot 16 in the middle region of the open metal ring 1 is greater than 2.0 times the height of the first dielectric layer, which facilitates the welding of the feeding point later. The length and width of the two rectangular notches 8 in the edge along the diameter direction are both less than λ0 / 10, where λ0 is the free space wavelength corresponding to the working center frequency point.

[0033] As shown in Figure 4 The three specifications of air cavities provided by the first dielectric layer 2 are respectively: eight first air cavities 9 with the same radius located around, a second air cavity 10 formed in the middle region of the upper surface, and a third air cavity 11 formed in the middle region of the lower surface. The diameter of the second air cavity 10 is the same as the diameter of the circular patch slot 16 in the middle region of the open metal ring 1, and the diameter ratio of the second air cavity 10 to the third air cavity 11 is 1:1.5. By loading the air cavities, the equivalent dielectric constant of the first dielectric layer 2 is reduced, and the working bandwidth of the antenna unit is increased.

[0034] As shown in Figure 5 The feeding point 15 of the circular polarization radiation unit 4 is located at the geometric center of each antenna unit, the axial ratio bandwidth of the antenna is improved by suppressing cross-polarization, and the large-angle circular polarization scanning capability is improved by cooperating with the open metal ring 1. The opening direction of the C-shaped slot 12 is rotated by 45° relative to the rectangular perturbation patch 14, and the interaction between the two changes the phase difference between the antenna orthogonal modes TM10 mode and TM01 mode to realize circular polarization radiation.

[0035] The Ka-band low-profile wideband circularly polarized large-angle scanning antenna in the application has a profile height less than 0.08λ0, and λ0 is the free space wavelength corresponding to a working center frequency point, and an air cavity is reserved in the middle part to facilitate welding of a later feeding point, and the design method effectively reduces the processing difficulty of the antenna.

[0036] The Ka-band low-profile wideband circularly polarized large-angle scanning antenna in the application has a relative impedance bandwidth of the circularly polarized radiation unit greater than 20%, and the circularly polarized axial ratio is less than 3dB during 0° to 60° scanning of an antenna beam.

[0037] The working principle of the antenna is as follows:

[0038] An electromagnetic wave signal is fed in through a center feeding point of the antenna, and according to the microstrip antenna theory, the surface current of the microstrip patch antenna is in a sinusoidal distribution, so the surface current wave peak of the microstrip patch is located at the geometric center thereof, and at this time, the input impedance of the feeding point is close to a short circuit state. Since the port impedance of the coaxial feeding is 50Ω, impedance matching cannot be achieved between the two. In the application, a C-shaped groove 12 is etched at the center position of the antenna, and the C-shaped groove 12 effectively changes the radial current distribution of the microstrip patch 13, so that the geometric center point of the microstrip patch 13 is no longer at the surface current wave peak, and the input impedance is also no longer zero. By adjusting the size of the C-shaped groove 12, impedance matching is achieved between the antenna and the coaxial feeding.

[0039] There is a certain structural discontinuity at the contact point of the coaxial probe and the microstrip patch, and when the feeding point deviates from the geometric center of the microstrip patch, the structural discontinuity causes the cross-polarization of the electromagnetic wave radiated by the microstrip patch to increase, and the size of the cross-polarization is proportional to the distance of the structural discontinuity point from the geometric center point. Therefore, the center feeding is adopted in the application, and the advantage is that the influence of the structural discontinuity from the feeding point 15 on the radiation performance of the microstrip patch 13 is reduced to a minimum. The microstrip patch 13 is loaded with two rectangular perturbation patches 14 along the diameter direction, and the two rectangular perturbation patches 14 play a field perturbation role. When the opening direction of the C-shaped groove 12 is rotated by 45° relative to the rectangular perturbation patch 14, the interaction between the two causes the phase difference between the TM10 mode and the TM01 mode of the antenna to be 90°, and finally circularly polarized radiation is achieved.

[0040] According to the transmission line theory, the circularly polarized radiation unit 4 and the second dielectric layer 5 in the present antenna unit are equivalent to impedance R1, and the open metal ring 1 and the first dielectric layer 2 are equivalent to impedance R T The equivalent dielectric constant of the microstrip plate can be adjusted by adjusting the size of the air cavity, so R T is adjustable. Since the feeding port impedance is 50Ω and the free space wave impedance is 377Ω, R TThe impedance matching of the whole antenna is improved, and the working bandwidth of the antenna is widened. Meanwhile, the open metal ring 1 is isotropic to electromagnetic waves incident in all directions, so that the antenna has good circular polarization axial ratio characteristics when the beam is scanned to a large angle.

[0041] Although the present application has been described in detail by the preferred embodiments, it should be appreciated that the above description should not be considered to limit the present application. Various modifications and substitutions will be apparent to those skilled in the art after reading the above description. Therefore, the scope of the present application should be defined by the appended claims.

Claims

1. A Ka-band low-profile broadband circularly polarized large-angle scanning antenna, characterized in that, It includes an open metal ring, a first dielectric layer of a loaded air cavity, an adhesive layer, a circularly polarized radiation unit, a second dielectric layer, a feed probe, and a metal ground; The open metal ring is located on the upper surface of the first dielectric layer. The lower surface of the first dielectric layer is connected to the upper surface of the second dielectric layer through the adhesive layer. The circularly polarized radiation unit is also provided between the upper surface of the second dielectric layer and the adhesive layer. The lower surface of the second dielectric layer is connected to the metal ground. The feed probe is connected to the feed point of the circularly polarized radiation unit. The open metal ring has a circular patch groove in the middle area and two symmetrical rectangular notches along the diameter direction at the edge. The first dielectric layer has three types of air cavities: eight first air cavities with the same radius around the perimeter, a second air cavity formed in the middle area of ​​the upper surface, and a third air cavity formed in the middle area of ​​the lower surface. The diameter of the second air cavity is the same as the diameter of the circular patch groove in the middle area of ​​the open metal ring. The diameter ratio of the second air cavity to the third air cavity is 1:1.

5. The eight first air cavities with the same radius are located at the four corners of the first dielectric layer, with four located at the four corners of the upper surface and the other four located at the four corners of the lower surface. The circularly polarized radiation unit is a circular microstrip patch with a C-shaped groove etched in the center, and two symmetrical rectangular micro-perturbation patches are provided along the diameter direction.

2. The Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, The diameter of the circular patch groove in the middle region of the open metal ring is greater than 2.0 times the thickness of the first dielectric layer.

3. The Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, The length and width of the two rectangular notches along the diameter direction at the edge of the open metal ring are both less than [a certain value]. λ 0 / 10, of which λ 0 represents the free-space wavelength corresponding to the operating center frequency.

4. The Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, In the circularly polarized radiation unit, the opening direction of the C-shaped groove is rotated by 45° relative to the rectangular perturbation patch.

5. The Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, The feed point of the circularly polarized radiating element is located at the geometric center of the antenna element.

6. The Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, The circularly polarized radiating element has a relative impedance bandwidth of 20%, and the circular polarization axial ratio is less than 3dB during the antenna beam scanning process from 0° to 60°.

7. A Ka-band low-profile broadband circularly polarized large-angle scanning antenna according to claim 1, characterized in that, The antenna's profile height is less than 0.08λ0, where λ0 is the free-space wavelength corresponding to the operating center frequency.

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