X-band broadband wide-beam circularly polarized conformal microstrip antenna

Abstract

The invention belongs to the technical field of wireless communication, and particularly relates to an X-band broadband wide-beam circularly polarized conformal microstrip antenna. According to the technical scheme, the X-band broadband wide-beam circularly-polarized conformal microstrip antenna comprises a first-layer dielectric substrate and a second-layer dielectric substrate, an antenna pattern and four perturbation metal patterns located around the antenna pattern are printed on the first-layer dielectric substrate, and four perturbation metal patterns are also printed on the second-layer dielectric substrate; and short-circuit probes are loaded on the four perturbation metal patterns on the first layer of dielectric substrate. The invention provides an X-band broadband wide-beam circularly polarized conformal microstrip antenna, which realizes an X-band circularly polarized radiation characteristic and a broadband wide-beam characteristic.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless communications, and in particular relates to an X-band wide bandwidth beam circularly polarized conformal microstrip antenna. Background Art

[0002] In recent years, the demand for carrier conformal antennas has been increasing day by day. Microstrip antennas are widely used due to their small size, low profile and easy conformity with carriers, but microstrip antennas generally have the characteristics of narrow bandwidth. For communications between carriers and between carriers and satellites, circularly polarized antennas are mostly used, and the 3dB axial ratio beam coverage range is required to be greater than or equal to 120° as much as possible. Circularly polarized antennas that achieve this beam coverage range usually have the characteristics of narrow bandwidth. Therefore, circularly polarized conformal microstrip antennas that can achieve wide bandwidth beams at the same time have broad application prospects.

[0003] The main methods of widening the frequency band of microstrip antennas include loading matching branches and multi-layer dielectric coupling. Loading matching branches can widen the working frequency band of the antenna by adjusting the impedance matching of the antenna; multi-layer dielectric coupling can stimulate multiple resonance points in a wide frequency band, thereby widening the working bandwidth of the antenna. The main methods of realizing circular polarization radiation characteristics of microstrip antennas include single feed point technology and multi-feed point technology. Among them, the single feed point technology is mainly realized by geometrically perturbing the radiating patch of the antenna, and the 3dB axial ratio bandwidth is narrow; the multi-feed point technology loads the feeding network and feeds the radiating patch of the antenna at multiple points to stimulate the circular polarization radiation characteristics of the antenna, and the 3dB axial ratio bandwidth is wide.

[0004] For carrier conformal antennas, the feeding network of multi-feed point circularly polarized antennas will occupy limited resources on the carrier surface, and the frequency band of single-feed point circularly polarized antennas is relatively narrow. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the object of the present invention is to provide an X-band wide bandwidth beam circularly polarized conformal microstrip antenna to achieve X-band circular polarization radiation characteristics and wide bandwidth beam characteristics.

[0006] The technical solution adopted by the present invention is: An X-band wide bandwidth beam circularly polarized conformal microstrip antenna comprises a first dielectric substrate and a second dielectric substrate, wherein an antenna pattern and four perturbation metal patterns around the antenna pattern are printed on the first dielectric substrate, and four perturbation metal patterns are also printed on the second dielectric substrate; short-circuit probes are loaded on the four perturbation metal patterns on the first dielectric substrate.

[0007] The antenna pattern is printed on the first dielectric substrate of the present invention, so as to realize X-band circular polarization radiation characteristics.

[0008] Using coaxial probe feeding will make the input impedance present inductive reactance characteristics, resulting in input-output mismatch and large reflection coefficient. In the present invention, a second dielectric substrate is covered on the first dielectric substrate, and perturbation metal patterns are provided on both the first dielectric substrate and the second dielectric substrate, which will form a capacitive structure to offset the inductive reactance characteristics of the probe feeding and broaden the impedance bandwidth.

[0009] The four perturbation metal patterns on the first dielectric substrate are loaded with short-circuit probes, which can effectively broaden the circularly polarized 3dB axial ratio beam bandwidth.

[0010] As a preferred solution of the present invention, the first dielectric substrate is provided with a through hole near the geometric center, a feeding probe is passed through the through hole, and the feeding probe is connected to the antenna pattern.

[0011] As a preferred solution of the present invention, the dielectric constants of the first dielectric substrate and the second dielectric substrate are both 2.2, and the loss tangents are both 0.001; the models of the first dielectric substrate and the second dielectric substrate are both Rogers5880.

[0012] As a preferred solution of the present invention, air with a height of 1 mm is filled between the first dielectric substrate and the second dielectric substrate.

[0013] As a preferred solution of the present invention, the thickness of the first dielectric substrate is 1.575 mm.

[0014] As a preferred solution of the present invention, the thickness of the second dielectric substrate is 1 mm.

[0015] As a preferred solution of the present invention, the antenna pattern includes a square loop antenna and an arc-shaped delay line connected to the inside of the loop antenna.

[0016] As a preferred embodiment of the present invention, the circumference of the loop antenna is equal to the wavelength; the length of the arc delay line is 1 / 4 wavelength. For the loop antenna, when the wavelength is equal to the circumference of the loop antenna, the circular polarization mode TM11 of the loop antenna can be effectively excited. For the arc delay line, when the length of the arc delay line is 1 / 4 wavelength, a continuous current with a phase difference of 90° is provided to the loop antenna to achieve right-hand circular polarization.

[0017] As a preferred solution of the present invention, it also includes a frame, a radio frequency connector is connected to the bottom of the frame, the first dielectric substrate and the second dielectric substrate are arranged in the frame, and an antenna cover is connected to the top of the frame.

[0018] As a preferred solution of the present invention, the material of the antenna cover is polytetrafluoroethylene, the dielectric constant is 2.0-2.2, and the tangent loss factor is 0.001.

[0019] The beneficial effects of the present invention are: 1. The antenna pattern is printed on the first dielectric substrate of the present invention, which can realize X-band circular polarization radiation characteristics.

[0020] 2. When a coaxial probe is used for feeding, the input impedance will show an inductive characteristic, resulting in input-output mismatch and a large reflection coefficient. In the present invention, a second dielectric substrate is covered on the first dielectric substrate, and a perturbation metal pattern is arranged on both the first dielectric substrate and the second dielectric substrate, so that a capacitive structure is formed to offset the inductive characteristic of the probe feeding and broaden the impedance bandwidth.

[0021] 3. The four perturbation metal patterns on the first dielectric substrate are loaded with short-circuit probes, which can effectively broaden the circularly polarized 3dB axial ratio beam bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the structure of the present invention; Figure 2 is a front view of the first dielectric substrate; Figure 3 is the front view of the antenna pattern; Figure 4 is a schematic diagram of the structure of the second dielectric substrate; Figure 5 This is an exploded view of the antenna; Figure 6 This is the antenna simulation model diagram; Figure 7 It is a curve diagram of return loss parameters; Figure 8 is the standing wave ratio curve; Fig. 9 It is the 3dB axial ratio bandwidth curve; Fig.10 It is the 3dB axial ratio beam curve; Fig.11 It is the XOZ plane antenna gain diagram; Fig.12 It is the YOZ surface antenna gain diagram; Fig.13 is the antenna gain pattern; Fig.14 This is the antenna assembly diagram.

[0023] In the figure: 1-first dielectric substrate; 2-second dielectric substrate; 3-antenna pattern; 4-perturbation metal pattern; 5-short-circuit probe; 6-feeding probe; 7-frame; 8-RF connector; 9-radome; 31-loop antenna; 32-arc delay line. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0026] like Figure 1 to Figure 4 As shown, the X-band wide bandwidth beam circularly polarized conformal microstrip antenna of this embodiment comprises a first dielectric substrate 1 and a second dielectric substrate 2, on which an antenna pattern 3 and four perturbation metal patterns 4 located around the antenna pattern 3 are printed, and on which the second dielectric substrate 2 is also printed four perturbation metal patterns 4; the four perturbation metal patterns 4 on the first dielectric substrate 1 are all loaded with short-circuit probes 5. The first dielectric substrate 1 is provided with a through hole near the geometric center, and a feeding probe 6 is passed through the through hole, and the feeding probe 6 is connected to the antenna pattern 3.

[0027] The antenna pattern 3 is printed on the first dielectric substrate 1 of the present invention, so as to realize X-band circular polarization radiation characteristics.

[0028] Using coaxial probe feeding will make the input impedance present inductive reactance characteristics, resulting in input-output mismatch and large reflection coefficient. In the present invention, a second dielectric substrate 2 is covered on the first dielectric substrate 1, and a perturbation metal pattern 4 is provided on both the first dielectric substrate 1 and the second dielectric substrate 2, which will form a capacitive structure to offset the inductive reactance characteristics of the probe feeding and broaden the impedance bandwidth.

[0029] The four perturbation metal patterns 4 on the first dielectric substrate 1 are all loaded with short-circuit probes 5, which can effectively broaden the circular polarization 3dB axial ratio beam bandwidth.

[0030] Specifically, the first dielectric substrate 1 and the second dielectric substrate 2 are both Rogers 5880 low-loss dielectric substrates with a dielectric constant of 2.2 and a loss tangent of 0.001.

[0031] The thickness of the first dielectric substrate 1 is 1.575 mm, the printed antenna pattern 3 and four perturbation metal patterns 4 around the antenna pattern 3 are printed on the upper layer of the first dielectric substrate 1, and the bottom layer of the first dielectric substrate 1 is entirely made of metal sheets as antenna ground planes.

[0032] The thickness of the second dielectric substrate 2 is 1 mm. Four perturbation metal patterns 4 are printed on the upper layer of the second dielectric substrate 2. The second dielectric substrate 2 serves as a covering layer of the first antenna structure. Air with a height of h is filled between the first dielectric substrate 1 and the second dielectric substrate 2.

[0033] Specifically, if Figure 3 As shown, the antenna pattern 3 includes a square loop antenna 31 and an arc-shaped delay line 32 connected to the inside of the loop antenna 31. The circumference of the loop antenna 31 is equal to the wavelength; the length of the arc-shaped delay line 32 is 1 / 4 of the wavelength.

[0034] For the loop antenna 31, when the circumference of the loop antenna 31 is equal to the wavelength, the circular polarization mode of the loop antenna 31 can be effectively excited. 1 Calculate using formula (1): (1); Where c is the speed of light in free space, d 1 is the outer side length of the loop antenna 31, d 2 is the inner side length of the loop antenna 31, ε e is the dielectric constant of the dielectric substrate, f TM1 is the frequency in circular polarization mode.

[0035] Then, according to the selected width of the loop antenna 31, the outer ring side length d of the loop antenna 31 is calculated. 1 and the inner side length d of the loop antenna 31 2 .

[0036] For the arc delay line 32, when the length of the arc delay line 32 is 1 / 4 wavelength, a continuous current with a phase difference of 90° is provided to the loop antenna 31 to achieve right-hand circular polarization. The arc delay line 32 in the present invention is a three-quarter arc. The length L of the arc delay line 32 is 2 Calculate using formula (2).

[0037] (2); Among them, r 2 is the outer diameter of the arc, r 1 is the inner diameter of the arc, c is the speed of light in free space, ε e is the dielectric constant of the dielectric substrate, and f is the frequency.

[0038] Then, according to the selected width of the arc-shaped delay line 32, the inner radius r of the arc-shaped delay line 32 is calculated. 1 and the outer diameter of the arc r 2 .

[0039] The present invention also includes a frame 7, a radio frequency connector 8 is connected to the bottom of the frame 7, a first dielectric substrate 1 and a second dielectric substrate 2 are arranged in the frame 7, and an antenna cover 9 is connected to the upper part of the frame 7. The antenna is placed in the aluminum alloy structure frame 7, and is fixed to the metal shell with M2.5 screws on all sides. All screws are reinforced with thread locking agents, and have good reliability. The antenna cover 9 is made of polytetrafluoroethylene, whose dielectric constant is about 2.1, the tangent loss factor is 0.001, and the temperature resistance can reach 200°C for long-term use. The overall size of the antenna is 78mm×55mm×13mm.

[0040] Assume that the size is W (about 1 / 2 wavelength, corresponding to the electrical length W e ) is a rectangular patch circularly polarized microstrip antenna with an operating wavelength of λ. Its horizontal electric field component E θ and the vertical electric field component E φ Completely vertical, the angle is 90°. According to Huygens wave propagation theory and antenna theory: (3); (4); in, θ W represents the angle between the electric field vector of the rectangular circularly polarized microstrip antenna and the horizontal direction. e is the electrical length of the antenna, that is, the ratio of the physical length of the antenna to the wavelength.

[0041] Then the 3dB beamwidth of AR is: (5); The electrical length is W e for: (6); Among them, ε reff is the effective dielectric constant of the dielectric substrate, ε r is the dielectric constant of the dielectric substrate, and h is the thickness of the dielectric substrate.

[0042] From equation (5), we can see that the 3dB beamwidth is the electrical length W e and the working wavelength λ. When the working wavelength is determined, the 3dB beam width is only related to the electrical length. From equation (6), it can be seen that the electrical length of the rectangular patch microstrip antenna is related to the effective dielectric constant and thickness of the selected dielectric substrate.

[0043] In order to expand the impedance bandwidth of the antenna, the present invention selects the Rogers5800 dielectric substrate with a low effective dielectric constant, whose dielectric constant is 2.2 and common thickness is 1.575mm. Based on the selection of the dielectric substrate, the electrical length dimension is basically determined. Therefore, loading the short-circuit probe 5 in the antenna introduces an inductance component, which can effectively change the electrical length according to the transmission line theory. By loading the short-circuit probe 5 of the appropriate position and size, a better 3dB beam bandwidth can be achieved.

[0044] Simulation results and analysis: Modeling and simulation are performed in the electromagnetic simulation software HFSS. Figure 6 shown.

[0045] The antenna size after simulation optimization is: W=48mm, w 1 =8.4mm, w 2 =6.4mm, w r1 =1.2mm, (p x , p y )=(2.5mm, 0mm), (p x1 , p y1 )=(5mm, 2.8mm), the other three short-circuit probes 5 are rotated 90°, d 1 =7.4mm, d 2 =5.7mm, r 2 =2.2mm, r 1 =0.4mm, w f =1mm, w 3 =8.6mm, w 4 =7mm, w r2 =1.6mm, h=1mm.

[0046] Figure 7 is the return loss parameter curve of the antenna, Figure 7 It can be seen that the return loss is less than -10dB in the frequency range of 7.79GHz to 10.07GHz, and the impedance relative bandwidth is 25.33%. Figure 8 is the standing wave ratio curve of the antenna, Figure 8 It can be seen that the standing wave ratio is less than 2 in the frequency range of 7.77GHz to 10.17GHz. Figure 7 and Figure 8 Among them, m1, m2 and m3 are the selected characteristic points, which are the return loss and standing wave ratio of the antenna when the frequencies are 8.5G, 9G and 9.5G.

[0047] Fig. 9 is the 3dB axial ratio bandwidth curve of the antenna when Theat=0°, Phi=0°, Fig. 9It can be seen that the axial ratio of the antenna is less than 3dB in the frequency range of 8.4GHz to 9.72GHz, and the axial ratio relative bandwidth is 14.67%. Fig. 9 Here, m1, m2 and m3 are selected characteristic points, which are the 3dB axial ratio bandwidths when Theat=0° and Phi=0° when the antenna frequencies are 8.5G, 9G and 9.5G. Fig.10 This is the 3dB axial ratio beam curve of the antenna at the center frequency of 9GHz and Phi=0°. It can be seen from the figure that the axial ratio is less than 3dB in the range of (-65.66°~51.59°), covering a beam range of 117°. Fig.10 The point m1 in is the selected feature point, which represents the axial ratio of the antenna when Phi=0° and Theat=0°.

[0048] Fig.11 and Fig.12 They are the radiation patterns of the XOZ and YOZ planes when the antenna works at 9GHz, where the red curve is the right-hand polarization gain and the blue curve is the left-hand polarization gain. When Phi=0° and Theat=0°, the antenna gain is 8.89dB, the cross polarization is less than -25dB, and the -3dB beam width is greater than 120°. Fig.11 and Fig.12 Point m1 is the gain of the antenna when Phi=0°, Theat=0°, points m2 and m3 are the characteristic points where the gain of the antenna is ≥-3dB in the YOZ plane radiation pattern, and points m4 and m5 are the characteristic points where the gain of the antenna is ≥-3dB in the XOZ plane radiation pattern.

[0049] Fig.13 This is the gain diagram of the antenna changing with frequency when Phi=0° and Theat=0°. It can be seen from the figure that the gain is greater than 7dB@(Phi=0°&Theat=0°) within the antenna operating frequency band. Fig.13 Where m1, m2 and m3 are the selected characteristic points, which are the gain values ​​of the antenna when Theat=0° and Phi=0° at the frequency points of 8.5G, 9G and 9.5G.

[0050] Fig.14 It is a 3D schematic diagram of the antenna radiation direction, that is, the antenna radiates outward in a semicircular shape, covering 360° in the horizontal direction and 90° in the elevation direction.

[0051] Physical processing and testing: The HFSS model was imported into AD software for printed circuit board production. The first dielectric substrate 1 and the second dielectric substrate 2 were made of Rogers 5880 material, wherein the thickness of the first dielectric substrate 1 was 1.575 mm, and the thickness of the second dielectric substrate 2 was 1 mm.

[0052] The four vias on the periphery of the first dielectric layer are plugged with copper paste, contacting the top metal patch and the bottom ground, and the middle via is a metalized via for welding probes. The second dielectric substrate 2 has only a top metal patch, and the bottom Rogers 5880 is exposed.

[0053] The actual antenna consists of an antenna radiation unit (a first dielectric substrate 1), an antenna covering layer (a second dielectric substrate 2), an antenna cover 9, a frame 7, a 1 mm gasket and a connector.

[0054] The present invention is not limited to the above-mentioned optional implementation modes. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that fall within the scope defined by the claims of the present invention fall within the protection scope of the present invention.

Claims

1. An X-band wide bandwidth circularly polarized conformal microstrip antenna, characterized in that: The invention comprises a first dielectric substrate (1) and a second dielectric substrate (2); an antenna pattern (3) and four perturbation metal patterns (4) located around the antenna pattern (3) are printed on the first dielectric substrate (1); and four perturbation metal patterns (4) are also printed on the second dielectric substrate (2); and short-circuit probes (5) are loaded on the four perturbation metal patterns (4) on the first dielectric substrate (1).

2. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: The first dielectric substrate (1) is provided with a through hole near the geometric center, a feeding probe (6) is passed through the through hole, and the feeding probe (6) is connected to the antenna pattern (3).

3. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: The dielectric constants of the first dielectric substrate (1) and the second dielectric substrate (2) are both 2.2, and the loss tangents are both 0.001; the models of the first dielectric substrate (1) and the second dielectric substrate (2) are both Rogers 5880.

4. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: Air with a height of 1 mm is filled between the first dielectric substrate (1) and the second dielectric substrate (2).

5. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: The thickness of the first dielectric substrate (1) is 1.575 mm.

6. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: The thickness of the second dielectric substrate (2) is 1 mm.

7. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: The antenna pattern (3) comprises a square loop antenna (31) and an arc-shaped delay line (32) connected to the inside of the loop antenna (31).

8. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 7, characterized in that: The circumference of the loop antenna (31) is equal to the wavelength; the length of the arc-shaped delay line (32) is 1 / 4 of the wavelength.

9. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 1, characterized in that: It also comprises a frame (7), the bottom of the frame (7) being connected to a radio frequency connector (8), the first layer of dielectric substrate (1) and the second layer of dielectric substrate (2) being arranged in the frame (7), and the upper part of the frame (7) being connected to an antenna cover (9).

10. The X-band wide bandwidth circularly polarized conformal microstrip antenna according to claim 9, characterized in that: The material of the radome (9) is polytetrafluoroethylene, with a dielectric constant of 2.0 to 2.2 and a tangent loss factor of 0.001.

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