Ultra-wideband circularly polarized vivaldi antenna

Abstract

The application relates to an ultra-wideband circularly polarized Vivaldi antenna, which comprises a rotationally symmetric antenna and a feed network; the rotationally symmetric antenna is arranged on the feed network; the rotationally symmetric antenna comprises four Vivaldi antenna units, the four Vivaldi antenna units are orthogonally arranged in sequence, and are fixedly connected with the feed network; each Vivaldi antenna unit comprises a radiation arm, a first ground plane and a substrate; the radiation arm and the first ground plane are arranged on a first surface of the substrate, and a first side of the radiation arm is connected with the first ground plane; the first ground plane of a latter Vivaldi antenna unit is connected with a second side of the radiation arm of a former Vivaldi antenna unit, and serves as a second ground plane of the former Vivaldi antenna unit. The application adopts a half-mode form of the Vivaldi antenna, the antenna has a symmetrical and stable radiation pattern and a compact aperture size through structural multiplexing of the ground planes of the antenna units; and the antenna has good circular polarization performance in combination with the feed network which has good amplitude and phase responses.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, specifically relating to an ultra-wideband circularly polarized Vivaldi antenna. Background Technology

[0002] Circularly polarized antennas have been widely used in satellite communications, radar detection, and wireless communication systems due to their advantages such as resistance to multipath effects and insensitivity to antenna polarization direction. Circularly polarized Vivaldi antennas, in particular, possess advantages such as ultra-wideband capability, low cost, unidirectional radiation, and ease of manufacture. However, due to their radiation principle, Vivaldi antennas have a relatively large aperture, which poses many challenges in their specific applications.

[0003] The implementation of circularly polarized Vivaldi antennas can be broadly categorized into two types: The first type includes two orthogonally placed linearly polarized Vivaldi antenna elements, a 1-to-2 power divider, and a phase shifter; the second type includes four centrally rotated Vivaldi antennas or Vivaldi-like antenna structures, along with a 1-to-4 90° sequential phase feed network connected to the antennas. The first type is relatively simple in principle and, due to the correlation between its electrical performance and that of the Vivaldi antenna, possesses ultra-wideband impedance matching and unidirectional end-fire characteristics. (Generally, an antenna with a octave bandwidth greater than 2 is considered ultra-wideband, or, using relative bandwidth as a characterization, when the relative bandwidth is greater than 25% or greater than 20% and the absolute bandwidth is less than 500MHz, it can also be considered ultra-wideband.) However, antennas based on this implementation have a large aperture, and miniaturization depends entirely on the size of the antenna elements, severely limiting its development due to technological constraints. Compared to the first and second types, the design freedom is significantly improved, allowing for optimized design for extended bandwidth and miniaturized aperture. However, existing miniaturization technologies of this type are often based on sacrificing antenna bandwidth or pattern stability, which has technical defects. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides an ultra-wideband circularly polarized Vivaldi antenna. The technical problem to be solved by this invention is achieved through the following technical solution:

[0005] This invention provides an ultra-wideband circularly polarized Vivaldi antenna, comprising: a rotationally symmetric antenna and a feed network;

[0006] The rotationally symmetric antenna is disposed on the feed network;

[0007] The rotationally symmetric antenna includes four Vivaldi antenna elements, which are orthogonally connected in pairs; all four Vivaldi antenna elements are fixedly connected to the feed network.

[0008] The Vivaldi antenna element includes: a radiating arm, a first ground plane, and a substrate;

[0009] Both the radiating arm and the first ground plane are disposed on the first surface of the substrate, and the first side of the radiating arm is connected to the first ground plane;

[0010] The first ground plane of the subsequent Vivaldi antenna element is connected to the second side of the radiating arm of the previous Vivaldi antenna element and serves as the second ground plane of the previous Vivaldi antenna element; the second ground plane of the previous Vivaldi antenna element intersects with the substrate of the previous Vivaldi antenna element, and the second ground plane of the previous Vivaldi antenna element is symmetrically arranged about the intersection line.

[0011] In one embodiment of the present invention, the Vivaldi antenna element further includes: a feed band;

[0012] The feed strip is disposed on the first surface of the substrate, on the same side as the first side of the radiating arm; the first end of the feed strip is connected to the radiating arm, and the second end of the feed strip is connected to the feed network.

[0013] In one embodiment of the present invention, the length L of the first ground plane is:

[0014] L = l × R + l²;

[0015] Where l is the length of the radiating arm; R is the first coefficient; and l2 is the length of the feed conductor.

[0016] In one embodiment of the present invention, the radiating arm of the preceding Vivaldi antenna element is enclosed by an outer tapered curve, an inner tapered curve, a feed conductor, and a first ground plane, wherein the outer tapered curve is disposed away from the feed network, and the inner tapered curve is disposed close to the feed network;

[0017] A radiation gap is formed between the outer tapered curve of the first Vivaldi antenna element and the first ground plane, and between the first ground plane of the second Vivaldi antenna element.

[0018] In one embodiment of the present invention, the external tapered curve y outerdege for:

[0019] y outerdege =w·(exp(k1·x1)-1) / (exp(k1·l)-1)+w g ;

[0020] Where w is the width of the radial arm; k1 is the curvature index of the external tapered curve; x1 is the coordinate value of the external tapered curve on the x-axis; w g This is the distance between the starting point of the outer tapered curve and the first ground plane of the next Vivaldi antenna element.

[0021] In one embodiment of the present invention, the inner taper curve y innerdege for:

[0022] y innerdege =w1·(exp(k2·x2)-1) / (exp(k2·l1)-1)+w2+w g ;

[0023] Where w1 is the width of the inner tapered curve; l1 is the length of the inner tapered curve; k2 is the curvature index of the inner tapered curve; x2 is the coordinate value of the outer tapered curve on the x-axis; and w2 is the width of the feed conductor.

[0024] In one embodiment of the present invention, the power supply network includes: an ultra-wideband power divider, two Wilkinson power dividers, and two phase shifters;

[0025] The ultra-wideband power divider includes one input port and two output ports. The input port is connected to an external device, and the two output ports output differential output signals respectively. Each of the output ports is connected in sequence to a Wilkinson power divider and a phase shifter.

[0026] The Wilkinson power divider is a 1-to-2 power divider, and the branches are isolated from each other; the output signals of the phase shifter are 90° out of phase.

[0027] In one embodiment of the present invention, the ultra-wideband power divider includes: a microstrip structure, a dielectric substrate, and a ground plane;

[0028] The microstrip structure, the dielectric substrate, and the ground plane are arranged sequentially from top to bottom;

[0029] The microstrip structure includes: a first microstrip line, a second microstrip line, and a third microstrip line;

[0030] The second microstrip line serves as an input microstrip line and is positioned between the first microstrip line and the third microstrip line; the first microstrip line and the third microstrip line serve as output microstrip lines, respectively.

[0031] In one embodiment of the present invention, the first microstrip line, the second microstrip line and the third microstrip line each include: a first stub and a microstrip line;

[0032] Wherein, the first branch is a fan-shaped branch, the terminal of the microstrip line is connected to the center of the first branch, and the fan-shaped branch protrudes towards the terminal of the microstrip line;

[0033] The microstrip lines in the first, second, and third microstrip lines are parallel to each other.

[0034] In one embodiment of the present invention, a rectangular groove and two fan-shaped groove branches are provided on the floor;

[0035] The rectangular groove is perpendicular to the microstrip line, and the two ends of the rectangular groove are respectively connected to the centers of the two fan-shaped groove branches; the two fan-shaped groove branches protrude towards the two ends of the rectangular groove.

[0036] The two fan-shaped groove branches partially overlap with the first branches of the first microstrip line and the third microstrip line, respectively, and the fan-shaped groove branches are the same size as the first branches.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The ultra-wideband circularly polarized Vivaldi antenna of the present invention employs a half-mode Vivaldi antenna, with four Vivaldi antenna elements sequentially orthogonally connected in pairs to form a rotationally symmetric structure. A first ground plane is coplanarly disposed on one side of the radiating arm. This first ground plane connects to the second side of the radiating arm of the preceding Vivaldi antenna element, serving as the second ground plane of the preceding Vivaldi antenna element. In the preceding Vivaldi antenna element, the second ground plane is perpendicular to the radiating arm. By reusing the ground plane structure, no additional second ground plane is required, thus solving the problem of asymmetrical radiation pattern in half-mode Vivaldi antennas. This results in a symmetrical and stable radiation pattern, ultra-wideband impedance and axial ratio bandwidth, and a compact aperture size.

[0039] 2. The ultra-wideband circularly polarized Vivaldi antenna of the present invention employs a compact 90° sequential phase feed network, which is integrated into the bottom of the rotationally symmetric antenna. An ultra-wideband power divider splits one signal into two differential output signals with opposite phases. The microstrip line stubs are fan-shaped and convex towards the open circuit direction, achieving ultra-wideband impedance matching. After being split again by a Wilkinson power divider and isolated, the output phase of the feed signal is processed by a phase shifter to be 90° out of phase. Combined with the feed network with good amplitude and phase response, the antenna has good circular polarization performance.

[0040] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of an ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention;

[0042] Figure 2 This is a schematic diagram of the structure of the Vivaldi antenna element according to an embodiment of the present invention;

[0043] Figure 3 This is a partial enlarged view of the Vivaldi antenna element according to an embodiment of the present invention;

[0044] Figure 4 This is a front view of the Vivaldi antenna element according to an embodiment of the present invention;

[0045] Figure 5 This is a schematic diagram of the power supply network according to an embodiment of the present invention;

[0046] Figure 6 This is a top view of the structure of the ultra-wideband power divider according to an embodiment of the present invention;

[0047] Figure 7 This is a front view of the structure of the ultra-wideband power divider according to an embodiment of the present invention;

[0048] Figure 8 This is a bottom view of the structure of the ultra-wideband power divider according to an embodiment of the present invention;

[0049] Figure 9 This is a simulation result diagram of the reflection coefficient of the Vivaldi antenna element according to an embodiment of the present invention;

[0050] Figure 10 This is the normalized radiation pattern of the Vivaldi antenna element in the E-plane at 0.8 GHz according to an embodiment of the present invention.

[0051] Figure 11 This is the normalized radiation pattern of the Vivaldi antenna element in the E-plane at 1.3 GHz according to an embodiment of the present invention.

[0052] Figure 12 This is a simulation result of the reflection coefficient of the ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention;

[0053] Figure 13 This is a simulation result diagram of the axial ratio and achievable gain of the ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention;

[0054] Figure 14 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoy plane at 0.6 GHz, according to an embodiment of the present invention.

[0055] Figure 15 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoz plane at 0.6 GHz, according to an embodiment of the present invention.

[0056] Figure 16 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoy plane at 1 GHz, according to an embodiment of the present invention.

[0057] Figure 17 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoz plane at 1 GHz, according to an embodiment of the present invention.

[0058] Figure 18 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoy plane at 1.4 GHz, according to an embodiment of the present invention.

[0059] Figure 19 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoz plane at 1.4 GHz, according to an embodiment of the present invention.

[0060] Icons: 1- Rotationally symmetric antenna; 10- Vivaldi antenna element; 101- Radiating arm; 102- First ground plane; 103- Second ground plane; 104- Feed conductor; 105- Feed connector; 106- Substrate; 2- Feed network; 21- Ultra-wideband power divider; 210- Microstrip structure; 211- First microstrip line; 2111- First stub; 2112- Microstrip line; 212- Second microstrip line; 213- Third microstrip line; 220- Dielectric substrate; 230- Ground plane; 231- Rectangular slot line; 232- Sector stub of fan-shaped slot line; 22- Wilkinson power divider; 23- Phase shifter. Detailed Implementation

[0061] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description of an ultra-wideband circularly polarized Vivaldi antenna according to the present invention is provided in conjunction with the accompanying drawings and specific embodiments.

[0062] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0063] Example 1

[0064] Please refer to the above. Figure 1 and Figure 2 , Figure 1 This is a schematic diagram of the structure of an ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the Vivaldi antenna element according to an embodiment of the present invention.

[0065] As shown in the figure, the ultra-wideband circularly polarized Vivaldi antenna of this embodiment includes: a rotationally symmetric antenna 1 and a feed network 2, wherein the rotationally symmetric antenna 1 is disposed on the feed network 2.

[0066] In this embodiment, the rotationally symmetric antenna 1 includes: four Vivaldi antenna elements 10, which are orthogonally connected in pairs, and all four Vivaldi antenna elements 10 are fixedly connected to the feed network 2.

[0067] The Vivaldi antenna element 10 includes a radiating arm 101, a first ground plane 102, and a substrate 106. The radiating arm 101 and the first ground plane 102 are both disposed on the first surface of the substrate 106, and the first side of the radiating arm 101 is connected to the first ground plane 102. The first ground plane 102 of the subsequent Vivaldi antenna element 10 is connected to the second side of the radiating arm 101 of the previous Vivaldi antenna element 10, and serves as the second ground plane 103 of the previous Vivaldi antenna element 10. The second ground plane 103 of the previous Vivaldi antenna element 10 intersects with the substrate 106 of the previous Vivaldi antenna element 10, and the second ground plane 103 of the previous Vivaldi antenna element 10 is symmetrically arranged about the intersection line.

[0068] In an alternative implementation, the complete functionality of a single Vivaldi antenna element 10 includes: a radiating arm 101, a first ground plane 102, a second ground plane 103, and a substrate 106. That is, through structural reuse, the radiating arm 101 has a coplanar intersecting first ground plane 102 and a perpendicularly intersecting second ground plane 103.

[0069] In an optional implementation, the first ground plane 102 and the second ground plane 103 of the Vivaldi antenna element 10 are spaced apart by the radiating arm 101 of the element, and the first ground plane 102 and the second ground plane 103 are of equal size.

[0070] In an alternative embodiment, the substrate 106 has a certain thickness to maintain a certain rigidity of the Vivaldi antenna element 10.

[0071] It is worth noting that the four Vivaldi antenna elements 10 are half-mode Vivaldi antenna elements, arranged in pairs orthogonally to form a rotationally symmetric structure. Half-mode antennas are inherently compact, and the use of ground-plane structural reuse between the Vivaldi antenna elements 10 fully utilizes the performance of the half-mode antenna, while maintaining a stable and symmetrical radiation pattern.

[0072] In one optional implementation, based on the working principle of the antenna, it can be known that by changing the input-output relationship between the rotationally symmetric antenna 1 and the feed network 2, the antenna can be either a transmitting antenna or a receiving antenna. The following explanation uses the transmitting antenna as an example.

[0073] Please see Figure 3 , Figure 3 This is a partially enlarged view of the Vivaldi antenna element according to an embodiment of the present invention.

[0074] As shown in the figure, the Vivaldi antenna element 10 in this embodiment further includes: a feed conductor 104;

[0075] The feed strip 104 is disposed on the first surface of the substrate 106, on the same side as the first side of the radiating arm 101; the first end of the feed strip 104 is connected to the radiating arm 101, and the second end is connected to the feed network 2.

[0076] Please see Figure 4 , Figure 4 This is a front view of the Vivaldi antenna element according to an embodiment of the present invention.

[0077] As shown in the figure, the length L of the first ground plane 102 in this embodiment is:

[0078] L=l×R+l2(1);

[0079] Where l is the length of the radiating arm; R is the first coefficient, with a value range of 1≤R≤1.2; and l2 is the length of the feed conductor.

[0080] In an alternative implementation, the first ground plane 102 and the second ground plane 103 have the same dimensions.

[0081] In this embodiment, the radiating arm 101 of the previous Vivaldi antenna element 10 is enclosed by an outer tapered curve, an inner tapered curve, a feed conductor 104 and a first ground plane 102. The outer tapered curve is set away from the feed network 2, and the inner tapered curve is set close to the feed network 2.

[0082] In this configuration, a radiation gap is formed between the outer tapered curve of the preceding Vivaldi antenna element 10 and the first ground plane 102, and between the first ground plane 102 of the following Vivaldi antenna element 10. By adjusting the outer tapered curve to change the radiation gap, the selection of the antenna radiation wavelength can be achieved.

[0083] In an alternative implementation, the inner taper profile is used for impedance matching.

[0084] In this embodiment, the external tapered curve y outerdege for:

[0085] y outerdege =w·(exp(k1·x1)-1) / (exp(k1·l)-1)+w g (2);

[0086] Where w is the width of the radiating arm, and its value ranges from 0.2λ. L ≤w≤0.5λ L ;λ L λ is the antenna radiation wavelength; L =c / f L c is the speed of light in a vacuum, f L is the lowest cutoff operating frequency of the Vivaldi antenna element; k1 is the curvature index of the outer taper curve; x1 is the coordinate value of the outer taper curve on the x-axis; w g The external tapered curve y outerdege The distance between the starting point and the first ground plane of the next Vivaldi antenna element is in the range of 0.1mm ≤ w g ≤1mm.

[0087] In an optional implementation, the inner taper curve y innerdege for:

[0088] y innerdege =w1·(exp(k2·x2)-1) / (exp(k2·l1)-1)+w2+w g (3);

[0089] Where w1 is the width of the inner tapered curve, with a value range of 0≤w1≤w; l1 is the length of the inner tapered curve, with a value range of 0≤l1≤l; k2 is the curvature index of the inner tapered curve; x2 is the coordinate value of the outer tapered curve on the x-axis; and w2 is the width of the feed conductor.

[0090] Please see Figure 5 , Figure 5 This is a schematic diagram of the power supply network according to an embodiment of the present invention.

[0091] As shown in the figure, the power supply network 2 in this embodiment includes: an ultra-wideband power divider 21, two Wilkinson power dividers 22, and two phase shifters 23.

[0092] It is worth noting that the antenna emits an electromagnetic wave. Since a half-mode antenna is used, four outputs are required. The feed network 2 is the channel connecting the external device and the four Vivaldi antenna elements 10. Correspondingly, the output branches of the feed network 2 should also be four, namely port 1 to port 4.

[0093] In this embodiment, the ultra-wideband power divider 21 includes one input port and two output ports. The input port is connected to an external device, and the two output ports output differential output signals respectively. Each output port is connected in sequence to a Wilkinson power divider 22 and a phase shifter 23.

[0094] Among them, the Wilkinson power divider 22 is a 1-to-2 power divider, which is used to further divide the differential output signal of the ultra-wideband power divider 21 into two power divider signals with the same amplitude and phase, and the two power divider signals are isolated from each other; the phase shifter 23 takes the two power divider signals as input, shifts the two power divider signals by one phase, and outputs two feed signals with the same amplitude and a phase difference of 90°. The two phase shifters 23 output a total of 4 feed signals with the same amplitude and a phase difference of 90° between the signals, which are connected to the four Vivaldi antenna elements 10.

[0095] In an alternative implementation, the ultrawideband power divider 21, the two Wilkinson power dividers 22, and the two phase shifters 23 are connected via microstrip lines with a characteristic impedance of 50 ohms.

[0096] Please refer to the above. Figure 6 , Figure 7 and Figure 8 , Figure 6 This is a top view of the structure of the ultra-wideband power divider according to an embodiment of the present invention; Figure 7 This is a front view of the structure of the ultra-wideband power divider according to an embodiment of the present invention; Figure 8 This is a top view of the structure of the ultra-wideband power divider according to an embodiment of the present invention.

[0097] As shown in the figure, the ultra-wideband power divider 21 of this embodiment includes: a microstrip structure 210, a dielectric substrate 220 and a ground plane 230 arranged sequentially from top to bottom.

[0098] The microstrip structure 210 includes a first microstrip line 211, a second microstrip line 212, and a third microstrip line 213.

[0099] In this embodiment, the first microstrip line 211, the second microstrip line 212, and the third microstrip line 213 are arranged in parallel; the second microstrip line 212 serves as an input microstrip line, located between the first microstrip line 211 and the third microstrip line 213, and is input through port a; the first microstrip line 211 and the third microstrip line 213 serve as output microstrip lines, and are output through ports c and b respectively.

[0100] In an alternative implementation, the transmission paths of the first microstrip line 211 and the third microstrip line 213 are opposite.

[0101] In this embodiment, the first microstrip line 211, the second microstrip line 212, and the third microstrip line 213 each include: a first stub 2111 and a microstrip line 2112;

[0102] Among them, the first branch 2111 is a fan-shaped branch, the terminal of the microstrip line 2112 is connected to the center of the first branch 2111, and the fan-shaped branch protrudes towards the terminal of the microstrip line 2112, that is, the open-circuit direction; the microstrip line 2112 in the first microstrip line 211, the second microstrip line 212 and the third microstrip line 213 are parallel to each other.

[0103] In an optional implementation, the first stub 2111 in the second microstrip line 212 is used to achieve ultra-wideband impedance matching; the first stub 2111 in the first microstrip line 211 and the third microstrip line 213 are used to achieve ultra-wideband impedance matching and stable power distribution; that is, by utilizing the fan-shaped first stub 2111, the operating bandwidth of the ultra-wideband power divider 21 is extended, making its operating bandwidth ultra-wideband.

[0104] In this embodiment, the floor 230 is provided with a rectangular groove 231 and two fan-shaped groove branches 232;

[0105] In this configuration, the rectangular slot line 231 is perpendicular to the microstrip line 2112, and the rectangular slot line 231 and the microstrip line 2112 have a mutual coupling effect. The two ends of the rectangular slot line 231 are respectively connected to the centers of two fan-shaped slot line stubs 232. The two fan-shaped slot line stubs 232 protrude towards the two ends of the rectangular slot line 231. The two fan-shaped slot line stubs 232 partially overlap with the first stub 2111 of the first microstrip line 211 and the third microstrip line 213, respectively, and the fan-shaped slot line stubs 232 and the first stub 2111 are of equal size, which is used to achieve impedance matching and stable power distribution in ultra-wideband applications.

[0106] It is worth noting that the electromagnetic wave is input through the second microstrip line 212, and the energy is transferred to the rectangular slot line 231 through the coupling between the microstrip line 2112 of the second microstrip line 212 and the rectangular slot line 231. At this time, the electromagnetic wave is equally transmitted to the fan-shaped slot line stubs 232 at both ends. Since the transmission paths of the first microstrip line 211 and the third microstrip line 213 are opposite, the coupling paths are also opposite. Therefore, the electromagnetic energy is coupled from the rectangular slot line 231 to the first microstrip line 211 and the third microstrip line 213 respectively along the opposite coupling paths. Among them, the signals coupled to the first microstrip line 211 and the third microstrip line 213 have the same amplitude and opposite phase, which are a pair of differential output signals, and then output by the microstrip line 2112 of the first microstrip line 211 and the third microstrip line 213 respectively.

[0107] Example 2

[0108] In this embodiment, the ultra-wideband circularly polarized Vivaldi antenna operates from 0.52 GHz to 1.47 GHz and includes: a rotationally symmetric antenna 1 and a feed network 2, wherein the rotationally symmetric antenna 1 is disposed on the feed network 2.

[0109] In this embodiment, the rotationally symmetric antenna 1 is based on a modified half-mode Vivaldi antenna element 10, comprising four mutually orthogonal Vivaldi antenna elements 10, forming a rotationally symmetric structure.

[0110] In this embodiment, the rotationally symmetric antenna 1 includes four Vivaldi antenna elements 10, which are orthogonal to each other and are all fixedly connected to the feed network 2.

[0111] The Vivaldi antenna element 10 includes: a radiating arm 101, a first ground plane 102, a second ground plane 103, and a substrate 106. The radiating arm 101 is disposed on the first surface of the substrate 106, and the radiating arms 101 of the four Vivaldi antenna elements 10 are arranged facing each other. The first side of the radiating arm 101 is connected to the first ground plane 102, the radiating arm 101 and the first ground plane 102 are perpendicular to each other, and the first ground plane 102 is symmetrical about the substrate 106. The first ground plane 102 of the previous Vivaldi antenna element 10 is connected to the second side of the radiating arm 101, serving as the second ground plane 103 of the next Vivaldi antenna element 10, thus forming a ground plane reuse structure among the antenna elements.

[0112] In this embodiment, the Vivaldi antenna element 10 further includes: a feed conductor 104;

[0113] The feed strip 104 is disposed on the first surface of the substrate 106, on the same side as the first side of the radiating arm 101; the first end of the feed strip 104 is connected to the radiating arm 101, and the second end is connected to the feed network 2.

[0114] In an optional implementation, when simulating a single Vivaldi antenna element 10 and the rotationally symmetric antenna 1 as a whole, a feed connector 105 is connected to the second end of the feed conductor 104 of the Vivaldi antenna element 10 to simulate the output signal state of the feed network 2 when it is not connected to the feed network 2.

[0115] In an optional implementation, the power supply connector 105 is a power supply SMA connector (SubMiniature version A).

[0116] In this embodiment, the substrate 106 has a dielectric constant ε r =2.2, F4B material with thickness t1=1mm.

[0117] In this embodiment, the length L of the second ground plane 103 is:

[0118] L = l × R + l2(1);

[0119] The length of the radiating arm is l = 250 mm; the first coefficient R = 1.1; and the length of the feed conductor is l2 = 75 mm.

[0120] In this embodiment, the radiating arm 101 is enclosed by an outer tapered curve, an inner tapered curve, and a first ground plane 102 of the feed conductor 104. The outer tapered curve is set away from the feed network 2, and the inner tapered curve is set close to the feed network 2.

[0121] A radial gap is formed between the outer conical curve, the first ground plane 102, and the second ground plane 103.

[0122] In this embodiment, the external tapered curve y outerdege for:

[0123] Wherein, the width of the radiating arm w = 125 mm; the curvature index of the external tapered curve k1 = 0.05; the external tapered curve y outerdege The distance w between the starting point and the first ground plane of the next Vivaldi antenna element g =0.1mm.

[0124] In this embodiment, the inner taper curve y innerdege ,for:

[0125] y innerdege =w1·(exp(k2·x2)-1) / (exp(k2·l1)-1)+w2+w g (3);

[0126] Among them, the width of the inner tapered curve w1 = 119 mm; the length of the inner tapered curve l1 = 30 mm; the bending index of the inner tapered curve k2 = 6 mm; and the width of the feed conductor w2 = 6 mm.

[0127] In this embodiment, the width h of the first ground plane 102 and the second ground plane 103 is the same, both being 30mm.

[0128] In this embodiment, the power supply network 2 includes: an ultra-wideband power divider 21, two Wilkinson power dividers 22, and two phase shifters 23;

[0129] The ultra-wideband power divider 21 includes one input port and two output ports. The input port is connected to an external device, and the two output ports output differential output signals respectively. Each output port is connected in sequence to a Wilkinson power divider 22 and a phase shifter 23.

[0130] In an alternative implementation, the ultrawideband power divider 21, the two Wilkinson power dividers 22, and the two phase shifters 23 are connected by microstrip lines with a characteristic impedance of 50 ohms.

[0131] In an optional implementation, the Wilkinson power divider 22 is a 1-to-2 power divider, and the branches are isolated from each other; the output signals of the phase shifter 23 are 90° out of phase.

[0132] In this embodiment, the ultra-wideband power divider 21 includes: a microstrip structure 210, a dielectric substrate 220, and a ground plane 230; the microstrip structure 210, the dielectric substrate 220, and the ground plane 230 are arranged sequentially from top to bottom;

[0133] The microstrip structure 210 includes a first microstrip line 211, a second microstrip line 212, and a third microstrip line 213; the first microstrip line 211, the second microstrip line 212, and the third microstrip line 213 are arranged in parallel; the second microstrip line 212 serves as an input microstrip line and is located between the first microstrip line 211 and the third microstrip line 213; the first microstrip line 211 and the third microstrip line 213 serve as output microstrip lines, respectively.

[0134] In this embodiment, the dielectric substrate 220 adopts a dielectric constant ε r =2.7, thickness t2=0.5mm F4B material.

[0135] In this embodiment, the first microstrip line 211, the second microstrip line 212, and the third microstrip line 213 each include: a first stub 2111 and a microstrip line 2112;

[0136] Among them, the first branch 2111 is a fan-shaped branch, and the terminal of the microstrip line 2112 is connected to the center of the first branch 2111; the microstrip lines 2112 in the first microstrip line 211, the second microstrip line 212 and the third microstrip line 213 are parallel to each other.

[0137] In this embodiment, port a is a signal input port, port b is a signal in-phase output port, and port c is a signal out-of-phase output port. The signal amplitudes output by ports b and c are equal, but their phases are opposite.

[0138] In this embodiment, the radius r of the first branch 2111 is 9 mm, the unfolding angle θ is 170°, and the spacing M between the microstrip lines 2112 of the second microstrip line 212 and the third microstrip line 213 is 24 mm.

[0139] In this embodiment, the floor 230 is provided with a rectangular groove 231 and two fan-shaped groove branches 232;

[0140] The rectangular slot line 231 is perpendicular to the microstrip line 2112; two fan-shaped slot line branches 232 are respectively set at both ends of the rectangular slot line 231.

[0141] In this embodiment, the length l of the rectangular groove line 231 a =50mm, width w a =0.5mm.

[0142] In this embodiment, the two fan-shaped slot line branches 232 partially overlap with the first branch 2111 of the first microstrip line 211 and the third microstrip line 213, respectively, and the fan-shaped slot line branches 232 and the first branch 2111 are of the same size.

[0143] In this embodiment, the signal is input from the input port and output from port 1 to port 4 accordingly. The amplitudes of the four output ports are almost identical, and the phase response is as follows: port 1 leads port 2 by 90°, port 2 leads port 3 by 90°, port 3 leads port 4 by 90°, and port 4 leads port 1 by 90°.

[0144] Please see Figure 9 , Figure 9 This is a simulation result diagram of the reflection coefficient of the Vivaldi antenna element according to an embodiment of the present invention.

[0145] As shown in the figure, the reflection coefficient of the Vivaldi antenna element in this embodiment is simulated. The horizontal axis represents frequency in GHz, ranging from 0.4 to 1.8 GHz, and the vertical axis represents the reflection coefficient amplitude in dB, ranging from -40 dB to 0 dB. Within the 0.51–1.58 GHz frequency band, the reflection coefficient is less than -10 dB. The Vivaldi antenna element has a relative impedance bandwidth of 102.4%, indicating that the antenna element has ultra-wideband impedance matching performance.

[0146] Please refer to the above. Figure 10 and Figure 11 , Figure 10 This is the normalized radiation pattern of the Vivaldi antenna element in the E-plane at 0.8 GHz according to an embodiment of the present invention. Figure 11 This is the normalized radiation pattern of the Vivaldi antenna element in the E-plane at 1.3 GHz according to an embodiment of the present invention.

[0147] As shown in the figure, the longitude coordinates of the polar coordinates represent angles, ranging from 0° to 360°, while the latitude coordinates represent normalized directivity coefficients, ranging from -50 to 0 dB. The radiation pattern illustrates the antenna's radiation characteristics. At 0.8 GHz and 1.3 GHz, the E-plane radiation pattern of the Vivaldi antenna element is directional but not symmetrical; it exhibits a certain angular deflection. This is because the additional second ground plane 103 within a single Vivaldi antenna element is not ideal.

[0148] Please see Figure 12 , Figure 12 This is a simulation result of the reflection coefficient of the ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention.

[0149] As shown in the figure, the horizontal axis represents frequency in GHz, ranging from 0.4 to 2 GHz, and the vertical axis represents the reflection coefficient amplitude in dB, ranging from -55 dB to 5 dB. Within the 0.52–1.83 GHz frequency band, the reflection coefficient of the ultra-wideband circularly polarized Vivaldi antenna is less than -10 dB, exhibiting a relative impedance bandwidth of 111.5%, indicating that the antenna possesses ultra-wideband impedance matching performance.

[0150] Please see Figure 13 , Figure 13 The diagram shows the simulation results of the axial ratio and achievable circular polarization gain of the ultra-wideband circularly polarized Vivaldi antenna according to an embodiment of the present invention.

[0151] As shown in the figure, the horizontal axis represents frequency in GHz, ranging from 0.4 to 1.8 GHz. The left vertical axis represents the axial ratio in decibels (dB), ranging from 0 to 15 dB. Within the 0.49–1.47 GHz band, the antenna's axial ratio is less than 3 dB, indicating a 100% relative axial ratio bandwidth. This demonstrates good circular polarization performance within this band. The right vertical axis represents the gain in decibels (dBic), ranging from 40 to 10 dBic. Within the 0.52–1.47 GHz band, circular polarization can achieve a gain greater than 0 dBic, with a maximum achievable gain of 7.2 dBic, achieved at 1.37 GHz.

[0152] Please refer to the above. Figures 14-19 , Figure 14 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoy plane at 0.6 GHz, according to an embodiment of the present invention. Figure 15 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoz plane at 0.6 GHz, according to an embodiment of the present invention. Figure 16 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoy plane at 1 GHz, according to an embodiment of the present invention.

[0153] Figure 17 This is the normalized radiation pattern of the ultrawideband circularly polarized Vivaldi antenna in the xoz plane at 1 GHz, according to an embodiment of the present invention. Figure 18 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoy plane at 1.4 GHz, according to an embodiment of the present invention. Figure 19 This is the normalized radiation pattern of the ultra-wideband circularly polarized Vivaldi antenna in the xoz plane at 1.4 GHz, according to an embodiment of the present invention.

[0154] As shown in the figure, the longitude coordinates of the polar coordinates are angles, ranging from 0° to 360°, and the latitude coordinates are normalized directivity coefficients, ranging from -30 to 0 dB. The radiation pattern describes the radiation characteristics of the ultra-wideband circularly polarized Vivaldi antenna, that is, the radiation pattern is end-firing at 0.6 GHz, 1 GHz and 1.4 GHz and is symmetrical. It can be seen that the rotationally symmetrical structure of the antenna effectively overcomes the problem of asymmetry in the E-plane radiation pattern of the half-mode Vivaldi antenna.

[0155] The ultra-wideband circularly polarized Vivaldi antenna of this invention employs a half-mode Vivaldi antenna. Four Vivaldi antenna elements are sequentially orthogonally connected in pairs to form a rotationally symmetric structure. A first ground plane is coplanarly disposed on one side of the radiating arm. This first ground plane connects to the second side of the radiating arm of the preceding Vivaldi antenna element, serving as the second ground plane of the preceding Vivaldi antenna element. In the preceding Vivaldi antenna element, the second ground plane is perpendicular to the radiating arm. By reusing the ground plane structure, no additional second ground plane is required, thus solving the problem of asymmetrical radiation pattern in half-mode Vivaldi antennas. This results in a symmetrical and stable radiation pattern, ultra-wideband impedance and axial ratio bandwidth, and a compact aperture size.

[0156] The ultra-wideband circularly polarized Vivaldi antenna of this invention employs a compact 90° sequential phase feed network integrated at the bottom of the rotationally symmetric antenna. An ultra-wideband power divider splits a single signal into two differential output signals with opposite phases. The microstrip line stubs are fan-shaped and convex towards the open circuit direction, achieving ultra-wideband impedance matching. After being split again by a Wilkinson power divider and isolated, the output phase of the feed signal is processed by a phase shifter to be 90° out of phase. Combined with the feed network having good amplitude and phase response, the antenna has excellent circular polarization performance.

[0157] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or device comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or device comprising said element. Terms such as "connected" or "linked" are not limited to physical or mechanical connections but can include electrical connections, whether direct or indirect. The orientations or positional relationships indicated by terms such as "upper," "lower," "left," and "right" are based on the orientations or positional relationships shown in the accompanying drawings and are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention.

[0158] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. An ultra-wideband circularly polarized Vivaldi antenna, characterized in that, include: Rotationally symmetric antenna (1) and feed network (2); The rotationally symmetric antenna (1) is disposed on the feed network (2); The rotationally symmetric antenna (1) includes four Vivaldi antenna elements (10), which are orthogonally connected in pairs; all four Vivaldi antenna elements (10) are fixedly connected to the feed network (2). The Vivaldi antenna element (10) includes: a radiating arm (101), a first ground plane (102), and a substrate (106); The radiation arm (101) and the first ground plane (102) are both disposed on the first surface of the substrate (106), and the first side of the radiation arm (101) is connected to the first ground plane (102); The first ground plane (102) of the subsequent Vivaldi antenna unit (10) is connected to the second side of the radiating arm (101) of the previous Vivaldi antenna unit (10) and serves as the second ground plane (103) of the previous Vivaldi antenna unit (10); the second ground plane (103) of the previous Vivaldi antenna unit (10) intersects with the substrate (106) of the previous Vivaldi antenna unit (10), and the second ground plane (103) of the previous Vivaldi antenna unit (10) is symmetrically arranged about the intersection line; The power supply network (2) includes: an ultra-wideband power divider (21), two Wilkinson power dividers (22) and two phase shifters (23); The ultra-wideband power divider (21) includes one input port and two output ports. The input port is connected to an external device, and the two output ports output differential output signals respectively. Each of the output ports is connected in sequence to a Wilkinson power divider (22) and a phase shifter (23). The Wilkinson power divider (22) is a one-to-two power divider, and the branches are isolated from each other; the output signals of the phase shifter (23) are 90° out of phase.

2. The ultra-wideband circularly polarized Vivaldi antenna according to claim 1, characterized in that, The Vivaldi antenna element (10) further includes: a feed conductor (104); The feed strip (104) is disposed on the first surface of the substrate (106) and located on the same side as the first side of the radiating arm (101); the first end of the feed strip (104) is connected to the radiating arm (101), and the second end of the feed strip (104) is connected to the feed network (2).

3. The ultra-wideband circularly polarized Vivaldi antenna according to claim 1, characterized in that, Length of the first ground plane (102) for: ； in, The length of the radiating arm; The first coefficient; This represents the length of the feed conductor.

4. The ultra-wideband circularly polarized Vivaldi antenna according to claim 1, characterized in that, The radiating arm (101) of the previous Vivaldi antenna element (10) is enclosed by an outer tapered curve, an inner tapered curve, a feed strip (104) and a first ground plane (102), wherein the outer tapered curve is set away from the feed network (2) and the inner tapered curve is set close to the feed network (2); A radiation gap is formed between the outer taper curve of the first Vivaldi antenna element (10) and the first ground plane (102) of the second Vivaldi antenna element (10).

5. The ultra-wideband circularly polarized Vivaldi antenna according to claim 4, characterized in that, The outer taper curve for: ； in, The width of the radiating arm; The curvature index of the external taper curve; The coordinates of the external taper curve on the x-axis; This is the distance between the starting point of the outer tapered curve and the first ground plane of the next Vivaldi antenna element.

6. The ultra-wideband circularly polarized Vivaldi antenna according to claim 5, characterized in that, The inner taper curve for: ； in, The width of the inner taper curve; The length of the inner taper curve; The curvature index of the inner taper curve; The coordinates of the external taper curve on the x-axis; The width of the feed conductor.

7. The ultra-wideband circularly polarized Vivaldi antenna according to claim 1, characterized in that, The ultra-wideband power divider (21) includes: a microstrip structure (210), a dielectric substrate (220), and a ground plane (230); The microstrip structure (210), the dielectric substrate (220), and the ground plane (230) are arranged sequentially from top to bottom; The microstrip structure (210) includes: a first microstrip line (211), a second microstrip line (212), and a third microstrip line (213); The second microstrip line (212) serves as an input microstrip line and is positioned between the first microstrip line (211) and the third microstrip line (213); the first microstrip line (211) and the third microstrip line (213) serve as output microstrip lines, respectively.

8. The ultra-wideband circularly polarized Vivaldi antenna according to claim 7, characterized in that, The first microstrip line (211), the second microstrip line (212), and the third microstrip line (213) each include: a first stub (2111) and a microstrip line (2112); Wherein, the first branch (2111) is a fan-shaped branch, the terminal of the microstrip line (2112) is connected to the center of the first branch (2111), and the fan-shaped branch protrudes toward the terminal of the microstrip line (2112); The microstrip line (2112) in the first microstrip line (211), the second microstrip line (212), and the third microstrip line (213) are parallel to each other.

9. The ultra-wideband circularly polarized Vivaldi antenna according to claim 8, characterized in that, The floor (230) has rectangular grooves (231) and two fan-shaped groove branches (232); The rectangular groove (231) is perpendicular to the microstrip line (2112), and the two ends of the rectangular groove (231) are respectively connected to the centers of the two fan-shaped groove branches (232); the two fan-shaped groove branches (232) protrude towards the two ends of the rectangular groove (231); The two fan-shaped groove branch segments (232) partially overlap with the first branch segment (2111) of the first microstrip line (211) and the third microstrip line (213), respectively, and the fan-shaped groove branch segment (232) is the same size as the first branch segment (2111).

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