Broadband circular polarization vivaldi antenna based on spatial spiral structure

Abstract

The invention discloses a broadband circularly polarized vivaldi antenna based on a spatial spiral structure, belongs to the technical field of circularly polarized antennas, solves the problem of how to reduce the azimuth sensitivity of the vivaldi antenna, and comprises a dielectric substrate and a radiation unit, the upper surface of the dielectric substrate is provided with a metal grounding layer, the metal grounding layer is provided with a circular resonant cavity and a slot line, one end of the slot line is connected with the circular resonant cavity, and the other end of the slot line extends in the direction away from the dielectric substrate; the radiation unit comprises metal elements, and the two metal elements form a double-helix structure by taking the extension direction of the slot line as a central axis; according to the invention, a traditional vivaldi antenna is subjected to spatial spiraling, a spiral phase delay mechanism is utilized, a 90-degree phase difference is naturally generated in a broadband, a traditional phase shifter is replaced, circularly polarized waves are generated, and the broadband circular polarization characteristic can be realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of circularly polarized antennas, and relates to a wideband circularly polarized Vivaldi antenna based on a space spiral structure. BACKGROUND

[0002] At the critical point of 6G technology evolution, modern wireless systems are facing the paradigm reconstruction of physical layer devices, and new scenarios such as space-ground integrated network, millimeter wave perception fusion communication and quantum encryption transmission put forward new requirements for the core components of radio frequency front end.

[0003] The Vivaldi antenna is a wideband, low-profile directional antenna, which belongs to a planar structure antenna and is composed of a gradually expanding slot line. The shape of the Vivaldi antenna is similar to that of a violin designed by the musician Vivaldi and is therefore named. The Vivaldi antenna has excellent radiation characteristics and a wide frequency band, is famous for its wideband characteristics and high gain, and has a simple structure design. It is an end-fire type ultra-wideband traveling wave antenna and is widely used in the fields of ultra-wideband wireless communication, direction finding, wideband phased array radar and radio astronomy.

[0004] The electromagnetic wave transmitted or received by the antenna has an electric field direction, which defines the polarization mode of the wave. The traditional Vivaldi antenna is a linearly polarized antenna, and linear polarization has high requirements for the direction of the antenna. The receiving effect of the antenna depends on the matching degree of the polarization direction of the transmitting and receiving antennas: if the polarization directions are completely consistent, the maximum receiving signal can be obtained; if the polarization directions are partially deviated, the receiving signal will be greatly attenuated or almost no signal can be received. Therefore, the linearly polarized antenna has strict requirements for the installation angle and attitude adjustment, and has high requirements for the azimuth sensitivity of the antenna. The circularly polarized antenna has the same induced signal regardless of the polarization direction of the receiving antenna. If the Vivaldi antenna adopts the circular polarization mode, the azimuth sensitivity of the system can be reduced.

[0005] The prior art such as the invention patent with the application publication number CN119253274A discloses an ultra-wideband compact circularly polarized antenna based on a miniaturized phase shifter. Two orthogonal Vivaldi antennas and a feed network are cascaded to realize the wideband matching characteristics by designing a metal coupling sheet, a sawtooth structure and a Γ-shaped balun to form the Vivaldi antenna. However, the design is composed of multiple units, and the size is large, which limits its use in space-limited platforms. In addition, the structure of the feed part is complex, which increases the processing complexity. SUMMARY

[0006] The technical problem to be solved by the application is how to reduce the azimuth sensitivity of the Vivaldi antenna.

[0007] The application solves the above technical problems through the following technical scheme:

[0008] The wideband circularly polarized Vivaldi antenna based on a spatial spiral structure comprises a dielectric substrate and a radiation unit.

[0009] The upper surface of the dielectric substrate is provided with a metal ground layer, the metal ground layer is provided with a circular resonant cavity and a slot line, one end of the slot line is connected with the circular resonant cavity, the other end of the slot line extends away from the dielectric substrate, and the extension direction of the slot line is perpendicular to the bottom edge of the dielectric substrate.

[0010] The radiation unit comprises metal elements, the two metal elements are arranged as a double spiral structure with the extension direction of the slot line as the central axis, one end of the metal element is fixedly connected with the edge of the metal ground layer, the other end of the metal element extends along the slot line, and the opening width of the other end of the metal element increases exponentially.

[0011] The lower surface of the dielectric substrate is provided with a microstrip feed line, the input port of the microstrip feed line is aligned with any bottom edge of the dielectric substrate, and the output end of the microstrip feed line is coupled to feed power to the slot line.

[0012] Further, the microstrip feed line comprises a rectangular microstrip line, an L-shaped microstrip line and a fan-shaped stub; one end of the rectangular microstrip line serves as an input port, the other end of the rectangular microstrip line is connected with the short edge of the L-shaped microstrip line, and the long edge of the L-shaped microstrip line is connected with the fan-shaped stub.

[0013] Further, the long edge of the L-shaped microstrip line is perpendicular to the rectangular microstrip line and parallel to the input port, the bottom edge, the extension direction of the slot line is away from the bottom edge, and the extension direction of the slot line is parallel to the rectangular microstrip line.

[0014] Further, the dielectric substrate adopts Rogers RT5880, the relative dielectric constant is 2.2, and the dielectric loss tangent is 0.0009.

[0015] Further, the size of the metal ground layer is 80*15mm.

[0016] Further, the length of the rectangular microstrip line is 8mm, the width is 1.47mm; the length of the long edge of the L-shaped microstrip line is 8.22mm, the width is 0.78mm; the length of the short edge of the L-shaped microstrip line is 4.11mm, the width is 0.55mm; and the radius of the fan-shaped stub is 3.02mm.

[0017] Further, the working frequency band of the antenna is 3GHz-3.5GHz.

[0018] The application has the following advantages:

[0019] The vivaldi antenna of the application replaces the planar horn mouth shape radiation arm of the traditional vivaldi antenna with a radiation unit which presents a double helix structure in space, uses a helix phase delay mechanism to naturally generate a 90° phase difference in a wide frequency band, replaces the traditional phase shifter, generates a circularly polarized wave by adopting the space helix of the traditional vivaldi antenna, can realize the wideband circular polarization characteristic, can maintain the end-fire characteristic while maintaining the circular polarization performance, and realizes the helix-traveling wave composite structure; the vivaldi antenna design method of the application can be used for the design of a new type of circularly polarized antenna, and has good application value in the fields of wideband wireless communication, direction finding, wideband phased array radar and radio astronomy. BRIEF DESCRIPTION OF DRAWINGS

[0020] Fig. 1(a) is a schematic diagram of the overall structure of the vivaldi antenna of the embodiment one of the application;

[0021] Fig. 1(b) is a schematic diagram of a partial enlargement of the dielectric substrate of the embodiment one of the application;

[0022] Fig. 2(a) is a schematic diagram of the vivaldi antenna of the embodiment one of the application from the top;

[0023] Fig. 2(b) is a schematic diagram of the vivaldi antenna of the embodiment one of the application from the bottom;

[0024] Figure 3 Fig. 3 is a schematic diagram of the vivaldi antenna of the embodiment one of the application from the side;

[0025] Figure 4 Fig. 4 is a schematic diagram of the vivaldi antenna of the embodiment one of the application from the front;

[0026] Figure 5 Fig. 5 is a differential reflection coefficient curve diagram of the radiation unit of the embodiment one of the application;

[0027] Figure 6 Fig. 6 is an axial ratio curve diagram of the vivaldi antenna of the embodiment one of the application at 3-3.5GHz;

[0028] Fig. 7(a) is a radiation pattern diagram of the vivaldi antenna of the embodiment one of the application at Phi=0°, 3.1GHz;

[0029] Fig. 7(b) is a radiation pattern diagram of the vivaldi antenna of the embodiment one of the application at Phi=90°, 3.1GHz;

[0030] Fig. 7(b) is a radiation pattern diagram of the vivaldi antenna of the embodiment one of the application at Phi=90°, 3.1GHz; DETAILED DESCRIPTION

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0033] Example 1

[0034] like Figures 1(a) to 4 As shown, specifically, a broadband circularly polarized Vivaldi antenna based on a spatial spiral structure is disclosed, including a dielectric substrate 5 and a radiating element 7;

[0035] A metal ground layer is provided on the upper surface of the dielectric substrate 5. The metal ground layer has a circular resonant cavity 4 and a groove line 6. One end of the groove line 6 is connected to the circular resonant cavity 4, and the other end of the groove line 6 extends away from the dielectric substrate 5. The extension direction of the groove line 6 is perpendicular to the bottom edge of the dielectric substrate 5.

[0036] Furthermore, the metal ground layer is disposed on the upper surface of the dielectric substrate 5 by means of copper plating, ensuring the stability of the signal return path, while shielding and isolating external signal interference. In this embodiment, the circular resonant cavity 4 is used to improve impedance matching, specifically by converting the unbalanced microstrip line feed into a balanced slot line radiation structure, eliminating common-mode current interference, and improving signal transmission efficiency.

[0037] In this embodiment, the dielectric substrate 5 is Rogers RT5880 with a relative permittivity of 2.2 and a dielectric loss tangent of 0.0009; the size of the metal ground layer is 80×15mm.

[0038] In this embodiment, the radius of the circular resonant cavity 4 is 1.5 mm.

[0039] In this embodiment, the groove line 6 has a width of 0.4 mm and a length of 3 mm on the dielectric substrate 5.

[0040] The radiation unit 7 includes a metal element. Two metal elements form a double helix structure with the extension direction of the groove line 6 as the central axis. One end of the metal element is fixedly connected to the edge of the metal grounding layer, and the other end of the metal element extends along the groove line 6. The opening width of the other end of the metal element gradually changes in an exponential manner, specifically increasing exponentially.

[0041] In the embodiment, the radiation unit 7 is composed of two metal elements with exponentially varying open width along the extension direction of the slot line 6, the material of the metal elements is copper, the bending path of the spiral structure forces the separation of the current components, the angular current path is λ / 4 longer than the radial current path, and a 90° phase difference is formed; the exponentially varying structure maintains the orthogonal phase difference generated by the spiral under the premise of maintaining the spiral, and maintains the circular polarization characteristics through the phase continuity of the traveling wave and the invariable path delay.

[0042] In the embodiment, the length of the metal element is 120 mm, the initial width is 39.8 mm, the exponential variation factor p is 5, and the spiral factor n is 2.08.

[0043] The lower surface of the dielectric substrate 5 is provided with a microstrip feed line, the input port of the microstrip feed line is aligned with any bottom edge of the dielectric substrate 5, and the output end of the microstrip feed line is coupled to the slot line 6 for feeding.

[0044] Further, the microstrip feed line includes a rectangular microstrip line 1, an L-shaped microstrip line 2, and a fan-shaped stub 3; one end of the rectangular microstrip line 1 serves as an input port, the other end of the rectangular microstrip line 1 is connected to the short side of the L-shaped microstrip line 2, and the long side of the L-shaped microstrip line 2 is connected to the fan-shaped stub 3. In the embodiment, the fan-shaped structure of the stub can guide the current to distribute along a specific path, suppress non-radiation modes, and thus improve the main lobe gain. The geometric symmetry helps to maintain stable current distribution in a wide frequency band and avoid performance fluctuations caused by frequency changes. In the embodiment, an electrical path is not required between the upper and lower surfaces of the dielectric substrate 5, and only the coupling feeding mode is used to transmit the electromagnetic signal from the microstrip line to the slot line 6 without electrical connection.

[0045] Specifically, the long side of the L-shaped microstrip line 2 is perpendicular to the rectangular microstrip line 1 and parallel to the bottom edge aligned with the input port, and the extension direction of the slot line 6 is away from the bottom edge and parallel to the rectangular microstrip line 1. The input port is a microstrip single feed, which has the advantages of simple structure, low cost, and easy implementation.

[0046] As shown in Figures 2(a) to 2(b) The projection of the connection between the L-shaped microstrip line 2 and the fan-shaped stub 3 on the metal ground layer coincides with one end of the slot line 6.

[0047] Further, the length of the rectangular microstrip line 1 is 8 mm, and the width is 1.47 mm; the length of the long side of the L-shaped microstrip line 2 is 8.22 mm, and the width is 0.78 mm; the length of the short side of the L-shaped microstrip line 2 is 4.11 mm, and the width is 0.55 mm; and the radius of the fan-shaped stub 3 is 3.02 mm.

[0048] Working principle:

[0049] In the working process of the vivaldi antenna, the microstrip feed line arranged on the lower surface of the dielectric substrate 5 receives electromagnetic signals through the input port, and the energy is coupled and fed through the fan-shaped stub 3 and the slot line 6. The slot line part confines the energy inside the slot line 6 and transmits the energy to the radiation unit 7, and finally the energy is radiated outward by the radiation unit 7 in the spiral structure. The vivaldi antenna can realize stable circularly polarized wave radiation in a wide frequency band. The transition from the transmission mode to the radiation mode is as follows: the radiation of the vivaldi antenna in the spiral structure is the process of gradually releasing energy in the slot line in the spiral structure, and the core is the mode conversion guided by the gradual change structure. At the beginning of the slot line, the slot width is very narrow, and the electromagnetic wave is mainly in the transmission mode, and the radiation is weak; as the spiral extends, the pitch gradually increases according to the design rule, and the energy is no longer confined in the slot, and the electromagnetic wave is mainly in the radiation mode, and begins to radiate to the space, and the phase superposition effect is that each segment of the slot line in the spiral structure part can be regarded as a small radiation unit. Due to the gradual change of the spiral parameters (pitch, angle), the radiation units at different positions produce constructive interference in a specific direction, enhancing the main lobe gain, while the side lobe direction is suppressed due to phase cancellation, thereby having an end-fire characteristic.

[0050] As shown in Figures 5 to 6 , the wideband circularly polarized vivaldi antenna based on the spatial spiral structure is subjected to electromagnetic simulation test, Figure 5 is a differential reflection coefficient curve of the radiation unit 7, Figure 6 is an axial ratio curve of the vivaldi antenna designed by using the above parameters in the frequency band of 3-3.5 GHz. In the frequency band of 3-3.5 GHz, the reflection coefficient is less than -10 dB, and the axial ratio is lower than 3 dB. As shown in FIG. 7(a), the radiation pattern when 3.1 GHz, Phi=0°, and FIG. 7(b) is the radiation pattern when 3.1 GHz, Phi=90°, wherein the solid line is left-handed polarization, and the dashed line is right-handed polarization. The vivaldi antenna presents stable radiation at 3.1 GHz, and has good wideband circularly polarized characteristics.

[0051] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0052] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A broadband circularly polarized vivaldi antenna based on spatial spiral structure, characterized in that, The antenna comprises a dielectric substrate and a radiation unit. The upper surface of the dielectric substrate is provided with a metal ground layer, the metal ground layer is provided with a circular resonant cavity and a slot line, one end of the slot line is connected with the circular resonant cavity, the other end of the slot line extends away from the dielectric substrate, and the extension direction of the slot line is perpendicular to the bottom edge of the dielectric substrate. The radiation unit comprises metal elements, two metal elements are arranged as a double helix structure with the extension direction of the slot line as the central axis, one end of the metal element is fixedly connected with the edge of the metal ground layer, the other end of the metal element extends along the slot line, and the opening width of the other end of the metal element increases exponentially. The lower surface of the dielectric substrate is provided with a microstrip feed line, the input port of the microstrip feed line is aligned with any bottom edge of the dielectric substrate, and the output end of the microstrip feed line is coupled to the slot line.

2. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 1, wherein, The microstrip feed line comprises a rectangular microstrip line, an L-shaped microstrip line and a fan-shaped stub; one end of the rectangular microstrip line serves as an input port, the other end of the rectangular microstrip line is connected with the short edge of the L-shaped microstrip line, and the long edge of the L-shaped microstrip line is connected with the fan-shaped stub.

3. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 2, wherein, The long edge of the L-shaped microstrip line is perpendicular to the rectangular microstrip line and parallel to the bottom edge aligned with the input port, the extension direction of the slot line is away from the bottom edge, and the extension direction of the slot line is parallel to the rectangular microstrip line.

4. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 1, wherein, The dielectric substrate adopts Rogers RT5880, the relative dielectric constant is 2.2, and the dielectric loss tangent is 0.0009.

5. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 1, wherein, The size of the metal ground layer is 80*15 mm.

6. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 1, wherein, The length of the rectangular microstrip line is 8 mm, and the width is 1.47 mm; the length of the long edge of the L-shaped microstrip line is 8.22 mm, and the width is 0.78 mm; the length of the short edge of the L-shaped microstrip line is 4.11 mm, and the width is 0.55 mm; and the radius of the fan-shaped stub is 3.02 mm.

7. The spatial-spiral-structure-based wideband circularly-polarized Vivaldi antenna according to claim 1, wherein, The working frequency band of the antenna is 3 GHz-3.5 GHz.

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