Polarization diversity conformal quasi-end-on-fire antenna array device

Abstract

The invention relates to the technical field of radar antennas, in particular to a polarization diversity conformal quasi-end-on-fire antenna array device which is provided with a cylindrical metal carrier, the antenna array device has an approximate dual-polarization radiation pattern, and a main beam is approximate to end-on-fire, namely along the cylindrical axis direction of the metal carrier; more than two dual-polarization broadband antenna units are arranged on the surface of a metal carrier, each antenna unit can receive approximately orthogonal radiation source signal components of radiation source signals, an approximately horizontal polarization antenna in each antenna unit adopts a conformal printing yagi-directional antenna, and the radiation source signal components of the radiation source signals are approximately orthogonal radiation source signal components of the radiation source signals. The approximately vertical polarization antenna adopts a cylindrical conformal fan-shaped H-surface horn antenna; a cylindrical conformal electromagnetic band gap (EBG) structure is also arranged on the surface of the cylindrical metal carrier; compared with the prior art, the antenna has the characteristics of low profile, compact structure, low cost, quasi-end-fire radiation pattern and the like, and is suitable for occasions of aircraft carrier radar seekers, electronic reconnaissance systems and the like.

Description

Technical Field

[0001] This invention relates to the field of radar antenna technology, specifically to a polarization diversity conformal quasi-end-fire antenna array device with characteristics such as low profile, compact structure, low cost, and quasi-end-fire radiation pattern, suitable for applications such as radar seekers for aircraft carriers and electronic reconnaissance systems. Background Technology

[0002] In passive radar seekers, the antenna primarily functions to receive signals from radiating sources. To measure and resolve signals from multiple sources, multiple antenna elements are typically placed on the aircraft platform to form an array structure, creating a multi-baseline measurement pattern. Commonly used antenna types include log-periodic antennas, Vivaldi antennas, equiangular spiral antennas, Archimedes spiral antennas, and zigzag-arm antennas. These types of antennas typically exhibit broadband impedance and pattern characteristics. Due to the very limited space on the aircraft platform, the design of passive receiving antennas requires full utilization of the platform's size and shape characteristics; miniaturization and low-profile design are among the key challenges.

[0003] In active and passive radar antenna systems, the active radar antenna is typically located in the middle of the antenna aperture, while the passive radar antenna is located at the circumferential edge of the aperture. To fully utilize the antenna mounting space, the passive radar antenna can be designed and laid out conformally to the carrier surface. Depending on the radar's detection area and operating mode, the passive radar antenna is usually required to have an approximate end-fire pattern. Due to the influence of the carrier, the radiation characteristics of a broadband antenna change significantly compared to free space. For antennas that need to be mounted on a cylindrical metal carrier surface, conformal end-fire antennas can be used, such as Vivaldi conformal antennas and log-periodic conformal antennas. Due to the electrical boundary conditions of the metal carrier surface, a noticeable upward tilting of the radiation pattern occurs when the antenna is close to the cylindrical metal conductor surface, which affects the radar's detection performance to some extent. To improve the ability to resolve and identify radiation source signals, broadband array antennas are usually required to sense the polarization information of the radiation source signal. Therefore, the design and development of broadband polarization-sensitive array antennas has become one of the important tasks in this antenna design field. Summary of the Invention

[0004] This invention addresses the shortcomings and deficiencies of existing technologies by proposing a polarization diversity conformal quasi-end-fire antenna array device with characteristics such as low profile, compact structure, low cost, and quasi-end-fire radiation pattern, suitable for applications such as aircraft carrier radar seekers and electronic reconnaissance systems.

[0005] This invention achieves its purpose through the following measures: A polarization diversity conformal quasi-end-fire antenna array device is characterized by comprising a cylindrical metal carrier, the antenna array device having an approximately dual-polarized radiation pattern, the main beam being approximately end-fired, i.e., along the cylindrical axis of the metal carrier; two or more dual-polarized broadband antenna elements are disposed on the surface of the metal carrier, each antenna element being capable of receiving approximately orthogonal radiation source signal components, wherein the approximately horizontally polarized antenna in each antenna element is a conformal printed Yagi directional antenna, and the approximately vertically polarized antenna is a cylindrical conformal sector-shaped H-plane horn antenna. The cylindrical conformal electromagnetic bandgap structure EBG is also arranged on the surface of the cylindrical metal carrier to improve the radiation characteristics of the printed Yagi directional antenna. The cylindrical conformal sector H-plane horn antenna includes a cylindrical conformal rectangular waveguide, a cylindrical conformal H-plane sector horn, and a dielectric block. The dielectric block is arranged between the electromagnetic bandgap structure EBG and the Yagi directional antenna. The dielectric block is located at the front end of the cylindrical conformal H-plane sector horn to form a dielectric loading. The horn of the cylindrical conformal H-plane sector horn is filled with a dielectric material, and the dielectric material has the same dielectric constant as the dielectric block.

[0006] The conformal printed Yagi directional antenna described in this invention is printed on a single-layer microwave dielectric substrate, specifically on a flexible printed circuit board. The conformal printed Yagi directional antenna has an end-fire radiation pattern and is arranged conformally above a metal cylindrical surface. That is, the flexible printed circuit board is arranged around the surface of the metal carrier, with a gap between it and the surface of the metal carrier. The polarization direction of the radiation field of the conformal printed Yagi directional antenna is approximately parallel to the surface of the metal cylindrical conductor, effectively saving installation space. By using a flexible printed circuit board with a conformal metal carrier to set the Yagi directional antenna structure, both the feed part and the radiating element part of the Yagi directional antenna exhibit the curved shape of the conformal cylindrical metal carrier. The conformal printed Yagi directional antenna uses symmetrical printed elements with non-planar feeds on the upper and lower sides of the dielectric substrate as exciters. The length of the director gradually decreases in the axial direction. Each director element is divided into upper and lower parts on the dielectric substrate, which are interconnected by conductive vias. The active symmetrical oscillator and the passive director element have the same width, and a linear tapered balun is introduced. A truncated ground plane is used as a reflector. There is one active element and three director elements. The lengths of the active element and the director elements are denoted as L1, L2, L3, and L4, respectively. The distance between the active element and the balun is d1, the distance between the active element and the first director element is d2, the distance between the second director element and the first director element is d3, and the distance between the third director element and the second director element is d4. The length of the linear tapered balun is d0. The width of the microstrip line is w_MSL, the width of the microstrip line ground plane is W_gnd, and the characteristic impedance of the microstrip line is 50 ohms.

[0007] In each antenna element of this invention, the antenna with a polarization direction approximately perpendicular to the surface of the cylindrical metal carrier adopts a cylindrical conformal H-plane sector horn antenna. To achieve miniaturization of the horn antenna, a dielectric-filled horn structure is introduced. To improve the radiation pattern of the horn antenna, a dielectric block is loaded at the front end of the aperture of the cylindrical conformal H-plane sector horn. This dielectric block also serves to support the printed Yagi-guided antenna, improving the low profile. Considering the shape characteristics of the cylindrical metal carrier structure, the vertically polarized antenna element uses a cylindrical curved rectangular waveguide for feeding. At the end of the conformal rectangular waveguide, the horn aperture gradually opens in the H-plane, forming an effective aperture, constituting an H-plane cylindrical conformal sector horn radiator. Based on the cylindrical conformal H-plane sector horn, a dielectric material with a relative permittivity of [insert relative permittivity here]. The radiation characteristics of the cylindrical conformal horn are improved by changing its internal field distribution; the dielectric material is extended along the axial direction of the cylinder to form a dielectric block loaded at the front end of the cylindrical conformal antenna. The dielectric block and the filling dielectric material achieve the goals of miniaturization and pattern adjustment of the cylindrical conformal horn antenna.

[0008] The bandgap characteristics of the electromagnetic bandgap structure EBG described in this invention can be used to suppress surface waves of microstrip antennas and improve the radiation performance of the antenna. This invention employs a mushroom-shaped electromagnetic bandgap structure EBG, also known as a high-impedance surface (HIS). Its bandgap characteristics are generated by the resonance or harmonic mechanism of the periodic unit. The patch shape is square, and the capacitance C is generated by the coupling of the edges of two adjacent patches. Its calculation formula is as follows: (1), where It is the patch width. It is the width of the gap between two adjacent patches. It is the relative permittivity, inductance The loop formed by the metal holes is determined by the thickness and permeability of the medium, and its calculation formula is as follows: (2), The impedance of the entire parallel LC circuit can be calculated using the following formula: (3) The resonant frequency of this circuit is: (4), At low frequencies, the circuit impedance is inductive, supporting TM wave transmission; at high frequencies, the circuit impedance is capacitive, supporting TE wave transmission. When near the point of contact, the circuit exhibits high impedance, and the EBG structure does not allow any electromagnetic waves to propagate, thus creating a frequency bandgap.

[0009] This invention proposes a polarization diversity array antenna device conformally placed on the surface of a metal cylinder. Addressing the boundary conditions of the cylindrical metal surface, this invention designs a quasi-end-fire antenna array employing polarization diversity. The approximately vertically polarized antenna utilizes a dielectric-loaded fan-shaped horn antenna; the approximately horizontally polarized antenna utilizes a cylindrical conformally printed Yagi antenna. To reduce the influence of the metal carrier on the printed Yagi antenna and improve the radiation pattern, a mushroom-shaped electromagnetic bandgap (EBG) structure is loaded onto the metal cylindrical surface. This invention's polarization diversity conformally placed quasi-end-fire antenna array device combines the characteristics of the carrier material and shape, starting from the end-fire characteristics of the radiation pattern, and integrates two conformally fired antenna structures. The design principle is simple, easy to manufacture, and low-cost, making it suitable for engineering applications. This array antenna features a low profile, compact structure, low cost, and a quasi-end-fire radiation pattern, making it suitable for engineering implementation. The polarization diversity array antenna device conformally placed on the surface of a metal cylinder proposed in this invention is suitable for applications such as aircraft carrier radar seekers and electronic reconnaissance systems. Attached Figure Description

[0010] Appendix Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0011] Appendix Figure 2 This is a schematic diagram of the structure after removing the printed dielectric substrate and the front-end loaded dielectric block in this invention.

[0012] Appendix Figure 3 This is a schematic diagram of the structure for removing the printed media substrate according to the present invention.

[0013] Appendix Figure 4 This is a schematic diagram of the structure of the draft antenna after removing the dielectric substrate according to the present invention, wherein, Figure 4 (a) is a 3D view, (b) is a top view, (c) is a left view, and (d) is a right view.

[0014] Appendix Figure 5 This is a structural diagram of the cylindrical conformal H-plane horn antenna in this invention, wherein... Figure 5 (a) is a three-dimensional view of any H-plane horn antenna, (b) is an end view of any H-plane horn antenna, (c) is a front view of any H-plane horn antenna, and (d) is a left view of any H-plane horn antenna.

[0015] Appendix Figure 6 This is a schematic diagram of the electromagnetic bandgap structure EBG relative to the cylindrical metal carrier in this invention, wherein... Figure 6 (a) is a 3D view, (b) is a top view, (c) is a left view, and (d) is a magnified view.

[0016] Appendix Figure 7 This is a graph showing the simulation results of the scattering parameters of the antenna device in this embodiment of the invention. Figure 7 (a) is the return loss curve of the port with approximately horizontal polarization, (b) is the return loss curve of the port with approximately vertical polarization, and (c) is the isolation curve between the horizontal and vertical polarization ports.

[0017] Figure 8 These are simulation results of the radiation pattern of the horizontal polarization port of the antenna device in this embodiment of the invention at a frequency of 6 GHz. Figure 8 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0018] Figure 9 This is a simulation result of the radiation pattern of the vertical polarization port of the antenna device in this embodiment of the invention at a frequency of 6 GHz, wherein... Figure 9 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0019] Figure 10 This is a simulation result of the radiation pattern of the horizontal polarization port of the antenna device in this embodiment of the invention at a frequency of 7 GHz, wherein... Figure 10 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0020] Figure 11 This is a simulation result of the radiation pattern of the vertical polarization port of the antenna device according to an embodiment of the present invention at a frequency of 7 GHz, wherein... Figure 11 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0021] Figure 12 These are simulation results of the radiation pattern of the horizontal polarization port of the antenna device in this embodiment of the invention at a frequency of 8 GHz. Figure 12 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0022] Figure 13 This is a simulation result of the radiation pattern of the vertical polarization port of the antenna device in this embodiment of the invention at a frequency of 8 GHz, wherein... Figure 13 In the diagram, (a) is the three-dimensional gain pattern, (b) is the three-dimensional axial ratio pattern, (c) is the gain pattern in the xoz plane, and (d) is the gain pattern in the yoz plane.

[0023] Reference numerals: 1. Cylindrical metal carrier; 2. Dielectric substrate; 3. Conformal printed Yagi director antenna; 4. Cylindrical conformal H-plane sector horn; 5. Electromagnetic bandgap structure EBG; 6. Dielectric block; 7. Ground plane; 8. Feed microstrip line; 9. Balun; 10. Director element; 11. Conductive via; 12. Rectangular waveguide; 13. Cylindrical conformal H-plane sector horn; 14. Dielectric material. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] As shown in the attached figures, this invention proposes a polarization diversity conformal quasi-end-fire antenna array device, comprising a cylindrical metal carrier 1. The antenna array device has an approximately dual-polarized radiation pattern, with the main beam approximately end-fired, i.e., along the cylindrical axis of the metal carrier. Two or more dual-polarized broadband antenna elements are disposed on the surface of the metal carrier. Each antenna element can receive approximately orthogonal radiation source signal components. Specifically, in each antenna element, the approximately horizontally polarized antenna is a conformal printed Yagi directional antenna 3, and the approximately vertically polarized antenna is a cylindrical conformal sector-shaped H-plane horn antenna 4. The surface of the shaped metal carrier 1 is also arranged with a cylindrical conformal electromagnetic bandgap structure EBG5 to improve the radiation characteristics of the printed Yagi directing antenna; the cylindrical conformal sector H-plane horn antenna 4 includes a cylindrical conformal rectangular waveguide 12, a cylindrical conformal H-plane sector horn 13 and a dielectric block 6, wherein the dielectric block 6 is arranged between the electromagnetic bandgap structure EBG5 and the Yagi directing antenna, and the dielectric block 6 is located at the front end of the cylindrical conformal H-plane sector horn 13 to form a dielectric loading, and the horn interior of the cylindrical conformal H-plane sector horn 13 is filled with dielectric material 14, and the dielectric material 14 has the same dielectric constant as the dielectric block 6.

[0026] The conformal printed Yagi directional antenna 3 described in this invention is printed on a single-layer microwave dielectric substrate 2, specifically on a flexible printed circuit board. The conformal printed Yagi directional antenna 3 has an end-fire radiation pattern and is arranged above the surface of a cylindrical metal carrier 1 using a conformal arrangement of cylindrical surfaces. Specifically, the flexible printed circuit board surrounds the surface of the cylindrical metal carrier 1 and has a gap from the surface of the cylindrical metal carrier 1. The polarization direction of the radiation field of the conformal printed Yagi directional antenna 3 is approximately parallel to the surface of the cylindrical metal conductor, effectively saving installation space. By using a flexible printed circuit board with a conformal metal carrier to set the Yagi directional antenna structure, both the feed portion and the radiating element portion of the Yagi directional antenna exhibit the curved shape of the conformal cylindrical metal carrier 1. The conformal printed Yagi directional antenna 3 uses symmetrically printed elements fed from opposite sides on the upper and lower surfaces of the dielectric substrate 2 as exciters. The length of the director gradually decreases in the axial direction, and each director element is divided into sections on the dielectric substrate 2. The upper and lower parts are interconnected by conductive vias 11. The symmetrical active oscillator and the passive director oscillator have the same width. Since the symmetrical oscillator uses a balanced feed and the microstrip line uses an unbalanced feed, an unbalanced-to-balanced converter, balun 9, is introduced from the microstrip line to the dual-line. Balun 9 adopts an ultra-wideband linear gradient structure and also has impedance transformation functionality. A truncated ground plane 7 is used as a reflector. There is one active oscillator and three director oscillators 10. The lengths of the director elements 10 are denoted as L1, L2, L3, and L4, respectively. The distance between the active element and the balun 9 is d1, the distance between the active element and the first director element is d2, the distance between the second director element and the first director element is d3, the distance between the third director element and the second director element is d4, the length of the linear tapered balun is d0, the width of the feed microstrip line 8 is w_MSL, the width of the feed microstrip line ground plane 7 is W_gnd, and the characteristic impedance of the microstrip line is 50 ohms.

[0027] In each antenna unit of this invention, the antenna with a polarization direction approximately perpendicular to the surface of the cylindrical metal carrier 1 adopts a cylindrical conformal H-plane sector horn antenna. To achieve miniaturization of the horn antenna, a dielectric material 14 is introduced to fill the horn structure. To improve the radiation pattern of the horn antenna, a dielectric block is loaded at the front end of the aperture of the cylindrical conformal H-plane sector horn. This dielectric block also serves to support the printed Yagi directional antenna, improving the low profile. Considering the shape characteristics of the cylindrical metal carrier structure, the vertically polarized antenna unit uses a rectangular waveguide 12 that conforms to the cylinder and is bent accordingly. At the end of the cylindrical conformal rectangular waveguide 12, the horn aperture gradually opens in the H-plane, forming an effective aperture and constituting a cylindrical conformal H-plane sector horn radiator. Based on the cylindrical conformal H-plane sector horn, a dielectric material with a relative permittivity of [missing information] is loaded inside it. The radiation characteristics of the cylindrical conformal horn are improved by changing its internal field distribution; the dielectric material is extended along the axial direction of the cylinder to form the dielectric block 6 loaded at the front end of the cylindrical conformal antenna. The dielectric block 6 and the filling dielectric material achieve the goals of miniaturization and pattern adjustment of the cylindrical conformal horn antenna.

[0028] The electromagnetic bandgap structure EBG described in this invention adopts a cylindrical metal conformal structure. The bandgap characteristics can be used to suppress surface waves of microstrip antennas and improve the radiation performance of the antenna. The electromagnetic bandgap structure EBG adopts a mushroom-shaped electromagnetic bandgap structure, also known as a high impedance surface. Its bandgap characteristics are generated by the resonance or resonant mechanism of the periodic unit. The patch shape is square. Example

[0029] This example proposes a polarization diversity array antenna device conformally placed on the surface of a cylindrical metal structure, exhibiting an approximately dual-polarized radiation pattern. The main beam is approximately end-fired, i.e., along the cylindrical axis. Several dual-polarized broadband antenna elements are placed on the cylindrical metal surface, each capable of receiving approximately orthogonal radiation source signal components. The approximately horizontally polarized antenna employs a conformal printed Yagi directional antenna, while the approximately vertically polarized antenna employs a cylindrical conformal sector-shaped H-plane horn antenna. Since the cylindrical metal surface represents an electrical boundary condition, the printed Yagi directional antenna is affected by this boundary condition, resulting in decreased radiation efficiency and a noticeable upward tilting of the radiation pattern. To improve the radiation characteristics of the printed Yagi directional antenna and achieve a quasi-end-fired pattern within a certain wavelength range, an electromagnetic bandgap (EBG) structure is arranged on the cylindrical metal surface. Based on the special reflection phase characteristics of the EBG structure, the influence of the metal surface on the radiation characteristics of the printed Yagi directional antenna is reduced. Between the EBG structure and the printed Yagi directional antenna, a dielectric block structure is placed. This dielectric block is also located at the front end of the cylindrical conformal H-plane sector horn, forming a dielectric loading effect, which has a certain radiation pattern improvement and antenna miniaturization effect. The cylindrical conformal H-plane sector horn is also filled with dielectric material, which has the same dielectric constant as the dielectric loaded at its front end. Therefore, the designed cylindrical conformal H-plane sector horn antenna is a dielectric-filled horn antenna.

[0030] As attached Figure 1 As shown, the overall structure of the polarization diversity array antenna device in this example includes a cylindrical metal carrier 1, and a dielectric substrate 2 for a printed Yagi-guided antenna is arranged around the cylindrical metal carrier 1. Figure 2 To conceal the overall structure of the quasi-end-radius polarization diversity array antenna, including the printed dielectric substrate and the front-end loaded dielectric block, as shown in the diagram... Figure 3 As shown, this example includes a conformal printed Yagi directional antenna 3, a conformal H-plane sector horn antenna 4, a conformal EBG structure 5, and a loading medium block 6 at the front end of the horn antenna.

[0031] This example uses a printed Yagi directional antenna as an approximate horizontally polarized radiator. Yagi directional antennas are characterized by strong directivity, high gain, simple structure, and ease of fabrication. A Yagi antenna consists of an active dipole, a passive reflector, and several passive directors arranged in a row. It is a traveling-wave antenna that utilizes the mutual coupling of current elements in the standing waves to generate unidirectional radiation. The reflectors and directors before and after the dipole form an end-fire beam. With proper design of the size and spacing of the reflectors and directors, the current generated on the active dipole is increased, thus obtaining the directional radiation direction of the antenna. Microstrip quasi-Yagi antennas are printed on a single-layer microwave dielectric substrate, making them easier to integrate with microwave integrated circuits. In addition to their simple structure and high gain, microstrip quasi-Yagi antennas also offer advantages such as small size, light weight, conformal compatibility, and a large impedance bandwidth. The printed Yagi directional antenna designed in this example has an end-fire radiation pattern. It is arranged in a conformal manner above a certain distance on a metal cylindrical surface, and the polarization direction of the radiation field is close to parallel to the surface of the metal cylindrical conductor, effectively saving installation space. The printed Yagi directional antenna structure is fabricated using a flexible printed circuit board, and the entire antenna's feed section and radiating element section are cylindrical curved shapes. When this distance is much smaller than a quarter wavelength, the antenna's radiation efficiency is significantly reduced due to the mirror effect. Therefore, it is necessary to change the boundary conditions of the printed Yagi directional antenna's carrier surface, changing the ideal electrical boundary to a hybrid structure of dielectric block and EBG.

[0032] Figure 4 (a) is a structural model of a printed Yagi director antenna with a hidden dielectric substrate, wherein 7 is the ground plane of the feed microstrip line, 8 is the feed microstrip line, 9 is the balun of the microstrip tapered line, 10 is the printed director element, and 11 is the conductive via of the printed director element.

[0033] In this example, the printed Yagi director antenna uses symmetrical printed dipoles fed outwards on the upper and lower sides of the dielectric substrate as exciters. The length of the director gradually decreases in the axial direction. Each director dipole is divided into upper and lower parts on the dielectric substrate, interconnected by conductive vias. The active symmetrical dipole exciter and the passive director dipole have the same width. The symmetrical dipole is balanced fed, while the microstrip line is unbalanced fed. Therefore, this invention introduces a microstrip-to-dual-line unbalanced-to-balance converter (balun). This balun adopts an ultra-wideband linearly tapered structure and also has impedance transformation functionality. The truncated ground plane serves as a reflector. The lengths of the active dipole and the director dipole are L1, L2, L3, and L4, respectively. The distance between the active dipole and the balun is d1, the distance between the active dipole and the first director dipole is d2, the distance between the second director dipole and the first director dipole is d3, and the distance between the third director dipole and the second director dipole is d4. The length of the linear gradient balun is d0, the width of the microstrip line is w_MSL, the width of the microstrip line ground plane is W_gnd, and the characteristic impedance of the microstrip line is 50 ohms.

[0034] This example designs an antenna with a polarization direction approximately perpendicular to the surface of a cylindrical metal structure. The antenna employs a cylindrical conformal H-plane sector-shaped horn antenna. To achieve miniaturization, this invention introduces a dielectric-filled horn design. To improve the radiation pattern of the horn antenna, a dielectric block is loaded at the front end of the aperture of the cylindrical conformal H-plane sector-shaped horn. This dielectric block also serves to support the printed Yagi-type directional antenna, improving the low profile. Considering the shape characteristics of the cylindrical metal carrier structure, the vertically polarized antenna element uses a cylindrical curved rectangular waveguide for feeding. At the end of the conformal rectangular waveguide, the horn aperture gradually widens in the H-plane, forming an effective aperture. A cylindrical conformal sector horn radiator with an H-plane shape is constructed. Based on the cylindrical conformal H-plane sector horn, a dielectric material with a certain dielectric constant is loaded inside it. The relative dielectric constant is changed to improve the radiation characteristics of the cylindrical conformal horn by altering its internal field distribution. The filled dielectric block structure is extended along the axial direction of the cylinder to form the dielectric block loaded at the front end of the cylindrical conformal antenna. The dielectric material serves to achieve miniaturization and pattern adjustment of the cylindrical conformal horn antenna. This structure is simple. Based on the basic horn radiation characteristics, the parameters of the cylindrical conformal horn antenna are designed and optimized using full-wave electromagnetic simulation technology. The antenna structure design is convenient.

[0035] Figure 5 (a) is the structural model of a cylindrical conformal H-plane horn antenna. Figure 5 (b) Figure 5 (c) and Figure 5(d) are the front view, left view and top view of the cylindrical conformal H-plane horn antenna, respectively; where 12 is the cylindrical conformal rectangular waveguide, 13 is the cylindrical conformal H-plane horn, and 14 is the dielectric material filling the horn antenna; To reduce the profile height of printed Yagi-oriented antennas, improve their end-fire pattern characteristics, and enhance radiation resistance and efficiency, a cylindrical conformal EBG structure is arranged on a cylindrical metal surface. This forms a complex hybrid electromagnetic structure with the dielectric block, altering the electromagnetic boundary conditions of the cylindrical conformal printed Yagi-oriented antenna and reducing the influence of the metal carrier platform on its radiation characteristics. Electromagnetic bandgap (EBG) structures, as a special type of artificial electromagnetic material, are now widely used in microwave and antenna fields. The unique bandgap and co-directional reflection characteristics of EBG structures have led to their widespread application in the electromagnetic field. Using EBG structures in microwave device design can improve device performance; the bandgap characteristics of EBG structures can be used to suppress surface waves in microstrip antennas, improving their radiation performance. Mushroom-shaped EBG structures, also known as high-impedance surfaces (HIS), have bandgap characteristics generated by the resonance or harmonic mechanism of periodic units. The commonly used patch shape is square, and its structure is as follows: Figure 6 As shown in (d), the capacitor C is generated by the coupling between the edges of two adjacent patches, and its calculation formula is: (1), In the formula It is the patch width. It is the width of the gap between two adjacent patches. It is the relative permittivity, inductance The circuit formed by the metal holes is mainly determined by the thickness and permeability of the medium, and its calculation formula is as follows: (2), The impedance of the entire parallel LC circuit can be calculated using the following formula: (3), The resonant frequency of this circuit is: (4), At low frequencies, the circuit impedance is inductive, supporting TM wave transmission; at high frequencies, the circuit impedance is capacitive, supporting TE wave transmission. When near the surface, the loop exhibits high impedance, and the EBG structure does not allow any electromagnetic wave transmission, thus forming a frequency bandgap. For the design of a cylindrical conformal mushroom-shaped EBG structure, based on the above basic principles and design methods, basic parameter settings are performed. Combining the shape characteristics and boundary conditions of the cylindrical surface, full-wave electromagnetic simulation technology is used for parameter scanning and optimization, and then the specific dimensions and parameters of the cylindrical conformal EBG structure are determined. Figure 6 (a) is a conformal EBG structure model of a cylinder. Figure 6 Image (b) is a top view of the cylindrical conformal EBG structure. Figure 6 (c) is the left view of the cylindrical conformal EBG structure model. Figure 6 The middle (d) is a magnified view of a cylindrical conformal EBG structure.

[0036] This example designs a quasi-end-radio polarized diversity array antenna device conforming to the surface of a cylindrical metal carrier. The performance of the array antenna was simulated using full-wave electromagnetic simulation software. The simulation results verify the feasibility of the proposed quasi-end-radio polarized diversity array antenna device conforming to the surface of a cylindrical metal carrier.

[0037] The simulation results of the port scattering parameters of the quasi-end polarized diversity array antenna device conforming to the surface of the cylindrical metal carrier designed in this example are as follows: Figures 7 to 11 As shown, the return loss at the two ports of the antenna is acceptable near 6GHz, 7GHz and 8GHz, and the isolation between the ports is about 20dB, indicating good isolation characteristics.

[0038] Simulation results of the radiation pattern characteristics of the conformal polarization diversity antenna element designed in this example, which conforms to the surface of the cylindrical metal carrier, at typical operating frequencies of 6 GHz, 7 GHz, and 8 GHz are as follows: Figure 13 As shown, at frequencies of 6 GHz, 7 GHz, and 8 GHz, the upward tilting effect of the radiated wave of the designed conformal polarization diversity antenna to the cylindrical metal carrier surface is improved, and the radiation pattern has a larger beam coverage range, achieving the performance of polarization diversity.

[0039] In summary, the polarization diversity array antenna device conformally placed to the surface of a metal cylinder proposed in this invention has characteristics such as low profile, compact structure, low cost, and quasi-end-fire radiation pattern, making it suitable for engineering implementation. The polarization diversity array antenna device conformally placed to the surface of a metal cylinder proposed in this invention is applicable to applications such as aircraft carrier radar seekers and electronic reconnaissance systems.

Claims

1. A polarization diversity conformal quasi-endfire antenna array device, characterized in that, The device comprises a cylindrical metal carrier and an antenna array with an approximately dual-polarized radiation pattern. The main beam is approximately end-fired, i.e., along the cylindrical axis of the metal carrier. Two or more dual-polarized broadband antenna elements are arranged on the surface of the metal carrier. Each antenna element can receive approximately orthogonal radiation source signal components. In each antenna element, the approximately horizontally polarized antenna is a conformal printed Yagi directional antenna, and the approximately vertically polarized antenna is a cylindrical conformal sector H-plane horn antenna. A cylindrical conformal electromagnetic bandgap structure (EBG) is also arranged on the surface of the cylindrical metal carrier to improve the radiation characteristics of the printed Yagi directional antenna. The cylindrical conformal sector H-plane horn antenna includes a cylindrical conformal rectangular waveguide, a cylindrical conformal H-plane sector horn, and a dielectric block. The dielectric block is positioned between the electromagnetic bandgap structure (EBG) and the Yagi directional antenna, forming a dielectric loading at the front end of the cylindrical conformal H-plane sector horn. The interior of the cylindrical conformal H-plane sector horn is filled with a dielectric material, which has the same dielectric constant as the dielectric block.

2. The polarization diversity conformal quasi-endfire antenna array device according to claim 1, characterized in that, The conformal printed Yagi antenna is printed on a single-layer microwave dielectric substrate, specifically on a flexible printed circuit board. The conformal printed Yagi antenna has an end-fire radiation pattern and is arranged above the surface of a cylindrical metal carrier in a conformal manner. That is, the flexible printed circuit board is arranged around the surface of the cylindrical metal carrier and is spaced apart from the surface of the cylindrical metal carrier. The polarization direction of the radiation field of the conformal printed Yagi antenna is approximately parallel to the surface of the cylindrical metal conductor.

3. The polarization diversity conformal quasi-endfire antenna array device according to claim 2, characterized in that, The conformal printed Yagi director antenna uses symmetrical printed dipoles fed outwards on the upper and lower sides of a dielectric substrate as exciters. The length of the director gradually decreases in the axial direction. Each director dipole is divided into upper and lower parts on the dielectric substrate, which are interconnected by conductive vias. The symmetrical active dipole exciter and the passive director dipole have the same width. Since the symmetrical dipole uses balanced feeding and the microstrip line uses unbalanced feeding, an unbalanced-to-balanced converter, i.e., a balun, is introduced from the microstrip line to the dual-line. The balun adopts an ultra-wideband linearly tapered structure and also has impedance transformation function. The ground plane is used as a reflector. There is one active oscillator and three director oscillators. The lengths of the active oscillator and the director oscillators are denoted as L1, L2, L3 and L4, respectively. The distance between the active oscillator and the balun is d1, the distance between the active oscillator and the first director oscillator is d2, the distance between the second director oscillator and the first director oscillator is d3, and the distance between the third director oscillator and the second director oscillator is d4. The length of the linear tapered balun is d0. The width of the feed microstrip line is w_MSL, the width of the ground plane of the feed microstrip line is W_gnd, and the characteristic impedance of the microstrip line is 50 ohms.

4. The polarization diversity conformal quasi-endfire antenna array device according to claim 2, characterized in that, In each antenna element, the antenna with a polarization direction approximately perpendicular to the surface of the cylindrical metal carrier adopts a cylindrical conformal H-plane sector horn antenna. To achieve miniaturization of the horn antenna, a dielectric material is introduced to fill the horn structure. To improve the radiation pattern of the horn antenna, a dielectric block is loaded at the front end of the aperture of the cylindrical conformal H-plane sector horn. The vertically polarized antenna element uses a rectangular waveguide that conforms to the cylinder and is bent, i.e., a cylindrical conformal rectangular waveguide. At the end of the cylindrical conformal rectangular waveguide, the horn aperture gradually opens in the H-plane, forming an effective aperture, constituting a cylindrical conformal H-plane sector horn radiator. Based on the cylindrical conformal H-plane sector horn, a dielectric material is loaded inside it, with a relative permittivity of [insert value here]. The dielectric material is extended along the axial direction of the cylinder to form the dielectric block loaded at the front end of the cylindrical conformal antenna.

5. The polarization diversity conformal quasi-end-fire antenna array device according to claim 4, characterized in that, The electromagnetic bandgap structure EBG adopts a cylindrical metal conformal structure, and the electromagnetic bandgap structure EBG adopts a mushroom-shaped electromagnetic bandgap structure EBG. The patch shape is square, and the capacitance C is generated by the coupling of the edges of two adjacent patches. The calculation formula is: (1), where It is the patch width. It is the width of the gap between two adjacent patches. It is the relative permittivity, inductance The loop formed by the metal holes is determined by the thickness and permeability of the medium, and its calculation formula is as follows: （2）， The impedance of the entire parallel LC circuit can be calculated using the following formula: (3) The resonant frequency of this circuit is: (4)， At low frequencies, the circuit impedance is inductive, supporting TM wave transmission; at high frequencies, the circuit impedance is capacitive, supporting TE wave transmission. When near the point of contact, the circuit exhibits high impedance, and the EBG structure does not allow any electromagnetic waves to propagate, thus creating a frequency bandgap.

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