A parasitically loaded dual-arm helical antenna

Abstract

This invention discloses a parasitic-loaded double-arm spiral antenna, belonging to the field of antenna technology. It includes a top spiral assembly, a loaded spiral assembly, a metal ground plane, a feed balun, and connectors. The feed balun passes through the center of the metal ground plane, and its outer conductor is fixed to the metal ground plane. The top spiral assembly and the loaded spiral assembly surround the feed balun. The top spiral assembly includes two top spirals, an upper horizontal arm, and a lower horizontal arm. Both the upper and lower horizontal arms are fixed to the outer conductor of the feed balun and are perpendicular to it. The two ends of the top spirals are connected to the two ends of the upper and lower horizontal arms, respectively. This invention achieves wide-bandwidth circularly polarized beam radiation by introducing a parasitic-loaded spiral assembly into the double-arm spiral antenna. The antenna features a fully metallized self-supporting structure design, which is compact, easy to manufacture, and highly reliable, and has broad application prospects in wireless communication systems.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and more specifically, to a parasitic double-arm helical antenna suitable for satellite communication, navigation terminals, and portable communication devices. Background Technology

[0002] Currently, the main types of circularly polarized wide-beam antennas used are microstrip antennas and helical antennas. Microstrip antennas have the advantages of simple structure and low profile. They typically use high-dielectric-constant printed circuit boards to reduce the antenna aperture size and achieve wide beam requirements, but this increases antenna loss and reduces efficiency. When used as wide-beam antennas, cross-shaped dipole antennas have a relatively high antenna height and require an additional circular polarization network, making the equipment relatively complex. Helical antennas, when used as wide-beam antennas, are typically four-arm or two-arm helical antennas. Four-arm helical antennas are small and compact, achieving hemispherical radiation beams and good axial ratio characteristics. Their radiation performance is less affected by the carrier, but their bandwidth is narrow, making them unsuitable for broadband applications. Two-arm helical antennas are also compact, achieving hemispherical radiation beams and good axial ratio characteristics. Their radiation performance is less affected by the carrier, and while they have some broadband characteristics, they still cannot meet ultra-wideband requirements.

[0003] Besides the antennas mentioned above, the conical log-spiral antenna is also a typical form of ultra-wideband circularly polarized antenna. It operates with a slow-wave structure from the top feed to the working region, transitioning to a fast-wave structure within the conical working region. Based on the phase-matching principle of electromagnetic field boundary conditions, it can achieve broadband and high-performance unidirectional radiation without a reflecting or absorbing cavity. However, it suffers from relatively high profile and poor beamwidth stability. Furthermore, conical log-spiral antennas typically employ a Marchand balun and printed microstrip dual-wire feed configuration. The printed feed lines are connected to the spiral line via vertical transition solder points, resulting in a complex overall antenna structure and lower engineering reliability.

[0004] The methods described above all have certain limitations in engineering applications, especially in achieving miniaturization, wide bandwidth, high efficiency, and structural reliability simultaneously. Therefore, it is essential to research a circularly polarized wide-beam antenna with a simple structure, good wide beam characteristics, and excellent bandwidth. Summary of the Invention

[0005] The present invention aims to provide a tail-loaded double-arm spiral antenna to solve the problems existing in the existing broadband circularly polarized antennas, and to achieve wide bandwidth, good circular polarization characteristics and stable radiation pattern.

[0006] Therefore, the technical solution adopted in this invention is as follows: A parasitic loaded double-arm helical antenna includes a top helical assembly, a loading helical assembly, a metal ground plane, a feed balun, and a connector; characterized in that the feed balun passes through the center of the metal ground plane, and the outer conductor of the feed balun is fixed to the metal ground plane; the top helical assembly and the loading helical assembly surround the feed balun.

[0007] The top spiral assembly includes two top spirals, an upper horizontal arm, and a lower horizontal arm; both the upper and lower horizontal arms are fixed on the outer conductor of the feed balun and are perpendicular to the feed balun; the bottom ends of the two top spirals are respectively connected to the two ends of the lower horizontal arm, and the top ends of the two top spirals are respectively connected to the two ends of the upper horizontal arm. The loading spiral assembly includes a loading cross arm and two loading spirals. The loading cross arm is fixed on the outer conductor of the feed balun and is located between the upper and lower cross arms. The loading cross arm and the lower cross arm are perpendicular and orthogonal in the horizontal projection. The top end of the loading spiral is connected to the loading cross arm, and the bottom end is connected to the metal floor. The loading spiral assembly has no contact with the top spiral assembly.

[0008] The connector is mounted on a metal floor, and the connector core is connected to the inner conductor of the power supply balun.

[0009] Furthermore, the winding centers of both the top helix and the loading helix coincide with the center of the feed balun axis.

[0010] Furthermore, the number of turns of the top spiral is less than or equal to 3.

[0011] Furthermore, the top spiral is conical, and the loading spiral can be conical or cylindrical, with the number of turns being 0.25 or 0.5.

[0012] Furthermore, the top helix can be a metal helix of any cross-sectional shape, or a metal coating structure on the surface of the medium.

[0013] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: 1. This invention adds a loading spiral component below the spiral of a traditional double-arm spiral antenna to form a parasitic structure, which changes the current distribution on the feed balun and the spiral, broadens the antenna's impedance bandwidth and circular polarization bandwidth, while the antenna has good wide beam stability and front-to-back ratio in the ultra-wideband bandwidth.

[0014] 2. This invention achieves a fully metallized self-supporting structure design by integrating the top spiral, the loading spiral assembly, and the coaxial balun into a single unit. This results in good structural stability and high structural strength, greatly improving the reliability of the force antenna.

[0015] 3. The present invention can select different loading component sizes according to the communication to achieve antenna pattern shaping and meet different wide beam communication application scenarios. Attached Figure Description

[0016] Figure 1 This is an overall structural diagram of an embodiment of the present invention.

[0017] In the diagram: 1. Upper crossarm, 2. Top spiral, 3. Lower crossarm, 4. Support rod, 5. Loading crossarm, 6. Loading spiral, 7. Metal floor, 8. Connector. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It should be noted that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0019] I. Overall Structure and Component Composition like Figure 1 As shown, this embodiment provides a parasitic loaded dual-arm spiral antenna, comprising: a top spiral assembly, a loading spiral assembly, a metal ground plane 7, a feed balun 4, and a connector 8. The feed balun 4 passes through the center of the metal ground plane 7, and the outer conductor of the feed balun 4 is fixed to the metal ground plane 7; the top spiral assembly and the loading spiral assembly surround the feed balun 4.

[0020] The top spiral assembly includes two top spirals 2, an upper horizontal arm 1, and a lower horizontal arm 3; the upper horizontal arm 1 and the lower horizontal arm 3 are both fixed on the outer conductor of the feed balun 4 and are perpendicular to the feed balun 4; the bottom ends of the top spirals 2 are respectively connected to the two ends of the lower horizontal arm 1, and the top ends of the top spirals 2 are respectively connected to the two ends of the upper horizontal arm 3. The loading spiral assembly includes a loading horizontal arm 5 and two loading spirals 6. The loading horizontal arm 5 is fixed on the outer conductor of the feed balun 4 and is located between the upper horizontal arm 1 and the lower horizontal arm 3. The loading horizontal arm 5 and the lower horizontal arm 3 are perpendicular and orthogonal in the horizontal projection. The top end of the loading spiral 6 is connected to the loading horizontal arm, and the bottom end is connected to the metal ground plate 7. The loading spiral assembly has no contact with the top spiral assembly (e.g., Figure 1 As shown, the loading crossarm 5 is positioned above the lower crossarm 3 in the height direction, but maintains a gap with the spiral.

[0021] The connector 8 is mounted on the metal floor 7, and the inner core of the connector 8 is connected to the inner conductor of the power supply balun 4.

[0022] II. The relationship between the components 1. Connection between the crossarm and the support rod

[0023] The upper cross arm 1, lower cross arm 3, and each loading cross arm 5 are all fixed to the outer conductor of the power supply balun 4, which can be achieved through welding, threaded tightening, interference fit, and integral machining. This fixing structure provides reliable mechanical support and ensures the electrical connection of the spirals on both sides.

[0024] 2. Connection and winding methods of helices

[0025] The two ends of the top spiral 2 are welded or pressed to the ends of the upper cross arm 1 and the lower cross arm 3 respectively, and the winding center coincides with the axis of the support rod 4.

[0026] The upper end of the loading spiral 6 is connected to the end of the loading crossarm 5, and the lower end is connected to the metal floor 7. The loading spiral 6 is also symmetrically arranged around the axis of the support rod 4 and is coaxial with the top spiral 2.

[0027] The top helix uses a conical winding method (i.e., the radius varies with height). The loading helix can be wound in a conical or cylindrical manner. The number of turns in the loading helix is ​​0.25 or 0.5 to achieve a compact parasitic loading effect.

[0028] 3. Power supply balun and connector

[0029] The power supply balun 4 adopts a coaxial balun structure. The outer conductor of the power supply balun 4 is short-circuited and fixedly connected to the middle position of the upper horizontal arm 1, the lower horizontal arm 3 and the loading horizontal arm 5 respectively.

[0030] After the inner conductor of the power supply balun 4 extends downward through the metal floor 7, it connects to the center pin of the connector (8) mounted on the bottom surface of the metal floor 7.

[0031] III. Implementation Principle and Signal Feeding Process 1. Incentive methods External radio frequency signals enter the antenna through connector 8, are transmitted upwards through the inside of the feed balun 4, and feed the top spiral assembly. Equal and opposite currents flow through the two top spiral lines 2. The top spiral assembly, through coupling, feeds the loading spiral assembly. The currents on the top spiral assembly and the loading spiral assembly work together to radiate spatially circularly polarized radio frequency signals.

[0032] 2. Radiation Mechanism The helical antenna is a classic form of broadband circularly polarized antenna. By adjusting the rise angle of the helix, the current in the helix can form multiple modes. When the antenna rise angle meets certain requirements, good broadband circularly polarized radiation characteristics can be obtained through its own helical structure. In this invention, the loading helical assembly's loading cross arm 5 is fixed to the outer conductor of the feeding balun 4, and the bottom end of the loading helix 6 is fixed to the metal ground plane 7. Therefore, the loading helical assembly is not directly fed, but rather fed through coupling via the top helical assembly. This parasitic coupling method makes the loading helical assembly equivalent to adding a parallel resonant circuit outside the main radiating arm, thereby improving the antenna's impedance bandwidth. The loading helical assembly is fed through coupling via the top helical assembly, and its helical structure improves the antenna's low-frequency circularly polarized radiation characteristics, forming good circularly polarized radiation at low frequencies. The antenna of this invention has an axial ratio of less than 3dB within the ultra-wideband bandwidth, exhibiting good wide beam stability and a low front-to-back ratio.

Claims

1. A parasitically loaded dual-arm helical antenna comprising a top helical element, a loaded helical element, a metallic ground plane, a feed balun, and a connector; wherein, The feed balun passes through the center of the metal floor, and the outer conductor of the feed balun is fixed to the metal floor; the top spiral assembly and the loading spiral assembly surround the feed balun. The top spiral assembly includes two top spirals, an upper horizontal arm, and a lower horizontal arm; both the upper and lower horizontal arms are fixed on the outer conductor of the feed balun and are perpendicular to the feed balun; the bottom ends of the top spirals are connected to the two ends of the lower horizontal arm, and the top ends of the top spirals are connected to the two ends of the upper horizontal arm. The loading spiral assembly includes a loading cross arm and two loading spirals. The loading cross arm is fixed on the outer conductor of the feed balun and is located between the upper and lower cross arms. The loading cross arm and the lower cross arm are perpendicular and orthogonal in the horizontal projection. The top end of the loading spiral is connected to the loading cross arm, and the bottom end is connected to the metal floor. The loading spiral assembly has no contact with the top spiral assembly. The connector is mounted on a metal floor, and the connector core is connected to the inner conductor of the power supply balun.

2. A parasitically loaded dual arm spiral antenna according to claim 1, wherein, The winding centers of both the top spiral and the loading spiral coincide with the center of the feed balun axis.

3. A parasitically loaded dual arm spiral antenna according to claim 1, wherein, The number of turns of the top spiral is less than or equal to 3.

4. A parasitically loaded dual arm spiral antenna according to claim 1, wherein, The top spiral is conical, and the loading spiral can be conical or cylindrical, with 0.25 or 0.5 turns.

5. A parasitically loaded dual arm spiral antenna according to claim 1, wherein, The top helix can be a metal helix of any cross-sectional shape, or a metal coating structure on the surface of the medium.

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