A four-armed spiral antenna

Abstract

The quad-arm spiral antenna disclosed in this invention includes: a double-layer self-phase-shifting feed printed circuit board, a choke metal sheet, a feed coaxial line, a metal base, and a quad-arm spiral printed circuit board. The four spiral antenna arms on the quad-arm spiral printed circuit board are symmetrically rotated 90° around the axis of the double-layer self-phase-shifting feed printed circuit board. Four fan-shaped copper-clad structures formed by internal micro-strip lines on the double-layer self-phase-shifting feed printed circuit board are welded to the tops of the four spiral antenna arms, respectively, to achieve 0°, -90°, -180°, and -270° feeding of the four spiral antenna arms. A metal ring at the lower end of the choke metal sheet is located approximately one-quarter of the center frequency wavelength below the bottom of the double-layer self-phase-shifting feed printed circuit board. Four thin metal filaments extending upwards from the edge are welded to the four fan-shaped copper-clad structures on the double-layer self-phase-shifting feed printed circuit board, respectively, to choke the current in the outer conductor of the feed coaxial line, achieving balanced feeding. This invention is suitable for the design and use of quad-arm spiral antennas in the C-band and above frequency bands.

Description

Technical Field

[0001] This invention belongs to the technical field of circularly polarized antennas, and particularly relates to a four-arm spiral antenna that can achieve self-phase-shift balanced feeding and wide beam radiation. Background Technology

[0002] The quad-arm helical antenna has a heart-shaped circularly polarized radiation pattern, which can maintain good circular polarization characteristics and high gain at low elevation angles, i.e., wide beam. It also has a compact and simple structure that is independent of the reference ground, and has been widely used in satellite navigation and communication fields such as GPS, BeiDou, and maritime communications.

[0003] Because the coaxial feed line is an unbalanced feed structure, a typical feeding method for achieving self-phase-shifted circular polarization radiation in a quad-helical antenna is a coaxial slotted balun feed. This involves creating a narrow slot on the coaxial feed line, and the characteristic impedance within the coaxial feed line must change from 50Ω to 70Ω. This is achieved by combining the quarter-impedance transformation principle to achieve balanced feeding and impedance matching. Simultaneously, the lengths of the two orthogonal arms in the quad-helical antenna must be unequal to satisfy a 90° phase difference. This type of quad-helical antenna typically has a relative bandwidth of approximately 10%.

[0004] However, as the frequency of the received signal increases to the C-band and above (4.0–8.0 GHz), this traditional self-phase-shift fed quad-helical antenna requires extremely precise processing and installation. For example, when used in the C-band, a slot with a width of 0.05 mm precision must be cut on the outer conductor of the thin feed coaxial line (approximately 2.2 mm in diameter), and the inner conductor must have a diameter gradient of 0.05 mm precision to achieve impedance transformation. The thickness of the antenna arms from the coaxial to the helical shape and the welding all have a significant impact on the antenna radiation performance. Therefore, the traditional self-phase-shifted quad-helical antenna is no longer suitable for the C-band and above. Summary of the Invention

[0005] To address the issue that traditional self-phase-shifting quad-helical antennas are no longer applicable in the C-band and above, this invention provides a quad-helical antenna that achieves balanced feeding of the inner and outer conductors of the coaxial feed line without the need for slotting on the outer conductor or gradually changing the diameter of the inner conductor, thus obtaining a wide beam radiation effect.

[0006] The quad-helical antenna provided in this embodiment of the invention includes: a double-layer self-phase-shifting feed printed circuit board, a choke metal sheet, a feed coaxial line, a metal base, and a quad-helical printed circuit board. The double-layer self-phase-shifting feed printed circuit board, the choke metal sheet, and the feed coaxial line together constitute the self-phase-shifting balanced feed structure of the quad-helical antenna, and the quad-helical printed circuit board constitutes the antenna radiator of the quad-helical antenna.

[0007] The inner and outer conductors of the feed coaxial line are respectively soldered to the top and bottom copper layers of the double-layer self-phase-shifting feed printed circuit board for conduction.

[0008] The four spiral antenna arms on the four-arm spiral printed circuit board are symmetrically rotated 90° around the axis of the double-layer self-phase-shifting feed printed circuit board, and the bottom of the four spiral antenna arms is short-circuited to the outer conductor of the feed coaxial line.

[0009] The dual-layer self-phase-shifting feed printed circuit board forms four fan-shaped copper-clad structures through internal micro-strip lines, which are respectively soldered to the top of the four spiral antenna arms to achieve 0°, -90°, -180° and -270° feeding of the four spiral antenna arms;

[0010] The choke metal sheet includes a metal ring and four metal filaments. The metal ring is located approximately one-quarter of the center frequency wavelength below the bottom of the double-layer self-phase-shifting feed printed circuit board and is welded to the outer conductor of the feed coaxial line for conduction. The bottoms of the four metal filaments are connected to the outer edge of the metal ring and extend upwards to be welded to the four fan-shaped copper-clad structures on the double-layer self-phase-shifting feed printed circuit board for conduction. This chokes the current in the outer conductor of the feed coaxial line, achieving balanced feeding of the inner and outer conductors of the feed coaxial line.

[0011] The technical solutions of the embodiments of the present invention can achieve the following beneficial effects:

[0012] The quad-arm spiral antenna provided in this embodiment of the invention does not require slotting on the outer conductor of the feed coaxial line, nor does it require gradually changing the diameter of the inner conductor of the feed coaxial line. By setting a choke metal plate at approximately one-quarter of the center frequency wavelength from the feed point, and utilizing the principle of one-quarter open-circuit and short-circuit transformation of transmission lines, when the metal ring plate at the lower end is short-circuited with the outer conductor of the feed coaxial line, the electromagnetic wave reaches the fan-shaped arm in the double-layer self-phase-shift feed printed circuit board after one-quarter of the wavelength, forming a virtual break, that is, the current flowing through the outer wall of the outer conductor is zero at this point. This ensures the balanced feeding of the inner and outer conductors of the feed coaxial line to the double-layer self-phase-shift feed printed circuit board within the operating frequency band, ensuring the balanced feeding of the quad-arm spiral antenna, enabling the antenna to have symmetrical beam radiation capability in a very wide-angle spatial domain, and obtaining a wide beam radiation effect.

[0013] Furthermore, the choke metal sheet structure of this invention is simple and easy to process and assemble; the four spiral antenna arms rotate 90° symmetrically around the axis of the double-layer self-phase-shifting feed printed circuit board, which facilitates the installation of the four-arm spiral printed circuit board and ensures that the coaxial spacing between the feed coaxial line and the four spiral antenna arms is the same, reducing the difficulty of antenna processing and assembly and the requirements for accuracy, and is especially suitable for the design and use of four-arm spiral antennas in C-band and above frequency bands. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of this invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention, and those skilled in the art can obtain other drawings based on these drawings. Throughout the drawings, the same reference numerals denote the same parts.

[0015] Figure 1 A front view schematic diagram of the composition of a four-arm helical antenna provided in an embodiment of the present invention;

[0016] Figure 2 A top view schematic diagram of the bottom copper layer structure and metal via distribution of a double-layer self-phase-shift fed printed circuit board provided in an embodiment of the present invention;

[0017] Figure 3 A top view schematic diagram of the intermediate copper-clad layer structure of a double-layer self-phase-shift fed printed circuit board provided in an embodiment of the present invention;

[0018] Figure 4 This is a top view schematic diagram of the top copper cladding layer structure of a double-layer self-phase-shift fed printed circuit board provided in an embodiment of the present invention;

[0019] Figure 5 This is a schematic diagram of the choke metal sheet provided in an embodiment of the present invention;

[0020] Figure 6 A comparative schematic diagram of the gain symmetry in the wide-angle domain of a four-arm spiral antenna with and without a choke metal plate, provided as an embodiment of the present invention;

[0021] Figure 7 A schematic diagram comparing the axial ratio symmetry of a four-arm spiral antenna with and without a choke metal plate in a wide-angle domain, provided as an embodiment of the present invention.

[0022] Figure 8 This is a schematic diagram comparing the voltage standing wave ratio (VSWR) characteristics of a four-arm spiral antenna with and without a choke metal strip in its operating frequency band, as provided in an embodiment of the present invention.

[0023] Figure label:

[0024] 1-Double-layer self-phase-shift fed printed circuit board; 1a-Center metal via of the double-layer self-phase-shift fed printed circuit board (first ring of vias from the center outwards); 1a'-Second ring of vias (several) of the double-layer self-phase-shift fed printed circuit board from the center outwards; 1a”-Third ring of vias (4) of the double-layer self-phase-shift fed printed circuit board from the center outwards; 1a”'-Fourth ring of vias (4) of the double-layer self-phase-shift fed printed circuit board from the center outwards; 1b-Bottom layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1c-Center ring of the middle layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1c'-Three-quarter ring of the middle layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1c”-Large fan-shaped copper-clad structure (2) of the middle layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board. ; 1c”'-Small fan-shaped copper-clad structure (2 pieces) of the middle layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1c””-Rectangular copper-clad structure of the middle layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1d-Three-quarter ring of the top layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1d’-Large fan-shaped copper-clad structure (2 pieces) of the top layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1d”-Small fan-shaped copper-clad structure (2 pieces) of the top layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 1d”’-Rectangular copper-clad structure of the top layer copper-clad structure of the double-layer self-phase-shift fed printed circuit board; 2-Choke metal sheet; 2a-Metal ring sheet; 2b-Metal wire (four pieces); 3-Feeding coaxial line; 4-Metal base; 5-Four-arm spiral printed circuit board. Detailed Implementation

[0025] The invention will now be described in more detail with reference to the accompanying drawings. These embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Although exemplary embodiments of the invention are shown in the drawings, it should be understood that the drawings form part of the invention and, together with the embodiments of the invention, are used to illustrate the principles of the invention, and are not intended to limit the scope of the invention. The invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0026] See Figures 1-5 The present invention provides a four-arm helical antenna, the specific details of which are as follows:

[0027] Figure 1 This is a front view schematic diagram of the composition of a four-arm helical antenna provided in an embodiment of the present invention. Figure 1 As shown, the quad-helical antenna provided in this embodiment of the invention includes a double-layer self-phase-shifting feed printed circuit board 1, a choke metal sheet 2, a feed coaxial line 3, a metal base 4, and a quad-helical printed circuit board 5. The double-layer self-phase-shifting feed printed circuit board 1, the choke metal sheet 2, and the feed coaxial line 3 together constitute the feed structure of the quad-helical antenna, and the quad-helical printed circuit board 5 constitutes the antenna radiator of the quad-helical antenna.

[0028] The inner and outer conductors of the feed coaxial line 3 are soldered to the top and bottom copper layers of the double-layer self-phase-shift feed printed circuit board 1, respectively. The four spiral antenna arms on the four-arm spiral printed circuit board 5 are rotated 90° symmetrically around the axis of the double-layer self-phase-shift feed printed circuit board 1, and the bottom of the four spiral antenna arms is short-circuited to the outer conductor of the feed coaxial line 3.

[0029] The double-layer self-phase-shifting feed printed circuit board 1 forms four fan-shaped copper-clad structures through internal micro-strip lines. The four fan-shaped copper-clad structures extend to the edge of the double-layer self-phase-shifting feed printed circuit board 1 and are soldered to the top of the four spiral antenna arms respectively to achieve 0°, -90°, -180° and -270° feeding of the four spiral antenna arms.

[0030] Figure 5 This is a schematic diagram of the choke metal sheet 2 provided in an embodiment of the present invention. (Also combined with...) Figure 5 As shown, the choke metal plate 2 includes a metal ring plate 2a and four metal filaments 2b. The metal ring plate 2a is located about one-quarter of the center frequency wavelength below the welding point between the bottom of the double-layer self-phase-shifting feed printed circuit board 1 and the outer conductor of the feed coaxial line 3, and is welded and connected to the outer conductor of the feed coaxial line 3. The bottom of the four metal filaments 2b is connected to the outer edge of the metal ring plate 2a, and extends upward to be welded and connected to four fan-shaped copper-clad structures on the double-layer self-phase-shifting feed printed circuit board 1, thereby choking the current of the outer conductor of the feed coaxial line 3 and achieving balanced feeding of the inner and outer conductors of the feed coaxial line 3.

[0031] As can be seen, the quad-arm spiral antenna provided by this invention does not require slotting on the outer conductor of the feed coaxial line, nor does it require gradually changing the diameter of the inner conductor of the feed coaxial line. By setting a choke metal plate at approximately one-quarter of the center frequency wavelength from the feed point, and utilizing the principle of one-quarter open-circuit and short-circuit transformation of transmission lines, when the metal ring plate at the lower end is short-circuited with the outer conductor of the feed coaxial line, the electromagnetic wave reaches the fan-shaped arm in the double-layer self-phase-shift feed printed circuit board after one-quarter of the wavelength, forming a virtual break, that is, the current flowing through the outer wall of the outer conductor is zero at this point. This ensures the balanced feeding of the inner and outer conductors of the feed coaxial line to the double-layer self-phase-shift feed printed circuit board within the operating frequency band, ensuring the balanced feeding of the quad-arm spiral antenna, enabling the antenna to have symmetrical beam radiation capability in a very wide-angle spatial domain, and obtaining a wide beam radiation effect.

[0032] Furthermore, the choke metal sheet structure of this invention is simple and easy to process and assemble; the four spiral antenna arms rotate 90° symmetrically around the axis of the double-layer self-phase-shifting feed printed circuit board, which facilitates the installation of the four-arm spiral printed circuit board and ensures that the coaxial spacing between the feed coaxial line and the four spiral antenna arms is the same, reducing the difficulty of antenna processing and assembly and the requirements for accuracy, and is especially suitable for the design and use of four-arm spiral antennas in C-band and above frequency bands.

[0033] In a preferred embodiment of the present invention, the quad-arm spiral antenna operates in the range of 6.3 GHz to 7.3 GHz, with a center frequency of 6.8 GHz and an operating bandwidth of up to 14.7%. Compared with the traditional slotted balun self-phase-shifting quad-arm spiral antenna, the relative bandwidth is broadened by about 4.7%.

[0034] In a preferred embodiment of the present invention, the double-layer self-phase-shift fed printed circuit board 1 is circular and is made of two layers of high-frequency microwave board Rogers 5880 material (relative permittivity 2.2) with a thickness of 0.254 mm bonded together, with the adhesive layer thickness being approximately 0.1 mm.

[0035] In a preferred embodiment of the present invention, the power supply coaxial cable 3 is an SFT-50-2-1 type semi-rigid cable with an inner conductor diameter of 0.53 mm and an outer conductor diameter of 2.18 mm. The inner conductor extends about 1 mm beyond the outer conductor to facilitate passing through the central metal through hole of the double-layer self-phase-shifting power supply printed circuit board 1.

[0036] In a preferred embodiment of the present invention, the metal base 4 is also circular, 3mm thick, and has the same diameter as the double-layer self-phase-shifting feed printed circuit board 1. Its main function is to short-circuit the four spiral antenna arms on the four-arm spiral printed circuit board 5 with the outer conductor of the feed coaxial line 3 at the bottom.

[0037] In a preferred embodiment of the present invention, the initial diameter of the double-layer self-phase-shift fed printed circuit board 1 is one-quarter of the center frequency dielectric wavelength.

[0038] It should be noted that the formula for the center frequency dielectric wavelength is:

[0039]

[0040] Where, λ e Let λ be the wavelength of an electromagnetic wave of a certain frequency in the medium, and ε be the wavelength of the electromagnetic wave of that frequency in air. r is the relative permittivity of the dielectric material at that frequency.

[0041] Furthermore, the wavelength and frequency of the same electromagnetic wave have the following relationship:

[0042] Formula (II) for λ = c / f

[0043] Where c is the speed of light, with an exact value of 299,792,458 m / s; f is the frequency of the electromagnetic wave; and λ is the wavelength of the electromagnetic wave.

[0044] In a preferred embodiment of the present invention, the center frequency of the four-arm helical antenna is 6.8 GHz, and according to formula (II), the wavelength of one-quarter center frequency is 11 mm; the relative permittivity of the selected dielectric substrates is 2.2, and according to formula (I), the wavelength of the dielectric substrate of one-quarter center frequency is 7.4 mm.

[0045] Therefore, in the preferred embodiment of the present invention, the initial diameter of the double-layer self-phase-shift fed printed circuit board 1 is 7.4 mm, and after simulation optimization, the final value is 8.8 mm.

[0046] In a preferred embodiment of the present invention, the four-arm spiral printed circuit board 5 includes a dielectric cylinder and four spiral antenna arms disposed on the outer circumference of the dielectric cylinder. The dielectric cylinder is fixed on a metal base 1 and is made of Rogers 5880 material with a thickness of 0.127 mm. The diameter of the dielectric cylinder is the same as the diameter of the double-layer self-phase-shifting feed printed circuit board 1. The angular width of the spiral lines of the four spiral antenna arms is the same as the fan angle of the fan-shaped copper-clad structure in the double-layer self-phase-shifting feed printed circuit board 1, so as to facilitate the soldering and connection of the tops of the four fan-shaped copper-clad structures on the double-layer self-phase-shifting feed printed circuit board 1 with the tops of the four spiral antenna arms respectively.

[0047] The spiral curve satisfies the following three-dimensional equation:

[0048]

[0049]

[0050]

[0051] Let the origin of the coordinate system be located at the center of the bottom axis of the four-armed helical antenna, where, Let be the angle variable between a point on the spiral line and the X-axis as projected onto the XOY plane. The value changes from -N.360deg to 0deg; N is the total number of turns of the helix, h is the total height of the quad-arm helical antenna, r is the radius of the helix, and α is the fan angle of the fan-shaped copper-clad structure in the double-layer self-phase-shifted feed printed circuit board 1.

[0052] In a preferred embodiment of the present invention, N is 2.5 turns, h is initially N.λc / 2, λc is the center frequency wavelength, i.e. h is initially 55mm, and after simulation optimization, it is taken as 45mm; r is taken as the same as the radius of the double-layer self-phase-shift fed printed circuit board 1, which is 4.4mm; α is taken as 48°.

[0053] In a preferred embodiment of the present invention, the four-arm spiral printed circuit board 5 is disposed between the double-layer self-phase-shifting feed printed circuit board 1 and the metal base 4, and its height is consistent with the height of the feed coaxial line 3, so as to facilitate the installation of the four-arm spiral printed circuit board 5 and reduce the processing and assembly difficulty of the antenna.

[0054] In a preferred embodiment of the present invention, the double-layer self-phase-shifting feed printed circuit board 1 has a three-layer copper-clad structure. From bottom to top, the bottom and middle copper-clad structures are located at the bottom and top of the lower printed circuit board, respectively, and the top copper-clad structure is located at the top of the upper printed circuit board. The two printed circuit boards are bonded together by an adhesive layer. The inner conductor of the feed coaxial line 3 is soldered to the top copper-clad layer of the double-layer self-phase-shifting feed printed circuit board 1 through a central metal through-hole, and the outer conductor of the feed coaxial line 3 is soldered to the bottom copper-clad layer of the double-layer self-phase-shifting feed printed circuit board 1.

[0055] Figure 2 This is a top view schematic diagram of the bottom copper layer structure and metal via distribution of the double-layer self-phase-shift fed printed circuit board 1 provided in an embodiment of the present invention. Figure 2 As shown, the double-layer self-phase-shifting feed printed circuit board 1 has four rings of metal vias from the center outwards; the first ring of vias is the central metal via 1a, which is one in total, penetrating both layers of the printed circuit board and used to pass through the inner conductor of the feed coaxial line 3. In a preferred embodiment of the present invention, the diameter of the metal via 1a is 0.6 mm; the second ring of vias 1a' penetrates the bottom printed circuit board and is used for electrical conduction between the bottom and middle copper-clad structures. In a preferred embodiment of the present invention, the second ring of vias 1a' is 12 in total, evenly distributed on a circular line with a diameter of 2 mm at 30° angular intervals. Figure 3 The middle layer of the double-layer self-phase-shifting fed printed circuit board 1 has a copper-clad structure with a central ring 1c (center circle line). Each through-hole has a diameter of 0.26 mm. The third ring has four through-holes 1a”, which penetrate both layers of the printed circuit board and are used to pass through the four metal wires 2b of the choke metal sheet 2. In a preferred embodiment of the invention, the third ring of through-holes 1a” is evenly distributed at 90° angles along a circle line with a diameter of 4.9 mm. Figure 5 The four metal wires 2b of the choke metal sheet 2 are arranged in a central circular line, and the diameter of each through hole is 0.5 mm. The fourth ring of through holes 1a””, a total of 4, are located at the edge of the double-layer self-phase-shifting feed printed circuit board 1, penetrating the two layers of the printed circuit board, and are used for electrical conduction between the middle layer and the top copper-clad structure. In the preferred embodiment of the present invention, the fourth ring of through holes 1a”” are evenly distributed on a circular line with a diameter of 8.1 mm at 90° angles (ensuring that the through holes are within the double-layer self-phase-shifting feed printed circuit board 1), and the diameter of each through hole is 0.5 mm.

[0056] Still Figure 2As shown, the bottom copper-clad structure of the double-layer self-phase-shifting printed circuit board 1 is a ring 1b; the outer diameter of the ring 1b is smaller than the diameter at the location of the third ring via 1a', ensuring no electrical contact between them; the inner diameter of the ring 1b is smaller than the diameter of the outer conductor of the feed coaxial line 3, and the outer conductor of the feed coaxial line 3 is soldered to the ring 1b for conduction; the inner diameter of the ring 1b is larger than the diameter of the inner conductor of the feed coaxial line 3, ensuring a gap of more than 0.35mm between it and the pad of the metal via 1a' through which the inner conductor of the feed coaxial line 3 passes; the second ring via 1a' is located inside the ring 1b and close to the inner diameter of the ring 1b, preferably tangent to the inner diameter 1b. In a preferred embodiment of the present invention, the inner diameter of the ring 1b is 1.6mm and the outer diameter is 3.68mm.

[0057] Figure 3 This is a top view schematic diagram of the intermediate copper-clad layer structure of the double-layer self-phase-shift fed printed circuit board 1 provided in an embodiment of the present invention. Figure 3As shown, the copper-clad structure of the middle layer of the double-layer self-phase-shift fed printed circuit board 1, from the center outwards, includes a circular ring 1c, a three-quarter circular ring 1c', two large fan-shaped structures 1c”, two small fan-shaped structures 1c”’, and a rectangular copper-clad structure 1c””. The central circular ring 1c covers the location of the second ring of vias 1a', ensuring electrical conductivity between the bottom layer and the middle layer copper-clad structure. In a preferred embodiment of the present invention, the inner diameter of the central circular ring 1c is 1.6mm and the outer diameter is 2.4mm. The initial value of the inner diameter of the three-quarter circular ring 1c' is taken as 0.1 times the wavelength of the center frequency medium. 0.4 times (i.e., three-quarters of the circumference equals one-quarter of the center frequency dielectric wavelength). In a preferred embodiment of the present invention, the initial inner diameter of the three-quarters ring 1c' is 2.98 mm, which is optimized to 2.8 mm through simulation. The width of the three-quarters ring 1c' is approximately 100 Ω characteristic impedance width based on the selected printed circuit board material and thickness. Simultaneously, it is prioritized to ensure that the outer diameter of the three-quarters ring 1c' is smaller than the diameter at the location of the third through-hole 1a”, ensuring no electrical contact between the two. In a preferred embodiment of the present invention, the width of the three-quarters ring 1c' is 0.4 mm. The outer diameter is 3.6 mm; the two large fan-shaped sections 1c” are positioned at 90° with the center of the printed circuit board as the axis; the inner diameter of the large fan-shaped section 1c” is three-quarters of the inner diameter of the ring (2.8 mm), the outer diameter of the large fan-shaped section 1c” is the diameter of the printed circuit board (8.8 mm), and the fan angle is in the range of 45° to 50°. In the preferred embodiment of the present invention, the fan angle is 48°; one of the large fan-shaped sections 1c” is electrically connected to the central ring 1c through a rectangular copper-clad structure 1c””; the two small fan-shaped sections 1c”’ are positioned at 180° with the two large fan-shaped sections 1c” with the center of the printed circuit board as the axis. The outer diameter of the small sector 1c”' is the printed circuit board diameter (8.8mm), and the sector angle is the same as that of the large sector 1c”' (48°); the inner diameter of the small sector 1c”' is taken to cover the position of the fourth ring through hole 1a”'. In the preferred embodiment of the present invention, the inner diameter of the small sector 1c”' is 7.4mm; the three-quarter ring 1c’ connects the two large sector 1c”'; the relative position of the two large sector 1c”' and the three-quarter ring 1c’ determines the circular polarization direction (left-hand or right-hand) of the four-arm spiral antenna. In the preferred embodiment of the present invention, the four-arm spiral antenna is right-hand circularly polarized.

[0058] It should be noted that the method for determining whether an antenna is left-handed or right-handed circularly polarized is as follows:

[0059] Extend your palm, with your thumb pointing in the direction of antenna radiation. Turn your four fingers from the feed arm with the phase leading (0° phase) to the feed arm with the phase lagging (-90° phase). If the direction of the four fingers of your right hand is as described above, it is right-hand circular polarization; otherwise, it is left-hand circular polarization.

[0060] In a preferred embodiment of the present invention, the circular ring 1c and the bottom copper-clad structure 1b are connected through the second through-hole 1a'. The bottom copper-clad structure 1b is welded to the outer conductor of the feed coaxial 3. The feed current on the outer conductor of the feed coaxial 3 first flows to the large fan-shaped copper-clad area connected to the circular ring 1c through the rectangular copper-clad structure 1c””. The feed of this large fan-shaped copper-clad area is ahead (0° phase). The current then flows through three-quarters of the circular ring 1c' to another large fan-shaped copper-clad area. The feed of this other large fan-shaped copper-clad area is lagging (-90° phase), which coincides with the bending direction of the four fingers of the right hand. Therefore, in the preferred embodiment of the present invention, the four-arm spiral antenna is right-hand circularly polarized.

[0061] Figure 4 This is a top view schematic diagram of the top copper layer structure of the double-layer self-phase-shift fed printed circuit board 1 provided in an embodiment of the present invention. Figure 4 As shown, the top copper-clad structure in the double-layer self-phase-shift fed printed circuit board 1, from the center outwards, includes a three-quarter ring 1d, two large sectors 1d', two small sectors 1d”, and a rectangular copper-clad structure 1d”’. The three-quarter ring 1d, two large sectors 1d', and two small sectors 1d” in the top copper-clad structure have the same dimensions as the three-quarter ring 1c' and sectors (1c”, 1c”’) in the middle copper-clad structure, and are rotated 180° around the center of the printed circuit board 1. One of the large sectors is electrically connected to the central metal via 1a through the rectangular copper-clad structure 1d”’. The large sector in the top copper-clad structure connected to the central metal via 1a and the large sector in the middle copper-clad structure connected to the central ring 1c are in a 180° positional relationship around the center of the double-layer self-phase-shift fed printed circuit board 1. In a preferred embodiment of the present invention, the four large sectors (1c”, 1d’) in the double-layer self-phase-shifting fed printed circuit board 1 present feeding phases of 0°, -90°, -180° and -270° in a counterclockwise direction, satisfying the right-hand rule and being right-hand circular polarization.

[0062] like Figure 5As shown, the choke metal plate 2 includes a metal ring plate 2a and four metal filaments 2b. The inner diameter of the metal ring 2a is the diameter of the outer conductor of the feed coaxial line 3 (2.18 mm); the outer diameter of the metal ring 2a is smaller than the diameter of the double-layer self-phase-shifting feed printed circuit board 1 to ensure no contact with the four-arm spiral printed circuit board 5; in the preferred embodiment of the present invention, the outer diameter of the metal ring 2a is 5.6 mm and the thickness is 0.8 mm; the bottom of the four metal wires 2b is connected (welded) to the outer edge of the metal ring 2a, and the top ends pass through the third through hole 1a” of the double-layer self-phase-shifting feed printed circuit board 1 and are welded to conduct; in the preferred embodiment of the present invention, the diameter of the four metal wires 2b is 0.3 mm; the metal ring 2a is located about one-quarter of the center frequency wavelength downward from the bottom of the double-layer self-phase-shifting feed printed circuit board 1 and is welded to conduct with the outer conductor of the feed coaxial line; in the preferred embodiment of the present invention, the initial distance between the metal ring 2a and the bottom of the double-layer self-phase-shifting feed printed circuit board 1 is 11 mm, which is optimized by simulation to 9 mm.

[0063] Figure 6 This is a comparative schematic diagram showing the gain symmetry of a four-arm helical antenna with and without a choke plate in a wide-angle range, provided as an embodiment of the present invention. Figure 6 As shown, with reference to a preferred embodiment of the present invention, the beam symmetry of the right-hand circularly polarized gain pattern of the quad-arm spiral antenna in the ±70° spatial range was compared with and without the choke metal piece 2 at the center frequency. It can be clearly observed that when the quad-arm spiral antenna has the choke metal piece 2, compared to when it does not, the antenna axial gain is 0.6 dBic higher, and the gain value in the ±70° spatial range differs by only 0.02 dBic. However, without the choke metal piece 2, the gain value in the ±70° spatial range differs by 1.1 dBic. This indicates that the introduction of the choke metal piece 2 plays a good role in power supply balance, giving the antenna an extremely wide symmetrical beam.

[0064] Axial ratio is one of the key indicators for judging the quality of circular polarization of a circularly polarized antenna. Generally, it is required to be less than 3dB in the antenna axis and less than 6dB in the extremely wide spatial domain. Figure 7 This is a schematic diagram comparing the axial ratio symmetry of a four-arm helical antenna with and without a choke plate in a wide-angle range, provided as an embodiment of the present invention. Figure 7As shown, with reference to a preferred embodiment of the present invention, the beam symmetry of the quad-helical antenna axial ratio pattern in the ±70° spatial range was compared with and without the choke metal piece 2 at the center frequency. It can be clearly observed that when the quad-helical antenna has the choke metal piece 2, compared to without it, although the axial ratio is slightly increased by 1 dB (the axial ratio value is controlled at 1.38 dB), the axial ratio value in the ±70° spatial range differs by only 0.23 dBic (the maximum axial ratio value in the ±70° spatial range is controlled at 3.35 dB). Without the choke metal piece 2, the gain value in the ±70° spatial range differs by 2.53 dBic (the maximum axial ratio value in the ±70° spatial range is 5 dB). This indicates that the introduction of the choke metal piece 2 plays a good role in power supply balancing, giving the antenna an extremely wide symmetrical beam.

[0065] Figure 8 This is a schematic diagram comparing the voltage standing wave ratio (VSWR) characteristics of a four-arm helical antenna with and without a choke in its operating frequency band, as provided in an embodiment of the present invention. Figure 8 As shown, with reference to the preferred embodiment of the present invention, the voltage standing wave ratio (VSWR) characteristics of the quad-arm spiral antenna with and without the choke metal sheet 2 were compared. In the 6.3-7.3 GHz frequency band, the VSWR of both is less than 1.8, indicating that the introduction of the choke metal sheet 2 has no significant impact on the impedance matching characteristics of the quad-arm spiral antenna. Its main function is to balance the current of the inner and outer conductors of the feed coaxial cable 3.

[0066] Finally, it should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion. Without further limitations, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, goods, or apparatus that include the element.

[0067] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or equivalent substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A four-arm helical antenna, characterized by, The application relates to a four-arm spiral antenna, which comprises a double-layer self-phase shift feeding printed board, a choke metal sheet, a feeding coaxial line, a metal base and a four-arm spiral printed board, wherein the double-layer self-phase shift feeding printed board, the choke metal sheet and the feeding coaxial line jointly form a self-phase shift balanced feeding structure of the four-arm spiral antenna, and the four-arm spiral printed board forms an antenna radiator of the four-arm spiral antenna. Inner and outer conductors of the feeding coaxial line are respectively welded with a top copper layer and a bottom copper layer of the double-layer self-phase shift feeding printed board. Four spiral antenna arms arranged on the four-arm spiral printed board are symmetrically arranged at an angle of 90 degrees with the axis of the double-layer self-phase shift feeding printed board as the center, and the bottom of the four spiral antenna arms is short-circuited with the outer conductor of the feeding coaxial line. The double-layer self-phase shift feeding printed board forms four fan-shaped copper structures through internal microstrip lines, and the four fan-shaped copper structures are respectively welded with the top of the four spiral antenna arms to realize 0 degree, -90 degree, -180 degree and -270 degree feeding of the four spiral antenna arms. The choke metal sheet comprises one metal ring sheet and four metal filaments, wherein the metal ring sheet is arranged at a position about one fourth of the center frequency wavelength below the bottom of the double-layer self-phase shift feeding printed board and is welded with the outer conductor of the feeding coaxial line; the bottom of the four metal filaments is connected with the outer edge of the metal ring sheet and extends upwards to be welded with the four fan-shaped copper structures on the double-layer self-phase shift feeding printed board to choke the current of the outer conductor of the feeding coaxial line and realize balanced feeding of the inner and outer conductors of the feeding coaxial line. The double-layer self-phase shift feeding printed board is circular and has a diameter of about one fourth of the center frequency dielectric wavelength.

2. The four-arm helical antenna of claim 1, wherein, The double-layer self-phase shift feeding printed board has three copper layers, wherein the bottom layer and the middle layer are arranged at the bottom and the top of the lower printed board from bottom to top, and the top layer is arranged at the top of the upper printed board; the two printed boards are bonded by an adhesive layer.

3. The four-arm helical antenna of claim 2, wherein, The double-layer self-phase shift feeding printed board has four metal through holes from the center to the outside, wherein the first circle of through holes is one central metal through hole penetrating through the two printed boards and used for penetrating the inner conductor of the feeding coaxial line; the second circle of through holes is a plurality of through holes penetrating through the bottom layer and used for electrical conduction of the bottom layer and the middle layer; the third circle of through holes is four through holes penetrating through the two printed boards and used for penetrating the four metal filaments of the choke metal sheet; and the fourth circle of through holes is four through holes located at the edge of the printed board and penetrating through the two printed boards and used for electrical conduction of the middle layer and the top layer.

4. The quadrafoil antenna of claim 3, wherein, The bottom layer of the double-layer self-phase shift feeding printed board is a circular ring, the outer diameter of the circular ring is smaller than the diameter of the third circle of through holes to ensure that the two are not in electrical contact, the inner diameter of the circular ring is smaller than the diameter of the outer conductor of the feeding coaxial line and the outer conductor of the feeding coaxial line is welded with the circular ring, the inner diameter of the circular ring is larger than the diameter of the inner conductor of the feeding coaxial line and ensures that there is a gap of more than 0.35 mm between the inner conductor of the feeding coaxial line and the metal through hole pad, and the second circle of through holes is located in the circular ring.

5. The quadrafoil antenna of claim 4, wherein, ​ 6. The quadrafoil antenna of claim 5, wherein, The middle layer copper structure of the double-layer self-phase shift feeding printed board comprises a circular ring, a three-quarter circular ring, two large sectors and two small sectors from the center to the outside; the center circular ring covers the position of the second circle of through holes to ensure the electrical conduction of the bottom layer and the middle layer copper structure; the inner diameter of the three-quarter circular ring is about 0.4 times of the 1 / 4 center frequency dielectric wavelength; the width of the three-quarter circular ring is about 100Ω characteristic impedance width according to the selected printed board material and thickness, while the outer diameter of the three-quarter circular ring is less than the diameter of the third circle of through holes to ensure that the two are not in electrical contact; the two large sectors are in a 90° position relationship with the center of the printed board as the axis; the inner diameter of the large sector is the inner diameter of the three-quarter circular ring, the outer diameter of the large sector is the diameter of the printed board, and the sector angle is in the interval of 45°-50°; one of the large sectors is electrically connected to the center circular ring through the rectangular copper structure; the two small sectors are in a 180° position relationship with the center of the printed board as the axis; the outer diameter of the small sector is the diameter of the printed board, and the sector angle is consistent with that of the large sector; the inner diameter of the small sector covers the position of the fourth circle of through holes; the three-quarter circular ring together with the two large sectors; the relative position of the two large sectors and the three-quarter circular ring determines the circular polarization rotation direction of the four-arm spiral antenna.

7. The quadrafoil antenna of claim 6, wherein, The top layer copper structure of the double-layer self-phase shift feeding printed board comprises a three-quarter circular ring, two large sectors and two small sectors from the center to the outside; the three-quarter circular ring, the two large sectors and the two small sectors are in a 180° position relationship with the three-quarter circular ring and the sectors in the middle layer copper structure with the center of the printed board as the axis; one of the large sectors is electrically connected to the center metal through hole through the rectangular copper structure; the large sector connected to the center metal through hole is in a 180° position relationship with the large sector connected to the center circular ring in the middle layer copper structure with the center of the printed board as the axis.

8. The quadrafoil antenna of claim 1, wherein, The metal circular ring of the choke metal sheet is sleeved on the feeding coaxial line, the inner diameter of the metal circular ring is the outer conductor diameter of the feeding coaxial line, and the outer diameter of the metal circular ring is less than the diameter of the double-layer self-phase shift feeding printed board to ensure no electrical contact with the four spiral antenna arms.

9. The quadrafoil antenna of claim 1, wherein, The four-arm spiral printed board comprises a dielectric cylinder and the four spiral antenna arms arranged on the outer arm circumference of the dielectric cylinder; the diameter of the dielectric cylinder is consistent with the diameter of the double-layer self-phase shift feeding printed board; the angular width of the spiral line of the four spiral antenna arms is consistent with the sector angle of the sector copper structure in the double-layer self-phase shift feeding printed board.

10. The quadrafoil antenna of claim 9, wherein, The height of the four-arm spiral printed board is consistent with the height of the feeding coaxial line.

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