Wide-beam circularly polarized antenna with four-arm helical structure and application thereof

Abstract

The application discloses a wide-beam circularly polarized antenna unit with a four-arm spiral structure and application thereof, which comprises four vertically-enclosed top-layer dielectric substrates, a horizontally-placed middle-layer dielectric substrate and a bottom-layer dielectric substrate, an oblique monopole metal strip located in the inner side of the vertical dielectric substrate, a metal column located at the bottom of the monopole metal strip, a square metal patch located on the middle-layer dielectric substrate and a metal floor on the lower surface, and a feed network located on the lower surface of the bottom-layer dielectric substrate. The feed network feeds the square patch through the metal column to realize right circularly polarized radiation. The monopole metal strip is reversely inclined and the phase shift line of the feed network is exchanged to realize the change of the circularly polarized radiation rotation direction. The phased array antenna with wide-angle scanning characteristics is obtained by arraying the circularly polarized antenna units. The oblique monopole structure can simultaneously expand the half-power beam width and the circularly polarized axial ratio beam width, and the scanning range of the phased array formed by the units can reach ±60° and keep good circularly polarized performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of microwave antennas, and particularly relates to a wide-beam circularly polarized antenna with a four-arm spiral structure and application thereof. BACKGROUND

[0002] Circularly polarized antennas have multiple advantages such as polarization mismatch suppression, anti-multipath interference and Faraday rotation avoidance, and circularly polarized phased arrays have very wide application value and are commonly used in satellite communication, automobile navigation and other fields. The main beam scanning range of most planar microstrip circularly polarized phased array antennas is only 90-100°, and the gain fluctuation is large. Meanwhile, as the scanning angle increases, the axial ratio cannot meet the use requirements, and it is necessary to design an antenna unit with a wide beam width and good circular polarization performance.

[0003] In recent years, much research has been done on how to expand the beam width of an antenna unit. In 2018, W.J. Yang et al. published an article entitled "A low-profile wideband circularly polarized crossed-dipole antenna with wide axial-ratio and gain beamwidths" in IEEE Transactions on Antennas and Propagation. (vol. 66, no. 7, pp. 3346-3353, Jul. 2018). In the article, two pairs of magnetic dipoles composed of triangular metal patches and metal blocks are introduced into a crossed-dipole trapezoidal patch antenna to improve the half-power beam width and impedance bandwidth. The impedance bandwidth of the antenna is 78.3%, and the half-power beam width in the operating frequency band is more than 110°, but the 3dB axial ratio beam width in most of the frequency band is only 120°, which will affect the circular polarization performance of the antenna array after arraying.

[0004] In 2021, R. Sen et al. published an article entitled "S-Band Full-Metal Circularly Polarized Cavity-Backed Slot Antenna With Wide Bandwidth and Wide Beamwidth" in IEEE Transactions on Antennas and Propagation. (vol. 69, no. 9, pp. 5963-5968, Sept. 2021), in which a pair of triangular lenses is placed on the corners of the cavity to generate TE101 and TE011 modes under orthogonal electric fields, forming circularly polarized radiation. By changing the size of the cavity slot and the lens, the 3dB axial ratio beamwidth and the axial ratio bandwidth are improved. The 3dB axial ratio beamwidth of the antenna is 180°, but the half-power beamwidth is only 75°, and the size profile is high, at 0.7λ0x 0.7λ0x 0.58λ0.

[0005] In 2022, Y. Luo et al. published an article entitled "Beamwidth-Enhanced Circularly Polarized Antenna Using Non-Uniformly Compressed High-Order Mode Dipoles" in IEEE Transactions on Antennas and Propagation. (vol. 70, no. 9, pp. 7831-7842, Sept. 2022), which first uses non-uniformly compressed high-order mode dipoles to improve the E-plane beamwidth, and then places the dipoles in a cross combination to obtain a wider half-power beamwidth and 3dB axial ratio beamwidth. The half-power beamwidth of the antenna is greater than 109° in both main planes, and the 3dB axial ratio beamwidth is greater than 118°, but the size of the antenna unit is large, at 1.86λ0x 1.86λ0x 0.25λ0, which is not suitable for forming a phased array.

[0006] To meet the needs of satellite communication, automotive navigation and other fields, the performance requirements of circularly polarized antennas are becoming higher and higher, and it is necessary to have wider half-power beamwidth and 3dB axial ratio beamwidth. Under the condition of meeting the above conditions, circularly polarized wide-angle phased arrays also have certain requirements for the size of the antenna unit. SUMMARY

[0007] The present application aims to overcome the defects of the prior art, and provides a wide-beam circularly polarized antenna with a four-arm spiral structure and an application thereof. The present application improves the half-power beam width and 3dB axial ratio angle range of the antenna unit by loading four obliquely placed monopole metal strips around the square radiation patch, and a wide-angle scanning phased array composed of the antenna unit achieves a scanning range of ±60° and maintains good circular polarization effect.

[0008] The technical problem of the present application is solved as follows:

[0009] A wide-beam circularly polarized antenna with a four-arm spiral structure is closely attached from top to bottom, and includes four vertically arranged top layer dielectric substrates S1, S2, S3, and S4, an intermediate layer dielectric substrate S5, a metal ground plate M, and a bottom layer dielectric substrate S6.

[0010] The inner side of the vertical dielectric substrates S1, S2, S3, and S4 is provided with oblique monopole metal strips P1, P2, P3, and P4, and the four metal strips have consistent oblique directions and form a spiral shape. A metal column C1, C2, C3, or C4 is connected to the bottom of each metal strip, and the metal column is embedded into the intermediate layer dielectric substrate S5 and connected to the metal ground plate M at the bottom of the dielectric plate. S1, P1, and C1 form a basic monopole antenna structure, and S1, P1, and C1 are sequentially rotated by 90°, 180°, and 270° around the center as the origin to obtain the remaining three monopole structures S2, P2, and C2, S3, P3, and C3, and S4, P4, and C4.

[0011] A square radiation patch P5 is arranged on the upper surface of the intermediate layer dielectric substrate S5, and the lower surface of S5 is the metal ground plate M. P5 is fed by two metal columns C5 and C6, C5 and C6 pass through the intermediate layer dielectric substrate S5, the metal ground plate M, and the bottom layer dielectric substrate S6 are connected to the feed network N on the lower surface of S6, and two circular holes are formed in the metal ground plate M to facilitate the passage of C5 and C6 without contacting M.

[0012] The lower surface of the bottom layer dielectric substrate S6 is a microstrip feed network N. N is composed of a one-to-two equal-amplitude Wilson power divider and two sections of microstrip phase shift lines, and the input impedance is 50 ohms. The power divider includes three sections of microstrip lines N1, N2, and N3, and a patch resistor R with a resistance of 100 ohms. The two sections of microstrip phase shift lines are N4 and N5.

[0013] The wide-beam circularly polarized antenna with a four-arm helical structure is used as an antenna element. These elements are arranged in a 2×8 array with equal spacing, and the center-to-center distance between adjacent elements is 0.4λ0 (λ0 is the wavelength corresponding to the center frequency of the antenna's operating band). The signal input ports of the 16 antenna elements are located on the two long sides of the array antenna. All antenna element ports are microstrip fed, and the input impedance of the ports is 50 ohms.

[0014] The beneficial effects of this invention are:

[0015] (1) This invention utilizes inclined monopole metal strips on the inner side of a vertical dielectric plate and metal pillars connected to their bottom ends to form an inclined monopole antenna with a ground plane. The radiation modes of these four monopoles can be equivalent to a ring dipole model of a four-arm spiral antenna. This model consists of a pair of horizontally orthogonally placed ring dipoles and a pair of horizontally orthogonally placed current loops, which can form circularly polarized radiation. This radiation can be superimposed on the radiation field of the square patch antenna, which can widen the antenna's half-power beamwidth and 3dB axial ratio beamwidth.

[0016] (2) The dielectric substrate used in the square radiating patch of the present invention has a high dielectric constant and a thicker thickness, which can effectively reduce the size of the antenna and make the antenna easier to meet the array requirements.

[0017] (3) The antenna and feed network described in this invention have a simple structure and achieve the effect of a wide-beam circularly polarized antenna while meeting the requirements of a small size, which greatly reduces the design difficulty.

[0018] (4) The antenna described in this invention can achieve right-hand circular polarization radiation. To achieve left-hand circular polarization radiation, it is only necessary to tilt the four monopole metal strips at opposite angles and swap the two phase shift lines of the feed network.

[0019] (5) The 2×8 array composed of wide beam circular polarization antenna elements with four-arm spiral structure described in this invention can achieve ±60° circular polarization beam scanning, and the axial ratio of each scanning beam is less than 6dB, which has good circular polarization performance. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the three-dimensional structure of the wide-beam circularly polarized antenna with a four-arm helical structure described in this invention.

[0021] Figure 2 for Figure 1 Side view of the antenna described in the image;

[0022] Figure 3 for Figure 1 Top view of the antenna described in the image;

[0023] Figure 4For Figure 2 top view of the metal floor M;

[0024] Figure 5 For Figure 2 top view of the feed network N;

[0025] Figure 6 S parameter diagram of the antenna described in Example One;

[0026] Figure 7 axial ratio diagram of the antenna described in Example One;

[0027] Figure 8 pattern diagram of the antenna described in Example One at 1.35 GHz frequency point, wherein (a) φ = 0° plane; (b) φ = 90° plane;

[0028] Figure 9 S parameter diagram of the feed network described in Example One;

[0029] Figure 10 two-port phase difference diagram of the feed network described in Example One;

[0030] Figure 11 structure diagram of the 2x8 phased array antenna described in Example Two;

[0031] Figure 12 feed network diagram of the 2x8 phased array antenna described in Example Two;

[0032] Figure 13 beam scanning pattern diagram of the 2x8 phased array antenna described in Example Two;

[0033] Figure 14 axial ratio diagram of the 2x8 phased array antenna described in Example Two. DETAILED DESCRIPTION

[0034] The present application will be further described below in conjunction with the accompanying drawings and examples.

[0035] Example One

[0036] The present embodiment provides a wide-beam circularly polarized antenna with a four-arm spiral structure, a perspective structural diagram of which is shown in Figure 1 a side view of which is shown in Figure 2 From top to bottom, the first are four vertically and circumferentially placed top layer dielectric substrates S1, S2, S3, S4, then is the middle layer dielectric substrate S5, followed by the metal floor M, and finally is the bottom layer dielectric substrate S6. Each layer of dielectric substrate and metal floor is closely attached from top to bottom, wherein S5, M, S6 have the same plane size. A top view of the antenna is shown in Figure 3As shown, the inner side of each vertical dielectric substrate is provided with an inclined monopole metal strip P1, P2, P3, P4, which has the same inclination angle, and the bottom of each monopole metal strip is connected with a metal column C1, C2, C3, C4. The four vertical dielectric substrates and the inclined monopole patch and the metal column at the bottom form a right-handed four-arm helical antenna. There is a square radiation patch P5 in the middle of the middle layer dielectric substrate S5, which has two feeding ports connected with the metal columns C5 and C6 respectively. The top view of the metal floor M is shown in Fig. 3. Figure 4 As shown, two complete circular holes are engraved for the passage of the metal columns C5 and C6. The feeding network N is located on the lower surface of the bottom layer dielectric substrate S6, and the top view of the feeding network N is shown in Fig. 4. Figure 5 As shown, it is composed of a one-to-two Wilson power divider and two sections of phase shift lines. The power divider includes a 50-ohm impedance input microstrip line N1, two sections of 70.7-ohm quarter-wavelength transformation lines N2 and N3, and a 100-ohm patch resistor R. The two sections of phase shift lines have an impedance of 50 ohms, which are a 0° reference phase shift line N4 and a 90° phase shift line N5 respectively. The signal amplitude of the two output ports of the feeding network is equal, and the phase difference is 90°. The antenna can realize right-handed circular polarized radiation. If left-handed circular polarized radiation is required, only the inclination direction of each monopole metal strip needs to be reversed, and the positions of the two sections of phase shift lines of the feeding network need to be exchanged to change the rotation direction of the circular polarized radiation.

[0037] The material of the four vertical dielectric substrates S1, S2, S3 and S4 is Rogers RT / duroid 5880, the relative dielectric constant is 2.2, the loss tangent is 0.0009, and the thickness is 2 mm. The size of each vertical dielectric substrate is 24.5 mm x 20 mm. The bottom edge of the inclined monopole metal strip P1, P2, P3 and P4 is located at the center of the bottom edge of each vertical dielectric substrate, the width is 4 mm, and the top edge is located at the edge of the top edge of each vertical dielectric substrate. The angle of the monopole is 40°. The metal column C1, C2, C3 and C4 is located below the center of the bottom edge of each monopole, the diameter is 3 mm, the height is 6 mm, and is embedded in the middle layer dielectric substrate S5 connected to the metal ground plate M. The material of the middle layer dielectric substrate S5 is Rogers RT / duroid 6006, the relative dielectric constant is 6.15, the loss tangent is 0.0019, the thickness is 6 mm, and the size is 80 mm x 80 mm. The size of the square radiation patch is 20 mm x 20 mm, the diameter of the two feeding copper columns C5 and C6 is 1.2 mm, the feeding position is located at the center point 10 mm of the square radiation patch, the height is 6.254 mm, and passes through the middle layer dielectric substrate, the metal ground plate M and the bottom layer dielectric plate S6 to be connected to the feeding network N. The size of the metal ground plate M is 80 mm x 80 mm, the diameter of the two circular vias is 3 mm, and the center is located at a distance of 10 mm from the center point of the metal ground plate. The material of the bottom layer dielectric substrate S6 is Rogers RO4003, the relative dielectric constant is 3.55, the loss tangent is 0.0027, the thickness is 0.254 mm, and the size is 80 mm x 80 mm. The line width of the 50 ohm microstrip line in the feeding network N is 1.13 mm, the line width of the 70 ohm microstrip line is 0.627 mm, the length of N1 in the one-to-two power divider is 34 mm, the lengths of the two quarter wavelength conversion lines N2 and N3 are 39 mm, the size of the patch resistor R is 2.5 mm x 1 mm, and the lengths of the two phase shift lines N4 and N5 are 20.301 mm and 56.366 mm respectively.

[0038] The size of the antenna described in the embodiment is 0.36λ0x 0.36λ0(λ0is the wavelength corresponding to the center frequency of the operating frequency band of the antenna), and in the case of not accessing the feeding network, the two feeding ports are directly fed in an ideal case. The S parameter simulation result is as shown in Figure 6 The working frequency band is: 1.32 GHz-1.39 GHz (relative bandwidth 5%). After accessing the feeding network, the two main plane patterns of the antenna at 1.35 GHz are as shown in Figure 7 The maximum gain of the antenna is 3.47 dB, and the half-power beamwidth of the two main planes is 110°. The axial ratio diagram of the two main planes of the antenna at 1.35 GHz is as shown in Figure 8 The beamwidth with an axial ratio less than 3 dB is 156° and 175° respectively.

[0039] The S parameter simulation results of the antenna feed network described in the embodiment when working with an ideal matching load alone are shown in Figure 9 The working frequency band is 0.39GHz-2.06GHz (relative bandwidth 121%), and the isolation is greater than 25dB in the working frequency band of the antenna, which can well adapt to the antenna unit. The phase difference of the two output ports of the feed network is shown in Figure 10 The output phase difference is within 90°±2° in the frequency band of 1.32GHz-1.39GHz, which can meet the needs of circular polarization radiation.

[0040] Embodiment Two

[0041] A circularly polarized wide-angle scanning phased array is composed of a 2x8 array of the antenna described in Embodiment One as a unit antenna arranged at equal intervals, and the structure is shown in Figure 11 The unit interval is 90mm (0.4λ0). The schematic diagram of the feed network of the array is shown in Figure 12 The input ports of the feed network are arranged on the two long sides of the array, and eight input ports are designed at equal intervals on each long side. The feed method is side feed.

[0042] The simulation analysis of the phased array is performed, and the beam scanning pattern is shown in Figure 13 The scanning range of the array can reach ±60°, and the gain flatness is 2.7dB. The axial ratio of the scanning beam of the array is shown in Figure 14 In the scanning range of ±45°, the scanning beam of the antenna satisfies the axial ratio less than 3dB, and in the scanning range of more than ±45°, the axial ratio can also satisfy less than 6dB. The phased array maintains good circular polarization performance in the scanning process.

Claims

1. A wide-beam circularly polarized antenna with a four-arm helical structure, characterized in that, From top to bottom, it includes four top-layer dielectric substrates S1, S2, S3, S4 placed vertically, one middle-layer dielectric substrate S5 placed horizontally, one metal ground plate M placed horizontally, and one bottom-layer dielectric substrate S6 placed horizontally; The inner side of each vertical dielectric substrate is provided with an inclined monopole metal strip P1, P2, P3, P4, the bottom of the monopole metal strip is provided with a metal column C1, C2, C3, C4, the metal column is embedded into the middle-layer dielectric substrate S5, and the lower end is connected to the metal ground plate M; the upper surface of the middle-layer dielectric substrate S5 is provided with a square radiation patch P5, P5 is fed by two metal columns C5 and C6, C5 and C6 pass through the middle-layer dielectric substrate S5, the metal ground plate M and the bottom-layer dielectric substrate S6 in turn and are connected to a feed network N; the metal ground plate M has two circular vias for C5 and C6 to pass through; The feed network N is located on the lower surface of the bottom-layer dielectric substrate S6 and is composed of a one-to-two equal-amplitude Wilson power divider and two sections of phase shift lines, the power divider includes one section of input microstrip line N1, two sections of quarter-wavelength transformation lines N2 and N3, one patch resistor R, and two sections of phase shift lines including one section of 0° reference phase shift line N4 and one section of 90° phase shift line N5.

2. A wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, characterized in that, By adjusting the size of the square radiation patch P5, the resonant frequency point of the antenna can be adjusted.

3. The wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, wherein, By adjusting the height and thickness of the vertical dielectric substrates S1, S2, S3, S4, the half-power beam width and 3dB axial ratio beam width of the antenna can be changed.

4. The wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, characterized in that, By adjusting the length, width and inclination angle of the inclined monopole metal strips P1, P2, P3, P4, the half-power beam width and 3dB axial ratio beam width of the antenna can be changed.

5. The wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, characterized in that, By making the monopole metal strips P1, P2, P3, P4 inclined at opposite angles, the handedness of the circularly polarized radiation of the antenna can be changed.

6. A wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, characterized in that, By adjusting the size of the metal ground plate M, the half-power beam width and 3dB axial ratio beam width of the antenna can be changed.

7. The wide-beam circularly polarized antenna with four-arm helical structure according to claim 1, wherein, The antenna port adopts a microstrip feed mode, and the input impedance of the port is 50 ohms.

8. Use of a wide-beam circularly polarized antenna with a four-arm helical structure according to any one of claims 1-7, characterized in that, The wide-beam circularly polarized antenna with a four-arm spiral structure serves as a unit antenna, multiple unit antennas are arranged at equal intervals to form a 2×8 array circularly polarized phased array with wide-angle scanning characteristics, and adjacent unit antennas are closely attached; 16 signal input ports of the array are located on two long edges of the array antenna, 8 feed ports are arranged on each long edge, and the feed mode is side feed.

9. The application of a wide-beam circularly polarized antenna with four-arm helical structure according to claim 8, characterized in that, The antenna ports of the circularly polarized phased array all adopt a microstrip feed mode, and the input impedance of the port is 50 ohms.

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