Dual-mode spiral antenna with parasitic spiral

Abstract

The invention provides a dual-mode helical antenna with a parasitic helix. The dual-mode helical antenna comprises a main helix, the parasitic helix, a dielectric substrate and the like. The parasitic spiral is located in the main spiral and isolated through insulation foam paper. The design of the main helix simultaneously meets the requirements of a normal mode and an axial mode under a specific wavelength, the normal mode is excited in a 4G / 5G frequency band, and the axial mode is excited in a Ku frequency band. By introducing a parasitic spiral, the impedance matching of a normal mode is improved in a 4G / 5G frequency band, and the bandwidth is improved; in the Ku frequency band, the axial ratio is improved, so that the axial ratio is all lt in the working frequency band; and 3dB. The antenna achieves 8 times of frequency ratio, and the size is only 1 / 5 of that of a traditional scheme. Coaxial line coplanar feed is adopted, a balun or a power divider is omitted, and insertion loss gt is reduced; and 1.5 dB. The ground mode covers 4G / 5G, and the omnidirectional gain is greater than or equal to 1.89 dBi; the satellite mode supports Ku wave band left-hand circular polarization, the directional gain is larger than or equal to 12.94 dBic, and the ITU standard is met.

Description

Technical Field

[0001] This application belongs to the field of antennas, and particularly relates to a dual-mode helical antenna with parasitic helixes. Background Art

[0002] When realizing a dual-band antenna by using multiple modes of an antenna, the size can be reduced and the design can be simplified by eliminating the need for additional filtering structures.

[0003] In [1], the TE111 and TE113 modes of a rectangular DRA operate in the frequency bands of 3.47 GHz and 5.24 GHz respectively. Similarly, [2] adopts the quasi-TE111 and quasi-TE113 modes in a rectangular DRA to achieve the frequency bands of 1.58 GHz and 2.5 GHz. In [3], a cylindrical DRA operates in the HEM111 and HEM113 modes to provide a dual-band of 1.8 GHz and 2.4 GHz.

[0004] However, the resonant frequency ratio of such a DRA is generally limited to no more than 3.

[0005] A hybrid dual-mode dual-band antenna is introduced in [4], where the dielectric region and air region of a hollow DRA satisfy the resonant conditions of a Fabry-Perot resonator antenna (FPRA) at millimeter-wave frequencies, and at the same time, the HEM111 mode is excited at microwave frequencies to achieve a large frequency ratio from 2.4 GHz to 24 GHz.

[0006] Although the hybrid dual-mode dual-band antenna in [4] can achieve a large frequency ratio, it requires dual-port feeding, which will make the antenna structure complex.

[0007] Helical antennas have received extensive attention due to their advantages such as simple structure, wideband, and inherently circular polarization. There are two different operating modes of helical antennas: axial mode and normal mode. In the axial mode, the antenna exhibits directional radiation, can achieve circular polarization, and can meet the requirements of satellite communication; in the normal mode, the antenna exhibits omnidirectional radiation and is suitable for ground communication. However, the two modes are completely opposite in terms of input impedance. In the axial mode, the input impedance exceeds 100 ohms; while in the normal mode, due to the volume of the antenna being significantly smaller than the wavelength at its operating frequency, the input impedance drops to only a few ohms, and the small input impedance will result in a relatively narrow bandwidth. It is very difficult to achieve impedance matching for both modes at the same time. Currently, there is no design that combines these two modes, and generally only one of the modes is utilized alone.

[0008] [1]X.S. Fang and K.W. Leung, “Designs of Single-, Dual-, Wide-Band Rectangular Dielectric Resonator Antennas,” IEEE Trans. Antennas Propag., vol. 59, no. 6, pp. 2409 - 2414, June 2011.

[0009] [2]X.S. Fang, K.W. Leung and E.H. Lim, “Singly-Fed Dual-Band Circularly Polarized Dielectric Resonator Antenna,” IEEE Antennas and Wireless Propagation Letters, vol. 13, pp. 995 - 998, 2014.

[0010] [3]X.S. Fang and K.W. Leung, “Linear- / Circular-Polarization Designs of Dual- / Wide-Band Cylindrical Dielectric Resonator Antennas,” IEEE Trans. Antennas Propag., vol. 60, no. 6, pp. 2662 - 2671, June 2012.

[0011] [4]L.Y. Feng and K.W. Leung, “Dual-Fed Hollow Dielectric Antenna for Dual-Frequency Operation With Large Frequency Ratio,” IEEE Trans. Antennas Propag., vol. 65, no. 6, pp. 3308 - 3313, June 2017. Summary of the Invention

[0012] The object of the present application is to overcome the defects existing in the above-mentioned prior art and provide a dual-mode helical antenna with a parasitic helix.

[0013] The present application provides a dual-mode helical antenna with a parasitic helix, including: a main helical structure, a parasitic helical structure, a dielectric substrate, a single-port feeding structure and a parasitic helix fixing structure;

[0014] The parasitic spiral structure is located at the inner center position of the main spiral structure;

[0015] The main spiral structure is welded to the upper surface of the dielectric substrate;

[0016] The single-port feeding structure is welded and fixed through an SMA connector at the bottom of the dielectric substrate and is directly electrically connected to the bottom of the main spiral structure;

[0017] The parasitic spiral structure is isolated from the main spiral structure by insulating foam paper;

[0018] The main spiral structure: In the axial mode, the main spiral radius R 1 satisfies 0.25 < 2R 1 / λ 0 <0.46, and the spiral circumference C 1 = 2πR 1 , satisfies 3 / 4 < C 1 / λ 0 <4 / 3, and the spiral pitch H 1 ≈ λ 0 / 4; In the normal mode, the main spiral radius R 1 satisfies 2R 1 / λ 0 <0.18;

[0019] The parasitic spiral structure: provides a resonance point in the 4G / 5G frequency band.

[0020] Optionally, the diameter ratio of the main spiral structure to the parasitic spiral structure is 2.03:1, and the turn difference is less than 0.05 turns, forming a nested double-spiral structure.

[0021] Optionally, the number of turns N of the parasitic spiral ranges from 5.4 ≤ N ≤ 6.0, and the resonant frequency in the low-frequency band is adjustable within the range of 2.4 - 2.46 GHz by adjusting the N value.

[0022] Optionally, a full-metal ground plane is provided at the bottom of the dielectric substrate, and its size is the same as that of the dielectric substrate.

[0023] Optionally, the inner conductor of the coaxial cable of the single-port feeding structure passes through a through-hole on the dielectric substrate and is connected to the main spiral structure, and the outer conductor is welded to the ground plane, forming a coplanar feeding structure.

[0024] This application also provides a dual-mode spiral antenna with a parasitic spiral. Based on the above dual-mode spiral antenna with a parasitic spiral, it includes:

[0025] The parasitic spiral structure is replaced with a hollow copper tube monopole structure, and the outer diameter of the hollow copper tube monopole structure is the same as the diameter of the parasitic spiral structure, and the height is equal to the axial length of the parasitic spiral structure.

[0026] The beneficial effects of this application are as follows:

[0027] This application provides a dual-mode spiral antenna with parasitic spirals, including: a main spiral structure, a parasitic spiral structure, a dielectric substrate, a single-port feeding structure, and a parasitic spiral fixing structure; the parasitic spiral structure is located at the center position inside the main spiral structure; the main spiral structure is welded to the upper surface of the dielectric substrate; the single-port feeding structure is welded and fixed through the SMA connector at the bottom of the dielectric substrate and is directly electrically connected to the bottom of the main spiral structure; the parasitic spiral structure is isolated from the main spiral structure by insulating foam paper; the main spiral structure: in the axial mode, the main spiral radius R 1 satisfies 0.25 < 2R 1 / λ 0 < 0.46, and the spiral circumference C 1 = 2πR 1 , satisfies 3 / 4 < C 1 / λ 0 < 4 / 3, and the spiral pitch H 1 ≈ λ 0 / 4; in the normal mode, the main spiral radius R 1 satisfies 2R 1 / λ 0 < 0.18; the parasitic spiral structure: provides a resonance point in the 4G / 5G frequency band. This application realizes an 8-fold frequency ratio through dual-mode collaborative work, with a 267% improvement compared to the dielectric resonator antennas in references [1]-[3]; the overall size is reduced to 20mm × 20mm × 4.43mm, and the volume is only 1 / 5 of the traditional dual-antenna stacking scheme. Coaxial coplanar feeding (SMA direct welding) is adopted, eliminating the balun or power divider in the dual-port design, reducing the insertion loss by > 1.5dB, and reducing the structural complexity by 60%. The ground mode covers the 4G and 5G frequency bands, with an omnidirectional radiation gain ≥ 1.89dBi; the satellite mode supports left-handed circular polarization in the Ku band, with a directional gain ≥ 12.94dBic, meeting the ITU satellite communication standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the antenna in this application;

[0029] Figure 2 is a schematic diagram of the simulated input impedance of the antenna in this application in the 4G and 5G frequency bands;

[0030] Figure 3 is a diagram of |S 11 | of the antenna in this application in the 4G and 5G frequency bands under different N values;

[0031] Figure 4 is a schematic diagram of the antenna evolution diagram in this application;

[0032] Figure 5 are the |S comparison schematic diagrams of the left antenna, middle antenna, and right antenna in the 4G and 5G frequency bands in this application; 11 |Comparison schematic diagram;

[0033] Figure 6 are the |S comparison schematic diagrams of the left antenna, middle antenna, and right antenna in the Ku band in this application; 11 |Comparison schematic diagram;

[0034] Figure 7 are the gain and AR schematic diagrams of the left antenna and right antenna in this application;

[0035] Figure 8 is the physical schematic diagram of the antenna in this application;

[0036] Figure 9 are the measured |S 11 |and the comparison schematic diagram of the gain and simulation results in the 4G and 5G frequency bands in this application;

[0037] Figure 10 is the comparison schematic diagram of the measurement and simulation results of the E-plane and H-plane radiation patterns of the antenna at 2.5 GHz, 14 GHz, 17 GHz, and 20 GHz in this application;

[0038] Figure 11 is the schematic diagram of the copper tube in the structure of the antenna in this application. Detailed implementation manners

[0039] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be fully conveyed to those skilled in the art.

[0040] Please refer to Figure 1 as shown, this application provides a dual-mode helical antenna with parasitic helixes.

[0041] As Figure 1 shown, the antenna is fed by a 50Ω coaxial cable through a single port and combines two modes of the helical antenna.

[0042] The antenna is composed of a main helix and parasitic helixes, and the parasitic helixes are located inside the main helix.

[0043] The antenna is mounted on a single-layer Taconic TLC TM substrate, with a length W g = 20 mm, a width L g = 20 mm, and a thickness Hg = 1.14 mm, and the dielectric constant of the substrate is 3.2.

[0044] The main helix is placed on the substrate, and the helix pitch H 1 = 4.43 mm, and the helix diameter 2R 1 = 5.8 mm, the number of turns is 5.85, and the helix wire diameter D 1 = 1.13 mm.

[0045] The bottom of the main helix is parallel to the substrate for impedance matching in the Ku band.

[0046] The central parasitic helix, helix pitch H 4 = 6 mm, and the helix diameter 2R 2 = 2.86 mm, the number of turns is 5.8, and the wire diameter D 2 = 1.1 mm.

[0047] In the 4G and 5G frequency bands, the parasitic helix improves impedance matching and increases the operating bandwidth. In the Ku band, the parasitic helix increases its AR bandwidth. The antenna consists of three parts, namely the main helix and parasitic helix part, the feeding part, and the dielectric floor part.

[0048] In the 4G and 5G frequency bands, the antenna operates in the normal mode. The main helix diameter is 2R 1 , and the wavelength of the center frequency is denoted as λ 0 , and the following conditions need to be met:

[0049] 2R 1 / λ 0 < 0.18

[0050] With the given parameters, the main helix diameter is 2R 1 = 5.8 mm, and the wavelength of the center frequency is approximately λ 0 ≈ 116 mm. Therefore, the ratio 2R 1 / λ 0 = 0.05, meeting the above conditions.

[0051] In the Ku band, the antenna operates in the axial mode. The main helix diameter is 2R 2 , and the wavelength of the center frequency is denoted as λ 0 , and the following conditions need to be met:

[0052] 0.25 < 2R / λ 0 < 0.46

[0053] With the given parameters, the main helix diameter is 2R 1 = 5.8 mm, and the wavelength of the center frequency is approximately λ 0 ≈ 18 mm. Therefore, the ratio 2R 1 / λ 0= 3.2, meeting the above conditions.

[0054] To achieve circular polarization in the Ku band, the helix circumference C and the helix pitch H must meet the following conditions:

[0055]

[0056] The helix circumference is calculated as C = 2πR 1 ≈ 18 mm, obtaining the ratio C / λ 0 = 1, the main helix pitch H 1 = 4.43 mm, λ 0 / 4 = 4.5 mm, meeting the above conditions.

[0057] Therefore, the antenna can simultaneously meet the design requirements for normal mode operation in the 4G and 5G frequency bands and axial mode operation in the Ku band.

[0058] The main helix and the parasitic helix are made by metal 3D printing technology.

[0059] During production, first upload the file generated by the slicing software to the 3D printer, and start printing after selecting the corresponding file. The 3D printer will deposit, cure, or sinter the copper material layer by layer on the printing platform according to the slicing data, gradually constructing the shape of the helix.

[0060] After printing is completed, since the volume of the main helix and the parasitic helix is very small, it is impossible to use a machine to remove the support material. Tools such as tweezers and pliers need to be used to manually remove the support material, and then the helix is surface-treated with sandpaper to make it smooth. Finally, use a caliper to measure whether the helix processed by 3D printing meets the accuracy requirements.

[0061] The dielectric floor part uses a Taconic TLC single-layer substrate with a length and width of 2 mm and a thickness of 1.14 mm TM The dielectric constant of this substrate is 3.2.

[0062] For the last part, the feeding structure part, the feeding part uses SMA coaxial feeding. The SMA socket is directly welded to the bottom of the substrate, and after drilling holes in the substrate, the coaxial cable is passed through and contacts the main helix for feeding.

[0063] The main helix is welded to the substrate, and the parasitic helix is fixed in the middle of the main helix by foam paper, and the foam paper plays a role in isolating the main helix and the parasitic helix. The finished antenna is small in volume and compact in structure.

[0064] Please refer to Figure 2 as shown Figure 2 for the simulated input impedance of the antenna in the 4G and 5G frequency bands.

[0065] It can be clearly seen that there are two resonance modes near 2.46 GHz and 2.77 GHz respectively.

[0066] Please refer to Figure 3 as shown Figure 3 which is a parameter scan of the number of turns N of the parasitic helix.

[0067] The simulation results show that when the value of N increases from 5.4 to 6.0, the first resonance frequency decreases from 2.46 GHz to 2.4 GHz. In contrast, the second resonance frequency is not affected by the change of N, which indicates that the first resonance frequency is generated by the parasitic helix, while the second resonance frequency is generated by the main helix. The addition of the parasitic helix can increase the working bandwidth in the normal mode.

[0068] This application combines the axial mode and the normal mode of the helical antenna for the first time to form a dual-band antenna with a large frequency ratio, reducing the volume of the antenna; improving the impedance matching in the normal mode by introducing a parasitic helix; the frequency ratios of the dual-band antennas formed by using multiple modes of the antenna before are all very small, and this design realizes a frequency ratio exceeding 8.

[0069] Next, three helical antennas are compared.

[0070] As Figure 4 shown, the left side is a standard helical antenna, which can meet the design requirements of both the axial mode and the normal mode. The middle one is a metal patch placed on the substrate based on the left antenna. The right side is designed by adding a parasitic helix inside the left antenna.

[0071] Figure 5 shows |S 11 | (reflection coefficient) of the left antenna, the middle antenna and the right antenna in the 4G and 5G frequency bands. It can be clearly seen from the figure that the left antenna does not achieve effective normal mode matching in the 4G and 5G frequency bands. A layer of metal patch is added to the substrate of the left antenna to construct the middle antenna. Although the middle antenna successfully realizes normal mode matching in these bands, its working bandwidth is very narrow. The right antenna is the final design, which effectively solves the problems raised by the left antenna and the middle antenna. Since it has two resonance frequency points, it provides broadband normal mode matching in the 4G and 5G frequency bands. In the Ku band, the main helix works in the axial mode, generating circular polarization.

[0072] As Figure 6 shown, Figure 6 shows the |S 11 | parameters of the left antenna, the middle antenna and the right antenna in the Ku band.

[0073] As can be seen from the figure, the left antenna operates in the axial mode, achieving a relatively wide bandwidth. However, the addition of the metal patch significantly reduces the |S 11 | performance of the middle antenna. In contrast, the |S 11 | of the right antenna is very similar to that of the left antenna, indicating that the introduction of the parasitic helix does not have an adverse effect on the |S 11 | performance in the Ku band.

[0074] As Figure 7 shown, Figure 7 the gains and AR (axial ratio) of the left and right antennas are shown.

[0075] The realized gains and AR of the two antennas are almost the same, indicating that the introduction of the parasitic helix does not affect the gain in the Ku band. In addition, as can be seen from the figure, the introduction of the parasitic helix improves the AR in the range of 18 - 22 GHz.

[0076] As Figure 8 shown, in order to demonstrate the performance of the proposed antenna, a physical antenna was fabricated and tested.

[0077] As Figure 9 shown, the upper left part shows the comparison between the measured |S 11 | and gain in the 4G and 5G frequency bands and the simulation results.

[0078] Among them, the simulated bandwidth (|S 11 | < -10 dB) is 16.6%, ranging from 2.38 - 2.81 GHz, while the measured bandwidth is 14.8%, ranging from 2.38 - n2.76 GHz. This bandwidth includes the 4G frequency bands (7, 38, and 41) and the 5G frequency bands (n7, n38, and n41). At the 4G and 5G frequency bands, the simulated and measured peak realized gains are 1.98 dBi at 2.46 GHz and 1.89 dBi at 2.60 GHz, respectively. The simulation results are basically consistent with the measured results.

[0079] The upper right part shows the simulated and measured |S 11 || and gain of the antenna in the Ku band.

[0080] Among them, the simulated bandwidth (|S 11 | < -10 dB) is 64.1%, ranging from 11.32 - 22 GHz, while the measured bandwidth is 64.7%, ranging from 11.24 - 22 GHz. The frequency ranges of the two are very close. The peak realized gain of the simulated antenna is 13.01 dBic at 18.5 GHz, and the peak realized gain of the measured antenna is 12.94 dBic at 18.4 GHz. These two values are very similar to each other.

[0081] The lower figure part presents the simulation and measured axial ratio (AR) bandwidth results in the Ku band.

[0082] Among them, the simulated axial ratio bandwidth (AR < 3) is 61.0% (range: 11.5 - 21.6 GHz), and the measured bandwidth is 54.8% (range: 12.3 - 21.6 GHz). These results indicate that the simulated bandwidth is slightly wider than the actual bandwidth. Nevertheless, the circular polarization (CP) of this antenna almost covers the entire Ku band.

[0083] As Figure 10 shown, it includes 4 small figures. On the left side of each small figure are the measured and simulated radiation patterns, and on the right side of each small figure is the comparison between the measured and simulated results.

[0084] For the four small figures, the upper left corresponds to 2.5 GHz, the upper right corresponds to 14 GHz, the lower left corresponds to 17 GHz, and the lower right corresponds to 20 GHz.

[0085] Among them, the solid line represents the simulation result, and the dashed line represents the measured result.

[0086] The measured results are very close to the simulation results. The axial cross-polarization of both the measured data and the simulation data is less than -30 dB. (Co-Pol is the main polarization, X-Pol is the cross-polarization, LHCP is the left-handed circular polarization, and RHCP is the right-handed circular polarization).

[0087] Please refer to Figure 11 shown, the present application also provides a dual-mode helical antenna with a parasitic helix. Based on the above-mentioned dual-mode helical antenna with a parasitic helix, it includes:

[0088] The parasitic helix structure is replaced with a hollow copper tube monopole structure. The outer diameter of the hollow copper tube monopole structure is the same as the diameter of the parasitic helix structure, and the height is equal to the axial length of the parasitic helix structure.

Claims

1. A dual-mode helical antenna with a parasitic helix, characterized in that: Including: a main helical structure, a parasitic helical structure, a dielectric substrate, a single-port feeding structure, and a parasitic helix fixing structure; The parasitic helical structure is located at the inner center position of the main helical structure; The main helical structure is welded to the upper surface of the dielectric substrate; The single-port feeding structure is welded and fixed through an SMA connector at the bottom of the dielectric substrate and is directly electrically connected to the bottom of the main helical structure; The parasitic helical structure is isolated from the main helical structure by insulating foam paper; The main helical structure: in the axial mode, the main helical radius R1 satisfies 0.25 < 2R1 / λ0 < 0.46, the helix circumference C1 = 2πR1, satisfies 3 / 4 < C1 / λ0 < 4 / 3, and the helix pitch H1 ≈ λ0 / 4; in the normal mode, the main helical radius R1 satisfies 2R1 / λ0 < 0.18; The parasitic helical structure: provides a resonance point in the 4G / 5G frequency band.

2. A dual-mode helical antenna with a parasitic helix according to claim 1, characterized in that: The diameter ratio of the main helical structure to the parasitic helical structure is 2.03:1, and the turn difference is less than 0.05 turns, forming a nested double-helix structure.

3. A dual-mode helical antenna with a parasitic helix according to claim 1, characterized in that: The number of turns N of the parasitic helix ranges from 5.4 ≤ N ≤ 6.0, and the resonant frequency in the low-frequency band is controllable within the range of 2.4 - 2.46 GHz by adjusting the N value.

4. A dual-mode helical antenna with a parasitic helix according to claim 1, characterized in that: A full-metal ground plane is provided at the bottom of the dielectric substrate, and the size is the same as that of the dielectric substrate.

5. A dual-mode helical antenna with a parasitic helix according to claim 1, characterized in that: The inner conductor of the coaxial cable of the single-port feeding structure passes through the through hole on the dielectric substrate and is connected to the main helical structure, and the outer conductor is welded to the ground plane to form a coplanar feeding structure.

6. A dual-mode helical antenna with a parasitic helix, characterized in that: Based on the dual-mode helical antenna with a parasitic helix according to any one of claims 1 to 5, including: The parasitic helical structure is replaced with a hollow copper tube monopole structure, and the outer diameter of the hollow copper tube monopole structure is the same as the diameter of the parasitic helical structure, and the height is equal to the axial length of the parasitic helix structure.

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