A dual-polarized four-arm helix antenna and its manufacturing method

Abstract

The present application relates to a dual-polarized quadrifilar helix antenna and a preparation method thereof, including a radiation unit, a double-layer dielectric plate and an SMA connector; the radiation unit includes four helical arm units, and each helical arm unit is composed of two half-turn helical antennas with opposite helix directions; the double-layer dielectric plate includes an upper dielectric plate and a lower dielectric plate, and the surfaces of the upper dielectric plate and the lower dielectric plate include a feeding network; the helical antenna and the SMA connector are integrated on the feeding network; a ground plane is arranged between the upper dielectric plate and the lower dielectric plate; the ground plane includes a DGS structure; the cross-section of the helical antenna is lower than 0.25 wavelengths.

Description

Technical Field

[0001] This application relates to the technical field of antennas, and particularly relates to a dual-polarized four-arm helix antenna and a preparation method thereof. Background Art

[0002] The helix antenna was first proposed by Kraus in the 1940s, and the circular polarization radiation characteristics of the helix antenna were verified using the linear polarization characteristics of the dipole. Subsequently, Gerst and Worden proposed the structure of the multi-arm helix. In 1968, Kilgus developed a resonant four-arm helix antenna (Quadrifilar Helix Antenna, QHA), and analyzed the radiation characteristics of the four-arm helix antenna using the loop dipole model, obtaining the heart-shaped radiation pattern and good circular polarization characteristics of the four-arm helix antenna.

[0003] The radiator of the four-arm helix antenna is four rotating helix arms, which are centrosymmetric in structure. The actual length of the helix arm is an integer multiple of one-quarter of the operating wavelength, i.e., M*λ / 4 (M is an integer). When M is odd, the tops of the four arms are open-circuited; when M is even, the tops of the four arms are short-circuited. For the feeding of the helix arms, equal-amplitude feeding is required, and there is a sequential 90° phase difference. If the sequential manner of the phase difference is changed, the polarization of the radiated electromagnetic wave will switch between left-handed circular polarization and right-handed circular polarization. The four-arm helix antenna can be without a reference ground in structure, or can adopt a lightweight printed structure; it has excellent circular polarization performance, good wide-angle axial ratio, wide beamwidth, and low elevation angle gain. In the past few decades, the four-arm helix antenna has been widely used in the field of satellite communication technology due to its good circular polarization performance and relatively regular radiation pattern.

[0004] In the past few decades, the mobile wireless communication industry has experienced rapid development from traditional basic services with voice as the information carrier to today's diverse mobile broadband data services. Its top-down integrated network has become one of the basic information networks for human social connectivity. With the development of relevant software and hardware technologies and the continuous growth of various demands, the wide applicability and access convenience unique to mobile wireless communication enable it to gradually expand from person-to-person communication to the "everything" connection between people and things, things and things, and the era of everything connection is coming. To achieve these goals, polarization diversity technology, large-scale MIMO technology, etc. have been applied to the base station field to solve problems such as limited spectrum resources and high energy consumption in wireless communication systems. However, in the current 5G era, there are still many problems. For example, the system frequency bands are mixed, and the requirement for multi-band compatibility is high, especially for the Internet of Things and other applications that use lower frequency bands. These all urgently require the realization of more miniaturized and higher-performance base station antennas.

[0005] To combat multipath fading, base station antennas usually adopt dual-polarized antennas. In terms of form, base station antennas mainly use magnetoelectric dipole antennas, symmetrical dipoles, and microstrip patch antennas. Among them, microstrip patch antennas are widely used in the communication field due to their planar structure, stability, easy processing through printed circuit boards, low cost, low profile, and easy integration with active circuits. However, there are still some problems to be solved in current base station antennas. For example, the low-profile problem of base station antennas. A relatively novel approach in base station antennas is to use a new type of artificial magnetic conductor reflector to achieve a low profile. However, in practical applications, many factors need to be considered for this new material, such as cost, structural complexity, etc. Therefore, using this material to achieve a low-profile antenna is still relatively limited in practical applications. Currently, reducing the antenna profile still mainly relies on traditional conductor reflectors. If a conductor reflector is used, the distance between the antenna radiation unit and the reflector needs to be 0.25 wavelengths so that the electromagnetic wave reflected by the reflector and the electromagnetic wave directly radiated by the radiation unit can achieve in-phase superposition in the far field and realize directional radiation. But using a metal reflector means that the antenna profile is 0.25 wavelengths, which is an obstacle to the low profile of the antenna.

[0006] Currently, there is little work on realizing the function of a helical antenna radiating linearly polarized waves. In the last century, a helical antenna that can achieve linear polarization was reported. However, this antenna has a relatively high profile, a large ground plane, and can only achieve single linear polarization. In the research of reconfigurable antennas, a helical antenna that can achieve the mutual conversion between circular polarization and linear polarization has been reported. However, this antenna can also only achieve single linear polarization and has a relatively high profile. But there is still no four-arm helical antenna that can radiate dual linear polarization, nor a dual-linear polarization four-arm helical antenna applied in the base station frequency band. Summary of the Invention

[0007] The purpose of the present invention is to realize the dual-linear polarization radiation of a helical antenna. The present application provides a dual-linear polarization four-arm helical antenna and its manufacturing method, adopting the following technical solutions:

[0008] A dual-linear polarization four-arm helical antenna includes a radiation unit, a double-layer dielectric board, and an SMA connector; the radiation unit includes two pairs of helical arms, and each helical arm is composed of two half-turn helices with opposite winding directions;

[0009] The double-layer dielectric board includes an upper dielectric board and a lower dielectric board, and the surfaces of the upper dielectric board and the lower dielectric board include a feeding network; the helical antenna and the SMA connector are integrated on the feeding network;

[0010] A ground plane is arranged between the upper dielectric board and the lower dielectric board; the ground plane includes a DGS structure;

[0011] The profile of the helical antenna is lower than 0.25 wavelengths.

[0012] In a preferred embodiment, the spiral arms are composed of two half-turn spirals wound in opposite directions; the cross-section of the spiral antenna is set to 0.15 wavelengths.

[0013] In a preferred embodiment, the ports of a pair of the spiral arms are set for differential feeding, so that a pair of the spiral arms radiate two circularly polarized waves with opposite rotation directions, and the circularly polarized waves are superposed in the far field to form a linearly polarized wave;

[0014] Two pairs of the spiral arms radiate ±45° dual linearly polarized waves.

[0015] In a preferred embodiment, when one pair of spiral antennas in two pairs of the spiral arms is excited, the other pair of spiral antennas parasitize, and this parasitizing method can greatly improve the cross polarization and isolation degree, and can generate lower cross polarization and higher gain.

[0016] In a preferred embodiment, both the upper dielectric plate and the lower dielectric plate are printed with a feeding network. The feeding network is of a circular structure, can perform amplitude-phase regulation, and can realize rich polarization forms of the antenna. The circular diameter of the feeding network is smaller than the spiral diameter of the spiral antenna, and the feeding network can realize the miniaturization of the antenna.

[0017] In a preferred embodiment, the feeding network includes a microstrip, b microstrip, c microstrip, d microstrip, e microstrip, f microstrip, g microstrip, h microstrip, i microstrip, j microstrip. The difference between the sum of the lengths of d microstrip, e microstrip, f microstrip and the sum of the lengths of g microstrip, h microstrip, i microstrip satisfies a phase difference of 180°;

[0018] The a microstrip is connected to the port of the inner spiral antenna of the spiral arm unit, and the j microstrip is provided with a hole and welded to the probe of the SMA connector;

[0019] The b microstrip is used for impedance transformation, and the c microstrip is a quarter impedance transformer.

[0020] In a preferred embodiment, the b microstrip, d microstrip, e microstrip, f microstrip, g microstrip, h microstrip, i microstrip are all 100-ohm microstrips.

[0021] In a preferred embodiment, the ground plane includes a DGS structure with 4 C-shaped patterns etched; the DGS structures are symmetrically arranged, and the DGS structure can effectively reduce the back lobe of the antenna, and can realize the function of greatly suppressing the radiation of the back lobe of the linearly polarized spiral antenna under a small ground plane structure without affecting other radiation directions.

[0022] A preparation method of a dual linearly polarized four-arm spiral antenna includes the following steps:

[0023] Step 1: Use an antenna to form a spiral antenna by winding around two semi-circular spirals with opposite winding directions, and wind two such spiral antennas clockwise to form a pair of spiral arms. Two pairs of such spiral arms form a radiation element. The circumference of one antenna is determined according to the formula l = c / f (where l represents the circumference of one turn of the spiral, c represents the speed of light, and f represents the operating frequency).

[0024] Step 2: The two ports of a pair of spiral arm units are fed differentially. Design a feeding network based on the input impedance of the spiral antenna port and in combination with the size parameters of the double-layer dielectric plate. Determine the thickness and length of the microstrip of the feeding network according to the center frequency of the spiral antenna.

[0025] Step 3: Set a ground plane in the middle of the double-layer dielectric plate and press the double-layer dielectric plate. Etch a C-shaped DGS structure on the ground plane. Determine the size of the C-shaped DGS on the ground plane according to the operating frequency band of the spiral antenna.

[0026] Step 4: Integrate the spiral antenna, feeding network and SMA connector by welding to obtain a dual-linear polarization four-arm spiral antenna.

[0027] Step 5: Use a vector network analyzer and an anechoic chamber to test the above antenna.

[0028] In a preferred embodiment, the spiral antenna is made of metal with a diameter of 1 mm, and the spiral arms of the spiral antenna are prepared by 3D printing technology.

[0029] The double-layer dielectric plate is a double-layer Rogers 4003 plate.

[0030] In summary, the present application includes the following beneficial effects:

[0031] 1. In terms of the antenna structure, the antenna in the present invention for the first time uses two pairs of anti-wound spiral antennas to achieve the function of dual-linear polarization. Compared with the traditional spiral antenna that radiates circularly polarized waves, it realizes low-profile and radiation of dual-linear polarization waves. Compared with the traditional base station antenna using a reflector, it realizes a profile lower than 0.25 wavelengths. The present invention can achieve ±45° dual-linear polarization radiation of the antenna.

[0032] 2. The dual-linear polarization four-arm spiral antenna uses DGS (defected ground structure), which can effectively reduce the ground plane area and improve the front-to-back ratio. The spiral antenna of the radiation main body uses a metal material with a diameter of 1 mm, and the double-layer dielectric plate uses low-cost Rogers4003, which has the advantages of low cost, low profile, miniaturization, light weight, low back lobe, low cross polarization and high isolation.

[0033] 3. It has certain application value in the base station aspect, and can be further designed in the later work to achieve lower cross polarization and wider bandwidth.

[0034] 4. The present invention proposes a dual-polarized antenna based on a four-arm helix with forward and reverse winding. The antenna profile is only 0.15 wavelengths, and the diameter is only 0.33 wavelengths. Each helical arm is spliced by helical lines with half a turn of forward and reverse winding respectively. Two opposite helical arms are differentially fed to radiate two circularly polarized waves with opposite rotation directions, which are then combined into a linearly polarized wave. Two pairs of such helical antennas radiate linearly polarized waves perpendicular to each other. When one pair is excited, the other pair is parasitic, having the advantages of high isolation and low cross-polarization. The feeding network uses a double-layer dielectric plate and realizes miniaturization. Its main size is smaller than the diameter of the helical arm. The defected ground structure also effectively reduces the antenna back lobe under the small ground plane. The present invention can be widely applied to the field of base station antennas, with the advantages of low cost, miniaturization, high isolation, and low cross-polarization. Description of the Drawings

[0035] Figure 1 is a three-dimensional schematic diagram of the dual-polarized four-arm helix antenna of the present invention;

[0036] Figure 2 is a schematic diagram of a single helical antenna of the helical arm unit in the present invention;

[0037] Figure 3 is a schematic diagram of the structure of the feeding network on the upper dielectric plate of the present invention (where a is a top view and b is a three-dimensional view);

[0038] Figure 4 is a schematic diagram of the structure of the feeding network of the lower dielectric plate of the present invention (where a is a top view and b is a three-dimensional view);

[0039] Figure 5 is a top view of the double-layer dielectric plate of the present invention (where a is the upper dielectric plate and b is the lower dielectric plate);

[0040] Figure 6 is a schematic diagram of the ground plane with the etched DGS structure in the present invention;

[0041] Figures 7 - 11 is the performance diagram of the antenna in the present invention;

[0042] Figure 12 is the processing technology flow chart of the present invention. Detailed Description of the Invention

[0043] The following will further elaborate on the present application Figure 1 with reference to the accompanying drawings.

[0044] The object of the present invention is to achieve dual - linear - polarization radiation of a helical antenna, and a dual - linear - polarization four - arm helical antenna is proposed, which is a low - profile antenna with dual - linear - polarization based on a counter - wound four - arm helix. The profile of this antenna is only 0.15λ; two circular - polarization waves with opposite rotation directions are radiated by a pair of helical arms. One helical arm consists of two half - turns of helix with opposite rotation directions. The two ports of a pair of helical antennas are fed differentially, thereby realizing the radiation of linear - polarization waves; two pairs of such helical antennas constitute the main body of radiation. When one pair is excited, the other pair is used as parasitic, thereby obtaining the performance of low cross - polarization; at the same time, a double - layer dielectric plate is adopted to design the feeding network, and the sizes of the main bodies of the two - layer feeding networks are both smaller than the diameter of the helical arms, thereby realizing the miniaturization of the feeding network; and a ground plane with a DGS structure is arranged inside the double - layer dielectric plate. The DGS structure effectively realizes the low - sidelobe performance under the small ground plane and has applicability in the base - station field.

[0045] To achieve the above object, the present invention adopts the following technical solutions.

[0046] 1) In terms of preparation: The radiating main body helical arms of the helical antenna are prepared by 3D printing technology, and the material is metal with a diameter of 1 mm. The double - layer dielectric plate for printing the feeding network is printed with two Rogers 4003 plates, which are divided into an upper - layer dielectric plate and a lower - layer dielectric plate. First, the respective feeding networks are printed on the upper - layer dielectric plate and the lower - layer dielectric plate respectively, and a C - shaped DGS structure is etched on the ground plane. Then, the upper - layer dielectric plate and the lower - layer dielectric plate are laminated, and this ground plane is laminated between the upper - layer dielectric plate and the lower - layer dielectric plate; the feeding connection is welded by an SMA connector. Finally, four helical antennas and two SMA connectors are welded to the feeding network to obtain the final dual - linear - polarization four - arm helical antenna.

[0047] 2) In terms of design: The design method of the present invention includes the following steps:

[0048] Step 1: Use one helix consisting of two half - turns of helix with opposite rotation directions to form one helical - arm unit, and two pairs of such helical arms form a radiation unit. Among them, according to the formula l = c / f (where l represents the circumference of one turn of the helix, c represents the speed of light, and f represents the operating frequency), the value of the circumference of one turn of the helix is determined.

[0049] Step 2: Design the feeding network according to the input impedance of the helical - antenna port and in combination with the parameters of the Rogers 4003 plate. The two ports of a pair of helical antennas are fed differentially. According to the center frequency point, the thickness and length of the microstrip are determined, and these parameters are further optimized.

[0050] Step 3: Determine the size of the C - shaped DGS on the ground plane according to the operating frequency band of the antenna, and further optimize the size parameters of the slot.

[0051] Step 4: Integrate the helical antenna, feed network, and SMA connector to obtain a dual-linear-polarized four-arm helical antenna.

[0052] Step 5: Test the above antenna using a vector network analyzer and an anechoic chamber. Among them, use HFSS simulation software to design and simulate the waveguide.

[0053] Among them, two Rogers 4003 plates are drilled, copper-clad, and etched. According to the thickness of the helical antenna, rivet-shaped holes are drilled on both the upper dielectric plate and the lower dielectric plate; holes slightly larger in diameter are opened near the holes where the rivet-shaped holes pass through the floor to prevent contact with the floor.

[0054] The detailed design flowchart is shown in Figure 12 。

[0055] Specifically, the present invention provides a novel dual-linear-polarized four-arm helical antenna with a center frequency of 2.2 GHz. The radiation unit consists of two sections of helical arm units wound in opposite directions. The helical arms are prepared by 3D printing technology. The feed network is prepared using two layers of Rogers 4003 plates. Finally, the helical arms, feed network, and SMA connector are welded to form the final antenna. The specific design steps are as follows:

[0056] Please refer to Figure 1 , Figure 1 for the overall three-dimensional structure of the dual-linear-polarized four-arm helical antenna. The four helical antennas are divided into Antenna 1, Antenna 2, Antenna 3, and Antenna 4. The four helical antennas serve as the radiation units of the antenna. Among them, Antenna 1 and Antenna 3 are a pair, which can emit linearly polarized waves with a radiation of +45°; Antenna 2 and Antenna 4 are another pair, which can emit linearly polarized waves with a radiation of -45°. The feed networks printed on the upper dielectric plate and the lower dielectric plate (i.e., the dielectric 7 of the double-layer Rogers 4003) are the upper feed network 5 and the lower feed network 6; the floor 8 is located in the middle of the dielectric 7 of the double-layer Rogers 4003; a C-shaped groove 9 is etched on the floor 8; a first SMA connector 11 and a second SMA connector 12 are arranged between the upper dielectric plate and the lower dielectric plate. The probes of the SMA connectors are welded to the upper feed network 5 and the lower feed network 6 respectively, and the outer conductors of the SMA connectors are welded to the floor 8.

[0057] Please refer to Figure 2 , Figure 2 for a single helical antenna in the radiation unit of the dual-linear-polarized four-arm helical antenna. The material of the helical antenna is metal, and the diameter of the metal is 1 mm (the diameter is marked as 14 in the figure). This diameter needs to comprehensively consider the antenna input impedance and gain. The single helical antenna consists of two half-turn helices. Due to the opposite-wound structure, among them, as Figure 2, at a working frequency of 2.2G, the perimeter of one turn of the helix is set to 136mm (marked 13 in the figure as the perimeter of one turn of the helix); the pitch is set to 29.92mm (marked 15 in the figure as the pitch), and the pitch affects the gain and axial ratio of the linear polarized wave of the antenna; the height of the connection port of the helical antenna for support is set to 6.27mm (marked 16 in the figure as the height of the connection port). The setting of the height of this connection port also affects the radiation performance of the antenna.

[0058] Please refer to Figure 3 , Figure 3 is the structure of the feeding network on the upper dielectric board, as Figure 3 , the feeding network of the upper dielectric board includes microstrip a, microstrip b, microstrip c, microstrip d, microstrip e, microstrip f, microstrip g, microstrip h, microstrip i, and microstrip j.

[0059] Microstrip a of the feeding network connected to the helical antenna has little effect on the input impedance. Mainly considering the size, and microstrip a of the feeding networks on the upper and lower dielectric boards is the same; microstrip b is used for impedance transformation to transform the imaginary part of the input impedance to zero; microstrip c is a quarter impedance transformer, and its size depends on the input impedance of microstrip b and the characteristic impedance of microstrip d. For the overall design simplification of the feeding network, microstrip b, microstrip d, microstrip e, microstrip f, microstrip g, microstrip h, and microstrip i all use 100-ohm microstrips; the difference between the sum of the lengths of microstrip d, e, and f and the sum of the lengths of microstrip g, h, and i needs to satisfy a phase difference of 180° to achieve differential feeding; microstrip j has small holes drilled and is welded to the probe of the energy input port SMA, and the impedance of microstrip j is matched with SMA; a rivet-shaped via hole is drilled at the connection of microstrip a and the helical antenna, and the via hole is copper-plated on the inner wall of the dielectric, and the distance between the corresponding two via holes on the feeding network is set at 42.23mm.

[0060] After appropriately optimizing the above parameters, the sizes of each microstrip of the feeding network on the upper dielectric board are as Figure 3, the diameter of the small hole opened on the microstrip j is 0.64 mm, and the length and width of the microstrip j are set to 12 mm and 1.78 mm. The inner and outer diameters of the via hole opened on the microstrip a are 1 mm and 1.13 mm, and the height of the via hole is set to 1.03 mm. The width of the microstrip a is set to 0.61 mm, and the length of the microstrip a is set to 5.59 mm. This length starts from the midpoint of the via hole. The microstrip a bends a certain length at the end and is connected to the microstrip b, and this length is set to 2 mm. The arc length of the microstrip b is set to 4.75 mm. The length and width of the microstrip c are set to 19.98 mm and 3 mm. The length of the microstrip d is set to 12.22 mm. The length of the microstrip e is set to 5 mm. The length of the microstrip f is set to 37.55 mm. The lengths of the microstrip g, microstrip h, and microstrip i are set to 3 mm, 5 mm, and 3.62 mm respectively. Among them, the widths of the microstrip b, d, e, f, g, h, and i are all set to 0.42 mm.

[0061] corresponds to Figure 3 After appropriately optimizing the above parameters, the values corresponding to the labels 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 on the figure are 0.64, 1, 1.13, 5.59, 0.61, 2, 4.75, 0.42, 19.98, 3, 12.22, 5, 37.55, 3, 5, 3.62, 1.78, 12, 1.03 mm respectively.

[0062] Please refer to Figure 4 , Figure 4 is the structure of the feeding network of the lower dielectric substrate. The overall structure is similar to that of the feeding network of the upper dielectric substrate. The difference is that the feeding network of the lower dielectric substrate is transitioned to the feeding network of the upper dielectric substrate through copper posts. The design principle and optimization process are the same as those of the feeding network of the upper dielectric substrate. Finally, the dimensions of each microstrip of the feeding network of the lower dielectric substrate are as Figure 4, the length and width of the copper pillar are set to 1.696 mm and 0.37 mm respectively, the diameter of the small hole opened on j is 0.64 mm, and the length and width of the microstrip j are set to 15 mm and 1.41 mm respectively. The inner and outer diameters of the via hole opened on the microstrip a are 1 mm and 1.13 mm respectively, and the height of the via hole is set to 1.03 mm. The width of the microstrip a is set to 0.61 mm, and the length of the microstrip a is set to 5.59 mm. This length starts from the midpoint of the via hole. The microstrip a bends a certain length at the end and is connected to the microstrip b, and this length is set to 2 mm. The arc length of the microstrip b is set to 6.68 mm. The length and width of the microstrip c are set to 19.77 mm and 4.14 mm respectively. The length of the microstrip d is set to 9.62 mm. The length of the microstrip e is set to 5 mm. The length of the microstrip f is set to 31.42 mm. The lengths of the microstrip g, microstrip h, and microstrip i are set to 3 mm, 5 mm, and 3.15 mm respectively. Among them, the widths of the microstrip b, d, e, f, g, h, and i are all set to 0.42 mm.

[0063] corresponding to Figure 4 , the values corresponding to the labels 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 on the figure after appropriately optimizing the above parameters are 6.68, 4.14, 19.77, 9.62, 5, 31.42, 3, 5, 3.15, 10, 1.41, 5, 42.23, 0.37, 1.696 mm respectively.

[0064] Please refer to Figure 5 , Figure 5 is the top view of the upper dielectric plate and the lower dielectric plate. The diameters of the upper dielectric plate and the lower dielectric plate are set at 51 mm. In the upper dielectric plate, four plug-in holes are drilled at the insertion positions corresponding to the four spiral antennas. The diameter of the plug-in hole is the same as the diameter of the spiral antenna, and the diameter of the plug-in hole is set to 1 mm. Among them, the diameters of the holes corresponding to the probes and the holes of the transition copper pillars depend on the sizes of the probes and the transition copper pillars of the SMA connectors, and the first probe hole and the transition copper pillar hole are set respectively. The diameters of the first probe hole and the transition copper pillar hole are set at 0.64 mm and 0.37 mm respectively. Except that the hole corresponding to the probe of the SMA connector on the lower dielectric plate is replaced by a slot in the shape of the SMA outer conductor, the other opening conditions are the same as those of the upper dielectric. The length and width of this slot are set to 15.8 mm and 5.7 mm.

[0065] corresponding to Figure 5 , the values corresponding to the labels 52, 53, 54, 55, 56, 57, 58 on the figure are 1, 0.64, 0.37, 51, 12.2, 15.8, 5.7 mm respectively.

[0066] Please refer to Figure 6 ,Figure 6 It is the floor of the etched C-shaped DGS structure, and the size of the C shape is determined by the operating frequency band of the antenna; the holes opened at the insertion points of the four spiral arms, the holes opened at the insertion points of the SMA probes, and the holes opened at the transition copper posts are slightly thicker than themselves to avoid contact with the floor; the size of the C shape is set such that the inner radian is 79° (corresponding to label 60 in the figure), the outer radian is 81° (corresponding to label 59 in the figure), the slot width is 1 mm (corresponding to label 62 in the figure), and the interval radian at the first and last segments is 10° (corresponding to label 61 in the figure).

[0067] For the performance diagram of the antenna, please refer to Figures 7 - 11 。

[0068] Figure 7 It is the performance diagram of the proposed invented antenna within the operating frequency band. Figure 7 They are the S parameters of the antenna. The impedance bandwidth below -10 dB is 2.13 - 2.37 GHz (10.9%), and the isolation within the frequency band is lower than -25 dB.

[0069] Figure 8 is the gain diagram of two antennas (where, (a) +45° linear polarization, (b) -45° linear polarization). The maximum gain of the antenna reaches 8.33 dBi, and the average gain of the two antennas is 8 dBi within 2.13 - 2.32; the cross polarization of the two antennas is lower than -17 dB within 2.13 - 2.37 GHz; the bandwidths of the front-to-back ratio of the two antennas greater than 15 dB both reach 190 MHz.

[0070] Figure 9 is the radiation pattern of the +45° linear polarization antenna at 2.15 GHz (Figure a), 2.2 GHz (Figure b), and 2.25 GHz (Figure c) in the E-plane and H-plane. The radiation patterns of the E-plane and H-plane of the antenna have almost no distortion within the frequency band, and the cross polarization performance is excellent, with an average value of -35 dB.

[0071] Figure 10 is the radiation pattern of the -45° linear polarization antenna at 2.15 GHz (Figure a), 2.2 GHz (Figure b), and 2.25 GHz (Figure c) in the E-plane and H-plane. The main polarization radiation patterns of the E-plane and H-plane of the antenna have almost no distortion within the frequency band, and the cross polarization performance is slightly worse than that of the +45° linear polarization, with an average value of -28 dB.

[0072] Figure 11 It is the half-power beam width diagram of the antenna. The E-plane half-power beam widths of the +45° and -45° polarizations of the antenna are almost the same, and the same is true for the H-plane. The average beam width of the E-plane is 63°, and the average beam width of the H-plane is 71°.

[0073] Please refer to Figure 12 , Figure 12The flowchart for the preparation of the proposed antenna is as follows. Four helical antennas are fabricated by 3D printing technology. After the upper and lower dielectric substrates are printed, perforated, copper-clad respectively and then laminated, the helical antennas are finally inserted into the corresponding holes and welded, and the SMA connectors are welded to the corresponding positions to obtain the final dual-linear-polarization four-arm helical antenna.

[0074] The above are all the preferred embodiments of this application, and the protection scope of this application is not limited thereby. Therefore, all equivalent changes made according to the structure, shape, and principle of this application should be covered within the protection scope of this application.

Claims

1. A dual-polarized four-arm helical antenna, characterized in that: It includes a radiation unit, a double-layer dielectric board and an SMA connector; the radiation unit includes two pairs of spiral arms, and the spiral arms are composed of two half-turn spirals with opposite winding directions; The double-layer dielectric board includes an upper dielectric board and a lower dielectric board, and the surfaces of the upper dielectric board and the lower dielectric board include a feeding network; the spiral antenna and the SMA connector are integrated on the feeding network; A ground plane is arranged between the upper dielectric board and the lower dielectric board; the ground plane includes a DGS structure; The cross-section of the spiral antenna is less than 0.25 wavelengths; the spiral arms are composed of two half-turn spirals wound in reverse; the cross-section of the spiral antenna is set to 0.15 wavelengths; The feeding network is a circular structure, and the circular diameter of the feeding network is less than the spiral diameter of the spiral antenna; the feeding network includes a microstrip a, a microstrip b, a microstrip c, a microstrip d, a microstrip e, a microstrip f, a microstrip g, a microstrip h, a microstrip i, a microstrip j, and the difference between the sum of the lengths of the microstrips d, e, f and the sum of the lengths of the microstrips g, h, i satisfies a phase difference of 180°; The microstrip a is connected to the port of the inner spiral antenna of the spiral arm unit, and the microstrip j is provided with a hole for welding with the probe of the SMA connector; the microstrip b is used for impedance transformation, and the microstrip c is a quarter impedance transformer.

2. The dual-polarized four-arm helix antenna according to claim 1, wherein: The ports of a pair of the spiral arms are set for differential feeding so that a pair of the spiral arms radiate two circularly polarized waves with opposite winding directions, and the circularly polarized waves are superimposed in the far field to form a linearly polarized wave; Two pairs of the spiral arm units radiate ±45° dual linearly polarized waves.

3. A dual-polarized quadrifilar helix antenna according to claim 2, characterized in that: When one pair of spiral antennas in two pairs of the spiral arm units is excited, the other pair of spiral antennas is parasitic.

4. A dual-polarized quadrifilar helix antenna according to claim 1, characterized in that: The microstrips b, d, e, f, g, h, i are all 100-ohm microstrips.

5. A dual-polarized quadrifilar helix antenna according to claim 1, characterized in that: The ground plane includes a DGS structure etched with 4 C-shaped patterns; the DGS structures are symmetrically arranged.

6. A preparation method of a dual-polarized quadrifilar helix antenna, characterized in that: It includes the following steps: Step 1, use an antenna to wind two half-turn spirals with opposite winding directions to form a spiral antenna, and wind two such spiral antennas clockwise to form a pair of spiral arms, and two pairs of such spiral arms form a radiation unit; the circumference of an antenna is determined according to the formula l = c / f, where l represents the circumference of one turn of the spiral, c represents the speed of light, and f represents the operating frequency; the spiral arms are composed of two half-turn spirals wound in reverse; the cross-section of the spiral antenna is set to 0.15 wavelengths; Step 2: The two ports of a pair of spiral arms are differentially fed. The feeding network is designed according to the input impedance of the spiral antenna ports and in combination with the size parameters of the double-layer dielectric substrate. The thickness and length of the microstrip of the feeding network are determined according to the center frequency of the spiral antenna. The feeding network is of a ring structure, and the ring diameter of the feeding network is smaller than the spiral diameter of the spiral antenna. The feeding network includes microstrip a, microstrip b, microstrip c, microstrip d, microstrip e, microstrip f, microstrip g, microstrip h, microstrip i, and microstrip j. The difference between the sum of the lengths of microstrip d, microstrip e, and microstrip f and the sum of the lengths of microstrip g, microstrip h, and microstrip i satisfies a phase difference of 180°. Microstrip a is connected to the port of the inner spiral antenna of the spiral arm unit, and microstrip j is provided with a hole for welding with the probe of the SMA connector. Microstrip b is used for impedance transformation, and microstrip c is a quarter impedance transformer. Step 3: A ground plane is arranged in the middle of the double-layer dielectric substrate and the double-layer dielectric substrate is laminated. A C-shaped DGS structure is etched on the ground plane, and the size of the C-shaped DGS on the ground plane is determined according to the operating frequency band of the spiral antenna. Step 4: The spiral antenna, the feeding network, and the SMA connector are welded and integrated to obtain a dual-linear-polarization four-arm spiral antenna. Step 5: The above antenna is tested using a vector network analyzer and a microwave anechoic chamber.

7. The preparation method of a dual-polarized quadrifilar helix antenna according to claim 6, characterized in that: The spiral antenna is made of metal with a thickness of 1 mm in diameter, and the spiral arms of the spiral antenna are prepared by 3D printing technology. The double-layer dielectric substrate is a double-layer Rogers 4003 board.

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