A broadband four-way dual circularly polarized power divider for waveguide array antenna

Abstract

The present invention discloses a broadband four-way dual circular polarization power divider for waveguide array antenna, belonging to the field of antenna technology. The power divider includes a feeding square waveguide, a power division network, and a radiation horn connected in sequence; wherein the power division network includes a cross-matching waveguide, a stepped cross coaxial waveguide, and four rectangular waveguides connected in sequence; the radiation horn is composed of a coaxial square waveguide, four radiation horn units, and four matching stepped frustums. When a linearly polarized wave is fed, the four radiation horn units can radiate four linearly polarized waves of the same phase and power; when a circularly polarized wave is fed, the four radiation horn units can radiate four circularly polarized waves of the same phase and power. The present invention has the advantages of wide bandwidth, low transmission loss, and simple structure; at the same time, the output port is compact, and as a waveguide array antenna unit, it can effectively suppress grating lobes; it adopts an all-metal waveguide structure, so it also has the advantages of low loss, high efficiency, and high power capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of antennas, and in particular relates to a broadband four-way dual circular polarization power divider for a waveguide array antenna. Background Art

[0002] Antennas are windows for transmitting and receiving electromagnetic waves in wireless communication systems. They are used to realize the mutual conversion between free space beams and modes in waveguide structures. The quality of their performance has an important impact on the communication effect of the entire system. Compared with linearly polarized antennas, circularly polarized antennas have the advantages of resisting cloud and rain attenuation, suppressing multipath interference, and eliminating polarization distortion caused by the Faraday rotation effect of the ionosphere. Therefore, they are widely used in communication, radar, electronic countermeasures and other fields. Compared with single circularly polarized antennas, dual circularly polarized antennas can greatly improve communication capacity and realize the function of simultaneous transmission and reception.

[0003] The all-metal waveguide array antenna has low loss, high efficiency and large power capacity, and is widely used in the field of satellite communications. In waveguide array antennas, the power divider in the beamforming network is crucial. The first-stage beamforming network directly connected to the radiating element has an important impact on the performance of the array antenna. The use of two-way, three-way, or even four-way couplers and power dividers can realize a dual-polarization beamforming network, but the spacing between array elements is greater than the wavelength λ0 in free space, which will lead to the appearance of beam grating lobes. The beamforming network composed of dual-polarization directional couplers can realize array elements with sub-wavelength spacing, but because multiple slots are required to achieve high coupling levels, it will lead to larger cross-sectional dimensions and increased mechanical complexity.

[0004] In the existing technology, Chinese patent application number CN201610792694.6 discloses a dual circularly polarized flat waveguide array antenna, in which a four-way power divider is composed of a square waveguide resonant cavity, a ridge waveguide resonant cavity and a square waveguide radiation port. This power divider has a simple structure and a compact distance between the output ports, but the bandwidth is less than 20%. Chinese patent application number CN201822273206.8 discloses an ultra-wideband dual circularly polarized array antenna, in which a four-way power divider is composed of a transmembrane cavity, a porous coupling plate and an open waveguide. A corrugated phase shift structure is used on the transmembrane cavity to widen the working bandwidth, and the power divider has the advantage of a small size, but the circular polarization axis of the antenna is relatively poor and the radiation efficiency is low. The document “JL Cano, A. Mediavilla, S. Dragas, and A. Tazon, “Novel broadband circular waveguide four-way power divider for dual polarization applications,” IEEE Microw. Wireless Compon. Lett., vol. 26, no. 2, pp. 98-100, Feb. 2016.” uses four dual-probe orthogonal mode couplers to interconnect to achieve four-way power distribution, which has the advantage of low profile, but the four output ports are not in phase, and the output port spacing is greater than 1.2λ0 at the lowest operating frequency and the port spacing is too large. The four-way power divider in the document “Nelson JG Fonsca, “Broadband Waveguide Dual-Polarization Four-Way Power Divider for Small Passive Arrays,” IEEE Microw. Wireless Compon. Lett., vol. 31, no. 8, pp. 985-988, Aug. 2021.” consists of a turnstile, an offset twisted waveguide, an ET connector and an orthogonal mode coupler. The distance between the output ports of the power divider is very compact (only 0.7λ0), and the relative bandwidth of the power divider reaches 20%, but the structure is complex. Summary of the invention

[0005] The purpose of the present invention is to provide a broadband four-way dual circular polarization power divider using a novel topological structure, which solves the problems of the existing four-way circular polarization power divider having a narrow bandwidth, a complex structure, an incompletely co-phased output beam, and being unfavorable for realizing an array antenna system.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A broadband four-way dual circular polarization power divider for a waveguide array antenna, characterized by comprising a feeding square waveguide, a power division network, and a radiation horn connected in sequence.

[0008] The input port of the feeding square waveguide feeds a linear polarized wave or a circular polarized wave; when a linear polarized wave is fed, it is TE 10 Die or TE 01 mode; when a circularly polarized wave is fed, it is a pair of equal-amplitude orthogonal TE 10 Die and TE 01 mold.

[0009] The power division network comprises a cross matching waveguide, a stepped cross coaxial waveguide and four rectangular waveguides which are connected in sequence.

[0010] The cross-matching waveguide has a coaxial inner conductor at its rear section, which is used to realize the TE in the feeding square waveguide. 10 Die or TE 01 Mode conversion to TEM mode in a stepped cross-coaxial waveguide.

[0011] The stepped cross coaxial waveguide is composed of at least two cross coaxial waveguides, the inner conductor of the cross coaxial waveguide is an axial extension of the inner conductor of the cross matching waveguide; the arm lengths of the cross coaxial waveguides are the same, and the arm widths gradually decrease. The stepped cross coaxial waveguide realizes the transformation of the fundamental mode TEM mode of the cross coaxial waveguide to the second highest order TE mode of the cross coaxial waveguide through the change in the width direction. 10 Mode conversion. By increasing the number of steps, the working bandwidth of the stepped cross coaxial waveguide can be extended.

[0012] The four rectangular waveguides have the same size and are arranged in a cross shape; the central axis between the four rectangular waveguides coincides with the central axis of the step cross coaxial waveguide, the outer side surface of each rectangular waveguide farther from the central axis is located in the same plane as the outer side surface of the cross coaxial waveguide, and the narrow side size of the rectangular waveguide is smaller than the arm width of the step cross coaxial waveguide.

[0013] The radiation horn coincides with the central axis of the stepped cross coaxial waveguide, and is composed of a coaxial square waveguide, four radiation horn units, and four matching stepped frustums. The outer side surfaces of the coaxial square waveguide are parallel to the outer side surfaces of the four rectangular waveguides, and the inner conductor of the coaxial square waveguide is a square inner conductor; the four radiation horn units are sub-wavelength square horns with the same structure, which are arranged at the output end of the coaxial square waveguide in a 2×2 array, and the side length of the array formed is the same as the side length of the coaxial square waveguide and does not exceed the maximum arm length of the stepped cross coaxial waveguide; the four matching stepped frustums are respectively arranged in one radiation horn unit to achieve impedance matching between the coaxial square waveguide and the radiation horn unit, and finally the four radiation horn units can radiate linearly polarized waves or circularly polarized waves with equal amplitude and phase; by increasing the order of the matching stepped frustum, the working bandwidth of the dual circularly polarized power divider can be expanded.

[0014] Furthermore, the side length of the square inner conductor of the coaxial square waveguide is the same as the spacing between adjacent radiation speaker units.

[0015] Furthermore, the inner conductor of the cross coaxial waveguide and the inner conductor of the cross matching waveguide are cylindrical inner conductors or square inner conductors; when a square inner conductor is used, the square inner conductor is chamfered to facilitate process implementation.

[0016] Furthermore, the waveguide is chamfered along the direction of electromagnetic wave propagation to facilitate process implementation.

[0017] Furthermore, the broadband four-way dual circular polarization power divider of the waveguide array antenna of the present invention can be manufactured by CNC milling, 3D printing, injection molding and other methods.

[0018] The working principle of the broadband four-way dual circular polarization power divider of the present invention is as follows:

[0019] When the linearly polarized TE 10 mode, it enters the step cross coaxial waveguide through the cross matching waveguide and is converted into the cross coaxial waveguide TEM mode; as the width of the step cross coaxial waveguide changes, the coaxial TEM mode is further converted into the coaxial TE 10 Mode. Due to the TE 10 Mode field distribution and rectangular waveguide TE 10 The high similarity of the modes can achieve equal amplitude and same phase TE of electromagnetic waves in different polarization directions by setting a rectangular waveguide pair with orthogonal polarization at the back end of the step coaxial cross waveguide. 10 The two rectangular waveguide TEs with equal amplitude and phase are then connected through a coaxial square waveguide. 10 The mode realizes further power division and feeds the power into the radiating speaker unit in an equal-amplitude and same-phase manner, thus realizing four-way equal-amplitude and same-phase power output.

[0020] Since the four-way dual circular polarization power divider structure proposed in the present invention has a high degree of symmetry, when the TE 01 In the same mode, four equal-amplitude and in-phase power outputs can also be achieved in the radiating square waveguide. During the entire beam propagation process, the two polarized output beams can maintain the same amplitude and in-phase output state; therefore, when a linear polarization wave of any polarization direction is fed into the feeding square waveguide, the four radiating speaker units can radiate four linear polarization waves of the same phase and power; when a circular polarization wave is fed into the feeding square waveguide, that is, a TE wave of equal amplitude, orthogonal and 90° phase difference, 10 Die and TE 01 Mode, the four radiating speaker units can radiate four circularly polarized waves with the same phase and power.

[0021] The present invention has the following advantages:

[0022] 1. The four-way dual circular polarization power divider of the present invention can generate four-way dual circular polarization outputs with equal amplitude and phase in a wide band, and has low transmission loss.

[0023] 2. The four-way dual circular polarization power divider of the present invention has a simple structure, has no complicated waveguide structure, is conducive to mechanical processing and assembly, and has high reliability.

[0024] 3. The four output ports of the four-way dual circular polarization power divider of the present invention are closely spaced, less than a free space wavelength; the output ports serve as waveguide array antenna units and can effectively suppress grating lobes.

[0025] 4. The four-way dual circular polarization power divider of the present invention can realize dual circular polarization output. This polarization multiplexing method can increase the communication capacity.

[0026] 5. The four-way dual circular polarization power divider of the present invention is a full metal waveguide structure, and therefore has the advantages of low loss, high efficiency and high power capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the four-way dual circular polarization power divider of the present invention.

[0028] Figure 2 It is a schematic diagram of the cavity structure of the four-way dual circular polarization power divider of the present invention.

[0029] Figure 3 It is a schematic diagram of the disassembled structure of the cavity part of an embodiment of the present invention.

[0030] Figure 4 It is a reflection curve diagram of the input port of the four-way dual circular polarization power divider according to an embodiment of the present invention.

[0031] Figure 5 It is a transmission coefficient amplitude diagram of the output port of the four-way dual circular polarization power divider according to an embodiment of the present invention.

[0032] Figure 6 It is a transmission coefficient phase diagram of the output port of the four-way dual circular polarization power divider according to an embodiment of the present invention.

[0033] Explanation of the accompanying figures: 1 is a feeding square waveguide, 2 is a cross-matching waveguide, 201 is an inner conductor of a cross-matching waveguide, 3 is a stepped cross-coaxial waveguide, 301 is an inner conductor of a stepped cross-coaxial waveguide, 4 is a rectangular waveguide, 5 is a radiation horn, 501 is a coaxial square waveguide, 502 is a matching stepped cone, 503 is a radiation horn unit, and 504 is an inner conductor of a coaxial square waveguide. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below with reference to the accompanying drawings and specific examples.

[0035] like Figure 1 As shown, a fully metal structure broadband four-way dual circular polarization power divider is only composed of three sections of metal components after processing. The first section of metal components from bottom to top is the first stage of the cross matching waveguide and the step coaxial cross waveguide, the second section of metal components is the second stage of the step coaxial cross waveguide and the four rectangular waveguides arranged in a cross, and the third section of metal components is the radiation horn. In order to ensure the assembly accuracy of the embodiment, positioning pins are installed between the three sections of metal components. It can be seen from the actual processing diagram that this embodiment has a simple structure and is easy to process and assemble.

[0036] like Figure 2 , Figure 3 As shown, this embodiment includes a feeding square waveguide, a power division network, and a radiation horn connected in sequence.

[0037] The size of the feeding square waveguide is 9.4 mm × 9.4 mm, and the length is 19.2 mm. The input port feeds a linearly polarized wave or a circularly polarized wave. When a linearly polarized wave is fed, it is TE 10 Die or TE 01 mode; when a circularly polarized wave is fed, it is a pair of equal-amplitude orthogonal TE 10 Die and TE 01 mold.

[0038] The power division network comprises a cross matching waveguide, a stepped cross coaxial waveguide and four rectangular waveguides which are connected in sequence.

[0039] The cross-matching waveguide has an arm length of 13.6 mm, an arm width of 8 mm, and a length of 6.3 mm. A coaxial inner conductor with a length of 3 mm is arranged at the rear section. The coaxial inner conductor is a square inner conductor after chamfering. The cross-matching waveguide is used to realize TE in the feeding square waveguide. 10 Die or TE 01 Mode conversion to TEM mode in a stepped cross-coaxial waveguide.

[0040] The step cross coaxial waveguide is composed of two cross coaxial waveguides. The inner conductor of the cross coaxial waveguide is an axial extension of the inner conductor of the cross matching waveguide. The inner conductor can suppress the generation of high-order modes in the cross matching waveguide and the step cross coaxial waveguide. The arm lengths of the two cross coaxial waveguides are both 24 mm. The arm width of the first-level cross coaxial waveguide is 6.3 mm and the length is 5 mm. The arm width of the second-level cross coaxial waveguide is 5.4 mm and the length is 3.5 mm. The step cross coaxial waveguide realizes the transformation of the fundamental mode TEM mode of the cross coaxial waveguide to the secondary high-order TE mode of the cross coaxial waveguide through the change in the width direction. 10 Mode conversion. By increasing the number of steps, the working bandwidth of the stepped cross coaxial waveguide can be extended.

[0041] The four rectangular waveguides have a width x narrow side of 9.6 mm x 4.8 mm and a length of 3 mm, and are arranged in a cross shape, making the structure more compact; the central axis between the four rectangular waveguides coincides with the central axis of the stepped cross coaxial waveguide, and the outer side of each rectangular waveguide farther from the central axis is in the same plane as the outer side of the cross coaxial waveguide. The guided wave transmitted in the rectangular waveguide is the main mode TE 10 .

[0042] The radiation horn coincides with the central axis of the stepped cross coaxial waveguide, and is composed of a coaxial square waveguide, four radiation horn units, and four matching stepped frustums.

[0043] Among them, the outer side surfaces of the coaxial square waveguide are parallel to the outer side surfaces of the four rectangular waveguides, the side length of the coaxial square waveguide is 22.5mm, and its inner conductor is a square inner conductor with a side length of 2.5mm; the four radiation horn units are sub-wavelength square horns with a side length of 10mm and a length of 15mm, that is, the side length is less than a free space wavelength; the four radiation horn units are arranged in a 2×2 array at the output end of the coaxial square waveguide, and the side length of the formed array is the same as the side length of the coaxial square waveguide; the four matching stepped cones are respectively arranged in one radiation horn unit, and the first-level radius of the matching stepped cone is 2.95mm and the length is 2.2mm, and the second-level radius is 1.7mm and the length is 2.7mm, so as to realize impedance matching between the coaxial square waveguide and the radiation horn unit; finally, the four radiation horn units can radiate linearly polarized waves or circularly polarized waves with equal amplitude and phase; by increasing the order of the matching stepped cone, the working bandwidth of the dual circularly polarized power divider can be expanded.

[0044] To facilitate processing, all waveguide structures are chamfered along the direction of electromagnetic wave propagation.

[0045] In this embodiment, the ports of the four radiating horn units are closely spaced, and the center distance between the ports is 12.5 mm, which is only 0.79λ0 (λ0 is the wavelength corresponding to the center frequency 19.05 GHz), which is less than a free space wavelength, while the distance between the output ports of most current four-way dual circular polarization power dividers is greater than one wavelength. When the radiating square horn of this embodiment is used as an array antenna unit, the grating lobe can be effectively suppressed.

[0046] Figure 4 The reflection coefficient curve of the input port of this embodiment is given. In the frequency range of 16-22.5GHz, the two reflection coefficients of the input port are less than -20dB, indicating that the return loss of the proposed power divider structure is very small, which is conducive to the external radiation of electromagnetic energy.

[0047] Figure 5 The amplitude curve of one of the polarized waves of the input port of this embodiment at the output port is given. In the frequency range of 17GHz-21.1GHz, the relative bandwidth is 21.5%, and the transmission efficiency from the input port to the output port is -6.1dB. Obviously, the amplitude curves of the four output ports completely overlap, indicating that the proposed power divider structure achieves one-to-four equal power distribution.

[0048] Figure 6 The phase curve of one of the polarized waves of the input port of this embodiment at the output port is given. In the frequency range of 17GHz-21.1GHz, the phase curves of the four output ports completely overlap, indicating that the output ports of the proposed power divider structure are in-phase outputs.

[0049] Due to the symmetry of the structure, the two polarized waves at the input port in this embodiment have exactly the same amplitude and phase characteristics at the output port. Therefore, according to the different polarization states of the input port beams, this embodiment can achieve four-way equal-amplitude and in-phase power splitting output of the input circularly polarized wave / linearly polarized wave in a wide frequency band, and the distance between adjacent output ports is less than one wavelength, which proves that the broadband four-way dual circularly polarized power splitter proposed by the present invention is suitable for waveguide array antennas.

[0050] The above description is only a specific implementation mode of the present invention. The present invention can also be applied to broadband four-way dual circular polarization power dividers in other frequency bands. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention should be regarded as equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A broadband four-way dual circular polarization power divider for a waveguide array antenna, characterized in that: It includes a feeding square waveguide, a power division network, and a radiation horn connected in sequence; The input port of the feeding square waveguide feeds a linear polarized wave or a circular polarized wave; when a linear polarized wave is fed, it is TE 10 Die or TE 01 mode; when a circularly polarized wave is fed, it is a pair of equal-amplitude orthogonal TE 10 Die and TE 01 mold; The power division network includes a cross-matching waveguide, a stepped cross-coaxial waveguide, and four rectangular waveguides connected in sequence; The cross-matching waveguide has a coaxial inner conductor at its rear section, which is used to realize the TE in the feeding square waveguide. 10 Die or TE 01 Mode conversion to TEM mode in a stepped cross-coaxial waveguide; The stepped cross coaxial waveguide is composed of at least two cross coaxial waveguides, the inner conductor of the cross coaxial waveguide is an axial extension of the inner conductor of the cross matching waveguide; the arm lengths of the cross coaxial waveguides are the same, and the arm widths gradually decrease; The four rectangular waveguides have the same size and are arranged in a cross shape; the central axis between the four rectangular waveguides coincides with the central axis of the step cross coaxial waveguide, the outer side of each rectangular waveguide farther from the central axis is located in the same plane as the outer side of the cross coaxial waveguide, and the narrow side of the rectangular waveguide is smaller than the arm width of the step cross coaxial waveguide; The radiation horn coincides with the central axis of the stepped cross coaxial waveguide, and is composed of a coaxial square waveguide, four radiation horn units, and four matching stepped frustums; wherein the outer side surfaces of the coaxial square waveguide are respectively parallel to the outer side surfaces of the four rectangular waveguides, and the inner conductor of the coaxial square waveguide is a square inner conductor; the four radiation horn units are sub-wavelength square horns with the same structure, which are arranged in a 2×2 array at the output end of the coaxial square waveguide, and the side length of the formed array is the same as the side length of the coaxial square waveguide and does not exceed the maximum arm length of the stepped cross coaxial waveguide; the four matching stepped frustums are respectively arranged in one radiation horn unit to achieve impedance matching between the coaxial square waveguide and the radiation horn unit, and finally the four radiation horn units can radiate linearly polarized waves or circularly polarized waves with equal amplitude and in phase.

2. A broadband four-way dual circular polarization power divider for a waveguide array antenna as claimed in claim 1, characterized in that: The side length of the square inner conductor of the coaxial square waveguide is the same as the spacing between adjacent radiation speaker units.

3. A broadband four-way dual circular polarization power divider for a waveguide array antenna as claimed in claim 2, characterized in that: The inner conductor of the cross coaxial waveguide and the inner conductor of the cross matching waveguide are cylindrical inner conductors or square inner conductors; when the square inner conductor is used, the square inner conductor is chamfered.

4. A broadband four-way dual circular polarization power divider for a waveguide array antenna as claimed in claim 3, characterized in that: The waveguide is angled along the direction of electromagnetic wave propagation.

5. A broadband four-way dual circular polarization power divider for a waveguide array antenna as claimed in claim 4, characterized in that: The broadband four-way dual circular polarization power divider for the waveguide array antenna is manufactured by CNC milling, 3D printing and injection molding.

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