Broadband radiation unit for dual circularly polarized waveguide array antenna

Abstract

The invention discloses a broadband radiation unit for a dual circularly polarized waveguide array antenna, and belongs to the technical field of antennas. The radiation unit comprises an input square waveguide, a coaxial square waveguide, an in-step four-ridge coaxial waveguide and a radiation grid which are arranged in sequence, the input square waveguide is used for feeding in an orthogonal TE10 mode or TE01 mode; the coaxial square waveguide and the in-step four-ridge coaxial waveguide are used for realizing impedance matching of a broadband and inhibiting transmission of a high-order mode; the radiation grid is used for dividing the power of an input signal into four paths and radiating the input signal into a free space, thereby achieving the radiation of a circularly polarized beam. The radiation unit can work in a broadband, and has the advantages of being high in efficiency, small in transmission loss, simple in structure, high in robustness and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of antennas, and in particular relates to a broadband radiation unit for a dual circularly polarized waveguide array antenna. Background Art

[0002] The rapid development of 5G communication technology and the advent of the information age have placed higher demands on wireless communication systems and satellite navigation technologies. Channel capacity and signal transmission stability are key performance indicators for wireless communication. Compared to linearly polarized antennas, circularly polarized antennas offer significant advantages, such as doubled data capacity, robustness to cloud and rain attenuation, multipath interference, and polarization interference, resulting in greater communication stability in complex environments. Compared to single circularly polarized antennas, dual circularly polarized antennas can simultaneously transmit and receive signals, further improving system efficiency and performance. These characteristics make dual circularly polarized antennas crucial in a variety of high-end applications, including satellite navigation, electronic countermeasures, radio astronomy, and autonomous driving, providing strong support for the future evolution of wireless communication technology.

[0003] At present, there are many ways to realize dual circular polarization antennas, including: microstrip array antennas, waveguide array antennas, SIW (substrate integrated waveguide) array antennas, magnetoelectric dipole antennas, etc. Among them, the waveguide structure is particularly suitable for the design of high-power, high-gain, and high-radiation efficiency antenna arrays due to its low loss and high efficiency. However, the existing waveguide array antennas still face many challenges, such as the difficulty in achieving comprehensive optimization of dual circular polarization, broadband operation, and high efficiency, which limits its promotion and development in certain high-end applications. In the design of dual circular polarization waveguide array antennas, the radiating unit is particularly critical, and its design determines the performance of the entire array. At present, there have been many studies on dual circular polarization radiating units at home and abroad. Chinese patent application number CN202211536085.6 discloses a dual-mode dual circular polarization antenna array, whose radiating unit consists of a three-stage stepped gradient horn and a cylindrical radiating unit. The design structure is relatively simple, with a cross-sectional height of approximately 0.4λ0, and has good engineering feasibility. However, its impedance bandwidth (S 11 <–20dB) is less than 20%, and there is still a problem of bandwidth limitation in broadband application scenarios. Chinese patent application number CN202211056828.X discloses a broadband dual circular polarization four-way power divider. The power divider achieves efficient radiation of dual polarized electromagnetic waves by using a cross waveguide power dividing network, a waveguide OMT and a square waveguide radiation layer. The proposed structural unit spacing is 0.79λ0, which is conducive to achieving large angle scanning, and its impedance bandwidth (S 11<–20dB) reached 22%. However, due to the limited improvement of OMT performance in the radiation layer, it is difficult to further expand the bandwidth. In addition, the cross-section height of the proposed structure is 2.05λ0, which is difficult to meet the actual demand for extremely low-profile structures. The literature "J.Wu, YJCheng, HBWang, YCZhong, D.Ma, and Y.Fan,'Awideband dual circularly polarized full-corporate waveguide arra y antenna fed by triple-resonant cavities,'IEEETrans.Antennas Propag.,vol.65,no.4,pp.2135–2139,Apr.2017." proposed a broadband dual circularly polarized antenna array based on triple-resonant cavities. Its radiation layer consists of a four-way power divider composed of three cavities and a diaphragm circular polarizer. It has a low cross-section (only 0.85λ0) and can achieve an impedance bandwidth of about 17% (S 11 <–20dB) to achieve good circularly polarized radiation. However, when the operating frequency band is extended to the multi-mode region, the excited high-order symmetrical modes will interfere with the main mode transmission, limiting the overall bandwidth expansion capability. The document "NJGFonseca,'Br oadband waveguide dual-polarizationfour-way power divider for small passive arrays,'IEEE Microw.Wireless Compon. Lett.,vol.31,no.8,pp.985–988,Aug.2021." proposes a broadband dual-polarization four-way power divider suitable for small passive arrays. The design adopts a coaxial feeding waveguide, four polarization twisted structures, and forms a 2×2 array through OMT and T-type structure. It has a compact structure and is easy to implement. It can achieve dual-polarization radiation in the 17.7–20.2GHz frequency band. Although the use of the polarization twisted structure effectively reduces the cross-sectional height of the radiating unit (1.27λ0), due to the introduction of the OMT structure, its impedance bandwidth (S 11 <–20dB) failed to break through 20%. In addition, the integrated arrangement of the upper OMT and T-junction leads to an increase in the unit cell spacing, which is prone to side lobes under large-angle scanning conditions.

[0004] In summary, the development of compact, wide-band, low-profile dual circularly polarized waveguide array antenna radiating units remains a major challenge, and further research and breakthroughs are urgently needed in structural optimization, loss reduction, and broadband expansion. Summary of the Invention

[0005] In order to solve the problems of complex structure, insufficient bandwidth, low efficiency and the like of existing waveguide array antennas, the present invention proposes a broadband radiating unit for a dual circularly polarized waveguide array antenna.

[0006] The technical solution adopted in the present invention is as follows:

[0007] A broadband radiating unit for a dual circularly polarized waveguide array antenna, wherein the radiating unit is arrayed in a two-dimensional periodic arrangement;

[0008] The radiation unit includes an input square waveguide, a coaxial square waveguide, a stepped four-ridge coaxial waveguide, and a radiation grid arranged in sequence from bottom to top;

[0009] The input square waveguide is used to feed the orthogonal TE 10 Die or TE 01 mold;

[0010] The coaxial square waveguide and the stepped inner quad-ridge coaxial waveguide are used to feed the TE 10 Die or TE 01 The mode is input to the radiation grid, and broadband impedance matching is achieved and the transmission of high-order modes is suppressed;

[0011] The radiation grid is used to convert the input TE 10 Die or TE 01 The mode power is divided into four paths and radiated into free space, realizing the radiation of circularly polarized beams.

[0012] Furthermore, the stepped inner four-ridged coaxial waveguide includes a primary inner four-ridged coaxial waveguide and a secondary inner four-ridged coaxial waveguide; the primary inner four-ridged coaxial waveguide includes a primary inner four-ridged square waveguide and an inner conductor therein; the secondary inner four-ridged coaxial waveguide includes a secondary inner four-ridged square waveguide and an inner conductor therein; wherein the side length of the square waveguide, the waveguide side length of the coaxial square waveguide, the side length of the primary inner four-ridged square waveguide, and the side length of the secondary inner four-ridged square waveguide increase successively, the inner conductors are connected to each other and the radius remains unchanged.

[0013] Furthermore, the height of the ridge in the secondary inner four-ridged coaxial waveguide is greater than the height of the ridge in the primary inner four-ridged square waveguide, and the width is smaller than the width of the ridge in the primary inner four-ridged square waveguide, so as to achieve good broadband impedance matching.

[0014] Furthermore, a circle of square annular grooves is provided on the outer side of the radiation grid to reduce the mutual coupling effect between the radiating units after the antenna array is formed, thereby improving the isolation of the antenna array.

[0015] Furthermore, the radiation grid is composed of a square waveguide and a cross diaphragm inside the square waveguide; wherein the cross diaphragm is connected to the inner conductor to fix the inner conductor and improve the process feasibility.

[0016] Furthermore, the radiation unit period is 0.8λ0, where λ0 is a free space wavelength corresponding to the center frequency.

[0017] The broadband working principle of this radiating unit is as follows:

[0018] First, due to the high similarity between the inner quad-ridged waveguide and the square waveguide, it can be directly connected to the square waveguide to achieve transition without introducing an additional transition section, which improves the compactness of the structure. The high-order modes that are easily excited in the inner quad-ridged waveguide include: TE 11 ,TM 11 TE 20 U TE 20 L In addition, there are TE 12 TE 21 ,TM 12 ,TM 21 ,TM 22 TE 22 TE 30 TE 03 By cascading the inner quad-ridge waveguide and the coaxial square waveguide, a rotationally symmetrical three-step cavity is formed, and a symmetrical excitation method is adopted. The asymmetric high-order mode will not be excited. Therefore, only TE is propagated in the cavity. 10 TE 01 TE 21 TE 12 ,TM 21 ,TM 12 When the working bandwidth does not exceed 20%, these symmetrical modes will not have a significant impact on the main mode transmission; but when the working bandwidth is extended to more than 30%, TE 21 TE 12 ,TM 21 ,TM 12 In order to suppress the above interference mode, the present invention introduces an inner conductor into the inner quad-ridged waveguide, performs dispersion control on the inner quad-ridged coaxial waveguide and the coaxial square waveguide, and improves the bandwidth of the single-mode working area; the introduced coaxial inner conductor can disrupt the TE 21 TE 12 The electric field distribution of the inner quad-ridge waveguide can be changed to suppress its propagation, and on the other hand, the mode distribution of the inner quad-ridge waveguide can be changed to make the TM 21 ,TM 12 The cutoff frequency of the mode shifts toward higher frequencies.

[0019] Secondly, the inner quad-ridge waveguide and the radiation grid have a certain symmetry in structure, and the two are easy to match in terms of electric field distribution and impedance characteristics. 10Mode and TE 01 The mode can be better coupled to the four corners of the inner four-ridged waveguide, thereby realizing four-way beam transmission between the inner four-ridged waveguide and the radiation grid.

[0020] In summary, the radiation unit of the present invention can broaden the working bandwidth and achieve TE in a broadband range. 10 (or TE 01 ) mode to the four-way beam transmission of the radiation grid, completing efficient dual-polarization radiation within 35% bandwidth.

[0021] When the linearly polarized TE 10 Die or TE 01 In the mode, the radiating unit can achieve four-way power output with equal amplitude and phase. During the entire beam transmission process, the output beams in the two polarization directions can maintain equal amplitude and phase. Therefore, no matter which direction of linear polarization wave is fed into the input square waveguide, the radiating grid can output four-way linear polarization wave with equal amplitude and phase; when the circular polarization wave is fed (i.e., equal amplitude orthogonal TE with a phase difference of 90°), the radiating grid can output four-way linear polarization wave with equal amplitude and phase. 10 With TE 01 The radiating grid can also output four circularly polarized waves with equal amplitude and phase. Therefore, this radiating unit is not only suitable for waveguide dual linear polarization array antennas, but also for waveguide dual circular polarization array antennas.

[0022] The present invention has the following advantages:

[0023] 1. The radiation unit of the present invention can operate in a wide frequency band, with high efficiency and low transmission loss;

[0024] 2. The radiation unit structure of the present invention is simple in design, without complex waveguide structure, easy to machine and assemble, and has strong robustness;

[0025] 3. The radiating elements of the present invention are spaced closely together, less than one free-space wavelength, effectively suppressing grating lobes.

[0026] 4. The radiating unit of the present invention can realize dual circular polarization radiation, which improves the channel capacity and enhances the ability to resist cloud and rain and multipath attenuation;

[0027] 5. The radiation unit of the present invention has fewer layers and a lower cross-section, which improves space utilization;

[0028] 6. The present invention provides a slot structure between adjacent radiating elements, which reduces the mutual coupling between elements and improves the isolation of the antenna array. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A perspective view of the overall structure of the radiation unit of the present invention;

[0030] Figure 2This is an exploded view of the overall structure of the radiation unit of the present invention;

[0031] Figure 3 This is an exploded view of the cavity structure of the radiation unit of the present invention;

[0032] Figure 4 This is a top view of the overall structure of the radiation units of the present invention after being arrayed;

[0033] Figure 5 is a reflection coefficient simulation curve of the radiation unit of the present invention;

[0034] Figure 6 is a transmission coefficient amplitude simulation curve of the radiation unit of the present invention;

[0035] Figure 7 is a transmission coefficient phase simulation curve of the radiation unit of the present invention;

[0036] Figure 8 is a simulation curve of polarization isolation of the radiation unit of the present invention;

[0037] Explanation of the accompanying numbers: 1 is the input square waveguide, 2 is the stepped inner four-ridged coaxial waveguide, 3 is the radiation grid, 301 is the square ring groove, 4 is the coaxial square waveguide, 5 is the primary four-ridged coaxial waveguide, 6 is the secondary inner four-ridged coaxial waveguide, 401, 501, and 601 are the inner conductors of the corresponding waveguides respectively. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further described below with reference to the accompanying drawings:

[0039] This embodiment provides a broadband radiating unit for a dual circularly polarized waveguide array antenna, such as Figure 1 and Figure 3 As shown, Figure 1 and Figure 2 The three-dimensional diagram and exploded diagram of the overall structure of the radiation unit are respectively illustrated, including the input square waveguide, coaxial square waveguide, stepped four-ridge coaxial waveguide, and radiation grid arranged in sequence from bottom to top.

[0040] The input square waveguide is used to feed two orthogonal TE 10 Die or TE 01 mold.

[0041] The coaxial square waveguide and the stepped inner quad-ridge coaxial waveguide are used to feed the TE 10 Die or TE 01 The mode is input to the radiating grid, and broadband impedance matching is achieved and the transmission of high-order modes is suppressed.

[0042] The radiation grid is used to convert the input TE 10 Die or TE 01The mode power is split into four paths and radiated into free space.

[0043] The central axes of the input square waveguide, the coaxial square waveguide, the stepped four-ridge coaxial waveguide and the radiation grid are aligned.

[0044] The stepped inner four-ridged coaxial waveguide includes a primary inner four-ridged coaxial waveguide and a secondary inner four-ridged coaxial waveguide; the primary inner four-ridged coaxial waveguide includes a primary inner four-ridged square waveguide and an inner conductor therein; the secondary inner four-ridged coaxial waveguide includes a secondary inner four-ridged square waveguide and an inner conductor therein; wherein the side length of the square waveguide, the waveguide side length of the coaxial square waveguide, the side length of the primary inner four-ridged square waveguide, and the side length of the secondary inner four-ridged square waveguide increase successively, the inner conductors are connected to each other and the radius remains unchanged.

[0045] The radiation grid consists of a square waveguide and a cross diaphragm inside it; the cross diaphragm is connected to the inner conductor to fix the inner conductor and improve process feasibility; a circle of square ring grooves is provided on the outside of the radiation grid to reduce the mutual coupling effect between the radiating units after the antenna array is formed, thereby improving the isolation of the antenna array.

[0046] Specifically, in this embodiment, the side length of the input square waveguide is 6.2mm; the side length of the coaxial square is 9.3mm, and a coaxial inner conductor with a length of 2.4mm is provided at the rear end for connecting the TE 10 Die or TE 01 Mode conversion to TE in inner quad-ridged coaxial waveguide 10 Die or TE 01 mode; the side length of the primary inner four-ridged waveguide is 11.2mm, the ridge length is 1mm, and the ridge width is 0.5mm; the side length of the secondary inner four-ridged waveguide is 13.4mm, the ridge length is 1.2mm, and the ridge width is 0.8mm. The radius of the inner conductor inserted in the cavity is 0.9mm to achieve impedance matching in the stepped inner four-ridged waveguide; the side length of the square waveguide in the radiation grid is 6.2mm, the width of the cross diaphragm is 1.2mm, the length is 13.6mm, the width of the square annular groove is 0.8mm, and the outer side length is 16mm, that is, the periodic side length of the radiation unit in this embodiment is also 16mm.

[0047] Figure 4 The overall structure of the radiating units arranged in a 4x4 periodic array is illustrated. The square ring grooves of the radiating units are loaded between adjacent units to reduce the mutual coupling effect between the units and improve the port isolation of the array antenna.

[0048] Figure 5The simulated reflection coefficient curve of the radiating element is shown. In the frequency range of 27–39.5 GHz, the reflection coefficient of both polarizations at the input port is better than -20 dB, indicating that the radiating element has minimal return loss, which helps improve antenna efficiency.

[0049] Figure 6 The simulated transmission coefficient amplitude curve from the input port to any output port of the radiating element is shown. Within the frequency range of 27–39 GHz, the transmission coefficient amplitude of each output port is within -6.2 dB, and the amplitude curves of the four output ports completely overlap, indicating that the radiating element achieves equal power distribution.

[0050] Figure 7 The transmission phase simulation curve from the input port to any output port of the radiating unit is shown. In the frequency range of 27–39 GHz, the transmission phase curves of the four output ports are basically consistent, indicating that the radiating unit achieves in-phase output.

[0051] Figure 8 The polarization isolation simulation curve of the output port of the radiation unit is shown, that is, the input port is fed into TE 10 Mould and TE 01 In the frequency range of 27–39.5 GHz, the polarization isolation is better than 20 dB, indicating that the orthogonal mode has minimal impact on the main mode transmission and has good polarization purity.

[0052] The above is only one specific embodiment of the present invention. The present invention is also applicable to broadband dual circularly polarized waveguide array antennas and dual linearly polarized waveguide array antennas in other frequency bands. Any equivalent transformation, substitution, combination or simplification made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A broadband radiating unit for a dual circularly polarized waveguide array antenna, wherein the radiating unit is arranged in a two-dimensional periodic manner; characterized in that: The radiation unit includes an input square waveguide, a coaxial square waveguide, a stepped four-ridge coaxial waveguide, and a radiation grid arranged in sequence from bottom to top; The input square waveguide is used to feed the orthogonal TE 10 Die or TE 01 mold; The coaxial square waveguide and the stepped inner quad-ridge coaxial waveguide are used to feed the TE 10 Die or TE 01 The mode is input to the radiation grid, and broadband impedance matching is achieved and the transmission of high-order modes is suppressed; The radiation grid is used to convert the input TE 10 Die or TE 01 The mode power is divided into four paths and radiated into free space, realizing the radiation of circularly polarized beams.

2. A broadband radiation unit for a dual circularly polarized waveguide array antenna according to claim 1, characterized in that: The stepped inner four-ridged coaxial waveguide includes a primary inner four-ridged coaxial waveguide and a secondary inner four-ridged coaxial waveguide; the primary inner four-ridged coaxial waveguide includes a primary inner four-ridged square waveguide and an inner conductor therein; the secondary inner four-ridged coaxial waveguide includes a secondary inner four-ridged square waveguide and an inner conductor therein; wherein the side length of the square waveguide, the waveguide side length of the coaxial square waveguide, the side length of the primary inner four-ridged square waveguide, and the side length of the secondary inner four-ridged square waveguide increase successively, the inner conductors are connected to each other and the radius remains unchanged.

3. A broadband radiation unit for a dual circularly polarized waveguide array antenna according to claim 2, characterized in that: The height of the ridge in the secondary inner four-ridged coaxial waveguide is greater than the height of the ridge in the primary inner four-ridged square waveguide, and the width is smaller than the width of the ridge in the primary inner four-ridged square waveguide, so as to achieve good broadband impedance matching.

4. A broadband radiation unit for a dual circularly polarized waveguide array antenna according to claim 2 or 3, characterized in that: A circle of square ring-shaped grooves is provided on the outer side of the radiation grid to reduce the mutual coupling effect between the radiating units after the antenna array is formed and improve the isolation of the antenna array.

5. The broadband radiation unit for a dual circularly polarized waveguide array antenna according to claim 4, characterized in that: The radiation grid is composed of a square waveguide and a cross diaphragm inside the square waveguide; wherein the cross diaphragm is connected to the inner conductor to fix the inner conductor.

6. The broadband radiation unit for a dual circularly polarized waveguide array antenna according to claim 5, characterized in that: The radiation unit period is 0.8λ0, where λ0 is a free space wavelength.

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