Circularly polarized antenna elements and spaceborne phased array antennas

Abstract

The present disclosure relates to the technical field of antennas, and particularly relates to a circularly polarized antenna unit and a satellite-borne phased array antenna. The circularly polarized antenna unit comprises: a power-division feeding network, an orthogonal feeding conversion structure, which is arranged above the power-division feeding network and is electrically connected with the power-division feeding network, a radiation unit, which is arranged above the orthogonal feeding conversion structure and comprises a first dielectric substrate and four radiation arms arranged on the upper surface of the first dielectric substrate, the four radiation arms are symmetrically distributed in cross and are all electrically connected with the orthogonal feeding conversion structure, and a ring-shaped metal strip, which is arranged on the first dielectric substrate and is located at the periphery of the four radiation arms. The present disclosure arranges the ring-shaped metal strip, so that the coupling energy of the low frequency band is redistributed and suppressed, thereby ensuring the stability of the radiation performance of the circularly polarized antenna unit in the low frequency range, being conducive to widening the working frequency band of the circularly polarized antenna unit and realizing the wide frequency band pursuit of the circularly polarized antenna unit.

Description

Technical Field

[0001] This disclosure relates to the field of antenna technology, specifically to a circularly polarized antenna element and a spaceborne phased array antenna. Background Technology

[0002] With the rapid development of mobile phone direct satellite communication technology, broadband has become an important development trend for satellite phased array antennas. Wide bandwidth means greater communication capacity, stronger anti-interference ability and more flexible frequency reuse capability, realizing stable and reliable broadband communication between satellites and ground terminals.

[0003] In the design of phased array antennas, the array spacing is usually designed according to the highest frequency point to avoid generating grating lobes. This results in a smaller spacing between antenna elements, which in turn leads to stronger mutual coupling in the low-frequency radiation, and the antenna's operating frequency band cannot be extended to the low-frequency direction. Summary of the Invention

[0004] To overcome the problems existing in the related art, an exemplary embodiment of this disclosure provides a circularly polarized antenna unit in a first aspect. The circularly polarized antenna unit includes: a power divider feed network for outputting two unbalanced signals with equal amplitude and a phase difference of 90 degrees; an orthogonal feed conversion structure disposed above and electrically connected to the power divider feed network for converting the unbalanced signals output by the power divider feed network into balanced signals; a radiating element disposed above the orthogonal feed conversion structure, including a first dielectric substrate and four radiating arms disposed on the upper surface of the first dielectric substrate, the four radiating arms being orthogonally symmetrically distributed in a cross shape and all electrically connected to the orthogonal feed conversion structure; and an annular metal strip disposed on the first dielectric substrate and located around the four radiating arms.

[0005] In some embodiments, the circumference and / or width of the annular metal strip are configured such that the radiating aperture of the radiating element is reduced to 0.32. ~0.36 ,in, The wavelength corresponds to the center frequency of the operating frequency band of the circularly polarized antenna element.

[0006] In some embodiments, the inner diameter circumference of the annular metal strip is 160mm-200mm, and it is configured to adjust the frequency point of the parasitic resonance of the annular metal strip.

[0007] In some embodiments, the width of the annular metal strip is 1mm-3mm, and it is configured to adjust the coupling coefficient between the annular metal strip and the radiating element.

[0008] In some embodiments, the annular metal strip has a uniform width structure in the extending direction.

[0009] In some embodiments, the annular metal strip includes: a first annular sub-metal strip disposed on the upper surface of the first dielectric substrate; and / or, a second annular sub-metal strip disposed on the lower surface of the first dielectric substrate.

[0010] In some embodiments, the power divider feed network is a Wilkinson power divider structure, wherein an isolation resistor is provided between the two output branches.

[0011] In some embodiments, the circularly polarized antenna unit further includes a metal shield disposed above the isolation resistor and connected to the substrate of the Wilkinson power divider structure.

[0012] In some embodiments, the orthogonal power supply conversion structure includes a pair of orthogonally arranged second dielectric substrates. Each second dielectric substrate has a microstrip transmission line and a wedge-shaped ground plane etched on its surface. The two ends of the microstrip transmission line are electrically connected to the power divider network and the radiating unit, respectively. The wedge-shaped ground plane is arranged with a gradually changing width along the longitudinal direction of the second dielectric substrate to achieve impedance matching and balanced signal conversion in a wide frequency band.

[0013] In some embodiments, the circularly polarized antenna unit further includes a cavity, which is cylindrical in shape. The cavity includes: a base plate disposed below the power divider feed network; and a sidewall connected to the periphery of the base plate at its bottom and extending upward along the periphery of the base plate, disposed outside the power divider feed network, the orthogonal feed conversion structure, and the radiating element.

[0014] In some embodiments, the circularly polarized antenna unit further includes: an antenna radome disposed on the top of the sidewall, which together with the cavity forms a closed space to accommodate the power divider feed network, the orthogonal feed conversion structure, and the radiating element.

[0015] In some embodiments, the circularly polarized antenna element further includes a support member disposed around the orthogonal feed conversion structure, wherein the bottom end of the support member is connected to the cavity and the top end is connected to the radome.

[0016] Secondly, this disclosure also provides a spaceborne phased array antenna, including a plurality of circularly polarized antenna elements as described in the first aspect, wherein the plurality of circularly polarized antenna elements are arrayed to radiate together.

[0017] In some embodiments, the plurality of circularly polarized antenna elements are arranged in a rectangular array, and the spacing between two adjacent circularly polarized antenna elements is 0.5. ~0.55 ,in, The wavelength is the wavelength corresponding to the highest frequency point in the operating frequency band of the circularly polarized antenna element.

[0018] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects: In this disclosure, the annular metal strip can be disposed as a parasitic structure on the periphery of the radiating arm, generating parasitic resonance around the main radiator through electromagnetic coupling. This parasitic resonance can exhibit high impedance characteristics near a specific frequency point. When the surface wave energy with strong coupling in the low-frequency band attempts to pass through the area where the annular metal strip is located, the annular metal strip can exhibit high impedance characteristics, thereby effectively blocking the surface wave and preventing it from propagating along the first dielectric substrate to the adjacent circularly polarized antenna element. Thus, without adding an additional decoupling structure, effective suppression of low-frequency mutual coupling is achieved, thereby ensuring the stability of the radiation performance of the circularly polarized antenna element in the low-frequency range. This is beneficial for widening the operating frequency band of the circularly polarized antenna element and realizing the wideband pursuit of the circularly polarized antenna element. Attached Figure Description

[0019] This disclosure can be better understood by describing exemplary embodiments of the present disclosure in conjunction with the accompanying drawings, in which: Figure 1 This is an exploded view of a circularly polarized antenna element according to exemplary embodiments of the present disclosure; Figure 2 This is a partial schematic diagram of a circularly polarized antenna element according to exemplary embodiments of the present disclosure; Figure 3 This is a partial exploded view of a circularly polarized antenna element according to an exemplary embodiment of the present disclosure; Figure 4 This is a partial exploded view of a circularly polarized antenna element according to an exemplary embodiment of the present disclosure; Figure 5 This is an exploded view of an orthogonal power conversion structure according to exemplary embodiments of the present disclosure; Figure 6 This is a structural schematic diagram of a support member according to an exemplary embodiment of the present disclosure; Figure 7 This is a simulated port VSWR curve of a circularly polarized antenna element according to an exemplary embodiment of the present disclosure; Figure 8 This is a simulation curve of the axial ratio of a circularly polarized antenna element according to an exemplary embodiment of the present disclosure; Figure 9 This is a gain simulation curve of a circularly polarized antenna element according to an exemplary embodiment of the present disclosure; Figure 10 This is a gain pattern of a circularly polarized antenna element at the center frequency, as shown in an exemplary embodiment of the present disclosure. Figure 11This is an exemplary embodiment of the present disclosure showing a beam scanning pattern of a spaceborne phased array antenna at a frequency of 1.5 GHz and a beam angle of 0° to 55°. Figure 12 This is an exemplary embodiment of the present disclosure showing a beam scanning pattern of a spaceborne phased array antenna at a frequency of 2.2 GHz and a beam angle of 0° to 55°. Figure 13 This is an active VSWR curve of a spaceborne phased array antenna under 0° and 55° beam scanning, as shown in an exemplary embodiment of the present disclosure.

[0020] Figure label: 10. Power divider network; 1a. First port; 1b. Second port; 1c. Third port; 11. Isolation resistor; 20. Orthogonal feed conversion structure; 2a. Second dielectric substrate; 21. Microstrip transmission line; 22. Wedge-shaped ground plane; 30. Radiation unit; 31. First dielectric substrate; 32. Radiation arm; 40. Annular metal strip; 41. First annular sub-metal strip; 42. Second annular sub-metal strip; 50. Metal shielding cover; 60. Cavity; 61. Base plate; 62. Side wall; 70. Antenna radome; 80. Support component; 81. Support plate; 82. Support foot. Detailed Implementation

[0021] The following describes specific embodiments of this disclosure. It should be noted that, in order to maintain brevity, this specification cannot provide a detailed description of all features of the actual embodiments. It should be understood that, in the actual implementation of any embodiment, just as in any engineering or design project, various specific decisions are often made to achieve the developer's specific goals and to meet system-related or business-related constraints, and this can change from one embodiment to another. Furthermore, it is understood that although the efforts made in this development process may be complex and lengthy, for those skilled in the art related to the content of this disclosure, changes in design, manufacturing, or production based on the technical content disclosed herein are merely conventional technical means and should not be construed as insufficient content of this disclosure.

[0022] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms “first,” “second,” and similar terms used in this disclosure do not indicate any order, quantity, or importance, but are merely used to distinguish different components. The terms “a” or “one,” etc., do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising,” “including,” etc., mean that the element or object preceding “comprising” or “including” encompasses the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected,” “linked,” etc., are not limited to physical or mechanical connections, nor are they limited to direct or indirect connections.

[0023] To solve the above technical problems, refer to Figure 1 As shown, this disclosure provides a circularly polarized antenna element, which may include: a power divider feed network 10, an orthogonal feed conversion structure 20, a radiating element 30, and an annular metal strip 40.

[0024] The power divider feed network 10 outputs two unbalanced signals with equal amplitude and a 90-degree phase difference. The output of these two unbalanced signals by the power divider feed network 10 is a prerequisite for generating circularly polarized radiation. The equal amplitude and 90° phase difference output of the power divider feed network 10 are fundamental guarantees for maintaining a low axial ratio (e.g., AR ≤ 3dB) in the circularly polarized antenna element over a wide bandwidth. In the circularly polarized antenna element, the orthogonally placed radiating arms 32 in the radiating element 30 are superimposed in the far field by excitation signals with equal amplitude and a 90° phase difference to form a circularly polarized wave.

[0025] The quadrature feed conversion structure 20 is disposed above and electrically connected to the power divider feed network 10. It is used to convert the unbalanced signal output by the power divider feed network 10 into a balanced signal. The power divider feed network 10 outputs an unbalanced signal. The orthogonally placed radiating arms 32 require balanced feeding to excite symmetrical radiation modes. Therefore, the quadrature feed conversion structure 20 can perform mode conversion between unbalanced and balanced signals to ensure that radio frequency energy is efficiently transmitted from the power divider feed network 10 to the radiating unit 30.

[0026] The radiating element 30, disposed above the orthogonal feed conversion structure 20, includes a first dielectric substrate 31 and four radiating arms 32 disposed on the upper surface of the first dielectric substrate 31. The four radiating arms 32 are arranged in a cross-shaped orthogonal symmetrical distribution and are all electrically connected to the orthogonal feed conversion structure 20. The cross-shaped orthogonal symmetrical distribution of the four radiating arms 32 can form an orthogonal dipole structure. Under excitation by a 90° phase difference signal, one pair of radiating arms 32 generates a horizontal polarization component, and the other pair of radiating arms 32 generates a vertical polarization component. The two polarization components are superimposed in the far field with a 90° phase difference, thereby synthesizing a circularly polarized wave. The cross-shaped orthogonal symmetrical geometric layout can ensure that the amplitudes of the two orthogonal polarization components are equal, which is the geometric basis for realizing low axial ratio circular polarization. The symmetrical structure also makes the polarization characteristics of the spaceborne phased array antenna relatively stable within a ±55° beam scanning range.

[0027] An annular metal strip 40 is disposed on the first dielectric substrate 31 and located around the four radiating arms 32. The arrangement of the annular metal strip 40 is equivalent to introducing a parasitic coupling path around the radiating unit 30, which redistributes and suppresses the coupling energy in the low-frequency band without adding an additional decoupling structure, effectively suppressing the strong coupling effect in the low-frequency band.

[0028] According to this embodiment, the annular metal strip 40 can be disposed as a parasitic structure around the radiating arm 32, generating parasitic resonance around the main radiator through electromagnetic coupling. This parasitic resonance can exhibit high impedance characteristics near a specific frequency point. When the surface wave energy with strong coupling in the low-frequency band attempts to pass through the area where the annular metal strip 40 is located, the annular metal strip 40 can exhibit high impedance characteristics, thereby effectively blocking the surface wave and preventing it from propagating along the first dielectric substrate 31 to the adjacent circularly polarized antenna element. Thus, without adding an additional decoupling structure, effective suppression of low-frequency mutual coupling is achieved, thereby ensuring the stability of the radiation performance of the circularly polarized antenna element in the low-frequency range. This is beneficial for widening the operating frequency band of the circularly polarized antenna element and realizing the wideband pursuit of the circularly polarized antenna element.

[0029] In some embodiments, refer to Figure 2 As shown, the circumference and / or width of the annular metal strip 40 are configured such that the radiating aperture of the radiating element 30 is reduced to 0.32. ~0.36 ,in, This refers to the wavelength corresponding to the center frequency point of the operating frequency band of the circularly polarized antenna element.

[0030] When the inner diameter circumference of the annular metal strip 40 is close to the electrical length of a certain resonant mode in the target frequency band (e.g., a 1-wavelength loop resonance or a 0.5-wavelength loop resonance), the annular metal strip 40 can generate a resonance effect near the target frequency. In the resonant state, the induced current on the annular metal strip 40 is large, and its equivalent impedance also exhibits a specific value, thereby effectively cutting off the propagation path of the surface wave.

[0031] The width of the ring-shaped metal strip 40 affects its equivalent characteristic impedance and quality factor (Q value). A wider ring-shaped metal strip 40 has lower resistive loss, while a narrower ring-shaped metal strip 40 has a lower Q value and a flatter resonance curve, which is beneficial for widening the effective frequency band of coupling suppression. By reasonably optimizing the width of the ring-shaped metal strip 40, it is possible to effectively suppress bandwidth widening while ensuring sufficient coupling suppression, thereby covering a wider frequency range.

[0032] Changing the inner diameter circumference of the annular metal strip 40 will simultaneously change the total length and enclosed area of ​​the annular metal strip 40. Changing the width of the annular metal strip 40 will change the resistance characteristics and parasitic capacitance of the annular metal strip 40. Through the synergistic optimization of the two, the electromagnetic response characteristics of the annular metal strip 40 can be controlled in multiple dimensions to achieve a better coupling suppression effect.

[0033] In some embodiments, refer to Figure 2 As shown, the inner diameter of the annular metal strip 40 is 160mm-200mm, and it is configured to adjust the frequency point of the parasitic resonance of the annular metal strip 40.

[0034] The target operating frequency band of the circularly polarized antenna element can be 1.45 GHz to 2.25 GHz, with a center frequency of approximately 1.85 GHz. The wavelength of this frequency band in vacuum is approximately 162 mm (center frequency) to 207 mm (1.45 GHz). Considering the shortening effect of the first dielectric substrate 31 on electromagnetic waves (i.e., the dielectric constant shortens the wavelength), the inner circumference of the annular metal strip 40 is designed to be 160 mm to 200 mm, corresponding to an electrical length of approximately 0.9 to 1.2 wavelengths within the operating frequency band. This electrical length range allows the annular metal strip 40 to form an effective loop resonance within the target frequency band, generating high impedance characteristics sufficient to suppress surface wave propagation and ensuring that the parasitic resonant frequency is configured within the target range that can effectively compensate for impedance mismatch at the low-frequency end.

[0035] As a parasitic resonant structure, the inner diameter of the ring metal strip 40 determines the frequency position of the parasitic resonance. By setting different inner diameters, the parasitic resonant frequency of the ring metal strip 40 will shift within the frequency band. When the parasitic resonant frequency falls on the target frequency band that needs to be suppressed (e.g., near the low-frequency end of 1.45GHz), the ring metal strip 40 exhibits high impedance characteristics in this frequency band, which can suppress the propagation of surface waves to a large extent, thereby improving the impedance matching and radiation efficiency of this frequency band.

[0036] In some embodiments, refer to Figure 2 As shown, the width of the annular metal strip is 1mm-3mm, and it is configured to adjust the coupling coefficient between the annular metal strip 40 and the radiating element 30.

[0037] The annular metal strip 40 and the radiating element 30 interact through electromagnetic field coupling. The magnitude of the coupling coefficient affects the strength of the influence of the annular metal strip 40 on the radiating element 30. If the coupling coefficient is too small, the annular metal strip 40 is insufficient in suppressing the edge current of the radiating arm 32, and cannot effectively compress the radiating aperture of the radiating element 30. If the coupling coefficient is too large, the annular metal strip 40 will excessively affect the main resonance of the radiating element 30, leading to a shift in the center frequency or a decrease in gain. Therefore, changing the width of the annular metal strip 40 will alter the capacitive coupling area and mutual inductance coefficient between the annular metal strip 40 and the radiating arm 32, thereby achieving precise control of the coupling coefficient. By limiting the width of the annular metal strip 40 to the range of 1mm-3mm, the coupling coefficient is optimized within the optimal range that can effectively compress the radiating aperture without excessively affecting the resonance of the main radiator.

[0038] In some embodiments, refer to Figure 2 As shown, the annular metal strip 40 has a uniform width structure in the extension direction, and the radiating element 30 of the four-leaf clover structure is cross-shaped orthogonally symmetrical. The uniform width structure of the annular metal strip 40 can ensure that the coupling effect of the annular metal strip 40 on the four radiating arms 32 is the same, maintaining the fourfold rotational symmetry of the antenna structure. Circular polarization is extremely sensitive to the symmetry of the structure. The uniform width structure can ensure that the circular polarization antenna element maintains good circular polarization axial ratio performance in a wide frequency band and a large scanning angle range.

[0039] Meanwhile, the equal-width structure means that the processing parameters of the annular metal strip 40 are simple and the shape is regular, which is conducive to improving the processing accuracy and consistency of PCB etching, reducing the manufacturing cost of circularly polarized antenna elements, and is suitable for the mass production needs of spaceborne phased array antennas.

[0040] In some embodiments, refer to Figure 3 As shown, the annular metal strip 40 may include a first annular sub-metal strip 41 disposed on the upper surface of the first dielectric substrate 31.

[0041] The first annular sub-metal strip 41, disposed on the upper surface of the first dielectric substrate 31, and the four radiating arms 32 are located on the same plane. The co-layer structure allows for direct electromagnetic coupling between the annular metal strip 41 and the radiating arms 32. The coupling between them is achieved through spatial electromagnetic field coupling, resulting in a short coupling path and high coupling efficiency. The first annular metal strip 41 can directly constrain the surface current distribution at the ends of the radiating arms 32, forcing the radiated energy to concentrate in the inner ring region, thereby compressing the equivalent radiating aperture of the circularly polarized antenna element.

[0042] In some other embodiments, the annular metal strip 40 may include a second annular sub-metal strip 42 disposed on the lower surface of the first dielectric substrate 31.

[0043] The second annular sub-metal strip 42 disposed on the lower surface of the first dielectric substrate 31 mainly acts on the surface waves propagating on the lower surface of the first dielectric substrate 31. This part of the surface waves is also one of the main propagation paths of mutual coupling between the circularly polarized antenna elements distributed in the array. By forming a high impedance boundary in its region, the second annular sub-metal strip 42 on the lower surface can block the surface waves propagating along the lower surface of the first dielectric substrate 31, further enhancing the suppression effect of mutual coupling between the circularly polarized antenna elements.

[0044] In some embodiments, refer to Figure 3 As shown, a first annular sub-metal strip 41 and a second annular sub-metal strip 42 are respectively disposed on the upper and lower surfaces of the first dielectric substrate 31. The two are capacitively coupled in a vertical direction through the first dielectric substrate 31, which achieves extremely high surface impedance to surface waves, so that surface waves cannot propagate in a wide frequency range, thereby achieving a wider and more efficient mutual coupling suppression effect between circularly polarized antenna elements.

[0045] The double-layered annular metal strip 40 is symmetrically distributed above and below the first dielectric substrate 31, which can ensure the symmetrical distribution of the electromagnetic field on the upper and lower sides of the first dielectric substrate 31, avoid introducing additional cross-polarization components, and help the circularly polarized antenna element maintain stable circular polarization axial ratio performance in a wide frequency band.

[0046] The double-layered annular metal strips 40 are respectively etched on the upper and lower surfaces of the first dielectric substrate 31. Without the need to add an additional dielectric or metal layer, the antenna can maintain its low profile characteristics while improving its wideband radiation performance, thus meeting the requirements of lightweight and low profile for spaceborne equipment.

[0047] In some embodiments, refer to Figure 4 As shown, the power divider network 10 is a Wilkinson power divider structure. The Wilkinson power divider structure has a first port 1a, a second port 1b and a third port 1c, and an isolation resistor 11 is provided between the two output branches of the Wilkinson power divider structure.

[0048] The first port 1a serves as an input port for receiving radio frequency signals from the transmitter or the front-end receiving link. The input radio frequency signals are transmitted to the second port 1b and the third port 1c through two channels. The microstrip line lengths corresponding to the two channels are different, so that the output signals of the second port 1b and the third port 1c have a 90° phase difference.

[0049] The two output ports (i.e., port 1b and port 1c) of the Wilkinson power divider exhibit equal amplitude and in-phase output characteristics. By adding a phase delay line of a specific length to one output branch of the Wilkinson power divider, two equal amplitude signals with a 90° phase difference can be output. The Wilkinson power divider offers advantages such as simple structure, low insertion loss, good fabrication consistency, and ease of integration onto printed circuit boards (PCBs), making it suitable for the lightweight and high reliability requirements of spaceborne phased array antennas.

[0050] When the reflection coefficients of the two output ports are inconsistent (e.g., due to the input impedance variation of the circularly polarized antenna element at different frequencies or under different ambient temperatures), the unbalanced energy between the two output branches can be absorbed by the isolation resistor 11, thereby maintaining a high degree of isolation between the two outputs. This prevents the deterioration of the circular polarization axial ratio of the radiating element 30 caused by the change in the amplitude ratio or phase difference of the two output signals with frequency.

[0051] The isolation resistor 11 ensures that the two output signals of the Wilkinson power divider remain at the same amplitude and 90° phase difference over a wide frequency range, thereby ensuring the axial ratio stability of the radiating unit 30 over a wide frequency range.

[0052] In some embodiments, refer to Figure 4 As shown, the circularly polarized antenna unit may further include: a metal shield 50, disposed above the isolation resistor 11 and connected to the substrate of the Wilkinson power divider structure.

[0053] As a thin-film element, the resistance stability of the isolation resistor 11 is affected by the integrity of the thin-film material. If the thin film is damaged, it may cause lattice displacement or ionization effects, resulting in irreversible drift of the resistance value of the isolation resistor 11, or even causing the isolation resistor 11 to open or short-circuit.

[0054] In applications where circularly polarized antenna elements are used (e.g., in space environments), high-energy particles (e.g., protons, electrons, heavy ions) exist, possessing extremely strong penetrating capabilities. The metal shield 50 provides physical shielding for the isolation resistor 11, effectively protecting it from electromagnetic radiation in space or breakdown by high-energy particles. This ensures the stability of the isolation resistor 11's resistance value, extends its operational lifespan, and prevents its failure from deteriorating the circular polarization axial ratio of the circularly polarized antenna element, thereby improving the on-orbit reliability and lifespan of the spaceborne phased array antenna.

[0055] Meanwhile, the metal shield 50, as a grounding conductor, plays a certain role in shielding the electromagnetic field above the isolation resistor 11, reducing the impact of external electromagnetic interference on the power distribution feed network 10, and also reducing the electromagnetic leakage of the power distribution feed network 10 to other spaceborne electronic equipment.

[0056] In some embodiments, refer to Figure 5 As shown, the orthogonal power supply conversion structure 20 includes a pair of orthogonally arranged second dielectric substrates 2a. Each second dielectric substrate 2a has a microstrip transmission line 21 and a wedge-shaped ground plane 22 etched on its surface. The two ends of the microstrip transmission line 21 are electrically connected to the power distribution network 10 and the radiation unit 30, respectively. The wedge-shaped ground plane 22 is arranged with a gradually changing width along the longitudinal direction of the second dielectric substrate 2a, which is used to achieve impedance matching and balanced signal conversion in a wide frequency band.

[0057] The microstrip transmission line 21 is etched on the surface of the second dielectric substrate 2a. One end of the line is electrically connected to the output port of the power divider network 10, and the other end is electrically connected to the radiating arm 32. It is responsible for transmitting radio frequency signals from the power divider network 10 to the radiating unit 30. The microstrip transmission line 21 has the advantages of simple structure, easy processing, and compatibility with PCB technology.

[0058] The wedge-shaped ground plane 22 has a gradually changing width along the longitudinal direction of the substrate. When the characteristic impedance of the microstrip transmission line 21 changes slowly along the propagation direction, matching between different impedances can be achieved in a wide frequency range, and the reflection coefficient fluctuates less with frequency. The microstrip transmission line 21 transmits an unbalanced signal relative to the ground plane. Through the gradual design of the wedge-shaped ground plane 22, the mode of the microstrip transmission line 21 gradually evolves with the change of the ground plane width, transitioning from the unbalanced mode of the microstrip transmission line 21 to the balanced feeding mode of the dipole radiating arm 32, thus completing the signal conversion.

[0059] In some embodiments, refer to Figure 1As shown, the circularly polarized antenna element also includes a cavity 60, which is cylindrical in shape. The cylindrical cavity 60 (e.g., a circular or square cylinder) occupies a regular geometric space on a two-dimensional plane, which makes it easy to arrange the elements in a rectangular or triangular grid in the array, ensuring that the spacing between the elements is precisely controllable and facilitating the regular array arrangement of multiple circularly polarized antenna elements.

[0060] The cavity 60 may include a base plate 61 and a side wall 62. The base plate 61 is disposed below the power distribution feed network 10. The side wall 62 is connected to the periphery of the base plate 61 at its bottom and extends upward along the periphery of the base plate 61. It is disposed outside the power distribution feed network 10, the orthogonal feed conversion structure 20 and the radiation unit 30.

[0061] First, the base plate 61 is located at the bottom of the entire antenna structure, which can provide a rigid mounting reference and mechanical support foundation for the power divider feed network 10, the orthogonal feed conversion structure 20 and the radiating element 30, so that the circularly polarized antenna element can withstand the severe vibration in the application scenario (e.g., rocket launch process) and meet the reliability requirements of the spaceborne phased array antenna.

[0062] Meanwhile, the base plate 61, acting as a metallic reflector, reflects the radiated energy from the antenna in the rear (towards the satellite) direction back to the front (towards the Earth), thereby improving the antenna's positive gain. In the array environment of a spaceborne phased array antenna, the base plate 61 can also provide a unified grounding reference surface for multiple circularly polarized antenna elements, ensuring the consistency of the radiation performance of each circularly polarized antenna element in the array.

[0063] Secondly, the sidewall 62 extends upward along the periphery of the base plate 61 and is disposed on the outside of the radio frequency component. The sidewall 62 can reflect and confine the electromagnetic waves leaking from the side of the radiation unit 30, preventing them from leaking laterally to adjacent units, thereby increasing the isolation between units from the physical structure level.

[0064] In some embodiments, refer to Figure 1 As shown, the circularly polarized antenna unit may further include: an antenna radome 70, which is disposed on the top of the side wall 62 and together with the cavity 60 forms a closed space to accommodate the power divider feed network 10, the orthogonal feed conversion structure 20 and the radiating element 30.

[0065] The radome 70, together with the metal cavity 60 (composed of a base plate 61 and side walls 62), forms a complete sealed cavity 60, housing all radio frequency functional components (power divider feed network 10, orthogonal feed conversion structure 20, and radiating element 30) within the cavity 60. This cavity 60 structure provides multi-directional physical protection for the internal components of the spaceborne phased array antenna, effectively resisting interference from high and low temperature shocks, electromagnetic radiation, and atomic oxygen erosion in the space environment on the circularly polarized antenna element. At the same time, it can also reduce electromagnetic interference from the spaceborne phased array antenna to other electronic devices on the satellite (e.g., power supply, integrated electronics).

[0066] In some embodiments, the sealed cavity 60 may be filled with inert gas or maintain a certain pressure to prevent micro-discharge phenomena that may occur under low pressure. That is, when the radio frequency power of the circularly polarized antenna element is large, tiny metal burrs or dielectric surfaces in the vacuum may be subject to electron avalanche breakdown, resulting in sudden degradation or even permanent damage to radio frequency performance.

[0067] In some embodiments, the radome 70 may be made of a wave-transparent material (e.g., polyimide, quartz fiber reinforced polyimide, etc.), which can reduce the weakening of the radiation performance of the spaceborne phased array antenna while achieving mechanical protection, and ensure that radio frequency energy is radiated outward through the radome 70 with high efficiency.

[0068] In some embodiments, the radome 70 can be connected to the first dielectric substrate 31 in the radiating unit 30 to support and fix the radome 70 by the radiating unit 30, ensuring the stability of the relative position between the radome 70 and the radiating unit 30, and ensuring the effective protection of the radome 70 for the radiating unit 30 or other components.

[0069] In some embodiments, refer to Figure 1 and Figure 6 As shown, the circularly polarized antenna unit may further include: a support member 80, which is disposed around the orthogonal feed conversion structure 20, with the bottom end of the support member 80 connected to the cavity 60 and the top end connected to the radome 70.

[0070] First, the radome 70 has a large area and can withstand strong vibration and impact loads in some scenarios (e.g., rocket launch process). The support 80 connects the cavity 60 and the radome 70, providing an intermediate support point for the radome 70, shortening the span of the radome 70, increasing the natural frequency of the overall structure of the circularly polarized antenna unit, and preventing the circularly polarized antenna unit from resonating with other vibrations in the application scenario (e.g., low-frequency components of rocket launch vibration).

[0071] Secondly, the support member 80 can also limit the position of the orthogonal feed conversion structure 20, reduce the possibility of deformation or displacement of the orthogonal feed conversion structure 20, improve the stability of the electrical connection between the orthogonal feed conversion structure 20 and the power divider feed network 10, and between the orthogonal feed conversion structure 20 and the radiating element 30, thereby improving the working stability of the circularly polarized antenna element.

[0072] In some embodiments, refer to Figure 1 and Figure 6 As shown, the support member 80 may include a support plate 81 and a support foot 82. The support plate 81 can be connected to the first dielectric substrate 31 in the radiating unit 30 to support and fix the radiating unit 30. The support foot 82 is located below the support plate 81 and can be connected to both the support plate 81 and the base plate 61. By connecting the support plate 81 and the support foot 82 as intermediate elements, the structural strength between the radiating unit 30 and the base plate 61 is enhanced, thereby increasing the stability of the circularly polarized antenna unit.

[0073] In some embodiments, the support member 80 is made of polyimide dielectric material. Polyimide has excellent mechanical properties (e.g., high specific strength, high modulus), high and low temperature resistance (maintaining stable performance within the range of -269°C to 400°C), and radiation resistance, making it suitable for applications of spaceborne phased array antennas. Simultaneously, the polyimide dielectric support member 80 has low conductivity, reducing the likelihood of obstructing or interfering with the electromagnetic radiation of the circularly polarized antenna element, thus ensuring good radio frequency performance of the circularly polarized antenna element.

[0074] In some embodiments, the substrates corresponding to the power distribution feed network 10, the orthogonal feed conversion structure 20, and the radiation unit 30 can all be electromagnetic radiation resistant PCBs. The overall structure meets the requirements of lightweight, high reliability, low cost, and easy mass production for spaceborne equipment, and is suitable for application scenarios such as low-orbit satellite phased arrays and space-ground integrated communication.

[0075] The circularly polarized antenna element provided in this embodiment operates at a frequency of 1.45 GHz to 2.25 GHz, and its port VSWR, axial ratio, gain, and radiation direction are as follows: Reference Figure 7 As shown, the VSWR of the circularly polarized antenna element is less than 1.5 throughout the entire target operating frequency band from 1.45 GHz to 2.25 GHz, indicating that the circularly polarized antenna element has good impedance matching characteristics within the 43% impedance bandwidth, which can effectively ensure that the radio frequency energy is efficiently transmitted from the power divider feed network 10 to the radiating element 30.

[0076] Reference Figure 8As shown, the axial ratio of the circularly polarized antenna element is less than 3dB throughout the entire target operating frequency band from 1.45GHz to 2.25GHz, indicating that the circularly polarized antenna element has good circular polarization radiation characteristics within the target operating frequency band and can meet the polarization purity requirements of satellite communication.

[0077] Reference Figure 9 and Figure 10 As shown, within the entire target operating frequency band of 1.45GHz to 2.25GHz, the gain range of the circularly polarized antenna element is 6.3dBi to 6.6dBi, and the 3dB beamwidth range is 84° to 90°. The circularly polarized antenna element has high radiation efficiency and wide beam coverage capability, which can provide a good unit performance foundation for array synthesis of high gain and wide-angle scanning.

[0078] Based on the same inventive concept, this disclosure also provides a spaceborne phased array antenna, including multiple circularly polarized antenna elements as in any of the foregoing embodiments, wherein the multiple circularly polarized antenna elements are arrayed together to radiate together.

[0079] The annular metal strip 40 can be disposed as a parasitic structure around the radiating arm 32, generating parasitic resonance around the main radiator through electromagnetic coupling. This parasitic resonance can exhibit high impedance characteristics near a specific frequency point. When the surface wave energy with strong coupling in the low frequency band attempts to pass through the area where the annular metal strip 40 is located, the annular metal strip 40 can exhibit high impedance characteristics, thereby effectively blocking the surface wave and preventing it from propagating along the first dielectric substrate 31 to the adjacent circularly polarized antenna element. Thus, without adding an additional decoupling structure, effective suppression of low-frequency mutual coupling is achieved, thereby ensuring the stability of the radiation performance of the circularly polarized antenna element in a wide frequency range.

[0080] In some embodiments, multiple circularly polarized antenna elements are arranged in a rectangular array, with a spacing of 0.5 between adjacent circularly polarized antenna elements. ~0.55 ,in, This refers to the wavelength corresponding to the highest frequency point in the operating frequency band of the circularly polarized antenna element.

[0081] Rectangular arrays are regular two-dimensional array arrangements. Their array factor radiation patterns are separable, making the phase calculation of the beamforming network and the design of the feeding network relatively simple. The rectangular arrangement makes the mutual coupling environment between circularly polarized antenna elements periodic, which facilitates mutual coupling compensation through simulation and testing, and also facilitates layout design on spaceborne platforms.

[0082] According to array antenna theory, to avoid grating lobes during beam scanning, the spacing d between adjacent circularly polarized antenna elements should satisfy: d < / (1+sinθ) is used to avoid generating grating lobes during beam scanning, where Here, θ represents the wavelength corresponding to the highest frequency point, and θ is the beam scanning angle. Therefore, the element spacing is set to 0.5. ~0.55 ( The highest frequency wavelength is used to ensure that the satellite phased array antenna will not generate grating lobes at the highest frequency and maximum scanning angle (±55°). The appearance of grating lobes will disperse some of the radiated energy to undesirable directions, which will not only reduce the main lobe gain, but may also cause interference from neighboring satellites or ground multipath interference. The reason for using the highest frequency wavelength as the normalization reference is that the conditions for grating lobe generation are the most stringent at the highest frequency (the high frequency wavelength is the shortest, and the electrical size is the largest at the highest frequency for the same physical spacing, making it easier to meet the conditions for grating lobe generation). As long as grating lobes are not generated at the highest frequency, all lower frequency points can meet the grating lobe-free condition.

[0083] 0.5 ~0.55 It is set based on the highest frequency point, but for the low frequency band (e.g., 1.45GHz in the operating frequency band of 1.45GHz~2.25GHz), the electrical size corresponding to this spacing is only about 0.32λ~0.35λ. Through the coupling suppression design of the annular metal strip 40 (reducing the radiation aperture to 0.32λ1~0.36λ1, matching the reduction of the spacing), the physical electromagnetic boundary between the units is increased under the same compact spacing, and the mutual coupling in the low frequency band can be effectively suppressed, achieving the dual goal of "reducing grid lobes at high frequencies and reducing mutual coupling at low frequencies".

[0084] In this embodiment, 64 circularly polarized antenna elements were arranged in an 8×8 rectangular array for array testing. The spacing between the elements was 0.5 times the wavelength corresponding to the highest frequency point (2.25 GHz). ~0.55 The configuration includes the beam scanning direction of the spaceborne phased array antennas at low frequency (1.5 GHz) and high frequency (2.2 GHz) from 0° to 55°, as well as the active VSWR at 0° and 55° scanning angles, as shown below: Reference Figure 11 As shown, Figure 11 The image shows the beam pattern of the spaceborne phased array antenna in this disclosure at a frequency of 1.5 GHz and a beam angle of 0° to 55°. At the low frequency of 1.5 GHz, the main lobe of the satellite phased array antenna is clear and the side lobe level is low within the scanning range of 0° to 55°. No grating lobes appear, and the gain decreases slowly during beam scanning. This indicates that the annular metal strip 40 set in this disclosure has a significant mutual coupling suppression effect in the low frequency band. As a result, even with a small spacing set according to the highest frequency point (corresponding to only about 0.32λ to 0.35λ in the low frequency band), the radiation performance in the low frequency band is not deteriorated due to the small element spacing.

[0085] Reference Figure 12 As shown, Figure 12 The image shows the beam pattern of the spaceborne phased array antenna in this disclosure at a frequency of 2.2 GHz, spanning from 0° to 55°. At the high frequency of 2.2 GHz, the main lobe of this array-arranged spaceborne phased array antenna is clear, the sidelobe level is low, and no grating lobes appear within the 0° to 55° scanning range, indicating good pattern performance. This demonstrates that the element spacing in this disclosure is set to 0.5 at the highest frequency. ~0.55 The design principles can effectively prevent the generation of grid lobes.

[0086] Reference Figure 13 As shown, Figure 13 The diagram shows the active standing wave ratio (VSWR) curves of the spaceborne phased array antenna in this disclosure under 0° and 55° beam scanning. Regardless of whether it is scanning at 0° or 55°, the VSWR of the array is less than 3.5 in the entire target operating frequency band. This indicates that the circularly polarized antenna elements of the array still maintain a good impedance matching state during wide-angle scanning, and the mutual coupling effect is effectively suppressed. This demonstrates that this disclosure has good impedance stability in the ±55° wide-angle scanning range.

[0087] This disclosure uses specific terms to describe embodiments of the present disclosure. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the present disclosure. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the present disclosure can be appropriately combined.

[0088] In the context of this disclosure, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" do not specifically refer to the singular and may also include the plural. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of expressly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0089] In this disclosure, "multiple" refers to two or more, and other quantifiers are similar. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. The singular forms "a," "," and "the" are also intended to include the plural forms unless the context clearly indicates otherwise.

[0090] In this disclosure, terms such as "first" and "second" are used to describe various types of information, but this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another and do not indicate a specific order or degree of importance. In fact, expressions such as "first" and "second" are completely interchangeable. For example, without departing from the scope of this disclosure, first information can also be referred to as second information, and similarly, second information can also be referred to as first information.

[0091] In this disclosure, the orientations or positional relationships indicated by terms such as "center," "longitudinal," "lateral," "front," "rear," "upper," "lower," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the purpose of facilitating the description of this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation.

[0092] In this disclosure, terms such as "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral molding; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between the two components; they can refer to a direct connection between two components without the presence of other components, or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0093] Similarly, it should be noted that, in order to simplify the description of this disclosure and thus aid in the understanding of one or more embodiments, the foregoing description of embodiments of this disclosure may sometimes combine multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of this disclosure requires more features than the features claimed. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0094] The basic concepts have been described above. It is obvious that the above disclosure is merely illustrative and does not constitute a limitation of this disclosure. Although not explicitly stated herein, various modifications, improvements, and corrections may be made to this disclosure by those skilled in the art. Such modifications, improvements, and corrections are suggested in this disclosure and therefore remain within the spirit and scope of the embodiments of this disclosure.

Claims

1. A circularly polarized antenna element, characterized in that, The circularly polarized antenna element includes: A power divider network is used to output two unbalanced signals with equal amplitude and a 90-degree phase difference. An orthogonal power conversion structure is disposed above the power divider network and electrically connected to the power divider network, and is used to convert the unbalanced signal output by the power divider network into a balanced signal. A radiating unit is disposed above the orthogonal feed conversion structure, including a first dielectric substrate and four radiating arms disposed on the upper surface of the first dielectric substrate. The four radiating arms are orthogonally symmetrically distributed in a cross shape and are all electrically connected to the orthogonal feed conversion structure. An annular metal strip is disposed on the first dielectric substrate and located on the periphery of the four radiating arms.

2. The circularly polarized antenna element according to claim 1, characterized in that, The circumference and / or width of the annular metal strip are configured such that the radiating aperture of the radiating element is reduced to 0.

32. ~0.36 ,in, The wavelength corresponds to the center frequency of the operating frequency band of the circularly polarized antenna element.

3. The circularly polarized antenna element according to claim 1, characterized in that, The inner circumference of the annular metal strip is 160mm-200mm, and it is configured to adjust the frequency point of the parasitic resonance of the annular metal strip.

4. The circularly polarized antenna element according to claim 1, characterized in that, The width of the annular metal strip is 1mm-3mm, and it is configured to adjust the coupling coefficient between the annular metal strip and the radiating element.

5. The circularly polarized antenna element according to claim 4, characterized in that, The annular metal strip has a uniform width structure in the extending direction.

6. The circularly polarized antenna element according to claim 1, characterized in that, The annular metal strip includes: A first annular sub-metal strip is disposed on the upper surface of the first dielectric substrate; and / or, The second annular sub-metal strip is disposed on the lower surface of the first dielectric substrate.

7. The circularly polarized antenna element according to claim 1, characterized in that, The power divider feeder network is a Wilkinson power divider structure, which has an isolation resistor between the two output branches.

8. The circularly polarized antenna element according to claim 7, characterized in that, The circularly polarized antenna element further includes: A metal shield is disposed above the isolation resistor and connected to the substrate of the Wilkinson power divider structure.

9. The circularly polarized antenna element according to claim 1, characterized in that, The orthogonal power supply conversion structure includes a pair of orthogonally arranged second dielectric substrates. Each second dielectric substrate has a microstrip transmission line and a wedge-shaped ground plane etched on its surface. The two ends of the microstrip transmission line are electrically connected to the power divider network and the radiating unit, respectively. The wedge-shaped ground plane is arranged with a gradually changing width along the longitudinal direction of the second dielectric substrate to achieve impedance matching and balanced signal conversion in a wide frequency band.

10. The circularly polarized antenna element according to claim 1, characterized in that, The circularly polarized antenna element further includes a cavity, which is cylindrical in shape. The cavity includes: The base plate is located below the power distribution feeder network; The sidewalls and bottom are connected to the periphery of the base plate and extend upward along the periphery of the base plate, and are disposed on the outside of the power distribution feed network, the orthogonal feed conversion structure and the radiation unit.

11. The circularly polarized antenna element according to claim 10, characterized in that, The circularly polarized antenna element further includes: The radome, located on the top of the sidewall, together with the cavity, forms a closed space to accommodate the power divider feed network, the orthogonal feed conversion structure, and the radiating element.

12. The circularly polarized antenna element according to claim 1, characterized in that, The circularly polarized antenna element further includes: A support member is disposed around the orthogonal feed conversion structure. The bottom end of the support member is connected to the cavity, and the top end is connected to the antenna cover.

13. A spaceborne phased array antenna, characterized in that, The spaceborne phased array antenna includes a plurality of circularly polarized antenna elements as described in any one of claims 1-12, and the plurality of circularly polarized antenna elements are arrayed together to radiate together.

14. The spaceborne phased array antenna according to claim 10, characterized in that, The multiple circularly polarized antenna elements are arranged in a rectangular array, with a spacing of 0.5 units between adjacent circularly polarized antenna elements. ~0.55 ,in, The wavelength is the wavelength corresponding to the highest frequency point in the operating frequency band of the circularly polarized antenna element.

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