A high-gain broadband circularly polarized antenna based on coplanar waveguide

Abstract

This invention provides a high-gain broadband circularly polarized antenna based on a coplanar waveguide, comprising a dielectric substrate, a metallic radiating structure, and a coaxial feed structure. The dielectric substrate is generally rectangular. The metallic radiating structure includes a rectangular metal patch covering the upper surface of the dielectric substrate, an irregularly shaped groove etched on the rectangular metal patch, and a C-shaped coupling stub printed within the irregularly shaped groove. The coaxial feed structure includes a feed microstrip line printed within the irregularly shaped groove and a coaxial line connected to the feed microstrip line. The C-shaped coupling stub is printed inside the chamfered rectangular groove. This invention, through its low-loss, highly integrated structure, achieves simultaneous expansion of impedance bandwidth and axial ratio bandwidth, significantly improving the versatility of the unit antenna and the reliability of the communication link, and has broad application prospects in multi-band wireless communication, the Internet of Things, and satellite communication.

Description

Technical Field

[0001] This invention relates to the field of communication antennas, and more specifically to a high-gain broadband circularly polarized antenna based on a coplanar waveguide. Background Technology

[0002] As wireless communication technology rapidly evolves towards multi-band, wide-bandwidth, miniaturization, and high integration, systems such as satellite communication, 5G / 6G mobile communication, the Internet of Things, and high-precision navigation and positioning place stringent demands on the polarization characteristics, bandwidth performance, profile height, and engineering adaptability of antennas. Circularly polarized antennas, capable of receiving electromagnetic waves in any polarization direction and effectively suppressing multipath fading and Faraday rotation effects, have become a core component in wireless communication systems.

[0003] Although existing technologies have made many breakthroughs in the design and implementation of broadband circularly polarized antennas, various technical solutions for existing broadband circularly polarized antennas suffer from performance and structural imbalances. Either the core advantages of low profile and easy integration are sacrificed to achieve broadband characteristics, or the bandwidth performance and polarization purity of the antenna are compromised in order to simplify the structure. Furthermore, some solutions have excessively high requirements for processing technology and material parameters, making it difficult to ensure consistency in mass production, which also limits their large-scale engineering applications and industrialization.

[0004] For example, Chinese invention patent CN107394381B provides a low-profile broadband circularly polarized array antenna using stacked traveling wave antenna elements. Although it achieves broadband circularly polarized radiation and high gain characteristics in the millimeter-wave band, the overall structure is a complex structure of multi-layer dielectric boards stacked together. It requires high-precision PCB bonding technology for processing, which not only makes the processing process cumbersome and the manufacturing cost high, but also makes the overall size of the antenna too large. It is difficult to adapt to the application requirements of miniaturization of elements in the microwave band, and the versatility of the technical solution is limited.

[0005] For example, the broadband circularly polarized dipole antenna and wireless communication device disclosed in Chinese invention patent CN116505254B achieves a wide axial ratio bandwidth through the coupling design of radiating arm stubs and parasitic patches. However, its three-dimensional structure composed of multiple dielectric substrates results in a high profile, which cannot meet the integration requirements of modern wireless communication systems for planar antennas and low profiles. In addition, its axial ratio bandwidth is much narrower than its impedance bandwidth, causing the impedance bandwidth and axial ratio bandwidth to mutually restrict each other, making it difficult to achieve synchronous matching of dual broadband bandwidths.

[0006] It is evident that existing broadband circularly polarized antennas still have significant room for improvement in terms of simultaneously expanding impedance bandwidth and axial ratio, and balancing low loss with high integration. Summary of the Invention

[0007] The purpose of this invention is to address the problems existing in the prior art by providing a high-gain broadband circularly polarized antenna based on a coplanar waveguide, which achieves simultaneous expansion of impedance bandwidth and axial ratio bandwidth through a low-loss, highly integrated structure.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A high-gain broadband circularly polarized antenna based on a coplanar waveguide includes a dielectric substrate, a metallic radiating structure, and a coaxial feeding structure.

[0010] The dielectric substrate is rectangular in shape. The metal radiation structure includes a rectangular metal patch covering the upper surface of the dielectric substrate, an irregular groove etched on the rectangular metal patch, and a C-shaped coupling branch printed in the irregular groove. The coaxial feeding structure includes a feeding microstrip line printed in the irregular groove and a coaxial line connected to the feeding microstrip line.

[0011] In the metallic radiating structure, the irregularly shaped slot includes a first rectangular slot, a second rectangular slot, and a chamfered rectangular slot that are interconnected as a single unit. The first rectangular slot is located in the middle of the rectangular metal patch and extends along the Y-axis. The second rectangular slot and the chamfered rectangular slot both extend along the X-axis. The end of the second rectangular slot facing the negative X-axis direction is connected to the first rectangular slot, and the end of the chamfered rectangular slot facing the positive X-axis direction is connected to the first rectangular slot. The corners of the chamfered rectangular slot facing the negative X-axis direction and the positive Y-axis direction are chamfered. The chamfer is used to change the current distribution path on the antenna surface, regulate the antenna resonance characteristics, and provide a phase basis for circularly polarized radiation. The C-shaped coupling stub is printed inside the chamfered rectangular slot and is located on the side of the feed microstrip line facing the negative X-axis direction. It is used to regulate the current on the antenna surface through the load effect, suppress the fluctuation of the impedance and axial ratio curves, and achieve synergistic optimization of impedance bandwidth and axial ratio bandwidth.

[0012] In the coaxial feeding structure, the feeding microstrip line is printed inside the first rectangular slot and extends along the Y-axis to form a coplanar waveguide feeding structure with the first rectangular slot; the coaxial line is introduced from the end of the first rectangular slot facing the negative Y-axis, the outer conductor of the coaxial line is electrically connected to the rectangular metal patch, and the inner conductor of the coaxial line is electrically connected to the end of the feeding microstrip line facing the negative Y-axis.

[0013] Furthermore, the C-shaped coupling stub includes a first microstrip line, a second microstrip line, and a third microstrip line connected in sequence. The first and third microstrip lines extend along the Y-axis, and the second microstrip line extends along the X-axis. The two ends of the second microstrip line are respectively connected to the ends of the first and third microstrip lines facing the positive Y-axis, so that the three microstrip lines are connected as a whole in a C-shape.

[0014] Furthermore, the metal radiation structure also includes a fourth rectangular groove, a fifth rectangular groove, and a sixth rectangular groove etched on a rectangular metal patch. The fourth rectangular groove, the fifth rectangular groove, and the sixth rectangular groove all extend along the Y-axis direction and are connected to the irregular groove as a whole.

[0015] Among them, the end of the fourth rectangular slot facing the negative Y-axis is perpendicularly connected to the side of the chamfered rectangular slot facing the positive Y-axis, which is used to work in conjunction with the chamfer of the chamfered rectangular slot to introduce additional resonant modes and extend the impedance bandwidth in the low frequency band.

[0016] The end of the fifth rectangular slot facing the negative Y-axis is perpendicularly connected to the end of the second rectangular slot facing the positive X-axis, which is used to adjust the antenna surface current phase and improve the circular polarization axial ratio performance.

[0017] The end of the sixth rectangular slot facing the positive Y-axis is perpendicularly connected to the side of the chamfered rectangular slot facing the negative Y-axis. This is used to optimize impedance matching in the low-frequency band and further extend the low-frequency operating bandwidth.

[0018] Furthermore, the metal radiating structure also includes a first L-shaped groove and a second L-shaped groove etched on a rectangular metal patch. The first L-shaped groove, the second L-shaped groove, and the irregular groove are not connected to each other. The first L-shaped groove and the second L-shaped groove are asymmetrically distributed. The first L-shaped groove is located outside the negative X-axis direction of the irregular groove to introduce additional resonant modes, enhance electromagnetic coupling between multiple modes, and expand the axial ratio bandwidth of the antenna. The second L-shaped groove is located outside the positive X-axis direction of the irregular groove to work with the first L-shaped groove to expand the impedance bandwidth and circular polarization operating frequency band of the antenna.

[0019] Furthermore, the first L-shaped groove includes a seventh rectangular groove and an eighth rectangular groove that are perpendicularly connected to each other. The seventh rectangular groove extends along the X-axis direction, and the eighth rectangular groove extends along the Y-axis direction. The end of the seventh rectangular groove facing the negative X-axis direction is perpendicularly connected to the end of the eighth rectangular groove facing the positive Y-axis direction.

[0020] Furthermore, the second L-shaped groove includes a ninth rectangular groove and a tenth rectangular groove that are perpendicularly connected to each other. The ninth rectangular groove extends along the X-axis direction, and the tenth rectangular groove extends along the Y-axis direction. The end of the ninth rectangular groove facing the positive X-axis direction is perpendicularly connected to the end of the tenth rectangular groove facing the negative Y-axis direction.

[0021] Furthermore, the coaxial line is a 50Ω coaxial line, and the feed microstrip line is a 50Ω coplanar waveguide feed line.

[0022] This invention achieves simultaneous expansion of impedance bandwidth and axial ratio bandwidth while ensuring stable circular polarization radiation characteristics over a wide bandwidth, significantly improving the versatility of the unit antenna and the reliability of the communication link. It has broad application prospects in multi-band wireless communication, Internet of Things, satellite communication and other fields.

[0023] Meanwhile, this invention achieves low profile and miniaturization of the antenna through a simple integrated planar structure, perfectly adapting to the development trend of miniaturization, high integration, and lightweight in modern wireless communication terminals, and is easy to conformally integrate with RF circuits. Furthermore, thanks to the single-layer dielectric structure and simple feeding path, this invention does not introduce complex feeding networks or multi-layer dielectric interfaces, reducing dielectric loss and reflection loss during electromagnetic signal transmission, and achieving low-loss, high-matching feeding performance. Attached Figure Description

[0024] Figure 1 This is a top view of a high-gain broadband circularly polarized antenna based on a coplanar waveguide, provided in an embodiment of the present invention.

[0025] Figure 2 This is a side view of a high-gain broadband circularly polarized antenna based on a coplanar waveguide, provided in an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of antenna A as a comparative example.

[0027] Figure 4 This is a schematic diagram of antenna B as a comparative example.

[0028] Figure 5 This is a schematic diagram of antenna C as a comparative example.

[0029] Figure 6 This is a comparison diagram of the reflection coefficients of antenna A, antenna ratio B, antenna C, and the embodiment of the present invention.

[0030] Figure 7 This is a comparison chart of antenna A, antenna ratio B, antenna C and the simulated axial ratio of the embodiment of the present invention.

[0031] Figure 8 This is a simulated reflection coefficient curve of an embodiment of the present invention.

[0032] Figure 9 This is a simulation axis ratio curve diagram of an embodiment of the present invention.

[0033] Figure 10 This is a simulated radiation efficiency curve of an embodiment of the present invention.

[0034] Figure 11 This is a simulation gain curve diagram of an embodiment of the present invention.

[0035] Figure 12 This is the radiation pattern at the center frequency of 2.8 GHz in an embodiment of the present invention. Detailed Implementation

[0036] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 and Figure 2 As shown in the figure, an embodiment of the present invention provides a high-gain broadband circularly polarized antenna based on a coplanar waveguide, comprising a dielectric substrate 10, a metallic radiating structure, and a coaxial feeding structure.

[0038] The dielectric substrate 10 is generally rectangular; the metal radiation structure includes a rectangular metal patch 1 covering the upper surface of the dielectric substrate 10, an irregular groove 2 etched on the rectangular metal patch 1, and a C-shaped coupling branch 5 printed in the irregular groove 2; the coaxial feeding structure includes a feeding microstrip line 3 printed in the irregular groove 2 and a coaxial line 4 connected to the feeding microstrip line 3.

[0039] Specifically, such as Figure 1 As shown, in the metal radiation structure, the irregular groove 2 includes a first rectangular groove 21, a second rectangular groove 22, and a chamfered rectangular groove 23 that are interconnected. The first rectangular groove 21 is located in the middle of the rectangular metal patch 1 and extends along the axis in the Y-axis direction. The second rectangular groove 22 and the chamfered rectangular groove 23 both extend along the X-axis direction. The end of the second rectangular groove 22 facing the negative X-axis direction is connected to the first rectangular groove 21, and the end of the chamfered rectangular groove 23 facing the positive X-axis direction is connected to the first rectangular groove 21. The corners of the chamfered rectangular groove 23 facing the negative X-axis direction and the positive Y-axis direction are provided with a 45° chamfer 230. The chamfer 230 is used to change the current distribution path on the antenna surface, adjust the antenna resonance characteristics, and provide a phase basis for circularly polarized radiation.

[0040] The C-shaped coupling stub 5 is printed inside a chamfered rectangular slot and is used to finely control the antenna surface current through the load effect, suppress fluctuations in the impedance and axial ratio curves, and achieve synergistic optimization of impedance bandwidth and axial ratio bandwidth. Specifically, the C-shaped coupling stub 5 includes a first microstrip line, a second microstrip line, and a third microstrip line connected in sequence. The first and third microstrip lines extend along the Y-axis, and the second microstrip line extends along the X-axis. The two ends of the second microstrip line are respectively connected to the ends of the first and third microstrip lines facing the positive Y-axis, so that the three microstrip lines are connected as a whole in a C-shape.

[0041] Furthermore, the metal radiation structure also includes a fourth rectangular groove 51, a fifth rectangular groove 52 and a sixth rectangular groove 53 etched on the rectangular metal patch 1. The fourth rectangular groove 51, the fifth rectangular groove 52 and the sixth rectangular groove 53 all extend along the Y-axis direction and are connected to the irregular groove 2 as a whole.

[0042] Among them, the end of the fourth rectangular slot 51 facing the negative Y-axis is vertically connected to the side of the chamfered rectangular slot 23 facing the positive Y-axis, which is used to work in conjunction with the chamfered corner 230 of the chamfered rectangular slot 23 to introduce additional resonant modes and extend the low-frequency impedance bandwidth.

[0043] The end of the fifth rectangular slot 52 facing the negative Y-axis is perpendicularly connected to the end of the second rectangular slot 22 facing the positive X-axis, which is used to adjust the antenna surface current phase and improve the circular polarization axial ratio performance.

[0044] The end of the sixth rectangular slot 53 facing the positive Y-axis is vertically connected to the side of the chamfered rectangular slot 23 facing the negative Y-axis, which is used to optimize impedance matching in the low-frequency band and further extend the low-frequency operating bandwidth.

[0045] Furthermore, the metal radiating structure also includes a first L-shaped groove 61 and a second L-shaped groove 62 etched on the rectangular metal patch 1. The first L-shaped groove 61 and the second L-shaped groove 62 are not connected to the irregular groove 2. The first L-shaped groove 61 and the second L-shaped groove 62 are generally asymmetrically distributed. The first L-shaped groove 61 is located outside the negative X-axis direction of the irregular groove 2 to introduce additional resonant modes, enhance electromagnetic coupling between multiple modes, and expand the axial ratio bandwidth of the antenna. The second L-shaped groove 62 is located outside the positive X-axis direction of the irregular groove to work with the first L-shaped groove 61 to expand the impedance bandwidth and circular polarization operating frequency band of the antenna.

[0046] Specifically, the first L-shaped groove 61 includes a seventh rectangular groove 611 and an eighth rectangular groove 612 that are perpendicularly connected to each other. The seventh rectangular groove 611 extends along the X-axis, and the eighth rectangular groove 612 extends along the Y-axis. The end of the seventh rectangular groove 611 facing the negative X-axis direction is perpendicularly connected to the end of the eighth rectangular groove 612 facing the positive Y-axis direction. The second L-shaped groove 62 includes a ninth rectangular groove 621 and a tenth rectangular groove 622 that are perpendicularly connected to each other. The ninth rectangular groove 621 extends along the X-axis, and the tenth rectangular groove 622 extends along the Y-axis. The end of the ninth rectangular groove 621 facing the positive X-axis direction is perpendicularly connected to the end of the tenth rectangular groove 622 facing the negative Y-axis direction.

[0047] In the coaxial feed structure, the feed microstrip line 3 is printed inside the first rectangular slot 21 and extends along the Y-axis to form a coplanar waveguide feed structure with the first rectangular slot 21. The coaxial line 4 is introduced from the end of the first rectangular slot 21 facing the negative Y-axis. The outer conductor of the coaxial line 4 is electrically connected to the rectangular metal patch 1, and the inner conductor of the coaxial line 4 is electrically connected to the end of the feed microstrip line 3 facing the negative Y-axis. In this embodiment, the coaxial line 4 is a 50Ω coaxial line, and the feed microstrip line 3 is a 50Ω coplanar waveguide feed line. The coaxial line 4 and the feed microstrip line 3 are used to provide radio frequency excitation signals to the irregular slot 2, realizing impedance matching and signal transmission between the antenna and the feed network.

[0048] Combination Figure 2 As shown, the antenna in this embodiment of the invention adopts an integrated planar structure with a single-layer dielectric substrate. Figure 2 The side view diagram clearly shows the antenna's longitudinal cross-sectional structure and feed connection. The 50Ω coaxial line 4 is introduced from the side of the dielectric substrate 10. The inner conductor of the coaxial line 4 is welded to the feed microstrip line 3 for electrical connection, while the outer conductor of the coaxial line 4 is welded to the rectangular metal patch 1 on the upper surface of the dielectric substrate 10, forming a stable 50Ω impedance-matched feed path. Regarding the feed structure, this embodiment arranges the 50Ω feed microstrip line 3 on the central axis of the irregular slot 2, forming a coplanar waveguide feed structure with the first rectangular slot 21. This coplanar waveguide feed structure not only achieves good impedance matching characteristics but also significantly reduces radiation loss due to the coplanar arrangement of the signal lines and ground layer, facilitating monolithic integration with the front-end RF circuitry.

[0049] To verify the technical effect of this embodiment, three comparative examples are provided below for illustration: antenna A, antenna B, and antenna C. It should be noted that the structures of antennas B and C are not prior art. Antennas A, B, and C are provided here for comparison only to demonstrate the design process and optimization ideas of this invention, so as to better understand the technical effect of this invention.

[0050] like Figure 3 As shown, antenna A is a traditional patch antenna fed by a coplanar waveguide. Its structure is simple, mainly composed of slots and a feeding microstrip line. The slot in antenna A consists of three interconnected rectangular slots. Compared to the irregular slot 2 in this embodiment, the chamfered corner 230° has been removed. Furthermore, antenna A does not contain the C-shaped coupling stub 5, the fourth rectangular slot 51, the fifth rectangular slot 52, the sixth rectangular slot 53, the first L-shaped slot 61, and the second L-shaped slot 62 found in this embodiment. Figure 6It is evident that antenna A exhibits three resonant points at approximately 2.40 GHz, 3.00 GHz, and 4.50 GHz, respectively, only meeting the -10 dB impedance matching requirement within a limited narrow frequency band, indicating a severely inadequate broadband adaptability. Furthermore, due to... Figure 7 It is evident that antenna A only meets the 3dB axial ratio requirement within an extremely narrow frequency band. The 3dB axial ratio bandwidth is less than 10%, resulting in extremely poor circular polarization performance. It can only achieve circular polarization radiation near a single frequency point, which cannot meet the application requirements of broadband circular polarization.

[0051] like Figure 4 As shown, to improve the impedance matching characteristics of antenna A and extend the circular polarization bandwidth, antenna B introduces three additional rectangular slots and chamfered structures based on antenna A. The chamfered structures can change the current distribution path on the antenna surface, providing a phase basis for circular polarization radiation. Compared with the embodiment of the present invention, antenna B lacks the C-shaped coupling stub 5, the first L-shaped slot 61, and the second L-shaped slot 62. Figure 6 As can be seen, after structural optimization, the impedance bandwidth of antenna B extends to lower frequencies, and the resonant point shifts to lower frequencies, achieving good impedance matching in the approximately 1.85-4.53 GHz frequency band. However, its low-frequency matching stability is insufficient, and Si in some frequency bands... 11 The curve still exhibits significant fluctuations. Meanwhile, due to... Figure 7 It is evident that antenna B, through structural optimization, added a circular polarization resonant mode and initially expanded the axial ratio bandwidth. However, the axial ratio deteriorated rapidly in the high-frequency band, and the 3dB axial ratio bandwidth only covered 1.8-3.0GHz. Its high-frequency circular polarization performance failed, and it still could not achieve continuous broadband circular polarization.

[0052] like Figure 5 As shown, to further extend the antenna's impedance bandwidth and circular polarization operating frequency band, antenna C incorporates two asymmetrically distributed L-shaped slots on top of antenna B. These two L-shaped slots can introduce additional resonant modes, enhancing electromagnetic coupling between multiple modes and contributing to further extending the antenna's operating bandwidth. Compared to the embodiment of this invention, antenna C only lacks the C-shaped coupling stub 5. Figure 6 As can be seen, compared with antenna B, antenna C's impedance bandwidth extends further into lower frequencies, resulting in an overall improvement in full-band matching performance. However, significant fluctuations in impedance matching occur in the approximately 3.50-3.90 GHz band, indicating that high-frequency matching stability remains lacking. Meanwhile, due to... Figure 7 It is evident that although the axial ratio bandwidth of antenna C has been further broadened, the axial ratio exceeds the standard above 3.5 GHz, the circular polarization operating frequency band is discontinuous, the axial ratio curve has obvious fluctuations, and the circular polarization stability across the entire frequency band is insufficient, which still cannot meet the application requirements of high-performance broadband circular polarization antennas.

[0053] To address the technical problems of insufficient bandwidth and poor circular polarization stability in the aforementioned antennas, this invention adds a C-shaped coupling stub 5 to the antenna C, achieving final optimization of the antenna structure. By finely controlling the surface current of the antenna through the load effect of the C-shaped coupling stub 5, fluctuations in the impedance-axial ratio curves can be suppressed, achieving synergistic optimization of impedance bandwidth and axial ratio bandwidth. Figure 6 As can be seen, the antenna of this embodiment achieves continuous and stable -10dB impedance matching in the approximately 1.71-4.16GHz frequency band, with a relative impedance bandwidth as high as 91.4%. Its broadband impedance matching performance is significantly better than the previous three antenna structures. Furthermore, this embodiment exhibits a large resonance depth, stable matching, and no significant fluctuations. Meanwhile, due to… Figure 7 As can be seen, the embodiments of the present invention achieve an axial ratio of less than 3dB across the entire frequency band of approximately 1.73-3.93GHz, with a relative axial ratio bandwidth of 73.9%. Its circular polarization performance is continuous, stable, and flat, and its overall circular polarization performance is significantly superior to that of antennas A, B, and C. Therefore, the embodiments of the present invention can effectively suppress multipath interference and polarization mismatch loss, and can effectively meet the broadband circular polarization application requirements of multi-band wireless communication systems.

[0054] Figures 8 to 12 The various performance indicators of the embodiments of the present invention are shown.

[0055] Specifically, Figure 8 This is a simulated reflection coefficient curve of an embodiment of the present invention. The horizontal axis represents the operating frequency, ranging from 1.5 GHz to 4.5 GHz, and the vertical axis represents the reflection coefficient S11, in dB. In engineering, -10 dB is typically used as the threshold standard for impedance matching. As shown in the figure, the antenna of the present invention achieves a reflection coefficient S11 below -10 dB across the entire operating frequency band from 1.6 GHz to 4.3 GHz, realizing excellent impedance matching in ultra-wideband applications. Specifically, the antenna forms two deep resonant points near 1.8 GHz and 4.0 GHz, with minimum return losses better than -20 dB in both cases. Furthermore, the curves across the entire frequency band are smooth with no obvious sharp dips, demonstrating the excellent design matching between the coplanar waveguide feeding structure and the irregular slot radiation structure in this embodiment of the present invention.

[0056] Figure 9 This is a simulation axial ratio curve of an embodiment of the present invention. The horizontal axis represents the operating frequency, and the vertical axis represents the axial ratio, in dB. The 3dB dashed line represents the engineering threshold for circular polarization radiation. As shown in the figure, the axial ratio of the antenna is below 3dB in the 1.8GHz to 3.9GHz frequency band, achieving excellent broadband circular polarization radiation characteristics. This indicates that by loading an L-shaped slot and a C-shaped coupling stub structure, the current distribution on the antenna surface is effectively controlled, generating orthogonal and equal-amplitude field components, ensuring stable circular polarization performance over a wide frequency range, and effectively suppressing multipath interference and polarization loss.

[0057] Figure 10 This is a simulated radiation efficiency curve of an embodiment of the present invention. The horizontal axis represents the operating frequency, and the vertical axis represents the radiation efficiency, in percentage (%). As shown in the figure, the antenna's radiation efficiency remains above 80% throughout the operating frequency band from 1.8 GHz to 4.2 GHz, and is stably maintained at a high level of 85% to 95% in the core frequency band from 2.0 GHz to 4.0 GHz, with a peak efficiency approaching 95%. This excellent radiation efficiency confirms that the antenna structure of this embodiment has low loss, extremely high energy conversion efficiency between the feed and radiating elements, and possesses excellent energy transmission and radiation capabilities.

[0058] Figure 11 This is a simulation gain curve of an embodiment of the present invention. The horizontal axis represents the operating frequency, and the vertical axis represents the gain, in dB. As shown in the figure, the antenna gain remains consistently above 3 dBi within the operating frequency band of 1.8 GHz to 4.2 GHz, reaching a peak value (approximately 4.5 dBi) near the center frequency point of 2.5 GHz to 3.0 GHz. It then decreases slightly at higher frequencies but remains above 3.5 dBi. This stable high-gain characteristic indicates that the embodiment of the present invention possesses excellent signal focusing capability over a wide frequency range, effectively improving the signal coverage and transmission quality of the wireless link.

[0059] Figure 12 The figure shows the radiation pattern of this embodiment of the invention at a center frequency of 2.8 GHz. As can be seen from the figure, the radiation pattern of this embodiment at this frequency is symmetrical and full, with the main radiation direction concentrated in the antenna normal (0° direction), exhibiting good directional radiation characteristics. Simultaneously, the radiation patterns in the XOZ and YOZ planes show good consistency, with an excellent front-to-back radiation ratio and low sidelobe levels. This indicates that this embodiment of the invention achieves high energy concentration efficiency within the core operating frequency band, with no significant energy waste, and possesses excellent wireless communication coverage performance.

[0060] In summary, the embodiments of the present invention achieve S in the 1.8~4.2GHz frequency band. 11 With an impedance matching of <-10dB and a relative impedance bandwidth of 80%, this invention achieves an axial ratio of less than 3dB within the 2.2~3.8GHz frequency band, resulting in a relative axial ratio bandwidth of approximately 53.3%. Furthermore, the embodiment of this invention maintains a stable radiation efficiency of 80%~95% within the core operating frequency band, with a gain maintained at 3.5~4.5dBi, demonstrating excellent radiation performance. Therefore, this invention, while simultaneously expanding impedance bandwidth and axial ratio bandwidth, ensures stable circularly polarized radiation characteristics over a wide bandwidth, significantly improving the versatility of the unit antenna and the reliability of communication links. It has broad application prospects in multi-band wireless communication, the Internet of Things, and satellite communication.

[0061] Compared with existing technologies, this invention achieves a significant and simultaneous expansion of the impedance bandwidth and axial ratio bandwidth of the unit antenna by co-integrating a composite slot structure—comprising an irregularly shaped slot, a C-shaped coupling stub, two asymmetrical L-shaped slots, and three rectangular slots—on the metal ground plane of a single-layer dielectric substrate, combined with a 50Ω coaxial feed layout. This solves the technical bottleneck of the mutual constraint between impedance bandwidth and axial ratio bandwidth in traditional unit circularly polarized antennas. Specifically, the irregularly shaped slot and the C-shaped coupling stub excite orthogonal degenerate modes through coupling, effectively expanding the axial ratio bandwidth while ensuring stable circular polarization radiation. The coordinated design of the two asymmetrical L-shaped slots and the three rectangular slots introduces multiple resonant modes, significantly broadening the antenna's impedance bandwidth while maintaining its electromagnetic symmetry.

[0062] This invention employs an integrated planar structure with a single-layer dielectric substrate, no metal ground layer on the back, and 50Ω coaxial direct feeding. The dielectric substrate thickness is only 0.8 mm, achieving an ultra-low profile antenna design. Compared to the complex multi-layer stacked arrays or three-dimensional dipole antennas in existing technologies, this invention has no multi-layer stacking, no metallized vias, and no additional support structures. This structural design not only achieves a low profile and miniaturization of the antenna but also significantly reduces processing costs and assembly difficulty. It perfectly adapts to the development trend of miniaturization, high integration, and lightweighting in modern wireless communication terminals and is easy to conformally integrate with RF circuits.

[0063] Thanks to its single-layer dielectric structure and simple feeding path, this invention avoids complex feeding networks or multi-layer dielectric interfaces, reducing dielectric loss and reflection loss during electromagnetic signal transmission and achieving low-loss, high-matching feeding performance. The antenna maintains a stable radiation efficiency of 80%–95% within its core operating frequency band of 2.0–4.0 GHz, with a peak efficiency of approximately 94%, ensuring efficient signal transmission and energy utilization over a wide bandwidth, significantly outperforming some complex traditional antennas.

[0064] Meanwhile, the antenna of this invention exhibits excellent gain performance across the entire operating frequency band, maintaining a gain of 3.5~4.5 dBi in the core circularly polarized frequency band, with a peak gain reaching 4.6 dBi. Radiation pattern tests show that the antenna maintains good omnidirectional and directional radiation characteristics at key frequency points such as 1.8GHz, 2.8GHz, and 3.8GHz. The main lobe of this invention features concentrated energy, low sidelobe levels, and an excellent front-to-back radiation ratio, effectively covering the target communication area and meeting the application requirements of multi-band wireless communication systems for high-gain and low-interference antennas. Furthermore, this invention involves only single-layer metal etching and simple coaxial mounting, requiring low-precision PCB processing technology, eliminating the need for high-precision bonding processes and complex assembly procedures, and exhibiting high tolerance for substrate parameters. This structural design significantly reduces the process threshold and manufacturing cost for mass production, effectively ensuring product mass production consistency and large-scale engineering application prospects, perfectly solving the pain point of excessively high process requirements in existing technologies.

[0065] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A high-gain broadband circularly polarized antenna based on a coplanar waveguide, characterized in that, This includes dielectric substrates, metal radiating structures, and coaxial feed structures; The dielectric substrate is rectangular in shape. The metal radiation structure includes a rectangular metal patch covering the upper surface of the dielectric substrate, an irregular groove etched on the rectangular metal patch, and a C-shaped coupling branch printed in the irregular groove. The coaxial feeding structure includes a feeding microstrip line printed in the irregular groove and a coaxial line connected to the feeding microstrip line. In the metallic radiating structure, the irregularly shaped slot includes a first rectangular slot, a second rectangular slot, and a chamfered rectangular slot that are interconnected as a single unit. The first rectangular slot is located in the middle of the rectangular metal patch and extends along the Y-axis. The second rectangular slot and the chamfered rectangular slot both extend along the X-axis. The end of the second rectangular slot facing the negative X-axis direction is connected to the first rectangular slot, and the end of the chamfered rectangular slot facing the positive X-axis direction is connected to the first rectangular slot. The corners of the chamfered rectangular slot facing the negative X-axis direction and the positive Y-axis direction are chamfered. The chamfer is used to change the current distribution path on the antenna surface, regulate the antenna resonance characteristics, and provide a phase basis for circularly polarized radiation. The C-shaped coupling stub is printed inside the chamfered rectangular slot and is located on the side of the feed microstrip line facing the negative X-axis direction. It is used to regulate the current on the antenna surface through the load effect, suppress the fluctuation of the impedance and axial ratio curves, and achieve synergistic optimization of impedance bandwidth and axial ratio bandwidth. In the coaxial feeding structure, the feeding microstrip line is printed inside the first rectangular slot and extends along the Y-axis to form a coplanar waveguide feeding structure with the first rectangular slot; the coaxial line is introduced from the end of the first rectangular slot facing the negative Y-axis, the outer conductor of the coaxial line is electrically connected to the rectangular metal patch, and the inner conductor of the coaxial line is electrically connected to the end of the feeding microstrip line facing the negative Y-axis.

2. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 1, characterized in that, The C-shaped coupling stub includes a first microstrip line, a second microstrip line, and a third microstrip line connected in sequence. The first and third microstrip lines extend along the Y-axis, and the second microstrip line extends along the X-axis. The two ends of the second microstrip line are respectively connected to the ends of the first and third microstrip lines facing the positive Y-axis, so that the three microstrip lines are connected as a whole in a C-shape.

3. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 2, characterized in that, The metal radiation structure also includes a fourth rectangular groove, a fifth rectangular groove, and a sixth rectangular groove etched on a rectangular metal patch. The fourth rectangular groove, the fifth rectangular groove, and the sixth rectangular groove all extend along the Y-axis and are connected to the irregular groove as a whole. Among them, the end of the fourth rectangular slot facing the negative Y-axis is perpendicularly connected to the side of the chamfered rectangular slot facing the positive Y-axis, which is used to work in conjunction with the chamfer of the chamfered rectangular slot to introduce additional resonant modes and extend the impedance bandwidth in the low frequency band. The end of the fifth rectangular slot facing the negative Y-axis is perpendicularly connected to the end of the second rectangular slot facing the positive X-axis, which is used to adjust the antenna surface current phase and improve the circular polarization axial ratio performance. The end of the sixth rectangular slot facing the positive Y-axis is perpendicularly connected to the side of the chamfered rectangular slot facing the negative Y-axis. This is used to optimize impedance matching in the low-frequency band and further extend the low-frequency operating bandwidth.

4. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 3, characterized in that, The metal radiating structure also includes a first L-shaped groove and a second L-shaped groove etched on a rectangular metal patch. The first L-shaped groove, the second L-shaped groove, and the irregular groove are not connected to each other. The first L-shaped groove and the second L-shaped groove are asymmetrically distributed. The first L-shaped groove is located outside the negative X-axis direction of the irregular groove to introduce additional resonant modes, enhance electromagnetic coupling between multiple modes, and expand the axial ratio bandwidth of the antenna. The second L-shaped groove is located outside the positive X-axis direction of the irregular groove to work with the first L-shaped groove to expand the impedance bandwidth and circular polarization operating frequency band of the antenna.

5. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 4, characterized in that, The first L-shaped groove includes a seventh rectangular groove and an eighth rectangular groove that are perpendicularly connected to each other. The seventh rectangular groove extends along the X-axis direction, and the eighth rectangular groove extends along the Y-axis direction. The end of the seventh rectangular groove facing the negative X-axis direction is perpendicularly connected to the end of the eighth rectangular groove facing the positive Y-axis direction.

6. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 5, characterized in that, The second L-shaped groove includes a ninth rectangular groove and a tenth rectangular groove that are perpendicularly connected to each other. The ninth rectangular groove extends along the X-axis direction, and the tenth rectangular groove extends along the Y-axis direction. The end of the ninth rectangular groove facing the positive X-axis direction is perpendicularly connected to the end of the tenth rectangular groove facing the negative Y-axis direction.

7. The high-gain broadband circularly polarized antenna based on a coplanar waveguide according to claim 1, characterized in that, The coaxial line is a 50Ω coaxial line, and the feed microstrip line is a 50Ω coplanar waveguide feed line.

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