Sub-6G circularly polarized filtering antenna

Abstract

The invention relates to a Sub-6G circularly polarized filtering antenna which sequentially comprises a dielectric substrate I, a metal floor, a coaxial feeder line and a dielectric substrate II from bottom to top, the upper surface of the second dielectric substrate is provided with a first antenna radiation unit and a peripheral conductor frame, and the lower surface is provided with a second antenna radiation unit. The first antenna radiation unit comprises a main radiator, a first parasitic patch, a second parasitic patch and a T-shaped belt. The second antenna radiation unit and the first antenna radiation unit are the same in structure, and the whole second antenna radiation unit rotates by 180 degrees relative to the first antenna radiation unit. According to the invention, the gaps are arranged between the peripheral conductor frames and are combined with the triangular chamfers, so that independent adjustment of low-frequency filtering is realized under the condition that the perimeter of the outer filtering ring is kept unchanged as much as possible. Based on the cooperative coupling resonance effect of the T-shaped band, the parasitic patch I and the parasitic patch II, a high-conduction pass band is formed in a target high-frequency band, a strong-suppression stop band is formed outside the high-frequency band, the pass band gain of filtering is high, the out-of-band suppression ratio is large, and the pass-stop band boundary is clear.

Description

Technical Field

[0001] This invention belongs to the field of antenna technology, and specifically relates to a Sub-6G circularly polarized filter antenna. Background Technology

[0002] Currently, with the increasing demands for miniaturized, broadband, and highly isolated RF front-ends in 5G and future 6G systems, filtering antenna technology has gradually become a research hotspot in Sub-6GHz communication systems. This type of antenna, by introducing filtering units into its radiating structure, can suppress out-of-band signals while achieving antenna radiation functionality, reducing the number of system-level filters and thus achieving high integration, low loss, and compact design. However, existing technologies still have the following shortcomings: Limited bandwidth and reduced polarization purity: Most Sub-6GHz filtering antennas are based on linearly polarized patches or inverted-F structures, with bandwidth generally less than 15%, making it difficult to simultaneously cover multiple 5G or Wi-Fi bands. Introducing circular polarization structures (such as dual-fed or scrambling angles) further reduces the axial bandwidth, making it difficult to balance filtering and circular polarization performance. Severe coupling between filtering and radiation characteristics: Traditional methods often use slots, parasitic loops, or band-stop resonant stubs in radiating patches or feed networks to achieve filtering, but these structures disrupt the symmetry of current distribution, leading to deterioration of circular polarization performance or a decrease in gain. Complex feed structure and difficult fabrication: Some patents use multilayer substrates or substrate integrated waveguides (SIW) to achieve filtering transmission paths. While the filtering effect is good, the structure is complex and has high losses, hindering the mass production of low-cost Sub-6GHz communication terminals. Summary of the Invention

[0003] This invention addresses the problems in the background technology by developing a Sub-6G circularly polarized filter antenna that achieves optimal synergy in impedance matching, circular polarization performance, and high- and low-frequency filtering performance. It not only effectively solves many technical pain points of existing circularly polarized filter antennas but also accurately matches the actual needs of wireless communication systems, demonstrating outstanding technical improvement value and broad application prospects.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A Sub-6G circularly polarized filter antenna comprises, from bottom to top, a dielectric substrate one, a metal ground plane, a coaxial feed line, and a dielectric substrate two. The metal ground plane is printed on the upper surface of the dielectric substrate one and is connected to the dielectric substrate two via the coaxial feed line. The upper surface of the dielectric substrate two is provided with an antenna radiating element one and an outer conductor frame, and the lower surface is provided with an antenna radiating element two. The antenna radiating element one includes a main radiator, a parasitic patch one, a parasitic patch two, and a T-shaped strip. The main radiator includes a phase delay loop located at the center of the dielectric substrate two and two vertical rectangular main radiating arms connecting its ends. One of the rectangular main radiating arms has diagonally cut square parasitic patches one on each side. Parasitic patches 2 are provided at relatively opposite positions. Parasitic patches 2 are patch combination structures formed by connecting a square patch with one corner cut and two rectangular patches. The plane of the cut part is parallel to the plane of the cut part of parasitic patch 1. A pair of T-shaped strips are added to both sides of each main radiating arm. The T-shaped strips maintain a gap with parasitic patches 1 and parasitic patches 2. The antenna radiating element 2 has the same structure as antenna radiating element 1. Its whole is rotated 180° relative to the other rectangular main radiating arm of antenna radiating element 1. The conductor frame is composed of a patch frame composed of four rectangular metal patches and triangular patches. There are gaps between each patch frame. The frame surrounds the antenna radiating elements on the upper and lower surfaces of the dielectric substrate 2.

[0005] Furthermore, both dielectric substrate one and dielectric substrate two are Fr4 substrates.

[0006] Furthermore, the two ends of the coaxial feed line are respectively connected to the center positions of dielectric substrate one and dielectric substrate two.

[0007] Furthermore, the phase delay ring is made of metal.

[0008] Compared with the prior art, the present invention has the following beneficial effects: 1. The circularly polarized filter antenna of the present invention achieves adjustable low-frequency filtering by setting gaps between the outer conductor frames and combining them with triangular chamfers, while keeping the perimeter of the outer filter ring as unchanged as possible, and by adjusting the size of the chamfers individually, without affecting the existing high-frequency filtering performance, circular polarization, and S11.

[0009] 2. The circularly polarized filter antenna of the present invention has excellent high-frequency filtering effect and strong high-frequency selectivity. Relying on the synergistic coupling resonance of the T-band, parasitic patch one and parasitic patch two, a high-conductivity passband is formed in the target high-frequency band, and a strong-suppression stopband is formed outside the high-frequency band. The filtered passband gain is high, the out-of-band rejection ratio is large, and the passband and stopband boundaries are clear.

[0010] 3. This invention eliminates the need for external filtering components, resulting in high integration and compact size: By integrating the filtering function into the antenna's own radiation-assisted structure, it eliminates the need for external filtering circuits / filters in traditional antennas, significantly reducing the overall size and structural complexity of the antenna. This makes it suitable for miniaturized and integrated antenna applications while avoiding signal transmission losses caused by external filtering.

[0011] 4. Precise and controllable structural design with strong adjustable filtering frequency band: By adjusting the size of the dual parasitic patches, the stub parameters of the T-shaped strip, and the size of the coupling gap between the three, the target high-frequency filtering frequency band can be flexibly adjusted to meet the needs of different high-frequency communication scenarios. The design of the structural parameters has a high fault tolerance rate and good process adaptability.

[0012] 5. Simple structure, easy to process and mass-produce: The invented filter structure is a patch or strip planar structure without complex irregular structure. It can be integrally formed with the antenna body using the same PCB / FPC etching process. The processing difficulty is low, the production cost is low, and it has good prospects for industrial mass production.

[0013] 6. The circularly polarized filter antenna of the present invention has an impedance matching range of 2.299-4.209GHz with an impedance matching of less than -10dB and a relative bandwidth of 58.7%; the axial ratio range is 2.884-3.999GHz with an axial ratio of less than 3dB and a relative bandwidth of 32.4%; the antenna performs excellently in all aspects and can meet the requirements of wireless communication systems. Attached Figure Description

[0014] Figure 1 This is a schematic cross-sectional view of the overall structure of the present invention.

[0015] Figure 2 This is a top view of the structure of the present invention.

[0016] Figure 3 This is a side view of the present invention.

[0017] Figure 4 This is a schematic cross-sectional view of the dielectric substrate II of the present invention.

[0018] Figure 5 This is a diagram showing the axial ratio of the antenna of the present invention.

[0019] Figure 6 This is the impedance matching diagram of the antenna of the present invention.

[0020] Figure 7 This is the antenna gain diagram of the present invention.

[0021] Figure 8 This is the radiation pattern of the antenna of the present invention in the YOZ direction at 3.5 GHz.

[0022] Figure 9 This is the radiation pattern of the antenna of the present invention in the YOZ direction at 3.5 GHz. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0024] like Figures 1 to 4 As shown, the Sub-6G circularly polarized filter antenna structure of the present invention includes, from bottom to top, a 0.787mm Fr4 substrate layer 100, a metal ground plane 200, a coaxial feed line 300, and a 0.787mm Fr4 substrate layer 400.

[0025] The upper surface of the Fr4 substrate layer 400 is provided with an antenna radiating element and an outer conductor frame, and the lower surface is provided with an antenna radiating element.

[0026] The antenna radiating element on the upper surface includes a metallic phase delay ring 407, two vertical rectangular main radiating arms 406, a parasitic patch 404, a parasitic patch 403, and a T-shaped strip 405. The antenna radiating element on the lower surface has the same structure as the one on the upper surface, but its overall structure is rotated 180° relative to the upper surface antenna radiating element.

[0027] The antenna is fed through a coaxial feed line 300, and energy is transferred to a metallic phase delay ring 407, then transitions to a rectangular main radiating arm 406. The impedance bandwidth and axial ratio bandwidth of the antenna can be adjusted by changing the inner and outer diameters of the phase delay ring and the length and width of the rectangular dipole arm (main radiating arm). Around the main radiator formed by the rectangular main radiating arm 406 and the phase delay ring 407, there is a ring of diagonally cut square parasitic patches 404. These patches couple with the main radiating arm, increasing the antenna's resonant point and widening the effective operating bandwidth while enhancing the antenna's circular polarization performance. Then, a new parasitic patch 403 is added opposite to the parasitic patch 404. This patch combination consists of a cut square patch and two connected rectangular patches. The interaction between these two, along with the main radiating arm, further widens the antenna's matching performance and circular polarization effect. Finally, a pair of T-shaped strips 405 are added on both sides of each main radiating arm 406, maintaining a certain gap between the T-shaped strips 405 and the parasitic patches 403 and 404.

[0028] The T-band 405, parasitic patch 403, and parasitic patch 404 interact to form a stable closed-loop coupling link, enabling high-frequency signals to be efficiently transmitted from the main radiating arm to the two parasitic patches and radiated, forming a high-frequency passband. In the high-frequency out-of-band band, the tuning effect of the T-band 405 fails, the symmetrical resonance characteristics of parasitic patch 403 and parasitic patch 404 deviate, and the closed-loop coupling link of the three breaks, resulting in the ineffective transmission of out-of-band signals and a sharp increase in reflection loss, thus suppressing high-frequency out-of-band signals, i.e., achieving a high-frequency filtering effect. It should be noted that any combination of the two lacks a key element of high-frequency filtering: when only parasitic patch 403 and parasitic patch 404 are combined, the lack of tuning bridging with T-band 405 prevents high-frequency impedance matching with the main radiating arm, resulting in excessive high-frequency signal transmission loss and the inability to form a stable high-frequency passband and filtering characteristics; when only parasitic patch 403 and T-band 405, or only parasitic patch 404 and T-band 405 are combined, the lack of complementary resonance of symmetrical parasitic patches leads to asymmetrical high-frequency coupling modes, disrupting the stability of the resonant circuit, preventing the formation of clear high-frequency bandpass / bandstop boundaries, and thus failing to achieve effective high-frequency filtering.

[0029] Meanwhile, each arm of the T-shaped strip 405 maintains a small gap (typically 0.15-0.75 mm) with the parasitic patches 403 and 404. This gap is a non-contact electromagnetic coupling gap, and its core function is to establish a near-field electromagnetic coupling relationship between the T-shaped strip 405 and the parasitic patches 403 and 404, rather than direct electrical conduction. The high-frequency filtering effect of this application essentially relies on the symmetrical resonance characteristics of the parasitic patches 403 and 404, combined with the tuning characteristics of the T-shaped strip 405, to form frequency-selective filtering through the coupling resonance between the three. If this gap is eliminated and the three are directly connected, a rigid electrical conduction will be formed, destroying the resonance mechanism of electromagnetic coupling, causing the original coupled resonance mode to disappear, and only a single conductive radiation structure will be formed. The core function of high-frequency filtering will also be completely lost. Furthermore, if the size of the gap is too large, the electromagnetic coupling strength between the T-shaped strip 405 and the parasitic patches 403 and 404 will be insufficient, and the three will not be able to form a coordinated resonance, resulting in a decrease in the passband gain and a weakening of the out-of-band suppression effect of the high-frequency filter. If the size of the gap is too small, the coupling strength will be too high, the resonant frequency will shift, and the frequency band of the high-frequency filter will deviate from the target frequency band, neither of which can achieve the high-efficiency high-frequency filtering effect required by this application. Therefore, the size parameters and relative position of the gap are adapted to the structural dimensions of the parasitic patches 403, 404, and T-shaped strip 405, together forming a complete technical solution for realizing high-frequency filtering.

[0030] The antenna radiating element is surrounded by a conductor frame formed by a patch combination 401 consisting of rectangular and triangular metal patches. This frame is not closed, with a gap 402 (typically 1-3mm) between each of the four sides. The conductor frame formed by the rectangular patches without the triangular patches provides some low-frequency filtering, but its length and width need to be adjusted to change the position of the filtering null point. To simplify adjustment, this invention adds triangular metal patches to both ends of the rectangular metal patches. By adjusting the side length of the triangular metal patches, the low-frequency filtering null point can be controlled.

[0031] This concludes the antenna design process. Through these modifications, the antenna achieved excellent filtering performance and a high 3dB gain bandwidth. It also exhibits good circular polarization performance.

[0032] like Figure 5 , Figure 6 and Figure 7 As shown, the simulated axial ratio bandwidth of this antenna is 2.884-3.999GHz, with an axial ratio relative bandwidth of 32.4%. The frequency range with impedance matching below -10dB is 2.299-4.209GHz, with an impedance matching relative bandwidth of 58.7%. like Figure 8 and Figure 9 The image shows the radiation pattern of the circularly polarized filter antenna in the YOZ plane at 3.5 GHz. It can be seen that the antenna has good left-handed polarization characteristics.

[0033] This invention, through the innovative collaborative design of a low-frequency filtering unit (conductor frame: rectangular metal patch + triangular chamfered patch) and a high-frequency filtering unit (radiating unit: stepped parasitic patch + square auxiliary patch), not only achieves the organic integration of high and low frequency dual-band filtering and circularly polarized radiation, but also forms a significant technical advantage with its superior performance parameters, fully meeting the stringent requirements of wireless communication systems. The specific advantages in terms of performance parameters are as follows: (1) The antenna of the present invention has an ultra-wide impedance matching bandwidth and its impedance matching performance far exceeds that of existing similar antennas, effectively ensuring stable signal transmission in a wide frequency band.

[0034] (2) The antenna of the present invention has excellent circular polarization performance, axial ratio bandwidth covers key communication frequency bands, and high polarization purity, which can effectively improve the anti-interference capability and signal quality of wireless communication.

[0035] (3) The antenna of the present invention achieves the performance synergy of wide impedance matching, excellent circular polarization and high and low frequency dual filtering, without performance loss, and its comprehensive performance far exceeds that of existing single-function optimized antennas.

[0036] (4) The performance coverage of the antenna of the present invention is precisely adapted to the requirements of wireless communication system, and its practicality and scenario adaptability are extremely strong.

[0037] (5) While ensuring excellent performance, the antenna of the present invention also takes into account the advantages of miniaturization and low cost. All functional units of the present invention are integrated into the planar structure of a single Fr4 substrate. The triangular chamfer of the low-frequency filter unit makes full use of the internal space. The high-frequency filter unit is a compact patch structure with no redundant volume. Moreover, all structures can be integrally formed by conventional PCB etching process without the need for three-dimensional metal parts, metal cavities or dielectric blocks. The processing difficulty is low and the cost is controllable.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A Sub-6G circularly polarized filter antenna, characterized in that: From bottom to top, the structure includes a dielectric substrate 1, a metal ground plane, a coaxial feed line, and a dielectric substrate 2. The metal ground plane is printed on the upper surface of dielectric substrate 1 and is connected to dielectric substrate 2 via the coaxial feed line. The upper surface of dielectric substrate 2 is provided with antenna radiating element 1 and an outer conductor frame, and the lower surface is provided with antenna radiating element 2. Antenna radiating element 1 includes a main radiator, parasitic patch 1, parasitic patch 2, and a T-shaped strip. The main radiator includes a phase delay loop located at the center of dielectric substrate 2 and two vertical rectangular main radiating arms connecting its ends. One of the rectangular main radiating arms has diagonally cut square parasitic patches 1 on both sides, and each parasitic patch 1 has a corresponding position. Parasitic patch two is a patch combination structure formed by connecting a square patch with one corner cut and two rectangular patches. The plane of its cut part is parallel to the plane of the cut part of parasitic patch one. A pair of T-shaped strips are added to both sides of each main radiating arm. The T-shaped strips maintain a gap with parasitic patch one and parasitic patch two. Antenna radiating element two has the same structure as antenna radiating element one. Its whole is rotated 180° relative to the other rectangular main radiating arm of antenna radiating element one. The conductor frame is composed of a patch frame composed of four rectangular metal patches and triangular patches. There are gaps between each patch frame. The frame surrounds the antenna radiating elements on the upper and lower surfaces of the dielectric substrate two.

2. The Sub-6G circularly polarized filter antenna as described in claim 1, characterized in that: Both dielectric substrate one and dielectric substrate two are Fr4 substrates.

3. The Sub-6G circularly polarized filter antenna as described in claim 1, characterized in that: The two ends of the coaxial feed line are respectively connected to the center positions of dielectric substrate one and dielectric substrate two.

4. A Sub-6G circularly polarized filter antenna as described in claim 1, characterized in that: The phase delay ring is made of metal.

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