Filtering antenna
By employing a filter structure with multiplexed orthogonal polarized radiators in 5G base station antennas, utilizing low-frequency out-of-band radiation suppression metal connection structures and high-frequency out-of-band radiation nulls, the problems of complexity and energy loss in traditional filter antenna design are solved, achieving a highly efficient frequency filtering effect, which is suitable for 5G base station antenna array systems.
Patent Information
- Application Number
- CN202511835822.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-08
- Publication Date
- 2026-02-13
AI Technical Summary
In traditional base station systems, the tight arrangement of dual-polarized symmetrical dipole antennas leads to enhanced port coupling and deterioration of inter-frequency port isolation, affecting communication quality. Existing filtering schemes increase circuit area or cause energy loss, increasing design complexity.
By using a multiplexed orthogonal polarized radiator as the filtering structure, and utilizing the low-frequency out-of-band radiation suppression metal connection structure and the high-frequency out-of-band radiation zero point, frequency filtering effects are achieved in both the low-frequency and high-frequency out-of-band areas without the need for additional parasitic filtering devices.
It achieves good radiation suppression performance outside the high and low frequency bands, with an out-of-band radiation suppression level of less than -10dB. The high and low frequency sidebands have good frequency roll-off performance, and the simple structure is suitable for 5G base station antenna array systems.
Smart Images
Figure CN121529183A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of antenna technology, specifically to a filter antenna with dual polarization function, which is particularly suitable for 5G base station antenna array systems. Background Technology
[0002] Traditional base station systems widely use dual-polarized symmetrical dipole antennas. In order to reduce the overall size of the antenna array, antennas of different operating frequency bands need to be arranged closely or interleaved. These arrangements strengthen the port coupling of antennas of different operating frequency bands, leading to the deterioration of the isolation between different frequency ports and affecting the communication quality of the base station system.
[0003] Existing solutions to address the aforementioned port isolation degradation primarily involve using filter antenna elements. There are three main implementation methods for filter antennas: the first is direct cascaded filters; however, the use of filters increases circuit area and introduces unnecessary insertion loss. The second method uses non-reflective filter antennas, which typically requires designing additional absorption filter circuits and using loads to absorb excitation energy, resulting in significant energy loss. The third method uses parasitic devices to achieve filtering performance, which undoubtedly increases the design complexity of the filter antenna. Therefore, there is an urgent need for a filter antenna that requires no additional filtering components, has a simple structure, and offers excellent filtering performance. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a dual-polarized filter antenna that uses a multiplexed orthogonally polarized radiator as the filtering structure. This antenna utilizes a low-frequency out-of-band radiation suppression metal connection structure to generate a low-frequency out-of-band radiation null, achieving a low-frequency out-of-band filtering effect. During excitation of one polarization, the other orthogonally polarized radiator acts as a filter for that polarization, generating a high-frequency out-of-band radiation null, thus improving high-frequency out-of-band radiation suppression performance. Good filtering performance can be achieved without the need for additional parasitic filtering devices. The antenna operates in the 3.0–3.7 GHz frequency band, with an out-of-band radiation suppression level of less than -10 dB. It exhibits good frequency roll-off performance in both high and low frequency sidebands and can be applied to 5G base station antenna array systems.
[0005] The present invention adopts the following technical solution:
[0006] A filter antenna includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate; the second dielectric substrate and the third dielectric substrate are orthogonally interposed between the first dielectric substrate and the fourth dielectric substrate.
[0007] The upper surface of the first dielectric substrate is etched with a symmetrical dipole antenna radiator. A low-frequency out-of-band radiation suppression metal connection structure is integrated on the symmetrical dipole antenna radiator. This structure provides an additional current transmission path, generates a low-frequency out-of-band radiation null, improves low-frequency out-of-band radiation suppression performance, and achieves a low-frequency out-of-band filtering effect. A rectangular impedance adjustment slot is etched on the symmetrical dipole antenna radiator. The lower surface of the first dielectric substrate is etched with a symmetrical dipole orthogonally polarized radiator orthogonal to the symmetrical dipole antenna radiator. This orthogonally polarized radiator generates a high-frequency out-of-band radiation null, improves high-frequency out-of-band radiation suppression performance, and achieves a high-frequency out-of-band filtering effect. By using the orthogonally polarized radiator as a filtering element, dual polarization and high-frequency out-of-band filtering performance can be achieved without using other parasitic filtering devices. A first slot structure is etched on the first dielectric substrate. The rectangular impedance adjustment slot is used to improve in-band impedance matching performance.
[0008] The upper surface of the second dielectric substrate is etched with a first metal feed line, the lower surface of the second dielectric substrate is etched with a first balun floor, and the top and bottom of the second dielectric substrate are respectively etched with a first non-metallic plug structure and a second non-metallic plug structure; the symmetrical dipole antenna radiator is connected to the first balun floor through a first slot structure and a first non-metallic plug structure.
[0009] The third dielectric plate is mirror-symmetrical to the second dielectric plate. The upper surface of the third dielectric plate is etched with a second metal feed line, and the lower surface of the third dielectric plate is etched with a second balun floor. The top and bottom of the third dielectric plate are respectively etched with a first non-metallic plug structure and a second non-metallic plug structure. The first non-metallic plug structure is fitted into the first slot structure. The symmetrical oscillator orthogonally polarized radiator is connected to the second balun floor through the first slot structure and the first non-metallic plug structure, thereby realizing the mechanical fixation and electrical connection between the symmetrical oscillator orthogonally polarized radiator and the second balun floor.
[0010] The upper surface of the fourth dielectric plate is fully covered by an etched metal floor. The fourth dielectric plate is etched with a second non-metallic slot structure, a non-metallic circular slot structure, and a metallized through-hole structure. The lower surface of the fourth dielectric plate is etched with a circular metal structure, which is connected to the metal floor through the through-hole structure.
[0011] The first balun floor and the second balun floor are connected to the metal floor through a second non-metallic plug structure and a second non-metallic slot structure; the inner conductors of the two coaxial feed wires are connected to the first metal feed wire and the second metal feed wire through a non-metallic circular slot structure, and the outer conductors of the two coaxial feed wires are connected to the annular metal structure.
[0012] The operating frequency band of the filter antenna covers 3.0 to 3.7 GHz.
[0013] The out-of-band radiation suppression level of the filtered antenna is less than -10dB, and the high and low frequency sidebands have good frequency roll-off performance.
[0014] All media boards use Rogers RO4003 substrates.
[0015] The radiator of the symmetrical dipole antenna is made of copper foil.
[0016] The filtered antenna can be applied to 5G base station antenna array systems.
[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0018] 1. This invention uses a symmetrical oscillator orthogonally polarized radiator to generate a high-frequency out-of-band radiation zero, thereby improving the high-frequency out-of-band radiation suppression performance and achieving a high-frequency out-of-band frequency filtering effect. By using the orthogonally polarized radiator as a filtering element, dual polarization and high-frequency out-of-band filtering performance can be achieved without the need for other parasitic filtering devices. This solves the problems of complex design and tolerance sensitivity of traditional parasitic structures. At the same time, low-frequency filtering is achieved by integrating a low-frequency out-of-band radiation suppression metal connection structure, replacing independent filters or absorption circuits and solving the defects of increased area and high insertion loss caused by additional devices.
[0019] 2. This invention uses a low-frequency band external radiation suppression metal connection structure to provide an additional current transmission path, generate a low-frequency band external radiation zero point, improve the low-frequency band external radiation suppression performance, and achieve a low-frequency band external frequency filtering effect.
[0020] 3. The out-of-band radiation suppression level of this invention is less than -10dB, and the high and low frequency sidebands have good frequency roll-off performance.
[0021] 4. The present invention has a simple structure and adopts an orthogonal cross-insertion structure of dielectric substrate, which has high integration and is suitable for the miniaturization layout requirements of base station antenna arrays; it uses Rogers RO4003 substrate, which has stable dielectric constant, low loss tangent, and antenna radiation efficiency ≥90%; it can be applied to 5G base station antenna array systems. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of a filter antenna structure according to the present invention;
[0023] Figure 2 This is a schematic diagram of the etched metal structure on the upper and lower surfaces of the first dielectric substrate;
[0024] Figure 3 This is a schematic diagram of the etched metal structure on the upper and lower surfaces of the second dielectric substrate;
[0025] Figure 4 This is a schematic diagram of the etched metal structure on the upper and lower surfaces of the third dielectric substrate;
[0026] Figure 5 This is a schematic diagram of the etched metal structure on the upper and lower surfaces of the fourth dielectric substrate;
[0027] Figure 6 The graph shows the simulation and test results of the antenna S-parameters changing with frequency.
[0028] Figure 7 The graph shows the simulation and test results of antenna gain and radiation efficiency as a function of frequency.
[0029] Figure 8 These are simulation and test results of the radiation patterns of antenna port 1 in the E-plane and H-plane at a frequency of 3.3 GHz;
[0030] Figure 9 The diagram shows the simulation and test results of the radiation patterns of antenna port 2 in the E-plane and H-plane at a frequency of 3.3 GHz.
[0031] The markings in the figure are as follows: 1-First dielectric substrate, 2-Second dielectric substrate, 3-Third dielectric substrate, 4-Fourth dielectric substrate, 5-Symmetric dipole antenna radiator, 6-Low-frequency band external radiation suppression metal connection structure, 7-Rectangular slot structure, 8-First slot structure, 9-Second balun ground plane, 10-First balun ground plane, 11-Second metal feed line, 12-First metal feed line, 13-First non-metallic plug structure, 14-Second non-metallic plug structure, 15-Second non-metallic slot structure, 16-Coaxial feed line, 17-Metallic ground plane, 18-Non-metallic circular slot structure, 19-Metalized through-hole structure, 20-Annular metal structure, 21-Symmetric dipole orthogonally polarized radiator. Detailed Implementation
[0032] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.
[0033] like Figures 1-5 As shown, the filtering antenna in this embodiment of the invention includes a first dielectric substrate 1, a second dielectric substrate 2, a third dielectric substrate 3, and a fourth dielectric substrate 4; the second dielectric substrate 2 and the third dielectric substrate 3 are orthogonally interposed between the first dielectric substrate 1 and the fourth dielectric substrate 4; each dielectric substrate uses a Rogers RO4003 substrate.
[0034] The upper surface of the first dielectric substrate 1 is etched with a symmetrical dipole antenna radiator 5. The symmetrical dipole antenna radiator 5 uses a low-frequency band out-of-band radiation suppression metal connection structure 6, and a rectangular slot structure 7 is etched on it. The rectangular slot structure 7 is used to adjust the in-band impedance, enabling good matching of the antenna in the 3.0–3.7 GHz frequency band. The symmetrical dipole antenna radiator 5 is made of copper foil. The lower surface of the first dielectric substrate 1 is etched with a symmetrical dipole orthogonally polarized radiator 21 arranged at 90° orthogonal to the symmetrical dipole antenna radiator 5. The first dielectric substrate 1 also has a first slot structure 8 etched through both the upper and lower surfaces.
[0035] The upper surface of the second dielectric substrate 2 is etched with a first metal feed line 12, the lower surface of the second dielectric substrate 2 is etched with a first balun ground plane 10, the top of the second dielectric substrate 2 is etched with a first non-metallic plug structure 13, and the bottom of the second dielectric substrate 2 is etched with a second non-metallic plug structure 14. The first non-metallic plug structure 13 is fitted into the first slot structure 8 to achieve mechanical fixation and electrical connection between the symmetrical dipole antenna radiator 5 and the first balun ground plane 10. The second non-metallic plug structure 14 cooperates with the second non-metallic slot structure 15 to achieve positioning connection between the second dielectric substrate 2 and the fourth dielectric substrate 4 and electrical connection between the first balun ground plane 10 and the metal ground plane 17. The symmetrical dipole antenna radiator 5 is connected to the first balun ground plane 10 through the first slot structure 8 and the first non-metallic plug structure 13.
[0036] The structure of the third dielectric substrate 3 is mirror-symmetrical to that of the second dielectric substrate 2. The upper surface of the third dielectric substrate 3 is etched with a second metal feed line 11, and the lower surface of the third dielectric substrate 3 is etched with a second balun floor 9. The top and bottom of the third dielectric substrate 3 are also etched with a first non-metallic plug structure 13 and a second non-metallic plug structure 14. The symmetrical oscillator orthogonally polarized radiator 21 is connected to the second balun floor 9 via a first slot structure 8 and a first non-metallic plug structure 13. The function of the second balun floor 9 is the same as that of the first balun floor 10.
[0037] The upper surface of the fourth dielectric plate 4 is fully etched with a metal ground plate 17. A second non-metallic slot structure 15 is etched on the fourth dielectric plate 4 at the position corresponding to the second non-metallic plug structure 14. The second non-metallic slot structure 15 is used to fit and insert with the second non-metallic plug structure 14, achieving positioning and connection between the second dielectric plate 2, the third dielectric plate 3, and the fourth dielectric plate 4, while ensuring tight contact and conductivity between the first balun ground plate 10, the second balun ground plate 9, and the metal ground plate 17. A non-metallic circular slot structure 18 and a metallized through-hole structure 19 are etched at the center of the fourth dielectric plate 4. The non-metallic circular slot structure 18 is used for the insertion and positioning of the inner conductor of the coaxial feed line 16, ensuring precise docking between the inner conductor and the feed line. The metallized through-hole structure 19 is used to realize the circular metal structure 2. The fourth dielectric plate 4 is electrically connected to the metal ground plate 17; the lower surface of the fourth dielectric plate 4 is etched with a circular metal structure 20, which is electrically connected to the metal ground plate 17 through a metallized through-hole structure 19, and is used to collect the current of the outer conductor of the coaxial feeder 16 and conduct it to the metal ground plate 17; the first balun ground plate 10 and the second balun ground plate 9 are fitted tightly to the metal ground plate 17 through the matching insertion of the second non-metallic plug structure 14 and the second non-metallic slot structure 15, respectively, to realize the grounding circuit conduction; the inner conductors of the two coaxial feeder 16 are connected to the first metal feeder 12 and the second metal feeder 11 through the non-metallic circular slot structure 18, and the outer conductors of the two coaxial feeder 16 are connected to the circular metal structure 20 to form a complete power supply circuit.
[0038] The low-frequency out-of-band radiation suppression metal connection structure 6 provides an additional current transmission path for the symmetrical dipole antenna radiator 5 and the symmetrical dipole orthogonally polarized radiator 21, generating a low-frequency out-of-band radiation null, improving the low-frequency out-of-band radiation suppression performance, and achieving a low-frequency out-of-band frequency filtering effect. The symmetrical dipole orthogonally polarized radiator 21 is used to generate a high-frequency out-of-band radiation null in the high-frequency out-of-band (>3.7GHz), improving the high-frequency out-of-band radiation suppression performance, and achieving a high-frequency out-of-band frequency filtering effect. By using the orthogonally polarized radiator as a filtering element, dual polarization and high-frequency out-of-band filtering performance can be achieved without using other parasitic filtering devices.
[0039] The working process of the filter antenna of this invention mainly includes three core components: radiation, filtering, and feeding.
[0040] 1. Power supply stage: The inner conductor of the coaxial feed line 16 is connected to the first metal feed line 12 and the second metal feed line 11 respectively through the non-metallic circular slot structure 18, transmitting the excitation signal to the corresponding polarized radiator (symmetric dipole antenna radiator 5 or symmetric dipole orthogonally polarized radiator 21); the outer conductor of the coaxial feed line 16 is connected to the annular metal structure 20, and is conducted to the metal ground plane 17 through the metallized through-hole structure 19 to form a grounding loop. At the same time, the first balun ground plane 10 and the second balun ground plane 9 realize the conversion from unbalanced power supply to balanced power supply, ensuring symmetrical excitation of the radiator.
[0041] 2. Radiation stage: When the signal excites the radiator 5 of the symmetrical dipole antenna, it achieves good matching by adjusting the in-band impedance through the rectangular slot structure 7, thereby radiating electromagnetic energy; the orthogonally polarized radiator 21 of the symmetrical dipole acts as a filter structure in the unexcited state, generating a radiation null point outside the high-frequency band.
[0042] 3. Filtering stage: The low-frequency out-of-band radiation suppression metal connection structure 6 provides an additional current transmission path for the symmetrical dipole antenna radiator 5. This path generates current phase cancellation outside the low-frequency band (<3.0GHz), forming a low-frequency radiation null. The symmetrical dipole orthogonal polarized radiator 21 and the excitation polarized radiator are electromagnetically coupled, generating resonance suppression outside the high-frequency band (>3.7GHz), forming a high-frequency radiation null. The two work together to achieve high and low frequency out-of-band filtering, ensuring that the out-of-band radiation suppression level is less than -10dB without additional filtering devices.
[0043] like Figure 6 The figure shown is a simulation and test result diagram of the antenna S-parameters as a function of frequency according to an embodiment of the present invention. The antenna operates in a frequency band covering 3.0–3.7 GHz; the in-band test S-parameters are shown. 11 and S 22 All values are less than -10dB, and the test isolation for in-band port 1 and port 2 is less than -25dB.
[0044] like Figure 7 The figure shown is a simulation and test result graph of the antenna gain and radiation efficiency as a function of frequency in an embodiment of the present invention. The average in-band gain of the antenna is 7.1 dBi, the in-band radiation efficiency is greater than 90%, the out-of-band radiation suppression level is less than -10 dB, and the high and low frequency sidebands have good frequency roll-off performance.
[0045] like Figure 8-9 The figure shown is a simulation and test result diagram of the antenna port 1 and port 2 at 3.3 GHz E-plane and H-plane radiation patterns according to an embodiment of the present invention. The antenna radiation pattern is a directional radiation mode. The simulation and test front-to-back ratio is greater than 14 dB, and the simulation and test cross-polarization level is less than -18 dB.
[0046] Experiments show that, compared to other implementations of filter antennas, such as cascaded filters, absorption filter circuits, and parasitic elements, the filter antenna of this invention achieves low-frequency filtering performance using a low-frequency out-of-band radiation suppression metal connection structure. When one polarization of the antenna is excited, another orthogonally polarized radiator acts as the filter for that polarization, achieving good high-frequency filtering performance without the need for additional parasitic filter components. The antenna's out-of-band radiation suppression level is less than -10dB, and its high and low frequency sidebands exhibit good frequency roll-off performance, making it suitable for application in 5G base station antenna array systems.
[0047] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to these embodiments. Any modifications, combinations and simplifications made without departing from the principles and essence of the present invention are included within the protection scope of the present invention.
Claims
1. A filter antenna, characterized in that... It includes a first dielectric substrate, a second dielectric substrate, a third dielectric substrate, and a fourth dielectric substrate; the first dielectric substrate and the fourth dielectric substrate are interposed in an orthogonal manner with the second dielectric substrate and the third dielectric substrate. The upper surface of the first dielectric substrate is etched with a symmetrical dipole antenna radiator. A low-frequency out-of-band radiation suppression metal connection structure is integrated on the symmetrical dipole antenna radiator. This structure provides an additional current transmission path, generates a low-frequency out-of-band radiation null, improves low-frequency out-of-band radiation suppression performance, and achieves a low-frequency out-of-band filtering effect. A rectangular impedance adjustment slot is etched on the symmetrical dipole antenna radiator. The lower surface of the first dielectric substrate is etched with a symmetrical dipole orthogonally polarized radiator orthogonal to the symmetrical dipole antenna radiator. This orthogonally polarized radiator generates a high-frequency out-of-band radiation null, improves high-frequency out-of-band radiation suppression performance, and achieves a high-frequency out-of-band filtering effect. By using the orthogonally polarized radiator as a filtering element, dual polarization and high-frequency out-of-band filtering performance can be achieved without using other parasitic filtering devices. A first slot structure is etched on the first dielectric substrate. The rectangular impedance adjustment slot is used to improve in-band impedance matching performance. The upper surface of the second dielectric substrate is etched with a first metal feed line, the lower surface of the second dielectric substrate is etched with a first balun floor, and the top and bottom of the second dielectric substrate are respectively etched with a first non-metallic plug structure and a second non-metallic plug structure; the symmetrical dipole antenna radiator is connected to the first balun floor through a first slot structure and a first non-metallic plug structure. The upper surface of the third dielectric substrate is etched with a second metal feed line, the lower surface of the third dielectric substrate is etched with a second balun floor, and the top and bottom of the third dielectric substrate are respectively etched with a first non-metallic plug structure and a second non-metallic plug structure; the symmetrical oscillator orthogonally polarized radiator is connected to the second balun floor through a first slot structure and a first non-metallic plug structure. The upper surface of the fourth dielectric plate is fully covered by an etched metal floor. The fourth dielectric plate is etched with a second non-metallic slot structure, a non-metallic circular slot structure, and a metallized through-hole structure. The lower surface of the fourth dielectric plate is etched with a circular metal structure, which is connected to the metal floor through the through-hole structure. The first balun floor and the second balun floor are connected to the metal floor via a second non-metallic plug structure and a second non-metallic slot structure. The inner conductors of the two coaxial feed lines are connected to the first and second metal feed lines through a non-metallic circular slot structure, and the outer conductors of the two coaxial feed lines are connected to a circular metal structure.
2. The filter antenna as described in claim 1, characterized in that... Its operating frequency band is 3.0 to 3.7 GHz.
3. The filter antenna as described in claim 1, characterized in that... Its out-of-band radiation suppression level is less than -10dB.
4. The filter antenna as described in claim 1, characterized in that... The first, second, third, and fourth dielectric substrates all use Rogers RO4003 substrates.
5. A filter antenna as described in claim 1, characterized in that... The radiator of the symmetrical dipole antenna is made of copper foil.