Broadband wave-transparent base station antenna

Abstract

The invention provides a broadband wave-transparent base station antenna, relates to the technical field of microwave and millimeter wave communication, and solves the technical problem that most common-caliber base station antenna design schemes in the prior art are relatively narrow in wave-transparent bandwidth. According to the technical scheme, the antenna comprises a low-frequency radiation unit, a high-frequency radiation unit and a rectangular reflection ground; the four high-frequency radiation units are arranged at the four corner ends of the low-frequency radiation unit respectively. Compared with a traditional frequency selective surface structure, more capacitance and inductance components are introduced, and the broadband wave-transparent performance is achieved.

Description

Technical Field

[0001] This invention relates to the field of microwave and millimeter-wave communication technology, specifically to a broadband transparent base station antenna. Background Technology

[0002] With the rapid development of mobile communication technology, antenna integration is constantly improving, and more frequency bands are being introduced for mobile communication, making the base station environment increasingly complex. At the same time, mobile communication base station resources are limited, site selection is difficult, and 2G, 3G, 4G, and 5G communication networks will coexist for a long time. Therefore, multi-standard, multi-band common-aperture base station antennas have significant research value and application prospects. Among the four high- and low-frequency antenna array schemes for common-aperture antennas, the staggered arrangement scheme has become the most ideal antenna array scheme for common-aperture base station antennas due to its flexible array configuration and high degree of design freedom. However, for the staggered arrangement, its overall width is relatively small, and there is obstruction between high- and low-frequency antennas, resulting in more severe scattering interference.

[0003] Existing solutions typically employ either frequency-selective surface (FSS) or filter stub-based low-frequency antenna designs to create staggered, multi-band, common-aperture antennas. FSS-based low-frequency antenna designs allow for independent control of transmission performance and antenna impedance, offering flexibility and convenience. However, they suffer from narrow transmission bandwidth and relatively weak transmission capability, making broadband designs difficult to achieve. Filter stub-based low-frequency antenna designs offer strong single-frequency transmission capability, but also suffer from narrow transmission bandwidth. Furthermore, the filter stub affects the characteristic impedance of the low-frequency antenna, causing transmission performance and antenna impedance to interact and become difficult to control independently, increasing design complexity.

[0004] Therefore, it is necessary to propose a broadband transparent base station antenna with independent controllability and broadband transparency characteristics. Summary of the Invention

[0005] Therefore, this invention solves the technical problem that most existing common-aperture base station antenna designs have narrow transmission bandwidth. The broadband transparent base station antenna provided by this invention, compared to traditional frequency-selective surface structures, introduces more capacitive and inductive components, achieving broadband transmission performance. Furthermore, by using a hybrid metal parasitic strip structure, the transmission bandwidth is further broadened. Simultaneously, the transmission performance of the aforementioned structure is independent of the impedance performance of the low-frequency antenna itself, reducing design complexity. Ultimately, this invention achieves broadband transmission of the high-frequency band from 1.7 GHz to 2.7 GHz while operating at low frequencies of 690 MHz to 960 MHz.

[0006] The present invention provides a broadband transparent base station antenna, comprising: a rectangular reflective ground, wherein a low-frequency radiating element is disposed on the rectangular reflective ground; and four sets of high-frequency radiating elements are uniformly disposed around the low-frequency radiating element on the rectangular reflective ground.

[0007] Furthermore, the low-frequency radiating unit includes a feeding structure disposed on a rectangular reflective ground, a balun disposed on the feeding structure, and a dielectric substrate disposed on the balun; a radiating arm and a filtering structure are disposed on the upper surface of the dielectric substrate; and a parasitic strip structure is disposed on the lower surface of the dielectric substrate. The balun is a conversion device used to connect balanced and unbalanced circuits; its core functions include signal conversion, impedance matching, and common-mode interference suppression.

[0008] Furthermore, the radiating arms are rectangular frame structures, with four sets arranged in a grid pattern on the dielectric substrate.

[0009] Furthermore, each of the aforementioned radiating arms is equipped with a filtering structure.

[0010] Furthermore, the filtering structure includes three cascaded metal strips arranged in a 2x2 array at the center of the inner side of the radiating arm and located on the upper surface of the dielectric substrate, providing a relatively wide transmission performance.

[0011] Furthermore, parasitic strip structures are provided on the lower surface of the dielectric substrate corresponding to each group of radiating arm regions.

[0012] Furthermore, the high-frequency radiating unit includes a main radiator and a non-metallic structure. The main radiator is separated from the rectangular reflective ground by the non-metallic structure, maintaining an ungrounded state. The non-metallic structure is specifically made of Arlon AD300A, with a dielectric constant of 3 and a loss tangent of 0.002.

[0013] Furthermore, the radiating arm, balun, feeding structure, filtering structure, and parasitic strip structure are all made of copper.

[0014] Furthermore, the dielectric substrate has a dielectric constant of 4.7 and a loss tangent of 0.02.

[0015] Furthermore, the four sets of high-frequency radiation units are located at the four corners of the low-frequency radiation unit in the top view direction.

[0016] The present invention has the following advantages over the prior art:

[0017] 1. This invention provides a broadband transparent base station antenna. Compared to traditional frequency-selective surface structures, it introduces more capacitive and inductive components, achieving broadband wave transmission performance. Furthermore, by using a hybrid metal parasitic strip structure, the wave transmission bandwidth is further broadened. Simultaneously, the wave transmission performance of the aforementioned structure is independent of the impedance performance of the low-frequency antenna itself, reducing design complexity. Ultimately, this invention achieves broadband wave transmission of the high-frequency band (1.7 GHz - 2.7 GHz) while operating at low frequencies of 690 MHz to 960 MHz.

[0018] 2. The present invention provides a broadband transparent base station antenna. By loading a novel frequency selective surface (FSS) unit, i.e., a filtering structure, on the inner side of the annular dipole arm (i.e., the radiating arm), the present invention achieves wave transmission capability in the 1.9GHz-2.7GHz frequency band. Furthermore, the present invention loads a parasitic metal strip on the lower surface of the dielectric substrate below the annular dipole arm, thereby widening the wave transmission bandwidth to the full 1.7GHz-2.7GHz frequency band.

[0019] 3. The broadband transparent base station antenna provided by this invention differs from the traditional frequency selective surface (FSS) structure. This invention proposes a novel frequency selective surface (FSS) structure, namely a filtering structure, which consists of three cascaded frequency selective surface units arranged in a 2*2 array. By introducing more capacitive and inductive components, it obtains broadband transparent characteristics of 1.9 GHz-2.7 GHz. At the same time, it is relatively independent and controllable and will not affect the impedance performance of the low-frequency oscillator itself.

[0020] 4. This invention provides a broadband transparent base station antenna that incorporates multiple hybrid structures. Based on the novel frequency-selective surface unit, a parasitic metal strip is added to the lower surface of the dielectric substrate below the low-frequency dipole arm. This strip carries a current with the same amplitude but opposite phase to the low-frequency dipole arm, thereby canceling the high-frequency induced current on the low-frequency dipole and thus broadening its wave transmission capability, achieving a wide frequency band of 1.7 GHz-2.7 GHz. Similarly, this structure is relatively controllable and does not affect the impedance performance of the low-frequency dipole itself.

[0021] 5. This invention provides a broadband transparent base station antenna that achieves broadband transparency across the entire frequency band from 1.7 GHz to 2.7 GHz through a hybrid design of a frequency-selective surface and parasitic stripes, while simultaneously achieving a -15 dB impedance bandwidth within the 690 MHz-960 MHz range for the low-frequency antenna itself. The structure is simple and the design complexity is low. The hybrid design of the frequency-selective surface and parasitic stripes proposed in this invention is simple, and its transparency performance and low-frequency impedance performance are relatively independent, facilitating separate control. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0024] Figure 2 This is a top view of the present invention;

[0025] Figure 3 This is a schematic diagram of the low-frequency radiation unit structure of the present invention;

[0026] Figure 4 This is a top view of the dielectric substrate of the present invention;

[0027] Figure 5 This is a bottom view of the dielectric substrate of the present invention;

[0028] Figure 6 This is a schematic diagram of the high-frequency radiation unit structure of the present invention;

[0029] Figure 7 This is a diagram illustrating the design evolution of the frequency-selective surface unit of this invention.

[0030] Figure 8 This is a diagram showing the normalized RCS values ​​corresponding to the frequency-selective surface units of the present invention.

[0031] Figure 9 This is a diagram showing the normalized RCS values ​​corresponding to the parasitic metal strip of the present invention.

[0032] Figure 10 This is the radiation pattern of the HB unit of the present invention;

[0033] Figure 11 This is a comparison diagram of the HB 3dB beamwidth of the present invention;

[0034] Figure 12 This is a diagram of the S-parameters of the LB antenna of the present invention;

[0035] Figure 13 This is a gain diagram of the LB antenna of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 1. Low-frequency radiating unit; 2. High-frequency radiating unit; 3. Rectangular reflective ground; 4. Dielectric substrate; 11. Radiating arm; 12. Balun; 13. Feeding structure; 14. Filtering structure; 15. Parasitic strip structure; 16. Main radiator; 17. Non-metallic structure. Detailed Implementation

[0038] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] In the description of this invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] Example 1

[0041] Figure 1 This is a schematic diagram of the overall structure of the broadband transparent base station antenna provided in this embodiment, which includes a low-frequency radiating element 1, a high-frequency radiating element 2, and a rectangular reflective ground 3. Figure 2 As shown, in the top view direction, a high-frequency radiation unit 2 is provided at each of the four corner positions of the low-frequency radiation unit 1. Figure 1 The main viewing angle of the antenna is shown. The overall height of the low-frequency radiating element 1 is 80mm, and its planar dimensions are 130mm × 130mm.

[0042] like Figure 3As shown, the dielectric substrate 4 region is a perspective view. The low-frequency radiating unit 1 includes four radiating arms 11, baluns 12 for supporting the radiating arms 11, and a feeding structure 13, a filtering structure 14, and a parasitic strip structure 15 for feeding the radiating arms 11. The radiating arms 11, baluns 12, feeding structure 13, filtering structure 14, and parasitic strip structure 15 are made of copper. The radiating arms 11 and filtering structure 14 are printed on the upper surface of the dielectric substrate 4, which is made of FR4 (dielectric constant 4.7, loss tangent 0.02). The parasitic strip structure 15 is disposed on the lower surface of the dielectric substrate 4. The filtering structure 14 is a novel frequency selective surface (FSS) unit, comprising three cascaded metal strips arranged in a 2*2 pattern at the center of the four inner ring arms of the low-frequency radiating arms 11, located on the upper surface of the dielectric substrate 4. It provides a relatively wide bandwidth transmission performance. The parasitic strip structures 15 are located directly below the low-frequency radiation arms 11, corresponding to the low-frequency radiation arms 11 on the lower surface of the dielectric substrate 4. Figure 4 and Figure 5 The top and bottom views of dielectric substrate 4 are shown. Figure 6 As shown, the high-frequency radiation unit 2 includes a main radiator 16 and a non-metallic structure 17. The main radiator 16 is separated from the rectangular reflective ground 3 by the non-metallic structure 17, and remains ungrounded.

[0043] Most existing common-aperture base station antenna designs suffer from narrow transmission bandwidth, making it difficult to achieve transmission over a wide frequency band (1.7 GHz-2.7 GHz) while maintaining the -15 dB impedance bandwidth of the low-frequency element (690 MHz-960 MHz). Mainstream transmission technologies, such as adding frequency selective surfaces (FSS) to the dipole arms and filter stubs, cannot avoid this drawback. Other technologies, such as introducing chokes and ferrite cores, not only increase the antenna's structural complexity and manufacturing costs but also disrupt the low-frequency antenna's inherent impedance characteristics. Furthermore, the transmission performance and the low-frequency impedance performance interfere with each other, making independent control difficult, significantly increasing design complexity.

[0044] Compared to traditional frequency-selective surface structures, this invention introduces more capacitive and inductive components, achieving broadband wave transmission performance. Furthermore, by using a hybrid metal parasitic stripe structure, the wave transmission bandwidth is further broadened. Simultaneously, the wave transmission performance of the aforementioned structure is independent of the impedance performance of the low-frequency antenna itself, reducing design complexity. Ultimately, this invention achieves broadband wave transmission in the high-frequency range of 1.7 GHz to 2.7 GHz while operating at low frequencies of 690 MHz to 960 MHz.

[0045] Radar cross section (RCS) is a crucial concept in radar stealth technology; it is a physical quantity that measures a target object's ability to scatter incident electromagnetic waves. The radar target and the scattered energy can be expressed as the product of an effective area and the incident power density; this area is commonly referred to as the radar cross section. Generally, an antenna with a normalized RCS value ≤ -6 dB is considered to have good wave transmission performance. Figure 7 The diagram illustrates the design evolution of the frequency-selective surface involved in this invention. Figure 8 Normalized RCS values ​​for frequency-selective surface elements from AN1 to ANT4 are given to evaluate their wave transmission performance.

[0046] like Figure 8 As shown, the normalized RCS value of ANT1 in the target frequency band of 1.7 GHz-2.7 GHz is greater than 0 dB, indicating that the LB antenna constructed with traditional ring dipole arms has a severe blocking effect on the HB antenna and lacks wave transmission capability. ANT2 loads four square ring-shaped FSS elements in a 2*2 array at the center of the inner side of the ring dipole arm of ANT1. ANT2 can be equivalent to an LC parallel resonator, exhibiting bandpass characteristics; however, its passband is small, with an RCS bandwidth of -6 dB only 2.24 GHz-2.68 GHz, which is insufficient to meet design requirements. Therefore, this paper proposes a novel FSS element, which reconstructs the square ring-shaped FSS to obtain a wider wave transmission bandwidth. The novel FSS element cascades multiple metal strips, occupying less area and having a larger adjustable space, while introducing more capacitive and inductive components, thereby achieving a wider wave transmission bandwidth. Figure 8 As shown, the -6 dB RCS bandwidth of ANT3 is only 2.04 GHz–2.58 GHz, while the normalized -6 dB RCS bandwidth of ANT4 further covers 1.9 GHz to 2.7 GHz. To further improve the transmission bandwidth, a parasitic strip is loaded directly below the ring dipole arm, which achieves scattered field cancellation by generating currents of equal amplitude but opposite direction. Figure 8 As shown, the parasitic stripe introduces a new resonant point on the normalized RCS, and the normalized -6dBRCS is achieved from 1.7 GHz to 2.7 GHz by using a hybrid approach of the two structures.

[0047] Figure 10The radiation patterns of the HB element under two different conditions are presented. It can be clearly seen that the proposed LB element with a frequency selective surface (FSS) and a stripe hybrid structure can effectively recover the HB radiation pattern with almost no impact on gain. Therefore, this study demonstrates that the proposed ring LB element with a loaded frequency selective surface (FSS) and stripe hybrid structure can effectively recover the HB radiation pattern. The comparison of the 3dB beamwidth of the high-frequency antenna when the low-frequency antenna of this invention is placed in a 1:4 interleaved array is shown in the figure. Figure 11 As shown, it can be seen that after adding the designed low-frequency antenna, the 3dB beamwidth of the high-frequency antenna remains very stable without any obvious abrupt change, which verifies the reliability of the transmission performance across the entire frequency band.

[0048] The low-frequency antenna performance of the present invention is as follows: Figure 12 , Figure 13 As shown, the VSWR is less than 1.4 (S11 & S22 are approximately -15dB), the bandwidth range is 690 MHz to 960 MHz, and the low-frequency antenna gain is greater than 7.8dB. It can be seen that the low-frequency antenna itself is working normally.

[0049] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A broadband transparent wave base station antenna, characterized in that, include: A rectangular reflective ground (3) is provided with a low-frequency radiation unit (1); four sets of high-frequency radiation units (2) are evenly arranged around the low-frequency radiation unit (1) on the rectangular reflective ground (3).

2. The broadband transparent wave base station antenna according to claim 1, characterized in that, The low-frequency radiation unit (1) includes a feeding structure (13) disposed on a rectangular reflective ground (3), a balun (12) disposed on the feeding structure (13), and a dielectric substrate (4) disposed on the balun (12); a radiation arm (11) and a filter structure (14) are disposed on the upper surface of the dielectric substrate (4); and a parasitic strip structure (15) is disposed on the lower surface of the dielectric substrate (4).

3. The broadband transparent base station antenna according to claim 2, characterized in that, The radiating arm (11) is a rectangular frame structure, and there are four sets of it on the dielectric substrate (4), arranged in a grid pattern.

4. The broadband transparent base station antenna according to claim 3, characterized in that, Each of the aforementioned radiating arms (11) is equipped with a filter structure (14).

5. The broadband transparent base station antenna according to claim 4, characterized in that, The filter structure (14) includes three cascaded metal strips arranged in a 2x2 array at the center of the inner side of the radiating arm (11) and located on the upper surface of the dielectric substrate (4).

6. The broadband transparent base station antenna according to claim 5, characterized in that, Parasitic strip structures (15) are provided on the lower surface of the dielectric substrate (4) corresponding to each group of radiating arms (11).

7. The broadband transparent base station antenna according to claim 6, characterized in that, The high-frequency radiation unit (2) includes a main radiator (16) and a non-metallic structure (17), with the main radiator (16) separated from the rectangular reflective ground (3) by the non-metallic structure (17).

8. The broadband transparent base station antenna according to claim 7, characterized in that, The radiating arm (11), balun (12), feeding structure (13), filtering structure (14) and parasitic strip structure (15) are all made of copper.

9. The broadband transparent base station antenna according to claim 8, characterized in that, The dielectric substrate (4) has a dielectric constant of 4.7 and a loss tangent of 0.

02.

10. The broadband transparent base station antenna according to claim 9, characterized in that, The four sets of high-frequency radiation units (2) are located at the four corners of the low-frequency radiation unit (1) in the top view direction.

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