Low-profile dual-frequency shared aperture antenna array based on tightly coupled loading buffer structure

Abstract

The present invention specifically relates to a low-profile, dual-frequency, shared-aperture antenna array based on a tightly coupled, loaded buffer structure, comprising: a low-frequency antenna, a high-frequency antenna, a tightly coupled buffer layer, a side reflector, and a metal floor. The low-frequency and high-frequency antennas are arranged within the same aperture and placed together on the metal floor. The tightly coupled buffer layer is placed above the low-frequency antenna and surrounds the high-frequency antenna, ensuring tight coupling between the two antennas across different frequency bands. The side reflector is located between the low-frequency and high-frequency antennas. The present invention achieves a low profile and cross-frequency interference suppression by loading a tightly coupled buffer layer between the low-frequency and high-frequency antennas and combining the side reflectors and metal floor.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications and antenna technology, and in particular to a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure. Background Art

[0002] As mobile communication systems continue to increase their demand for network capacity and multi-band coverage, base station antennas are gradually moving towards multi-frequency sharing or shared apertures. Deploying low-frequency and high-frequency antennas on the same platform can effectively save installation space and reduce deployment costs. However, placing antennas of different frequency bands close together in the same aperture often leads to the following problems:

[0003] 1. Low-frequency antennas block high-frequency antennas

[0004] Antennas in lower frequency bands are larger in size and can easily physically block high-frequency antennas, leading to problems such as pattern distortion and gain reduction of high-frequency antennas within their operating frequency bands.

[0005] 2. Cross-frequency interference

[0006] When different frequency bands share or have adjacent apertures, unwanted interference such as scattering and coupling is likely to occur between low-frequency and high-frequency antennas, which not only reduces port isolation but also deteriorates the overall radiation performance.

[0007] 3. The profile height is difficult to reduce

[0008] In dual-band or multi-band co-aperture base station antennas, low-profile low-frequency antennas have less shielding effect on high-frequency antennas than traditional low-frequency antennas of standard height. However, simply reducing the profile of the low-frequency antenna will lead to a decrease in the impedance matching and bandwidth performance of the low-frequency antenna.

[0009] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0010] In order to achieve low-profile design while maintaining good bandwidth and isolation, the present invention provides a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure, which can simultaneously take into account the three key requirements of profile height, cross-frequency interference suppression and broadband coverage.

[0011] Other features and advantages of the present invention will become apparent from the following detailed description, or may be learned in part by practice of the present invention.

[0012] According to a first aspect of the present invention, there is provided a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure, comprising:

[0013] Low-frequency antenna, high-frequency antenna, tightly coupled buffer layer, side reflector and metal floor;

[0014] The low-frequency antenna and the high-frequency antenna are arranged within the same aperture range and placed together on the metal floor;

[0015] The tightly coupled buffer layer is placed above the low-frequency antenna and surrounds the high-frequency antenna, so that the two maintain tight coupling in different frequency bands;

[0016] The side reflection plate is located between the low-frequency antenna and the high-frequency antenna.

[0017] In some exemplary embodiments, the low-frequency antenna includes four low-frequency dipole antenna units, each of which has an L-shaped structure and is placed perpendicular to the metal floor, and the four low-frequency dipole antenna units form a hollow cavity structure; two low-frequency dipole antenna units located at diagonal positions form a group, and are fed with equal amplitude and in phase to form radiation of one polarization; two low-frequency dipole antenna units at another group of diagonal positions are fed with equal amplitude and in phase to form radiation of another orthogonal polarization.

[0018] In some exemplary embodiments, the low-frequency dipole antenna includes a low-frequency dielectric plate, a dipole arm, and a feed balun, wherein the floor of the dipole arm and the feed balun is printed on the outside of the low-frequency dielectric plate, and the inner core of the feed balun is printed on the inside of the low-frequency dielectric plate and is located at the four corners of the hollow cavity structure.

[0019] In some exemplary embodiments, a short-circuit metal strip is provided between two adjacent low-frequency dipole antenna units, the short-circuit metal strip is connected to the metal floor below, and the short-circuit metal strip is located on the outside of the low-frequency dielectric plate, and a gap is provided between the short-circuit metal strip and the dipole arm of the low-frequency dipole antenna unit.

[0020] In some exemplary embodiments, the high-frequency antenna includes a dual-polarization cross-dipole unit and a feeding structure. The dual-polarization cross-dipole unit is placed horizontally and includes a high-frequency dielectric plate and a dipole arm printed on the upper surface of the high-frequency dielectric plate. The dipole arm is a square aperture structure. A square through hole is opened in the central area of ​​the high-frequency dielectric plate for positioning the vertically placed dielectric plate printed with the high-frequency antenna feeding structure, and allowing the feeding structure to pass through the positioning hole to connect to the high-frequency antenna dipole arm.

[0021] In some exemplary embodiments, a plurality of slot structures are etched on the dipole arm to extend the bandwidth of the high-frequency antenna.

[0022] In some exemplary embodiments, the feeding structure of the high-frequency antenna is a feeding balun, which is composed of a pair of cross-placed dielectric plates and a feeding balun structure printed thereon, wherein the floor of the feeding balun is printed on one side of the dielectric plate, and the inner core of the balun is printed on the other side of the dielectric plate, and the bottom of the balun is connected to the port of the coaxial feed line.

[0023] In some exemplary embodiments, the tightly coupled buffer layer includes a horizontally placed dielectric plate with a hollow center and a metal patch printed on an upper surface of the dielectric plate.

[0024] In some exemplary embodiments, the side reflector is a square structure formed by four vertically placed metal plates.

[0025] A debugging method for a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure, comprising:

[0026] By modifying the shape of the metal patch of the tightly coupled buffer layer and adjusting the height and position of the side reflector, the matching performance and radiation performance of the high and low frequency antennas can be further optimized to meet the comprehensive requirements of multi-standard base station antennas for matching, radiation performance, volume and cost.

[0027] The low-profile dual-band shared-aperture antenna array based on a tightly coupled loaded buffer structure provided by the embodiments of the present invention achieves low profile, broadband coverage, and cross-frequency interference suppression by introducing a tightly coupled buffer layer between the low-frequency antenna unit and the high-frequency antenna unit, combined with side reflectors and metal floor designs. This has the following advantages:

[0028] 1. Significantly reduce profile height

[0029] While ensuring the performance of the low-frequency antenna, the overall size of the antenna is made smaller and lighter, and the blocking and scattering effects of cross-frequency interference on the high-frequency antenna are effectively reduced.

[0030] 2. Low-frequency antenna broadband coverage

[0031] While reducing the low-frequency antenna profile, it still achieves good impedance matching and stable radiation characteristics over a wide bandwidth, meeting the requirements of mobile communications for wider bandwidth and high gain.

[0032] 3. High-frequency antenna bandwidth expansion

[0033] With the help of the electromagnetic coupling effect of the tightly coupled buffer layer, additional resonance is introduced in the high frequency band to expand the working bandwidth of the high frequency antenna.

[0034] 4. Effectively suppress cross-frequency scattering interference

[0035] Thanks to the low-profile structure of the low-frequency antenna, its shielding effect on the high-frequency antenna is significantly reduced. This suppresses the induced current on the low-frequency antenna when the high-frequency antenna is operating, thereby reducing the scattering effect of this induced current on the high-frequency antenna. This allows the high-frequency antenna to maintain good radiation characteristics without the need for additional complex de-scattering or frequency-selective structures.

[0036] 5. Effectively suppress cross-frequency coupling interference

[0037] The tightly coupled buffer layer acts as an electromagnetic buffer. Whether the low-frequency or high-frequency antenna is excited, electromagnetic energy is coupled to the tightly coupled buffer layer, significantly reducing the electromagnetic energy coupled to the antenna port of the other frequency band. This design achieves excellent cross-band port isolation without the need for complex decoupling or filtering structures.

[0038] 6. Compatibility and scalability

[0039] This solution is scalable and can be flexibly expanded to shared-aperture antenna scenarios in more operating frequency bands according to future needs to meet the application requirements of multi-frequency, multi-standard communication systems.

[0040] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are incorporated into and constitute a part of this specification, illustrate embodiments consistent with the present invention, and together with the description, serve to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and it is clear that those skilled in the art can derive other drawings based on these drawings without inventive effort.

[0042] Figure 1 Schematic diagram of the structure of a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to an embodiment of the present invention;

[0043] Figure 2 Schematic diagram of the evolution process and key geometric structure of the low-frequency antenna in an embodiment of the present invention;

[0044] Figure 3 for Figure 2 Comparison of the input impedance of port C1 for various low-frequency antenna models in the 0.69-0.96 GHz range: (a) Smith chart (normalized to 50Ω); (b) reflection coefficient;

[0045] Figure 4This is a schematic diagram of the structure of a low-profile broadband low-frequency antenna in an embodiment of the present invention, that is, a feed balun is added to the low-frequency antenna model: the upper half is the overall structure and local amplification; the lower half is the hollow cavity composed of low-frequency dipoles and local amplification;

[0046] Figure 5 Performance simulation diagrams of the low-profile, broadband, low-frequency antenna in an embodiment of the present invention: (a) Smith chart (normalized to 50Ω) in the 0.69-0.96 GHz range; (b) S-parameters; (c) radiation pattern of the C1 port in the yoz plane; (d) LB band gain;

[0047] Figure 6 Schematic diagram of the structure of a high-frequency antenna according to an embodiment of the present invention;

[0048] Figure 7 Performance simulation diagrams of the high-frequency antenna according to an embodiment of the present invention: (a) S parameters; (b) gain; (c) radiation pattern of port 5 in the yoz plane;

[0049] Figure 8 Schematic diagram comparing the port reflection coefficients of the high-frequency antenna according to an embodiment of the present invention under three conditions: condition A: high-frequency antenna only; condition B: high-frequency antenna + tightly coupled buffer layer; condition C: high-frequency antenna + tightly coupled buffer layer + low-frequency antenna.

[0050] Figure 9 Schematic diagram of the current distribution of the tightly coupled buffer layer and the high-frequency antenna unit at the corresponding resonance points of Case A and Case B, that is, excited by port 5 (-45° polarization);

[0051] Figure 10 Four scenarios of high-frequency antenna scattering and performance comparison: (a) is a schematic diagram of the four scenarios for evaluating high-frequency antenna scattering; (b) is a schematic diagram of the comparison of high-frequency antenna gain in the four scenarios; (c) is a schematic diagram of the high-frequency antenna co-polarization radiation pattern at 1.5 GHz, 1.9 GHz, 2.3 GHz, and 2.7 GHz for scenarios 1, 2, and 4;

[0052] Figure 11 Schematic diagram comparing the cross-frequency coupling coefficients without and with a tight-coupling buffer layer: (a) without a tight-coupling buffer layer; (b) with a tight-coupling buffer layer;

[0053] Figure 12 Schematic diagram of the current amplitude distribution of the low-frequency antenna and high-frequency antenna of the dual-frequency antenna array at different frequencies: (a) low-frequency antenna; (b) high-frequency antenna;

[0054] Figure 13 The following is a physical picture of the antenna array and a schematic diagram of the darkroom test;

[0055] Figure 14 Schematic diagram comparing the measured and simulated results of the low-frequency antenna: (a) S parameters; (b) gain; (c) radiation pattern of the C1 port in the YOZ plane;

[0056] Figure 15 Schematic diagram comparing the measurement and simulation results of the high-frequency antenna: (a) S parameters; (b) gain; (c) radiation pattern of port 5 in the yoz plane;

[0057] Figure 16 Schematic diagram of the measurement and simulation comparison of the cross-frequency coupling coefficient between the low-frequency antenna and the high-frequency antenna: (a) low-frequency band; (b) high-frequency band.

[0058] In the figures, the reference numerals are as follows:

[0059] 1-low-frequency antenna; 2-high-frequency antenna; 3-tightly coupled buffer layer; 4-side reflector; 5-metal floor; 11-feeding port of the first low-frequency dipole antenna unit; 12-feeding port of the second low-frequency dipole antenna unit; 13-feeding port of the third low-frequency dipole antenna unit; 14-feeding port of the fourth low-frequency dipole antenna unit; 1a-feeding balun core of the low-frequency dipole antenna unit; 1b-feeding balun floor of the low-frequency antenna; 1c-dipole arm of the low-frequency dipole antenna unit; 1d-short-circuited metal strip; 1e-metal through-hole; 21-first feeding port of the high-frequency antenna (high-frequency -45°); 22-second feeding port of the high-frequency antenna (high-frequency +45°); 2a-feeding balun of the high-frequency antenna; 2b-dipole arm of the high-frequency antenna; 2c-through-hole; 2α-high-frequency antenna balun core; 2β-high-frequency antenna balun floor. DETAILED DESCRIPTION

[0060] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0061] In addition, the accompanying drawings are merely schematic illustrations of the present invention and are not necessarily drawn to scale. Identical reference numerals in the figures denote identical or similar parts, and thus repetitive descriptions thereof will be omitted. Some of the blocks shown in the accompanying drawings are functional entities that do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in software, in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices.

[0062] In the related art, the following methods are disclosed to address the problems caused by placing antennas of different frequency bands closely together in the same aperture:

[0063] 1. Give low-frequency antennas the "electromagnetic stealth" feature in high-frequency bands:

[0064] Choke filter structures, slot structures, frequency selective surfaces, split resonant rings, or metasurfaces are integrated into low-frequency antennas to suppress the induced currents on the high-frequency antennas during operation, reducing their scattering effects on the high-frequency antennas, thereby making the low-frequency antennas "electromagnetically invisible" in the high-frequency band. However, these measures often lead to varying degrees of degradation in the performance of the low-frequency antennas or increase the difficulty of impedance matching.

[0065] 2. Use embedded solution:

[0066] The high-frequency antenna is embedded inside the bowl-shaped low-frequency antenna, but this method usually cannot effectively solve the cross-band interference. It is often necessary to raise the height of the high-frequency antenna or add special baffles to achieve better results.

[0067] 3. Use stacking solution:

[0068] The high-frequency antenna is moved above or below the low-frequency antenna and isolated with the help of a frequency selective surface, but this increases the structural complexity and manufacturing cost of the antenna.

[0069] 4. Use back cavity structure:

[0070] Raising the high-frequency antenna to the same height as the low-frequency antenna, embedding it into the low-frequency radiator, and then adding a metal back cavity as a high-frequency reflector to improve the high-frequency radiation pattern and gain; however, this also makes the overall antenna more complex.

[0071] In summary, these methods still have one or more shortcomings in terms of manufacturing complexity, cost, and even bandwidth or profile height. The fundamental reason is that for dual-band base station antennas with conventional profile heights, cross-frequency interference is difficult to avoid, and cross-frequency decoupling is often achieved only through additional structures. For low-profile base station antennas, reducing the profile can seriously affect the matching and bandwidth performance of the low-frequency antenna.

[0072] In response to the shortcomings and deficiencies of the existing technology, this example embodiment provides a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loaded buffer structure. A tightly coupled buffer layer is set between the low-frequency antenna and the high-frequency antenna, and combined with side reflectors and metal floors to achieve low profile, broadband coverage and cross-frequency interference suppression.

[0073] The structure of the low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure in this example implementation will be described in more detail below with reference to the accompanying drawings and embodiments.

[0074] refer to Figure 1 The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure shown includes: a low-frequency antenna 1, a high-frequency antenna 2, a tightly coupled buffer layer 3, a side reflector 4 and a metal floor 5; the low-frequency antenna 1 and the high-frequency antenna 2 are arranged within the same aperture range and are placed together on the metal floor 5; the tightly coupled buffer layer 3 is placed above the low-frequency antenna 1 and surrounds the high-frequency antenna 2, so that the two maintain tight coupling in different frequency bands; the side reflector 4 is located between the low-frequency antenna 1 and the high-frequency antenna 2.

[0075] Both the low-frequency antenna 1 and the high-frequency antenna 2 are dual-polarized antennas. The low-frequency antenna 1 uses four dipole antenna units to form a hollow cavity structure and is loaded with a tightly coupled buffer layer 3 to achieve low-profile broadband coverage (0.69–0.96 GHz). The high-frequency antenna 2 can use cross-dipole units to cover target high-frequency ranges such as 1.47–2.7 GHz.

[0076] For example, Figure 1 As shown, the low-frequency antenna 1 consists of four dipole antenna elements, preferably arranged in a bowl-shaped configuration, i.e., a hollow cavity structure. A horizontally placed, printed, tightly coupled buffer layer 3 is placed above the four dipole antenna elements. The dipole antenna elements are L-shaped and placed perpendicular to the metal floor 5. Two diagonally positioned low-frequency dipole antenna elements are fed with equal amplitude and in-phase power, resulting in radiation of one polarization. Another set of antenna elements is fed with equal amplitude and in-phase power, resulting in radiation of the other polarization. The two polarizations are orthogonal to each other.

[0077] Specifically, the feeding ports 11 and 13 of the first low-frequency dipole antenna unit in the figure and the feeding port of the third low-frequency dipole antenna unit are fed with equal amplitude and in-phase by a power divider to form the first port of the low-frequency antenna, and the first port of the low-frequency antenna is a port, and the feeding port 12 of the second low-frequency dipole antenna unit and the feeding port 14 of the fourth low-frequency dipole antenna unit are fed with equal amplitude and in-phase by a power divider to form the second port of the low-frequency antenna.

[0078] Furthermore, if Figure 4As shown, the low-frequency dipole antenna unit includes a low-frequency dielectric plate, a dipole arm, and a feed balun. The dipole arm 1c and the feed balun floor 1b are printed on the outside of the low-frequency dielectric plate, which is placed vertically within the low-frequency antenna's hollow cavity. The feed balun core 1a is printed on the inside of the low-frequency dielectric plate, which is placed vertically within the low-frequency antenna's hollow cavity. Metal through-holes 1e and metal strips connecting the upper and lower metal through-holes are provided on the inside and outside of the low-frequency dielectric plate. Both the metal through-holes and the metal strips are used to adjust the impedance matching of the low-frequency antenna. A square slot is provided on the lower edge of the feed balun dielectric plate. This slot not only allows the low-frequency antenna 1 to be inserted into the metal floor 5 and ensures the correct positional relationship between the two, but also allows the feed circuit to extend below the metal floor 5 and connect to the RF connector.

[0079] Furthermore, a short-circuit metal strip 1d is provided between the low-frequency dipole antenna units. The short-circuit metal strip 1d is connected to the metal floor 5 below, and a gap is provided between the short-circuit metal strip 1d and the dipole arm 1c of the low-frequency dipole antenna unit. The loading of the short-circuit metal strip 1d can introduce additional resonance and optimize the impedance bandwidth of the high- and low-frequency antennas. A positioning block is provided on the upper edge of the low-frequency dielectric plate to ensure the correct positional relationship between the low-frequency antenna 1 and the tightly coupled buffer layer 3. The loading of the tightly coupled buffer layer 3 can achieve a low profile of the low-frequency antenna and ensure its broadband coverage (0.69–0.96GHz).

[0080] like Figure 2 Figure 1 shows the evolutionary process and key geometric structures of the low-profile, broadband, low-frequency antenna described in the present invention, including Model 1, Model 2, Model 3, and Model 4. This process illustrates the gradual evolution from the traditional bowl-shaped structure (Model 1) to Model 4, which features a lower profile and multiple resonance points. Model 1 utilizes a conventional bowl-shaped four-arm dipole with a cross-section height of approximately 0.24λ0\lambda_0 (λ0\lambda_0 is the free-space wavelength at 0.82 GHz). This configuration only has a single resonance, resulting in a relatively limited bandwidth. Model 2 reduces the cross-section to approximately 0.098λ0\lambda_0 without changing the aperture size, but this introduces a strong inductive effect, degrading the matching performance. Model 3 incorporates a tightly coupled buffer layer, creating additional capacitance compensation at low frequencies, compensating for the inductive effect in Model 2 and forming a new resonance near 0.71 GHz, thus expanding the bandwidth. Model 4 further improves high-end impedance matching by adding a shorting metal strip, introducing a third resonance point at approximately 0.95 GHz. The model can cover about 0.69–0.96 GHz with a cross section of only 0.098λ0\lambda_0. Without introducing a feed balun, the input impedance of the C1 port of each model is as follows: Figure 3As shown in the figure, Models 3 and 4 significantly expand the bandwidth and improve the matching. The schematic diagram of the structure after adding a feed balun to Model 4, namely the low-frequency antenna (Model 5): The overall structure and a zoomed-in view show the floor and core of the feed balun printed on the upper and lower layers of the dielectric plate respectively; the zoomed-in view of the hollow cubic dipole more intuitively shows the four-arm bowl-shaped dipole arrangement. Figure 5 The performance of this low-frequency antenna (model 5) is shown below: (a) Smith chart (normalized to 50Ω) in the 0.69-0.96 GHz range; (b) S-parameters; (c) radiation pattern of the C1 port in the yoz plane; (d) gain in the low-frequency band. Test / simulation data show that:

[0081] 1. The reflection coefficient is lower than -10dB, covering 0.69--0.96GHz (bandwidth 32.7%), and it still maintains good impedance matching under the condition of low profile 0.087λL\lambda_L;

[0082] 2. The gain reaches 7.7-8.9dBi within this bandwidth, and the XPD (cross-polarization suppression) in the main beam direction is higher than 45dB;

[0083] 3. Isolation (c1 to c2) can reach over 51.2dB.

[0084] In summary, by loading short-circuit metal strips on the low-frequency antenna dielectric board and combining it with a tightly coupled buffer layer (TCBL), an extremely low profile (~0.087λL\lambda_L) and broadband coverage can be achieved.

[0085] For example, Figure 6As shown, the high-frequency antenna 2 adopts a dual-polarization cross-dipole unit, which is suitable for 1.7-2.7GHz or other target high-frequency ranges; the dipole arm 2b is printed on a horizontally placed high-frequency dielectric plate and is a square structure with multiple slot structures etched thereon for expanding the bandwidth of the high-frequency antenna; a square through hole 2c is opened in the central area of ​​the horizontally placed dielectric plate of the high-frequency antenna for accurately positioning the vertically placed dielectric plate printed with the high-frequency antenna feeding structure, and allowing the feeding structure to pass through the positioning hole and be connected to the high-frequency antenna dipole arm; the feeding structure (feed balun) of the high-frequency antenna consists of a pair of cross-placed dielectric plates and the feeding structure printed thereon. The electric balun structure is composed of the ground plane 2β of the feed balun printed on one side of the dielectric board, and the balun core 2α printed on the other side of the dielectric board, and the bottom of the feed balun 2a is connected to the RF connector; through the electromagnetic coupling with the tight-coupled buffer layer, the high-frequency antenna will generate additional resonant modes, so that the original high-frequency bandwidth of about 45% is expanded to about 59% or wider, thereby adapting to the demand for a larger number of channels; in the high-frequency band, the tight-coupled buffer layer can also naturally block the energy radiated by the high-frequency antenna from coupling to the low-frequency antenna port, effectively improving the isolation between the high-frequency and low-frequency antennas, and avoiding the need to add additional filtering structures and other complex designs to the low-frequency antenna.

[0086] Figure 7 The performance of the high-frequency antenna when operating alone is shown, namely (a) S-parameters, (b) gain, and (c) the radiation pattern of port 5 in the yoz plane. Test results show that in the 1.7–2.7 GHz range, approximately 45.5% bandwidth (|S55| < -14 dB) is achieved, inter-port isolation is better than 26.4 dB, gain is maintained between 8.1–9.3 dBi, and main-beam XPD exceeds 20 dB.

[0087] Figure 8 A comparison diagram of |S55| of the high-frequency antenna in three situations is given, namely:

[0088] · Case A: High-frequency antenna only;

[0089] · Case B: HF antenna + TCBL;

[0090] · Case C: high-frequency antenna + TCBL + low-frequency antenna.

[0091] As shown in the figure, after adding the TCBL (Case B), an additional resonance appears at 1.5 GHz, expanding the bandwidth from the original 45.5% to approximately 60.2%. Even when co-located with a low-frequency antenna (Case C), the high-frequency bandwidth remains stable at 1.47–2.7 GHz (59.0%), and inter-port isolation is not significantly affected.

[0092] Figure 9 The current distribution at the corresponding resonant points of Case A and Case B is shown. It can be seen that when the TCBL exists, the TCBL itself takes on an additional resonant current path, thereby expanding the overall bandwidth and blocking some coupling energy.

[0093] Exemplarily, the tightly coupled buffer layer 3 is located above the low-frequency antenna and around the high-frequency antenna; the tightly coupled buffer layer is a layer of conductor composite structure that maintains tight coupling with the high and low-frequency antennas; it is composed of four L-shaped right-angled metal structures and is printed on the upper layer of the dielectric plate on which the low-frequency antenna is horizontally placed; a plurality of square positioning holes are provided for installation and integration with the low-frequency antenna; necessary capacitance compensation and resonance are formed through tight coupling: it plays a capacitance compensation role in the low-frequency band and reduces the low-frequency antenna profile; it introduces new resonance in the high-frequency band, expands the high-frequency bandwidth, and naturally blocks cross-frequency energy coupling.

[0094] Furthermore, the tight coupling buffer layer 3 has a thickness of 1-3 mm.

[0095] Exemplarily, the side reflector 4 is located between the high- and low-frequency antennas and is installed on the surface of the metal floor at a specific distance; a square positioning block is designed on the lower edge of the side reflector, which can cooperate with the slot on the metal floor to ensure the accuracy of the installation position; the side reflector 4 is conducive to optimizing the antenna radiation pattern, reducing unnecessary energy leakage, and making the high-frequency antenna gain curve smoother.

[0096] Furthermore, the height of the side reflector 4 is as close as possible to the cross section of the low-frequency antenna, and the installation position can be adjusted within the range of 5-10 mm according to the high-frequency gain requirement.

[0097] For example, the metal floor 5 serves as the installation reference surface for the entire antenna, and the low-frequency antenna and the high-frequency antenna are fixed on it; the lower edge of the low-frequency antenna and the high-frequency antenna dielectric board has a square slot or slot that cooperates with the metal floor, and is fixed with screws or buckles to ensure the precise alignment of the antenna in the vertical and horizontal directions.

[0098] Furthermore, the metal floor is a metal plate having a thickness of 1–2 mm.

[0099] Figure 10 (a) further provides schematic diagrams of four scenarios for evaluating high-frequency antenna scattering (e.g., high frequency only, high frequency + conventional low frequency, high frequency + low-profile low frequency of the present invention, high frequency + low-profile low frequency of the present invention + side reflectors). Figure 10 (b) Gain and Figure 11 (c) Comparison of the radiation patterns shows that the high-frequency antenna gain is more stable and beam distortion is significantly reduced when the low-profile low-frequency antenna + side reflector solution of the present invention is used. In traditional staggered or embedded designs, the high-frequency antenna is significantly blocked by the low-frequency antenna, and the gain fluctuation can reach up to 6.8dB; Figure 10(b) Under this scheme, the high-frequency gain fluctuation is reduced to within 1.7dB, and the beam shape is more uniform.

[0100] Figure 11 The comparison of the cross-band coefficients without TCBL (a) and with TCBL (b) is shown: the coupling from the low-frequency port to the high-frequency band is improved from -10.7dB to -25.4dB;

[0101] Figure 12 Further explanation from the perspective of current distribution shows that at high frequencies such as 1.5 GHz, 2.2 GHz, and 2.7 GHz, the tightly coupled buffer layer naturally blocks the coupling path.

[0102] Comparison between measured and simulation results:

[0103] Figure 13 The following are images of the antenna array and a schematic diagram of the darkroom test. Using a far-field measurement system built with a Rohde & Schwarz ZNBT8 network analyzer and a Keysight N5183A MXG signal source / N5264B PNA-X tester, the following conclusions were obtained:

[0104] Low frequency band:

[0105] like Figure 14 As shown, the S-parameter simulation is highly consistent with the test, the reflection coefficient bandwidth covers 0.69–0.96 GHz, the gain is between 6.3–8.4 dBi, and the port isolation is better than 28.6 dB.

[0106] High frequency band:

[0107] Figure 15 It shows that in the range of 1.47–2.7 GHz (59.0%), |S55|, |S66| < -14 dB, isolation < -22.3 dB, and gain of about 6.6–8.0 dBi are maintained;

[0108] Figure 16 A comparison of the cross-frequency coupling between the low-frequency antenna and the high-frequency antenna shows that when no tight-coupling buffer layer is present, the value is only about -10 dB at some frequencies, while an improvement of -20 dB to -25 dB can be achieved under the solution of the present invention.

[0109] The low-profile dual-band shared aperture antenna array based on a tightly coupled loading buffer structure provided by the embodiments of the present invention achieves significant improvements in profile height, cross-band isolation, and high-frequency bandwidth:

[0110] The low-frequency operating bandwidth is 0.69–0.96 GHz, and the cross-section is only 0.087λL\lambda_L;

[0111] The high-frequency bandwidth is increased from 45% to 59%, and port isolation is significantly improved;

[0112] When side reflectors are used, the high-frequency antenna pattern and gain fluctuation can be further optimized.

[0113] If support for three or more frequency bands is required in the future, a higher level of multi-frequency common aperture antenna integration can be achieved by adding additional tightly coupled buffer layers, or moderately expanding the aperture on the metal floor, and combining similar tight coupling principles to fine-tune antennas of different frequency bands.

[0114] The low-profile dual-band shared-aperture antenna array based on a tightly coupled loaded buffer structure provided by the present invention builds on the concept of tight coupling by loading a tightly coupled buffer layer between the low-frequency and high-frequency antennas, combined with features such as side reflectors and a metal floor, to achieve low profile, broadband coverage, and cross-frequency interference suppression. Compared to existing technologies, it offers the following advantages:

[0115] 1. Coexistence of low profile and broadband

[0116] By utilizing the capacitive compensation effect of the tightly coupled buffer layer on the low-frequency antenna, the broadband coverage of the low-frequency antenna is maintained while significantly reducing the vertical height of the overall antenna.

[0117] 2. Cross-frequency interference suppression

[0118] Without adding dedicated filtering surfaces or complex metal rings, the tightly coupled buffer layer can naturally reduce the blocking effect of the low-frequency antenna on the high-frequency antenna, thereby reducing the cross-frequency scattering interference of the low-frequency antenna on the high-frequency antenna and effectively improving the radiation performance of the high-frequency antenna.

[0119] The tightly coupled buffer layer also acts as an electromagnetic buffer. When a high-frequency or low-frequency antenna is excited, it reduces the electromagnetic energy coupled to the antenna port of the other frequency band. This suppresses cross-frequency coupling interference, thereby achieving excellent cross-frequency port isolation performance without the need for complex decoupling or filtering structures.

[0120] 3. High-frequency broadband extension

[0121] Compared with conventional high-frequency antennas, the present invention introduces new resonance in the high-frequency band through a tightly coupled buffer layer, thereby increasing the bandwidth of the high-frequency antenna from 45% to 59% or higher.

[0122] 4. Compatibility and scalability

[0123] By modifying the shape and layering of the tightly coupled buffer layer and adjusting the position of the metal floor and side reflectors, this solution can further adapt to the design of shared-aperture antennas for three or even more frequency bands, meeting the comprehensive requirements of future multi-standard base station antennas for bandwidth, volume, and cost.

[0124] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the claims.

[0125] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings and that various modifications and variations can be made without departing from the scope thereof, which is limited only by the appended claims.

Claims

1. A low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure, characterized in that: include: A low-frequency antenna (1), a high-frequency antenna (2), a tightly coupled buffer layer (3), a side reflector (4), and a metal floor (5); The low-frequency antenna (1) and the high-frequency antenna (2) are arranged within the same caliber range and are placed together on the metal floor (5); The tightly coupled buffer layer (3) is placed above the low-frequency antenna (1) and surrounds the high-frequency antenna (2), so that the two maintain tight coupling in different frequency bands; the tightly coupled buffer layer (3) is a layer of conductor composite structure, which maintains tight coupling with the high-frequency and low-frequency antennas; it is composed of four L-shaped right-angle metal structures and is printed on the upper layer of the dielectric plate on which the low-frequency antenna is horizontally placed; The side reflection plate (4) is located between the low-frequency antenna (1) and the high-frequency antenna (2).

2. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 1, characterized in that: The low-frequency antenna (1) comprises four low-frequency dipole antenna units, each low-frequency dipole antenna unit is an L-shaped structure and is placed perpendicular to the metal floor (5), and the four low-frequency dipole antenna units form a hollow cavity structure; Two low-frequency dipole antenna units located at diagonal positions form a group, and are fed with equal amplitude and in phase to form radiation of one polarization; two low-frequency dipole antenna units at another diagonal position are fed with equal amplitude and in phase to form radiation of another orthogonal polarization.

3. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure according to claim 2, characterized in that: The low-frequency dipole antenna unit includes a low-frequency dielectric plate, a dipole arm and a feed balun. The floor of the dipole arm and the feed balun is printed on the outside of the low-frequency dielectric plate, and the inner core of the feed balun is printed on the inside of the low-frequency dielectric plate and located at the four corners of the hollow cavity structure.

4. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 2, characterized in that: A short-circuit metal strip is provided between two adjacent low-frequency dipole antenna units. The short-circuit metal strip is connected to the metal floor (5) below. The short-circuit metal strip is located outside the low-frequency dielectric plate and a gap is provided between the short-circuit metal strip and the dipole arm of the low-frequency dipole antenna unit.

5. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure according to claim 1, characterized in that: The high-frequency antenna (2) comprises a dual-polarization cross-dipole unit and a feeding structure. The dual-polarization cross-dipole unit is placed horizontally and comprises a high-frequency dielectric plate and a dipole arm printed on the upper surface of the high-frequency dielectric plate. The dipole arm is a square aperture structure. A square through hole is opened in the central area of ​​the high-frequency dielectric plate for positioning the dielectric plate printed with the high-frequency antenna feeding structure placed vertically and allowing the feeding structure to pass through the positioning hole to be connected to the high-frequency antenna dipole arm.

6. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 5, characterized in that: A plurality of slot structures are etched on the dipole arm to expand the bandwidth of the high-frequency antenna.

7. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 5, characterized in that: The feeding structure of the high-frequency antenna is a feeding balun, which consists of a pair of cross-placed dielectric plates and a feeding balun structure printed thereon. The floor of the feeding balun is printed on one side of the dielectric plate, while the balun core is printed on the other side of the dielectric plate. The bottom of the balun is connected to the port of the coaxial feed line.

8. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 1, characterized in that: The tightly coupled buffer layer (3) comprises a dielectric plate placed horizontally and hollowed out in the middle, and a metal patch printed on the upper surface of the dielectric plate.

9. The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading and buffering structure according to claim 1, characterized in that: The side reflection plate (4) is a square structure formed by four vertically placed metal plates.

10. A debugging method for a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure according to any one of claims 1 to 9, characterized in that: include: By modifying the shape of the metal patch of the tightly coupled buffer layer (3) and adjusting the height and position of the side reflector (4), the matching performance and radiation performance of the high and low frequency antennas can be further optimized to meet the comprehensive requirements of multi-standard base station antennas for matching, radiation performance, volume and cost.

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