Low-profile dual-frequency shared aperture antenna array based on tight coupling loading buffer structure

Abstract

The invention particularly relates to a low-profile dual-frequency shared aperture antenna array based on a tight coupling loading buffer structure. The low-profile dual-frequency shared aperture antenna array comprises a low-frequency antenna, a high-frequency antenna, a tight coupling buffer layer, a side reflecting plate and a metal floor, the low-frequency antenna and the high-frequency antenna are arranged in the same aperture range and are jointly placed on the metal floor; the tight coupling buffer layer is placed above the low-frequency antenna and surrounds the high-frequency antenna, so that the low-frequency antenna and the high-frequency antenna are tightly coupled at different frequency bands; the side reflecting plate is located between the low-frequency antenna and the high-frequency antenna. According to the invention, the tight coupling buffer layer is loaded between the low-frequency antenna and the high-frequency antenna, and the side reflecting plate and the metal floor are combined to realize low profile and cross-frequency interference suppression.

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 the demand for network capacity and multi-band coverage in mobile communication systems continues to increase, 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, when antennas of different frequency bands are closely placed in the same aperture, the following problems often arise:

[0003] 1. Low-frequency antenna blocks high-frequency antenna

[0004] The antennas in lower frequency bands are larger in size and can easily physically block the high-frequency antennas, causing problems such as distortion of the radiation pattern and reduction in gain of the 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, directly reducing the profile of low-frequency antennas will lead to a decrease in impedance matching and bandwidth performance of low-frequency antennas.

[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 the prior art known to ordinary technicians in the 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, side reflector and metal floor;

[0014] The low-frequency antenna and the high-frequency antenna are arranged within the same aperture range and are 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 is an L-shaped structure and is placed perpendicular to a metal floor, and the four low-frequency dipole antenna units form a hollow cavity structure; two low-frequency dipole antenna units located at a diagonal position form a group, and are fed with equal amplitude and in phase to form radiation of one polarization; and 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 board, a dipole arm and a feed balun, the dipole arm and the floor of the feed balun are printed on the outside of the low-frequency dielectric board, and the inner core of the feed balun is printed on the inside of the low-frequency dielectric board and located at the four corners of the hollow cavity structure.

[0019] In some exemplary embodiments, a short-circuit metal strip is arranged 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 arranged 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 board and a dipole arm printed on the upper surface of the high-frequency dielectric board, and the dipole arm is a square aperture structure; a square through hole is opened in the central area of ​​the high-frequency dielectric board for positioning the vertically placed dielectric board printed with the high-frequency antenna feeding structure, and allowing the feeding structure to pass through the positioning hole to be connected 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 balun core 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 dielectric plate placed horizontally and hollowed out in the middle, and a metal patch printed on an upper surface of the dielectric plate.

[0024] In some exemplary embodiments, the side reflective plate 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-frequency shared aperture antenna array based on a tightly coupled loading buffer structure provided by the embodiment 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 and combining designs such as side reflectors and metal floors. It has the following advantages:

[0028] 1. Significantly reduce profile height

[0029] Under the premise of 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 needs 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, the shielding effect of the low frequency antenna on the high frequency antenna is significantly reduced, which suppresses the induced current on the low frequency antenna when the high frequency antenna is working, thereby reducing the scattering effect of the induced current on the high frequency antenna. This allows the high frequency antenna to maintain good radiation characteristics without the need to introduce additional complex de-scattering or frequency selection structures.

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

[0037] The tightly coupled buffer layer acts as an "electromagnetic buffer layer". Whether the low-frequency or high-frequency antenna is excited, the electromagnetic energy will be coupled to the tightly coupled buffer layer, thereby significantly reducing the electromagnetic energy coupled to the antenna port of another frequency band. This design achieves good cross-frequency port isolation without the need to introduce additional complex decoupling or filtering structures.

[0038] 6. Compatibility and scalability

[0039] The 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 and 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 herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0042] Figure 1 It is a structural schematic diagram of a low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer 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 Schematic diagram of the comparison of the input impedance of port c1 of each low-frequency antenna model in the range of 0.69-0.96GHz: (a) Smith chart (normalized to 50Ω); (b) reflection coefficient;

[0045] Figure 4It is a structural schematic diagram 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 part is the overall structure and the local enlargement; the lower part is the hollow cavity composed of the low-frequency dipole and the local enlargement;

[0046] Figure 5 The performance simulation diagram of the low-profile broadband low-frequency antenna in the embodiment of the present invention is as follows: (a) Smith chart in the range of 0.69-0.96GHz (normalized to 50Ω); (b) S parameters; (c) radiation pattern of the c1 port in the yoz plane; (d) LB band gain;

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

[0048] Figure 7 Performance simulation diagram of the high-frequency antenna of an embodiment of the present invention: (a) S parameter; (b) gain; (c) radiation pattern of port No. 5 in the yoz plane;

[0049] Figure 8 Schematic diagram of comparison of port reflection coefficients of the high-frequency antenna of an embodiment of the present invention in three situations, namely, situation A: high-frequency antenna only; situation B: high-frequency antenna + tightly coupled buffer layer; situation C: high-frequency antenna + tightly coupled buffer layer + low-frequency antenna;

[0050] Fig. 9 Schematic diagram of 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, i.e., excited by port 5 (-45° polarization);

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

[0052] Fig.11 Schematic diagram of the comparison of cross-frequency coupling coefficients in two cases without and with a tightly coupled buffer layer: (a) without a tightly coupled buffer layer; (b) with a tightly coupled buffer layer;

[0053] Fig.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] Fig.13 The following is a physical picture of the antenna array and a schematic diagram of the darkroom test;

[0055] Fig.14 Schematic diagram of the comparison between the measurement and simulation results of the low-frequency antenna: (a) S parameters; (b) gain; (c) radiation pattern of the c1 port in the yoz plane;

[0056] Fig.15 Schematic diagram of the comparison between 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] Fig.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 figure, 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- balun core of the high frequency antenna; 2β- balun floor of the high frequency antenna. DETAILED DESCRIPTION

[0060] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and 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 only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0062] In the related art, the following method is disclosed to solve the problem that occurs when antennas of different frequency bands are closely placed in the same aperture:

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

[0064] Choke filter structures, slot structures, frequency selective surfaces, open resonant rings or metasurfaces are integrated into low-frequency antennas to suppress the induced current on the low-frequency antenna when the high-frequency antenna is working, and reduce its scattering effect on the high-frequency antenna, thereby making the low-frequency antenna "electromagnetically invisible" in the high-frequency band. However, these measures often lead to different degrees of degradation of the performance of the low-frequency antenna or increase the difficulty of its 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 solve the cross-band interference well. 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 will increase the structural complexity and manufacturing cost of the antenna.

[0069] 4. Use back cavity structure:

[0070] The high-frequency antenna is raised to the same height as the low-frequency antenna, embedded in the low-frequency radiator, and an additional metal back cavity is set as a high-frequency reflection surface to improve the high-frequency radiation pattern and gain; however, this will also make 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 can only be achieved through additional structures; for low-profile base station antennas, reducing the profile will seriously affect the matching and bandwidth performance of the low-frequency antenna.

[0072] In response to the shortcomings and deficiencies of the prior art, this example implementation provides a low-profile dual-frequency shared-aperture antenna array based on a tightly coupled loaded buffer structure, in which a tightly coupled buffer layer is arranged 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] Below, 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 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 is composed of four dipole antenna units and preferably arranged in a bowl shape, i.e., a hollow cavity structure; a horizontally placed printed tight coupling buffer layer 3 is loaded above the four dipole antenna units. The dipole antenna unit is an L-shaped structure and is placed vertically on the metal floor 5. By feeding two low-frequency dipole antenna units at the diagonal position with equal amplitude and phase together to form one polarized radiation, and feeding another group of antenna units with equal amplitude and phase together to form another polarized radiation, 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 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 vertically placed in the hollow cavity of the low-frequency antenna. The feed balun core 1a is printed on the inside of the low-frequency dielectric plate vertically placed in the hollow cavity of the low-frequency antenna. Metal through holes 1e and metal strips connecting the upper and lower metal through holes are provided inside and outside the low-frequency dielectric plate. The metal through holes and the metal strips are used to adjust the impedance matching of the low-frequency antenna. A square card slot is provided at the lower edge of the feed balun dielectric plate, which is not only used to insert the low-frequency antenna 1 pair onto the metal floor 5 and ensure the correct positional relationship between the two, but also used to extend the feed circuit to the bottom of the metal floor 5 and connect it 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 1a 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 As shown, the evolution process and key geometric structure of the low-profile broadband low-frequency antenna of the present invention are schematically shown, including model 1, model 2, model 3, and model 4. This process illustrates how to gradually evolve from the traditional bowl-shaped structure (model 1) to model 4 with lower profile and multi-resonance point characteristics. Among them, model 1 adopts a conventional bowl-shaped four-arm dipole with a profile height of about 0.24λ0\lambda_0 (λ0\lambda_0 is the free space wavelength at 0.82GHz). At this time, there is only a single resonance, and the bandwidth is relatively limited; model 2 reduces the profile to about 0.098λ0\lambda_0 without changing the aperture size, but will introduce a strong inductive effect, making the matching performance worse; after adding a tightly coupled buffer layer to model 3, additional capacitance compensation can be formed in the low frequency band, compensating for the inductive effect in model 2, forming a new resonance near 0.71GHz, so that the bandwidth is expanded; model 4 adds a short-circuited metal strip to further improve the high-end impedance matching, and introduces a third resonance point at about 0.95GHz. 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, it can be seen that models 3 and 4 significantly expand the bandwidth and improve the matching. The structural diagram after adding the feed balun on the basis of model 4, that is, the low-frequency antenna (model 5): It is the overall structure and the partial enlargement. It can be seen that the floor and the inner core of the feed balun are printed on the upper and lower layers of the dielectric plate respectively; it is a partial enlargement of the hollow cubic dipole, which can more intuitively present the four-arm bowl-shaped dipole arrangement. Figure 5 The performance of the low-frequency antenna (model 5) is shown below: (a) Smith circle diagram in the range of 0.69--0.96 GHz (normalized to 50Ω); (b) S parameters; (c) radiation pattern of the c1 port in the yoz plane; (d) gain in the low-frequency band.

[0081] Test / simulation data show that:

[0082] 1. The reflection coefficient is lower than -10dB, covering 0.69--0.96GHz (bandwidth 32.7%), and still maintains good impedance matching under the condition of low profile 0.087λL\lambda_L;

[0083] 2. The gain is 7.7-8.9dBi in this bandwidth, and the XPD (cross-polarization suppression) is higher than 45dB in the main beam direction;

[0084] 3. Isolation (c1 to c2) can reach over 51.2dB.

[0085] In summary, it can be seen that by loading short-circuited 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.

[0086] 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, which 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 a 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 (feeding balun) of the high-frequency antenna is composed of a pair of cross-placed dielectric plates and the feeding structure printed thereon. The electric balun structure is composed of a feed balun floor 2β printed on one side of the dielectric board, and a balun core 2α printed on the other side of the dielectric board, and a feed balun 2a is connected to a RF connector below; through electromagnetic coupling with a tightly coupled buffer layer, the high-frequency antenna will generate an additional resonant mode, so that the original high-frequency bandwidth of about 45% is expanded to about 59% or wider, thereby adapting to a larger number of channel requirements; in the high-frequency band, the tightly 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 to the low-frequency antenna and other complex designs.

[0087] Figure 7 The performance of the high-frequency antenna when working alone is shown, namely (a) S parameters, (b) gain, and (c) radiation pattern of port 5 in the yoz plane. The test results show that about 45.5% bandwidth (|S55|<-14dB) is obtained in the range of 1.7–2.7GHz, the isolation between ports is better than 26.4dB, the gain is maintained between 8.1–9.3dBi, and the main beam XPD exceeds 20dB.

[0088] Figure 8 A comparison diagram of |S55| of the high-frequency antenna in three situations is given, namely:

[0089] · Case A: High frequency antenna only;

[0090] · Case B: HF antenna + TCBL;

[0091] · Case C: high frequency antenna + TCBL + low frequency antenna.

[0092] As can be seen from the figure, after adding TCBL (case B), an additional resonance appears at 1.5GHz, and the bandwidth is expanded from the original 45.5% to about 60.2%. Even when it is co-located with the low-frequency antenna (case C), the high-frequency bandwidth can still be stably maintained at 1.47-2.7GHz (59.0%), and the isolation between ports is not significantly affected.

[0093] Fig. 9 The current distribution at the corresponding resonance point of case A and case B is shown. It can be seen that when TCBL exists, TCBL itself takes on an additional resonant current path, thereby expanding the overall bandwidth and blocking part of the coupling energy.

[0094] 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, which maintains tight coupling with the high and low-frequency antennas; it is composed of four L-shaped right-angle metal structures, which are printed on the upper layer of the dielectric board horizontally placed on the low-frequency antenna; 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 cross-frequency antenna profile; it introduces new resonance in the high-frequency band, expands the high-frequency bandwidth, and naturally blocks cross-frequency energy coupling.

[0095] Furthermore, the tight coupling buffer layer 3 has a thickness of 1-3 mm.

[0096] 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 at 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.

[0097] 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.

[0098] Exemplarily, the metal floor 5 serves as the installation reference plane for the entire antenna, and the low-frequency antenna and the high-frequency antenna are fixed thereon; the lower edges of the low-frequency antenna and the high-frequency antenna dielectric plates have square slots or slots that cooperate with the metal floor, and are fixed with screws or buckles to ensure the precise alignment of the antenna in the vertical and horizontal directions.

[0099] Furthermore, the metal floor is a 1-2 mm thick metal plate.

[0100] Fig.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). Fig.10 (b) For gain and Fig.11 (c) The comparison of the directional patterns shows that when the low-profile low-frequency + side reflector solution of the present invention is used, the high-frequency antenna gain is more stable and the beam distortion is significantly reduced. In the traditional staggered or embedded design, the high-frequency antenna is significantly blocked by the low-frequency antenna, and the gain fluctuation can reach up to 6.8dB; Fig.10(b) Under this scheme, the high-frequency gain fluctuation is reduced to within 1.7 dB, and the beam shape is more uniform.

[0101] Fig.11 The comparison of various cross-band coefficients without TCBL (a) and with TCBL (b) is shown: the coupling from the low-frequency port into the high-frequency band is improved from -10.7dB to -25.4dB;

[0102] Fig.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 forms a natural blockage on the coupling path.

[0103] Comparison between measured and simulated results:

[0104] Fig.13 The following are the actual pictures of the antenna array and the darkroom test schematic diagram. The far-field measurement system built with the Rohde & Schwarz ZNBT8 network analyzer and the Keysight N5183A MXG signal source / N5264BPNA-X tester has obtained the following conclusions:

[0105] Low frequency band:

[0106] like Fig.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.

[0107] High frequency band:

[0108] Fig.15 It shows that in the range of 1.47–2.7GHz (59.0%), |S55|, |S66|<-14dB, isolation <-22.3dB, and gain of about 6.6–8.0dBi are maintained;

[0109] Fig.16 A comparison is made between the cross-frequency coupling of the low-frequency antenna and the high-frequency antenna. It can be seen that when there is no tightly coupled buffer layer, the value is only about -10dB at some frequency points, while under the solution of the present invention, an improvement of -20dB to -25dB can be achieved.

[0110] The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure provided by the embodiment of the present invention has achieved significant improvements in profile height, cross-frequency isolation and high-frequency bandwidth:

[0111] The low-frequency operating bandwidth is 0.69–0.96 GHz, and the cross section is only 0.087λL\lambda_L;

[0112] The high-frequency bandwidth is increased from 45% to 59%, and the port isolation is significantly improved;

[0113] When side reflectors are used, the high-frequency antenna pattern and gain fluctuation can be further optimized.

[0114] If it is necessary to support three or more frequency bands in the future, it is possible to achieve a higher level of multi-frequency common-aperture antenna integration by adding additional tightly coupled buffer layers, or moderately expanding the aperture on the metal floor, and fine-tuning antennas of different frequency bands based on similar tight coupling principles.

[0115] The low-profile dual-frequency shared aperture antenna array based on a tightly coupled loading buffer structure provided by the embodiment of the present invention, based on the concept of tight coupling, loads a tightly coupled buffer layer between the low-frequency antenna and the high-frequency antenna, and combines the side reflector and metal floor and other characteristic designs to successfully achieve the goals of low profile, broadband coverage and cross-frequency interference suppression. Compared with the existing technology, the advantages are as follows:

[0116] 1. Low profile and broadband coexistence

[0117] 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.

[0118] 2. Cross-frequency interference suppression

[0119] Without adding special filtering surfaces or complex metal rings and other units, the tightly coupled buffer layer can be used to 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;

[0120] The tightly coupled buffer layer also acts as an "electromagnetic buffer layer". It can reduce the electromagnetic energy coupled to the antenna port of another frequency band when the high-frequency or low-frequency antenna is excited, that is, suppress the cross-frequency coupling interference, thereby achieving excellent cross-frequency port isolation performance without the need to introduce additional complex decoupling or filtering structures.

[0121] 3. High-frequency broadband expansion

[0122] 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.

[0123] 4. Compatibility and scalability

[0124] By modifying the shape and layering of the tightly coupled buffer layer and adjusting the position of the metal floor and the side reflector, this solution can further adapt to the design of shared-aperture antennas for three or even more frequency bands, and meet the comprehensive requirements of future multi-standard base station antennas for bandwidth, volume and cost.

[0125] Other embodiments of the 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 invention that follow the general principles of the invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0126] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention 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 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 buffer structure according to claim 1, characterized in that: The low-frequency antenna (1) comprises four low-frequency dipole antenna units, each of which is an L-shaped structure and is placed vertically on 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 group of diagonal positions 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 board, 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 board, and the inner core of the feed balun is printed on the inside of the low-frequency dielectric board and is 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 buffer structure according to claim 2, characterized in that: A short-circuit metal strip is arranged between two adjacent low-frequency dipole antenna units. The short-circuit metal strip is connected to the metal floor (5) at its bottom. The short-circuit metal strip is located outside the low-frequency dielectric plate and a gap is arranged 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 and vertically placed, and allows the feeding structure to pass through the positioning hole so as 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 buffer 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 buffer 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, and 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 buffer 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 buffer 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, 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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