Wide-angle scanning co-polarized dual-polarized tight-coupling array antenna

Abstract

The application belongs to the technical field of antennas and relates to a wide-angle scanning co-aperture dual-polarized tight coupling array antenna, which comprises a low-frequency antenna array surface, a low-frequency vertical branch, a low-frequency feed balun, a high-frequency antenna array surface, a low-frequency feed network and a coaxial joint. The application avoids loading of resistive materials by decomposing a traditional ultra-wideband tight coupling array antenna into two antennas with smaller bandwidths and arranging the two antennas in a co-aperture mode. The upper low-frequency antenna unit is divided into multiple sub-units, and a meandering line design is adopted to realize electromagnetic transparency of the lower high-frequency antenna. Loading of the vertical branch further suppresses mutual interference between the high-frequency and low-frequency antennas. The low-frequency sub-units after fractalization are combined into a large unit by a power divider. In a working frequency band of 2GHz-6GHz and 7GHz-18GHz, the average efficiency reaches 85%, and the active standing wave ratio is less than 4 within a scanning range of ±60°, thereby overcoming the problems of the traditional design that cannot simultaneously achieve ultra-wideband, high efficiency, wide-angle scanning and dual polarization.

Description

Technical Field

[0001] This invention belongs to the field of antenna engineering technology and relates to a common aperture dual-polarized tightly coupled array antenna capable of wide-angle scanning, in order to meet the performance requirements of high efficiency, dual polarization and wide-angle scanning in ultra-wideband phased array engineering applications. Background Technology

[0002] With the rapid development of modern communication systems, higher demands are being placed on phased array antennas with ultra-wideband, high efficiency, and wide-angle scanning characteristics. Tightly coupled dipole antenna arrays introduce coupling structures between antenna elements to approximately form a stable, continuous current distribution on the array surface. This results in a slow change in the antenna's input impedance bandwidth with frequency. Furthermore, the introduction of capacitive coupling also counteracts the inductive effect generated by the ground plane, thus giving tightly coupled antenna arrays inherently wideband characteristics. Further, through careful design of the dipole elements and feeding structure, as well as the loading of a wide-angle matching layer, ultra-wideband and wide-angle scanning of the tightly coupled array can be achieved. In addition, compared to traditional wideband antennas such as Vivaldi, tightly coupled arrays also offer numerous advantages such as miniaturization, low profile, and ease of conformal design.

[0003] In the process of further widening tightly coupled antennas, at the low-frequency end, due to the antenna profile being too low, some energy is reflected by the ground plane and cancels out another portion, preventing normal outward radiation and ultimately limiting its low-frequency bandwidth expansion. At the high-frequency end, when the antenna profile exceeds half a wavelength, a short-circuit resonance forms between the feed balun and the ground plane, disrupting the antenna's performance and further limiting its bandwidth expansion towards higher frequencies. To address these issues, a conventional solution is to introduce resistive structures to absorb unwanted energy. For example, in the paper "A Ferrite-Loaded Ultralow Profile Ultrawideband Tightly Coupled Dipole Array," the authors added a ferrite structure between the antenna and the ground plane to absorb back radiation, ultimately achieving a 10th-harmonic bandwidth with a low profile. In the paper "Phased ArrayWith Low-Angle Scanning and 46:1 Bandwidth," the authors designed a multi-layered resistive frequency-selective surface to absorb common-mode resonances at multiple frequencies, ultimately achieving an ultrawide bandwidth of 46th harmonics. However, while absorbing useless energy, the aforementioned resistive materials also absorb normally radiated electromagnetic waves, causing a significant decrease in antenna efficiency, and even resulting in a loss of more than 50% in some frequency bands. This has a great impact on the performance of the entire communication system.

[0004] To address the trade-off between bandwidth and efficiency in tightly coupled arrays, the paper "An Extremely Wideband Tightly Coupled Dipole Array With Shared-Aperture Configuration" proposes incorporating the concept of shared aperture into the design. The authors arrange two tightly coupled arrays with smaller bandwidths under the same aperture plane, achieving a combined bandwidth of 23.2 octaves. Since no resistive materials are required, the average efficiency of the array reaches 80%. However, due to the complex coupling relationship between the two frequency bands, the authors only achieved a maximum scan angle of ±30° in single-polarization mode, which still presents certain limitations in practical engineering.

[0005] As a crucial component in key fields such as satellite communication, electronic warfare, and military radar, phased array antennas have always faced the urgent need for a combination of ultra-wideband, high efficiency, wide-angle scanning, and multi-polarization performance. Existing tightly coupled antenna designs have struggled to achieve both ultra-wideband and high efficiency, or fail to meet other important performance indicators such as wide-angle scanning. To address this issue, the co-aperture dual-polarization tightly coupled array antenna with wide-angle scanning proposed in this invention is of significant importance. Summary of the Invention

[0006] Based on the aforementioned background technology, and addressing the shortcomings of existing technologies, this invention provides a wide-angle scanning common-aperture dual-polarized tightly coupled array antenna. The antenna consists of two tightly coupled arrays of two frequency bands, both of which radiate in a dual-polarized manner. The low-frequency antenna is placed above the high-frequency antenna. After electromagnetic transparency treatment, the mutual coupling between the two frequency band antennas is reduced, ensuring that the high-frequency and low-frequency arrays can operate normally under the same aperture. While achieving high radiation efficiency, a special loading is applied to the low-frequency antenna to solve the problem that existing common-aperture tightly coupled arrays cannot perform wide-angle scanning. Ultimately, the antenna operates in the frequency bands of 2GHz to 6GHz and 7GHz to 18GHz, which is a 9th octave bandwidth.

[0007] To achieve the above objectives, the present invention adopts the following solution:

[0008] This invention provides a co-aperture dual-polarization tightly coupled array antenna capable of wide-angle scanning. The aperture element, from top to bottom, includes a low-frequency antenna array, a low-frequency vertical stub, a low-frequency feed balun, a high-frequency antenna array, a low-frequency feed network, and a coaxial connector.

[0009] The low-frequency antenna array consists of nine groups of dual-polarized low-frequency dipole elements. Each antenna element has six slots of unequal length on each arm to form a meandering structure. The dual-polarized low-frequency dipoles are identical in shape and are printed on both sides of a Rogers 4003 dielectric substrate, with the ends of the dipole arms partially overlapping vertically. A square hole is made in the substrate at each dipole feed point to insert a low-frequency feed balun; a square hole is also made at the third slot of each dipole arm to insert a low-frequency vertical stub.

[0010] The low-frequency vertical stub is a slender rectangular patch printed on a Rogers 5880 dielectric substrate. After being inserted into the low-frequency antenna array, it is connected to the upper end and the low-frequency dipole arm.

[0011] The low-frequency feeding balun is a microstrip gradient balun, printed on both sides of the Rogers 6002 dielectric substrate, with the metal portion on the ground plane side hollowed out.

[0012] The high-frequency antenna array consists of nine sets of dual-polarized high-frequency dipoles and Marchand baluns. The dipoles and baluns are printed on one side of a Rogers 6002 dielectric layer, and the other side is printed with inter-unit coupling patches and gradient feed lines. The dual-polarized antennas are arranged in a vertical grid and the feed end is extended to pass through the low-frequency feed network and connect to a coaxial junction.

[0013] The low-frequency feed network consists of a three-layer metal structure and two layers of Rogers 5800 dielectric substrate. The top and bottom sides are equipped with dual-polarized 1-to-9 Wilkinson power dividers. The output of the power divider is connected to the low-frequency feed balun, and the input is connected to a coaxial connector after a vertical bend. The common ground of the entire common-aperture antenna is located between the two base halves. The low-frequency feed network is designed to allow the insertion and passage of both the low-frequency feed balun and the high-frequency antenna array.

[0014] The 1-to-9 Wilkinson power divider is composed of four cascaded 1-to-3 unequal-division Wilkinson power dividers. The power dividers are isolated using 100Ω surface-mount resistors, and the dual-polarization power dividers exhibit consistent performance.

[0015] Compared to traditional tightly coupled array antennas, this invention employs a dual-frequency common-aperture configuration to synthesize ultra-wideband antennas. It innovatively decomposes a large-size low-frequency antenna element into nine smaller elements connected by a power divider, thereby achieving superior electromagnetic transparency. Furthermore, it introduces low-frequency vertical stubs, which greatly suppresses mutual interference between high- and low-frequency antennas. Ultimately, under the premise of dual polarization, the antenna achieves an average total efficiency of 85% within a 9th octave bandwidth without the need for resistive materials, and can meet the requirement of an active VSWR of less than 4 within a ±60° range. In addition, the antenna profile height is only 0.067 times the wavelength, classifying it as a low-profile array antenna. Attached Figure Description

[0016] Figure 1This is a schematic diagram of the unit structure of the present invention under a periodic environment.

[0017] Figure 2 yes Figure 1 The image shows a front view of a small element within a large low-frequency antenna element in the antenna structure shown.

[0018] Figure 3 yes Figure 2 Left view of the antenna structure shown.

[0019] Figure 4 yes Figure 1 The front view of a high-frequency antenna element in the antenna structure shown.

[0020] Figure 5 yes Figure 4 The right view of the antenna structure shown.

[0021] Figure 6 yes Figure 1 The front view of the low-frequency feed network in the antenna structure shown.

[0022] Figure 7 yes Figure 6 The exploded diagram of the low-frequency power supply network is shown.

[0023] Figure 8 yes Figure 1 The low-frequency active VSWR diagram of the antenna structure shown.

[0024] Figure 9 yes Figure 1 The high-frequency active VSWR diagram of the antenna structure shown.

[0025] Figure 10 yes Figure 1 The diagram shows the overall efficiency of the antenna structure. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The present invention includes, but is not limited to, the specific working states of the antennas listed below.

[0027] Reference Figure 1 , reference Figure 2 , reference Figure 3 , reference Figure 4 , reference Figure 5 , reference Figure 6 , reference Figure 7 .

[0028] like Figure 1As shown, this invention provides a unit structure for a wide-angle scanning, co-aperture dual-polarized tightly coupled array antenna in a periodic environment (the illustrated structure in a periodic environment, with the left and right sides and the front and rear boundaries considered interconnected), including a low-frequency antenna array 1, a low-frequency vertical stub 2, a low-frequency feed balun 3, a high-frequency antenna array 4, a low-frequency feed network 5, and a coaxial connector 6. The low-frequency antenna unit is composed of 9 sub-units, employing a fractal structure to achieve better electromagnetic transparency. The low-frequency antenna array is horizontally positioned directly above the aperture. The low-frequency vertical stub and the low-frequency feed balun connect to the low-frequency antenna array and are perpendicular to the low-frequency feed network. The output terminals of the low-frequency feed balun are connected to the output terminals of each feed network. The high-frequency antenna array is vertical, with 9 independent dipoles for each polarization within the co-aperture unit. The dual-polarized high-frequency antennas are perpendicularly interleaved to form a grid, positioned below the high-frequency antenna array. The feed terminals extend and pass through the low-frequency feed network before connecting to the coaxial port. In practical engineering applications, this common aperture array unit can be expanded into an array of arbitrary size along the length and width directions.

[0029] The low-frequency antenna array is composed of, for example... Figure 2 The antenna consists of nine identical dual-polarized dipole units, each dipole arm having a meandering slotted structure. This design extends the current path flowing through the antenna, thereby reducing interference to the high-frequency antenna. The horizontally polarized patch 1.1 and the vertically polarized patch 1.2 are printed on the upper and lower sides of the low-frequency array substrate 1.3, respectively. The dual-polarized patches are centrally symmetrical and overlap at their ends to form capacitive coupling.

[0030] The low-frequency vertical stub is a short strip-shaped metal patch 2.1, printed on a vertical stub substrate 2.2. This stub is inserted into the slot of each dipole arm (the third arm outwards from the feed point) and the metal parts are soldered together, with the side of the stub with the printed patch facing the feed point. Figure 1 The common-aperture element shown should have a total of 36 branches. By loading vertical branches, the mutual interference between high and low frequencies of the common-aperture array during large-angle scanning can be further suppressed.

[0031] The low-frequency feed balun is an improved microstrip graded balun. The balun ground plane 3.1 is an exponentially graded line patch with a cutout design to improve impedance matching. It is printed on one side of the low-frequency balun substrate 3.2, with its two ends soldered to one arm of the low-frequency dipole and the ground plane, respectively. The other side of the substrate 3.2 has feed microstrip lines printed on it. Depending on the low-frequency feed requirements, these are divided into vertically polarized feed lines 3.3 that pass through the ground plane at the bottom, and horizontally polarized feed lines 3.4 that do not pass through the ground plane. The upper ends of both are soldered to the other arm of the low-frequency dipole patch, and the lower ends are soldered to the corresponding low-frequency feed network output. Figure 1 The common-aperture unit shown should contain a total of 18 low-frequency feed baluns.

[0032] The high-frequency antenna array consists of a high-frequency dipole body 4.1 printed on one side of the high-frequency antenna substrate 4.3, a coupling patch 4.2 printed on the other side, and a tapered feed line 4.4. The feed utilizes a Marchand balun, and the tapered feed line achieves a 50Ω input impedance change to the dipole. The dual-polarized antennas are completely uniform except for the slotted area of ​​the coupling patch, and are arranged in a 3×3 grid pattern within a common aperture element. The high-frequency antenna array feed terminal 4.5 extends to pass through the low-frequency feed network and is welded to the coaxial connector 6.

[0033] The low-frequency feed network, from top to bottom, consists of an upper power divider 5.1, an upper dielectric substrate 5.4, a metal ground plane 5.3, a lower dielectric substrate 5.5, and a lower power divider 5.2. Both power dividers are cascaded from four 1-to-3 unequal power dividers to form a 1-to-9 power divider, using 16 100Ω surface mount resistors 5.6 for port isolation. The two power dividers operate identically except for some differences in winding. The upper power divider's input terminal 5.1.1 is vertically bent and then passes through two dielectric substrates and the metal ground plane before being welded to a coaxial connector; its nine output terminals 5.1.2 are welded to the horizontally polarized feed line 3.4. The lower power divider's input terminal 5.2.1 is directly bent and then welded to a coaxial connector; its nine output terminals are welded to the vertically polarized feed line 3.3. The nine sub-units of the low-frequency antenna array are thus combined into a single large unit via the power divider, reducing the number of coaxial connectors required. In actual manufacturing, both the power divider and the ground plane are directly printed on the dielectric substrate, and the two substrates are bonded together. The low-frequency feed balun and the high-frequency antenna array are inserted integrally into the slots reserved in the upper dielectric substrate, and the balun ground plane 3.1 and the high-frequency dipole 4.1 are welded to the ground plane. The vertically polarized balun further passes through the reserved gap between the ground plane and the lower substrate, so that the vertically polarized feed line 3.3 is welded to the output end of the lower power divider; the high-frequency antenna array feed end 4.5 also further passes through the reserved gap between the metal ground plane and the lower substrate, and is welded to the coaxial connector.

[0034] The low-frequency array substrate 1.3 is a Rogers 4003 dielectric substrate, the vertical stub substrate 2.2 is a Rogers 5880 dielectric substrate, the low-frequency balun substrate 3.2 is a Rogers 6002 dielectric substrate, and the high-frequency antenna substrate 4.3, the upper dielectric substrate 5.4, and the lower dielectric substrate 5.5 are all Rogers 5880 dielectric substrates.

[0035] All coaxial connectors have an input impedance of 50Ω, and any feasible model can be adopted according to actual manufacturing requirements.

[0036] Since the dual-polarized antennas in the wide-angle scanning co-aperture dual-polarized tightly coupled array antenna proposed in this invention are centrally symmetrically distributed, taking horizontal polarization as an example, the following is given: Figure 1 The simulation results of the common aperture antenna element shown are in a periodic environment.

[0037] Figure 8 for Figure 1 The active VSWR of the antenna structure in the low-frequency band (2GHz-6GHz) shows that the active VSWR of the E-plane is below 2.5 and the active VSWR of the H-plane is below 4 when the maximum scanning angle is 60°.

[0038] Figure 9 for Figure 1 The active VSWR of the antenna structure shown is in the high-frequency band (7GHz-18GHz). It can be seen that the active VSWR of both the E-plane and H-plane is below 3.8 when the maximum scanning angle is 60°.

[0039] Figure 10 for Figure 1 The overall efficiency diagram of the antenna structure shown indicates that the average overall efficiency of the antenna reaches 85% within the operating frequency band, with a slight decrease around 7GHz due to the proximity of high and low frequencies. Compared to existing resistive materials or simple co-aperture tightly coupled arrays, this invention simultaneously possesses ultra-wideband, high efficiency, wide-angle scanning, and dual polarization.

[0040] The above description and embodiments are only some preferred examples of the present invention and do not constitute any limitation on the present invention. For those skilled in the art, this application can have various modifications and variations, but modifications and changes based on the concept of the present invention are still within the protection scope of the claims of the present invention.

Claims

1. A common-aperture dual-polarization tightly coupled array antenna capable of wide-angle scanning, characterized in that, It includes, from top to bottom, a low-frequency antenna array, a low-frequency vertical stub, a low-frequency feed balun, a high-frequency antenna array, a low-frequency feed network, and a coaxial connector; The low-frequency antenna array includes a low-frequency array dielectric substrate and low-frequency dipole units. The low-frequency antenna array has a horizontal structure. The dual-polarized dipole units are printed on the upper and lower sides of the substrate, and each unit is composed of nine dual-polarized low-frequency dipole units. They overlap vertically at the ends of the dipole arms. Each unit is connected to a low-frequency vertical stub and a low-frequency feed balun. Electromagnetic transparency is achieved by creating a meandering line design by opening six slots of unequal length in each dipole arm. The low-frequency vertical stub includes a metal strip patch and a vertical stub dielectric substrate. It is connected to the low-frequency dipole arm by inserting it into the third slot from the input end of each dipole arm, with one side of the patch facing the input end. The electromagnetic transparency effect of the low-frequency antenna requires a total of 36 vertical stubs in the low-frequency antenna array unit. The low-frequency feed balun includes an exponentially graded balun floor, a microstrip feed line, and a low-frequency balun substrate. The graded balun floor is hollowed out to tune impedance matching. There are a total of 9 low-frequency feed baluns in each polarization. All the low-frequency feed baluns in each polarization are connected to the low-frequency feed network below to form an input port, thereby avoiding waste of back-end RF components. The high-frequency antenna array includes a high-frequency dipole body, a gradient Marchand balun, a coupling patch, and a high-frequency antenna substrate. The gradient feed line realizes the change from 50Ω input impedance to the dipole. The high-frequency dipole body and the gradient feed line, along with the coupling patch, are printed on both sides of the high-frequency antenna substrate. The low-frequency power supply network consists of an upper power divider, an upper dielectric substrate, a metal ground plane, a lower dielectric substrate, and a lower power divider, arranged from top to bottom. Both power dividers are cascaded 1-to-9 Wilkinson power dividers, which are derived from four 1-to-3 unequal power dividers. The power dividers are printed on the upper and lower sides of the two dielectric substrates, respectively, and a metal ground plane is printed in the middle of the substrates and tightly attached.

2. The wide-angle scanning common-aperture dual-polarization tightly coupled array antenna according to claim 1, characterized in that, The low-frequency feed balun is a vertical structure, inserted upwards into each dipole port and connected to the port, and inserted downwards into the low-frequency feed network until the gradient index balun ground is connected to the ground. The upper end of the balun microstrip feed line is connected to one arm of the dipole, and the lower end is connected to the output port of the power divider. The horizontally polarized feed line is directly connected to the upper power divider, and the vertically polarized feed line is extended and passes through the reserved gap in the low-frequency feed network to connect to the lower power divider.

3. The wide-angle scanning common-aperture dual-polarization tightly coupled array antenna according to claim 1, characterized in that, The high-frequency antenna array has a vertical structure and is placed between the low-frequency antenna array and the low-frequency feed network. The dual-polarized high-frequency antennas are staggered at the slots of the metal patch to form a grid structure. There are a total of 9 independent high-frequency antennas under the common aperture unit. Except for the coupling patch, the dual-polarized high-frequency antenna units have completely identical structures. The main body of the high-frequency antenna passes through the upper dielectric substrate of the low-frequency feed network and is connected to the metal ground plane. The feed port extends through the lower dielectric substrate and connects to the coaxial connector.

4. A common-aperture dual-polarization tightly coupled array antenna capable of wide-angle scanning according to claim 1, characterized in that, The low-frequency power supply network is a horizontal structure. The upper and lower power dividers have the same performance except for slight differences in winding. Each power divider requires eight 100Ω chip resistors. The output of the upper power divider is connected to a horizontally polarized low-frequency power supply balun, and the input is connected to a coaxial connector after passing through two layers of dielectric substrate via a vertically bent structure. The output of the lower power divider is connected to a vertically polarized low-frequency power supply balun, and the input is connected to a coaxial connector via a vertically bent structure. The low-frequency power supply network needs to reserve gaps to allow the aforementioned structures to be inserted or passed through, and the metal parts must be kept separate.

5. A common-aperture dual-polarization tightly coupled array antenna capable of wide-angle scanning according to claim 1, characterized in that, The low-frequency array dielectric substrate is a Rogers 4003 dielectric substrate, the vertical stub substrate is a Rogers 5880 dielectric substrate, the low-frequency balun substrate is a Rogers 6002 dielectric substrate, and the high-frequency antenna substrate, upper dielectric substrate, and lower dielectric substrate are all Rogers 5880 dielectric substrates; all coaxial connectors have an input impedance of 50Ω.

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