A wavelength scaled array antenna based on interface capacitance recovery

Abstract

This invention discloses a wavelength-scaled array antenna based on interface capacitance recovery, belonging to the field of phased array antenna technology. The array antenna of this invention reconstructs the local electromagnetic boundary conditions equivalent to an ideal infinite-period array from the underlying circuit level by precisely implementing topological recovery of coupling capacitance and radiation slot capacitance at the boundaries of elements of different scales. This invention eliminates the need for any bulky macroscopic stepped transition structures or complex external impedance matching networks, perfectly compatible with low-profile multilayer PCB processes. While significantly reducing the number of active array elements and supporting RF channels and substantially lowering the hardware cost of the phased array system, it completely eliminates interface active impedance abrupt changes, achieving large-angle, blind-zone-free, high-quality beam scanning of the array over an ultra-wide bandwidth. This invention provides an innovative architecture and complete design principles with significant engineering practical value for low-cost, highly integrated, high-performance ultra-wideband phased array antenna systems.

Description

Technical Field

[0001] This invention belongs to the field of phased array antenna technology, specifically involving ultra-wideband tightly coupled arrays and low-cost phased array technology. Specifically, it relates to a wavelength-scaled array antenna based on interface capacitance recovery, which uses interface capacitance recovery to suppress impedance discontinuities at the junctions of subarrays of different physical scales. Background Technology

[0002] Phased array antennas enable rapid beam pointing control via electronic means and are widely used in radar detection, satellite communications, and other fields. In recent years, as system requirements for operating frequency bands and spatial scanning angles have increased, the number of active RF channels, phase shifters, and transceiver components required for the array has increased dramatically. This has not only led to high hardware costs but also caused an exponential increase in the complexity of the feed network, system power consumption, and the difficulty of array calibration.

[0003] To reduce the system cost of broadband phased arrays, existing technologies mainly include reconfigurable arrays (as described in patent document CN113851833A, application number 202111220999.7) and large-pitch sparse arrays (as described in patent document CN121642538A, application number 202511875078.2). While reconfigurable arrays can reduce the number of independent phase-shifting channels to some extent, the introduction of active devices such as diodes and RF switches, along with their drive control networks, significantly increases the complexity of the hardware structure. Furthermore, the high-frequency parasitic effects of these devices inevitably introduce insertion loss. Large-pitch sparse arrays reduce the number of array elements by breaking the Nyquist sampling theorem, but their aperiodic or non-uniform physical layout typically greatly increases the difficulty of RF channel wiring, array synthesis algorithms, and manufacturing consistency.

[0004] Against this backdrop, wavelength-scaled arrays have been proposed as a highly promising architecture. Their basic idea is based on the principle of electromagnetic scaling, integrating subarrays of different physical scales within the same physical aperture. This architecture can significantly reduce the total number of active elements and transceiver channels while maintaining full-band radiation and scanning capabilities. Planar ultra-wideband modular antennas are often used as the ideal basic unit for wavelength-scaled arrays due to their advantages such as low profile, ease of PCB manufacturing, high modular integration, and strong dual-polarization expansion capabilities. However, wavelength-scaled arrays face a key technical bottleneck in practical engineering applications: the physical discontinuity at the boundaries of subarrays of different scales can cause severe local electromagnetic discontinuities. For tightly coupled arrays, the core mechanism for achieving broadband matching lies in utilizing capacitive coupling between adjacent elements. When a larger-scaled element is directly spliced ​​with a smaller-scale reference element, the inter-element coupling capacitance at the boundary deviates from its target value in an ideal infinite-period array. Furthermore, for slotted tightly coupled arrays, the radiation slots along the orthogonal direction are abruptly truncated at the physical boundary, causing a sudden drop in the equivalent parallel radiation capacitance at the interface. The drastic changes in the local capacitance environment will directly cause a sudden change in the active input impedance of the interface unit. Macroscopically, this manifests as a spike in the active VSWR during broadband operation and beam scanning, and leads to a significant decrease in the antenna's actual gain.

[0005] Therefore, there is an urgent need for a wavelength-scale array antenna that can precisely adjust the interface equivalent capacitance without the need for additional complex external matching networks or heavy transition structures, and is suitable for wide bandwidth scanning systems. Summary of the Invention

[0006] The purpose of this invention is to solve the technical problems of active impedance abrupt change, active VSWR deterioration, and broadband scanning performance degradation at the junction of subarrays of different scales in existing wavelength scaled arrays, and to provide a wavelength scaled array antenna based on interface capacitance recovery.

[0007] The technical problem addressed by this invention is solved as follows:

[0008] A wavelength scaling array antenna based on interface capacitance recovery has a two-dimensional planar square grid arrangement and forms a concentric square ring nested structure from the inside out. It includes a reference antenna subarray in the central region, a scaling antenna subarray surrounding the reference antenna subarray, and dummy elements on the outermost periphery.

[0009] The reference antenna subarray consists of multiple reference antenna elements with a first physical scale; the scaled antenna subarray consists of multiple scaled antenna elements with a second physical scale. The scaled antenna elements have the same structure as the reference antenna elements, and the second physical scale is larger than the first physical scale.

[0010] A transition interface is formed at the interface between the reference antenna subarray and the scaled-down antenna subarray, including the inter-element coupling capacitance recovery interface and the radiation slot capacitance recovery interface. By adjusting the geometric topology of the reference antenna element and the scaled-down antenna element at the interface, the interface equivalent capacitance at the transition interface is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array.

[0011] Furthermore, the reference antenna elements in the central area are arranged in an 8×8 uniform pattern; 48 scaled-down antenna elements are arranged around the reference antenna elements; 36 dummy elements are further arranged around the scaled-down antenna elements. The dummy elements have the same structure as the scaled-down antenna elements, but are not connected to the active RF channel, and are connected to the matching load at their ends.

[0012] Furthermore, the reference antenna element operates in the first frequency band, with a frequency of 3 GHz to 8 GHz; the scaled-down antenna element operates in the second frequency band, with a frequency of 3 GHz to 4 GHz; the physical aperture area of ​​the scaled-down antenna element is four times that of the reference antenna element; in the first frequency band of 3 GHz to 4 GHz, both the reference antenna element and the scaled-down antenna element are excited simultaneously, with an excitation power ratio of 1:4 between the scaled-down antenna element and the reference antenna element; in the second frequency band of 4 GHz to 8 GHz, only the reference antenna element is excited.

[0013] Furthermore, both the reference antenna element and the scaled-down antenna element adopt a planar ultra-wideband modular antenna structure, which, from top to bottom, includes a suspended artificial dielectric layer 1, an air isolation layer 11, a top metal radiating layer 3, a first dielectric substrate 10, a feed network 6, a second dielectric substrate 9, and a bottom ground metal layer 7, all tightly bonded together. The upper and lower surfaces of the suspended artificial dielectric layer 1 are both square metal patches arranged in a 4×4 pattern. The top metal radiating layer 3 includes two metal patches, with an exponentially gradient radiation gap 4 between them to achieve a smooth impedance transition. A parasitic bowtie gap 2 is formed between the top metal radiating layer 3 and the edge of the first dielectric substrate 10 to provide capacitive coupling between adjacent antenna elements. The feed network 6 includes microstrip metal... The antenna unit is fed using a coaxial SMA feed interface 8. The outer conductor is connected to the bottom ground metal layer 7, and the inner core passes through the second dielectric substrate 9 to connect to one end of the microstrip metal probe and then through the first dielectric substrate 10 to connect to the first metal patch. Several metal short-circuit posts 5 pass through the first dielectric substrate 10 and the second dielectric substrate 9, connecting the top metal radiating layer 3 and the bottom ground metal layer 7. The connection position is on the edge of the first metal patch near the edge of the first dielectric substrate 10, which is used to shorten the equivalent waveguide loop and suppress common-mode resonance in the operating frequency band.

[0014] Furthermore, the thickness of the air isolation layer 11 is 5 mm; both the first dielectric substrate 10 and the second dielectric substrate 9 are made of F4BM220 dielectric material with a dielectric constant of 2.2 and a loss tangent of 0.002; the first dielectric substrate 10 of the scaled antenna unit and the reference antenna unit are laid together into a large dielectric substrate, and the second dielectric substrate 9 of the scaled antenna unit and the reference antenna unit are laid together into a large dielectric substrate.

[0015] Furthermore, by adjusting the curve profile and size of the metal patch exponentially gradient radiation slot 4 and the parasitic bowtie slot 2 at the junction of adjacent reference antenna elements and scaled antenna elements, the interface equivalent capacitance at the junction is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array.

[0016] Furthermore, in the inter-element coupling capacitance recovery interface, the metal edge of the scaled-down antenna element forms an asymmetric coplanar gap with the metal edges of the two adjacent reference antenna elements. By adjusting the metal width and slot width of the asymmetric coplanar gap, the equivalent coupling capacitance shift caused by the change in physical boundary is compensated, so that the equivalent coupling capacitance of the adjusted transition interface is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array. The recovery condition is expressed as:

[0017]

[0018] in, The radiation slot capacitance of the scaled-down antenna element at the interface. Let be the coupling capacitance of a scaled-down antenna element in an ideal infinite-period array. The equivalent capacitance between the scaled-down antenna element and the reference antenna element at the interface is expressed as:

[0019]

[0020] in, and These are the radiation slot capacitances of the two reference antenna elements at the interface. and These are the coupling capacitances between the scaled-down antenna element and the two reference antenna elements at the interface.

[0021] Furthermore, in the radiation slot capacitance recovery interface, the metal structure of the scaled-down antenna element is located beside the truncated radiation slot of the reference antenna element, establishing an edge electric field between the edge of the truncated radiation slot and the adjacent scaled-down antenna element structure, and forming a stable parasitic metal boundary. By adjusting the position, size, and spacing between the parasitic metal boundary and the truncated slot, the decrease in equivalent radiation slot capacitance caused by the truncation of the radiation slot is compensated. The recovery condition is expressed as:

[0022]

[0023] in, Let be the equivalent capacitance of the two reference antenna elements. , and These are the radiation slot capacitances of the two reference antenna elements, respectively. This is the coupling capacitance of the reference antenna element in an ideal infinite periodic array.

[0024] The beneficial effects of this invention are:

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] (1) Advantages of active channel reduction and low cost: Addressing the core pain point of high cost in broadband phased array systems, this invention achieves full-band coverage with only 112 active elements under the condition of a common aperture by using a unique wavelength-scaling nested architecture and frequency-dependent excitation strategy. Compared with the 256 elements required to fill the array with uniform antenna elements under the same physical aperture, this invention significantly reduces the number of array antenna elements and the number of corresponding T / R transceiver channels by 56%, greatly reducing the hardware cost, wiring complexity and power consumption of the system.

[0027] (2) Elimination of active impedance abrupt changes and excellent broadband matching performance: This invention eliminates capacitive disturbances at the junctions of subarrays of different scales by implementing a precise interface capacitance recovery mechanism at the underlying equivalent circuit level. Experimental results show that, without the need for any external impedance matching components, the active VSWR of the representative reference unit and the scaled-down unit in the side-emitting direction is stably maintained below 3, eliminating the interface VSWR spike phenomenon commonly found in conventional wavelength scaled-down arrays and ensuring high-efficiency energy radiation across the entire frequency band.

[0028] (3) Ultra-wide bandwidth angle two-dimensional blind zone-free scanning capability: After compensating for the internal local electromagnetic environment and introducing a suspended artificial dielectric layer, the array exhibits excellent wide-angle scanning impedance characteristics. At key frequencies such as 3 GHz and 8 GHz, the scanning angle of the array in the E-plane, H-plane, and D-plane (diagonal plane) can reach or exceed ±60°. Within the entire ±60° wide-angle scanning range, the measured active VSWR of representative antenna elements is below 3.5, the beam shape is well maintained, and no serious beam distortion or blind zone is observed.

[0029] (4) No macroscopic transition structure required, achieving high integration and low profile manufacturing: The compact hybrid structure of the suspended dielectric layer, double-layer RF board and three metal layers of the present invention is fully compatible with the standard multilayer PCB lamination process, giving the antenna array extremely excellent low profile characteristics and the potential for highly modular integration. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the position and quantity distribution of the three types of array elements in the array antenna described in this invention;

[0031] Figure 2 This is a schematic diagram of the three-dimensional layered structure of the planar ultra-wideband modular antenna element in the array antenna of the present invention;

[0032] Figure 3 This is a schematic diagram of the physical transition position connection in the wavelength scaling array architecture based on a slotted tight coupling structure in this invention;

[0033] Figure 4 This is a schematic diagram of the equivalent circuit model of the interface capacitance recovery strategy in the embodiment;

[0034] Figure 5 This is a schematic diagram illustrating the principle of inter-unit coupling capacitance recovery and the antenna unit arrangement in the embodiment;

[0035] Figure 6 This is a schematic diagram illustrating the principle of radiating slot capacitance recovery and the antenna element arrangement in the embodiment.

[0036] Figure 7 This is a three-dimensional schematic diagram of the physical connection between the reference antenna element and the scaled-down antenna element at the transition position in the embodiment.

[0037] Figure 8 This is a diagram showing the active VSWR distribution of the entire array after dummy elements are added to the outermost edge of the array in the embodiment.

[0038] Figure 9 The above are measured active VSWR curves of a representative reference antenna element and a scaled-down antenna element at different scanning angles in the embodiment.

[0039] Figure 10 The images show the beam scanning patterns of the wavelength scaling array at different operating frequencies and different scanning planes in the embodiments. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] This embodiment provides a wavelength-scaled array antenna based on interface capacitance recovery, which addresses the problems of active impedance abrupt changes, active VSWR degradation, and broadband scanning performance decline that easily occur at the boundaries of subarrays of different physical scales in existing wavelength-scaled arrays. The core idea is to directly adjust the local geometric topology of the reference antenna element and the scaled antenna element at the boundary, without introducing additional macroscopic transition structures or external impedance matching networks at the boundary. This restores the altered equivalent capacitance at the boundary to the target equivalent capacitance of the entire array in an ideal infinite-period array, thereby suppressing the active input impedance abrupt changes at the boundaries of elements of different scales.

[0042] The schematic diagram of the array antenna array layout described in this embodiment is as follows: Figure 1 As shown, the overall arrangement is a two-dimensional planar square grid, forming a concentric square ring nested structure from the inside out. Depending on the position and function of the array elements in the array, the array antenna includes a reference antenna subarray located in the central region, a scaled-down antenna subarray surrounding the reference antenna subarray, and dummy elements located on the outermost periphery of the array that do not function as radiating elements.

[0043] The reference antenna subarray consists of multiple reference antenna elements with a first physical scale; the scaled-down antenna subarray consists of multiple scaled-down antenna elements with a second physical scale. The scaled-down antenna elements have the same structure as the reference antenna elements, but the second physical scale is larger than the first physical scale. In this embodiment, the reference antenna elements in the central region are arranged in an 8×8 uniform pattern, totaling 64; 48 scaled-down antenna elements are arranged around the reference antenna elements; and 36 dummy elements are further arranged around the scaled-down antenna elements. The 64 reference antenna elements and the 48 scaled-down antenna elements together constitute an active radiating array, with a total of 112 active elements. The dummy elements have the same structure as the scaled-down antenna elements, but are not connected to the active RF channel. They are connected to a matching load at their ends to provide a nearly continuous boundary electromagnetic environment and suppress surface current cutoff and boundary effects at the outer edge of the finite array.

[0044] In the array antenna described in this embodiment, the reference antenna element and the scaled-down antenna element operate in two different excitation modes at different frequency bands: the reference antenna element operates in the first band, with a frequency of 3 GHz to 8 GHz; the scaled-down antenna element operates in the second band, with a frequency of 3 GHz to 4 GHz; the physical aperture area of ​​the scaled-down antenna element is four times that of the reference antenna element. The array antenna in this embodiment is configured to use a dynamic excitation method related to the operating frequency: in the low-frequency operating band of 3 GHz to 4 GHz, both the reference antenna element in the central region and the scaled-down antenna elements in the periphery are simultaneously excited, allowing all 112 active elements to participate in radiation; in the high-frequency operating band of 4 GHz to 8 GHz, the peripheral scaled-down antenna elements are turned off, and only the 64 reference antenna elements in the central region are excited. To obtain a uniform equivalent aperture power density in the low-frequency full-array operating mode, the excitation power ratio of the two types of elements is configured according to the aperture area ratio of the scaled-down antenna element to the reference antenna element. Specifically, when the aperture area of ​​the scaled-down antenna element is four times that of the aperture area of ​​the reference antenna element, the excitation power ratio of the scaled-down antenna element to the reference antenna element is strictly set to 1:4 (corresponding to an amplitude ratio of 1:2) to compensate for the 1:4 physical area difference between the two and ensure that the equivalent power density on the array aperture surface is uniform.

[0045] Both the reference antenna element and the scaled-down antenna element adopt a planar ultra-wideband modular antenna structure, and its three-dimensional layered structure diagram is shown below. Figure 2 As shown, from top to bottom, the antenna includes, in sequence, a suspended artificial dielectric layer 1, an air isolation layer 11, a top metal radiating layer 3, a first dielectric substrate 10, a feed network 6, a second dielectric substrate 9, and a bottom ground metal layer 7, all tightly bonded together. The upper and lower surfaces of the suspended artificial dielectric layer 1 are composed of square metal patches arranged in a 4×4 pattern. The top metal radiating layer 3 includes two metal patches, with an exponentially gradient radiation gap 4 between them to achieve a smooth impedance transition. A parasitic bowtie gap 2 is formed between the top metal radiating layer 3 and the edge of the first dielectric substrate 10 to provide capacitive coupling between adjacent antenna elements. The feed network 6 includes a microstrip metal probe and a triangular matching stub connected in sequence. One end of the pin corresponds to the center position of the first metal patch, and the other end is connected to the triangular matching stub, which corresponds to the center position of the second metal patch. The antenna element is fed using the coaxial SMA feed interface 8. The outer conductor is connected to the bottom ground metal layer 7, and the inner core passes through the second dielectric substrate 9 to connect to one end of the microstrip metal probe, and passes through the first dielectric substrate 10 to connect to the first metal patch. Several metal short-circuit posts 5 pass through the first dielectric substrate 10 and the second dielectric substrate 9, connecting the top metal radiating layer 3 and the bottom ground metal layer 7. The connection position is the edge of the first metal patch near the edge of the first dielectric substrate 10, which is used to shorten the equivalent waveguide loop and suppress common-mode resonance in the operating frequency band.

[0046] In this embodiment, an air isolation layer 11 is provided between the suspended artificial dielectric layer 1 and the top metal radiating layer 3. The thickness of the air isolation layer 11 is optimized to 5 mm to improve the active VSWR and expand the scanning bandwidth during large-angle scanning of the H-plane, while avoiding excessively high equivalent dielectric constants that could lead to wide-edge matching deterioration or scanning blind zones. In this embodiment, both the first dielectric substrate 10 and the second dielectric substrate 9 are made of F4BM220 dielectric material with a dielectric constant of 2.2 and a loss tangent of 0.002. To meet the requirements of printed circuit board lamination, the reference antenna element and the scaled-down antenna element preferably share the same dielectric material, stacking relationship, and cross-sectional height.

[0047] A schematic diagram of the physical transition connection in a wavelength scaling array architecture based on a slotted tight coupling structure is shown below. Figure 3As shown, at the physical boundary between the reference antenna subarray and the scaled-down antenna subarray, the local electromagnetic environment, which was originally continuous in the infinite periodic array, is disrupted due to the different physical dimensions of adjacent antenna elements. This disruption mainly includes two types: first, the capacitive coupling path between antenna elements along the antenna element arrangement direction changes, causing the coupling capacitance between antenna elements to deviate from the ideal periodic state; second, the radiation slots in the orthogonal direction are truncated at the boundary, causing the parallel capacitance of the radiation slots to decrease. To address this, this embodiment changes the connection topology between the reference antenna element and the scaled-down antenna element at the transition surface. The transition interface topology includes at least one of the inter-element coupling capacitance recovery topology and the radiation slot capacitance recovery topology. By adjusting the curve profile and size of the metal patch exponentially gradient radiation slot 4 and the parasitic bowtie slot 2 at the boundary between adjacent reference antenna elements and scaled-down antenna elements, the interface equivalent capacitance at the boundary is made close to or equal to the target equivalent capacitance of the corresponding complete element in the ideal infinite periodic array.

[0048] The equivalent circuit model diagram of the interface capacitance recovery strategy is shown below. Figure 4 As shown, for tightly coupled arrays, the coupling capacitance between antenna elements and the parallel capacitance of the radiating slots jointly affect the active input impedance of the elements. When the reference antenna element and the scaled-down antenna element are directly spliced, the equivalent capacitance at the interface changes abruptly, causing a discontinuity in the active impedance. To address this, this embodiment proposes an interface capacitance recovery strategy. Its core mechanism is: without introducing any external impedance matching network, but by adjusting the physical topology of the antenna itself, the disturbed coupling capacitance between elements and the parallel capacitance of the radiating slots at the interface are precisely restored to the target capacitance values ​​in an ideal infinite-period array, thereby completely eliminating the abrupt change in the active input impedance at the interface from the underlying circuit level. Specifically, this embodiment uses local geometric topology recovery to ensure that the capacitance at the interface satisfies the following relationship:

[0049]

[0050] in, This represents the coupling capacitance of the edge antenna element. This represents the coupling capacitance of an antenna element in an ideal infinite-period array. This represents the radiation slot capacitance of the edge antenna element. This represents the radiation slot capacitance of an antenna element in an ideal infinite periodic array.

[0051] When the above conditions are met, the active input impedance at the junction can be approximately restored to the active input impedance under ideal periodic conditions, thereby reducing the active VSWR spike.

[0052] The principle of inter-element coupling capacitance recovery and the schematic diagram of antenna element arrangement are shown below. Figure 5As shown, this is used to compensate for the inter-element coupling capacitance shift at the interface of antenna elements of different scales. Specifically, the metal edge of the scaled-down antenna element forms an asymmetric coplanar gap with the metal edges of at least two adjacent reference antenna elements. Due to the different scales of the antenna elements on both sides of the interface, the metal width, slot width, and edge profile of this asymmetric coplanar gap no longer satisfy the symmetry relationship in a uniform periodic array. Therefore, this embodiment compensates for the equivalent coupling capacitance shift caused by the change in physical boundary scale by adjusting the local metal width, local slot width, linear gradient profile of the parasitic bowtie slot, and exponential gradient profile of the radiating slot on both sides of the asymmetric coplanar gap, so that the adjusted interface equivalent coupling capacitance matches the target coupling capacitance in an ideal infinite periodic array. The recovery condition can be expressed as:

[0053]

[0054] in, The radiation slot capacitance of the scaled-down antenna element at the edge location. Let be the coupling capacitance of a scaled-down antenna element in an ideal infinite-period array. The equivalent capacitance between the scaled-down antenna element and the reference antenna element at the interface is expressed as:

[0055]

[0056] in, and These are the radiation slot capacitances of the two reference antenna elements at the interface. and These are the coupling capacitances between the scaled-down antenna element and the two reference antenna elements at the interface.

[0057] By optimizing the geometry of the metal edges and gap edges at the junction, the two sides of the above equation can be made equal, thereby restoring the target coupling capacitance.

[0058] The principle of radiating slot capacitance recovery and the schematic diagram of antenna element arrangement are shown below. Figure 6 As shown, this method compensates for the decrease in parallel capacitance caused by the truncation of the radiation slot at the junction of the reference antenna element. Specifically, the metal structure of the scaled-down antenna element is arranged beside the truncated radiation slot of the reference antenna element, establishing an edge electric field between the edge of the truncated radiation slot and the adjacent scaled-down antenna element structure, forming a stable parasitic metal boundary. By adjusting the position, size, and spacing between the parasitic metal boundary and the truncated slot, the decrease in equivalent radiation slot capacitance caused by the truncation of the radiation slot can be compensated. The restored equivalent radiation slot parallel capacitance can be expressed as:

[0059]

[0060] in, Let be the equivalent capacitance of the two reference antenna elements. , and These are the radiation slot capacitances of the two reference antenna elements, respectively. This is the coupling capacitance of the reference antenna element in an ideal infinite periodic array.

[0061] By adjusting the geometric parameters of the parasitic metal boundary, both sides of the above equation can be made equal, so that the restored equivalent radiation slot capacitance is close to or equal to the target radiation slot capacitance under an uninterrupted ideal periodic environment.

[0062] The three-dimensional schematic diagram of the physical connection between the reference antenna element and the scaled-down antenna element at the transition position in this embodiment is shown below. Figure 7 As shown, two typical physical transition interfaces can be formed between the reference antenna element and the scaled-down antenna element: one corresponds to the interface for recovering the coupling capacitance between antenna elements, and the other corresponds to the interface for recovering the capacitance of the radiating slot. Since the metal edge, slot edge, and gradient profile at the interface all change continuously with position, this embodiment can use the integral conformal mapping method to extract the distributed capacitance under different interface topologies. For the asymmetric coplanar gap that changes with position, its distributed capacitance can be expressed as:

[0063]

[0064] Where K is the first-kind complete elliptic integral, and k(y) is a modulus parameter determined by the local metal width function, the gap width function, and the gradient profile function. is the equivalent dielectric constant of the dielectric substrate. By reverse designing the geometric boundaries on the integration path, the required recovery capacitance can be synthesized, and a complete wavelength-scaled array antenna can be formed by combining transition interfaces that satisfy the capacitance recovery condition.

[0065] The antenna design process described in this embodiment is as follows:

[0066] First, the operating frequency bands, physical dimensions, and array topologies of the reference antenna element and the scaled-down antenna element are determined. Second, an equivalent circuit model of the transition position between the reference antenna element and the scaled-down antenna element is established, and the influence mechanism of the coupling capacitance between elements and the radiation slot capacitance on the active impedance of the interface is analyzed. Third, the distributed capacitance under different interface topologies is extracted using the integral conformal mapping method. Subsequently, the metal edge, slot edge, parasitic metal boundary, and gradient profile at the interface are adjusted in reverse so that the modified interface equivalent capacitance is close to or equal to the target equivalent capacitance in an ideal infinite period array. Finally, a wavelength-scaled array is formed based on the transition interface combination that satisfies the capacitance recovery condition, and a low-frequency full array excitation strategy and a high-frequency central subarray excitation strategy are planned according to the operating frequency band. At the same time, dummy elements are arranged on the outermost edge of the array to improve the boundary electromagnetic environment.

[0067] In this embodiment, the active VSWR distribution of the entire array after loading dummy elements on the outermost periphery is shown in the figure below. Figure 8 As shown, after interface capacitance recovery and loading of peripheral dummy elements, the active VSWR distribution of the array is significantly improved, with the active VSWR of all array elements in the side-firing direction being less than 3. No significant VSWR abrupt changes or isolated spikes were observed in the central reference antenna subarray, the peripheral scaled-down antenna subarray, or the area where they meet, indicating that the local electromagnetic environment at the interface has been effectively restored. Simultaneously, the dummy elements placed on the periphery of the array provide an approximately continuous electromagnetic boundary for the outermost active elements, reducing the surface current cutoff effect caused by the finite aperture outer edge, thereby improving the broadband matching state of the entire array.

[0068] like Figure 9 As shown, in this embodiment, the measured active VSWR curves of the representative reference antenna element and the scaled-down antenna element at different scanning angles all maintain a low level. In the low-frequency full array operating mode, the reference antenna element and the scaled-down antenna element work together, and the array can achieve stable matching in the 3 GHz to 4 GHz frequency band. In the high-frequency center subarray operating mode, the peripheral scaled-down antenna elements are turned off, and the central reference antenna subarray maintains a good active VSWR in the 4 GHz to 8 GHz frequency band. Test or simulation results show that when the array is scanned to the side-firing direction in the E-plane, H-plane, and D-plane (diagonal plane) and at large angles such as 45° and 60°, the measured active VSWR of the representative antenna element is below 3.5. Both types of elements exhibit stable impedance characteristics in the corresponding operating frequency bands, verifying the effect of the interface capacitance recovery strategy on suppressing active impedance abrupt changes under wide-bandwidth and wide-angle scanning conditions.

[0069] like Figure 10 As shown, in this embodiment, the wavelength-scaled array exhibits good beam scanning capabilities in the E-plane, H-plane, and D-plane patterns at different operating frequencies and scanning planes. Utilizing the nested co-aperture structure of the central reference subarray and the peripheral scaled subarrays, along with capacitance recovery at the interface and optimization of the peripheral dummy element boundaries, this array can achieve two-dimensional wide-angle scanning within a range of approximately ±60°. During scanning, it maintains good main lobe shape, sidelobe suppression, and cross-polarization control capabilities, without exhibiting significant scanning blind zones or severe beam distortion.

[0070] Compared to the traditional approach of filling the entire common-aperture array with uniform small-scale elements, this embodiment achieves a wideband coverage of 3 GHz to 8 GHz using only 112 active antenna elements; while filling the entire array with reference antenna elements at the same physical aperture would require approximately 256 active elements. Therefore, this embodiment significantly reduces the number of array elements and the number of corresponding T / R transceiver channels, lowering system hardware costs, wiring complexity, and power consumption. Furthermore, this embodiment eliminates capacitive disturbances at the boundaries between subarrays of different scales at the equivalent circuit level through an interface capacitance recovery mechanism, eliminating the need for additional external impedance matching components or bulky macroscopic transition structures. It is compatible with low-profile multilayer PCB lamination processes and possesses high engineering integration and manufacturing feasibility.

[0071] This invention overcomes the bottleneck of physical and local electromagnetic discontinuities at the splicing interface of traditional wavelength-scaled arrays. By precisely implementing topological restoration of coupling capacitance and radiation slot capacitance at the boundaries of units of different scales, it reconstructs the local electromagnetic boundary conditions equivalent to an ideal infinite-period array from the underlying circuit level. This solution does not require the introduction of any bulky macroscopic stepped transition structure or complex external impedance matching network, and is perfectly compatible with low-profile multilayer PCB technology. While significantly reducing the number of active array units and supporting RF channels and significantly reducing the hardware cost of the phased array system, it completely eliminates the interface active impedance abrupt change, achieving large-angle, blind-zone-free, high-quality beam scanning of the array over an ultra-wide bandwidth. This invention provides an innovative architecture and complete design principles with high engineering practical value for low-cost, highly integrated, high-performance ultra-wideband phased array antenna systems.

Claims

1. A wavelength scaled array antenna based on interface capacitance recovery, characterized by, The overall arrangement is a two-dimensional planar square grid, forming a concentric square ring nested structure from the inside out. It includes a reference antenna subarray located in the central region, a scaled-down antenna subarray surrounding the reference antenna subarray, and dummy elements located on the outermost periphery. The reference antenna subarray consists of multiple reference antenna elements with a first physical scale; The scaled-down antenna subarray is composed of multiple scaled-down antenna elements with a second physical scale. The scaled-down antenna elements have the same structure as the reference antenna elements, and the second physical scale is larger than the first physical scale. A transition interface is formed at the interface between the reference antenna subarray and the scaled-down antenna subarray, including the inter-element coupling capacitance recovery interface and the radiation slot capacitance recovery interface. By adjusting the geometric topology of the reference antenna element and the scaled-down antenna element at the interface, the interface equivalent capacitance at the transition interface is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array.

2. The interface capacitance recovery based wavelength scaled array antenna according to claim 1, wherein, The reference antenna elements in the central area are arranged in an 8×8 uniform pattern; 48 scaled antenna elements are arranged around the reference antenna elements; 36 dummy elements are arranged around the scaled antenna elements. The dummy elements have the same structure as the scaled antenna elements, but are not connected to the active RF channel, and are connected to the matching load at the end.

3. The interface capacitance recovery based wavelength scaled array antenna of claim 1, wherein, The reference antenna element operates in the first frequency band, from 3 GHz to 8 GHz; the scaled-down antenna element operates in the second frequency band, from 3 GHz to 4 GHz; the physical aperture area of ​​the scaled-down antenna element is four times that of the reference antenna element; in the first frequency band from 3 GHz to 4 GHz, both the reference antenna element and the scaled-down antenna element are excited simultaneously, with an excitation power ratio of 1:4 between the scaled-down antenna element and the reference antenna element; in the second frequency band from 4 GHz to 8 GHz, only the reference antenna element is excited.

4. The interface capacitance recovery based wavelength scaled array antenna of claim 1, wherein, Both the reference antenna unit and the scaled-down antenna unit adopt a planar ultra-wideband modular antenna structure, which includes, from top to bottom, a suspended artificial dielectric layer (1), an air isolation layer (11), a top metal radiating layer (3), a first dielectric substrate (10), a feed network (6), a second dielectric substrate (9), and a bottom ground metal layer (7) that are tightly attached together. The upper and lower surfaces of the suspended artificial dielectric layer (1) are square metal patches arranged in a 4×4 pattern. The top metal radiating layer (3) includes two metal patches, and an exponentially gradient radiating gap (4) is formed between the two metal patches to achieve a smooth impedance transition; a parasitic bowtie gap (2) is formed between the top metal radiating layer (3) and the edge of the first dielectric substrate (10) to provide capacitive coupling between adjacent antenna elements; the feed network (6) includes a microstrip metal probe and a triangular matching stub connected in sequence, one end of the microstrip metal probe corresponds to the center position of the first metal patch, and the other end is connected to the triangular matching stub, which corresponds to the center position of the second metal patch; the antenna elements are fed using a coaxial SMA feed interface (8), the outer conductor is connected to the bottom ground metal layer (7), and the inner core passes through the second dielectric substrate (9) to connect to one end of the microstrip metal probe and passes through the first dielectric substrate (10) to connect to the first metal patch; Several metal short-circuit posts (5) pass through the first dielectric substrate (10) and the second dielectric substrate (9), connecting the top metal radiation layer (3) and the bottom ground metal layer (7). The connection position is the edge of the first metal patch near the edge of the first dielectric substrate (10), which is used to shorten the equivalent waveguide loop and suppress common-mode resonance in the working frequency band.

5. The interface capacitance recovery based wavelength scaled array antenna according to claim 4, wherein, The thickness of the air isolation layer (11) is 5 mm; the first dielectric substrate (10) and the second dielectric substrate (9) are both made of F4BM220 dielectric material with a dielectric constant of 2.2 and a loss tangent of 0.002; the first dielectric substrate (10) of the scaled antenna unit and the reference antenna unit are stretched into a large dielectric substrate, and the second dielectric substrate (9) of the scaled antenna unit and the reference antenna unit are stretched into a large dielectric substrate.

6. The interface capacitance recovery based wavelength scaled array antenna of claim 4, wherein, By adjusting the curve profile and size of the metal patch exponentially gradient radiation slot (4) and parasitic bowtie slot (2) at the junction of adjacent reference antenna elements and scaled antenna elements, the interface equivalent capacitance at the junction is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array.

7. The interface capacitance recovery based wavelength scaled array antenna of claim 4, wherein, In the inter-element coupling capacitance recovery interface, the metal edge of the scaled-down antenna element forms an asymmetric coplanar gap with the metal edges of the two adjacent reference antenna elements. By adjusting the metal width and gap width of the asymmetric coplanar gap, the equivalent coupling capacitance shift caused by the change in physical boundary is compensated, so that the equivalent coupling capacitance of the adjusted transition interface is restored to the target equivalent capacitance of the complete antenna element corresponding to the ideal infinite period array. The recovery condition is expressed as: in, The radiation slot capacitance of the scaled-down antenna element at the interface. Let be the coupling capacitance of a scaled-down antenna element in an ideal infinite-period array. The equivalent capacitance between the scaled-down antenna element and the reference antenna element at the interface is expressed as: in, and These are the radiation slot capacitances of the two reference antenna elements at the interface. and These are the coupling capacitances between the scaled-down antenna element and the two reference antenna elements at the interface.

8. The wavelength-scaling array antenna based on interface capacitance recovery according to claim 4, characterized in that, In the radiating slot capacitance recovery interface, the metal structure of the scaled-down antenna element is located next to the truncated radiating slot of the reference antenna element, establishing an edge electric field between the edge of the truncated radiating slot and the adjacent scaled-down antenna element structure, and forming a stable parasitic metal boundary. By adjusting the position, size, and spacing between the parasitic metal boundary and the truncated slot, the decrease in equivalent radiating slot capacitance caused by the truncation of the radiating slot is compensated. The recovery condition is expressed as: in, Let be the equivalent capacitance of the two reference antenna elements. , and These are the radiation slot capacitances of the two reference antenna elements, respectively. This is the coupling capacitance of the reference antenna element in an ideal infinite periodic array.

Images