Diffraction phased array antenna based on space feeding

Abstract

The present invention discloses a diffraction phased array antenna based on space feeding. The diffraction phased array antenna includes a space feed source and a radiation panel. The space feed source and the radiation panel are arranged in parallel and spaced apart. The geometric centers of the space feed source and the radiation panel are at the same height, and the space feed source and the radiation panel are arranged in close proximity. The radiation panel is a planar aperture formed by a periodic uniform or non-uniform arrangement of multiple reconfigurable artificial surface units. The electromagnetic waves radiated by the space feed source propagate through free space and are incident on the radiation panel. The multiple reconfigurable artificial surface units independently perform phase compensation on the electromagnetic waves incident on themselves in the incident field, thereby obtaining a target diffraction phased array. The present invention adopts a space feed source, and an aspheric wave field is incident on the radiation panel. With the help of the phase reconfigurability of the artificial surface, the incident electromagnetic wave is phase compensated. While improving the aperture efficiency, the fluctuation of the gain of different directional beams is reduced, thereby achieving a larger angular scanning range.

Description

Technical Field

[0001] The present invention belongs to the field of non-traditional phased array antennas and relates to a diffraction phased array antenna, in particular to a diffraction phased array antenna based on space feeding. Background Art

[0002] Traditional phased arrays use patch arrays as radiating panels, backed by a complex network of power splitters, RF amplifiers, phase shifters, attenuators, and other components. This system exhibits high losses in the millimeter-wave band, is costly, and faces technical bottlenecks such as heat dissipation. Therefore, space-fed phased arrays, which avoid the use of numerous RF components, have become the preferred solution for millimeter-wave bands. Space-fed phased arrays, such as transmission arrays and Fresnel zone panels, typically use a single horn antenna as the spatial feed source. This horn antenna, as an ideal point source, radiates spherical waves incident on the radiating panel. Based on the Huygens principle, each point on the radiating panel acts as a secondary radiator, phase-compensating the incident field and re-radiating it. These waves coherently superimpose in the far-field beam direction to produce a beam scan pattern. However, traditional space-fed phased arrays have several challenges: 1. The feed source is a single spherical wave feed, placed far away, resulting in a high profile for the phased array, limiting its application in millimeter-wave and even terahertz bands. 2. Beam gain decreases rapidly with increasing beam scanning angle, resulting in a spatial scanning range typically less than 60 degrees. 3. Large gain loss at wide angles and a wide main lobe hinder precise communication. The traditional solution is to increase transmit power and expand the array size to improve beam performance. However, in the millimeter wave band and even higher frequency bands, transmit power and array size are limited by low RF device efficiency and compact space, making them unable to meet expansion requirements. Summary of the Invention

[0003] In order to solve the problems existing in the background technology, the present invention proposes a large-angle scanning diffraction phased array antenna based on space feeding. The antenna array is used as the space feed source to break the limitation of a single spherical wave feed source. The spherical waves radiated by each array element of the fed antenna array propagate through free space, and the vector superposition of the spherical waves is performed on the radiation panel to form an incident total field with random amplitude and phase fluctuations. According to the required beam pointing, with the help of the phase reconfigurability of the artificial surface, the original incident total field is phase compensated to improve the aperture efficiency of the phased array. Without increasing the transmission power and expanding the aperture of the radiation panel, a large-angle scanning diffraction phased array with a beam scanning angle of up to 70 degrees and a gain fluctuation of no more than 4dB is achieved.

[0004] The technical solution adopted in the present invention is:

[0005] The present invention includes a space feed antenna array and a radiation panel. The space feed antenna array and the radiation panel are arranged in parallel and spaced apart. The geometric centers of the space feed antenna array and the radiation panel are at the same height. The space feed antenna array and the radiation panel are arranged in close proximity. The radiation panel is a planar aperture formed by a periodic uniform or non-uniform arrangement of multiple reconfigurable artificial surface units.

[0006] The electromagnetic waves radiated by the space-fed antenna array propagate through free space and are incident on the radiating panel, forming an incident field with non-uniform amplitude and phase distribution on the back of the radiating panel. The multiple reconfigurable artificial surface units of the radiating panel independently compensate the phase of the electromagnetic waves incident on themselves in the incident field to obtain the target diffraction phased array.

[0007] The space feed antenna array includes but is not limited to a patch array, a slot array, and a dipole array.

[0008] The spatial feed source feeding antenna array is a feeding antenna array composed of multiple array units; the number of array units N, the spacing d between two adjacent array units, and the distance F between the feeding antenna array and the radiation panel are determined by a method with the maximum aperture efficiency of the target diffraction phased array and the minimum gain drop when the beam is scanned to the maximum angle as optimization goals. The method includes but is not limited to simulation, analytical calculation and experimental measurement.

[0009] The close distance between the space feed antenna array and the radiation panel is specifically set as follows: the ratio of the distance F between the space feed antenna array and the radiation panel to the side length L of the radiation panel does not exceed 0.5.

[0010] The reconfigurable artificial surface unit includes but is not limited to a multi-layer dielectric structure welded with a PIN tube or a varactor diode, and the multi-layer dielectric structure performs phase compensation on the electromagnetic wave incident on itself according to beam pointing requirements.

[0011] The phase compensation specifically performs discrete phase compensation of 1 bit or multiple bits, or performs continuous phase compensation of 180 degrees or 360 degrees. The form of the feed antenna array used in the present invention is not limited, such as a patch array, a slot array or a dipole array. Each array element can be equivalent to an ideal spherical wave point source. The total incident field on the radiation panel is the vector superposition of the spherical wave field radiated by each ideal point source on the radiation panel. The traditional single spherical wave feed source forms an electric field distribution on the radiation panel with an amplitude that monotonically decreases from the center to the outside and a phase that monotonically increases from the center to the outside. The amplitude and phase of the incident total field under the action of the feed antenna array feed source depend on parameters such as the number of array elements N, the array element spacing d, and the distance F between the feed antenna array and the radiation panel. Therefore, the amplitude and phase of the incident total field vary with the parameters and there is no fixed distribution law.

[0012] Based on the phased array principle and the Huygens-Fresnel diffraction principle, the maximum aperture efficiency of the phased array and the gain drop when the beam is scanned to the maximum angle are used as the optimization objective functions. Through simulation, analytical calculation or experimental measurement methods, the number of array elements N of the feed antenna array, the spacing d between adjacent array elements, and the distance F between the feed antenna array and the radiating panel are parameter scanned to obtain the respective optimal solutions as design guidance.

[0013] Subsequently, according to the phase compensation scheme of the reconfigurable artificial surface (RAS) used on the radiation panel, the phase compensation of the incident total field is performed, so that the electromagnetic waves are coherently superimposed in the radiation far field after passing through each RAS unit, and the energy is concentrated in the required beam pointing direction to achieve beam scanning.

[0014] The beneficial effects of the present invention are as follows:

[0015] Under the condition of the same total input power, compared with a single spherical wave space feed, using an antenna array as a space feed for close-range feeding effectively reduces the profile height of the phased array, and the propagation path of the electromagnetic wave in free space becomes shorter, the corresponding propagation loss is reduced, and the power utilization is improved, which is of great significance for applications in the millimeter wave and terahertz frequency bands.

[0016] Compared with traditional space-fed phased arrays, which require standard horn antennas as feed sources, the present invention relaxes the requirements on the feed source and does not restrict the form of the incident electromagnetic wave. Any feed antenna array can be used as the feed source of the radiation panel, making the design of the phased array more flexible and changeable.

[0017] During the entire spatial beam scanning process, the beam gain maintains a small fluctuation. When the beam scanning angle is up to 70 degrees, the gain fluctuation does not exceed 4dB. This effectively solves the technical problem of rapid gain attenuation at large angles in traditional phased arrays, resulting in limited scanning angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a block diagram of the diffraction phased array structure based on array spatial feeding;

[0019] Figure 2 This is a block diagram of the structure of a traditional space-fed phased array;

[0020] Figure 3 is a schematic diagram of the structure of a patch array example;

[0021] Figure 4 This is a schematic diagram of the structure of a gap sky array example;

[0022] Figure 5 This is a schematic diagram of the structure of a half-wave oscillator array example;

[0023] Figure 6Amplitude and phase profiles of the total field incident on the array feed;

[0024] Figure 7 This is a comparison curve of aperture efficiency under different phase compensation methods;

[0025] Figure 8 This is a diagram of the Ka-band 1x2 patch array feed example structure;

[0026] Figure 9 for Figure 8 S11 result diagram of the feed antenna array;

[0027] Figure 10 Phase difference distribution corresponding to beam scanning based on 1x2 patch array spatial feeding;

[0028] Figure 11 Normalized beam gain pattern for beam scanning based on 1x2 patch array spatial feeding.

[0029] Among them: 1. Space-feed antenna array, 2. Radiating panel, 3. Array element, 4. Non-uniform field distribution based on array feeding, 5. Horn antenna, 6. Spherical wave, 7. Spherical wave field distribution, 8. Dielectric substrate of patch array, 9. Patch element, 10. Dielectric substrate of slot array, 11. Slot element, 12. Half-wave oscillator element, 13. Metal reflector, 14. Patch element of 1x2 patch array, 15. Upper dielectric substrate of 1x2 patch array, 16. Feeding metal hole of 1x2 patch element, 17. Lower dielectric substrate of 1x2 patch array, 18. 50-ohm microstrip line, 19. 100-ohm microstrip line. DETAILED DESCRIPTION

[0030] The present invention will be further described and illustrated below with reference to the accompanying drawings and examples: This example is based on the technical solution of the present invention, and the protection scope of the present invention includes but is not limited to the following examples.

[0031] like Figure 1 As shown, the present invention includes a space feed antenna array 1 and a radiating panel 2. The space feed antenna array 1 and the radiating panel 2 are arranged parallel to each other and spaced apart. The geometric centers of the space feed antenna array 1 and the radiating panel 2 are at the same height. The space feed antenna array 1 and the radiating panel 2 are arranged in close proximity to each other. This reduces the cross-sectional height of the diffraction phased array antenna. The cross-sectional height of the diffraction phased array antenna refers to the vertical distance from the back of the feed antenna array to the surface of the radiating panel that radiates electromagnetic waves.

[0032] The space feed antenna array 1 is a feed antenna array of any form, comprising a plurality of array elements 3 that can be equivalent to an ideal point source. Generally, the number of array elements is not less than 2 and the array elements are evenly distributed.

[0033] The radiation panel 2 is a planar aperture formed by a periodic uniform or non-uniform arrangement of multiple reconfigurable artificial surface (RAS, such as frequency selective surface) units;

[0034] The electromagnetic waves radiated by the feeding antenna array propagate through free space and are incident on the radiation panel 2, forming an incident field 4 with non-uniform amplitude and phase distribution on the back of the radiation panel 2. The multiple reconfigurable artificial surface units of the radiation panel 2 independently compensate the electromagnetic waves incident on themselves in the incident field 4, so that the electromagnetic waves emitted from the radiation surface of the radiation panel (2) converge along the specified beam direction. Even if the transmitted wave is deflected to the specified scanning direction, while achieving a larger scanning angle, the fluctuation of the beam gain pointing to different directions is reduced, and a target diffraction phased array is obtained.

[0035] like Figure 2 As shown in the figure, the traditional phased array uses a single antenna, usually a horn antenna 5, as a space feed source to feed the antenna array. The spherical wave 6 radiated by it propagates through free space and forms a regular incident field 7 on the radiating panel with a concentric annular distribution of amplitude and phase. Figure 2 The traditional single spherical wave feed source represented by a horn antenna is shown. The feeding antenna array of the present invention includes but is not limited to a patch array, a slot array, and a dipole array.

[0036] The number N of array elements 3 in the space-fed antenna array 1, the spacing d between two adjacent array elements 3, and the distance F between the space-fed antenna array 1 and the radiating panel 2 are determined using a method that optimizes the maximum aperture efficiency of the target diffraction phased array and the minimum gain drop when the beam is scanned to the maximum angle, including but not limited to simulation, analytical calculation, and experimental measurement. The spacing d between two adjacent array elements 3 refers to the distance between the geometric centers of two adjacent array elements 3. The distance F between the feed antenna array and the radiating panel 2 refers to the distance perpendicular to the plane of the radiating panel and the feed antenna array.

[0037] The close distance between the space feed antenna array 1 and the radiation panel 2 is specifically set as follows: the ratio F / L of the distance F between the space feed antenna array and the radiation panel 2 and the side length L of the radiation panel 2 does not exceed 0.5.

[0038] In the present invention, the electromagnetic wave incident on the radiation panel is not limited to a spherical wave, because this electromagnetic wave is a superposition of the spherical waves simultaneously radiated by multiple array elements (i.e., array elements 3) of the feed antenna array, which are approximately ideal point sources, on the radiation panel. Therefore, it is an arbitrary field with arbitrary amplitude and phase fluctuations, such as Figure 6 shown.

[0039] The reconfigurable artificial surface unit includes but is not limited to a multilayer dielectric structure welded with PIN tubes or varactor diodes. The multilayer dielectric structure performs phase compensation on the electromagnetic waves incident on itself according to the beam pointing requirements. The phase compensation specifically performs discrete phase compensation of 1 bit or multiple bits, or continuous phase compensation of 180 degrees or 360 degrees.

[0040] A Cartesian coordinate system is established on the plane where the radiation panel is located, with the geometric center of the radiation panel as the coordinate origin O(0,0), and set as the phase reference point. The current electric field phase values of the remaining points on the radiation panel and the equal phase difference line distribution of the ideal phase required for beam scanning are used as the basis for phase compensation. The non-center point on the aperture plane is recorded as P(x,y). The direction perpendicular to the radiation panel is the z-axis direction of the electromagnetic wave emission direction. The geometric center of the feed antenna array and the geometric center of the radiation panel are both on the z-axis. The two are placed parallel, and the distance between the geometric centers is represented by the parameter F. The side length of the radiation panel is set to L, then the focal diameter ratio F / L of the phased array based on array feeding in the present invention does not exceed 0.5. The electromagnetic wave radiated by the feed antenna array propagates through free space and is incident on the radiation panel to form an array-fed non-uniform field distribution 4 with random amplitude and phase fluctuations. The phase difference distribution can be a random distribution with no fixed rules in the shape of multiple ellipses, irregular polygons or other arbitrary closed-loop contour gradient forms. Each RAS unit on the radiation panel performs independent phase compensation on the incident electromagnetic wave, so that the transmitted wave energy is focused on the specified beam direction, realizing a diffraction phased array with small gain fluctuation during large-angle scanning.

[0041] like Figure 2 As shown, the traditional phased array uses a single horn antenna 5 as a spatial feed source to feed the antenna array. In order to achieve large-angle scanning, it is generally placed at a distance from the radiating panel, corresponding to a focal length ratio F / L of 0.6 to 0.8, and in some designs, F / L is 1. The horn antenna is equivalent to an ideal point source, and the spherical wave 6 it radiates propagates through free space, forming a spherical wave field distribution 7 with concentric annular distribution of amplitude and phase on the radiating panel. Figure 1 The incident field formed by the common feeding of multiple ideal point sources is irregular in shape as a whole.

[0042] The present invention does not require the excitation method of each element in the feed antenna array, because no matter which excitation method is used, each element is approximately an ideal power source and radiates spherical waves. Therefore, only the number of elements N and the element spacing d on the side of the feed antenna array facing the radiation panel are considered to affect the total incident field on the radiation panel. In addition, in actual engineering design, the number of elements N and the element spacing d of the feed antenna array, as well as the distance F of the feed antenna array from the radiation panel, need to be determined by the method of optimizing the objective function of the maximum aperture efficiency of the phased array and the degree of gain reduction when the beam is scanned to the maximum angle. The method includes but is not limited to simulation, analytical calculation and experimental measurement. Therefore, the following feed antenna array structure diagram is only a schematic display of the element form and distribution, and the number of elements, spacing and size are not set as parameters for specific examples.

[0043] Figure 3 A schematic diagram of a uniform patch array, a feed antenna array, is shown. Patch elements 9 are etched onto a dielectric substrate 8 and spaced evenly along the x and y axes. The shape and size of the patch elements are simulated and designed based on the operating frequency and electromagnetic wave polarization of the phased array RAS. Figure 3 The patch array in the figure consists of four rectangular patches, polarized horizontally along the narrow side of the patch element, with a spacing d of 2 wavelengths. Each patch element acts as a spherical wave source, emitting spherical waves of equal amplitude and phase that are incident on the radiating panel.

[0044] Figure 4 The image shows a 2x3 array of six evenly spaced rectangular slots (i.e., slot elements 11). The slot elements 11 are symmetrically distributed about the x and y axes of the slot array's dielectric substrate 10, with adjacent slots spaced three times the wavelength apart. Based on Babinet's reciprocity theorem, the slot elements can be considered dipole elements. When in-phase excited electromagnetic waves are incident on the radiating panel, the electric field polarization is perpendicular along the narrow edges of the slots.

[0045] Figure 5 The dipole array is formed by three half-wavelength dipole units 12 arranged at equal intervals horizontally. Since the dipole radiates uniformly in all directions on a plane perpendicular to the dipole arm, and the feed antenna array in the phased array only needs to radiate in the direction of the radiating panel in the forward direction, a metal reflector 13 of the same size as the feed antenna array is placed at a distance of one-quarter wavelength from the half-wave dipole array in the backward direction. This radiates the backward-radiated electromagnetic waves of the feed antenna array in an anti-phase manner, allowing the backward-radiated energy to be radiated back in the direction of the radiating panel.

[0046] Based on the design principle of the feed antenna array in the present invention, Figure 3 , Figure 4 and Figure 5Schematic diagrams of three different feeding antenna array structures are given. That is, no matter what excitation method is used, each array element can be approximately regarded as an ideal point source radiating spherical waves outward, which are superimposed on the radiation panel to form an incident total field with arbitrary amplitude and phase distribution. Figure 6 Figures (a) and (b) show the amplitude and phase distribution of the incident electric field on a square-aperture radiating panel. Normalized to the maximum amplitude on the panel, the amplitude attenuation at all other points ranges from 0 to -20 dB, with no regular pattern, unlike the monotonic radial decay of the amplitude from the center outward when using a traditional single spherical wave as a feed source. The phase distribution also fluctuates randomly between 0 and 360 degrees, unlike the monotonic radial increase of the phase from the center outward when using a traditional single spherical wave as a feed source.

[0047] Next, we will explain the working principle of the phased array based on array feeding. Figure 1 As shown, the aperture area is L x ×L y A Cartesian coordinate system is established with the geometric center point of the radiation panel as the origin. The origin O(0,0) is set as the phase reference point, and the point P with coordinates (x,y) represents any point on the radiation panel except the origin. An array feed containing N elements is placed at a distance F from the rear of the radiation panel. Assume that the array feed is located at (x n ,y n ,-F) coordinate point, the excitation current of the nth array element is Among them I n Indicates the amplitude of the excitation current of the nth array element, α n represents the phase of the nth array element excitation current, j represents the imaginary part of the imaginary number, n = 1, 2, 3...N, then the total incident field E at any point P(x, y) on the radiation panel is tot (x,y) can be expressed as:

[0048]

[0049] in, is the Green function expression of the spherical wave radiated by the nth array element. is the straight-line distance between the nth array element and point P(x,y) on the radiation panel. k is the free space wave number. E(x,y) represents the total incident field E at any point P(x,y) on the radiation panel. tot The magnitude of (x,y).

[0050] According to the phased array principle, for the specified beam deflection direction The ideal phase Ψ at point P(x,y) P (x,y) can be expressed as:

[0051]

[0052] Where θ0 represents the angle between the main lobe direction of the phased array beam and the z-axis. It represents the angle between the projection of the main lobe direction of the phased array beam on the xoy plane and the x-axis.

[0053] The phase difference ΔΦ(x,y) between point P(x,y) on the radiation panel and the phase reference point O(0,0) is calculated by the following formula:

[0054] ΔΦ(x,y)=Ψ P (x,y)-(Φ(x,y)-Φ(0,0)) (3)

[0055] Where Φ(x,y) and Φ(0,0) are the incident total field E at points P and O. tot Phase value of (x,y). Based on formulas (2) and (3), the phase difference ΔΦ(x,y) can be expressed as:

[0056]

[0057] Due to the periodicity of 2π, the phase difference ΔΦ(x,y) will be divided into four quadrants, as shown in formula (5):

[0058]

[0059] Where m is the period number, specifically an integer, Quadrant I represents the first quadrant, Quadrant II represents the second quadrant, Quadrant III represents the third quadrant, and Quadrant IV represents the fourth quadrant. For those points whose phase differences belong to quadrants one and four, the electromagnetic waves emitted from the radiating surface of the radiation panel 2 are coherently constructively superimposed in the far field. In particular, at points with zero phase difference, the emitted electromagnetic waves are in-phase superimposed in the far field, and the electric field can be maximized. However, for points whose phase differences belong to quadrants two and three, the emitted electromagnetic waves are incoherently superimposed in the far field, which has a canceling and weakening effect on the total field. Therefore, the phase compensation capability of each RAS unit on the radiation panel is usually used to provide additional phase for the emitted waves at each point, and the phase difference is compensated, so that as many emitted electromagnetic waves as possible are coherently superimposed in the far field, maximizing the radiation far field.

[0060] According to the different RAS compensation capabilities and methods, there are usually phase 1-bit type, 2-bit type, and continuous 180-degree multi-bit type. If the RAS is designed based on a PIN switch tube, the RAS unit can usually achieve 0 / 180-degree phase switching of the transmitted electromagnetic wave by controlling the opening and closing of the PIN tube, which is applied to the typical phase 1-bit 0-degree / 180-degree compensation method. Specifically, an additional phase of 180 degrees is provided for each point in the incoherent area, that is, the incoherent area is uniformly compensated by 180 degrees to turn it into a coherent area. A compensation value of 0 degrees is provided to each point originally in the coherent area, that is, the phase of the electromagnetic wave in the original coherent area does not change. In this way, all areas are turned into coherent areas, and the energy transmittance is improved. The specific phase compensation value ΔΨ(x,y) of the point P(x,y) can be calculated by the following formula:

[0061]

[0062] Another phase compensation method uses a RAS embedded with a varactor diode. Typically, the bias DC voltage of the varactor on the RAS is continuously varied, causing the phase of the electromagnetic wave transmitted through the RAS unit to continuously change, such as by 180 or 360 degrees. Based on this continuous 180-degree phase compensation method, the phase compensation value ΔΨ(x,y) at point P(x,y) on the radiating panel can be calculated using the following formula:

[0063]

[0064] Formula (7) shows that the specific operation of the continuous 180-degree phase compensation method is to fully compensate the phase difference areas in the first and second quadrants, that is, to reduce the original phase difference to 0. The phase difference area in the third quadrant is uniformly compensated by 180 degrees, and the phase difference area in the fourth quadrant is uniformly not compensated.

[0065] After compensation, the total radiation field at each point on the radiation panel needs to be added with the phase compensation value based on the original incident total field, which can be expressed as:

[0066]

[0067] Among them, E′ tot (x,y) represents the total radiation field at any point P(x,y) on the radiation panel, Indicates the definition symbol, that is, the previous E tot (x,y)e jΔΨ(x,y) Defined as E(x,y)e jΦ′(x,y) The representation method of .

[0068] After compensation, the corresponding phase difference becomes:

[0069] ΔΦ′(x,y)=Ψ P(x,y)-(Φ′(x,y)-Φ′(0,0)) (9)

[0070] Where Φ′(x,y) and Φ′(0,0) are the phase values of the total radiation field after compensation at point P and point O, respectively. Based on formula (9), the phased array aperture efficiency η is calculated as follows:

[0071] η=|∫∫E t ' ot (x,y)dS| 2 / S∫∫E′ tot (x,y)| 2 dS (10)

[0072] Where S = L x ×L y is the area of the radiation panel, ds represents the integral of the radiation panel area, || 2 Represents a mathematical operation that takes the modulus of a complex number within a symbol and then squares it.

[0073] Using aperture efficiency, one of the most important performance indicators of phased arrays, as a metric, we compared the advantages and disadvantages of the above-mentioned phase 1-bit mode and the continuous 180-degree compensation mode under different focal ratios. The results are as follows: Figure 7 As shown in the figure, when F / L exceeds 0.3, the aperture efficiency of both methods tends to saturate. Overall, the aperture efficiency of the continuous 180-degree compensation method is nearly 40% higher than that of the single-bit method, demonstrating the advantages of the continuous 180-degree compensation method in diffraction phased arrays.

[0074] According to the Huygens-Fresnel principle, the electric field of the phased array in the far radiation zone can be expressed as:

[0075]

[0076] The corresponding directivity coefficient can be expressed as:

[0077]

[0078] Among them, θ and They represent the pitch angle and azimuth angle of the spatial direction in spherical coordinates, that is, θ represents the angle between the space vector and the z-axis, Represents the angle between the projection of the space vector on the xoy plane and the x-axis. Indicates the phased array beam in space Directivity coefficient in the direction, Indicates the phased array beam in space The electric field strength in the direction. represents the main lobe of the phased array beam The electric field strength in the direction.

[0079] At this point, with the help of the Monte Carlo optimization algorithm, given the aperture area S of the radiation panel, the aperture efficiency of the phased array and the directivity coefficient of each beam, that is, the ideal gain, are calculated according to formulas (10) and (12), and the number N of the feed antenna array, the array element spacing d, and the focal length F are optimized to obtain the optimal values of the parameters N, d, and F under maximum aperture efficiency and minimum gain fluctuation for practical engineering design.

[0080] Take a diffraction phased array operating in the 5G millimeter wave 28 GHz frequency band as an example. The radiating panel in this example has a rectangular aperture of 6λ x 3λ. Microstrip patch arrays are the most common type of space-fed antenna array. After optimization, the number of patch array elements is 2, the spacing d is 30 mm, and the focal length F is 20 mm. Figure 8 (a) and (b) are diagrams of the top patch layer and bottom microstrip power layer structure of the 1x2 patch array, respectively. Two standard patch units 14 are placed 30 mm apart and parallel to each other on the upper dielectric substrate 15 of the 1x2 patch array. The lower surface of the upper dielectric substrate 15 of the 1x2 patch array is a whole piece of metal ground, namely the lower dielectric substrate 17 of the 1x2 patch array. A microstrip power splitter network is set on the lower dielectric substrate 17 of the 1x2 patch array. The 50-ohm microstrip line 18 serves as the total input port of the feeding antenna array, and two 100-ohm microstrip lines 19 are branched out on the left and right sides on the central axis of the dielectric board. The feeding metal hole 16 of each 1x2 patch unit, represented by the black dot, serves as a feeding through hole, which realizes impedance matching between the patch and the 100-ohm microstrip line for radiation excitation. The upper dielectric substrate 15 and the lower dielectric substrate 17 are both made of Rogers 4350B plates with a thickness of 0.254 mm. Figure 9 The S11 curve of this patch array is shown. The S11 of this fed antenna array is lower than -10dB in the 26GHz-28.6GHz frequency band, showing good broadband matching characteristics.

[0081] The 1x2 patch array is placed 20mm behind the radiating panel as the feed source. The RAS is designed as a multi-layer dielectric stack structure embedded with a varactor tube, which has a continuous 180-degree phase compensation capability. Assuming that the beam scans along the horizontal direction, that is, θ0 is scanned from 0° to 70° at intervals of 10°, and the phase difference distribution after phase compensation is calculated according to formula (9). Figure 10 As shown, each small figure represents the diffraction phase difference distribution corresponding to a beam pointing. From the figure, it can be seen that when the beam points to (20°, 0°), the area with a phase difference of 0 accounts for the largest proportion, representing the direction of this beam. The electromagnetic waves emitted from the radiation panel account for the largest proportion of the far-field superposition in-phase superposition, corresponding to the beam peak gain appearing in the 20° direction during the beam scanning process. Finally, the beam gain result calculated according to formula (12) is as follows Figure 11As shown, the gain and phase difference distribution mapping results are perfectly consistent, with peak gain occurring at 0°. The full scanning range reaches 70°, and the gain only drops by 3.94dB at this point. The overall profile height of the diffraction phased array in this example is 22mm, 60% lower than that of a traditional horn antenna.

[0082] In summary, the main innovation of this invention lies in the use of a feed antenna array for close-range spatial feeding of a phase-reconfigurable radiating panel. Compared to a single spherical wave feed source, this approach effectively reduces the profile height of the phased array, shortens the free-space propagation path of electromagnetic waves, reduces corresponding propagation losses, and improves power efficiency, which is of great significance for applications in the millimeter-wave and terahertz frequency bands.

[0083] Throughout the spatial beam scanning process, beam gain fluctuations remain minimal, with gain fluctuations of no more than 4dB at beam scanning angles up to 70°. This effectively addresses the technical challenges of traditional phased arrays, where gain attenuation at large angles leads to limited scanning angles. Diffraction phased array antennas can be used in RF, microwave, millimeter wave, and terahertz wave applications.

[0084] The examples described above are merely preferred examples of the present invention for fixed-aperture diffraction phased arrays in the 28 GHz frequency band and are not intended to limit the present invention in any way. Any person skilled in the art may utilize the above-disclosed technical content to create equivalent examples. However, any simple modifications, equivalent variations, and modifications to the above examples that do not depart from the technical solution of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A diffraction phased array antenna based on space feeding, characterized in that: The invention comprises a space feed antenna array (1) and a radiation panel (2), wherein the space feed antenna array (1) and the radiation panel (2) are arranged in parallel and spaced apart, the geometric centers of the space feed antenna array (1) and the radiation panel (2) are at the same height, and the space feed antenna array (1) and the radiation panel (2) are arranged in close proximity; the radiation panel (2) is a plane aperture formed by a periodic uniform or non-uniform arrangement of a plurality of reconfigurable artificial surface units; The electromagnetic waves radiated by the space feed source feeding antenna array (1) propagate through free space and are incident on the radiation panel (2), forming an incident field (4) with non-uniform amplitude and phase distribution on the back of the radiation panel (2). The multiple reconfigurable artificial surface units of the radiation panel (2) independently compensate the phases of the electromagnetic waves incident on themselves in the incident field (4), thereby obtaining a target diffraction phased array; The space feed source feeding antenna array (1) and the radiation panel (2) are arranged in close proximity, specifically, the ratio of the distance F between the space feed source feeding antenna array (1) and the radiation panel (2) to the side length L of the radiation panel (2) does not exceed 0.5; The phase compensation is specifically to perform continuous phase compensation of 0-180 degrees or 0-360 degrees; Each array element in the space feed antenna array (1) is excited in phase.

2. The diffraction phased array antenna based on space feeding according to claim 1, characterized in that: The space feed antenna array (1) includes but is not limited to a patch array, a slot array, and a dipole array.

3. The diffraction phased array antenna based on space feeding according to claim 1, characterized in that: The space feed source feeding antenna array (1) is a feeding antenna array composed of a plurality of array units (3); the number N of the array units (3), the spacing d between two adjacent array units (3), and the distance F between the feeding antenna array and the radiation panel (2) are determined by a method with the maximum aperture efficiency of the target diffraction phased array and the minimum gain drop when the beam is scanned to the maximum angle as optimization targets, and the method includes but is not limited to simulation, analytical calculation and experimental measurement.

4. The diffraction phased array antenna based on space feeding according to claim 1, characterized in that: The reconfigurable artificial surface unit includes but is not limited to a multi-layer dielectric structure welded with a PIN tube or a varactor diode, and the multi-layer dielectric structure performs phase compensation on the electromagnetic wave incident on itself according to beam pointing requirements.

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