CN111106445B - Low-profile two-dimensional Fresnel zone plate antenna based on planar caliber space feed - Google Patents
Low-profile two-dimensional Fresnel zone plate antenna based on planar caliber space feed Download PDFInfo
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- CN111106445B CN111106445B CN202010026720.0A CN202010026720A CN111106445B CN 111106445 B CN111106445 B CN 111106445B CN 202010026720 A CN202010026720 A CN 202010026720A CN 111106445 B CN111106445 B CN 111106445B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
- H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q1/00—Details of, or arrangements associated with, antennas
- H01Q1/50—Structural association of antennas with earthing switches, lead-in devices or lightning protectors
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
- H01Q13/10—Resonant slot antennas
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
- H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
- H01Q19/18—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces having two or more spaced reflecting surfaces
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- H—ELECTRICITY
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- H01Q21/00—Antenna arrays or systems
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/44—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element
- H01Q3/46—Active lenses or reflecting arrays
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
Abstract
The invention discloses a low-profile two-dimensional Fresnel zone plate antenna based on planar caliber space feed. The planar aperture feed source feeds power to the two-dimensional Fresnel zone plate in a short-distance space; the plane caliber feed source and the Fresnel zone plate have the same size and are fixedly connected in an insulating way; the plane aperture feed source comprises a plane aperture antenna and a power division network which are synthesized or separated independently, and the plane aperture antenna adopts a plane patch antenna array or a plane slot/opening array antenna structure; the power distribution network feeds the planar aperture antenna to generate emergent electromagnetic waves, the emergent electromagnetic waves vertically enter the two-dimensional Fresnel zone plate, and the phase of the emergent electromagnetic waves is distributed in a center-to-outside gradient mode on the surface of the two-dimensional Fresnel zone plate through the function of adjusting and controlling the phase shift. The invention adopts different plane caliber feed sources to form a generalized Fresnel diffraction pattern on the Fresnel zone plate, and realizes two-dimensional beam scanning of the Fresnel zone plate antenna by utilizing the phase shifting capability of the phase-reconfigurable Fresnel zone plate.
Description
Technical Field
The invention belongs to the field of Fresnel zone plate antennas with two-dimensional beam scanning, and particularly relates to a low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feed.
Background
The traditional Fresnel zone plate antenna consists of a Fresnel zone plate and a spherical wave space feed source represented by a horn antenna. According to the Huygens principle, the radiation far field is obtained by the coherent superposition of the radiation fields of all points of a Fresnel zone plate as a secondary emission source. The different paths of the spherical waves incident on the points of the Fresnel zone plate result in different phases of the secondary emission sources. And the shortest path of all paths of the emergent waves of the secondary emission sources to the far-field beam direction serves as a reference path, and the phase at the position of the shortest path serves as a reference phase. And the difference value between the phase at each point on the zone plate and the reference phase is used as a basis for judging whether the Fresnel zone plate antenna is bright or dark stripe. In a phase period of 360 degrees, emergent waves of secondary emission sources with the phase difference within the range of plus or minus 90 degrees belong to coherent phase long waves, the area is a bright stripe, and other areas on the area plate are dark stripes. The light and dark fringes combine to form a conventional fresnel diffraction pattern, as shown in fig. 9. The Fresnel zone plate with relatively large caliber is used for the space feed horn antenna with small caliber. The feed source is placed too close, and the oblique incidence at the edge of the Fresnel zone plate can increase the antenna loss. Too far placement, the phase difference on the fresnel zone plate is not sufficient to form a fresnel diffraction pattern of a particular beam pointing direction, and the antenna profile is increased.
In general terms, the conventional fresnel zone plate antenna has several major problems: 1. the formation of the fresnel diffraction pattern is limited to spherical wave incidence. 2. The optimal placement distance of the feed source is difficult to determine; 3. oblique incidence causes losses. 4. The antenna profile is high;
disclosure of Invention
In order to solve the problems in the background art, the invention discloses a low-profile two-dimensional Fresnel zone plate antenna based on planar caliber space feed. The low-profile planar aperture feed source is adopted to perform space feed at a short distance on the reconfigurable Fresnel zone plate, meanwhile, the phase reconfigurable characteristic of the two-dimensional Fresnel zone plate is utilized to form a generalized Fresnel diffraction pattern different from the traditional Fresnel diffraction pattern, and the placement position of the planar aperture feed source can be calculated to be the optimal placement distance within 0.1-3 times of the wavelength of the Fresnel zone plate, so that the profile height of the Fresnel antenna is integrally reduced, the loss caused by oblique incidence is reduced, the low-profile two-dimensional scanning Fresnel zone plate antenna under the condition of planar aperture close-distance space feed is obtained, and the problems of the traditional space feed mentioned in the background technology are solved.
The technical scheme adopted by the invention is as follows:
the two-dimensional Fresnel zone plate antenna comprises a two-dimensional Fresnel zone plate and a plane caliber feed source, wherein the two-dimensional Fresnel zone plate and the plane caliber feed source are oppositely arranged in parallel, and the distance between the two-dimensional Fresnel zone plate and the plane caliber feed source is short, so that the plane caliber feed source feeds the two-dimensional Fresnel zone plate in a short distance space; the plane size of the plane caliber feed source is the same as that of the Fresnel zone plate, and the plane caliber feed source and the Fresnel zone plate are fixedly connected through an insulating material, so that the integration of the low-profile antenna feed system is realized.
The plane aperture feed source comprises a plane aperture antenna and a power division network, wherein the plane aperture antenna comprises but is not limited to a plane patch antenna consisting of plane patch array elements or a plane slot antenna consisting of plane slot/opening array elements, and is different from the traditional spherical wave feed source such as a horn antenna, an opening waveguide antenna and the like; the surface of the plane aperture antenna, which does not face the Fresnel zone plate, is connected with a power division network, the plane aperture antenna is connected with the power division network through a microstrip line, and the power division network feeds the array element of the plane aperture antenna through the microstrip line; the power division network feeds the planar aperture antenna to generate emergent electromagnetic waves, the emergent electromagnetic waves are approximately vertically incident to the two-dimensional Fresnel zone plate, the power division network is a power division network with a phase shifting function, and the phase shifting function is regulated and controlled by controlling the length of the microstrip line, so that the phase of the emergent electromagnetic waves is distributed on the surface of the two-dimensional Fresnel zone plate in a manner of increasing or decreasing gradient from the center to the outside; the phase range of the gradient distribution is designed according to the size of the two-dimensional Fresnel zone plate, the required beam scanning angle range and the required generalized Fresnel diffraction pattern.
The other plane caliber feed source is a cavity slot antenna which integrates a plane caliber antenna and a power division network into a whole, the power division network is integrated on the surface of the plane caliber antenna which does not face to the Fresnel zone plate, the cavity slot antenna comprises a metal cavity slot antenna and a medium cavity slot antenna, the cavity slot antenna is provided with a coaxial port position, a rectangular slot is arranged on the surface of the cavity slot antenna which faces to the Fresnel zone plate, and a single coaxial port is arranged on the surface of the cavity slot antenna which does not face to the Fresnel zone plate to feed in the cavity; through the position of the coaxial port of the cavity slot antenna and the position and the size of the slot, the phase of the emergent wave of the cavity slot antenna is adjusted to be randomly distributed on the surface of the two-dimensional Fresnel zone plate, and a generalized Fresnel diffraction pattern different from the traditional Fresnel diffraction pattern is formed on the surface of the two-dimensional Fresnel zone plate. Thus, the low-profile two-dimensional scanning Fresnel zone plate antenna under the condition of planar caliber close-range space feed is obtained.
As shown in fig. 1, the plane size of the plane caliber feed source is the same as that of the fresnel zone plate, and the plane caliber feed source is placed beside the fresnel zone plate in parallel at a short distance, so that the electromagnetic wave incident on the fresnel zone plate is generally similar to vertical incidence, and the oblique incidence problem of the traditional space feed is well solved.
The planar aperture antenna adopts planar patch array elements or gap array elements to form an array antenna, specifically, surface etching patches or gaps are formed on the dielectric slab facing a Fresnel zone plate, the array elements are outwards divided into a plurality of groups along the center, one group at the center is only one array element, the rest groups are a plurality of array elements uniformly distributed along the annular interval, and the rings of the rest groups are concentrically arranged.
The cavity slot antenna is characterized in that rectangular slots which can be equivalent to dipoles are formed in the surface, facing the Fresnel zone plate, of the cavity. And calculating the position and the size of the gap and the position of the coaxial feed port by utilizing the resonance mode and the impedance matching of the resonant cavity. The metal cavity slot antenna and the dielectric cavity slot antenna are different in that the metal cavity is sealed by metal on the periphery, the front side and the back side of a dielectric plate of the dielectric cavity are made of metal, and one circle or two circles of metal through holes are formed in the periphery of the dielectric plate to prevent electromagnetic waves from leaking from the periphery.
The invention adopts the plane caliber feed source with the low section to replace the traditional spherical wave feed source such as a horn antenna, an opening waveguide antenna and the like, has lower section height compared with the spherical wave feed source such as the horn antenna, the opening waveguide antenna and the like, and also realizes the two-dimensional Fresnel zone plate antenna with the low section height. The section height is the plane direction perpendicular to the two-dimensional Fresnel zone plate and the plane caliber feed source.
The surface of the plane caliber feed source facing the Fresnel zone plate is set to be a plane or a curved surface close to the plane, so that the emergent area of the emergent wave can be increased, the emergent wave is approximately vertically incident to the Fresnel zone plate, and the loss caused by oblique incidence is reduced. . The curved surface close to the plane refers to the curved surface with the curvature radius larger than 10 times of the wavelength.
The incident angle of the emergent electromagnetic wave incident to the two-dimensional Fresnel zone plate is within 10 degrees.
The close distance between the two-dimensional Fresnel zone plate and the plane caliber feed source means that the distance between the two-dimensional Fresnel zone plate and the plane caliber feed source is in the range of 0.1 to 3 times of wavelength.
The emitted electromagnetic wave realized by the present invention is not limited to the spherical wave.
The two-dimensional Fresnel zone plate has the phase reconfigurable characteristic that the phase at each position of the surface of the Fresnel zone plate can be adjusted, and specifically, the two-dimensional Fresnel zone plate is formed by closely arranging a plurality of phase shifting unit arrays, and the phase of each phase shifting unit can be adjusted.
The design of the phase shift unit of the two-dimensional Fresnel zone plate comprises but is not limited to a frequency selective surface of a multilayer dielectric structure embedded with electronic tuning elements such as varactor diodes, PIN tubes and the like or a metamaterial unit and the like.
The air feed mode of the plane caliber feed source is suitable for any type of two-dimensional Fresnel zone plate, including but not limited to two-dimensional Fresnel zone plates composed of transparent/non-transparent areas, two-dimensional Fresnel zone plates composed of 0 phase/180-degree phase areas and phase reconfigurable Fresnel zone plates.
The generalized fresnel diffraction fringes are a single diffraction fringe with an elliptical contour gradient, a plurality of circular or elliptical diffraction fringes, or other diffraction fringes with any closed-loop contour gradient form, as shown in fig. 10.
And for the beam scanning direction emitted by the two-dimensional Fresnel zone plate, constructing a generalized Fresnel diffraction pattern according to the difference value between the phase of the incident electromagnetic wave at the central point of the two-dimensional Fresnel zone plate and the phase of each point of other non-central points, so that the emitted electromagnetic waves incident in different areas of the two-dimensional Fresnel zone plate are coherently superposed in the required beam scanning direction after passing through the generalized Fresnel diffraction pattern.
The invention simultaneously utilizes the phase reconfigurable characteristic of the two-dimensional Fresnel zone plate and the plane caliber feed source with special size and low section height, regulates and controls phase shift to carry out gradient distribution, dynamically compensates the original phase difference value, and realizes beam scanning of the two-dimensional Fresnel zone plate antenna. The reconstruction of the Fresnel diffraction pattern is realized by utilizing the phase compensation capability of the reconfigurable Fresnel zone plate, so that the two-dimensional beam scanning of the Fresnel zone plate antenna is realized, and the emergent electromagnetic waves are not limited to spherical waves and can be other waves with any phase fluctuation.
The invention replaces the traditional air feed mode of far distance spherical wave feed represented by horn antenna with low section plane caliber near distance aspheric wave feed, and forms generalized Fresnel diffraction pattern on the Fresnel zone plate by the calculation of equal phase difference point. The fresnel diffraction pattern and the beam pointing are in a one-to-one correspondence.
The design of the low-profile plane aperture feed source mainly comprises two forms, namely a plane aperture antenna and a power division network. Planar aperture antennas include, but are not limited to, planar patch antennas formed from planar patch elements, as shown in fig. 3, or planar slot antennas formed from slot elements, as shown in fig. 4. The power division network provides excitation for the array elements of the planar aperture antenna. Another planar aperture feed source is a cavity slot antenna, and as shown in fig. 5 and 6, a slot is opened on the surface of the three-dimensional closed metal cavity or medium integrated cavity facing the fresnel zone plate. When the cavity is in a resonance mode in the working frequency band of the Fresnel antenna, electromagnetic waves radiated from the slits on the surface of the cavity are incident on the Fresnel zone plate, and the phase of the electromagnetic waves fluctuates randomly.
One surface of the plane caliber feed source facing the Fresnel zone plate is a plane or a curved surface close to the plane. The low-profile plane aperture feed source is placed behind the Fresnel zone plate at a short distance and is parallel to the Fresnel zone plate, and the plane aperture feed source and the Fresnel zone plate are connected and fixed by using an insulating material, so that the integration of the low-profile antenna feed system is realized.
The generalized Fresnel diffraction pattern is defined by calculating the phase difference between the electromagnetic wave at the central point of the Fresnel zone plate and the electromagnetic waves at other points according to the required beam direction when the aspheric wave space feed is carried out by adopting a plane aperture feed source with a low section. Because the phase positions of the electromagnetic waves emitted by the plane caliber feed source on the surface of the Fresnel zone plate are randomly distributed, the phase difference between the electromagnetic waves at the central point of the Fresnel zone plate and the electromagnetic waves at other points is random and irregular, and the generalized Fresnel diffraction pattern formed by combining the curves with the equal phase difference is an irregular diffraction pattern. Therefore, as long as the design of the plane caliber feed source meets the condition that the phases of the emergent waves on the surface of the Fresnel zone plate are randomly distributed, a generalized Fresnel diffraction pattern can be naturally formed on the Fresnel zone plate.
The generalized Fresnel diffraction pattern and the beam direction are in one-to-one correspondence, namely the beam direction is unique after the electromagnetic wave penetrates through the set diffraction pattern. According to the difference of beam directions, the Fresnel zone plate with the reconfigurable phase provides additional phase values for each point by utilizing the phase shifting capacity of the Fresnel zone plate, compensates the original phase difference, and reforms a generalized Fresnel diffraction pattern corresponding to the beam directions one by one. The phase reconfigurable Fresnel zone plate comprises, but is not limited to, a compact distribution structure of units with phase shifting function. The electromagnetic waves of each point on the Fresnel zone plate penetrate through the generalized Fresnel diffraction pattern, and then the beams are deflected to the appointed direction, so that two-dimensional beam scanning is realized.
The invention has the following beneficial effects:
the low-profile plane caliber short-distance feed effectively reduces the profile of the antenna.
The formation of the generalized Fresnel diffraction pattern is not limited by the incidence of spherical waves, the principle is simple and easy to understand, and the application range is wide.
The method for feeding the low-profile plane aperture and the forming principle of the generalized Fresnel diffraction pattern can be widely applied to one-dimensional and two-dimensional beam scanning of any Fresnel zone plate antenna to realize beam control.
The invention can be used in the field of microwave and millimeter wave communication and imaging, and particularly can be used as a solution for a 5G millimeter wave phased array antenna.
The invention realizes the reconstruction of the generalized Fresnel diffraction pattern by utilizing the phase compensation capability of the reconfigurable Fresnel zone plate, thereby realizing the two-dimensional beam scanning of the Fresnel zone plate antenna.
Drawings
FIG. 1 is a block diagram of a two-dimensional Fresnel antenna configuration;
FIG. 2 is a block diagram of a planar aperture feed source;
FIG. 3 is a schematic structural diagram of an example of a planar patch antenna;
FIG. 4 is a schematic structural diagram of an example of a planar slot antenna;
FIG. 5 is a schematic diagram of an example structure of a metal cavity slot antenna;
FIG. 6 is a schematic diagram of an example structure of a dielectric cavity slot antenna;
FIG. 7 shows several phase distributions of the Fresnel zone plate along the central axis of the long side;
FIG. 8 is a schematic diagram illustrating a generalized Fresnel diffraction pattern forming principle;
FIG. 9 is a schematic diagram of a conventional Fresnel diffraction pattern;
FIG. 10 is a schematic diagram of a generalized Fresnel diffraction pattern;
fig. 11 is a graph showing the results of losses caused by different incident angles to the fresnel zone plate.
Wherein: 1. the Fresnel system comprises a two-dimensional Fresnel zone plate, 2. a planar aperture feed source, 3. a planar aperture antenna, 4. a power division network, 5. a microstrip line, 6. a planar patch antenna, 7. a patch element of the planar patch antenna, 8. a planar slot antenna, 9. a slot element of the planar slot antenna, 10. a metal cavity slot antenna, 11. a cavity slot antenna, 12. a dielectric cavity slot antenna, 13. a metalized through hole and 14. a generalized Fresnel diffraction pattern.
Detailed Description
The invention will be further described and illustrated with reference to the following figures and examples: the present embodiment 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 embodiments.
As shown in fig. 1, the two-dimensional fresnel zone plate antenna comprises a two-dimensional fresnel zone plate 1 and a low-profile planar aperture feed source 2. The plane caliber feed source is placed near the Fresnel zone plate and keeps parallel with the Fresnel zone plate, the phase of the emergent electromagnetic wave of the plane caliber feed source on the surface of the Fresnel zone plate is distributed randomly, and phi in figure 11，Ф2，Ф3，Фi，ФjRespectively, represent different phase values.
Fig. 2 is a block diagram of a low-profile planar aperture feed source, which includes a planar aperture antenna 3 and a power dividing network 4. The power distribution network is arranged on one side of the plane caliber antenna, which does not face the Fresnel zone plate. The power division network is composed of a coaxial feed port accessed with external energy and a plurality of groups of microstrip lines 5 connecting the coaxial feed port to the planar aperture antenna array element. The power division network provides excitation for the plane aperture antenna through the microstrip line, and the excitation comprises amplitude and phase.
Fig. 3 shows a structure of a planar aperture antenna, a planar patch antenna 6. The planar patch antenna is an array antenna composed of patch array elements 7. According to the requirements of the two-dimensional Fresnel zone plate antenna on working frequency, electromagnetic wave polarization mode and the like, the shape, size and arrangement mode of the planar patch array element are designed. The planar patch antenna in fig. 3 is composed of 3 circles of 13 square patch array elements, and the space between adjacent patch array elements is half wavelength. The length of the microstrip line from the power division network to the array element determines the phase value of the excitation. The microstrip line lengths from the power dividing network to the patches connected by the gray dashed line are the same, indicating that the power dividing network provides the same excitation for the same circle of patches connected by the gray dashed line. The lengths of the microstrip lines reaching different turns are different, and the phases of the excitations provided are different. Therefore, the microstrip lines from the power division network to the patch array elements of different circles are designed to have different lengths, and phase excitation with gradient distribution which is gradually increased or decreased from the center to the outside can be provided for the planar aperture antenna. Beta in FIG. 31，β2，β3And the phase values of the excitations respectively provided by the power division network for the 3 circles of patch array elements are represented. Another structure of a planar aperture antenna, a planar slot antenna and a planar patch antenna, is different in that the elements of the planar slot antenna are rectangular slots which can be equivalent to dipoles. Fig. 4 shows a planar slot antenna 8 with 25 rectangular slots 9 evenly distributed and with half a wavelength between adjacent slots. The principle of providing excitation for the slot array element by the power division network is the same as that of the planar patch antenna. Because the power division network provides excitation phases with gradient distribution for the planar aperture antenna array elements, the phases of the electromagnetic waves emitted from the planar aperture feed source to the Fresnel zone plate are also in gradient distribution. Using a planar aperture antenna and power dividerThe combination of the networks is used as a plane caliber feed source, the phase distribution trend of the emergent wave to the surface of the Fresnel zone plate has a trend of gradient decreasing or increasing from the center to two sides, and the increasing or decreasing trend can be realized through the power division network. When the plane aperture feed source is a cavity slot antenna, the power dividing network and the plane aperture antenna can be combined into a whole. Fig. 5 is a schematic front view of the structure of the metal cavity slot antenna 10. According to the working principle of the resonant cavity, the size of the cavity and the position of the coaxial feed port are optimized, electromagnetic waves entering the closed cavity through the coaxial mode can resonate, and respective resonant standing wave modes correspond to different frequency points. And forming a gap at the edge of each half-standing wave electric field according to the standing wave mode corresponding to the working frequency, wherein half standing waves are spaced between adjacent gaps. In FIG. 5, TE is a standing wave540The gap is formed in the mode. The slits are formed according to the resonance mode, the electromagnetic wave radiated from the slits is a plane wave in the radiation far-field region, and the phase distribution of the electromagnetic wave which is propagated to 0.1 to 3 times of the wavelength and reaches the surface of the Fresnel region plate is similar to water wave and has fluctuation. Fig. 6 shows a dielectric cavity slot antenna 12, which has the same slot principle as a metal cavity, and the only difference is that the metal cavity is enclosed with metal around, the inside is air, the enclosed dielectric cavity is metal on the front and back sides of a dielectric plate, and one or two circles of metallized through holes 13 are drilled around the dielectric plate to shield the electromagnetic wave propagating in the dielectric plate, so that the electromagnetic wave is not leaked out from the periphery of the dielectric plate, and the enclosed dielectric cavity is realized.
In summary, based on the design principle of the low-profile plane aperture feed source, the invention provides structural schematic diagrams of two large-class plane aperture feed sources, that is, unequal phase excitation is provided for array elements of different circles through a phase-shifting power division network on the back of a plane aperture, and emergent wave phases are randomly distributed through cavity slotting. In practical application, the feed source can be used as a feed source of a generalized two-dimensional Fresnel zone plate antenna according to the design requirements of the low-profile plane caliber feed source in the above claims.
Fig. 7 is a graph showing a simulation of the phase distribution of the outgoing wave of the feed at each point on the central axis of the fresnel zone plate along the long side when feeds of different forms are placed at 3 wavelengths from the fresnel zone plate. In this example Lx is the long side of the Fresnel zone plate. In the figure, a black solid line is an ideal point source and is used as a result of the outgoing wave of the spherical wave feed source, and the phase of the outgoing wave of the spherical wave feed source on the Fresnel zone plate gradually decreases from the center to two sides, namely, the phases of the two sides are lagged behind the central point. In the figure, a dark gray dotted line shows that the phase on the Fresnel zone plate shows fluctuation similar to the phase distribution of a plane wave in a near field region, corresponding to the metal cavity slot antenna shown in FIG. 5. The dotted light gray line in the figure is an example of an arbitrary distribution of phases on the fresnel zone plate. Through several curves in the figure, it can be seen that the phases on the fresnel zone plate based on the plane caliber feed source can be randomly distributed, including uniform distribution and non-uniform distribution.
The principle of forming the fresnel diffraction pattern in the broad sense will be described next. As shown in fig. 8, an xy rectangular coordinate system is established with the central point of the fresnel zone plate as the origin of coordinates. The origin of coordinates on the Fresnel zone plate is marked as O, and M points with coordinates (x, y) represent any other points on the Fresnel zone plate except the origin of coordinates. The emergent wave E of the emergent wave of the plane caliber feed source is along the wave vector k0The phase value of each point incident on the Fresnel zone plate is designated as phiin(x, y). Beam pointing in the far field of radiation for a two-dimensional fresnel sector plate antenna
RrefIs origin of coordinates O to beam pointing
Directional electromagnetic wave radiation path. RmIs M point-to-beam pointing
Directional electromagnetic wave radiation path. In beam pointing
Is an azimuth, i.e. path RrefThe angle with the x-axis. Theta0At a pitch angle, i.e. path RrefThe angle to the z-axis. According to the Huygens principle, the field of each point on the Fresnel zone plate can be regarded asThe radiation far field is the coherent superposition of the radiation fields of the secondary emission source. Pointing a beam with a coordinate origin
Path R ofrefIs a reference path, and its phase value is a reference phase
Reference phase
Incident phase phi equal to origin of coordinates Oin(0,0). The rest of each point path RmAnd R between the reference pathsrefDue to the path difference (R)m-Rref) The resulting phase difference k0(Rm-Rref) Is composed of
So that the phase of the remaining points
Equal to the incident phase phiin(x, y) and path difference (R)m-Rref) The sum of the resulting phase differences, i.e.
Wherein k is02 pi/lambda is the wave vector of free space, and lambda is the wavelength of the electromagnetic wave propagating in free space.
The phase difference between the electromagnetic wave at the central point of the Fresnel zone plate and the electromagnetic waves at the other points
Can be expressed as
According to
The areas with equal phase difference form generalized Fresnel diffraction fringes with equal phase difference lines. The generalized fresnel diffraction pattern (14) is a combination of all the generalized fresnel diffraction fringes on the fresnel zone plate, as shown in fig. 10, and lines of different gray levels represent lines of different equal phase differences. The diffraction fringe area is divided into a coherent constructive area and a coherent destructive area, wherein the phase difference of the coherent constructive area satisfies:
the other regions belong to the coherence-cancellation region. The electromagnetic wave of each point on the Fresnel zone plate is transmitted through the Fresnel diffraction pattern, and then the wave beam is deflected to a specified direction. The diffraction pattern and the beam direction are in one-to-one correspondence. Thus for a given fresnel zone plate size and its incident phase distribution phiin(x, y), the specific beam orientations can form uniquely defined generalized Fresnel diffraction patterns. Transparent/opaque fresnel zone plates exist in two electromagnetic states, the coherent constructive regions being electromagnetically transparent, allowing energy transmission, and the coherent destructive regions being electromagnetically opaque, blocking transmission of energy. The transparent/opaque fresnel zone plate blocks half of the energy transmission and therefore the antenna aperture is inefficient. The two-dimensional Fresnel zone plate with phase reconfigurability utilizes the phase shifting capability of the zone plate per se to change the original phase difference according to the beam direction
And dynamically compensating, wherein the dynamic compensation means that different points on the Fresnel zone plate provide different phase values according to different beam directions. The phase value of each point
The original phase difference can be changed by adding the compensation value provided by the Fresnel zone plate on the original basis
Areas with coherence cancellation in the Fresnel diffraction pattern are reduced, areas with coherence growth are increased, generalized Fresnel diffraction patterns corresponding to beam directions one by one are formed again, energy transmittance is improved, and the high-gain two-dimensional Fresnel zone plate antenna is achieved.
An example of the dynamic compensation implementation is given in the present invention, in which unit periods with phase shift function are designed to be closely distributed to form a phase reconfigurable fresnel zone plate. According to the magnitude of the phase shifting capacity of the unit, partial phase compensation or complete phase compensation is selected to be carried out, wherein the complete phase compensation requires the phase of the phase shifting unit to meet the requirement
The complete phase compensation technology can change all areas on the area plate into in-phase coherent areas, namely the phases of the rest points and the reference points on the area plate are equal, no phase difference exists, the radiation fields of the in-phase coherent areas are superposed in the same phase in the radiation far-field area, and the aperture efficiency of the antenna is greatly improved. If the phase shifting capability of the unit is limited, partial phase compensation technique can be adopted. The typical 0 degree/180 degree partial phase compensation technique is to set the phase value of the cell in the coherent cancellation area to 180 degrees, i.e. to uniformly compensate 180 degrees for the coherent cancellation area, so that it becomes a coherent cancellation area, and to set the phase value of the cell originally in the coherent cancellation area to 0 degrees, i.e. to not compensate for the original coherent cancellation. Thus all the areas are changed into coherent constructive areas, and the transmissivity of energy is improved. In another partial phase compensation technology, a designed phase shift unit has continuous phase shift capacity of 180 degrees, partial compensation is carried out on a coherent cancellation region, namely 180 degrees are compensated uniformly, so that the coherent cancellation region becomes a coherent constructive region, and complete compensation is carried out on an original coherent constructive region to become an in-phase coherent region. Through phase compensation, the energy transmittance of the Fresnel zone plate is increased, and the caliber efficiency of the two-dimensional Fresnel zone plate antenna is improved.
Compare traditional spherical wave feed source of using, the feed of plane bore feed source closely space has not only reduced the section height of fresnel zone plate antenna to the loss that oblique incidence caused has effectively been reduced. As shown in fig. 11, one surface of the fresnel zone plate facing the feed source in the operating frequency range of 27GHz-29GHz is set as port 1, the outgoing wave of the feed source is incident on the fresnel zone plate, the other surface of the fresnel zone plate is set as port 2, and the amplitude value of the transmission coefficient s21 of the fresnel zone plate is measured. The black solid line represents that the spherical wave emitted by the horn antenna is obliquely incident to the two-dimensional Fresnel zone plate at an angle of 45 degrees from the center line. The black dotted line represents that the emergent wave of the plane caliber feed source is perpendicular to the Fresnel zone plate, namely, the emergent wave keeps an angle of 0 degree with the center line and is incident to the Fresnel zone plate. From the figure, compared with the oblique incidence of 46 degrees, the amplitude value of the transmission coefficient can be kept stable in the whole working frequency range by the vertical incidence, and the amplitude value is improved. The amplitude of normal incidence is 3dB higher than 45 degree oblique incidence around the center frequency of 28GHz, which greatly reduces the loss caused by oblique incidence.
In summary, the main innovation point of the present invention is to provide a feeding method for feeding a two-dimensional fresnel zone plate by using a low-profile planar aperture feeding source. Compare traditional spherical wave feed, reduced the section height of fei nieer district board antenna, effectively solved the spherical wave feed oblique incidence simultaneously and caused the problem of great loss. And moreover, a forming principle and an implementation mode of the generalized Fresnel pattern with wider applicability than the traditional Fresnel diffraction pattern are provided, and the energy transmittance is improved through a phase compensation technology of a phase reconfigurable Fresnel zone plate, so that two-dimensional beam scanning is realized after electromagnetic waves pass through the generalized Fresnel pattern.
Claims (7)
1. The utility model provides a low section two dimension fresnel zone plate antenna based on plane bore space feed which characterized in that:
the two-dimensional Fresnel zone plate antenna comprises a two-dimensional Fresnel zone plate (1) and a plane caliber feed source (2), wherein the two-dimensional Fresnel zone plate and the plane caliber feed source are oppositely arranged in parallel, and the distance between the two-dimensional Fresnel zone plate and the plane caliber feed source is short, so that the plane caliber feed source feeds the two-dimensional Fresnel zone plate in a short-distance space; the plane size of the plane caliber feed source is the same as that of the Fresnel zone plate, and the plane caliber feed source and the Fresnel zone plate are fixedly connected through an insulating material;
the close distance between the two-dimensional Fresnel zone plate and the plane caliber feed source means that the distance between the two-dimensional Fresnel zone plate and the plane caliber feed source is in the range of 0.1 to 3 times of wavelength;
the plane aperture feed source comprises a plane aperture antenna (3) and a power division network (4), and the plane aperture antenna comprises a plane patch antenna (7) consisting of plane patch array elements (6) or a plane slot antenna (8) consisting of plane slot/opening array elements (9); the surface of the plane aperture antenna, which does not face the Fresnel zone plate, is connected with a power division network, the plane aperture antenna (3) is connected with the power division network (4) through a microstrip line (5), and the power division network feeds the array element of the plane aperture antenna through the microstrip line (5); the power division network feeds the planar aperture antenna to generate emergent electromagnetic waves, the emergent electromagnetic waves are approximately vertically incident to the two-dimensional Fresnel zone plate, the power division network is a power division network with a phase shifting function, and the phase shifting function is regulated and controlled by controlling the length of the microstrip line, so that the phase of the emergent electromagnetic waves is distributed on the surface of the two-dimensional Fresnel zone plate in a manner of increasing or decreasing gradient from the center to the outside;
or the plane aperture feed source is a cavity slot antenna which combines a plane aperture antenna and a power division network into a whole, the power division network (4) is integrated on the surface of the plane aperture antenna which does not face to the Fresnel zone plate, the cavity slot antenna is a metal cavity slot antenna (10) or a medium cavity slot antenna (12), a rectangular slot (11) is arranged on the surface of the cavity slot antenna which faces to the Fresnel zone plate, and a single coaxial port is arranged on the surface which does not face to the Fresnel zone plate to feed in the cavity; by adjusting the position of a coaxial port of the cavity slot antenna and the position and the size of the slot, the phases of emergent electromagnetic waves of the cavity slot antenna are randomly distributed on the surface of the two-dimensional Fresnel zone plate, and a generalized Fresnel diffraction pattern different from the traditional Fresnel diffraction pattern is formed on the surface of the two-dimensional Fresnel zone plate;
the generalized Fresnel diffraction pattern is a pattern formed by a single diffraction stripe with an oval contour line gradient, a plurality of circular or oval diffraction stripes or other diffraction stripes with any closed-loop contour line gradient form.
2. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 1, characterized in that: the planar aperture antenna is characterized in that patches are etched or gaps are formed in the surface, facing a Fresnel zone plate, of a dielectric plate, array elements are divided into a plurality of groups outwards along the center, one group located at the center is only one array element, the rest groups are a plurality of array elements uniformly distributed at intervals along the ring, and the rings of the rest groups are concentrically arranged.
3. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 1, characterized in that: the surface of the plane caliber feed source facing the Fresnel zone plate is set to be a plane or a curved surface close to the plane.
4. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 1, characterized in that: the incident angle of the emergent electromagnetic wave incident to the two-dimensional Fresnel zone plate is within 10 degrees.
5. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 1, characterized in that: the two-dimensional Fresnel zone plate has the phase reconfigurable characteristic and is formed by closely arranging a plurality of phase shifting unit arrays, and the phase of each phase shifting unit is adjustable.
6. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 5, wherein: the design of the phase shift unit of the two-dimensional Fresnel zone plate comprises a frequency selective surface or a metamaterial unit of a multilayer medium structure embedded with a varactor and an electronic tuning element.
7. The low-profile two-dimensional Fresnel zone plate antenna based on planar aperture space feeding according to claim 1, characterized in that: the air feed mode of the plane caliber feed source is suitable for any type of two-dimensional Fresnel zone plate, including but not limited to two-dimensional Fresnel zone plates composed of transparent/non-transparent areas, two-dimensional Fresnel zone plates composed of 0 phase/180-degree phase areas and phase reconfigurable Fresnel zone plates.
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| WO2019173369A1 (en) * | 2018-03-06 | 2019-09-12 | Corning Incorporated | Utilizing a fresnel zone plate lens to amplify a microwave signal attenuated by a microwave-reflecting window |
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| WO2019173369A1 (en) * | 2018-03-06 | 2019-09-12 | Corning Incorporated | Utilizing a fresnel zone plate lens to amplify a microwave signal attenuated by a microwave-reflecting window |
| CN110416733A (en) * | 2019-03-25 | 2019-11-05 | 华北水利水电大学 | Electromagnetic energy focus method and device under a kind of nlos environment |
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