CN112736483B - Polarization reconfigurable two-dimensional beam scanning holographic antenna and implementation method thereof - Google Patents
Polarization reconfigurable two-dimensional beam scanning holographic antenna and implementation method thereof Download PDFInfo
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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
- H01Q3/005—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system using remotely controlled antenna positioning or scanning
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/002—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices being reconfigurable or tunable, e.g. using switches or diodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/0033—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective used for beam splitting or combining, e.g. acting as a quasi-optical multiplexer
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Abstract
The invention discloses a polarization reconfigurable two-dimensional beam scanning holographic antenna and an implementation method thereof. The holographic impedance modulation surface comprises a plurality of impedance modulation units which are correspondingly connected to one node of a voltage control network, the surface impedance of the corresponding impedance modulation unit is controlled by the node voltage of the voltage control network, and when the impedance distribution of the holographic impedance modulation surface meets the coherent modulation, a surface wave source field generated by the antenna feed source can be converted into a target radiation field to radiate to a space; the invention does not need complex phase shift and feed network, has the advantage of low profile and avoids the feed source shielding problem in the radiation direction; the two problems that the polarization mode of radiation on a fixed working frequency cannot be changed and the radiation angle cannot be changed are solved; the invention has the advantages of low profile, easy integration, target wave beam reconstruction and the like, and has great advantages and development prospects in a microwave communication system.
Description
Technical Field
The invention relates to a microwave communication technology, in particular to a polarization reconfigurable two-dimensional beam scanning holographic antenna and an implementation method thereof.
Background
With the development of communication technology, the traditional single-function antenna is difficult to meet the increasing communication requirements, the reconfigurable antenna can realize the requirements of beam angle control, polarization mode control, working frequency band control and the like in one antenna, the use scenes of the antenna are greatly widened, and the reconfigurable antenna becomes an effective solution for simplifying an antenna system in a complex communication scene. The characteristic that the radiation beam of the high-gain antenna is extremely narrow cannot cover the communication requirement of a multi-azimuth user, so the radiation beam scanning capability is very important in the high-gain directional antenna; meanwhile, the polarization reconfigurable capability can realize frequency reuse in communication and improve the capacity of a communication system. Therefore, the antenna with the polarization reconfigurable capability and the beam scanning capability can reduce the complexity of a receiving and transmitting module of the communication system and improve the communication quality of the communication system.
At present, there are two main implementation modes for a polarization reconfigurable beam scanning two-dimensional antenna: 1) the phased array antenna realizes the scanning of radiation beams under different polarization modes by adjusting the feed phase of each antenna unit, and the mode needs complex phase shifting and feed networks, so the cost is high and the system is complex; 2) the electronic control wave beam reconfigurable reflection array can realize the scanning of the radiation wave beam of the antenna under different polarization modes by regulating and controlling the phase distribution on the reflection array surface in real time, and the feed horn irradiating the reflection array surface needs to be placed on the radiation surface of the array surface.
Disclosure of Invention
In order to solve the two problems that the polarization mode of radiation of the traditional holographic antenna on a fixed working frequency cannot be changed and the radiation angle cannot be changed, the invention provides the two-dimensional beam scanning holographic antenna with reconfigurable polarization and the implementation method thereof, and the two-dimensional beam scanning holographic antenna with reconfigurable polarization has the advantages of low profile, convenience in integration, reconfigurable beams and the like, and has great advantages and development prospects in a microwave communication system.
One object of the present invention is to propose a polarization reconfigurable two-dimensional beam scanning holographic antenna.
The polarization reconfigurable two-dimensional beam scanning holographic antenna of the present invention comprises: the holographic impedance modulation surface, the voltage control network and the antenna feed source; the holographic impedance modulation surface is connected to the voltage control network, and an antenna feed source is arranged in the center of the holographic impedance modulation surface; wherein the content of the first and second substances,
the holographic impedance modulation surface comprises V multiplied by H impedance modulation units or V multiplied by H-1 impedance modulation units, when V and H are not odd numbers completely, the holographic impedance modulation surface comprises V multiplied by H impedance modulation units, when V and H are both odd numbers, the center position is occupied by an antenna feed source, the holographic impedance modulation surface comprises V multiplied by H-1 impedance modulation units, and each impedance modulation unit comprises an upper substrate, a bottom substrate, a metal floor, an impedance modulation patch, a varactor, a grounding metal through hole and a center metal through hole; the upper layer substrate and the bottom layer substrate are respectively in a flat plate shape, a metal floor is arranged between the upper layer substrate and the bottom layer substrate, and the metal floor is grounded; an impedance modulation patch is arranged in the center of the upper surface of the upper substrate, and the shape of the impedance modulation patch is a centrosymmetric figure; arranging L variable capacitance diodes which are symmetrical about an x axis and a y axis at the edge of the impedance modulation patch, wherein L is a natural number more than or equal to 2, and the conduction direction of the variable capacitance diodes points to the center of the impedance modulation patch; the impedance modulation patch is provided with L grounding metal through holes which penetrate through the upper surface of the upper layer substrate to the metal floor corresponding to each variable capacitance diode, the cathode of each variable capacitance diode is connected with the impedance modulation patch, and the anode of each variable capacitance diode is connected to the metal floor through the corresponding grounding metal through hole; a central metal through hole penetrating through the upper surface of the upper-layer substrate to the lower surface of the bottom-layer substrate is formed below the impedance modulation patch, the central metal through hole is insulated from the metal floor, and the impedance modulation patch is connected with a voltage control network through the central metal through hole; the edges of the upper-layer substrate, the bottom-layer substrate and the metal floor of all the impedance modulation units are tightly attached and connected into a whole;
the voltage control network comprises an FPGA (field programmable gate array) control unit, a voltage transformation unit and V multiplied by H or V multiplied by H-1 nodes; the FPGA control unit is connected to the voltage transformation unit; v multiplied by H or V multiplied by H-1 nodes extend out of the voltage transformation unit corresponding to each impedance modulation unit, the nodes are wires, and the V multiplied by H or V multiplied by H-1 nodes are respectively connected to central metal through holes of the V multiplied by H or V multiplied by H-1 impedance modulation units corresponding to the impedance modulation units;
the antenna feed source is a monopole antenna and is vertically arranged in the center of the holographic impedance modulation surface;
obtaining a dispersion curve of the impedance modulation unit according to FDTD (finite difference time domain), obtaining an eigenfrequency of the impedance modulation unit through the dispersion curve of the impedance modulation unit, and obtaining a surface impedance of the impedance modulation unit through the eigenfrequency; the surface impedance is related to the capacitance, each node of the voltage control network applies voltage to the corresponding impedance modulation unit, reverse bias voltage is loaded to the variable capacitance diodes through the impedance modulation patches, the voltage change of the nodes of the voltage control network causes the change of the reverse bias voltage loaded by the variable capacitance diodes, the change of the loaded reverse bias voltage controls the simultaneous change of the capacitances of the variable capacitance diodes, the control of the capacitance of the impedance modulation unit through the node voltage of the voltage control network is realized, and the surface impedance of the corresponding impedance modulation unit is controlled; obtaining a surface impedance curve through the relation between the capacitance and the surface impedance; obtaining the impedance distribution of the whole holographic impedance modulation surface according to the surface impedance curve of each impedance modulation unit; the impedance distribution of the holographic impedance modulation surface is formed by the interference of a surface wave source field and a target radiation field, and when the impedance distribution of the holographic impedance modulation surface meets coherent modulation, the surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into the target radiation field to radiate to a space; and a target beam with a specific radiation angle and a specific polarization direction can be obtained through specific impedance distribution, so that the voltage distribution relation between the surface impedance of the impedance modulation unit and the corresponding node of the voltage control network is utilized, the polarization mode of the target beam and the impedance distribution of the radiation angle can be mapped to the voltage distribution of each node of the voltage control network, and the voltage distribution of the voltage control network controls the radiation angle and the polarization direction of the two-dimensional beam scanning holographic antenna with reconfigurable polarization.
The impedance modulation patch is made of metal with good conductivity, and the metal is copper, aluminum or aluminum alloy.
The size of the impedance modulation patch of each impedance modulation unit is the same, and the type of the varactor diode is also the same.
The upper substrate and the bottom substrate of the impedance modulation unit are square, the side length a of the impedance modulation unit is the side length of the square of the upper substrate and the bottom substrate,
the horizontal dimension of the impedance modulation patch is smaller than the side length of the impedance modulation unit.
V and H are ≥ lambda0A natural number of a, λ0The wavelength of a free space under the working frequency of the polarization reconfigurable two-dimensional beam scanning holographic antenna is shown, and a is the side length of the impedance modulation unit.
Another object of the present invention is to provide a method for implementing a polarization reconfigurable two-dimensional beam scanning holographic antenna.
The invention discloses a method for realizing a two-dimensional beam scanning holographic antenna with reconfigurable polarization, which comprises the following steps:
1) obtaining a dispersion curve of the impedance modulation unit according to FDTD (finite difference time domain), obtaining an eigenfrequency of the impedance modulation unit through the dispersion curve of the impedance modulation unit, and obtaining a surface impedance Z of the impedance modulation unit through the eigenfrequency:
wherein eta is0Is the free space wave impedance, c is the free space light velocity, a is the side length of the impedance modulation unit, phixThe phase difference corresponding to the surface wave crossing the impedance modulation unit in the x direction is shown, and omega is the eigenfrequency of the impedance modulation unit;
the surface impedance is related to the capacitance, voltage is applied to the corresponding impedance modulation unit through each node of the voltage control network, reverse bias voltage is loaded to the variable capacitance diodes through the impedance modulation patches, the voltage change of the nodes of the voltage control network causes the change of the reverse bias voltage loaded by the variable capacitance diodes, the change of the loaded reverse bias voltage controls the capacitance of the variable capacitance diodes to change simultaneously, the capacitance of the impedance modulation unit is controlled through the node voltage of the voltage control network, and therefore the surface impedance of the corresponding impedance modulation unit is controlled;
2) obtaining a surface impedance curve through the relation between the capacitance and the surface impedance; obtaining the impedance distribution of the whole holographic impedance modulation surface according to the surface impedance curve of each impedance modulation unit, thereby relating the impedance distribution of the holographic impedance modulation surface with the voltage distribution of the voltage control network;
3) the impedance distribution of the holographic impedance modulation surface is formed by the interference of a surface wave source field and a target radiation field, and when the impedance distribution Z (x, y) of the holographic impedance modulation surface satisfies a coherent modulation distribution:
wherein, XsIs the average impedance value of the impedance modulation unit, M is the impedance modulation depth, phiradAnd
respectively scanning the conjugate of a target radiation field and a surface wave source field of the holographic antenna for the two-dimensional wave beam with reconfigurable polarization;
4) and a target beam with a specific radiation angle and a specific polarization direction can be obtained through specific impedance distribution, so that the voltage distribution relation between the surface impedance of the impedance modulation unit and the voltage control network is utilized, the polarization mode of the target beam and the impedance distribution of the radiation angle can be mapped to the voltage distribution of each node of the voltage control network, and the voltage distribution of the voltage control network is used for controlling the radiation angle and the polarization direction of the two-dimensional beam scanning holographic antenna with reconfigurable polarization.
Wherein, in step 3), for the linearly polarized radiation target beam, the impedance distribution of the x-direction linear polarization and the y-direction linear polarization comprises the following steps:
i. when the holographic impedance modulation surface meets the following impedance distribution, a surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into a target radiation field to radiate to a space;
the target radiation field linearly polarized in the x-direction of the radiation in two dimensions in any direction to space is:
the target radiation field linearly polarized in the y direction of the two-dimensional arbitrary direction radiation to the space is:
wherein k is0Is the wavenumber in free space, theta is the elevation angle at which the target beam is pointed,
an azimuth angle pointed by the target beam;
with the antenna feed in the center of the holographic impedance modulation surface, the surface wave source field is:
wherein k istThe wave number in the surface wave propagation direction is r, and the distance from each point of a plane of the polarization reconfigurable two-dimensional beam scanning holographic antenna to a central feed source is r;
substituting the target radiation fields (3) and (4) linearly polarized in the x direction and the linearly polarized in the y direction and the surface wave source field (5) into the impedance distribution (2), so as to respectively obtain the impedance distributions of the linearly polarized radiation in the x direction and the linearly polarized radiation in the y direction as follows:
in step 3), for the circularly polarized radiation target beam, the impedance distribution of the left-hand circularly polarized and right-hand circularly polarized radiation comprises the following steps:
i. when the holographic impedance modulation surface meets the following impedance distribution, a surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into a target radiation field to radiate to a space;
circularly polarized target radiation field psi for radiation in two-dimensional arbitrary directions into spaceradIs decomposed into two X-direction linearly polarized target radiation fields psi with same amplitude and orthogonal phaseradxAnd a target radiation field psi linearly polarized in the y-directionradyAnd (3) the sum:
wherein, when the plus or minus sign is plus, the target radiation field is left-hand circularly polarized, and when the minus sign is right-hand circularly polarized, the target radiation field is selected;
and is
Wherein k is0Is the wavenumber in free space, theta is the elevation angle at which the target beam is pointed,
an azimuth angle pointed by the target beam; with the antenna feed in the center of the holographic impedance modulation surface, the surface wave source field is:
wherein k istThe wave number in the surface wave propagation direction is r, and the distance from each point of a plane of the polarization reconfigurable two-dimensional beam scanning holographic antenna to a central feed source is r;
substituting the left-hand and right-hand circularly polarized target radiation fields (8) and the surface wave source field (11) into the impedance distribution (2) to obtain impedance distributions for the left-hand and right-hand circularly polarized radiation, respectively, as:
wherein, when the plus or minus sign is plus, the impedance distribution type of the left-handed circular polarized radiation is adopted, and when the minus sign is minus, the impedance distribution type of the right-handed circular polarized radiation is adopted;
and the number of the first and second electrodes,
the invention has the advantages that:
the antenna feed source is integrated on the holographic impedance modulation surface, a complex phase shift and feed network is not needed, the advantage of low profile is achieved, and the problem of feed source shielding in the radiation direction is avoided; the two problems that the polarization mode of radiation of the traditional holographic antenna on a fixed working frequency cannot be changed and the radiation angle cannot be changed are solved; the holographic antenna has the advantages of low profile, convenience for integration, target beam reconstruction and the like, and has great advantages and development prospects in a microwave communication system.
Drawings
FIG. 1 is a schematic diagram of one embodiment of a polarization reconfigurable two-dimensional beam scanning holographic antenna of the present invention;
FIG. 2 is a cross-sectional view of an impedance modulation unit of an embodiment of a polarization reconfigurable two-dimensional beam scanning holographic antenna of the present invention;
FIG. 3 is a dispersion curve diagram of an impedance modulation unit according to an embodiment of the polarization reconfigurable two-dimensional beam scanning holographic antenna of the present invention;
FIG. 4 is an impedance graph of an impedance modulation unit according to an embodiment of the polarization reconfigurable two-dimensional beam scanning holographic antenna of the present invention;
FIG. 5 is an impedance distribution diagram of a holographic impedance modulation surface obtained by one embodiment of a polarization reconfigurable two-dimensional beam scanning holographic antenna according to the present invention, wherein (a) is linear polarization in the x-direction
The impedance distribution of the target beam pointing direction, (b) is under linear polarization in the y direction
θ is the impedance distribution pointed by the target beam of 30 °;
FIG. 6 is an impedance distribution diagram of a holographic impedance modulation surface obtained by a further embodiment of the polarization reconfigurable two-dimensional beam scanning holographic antenna according to the present invention, wherein (a) is in left-hand circular polarization
The impedance distribution of the target beam pointing at 30 degrees is (b) under right-hand circular polarization
θ is the impedance distribution pointed by the target beam of 30 °;
FIG. 7 is a main polarization pattern of an antenna scanning target beam in x-polarization direction obtained by one embodiment of a polarization reconfigurable two-dimensional beam scanning holographic antenna according to the present invention, wherein (a) is in azimuth
A main polarization pattern of the scanned target beam at 0 DEG in the elevation plane, and (b) a main polarization pattern of the scanned target beam at azimuth angle
A main polarization directional diagram of a scanning target beam on a pitching surface at 30 degrees;
FIG. 8 is a main polarization pattern of an antenna scanning target beam in the y-polarization direction obtained by one embodiment of a polarization reconfigurable two-dimensional beam scanning holographic antenna according to the present invention, wherein (a) is in azimuth
A main polarization pattern of the scanned target beam at 0 DEG in the elevation plane, and (b) a main polarization pattern of the scanned target beam at azimuth angle
The scanned target beam on the elevation plane at 30 deg. is the main polarization pattern.
Detailed Description
The invention will be further elucidated by means of specific embodiments in the following with reference to the drawing.
As shown in fig. 1, the polarization reconfigurable two-dimensional beam scanning holographic antenna of the present embodiment includes: the holographic impedance modulation surface 1, the voltage control network 2 and the antenna feed source 3; the holographic impedance modulation surface 1 is connected to a voltage control network 2, and an antenna feed source 3 is arranged at the center of the holographic impedance modulation surface 1; wherein the content of the first and second substances,
as shown in fig. 2, the holographic impedance modulation surface comprises V × H-1 impedance modulation units, each of which in the present embodiment comprises an upper substrate 103, a lower substrate 104, a metal floor 106, an impedance modulation patch 102, a varactor diode 101, a ground metal via 105, and a center metal via; the upper layer substrate 103 and the bottom layer substrate 104 are respectively in a flat plate shape, a metal floor 106 is arranged between the upper layer substrate and the bottom layer substrate, and the metal floor 106 is grounded; an impedance modulation patch 102 is arranged in the center of the upper surface of an upper substrate 103, and the shape of the impedance modulation patch 102 is a centrosymmetric square; four varactors 101 symmetrical about both the x-axis and the y-axis are arranged at the edge of the impedance modulation patch 102, i.e., L is 4, and the conduction directions of the varactors 101 point to the center of the impedance modulation patch 102; outside the impedance modulation patch 102, corresponding to each varactor 101, four grounding metal through holes penetrating through the upper surface of the upper substrate 103 to the metal floor 106 are formed, the cathode of each varactor 101 is connected with the impedance modulation patch 102, and the anode of each varactor 101 is connected to the metal floor 106 through the corresponding grounding metal through hole; a central metal through hole penetrating through the upper surface of the upper substrate 103 to the lower surface of the bottom substrate 104 is formed below the impedance modulation patch 102, the central metal through hole is insulated from the metal floor 106, and the impedance modulation patch 102 is connected with a voltage control network through the central metal through hole; the edges of the upper substrate 103, the bottom substrate 104 and the metal floor 106 of all the impedance modulation units are tightly attached and connected into a whole;
the voltage control network comprises an FPGA control unit, a voltage transformation unit and V multiplied by H < -1 > nodes; the FPGA control unit is connected to the voltage transformation unit; the voltage transformation unit extends out of V multiplied by H < -1 > nodes corresponding to each impedance modulation unit, the nodes are wires, and the V multiplied by H < -1 > nodes are respectively connected to central metal through holes of the V multiplied by H < -1 > impedance modulation units;
the antenna feed source is a monopole antenna and is vertically arranged in the center of the holographic impedance modulation surface.
In the present embodiment, V is 31, H is 31; the upper layer substrate is an F4BM220 high-frequency substrate with the thickness of 3mm, the bottom layer substrate is an FR-4 substrate with the thickness of 1mm, and the side length is 10 mm; the side length of the impedance modulation patch is 8 mm; the diameters of the grounding metal through hole and the central metal through hole are 0.5 m; the types of the variable capacitance diodes are the same and are MAVR-011020-.
The implementation method of the two-dimensional beam scanning holographic antenna with reconfigurable polarization comprises the following steps:
1) obtaining a dispersion curve of the impedance modulation unit according to FDTD (finite difference time domain), obtaining an eigenfrequency of the impedance modulation unit through the dispersion curve of the impedance modulation unit, and obtaining a surface impedance Z of the impedance modulation unit through the eigenfrequency:
wherein eta is0Is the free space wave impedance, c is the free space light velocity, a is the side length of the impedance modulation unit, phixThe phase difference corresponding to the surface wave crossing the impedance modulation unit in the x direction is shown, and omega is the eigenfrequency of the impedance modulation unit;
the surface impedance is related to the capacitance, voltage is applied to the corresponding impedance modulation unit through each node of the voltage control network, reverse bias voltage is loaded to the variable capacitance diodes through the impedance modulation patches, the voltage change of the nodes of the voltage control network causes the change of the reverse bias voltage loaded by the variable capacitance diodes, the change of the loaded reverse bias voltage controls the capacitance of the variable capacitance diodes to change simultaneously, the capacitance of the impedance modulation unit is controlled through the node voltage of the voltage control network, and therefore the surface impedance of the corresponding impedance modulation unit is controlled;
fig. 3 and 4 are dispersion curves of the impedance modulation unit and surface impedance curves at 6GHz, respectively, corresponding to different capacitance values. As the capacitance value of the varactor diode increases, the phase difference corresponding to the surface wave crossover unit increases, and the surface wave impedance of the impedance modulation unit increases. With this surface impedance curve, the impedance distribution of the holographic impedance modulation surface can be linked to the voltage distribution of the voltage control network.
2) Obtaining a surface impedance curve through the relation between the capacitance and the surface impedance; and obtaining the impedance distribution of the whole holographic impedance modulation surface according to the surface impedance curve of each impedance modulation unit, thereby relating the impedance distribution of the holographic impedance modulation surface with the voltage distribution of the voltage control network.
3) The impedance distribution of the holographic impedance modulation surface is formed by the interference of a surface wave source field and a target radiation field, and when the impedance distribution Z (x, y) of the holographic impedance modulation surface satisfies a coherent modulation distribution:
wherein, XsIs the average impedance value of the impedance modulation unit, M is the impedance modulation depth, phiradAnd
respectively carrying out conjugation on a target radiation field and a surface wave source field of a two-dimensional beam scanning holographic antenna with reconfigurable polarization, wherein x is the position in the x direction, and y is the position in the y direction;
for a linearly polarized radiation target beam, an x-direction linearly polarized and a y-direction linearly polarized impedance profile, comprising the steps of: i. when the holographic impedance modulation surface meets the following impedance distribution, a surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into a target radiation field to radiate to a space;
the target radiation field linearly polarized in the x-direction of the radiation in two dimensions in any direction to space is:
the target radiation field linearly polarized in the y direction of the two-dimensional arbitrary direction radiation to the space is:
wherein k is0Is the wavenumber in free space, theta is the elevation angle at which the target beam is pointed,
an azimuth angle pointed by the target beam;
with the antenna feed in the center of the holographic impedance modulation surface, the surface wave source field is:
wherein k istFor wave number in the propagation direction of surface wave, r is the plane of two-dimensional beam scanning holographic antenna with reconfigurable polarization
The distance from each point of the surface to the central feed source;
substituting the target radiation fields (3) and (4) linearly polarized in the x direction and the linearly polarized in the y direction and the surface wave source field (5) into the impedance distribution (2), so as to respectively obtain the impedance distributions of the linearly polarized radiation in the x direction and the linearly polarized radiation in the y direction as follows:
the impedance distribution of the holographic impedance modulation surface is shown in fig. 5 and 6, respectively. In FIG. 5, (a) is under linear polarization in the x-direction
An impedance distribution of a beam pointing at 30 DEG and (b) linear polarization in the y direction
θ is the impedance distribution of the 30 ° beam pointing. In FIG. 6, (a) is in left hand circular polarization
The impedance distribution of 30 DEG wave beam pointing, (b) is under right-hand circular polarization
θ is the impedance distribution of the 30 ° beam pointing.
Similarly, for circularly polarized radiation target beams, impedance distribution of left-hand circularly polarized radiation and right-hand circularly polarized radiation can be obtained by substituting left-hand circularly polarized target radiation fields and right-hand circularly polarized surface wave source fields into impedance distribution.
4) And a target beam with a specific radiation angle and a specific polarization direction can be obtained through specific impedance distribution, so that the voltage distribution relation between the surface impedance of the impedance modulation unit and the voltage control network is utilized, the polarization mode of the target beam and the impedance distribution of the radiation angle can be mapped to the voltage distribution of each node of the voltage control network, and the voltage distribution of the voltage control network is used for controlling the radiation angle and the polarization direction of the two-dimensional beam scanning holographic antenna with reconfigurable polarization.
In addition, the polarization and beam angle reconstruction rates of the two-dimensional beam scanning holographic antenna with reconfigurable polarization mainly depend on the voltage distribution refresh rate of the voltage control network, the voltage control network of the design example is controlled by the FPGA, and the refresh rate of the voltage distribution is approximately equal to the clock rate of the FPGA.
The antenna in the above example is implemented by adopting electromagnetic simulation softwareSimulation results show that the center working frequency is 6GHz, the voltage standing wave ratio is less than 2, the antenna is well matched with a feed source of 50 omega, and the gain fluctuation of the depression elevation angle in the range of-60 degrees of the omnidirectional angle is within 3 dB. The far field radiation characteristic results of the antenna are shown in fig. 7 and fig. 8, wherein fig. 7(a) and (b) are the azimuth angles under x-direction linear polarization, respectively
The main polarization directional diagram of the scanning beam on the elevation plane at 0 degree and 30 degree, and the azimuth angles under the right-hand circular polarization in FIGS. 8(a) and (b) respectively
The scanning beam main polarization directional diagram on the elevation surface is 0 degrees and 30 degrees.
Finally, it is noted that the disclosed embodiments are intended to aid in further understanding of the invention, but those skilled in the art will appreciate that: various substitutions and modifications are possible without departing from the spirit and scope of the invention and the appended claims. Therefore, the invention should not be limited to the embodiments disclosed, but the scope of the invention is defined by the appended claims.
Claims (8)
1. A polarization reconfigurable two-dimensional beam scanning holographic antenna, comprising: the holographic impedance modulation surface, the voltage control network and the antenna feed source; the holographic impedance modulation surface is connected to the voltage control network, and an antenna feed source is arranged in the center of the holographic impedance modulation surface; wherein the content of the first and second substances,
the holographic impedance modulation surface comprises V multiplied by H impedance modulation units or V multiplied by H-1 impedance modulation units, when V and H are not odd numbers completely, the holographic impedance modulation surface comprises V multiplied by H impedance modulation units, when V and H are both odd numbers, the center position is occupied by an antenna feed source, the holographic impedance modulation surface comprises V multiplied by H-1 impedance modulation units, and each impedance modulation unit comprises an upper substrate, a bottom substrate, a metal floor, an impedance modulation patch, a varactor, a grounding metal through hole and a center metal through hole; the upper layer substrate and the bottom layer substrate are respectively in a flat plate shape, a metal floor is arranged between the upper layer substrate and the bottom layer substrate, and the metal floor is grounded; an impedance modulation patch is arranged in the center of the upper surface of the upper substrate, and the shape of the impedance modulation patch is a centrosymmetric figure; arranging L variable capacitance diodes which are symmetrical about an x axis and a y axis at the edge of the impedance modulation patch, wherein L is a natural number more than or equal to 2, and the conduction direction of the variable capacitance diodes points to the center of the impedance modulation patch; the impedance modulation patch is provided with L grounding metal through holes which penetrate through the upper surface of the upper layer substrate to the metal floor corresponding to each variable capacitance diode, the cathode of each variable capacitance diode is connected with the impedance modulation patch, and the anode of each variable capacitance diode is connected to the metal floor through the corresponding grounding metal through hole; a central metal through hole penetrating through the upper surface of the upper-layer substrate to the lower surface of the bottom-layer substrate is formed below the impedance modulation patch, the central metal through hole is insulated from the metal floor, and the impedance modulation patch is connected with a voltage control network through the central metal through hole; the edges of the upper-layer substrate, the bottom-layer substrate and the metal floor of all the impedance modulation units are tightly attached and connected into a whole;
the voltage control network comprises a field programmable gate array FPGA control unit, a voltage transformation unit and V multiplied by H or V multiplied by H-1 nodes; the FPGA control unit is connected to the voltage transformation unit; v multiplied by H or V multiplied by H-1 nodes are extended out of the voltage transformation unit, the nodes are wires, the V multiplied by H or V multiplied by H-1 nodes are respectively connected with central metal through holes of the V multiplied by H or V multiplied by H-1 impedance modulation units, and V and H are more than or equal to lambda0A natural number of a, λ0Scanning free space wavelength under the working frequency of the holographic antenna for a two-dimensional wave beam with reconfigurable polarization, wherein a is the side length of an impedance modulation unit;
the antenna feed source is vertically arranged at the center of the holographic impedance modulation surface;
obtaining a dispersion curve of the impedance modulation unit according to a Finite Difference Time Domain (FDTD), obtaining an eigenfrequency of the impedance modulation unit through the dispersion curve of the impedance modulation unit, and obtaining a surface impedance of the impedance modulation unit through the eigenfrequency; the surface impedance is related to the capacitance, each node of the voltage control network applies voltage to the corresponding impedance modulation unit, reverse bias voltage is loaded to the variable capacitance diodes through the impedance modulation patches, the voltage change of the nodes of the voltage control network causes the change of the reverse bias voltage loaded by the variable capacitance diodes, the change of the loaded reverse bias voltage controls the simultaneous change of the capacitances of the variable capacitance diodes, the control of the capacitance of the impedance modulation unit through the node voltage of the voltage control network is realized, and the surface impedance of the corresponding impedance modulation unit is controlled; obtaining a surface impedance curve through the relation between the capacitance and the surface impedance; obtaining the impedance distribution of the whole holographic impedance modulation surface according to the surface impedance curve of each impedance modulation unit; the impedance distribution of the holographic impedance modulation surface is formed by the interference of a surface wave source field and a target radiation field, and when the impedance distribution of the holographic impedance modulation surface meets coherent modulation, the surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into the target radiation field to radiate to a space; and a target beam with a specific radiation angle and a specific polarization direction can be obtained through specific impedance distribution, so that the voltage distribution relation between the surface impedance of the impedance modulation unit and the corresponding node of the voltage control network is utilized, the polarization mode of the target beam and the impedance distribution of the radiation angle can be mapped to the voltage distribution of each node of the voltage control network, and the voltage distribution of the voltage control network controls the radiation angle and the polarization direction of the two-dimensional beam scanning holographic antenna with reconfigurable polarization.
2. The polarization reconfigurable two-dimensional beam scanning holographic antenna of claim 1, wherein the impedance modulation patch employs a metal having good electrical conductivity.
3. The polarization reconfigurable two-dimensional beam scanning holographic antenna of claim 2, wherein the impedance modulation patch employs copper, aluminum, or an aluminum alloy.
4. The polarization reconfigurable two-dimensional beam scanning holographic antenna of claim 1, wherein the antenna feed is a monopole antenna.
5. The polarization reconfigurable two-dimensional beam scanning holographic antenna of claim 1, wherein the upper substrate and the lower substrate of the impedance modulation unit have a square shape, a side length a of the impedance modulation unit is a side length of the square of the upper substrate and the lower substrate,
λ0the free-space wavelength at the operating frequency of the holographic antenna is scanned for a polarized reconfigurable two-dimensional beam.
6. A method for implementing a polarization reconfigurable two-dimensional beam scanning holographic antenna according to claim 1, characterized in that it comprises the following steps:
1) obtaining a dispersion curve of the impedance modulation unit according to a finite difference time domain method FDTD, obtaining an eigenfrequency of the impedance modulation unit through the dispersion curve of the impedance modulation unit, and obtaining a surface impedance Z of the impedance modulation unit through the eigenfrequency:
wherein eta is0Is the free space wave impedance, c is the free space light velocity, a is the side length of the impedance modulation unit, phixThe phase difference corresponding to the surface wave crossing the impedance modulation unit in the x direction is shown, and omega is the eigenfrequency of the impedance modulation unit; the surface impedance is related to the capacitance, voltage is applied to the corresponding impedance modulation unit through each node of the voltage control network, reverse bias voltage is loaded to the variable capacitance diodes through the impedance modulation patches, the voltage change of the nodes of the voltage control network causes the change of the reverse bias voltage loaded by the variable capacitance diodes, the change of the loaded reverse bias voltage controls the capacitance of the variable capacitance diodes to change simultaneously, the capacitance of the impedance modulation unit is controlled through the node voltage of the voltage control network, and therefore the surface impedance of the corresponding impedance modulation unit is controlled;
2) obtaining a surface impedance curve through the relation between the capacitance and the surface impedance; obtaining the impedance distribution of the whole holographic impedance modulation surface according to the surface impedance curve of each impedance modulation unit, thereby relating the impedance distribution of the holographic impedance modulation surface with the voltage distribution of the voltage control network;
3) the impedance distribution of the holographic impedance modulation surface is formed by the interference of a surface wave source field and a target radiation field, and when the impedance distribution Z (x, y) of the holographic impedance modulation surface satisfies a coherent modulation distribution:
wherein, XsIs the average impedance value of the impedance modulation unit, M is the impedance modulation depth, phiradAnd
respectively scanning the conjugate of a target radiation field and a surface wave source field of the holographic antenna for the two-dimensional wave beam with reconfigurable polarization;
4) and a target beam with a specific radiation angle and a specific polarization direction can be obtained through specific impedance distribution, so that the voltage distribution relation between the surface impedance of the impedance modulation unit and the voltage control network is utilized, the polarization mode of the target beam and the impedance distribution of the radiation angle can be mapped to the voltage distribution of each node of the voltage control network, and the voltage distribution of the voltage control network is used for controlling the radiation angle and the polarization direction of the two-dimensional beam scanning holographic antenna with reconfigurable polarization.
7. The method of claim 6, wherein in step 3), for linearly polarized radiation of the target beam, the x-direction linearly polarized and the y-direction linearly polarized impedance distributions comprise the steps of:
i. when the holographic impedance modulation surface meets the following impedance distribution, a surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into a target radiation field to radiate to a space;
the target radiation field linearly polarized in the x-direction of the radiation in two dimensions in any direction to space is:
the target radiation field linearly polarized in the y direction of the two-dimensional arbitrary direction radiation to the space is:
wherein k is0Is the wavenumber in free space, theta is the elevation angle at which the target beam is pointed,
an azimuth angle pointed by the target beam;
with the antenna feed in the center of the holographic impedance modulation surface, the surface wave source field is:
wherein k istThe wave number in the surface wave propagation direction is r, and the distance from each point of a plane of the polarization reconfigurable two-dimensional beam scanning holographic antenna to a central feed source is r;
substituting the target radiation fields (3) and (4) linearly polarized in the x direction and the linearly polarized in the y direction and the surface wave source field (5) into the impedance distribution (2), so as to respectively obtain the impedance distributions of the linearly polarized radiation in the x direction and the linearly polarized radiation in the y direction as follows:
8. the method of claim 6, wherein in step 3), the impedance distribution of the left-hand circularly polarized radiation and the right-hand circularly polarized radiation for the circularly polarized radiation target beam comprises the steps of:
i. when the holographic impedance modulation surface meets the following impedance distribution, a surface wave source field generated by an antenna feed source positioned in the center of the holographic impedance modulation surface can be converted into a target radiation field to radiate to a space;
circularly polarized target radiation field psi for radiation in two-dimensional arbitrary directions into spaceradIs decomposed into two X-direction linearly polarized target radiation fields psi with same amplitude and orthogonal phaseradxAnd a target radiation field psi linearly polarized in the y-directionradyAnd (3) the sum:
wherein, when the plus or minus sign is plus, the target radiation field is left-hand circularly polarized, and when the minus sign is right-hand circularly polarized, the target radiation field is selected;
and is
Wherein k is0Is the wavenumber in free space, theta is the elevation angle at which the target beam is pointed,
an azimuth angle pointed by the target beam;
with the antenna feed in the center of the holographic impedance modulation surface, the surface wave source field is:
wherein k istThe wave number in the surface wave propagation direction is r, and the distance from each point of a plane of the polarization reconfigurable two-dimensional beam scanning holographic antenna to a central feed source is r;
substituting the left-hand and right-hand circularly polarized target radiation fields (8) and the surface wave source field (11) into the impedance distribution (2) to obtain impedance distributions for the left-hand and right-hand circularly polarized radiation, respectively, as:
wherein, when the plus or minus sign is plus, the impedance distribution type of the left-handed circular polarized radiation is adopted, and when the minus sign is minus, the impedance distribution type of the right-handed circular polarized radiation is adopted;
and the number of the first and second electrodes,
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