CN110492238B

CN110492238B - Dynamic polarization and coupling control for steerable cylindrically fed holographic antennas

Info

Publication number: CN110492238B
Application number: CN201910789413.5A
Authority: CN
Inventors: 亚当·比利; 纳桑·昆兹; 米卡拉·约翰逊
Original assignee: Kymeta Corp
Current assignee: Kymeta Corp
Priority date: 2014-02-19
Filing date: 2015-01-20
Publication date: 2021-02-09
Anticipated expiration: 2035-01-20
Also published as: WO2015126550A1; BR112016018882B1; JP2017506471A; ES2935284T3; CN105960735B; EP3800735A1; BR112016018882A2; CN110492238A; TWI634701B; EP3800735B1; EP3108538A1; KR101864052B1; ES2856220T3; JP6339215B2; EP4191794A1; EP3108538A4; CN105960735A; TW201541714A; EP3108538B1; KR20160130975A

Abstract

An apparatus for a cylindrical feed antenna and a method of using the same are disclosed herein. In one embodiment, an antenna includes: an antenna feed section which inputs a cylindrical feed wave; a tunable slot array coupled to the antenna feed.

Description

Dynamic polarization and coupling control for steerable cylindrically fed holographic antennas

This application is a divisional application of the patent application entitled "dynamic polarization and coupling control for steerable cylindrically fed holographic antenna", filed on 2015, 20/1, application No. 201580003431.6.

Priority

This patent application claims priority from and incorporated by reference into a corresponding provisional patent application entitled "Polarization and Coupling Control from a cylindrical feed Holographic Antenna" (Polarization and Coupling Control from a cylindrical tubular magnetic Antenna) serial No. 61/941,801 filed on 2014, month 2 and 19, and a corresponding provisional patent application entitled "Metamaterial Antenna System for communication Satellite ground Stations" (a meta Antenna System for Communications satellites Earth Stations) "serial No. 62/012,897 filed on 2014, month 16.

Technical Field

Embodiments of the invention relate to the field of antennas; more particularly, embodiments of the present invention relate to a cylindrically fed antenna.

Background

The Thinkom (new kentucky) product using the PCB-based approach achieves dual circular polarization in the Ka band, typically using a variable tilted lateral branch or "VICTS" approach, with two types of mechanical rotation. The first type rotates one array relative to the other, and the second type rotates both arrays in azimuth. The main limitations are the scanning range (elevation between 20 and 70 degrees, lateral opposition is not possible) and the beam performance (sometimes only Rx is limited).

"Radial Line Slot Antenna for 12GHz DBS satellite reception (Radial Line Slot Antenna for 12GHz DBS satellite reception" by Ando et al and "Design and Experiments (Design and Experiments of a Novel Radial Line Slot Antenna for High-Power Microwave Applications)" by Yuan et al discuss various antennas. The limitation of the antennas described in these two articles is that the beam is formed at only one static angle. The feed structure described in the article is folded into two layers, where the first layer receives the pin feed and radiates the signal outward to the edge, bending the signal up to the top layer, which then is routed from the periphery to the center excitation fixed slot. The slots are typically oriented in orthogonal pairs, obtaining a fixed circular polarization for the transmit mode, with the opposite side being the receive mode. Finally, the absorption portion terminates any remaining energy.

"scalar and tensor holographic artificial impedance surface", author's square (Fong), cole berben (Colburn), Ottusch (Ottusch), Visher (Visher), western pepper (sievenpipe). While western peyer has shown how a dynamically scanned antenna would be implemented, the polarization fidelity maintained during scanning is questionable. This is because the required polarization control depends on the tensor impedance required at each radiating element. This is very easy to achieve by element-wise rotation. But as the antenna scans, the polarization at each element changes, so the required rotation also changes. Because these elements are fixed and cannot be rotated dynamically, there is no way to scan and maintain polarization control.

Industry standard methods of implementing beam scanning antennas with polarization control typically use a mechanical rotating disk or some type of mechanical motion in combination with electron beam steering. The most expensive category of choice is the full phased array antenna. The disk can receive multiple polarizations simultaneously, but requires a balanced ring (gimbal) to scan. In recent years, combining mechanical motion in one axis with electronic scanning in the orthogonal axis has produced high aspect ratio structures that require less volume but sacrifice beam performance or dynamic polarization control, such as the Thinkom system.

Existing approaches use waveguide and splitter feed structures to feed the antenna. However, the waveguide design has an impedance (bandgap created by a 1 wavelength periodic structure) that swings near the sides; need to be combined with different CTEs; a feed structure having an associated ohmic loss; and/or have thousands of vias extending to a ground plane.

Disclosure of Invention

An apparatus for cylindrically feeding an antenna and a method of using the same are disclosed herein. In one embodiment, an antenna includes: an antenna feed section which inputs a cylindrical feed wave; a tunable slot array coupled to the antenna feed.

Drawings

The inventions will be understood more fully from the detailed description given below and from the accompanying drawings of various embodiments of the inventions which, however, should not be taken to limit the inventions to the specific embodiments, but are for explanation and understanding only.

FIG. 1 illustrates a top view of one embodiment of a coaxial feed for providing a cylindrical wave feed.

Fig. 2A and 2B illustrate side views of embodiments of a cylindrical feed antenna structure.

Fig. 3 illustrates a top view of one embodiment of a slot-coupled patch antenna or diffuser.

Fig. 4 illustrates a side view of a slot-fed patch antenna that is part of a periodically-fed antenna system.

Fig. 5 illustrates an example of a dielectric material into which a feed wave is launched.

FIG. 6 illustrates one embodiment of an iris board (iris board) showing the slits and their orientation.

Fig. 7 illustrates the manner in which the orientation of an iris/patch combination is determined.

FIG. 8 illustrates iris sections divided into two groups, where the first group is rotated-45 degrees relative to the power feed vector and the second group is rotated +45 degrees relative to the power feed vector.

Fig. 9 illustrates an embodiment of a patch panel.

Fig. 10 illustrates an example of an element having the patch of fig. 9 determined to be off at an operating frequency.

Fig. 11 illustrates an example of an element having the patch of fig. 9 determined to be open at an operating frequency.

Fig. 12 illustrates the results of full wave modeling showing the electric field response to the on and off control/modulation scheme with respect to the elements of fig. 10 and 11.

Fig. 13 illustrates beamforming for an embodiment using a cylindrical feed antenna.

Fig. 14A and 14B illustrate patches and slots positioned in a honeycomb pattern.

Fig. 15A-15C illustrate patches and associated slots positioned in a loop to produce a radial layout, associated control patterns, and resulting antenna responses.

Fig. 16A and 16B illustrate right-hand circular polarization and left-hand circular polarization, respectively.

Fig. 17 illustrates a portion of a cylindrical feed antenna comprising a glass layer containing patches.

Fig. 18 illustrates a linear taper of the dielectric portion.

Fig. 19A illustrates an example of a reference wave.

Fig. 19B illustrates the object wave generated.

Fig. 19C is an example of the resulting sinusoidal modulation pattern.

Fig. 20 illustrates an alternative antenna embodiment in which each of the side portions includes a step that causes a traveling wave to be launched from the bottom layer to the top layer.

Detailed Description

Embodiments of the present invention include antenna design architectures that feed an antenna from a central point with an excitation (feed wave) that spreads out from the feed point in a cylindrical or concentric manner. The antenna operates with a feed wave by arranging a plurality of cylindrical feed sub-aperture antennas, such as patch antennas. In an alternative embodiment, the antenna is fed inwards from the periphery rather than outwards from the centre. This may be helpful because it counters amplitude excitation attenuation caused by aperture scattered energy. Scattering occurs similarly in both orientations, but the natural cone caused by focusing the energy in the feed wave as it travels inward from the surroundings counters the decreasing cone caused by intentional scattering.

Embodiments of the present invention include holographic antennas based on doubling the density typically required to achieve holography and filling holes with two types of orthogonal elements. In one embodiment, one set of elements is oriented linearly at +45 degrees with respect to the feed wave and a second set of elements is positioned at-45 degrees with respect to the feed wave. Both types illuminate through the same feed wave, which in one form is a parallel plate mode emitted through a coaxial pin feed.

In the following description, numerous details are set forth to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.

Some portions of the detailed description which follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as "processing" or "computing" or "calculating" or "determining" or "displaying" or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

Overview of an example of an antenna system

Embodiments of a metamaterial antenna system for a communication satellite ground station are described. In one embodiment, the antenna system is a component or subsystem of a satellite Earth Station (ES) operating on a mobile platform (e.g., aeronautical, maritime, terrestrial, etc.) that operates using the Ka-band or Ku-band for civilian commercial satellite communications. It is noted that embodiments of the antenna system may also be used for ground stations that are not on a mobile platform (e.g., fixed or transportable ground stations).

In one embodiment, the antenna system uses surface scattering metamaterial technology to form and steer the transmit and receive beams through separate antennas. In one embodiment, the antenna system is an analog system as compared to an antenna system that uses digital signal processing to electrically form and steer beams, such as a phased array antenna.

In one embodiment, the antenna system consists of three functional subsystems (1) a wave propagation structure consisting of a cylindrical wave feed architecture; (2) an array of wave scattering metamaterial unit cells; and (3) using holographic principles to command a control structure that forms an adjustable radiation field (beam) from the metamaterial scattering elements.

Examples of wave-propagating structures

FIG. 1 illustrates a top view of one embodiment of a coaxial feed for providing a cylindrical wave feed. Referring to fig. 1, the coaxial feeding portion includes a center conductor and an outer conductor. In one embodiment, a cylindrical wave feed architecture feeds an antenna from a central point with excitation that spreads out in a cylindrical manner from the feed point. That is, the cylindrical feed antenna generates a concentric feed wave that travels outward. Nevertheless, the shape of the cylindrical feed antenna around the cylindrical feed may be circular, square or any shape. In another embodiment, a cylindrical feed antenna generates an inwardly traveling feed wave. In this case the feed wave comes most naturally from a circular structure.

Figure 2A illustrates a side view of one embodiment of a cylindrical feed antenna structure. The antenna uses a double-layer feed structure (i.e., a double-layer feed structure) to generate an inwardly traveling wave. In one embodiment, the antenna comprises a circular outer shape, but this is not required. That is, non-circular inwardly running structures may be used. In one embodiment, the antenna structure in fig. 2A includes the coaxial feed of fig. 1.

Referring to fig. 2A, a coaxial pin 201 is used to excite a field on the lower layer of the antenna. In one embodiment, coaxial pin 201 is a conveniently available 50 Ω coaxial pin. The coaxial pin 201 is coupled (e.g., bolted) to the bottom of the antenna structure, which is a conductive ground plane 202.

An interstitial conductor (inter conductor)203 is separated from the conductive ground plane 202, which is an inner conductor. In one embodiment, the conductive ground plane 202 and the gap conductor 203 are parallel to each other. In one embodiment, the distance between the ground plane 202 and the gap conductor 203 is 0.1-0.15 ". In another embodiment, the distance may be λ/2, where λ is the wavelength of the traveling wave at the operating frequency.

The ground plane 202 is separated from the gap conductor 203 by a spacer 204. In one embodiment, the spacers 204 are foam or air-like spacers. In one embodiment, the spacer 204 comprises a plastic spacer.

On top of the gap conductor 203 is a dielectric layer 205. In one embodiment, dielectric layer 205 is plastic. Fig. 5 illustrates an example of a dielectric material into which a feed wave is launched. The purpose of dielectric layer 205 is to slow the traveling wave relative to free space velocity. In one embodiment, dielectric layer 205 slows the traveling wave by 30% relative to free space. In one embodiment, the refractive index suitable for beamforming is in the range 1.2-1.8, where by definition the refractive index in free space is equal to 1. For example, other dielectric spacer materials such as plastics may be used to achieve this effect. Note that materials other than plastic may be used as long as they achieve the desired wave-slowing effect. Alternatively, a material having a distributed structure may be used as the dielectric portion 205, such as a machinable or lithographically defined periodic subwavelength metal structure, for example.

An RF array 206 is on top of the dielectric 205. In one embodiment, the distance between the gap conductor 203 and the RF array 206 is 0.1-0.15 ". In another embodiment, the distance may be λ_eff/2, where λ_effIs the effective wavelength in the medium at the design frequency.

The antenna includes

sides

207 and 208. The

sides

207 and 208 are angled so that the traveling wave feed from the coaxial pin 201 propagates by reflection from the region below the interstitial conductor 203 (spacer layer) to the region above the interstitial conductor 203 (dielectric layer). In one embodiment, sides 207 and 208 are at a 45 angle. In alternative embodiments, the

sides

207 and 208 may be replaced with a continuous radius to achieve reflection. Although fig. 2A shows angled sides having an angle of 45 °, other angles may be used that enable signals to pass from lower layer feeds to upper layer feeds. That is, assuming that the effective wavelength at the lower feed is generally different from the effective wavelength at the upper feed, an angle of 45 ° from ideal may be used to assist in the transfer from the lower feed to the upper feed layer. For example, in another embodiment, the 45 ° angle is replaced with a single step such as that shown in fig. 20. Referring to fig. 20, stepped portions 2001 and 2002 are shown on one end of the antenna surrounding the dielectric layer 2005, the gap conductor 2003, and the spacer layer 2004. The same two steps are at the other ends of the layers.

In operation, when a feed wave is fed from the coaxial pin 201, the wave travels concentrically oriented outward from the coaxial pin 201 in the region between the ground plane 202 and the gap conductor 203. The concentrically output waves are reflected by

sides

207 and 208 and travel inward in the region between the gap conductor 203 and the RF array 206. Reflections from the edges of the circular periphery keep the waves in phase (i.e., it is an in-phase reflection). The traveling wave is slowed by dielectric layer 205. At this point, the traveling waves begin to interact with the elements in the RF array 206 and excite to obtain the desired scattering.

To terminate the traveling wave, a termination 209 is included in the antenna at the geometric center of the antenna. In one embodiment, the termination 209 includes a pin termination (e.g., a 50 Ω pin). In another embodiment, the termination 209 includes an RF absorber that terminates the unused energy to prevent the unused energy from reflecting back through the feed structure of the antenna. These may be used at the top of the RF array 206.

Fig. 2B illustrates another embodiment of an antenna system with an output wave. Referring to fig. 2B, the two

ground planes

210 and 211 and a dielectric layer 212 (e.g., a plastic layer, etc.) between the ground planes 210 and 211 are substantially parallel to each other. RF absorbers 213 and 214 (e.g., resistors) couple the two

ground planes

210 and 211 together. A coaxial pin 215 (e.g., 50 omega) feeds the antenna. The RF array 216 is on top of the dielectric layer 212. The RF array 216 is on top of the ground plane 211.

In operation, a feed wave is fed through the coaxial pin 215 and travels concentrically outward and interacts with the elements of the RF array 216.

The cylindrical feeding in both antennas of fig. 2A and 2B improves the service angle of the antenna. Instead of a service angle (service angle) of plus or minus 45 degrees azimuth (+ -45 ° Az) and plus or minus 25 degrees elevation (+ -25 ° El), in one embodiment the antenna system has a service angle of 75 degrees (75 °) from the line of sight in all directions. As with any beam forming antenna consisting of a number of individual radiators, the overall antenna gain depends on the gain of the constituent elements, which are angle dependent. When using a common radiating element, the overall antenna gain typically decreases as the beam is further off the line of sight. A significant gain reduction of about 6dB is expected at 75 degrees off the line of sight.

Embodiments of antennas with cylindrical feeds solve one or more problems. These include a significant simplification of the feed structure compared to antennas fed with a cooperative divider network, thus reducing the total antenna and antenna feed volume required; sensitivity to manufacturing errors and control errors is reduced by maintaining high beam performance with coarser control (always lengthened to simplify binary control); a more beneficial side lobe pattern (side lobe pattern) is obtained compared to a straight line feed, since the cylindrically directed feed waveguide causes the side lobes in the far field to be spatially different; and allows the polarization to be dynamic, including allowing left-hand circular polarization, right-hand circular polarization, and linear polarization, without the need for a polarizer.

Array of wave scattering elements

The RF array 206 of fig. 2A and the RF array 216 of fig. 2B include a wave scattering subsystem that includes a set of patch antennas (i.e., scatterers) that function as radiators. The set of patch antennas includes an array of scattering metamaterial elements.

In one embodiment, each scattering element in the antenna system is part of a unit cell consisting of a lower conductor, a dielectric substrate, and an upper conductor embedded in a complementary electrical inductance-capacitance resonator ("complementary electrical LC" or "CELC") etched into or deposited on the upper conductor.

In one embodiment, Liquid Crystal (LC) is injected into the space surrounding the scattering element. Liquid crystal is encapsulated in each unit cell and separates the lower conductor associated with the slot from the upper conductor associated with its patch. The liquid crystal has a dielectric constant that is a function of the orientation of the molecules comprising the liquid crystal, which orientation (and hence dielectric constant) can be controlled by adjusting the bias voltage across the liquid crystal. With this property, the liquid crystal acts as an on/off switch for transmitting energy from the guided wave to the CELC. When turned on, the CELC emits electromagnetic waves resembling an electrically small dipole antenna.

Controlling the thickness of the LC increases the beam switching speed. A fifty percent (50%) reduction in the spacing between the lower and upper conductors (thickness of the liquid crystal) results in a four-fold increase in speed. In another embodiment, the thickness of the liquid crystal results in a beam switching speed of about fourteen milliseconds (14 ms). In one embodiment, the LC is doped in a manner known in the art to improve responsiveness such that seven milliseconds (7ms) requirements can be met.

The CELC elements respond to magnetic fields applied parallel to the plane of the CELC elements and perpendicular to the CELC spacing. When a voltage is applied to the liquid crystal in the metamaterial scattering unit cell, the magnetic field component of the guided wave induces the magnetic excitation of the CELC, which in turn generates an electromagnetic wave at the same frequency as the guided wave.

The phase of the electromagnetic wave generated by a single CELC can be selected by the location of the CELC on the vector of the guided wave. Each cell produces a wave that is in phase with the guided wave parallel to the CELC. Because the CELC is smaller than the wavelength, the output wave has the same phase as that of the guided wave when it passes under the CELC.

In one embodiment, the cylindrical feed geometry of such an antenna system allows CELC elements to be positioned at 45 degree (45 °) angles to the vector of the waves in the wave feed. This position of the element can control the polarization of free space waves generated by or received by the element. In one embodiment, the CELCs are arranged at inter-element distances that are less than the free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in a 30GHz transmit antenna would be about 2.5mm (i.e., 1/4 for a 10mm free-space wavelength of 30 GHz).

In one embodiment, the CELC is implemented with a patch antenna that includes a patch co-located over a gap with liquid crystal therebetween. In this respect, the metamaterial antenna acts like a slot (scattering) waveguide. For a slot waveguide, the phase of the output wave depends on the position of the slot relative to the guided wave.

Fig. 3 illustrates a top view of one embodiment of a patch antenna or scattering element. Referring to fig. 3, the patch antenna includes a patch 301 co-located above a slot 302 with a Liquid Crystal (LC)303 in between the patch 301 and the slot 302.

Fig. 4 illustrates a side view of a patch antenna that is part of a periodically fed antenna system. Referring to fig. 4, the patch antenna is above a dielectric portion 402 (e.g., a plastic insert, etc.), the dielectric portion 402 being above the gap conductor 203 of fig. 2A (or a ground conductor such as in the case of the antenna in fig. 2B).

The iris plate 403 is a ground plane (conductor) with multiple slots, such as slot 403a on top of and above the dielectric 402. The slit may be referred to herein as an iris. In one embodiment, the apertures in the iris plate 403 are created by etching. Note that in one embodiment, the highest density of the slots or a portion of their unit cells is λ/2. In one embodiment, the density of slots/cells is λ/3 (i.e., 3 cells per λ). Note that other densities of unit cells may be used.

A patch plate 405 comprising a plurality of patches, such as patch 405a, is positioned over the iris plate 403 and separated by an intermediate dielectric layer. Each of the patches, such as patch 405a, is co-located with a slit in the iris plate 403. In one embodiment, the intermediate dielectric layer between the iris plate 403 and the patch plate 405 is the liquid crystal substrate layer 404. The liquid crystal acts as a dielectric layer between each patch and its co-located gap. Note that a substrate layer other than the LC may be used.

In one embodiment, the patch panel 405 comprises a Printed Circuit Board (PCB), each patch comprising metal on the PCB, wherein the metal around the patch has been removed.

In one embodiment, the patch panel 405 includes a via for each patch on a side of the patch panel opposite a side of the slot where the patch faces its apposition. The vias are used to connect one or more traces to the patch to provide voltage to the patch. In one embodiment, a matrix drive is used to apply voltages to the patches to control them. The voltages are used to tune or demodulate the various elements to achieve beam forming.

In one embodiment, the patch may be deposited on a glass layer, such as glass commonly used for LC displays (LCDs), such as Corning Eagle glass (Corning Eagle glass), for example, without the use of a circuit patch sheet. Fig. 17 illustrates a portion of a cylindrical feed antenna comprising a glass layer containing a patch. Referring to fig. 17, the antenna includes a conductive base or ground layer 1701, a dielectric layer 1702 (e.g., plastic), an iris plate 1703 (e.g., circuit board) including a slot, a liquid crystal substrate layer 1704, and a glass layer 1705 including a patch 1710. In one embodiment, the patch 1710 is rectangular in shape. In one embodiment, the slits and patches are arranged in rows and columns, and the orientation of the patches is the same for each row or column, while the orientation of co-located slits is respectively oriented the same relative to each other for the rows or columns.

In one embodiment, a cover (e.g., radome) covers the top of the patch-antenna stack to provide protection.

FIG. 6 illustrates one embodiment of an iris plate 403. This is the lower conductor of the CELC. Referring to FIG. 6, the iris plate includes an array of apertures. In one embodiment, each slot is oriented at either +45 degrees or-45 degrees with respect to the shockwave feed at a central location of the slot. In other words, the layout pattern of the scattering elements (CELCs) is arranged to the vector of the wave at ± 45 degrees. Below each slit is a circular opening 403b, which is essentially another slit. The slit is on the top of the iris plate and the circular or elliptical opening is on the bottom of the iris plate. Note that these openings are optional and may be about 0.001 "or 25mm deep.

The slot array can be loaded in an oriented and tuned manner. Each slot is tuned to provide the desired scattering at the operating frequency of the antenna (i.e., it is tuned to operate at a known frequency) by closing or opening the individual slot.

Fig. 7 illustrates the manner in which the orientation of an iris (slit)/patch combination is determined. Referring to fig. 7, letter a denotes a solid black arrow which indicates a power feeding vector from the cylindrical feeding position to the center of the element. Letter B denotes a dashed orthogonal line showing a vertical axis with respect to "a", and letter C denotes a dashed rectangular surrounding slit rotated by 45 degrees with respect to "B".

Fig. 8 illustrates the iris (slit) divided into two groups, where the first group is rotated by-45 degrees with respect to the power feeding vector and the second group is rotated by +45 degrees with respect to the power feeding vector. Referring to fig. 8, group a includes slots rotated by equal to-45 ° with respect to the feed vector, while group B includes slots rotated by equal to +45 ° with respect to the feed vector.

Note that the representation of the global coordinate system is not important, so that rotations of positive and negative angles are only important because they describe the relative rotation of the elements with respect to each other and the direction of the feed wave. To generate circular polarization from two sets of linearly polarized elements, the two sets of elements are perpendicular to each other and have equal amplitude excitations at the same time. Rotating them +/-45 degrees relative to the feed wave excitation immediately achieves the desired characteristics. Rotating one set by 0 degrees and the other by 90 degrees will achieve the goal of perpendicularity, rather than equal amplitude excitation.

Fig. 9 illustrates an embodiment of a patch panel 405. This is the upper conductor of the CELC. Referring to fig. 9, the patch panel includes a rectangular patch covering a slot and completing a linearly polarized patch/slot resonance pair to be closed and opened. The pair is closed or opened by applying a voltage to the patch using a controller. The required voltage depends on the liquid crystal mixture being used, the resulting threshold voltage is required to start tuning the liquid crystal, and the maximum saturation voltage (which does not have a higher voltage than it produces any effect other than a final drop or short through the liquid crystal). In one embodiment, the matrix drive is used to apply voltages to the patches in order to control the coupling.

Antenna system control

The control structure has 2 main components; a controller, which includes the drive electronics for the antenna system, is underneath the wave scattering structure, while the matrix-driven switching array is dispersed in the radiating RF array in such a way that it does not interfere with the radiation. In one embodiment, the drive electronics for the antenna system includes a commercial off-the-shelf LCD controller for a commercial television facility that adjusts the bias voltage for each scattering element by adjusting the amplitude of the AC bias signal to that element.

In one embodiment, the controller controls the control electronics using software. In one embodiment, the control of the polarization is part of the software control of the antenna, the polarization being pre-programmed to match the polarization of signals from the satellite service with which the ground station communicates, or to match the polarization of the receiving antenna on the satellite.

In one embodiment, the controller further comprises a microprocessor executing software. The control structure may also incorporate sensors (nominally including a GPS receiver, a three-axis compass and an accelerometer) to provide position and orientation information to the processor. The position and orientation information may be provided to the processor by other systems in the ground station and/or may not be part of the antenna system.

More particularly, the controller controls which elements are turned off and which elements are turned on at the operating frequency. The elements are selectively detuned for frequency operation by applying a voltage. The controller supplies an array of voltage signals to the RF radiating patches to generate a modulation or control pattern. The control mode causes the element to be turned on or off. In one embodiment, the control pattern resembles a square wave, with elements along one spiral (LHCP or RHCP) being "on" and those elements away from the spiral being "off" (i.e., a dual modulation pattern). In another embodiment, multi-state control is used, where individual elements are turned on and off to varying levels, more closely approximating a sine wave control pattern (i.e., a sine wave gray scale modulation pattern) versus a square wave. Some elements radiate more strongly than others, rather than some elements radiating and some elements not. Variable radiation is achieved by applying a specific voltage level that adjusts the liquid crystal dielectric constant to a varying amount, thereby variably detuning the elements and causing some elements to radiate more than others.

The generation of a focused beam by a metamaterial array of elements can be explained by the phenomena of constructive and destructive interference. If the phases of the individual electromagnetic waves are the same when they meet in free space, they sum (constructive interference) and if their phases are opposite when they meet in free space, the waves cancel each other (destructive interference). If the slots in a slot antenna are positioned such that each successive slot is at a different distance from the excitation point of the guided wave, the scattered wave from that element will have a different phase than the scattered wave of the previous slot. If the slots are spaced 1/4 apart by the guided wave wavelength, each slot will scatter waves one-quarter of the phase delay from the previous slot.

With an array, the number of modes capable of producing constructive and destructive interference can be increased so that, using the principles of holography, the beam can theoretically be directed in any direction, plus or minus ninety degrees (90 °) from the line of sight of the antenna array. Thus, by controlling which metamaterial unit cells are turned on or off (i.e., by changing the pattern of which unit cell is turned on and the pattern of which unit cell is turned off), different patterns of constructive and destructive interference may be generated, and the antenna may change the direction of the wave front. The time required to turn the unit cells on and off determines the speed at which the beam can be switched from one position to another.

Both the polarization and beam aiming angle are defined by modulating or specifying the pattern of which elements are controlled on or off. In other words, the frequency at which the beam is aimed and polarized in the desired manner depends on the control mode. Because the control mode is programmable, the polarization can be programmed for the antenna system. For most applications, the desired polarization state is circular or linear. The circular polarization states include helical polarization states, i.e., right-hand circular polarization and left-hand circular polarization for a feed wave fed from the center and traveling outward are shown in fig. 16A and 16B, respectively. Note that to get the same beam while switching the feed direction (e.g. from the incoming feed to the outgoing feed), the directional or inductive or helical modulation mode is reversed. Note that when it is stated that a given helical pattern of the opening and closing elements produces left-hand circular polarization or right-hand circular polarization, the direction of the feed wave (i.e., center or edge feed) is also specified.

The control pattern for each beam will be stored in the controller or calculated in flight, or some combination thereof. When the antenna control system determines where and where the antenna is located and aimed, it then determines where the target satellite is located based on the line of sight of the antenna. The controller then commands on and off patterns of individual unit cells in the array, which correspond to preselected beam patterns of the position of the satellites in view of the antenna.

In one embodiment, the antenna system generates one steerable beam for the uplink antenna and one steerable beam for the downlink antenna.

Fig. 10 illustrates an example of an element having the patch of fig. 9 determined to be off at an operating frequency, and fig. 11 illustrates an example of an element having the patch of fig. 9 determined to be on at an operating frequency. Fig. 12 illustrates the results of full wave modeling showing the electric field response to the on and off modulation modes with respect to the elements of fig. 10 and 11.

Fig. 13 illustrates beamforming. Referring to fig. 13, the interference pattern may be adjusted to provide an arbitrary antenna radiation pattern by identifying the interference pattern corresponding to the selected beam pattern and then adjusting the voltage across the scattering element to produce a beam according to holographic principles. The basic principles of holography are well known, including the terms "object beam" and "reference beam" as commonly used in connection with these principles. RF holography in the context of forming a desired "object beam" as a "reference beam" using a traveling wave is performed as follows.

The modulation mode is determined as follows. First, a reference wave (beam), sometimes referred to as a feed wave, is generated. Fig. 19A illustrates an example of a reference wave. Referring to FIG. 19A, ring 1900 is the phase front of the electric and magnetic fields of the reference wave. They exhibit a sinusoidal time variation. Arrow 1901 illustrates the outward propagation of the reference wave.

In this example, a TEM or Transverse electromagnetic (Transverse Electro-Magnetic) wave travels inward or outward. Propagation directions are also defined, and for this example, propagation out from the center feed point is selected. The plane of propagation is along the antenna surface.

An object wave, sometimes referred to as an object beam, is generated. In this example, the object wave is a TEM wave that travels in a direction deviating from 30 degrees from the orthogonal antenna surface, with the azimuth angle set to 0 degrees. A polarization is also defined, and for this example, right hand circular polarization is selected. Fig. 19B illustrates the object wave generated. Referring to FIG. 19B, a phase front 1903 of the electric and magnetic fields of a propagating TEM wave 1904 is shown. The electric field vectors at each phase wavefront, represented by arrows 1905, are at 90 degree intervals. In this example, they comply with the right-hand circular polarization selection.

Interferometric or modulation mode Re { [ a ] x [ B ] }

When a sine wave is multiplied by the complex conjugate of another sine wave and takes the real part, the resulting modulation pattern is also a sine wave. Spatially, the modulation pattern is a maximum, or a very strongly radiating position, when the maximum of the reference wave meets the maximum of the object wave (both of which are sinusoidal time variations). In practice, this interference is calculated at each scattering location and depends not only on the position of the element but also on the polarization of the element based on its rotation and the polarization of the object wave at the position of the element. Fig. 19C is an example of the resulting sinusoidal modulation pattern.

Note that it is further optional to simplify the resulting sine wave grayscale modulation pattern into a square wave modulation pattern.

Note that the voltage across the scattering element is controlled by a voltage applied between the patch and the ground plane, which is here a metallization on top of the iris plate.

Alternative embodiments

In one embodiment, the patches and the slits are positioned in a honeycomb pattern. Fig. 14A and 14B show an example of such a mode. Referring to fig. 14A and 14B, the honeycomb structure is shifted left or right every other row by half an element pitch or alternatively, every other column by half an element pitch up or down.

In one embodiment, the patches and associated slots are positioned in a ring to create a radial layout. In this case, the slit center is positioned on the ring. Fig. 15A illustrates an example of patches (and their co-located slits) positioned in a ring. Referring to fig. 15A, the centers of the patches and slots are on a ring and the ring is concentrically positioned relative to the feed or termination of the antenna array. Note that adjacent slits in the same ring are oriented at almost 90 deg. with respect to each other (when evaluated at their centers). More particularly, they are oriented at an angle equal to 90 ° plus the angular displacement along the ring comprising the geometric centres of the two elements.

Fig. 15B is an example of a control pattern for a ring-based aperture array such as that depicted in fig. 15A. Fig. 15C shows the resulting near and far fields of the beam pointing 30 deg. for LHCP, respectively.

In one embodiment, the feed structure is formed to control the coupling to ensure that the power radiated or scattered across the full 2D aperture is substantially constant. This is done by using a linear thickness taper in the dielectric, or a taper similar to that of the ridged feed network, which results in less coupling near the feed point and more coupling away from the feed point. By containing the energy in a smaller volume as the traveling wave propagates away from the feed point, the use of a linear taper for the height of the feed offsets the 1/r attenuation, which results in a larger percentage of the remaining energy in the feed scattered from each element. This is important to produce a uniform amplitude excitation across the aperture. For non-radially symmetric feed structures, such as structures with square or rectangular outer dimensions, the taper may be applied in a non-radially symmetric manner so that the power scattered across the aperture is approximately constant. Complementary technology requires tuning elements differently in the array based on how far they are from the feed point.

One example of tapering is achieved using a dielectric in the shape of a maxwell fish eye lens, which produces an inversely proportional increase in radiation intensity to cancel out the 1/r attenuation.

Fig. 18 illustrates a linear taper of the dielectric portion. Referring to fig. 18, a tapered dielectric 1802 with a coaxial feed 1800 is shown to provide a concentric feed wave to perform the elements (patch/iris pairs) of the RF array 1801. The dielectric portion 1802 (e.g., plastic) tapers in height from a maximum high velocity near the coaxial feed 1800 to a lower height at a point furthest from the coaxial feed 1800. For example, the height B is greater than the height a as it approaches the coaxial feed 1800.

In this regard, in one embodiment, the dielectric portion is formed in a non-radially symmetric shape to concentrate energy where needed. For example, in the case where the square antenna is fed from a single feed point as described above, the path length from the center of the square to the corner of the square is longer than the path length from the center of the square to the center of the side of the square by 1.4 times. Therefore, more energy is concentrated towards 4 corners than the 4 midpoints of the sides of the square, and the rate of energy scattering must also be different. The non-radially symmetrical shape of the feed portion and other structures can meet these requirements.

In one embodiment, different dielectric portions are stacked in a given feed structure to control the power scattered from the feed to the aperture as waves radiate outward. For example, when more than 1 different dielectric part media are stacked on top of each other, the electrical or magnetic energy intensity may be concentrated in a particular dielectric part. One particular example is the use of plastic and air-like foam layers having a total thickness of less than lambda at the operating frequency_effAnd/2, resulting in a higher concentration of magnetic field energy in the plastic than in the air-like foam.

In one embodiment, the control mode is spatially controlled for patch/iris detuning (e.g., few elements are initially turned on) to control coupling over the aperture and scatter more or less energy depending on the feed direction and desired aperture excitation weights. For example, in one embodiment, the control mode used at the beginning opens less slots than the rest of the time. For example, initially, some percentage (e.g. 40%, 50%) of the elements (patch/iris slit pairs) near the center of the cylindrical feed to be opened to form a beam are opened only during the first phase, and then the remaining elements away from the cylindrical feed are opened. In an alternative embodiment, the element may be continuously opened from the cylindrical feed as the wave propagates away from the feed. In another embodiment, the ridge feed network replaces the dielectric spacer (e.g. the plastic of spacer 205) and allows further control of the orientation of the propagating feed wave. Ridges may be used to create symmetric propagation in the feed (i.e., Poynting vectors are not parallel to the wave vector) to counteract 1/r attenuation. In this way, the use of ridges within the feed portion helps to direct energy where needed. By directing more ridges and/or variable height ridges to the low energy region, a more uniform illumination is produced at the aperture. This allows deviations from a purely radial feed configuration, since the propagation direction of the feed wave can no longer be oriented radially. The gaps above the ridges are strongly coupled, while those between the ridges are weakly coupled. Thus, the use of ridges and the arrangement of slots allows control of the coupling, depending on the desired coupling (to obtain the desired beam).

In another embodiment, a complex feed structure is used that provides non-circularly symmetric aperture illumination. Such applications may be square apertures of non-uniform illumination or substantially non-circular apertures. In one embodiment, non-radially symmetric dielectric portions are used that deliver more energy to some regions than others. That is, the dielectric portion can have different areas of dielectric portion control. One example of this is the distribution of dielectric portions that appear like maxwell fish-eye lenses. Such lenses deliver different amounts of power to different portions of the array. In another embodiment, a ridge feed structure is used to deliver more energy to some areas than others.

In one embodiment, a plurality of cylindrical-fed secondary aperture antennas of the type described herein are arranged in an array. In one embodiment, one or more additional feed structures are used. And in one embodiment, includes a distributed amplification point (amplification point). For example, the antenna system may include multiple antennas in an array, such as shown in fig. 2A or 2B. The array system may be 3x3 (9 antennas total), 4x4, 5x5, etc., but other configurations are possible. In such an arrangement, each antenna may have a separate feed. In an alternative embodiment, the number of amplification points may be smaller than the number of feeds.

Advantages and benefits

Improved beam performance

One advantage of embodiments of the inventive architecture is better beam performance than linear feeding. A natural, built-in taper at the edge may help to achieve good beam performance.

In array factor calculations, FCC shielding can be satisfied from a 40cm aperture using only open and close elements.

Using cylindrical feeding, embodiments of the present invention have no impedance swings near the sides, and no band gap created by the 1-wavelength periodic structure.

Embodiments of the present invention do not have the diffraction pattern problem when scanning the sides.

Dynamic polarization

There are (at least) two element designs that can be used with the architectures described herein: a circularly polarized element and a pair of linearly polarized elements. Using pairs of linear polarization elements, the circular polarization induction can be dynamically changed by phase delaying or phase advancing the modulation applied to one set of elements relative to the second set. To achieve linear polarization, the phase advance of one set relative to the second set (actually the orthogonal set) would be 180 degrees. Linear polarization can also be synthesized using only variations of small pieces of elements, providing a mechanism for tracking linear polarization.

Bandwidth of operation

The switched mode of operation has the opportunity to extend the dynamic and transient bandwidth because the mode of operation does not require each element to be tuned to a particular portion of its resonant curve. Without significant performance impact, the antenna can operate continuously with its range of amplitude and phase hologram portions. This brings the operating range closer to the total adjustable range.

The gap with the quartz/glass substrate may be small

The cylindrical feed structure may utilize a TFT architecture, which means functioning on quartz or glass. These substrates are much stiffer than circuit boards and there are better known techniques for obtaining gap sizes of about 3 um. A gap size of 3um will result in a switching speed of 14 ms.

Complexity reduction

The disclosed architecture described herein requires no mechanical work and requires only a single bonding stage in production. This architecture, in combination with switching to TFT driver electronics, eliminates expensive materials and some difficult requirements.

Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims, which in themselves recite only those features regarded as essential to the invention.

Claims

1. An antenna, comprising:

an antenna feed including a coaxial input to input a cylindrical feed wave;

a first layer comprising a first dielectric layer, wherein the antenna feed is coupled at a central bottom portion of the first layer to input the feed wave to the first layer through the coaxial input, the feed wave propagating outward from the coaxial input;

a Radio Frequency (RF) array coupled to the first layer and having a plurality of rings of radiating slots, a radiating slot of the plurality of rings of radiating slots interacting with the feed wave to obtain a desired scatter to produce a beam, wherein the RF array further comprises a plurality of patches, wherein each of the plurality of patches is co-located and separated from a slot of the plurality of rings of radiating slots, wherein a second dielectric layer of liquid crystal is between each slot of the plurality of rings of radiating slots and an associated patch of the plurality of patches to form a stacked relationship, wherein each ring of radiating slots is a ring-shaped structure having a plurality of radiating slots; and

a controller coupled to the RF array and configured to apply a control pattern to control radiation slots in the plurality of radiation slot rings to produce the beam based on applying voltages to patches in each patch/slot pair specified by the control pattern, and wherein the radiation slots are tuned to provide a desired scattering at a given frequency by adjusting voltages from the controller to dynamically reconfigure the beam according to an interference pattern corresponding to a selected beam pattern.

2. The antenna defined in claim 1 wherein the RF array comprises a plurality of surface scattering metamaterial antenna elements, each of which is constructed by a slot in the plurality of radiating slotted rings and an associated patch co-located over the slot.

3. The antenna defined in claim 2 wherein ones of the plurality of patches and ones of the plurality of slots are on first and second layers of glass, respectively.

4. The antenna defined in claim 1 wherein a slot of the plurality of slots is positioned to enable control of polarization.

5. The antenna of claim 1, wherein the coaxial input has an impedance of 50 ohms.

6. The antenna defined in claim 1 wherein each slot of the plurality of slots is oriented at either +45 degrees or-45 degrees relative to a cylindrical feed wave impinging at a central location of the each slot such that the slot array includes a first set of slots rotated +45 degrees relative to a direction of propagation of the cylindrical feed wave and a second set of slots rotated-45 degrees relative to the direction of propagation of the cylindrical feed wave.

7. The antenna of claim 1, the control mode controlling which patch/slot pair to open and close.

8. A method of operating an antenna, comprising:

feeding a feed wave from a coaxial input at a central position of the first layer;

propagating the feed wave outwardly and concentrically from the coaxial input through a bottom layer;

the feed wave interacts with slots of the RF array as the feed wave travels through the first dielectric layer, the slots being tuned to provide a desired scattering at a given frequency by using voltages from a controller to dynamically reconfigure the beam according to an interference pattern corresponding to a selected beam pattern;

applying a control pattern to control a plurality of radiating slot rings of the RF array to produce a beam, wherein the RF array further comprises a plurality of patches, wherein each of the plurality of patches is co-located over and separated from a slot of the plurality of slot rings, wherein a second dielectric layer of liquid crystal is between each slot of the plurality of slot rings and an associated patch of the plurality of patches to form a stacked relationship, each patch and associated slot being controlled based on applying a voltage to the patch specified by the control pattern.

Terminating the feed wave using an RF absorber at the first layer after the feed wave interacts with the slots of the RF array.

9. The method of claim 8, wherein the RF array comprises a plurality of surface scattering metamaterial antenna elements, each of the surface scattering metamaterial antenna elements constructed by a slot in the plurality of radiating slotted rings and an associated patch co-located over the slot.

10. The method of claim 8, wherein a patch of the plurality of patches is on a first glass layer and a slot of the plurality of slots is on a plate or a second glass layer.

11. The method of claim 8, wherein a slot of the plurality of slots is positioned to enable control of polarization.

12. The method of claim 8, wherein the control mode controls which patch/slot pair is opened and closed.

13. The method of claim 8, wherein each slot of the plurality of slots is oriented at either +45 degrees or-45 degrees relative to a cylindrical feed wave impinging at a central location of the each slot such that the slot array includes a first set of slots rotated +45 degrees relative to a direction of propagation of the cylindrical feed wave and a second set of slots rotated-45 degrees relative to the direction of propagation of the cylindrical feed wave.

14. The method of claim 8, wherein the coaxial input has an impedance of 50 ohms.