Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/20—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0012—Radial guide fed arrays
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/0006—Particular feeding systems
  • H01Q21/0031—Parallel-plate fed arrays; Lens-fed arrays
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/061—Two dimensional planar arrays
  • H01Q21/065—Patch antenna array
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/24—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction
• • 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
  • H01Q3/26—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture
  • H01Q3/28—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the relative phase or relative amplitude of energisation between two or more active radiating elements; varying the distribution of energy across a radiating aperture varying the amplitude
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
  • H01Q9/0442—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular tuning means
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
  • H01Q9/045—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular feeding means
  • H01Q9/0457—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with particular feeding means electromagnetically coupled to the feed line

Definitions

• Embodiments of the present invention relate to the field of antennas; more particularly, embodiments of the present invention relate to an antenna that is cylindrically fed.
• VCTS Variable Inclined Transverse Stub
• the waveguide designs have impedance swing near broadside (a band gap created by 1-wavelength periodic structures); require bonding with unlike CTEs; have an associated ohmic loss of the feed structure; and/or have thousands of vias to extend to the ground-plane.
• the antenna comprises an antenna feed to input a cylindrical feed wave and a tunable slotted array coupled to the antenna feed.
• Figure 1 illustrates a top view of one embodiment of a coaxial feed that is used to provide a cylindrical wave feed.
• Figures 2A and 2B illustrate side views of embodiments of a cylindrically fed antenna structure.
• Figure 3 illustrates a top view of one embodiment of one slot-coupled patch antenna, or scatterer.
• Figure 4 illustrates a side view of a slot-fed patch antenna that is part of a cyclically fed antenna system.
• Figure 5 illustrates an example of a dielectric material into which a feed wave is launched.
• Figure 6 illustrates one embodiment of an iris board showing slots and their orientation.
• Figure 7 illustrates the manner in which the orientation of one iris/patch combination is determined.
• Figure 8 illustrates irises grouped into two sets, with the first set rotated at -45 degrees relative to the power feed vector and the second set rotated +45 degrees relative to the power feed vector.
• Figure 9 illustrates an embodiment of a patch board.
• Figure 10 illustrates an example of elements with patches in Figure 9 that are determined to be off at frequency of operation.
• Figure 11 illustrates an example of elements with patches in Figure 9 that are determined to be on at frequency of operation.
• Figure 12 illustrates the results of full wave modeling that show an electric field response to an on and off control/modulation pattern with respect to the elements of Figures 10 and 11.
• Figure 13 illustrates beam forming using an embodiment of a cylindrically fed antenna.
• Figures 14A and 14B illustrate patches and slots positioned in a honeycomb pattern.
• Figures 15A-C illustrate patches and associated slots positioned in rings to create a radial layout, an associated control pattern, and resulting antenna response.
• Figures 16A and 16B illustrate right-hand circular polarization and left-hand circular polarization, respectively.
• Figure 17 illustrates a portion of a cylindrically fed antenna that includes a glass layer that contains the patches.
• Figure 18 illustrates a linear taper of a dielectric.
• Figure 19A illustrates an example of a reference wave.
• Figure 19B illustrates a generated object wave.
• Figure 19C is an example of the resulting sinusoidal modulation pattern.
• Figure 20 illustrates an alternative antenna embodiment in which each of the sides include a step to cause a traveling wave to be transmitted from a bottom layer to a top layer.
• Embodiments of the invention include an antenna design architecture that feeds the antenna from a central point with an excitation (feed wave) that spreads in a cylindrical or concentric manner outward from the feed point.
• the antenna works by arranging multiple cylindrically fed subaperture antennas (e.g., patch antennas) with the feed wave.
• the antenna is fed from the perimeter inward, rather than from the center outward. This can be helpful because it counteracts the amplitude excitation decay caused by scattering energy from the aperture. Scattering occurs similarly in both orientations, but the natural taper caused by focusing of the energy in the feed wave as it travels from the perimeter inward counteracts the decreasing taper caused by the intended scattering.
• Embodiments of the invention include a holographic antenna based on doubling the density typically required to achieve holography and filling the aperture with two types of orthogonal sets of elements.
• one set of elements is linearly oriented at +45 degrees relative to the feed wave, and the second set of elements is oriented at -45 degrees relative to the feed wave. Both types are illuminated by the same feed wave, which, in one form, is a parallel plate mode launched by a coaxial pin feed.
• the antenna system is a component or subsystem of a satellite earth station (ES) operating on a mobile platform (e.g., aeronautical, maritime, land, etc.) that operates using either Ka-band frequencies or Ku-band frequencies for civil commercial satellite communications.
• ES satellite earth station
• mobile platform e.g., aeronautical, maritime, land, etc.
• embodiments of the antenna system also can be used in earth stations that are not on mobile platforms (e.g., fixed or transportable earth stations).
• the antenna system uses surface scattering metamaterial technology to form and steer transmit and receive beams through separate antennas.
• the antenna systems are analog systems, in contrast to antenna systems that employ digital signal processing to electrically form and steer beams (such as phased array antennas).
• the antenna system is comprised of three functional subsystems: (1) a wave propagating structure consisting of a cylindrical wave feed architecture; (2) an array of wave scattering metamaterial unit cells; and (3) a control structure to command formation of an adjustable radiation field (beam) from the metamaterial scattering elements using holographic principles.
• FIG. 1 illustrates a top view of one embodiment of a coaxial feed that is used to provide a cylindrical wave feed.
• the coaxial feed includes a center conductor and an outer conductor.
• the cylindrical wave feed architecture feeds the antenna from a central point with an excitation that spreads outward in a cylindrical manner from the feed point. That is, a cylindrically fed antenna creates an outward travelling concentric feed wave. Even so, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square or any shape.
• a cylindrically fed antenna creates an inward travelling feed wave. In such a case, the feed wave most naturally comes from a circular structure.
• Figure 2A illustrates a side view of one embodiment of a cylindrically fed antenna structure.
• the antenna produces an inwardly travelling wave using a double layer feed structure (i.e., two layers of a feed structure).
• the antenna includes a circular outer shape, though this is not required. That is, non-circular inward travelling structures can be used.
• the antenna structure in Figure 2A includes the coaxial feed of Figure 1.
• a coaxial pin 201 is used to excite the field on the lower level of the antenna.
• coaxial pin 201 is a 50 ⁇ coax pin that is readily available.
• Coaxial pin 201 is coupled (e.g., bolted) to the bottom of the antenna structure, which is conducting ground plane 202.
• interstitial conductor 203 Separate from conducting ground plane 202 is interstitial conductor 203, which is an internal conductor.
• conducting ground plane 202 and interstitial conductor 203 are parallel to each other.
• the distance between ground plane 202 and interstitial conductor 203 is 0.1 - 0.15". In another embodiment, this distance may be ⁇ /2, where ⁇ is the wavelength of the travelling wave at the frequency of operation.
• Ground plane 202 is separated from interstitial conductor 203 via a spacer 204.
• spacer 204 is a foam or air-like spacer.
• spacer 204 comprises a plastic spacer.
• dielectric layer 205 On top of interstitial conductor 203 is dielectric layer 205.
• dielectric layer 205 is plastic.
• Figure 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 travelling wave relative to free space velocity. In one embodiment, dielectric layer 205 slows the travelling wave by 30% relative to free space.
• the range of indices of refraction that are suitable for beam forming are 1.2 - 1.8, where free space has by definition an index of refraction equal to 1.
• Other dielectric spacer materials such as, for example, plastic, 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.
• a material with distributed structures may be used as dielectric 205, such as periodic sub- wavelength metallic structures that can be machined or lithographically defined, for example.
• An RF-array 206 is on top of dielectric 205.
• the distance between interstitial conductor 203 and RF-array 206 is 0.1 - 0.15". In another embodiment, this distance may be A eff /2, where A eff is the effective wavelength in the medium at the design frequency.
• the antenna includes sides 207 and 208. Sides 207 and 208 are angled to cause a travelling wave feed from coax pin 201 to be propagated from the area below interstitial conductor 203 (the spacer layer) to the area above interstitial conductor 203 (the dielectric layer) via reflection. In one embodiment, the angle of sides 207 and 208 are at 45° angles.
• sides 207 and 208 could be replaced with a continuous radius to achieve the reflection.
• Figure 2A shows angled sides that have angle of 45 degrees, other angles that accomplish signal transmission from lower level feed to upper level feed may be used. That is, given that the effective wavelength in the lower feed will generally be different than in the upper feed, some deviation from the ideal 45° angles could be used to aid transmission from the lower to the upper feed level.
• the 45° angles are replaced with a single step such as shown in Figure 20. Referring to Figure 20, steps 2001 and 2002 are shown on one end of the antenna around dielectric layer 2005, interstitial conductor 2003, and spacer layer 2004. The same two steps are at the other ends of these layers.
• a termination 209 is included in the antenna at the geometric center of the antenna.
• termination 209 comprises a pin termination (e.g., a 50 ⁇ pin).
• termination 209 comprises an RF absorber that terminates unused energy to prevent reflections of that unused energy back through the feed structure of the antenna. These could be used at the top of RF array 206.
• Figure 2B illustrates another embodiment of the antenna system with an outgoing wave. Referring to Figure 2B, two ground planes 210 and 211 are substantially parallel to each other with a dielectric layer 212 (e.g., a plastic layer, etc.) in between ground planes 210 and 211.
• a dielectric layer 212 e.g., a plastic layer, etc.
• RF absorbers 213 and 214 couple the two ground planes 210 and 211 together.
• a coaxial pin 215 (e.g., 50 ⁇ ) feeds the antenna.
• An RF array 216 is on top of dielectric layer 212.
• a feed wave is fed through coaxial pin 215 and travels concentrically outward and interacts with the elements of RF array 216.
• the antenna system has a service angle of seventy five degrees (75°) from the bore sight in all directions.
• the overall antenna gain is dependent on the gain of the constituent elements, which themselves are angle-dependent.
• the overall antenna gain typically decreases as the beam is pointed further off bore sight. At 75 degrees off bore sight, significant gain degradation of about 6 dB is expected.
• Embodiments of the antenna having a cylindrical feed solve one or more problems. These include dramatically simplifying the feed structure compared to antennas fed with a corporate divider network and therefore reducing total required antenna and antenna feed volume; decreasing sensitivity to manufacturing and control errors by maintaining high beam performance with coarser controls (extending all the way to simple binary control); giving a more advantageous side lobe pattern compared to rectilinear feeds because the cylindrically oriented feed waves result in spatially diverse side lobes in the far field; and allowing polarization to be dynamic, including allowing left-hand circular, right-hand circular, and linear polarizations, while not requiring a polarizer.
• Array of Wave Scattering Elements include dramatically simplifying the feed structure compared to antennas fed with a corporate divider network and therefore reducing total required antenna and antenna feed volume; decreasing sensitivity to manufacturing and control errors by maintaining high beam performance with coarser controls (extending all the way to simple binary control); giving a more advantageous side lobe pattern compared to rectilinear feeds because the cylindrical
• RF array 206 of Figure 2 A and RF array 216 of Figure 2B include a wave scattering subsystem that includes a group of patch antennas (i.e., scatterers) that act as radiators. This group of patch antennas comprises an array of scattering metamaterial elements.
• each scattering element in the antenna system is part of a unit cell that consists of a lower conductor, a dielectric substrate and an upper conductor that embeds a complementary electric inductive-capacitive resonator ("complementary electric LC" or “CELC”) that is etched in or deposited onto the upper conductor.
• a complementary electric inductive-capacitive resonator (“complementary electric LC” or “CELC”) that is etched in or deposited onto the upper conductor.
• a liquid crystal is injected in the gap around the scattering element.
• Liquid crystal is encapsulated in each unit cell and separates the lower conductor associated with a slot from an upper conductor associated with its patch.
• Liquid crystal has a permittivity that is a function of the orientation of the molecules comprising the liquid crystal, and the orientation of the molecules (and thus the permittivity) can be controlled by adjusting the bias voltage across the liquid crystal. Using this property, the liquid crystal acts as an on/off switch for the transmission of energy from the guided wave to the CELC. When switched on, the CELC emits an electromagnetic wave like an electrically small dipole antenna.
• Controlling the thickness of the LC increases the beam switching speed.
• a fifty percent (50%) reduction in the gap between the lower and the upper conductor results in a fourfold increase in speed.
• the thickness of the liquid crystal results in a beam switching speed of approximately fourteen milliseconds (14 ms).
• the LC is doped in a manner well-known in the art to improve responsiveness so that a seven millisecond (7 ms) requirement can be met.
• the CELC element is responsive to a magnetic field that is applied parallel to the plane of the CELC element and perpendicular to the CELC gap complement.
• a voltage is applied to the liquid crystal in the metamaterial scattering unit cell, the magnetic field component of the guided wave induces a magnetic excitation of the CELC, which, in turn, produces an electromagnetic wave in the same frequency as the guided wave.
• the phase of the electromagnetic wave generated by a single CELC can be selected by the position of the CELC on the vector of the guided wave. Each cell generates a wave in phase with the guided wave parallel to the CELC. Because the CELCs are smaller than the wave length, the output wave has the same phase as the phase of the guided wave as it passes beneath the CELC.
• the cylindrical feed geometry of this antenna system allows the CELC elements to be positioned at forty five degree (45°) angles to the vector of the wave in the wave feed. This position of the elements enables control of the polarization of the free space wave generated from or received by the elements.
• the CELCs are arranged with an inter-element spacing that is less than a free-space wavelength of the operating frequency of the antenna. For example, if there are four scattering elements per wavelength, the elements in the 30 GHz transmit antenna will be approximately 2.5 mm (i.e., l/4th the 10 mm free-space wavelength of 30 GHz).
• the CELCs are implemented with patch antennas that include a patch co-located over a slot with liquid crystal between the two.
• the CELCs are implemented with patch antennas that include a patch co-located over a slot with liquid crystal between the two.
• metamaterial antenna acts like a slotted (scattering) wave guide.
• a slotted wave guide the phase of the output wave depends on the location of the slot in relation to the guided wave.
• FIG 3 illustrates a top view of one embodiment of one patch antenna, or scattering element.
• the patch antenna comprises a patch 301 collocated over a slot 302 with liquid crystal (LC) 303 in between patch 301 and slot 302.
• LC liquid crystal
• FIG 4 illustrates a side view of a patch antenna that is part of a cyclically fed antenna system.
• the patch antenna is above dielectric 402 (e.g., a plastic insert, etc.) that is above the interstitial conductor 203 of Figure 2 A (or a ground conductor such as in the case of the antenna in Figure 2B).
• An iris board 403 is a ground plane (conductor) with a number of slots, such as slot 403a on top of and over dielectric 402.
• a slot may be referred to herein as an iris.
• the slots in iris board 403 are created by etching. Note that in one embodiment, the highest density of slots, or the cells of which they are a part, is 1/2. In one embodiment, the density of slots/cells is 1/3 (i.e., 3 cells per ⁇ ). Note that other densities of cells may be used.
• a patch board 405 containing a number of patches, such as patch 405a, is located over the iris board 403, separated by an intermediate dielectric layer.
• Each of the patches, such as patch 405a, are co-located with one of the slots in iris board 403.
• the intermediate dielectric layer between iris board 403 and patch board 405 is a liquid crystal substrate layer 404.
• the liquid crystal acts as a dielectric layer between each patch and its co- located slot. Note that substrate layers other than LC may be used.
• patch board 405 comprises a printed circuit board (PCB), and each patch comprises metal on the PCB, where the metal around the patch has been removed.
• PCB printed circuit board
• patch board 405 includes vias for each patch that is on the side of the patch board opposite the side where the patch faces its co-located slot.
• the vias are used to connect one or more traces to a patch to provide voltage to the patch.
• matrix drive is used to apply voltage to the patches to control them.
• the voltage is used to tune or detune individual elements to effectuate beam forming.
• the patches may be deposited on the glass layer (e.g., a glass typically used for LC displays (LCDs) such as, for example, Corning Eagle glass), instead of using a circuit patch board.
• Figure 17 illustrates a portion of a cylindrically fed antenna that includes a glass layer that contains the patches.
• the antenna includes conductive base or ground layer 1701, dielectric layer 1702 (e.g., plastic), iris board 1703 (e.g., a circuit board) containing slots, a liquid crystal substrate layer 1704, and a glass layer 1705 containing patches 1710.
• the patches 1710 have a rectangular shape.
• the slots and patches are positioned in rows and columns, and the orientation of patches is the same for each row or column while the orientation of the co-located slots are oriented the same with respect to each other for rows or columns, respectively.
• a cap e.g., a radome cap covers the top of the patch antenna stack to provide protection.
• Figure 6 illustrates one embodiment of iris board 403. This is a lower conductor of the CELCs.
• the iris board includes an array of slots. In one
• each slot is oriented either +45 or -45 relative to the impinging feed wave at the slot's central location.
• the layout pattern of the scattering elements (CELCs) are arranged at +45 degrees to the vector of the wave.
• a circular opening 403b which is essentially another slot. The slot is on the top of the Iris board and the circular or elliptical opening is on the bottom of the Iris board. Note that these openings, which may be about 0.001 " or 25 mm in depth, are optional.
• the slotted array is tunably directionally loaded. By turning individual slots off or on, 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 given frequency).
• Figure 7 illustrates the manner in which the orientation of one iris (slot)/patch combination is determined.
• the letter A denotes a solid black arrow denoting power feed vector from a cylindrical feed location to the center of an element.
• the letter B denotes dashed orthogonal lines showing perpendicular axes relative to "A”
• the letter C denotes a dashed rectangle encircling slot rotated 45 degrees relative to "B”.
• Figure 8 illustrates irises (slots) grouped into two sets, with the first set rotated at
• group A includes slots whose rotation relative to a feed vector is equal to -45°
• group B includes slots whose rotation relative to a feed vector is +45°.
• Rotating one set 0 degrees and the other 90 degrees would achieve the perpendicular goal, but not the equal amplitude excitation goal.
• FIG 9 illustrates an embodiment of patch board 405.
• the patch board includes rectangular patches covering slots and completing linearly polarized patch/slot resonant pairs to be turned off and on. The pairs are turned off or on by applying a voltage to the patch using a controller. The voltage required is dependent on the liquid crystal mixture being used, the resulting threshold voltage required to begin to tune the liquid crystal, and the maximum saturation voltage (beyond which no higher voltage produces any effect except to eventually degrade or short circuit through the liquid crystal).
• matrix drive is used to apply voltage to the patches in order to control the coupling.
• the control structure has 2 main components; the controller, which includes drive electronics, for the antenna system, is below the wave scattering structure, while the matrix drive switching array is interspersed throughout the radiating RF array in such a way as to not interfere with the radiation.
• the drive electronics for the antenna system comprise commercial off-the shelf LCD controls used in commercial television appliances that adjust the bias voltage for each scattering element by adjusting the amplitude of an AC bias signal to that element.
• the controller controls the electronics using software controls.
• control of the polarization is part of the software control of the antenna and the polarization is pre-programmed to match the polarization of the signal coming from the satellite service with which the earth station is communicating or be pre-programmed to match the polarization of the receiving antenna on the satellite.
• the controller also contains a microprocessor executing the software.
• the control structure may also incorporate sensors (nominally including a GPS receiver, a three axis compass and an accelerometer) to provide location and orientation information to the processor.
• the location and orientation information may be provided to the processor by other systems in the earth station and/or may not be part of the antenna system.
• the controller controls which elements are turned off and those elements turned on at the frequency of operation.
• the elements are selectively detuned for frequency operation by voltage application.
• a controller supplies an array of voltage signals to the RF radiating patches to create a modulation, or control pattern.
• the control pattern causes the elements to be turned on or off.
• the control pattern resembles a square wave in which elements along one spiral (LHCP or RHCP) are "on” and those elements away from the spiral are "off (i.e., a binary modulation pattern).
• multistate control in which various elements are turned on and off to varying levels, further approximating a sinusoidal control pattern, as opposed to a square wave (i.e., a sinusoid gray shade modulation pattern). Some elements radiate more strongly than others, rather than some elements radiate and some do not. Variable radiation is achieved by applying specific voltage levels, which adjusts the liquid crystal permittivity to varying amounts, thereby detuning elements variably and causing some elements to radiate more than others.
• interference that can be produced can be increased so that beams can be pointed theoretically in any direction plus or minus ninety degrees (90°) from the bore sight of the antenna array, using the principles of holography.
• the antenna can change the direction of the wave front.
• the time required to turn the unit cells on and off dictates the speed at which the beam can be switched from one location to another location.
• the polarization and beam pointing angle are both defined by the modulation, or control pattern specifying which elements are on or off. In other words, the frequency at which to point the beam and polarize it in the desired way are dependent upon the control pattern. Since the control pattern is programmable, the polarization can be programmed for the antenna system.
• the desired polarization states are circular or linear for most applications.
• the circular polarization states include spiral polarization states, namely right-hand circular polarization and left-hand circular polarization, which are shown in Figures 16A and 16B, respectively, for a feed wave fed from the center and travelling outwardly.
• the orientation, or sense, or the spiral modulation pattern is reversed.
• the direction of the feed wave i.e. center or edge fed
• the control pattern for each beam will be stored in the controller or calculated on the fly, or some combination thereof.
• the antenna control system determines where the antenna is located and where it is pointing, it then determines where the target satellite is located in reference to the bore sight of the antenna.
• the controller then commands an on and off pattern of the individual unit cells in the array that corresponds with the preselected beam pattern for the position of the satellite in the field of vision of the antenna.
• the antenna system produces one steerable beam for the uplink antenna and one steerable beam for the downlink antenna.
• Figure 10 illustrates an example of elements with patches in Figure 9 that are determined to be off at frequency of operation
• Figure 11 illustrates an example of elements with patches in Figure 9 that are determined to be on at frequency of operation
• Figure 12 illustrates the results of full wave modeling that show an electric field response to the on and off modulation pattern with respect to the elements of Figures 10 and 11.
• Figure 13 illustrates beam forming.
• the interference pattern may be adjusted to provide arbitrary antenna radiation patterns by identifying an interference pattern corresponding to a selected beam pattern and then adjusting the voltage across the scattering elements to produce a beam according the principles of holography.
• the basic principle of holography including the terms "object beam” and “reference beam”, as commonly used in connection with these principles, is well-known.
• RF holography in the context of forming a desired "object beam” using a traveling wave as a "reference beam” is performed as follows.
• FIG. 19A illustrates an example of a reference wave.
• rings 1900 are the phase fronts of the electric and magnetic fields of a reference wave. They exhibit sinusoidal time variation.
• Arrow 1901 illustrates the outward propagation of the reference wave.
• a TEM, or Transverse Electro-Magnetic, wave travels either inward or outward. The direction of propagation is also defined and for this example outward propagation from a center feed point is chosen. The plane of propagation is along the antenna surface.
• An object wave sometimes called the object beam, is generated.
• the object wave is a TEM wave travelling in direction 30 degrees off normal to the antenna surface, with azimuth set to 0 deg.
• the polarization is also defined and for this example right handed circular polarization is chosen.
• Figure 19B illustrates a generated object wave. Referring to Figure 19B, phase fronts 1903 of the electric and magnetic fields of the propagating TEM wave 1904 are shown. Arrows 1905 are the electric field vectors at each phase front, represented at 90 degree intervals. In this example, they adhere to the right hand circular polarization choice.
• the resulting modulation pattern is also a sinusoid.
• the maxima of the reference wave meets the maxima of the object wave (both sinusoidally time- varying quantities)
• the modulation pattern is a maxima, or a strongly radiating site.
• this interference is calculated at each scattering location and is dependent on not just the position, but also the polarization of the element based on its rotation and the polarization of the object wave at the location of the element.
• Figure 19C is an example of the resulting sinusoidal modulation pattern.
• the voltage across the scattering elements is controlled by adjusting the voltage applied between the patches and the ground plane, which in this context is the metallization on the top of the iris board.
• the patches and slots are positioned in a honeycomb pattern.
• honeycomb structures are such that every other row is shifted left or right by one half element spacing or, alternatively, every other column is shifted up or down by one half the element spacing.
• the patches and associated slots are positioned in rings to create a radial layout.
• the slot center is positioned on the rings.
• Figure 15A illustrates an example of patches (and their co-located slots) being positioned in rings. Referring to Figure 15 A, the centers of the patches and slots are on the rings and the rings are
• adjacent slots located in the same ring are oriented almost 90° with respect to each other (when evaluated at their center). More specifically, they are oriented at an angle equal to 90° plus the angular displacement along the ring containing the geometric centers of the 2 elements.
• Figure 15B is an example of a control pattern for a ring based slotted array, such as depicted in Figure 15 A.
• the resulting near fields and far fields for a 30° beam pointing with LHCP are shown in Figure 15C, respectively.
• the feed structure is shaped to control coupling to ensure the power being radiated or scattered is roughly constant across the full 2D aperture. This is accomplished by using a linear thickness taper in the dielectric, or analogous taper in the case of a ridged feed network, that causes less coupling near the feed point and more coupling away from the feed point.
• the use of a linear taper to the height of the feed counteracts the 1/r decay in the travelling wave as it propagates away from the feed point by containing the energy in a smaller volume, which results in a greater percentage of the remaining energy in the feed scattering from each element. This is important in creating a uniform amplitude excitation across the aperture.
• this tapering can be applied in a non-radially symmetric manner to cause the power scattered to be roughly constant across the aperture.
• a complementary technique requires elements to be tuned differently in the array based on how far they are from the feed point.
• One example of a taper is implemented using a dielectric in a Maxwell fish-eye lens shape producing an inversely proportional increase in radiation intensity to counteract the 1/r decay.
• FIG. 18 illustrates a linear taper of a dielectric.
• a tapered dielectric 1802 is shown having a coaxial feed 1800 to provide a concentric feed wave to execute elements (patch/iris pairs) of RF array 1801.
• Dielectric 1802 e.g., plastic
• height B is greater than the height A as it is closer to coaxial feed 1800.
• dielectrics are formed with a non- radially symmetric shape to focus energy where needed.
• the path length from the center to a corner of a square is 1.4 times longer than from the center to the center of a side of a square. Therefore, more energy must be focused toward the 4 corners than toward the 4 halfway points of the sides of the square, and the rate of energy scattering must also be different.
• Non-radially symmetric shaping of the feed and other structures can accomplish these requirements
• dissimilar dielectrics are stacked in a given feed structure to control power scattering from feed to aperture as wave radiates outward.
• the electric or magnetic energy intensity can be concentrated in a particular dielectric medium when more than 1 dissimilar dielectric media are stacked on top of each other.
• One specific example is using a plastic layer and an air-like foam layer whose total thickness is less than A eff /2 at the operation frequency, which results in higher concentration of magnetic field energy in the plastic than the air-like foam.
• the control pattern is controlled spatially (turning on fewer elements at the beginning, for instance) for patch/iris detuning to control coupling over the aperture and to scatter more or less energy depending on direction of feeding and desired aperture excitation weighting.
• the control pattern used at the beginning turns on fewer slots than the rest of the time. For instance, at the beginning, only a certain percentage of the elements (e.g., 40%, 50%) (patch/iris slot pairs) near the center of the cylindrical feed that are going to be turned on to form a beam are turned on during a first stage and then the remaining are turned that are further out from the cylindrical feed.
• elements could be turned on continuously from the cylindrical feed as the wave propagates away from the feed.
• a ridged feed network replaces the dielectric spacer (e.g., the plastic of spacer 205) and allows further control of the orientation of propagating feed wave.
• Ridges can be used to create asymmetric propagation in the feed (i.e., the Poynting vector is not parallel to the wave vector) to counteract the 1/r decay.
• the use of ridges within the feed helps direct energy where needed. By directing more ridges and/or variable height ridges to low energy areas, a more uniform illumination is created at the aperture. This allows a deviation from a purely radial feed configuration because the direction of propagation of the feed wave may no longer be oriented radially. Slots over a ridge couple strongly, while those slots between the ridges couple weakly. Thus, depending on the desired coupling (to obtain the desired beam), the use of ridge and the placement of slots allows control of coupling.
• a complex feed structure that provides an aperture illumination that is not circularly symmetric is used.
• Such an application could be a square or generally non-circular aperture which is illuminated non-uniformly.
• a non- radially symmetric dielectric that delivers more energy to some regions than to others is used. That is, the dielectric can have areas with different dielectric controls.
• a dielectric distribution that looks like a Maxwell fish-eye lens. This lens would deliver different amounts of power to different parts of the array.
• a ridged feed structure is used to deliver more energy to some regions than to others.
• multiple cylindrically-fed sub-aperture antennas of the type described here are arrayed.
• one or more additional feed structures are used.
• distributed amplification points are included.
• an antenna system may include multiple antennas such as those shown in Figure 2A or 2B in an array.
• the array system may be 3x3 (9 total antennas), 4x4, 5x5, etc., but other configurations are possible.
• each antenna may have a separate feed.
• the number of amplification points may be less than the number of feeds.
• One advantage to embodiments of the present invention architecture is better beam performance than linear feeds.
• the natural, built-in taper at the edges can help to achieve good beam performance.
• the FCC mask can be met from a 40cm aperture with only on and off elements.
• embodiments of the invention have no impedance swing near broadside, no band-gap created by 1 -wavelength periodic structures.
• Embodiments of the invention have no diffractive mode problems when scanning off broadside.
• Dynamic Polarization There are (at least) two element designs which can be used in the architecture described herein: circularly polarized elements and pairs of linearly polarized elements. Using pairs of linearly polarized elements, the circular polarization sense can be changed dynamically by phase delaying or advancing the modulation applied to one set of elements relative to the second. To achieve linear polarization, the phase advance of one set relative to the second (physically orthogonal set) will be 180 degrees. Linear polarizations can also be synthesized with only element patter changes, providing a mechanism for tracking linear polarization
• On-off modes of operation have opportunities for extended dynamic and instantaneous bandwidths because the mode of operation does not require each element to be tuned to a particular portion of its resonance curve.
• the antenna can operate continuously through both amplitude and phase hologram portions of its range without significant
• the cylindrical feed structure can take advantage of a TFT architecture, which implies functioning on quartz or glass. These substrates are much harder than circuit boards, and there are better known techniques for achieving gap sizes around 3um. A gap size of 3um would result in a 14ms switching speed.
• Disclosed architectures described herein require no machining work and only a single bond stage in production. This, combined with the switch to TFT drive electronics, eliminates costly materials and some tough requirements.

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