JP6339215B2 - Dynamic polarization and coupling control for a moving cylindrical feed holographic antenna - Google Patents

Description

〔priority〕
This patent application is filed on February 19, 2014 with the corresponding US Provisional Patent Application No. 61 / 941,801 entitled “Polarization and Coupling Control from a Cylindrical Feed Holographic Antenna” and June 2014. Claims priority to the corresponding US Provisional Patent Application No. 62 / 012,897 entitled “Metamaterial Antenna System for Communication Satellite Ground Stations” filed on the 16th, and incorporates them by reference.

  Embodiments of the present invention relate to the field of antennas, and more particularly, embodiments of the present invention relate to antennas that are cylindrically fed.

  Thinkom products achieve double circular polarization in the Ka band using a PCB-based approach, typically using a variable tilt transverse stub or “VICTS” approach with two types of mechanical rotation . The first type rotates one array relative to another and the second type rotates both in azimuth. The main constraints are scanning range (elevation angle between 20 and 70 degrees, no broadside) and beam performance (sometimes limited to Rx only).

  Ando et al. “Radial slot antenna for 12 GHz DBS satellite reception” and Yuan et al. “Design and experiment of new radial slot antenna for high power microwave applications” discuss various antennas. The limitation of the antenna described in both these papers is that the beam is formed only at one stationary angle. The feed structure described in these papers is a folded double layer, where the first layer accepts the pin feed and emits a signal outward to the edge, which is folded to the upper layer and the upper layer Then, it transmits from the surroundings to the center while exciting the fixed slot on the way. The slots are typically oriented in orthogonal pairs, giving the opposite in fixed circular polarization and receive mode during transmission. Eventually, the absorber will extinguish any remaining energy.

  “Scalar and Tensor Holographic Artificial Impedance Surfaces” by Fong, Colburn, Otsch, Visher, Sievenpiper. Although Sievenpiper has shown a way to achieve a dynamic scanning antenna, there are doubts about the polarization fidelity maintained during scanning. This is because the required polarization control depends on the tensor impedance required in each radiating element. This is most easily achieved by element-by-element rotation. However, as the antenna scans, the polarization at each element changes and thus the required rotation also changes. Since these elements are fixed and cannot be dynamically rotated, there is no way to scan and maintain polarization control.

  Industry standard approaches to achieve a beam scanning antenna with polarization control typically use either a mechanical rotating disk or some type of mechanical i-movement in conjunction with electron beam steering. The most expensive class of options is the full phased array antenna. The disc can receive multiple polarizations simultaneously, but requires a gimbal to scan. More recently, by combining mechanical movement in one axis with electronic scanning in orthogonal axes, structures with a small aspect but high aspect ratio at the expense of beam performance or dynamic polarization control, such as the Thinkko system Was brought.

Ando et al. "Radial slot antenna for 12GHz DBS satellite reception" Yuan et al. "Design and experiment of a new radial slot antenna for high power microwave applications" "Scalar and tensor holographic artificial impedance surfaces" by Fong, Colburn, Otsch, Visher, Sievenpiper

  Conventional approaches use waveguide and divider feed structures to feed the antenna. However, the waveguide design has an impedance swing near the broadside (bandgap generated by a one-wavelength periodic structure), requires a junction with a different CTE, and has a resistive loss associated with the feed structure, And / or have thousands of vias to extend to the ground plane.

  An apparatus for a cylindrical feed antenna and a method of using the same are disclosed herein. In one embodiment, the antenna includes an antenna feed for inputting a cylindrical feed wave and a tunable slotted array coupled to the antenna feed.

  The invention should not be construed from the following detailed description, but from the accompanying drawings of various embodiments of the invention, which are not to be construed as limiting the invention to the particular embodiments, but are merely for explanation and understanding. Will be better understood.

FIG. 6 is a top view of one embodiment of a coaxial feed used to provide a cylindrical wave feed. It is a side view of one Embodiment of a cylindrical feed type antenna structure. It is a side view of one Embodiment of a cylindrical feed type antenna structure. FIG. 6 is a top view of one embodiment of a slot-coupled patch antenna or scatterer. It is a side view of the slot feed type patch antenna which is a part of the circulation feed type antenna system. FIG. 5 shows an example of a dielectric material into which a feed wave is launched. FIG. 4 is a diagram of one embodiment of an iris substrate showing slots and their orientation. FIG. 4 shows how the orientation of one iris / patch combination is determined FIG. 3 shows irises grouped into two sets where the first set is rotated −45 degrees with respect to the power feed vector and the second set is rotated +45 degrees with respect to the power feed vector. It is a figure which shows embodiment of a patch board | substrate. FIG. 10 illustrates an example of an element having the patch of FIG. 9 determined to be off at the operating frequency. FIG. 10 shows an example of an element having the patch of FIG. 9 determined to be on at the operating frequency. FIG. 12 shows the results of full wave modeling showing the electric field response to on and off control / modulation patterns for the elements of FIGS. FIG. 3 shows a beam formed using an embodiment of a cylindrical feed antenna. It is a figure which shows the patch and slot which were positioned by the honeycomb pattern. It is a figure which shows the patch and slot which were positioned by the honeycomb pattern. FIG. 6 shows patches and associated slots positioned in a ring to create a radial layout. FIG. 5 shows a control pattern associated with patches and associated slots positioned in a ring to create a radial layout. FIG. 6 shows the resulting antenna response with patches and associated slots positioned in a ring to create a radial layout. It is a figure which shows a right-handed circularly polarized wave. It is a figure which shows left-handed circularly polarized wave. FIG. 2 shows a portion of a cylindrical feed antenna that includes a glass layer that houses a patch. It is a figure which shows the linear taper of a dielectric material. It is a figure which shows the example of a reference wave. It is a figure which shows the produced | generated object wave. It is a figure which shows the example of the sine wave modulation pattern obtained. FIG. 6 shows an alternative antenna embodiment in which each of the sides includes transmitting a traveling wave from the bottom layer to the top layer.

  Embodiments of the present invention include an antenna design architecture that feeds an antenna from a central point using excitation (feed waves) that spreads out cylindrically or concentrically outward from the feed point. The antenna functions by arranging a plurality of cylindrical feed sub-aperture antennas (eg, patch antennas) having feed waves. In an alternative embodiment, the antenna is fed inward from the periphery rather than outward from the center. This can be useful because it cancels the amplitude excitation attenuation caused by scattering energy from the aperture. Scattering occurs in both directions as well, but the natural taper caused by the focusing of energy in the feed wave as the feed wave travels inward from the surrounding cancels the reduced taper caused by the intended scattering.

  Embodiments of the present invention include holographic antennas based on doubling the density typically required to achieve holography and filling the aperture with two types of orthogonal sets of 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 oriented at -45 degrees with respect to the feed wave. Both types are illuminated by the same feed wave, which in one form is a parallel plate mode fired by a coaxial pin feed.

  In the following description, numerous details are set forth to provide a more thorough explanation of the present invention. However, it will be apparent to those 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 not to obscure the present invention.

  Some of the detailed descriptions below 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. The algorithm is here and generally considered to be a consistent series of steps that yields the desired result. The steps are those requiring physical manipulation of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals that can be stored, transferred, combined, compared, and otherwise manipulated. It has proven advantageous 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 noted, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely advantageous labels applied to these quantities. As will be apparent from the following description, unless otherwise specified, descriptions that use terms such as "process", "computer", "calculation", "decision", or "display" throughout the description Manipulate data represented as physical (electronic) quantities in system registers and memory to store, transmit, or display computer system memory or registers, or other such information It will be appreciated that reference to actions and processing of a computer system or electronic computing device that translates into another data that is also expressed as a physical quantity within the device.

Overview of Antenna System Example An embodiment of a metamaterial antenna system for a communications satellite ground station will be described. In one embodiment, the antenna system is a satellite ground station (ES) operating on a mobile platform that operates using either Ka-band frequencies or Ku-band frequencies for commercial commercial satellite communications (eg, aviation, maritime , Land, etc.) components or subsystems. Note that embodiments of the antenna system can also be used with ground stations that are not on a mobile platform (eg, fixed or portable ground stations).

  In one embodiment, the antenna system forms a beam through separate antennas and uses surface scattering metamaterial technology to steer its transmission and reception. In one embodiment, the antenna system is an analog system as opposed to an antenna system (such as a phased array antenna) that uses digital signal processing to electrically form and steer the beam.

  In one embodiment, the antenna system includes the following three functional subsystems: (1) a wave propagation structure comprised of a cylindrical wave feed architecture, (2) an array of wave scattering metamaterial unit cells, and (3) holography. It consists of a control structure that commands the formation of an adjustable radiation field (beam) from the metamaterial scattering element using the principle.

Example Wave Propagation Structure FIG. 1 is a top view of one embodiment of a coaxial feed used to provide a cylindrical wave feed. Referring to FIG. 1, the coaxial feed includes a center conductor and an outer conductor. In one embodiment, the cylindrical wave feed architecture feeds the antenna from the center point using excitation that extends in a cylindrical fashion outward from the feed point. That is, the cylindrical feed antenna generates concentric feed waves that travel outward. Still, the shape of the cylindrical feed antenna around the cylindrical feed can be circular, square, or any shape. In another embodiment, the cylindrical feed antenna generates a feed wave that travels inward. In such cases, feed waves most naturally arise from a circular structure.

  FIG. 2A shows a side view of one embodiment of a cylindrical feed antenna structure. The antenna uses a double layer feed structure (ie, two layers of the feed structure) to create waves that travel inward. In one embodiment, this is not essential, but the antenna includes a circular outline. That is, a non-circular inwardly traveling structure can be used. In one embodiment, the antenna structure of FIG. 2A includes the coaxial feed of FIG.

  Referring to FIG. 2A, a coaxial pin 201 is used to excite the field to the lower level of the antenna. In one embodiment, the coaxial pin 201 is a readily available 50 Ω coaxial pin. Coaxial pin 201 is coupled (eg, bolted) to the bottom of the antenna structure, which is a conductive ground plane 202.

  Apart from the conductive ground plane 202, there is an intrusive conductor 203, which is an internal conductor. In one embodiment, the conductive ground plane 202 and the intrusive conductor 203 are parallel to each other. In one embodiment, the distance between the ground plane 202 and the intrusive conductor 203 is 0.1-0.15 ″. In another embodiment, this distance can be λ / 2, where Where λ is the wavelength of the traveling wave at the operating frequency.

  The ground plane 202 is separated from the intrusive conductor 203 through the spacer 204. In one embodiment, the spacer 204 is a foam or pneumatic spacer. In one embodiment, the spacer 204 includes a plastic spacer.

  A dielectric layer 205 is on the intrusive conductor 203. In one embodiment, the dielectric layer 205 is plastic. FIG. 5 shows an example of a dielectric material into which a feed wave is launched. The purpose of the dielectric layer 205 is to decelerate the traveling wave with respect to free space velocity. In one embodiment, the dielectric layer 205 decelerates the traveling wave by 30% relative to free space. In one embodiment, the range of refractive index that is appropriate for beamforming is 1.2-1.8, where free space has a refractive index equal to 1 by definition. This effect can be achieved using other dielectric spacer materials such as plastic. Note that materials other than plastic can be used as long as they achieve the desired wave-moderating effect. Alternatively, a material having a dispersive structure can be used as a dielectric 205, such as a subwavelength metal structure that can be formed, for example, by machining or lithographically.

An RF array 206 is on the dielectric 205. In one embodiment, the distance between the immersive conductor 203 and the RF array 206 is 0.1-0.15 ″. In another embodiment, this distance may be λ _eff / 2, Where λ _eff is the effective wavelength in the medium at the design frequency.

  The antenna includes side surfaces 207 and 208. The side surfaces 207 and 208 are angled so that the traveling wave fed from the coaxial pin 201 is propagated by reflection from the region below the immersive conductor 203 (spacer layer) to the region above the immersive conductor 203 (dielectric layer). I am doing. In one embodiment, the angle of sides 207 and 208 is 45 degrees. In an alternative embodiment, the sides 207 and 208 can be replaced with a continuous radius to achieve reflection. FIG. 2A shows a slanted side including an angle of 45 degrees, but other angles can be used to achieve signal propagation from the lower level feed to the upper level feed. That is, considering that the effective wavelength of the lower feed will generally be different from the upper feed, some deviation from the ideal 45 degree angle is used to transfer from the lower to the upper feed level. Can assist. For example, in another embodiment, a 45 degree angle is replaced in a single step as shown in FIG. Referring to FIG. 20, steps 2001 and 2002 are shown on one end of the antenna around a dielectric layer 2005, an intrusive conductor 2003, and a spacer layer 2004. The same two steps are at the other edge of these layers.

  In operation, when a feed wave is fed from the coaxial pin 201, the wave travels concentrically outward from the coaxial pin 201 in the region between the ground plane 202 and the intrusive conductor 203. The concentrically exiting waves are reflected by the side surfaces 207 and 208 and travel inward in the region between the intrusive conductor 203 and the RF array 206. Reflection from the edge around the circle leaves the wave in phase (ie it is an in-phase reflection). The traveling wave is decelerated by the dielectric layer 205. At this time, the traveling wave initiates interaction and excitation with elements in the RF array 206 to obtain the desired scattering.

  A termination 209 is included in the antenna at the geometric center of the antenna to extinguish the traveling wave. In one embodiment, termination 209 includes a pin termination (eg, a 50Ω pin). In another embodiment, termination 209 includes an RF absorber that extinguishes unused energy and prevents reflection of that unused energy through the antenna feed structure. These can be used on top of the RF array 206.

  FIG. 2B shows another embodiment of the antenna system with an exit wave. Referring to FIG. 2B, the two ground planes 210 and 211 are substantially parallel to a dielectric layer 212 (eg, a plastic layer, etc.) between the ground planes 210 and 211. RF absorbers 213 and 214 (eg, resistors) couple the two ground planes 210 and 211 together. A coaxial pin 215 (eg, 50Ω) feeds the antenna. The RF array 216 is over the dielectric layer 212.

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

  The cylindrical feed in both antennas of FIGS. 2A and 2B improves the angle of use of the antenna. Rather than a working angle of ± 45 degrees azimuth (± 45 ° Az) and ± 25 degrees elevation (± 25 ° El), in one embodiment, the antenna system is 75 degrees (75 ° from boresight) in all directions. ) Use angle. As with any beamforming antenna composed of many individual radiators, the overall antenna gain depends on the gain of the component, which itself depends on the angle. When using a common radiating element, the overall antenna gain typically decreases as the beam is directed far away from the boresight. A significant gain drop of about 6 dB is expected at 75 degrees off boresight.

  An embodiment of an antenna having a cylindrical feed solves one or more problems. They dramatically simplify the feed structure compared to antennas fed in an integrated divider network, thus reducing the overall required antenna and amount of antenna feed, coarser control (simple binary control Reducing the sensitivity to manufacturing and control errors by maintaining high beam performance, and cylindrically oriented feed waves provide spatially varying side lobes in the far field, compared to linear feeds The polarization is dynamic, including providing a more advantageous sidelobe pattern and enabling left-handed, right-handed, and linearly polarized waves without the need for a polarizer Including enabling.

Array of Wave Scattering Elements The RF array of FIG. 2A and the RF array 216 of FIG. 2B include a wave scattering subsystem that includes a group of patch antennas (ie, scatterers) that function as radiators. The patch antenna group includes an array of scattering metamaterial elements.

  In one embodiment, each scattering element in the antenna system is a complementary electrically inductive-capacitive resonator ("" etched or deposited on the lower conductor, dielectric substrate, and upper conductor. Part of a unit cell composed of an upper conductor that embeds a complementary electric LC "or" CELC ").

  In one embodiment, liquid crystal (LC) is injected into the gap around the scattering element. The liquid crystal is encapsulated within each unit cell and separates the lower conductor associated with the slot from the upper conductor associated with the patch. Liquid crystals have a dielectric constant that is a function of the orientation of the molecules containing the liquid crystal, and the orientation of the molecules (and thus the dielectric constant) can be controlled by adjusting the bias voltage across the liquid crystal. Using this characteristic, the liquid crystal functions as an on / off switch for energy transfer from the guide wave to the CELC. When the switch is turned on, CELC emits electromagnetic waves like an electrically minute dipole antenna.

  By controlling the LC thickness, the beam switching speed is increased. A 50% decrease in the gap (liquid crystal thickness) between the lower and upper conductors results in a four-fold speed increase. In another embodiment, the thickness of the liquid crystal provides a beam switching speed of about 14 milliseconds (14 ms). In one embodiment, the LC is doped in a manner known in the art to improve responsiveness to meet the 7 millisecond (7 ms) requirement.

  The CELC element is responsive to a magnetic field applied parallel to the plane of the CELC element and perpendicular to the CELC gap complement. When a voltage is applied to the liquid crystal in the metamaterial scattering unit cell, the magnetic field component of the guide wave induces CELC magnetic excitation, which in turn creates an electromagnetic wave with the same frequency as the guide wave.

  The phase of the electromagnetic wave generated by a single CELC can be selected by the position of CELC on the guide wave vector. Each cell generates a wave in phase with the guide wave parallel to CELC. Since CELC is smaller than the wavelength, the output wave has the same phase as the guide wave when the guide wave passes under CELC.

  In one embodiment, the cylindrical feed shape of the antenna system allows the CELC element to be positioned at 45 degrees (45 °) with respect to the wave vector in the wave feed. The positioning of this element allows control of the polarization of free space waves generated from or received by this element. In one embodiment, the CELC is arranged with an element spacing that is less than the free space wavelength of the antenna's operating frequency. For example, if there are four scattering elements per wavelength, the elements in a 30 GHz transmit antenna will be approximately 2.5 mm (ie, 1/4 of 30 mm free space wavelength 10 mm).

  In one embodiment, CELC is implemented using a patch antenna that includes a patch arranged over a slot with a liquid crystal in between. In this respect, the metamaterial antenna functions like a slot (scattering) waveguide. With respect to the slot waveguide, the phase of the output wave depends on the position of the slot with respect to the guide wave.

  FIG. 3 shows a top view of one embodiment of one patch antenna or scattering element. Referring to FIG. 3, the patch antenna includes a patch 301 having a liquid crystal (LC) 303 between the patch 301 and the slot 302 and arranged on the slot 302.

  FIG. 4 shows a side view of a patch antenna that is part of a circulating feed antenna system. Referring to FIG. 4, the patch antenna is above a dielectric 402 (eg, a plastic insert or the like) above the immersive conductor 203 of FIG. 2A (or a ground conductor as in the antenna of FIG. 2B). .

  The iris substrate 403 is a ground plane (conductor) having several slots, such as slots 403a over and across the dielectric 402. A slot may be referred to herein as an iris. In one embodiment, the slots in the iris substrate 403 are created by etching. Note that in one embodiment, the maximum density of a slot or a cell of which a slot is a part is λ / 2. In one embodiment, the slot / cell density is λ / 3 (ie, 3 cells per λ). Note that other cell densities can be used.

  A patch substrate 405 containing several patches, such as patch 405a, is positioned on the iris substrate 403 separated by an intermediate dielectric layer. Each of the patches, such as patch 405a, is juxtaposed with one of the slots in the iris substrate. In one embodiment, the intermediate dielectric layer between the iris substrate 403 and the patch substrate 405 is a liquid crystal substrate layer 404. The liquid crystal functions as a dielectric layer between each patch and its juxtaposed slot. Note that substrate layers other than LC can be used.

  In one embodiment, the patch substrate 405 includes a printed circuit board (PCB), each patch having metal on the PCB, where the metal around the patch has been removed.

  In one embodiment, the patch substrate 405 includes a via for each patch on the side of the patch substrate opposite to the side where the patch faces its juxtaposed slot. Vias are used to connect one or more traces to the patch in order to apply a voltage to the patch. In one embodiment, a voltage is applied to the patch using a matrix drive to control the patch. To achieve beamforming, voltages are used to tune or detune individual elements.

  In one embodiment, the patch is deposited on a glass layer (eg, glass typically used for liquid crystal displays (LCDs) such as Corning Eagle glass) instead of using a circuit patch substrate. Can be made. FIG. 17 shows a portion of a cylindrical feed antenna that includes a glass layer containing a patch. Referring to FIG. 17, the antenna includes a conductive base or ground layer 1701, a dielectric layer 1702 (eg, plastic), an iris substrate 1703 (eg, circuit board) that houses the slot and liquid crystal substrate layer 1704, and a patch. A glass layer 1705 containing 1710. In one embodiment, the patch 1710 includes a rectangular shape. In one embodiment, the slots and patches are positioned in rows and columns, and the patch orientation is the same for each row or column, while the juxtaposed slots are oriented in the same orientation relative to each other for the row or column. It is done.

  In one embodiment, a cap (eg, radome cap) covers the top of the patch antenna stack to provide protection.

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

  The slotted array is tuned and directed loaded. By turning individual slots off or on, each slot is tuned to provide the desired scattering at the operating frequency of the antenna (ie, tuned to operate at a given frequency).

  FIG. 7 is a diagram illustrating a manner in which the orientation of one iris (slot) / patch combination is determined. Referring to FIG. 7, the letter A shows a solid black arrow that represents the power feed vector from the cylindrical feed position to the center of the element. Character B represents a dashed orthogonal line indicating an axis perpendicular to “A”, and character C represents a dashed rectangular enclosure slot rotated 45 degrees relative to “B”.

  FIG. 8 is a diagram showing irises grouped into two sets where the first set is rotated −45 degrees with respect to the power feed vector and the second set is rotated +45 degrees with respect to the power feed vector. Referring to FIG. 8, group A includes slots whose rotation angle for the power feed vector is equal to −45 °, and group B includes slots whose rotation angle for the power feed vector is + 45 °.

  Note that the specification of the global coordinate system is not important, and thus the negative and positive angular rotations are only important to account for the relative rotation of the elements relative to each other and to the feed wave direction. In order to generate circular polarization from two sets of linearly polarized elements, the two sets of elements are perpendicular to each other and at the same time include equal amplitude excitation. By rotating the two sets of elements ± 45 degrees relative to the feed wave excitation, both desirable features are achieved simultaneously. By rotating one set to 0 degrees and the other set to 90 degrees, the goal of vertical is achieved, but the goal of equal amplitude excitation is not achieved.

  FIG. 9 shows an embodiment of the patch substrate 405. This is the upper conductor of CELC. Referring to FIG. 9, the patch substrate includes a rectangular patch that covers a slot and completes a linearly polarized patch / slot resonant pair that is turned on and off. This pair is turned on or off by applying a voltage to the patch using the controller. The required voltage depends on the liquid crystal mixture used, the resulting threshold voltage required to start tuning the liquid crystal, and the maximum saturation voltage (a high voltage above this will eventually degrade the liquid crystal or It produces no effect other than shorting through). In one embodiment, a matrix drive is used to apply a voltage to the patch to control the coupling of the resonant pair.

The antenna system control and control structure has two main components: the controller containing the drive electronics for the antenna system is under the wave scattering structure, while the matrix drive switching array prevents radiation Scattered throughout the radiating RF array in such a way. In one embodiment, the drive electronics for the antenna system includes a commercial off-the-shelf LCD control used in commercial television equipment that adjusts the bias voltage for each scatter element by adjusting the amplitude of the AC bias signal for the scatter element. Including a bowl.

  In one embodiment, the controller controls the electronic device using software control. In one embodiment, polarization control is part of the antenna software control, and the polarization is pre-programmed to match the polarization of the signal coming from the satellite service with which the ground station is communicating. Or preprogrammed to match the polarization of the receiving antenna on the satellite.

  In one embodiment, the controller also includes a microprocessor executing software. The control structure can also incorporate sensors (including nominally GPS receivers, 3-axis compass, and accelerometers) to provide position and orientation information to the processor. The position and orientation information can be provided to the processor by other systems at the ground station, and / or the position and orientation information may not be part of the antenna system.

  More specifically, the controller controls which elements are turned off and which are turned on at the operating frequency. The element is selectively detuned for frequency operation by applying a voltage. The controller feeds an array of voltage signals to the RF radiating patch to create a modulation or control pattern. The control pattern turns the element on or off. In one embodiment, the control pattern resembles a square wave with elements along one helix (LHCP or RHCP) “on” and elements off the helix “off” (ie, binary modulation). pattern). In another embodiment, in contrast to a square wave (ie, a sinusoidal gray shade modulation pattern), various elements are turned on and off to various levels to provide a multi-state control that further approximates the sinusoidal control pattern. use. It does not mean that some elements radiate and some elements do not radiate, some elements radiate more strongly than others. Variable radiation is achieved by applying a specific voltage level, which adjusts the dielectric constant of the liquid crystal to various amounts, thereby variably detuning the elements and some elements. More than other elements.

  The generation of a focused beam by the metamaterial array of elements can be explained by the phenomenon of constructive and destructive interference. Individual electromagnetic waves are added together if they are in phase when they meet in free space (constructive interference), and cancel each other if they are out of phase when they meet in free space (destructive interference). When the slot of the slot antenna is positioned so that each successive slot is located at a different distance from the excitation point of the guide wave, the scattered wave from that element has a phase different from that of the previous slot. become. If the slots are separated by a quarter of the guide wavelength, each slot will scatter a wave containing a quarter phase delay from the previous slot.

  Using this array, it is possible to generate constructive so that the beam can be directed in any direction ± 90 degrees (90 °) from the boresight of the antenna array using the principle of holography. And the number of patterns of destructive interference can be increased. Therefore, by controlling which metamaterial unit cells are turned on or off (ie by changing the pattern of which cells are turned on and which cells are turned off), constructive and destructive Different patterns of interference can be generated and the antenna can change the direction of the wavefront. The time required to turn the unit cell on and off determines the speed at which the beam can be switched from one position to another.

  Both polarization and beam pointing angle are defined by modulation, a control pattern that identifies which elements are on or off. In other words, the frequency for directing and polarizing the beam in a desirable manner depends on the control pattern. Since the control pattern is programmable, the polarization can be programmed for the antenna system. The desired polarization state is circular or linear polarization for most applications. The circular polarization state includes a spiral polarization state, that is, a right-handed circular polarization and a left-handed circular polarization, and the feed waves that are fed from the center and travel outward are shown in FIGS. 16A and 16B, respectively. . Note that in order to obtain the same beam while switching the feed direction (eg, from the inflow feed to the outflow feed), the orientation or orientation or the helical modulation pattern is reversed. Note that the direction of the feed wave (ie, center feed or edge feed) is also identified when stating that a fixed spiral pattern of on and off elements results in left-handed or right-handed circular polarization. I want to be.

  The control pattern for each beam is stored in the controller, calculated during operation, or a combination thereof. Once the antenna control system identifies where and where the antenna is located, the antenna control system then identifies where the target satellite is located relative to the antenna boresight. The controller then commands an on / off pattern of individual unit cells in the array corresponding to a preselected beam pattern with respect to satellite position in the antenna field of view.

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

  FIG. 10 shows an example of an element having the patch in FIG. 9 determined to be off at the operating frequency, and FIG. 11 shows an example of an element having the patch in FIG. 9 determined to be on at the operating frequency. Yes. FIG. 12 shows full-wave modeling results showing the electric field response for the on-off modulation pattern for the elements of FIGS.

  FIG. 13 shows beam forming. Referring to FIG. 13, by adjusting the interference pattern to identify the interference pattern corresponding to the selected beam pattern, and then adjusting the voltage across the scattering element to generate a beam according to the principles of holography, An antenna radiation pattern can be provided. The basic principles of holography are known, including the terms “object beam” and “reference beam”, which are generally used in connection with these principles. In connection with the step of using the traveling wave as the “reference beam” to form the desired “object beam”, RF holography is performed as follows.

  The modulation pattern is determined as follows. First, a reference wave (beam), sometimes called a feed wave, is generated. FIG. 19A shows an example of a reference wave. Referring to FIG. 19A, ring 1900 is a phase plane of the electromagnetic field of the reference wave. They show sinusoidal time variations. An arrow 1901 indicates outward propagation of the reference wave.

  In this example, the TEM, that is, the transverse electromagnetic wave, travels inward or outward. The direction of propagation is also defined, and in this example, outward propagation from the central feed point is selected. The propagation plane is along the antenna surface.

Sometimes an object wave called an object beam is generated. In this example, the object wave is a TEM wave that travels in a direction deviating 30 degrees from the normal of the antenna surface with the azimuth angle set to 0 degrees. Polarization is also defined, and right-handed circular polarization is selected in this example. FIG. 19B shows the generated object wave. Referring to FIG. 19B, a phase plane 1903 of the electromagnetic field of a propagating TEM wave 1904 is shown. Arrows 1905 are electric field vectors on each phase plane, and are represented at intervals of 90 degrees. In this example, they faithfully represent the choice of right hand circular polarization.
Interference or modulation pattern = Re {[A] x [B] ^* }

  When the sine wave is multiplied by the complex conjugate of another sine wave and its real part is taken, the resulting modulation pattern is also a sine wave. Spatially, where the maximum value of the reference wave meets the maximum value of the object wave (both sinusoidally varying in time), the modulation pattern is the maximum value, that is, a position that radiates strongly. In practice, this interference is calculated at each scattering position and does not depend only on that position, 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 obtained sinusoidal modulation pattern.

  Note that further selections can be made to simplify the resulting sinusoidal gray shade modulation pattern to a square wave modulation pattern.

  Note that the voltage across the scattering element is controlled by adjusting the voltage applied between the patch and a ground plane, which in this context is a metallization on the top of the iris substrate.

Alternative Embodiment In one embodiment, the patches and slots are positioned in a honeycomb pattern. Examples of such patterns are shown in FIGS. 14A and 14B. Referring to FIGS. 14A and 14B, the honeycomb structure is shifted to the left or right by half the element spacing for each row, or alternatively, shifted up or down by half the element spacing for each column. It is like.

  In one embodiment, the patches and associated slots are positioned in a ring to create a radial layout. In this case, the center of the slot is positioned on the ring. FIG. 15A shows an example of a patch (and its juxtaposed slot) positioned in a ring shape. Referring to FIG. 15A, the patch and slot centers are on the ring, and the ring is positioned concentrically with respect to the feed or termination point of the antenna array. Note that adjacent slots located in the same ring are oriented approximately 90 ° relative to each other (when evaluated at the slot center). More specifically, they are oriented at an angle plus 90 ° angular displacement along a ring that includes the geometric center of the two elements.

  FIG. 15B is an example of a control pattern for a ring-based slotted array as shown in FIG. 15A. The near and far fields obtained for a 30 ° beam pointing with LHCP are shown in FIG. 15C, respectively.

  In one embodiment, the feed structure is shaped to control the coupling to ensure that the power being radiated or scattered is approximately constant over the two-dimensional aperture. This is accomplished by using a linear thickness taper in the dielectric, or a similar taper in the case of a ridged feed network, so that small coupling near the feed point and large coupling away from the feed point. Is brought about. By utilizing the linear taper of the feed height, the energy contained in a smaller volume cancels the 1 / r attenuation of the traveling wave as it propagates from the feed point, which is scattered from each element. Bring the remaining energy in a larger proportion. This is important in creating uniform amplitude excitation across the aperture. For non-radial symmetric feed structures such as those having square or rectangular outer dimensions, this taper can be applied in a non-radial symmetric fashion to provide power that scatters to be approximately constant across the aperture. . Complementary techniques require the elements to be tuned separately in the array based on how far the element is from the feed point.

  An example of a taper is implemented using Maxwell's fisheye shaped dielectric that creates an inverse proportional increase in radiation intensity to offset 1 / r attenuation.

  FIG. 18 shows the linear taper of the dielectric. Referring to FIG. 18, a tapered dielectric 1802 is shown having a coaxial feed 1800 that provides concentric feed waves for implementing the elements (patch / iris pair) of the RF array 1801. The dielectric 1802 (eg, plastic) tapers in height from a maximum height near the coaxial feed 1800 to a lower height at the farthest point from the coaxial feed 1800. For example, the height B becomes greater than the height A when approaching the coaxial feed 1800.

  In line with this concept, in one embodiment, the dielectric is formed in a non-radial symmetric shape to focus the energy. For example, in the case of a square antenna fed from a single feed point as described herein, the path length from the center of the square to the corner is 1.4 times longer from the center of the square to the center of the side. That's it. Therefore, it is necessary to focus more energy toward the four corners than toward the four middle points of the square side, and the energy scattering rates need to be different. These requirements can be achieved by non-radially symmetrical shaping of the feed and other structures.

  In one embodiment, different dielectrics are stacked on a fixed feed structure to control power scattering from the feed to the aperture as the waves radiate outward. For example, when more than one different dielectric media are stacked together, the electrical or magnetic energy intensity can be concentrated on a particular dielectric medium. In one embodiment, a plastic layer and a pneumatic foam layer whose overall thickness is less than λ eff / 2 at the operating frequency is used, thereby providing a higher density of magnetic field energy in the plastic than in the pneumatic foam.

  In one embodiment, the control pattern is spatially controlled for patch / iris detuning (eg, a small number of elements are initially turned on) to control coupling across the aperture, feed direction and desired aperture excitation. Some energy is scattered according to the weighting. For example, in one embodiment, the first used control pattern turns on fewer slots than the remaining time. For example, initially only certain proportions of elements (eg, 40%, 50% patch / iris slot pairs) near the center of the cylindrical feed that is to be turned on to form the beam are in the first stage. It is turned on for a while and then the remaining part of the cylindrical feed is turned on. In another embodiment, the element can be turned on continuously from the cylindrical feed as the waves propagate from the feed. In another embodiment, the ridged feed network replaces a dielectric spacer (eg, plastic of spacer 205) and further allows direction control of the propagating feed wave. Ridges can be used to create asymmetric propagation in the feed (ie, the directional vector is not parallel to the wave vector) to cancel 1 / r attenuation. Thus, the use of ridges in the feed helps direct energy to where it is needed. By directing multiple ridges and / or variable height ridges in the low energy region, more uniform illumination is created in the aperture. Since it is no longer possible to direct the propagation direction of the feed wave radially, this allows a deviation from a purely radial feed configuration. Slots above the ridge are strongly coupled, while slots between ridges are weakly coupled. Therefore, depending on the desired coupling (to obtain the desired beam), the use of ridges and slot placement allows coupling control.

  In yet another embodiment, a complex feed structure is used that provides aperture illumination that is not circularly symmetric. Such an application may be a non-uniformly illuminated square or nearly non-circular aperture. In one embodiment, non-radially symmetric dielectrics are used that deliver more energy to some areas than others. That is, the dielectric can include regions that include different dielectric controls. An example is a dielectric distribution similar to Maxwell's fisheye lens. This lens will deliver different amounts of power to different parts of the array. In another embodiment, a ridged feed structure is used to deliver more energy to some areas than others.

In one embodiment, a plurality of cylindrical feed sub-aperture antennas of the type described herein are arranged. In one embodiment, one or more additional feed structures are used. Also in one embodiment, dispersion amplification points are included. For example, an antenna system can include multiple antennas in the array as shown in FIGS. 2A or 2B. The array system can be 3x3 (9 antennas in total), 4x4, 5x5, etc., but other configurations are possible. In such an arrangement, each antenna can include a separate feed. In another embodiment, the number of amplification points can be less than the number of feeds.
Improved beam performance

Benefits and benefits
Improved Beam Performance One advantage of the architecture embodiments of the present invention is better beam performance than a linear feed. A natural built-in taper at the edge can help achieve good beam performance.

  In the array factor calculation, the FCC mask can be filled from a 40 cm aperture with only on and off elements.

  Using a cylindrical feed, embodiments of the present invention have no impedance swing near the broadside and no band gap generated by a one-wavelength periodic structure.

  When scanning with the broadside removed, embodiments of the present invention do not have the diffraction mode problem.

Dynamic Polarization There are (at least) two element designs that can be used in the architecture described herein: a pair of circular and linear polarization elements. Using a pair of linear polarization elements, the circular polarization direction can be changed dynamically by phase delaying or advancing the modulation applied to one set of elements relative to the second. In order to achieve linear polarization, the advance of the first set of phases relative to the second (physically orthogonal set) will be 180 degrees. Linear polarization can also be synthesized with only element pattern changes, providing a mechanism for tracking linear polarization.

The on-off mode of operation bandwidth operation has the opportunity for extended dynamic bandwidth and instantaneous bandwidth applications because each element does not have to be tuned to a specific part of its resonance curve. The antenna can be operated continuously through both amplitude and phase hologram portions of its range without significant performance impact. This sets an operating range very close to the total tunable range.

The smaller gap cylindrical feed structure possible with a quartz / glass substrate can utilize the TFT architecture, which means it works on quartz or glass. These substrates are much harder than circuit boards and there are known techniques for achieving a gap size of about 3 μm. A gap size of about 3 μm will result in a switching speed of 14 ms.

Reduced Complexity The disclosed architecture described herein does not require machining operations during manufacture, and only requires one joining stage. This, in combination with a switch to TFT drive electronics, removes expensive materials and some stringent requirements.

  Many alternatives and modifications of the present invention will become apparent to those skilled in the art after reading the foregoing description, but it should be understood that any particular embodiment illustrated and described by way of illustration is considered limiting. It should be understood that this is never intended. Accordingly, references to details of various embodiments are not intended to limit the scope of the claims, which enumerate only features that are considered essential to the invention.

A Solid black arrow B indicating power feed vector from the feed position to the center of the element B Broken line rectangular encircling slot rotated 45 degrees with respect to broken line orthogonal line C “B” indicating an axis perpendicular to “A”

Claims (23)

An antenna feed for inputting a cylindrical feed wave, wherein the cylindrical feed wave propagates concentrically outwardly from the antenna feed;
A radio frequency (RF) slotted array coupled to the antenna feed and having a plurality of surface scattering metamaterial antenna elements;
And the cylindrical feed wave interacts with the radio frequency (RF) slotted array to generate a beam, the radio frequency (RF) slotted array being a cylinder incident at a central location of each slot. An antenna having a plurality of slots oriented at an angle with respect to a propagation direction of a shaped feed wave. Each slot is tuned to operate at the operating frequency of the antenna.
The antenna according to claim 1.   Each slot of the plurality of slots includes a first set of slots in which the slotted array is rotated +45 degrees relative to a cylindrical feed wave propagation direction, and -45 relative to the propagation direction of the cylindrical feed wave. And directed to either +45 degrees or -45 degrees with respect to the cylindrical feed wave incident on the central position of each slot so as to include a second set of slots rotated degrees. The antenna according to claim 2. The slotted array is
Multiple slots,
A plurality of patches, wherein each of the patches is juxtaposed over and separated from the slots in the plurality of slots to form a patch / slot pair, each patch / slot pair within the pair The plurality of patches being turned off or on based on voltage application to the patches;
including,
The antenna according to claim 1.   The antenna of claim 4, wherein a dielectric is between each slot of the plurality of slots and a patch associated with it in the plurality of patches.   The antenna according to claim 5, wherein the dielectric includes liquid crystal.   6. The antenna of claim 5, further comprising a controller that controls which patch / slot pairs are on and off, thereby applying a control pattern that causes beam generation.   The control pattern is used to turn on only a subset of the patch / slot pairs used to generate the beam during the first stage and then generate the beam during the second stage. 8. The antenna of claim 7, wherein the remaining patch / slot pairs are turned on.   The antenna of claim 4, wherein the plurality of patches are positioned in a plurality of rings, the plurality of rings being positioned concentrically with respect to the antenna feed of the slotted array.   The antenna according to claim 4, wherein the plurality of patches are included in a patch substrate.   The antenna according to claim 4, wherein the plurality of patches are included in a glass layer.   The antenna of claim 1, further comprising a dielectric layer into which the cylindrical feed wave travels. The ground plane,
A coaxial pin coupled to the ground plane for inputting the feed wave into an antenna, wherein the dielectric layer is between the ground plane and the slotted array;
The antenna according to claim 12, further comprising:   And further comprising at least one RF absorber coupled to the ground plane and the slotted array to extinguish unused energy and prevent reflection of the unused energy back through the antenna. The antenna according to claim 13. An immersive conductor, wherein the dielectric layer is between the immersive conductor and the slotted array;
A spacer between the immersive conductor and the ground plane;
A side area coupling the ground plane to the slotted array;
The antenna according to claim 13, further comprising:   The side area includes two side surfaces, each of the two side areas being angled to propagate the feed wave from the spacer layer of the feed to the dielectric layer of the feed. The antenna according to claim 15.   The antenna according to claim 15, wherein the spacer includes a foam.   The antenna according to claim 12, wherein the dielectric layer includes plastic.   The antenna according to claim 12, wherein the dielectric layer is tapered.   The antenna of claim 12, wherein the dielectric layer includes a plurality of areas having different dielectric constants.   The antenna of claim 12, wherein the dielectric layer includes a plurality of distributed structures that affect the propagation of the feed wave.   The antenna of claim 1, further comprising a ridged feed network into which the cylindrical feed wave travels. An antenna feed to input a cylindrical feed wave propagating concentrically from the feed;
A dielectric layer through which the feed wave travels;
A plurality of slots oriented at an angle with respect to the direction of propagation of the cylindrical feed wave;
A plurality of patches, each patch juxtaposed over the slots in the plurality of slots and separated therefrom using a liquid crystal layer to form a patch / slot pair; The plurality of patches being turned off or on based on application of a voltage to the patches in the pair specified by a control pattern;
Wherein the cylindrical feed wave interacts with the patch / slot pair to generate a beam when the cylindrical feed wave is incident on a central location of each slot.

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