Patent Grant
10535919
Embodiments of the invention relate generally to of a phased array antenna and more particularly, but not exclusively, to the coupling of a radome to an antenna panel.
Existing satellite systems variously provide a bulbous radome which has disposed therein an antenna coupled to be moved by a gimbal. The antenna usually includes a dish mounted on a stand, with the horn pointing in at the dish surface. Traditional Vehicle Mounted Earth Stations (VMESs), even those including various phased array devices, require motorization and mechanical pointing for some portion of their function.
Recent improvements in electronically steerable, beamforming antenna technologies offer the promise of new in-vehicle, on-vehicle and other applications which support, replace or supplement the use of consumer smartphones and on-board cellular technology modules. For at least this reason, there is expected to be an increasing premium placed on incremental improvements to the space efficiency of communication terminals which utilize electronically steerable antenna devices.
The various embodiments of the present invention are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which:
Embodiments described herein variously provide tightly integrated structures of a communication terminal which includes contiguous structure between a radome and an array of radio frequency (RF) elements—e.g., wherein the communication device omits any void layer between the radome and the array of RF elements. In conventional satellite communication systems, a radome is separated from antenna structure by an empty volume disposed therebetween. Unless otherwise indicated, “antenna structure” refers to herein to a structure that is to serve as at least part of an antenna—e.g., wherein an antenna structure is an entire antenna or, alternatively, merely a subset of all components of the antenna.
By integrating the elements such that there is no empty volume between the aperture and radome, some embodiments provide for a relatively low-profile (i.e., thinner) communication terminal without excessively sacrificing structural integrity. In some embodiments, the radome may function as a carrier during manufacture of the communication terminal—e.g., wherein the radome is used to move or otherwise position an array of RF elements that are variously disposed in or on one or more antenna panels. An antenna panel may, for example, include a thin-film-transistor (TFT) segment or other planar antenna structure. Although some embodiments are not limited in this regard, some or all such RF elements may be arranged as a structure—referred to herein as “antenna aperture” (also referred to herein as “aperture,” for brevity)—which, for example, is disposed around and/or above an input feed.
Some embodiments provide a layer of foam which facilitates more efficient fabrication processing—e.g., to improve the handling and/or protection of antenna structures prior to or during assembly with the radome. Alternatively or in addition, providing a layer of foam—e.g., in lieu of a gap layer which is typical in conventional antenna designs—enables a radome to be relatively close to antenna structures, resulting in a thinner (z-dimension) profile of a satellite communication terminal.
In the illustrative embodiment shown, communication device 100 includes a radome 110, a layer of foam 130 and antenna structures (such as the illustrative antenna panel 140 shown) which include an array of RF elements. Although the word “radome” originated as a portmanteau of “radar” and “dome,” it will be appreciated that radomes in various embodiments may have any of a variety of curved, or even flat, shapes. It will also be appreciated that embodiments described herein are not limited to the communication of radar signals, but may relate to RF satellite communication, for example.
Radome 110 may be any of a variety of structures that are to propagate RF communications to and/or from antenna panel 140—e.g., where radome 110 is further to provide structural and/or environmental protection of antenna panel 140. For example, radome 110 may comprise one or more dielectric materials—e.g., including any of a variety of plastics adapted from conventional radome designs—that are transparent to, or otherwise transmissive of, RF signals. Radome 110 may, for example, be a solid structure which does not include any porous (e.g., foam) material. Alternatively or in addition, at least a portion of radome 110 which extends over foam 130 may be curved to deviate from a flat plane—e.g., by at least 0.040 inches (and in some embodiments, by at least 0.060 inches). In one embodiment, radome 110 comprises stacked layers (not shown) of different dielectric materials—e.g., the stacked layers having a profile of signal propagation properties which is tuned for communications using antenna panel 140.
Radome 110 may form an exterior surface 112 of communication device 100—e.g., wherein radome 110 forms or is part of a chassis, housing or other enclosure which extends around antenna panel 140. Such an enclosure may be formed by any of a variety of one or more plastic, metal and/or other materials which, for example, are adapted from conventional communication terminal designs. In such an embodiment, antenna panel 140 may be disposed, directly or indirectly, on a lower portion of the enclosure (as represented by the illustrative support structure 150 shown). Support structure 150 may include or alternatively, be disposed under an antenna which includes antenna panel 140. For example, a RF feed structure (not shown) may be coupled to operate some or all RF elements—e.g., wherein the RF feed structure is a component of antenna panel 140, disposed in support structure 150 or disposed between antenna panel 140 and support structure 150.
Antenna panel 140 may provide some or all functionality of an electronically steerable (e.g., beam-forming) antenna. For example, antenna panel 140 may include a substrate—e.g., comprising quartz, glass, polyimide, printed circuit board, etc.—wherein metamaterials, thin-film-transistors (TFTs) and/or other structures variously formed in or on the substrate are configured as an array of elements to perform RF signal transmission and/or reception. Some or all such structures may, for example, be adapted from conventional flat panel array architectures, which are not detailed herein to avoid obscuring certain features of various embodiments. Although some embodiments are not limited in this regard, antenna panel 140 may be one of multiple substrates which, in combination with one another, form an antenna aperture. However, other embodiments are not limited to a particular RF array technology with which antenna panel 140 is to provide an electronically steerable antenna functionality.
As shown in
Foam 130 may include any of a variety materials that have a dielectric constant in a range of 1.0 to 1.25—e.g., at least for signals of up to 10 GHz. For example, foam 130 may include ROHACELL® 31 HF foam or any of a variety of other ROHACELL® foams from Evonik Industries Aktiengesellschaft of Essen, Germany.
Adhesive 120 may include any of a variety of materials to form an adhesive bond between radome 110 and either antenna panel 140 or any intermediary structure (not shown) that might facilitate coupling to antenna panel 140. In one embodiment, adhesive 120 includes any of a variety of pressure-sensitive adhesive (PSA) materials—e.g., including one or more styrene copolymers, acrylics and/or other materials adapted from conventional PSA products. Alternatively or in addition, adhesive 120 may include one or more materials which cure in response to heat, ultraviolet radiation, air and/or the like—e.g., wherein adhesive 120 is formed from a two-part epoxy adhesive mixture which is deposited just prior to an adhesion of foam 130 and radome 110.
Structures of communication device 100 extending from side 114 to antenna panel 140 may omit any gap layer and form a contiguous stack of materials. One or more materials of such a stack may form any of a variety of flat or curved surfaces, in different embodiments, and are not limited to the illustrative flat sides variously shown in
In one embodiment, foam 130 adjoins or is otherwise a closest structure to antenna panel 140 at side 134—e.g., other than any adhesive (not shown) that might couple foam 130 and antenna panel 140 to one another. In other embodiments, one or more other structures may be disposed between foam 130 and antenna panel 140. By way of illustration and not limitation, communication device 100 may further comprise one or more layers of structures that promote large angle beam direction and/or other signal propagation characteristics. In some embodiments, communication device 100 further comprises one or more additional layers of foam between foam 130 and antenna panel 140. Such one or more additional foam layers may, for example, include a foam layer which forms at least one machined surface.
Foam 130 may be somewhat thin between sides 132, 134—e.g., as compared to a thickness of radome 110 between sides 112, 114. For example, an average thickness of foam 130 may be equal to or less than 0.060 inches (e.g., wherein such average thickness is equal to or less than 0.040 inches and, in some embodiments, equal to or less than 0.030 inches).
In the example embodiment shown, method 200 includes, at 210, forming a first foam layer which is disposed on a radome. After the forming at 210, the first foam layer may include a first side and a second side opposite (e.g., side 134 and side 132, respectively). The forming at 210 may include depositing a foam material on the radome—e.g., wherein the foam material cures to adhere itself to the radome or wherein a previously-cured foam material is bonded to the radome with an adhesive. For example, method 200 may further comprise adhering the second side of the first foam layer to the radome with a pressure sensitive adhesive material. In some embodiments, the forming at 210 comprises machining the foam material, after deposition on the radome, to form a first machined surface at the first side of the first foam layer.
Referring now to
As illustrated at stage 301, a side 322 of foam material 320 may be cut or otherwise processed with a machining tool 316—e.g., where (at stage 302) such processing forms a machined surface 322′ of a resulting foam layer 320′. Such machining may be performed to reduce foam thickness and/or because of an uneven, curved or otherwise non-flat surface of side 322. To provide precise control over dimensions, flatness, alignment and/or other features, radome 310 may be secured to a machining table 340 during such machining and/or other processing. This securing may be provided by clamping, vacuum or other mechanisms that resist a shearing force during machining of side 322, while limiting the application of bending forces on radome 310.
Method 200 may further comprise, at 220, coupling an electronically steerable antenna panel to the first foam layer, via the first side, while the first foam layer is adhered to the radome. The coupling at 220 may, for example, include positioning the radome and the first foam layer onto a base structure while the antenna panel is disposed on the base structure. In such an embodiment, the positioning may include abutting a surface of a standoff with the base structure, wherein the standoff is coupled to and extends from the radome.
For example, referring now to the stage 303 shown in
By way of illustration and not limitation, as shown at stage 305, multiple alignment structures (e.g., including the illustrative posts 350 shown) may variously extend through a level in which one or more antenna panels 360 are disposed—e.g., wherein some or all such alignment structures are variously positioned around a periphery of the one or more antenna panels 360. In the example embodiment shown, posts 350 function may facilitate x-y plane alignment at least between some of through holes 314 and corresponding holes (or other fiducial structures) of alignment table 390. Alternatively or in addition, posts 350 may function as standoffs which limit an extent to which one or more structures may be subsequently brought into z-axis proximity with one or more antenna panels 360. In such an embodiment, some or all of posts 350 may be variously epoxied, threaded and/or otherwise affixed to radome 310.
Referring now to
In the example embodiment shown, base 392 includes threaded holes to facilitate coupling of the second assembly thereto. As shown at stage 307, screws 370 may be variously inserted through respective ones of the holes 314 in radome 310, the screws 370 to be coupled each with a respective threaded hole of base 392. Base 392 may include or otherwise accommodate any of a variety of additional or alternative structures to facilitate direct or indirect coupling with the second assembly. In such an embodiment, posts 350 may variously abut with a surface of base 392, whereby posts 350 assure that at least some minimum required z-axis distance (d1) is kept between one or more antenna panels 360 and said surface of base 392. Although shown as variously abutting respective flat surface regions of base 392, one or more of posts 350 may alternatively abut respective recessed surfaces of base 392—e.g., wherein base 392 forms holes and/or other features which, in combination with posts 350, facilitate three-dimensional alignment and positioning of the second assembly relative to base 392.
The distance d1 may allow for sufficient room to accommodate one or more structures (e.g., including the illustrative RF feed structure 362 shown). For example, distance d1 may assure that pressure applied using screws 370 does not result in damage to one or more panels 360, RF feed structure 362 and/or other structures between base 392 and radome 310. Alternatively or in addition, deformability of foam layer 320′ (and/or other foam layers disposed on one or more antenna panels 360) may mitigate structural damage by enabling compression stresses to be distributed across a wider area. In some embodiments, base 392 itself includes RF feed structure 362 and/or other antenna structure.
The processing illustrated by stages 300-306 is merely one example of an embodiment wherein a radome and an antenna are fixed relative to one another via contiguous structure including a foam material, wherein standoffs are provided to facilitate correct positioning of at least some antenna structure relative to other structure which is to provide structural support for that antenna structure. Such other structure may be coupled to the antenna or, alternatively, may be or otherwise include additional antenna structure.
In utilizing standoff structures, some embodiments accommodate variation, across the plane of base 392, in a vertical distance between a bottom of radome 310 and a top of base 392. For example, standoffs can be placed at a multitude of positions around a periphery of one or more antenna panels 360, where the standoffs are fixed in place such that respective bottoms of the standoffs are to be in the same plane as the top of base 392. Such positioning of the standoffs may mitigate cant and warpage of radome 310 which might otherwise be caused by the fastening of radome 310 to base 392. As a result, stresses on one or more antenna panels 360 may be prevented or otherwise reduced. Such standoff positioning may assure that an iris metal plane of an aperture (formed by one or more antenna panels 360) is in parallel with the various other planes of materials of an RF feed. Alternatively or in addition, the standoffs may facilitate improved z-axis (height) positioning of the iris metal plane above an RF feed or other underlying structure—e.g., even if an air gap is located below the iris.
In some embodiments, the coupling at 220 includes coupling the antenna panel to the first foam layer via one or more other structures. For example, such one or more other structures may include layers variously coupled each to the first foam layer via the first side, wherein coupling the electronically steerable antenna panel includes coupling the electronically steerable antenna panel to the first foam layer via the layers. The layers may facilitate signal shaping, beam direction and/or the like.
Although some embodiments are not limited in this regard, method 200 may additionally or alternatively include operation of a communication device such as one provided by the forming at 210 and coupling at 220. For example, method 200 may include, at 230, participating, with the antenna panel, in a communication of signals which are propagated via the radome and the first foam layer.
Communication device 450 is another example of an embodiment wherein RF elements are coupled only indirectly to a foam layer (and, in turn, to a radome)—e.g., wherein communication device 450 omits any gap layer between the RF elements and the foam layer. In the example embodiment shown, communication device 450 includes a radome 460, a foam layer 462 and antenna panels 474 having respective RF elements (not shown) variously disposed therein or thereon. Radome 460 may include stacked layers of dielectric materials which, in combination with each other, provide tuned signal propagation characteristics.
Antenna panels 474 may be disposed over a RF feed structure 476 which, in turn, is supported by a base 478—e.g., the RF feed structure 476 to further propagate signals to and/or from antenna panels 474. In the illustrative embodiment shown, a stack disposed between antenna panels 474 and foam layer 462 includes a foam layer 466 and other layers 464, 468 that, for example, aid in large angle beam direction and/or other signal propagation characteristics. However, such a stack may include any of a variety of other arrangements of more, fewer and/or different layered structures, in various embodiments. A clasp 480 and/or other fastener hardware may be coupled to base 478, wherein clasp 480 secures radome 460 onto foam layer 462, the stack, antenna panels 474 and RF feed structure 476. In other embodiments, base 478 itself includes RF feed structure 476 and/or other antenna structure.
Embodiments of flat panel antennas are disclosed. The flat panel antennas include one or more arrays of antenna elements on an antenna aperture. In one embodiment, the antenna elements comprises liquid crystal cells. In one embodiment, the flat panel antenna is a cylindrically fed antenna that includes matrix drive circuitry to uniquely address and drive each of the antenna elements that are not placed in rows and columns. In one embodiment, the elements are placed in rings.
In one embodiment, the antenna aperture having the one or more arrays of antenna elements is comprised of multiple segments coupled together. When coupled together, the combination of the segments form closed concentric rings of antenna elements. In one embodiment, the concentric rings are concentric with respect to the antenna feed.
In the following description, numerous details are set forth to provide a more thorough explanation of the present invention. It will be apparent, however, to one skilled in the art, that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.
Some portions of the detailed descriptions that follow are presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussion, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
In one embodiment, the flat panel antenna is part of a metamaterial antenna system. Embodiments of a metamaterial antenna system for communications satellite earth stations are described. In one embodiment, the antenna system is a component or subsystem of a satellite earth station (ES) operating on a mobile platform (e.g., aeronautical, maritime, land, etc.) that operates using either Ka-band frequencies or Ku-band frequencies for civil commercial satellite communications. Note that 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).
In one embodiment, the antenna system uses surface scattering metamaterial technology to form and steer transmit and receive beams through separate antennas. In one embodiment, 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).
In one embodiment, the antenna system is comprised of three functional subsystems: (1) a wave guiding structure consisting of a cylindrical wave feed architecture; (2) an array of wave scattering metamaterial unit cells that are part of antenna elements; and (3) a control structure to command formation of an adjustable radiation field (beam) from the metamaterial scattering elements using holographic principles.
In one embodiment, the antenna elements comprise a group of patch and slot antennas (unit cells). This group of unit cells comprises an array of scattering metamaterial elements. In one embodiment, 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. As would be understood by those skilled in the art, LC in the context of CELC refers to inductance-capacitance, as opposed to liquid crystal.
In one embodiment, a liquid crystal (LC) is disposed 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, in one embodiment, the liquid crystal integrates an on/off switch and intermediate states between on and off 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. Note that the teachings herein are not limited to having a liquid crystal that operates in a binary fashion with respect to energy transmission.
In one embodiment, the feed geometry of this antenna system allows the antenna elements to be positioned at forty five degree (45°) angles to the vector of the wave in the wave feed. Note that other positions may be used (e.g., at 40° angles). This position of the elements enables control of the free space wave received by or transmitted/radiated from the elements. In one embodiment, the antenna elements 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., ¼th the 10 mm free-space wavelength of 30 GHz).
In one embodiment, the two sets of elements are perpendicular to each other and simultaneously have equal amplitude excitation if controlled to the same tuning state. Rotating them +/−45 degrees relative to the feed wave excitation achieves both desired features at once. Rotating one set 0 degrees and the other 90 degrees would achieve the perpendicular goal, but not the equal amplitude excitation goal. Note that 0 and 90 degrees may be used to achieve isolation when feeding the array of antenna elements in a single structure from two sides as described above.
The amount of radiated power from each unit cell is controlled by applying a voltage to the patch (potential across the LC channel) using a controller. Traces to each patch are used to provide the voltage to the patch antenna. The voltage is used to tune or detune the capacitance and thus the resonance frequency of individual elements to effectuate beam forming. The voltage required is dependent on the liquid crystal mixture being used. The voltage tuning characteristic of liquid crystal mixtures is mainly described by a threshold voltage at which the liquid crystal starts to be affected by the voltage and the saturation voltage, above which an increase of the voltage does not cause major tuning in liquid crystal. These two characteristic parameters can change for different liquid crystal mixtures.
In one embodiment, a matrix drive is used to apply voltage to the patches in order to drive each cell separately from all the other cells without having a separate connection for each cell (direct drive). Because of the high density of elements, the matrix drive is the most efficient way to address each cell individually.
In one embodiment, the control structure for the antenna system 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. In one embodiment, 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.
In one embodiment, the controller also contains a microprocessor executing software. The control structure may also incorporate sensors (e.g., a GPS receiver, a three axis compass, a 3-axis accelerometer, 3-axis gyro, 3-axis magnetometer, etc.) 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.
More specifically, the controller controls which elements are turned off and which elements are turned on and at which phase and amplitude level at the frequency of operation. The elements are selectively detuned for frequency operation by voltage application.
For transmission, a controller supplies an array of voltage signals to the RF patches to create a modulation, or control pattern. The control pattern causes the elements to be turned to different states. In one embodiment, multistate control is used 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). In one embodiment, 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.
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 sum up (constructive interference) if they have the same phase when they meet in free space and waves cancel each other (destructive interference) if they are in opposite phase when they meet in free space. If the slots in a slotted antenna are positioned so that each successive slot is positioned at a different distance from the excitation point of the guided wave, the scattered wave from that element will have a different phase than the scattered wave of the previous slot. If the slots are spaced one quarter of a guided wavelength apart, each slot will scatter a wave with a one fourth phase delay from the previous slot.
Using the array, the number of patterns of constructive and destructive 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. Thus, by controlling which metamaterial unit cells are turned on or off (i.e., by changing the pattern of which cells are turned on and which cells are turned off), a different pattern of constructive and destructive interference can be produced, and the antenna can change the direction of the main beam. 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.
In one embodiment, the antenna system produces one steerable beam for the uplink antenna and one steerable beam for the downlink antenna. In one embodiment, the antenna system uses metamaterial technology to receive beams and to decode signals from the satellite and to form transmit beams that are directed toward the satellite. In one embodiment, 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). In one embodiment, the antenna system is considered a “surface” antenna that is planar and relatively low-profile, especially when compared to conventional satellite dish receivers.
Control module 680 is coupled to reconfigurable resonator layer 630 to modulate the array of tunable slots 610 by varying the voltage across the liquid crystal in
Radio Frequency (“RF”) holography is also possible using analogous techniques where a desired RF beam can be generated when an RF reference beam encounters an RF holographic diffraction pattern. In the case of satellite communications, the reference beam is in the form of a feed wave, such as feed wave 605 (approximately 20 GHz in some embodiments). To transform a feed wave into a radiated beam (either for transmitting or receiving purposes), an interference pattern is calculated between the desired RF beam (the object beam) and the feed wave (the reference beam). The interference pattern is driven onto the array of tunable slots 610 as a diffraction pattern so that the feed wave is “steered” into the desired RF beam (having the desired shape and direction). In other words, the feed wave encountering the holographic diffraction pattern “reconstructs” the object beam, which is formed according to design requirements of the communication system. The holographic diffraction pattern contains the excitation of each element and is calculated by w_hologram=w_in{circumflex over ( )}*w_out, with w_in as the wave equation in the waveguide and w_out the wave equation on the outgoing wave.
Reconfigurable resonator layer 630 also includes gasket layer 632 and patch layer 631. Gasket layer 632 is disposed between patch layer 631 and iris layer 633. Note that in one embodiment, a spacer could replace gasket layer 632. In one embodiment, iris layer 633 is a printed circuit board (“PCB”) that includes a copper layer as metal layer 636. In one embodiment, iris layer 633 is glass. Iris layer 633 may be other types of substrates.
Openings may be etched in the copper layer to form slots 612. In one embodiment, iris layer 633 is conductively coupled by a conductive bonding layer to another structure (e.g., a RF feed structure) in
Patch layer 631 may also be a PCB that includes metal as radiating patches 611. In one embodiment, gasket layer 632 includes spacers 639 that provide a mechanical standoff to define the dimension between metal layer 636 and patch 611. In one embodiment, the spacers are 75 microns, but other sizes may be used (e.g., 3-200 mm). As mentioned above, in one embodiment, the antenna aperture of
A voltage between patch layer 631 and iris layer 633 can be modulated to tune the liquid crystal in the gap between the patch and the slots (e.g., tunable resonator/slot 610). Adjusting the voltage across liquid crystal 613 varies the capacitance of a slot (e.g., tunable resonator/slot 610). Accordingly, the reactance of a slot (e.g., tunable resonator/slot 610) can be varied by changing the capacitance. Resonant frequency of slot 610 also changes according to the equation f=1/(2π√LC) where f is the resonant frequency of slot 610 and L and C are the inductance and capacitance of slot 610, respectively. The resonant frequency of slot 610 affects the energy radiated from feed wave 605 propagating through the RF feed structure. As an example, if feed wave 605 is 20 GHz, the resonant frequency of a slot 610 may be adjusted (by varying the capacitance) to 17 GHz so that the slot 610 couples substantially no energy from feed wave 605. Or, the resonant frequency of a slot 610 may be adjusted to 20 GHz so that the slot 610 couples energy from feed wave 605 and radiates that energy into free space. Although the examples given are binary (fully radiating or not radiating at all), full grey scale control of the reactance, and therefore the resonant frequency of slot 610 is possible with voltage variance over a multi-valued range. Hence, the energy radiated from each slot 610 can be finely controlled so that detailed holographic diffraction patterns can be formed by the array of tunable slots.
In one embodiment, tunable slots in a row are spaced from each other by λ/5. Other spacings may be used. In one embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/2, and, thus, commonly oriented tunable slots in different rows are spaced by λ/4, though other spacings are possible (e.g., λ/5, λ/6.3). In another embodiment, each tunable slot in a row is spaced from the closest tunable slot in an adjacent row by λ/3.
Embodiments of this invention use reconfigurable metamaterial technology, such as described in U.S. patent application Ser. No. 14/550,178, entitled “Dynamic Polarization and Coupling Control from a Steerable Cylindrically Fed Holographic Antenna”, filed Nov. 21, 2014 and U.S. patent application Ser. No. 14/610,502, entitled “Ridged Waveguide Feed Structures for Reconfigurable Antenna”, filed Jan. 30, 2015, to the multi-aperture needs of the marketplace.
Referring to
Separate from conducting ground plane 1002 is interstitial conductor 1003, which is an internal conductor. In one embodiment, conducting ground plane 1002 and interstitial conductor 1003 are parallel to each other. In one embodiment, the distance between ground plane 1002 and interstitial conductor 1003 is 0.1-0.15″. In another embodiment, this distance may be λ/2, where λ is the wavelength of the travelling wave at the frequency of operation.
Ground plane 1002 is separated from interstitial conductor 1003 via a spacer 1004. In one embodiment, spacer 1004 is a foam or air-like spacer. In one embodiment, spacer 1004 comprises a plastic spacer.
On top of interstitial conductor 1003 is dielectric layer 1005. In one embodiment, dielectric layer 1005 is plastic.
An RF-array 1006 is on top of dielectric layer 1005. In one embodiment, the distance between interstitial conductor 1003 and RF-array 1006 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 sides 1007 and 1008. Sides 1007 and 1008 are angled to cause a travelling wave feed from coax pin 1001 to be propagated from the area below interstitial conductor 1003 (the spacer layer) to the area above interstitial conductor 1003 (the dielectric layer) via reflection. In one embodiment, the angle of sides 1007 and 1008 are at 45° angles. In an alternative embodiment, sides 1007 and 1008 could be replaced with a continuous radius to achieve the reflection. While
In operation, when a feed wave is fed in from coaxial pin 1001, the wave travels outward concentrically oriented from coaxial pin 1001 in the area between ground plane 1002 and interstitial conductor 1003. The concentrically outgoing waves are reflected by sides 1007 and 1008 and travel inwardly in the area between interstitial conductor 1003 and RF array 1006. The reflection from the edge of the circular perimeter causes the wave to remain in phase (i.e., it is an in-phase reflection). The travelling wave is slowed by dielectric layer 1005. At this point, the travelling wave starts interacting and exciting with elements in RF array 1006 to obtain the desired scattering.
To terminate the travelling wave, a termination 1009 is included in the antenna at the geometric center of the antenna. In one embodiment, termination 1009 comprises a pin termination (e.g., a 50Ω pin). In another embodiment, termination 1009 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 1006.
In operation, a feed wave is fed through coaxial pin 1015 and travels concentrically outward and interacts with the elements of RF array 1016.
The cylindrical feed in both the antennas of
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.
RF array 1006 of
In one embodiment, 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.
In one embodiment, a liquid crystal (LC) 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 (the thickness of the liquid crystal) results in a fourfold increase in speed. In another embodiment, the thickness of the liquid crystal results in a beam switching speed of approximately fourteen milliseconds (14 ms). In one embodiment, 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. When 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.
In one embodiment, 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. In one embodiment, 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., ¼th the 10 mm free-space wavelength of 30 GHz).
In one embodiment, the CELCs are implemented with patch antennas that include a patch co-located over a slot with liquid crystal between the two. In this respect, the metamaterial antenna acts like a slotted (scattering) wave guide. With a slotted wave guide, the phase of the output wave depends on the location of the slot in relation to the guided wave.
In one embodiment, the antenna elements are placed on the cylindrical feed antenna aperture in a way that allows for a systematic matrix drive circuit. The placement of the cells includes placement of the transistors for the matrix drive.
In an initial approach to realize matrix drive circuitry on the cylindrical feed antenna with unit cells placed in a non-regular grid, two steps are performed. In the first step, the cells are placed on concentric rings and each of the cells is connected to a transistor that is placed beside the cell and acts as a switch to drive each cell separately. In the second step, the matrix drive circuitry is built in order to connect every transistor with a unique address as the matrix drive approach requires. Because the matrix drive circuit is built by row and column traces (similar to LCDs) but the cells are placed on rings, there is no systematic way to assign a unique address to each transistor. This mapping problem results in very complex circuitry to cover all the transistors and leads to a significant increase in the number of physical traces to accomplish the routing. Because of the high density of cells, those traces disturb the RF performance of the antenna due to coupling effect. Also, due to the complexity of traces and high packing density, the routing of the traces cannot be accomplished by commercial available layout tools.
In one embodiment, the matrix drive circuitry is predefined before the cells and transistors are placed. This ensures a minimum number of traces that are necessary to drive all the cells, each with a unique address. This strategy reduces the complexity of the drive circuitry and simplifies the routing, which subsequently improves the RF performance of the antenna.
More specifically, in one approach, in the first step, the cells are placed on a regular rectangular grid composed of rows and columns that describe the unique address of each cell. In the second step, the cells are grouped and transformed to concentric circles while maintaining their address and connection to the rows and columns as defined in the first step. A goal of this transformation is not only to put the cells on rings but also to keep the distance between cells and the distance between rings constant over the entire aperture. In order to accomplish this goal, there are several ways to group the cells.
The density of the cells after the transformation is determined by the number of cells that the next larger square contains in addition to the previous square. In one embodiment, using squares results in the number of additional antenna elements, ΔN, to be 8 additional cells on the next larger square. In one embodiment, this number is constant for the entire aperture. In one embodiment, the ratio of cellpitch1 (CP1: ring to ring distance) to cellpitch2 (CP2: distance cell to cell along a ring) is given by:
CP1/CP2=ΔN/2π
Thus, CP2 is a function of CP1 (and vice versa). The cellpitch ratio for the example in
CP1/CP2=8/2π=1.2732
which means that the CP1 is larger than CP2.
In one embodiment, to perform the transformation, a starting point on each square, such as starting point 1121 on square 1101, is selected and the antenna element associated with that starting point is placed on one position of its corresponding ring, such as starting point 1131 on ring 1111. For example, the x-axis or y-axis may be used as the starting point. Thereafter, the next element on the square proceeding in one direction (clockwise or counterclockwise) from the starting point is selected and that element placed on the next location on the ring going in the same direction (clockwise or counterclockwise) that was used in the square. This process is repeated until the locations of all the antenna elements have been assigned positions on the ring. This entire square to ring transformation process is repeated for all squares.
However, according to analytical studies and routing constraints, it is preferred to apply a CP2 larger than CP1. To accomplish this, a second strategy shown in
CP1/CP2=4/2π=0.6366
which results in CP2>CP1.
The transformation from octagon to concentric rings for cell placement according to
Note that the cell placements disclosed with respect to
In one embodiment, a TFT package is used to enable placement and unique addressing in the matrix drive.
Another important feature of the proposed cell placement shown in
In another embodiment, the matrix drive circuitry and cell placement on the cylindrical feed antenna is accomplished in a different manner. To realize matrix drive circuitry on the cylindrical feed antenna, a layout is realized by repeating a subsection of the array rotation-wise. This embodiment also allows the cell density that can be used for illumination tapering to be varied to improve the RF performance.
In this alternative approach, the placement of cells and transistors on a cylindrical feed antenna aperture is based on a lattice formed by spiral shaped traces.
Unlike the approaches for cell placement on the cylindrical feed antenna aperture discussed above, the approach discussed above in relation to
Due to the size of the cells and the required space between them for traces, the cell density cannot exceed a certain number. In one embodiment, the distance is λ/5 based on the frequency of operation. As described above, other distances may be used. In order to avoid an overpopulated density close to the center, or in other words to avoid an under-population close to the edge, additional spirals can be added to the initial spirals as the radius of the successive concentric rings increases.
Another advantage of the use of spirals for cell placement is the rotational symmetry and the repeatable pattern which can simplify the routing efforts and reducing fabrication costs.
In one embodiment, the antenna aperture is created by combining multiple segments of antenna elements together. This requires that the array of antenna elements be segmented and the segmentation ideally requires a repeatable footprint pattern of the antenna. In one embodiment, the segmentation of a cylindrical feed antenna array occurs such that the antenna footprint does not provide a repeatable pattern in a straight and inline fashion due to the different rotation angles of each radiating element. One goal of the segmentation approach disclosed herein is to provide segmentation without compromising the radiation performance of the antenna.
While segmentation techniques described herein focuses improving, and potentially maximizing, the surface utilization of industry standard substrates with rectangular shapes, the segmentation approach is not limited to such substrate shapes.
In one embodiment, segmentation of a cylindrical feed antenna is performed in a way that the combination of four segments realize a pattern in which the antenna elements are placed on concentric and closed rings. This aspect is important to maintain the RF performance. Furthermore, in one embodiment, each segment requires a separate matrix drive circuitry.
As the result of this segmentation method illustrated in
As shown in
As is evident from
The antenna feed is coupled to the rest of the segments when the open area exists because the feed comes from the bottom, and the open area can be closed by a piece of metal to prevent radiation from the open area. A termination pin may also be used. The use of substrates in this fashion allows use of the available surface area more efficiently and results in an increased aperture diameter.
Similar to the embodiment shown in
For both approaches described above, the cell placement may be performed based on a recently disclosed approach which allows the generation of matrix drive circuitry in a systematic and predefined lattice, as described above.
While the segmentations of the antenna arrays above are into four segments, this is not a requirement. The arrays may be divided into an odd number of segments, such as, for example, three segments or five segments.
Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that any particular embodiment shown and described by way of illustration is in no way intended to be considered limiting. Therefore, references to details of various embodiments are not intended to limit the scope of the claims which in themselves recite only those features regarded as essential to the invention.
Referring to
Diplexer 2445 may be coupled to a low noise block down converter (LNBs) 2427 to perform a noise filtering function and a down conversion and amplification function—e.g., including operations adapted from techniques known in the art. In one embodiment, LNB 2427 is in an out-door unit (ODU). In another embodiment, LNB 2427 is integrated into the antenna apparatus. LNB 2427 may be coupled to a modem 2460, which may be further coupled to computing system 2440 (e.g., a computer system, modem, etc.). Computing system 2440 is one example of hardware that may provide a user with some output which is based on—and/or some input which is to determine—signals communicated with antenna 2401. For example, computing system 2440 may include or couple to a display device which is to generate a display based on signal communication via antenna 2401.
Modem 2460 may include an analog-to-digital converter (ADC) 2422, which may be coupled to LNB 2427, to convert the received signal output from diplexer 2445 into digital format. Once converted to digital format, the signal may be demodulated by demodulator 2423 and decoded by decoder 2424 to obtain the encoded data on the received wave. The decoded data may then be sent to controller 2425, which sends it to computing system 2440.
Modem 2460 may additionally or alternatively include an encoder 2430 that encodes data to be transmitted from computing system 2440. The encoded data may be modulated by modulator 2431 and then converted to analog by digital-to-analog converter (DAC) 2432. The analog signal may then be filtered by a BUC (up-convert and high pass amplifier) 2433 and provided to one port of diplexer 2445. In one embodiment, BUC 2433 is in an out-door unit (ODU). Diplexer 2445 may support operations adapted from conventional interconnect techniques to provide the transmit signal to antenna 2401 for transmission.
Controller 2450 may control antenna 2401, including controller 2450 transmitting signals to configure beam steering, beamforming, frequency tuning and/or other operational characteristics of one or more antenna elements. Note that the full duplex communication system shown in
Techniques and architectures for providing satellite communication mechanisms are described herein. In the above description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of certain embodiments. It will be apparent, however, to one skilled in the art that certain embodiments can be practiced without these specific details. In other instances, structures and devices are shown in block diagram form in order to avoid obscuring the description.
Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.
Some portions of the detailed description herein 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 computing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of steps leading to a desired result. The steps are those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as bits, values, elements, symbols, characters, terms, numbers, or the like.
It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the discussion herein, it is appreciated that throughout the description, discussions utilizing terms such as “processing” or “computing” or “calculating” or “determining” or “displaying” or the like, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.
Certain embodiments also relate to apparatus for performing the operations herein. This apparatus may be specially constructed for the required purposes, or it may comprise a general purpose computer selectively activated or reconfigured by a computer program stored in the computer. Such a computer program may be stored in a non-transitory computer readable storage medium, such as, but is not limited to, any type of disk including floppy disks, optical disks, CD-ROMs, and magnetic-optical disks, read-only memories (ROMs), random access memories (RAMs) such as dynamic RAM (DRAM), EPROMs, EEPROMs, magnetic or optical cards, or any type of media suitable for storing electronic instructions, and coupled to a computer system bus.
The algorithms and displays presented herein are not inherently related to any particular computer or other apparatus. Various general purpose systems may be used with programs in accordance with the teachings herein, or it may prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will appear from the description herein. In addition, certain embodiments are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of such embodiments as described herein.
Besides what is described herein, various modifications may be made to the disclosed embodiments and implementations thereof without departing from their scope. Therefore, the illustrations and examples herein should be construed in an illustrative, and not a restrictive sense. The scope of the invention should be measured solely by reference to the claims that follow.
This application claims the benefit of a U.S. Provisional Application No. 62/340,986 filed on May 24, 2016, the entire contents of which are hereby incorporated by reference herein.
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