Controllable antenna arrays for wireless communications

Abstract

Examples disclosed herein describe an antenna architecture (e.g., a planar electronically steered antenna architecture) that enables operation at low elevation angles, down to zero degrees from the satellite. The proposed ‘3SA’ architecture may improve power consumption and array footprints. The proposed ‘3SA’ architecture can support aero terminal implementation on aircraft, enabling the use of GEO, MEO and LEO satellites even in regions having low elevation angles. The architecture may include a horizontal antenna array and vertical antenna array as well as a controller for switching between the antenna arrays.

Claims

1. An apparatus comprising: a horizontal antenna array configured to receive or transmit electromagnetic waves; two vertical antenna arrays installed back-to-back in or on a tail or a fin of an aircraft, each of the two vertical antenna arrays comprising: a receiving array configured to receive electromagnetic waves; and a transmitting array configured to transmit electromagnetic waves; and a controller configured to select an operating antenna array from the horizontal antenna array and one of the two vertical antenna arrays based on at least: an elevation angle between a location of the aircraft and an orbital location of a satellite, a skew angle between the operating antenna array and the satellite, a waveform or a throughput consideration, a transceiver power level, and a power spectral density (PSD) threshold allowance.

2. The apparatus of claim 1, wherein the controller is configured to cause the horizontal antenna array and the two vertical antenna arrays to operate at scan angles within a range determined based on a threshold indicating a maximum acceptable scan loss.

3. The apparatus of claim 1, wherein the apparatus is configured to communicate with the satellite that is one of a GEO satellite, MEO satellite, or LEO satellite.

4. The apparatus of claim 1, wherein the apparatus is configured to reduce a power provided to an unselected antenna array.

5. The apparatus of claim 1, wherein the controller is configured to select the operating antenna array independently of any communication with any equipment external to the apparatus.

6. The apparatus of claim 1, further comprising: an enclosure enclosing the horizontal antenna array and the two vertical antenna arrays.

7. The apparatus of claim 1, wherein the controller comprises: a processor; a GPS receiver; or one or more gyros.

8. The apparatus of claim 1, wherein the controller is configured to select the horizontal antenna array as the operating antenna array based on a determination that the elevation angle is greater than a threshold.

9. The apparatus of claim 1, wherein the controller is configured to select one of the two vertical antenna arrays as the operating antenna array based on a determination that the elevation angle is less than a threshold.

10. The apparatus of claim 1, wherein the controller is configured to select one of the two vertical antenna arrays as the operating antenna array based on the elevation angle and a type of the aircraft.

11. The apparatus of claim 1, wherein the horizontal antenna array comprises an electronically steerable array of antennas; and wherein the controller is configured to electronically steer the horizontal antenna array.

12. The apparatus of claim 1, wherein a boresight direction of the horizontal antenna array is approximately perpendicular to a boresight direction of one of the two vertical antenna arrays.

13. The apparatus of claim 1, wherein the apparatus is installed on an aircraft comprising a fuselage and the tail or the fin, the horizontal antenna array is installed in or on the fuselage and configured to receive or transmit electromagnetic waves.

14. The apparatus of claim 1, wherein the elevation angle ranges from 0 degree to 90 degree.

15. The apparatus of claim 13, wherein the controller is configured to select the horizontal antenna array as the operating antenna array based on a determination that the elevation angle is greater than a threshold.

16. The apparatus of claim 13, wherein the controller is configured to select one of the two vertical antenna arrays as the operating antenna array based on a determination that the elevation angle is less than a threshold.

17. The apparatus of claim 13, wherein the controller is configured to select one of the two vertical antenna arrays as the operating antenna array based on a position of the aircraft relative to a position of the satellite.

18. A method comprising: determining, by a controller installed on an aircraft, an elevation angle between a location of the aircraft and an orbital location of a satellite; based on at least the elevation angle, a skew angle between an operating antenna array and the satellite, a waveform or a throughput consideration, a transceiver power level, and a power spectral density (PSD) threshold allowance, selecting the operating antenna array from a horizontal antenna array installed in or on a fuselage of the aircraft and one of two vertical antenna arrays installed back-to-back in or on a tail or a fin of the aircraft, each of the two vertical antenna arrays comprising a receiving array and a transmitting array; and communicating with the satellite using the selected operating antenna array.

19. The method of claim 18, further comprising: switching from an unselected antenna array to the operating antenna array; and reducing power associated with the unselected antenna array, wherein the selecting the operating antenna array comprises determining, based on a comparison of the elevation angle to a threshold, the operating antenna array.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Having thus described the disclosure in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

(2) FIG. 1 shows an example of typical antenna element gain versus offset (scan) angle, in accordance with aspects of the disclosure.

(3) FIG. 2 shows global commercial aviation routes placed on a world map, with indications of the resulting elevation angles from a terminal to a GEO satellite, in accordance with aspects of the disclosure.

(4) FIG. 3 shows an example of a ‘3SA’ terminal architecture, in accordance with aspects of the disclosure.

(5) FIG. 4 shows an example of a ‘3SA’ antenna selection algorithm, in accordance with aspects of the disclosure.

(6) FIG. 5 shows an example of a ‘3SA’ terminal mounting on an aircraft, in accordance with aspects of the disclosure.

(7) FIG. 6 show an example implementation of a vertical antenna array installation on an aircraft (e.g., a Gulfstream G650 aircraft), in accordance with aspects of the disclosure.

(8) FIG. 7 shows example implementations of a ‘3SA’ terminal on aircraft (e.g., a Boeing 737 “Dorsal fin” or an Airbus 320 tail), in accordance with aspects of the disclosure.

DETAILED DESCRIPTION

(9) Wireless communications utilize antennas to transmit and receive signals between different devices. For example, a satellite communication system for commercial and/or non-commercial applications (e.g., aviation) may comprise antennas mounted on a remote station such as a fixed or mobile device (e.g., an aircraft), a satellite, and/or a ground earth station (GES) (e.g., a Hub station). The antennas may provide for reception and transmission of the electromagnetic signals communicated between, for example, the remote station(s) and/or other remote station(s) and/or Hub station(s). A variety of remote antenna types may be used including, but not limited to: steered flat panel antennas (e.g., mechanically steerable passive arrays and/or electronically steerable active arrays), reflectors and/or reflector arrays, hybrid steering antennas (combining mechanical steering with electronic steering), and electronic steerable antennas such as phased array antennas (PAA) which may include electronic beam steering capabilities.

(10) In some examples, mobile antennas may be arranged to be mounted on moving platforms such as aircraft (e.g., aero antennas) and may be variously configured. In some examples, these antennas may have a low profile to reduce air drag and fuel consumption. These antennas may optimize transmit and receive performance per a given footprint (e.g., given dimensions). These antennas may be disposed at a location such as on the top of a vehicle, train, boat, high altitude platforms (HAPS) satellite, and/or aircraft's fuselage. These antennas may be optimized to reduce operation and maintenance costs. These antennas may be configured to have low power consumption. These antennas may be configured to dissipate power when the vehicle is not moving (without air circulation around the antenna array). These antennas may support wide frequency bands, wide angle scanning performance, multi-beam operation, and fast beam steering.

(11) In some examples, the antenna may be used as a part of the ground-based antenna system that is a part of a satellite communication system (e.g., mobile devices with satellite communication features). The satellites of the satellite communication system may be in one or more constellations in one or more different orbits such as low Earth orbit (LEO), medium Earth Orbit (MEO), or geostationary earth orbit (GEO). For example, a LEO satellite constellation (e.g., a mega-constellation) may be composed of a plurality of (e.g., thousands) of satellites, based on architectures such as CubeSat architecture. The satellite constellation may be in communication with a number of ground stations. The space segment of the constellation may be organized in several orbital planes that may be deployed at different inclinations and altitudes. The satellites may move at high speeds (e.g., higher than 25,000 km/h) relative to the ground stations. Therefore, a communication link between a ground station and a satellite may be available for a short time (e.g., a few minutes) before handover to another satellite occurs.

(12) In another example, the antenna may be used as a payload for HAPS, LEO, and/or MEO satellites and may provide a relatively more power efficient beam scanning antenna solution with a relatively lower profile.

(13) A phased array antenna may be utilized as a mobile antenna. A phased array antenna may comprise multiple electronically-controlled antenna elements (e.g., fixed and/or variable beam antenna elements), which in combination may control the antenna's radiation and/or reception patterns. The phased array antenna's radiated beam and/or received beam may be electronically steered relative to a plane of the antenna array. Phase shifters and/or time-delay components may be connected to individual transmitting and/or receiving antenna elements (e.g., sub-arrays composed of antenna elements) to enable pointing of the beam in different directions. Individually controlling the amplitude and phase of each antenna element in a phased array antenna, in conjunction with beamforming techniques, may allow suppression of side lobes and may further allow creating radiation pattern nulls in certain directions and/or application specific patterns.

(14) Control circuitry may be variously configured to include such items as compact silicon technology based integrated circuits, one or more processors, controllers, programmable gate arrays (PGA), application-specific integrated circuits (ASICs), and/or custom controllers. The control circuitry may also include transmitters, receivers, modems, encoders, decoders, phase shifter(s) to adjust phase, beam steering circuits, polarization circuits, attenuators, filters, amplifiers (e.g., low noise amplifier(s)), and beam forming and polarization circuits, as well as other control and/or communication circuits for implementing transmit-only, receive-only, and/or transmit/receive components of a mobile communication system such as a mobile satellite terminal system. Technologies like SiGe BiCMOS and CMOS SOI (silicon-on-insulator) may allow combination of digital circuitry to control the steering in the array and a radio frequency (RF) signal path to achieve the phase and amplitude adjustment.

(15) Phased array antennas may comprise a single array for transmit-only, a single array for receive-only and/or as single array for transmit/receive. In addition, phased array antennas may comprise of a combination of array building blocks, often referred to as tiles, which may be combined in a group to form a larger array aperture.

(16) The gain of the antenna (also often referred to as power gain) is a key performance metric which combines the antenna's directivity and electrical efficiency. Looking at planar phased array antenna gain which reflects the radiation intensity in the desired directions versus the radiation intensity of an isotropic antenna (all angles), the gain value of the antenna is based on two factors: the gain of a single element (for example a patch antenna) and the number of elements in the array (which may depend on the array's geometric dimensions where, for example, an element occupies a certain area). The gain of an antenna element depends also on the scan angle offset from boresight. The total gain of the antenna (e.g., corresponding to the gain of the patch elements) may be affected also by the scan loss. For example, in a transmitting antenna, the antenna gain indicates how well the antenna may be converting the input power into radio waves which may be transmitted in a specific direction. For planar phased array antennas comprising multiple patch antenna elements, the total gain of the antenna may correspond to the summation of the gain for each antenna element (e.g., each patch antenna). Therefore, to increase the antenna gain, one may increase the number of patch elements thus increasing the size of the antenna aperture and in most cases, the power consumption of the array in accordance.

(17) It has been found that the planar phased array antennas may be susceptible to “scan loss”, which may account for a drop in antenna directivity versus scanning angle measured from the normal of the antenna plane (often referred to as boresight direction) towards the beam direction.

(18) The graph shown in FIG. 1 illustrates gain loss for a typical patch antenna element. The graph shows gain loss (Y-axis) for various angles offset from the boresight direction (X-axis). Maximum gain may be achieved when the offset angle (scan angle) is 0 degrees. When the scan angle is increased, a degradation in the patch antenna element gain may be presented. For example, at a scan angle of 45 (or −45) degrees, the element gain (100) may be about 1.5 dB lower than the maximal gain that may be achieved at boresight. In another example, at a scan angle of 60 (or −60) degrees, the element gain (105) may be about 4 dB lower than the maximal gain. Yet in another example, at a scan angle of 80 (or −80) degrees, the element gain (110) may be about 10.5 dB lower than the maximal gain. And, for scan angles of 90 (or −90) degrees, the element gain (120) may by degraded by over 18 dB compared to boresight gain. This gain degradation behavior may directly affect the gain efficiency of the antenna when operating at low elevation angles towards the satellite. In such cases, the scan loss may be significantly increased (because antenna elevation angle equals 90 degrees minus the antenna's scan angle). FIG. 2 demonstrates the elevation angles (220), including the low elevation angles like the 20 degree and 10 degree elevation angles, encountered when implementing planar phased array antennas or Electronically Steered Antennas (ESA) on aircrafts traveling at high latitude northern (or southern) routes.

(19) Examples disclosed herein describe an antenna architecture referred to as ‘3SA’ (three-ESA). The 3SA antenna architecture may significantly reduce the impact of operating at low elevation angles (high scan angles). The 3SA antenna architecture may be suitable for supporting communication over any of GEO satellites, MEO satellites and satellite constellations, or LEO satellite and satellite constellations.

(20) The 3SA terminal architecture may be based on separation of the antenna terminal into two orientations: a horizontal orientation (e.g., for operation at high elevation angles), and a vertical orientation (e.g., for operation at low elevation angles). With the 3SA architecture, a relatively low scan loss may be obtained, resulting in relatively low gain loss.

(21) A 3SA architecture may comprise one or more horizontal antenna arrays, one or more vertical antenna arrays, and an antenna controller. For example, one 3SA system may include one horizontal antenna array and two vertical antenna arrays as well as an antenna controller for controlling the three arrays. Each of the antenna arrays may be configured to receive and/or transmit electromagnetic waves. The antenna controller may be configured to determine a scan loss value, and when the scan loss value increases beyond a threshold (e.g., pre-set or pre-programmed threshold), to select a (different) operating antenna array from the two vertical Tx/Rx arrays and the horizontal Tx/Rx array. The antenna controller may be configured to select the operating antenna array independently of any modem or other equipment that may be coupled to the antenna. The controller may be configured to perform said selecting in accordance with an elevation angle calculation. In some embodiments, calculating the elevation angle may be based on an aircraft platform (terminal) location and on the satellite orbital location.

(22) In some embodiments, the two vertical antenna arrays may be installed inside or on a tail (or in a “dorsal fin”) of an aircraft. For example, the two vertical antenna arrays may be installed in a back-to-back arrangement (e.g., on opposite sides of the tail such that the boresight directions are approximately opposite of each other or more than 120 degrees apart), for at least the purpose of avoiding a line of sight blocking by the tail, as illustrated in FIG. 2 (showing that the side of the (tail of the) aircraft facing a satellite depends on whether the aircraft is flying eastwards or westwards). With the two vertical antenna arrays installed while facing back-to-back, a line of sight towards a satellite can be maintained whenever the terminal needs to use the vertical antenna arrays and regardless of the orientation of the aircraft towards the satellite (i.e. whether its left side or its right side faces the satellite). In some embodiments, the horizontal antenna array and the two vertical antenna arrays may be packed in a single enclosure (e.g., casing or housing).

(23) FIG. 3 shows a block diagram of a 3SA system. The 3SA system may comprise three receiver (Rx) arrays: a vertical left Rx array (300), a vertical right Rx Array (310) and a horizontal Rx Array (320). Similarly, the 3SA system may comprise three transmission (Tx) arrays: a vertical left Tx array (340), a vertical right Tx array (350), and a horizontal Tx array (360). The three Rx arrays may be coupled to an antenna RF down converter (330), and similarly the three Tx arrays may be coupled to an antenna RF up converter (370). The 3SA system may comprise an antenna controller, which may further comprise any of a central processing unit (CPU) (e.g., processor, microprocessor, microcontroller, etc.), a GPS receiver or one or more gyros. The CPU of the antenna controller may be configured to use control signals 380 for selecting an operating Rx array, and to use control signals 390 for selecting an operating Tx array. In some embodiments, only a selected array (of the 3 Rx arrays and/or the 3 Tx arrays) may be powered on, while the remaining (unselected) arrays may be kept powered off (e.g. until being selected) or in a low power consumption or standby mode, for at least the purpose of reducing the overall power consumption of the 3SA system.

(24) In some embodiments, the vertical left Rx array (300) and the vertical left Tx array (340) may be coupled to construct one of two vertical antenna arrays, while the vertical right Rx array (310) and the vertical right Tx array (350) may be coupled to construct the other of the two vertical antenna arrays. In addition, the horizontal Rx array (320) and the horizontal Tx array (360) may be coupled to construct the horizontal antenna array.

(25) FIG. 4 shows a diagram describing an algorithm for Tx and Rx array selection. In some embodiments, the antenna controller (e.g., a processor (400) of the antenna controller) may be configured (e.g., programmed or hardwired) to perform such algorithm. The algorithm may include a routine (410) for selecting operating arrays from among the available arrays (e.g., Rx apertures (425) and Tx apertures (435)), such as the horizontal Rx array (420), horizontal Tx array (431), vertical left Rx array (421), vertical left Tx array (432), vertical right Rx array (422), and vertical right Tx array (433). In some embodiments, selecting the operating arrays may comprise selecting a pair of corresponding Tx and Rx arrays, for example, selecting the vertical left Rx array (421) and the vertical left Tx array (432), As shown in the flow chart, several factors may influence the selecting, or trigger a change in the selecting, of an operating array, including an elevation angle of the currently operating array towards a currently used satellite (411), a skew angle of the antenna beam (412), one or more waveform/throughput considerations (413), RF level considerations (414), and Power Spectral Density (PSD) regulation considerations (415). For example, when operating at high elevation angles, an antenna horizontally mounted on top of an aircraft fuselage may be selected for use in transmitting or receiving. As a result of this selection, the scan angle towards the satellite may be kept under an x degrees threshold (e.g. 45 degrees) and the scan loss may be as low as 1.5 dB. This x degrees threshold may be stored in memory within the antenna controller. It also may be set before or during a flight. When the elevation angle towards the satellite is lower than 90-x degrees (e.g., 45 degrees per the given example), the antenna controller may determine to switch to a vertical antenna, which may be installed inside or on the aircraft tail or “dorsal fin”. When the antenna controller 400 determines to switch to a different array during a communication session, it may signal a modem (e.g., through an Ethernet connection) to stop transmitting prior to the switchover, and then resume transmission after the switchover, so no data will be lost.

(26) FIG. 4 also illustrates control and data lines from the controller (e.g., processor (400) to the various antenna arrays. These lines may carry control information for controlling the operation of the arrays (e.g., information for steering the arrays). These lines may also include feedback information indicating information about the arrays (e.g., their transmission or reception power, boresight direction, etc.). Further, FIG. 4 illustrates that the architecture may include a transceiver (445) for receiving and transmitting modem signals.

(27) FIG. 5 illustrates a possible installation scheme on a small turboprop aircraft where the horizontal Tx and Rx arrays to be used at high elevation angles may be installed on or in the fuselage (510), and the two vertical Tx and Rx arrays to be used at low elevation angles may be installed on or in a fin (520) that may be connected to the tail of the aircraft. A small aircraft with relatively small fuselage diameter puts mechanical and aerodynamic constraints on size (footprint area) of the satellite antenna that may be installed on or in the fuselage. In many cases, assuming a horizontal-plane only antenna, the link budget constrains may derive antenna footprint diameter to exceed the available installation area on the aircraft fuselage, thus prohibiting the use of satellite communication on these types of aircraft. A 3SA antenna architecture may significantly reduce the size of the needed antenna area, making the horizontal antenna small enough to be installed on or in the fuselage (510) in addition to the vertical array on or in the fin (520).

(28) FIG. 6 illustrates a possible installation scheme on a medium size business jet. The horizontal Tx and Rx arrays may be installed (or mounted) on the fuselage. In addition, the 4 vertical antenna arrays, e.g., left and right Tx arrays (630 and 631) and left and right Rx arrays (640 and 641), may be installed on or in a fin (620) that connects to the tail of the aircraft at a section (610) of the aircraft.

(29) FIG. 7 illustrates a possible installation scheme for installing (or mounting) a 3SA antenna architecture on a large aircraft, such as those in use for commercial aviation. For example, FIG. 7 shows that a vertical array may be installed (or mounted) on or in the tail (730) or a fin (710) of an aircraft. It also shows that a horizontal array may be installed (or mounted) on the fuselage (720 or 740) of the aircraft. As in the case of a small aircraft where the 3SA antenna architecture may decrease the size of a horizontal array installed on the fuselage (thus making the installation feasible or practical), the 3SA antenna architecture may provide a similar benefit in reducing the area occupied by the horizontal array on a large aircraft. The 3SA system may also have the benefit of utilizing the maximum allowable antenna dimension (gain) for reaching higher performance while operating at low antenna scan (and gain) loss. The 3SA antenna architecture allows operating at high gain for a given geometry and elevation angle case, before switching to the opposite orientation. For commercial aviation, increasing data throughput available to airline passengers may be desirable.

(30) Various aspects of the disclosure may be embodied as one or more methods, systems, apparatuses (e.g., components of a satellite communication network), and/or computer program products. Accordingly, those aspects may take the form of an entirely hardware embodiment, an entirely software embodiment, an entirely firmware embodiment, or an embodiment combining firmware, software, and/or hardware aspects. Furthermore, such aspects may take the form of a computer program product stored by one or more computer-readable storage media having computer-readable program code, or instructions, embodied in or on the storage media. Any suitable computer readable storage media may be utilized, including hard disks, CD-ROMs, optical storage devices, magnetic storage devices, and/or any combination thereof. In some embodiments, one or more computer readable media storing instructions may be used. The instructions, when executed, may cause one or more apparatuses to perform one or more acts described herein. The one or more computer readable media may comprise transitory and/or non-transitory media. In addition, various signals representing data or events as described herein may be transferred between a source and a destination in the form of electromagnetic waves traveling through signal-conducting media such as metal wires, optical fibers, and/or wireless transmission media (e.g., air and/or space).

(31) Modifications may be made to the various embodiments described herein by those skilled in the art. For example, each of the elements of the aforementioned embodiments may be utilized alone or in combination or sub-combination with elements of the other embodiments. It will also be appreciated and understood that modifications may be made without departing from the true spirit and scope of the present disclosure. The description is thus to be regarded as illustrative instead of restrictive on the present disclosure.