Patent Application
20170025751
This disclosure relates to fan beam antennas.
A communication network is a large distributed system for receiving information (signal) and transmitting the information to a destination. Over the past few decades the demand for communication access has dramatically increased. Although conventional wire and fiber landlines, cellular networks, and geostationary satellite systems have continuously been increasing to accommodate the growth in demand, the existing communication infrastructure is still not large enough to accommodate the increase in demand. In addition, some areas of the world are not connected to a communication network and therefore cannot be part of the global community where everything is connected to the internet.
Satellites are used to provide communication services to areas where wired cables cannot reach. Satellites may be geostationary or non-geostationary. Geostationary satellites remain permanently in the same area of the sky as viewed from a specific location on earth, because the satellite is orbiting the equator with an orbital period of exactly one day. Non-geostationary satellites typically operate in low- or mid-earth orbit, and do not remain stationary relative to a fixed point on earth; the orbital path of a satellite can be described in part by the plane intersecting the center of the earth and containing the orbit. Each satellite may be equipped with communication devices called inter-satellite links (or, more generally, inter-device links) to communicate with other satellites in the same plane or in other planes. The communication devices allow the satellites to communicate with other satellites. These communication devices are expensive and heavy. In addition, the communication devices significantly increase the cost of building, launching and operating each satellite; they also greatly complicate the design and development of the satellite communication system and associated antennas and mechanisms to allow each satellite to acquire and track other satellites whose relative position is changing. Each antenna has a mechanical or electronic steering mechanism, which adds weight, cost, vibration, and complexity to the satellite, and increases risk of failure. Requirements for such tracking mechanisms are much more challenging for inter-satellite links designed to communicate with satellites in different planes than for links, which only communicate with nearby satellites in the same plane, since there is much less variation in relative position. Similar considerations and added cost apply to high-altitude communication balloon systems with inter-balloon links.
One aspect of the disclosure provides a fan beam antenna. The fan beam antenna includes a parallel plate waveguide configured to guide electromagnetic energy of an emission beam and a reflector disposed on the parallel plate waveguide configured to reflect the electromagnetic energy of the emission beam. The antenna further includes a plurality of radiating elements disposed on the parallel plate waveguide configured to transmit and/or receive the electromagnetic energy of the emission beam and a microwave transceiver module in communication with the plurality of radiating elements. The fan beam antenna includes a rotation assembly disposed on the parallel plate waveguide configured to rotate the parallel plate waveguide about a rotation axis defined substantially normal to a broad surface of the parallel plate waveguide.
Implementations of the disclosure may include one or more of the following optional features. In some implementations, the axis of rotation is the sole axis of rotation. The rotation assembly is further configured to rotate the parallel plate waveguide while maintaining the parallel plate waveguide within a plane of rotation. Additionally or alternatively, the rotation assembly may include a motor coupled to the parallel plate waveguide and a position sensor configured to sense an angle of rotation of the parallel plate waveguide about the rotation axis.
In some examples, the rotation assembly further includes an antenna alignment controller in communication with the position sensor and the motor. The antenna alignment controller is configured to control the angle of rotation of the parallel plate waveguide about the rotation axis by comparing a first position of the fan beam antenna with a second position of the ground station and determining an alignment angle of rotation of the parallel plate waveguide about the rotation axis to establish a communication link between the fan beam antenna and the ground station.
The transceiver module may include a modem configured to provide data to the plurality of radiating elements. The plurality of radiating elements may be configured to transmit and receive data at a frequency greater than 5.8 GHz. The emission beam may have a half power full beam height along a first axis of between about 0.1 degrees and about 5 degrees and a beam width along a second axis perpendicular to the first axis of between about 10 degrees and about 70 degrees.
Another aspect of the disclosure provides a communication system. The communication system includes an unmanned aerial system, a fan beam antenna disposed on the unmanned aerial system, and a ground station in communication with the fan beam antenna disposed on the antenna aerial system. The fan beam includes a parallel plate waveguide configured to guide electromagnetic energy of an emission beam and a reflector disposed on the parallel plate waveguide configured to reflect the electromagnetic energy of the emission beam. The fan beam antenna further includes a plurality of radiating elements disposed on the parallel plate waveguide configured to transmit and/or receive the electromagnetic energy of the emission beam and a microwave transceiver module in communication with the plurality of radiating elements. This aspect may include one or more of the following optional features. The communication system further includes a rotation assembly disposed on the unmanned aerial system and rotatably supporting the fan beam antenna.
In some implementations, the unmanned aerial system moves along a closed loop path and the rotation assembly rotates about a rotation axis defined substantially normal to a broad surface of the parallel plate waveguide to maintain communication with the ground station. The rotation assembly is configured to rotate the fan beam antenna while maintaining the parallel plate waveguide within a plane of rotation. The rotation assembly may further include a motor coupled to the parallel plate waveguide and a position sensor configured to sense an angle of rotation of the parallel plate waveguide about the rotation axis. The motor may rotate the fan beam antenna in relation to a signal strength of the emission beam.
In some implementations, the unmanned aerial system includes a body, a global positioning system disposed on the body and an antenna alignment controller in communication with the global positioning system, the position sensor, and the motor. The antenna controller is configured to control the angle of rotation of the parallel plate waveguide about the rotation axis by controlling the motor. The antenna alignment controller controls the angle of rotation of the parallel plate waveguide about the rotation axis by comparing a first position determined by the global positioning system with a second position of the ground station and determining an alignment angle of rotation of the parallel plate waveguide about the rotation axis to establish a communication link between the fan beam antenna and the ground station. The plurality of radiating elements is configured to transmit and receive data at a frequency greater than 5.8 GHz. The emission beam may have a half power full beam height along a first axis of between about 0.1 degrees and about 5 degrees and a beam width along a second axis perpendicular to the first axis of between about 10 degrees and about 70 degrees.
Yet another aspect of the disclosure provides a method for operating a fan beam antenna. The method includes operating, using data processing hardware, an unmanned aerial system having a fan beam antenna in communication with the data processing hardware. The fan beam antenna includes a parallel plate waveguide configured to guide electromagnetic energy and a reflector disposed on the parallel plate waveguide and configured to reflect the electromagnetic energy. The fan beam antenna further includes a plurality of radiating elements disposed on the parallel plate waveguide configured to transmit a first emission beam to a ground station and/or receive a second emission beam from the ground station and a microwave transceiver module in communication with the plurality of radiating elements. The method further includes rotation the fan beam antenna to establish a communication link between the fan beam antenna and the ground station, transmitting, by the data processing hardware, downlink data in the first emission beam from the fan beam antenna to the ground station and receiving uplink data in the second emission beam from the ground station to the fan beam antenna of the unmanned aerial system. Rotating the fan beam antenna includes rotating the parallel plate waveguide about a rotation axis defined substantially normal to a broad surface of the parallel plate waveguide.
In some examples, the rotation axis is the sole axis of rotation. The method may further include rotating the fan beam antenna while maintaining the parallel plate waveguide within a plane of rotation. The method further includes receiving, at the data processing hardware, a first position from a global positioning system of the unmanned aerial system, comparing, at the data processing hardware, the first position with a second position of the ground station and controlling, by the data processing hardware, the rotating of the fan beam antenna to maintain the communication link between the fan beam antenna and the ground station.
The plurality of radiating elements may be configured to transmit and receive data at a frequency greater than 5.8 GHz. Each emission beam may have a half power full beam height along a first axis of between about 0.1 degrees and about 5 degrees and a beam width along a second axis perpendicular to the first axis of between about 10 degrees and about 70 degrees. The method may further include transmitting the downlink data in the first emission beam from the fan beam antenna to the ground station via an electromagnetic wave having a frequency greater than about 30 GHz.
The details of one or more implementations of the disclosure are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages will be apparent from the description and drawings, and from the claims.
Like reference symbols in the various drawings indicate like elements.
Referring to
The HAPs 200 may move about the earth 5 along a path, trajectory, or orbit 202 (also referred to as a plane, since their orbit or trajectory may approximately form a geometric plane). Moreover, several HAPs 200 may operate in the same or different orbits 202. For example, some HAPs 200 may move approximately along a latitude of the earth 5 (or in a trajectory determined in part by prevailing winds) in a first orbit 202a, while other HAPs 200 may move along a different latitude or trajectory in a second orbit 202b. The HAPs 200 may be grouped amongst several different orbits 202 about the earth 5 and/or they may move along other paths 202 (e.g., individual paths). Similarly, the satellites 300 may move along different orbits 302, 302a-n. Multiple satellites 300 working in concert form a satellite constellation. The satellites 300 within the satellite constellation may operate in a coordinated fashion to overlap in ground coverage. In the example shown in
Referring to
Communication balloons 200a are typically released in to the earth's stratosphere to attain an altitude between 11 to 23 miles and provide connectivity for a ground area of 25 miles in diameter at speeds comparable to terrestrial wireless data services (such as, 3G or 4G). The communication balloons 200a float in the stratosphere at an altitude twice as high as airplanes and the weather (e.g., 20 km above the earth's surface). The high-altitude balloons 200a are carried around the earth 5 by winds and can be steered by rising or descending to an altitude with winds moving in the desired direction. Winds in the stratosphere are usually steady and move slowly at about 5 and 20 mph, and each layer of wind varies in direction and magnitude.
Referring to
In some implementations, a satellite 300 includes a satellite body 304 having a data processing device 310, e.g., similar to the data processing device 310 of the HAPs 200. The data processing device 310 executes algorithms to determine where the satellite 300 is heading. The satellite 300 also includes an antenna 320 for receiving and transmitting a communication 20. The satellite 300 includes solar panels 308 mounted on the satellite body 204 for providing power to the satellite 300. In some examples, the satellite 300 includes rechargeable batteries used when sunlight is not reaching and charging the solar panels 308.
When constructing a global-scale communications system 100 using HAPs 200, it is sometimes desirable to route traffic over long distances through the system 100 by linking HAPs 200 to satellites 300 and/or one HAP 200 to another. For example, two satellites 300 may communicate via inter-device links and two HAPs 200 may communicate via inter-device links. Inter-device link (IDL) eliminates or reduces the number of HAPs 200 or satellites 300 to gateway 110 hops, which decreases the latency and increases the overall network capabilities. Inter-device links allow for communication traffic from one HAP 200 or satellite 300 covering a particular region to be seamlessly handed over to another HAP 200 or satellite 300 covering the same region, where a first HAP 200 or satellite 300 is leaving the first area and a second HAP 200 or satellite 300 is entering the area. Such inter-device linking IDL is useful to provide communication services to areas far from source and destination ground stations 110a, 110b and may also reduce latency and enhance security (fiber optic cables may be intercepted and data going through the cable may be retrieved). This type of inter-device communication is different than the “bent-pipe” model, in which all the signal traffic goes from a source ground station 110a to a satellite 300, and then directly down to a to destination ground station 110b (e.g., user terminal) or vice versa. The “bent-pipe” model does not include any inter-device communications. Instead, the satellite 300 acts as a repeater. In some examples of “bent-pipe” models, the signal received by the satellite 300 is amplified before it is re-transmitted; however, no signal processing occurs. In other examples of the “bent-pipe” model, part or all of the signal may be processed and decoded to allow for one or more of routing to different beams, error correction, or quality-of-service control; however no inter-device communication occurs.
In some implementations, large-scale communication constellations are described in terms of a number of orbits 202, 302, and the number of HAPs 200 or satellites 300 per orbit 202, 302. HAPs 200 or satellites 300 within the same orbit 202, 302 maintain the same position relative to their intra-orbit HAP 200 or satellite 300 neighbors. However, the position of a HAP 200 or a satellite 300 relative to neighbors in an adjacent orbit 202, 302 may vary over time. For example, in a large-scale satellite constellation with near-polar orbits, satellites 300 within the same orbit 202 (which corresponds roughly to a specific latitude, at a given point in time) maintain a roughly constant position relative to their intra-orbit neighbors (i.e., a forward and a rearward satellite 300), but their position relative to neighbors in an adjacent orbit 302 varies over time. A similar concept applies to the HAPs 200; however, the HAPs 200 move about the earth 5 along a latitudinal plane and maintain roughly a constant position to a neighboring HAP 200.
A source ground station 110a may be used as a connector between satellites 300 and the internet, or between HAPs 200 and user terminals 110b. In some examples, the system 100 utilizes the source ground station 110a as linking-gateways 110a for relaying a communication 20 from one HAP 200 or satellite 300 to another HAP 200 or satellite 300, where each HAP 200 or satellite 300 is in a different orbit 202, 302. For example, the linking-gateway 110a may receive a communication 20 from an orbiting satellite 300, process the communication 20, and switch the communication 20 to another satellite 300 in a different orbit 302. Therefore, the combination of the satellites 300 and the linking-gateways 110a provide a fully-connected system 100. For the purposes of further examples, the gateways 110 (e.g., source ground stations 110a and destination ground stations 110b), shall be referred to as ground stations 110.
One of the challenges associated with establishing a communication system between a HAP 200 and ground station 110 is the movement of the HAP 200. One solution to this problem is the use of an omnidirectional antenna system on the HAP 200 and ground station 110. This present disadvantages as an omnidirectional antenna has a lower gain and therefore range in exchange for its ability to receive from all directions. A directional antenna may be used to improve the gain and range of the system, but this presents its own challenges as depending on how directional the antenna is, the craft may move out of the antennas transmission or reception area. When using a directional antenna, a system needs to move both of the antennas (i.e., the HAP antenna and the ground terminal antenna) to keep the antennas aligned between the aircraft and the ground. This becomes more challenging with greater directionality of the antenna. Additionally, various conditions may cause the HAP 200 to unintentionally move location, such as, but not limited to, wind, thermals, other craft, turbulence, etc., making the system moving the antenna forced to rapidly correct if continuous communication is required. A highly directional antenna may create a narrow cone transmission shape requiring the antenna to be moved on two axes to maintain alignment. This disclosure presents a fan beam antenna 500 having a single axis controller that allows 360 degree rotation of the antenna for continuous coverage of a link to a fixed ground station, while the HAP 200 files a nominally circular flight path.
The combination of the parallel plate waveguide 514 and reflector 516 serves to direct electromagnetic energy from the circular array elements 512 that would be emitted in a direction other than the desired direction to be reflected in the desired direction. This allows the emitted electromagnetic energy to be focused into a beam or other desired shape. In some examples, the wide beam in one axis and narrow beam in a second axis creates a fan shape emission. The parallel plate waveguide 514 and reflector 516 may be composed of a material configured to reflect electromagnetic energy in the frequencies greater than 5.8 GHz such as, but not limited to, the microwave wave frequencies 5.8 GHz to 42 GHz and millimeter wave frequencies greater than 42 GHz. The parallel plate waveguide 514 and reflector 516 may be composed of a material configured to reflect electromagnetic energy only in the microwave wave frequencies of 5.8 GHz to 42 GHz or only in the millimeter wave frequencies greater than 42 GHz. Although the parallel plate waveguide 514 and reflector 516 geometry may be parabolic, the exact curvature may be optimized using simulations of the antenna to optimize the antenna pattern characteristics such as, but not limited to, the gain, sidelobe levels, width and reflected frequencies, etc.
In some examples, the circular array elements 512 are composed of a plurality of antenna elements or may be composed of non-circular elements. The circular array elements 512 may be various types of antennas such as, but not limited to, dipole, monopole, helical, yagi, spiral, parabolic, bow-tie, log-periodic, etc. Additionally, the circular array elements 512 may be configured to transmit on a specific frequency or multiple frequencies. The spacing, orientation, or location of the circular array elements 512 within the parallel plate waveguide 514 and reflector 516 may serve to increase the gain of the system or alter the frequency response of the antenna array 510.
A modem 624 receives a high speed data signal 628 containing data and information to be transmitted by the antenna array 510 and converts the high speed data signal 628 to a form suitable for the transceiver 620. The transceiver 620 converts the signal from the modem 624 to a suitable form to be transmitted by electromagnetic energy. The transceiver transmits the electromagnetic energy into the antenna array 510, which emits an emission beam 640. The emission beam 640 contains the high speed data signal 628 used for communicating with the ground station 110.
In some examples, the transceiver 620 outputs a radio frequency (RF) received power signal 622 to the antenna alignment controller 610. The RF received power signal 622 is an indication of signal strength of the emission beam 640 being received by the antenna array 510. The modem 624 may also transmit a baseband received signal power 626 to the antenna alignment controller 610. The baseband received signal power 626 may be an indicator of the quality and strength of the baseband carrier wave. The antenna alignment controller 610 can use the RF received power signal 622 and the baseband received signal power 626 to adjust the desired rotation angle 616 of the antenna array 510 for optimum reception. In some environments, due to interference, multi-pathing, or general radio noise, the optimal reception or transmission of the electromagnetic signal may not be a direct line between the antenna array 510 and ground station 110. The antenna alignment controller 610 can use the information from the RF received power signal 622 and baseband received signal power 626 to adjust the angle to mitigate these problems. Additionally, the antenna alignment controller 610 can use the information in the RF received power signal 622 and baseband received signal power 626 to determine if a HAP 200 is traveling out of range or through a null signal spot and may respond accordingly by altering its location, changing the signal power, or transmitting to a different ground station 110. The antenna alignment controller 610 may include data processing hardware 650. The data processing hardware 650 is the necessary hardware to process data including transmissions, positional computations and other necessary information. In one example, the data processing hardware 650 includes the modem 624, GPS 612, and the antenna alignment controller 610. The modem 624 processes general data, such as the high speed data 628. The GPS 612 receives data signals from positional satellites and processes them to determine the current systems location 614. In additional examples, the data processing hardware 650 is a computer processing unit (CPU), microcontroller, peripheral interface controller (PIC), or other controller. The antenna alignment controller 610 processes various information required for the operation of the fan beam antenna 500 including using the location 614 processed by the GPS 612, RF received power signal 622, and baseband received signal power 626 to determine the rotation angle 616.
At block 920, the method 900 includes rotating the fan beam antenna 500 to establish a communication link between the fan beam antenna 500 and the ground station 110. The rotating assembly 530 rotates the fan beam antenna 500. The rotation assembly 530 includes a motor 532 connected to the support plate 536. The motor may drive a belt 534 to control the rotation angle 616. The desired rotation angle 616 may be determined by the antenna alignment controller 610. The antenna alignment controller 610 may read the current rotation angle 616 of the fan beam antenna from the position sensor 538. The GPS 612 may report the location 614 of the fan beam antenna 500 to the antenna alignment controller 610. Using the location 614 the antenna alignment controller can determine the rotation angle 616 in order for the emission beam 640 to contact the ground station 110. At block 930, the method 900 includes transmitting, by the data processing hardware 650, downlink data 628 in the first emission beam 640 from the antenna array 510 to the ground station 110. Once the emission beam 640 is in contact with the ground station 110 data, such as the high speed data signal 628, it may be converted by the modem 624 and transceiver 620 into a format that is acceptable to communicate data using an electromagnetic beam through the emission beam 640. At block 940, the method 900 includes receiving uplink data 628 in the second emission beam 640 from the ground station 110 to the fan beam antenna 500 of the unmanned aerial system or HAP 200. The fan beam antenna 500 may receive data, such as the high speed data signal 628 from the ground station 110. When the fan beam antenna 500 is receiving data from the ground station 110, the parallel plate waveguide 514 and the reflector 516 channel the second emission beam 640 to the plurality of radiating elements 512. The transceiver 620 receives the signal from the plurality of radiating elements 512 and converts it into a suitable form for the modem 624. The modem 624 then converts the signal from the transceiver 620 into a high speed data signal 628.
In at least one example, rotating the fan beam antenna 500 includes rotating the parallel plate waveguide 514 about a rotation axis defined substantially normal to a broad surface of the parallel plate waveguide. The fan beam antenna 500 may be rotated while maintaining the parallel plate waveguide 514 within a plane of rotation. The method 900 may include the step of receiving, at the data processing hardware 650, a first position or location 614 from a global positioning system 612 of the unmanned aerial system or HAP 200. The data processing hardware 650 may then compare the first position or location 614 with a second position or location 614 of the ground station 110. The data processing hardware 650 may then control the rotating of the fan beam antenna 500 to maintain the communication link or emission beam 640 between the fan beam antenna 500 and the ground station 110. The plurality of radiating elements 512 may transmit and receive data, such as the high speed data signal 628 at a frequency greater than 5.8 GHz. The emission beam 640 may have a half power full beam height along a first axis, such as the x axis 810, of between about 0.1 degrees and about 5 degrees and a beam width along a second axis, such as the y axis 812 perpendicular to the first axis of between about 10 degrees and about 70 degrees. A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.
