Patent Description:
The following relates generally to antenna systems, and more specifically to an ultra-low cost high performance satellite aperture.

In satellite systems, many different antenna types are used with specialized properties for particular applications. For example, a satellite may utilize a dish antenna to receive and transmit signals. The dish antenna may consist of a parabolic reflective surface and a central feed horn. The parabolic surface facilitates the convergence of incident beams where the incident beams are reflected to the central feed horn, which is positioned at the focal point of the curvature. When the dish antenna receives signals, the incoming signal becomes much more consolidated due to the combined energy of individual radio signals. Another example of an antenna is an active electronically scanned array (AESA). An AESA is a type of phased array antenna in which the beam of signals can be steered electronically in any direction, without physically moving the antenna. The antenna consists of an array of regularly spaced small antennas each with a separate feed. The beam is steered electronically by controlling the phase of the radio waves transmitted and received by each of the multiple radiating elements in the antenna. This digitally controlled scanning nature of the AESA allows it to quickly scan any direction in comparison to a mechanically scanned radar, whose range is constrained by the direction it is facing and how quickly its motors can turn it. However, each antenna type has certain drawbacks that make them ill-suited for every application. For example, each antenna type varies in size, mechanical complexity, power, cooling, weight, price, etc., which may dictate which antenna is to be used for a particular function. In some cases, an antenna that is uncomplicated mechanically and low cost may be desired. <CIT> discloses a phased array antenna in space which receives a beacon signal from an earth based beacon station at each of a plurality of antenna elements which make up the array. <CIT> discloses a method and apparatus for reconfiguring a photonic TR beacon. <CIT> discloses a digital spacecraft antenna tracking system and method which utilize an array of antenna feed elements oriented relative to a shaped spacecraft reflector antenna system each of which generates an output signal corresponding to a received incident signal. <CIT> discloses fast training of phased arrays using multilateration estimate of the target device location. <CIT> discloses satellite communication systems, and one particular implementation relates to a satellite communications system that can create and reconfigure multiple beam coverage shapes and areas.

In an aspect, a method for receiving radio waves at an antenna system is provided as defined in claim <NUM>.

The described techniques relate to improved methods, systems, devices, and apparatuses for an ultra-low cost high performance satellite aperture. An antenna system of a satellite may consist of an antenna receiver that is coupled to a plurality of flexible couplings. The couplings may each be affixed to one or more antenna elements. The couplings may be deployed in space in an uncontrolled manner. Additionally, the spacing between the couplings, and in turn the antenna elements, may be spaced in an uncontrolled manner. The antenna elements may have no pointing requirements. The antenna system may receive training signals and associate an antenna element to a time of arrival based on the training signal. Upon receiving a data signal, the antenna system may apply coefficients determined from the association of the antenna element to the time of arrival to the data signal to discover wanted signal coherence among the antenna elements.

The described features generally relate to an antenna system where the antenna elements of the system each have an imprecise placement in space. Each of the antenna elements may be flexibly coupled to an antenna receiver, and the couplings may be deployed in space in an uncontrolled manner. Upon receiving data signals from a transmitter, the antenna system may apply linear algebra and multiple-input multiple-output (MIMO) signal processing to discover signal energy coherence to coherently add all the collected signal energy.

In contrast to other antenna systems, such as dish antenna systems, the present antenna system has low mechanical complexity and may be produced at low relative cost. For example, a dish antenna may have high manufacturing tolerances to maintain signal energy coherence. Also the high gain of the present system would be equivalent to the gain of a dish antenna with a very large diameter. Using a dish antenna with a very large diameter would not only increase manufacturing cost, but also its use would increase other costs such as transportation and integration costs since the dish antenna would need to be transported and assembled in space. In addition, the directionality of the present antenna system is configurable as opposed to conventional antenna systems, reducing mechanical complexity involved in antenna pointing.

This description provides examples, and is not intended to limit the scope, applicability or configuration of embodiments of the principles described herein. Rather, the ensuing description will provide those skilled in the art with an enabling description for implementing embodiments of the principles described herein. Various changes may be made in the function and arrangement of elements.

Thus, various embodiments may omit, substitute, or add various procedures or components as appropriate within the scope of the appended claims. For instance, it should be appreciated that the methods may be performed in an order different than that described, and that various steps may be added, omitted or combined within the scope of the appended claims. Also, aspects and elements described with respect to certain embodiments may be combined in various other embodiments. It should also be appreciated that the following systems, methods, and devices may individually or collectively be components of a larger system, wherein other procedures may take precedence over or otherwise modify their application.

<FIG> is a simplified diagram of a satellite communications system <NUM> in which the principles included herein may be described. The satellite communications system <NUM> may provide a communication service across at least portions of a visible earth area from the position of the satellite <NUM>. Satellite <NUM> may be any suitable type of satellite, for example a geostationary orbit (GEO) satellite, medium earth orbit (MEO) satellite, or low earth orbit (LEO) satellite. Satellite may provide the communication service via user beams <NUM>, which may each provide coverage for a user beam coverage area. Although only a single user beam <NUM> is illustrated, satellite <NUM> may be a multi-beam satellite, transmitting a number (e.g., typically <NUM>-<NUM>, etc.) of user beams <NUM> each directed at a different region of the earth. This can allow coverage of a relatively large geographical area and frequency re-use within the covered area. Frequency re-use in multi-beam satellite systems permits an increase in capacity of the system for a given system bandwidth.

Each satellite beam <NUM> of the satellite <NUM> may support a number of user terminals <NUM>. User terminals <NUM> may receive data from satellite <NUM> via forward downlink signals <NUM>-a and transmit data via return uplink signals <NUM>-a. A user terminal <NUM> may be any two-way satellite fixed or mobile ground station such as a very small aperture terminal (VSAT). Each satellite beam <NUM> may support other terminals such as multi-user access terminals <NUM>, which may also be fixed or located on a mobile platform <NUM> such as an aircraft, ship, vehicle, train, or the like. As illustrated in <FIG>, a satellite beam <NUM>, which may be assigned to a particular frequency range and polarization, may carry forward downlink signals <NUM> or return uplink signals <NUM> for both fixed terminals <NUM> and multi-user access terminals <NUM>. The forward downlink signals <NUM> or return uplink signals <NUM> for user terminals <NUM> and multi-user access terminals <NUM> may be multiplexed within the satellite beam <NUM> using multiplexing techniques such as time-division multiple access (TDMA), frequency-division multiple access (FDMA), multi-frequency time-division multiple access (MF-TDMA), code-division multiple access (CDMA), orthogonal frequency division multiple access (OFDMA), and the like.

Satellite communications system <NUM> includes a gateway system <NUM> and a network <NUM>, which may be connected together via one or more wired or wireless links. Gateway system <NUM> is configured to communicate with one or more user terminals <NUM> or multi-user access terminals <NUM> via satellite <NUM>. Network <NUM> may include any suitable public or private networks and may be connected to other communications networks (not shown) such as the Internet, telephony networks (e.g., Public Switched Telephone Network (PSTN), etc.), and the like. Network <NUM> may connect gateway system <NUM> with other gateway systems, which may also be in communication with satellite <NUM> or other satellites. Alternatively, a separate network linking gateways and other nodes may be employed to cooperatively service user traffic. Gateway system <NUM> may also be configured to receive return signals from user terminals <NUM> or multi-user access terminals <NUM> (via the satellite <NUM>) that are directed to a destination in network <NUM> or the other communication networks.

Gateway system <NUM> may be a device or system that provides an interface between network <NUM> and satellite <NUM>. Gateway system <NUM> may use an antenna <NUM> to transmit signals to and receive signals from satellite <NUM> via a forward uplink signals <NUM> and return downlink signals <NUM>. Antenna <NUM> may be two-way capable and designed with adequate transmit power and receive sensitivity to communicate reliably with satellite <NUM>. In one embodiment, satellite <NUM> is configured to receive signals from antenna <NUM> within a specified frequency band and specific polarization. Although illustrated as including one satellite <NUM>, satellite communications system <NUM> may include multiple satellites. The multiple satellites may have service coverage areas that at least partially overlap with each other.

Each satellite user beam <NUM> of satellite <NUM> supports user terminals <NUM> or multi-user access terminals <NUM> within its coverage area (e.g., providing uplink and downlink resources). Frequency re-use between satellite user beams <NUM> may be provided by assigning one, or more, ranges of frequencies (which may be referred to as channels) to each satellite user beam <NUM> and/or by use of orthogonal polarizations. A particular frequency range and/or polarization may be called a "color," and frequency re-use in a tiled spot beam satellite system may be according to color.

The coverage of different satellite user beams <NUM> may be non-overlapping or have varying measures of overlap, up to and including a <NUM>% overlap. In one example, satellite user beams <NUM> of satellite <NUM> may be tiled and partially overlapping to provide complete or almost complete coverage for a relatively large geographical area where partially overlapping or adjacent beams use different ranges of frequencies and/or polarizations (e.g., different colors).

Satellite <NUM> may provide network access service to communication devices (e.g., computers, laptops, tablets, handsets, smart appliances) connected to user terminal <NUM> or to communication devices <NUM> of passengers <NUM> on board mobile platform <NUM>. For example, passengers <NUM> may connect their communication devices <NUM> via wired (e.g., Ethernet) or wireless (e.g., WLAN) connections <NUM>. Multi-user access terminal <NUM> may obtain the network access service via user beam <NUM>.

Multi-user access terminal <NUM> may use an antenna <NUM> mounted on mobile platform <NUM> to communicate via forward downlink signals <NUM>-a and return uplink signals <NUM>-a. Where multi-user access terminal <NUM> is located on a mobile vehicle, antenna <NUM> may be mounted to an elevation and azimuth gimbal which points antenna <NUM> (e.g., actively tracking) at satellite <NUM>. Satellite communications system <NUM> may operate in the International Telecommunications Union (ITU) Ku, K, or Ka-bands (for example from <NUM> to <NUM> Giga-Hertz (GHz) in the downlink and <NUM> to <NUM> in the uplink portion of the Ka-band). Alternatively, satellite communications system <NUM> may operate in other frequency bands such as C-band, X-band, S-band, L-band, UHF, VHF, and the like.

It should be appreciated by a person skilled in the art that one or more aspects of the disclosure may be implemented in a system <NUM> to additionally or alternatively solve other problems than those described herein. Furthermore, aspects of the disclosure may provide technical improvements to "conventional" systems or processes as described herein. However, the description and appended drawings only include example technical improvements resulting from implementing aspects of the disclosure, and accordingly do not represent all of the technical improvements provided within the scope of the claims.

In one example, satellite <NUM> includes or is coupled with an antenna system <NUM> which includes an antenna transceiver system that is coupled to a plurality of flexible couplings. The couplings may each connect the receiver to one or more antenna elements. The antenna transceiver system may have one or more transceivers. The antenna system may be <NUM> may be packaged for deployment of satellite <NUM> in a compact arrangement of the flexible couplings and the antenna elements. Once the satellite <NUM> reaches a target orbit (e.g., LEO, MEO, GEO), the couplings may be deployed in space to spread the antenna elements over an area for the aperture of the antenna system. The deployed locations of each antenna element may not be predetermined or controlled during deployment. Thus, the spacing between the couplings, and in turn the antenna elements, may not be predefined prior to deployment, and may be spaced in an uncontrolled manner by the physical properties of the flexible couplings. Satellite <NUM> may possess one or more features as described herein with respect to the disclosed antenna system <NUM>.

After deployment, antenna system <NUM> of satellite <NUM> may receive training signals from various transmitting devices, such as antenna <NUM>, user terminal <NUM>, or antenna <NUM>. One or more antenna elements of antenna system <NUM> may receive these training signals and a processor of antenna system <NUM> may determine position-related information such as time-of-arrival (TOA) parameters and associate the TOA parameters to respective antenna elements. Antenna system <NUM> may further determine reception coefficients based on the TOA parameters. Each coefficient may be based on a unique (e.g., per transceiver) time of arrival signature (e.g., eigenmode). Antenna system <NUM> may receive subsequent signals from antenna <NUM>, user terminal <NUM>, or antenna <NUM> such as data signals, and a processor of antenna system <NUM> may process the data signals utilizing the coefficients. The transmitter transmitting the data signals may be a same or different transmitter from the one that transmitted the training signals.

Antenna system <NUM> may also allow frequency re-use between satellite user beams <NUM> to be obtained by the unique weighting of time-of-arrival between satellite user beams <NUM> end points where user beam end points are the satellite <NUM> and terminals (e.g., antennas of user terminal <NUM> or multi-user access terminal <NUM>). Because the weighting of time-of-arrivals is unique, the signal communications carried by satellite user beams <NUM> may be uniquely separated from other satellite user beams (e.g., through linear algebra). For example, each user beam <NUM> may be associated with a different set of coefficients. Hence the entire frequency assigned to each satellite user beam <NUM> may be reused by other satellite user beams with no or negligible impairment of system communication performance. The uniqueness of weighting of time-of-arrival between satellite user beams <NUM> and end points may be determined by the diameter of a volumetric 3D shape of antenna system <NUM>, the number of antenna elements of antenna system <NUM>, the separation between user terminals, or a combination thereof.

Multiple satellite user beams <NUM> and signals associated with the beams having the same frequency range can be received at the same time and distinguished via weighting coefficients. The size of the volumetric shape and number of elements determine the spatial or geographic resolution for distinguishing signals from different transmitters using different angles of arrival. The design may be able to achieve a resolution in the <NUM> to <NUM> range (e.g., with a volumetric 3D shape of approximately <NUM> and <NUM>,<NUM> elements in a LEO configuration), and thus may support very small effective user beams.

<FIG> illustrates an example of an antenna system <NUM>-a for wireless communications that supports an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. Antenna system <NUM>-a may include antenna transceiver system <NUM>, branches <NUM>, antenna elements <NUM>, and couplings <NUM>, and may be part of or coupled with a satellite <NUM>. Antenna system <NUM>-a may be an example or implement aspects of antenna system <NUM> of <FIG>. Antenna system <NUM>-a may be an example of an n-layer MIMO antenna. In some examples, antenna system <NUM>-a may be a <NUM>-layer MIMO antenna.

Antenna transceiver system <NUM> may receive signals, such as training signals and data signals. Antenna transceiver system <NUM> may include multiple transceivers <NUM> and a processor <NUM>. Each transceiver <NUM> may be connected to one or more antenna elements <NUM> (or leaf antennas), via a flexible coupling <NUM>. Flexible coupling <NUM> may be constructed out of a flexible or semi-rigid material (e.g., wire, coated wire, coaxial cable, twisted pairs of wires, shielded wires, electrically conductive mechanical swivels, springs, rotators, gimbles, etc.) that electrically couples to the one or more antenna elements while not constraining the deployed location of the one or more antenna elements <NUM> in each dimension. That is, the deployed positions of the one or more antenna elements <NUM> may be constrained by their position along the flexible coupling, but may otherwise be unconstrained in one or more spatial dimensions. In some cases, the manner of an uncontrolled deployment of antenna elements <NUM> is within a range of pliability of flexible coupling <NUM>. In some examples, antenna elements <NUM> may be attached to flexible coupling <NUM> via a coupler while in other examples, antenna elements <NUM> may be directly attached to flexible coupling <NUM>. Although the precise positioning of antenna elements <NUM> may be uncontrolled, spatial separation of the antenna elements may allow for mutual coupling to be insignificant. In some examples, antenna system <NUM>-a may include a quantity of antenna elements <NUM> greater than <NUM>, or greater than <NUM>.

The energy received by antenna system <NUM>-a may be proportional to the sum of the cross-sectional area of the effective aperture of antenna elements <NUM>. The array gain of antenna system <NUM>-a may be the sum of signal energy collected from the effective aperture of each antenna element <NUM>. The gain of antenna system <NUM>-a may be expressed as: <MAT> Antenna elements <NUM> may be randomly oriented (e.g., spatial locations not predetermined or precisely controlled) and may feature a large satellite aperture baseline. For example, antenna elements <NUM> may feature a baseline of greater than <NUM> meters, greater than <NUM> meters, greater than <NUM> meters, greater than a kilometer. Antenna system <NUM>-a may use various types of antenna elements <NUM> (e.g., dipole, biconic, monopole, patch), and each antenna element <NUM> may be the same type, or antenna system <NUM>-a may use a combination of different types, in some cases.

In their totality when deployed, antenna elements <NUM> may form a volumetric shape. In some examples, at least one dimension of the volumetric shape may be more than <NUM> times a distance of a wavelength of a data signal. In another example, an orientation of the volumetric shape is uncontrolled relative to an orbital position of the satellite, and in some cases an orientation of satellite <NUM> or antenna system <NUM>-a may be uncontrolled during orbit (e.g., satellite <NUM> or antenna system <NUM>-a may not use active attitude control). In some examples, the volumetric shape may be roughly spherical such that signals transmitted from any arbitrary angle and traversing the volumetric shape include a traversal of a diameter <NUM> (e.g., at least a minimum diameter) of the volumetric shape.

Antenna system <NUM>-a may have the same number of transceivers <NUM> as antenna elements <NUM>. For example, each of antenna elements <NUM> may be linked to its own transceiver <NUM> (e.g., each transceiver <NUM> may be coupled with a single antenna element <NUM>). Alternatively, antenna system <NUM>-a may have fewer transceivers <NUM> than antenna elements <NUM> (e.g., each transceiver <NUM> may be coupled with more than one antenna element <NUM>).

In some examples, each of antenna elements <NUM> may be connected to a transceiver <NUM> via a series of branches <NUM> and leaves <NUM>, with each branch <NUM> connected to one or more leaves <NUM>, and with each leaf <NUM> connected to one or more antenna elements <NUM>. In some examples, the quantity of branches <NUM> may be the same as the quantity of transceivers <NUM>. For example, at least a subset of the branches <NUM> may include more than one antenna element <NUM>, and each transceiver <NUM> may be coupled with one branch <NUM>. The number of antenna elements <NUM> may be identical across all branches <NUM> or they can be different to optimize the antenna array or for power management, interference tolerance, or failed antenna elements. Each branch <NUM> may include thermal management (e.g., a heating element), and power or amplification components. Each leaf <NUM> may couple one or more antenna elements <NUM> to the branch <NUM> via a direct connection or a coupling (e.g., RF coupler). Each branch <NUM> may include components for pre-processing RF signals from the leaves <NUM> coupled with the branch <NUM>. For example, each branch <NUM> may include analog or digital processing components such as filters, low-noise amplifiers, high-power amplifiers, phase shifters, mixers, analog-to-digital converters, or other signal processing components. In some examples, each branch <NUM> includes analog weighting circuitry (e.g., phase shifters, amplitude modulators) for applying analog beamforming weights to signals transmitted or received via the leaves <NUM> of the branch.

Each transceiver <NUM> may include components for RF communications (e.g., filters, a low-noise amplifier, high-power amplifiers, mixers, analog-to-digital converters, demodulators, or other signal processing components). For example, each transceiver <NUM> may include circuitry for MIMO processing such as for maximum ratio combining (MRC) of the signals from each branch <NUM>, leaf <NUM>, or antenna element <NUM> to which it is coupled.

Each branch <NUM> may be considered a sub-aperture of the total synthesized aperture of antenna system <NUM>-a. Although not controlled to be predetermined distances, each branch <NUM> may be separated from another by a branch distance <NUM> and each leaf <NUM> or antenna element <NUM> may be separated from another by leaf distance <NUM>. Thus, branch distance <NUM> and leaf distance <NUM> may be illustrated as average or minimum separable distances, while actual branch distances and leaf distances <NUM> between different branches <NUM> and leaves <NUM> may vary. Branch distance <NUM> or leaf distance <NUM> may provide sufficient separation between branches or leaves such that a time of arrival between the branches or leaves may be easily measured. For example, light travels one meter in <NUM> nanoseconds. Assuming that there is a <NUM> ns discrimination between time of arrival to match conventional digital logic processing, branch distance <NUM> or leaf distance <NUM> may be approximately <NUM> meters. Assuming that there is a <NUM> ns discrimination between time of arrival to match conventional digital logic processing, branch distance <NUM> or leaf distance <NUM> may be approximately <NUM> meters. Leaf distance <NUM> may be separated by a sufficient distance to simplify the radiation pattern into separate and independent collections of the base antenna element radiation pattern. For example, each branch may include leaves <NUM> or antenna elements <NUM> spaced along its length by the leaf distance <NUM> to provide discrimination in time of arrival for each leaf <NUM> (assuming relatively low fold over or loop back of the branch <NUM>. In some cases, some antenna elements <NUM> may end up having a leaf distance <NUM> of less than the minimum distance for discrimination. Where antenna elements <NUM> having less than a minimum leaf distance for discrimination are coupled with different transceivers <NUM> (e.g., via different branches <NUM>), the signals may be discriminated via the different transceivers. Where the antenna elements <NUM> are coupled with the same transceiver <NUM>, coefficients may be combined or the signal may be suppressed to reduce the effects of the composite signal for the antenna elements <NUM> without being discriminated.

In some cases, leaf distances <NUM> or branch distances <NUM> may be maintained using mechanical devices. For example, semi-rigid members (not shown) may be connected at a location along branches <NUM> and may provide a separating force that may tend to keep branches <NUM> apart from each other. The members may be foldable or collapsible for packaging for launch and orbit insertion of a satellite <NUM>. In other examples, the leaves <NUM> or branches <NUM> may be connected to an inflatable structure (e.g., balloon) that is inflated upon deployment. In other examples, a weighted object coupled with an end of a branch <NUM> may be ejected (e.g., via a spring) from satellite <NUM>, and may extend a flexible coupling (e.g., wire) of the branch to a desired extension from satellite <NUM>. In yet other examples, the mechanical force for maintaining branch distances <NUM> or leaf distances <NUM> may come from centrifugal force in deployment or operation. For example, a satellite <NUM> may be inserted into an orbit with a rotation or may use an attitude adjustment mechanism to establish a rotation, and the centrifugal force from the rotation may assist in maintaining the leaf distances <NUM> or branch distances <NUM>.

In addition to forces from pneumatic (inflation), spring, and centrifugal forces, additional examples for deploying leaves <NUM> or branches <NUM> and creating separation for leaf distances <NUM> or branch distances <NUM> include: mechanical ratchets or pawls; chemical reactions which may change structure and harden after deployment to maintain or guide leaf distances <NUM> and branch distances <NUM>; electrostatic forces which attract or repel leaves <NUM> and branches <NUM>; or thermal expansion of the mechanical structures which connect the leaves <NUM> and branches <NUM>. In some instances, miniature reaction jets, pyrotechnic devices, or ion thrusters may be used to deploy, maintain, or guide leaf distances <NUM> and branch distances <NUM> (e.g., to maintain a minimum distance, without strictly controlling position). Any combination or individual selection of these methods may be used.

In one example of a combination of these methods, a large array of patch antennas may be assembled as leaves <NUM> covering all <NUM> Pi steradians on an inflatable ball which also serves as a ground plane. These patch antenna leaves <NUM> may connect via flexible connectors to branches <NUM> which individually connect back to the satellite <NUM> (e.g., to transceivers <NUM>). At deployment, spring forces may be used to eject the branches <NUM> outward which may contain uninflated patch antennas. On reaching deployment, a chemical reaction may be used to harden the branches <NUM> and the leaves <NUM> including inflatable balls of patch antennas (which may be pyrotechnically inflated using pneumatic force to complete the deployment).

In a second example of how these methods may be combined, a large array of biconic antennas may be assembled as biconic antenna leaves <NUM> and may contain a mechanical spring which assumes a proper shape on release from a confining constraint. These biconic antenna leaves <NUM> may connect via flexible connectors to branches <NUM> which individually may connect back to the satellite <NUM>. At deployment, pneumatic forces may be used to inflate the branches <NUM> which may extend the branches outward and simultaneously release the biconic antenna leaves <NUM> from their confining constraint allowing the spring force to force each leaf <NUM> into a predefined shape. On reaching deployment, a chemical reaction may be used to harden the inflated branches to complete the deployment.

In a third example of how these methods may be combined, a large array of dipole antennas may be assembled as leaves <NUM> and may contain a mechanical spring which assumes a predefined shape on release from a confining constraint. These dipole antenna leaves <NUM> may connect via flexible connectors to branches <NUM> which individually may connect back to the satellite <NUM>. At deployment, spring forces may be used to launch the branches <NUM> outward which may release the dipole antenna leaves <NUM> from their confining constraint allowing the spring force to force each leaf <NUM> into the predefined shape. Electrostatic forces may be applied to each branch <NUM> and to each leaf <NUM> of like charge, forcing each leaf <NUM> and branch <NUM> to repel each other to complete the deployment.

In a fourth example of how these methods may be combined, a large array of mixed antenna types of leaves consisting of monopole and patch antennas may be assembled as leaves <NUM>. The leaves <NUM> may cover all <NUM> Pi steradians on a ball which may use spring tension to maintain its shape and may also serve as a ground plane. These monopole and patch antenna leaves <NUM> may connect via flexible connectors to branches <NUM> which individually may connect back to the satellite <NUM>. At deployment, spring forces may be used to launch the branches <NUM> outward which may release the monopole and patch antenna ball leaves <NUM> from their confining constraint allowing the spring force to force each leaf <NUM> into the proper shape. In conjunction with the initial spring forces for launching the branches <NUM> outward, thermal energy received from the sun may strike each branch <NUM> and the material of each branch may expand, forcing a mechanical network of ratchets and pawls to lock into place and forcing each leaf <NUM> and branch <NUM> to complete the deployment.

Interference tolerance within the linear dynamic range of antenna system <NUM>-a is managed via the MIMO selection of the data signal. Interference tolerance (dynamic range compression) is managed via the ratio of the number of antenna elements <NUM> needed to close the link between a user terminal on the ground, satellite <NUM>, and the total number of antenna elements <NUM>.

<FIG> illustrates an example of a signal receiving technique <NUM> for wireless communications that supports an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. In some examples, antenna elements <NUM> may implement aspects of antenna elements <NUM> as described in <FIG>.

Transmitting devices such as antenna <NUM> and/or user terminal <NUM> may send training signals <NUM> to antenna elements <NUM> prior to sending data signals <NUM>. Training signals (e.g., <NUM>-a, <NUM>-b,. <NUM>-n) may arrive at antenna elements <NUM> sequentially or in any overlapping order. In some examples, training signals <NUM> may be received concurrently (e.g., at least partially overlapping in time) at antenna elements <NUM> (e.g., and over the same frequency) if training signals <NUM> are coming from locations separated by a minimum spatial or geographic resolution (e.g., <NUM> - <NUM> range). Training signals <NUM> generally comprise sequences that are known in advance to satellite <NUM>. Training signals <NUM> may be encrypted in order to authenticate and ensure that training signals <NUM> from valid user terminals are processed. In some examples, training signals <NUM> are orthogonal sequences.

Training signals <NUM> may also convey additional information (e.g., through the use of multiple available sequences). In some examples, training signals <NUM> may include location information for a user terminal. For example, a user terminal could know its location (e.g., via GPS or other geolocation signals), and in some cases, may indicate a code associated with the location in the training signals <NUM>. In one example, each user beam is associated with a different code, and a user terminal may determine which beam is serving the user terminal (e.g., using the location information and stored beam coverage area information, or using received signals indicating the user beam). The user terminal may then select a code associated with the beam, or one of a group of codes associated with the beam (e.g., randomly). In some cases, the information may include a priority for the communications. For example, a certain user may have priority or may select between multiple priorities based on a type of data for communication. In other examples, training signals <NUM> may include information such as user terminal type, user type, etc. In some examples, the same transmitting device may send training signals <NUM> and data signals <NUM>. In other examples, the transmitting device sending training signals <NUM> may be different from the transmitting device sending data signals <NUM>. Due to antenna elements <NUM> shifting in space or changing attitude (e.g., without attitude control during orbit), antenna system <NUM> may continually or periodically receive training signals <NUM> for proper channel tracking as the channel and the distance from a particular antenna element <NUM> to the transmitting device regularly changes.

A transceiver (e.g., transceiver <NUM>) may receive a training signal <NUM>-a from one or more antenna elements <NUM> (e.g., antenna element <NUM>-a, antenna element <NUM>-b, and antenna element <NUM>-n). A training processor of antenna system <NUM> (e.g., processor <NUM>) may receive the signals from each respective antenna element <NUM> (e.g., from one or more transceivers) and determine a time of arrival for each of antenna elements <NUM> based on the received training signal <NUM>-a. A beam weight processor of antenna system <NUM> (e.g., processor <NUM>) may determine coefficients for each respective determined time of arrival. At a subsequent time, the one or more transceivers may receive data transmission <NUM>-a received at antenna elements <NUM>. The beam weight processor may then combine the received data signals from each antenna element <NUM> with a respective determined coefficient associated with each antenna element <NUM> to decode data signal <NUM>-a. For example, the beam weight processor may use maximum ratio combining (MRC) to combine the signals according to the determined coefficients. In some cases, the beam weight processor may generate signals for transmission from one or more antenna elements <NUM> based on the determined coefficients.

In one example, the transceiver may receive training signals associated with each data signal. For example, the transceiver may receive training signal <NUM>-b received at each antenna element <NUM> from the same or a different transmitter and determine a time of arrival for each of the plurality of antenna elements <NUM> based on the received training signal <NUM>-b. The beam weight processor may then update the previously determined coefficients (associated with training signal <NUM>-a) with newly determined coefficients from the time of arrival data associated with training signal <NUM>-b for reception of data signal <NUM>-b. Each additional data signal (e.g., data signal <NUM>-n) may be preceded by a training signal (e.g., training signal <NUM>-n).

In another example, the training processor may determine time of arrival information based on multiple training signals (e.g., training signals <NUM><NUM>-a and <NUM><NUM>-b) received from known locations and determine spatial information for each antenna element <NUM>. Using the spatial information, the beam weight processor may determine time of arrivals (e.g., eigenmodes) for each antenna element for a data transmission <NUM> from a known location (which may be the same as one of the known locations for the training signals, or a different location). The beam weight processor may then combine the received data transmission from each antenna element <NUM> with a respective determined coefficient associated with each antenna element <NUM> to decode the data transmission <NUM>.

As described above, antenna elements <NUM> may be associated with branches, where each branch may have multiple antenna elements <NUM> and may include circuitry for pre-processing signals. In some examples, determining the coefficients for each training signal <NUM> associated with a data signal <NUM> may be performed on a branch basis. For example, the antenna elements <NUM> on each branch may be characterized or calibrated based on training signals from one or more sources (e.g., from at least two physically separated transmitters), and the circuitry (e.g., analog weighting circuitry) of the branch may combine signals received by the elements <NUM> of the branch into a combined branch signal. The transceiver may then receive training signals associated with each data signal, and determine time of arrivals for each combined branch signal from each branch based on the training signals. The beam weight processor may then determine coefficients based on the determined time of arrivals associated with the training signal for reception of a data signal. In some cases, the time of arrivals associated with the branches may be used to refine the weights applied within each branch. For example, the relative locations for each leaf may be characterized and a direction for the training signal determined from the time of arrivals for refining the weighting used for the leaves of the branch (e.g., for the associated data signal). Coefficients may be applied to each branch for transmission of signals based on the determined time of arrivals, and the circuitry of each branch (e.g., analog weighting circuitry) may apply weightings to each leaf for the transmitted signals.

<FIG> illustrates an example of a signal receiving technique <NUM> for wireless communications that supports an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. In some examples, antenna system <NUM>-b may implement aspects of antenna system <NUM> as described in <FIG> and of antenna system <NUM>-a as described in <FIG>.

Uncorrelated energy <NUM> may illustrate vectors associated with uncorrelated signals received via each antenna element <NUM> of antenna system <NUM>-b. The beam weight processor may combine the uncorrelated signals of uncorrelated energy <NUM> according to the determined coefficients from one or more training signals <NUM> to result in correlated energy <NUM>. A total amplitude and total power calculation of correlated energy <NUM> may be calculated as follows: <MAT> <MAT>.

Where n is a total number of branches and k is a total number of leaves of antenna system <NUM>-b. A total amplitude and total power calculation of uncorrelated energy <NUM> may be calculated as follows: <MAT> <MAT>.

Where n is a total number of branches and k is a total number of leaves of antenna system <NUM>-b. A signal-to-noise ratio may be calculated as follows: <MAT>.

Here, uncorrelated noise power grows linearly while correlated signal power grows by a square.

<FIG> illustrates an example of an antenna system <NUM> for wireless communications that supports an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. Antenna system <NUM> may include antenna system <NUM>-c, dish <NUM>, and emitter <NUM>. In some examples, antenna system <NUM>-c may implement aspects of antenna system <NUM> as described in <FIG>, antenna system <NUM>-a as described in <FIG>, and antenna system <NUM>-b as described in <FIG>. Antenna system <NUM> may be referred to as a hybrid dish/MIMO antenna system.

Dish <NUM> may represent a dish that is not perfectly parabolic. A benefit to a dish <NUM> that is not perfectly parabolic is that it may have looser manufacturing requirements compared to a conventional parabolic dish which may lead to lower manufacturing and implementation costs. In addition, dish <NUM> may be larger than a parabolic dish manufactured to tolerances typically used in satellite communication. For example, typical large parabolic dishes for satellite communication may be approximately five (<NUM>) to fifteen (<NUM>) meters in diameter. In some cases dish <NUM> may be significantly larger than typical large parabolic dishes for satellite communication, such as having a diameter of <NUM> meters, <NUM> meters, <NUM> meters, or larger. Dish may be collapsed for launch of a satellite <NUM>, and may be extended to a deployed shape in a variety of ways. For example, dish <NUM> may be formed by a conductive coating on a balloon that is expanded when the antenna system <NUM> is deployed in orbit. Alternatively, deployment of dish <NUM> may be similar to deployment of a solar sail. Yet alternatively, dish <NUM> may be made up of multiple rigid elements, and may be unfolded in deployment.

Radio waves <NUM> may be received from a transmitter by dish <NUM> in an RF wavefront and reflected off of dish <NUM> to form a dispersed focal region. Antenna system <NUM>-c and its associated antenna elements may be at least partially within the formed dispersed focal region of dish <NUM>. In some examples, dish <NUM> may increase the RF flux power density into antenna system <NUM>-c, and the antenna array of antenna system <NUM>-c may be implemented such that a significant portion of the RF flux is captured by the antenna system <NUM>-c. An efficiency of dish <NUM> may be calculated by taking the flux power redirected into the antenna system <NUM>-c and dividing it by the flux power collected by the antenna system <NUM>-c.

As described above, training signals from a transmitter may be used to generate coefficients for reception or transmission of signals from the antenna elements of antenna system <NUM>. However, determination of the coefficients may include measurements of dish imperfections and antenna element locations. For example, a signal received at a given antenna element of antenna system <NUM>-c may be reflected from multiple locations on dish non-coherently, and the dish imperfections may be measured and combined with time of arrival information for the antenna elements to determine the coefficients for receiving the signal coherently.

Additionally or alternatively, one or more auxiliary satellites <NUM> may be used to synthesize locations of antenna elements of antenna system <NUM>-c. For example, one or more auxiliary satellites <NUM> may be positioned in a known location relative to antenna system <NUM>, and may transmit signals that may be measured at antenna system <NUM> (e.g., determining antenna vectors for each element of antenna system <NUM>-c). Using a known location of a transmitter, the dish imperfections may be measured to synthesize time of arrivals or antenna element coefficients in combination with training signals from the transmitter of a data signal, or without receiving training signals from the transmitter of the data signal.

<FIG> shows a block diagram <NUM> of an apparatus <NUM> for an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. In some examples, apparatus <NUM> may be an example of aspects of an antenna system <NUM> of <FIG>, <FIG>, <FIG>, and <FIG>. The apparatus <NUM> may include a receiver <NUM>, a training processor <NUM>, a beam weight processor <NUM>, and a transmitter <NUM>. The components may communicate via one or more buses.

The apparatus <NUM> and/or at least some of its various sub-components may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions of the apparatus <NUM> and/or at least some of its various sub-components may be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure. The apparatus <NUM> and/or at least some of its various sub-components may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical devices. In some examples, the apparatus <NUM> and/or at least some of its various sub-components may be a separate and distinct component in accordance with various aspects of the present disclosure. In other examples, the apparatus <NUM> and/or at least some of its various sub-components may be combined with one or more other hardware components, including but not limited to an I/O component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

The receiver <NUM> may receive information such as packets or user data. Information may be passed on to other components of the device <NUM>. The receiver <NUM> may include multiple receiver chains, where each receiver chain may include circuitry for processing a received RF signal (e.g., amplifiers, mixers, analog-to-digital converters, demodulators). Each receive chain of receiver <NUM> may include circuitry to combine energy coherently from multiple antennas (e.g., MRC circuitry).

The training processor <NUM> may receive signals from the antenna receiver associated with one or more training signals from a transmitter. It may also associate each of a plurality of antenna elements with a respective time of arrival based at least in part on one or more training signals. It may also determine a respective time of arrivals based at least in part on a location of a transmitter and respective time of arrival vectors. The one or more training signals may include an indicator of location information associated with the transmitter, an indicator of a user beam for the transmitter, a priority for communications from the transmitter, or a combination thereof. The training processor <NUM> may be configured to decrypt the one or more first signals to obtain the one or more training signals and validate the one or more training signals based on the decrypting.

The beam weight processor <NUM> may combine one or more signals associated with a data signal from a transmitter received via a receiver according to a plurality of coefficients determined based at least in part on associations between a plurality of antenna elements and respective time of arrivals. It may also update the plurality of coefficients based at least in part on a second respective time of arrivals. It may also generate one or more signals for transmission from a plurality of antenna elements to a target receiver based at least in part on a plurality of coefficients determined based at least in part on the associations between a plurality of antenna elements and respective time of arrivals.

The training processor <NUM> and the beam weight processor <NUM> may be examples of a processor that may include an intelligent hardware device, (e.g., a general-purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor. The processor may be configured to execute computer-readable instructions stored in memory to perform various functions.

The transmitter <NUM> may include multiple transmitter chains, where each transmitter chain may include circuitry for processing a digital signal to generate an RF signal for transmission (e.g., modulators, digital-to-analog converters, mixers, amplifiers). In some examples, the transmitter <NUM> may be collocated with a receiver <NUM> in a transceiver (e.g., which may include multiple receive/transmit chains).

<FIG> shows a flowchart illustrating a method <NUM> that supports an ultra-low cost high performance satellite aperture in accordance with aspects of the present disclosure. The operations of method <NUM> may be implemented by an antenna system or its components as described herein. For example, the operations of method <NUM> may be performed by an antenna system as described with reference to <FIG>. In some examples, an antenna system may execute a set of instructions to control the functional elements of the communication session delivery system to perform the functions described herein. Additionally or alternatively, a communication session delivery system may perform aspects of the functions described herein using special-purpose hardware.

At <NUM>, the antenna system may receive one or more training signals from a first transmitter via an antenna receiver. The one or more training signals may include an indicator of location information associated with the first transmitter, an indicator of a user beam for the first transmitter, a priority for communications from the first transmitter, or a combination thereof. In some examples, the one or more training signals may be encrypted (e.g., according to a public key associated with a user terminal, a user beam, a group of users, a terminal type, a user type, or a combination thereof). Receiving the training signals may include decrypting the training signals (e.g., according to a private key corresponding to the public key). The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a training processor as described with reference to <FIG>.

At <NUM>, the antenna system may associate a time of arrival based on the received one or more training signals with a respective antenna element. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a training processor as described with reference to <FIG>.

At <NUM>, the antenna system may receive one or more data signals from a second transmitter via an antenna receiver. In some examples, the second transmitter may be the same as the first transmitter. In other examples, the second transmitter may be different from the first transmitter. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a beam weight processor as described with reference to <FIG>.

At <NUM>, the antenna system may combine the one or more data signals in accordance with coefficients that were determined with the plurality of antenna elements of the antenna system and their respective time of arrivals. The operations of <NUM> may be performed according to the methods described herein. In some examples, aspects of the operations of <NUM> may be performed by a beam weight processor as described with reference to <FIG>.

Claim 1:
A method for receiving radio waves at an antenna system (<NUM>) of a satellite (<NUM>), comprising:
receiving one or more first signals using a plurality of antenna elements (<NUM>), the one or more first signals corresponding to a training signal (<NUM>) transmitted by a first transmitter, wherein the plurality of antenna elements (<NUM>) are each coupled with one of a plurality of flexible couplings (<NUM>), and wherein deployed positions of the plurality of antenna elements (<NUM>) are constrained by their position along a respective one of the flexible couplings (<NUM>), and are otherwise unconstrained in one or more spatial dimensions;
associating each of the plurality of antenna elements (<NUM>) with a first respective time of arrival based at least in part on the one or more first signals;
receiving one or more second signals using the plurality of antenna elements (<NUM>), the one or more second signals corresponding to a data signal (<NUM>) transmitted by a second transmitter; and
combining the one or more second signals according to a plurality of coefficients determined based at least in part on the associations between the plurality of antenna elements (<NUM>) and the first respective time of arrivals.