Patent Description:
An antenna array at a satellite in a geostationary orbit may illuminate a geographic area that is associated with a coverage area of the satellite. In some examples, the satellite may be used to support communications between access node terminals and user terminals in the coverage area. The satellite may also be used to detect signals emitted within a coverage area of the satellite. In some examples, the detection resolution of the satellite may be limited - e.g., due to the distance of the satellite from a target geographic area. For example, the satellite may be unable to detect signals that are transmitted or emitted within the geographic area at low power levels or not intentionally directed to the satellite.

<CIT> describes a beamformer for an end-to-end beamforming communications system.

A satellite communications system may include satellites in geostationary earth orbits (GEOs), which may be referred to as GEO satellites; and satellites in non-GEO earth orbits, which may be referred to as non-GEO satellites. In some examples, the non-GEOs are lower in altitude than the GEOs. Some examples of non-GEO satellites include satellites in medium earth orbits (MEOs), which may be referred to as MEO satellites; and satellites in low earth orbits (LEOs), which may be referred to as LEO satellites. Satellites (e.g., GEO, MEO, or LEO satellites) may be used to detect signals emitted from stationary or mobile sources on land, water, or in the sky. In some examples, a satellite network operator may use the detected signals to determine whether a known or unknown emitter is in a geographic area.

A GEO satellite may be used to detect known and unknown signal emitters in a geographic area. In some examples, a resolution of the GEO satellite associated with surveying particular geographic areas may be limited based on a size of an antenna array at the GEO satellite. Thus, for a GEO satellite, a 3dB boundary of a beam used to survey a geographic area of interest may be excessively large relative to a boundary of the geographic area of interest.

According to various aspects described herein, multiple non-GEO satellites may be used to survey a large geographic area with increased resolution - e.g., based on multiple non-GEO satellites having a larger aperture than a single satellite. A relay link is established between a first satellite (e.g., a GEO satellite) in a first orbit (e.g., a GEO) and a plurality of second satellites (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEOs). The use of second satellites as relay satellites to the first satellite can allow the second satellites to be relatively low complexity (e.g., lower cost, smaller size, etc.), as compared to fully functional satellites having high-power transponders and high-gain tracking antenna systems to transmit the signals directly to ground stations. The second satellites each has one or more antennas illuminated by at least a portion of one or more geographic areas and each detects signal components of one or more signals emitted in the one or more geographic areas. The second satellites relay the respective signal components of the one or more signals to the first satellite. When ground-based beamforming is used, the first satellite may transmit the signal components, or representations of the signal components, to a ground system in one or more signals. In some examples, the ground system may determine and apply beamforming weights to the one or more signals received from the first satellite to obtain one or more beam signals corresponding to signals detected in the one or more geographic areas.

In other examples, when on-board beamforming is used, the first satellite may process the signal components, determining and applying beamforming weights to the signal components to obtain one or more beams signals corresponding to signals detected from the one or more geographic areas. In such cases, the first satellite may transmit representations of the one or more beam signals to the ground system. By using the signal components detected at the one or more second satellites, post-processing may be performed that enables a processing system to focus on the one or more geographic areas with enhanced sensitivity, effectively increasing a detection resolution of the first satellite.

In some examples, in addition to the respective signal components received from the one or more second satellites, the first satellite may detect an additional signal component of the one or more signals in the one or more geographic areas - e.g., via a direct path. In such cases, the second satellites may effectively increase an aperture of the first satellite. In some examples, the first satellite may transmit the additional signal component of the one or more signals, or a representation of the detected additional signal component of the one or more signals, to the ground system. The ground system may use the additional signal component to obtain the representations of the one or more signals detected in the one or more geographic areas. In other examples, the first satellite may use the additional signal component to obtain the representations of the one or more signals. By supplementing a direct signal component received at the first satellite with the signal components received at the one or more second satellites, the quality of the signal detected by the first satellite may be improved relative to if only the direct signal component is used to detect the signal (e.g., the signal strength may be increased).

Aspects of the disclosure are initially described in the context of a satellite communications system. Specific examples are then described of a coverage diagram, process flow, and constellation diagram. Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams and flowcharts that relate to lensing using lower earth orbit repeaters.

<FIG> shows a diagram of a communications system that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. Satellite communications system <NUM> includes a network of satellites, including first satellite <NUM> and second satellites <NUM>. Satellite communications system <NUM> may also include a ground system <NUM> that includes one or more gateways <NUM>. The one or more gateways <NUM> may include (or be otherwise coupled with) beamformer <NUM>. In some examples, beamformer <NUM> may be included in ground station processor <NUM>. Ground station processor <NUM> may use beamformer <NUM> to determine beam coefficients. Ground station processor <NUM> may also be configured to demodulate (and, in some examples, decode) beam signals generated by beamformer <NUM>.

A satellite (e.g., first satellite <NUM> or a second satellite <NUM>) may be configured to support wireless communications between one or more access node terminals (e.g., in a ground system <NUM>) and user terminals located in a coverage area (e.g., coverage area <NUM>). A satellite may also be configured to detect signals emitted within coverage area <NUM>. In some examples, a satellite may include an antenna assembly having one or more antenna feed elements. Each of the antenna feed elements may also include, or be otherwise coupled with, a radio frequency (RF) signal transducer, a low noise amplifier (LNA), or power amplifier (PA), and may be coupled with one or more transponders in the satellite.

In some examples, some or all antenna feed elements at a satellite may be arranged as an array of constituent receive and/or transmit antenna feed elements that cooperate to enable various examples of beamforming, such as ground-based beamforming (GBBF), on-board beamforming (OBBF), end-to-end (E2E) beamforming, or other types of beamforming. For OBBF, the satellite may include N<NUM> transmitters and an N<NUM>xK<NUM> beam weight matrix may be used to generate K<NUM> user beams. Similarly, for GBBF, the satellite may include L<NUM> transmitters and receive L<NUM> signals corresponding to respective transmitters in the satellite (e.g., frequency-division multiplexed) from one or more access node terminals. The one or more access node terminals may apply an L<NUM>xK<NUM> beam weight matrix to generate K<NUM> user beams. For E2E beamforming, the satellite may include L<NUM> transponders. The L<NUM> transponders may be used to receive signals from M access node terminals, where the received signals may be weighted (e.g., weighting each of K<NUM> beam signals for respective sets of one or more access node terminals) before transmission by the access node terminals to support beamforming for K<NUM> user beams. It should be noted that the present examples describe the forward link, while similar arrangements may be made for the return link.

Satellites may be launched into different orbits - a GEO or a non-GEO orbit. A satellite in a GEO may be referred to as a GEO satellite. Non-GEO orbits may include MEOs, LEOs, equatorial low earth orbit (ELEO), and the like. A satellite in a MEO may be referred to as a MEO satellite, a satellite in a LEO may be referred to as a LEO satellite, and so on. A GEO satellite may orbit the earth at a speed that matches the rotational speed of the earth, and thus, may remain in a single location relative to a point on the earth. A LEO satellite may orbit the earth at a speed (e.g., relative to the ground) that exceeds the rotational speed of the earth, and thus, a location of the satellite relative to a point on the earth may change as the satellite travels through the LEO. LEO satellites may be launched with low inclination (e.g., ELEOs) or high inclination (e.g., polar orbits) to provide different types of coverage and revisit times for given regions of the earth. A MEO satellite may also orbit the earth at a speed that exceeds the rotational speed of the earth but may be at a higher altitude than a LEO satellite. A HEO satellite may orbit the earth in an elliptical pattern where the satellite moves closer to and farther from the earth throughout the HEO.

In some examples, GEO satellites may be more expensive and more architecturally complex (e.g., may include more repeaters, antenna elements, transponders, etc.) than non-GEO satellites. Despite the increased complexity of GEO satellites, networks of non-GEO satellites may be capable of providing services and surveilling the earth with more granularity than GEO satellites (e.g., based on being more numerous and closer to the earth). In some examples, GEO satellites and non-GEO satellites operate independently of one another. In some examples, first satellite <NUM> may be a GEO satellite. Second satellites <NUM> may include LEO satellites, MEO satellites, or a combination thereof.

In some examples, a satellite network may be used to surveil at least a portion of the earth for signals emitted from known and unknown transmitters. For example, a satellite network may use first satellite <NUM> to detect signals that originate from a geographic area (e.g., the geographic area encompassed by coverage area <NUM>). In some examples, first satellite <NUM> may transmit detected signal energy to a ground system <NUM> (e.g., to one or more of gateways <NUM>) that processes (e.g., determine and apply beamforming coefficients to) the detected signal energy to obtain one or more signals - e.g., when ground-based beamforming is used. In other examples, first satellite <NUM> may process (e.g., determine and apply beamforming coefficients to) the detected signal energy and transmit the one or more signals to the ground system <NUM> - e.g., when on-board beamforming is used.

A GEO satellite may be used to detect known and unknown signal emitters in a geographic area. In some examples, a resolution of the GEO satellite associated with surveying particular geographic areas may be limited based on a size of an antenna array at the GEO satellite and a distance of the GEO satellite from a point of interest. Thus, for a GEO satellite, a 3dB boundary of a beam used to survey a geographic area of interest may be excessively large relative to a boundary of the geographic area of interest.

According to various aspects described herein, multiple non-GEO satellites may be used to survey a large geographic area with increased resolution - e.g., based on multiple non-GEO satellites having a larger aperture than a single satellite (e.g., a GEO, MEO, or LEO satellite). A relay link is established between a first satellite <NUM> (e.g., a GEO satellite) in a first orbit (e.g., a GEO) and second satellites <NUM> (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEOs). The second satellites <NUM> each has one or more antennas illuminating at least a portion of one or more geographic areas <NUM> and each detects signal components <NUM> of one or more signals emitted in the one or more geographic areas. According to various aspects described herein, the one or more antennas of the second satellites <NUM> are described as being illuminated by (instead of illuminating) the portion of the one or more geographic areas <NUM>. It is worth noting that these terms may be used interchangeably to describe that the one or more antennas of the second satellites <NUM> may be used to transmit signals to or detect signals from the one or more geographic areas <NUM>.

The second satellites <NUM> relay the respective signal components <NUM> of the one or more signals to the first satellite <NUM>. When ground-based beamforming is used, the first satellite <NUM> may transmit the signal components, or representations of the signal components, in one or more signals to ground system <NUM>. In some examples, the ground system <NUM> may determine and apply beamforming weights to the one or more signals received from the first satellite <NUM> to obtain one or more beam signals corresponding to the one or more signals detected in the one or more geographic areas <NUM>.

In other examples, when on-board beamforming is used, the first satellite <NUM> may process the relayed signal components <NUM>, determining and applying beamforming weights to the signal components to obtain one or more beam signals corresponding to the one or more signals. In such cases, the first satellite <NUM> may transmit representations of the one or more beam signal signals to ground system <NUM>. By using the signal components detected at the one or more second satellites <NUM>, post-processing may be performed that enables a processing system to focus on the one or more geographic areas <NUM> with enhanced sensitivity, effectively increasing a detection resolution of the first satellite <NUM>.

In some examples, in addition to the respective signal components relayed from the one or more second satellites <NUM>, the first satellite <NUM> may detect an additional signal component (e.g., direct signal component <NUM>) of the one or more signals in the one or more geographic area - e.g., via a direct path. In such cases, the second satellites may effectively increase an aperture of the first satellite. In some examples, the first satellite <NUM> may use the additional signal component to obtain the representations of the one or more signals. In other examples, the first satellite <NUM> may transmit the additional signal component of the one or more signals, or a representation of the detected additional signal component of the one or more signals, to the ground system <NUM>. The ground system <NUM> may use the additional signal component to obtain the representations of the one or more signals detected in the one or more geographic areas <NUM>. By supplementing a direct signal component <NUM> received at the first satellite <NUM> with the signal components received at the one or more second satellites <NUM>, the quality of the signal detected by the first satellite <NUM> may be improved relative to if only the direct signal component <NUM> is used to detect the signal (e.g., the signal strength may be increased).

As RF signal energy radiates from an emitter (e.g., a transmitter or thermal energy emitter), each second satellite <NUM> detects components (e.g., having respective phase shifts or amplitude variations due to different channels between the emitter and the respective second satellite <NUM>) of the signal. When used in combination with first satellite <NUM> to detect signal components in geographic areas <NUM> corresponding to a location of an emitter (e.g., emitter <NUM>), the second satellites <NUM> may be referred to as relay satellites <NUM>. The geographic areas <NUM> may be positioned within coverage area <NUM> of first satellite <NUM>. For example, first relay satellite <NUM>-<NUM> may receive first detected signal component <NUM>-<NUM> based on a signal emitted from emitter <NUM> within first geographic area <NUM>-<NUM>. In some examples, first relay satellite <NUM>-<NUM> receives first detected signal component <NUM>-<NUM> via a first return channel (which may be referred to as ATL<NUM>), second relay satellite <NUM>-<NUM> receives a second detected signal component via a second return channel (which may be referred to as ATL<NUM>), and so on. In some examples, the return channels between the relay satellites <NUM> and first geographic area <NUM>-<NUM> may be included in a combined return channel matrix (which may be referred to as A<NUM>RTN). Relay satellites <NUM> may similarly receive signal components detected from other geographic areas <NUM> (including Pth geographic area <NUM>-P).

Return channels between relay satellite <NUM> and a set of geographic areas <NUM> are included in the combined return channel matrix A<NUM>RTN. The matrix A<NUM>RTN may include a quantity of rows that is based on a quantity of repeaters included in the relay satellites <NUM> and a quantity of the relay satellites <NUM>, and a quantity of columns that is based on a quantity of geographic areas <NUM> monitored by the relay satellites <NUM>. For example, if S relay satellites <NUM> include Q repeaters and are used to monitor P geographic areas <NUM>, the A<NUM>RTN matrix may have Q · S rows and P columns.

The relay satellites <NUM> relay the detected signal components <NUM> (or representations of the detected signal components) to first satellite <NUM>. In some examples, relaying the detected signal components <NUM> involves frequency-shifting the detected signal component, amplifying the detected signal components, or both, before the detected signal components are relayed to first satellite <NUM>.

<FIG> shows components of satellites that support lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. As depicted in <FIG>, a relay satellite <NUM> may include one or more repeaters <NUM> that are used to amplify and/or frequency shift a detected signal before relaying the detected signal to first satellite <NUM>. A repeater <NUM> may be a non-processing repeater. That is, the repeater <NUM> may perform operations that interpret or re-format data within the signal waveform. For example, the repeater <NUM> may not digitize, demodulate, decode, apply beamforming weights, or reformat the detected signals before relaying the detected signals to first satellite <NUM>. A repeater <NUM> may include frequency translator <NUM>, amplifier <NUM>, or both. Frequency translator <NUM> may be configured to shift a frequency of a detected signal (e.g., by mixing the detected signal with another frequency). In some examples, the frequency translators <NUM> in different relay satellites <NUM> may be configured to apply different frequency shifts to detected signals. Amplifier <NUM> may be configured to amplify a detected signal before relaying the amplified signal to first satellite <NUM>.

First relay satellite <NUM>-<NUM> sends first relayed signal component <NUM>-<NUM> (which may correspond to an amplified version of first detected signal component <NUM>-<NUM>) to first satellite <NUM>. In some examples, first relay satellite <NUM>-<NUM> transmits first relayed signal component <NUM>-<NUM> to first satellite <NUM> via a first return channel (which may be referred to as ALG<NUM>), second relay satellite <NUM>-<NUM> transmits a second transmitted signal component via a second return channel (which may be referred to as ALG<NUM>), and so on. The return channels between the relay satellites <NUM> and first satellite <NUM> may be included in a second combined return channel matrix (which may be referred to as A<NUM>RTN). The relay satellites <NUM> may similarly transmit signal components detected from other geographic areas <NUM> (including Pth geographic area <NUM>-P) via the second combined return channel A<NUM>RTN.

The matrix A<NUM>RTN may include a quantity of rows that is based on a quantity of uplink/downlink transponder paths at first satellite <NUM>, and a quantity of columns that is based on a quantity of relay satellites <NUM> and a quantity of repeaters included in the relay satellites <NUM>. For example, if first satellite <NUM> includes L uplink/downlink transponder paths and there are S relay satellites <NUM> with Q repeaters, the A<NUM>RTN matrix may have L rows and Q.

Thus, the return channel between the geographic areas <NUM> and first satellite <NUM> is a composite return channel that includes multiple components - a first channel component between the relay satellites <NUM> and the geographic areas <NUM> (which may be represented by A<NUM>RTN) and a second channel component between the relay satellites <NUM> and first satellite <NUM> (which may be represented by A<NUM>RTN). In some examples, the composite return channel between the geographic areas <NUM> and first satellite <NUM> may be represented by an A<NUM>RTNA<NUM>RTN matrix. In some examples, if first satellite <NUM> includes L uplink/downlink transponder paths and P geographic areas <NUM> are monitored, the A<NUM>RTNA<NUM>RTN matrix may have L rows and P columns.

In some examples, first satellite <NUM> may receive direct signal components from one or more of the geographic areas <NUM>. For example, first satellite <NUM> may receive direct signal component <NUM> from emitter <NUM> via a direct return channel (which may be represented as ATG) between first satellite <NUM> and first geographic area <NUM>-<NUM>. In some examples, the return channels between the geographic areas <NUM>, relay satellites <NUM>, and first satellite <NUM> may be combined with the direct return channel to form a composite return channel matrix (which may be represented as ARTN), where <MAT>. The matrix ARTN may include a quantity of rows that is based on a quantity of uplink/downlink transponder paths included in first satellite <NUM>, and a quantity of columns that is based on a quantity of geographic areas <NUM> monitored by the relay satellites <NUM>. For example, if first satellite <NUM> includes L uplink/downlink transponder paths and is used to monitor P geographic areas <NUM>, ARTN may have L rows and P columns.

Similarly, a full return channel between the geographic areas <NUM> and ground system <NUM> may be a composite return channel that includes multiple components. In some examples, the full return channel includes the channel component between the geographic areas <NUM> and first satellite <NUM> (which may be represented by A<NUM>RTNA<NUM>RTN or ARTN); a channel component within first satellite <NUM> between the uplink and downlink transponders on first satellite <NUM> (which may be represented by a matrix ERTN); and a channel component between first satellite <NUM> and ground system <NUM> (which may be represented by a matrix CRTN).

As depicted in <FIG>, first satellite <NUM> may include one or more transponders <NUM> that are used to amplify and/or frequency shift a detected signal before transmitting a received signal to first satellite <NUM>. A transponder <NUM> may include frequency translator <NUM>, amplifier <NUM>, or both. Frequency translator <NUM> may be configured to shift a frequency of a received signal (e.g., by mixing the detected signal with another frequency). Amplifier <NUM> may be configured to amplify a received signal before transmitting the amplified signal to ground system <NUM>. In some examples, the transponder <NUM> may be coupled with on-board processing components, such as beamformer <NUM>, a demodulator, a decoder, a reformatting component, or a combination thereof. In some examples, the on-board processing components may be included in an on-board processor <NUM>. In some examples, when beamformer <NUM> is included in first satellite <NUM>, ground system <NUM> may not use beamformer <NUM> to process signals received from first satellite <NUM>.

In some examples, the channel component within first satellite <NUM> is based on paths through transponders in first satellite <NUM>, where the matrix ERTN may include a quantity of rows and columns that are based on a quantity of transponders included in first satellite <NUM>. For example, if first satellite <NUM> includes L transponders, the ERTN matrix may include L rows and L columns.

Also, the channel component between first satellite <NUM> and ground system <NUM> (represented by the CRTN matrix) may be based on a quantity of ground stations included in ground system <NUM> and a quantity of repeaters included in first satellite <NUM>. For example, if ground system includes M ground stations (e.g., gateways) and first satellite <NUM> includes L uplink/downlink transponder paths, the CRTN matrix may include M rows and L columns.

In some examples, the full return channel between the geographic areas <NUM> and ground system <NUM> may be represented by a matrix HRTN, where HRTN = CRTNERTNA<NUM>RTNA<NUM>RTN. In some examples, if ground system <NUM> includes M ground stations and P geographic areas <NUM> are monitored, the HRTN matrix may have M rows and P columns.

In some examples, ground system <NUM> may estimate the full return channel HRTN based on signals received from known emitters positioned within coverage area <NUM>. Ground system <NUM> may use the signals received from the known emitters to determine return channels associated with the received signals and may interpolate the determined return channels to estimate the return channels between geographic areas <NUM> and ground system <NUM>. In some examples, ground system <NUM> may use the received signals to estimate a portion of the full return channel components. For example, ground system <NUM> may use the signals to estimate the channel component associated with A<NUM>RTN, where the other channel components may be estimated based on reference signals communicated between devices to support channel estimation.

Ground system <NUM> may use the estimated channel components to determine return covariance (which may be represented by the matrix RRTN). In some examples, the ground system may use the estimated channel component to determine a return covariance between signals received from different geographic areas <NUM> at M different ground stations, where <MAT>, where <MAT> is a noise term associated with a downlink (which may also be referred to as a forward link); <MAT> is a noise term associated with an uplink (which may also be referred to as a reverse link); and Im is an MxM identity matrix. In some examples, the return covariance may also include covariance caused by interfering user traffic (e.g., for J interferers). In such cases, <MAT> <MAT>, where JRTN may be the channel between the interferers and the ground system. Both of the RRTN and <MAT> matrices may have M rows and M columns.

Ground system <NUM> may use the estimated full return channel and estimated return covariance to determine beam coefficients to apply to signals received over the full return channel. In some examples, the beam coefficients are represented by the matrix BRTN, where BRTN = (RRTN -<NUM>HRTN)H. The matrix BRTN may include a quantity of rows that is based on a quantity of monitored geographic areas <NUM> and a quantity of columns based on a quantity of ground stations in a ground system <NUM>. For example, for P geographic areas and M ground stations, the matrix BRTN may include P rows and M columns. Thus, the beamformed channel between the ground system <NUM> and the one or more geographic areas <NUM> may be represented as HRTN-BF, where HRTN-BF = BRTNHRTN = BRTNCRTNERTNARTN.

In some examples, instead of applying the beam coefficients to signals received at ground system <NUM>, first satellite <NUM> may apply similarly determined beam coefficients to signals received from relay satellites <NUM>. In such examples, first satellite <NUM> may transmit a composite signal to ground system <NUM> that includes a representation of signals detected in each monitored geographic area <NUM>. When the beamforming is performed at first satellite <NUM>, the CRTN matrix may be an identity matrix (e.g., an MxL identity matrix, where M may equal <NUM>).

In some examples, instead of transmitting the signal components detected at relay satellites <NUM> to first satellite <NUM>, relay satellites <NUM> may transmit the detected signal components directly to ground system <NUM>. In addition to the signal components transmitted to ground system <NUM>, first satellite <NUM> may transmit a direct signal component to ground system <NUM>. In such cases, the signal components of a signal detected at relay satellites <NUM> may supplement the direct signal component of the signal detected by first satellite <NUM>.

Although generally described with reference to detecting signals originating from geographic areas <NUM> within coverage area <NUM>, similar techniques may be used to transmit signals to user terminals with geographic areas <NUM> on a forward link. In such cases, forward channels between ground system <NUM> and geographic areas <NUM> may similarly include multiple channel components, including a channel component between ground system <NUM> and first satellite <NUM>, a channel component between first satellite <NUM> and relay satellites <NUM>, and a channel component between relay satellites <NUM> and the geographic areas <NUM>. In such cases, ground system <NUM> may similarly estimate the forward channels (and, in some examples, individually estimate one or more of the forward channel components). Also, ground system <NUM> may determine and apply beam coefficients to signals to be transmitted in the different geographic areas - e.g., applying a first set of beam coefficients to a first signal to cause relay satellites <NUM> to focus a transmission of the first signal within first geographic area <NUM>-<NUM>, a second set of beam coefficients to a second signal to cause relay satellite <NUM> to focus a transmission of the second signal within a second geographic area, and so on. In such examples, first satellite <NUM> may transmit different components of a signal to the relay satellites <NUM>, and the relay satellites <NUM> may transmit the different signal components, the different signal components coherently combining within a desired geographic area <NUM>. In some examples, relay satellites <NUM> may reduce a transmission power of the different signal components to comply with signal strength thresholds on earth (e.g., as set by a regulatory agency).

<FIG> shows an example of a coverage diagram that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. Coverage diagram <NUM> depicts a coverage area of a first satellite (e.g., a GEO satellite, a first satellite <NUM> of <FIG>) and a GEO satellite that uses one or more second satellites (e.g., LEO satellites, MEO satellites, LEO and MEO satellites, relay satellites <NUM> of <FIG>) to focus on a geographic area.

In some examples, an antenna array at a first satellite is associated with coverage area <NUM>. The boundary of coverage area <NUM> may represent points from which signals received at the antenna array have a signal strength that is at a 3dB point. In some cases, coverage area <NUM> may represent the coverage area for a beamformed beam for transmission or reception from coverage area <NUM> via the first satellite. In some examples, the first satellite may be capable of processing signals received from within coverage area <NUM>. However, with regard to detecting signals within coverage area <NUM>, the first satellite may be unable to determine where within coverage area <NUM> the signal originated. As described herein to increase a detection resolution (and, in some examples, to effectively increase an aperture) of a first satellite, one or more second satellites (that orbit lower than the first satellite) may be used to detect signals originating from geographic regions within coverage area <NUM>.

In some examples, each of the second satellites may have a smaller coverage area <NUM> relative to the first satellite. Like coverage area <NUM>, the boundaries of coverage areas <NUM> may represent a 3dB point for detecting signals originating from within coverage areas <NUM>. For first focused coverage area <NUM>-<NUM>, for example, the corresponding second satellite may be capable of detecting signals originating from a geographic region corresponding to first focused coverage area <NUM>-<NUM>, but not signals originating from within coverage area <NUM> but outside of first focused coverage area <NUM>-<NUM>. In some examples, energy from within overlapping coverage areas <NUM> of the second satellites may be combined to focus on particular geographic areas <NUM>. For example, the second satellites may be used to focus on first geographic area <NUM>-<NUM>.

In some examples, the second satellites may be used to focus (e.g., simultaneously) on multiple geographic areas <NUM> within coverage area <NUM> for the detection of signals. For example, in addition to focusing on first geographic area <NUM>-<NUM>, the second satellites may be used to focus on other geographic areas (e.g., first geographic area <NUM>-<NUM>, Pth geographic area <NUM>-P). The different geographic areas <NUM> monitored using the second satellites may be non-overlapping or overlapping. In some examples, the second satellites may similarly be used to focus on one or more geographic areas within coverage area <NUM> for the transmission of signals to user devices within the one or more geographic areas.

<FIG> shows an exemplary set of operations that support lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. Process flow <NUM> may be performed by second satellites <NUM>, first satellite <NUM>, and ground system <NUM>, which may be examples of second satellites <NUM>, first satellite <NUM>, and ground system <NUM> as described in <FIG>. In some examples, process flow <NUM> illustrates an exemplary sequence of operations performed to support using lower earth orbit repeaters. For example, process flow <NUM> depicts operations for detecting signals transmitted in geographic areas within a coverage area of a GEO satellite.

It is understood that one or more of the operations described in process flow <NUM> may be performed earlier or later in the process, omitted, replaced, supplemented, or combined with another operation. Also, additional operations described herein that are not included in process flow <NUM> may be included.

At arrow <NUM>, emitter <NUM> emits a signal while positioned within a geographic area. In some examples, emitter <NUM> emits the signal while wirelessly communicating with another device that is not second satellites <NUM> or first satellite <NUM>. In other examples, emitter <NUM> involuntarily emits the signal (e.g., emitter <NUM> may be a rocket, and the signal may be associated with a flare produced by the rocket). Second satellites <NUM> detect the signal. That is, the signal radiates from the emitter <NUM> and each of the second satellites <NUM> detects a different signal component associated with the emitted signal. In some examples, in addition to being detected at second satellites <NUM>, a direct signal component of the emitted signal may be detected at first satellite <NUM>.

At arrows <NUM>, second satellites <NUM> relay the detected signal components (or representations of the received signal components) to first satellite <NUM>. In some examples, second satellites <NUM> may apply the detected signal components to one or more repeaters that are used to relay the detected signal components to first satellite <NUM>. A repeater may be used to amplify, apply a frequency shift to, or apply a phase shift to a detected signal component (or a combination thereof) before transmission to first satellite <NUM>. First satellite <NUM> receives the signal components at one or more antenna elements. First satellite <NUM> may also receive the direct signal component at one or more antenna elements.

At arrow <NUM>, first satellite <NUM> may transmit a representation of the signal emitted by emitter <NUM> to ground system <NUM>. First satellite <NUM> may transmit the signal components (in some examples, including the direct signal component) to ground system <NUM>. In some examples, first satellite <NUM> transmits the signal components to ground system <NUM> in one or more beams to one or more ground stations. Ground system <NUM> may receive the signal transmitted from first satellite <NUM>. In some examples, ground system <NUM> may receive the signal transmitted from first satellite <NUM> at one or more ground stations.

At block <NUM>, ground system <NUM> may estimate a channel (which may be referred to as a return channel and represented by HRTN) between ground system <NUM> and emitter <NUM> based on the received signals. In some examples, ground system <NUM> may also estimate the channel based on signals received from known transmitters located within or around a geographic area (e.g., a geographic area <NUM> in <FIG> or a geographic area <NUM> in <FIG>) that includes emitter <NUM>. In some examples, the signals received from the known transmitters may be transmitted concurrently with the signals detected by second satellites <NUM>. In some examples, the signals received from the known transmitters may be transmitted before the signals are detected by second satellites <NUM> - in some cases, the signals may be received by a different set of second satellites than second satellites <NUM>. That is, a channel estimation for relay by a given set of second satellites may be made using information of signals from known transmitters relayed by a different (e.g., non-overlapping, partially overlapping) set of second satellites.

To estimate the return channel, ground system <NUM> estimates a portion of the return channel between emitter <NUM> and second satellites <NUM> (which may be represented by A<NUM>RTN), a portion of the return channel between second satellites <NUM> and first satellite <NUM> (which may be represented by A<NUM>RTN), a portion of the return channel between uplink and downlink transponders within first satellite <NUM> (which may be represented by ERTN), and a portion of the return channel between first satellite <NUM> and ground system <NUM> (which may be represented by CRTN). When first satellite also receives a direct signal component, ground system may estimate a portion of the return channel between emitter <NUM> and first satellite <NUM> (which may be represented by ARTN).

In some examples, ground system <NUM> estimates the channel between emitter and second satellites <NUM> (A<NUM>RTN) based on interpolating signals transmitted by known transmitters within a vicinity of a set of monitored geographic areas. And estimates the channel (e.g., A<NUM>RTN, ERTN, and CRTN between second satellites <NUM> and ground system <NUM> based on reference signals transmitted from known transmitters in the set of monitored geographic areas. In other examples, the components of the channel are estimated individually. For example, the channel between second satellites <NUM> and first satellite <NUM> (A<NUM>RTN) may be estimated (e.g., by first satellite <NUM>) based on reference signals transmitted between second satellites <NUM> and first satellite <NUM>. The return channel of the transponders of the first satellite (ERTN) may also be estimated by first satellite <NUM>. First satellite <NUM> may indicate the estimated channels to ground system <NUM>. And the channel between first satellite <NUM> and ground system <NUM> (CRTN) may be estimated (e.g., by ground system <NUM>) based on reference signals transmitted between first satellite <NUM> and ground system <NUM>.

At block <NUM>, ground system <NUM> may estimate covariance associated with the return channel - e.g., based on the estimated return channel/components of the estimated return channel. The covariance may provide information regarding interference between transmissions of signal components detected in different geographic areas to ground system <NUM> and interference from other communications with ground system <NUM>. In some examples, the interference between signals components from different geographic areas may be represented by <MAT>. Also, the interference between J users may be represented by RRTN-int = <MAT>. And the combined covariance may be represented by <MAT>.

At block <NUM>, ground system <NUM> may use the estimated return channel and the estimated return covariance to determine beam coefficients to apply to signals received from first satellite <NUM>. In some examples, the beam coefficients may be represented by the matrix BRTN, where BRTN may equal (RRTN-<NUM>HRTN)H. In some examples, the beam coefficients and the return channel are determined based on a same time period, where the signals received to estimate the channel may also be used to determine the beam coefficients. In some examples, ground system <NUM> may constantly (e.g., every millisecond) update the estimated return channel and beam coefficients based on received signals. For example, the ground system <NUM> may process a first set of signals to estimate the return channel and reprocess the first set of signals to determine the beam coefficients based on the estimated return channel.

At block <NUM>, ground system <NUM> applies beam coefficients to the signal received from first satellite <NUM> to obtain one or more beam signals corresponding to one or more geographic areas. The one or more beam signals correspond to representations of one or more signals emitted in the geographic areas. The one or more beam signals may include a beam signal that is a representation of the signal emitted by emitter <NUM> in a geographic area. In some examples, when digital beamforming is used, applying the beam coefficients may include applying beam coefficients to a digital representation of the signal - e.g., by multiplying a beam coefficient matrix with a matrix representing the signal. In other examples, applying the beam coefficients may include combining components of the analog signal received at ground system <NUM> to obtain an analog beam signal.

At block <NUM>, ground system <NUM> may process (e.g., filter, analyze, demodulate, decode) the one or more beam signals to determine whether a signal has been detected in a geographic area of interest. In some examples, ground system <NUM> determines a type of signal (e.g., a communication signal, a signal associated with a rocket, etc.) that has been detected in a geographic area of interest.

As suggested above, an order of the operations of process flow <NUM> may be changed. In some examples, the operations for estimating a return channel and covariance associated with the return channel and determining beam coefficients may be performed by ground system <NUM> before the representation of the signal emitted by emitter <NUM> is received from first satellite <NUM>.

In some examples, operations of process flow <NUM> may be performed by different devices. For example, the operations for estimating a return channel and covariance associated with the return channel; determining beam coefficients; and applying beam coefficients may be performed by first satellite <NUM> (e.g., if first satellite is configured to perform OBBF). In such cases, first satellite <NUM> may transmit one or more beam signals corresponding to the signal emitted by emitter <NUM> to ground system <NUM>. And ground system <NUM> may process the received one or more beam signals as described herein.

Although described in the context of using second satellites <NUM> to detect signals via return channels associated with geographic areas within a coverage area of first satellite <NUM>, similar operations may be performed to estimate forward channels associated with the geographic areas and to use second satellites <NUM> to relay signals to user devices within the geographic areas.

<FIG> shows an example of a constellation diagram that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. Constellation diagram <NUM> depicts a set of second satellites (e.g., LEO satellites, MEO satellites, relay satellites <NUM> of <FIG>, etc.) that may be used in combination with a first satellite (e.g., a GEO satellite, first satellite <NUM> of <FIG>, etc.) to increase a detection resolution (and, in some examples, to effectively increase an aperture) of the first satellite for detecting signals within a coverage area. In some examples, the coverage areas of the second satellites <NUM> may correspond to respective focused coverage areas <NUM> described in <FIG>.

Constellation diagram <NUM> may include S second satellites <NUM>, where S may equal nine. Sets of the second satellites <NUM> may be positioned in different orbital planes <NUM> (e.g., in K orbital planes). In some examples, the second satellites <NUM> are distributed amongst three orbital planes <NUM>, where first orbital plane <NUM>-<NUM> may have a negative five (-<NUM>) degree inclination, second orbital plane <NUM>-<NUM> may have a zero (<NUM>) degree inclination, and third orbital plane <NUM>-<NUM> may have a five (<NUM>) degree inclination. In some examples, the second satellites <NUM> may be evenly distributed amongst the three orbital planes <NUM>, such that three of the second satellites <NUM> are included in each of the orbital planes. In some examples, the second satellites <NUM> included in a same orbital plane <NUM> may be separated from one another based on a degree of separation. For example, a degree of separation between the second satellites <NUM> included in a same orbital plane <NUM> may be equal to (or around) five (<NUM>) degrees.

<FIG> shows a block diagram of a signal analyzer that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. The signal analyzer <NUM> may be an example of aspects of a first satellite or ground station as described with reference to <FIG>. The signal analyzer <NUM>, or various components thereof, may be an example of means for performing various aspects of lensing using lower earth orbit repeaters as described herein. For example, the signal analyzer <NUM> may include a channel estimator <NUM>, a beamformer <NUM>, a signal manager <NUM>, a covariance estimator <NUM>, a demodulator <NUM>, a decoder <NUM>, or any combination thereof. Each of these components may communicate, directly or indirectly, with one another (e.g., via one or more buses).

The signal analyzer <NUM> may support communications in accordance with examples as disclosed herein. The beamformer <NUM> is configured as or otherwise support a means for obtaining beam coefficients of a beam associated with a geographic area based at least in part on an estimated return channel that comprises a first channel component between the geographic area and a plurality of second satellites and a second channel component between the plurality of second satellites and a first satellite; and forming a beam associated with the geographic area to obtain a beam signal based at least in part on the beam coefficients and a plurality of signal components of a signal originating from the geographic area and relayed by the plurality of second satellite to the first satellite.

In some examples, the channel estimator <NUM> may be configured as or otherwise support a means for estimating a return channel from a geographic area, the return channel comprising a first channel component between a first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographic area. In some examples, to support estimating the return channel of the geographic area, the channel estimator <NUM> may be configured as or otherwise support a means for determining a plurality of return channels based at least in part on one or more other signals received from known geographic locations. In some examples, the one or more other signals comprise one or more reference signals transmitted by transmitters in the known geographic locations. In some examples, to support estimating the return channel of the geographic area, the channel estimator <NUM> may be configured as or otherwise support a means for interpolating characteristics of the plurality of return channels to estimate characteristics of the return channel.

In some examples, the signal manager <NUM> may be configured as or otherwise support a means for obtaining a representation of the plurality of signal components relayed by the plurality of second satellites and a representation of a direct signal component of the signal received at the first satellite from the geographic area, wherein the beam signal is determined based at least in part on the representation of the plurality of signal components and the representation of the direct signal component.

In some examples, the covariance estimator <NUM> may be configured as or otherwise support a means for estimating a return covariance associated with the geographic area based at least in part on the return channel. In some examples, the beamformer <NUM> may be configured as or otherwise support a means for determining beam coefficients of the beam based at least in part on the return channel and the return covariance.

In some examples, to support obtaining the beam signal, the beamformer <NUM> may be configured as or otherwise support a means for applying beam coefficients of the beam to a representation of the plurality of signal components of the signal to obtain one or more beam signals.

In some examples, the channel estimator <NUM> may be configured as or otherwise support a means for estimating a plurality of return channels from a plurality of geographic areas, the plurality of return channels comprising the return channel and the plurality of geographic areas comprising the geographic area. In some examples, the covariance estimator <NUM> may be configured as or otherwise support a means for estimating a return covariance based at least in part on the plurality of return channels. In some examples, the beamformer <NUM> may be configured as or otherwise support a means for determining a plurality of beam coefficients of a plurality of beams based at least in part on the plurality of return channels and the return covariance.

In some examples, the beamformer <NUM> may be configured as or otherwise support a means for applying the plurality of beam coefficients of the plurality of beams to representations of pluralities of signal components associated with a plurality of signals originating from the plurality of geographic areas to obtain one or more beam signals, the one or more beam signals comprising the beam signal.

In some examples, the demodulator <NUM> may be configured as or otherwise support a means for demodulating the beam signal. In some examples, the decoder <NUM> may be configured as or otherwise support a means for decoding a demodulated beam signal.

<FIG> shows a diagram of a communications device that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. The communications device <NUM> may be an example of or include the components of a first satellite <NUM> (e.g., a geosynchronous satellite that support on-board beamforming) or ground system <NUM> as described herein. The communications device <NUM> may include components for processing signals, such as an input/output (I/O) controller <NUM>, a transceiver <NUM>, an antenna <NUM>, a signal analyzer <NUM>, a memory <NUM>, code <NUM>, and a processor <NUM>. These components may be in electronic communication or otherwise coupled (e.g., operatively, communicatively, functionally, electronically, electrically) via one or more buses (e.g., a bus <NUM>).

The I/O controller <NUM> may manage input and output signals for the communications device <NUM>. The I/O controller <NUM> may also manage peripherals not integrated into the communications device <NUM>. Additionally, or alternatively, the I/O controller <NUM> may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller <NUM> may be implemented as part of a processor, such as the processor <NUM>. In some cases, a user may interact with the communications device <NUM> via the I/O controller <NUM> or via hardware components controlled by the I/O controller <NUM>.

In some cases, antenna <NUM> may be a single antenna. In some other cases, the antenna <NUM> may include multiple antennas (or antenna elements), which may be capable of concurrently transmitting or receiving multiple wireless transmissions. The transceiver <NUM> may communicate bi-directionally, via the one or more antennas <NUM>, wired, or wireless links as described herein. The transceiver <NUM> may also include a modem to modulate the packets, to provide the modulated packets to one or more antennas <NUM> for transmission, and to demodulate packets received from the one or more antennas <NUM>.

The memory <NUM> may store code <NUM>. Code <NUM> may be computer-readable and computer-executable code and may include instructions that, when executed by the processor <NUM>, cause the communications device <NUM> to perform various functions described herein. The code <NUM> may be stored in a non-transitory computer-readable medium such as system memory or another type of memory.

The processor <NUM> may include an intelligent hardware device (e.g., a general-purpose processor, a DSP, a 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 <NUM> may be configured to operate a memory array using a memory controller. In some other cases, a memory controller may be integrated into the processor <NUM>. The processor <NUM> may be configured to execute computer-readable instructions stored in a memory (e.g., the memory <NUM>) to cause the communications device <NUM> to perform various functions (e.g., functions or tasks supporting reporting angular offsets across a frequency range). For example, the communications device <NUM> or a component of the communications device <NUM> may include a processor <NUM> and memory <NUM> coupled to the processor <NUM>, the processor <NUM> and memory <NUM> configured to perform various functions described herein. Processor <NUM> may include (or be an example of) ground station processor <NUM> or on-board processor <NUM>.

The signal analyzer <NUM> may support signal analysis at a first satellite (e.g., a geosynchronous satellite) or ground station in accordance with examples as disclosed herein. For example, the signal analyzer <NUM> may be configured as or otherwise support a means for obtaining beam coefficients of a beam associated with a geographic area based at least in part on an estimated return channel that comprises a first channel component between the geographic area and a plurality of second satellites and a second channel component between the plurality of second satellites and a first satellite. The signal analyzer <NUM> may be configured as or otherwise support a means for forming a beam associated with the geographic area to obtain a beam signal based at least in part on the beam coefficients and a plurality of signal components of a signal originating from the geographic area and relayed by the plurality of second satellite to the first satellite.

In some examples, the signal analyzer <NUM> may be configured to perform various operations (e.g., receiving, monitoring, transmitting) using or otherwise in cooperation with the transceiver <NUM>, the one or more antennas <NUM>, or any combination thereof. Although the signal analyzer <NUM> is illustrated as a separate component, in some examples, one or more functions described with reference to the signal analyzer <NUM> may be supported by or performed by the processor <NUM>, the memory <NUM>, the code <NUM>, or any combination thereof. For example, the code <NUM> may include instructions executable by the processor <NUM> to cause the communications device <NUM> to perform various aspects of reporting angular offsets across a frequency range as described herein, or the processor <NUM> and the memory <NUM> may be otherwise configured to perform or support such operations.

<FIG> shows a flowchart illustrating a method that supports lensing using lower earth orbit repeaters in accordance with examples as disclosed herein. The operations of the method are implemented by components of a first satellite (e.g., a geosynchronous satellite that support on-board beamforming) or ground station as described herein. In some examples, a first satellite or ground station may execute a set of instructions to control the functional elements of the first satellite or ground station to perform the described functions. Additionally, or alternatively, the first satellite or ground station may perform aspects of the described functions using special-purpose hardware.

At <NUM>, the method includes obtaining beam coefficients of a beam associated with a geographic area based at least in part on an estimated return channel that comprises a first channel component between the geographic area and a plurality of second satellites and a second channel component between the plurality of second satellites and a first satellite. The operations of <NUM> may be performed in accordance with examples as disclosed herein. In some examples, aspects of the operations of <NUM> may be performed by a channel estimator <NUM> as described with reference to <FIG>.

At <NUM>, the method includes forming a beam associated with the geographic area to obtain a beam signal based at least in part on the beam coefficients and a plurality of signal components of a signal originating from the geographic area and relayed by the plurality of second satellite to the first satellite. The operations of <NUM> may be performed in accordance with examples as disclosed herein. Aspects of the operations of <NUM> are performed by a beamformer <NUM> as described with reference to <FIG>.

In some examples, an apparatus as described herein may perform a method or methods, such as the method <NUM>. The apparatus may include, features, circuitry, logic, means, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for obtaining beam coefficients of a beam associated with a geographic area based at least in part on an estimated return channel that comprises channel components between the geographic area and a plurality of second satellites; and forming a beam associated with the geographic area to obtain a beam signal based at least in part on the beam coefficients and a plurality of signal components associated with a signal originating from the geographic area.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for receiving a representation of the plurality of signal components, wherein the beam signal is obtained based at least in part on applying the beam coefficients of the beam to the representation of the plurality of signal components.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for estimating a return channel from a geographic area, the return channel comprising a first channel component between a first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographic area.

In some examples of the method <NUM> and the apparatus described herein, estimating the return channel of the geographic area may include operations, features, circuitry, logic, means, or instructions for determining a plurality of return channels based at least in part on one or more other signals received from known geographic locations and interpolating characteristics of the plurality of return channels to estimate characteristics of the return channel.

In some examples of the method <NUM> and the apparatus described herein, the one or more other signals comprise one or more reference signals transmitted by transmitters in the known geographic locations.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for obtaining a representation of the plurality of signal components relayed by the plurality of second satellites and a representation of a direct signal component of the signal received at the first satellite from the geographic area, wherein the beam signal may be determined based at least in part on the representation of the plurality of signal components and the representation of the direct signal component.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for estimating a return covariance associated with the geographic area based at least in part on the return channel and determining beam coefficients of the beam based at least in part on the return channel and the return covariance.

In some examples of the method <NUM> and the apparatus described herein, obtaining the beam signal may include operations, features, circuitry, logic, means, or instructions for applying beam coefficients of the beam to a representation of the plurality of signal components of the signal to obtain one or more beam signals.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for estimating a plurality of return channels from a plurality of geographic areas, the plurality of return channels comprising the return channel and the plurality of geographic areas comprising the geographic area, estimating a return covariance based at least in part on the plurality of return channels, and determining a plurality of beam coefficients of a plurality of beams based at least in part on the plurality of return channels and the return covariance.

Some examples of the method <NUM> and the apparatus described herein may further include operations, features, means, or instructions for applying the plurality of beam coefficients of the plurality of beams to representations of pluralities of signal components associated with a plurality of signals originating from the plurality of geographic areas to obtain one or more beam signals, the one or more beam signals comprising the beam signal.

A system for communications is described. The system includes a first satellite in a first orbit, a plurality of second satellites in second orbits that are lower than the first orbit, wherein the plurality of second satellites are configured to detect respective signal components of a signal originating from a geographic area and to relay the respective signal components to the first satellite, and a beamformer configured to form a beam associated with the geographic area to obtain a beam signal based at least in part on the respective signal components and an estimated return channel, wherein the estimated return channel comprises channel components between the geographic area and the plurality of second satellites.

In some examples of the system, the first satellite comprises a plurality of transponders, wherein to transmit a representation of the signal to a ground system, each transponder of the plurality of transponders may be configured to receive the respective signal components relayed by the plurality of second satellites and to transmit a representation of the respective signal components to the ground system.

In some examples of the system, each satellite of the plurality of second satellites comprises at least one repeater, wherein to relay the respective signal components to the first satellite, repeaters of the plurality of second satellites may be configured to amplify the respective detected signal components and transmit respective amplified signal components to the first satellite. In some examples of the system, the at least one repeater may be a non-processing repeater.

In some examples of the system, the repeaters of the plurality of second satellites may be configured to transmit the respective amplified signal components at a same frequency as the respective signal components detected at the repeaters.

In some examples of the system, the repeaters of the plurality of second satellites may be configured to transmit the respective amplified signal components at a different frequency than the respective signal components detected at the repeaters.

In some examples of the system, each of the repeaters of the plurality of second satellites may be configured to transmit a respective amplified signal component at a respective frequency of a plurality of frequencies.

In some examples of the system, the respective signal components detected by the plurality of second satellites may be detected via a first channel between the plurality of second satellites and the geographic area, the respective signal components may be relayed to the first satellite via a second channel between the plurality of second satellites and the first satellite, and the first satellite may be configured to transmit a representation of the respective signal components to a ground system via a third channel between the first satellite and the ground system.

In some examples of the system, the beamformer may be further configured to estimate a return covariance associated with the estimated return channel, determine beam coefficients of the beam based at least in part on the estimated return channel and the return covariance, and apply the beam coefficients to the respective signal components to obtain the beam signal.

In some examples, the system may include a ground system comprising, a plurality of gateways configured to receive a representation of the respective signal components, and the beamformer, wherein the beamformer may be coupled with the plurality of gateways and configured to apply beam coefficients of the beam to the representation of the respective signal components to obtain the beam signal.

In some examples of the system, the first satellite comprises the beamformer and may be further configured to transmit the beam signal to a ground system.

In some examples of the system, the plurality of second satellites may be configured to detect a plurality of respective signal components of a plurality of signals originating from a plurality of geographic areas, the plurality of signals comprising the signal and the plurality of geographic areas comprising the geographic area and the beamformer may be configured to form a plurality of beams associated with the plurality of geographic areas to obtain a plurality of beam signals based at least in part on the plurality of respective signal components and a plurality of estimated return channels, the plurality of estimated return channels comprising the estimated return channel.

In some examples of the system, the beamformer may be further configured to estimate a return covariance associated with the plurality of geographic areas and determine beam coefficients of the beam based at least in part on the estimated return channel and the return covariance and to apply the beam coefficients of the beam to the plurality of respective signal components to obtain the plurality of beam signals.

In some examples of the system, the first satellite may be configured to detect a direct signal component of the signal.

In some examples of the system, the beamformer may be further configured to obtain the beam signal based at least in part on the direct signal component.

In some examples of the system, the beamformer may be further configured to estimate the estimated return channel based at least in part on other signals received from one or more other geographic areas. In some examples of the system, the other signals comprise one or more reference signals transmitted by transmitters in known locations.

In some examples of the system, the plurality of second satellites comprises a first set of satellites in a first orbital plane of the second orbits. In some examples of the system, the plurality of second satellites comprises a second set of satellites in a second orbital plane of the second orbits.

In some examples, the system includes a processor configured to demodulate the beam signal. In some examples, the system includes a processor that comprises the beamformer. In some examples of the system, the first orbit may be a geostationary orbit.

A communications device is described. The communications device may include a processor, memory coupled with the processor and comprising instructions executable by the processor to cause the communications device to, estimate a return channel from a geographic area, the return channel comprising a first channel component between a first satellite and a plurality of second satellites and a second channel component between the plurality of second satellites and the geographic area, and obtain, based at least in part on a plurality of signal components associated with a signal originating from the geographic area, a beam signal, wherein the plurality of signal components are relayed by respective second satellites of the plurality of second satellites.

In some examples of the communications device, the instructions for estimating the return channel may be further executable by the processor to determine a plurality of return channels based at least in part on one or more other signals received from known geographic locations and interpolate characteristics of the plurality of return channels to estimate characteristics of the return channel.

In some examples of the communications device, the instructions may be further executable by the processor to obtain a representation of the plurality of signal components relayed by the plurality of second satellites and a representation of a direct signal component of the signal received at the first satellite from the geographic area, wherein the beam signal may be determined based at least in part on the representation of the plurality of signal components and the representation of the direct signal component.

In some examples of the communications device, the instructions may be further executable by the processor to estimate a return covariance associated with the geographic area based at least in part on the return channel and determine beam coefficients of the beam based at least in part on the return channel and the return covariance.

In some examples of the communications device, the instructions for obtaining the beam signal may be further executable by the processor to apply beam coefficients of the beam to a representation of the plurality of signal components of the signal to obtain one or more beam signals.

In some examples of the communications device, the instructions may be further executable by the processor to estimate a plurality of return channels from a plurality of geographic areas, the plurality of return channels comprising the return channel and the plurality of geographic areas comprising the geographic area, estimate a return covariance based at least in part on the plurality of return channels, and determine a plurality of beam coefficients of a plurality of beams based at least in part on the plurality of return channels and the return covariance.

In some examples of the communications device, the instructions may be further executable by the processor to apply the plurality of beam coefficients of the plurality of beams to representations of pluralities of signal components associated with a plurality of signals originating from the plurality of geographic areas to obtain one or more beam signals, the one or more beam signals comprising the beam signal.

It should be noted that these methods describe examples of implementations, and that the operations and the steps may be rearranged or otherwise modified such that other implementations are possible. In some examples, aspects from two or more of the methods may be combined. For example, aspects of each of the methods may include steps or aspects of the other methods, or other steps or techniques described herein.

A processor may also be implemented as a combination of computing devices (e.g., a combination of a digital signal processor (DSP) and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

By way of example, and not limitation, non-transitory computer-readable media may include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory, compact disk read-only memory (CDROM) or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor.

Claim 1:
A method for communications, comprising:
obtaining beam coefficients of a beam associated with a geographic area (<NUM>) based at least in part on an estimated return channel that comprises a first channel component between the geographic area (<NUM>) and a plurality of second satellites (<NUM>) and a second channel component between the plurality of second satellites (<NUM>) and a first satellite (<NUM>), the plurality of second satellites being in second orbits that are lower than a first orbit of the first satellite (<NUM>) and having respective antennas that illuminate respective portions of the geographic area (<NUM>); and
forming, by a beamformer (<NUM>, <NUM>) located in a ground system (<NUM>) or in the first satellite (<NUM>), a beam associated with the geographic area (<NUM>) to obtain a beam signal based at least in part on the beam coefficients and respective relayed signal components (<NUM>) obtained from a plurality of signal components (<NUM>) of a signal originating from the geographic area (<NUM>), wherein the respective relayed signal components (<NUM>) are obtained from the plurality of signal components (<NUM>) by respective second satellites of the plurality of second satellites (<NUM>) and transmitted to the first satellite (<NUM>) by the respective second satellites of the plurality of second satellites (<NUM>).