Lens effect using a low Earth orbit repeater

Abstract

Methods, systems, and devices for communication operations are described. A first satellite may be in a first orbit, and a second set of satellites may be in a second orbit lower than the first orbit. The second satellite may detect signal components of a signal originating from a geographic region and relay the respective signal components to the first satellite. A beamformer connected to the first satellite may form a beam associated with the geographic region. The beamformer may also obtain a beam signal based on the respective signal components and a return channel, the return channel including at least one channel element between the geographic region and the second set of satellites.

Description

Technical Field

[0001] The following generally relates to communications, and more specifically to signal detection.

[0002] The antenna array of a geostationary satellite can irradiate a geographical area associated with the satellite's coverage area. In some examples, the satellite can be used to assist in communication between an access node terminal and a user terminal within the coverage area. The satellite may also be used to detect signals radiated within the satellite's coverage area. In some examples, for instance, due to the distance of the satellite from the target geographical area, the detection resolution of the satellite may be limited. For example, the satellite may not be able to detect signals transmitted or radiated at low power levels or within geographical areas not intentionally directed towards the satellite.

Summary of the Invention

[0003] The described technology relates to improved methods, systems, devices, and apparatuses that use low Earth orbit repeaters to assist in the lens effect. A first satellite may be in a first orbit, and a set of second satellites may be in a second orbit lower than the first orbit. The second satellites can detect signal components of signals originating from a geographical area within the coverage area of the first satellite. The second satellites can relay each signal component to the first satellite. A beamformer connected to the first satellite can form a beam associated with the geographical area. The beamformer can also obtain a beam signal based on each signal component to form a beam and obtain a return channel. The return channel can at least include a channel between the geographical area and the set of second satellites.

Brief Description of the Drawings

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DETAILED DESCRIPTION OF THE INVENTION

[0012] A satellite communication system can include satellites in a geostationary earth orbit (GEO), sometimes referred to as GEO satellites, and satellites in a non-GEO earth orbit, sometimes referred to as non-GEO satellites. In some examples, the non-GEO is at a lower altitude than the GEO. Some examples of non-GEO satellites include medium earth orbit (MEO) satellites, sometimes referred to as MEO satellites, and low earth orbit (LEO) satellites, sometimes referred to as LEO satellites. Satellites (e.g., GEO satellites, MEO satellites, or LEO satellites) can be used to detect signals radiated from stationary or mobile sources on land, water, or in the air. In some examples, a satellite network operator can use the detected signals to determine whether a known or unknown radiator is in a geographic area.

[0013] GEO satellites can be used to detect both known and unknown signal radiators within a geographic area. In some examples, the resolution of a GEO satellite related to the survey of a particular geographic area may be limited based on the size of the antenna array in the GEO satellite. Thus, in the case of GEO satellites, the 3dB boundary of the beam used to survey the geographic area of interest may be unduly large compared to the boundary of the geographic area of interest.

[0014] According to various aspects described herein, in order to increase resolution and survey a wide geographic area, for example, multiple non-GEO satellites can be used based on multiple non-GEO satellites having apertures larger than a single satellite. In some examples, a relay link can be established between a first satellite (e.g., a GEO satellite) in a first orbit (e.g., GEO) and one or more second satellites (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEO). By using one or more second satellites as relay satellites to the first satellite, the second satellites can be made of relatively low complexity (e.g., low cost, small size, etc.) compared to a fully functional satellite having a high-power transponder and a high-gain tracking antenna system for directly transmitting signals to a ground station. Each of the one or more second satellites can have one or more antennas irradiated by at least a portion of one or more geographic areas, and each can detect signal components of one or more signals radiated within one or more geographic areas. The one or more second satellites can relay the respective signal components of the one or more signals to the first satellite. In some examples, when ground-based beamforming is used, the first satellite can transmit a signal component or a representative of the signal component in one or more signals to a ground system. In some examples, the ground system can determine and apply beamforming weights to one or more signals received from the first satellite to obtain one or more beam signals corresponding to the signals detected in one or more geographic areas.

[0015] In other examples, when on-board beamforming is used, the first satellite can process the signal components, determine beamforming weights, apply them to the signal components, and obtain one or more beam signals corresponding to the signals detected from one or more geographic areas. In such a case, the first satellite can transmit a representative of the one or more beam signals to a ground system. By using the signal components detected by the one or more second satellites, post-processing can be performed that enables the processing system to focus on one or more geographic areas with enhanced sensitivity, effectively increasing the detection resolution of the first satellite.

[0016] In some examples, in addition to each signal component received from one or more second satellites, the first satellite can detect additional signal components of one or more signals in one or more geographic regions, for example, via a direct path. In such cases, the second satellites can effectively increase the aperture of the first satellite. In some examples, the first satellite can transmit to the ground system a representative of the additional signal components of one or more signals, or the detected additional signal components of one or more signals. The ground system can use the additional signal components to obtain a representative of one or more signals detected in one or more geographic regions. In other examples, the first satellite can use the additional signal components to obtain a representative of one or more signals. By complementing the direct signal components received at the first satellite with the signal components received at one or more second satellites, the quality of the signals detected by the first satellite can be improved compared to the case where only the direct signal components are used to detect the signals (for example, the signal strength can be increased).

[0017] Aspects of the present disclosure are first described in relation to satellite communication systems. Specific examples are then described with coverage diagrams, process flows, and constellation diagrams. Aspects of the present disclosure are further illustrated and described by apparatus diagrams and flowcharts related to the lens effect using low Earth orbit repeaters.

[0018] FIG. 1A shows a diagram of a communication system that uses a low Earth orbit repeater to assist with a lensing effect, according to an example disclosed in this specification. The satellite communication system 100 can include a network of satellites including a first satellite 105 and a second satellite 115. The satellite communication system 100 can also include a terrestrial system 130 including one or more gateways 135. The one or more gateways 135 may include (or alternatively be connected to) a beamformer 155. In some examples, the beamformer 155 can be included in a terrestrial station processor 153. The terrestrial station processor 153 can use the beamformer 155 to determine beam coefficients. The terrestrial station processor 153 may also be configured to demodulate (and in some examples, decode) a beam signal formed by the beamformer 155.

[0019] A satellite (e.g., the first satellite 105 or the second satellite 115) can be configured to assist with wireless communication between one or more access node terminals (e.g., of the terrestrial system 130) and user terminals located within a coverage area (e.g., coverage area 150). The satellite can also be configured to detect signals radiated within the coverage area 150. In some examples, the satellite can include an antenna assembly having one or more antenna feed elements. Each of the antenna feed elements may also include, or be otherwise connected to, a radio frequency (RF) signal transducer, a low noise amplifier (LNA), or a power amplifier (PA), and may be connected to one or more transponders of the satellite.

[0020] In some examples, some or all of the satellite's antenna feed elements may be arranged as an array of collaborative receive and / or transmit antenna feed elements 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. In the case of OBBF, the satellite can include N1 transmitters and can form K1 user beams using an N1xK1 beam weight matrix. Similarly, in the case of GBBF, the satellite includes L1 transmitters and can receive L1 signals (e.g., frequency-division multiplexed) corresponding to each of the transmitters within the satellite from one or more access node terminals. One or more access node terminals can apply an L1xK1 beam weight matrix to form K1 user beams. In the case of E2E beamforming, the satellite can include L1 transponders. The L1 transponders may be used to receive signals from M access node terminals, and the received signals may be weighted (e.g., weight each of the K1 beam signals for each respective set of one or more access node terminals) prior to transmission by the access node terminals to assist in beamforming of the K1 user beams. Although this example describes the forward link, it should be noted that a similar arrangement can be made for the return link.

[0021] The satellite may be launched into different orbits, i.e., GEO or non-GEO orbits. Satellites within GEO may be referred to as GEO satellites. Non-GEO orbits may include MEO, LEO, equatorial low Earth orbit (ELEO), etc. Satellites within MEO may be referred to as MEO satellites, and satellites within LEO may be referred to as LEO satellites, etc. GEO satellites can orbit the Earth at a speed that matches the Earth's rotation speed and can thus remain at a single position relative to a point on the Earth. LEO satellites can orbit the Earth at a speed that exceeds the Earth's rotation speed (e.g., relative to the ground), and thus the position of the satellite relative to a point on the Earth can change as the satellite passes through LEO. LEO satellites can be launched at low inclination (e.g., ELEO) or high inclination (e.g., polar orbit) to provide different types of coverage and revisit times for a given region of the Earth. MEO satellites also orbit the Earth at a speed that exceeds the Earth's rotation speed but are at a higher altitude than LEO satellites. HEO satellites can orbit the Earth in an elliptical pattern where the satellite approaches and recedes from the Earth over the entire HEO.

[0022] In some examples, GEO satellites may be more expensive and architecturally more complex than non-GEO satellites (e.g., may include more repeaters, antenna elements, transponders, etc.). Despite the increasing complexity of GEO satellites, a network of non-GEO satellites can provide services and monitor the Earth at a higher granularity than GEO satellites (e.g., based on being closer to the Earth in greater numbers). In some examples, GEO satellites and non-GEO satellites operate independently of each other. In some examples, the first satellite 105 may be a GEO satellite. The second satellite 115 can include LEO satellites, MEO satellites, or a combination thereof.

[0023] In some examples, a satellite network can be used to monitor at least a portion of the Earth for signals radiated from known and unknown transmitters. For example, a satellite network can use a first satellite 105 to detect signals originating from a geographic area (e.g., the geographic area encompassed by coverage area 150). In some examples, the first satellite 105 can transmit detected signal energy to a ground system 130 (e.g., to one or more of gateways 135) to process (e.g., determine and apply beamforming coefficients) the detected signal energy to obtain one or more signals, such as when ground-based beamforming is used. In other examples, the first satellite 105 can process (e.g., determine and apply beamforming coefficients) the detected signal energy and transmit one or more signals to the ground system 130, such as when on-board beamforming is used.

[0024] GEO satellites can be used to detect known and unknown signal radiators within a geographic area. In some examples, the resolution of a GEO satellite associated with the survey of a particular geographic area may be limited based on the size of the antenna array in the GEO satellite and the distance of the GEO satellite from the point of interest. Thus, for GEO satellites, the 3dB boundary of the beam used to survey the geographic area of interest may be unduly large compared to the boundaries of the geographic area of interest.

[0025] According to various aspects described herein, to increase resolution and survey a large geographical area, for example, multiple non-GEO satellites (e.g., GEO, MEO, or LEO) having apertures larger than a single satellite can be used, based on multiple non-GEO satellites. In some examples, a relay link can be established between a first satellite 105 (e.g., a GEO satellite) in a first orbit (e.g., GEO) and one or more second satellites 115 (e.g., non-GEO satellites) in one or more second orbits (e.g., one or more non-GEO). Each of the one or more second satellites 115 can have one or more antennas that irradiate at least a portion of one or more geographical areas 140, and each can detect signal components 125 of one or more signals radiated within one or more geographical areas. According to various aspects described herein, the one or more antennas of the second satellite 115 are described as being irradiated (instead of irradiating) by a portion of one or more geographical areas 140. It is noteworthy that these terms can be used interchangeably to describe that the one or more antennas of the second satellite 115 can be used to transmit signals to or detect signals from one or more geographical areas 140.

[0026] One or more of the second satellites 115 can relay the respective signal components 125 of one or more signals to the first satellite 105. In some examples, when ground-based beamforming is used, the first satellite 105 can transmit the signal components of one or more signals, or a representative of the signal components, to a ground system 130. In some examples, the ground system 130 can determine and apply beamforming weights to one or more signals received from the first satellite 105 to obtain one or more beam signals corresponding to the one or more signals detected in one or more geographical areas 140.

[0027] In other examples, when on-board beamforming is used, the first satellite 105 can process the relayed signal components 110, determine beamforming weights, apply them to the signal components, and obtain one or more beam signals corresponding to one or more signals. In such a case, the first satellite 105 can transmit a representative of the one or more beam signals to the ground system 130. By using the signal components detected by one or more second satellites 115, post-processing can be performed that enables the processing system to focus on one or more geographical regions 140 with enhanced sensitivity, effectively increasing the detection resolution of the first satellite 105.

[0028] In some examples, in addition to each signal component relayed from one or more second satellites 115, the first satellite 105 can detect additional signal components (e.g., direct signal components 120) of one or more signals within one or more geographical regions, for example, via a direct path. In such a case, the second satellite can effectively increase the aperture of the first satellite. In some examples, the first satellite 105 can use the additional signal components to obtain a representative of one or more signals. In other examples, the first satellite 105 can transmit an additional signal component of one or more signals, or a representative of the detected additional signal components of one or more signals, to the ground system 130. The ground system 130 can use the additional signal components to obtain a representative of one or more signals detected in one or more geographical regions 140. By complementing the direct signal components 120 received by the first satellite 105 with the signal components received by one or more second satellites 115, the quality of the signals detected by the first satellite 105 can be improved (e.g., the signal strength can be increased) compared to the case where only the direct signal components 120 are used to detect the signals.

[0029] When RF signal energy is radiated from a radiator (e.g., a transmitter or a thermal energy emitter), each second satellite 115 detects signal components (e.g., having respective phase shifts or amplitude fluctuations due to different channels between the radiator and each second satellite 115). When used in combination with the first satellite 105 to detect signal components within a geographic region 140 corresponding to the location of the radiator (e.g., radiator 145), the second satellite 115 may be referred to as a relay satellite 115. The geographic region 140 may be disposed within the coverage area 150 of the first satellite 105. For example, the first relay satellite 115-1 can receive the first detected signal component 125-1 based on a signal radiated from the radiator 145 within the first geographic region 140-1. In some examples, the first relay satellite 115-1 receives the first signal component 125-1 detected via a first return channel

Number

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[0030] In some examples, the return channels between the relay satellite 115 and a set of geographic regions 140 may be included in a combined return channel matrix A1 RTN The matrix A1 RTNcan include the number of rows based on the number of repeaters included in the relay satellite 115 and the number of relay satellites 115, and the number of columns based on the number of geographical regions 140 monitored by the relay satellite 115. For example, if S relay satellites 115 include Q repeaters and are used to monitor P geographical regions 140, A1 RTN The matrix can have Q·S rows and P columns.

[0031] The relay satellite 115 can relay the detected signal component 125 (or a representative of the detected signal component) to the first satellite 105. In some examples, relaying the detected signal component 125 can include frequency-shifting the detected signal component, amplifying the detected signal component, or both, before the detected signal component is relayed to the first satellite 105.

[0032] FIG. 1B shows the components of a satellite that uses a low Earth orbit repeater to assist with a lensing effect, according to an example disclosed herein. As shown in FIG. 1B, the relay satellite 115 may include one or more repeaters 160 that are used to amplify and / or frequency-shift a detected signal before relaying the detected signal to the first satellite 105. The repeater 160 may be a non-processing repeater. That is, the repeater 160 may not perform operations to analyze or reformat data within the signal waveform. For example, the repeater 160 may not digitize, demodulate, decode, apply beamforming weights, or reformat the detected signal before relaying the detected signal to the first satellite 105. The repeater 160 can include a frequency converter 165, an amplifier 170, or both. The frequency converter 165 can be configured to shift the frequency of the detected signal (e.g., by mixing the detected signal with another frequency). In some examples, the frequency converters 165 within different relay satellites 115 may be configured to apply different frequency shifts to the detected signal. The amplifier 170 may be configured to amplify the detected signal before relaying the amplified signal to the first satellite 105.

[0033] In some examples, the first relay satellite 115-1 can transmit the relayed first signal component 110-1 (which can correspond to an amplified version of the first detected signal component 125-1) to the first satellite 105. In some examples, the first relay satellite 115-1 is the first return channel

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[0034] Matrix A2 RTN may include the number of rows based on the number of uplink / downlink transponder paths in the first satellite 105 and the number of columns based on the number of relay satellites 115 and the number of repeaters included in the relay satellites 115. For example, if the first satellite 105 includes L uplink / downlink transponder paths and there are S relay satellites 115 having Q repeaters, the A2 RTN matrix can have L rows and Q·S columns.

[0035] Therefore, the return channel between the geographical region 140 and the first satellite 105 includes a plurality of elements, namely, the first channel element (which can be represented by A1 RTN ) between the relay satellite 115 and the geographical region 140 and the second channel element (A2 RTNIt may also be a composite return channel including (which can be represented by). In some examples, the composite return channel between the geographical area 140 and the first satellite 105 is A2 RTN A1 RTN It may be represented by a matrix. In some examples, when the first satellite 105 includes L uplink / downlink transponder paths and P geographical areas 140 are monitored, A2 RTN A1 RTN The matrix can have L rows and P columns.

[0036] In some examples, the first satellite 105 may directly receive signal components from one or more of the geographical areas 140. For example, the first satellite 105 can directly receive the signal component 120 from the radiator 145 via a direct return channel (which can be represented as A TG between the first satellite 105 and the first geographical area 140 - 1). In some examples, the return channel between the geographical area 140, the relay satellite 115, and the first satellite 105 may be combined with the direct return channel to form a combined return channel matrix (which may be represented as A RTN in the formula,

Number

[0037] Similarly, the complete return channel between the geographical area 140 and the terrestrial system 130 may be a composite return channel including multiple components. In some examples, the complete return channel is a channel element between the geographical area 140 and the first satellite 105, which is A2RTN A1 RTN or A RTN represented by) and (matrix E RTN represented by), a channel element in the first satellite 105 between the uplink transponder and the downlink transponder on the first satellite 105, and a channel element (matrix C RTN which can be represented by) between the first satellite 105 and the ground system 130, are included.

[0038] As shown in FIG. 1B, the first satellite 105 may include one or more transponders 175 used to amplify and / or frequency shift the detected signal before transmitting the received signal to the first satellite 105. The transponder 175 can include a frequency converter 165, an amplifier 170, or both. The frequency converter 180 can be configured to shift the frequency of the received signal (e.g., by mixing the detected signal with another frequency). The amplifier 185 may be configured to amplify the received signal before transmitting the amplified signal to the ground system 130. In some examples, the transponder 175 may be connected to on-board processing components such as a beamformer 190, 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 187. In some examples, if the beamformer 190 is included in the first satellite 105, the ground system 130 may not need to use the beamformer 155 to process the signal received from the first satellite 105.

[0039] In some examples, the channel element in the first satellite 105 is based on the path through the transponder in the first satellite 105, and the matrix E RTN may include the number of rows and columns based on the number of transponders included in the first satellite 105. For example, if the first satellite 105 includes L transponders, E RTN matrix may include L rows and L columns.

[0040] Also, the channel element (C RTN represented by a matrix) between the first satellite 105 and the terrestrial system 130 may be based on the number of terrestrial stations included in the terrestrial system 130 and the number of repeaters included in the first satellite 105. For example, if the terrestrial system includes M terrestrial stations (e.g., gateways) and the first satellite 105 includes L uplink / downlink transponder paths, C RTN matrix may include M rows and L columns.

[0041] In some examples, the full return channel between the geographic region 140 and the terrestrial system 130 may be represented by a matrix H RTN , where H RTN = C RTN E RTN A2 RTN A1 RTN . In some examples, if the terrestrial system 130 includes M terrestrial stations and P geographic regions 140 are monitored, the H RTN matrix can have M rows and P columns.

[0042] In some examples, the terrestrial system 130 can estimate the full return channel H RTN based on signals received from known radiators located within the coverage area 150. The terrestrial system 130 can use the signals received from the known radiators to determine the return channel associated with the received signals, and interpolate the determined return channels to estimate the return channel between the geographic region 140 and the terrestrial system 130. In some examples, the terrestrial system 130 can use the received signals to estimate a portion of the full return channel elements. For example, the terrestrial system 130 can use the signals to estimate the channel elements associated with A1 RTN , and the other channel elements can be estimated based on reference signals communicated between devices to assist in channel estimation.

[0043] The terrestrial system 130 is (matrix R RTNEstimated channel elements can be used to determine the return covariance, which can be represented by. In some examples, the terrestrial system can use the estimated channel elements to determine the return covariance between signals received from different geographic regions 140 at M different terrestrial stations, where

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[0044] The terrestrial system 130 can use the estimated full return channel and the estimated return covariance to determine the beamforming coefficients to be applied to the signals received via the full return channel. In some examples, the beamforming coefficients are represented by the matrix B RTN where B RTN =(R RTN -1 H RTN ) H is. The matrix B RTNmay include the number of rows based on the number of monitored geographical areas 140 and the number of columns based on the number of terrestrial stations within the terrestrial system 130. For example, in the case of P geographical areas and M terrestrial stations, the matrix B RTN may include P rows and M columns. Thus, the beamformed channel between the terrestrial system 130 and one or more geographical areas 140 is H RTN-BF which can be represented as, where H RTN-BF = B RTN H RTN = B RTN C RTN E RTN A RTN .

[0045] In some examples, instead of applying beam coefficients to the signals received at the terrestrial system 130, the first satellite 105 may apply the beam coefficients determined in the same way to the signals received from the relay satellite 115. In such examples, the first satellite 105 may transmit to the terrestrial system 130 a composite signal including a representative of the signals detected in each of the monitored geographical areas 140. If beamforming is performed at the first satellite 105, the C RTN matrix may be an identity matrix (e.g., an MxL identity matrix, where M may be equal to 1).

[0046] In some examples, instead of transmitting the signal components detected at the relay satellite 115 to the first satellite 105, the relay satellite 115 may transmit the detected signal components directly to the terrestrial system 130. In addition to the signal components transmitted to the terrestrial system 130, the first satellite 105 may transmit direct signal components to the terrestrial system 130. In such a case, the signal components of the signals detected at the relay satellite 115 may complement the direct signal components of the signals detected by the first satellite 105.

[0047] Although generally described with respect to detecting signals originating from the geographic region 140 within the coverage area 150, a similar technique can be used to transmit signals to user terminals having the geographic region 140 on the forward link. In such a case, the forward channel between the terrestrial system 130 and the geographic region 140 can similarly include a plurality of channel elements including a channel element between the terrestrial system 130 and the first satellite 105, a channel element between the first satellite 105 and the relay satellite 115, and a channel element between the relay satellite 115 and the geographic region 140. In such a case, the terrestrial system 130 can similarly estimate the forward channel (and in some examples, estimate one or more forward channel elements individually). Also, the terrestrial system 130 can determine and apply beam coefficients to signals transmitted within different geographic regions, for example, apply a first set of beam coefficients to a first signal to focus the transmission of the first signal within a first geographic region 140-1 to the relay satellite 115, and apply a second set of beam coefficients to a second signal to focus the transmission of the second signal within a second geographic region to the relay satellite 115, and so on. In such an example, the first satellite 105 can transmit different components of the signal to the relay satellite 115, and the relay satellite 115 can transmit different signal components, and the different signal components coherently combine within the desired geographic region 140. In some examples, the relay satellite 115 can reduce the transmission power of different signal components to comply with an on-earth signal strength threshold (e.g., set by a regulatory agency).

[0048] FIG. 2 shows an example of a coverage diagram that uses a low earth orbit repeater to assist with a lens effect, according to an example disclosed herein. The coverage diagram 200 shows the coverage area of a first satellite (e.g., a GEO satellite, the first satellite 105 of FIG. 1) and a GEO satellite that uses one or more second satellites (e.g., the LEO satellite, MEO satellite, LEO and MEO satellites, relay satellite 115 of FIG. 1) to focus on a geographic region.

[0049] In some examples, the antenna array in the first satellite is associated with a coverage area 250. The boundary of the coverage area 250 can represent the point at which the signal received by the antenna array has a signal strength at the 3 dB point. In some cases, the coverage area 250 can represent the coverage area of a beamformed beam for transmitting or receiving from the coverage area 250 via the first satellite. In some examples, the first satellite can process signals received from within the coverage area 250. However, with respect to detecting signals within the coverage area 250, the first satellite may not be able to determine where within the coverage area 250 the signal was transmitted. As described herein, to increase the detection resolution of the first satellite (in some examples, to effectively increase the aperture), one or more second satellites (orbiting at a lower orbit than the first satellite) can be used to detect signals originating from geographical regions within the coverage area 250.

[0050] In some examples, each of the second satellites can have a smaller coverage area 205 compared to the first satellite. Similar to the coverage area 250, the boundary of the coverage area 205 can represent the 3 dB point for detecting signals originating from within the coverage area 205. For example, for a focused first coverage area 205-1, the corresponding second satellite can detect signals originating from the geographical region corresponding to the focused first coverage area 205-1, but cannot detect signals originating outside the focused first coverage area 205-1 although within the coverage area 250. In some examples, the energy from within the overlapping coverage areas 205 of the second satellites can be combined to focus on a particular geographical region 240. For example, the second satellites can be used to focus on a first geographical region 240-1.

[0051] In some examples, the second satellite can be used to focus (e.g., simultaneously) on multiple geographical regions 240 within the coverage area 250 for signal detection. For example, in addition to focusing on the first geographical region 240-1, the second satellite can be used to focus on other geographical regions (e.g., the first geographical region 240-1, the Pth geographical region 240-P). The different geographical regions 240 monitored using the second satellite may or may not overlap. Similarly, in some examples, the second satellite can be used to focus on one or more geographical regions within the coverage area 250 for transmitting signals to user devices in one or more geographical regions.

[0052] Figure 3 shows an exemplary set of operations for assisting with a lensing effect using a low Earth orbit repeater, according to an example disclosed herein. The process flow 300 may be performed by a second satellite 303, a first satellite 305, and a ground system 307, which may be examples of the second satellite 115, the first satellite 105, and the ground system 130 as described in FIG. 1. In some examples, the process flow 300 shows an exemplary series of operations performed to assist with the use of a low Earth orbit repeater. For example, the process flow 300 shows operations for detecting a signal transmitted within a geographical region within the coverage area of a GEO satellite.

[0053] It is understood that one or more of the operations described in the process flow 300 may be performed earlier, later, omitted, replaced, supplemented, or combined with another operation in the process. Also, additional operations described herein that are not included in the process flow 300 may be included.

[0054] At arrow 315, the radiator 301 can radiate a signal while being disposed within a geographical area. In some examples, the radiator 301 radiates a signal while wirelessly communicating with another device that is not the second satellite 303 or the first satellite 305. In other examples, the radiator 301 radiates a signal unintentionally (e.g., the radiator 301 may be a rocket, and the signal may be associated with a flare formed by the rocket). One or more of the second satellites 303 may detect the signal. That is, the signal can be radiated from the radiator 301, and each of the second satellites 303 can detect different signal components associated with the radiated signal. In some examples, in addition to being detected by the second satellites 303, the direct signal component of the radiated signal may be detected by the first satellite 305.

[0055] At arrow 320, the second satellite 303 may relay the detected signal component (or a representative of the received signal component) to the first satellite 305. In some examples, the second satellite 303 may apply the detected signal component to one or more repeaters used to relay the detected signal component to the first satellite 305. The repeaters may be used to amplify the detected signal component (or combinations thereof), apply a frequency shift, or apply a phase shift before transmission to the first satellite 305. In some examples, the first satellite 305 may receive the signal component with one or more antenna elements. The first satellite 305 may also receive the direct signal component with one or more antenna elements.

[0056] At arrow 325, the first satellite 305 can transmit a representative of the signal radiated by the radiator 301 to the terrestrial system 307. The first satellite 305 may transmit signal components (in some examples, including the direct signal component) to the terrestrial system 307. In some examples, the first satellite 305 transmits signal components to the terrestrial system 307 in one or more beams to one or more terrestrial stations. The terrestrial system 307 can receive the signal transmitted from the first satellite 305. In some examples, the terrestrial system 307 can receive the signal transmitted from the first satellite 305 at one or more terrestrial stations.

[0057] At block 330, the terrestrial system 307 can estimate a channel (referred to as the return channel and denoted by H RTN that can be represented by) between the terrestrial system 307 and the radiator 301 based on the received signal. In some examples, the terrestrial system 307 can also estimate the channel based on signals received from known transmitters located within or around a geographic area (e.g., geographic area 140 of FIG. 1 or geographic area 240 of FIG. 2) that includes the radiator 301. In some examples, the signals received from the known transmitters can be transmitted simultaneously with the signals detected by the second satellite 303. In some examples, the signals received from the known transmitters can be transmitted before the signals are detected by the second satellite 303, and in some cases, the signals can be received by a different set of second satellites than the second satellite 303. That is, channel estimation for relaying by a given set of second satellites can be performed using information from signals from known transmitters relayed by different (e.g., non-overlapping, partially overlapping) sets of second satellites.

[0058] In some examples, to estimate the return channel, the terrestrial system 307 uses a part of the return channel between the radiator 301 and the second satellite 303 (denoted as A1 RTN which can be represented by), a part of the return channel between the second satellite 303 and the first satellite 305 (denoted as A2 RTNwhich can be represented by), a part of the return channel between the uplink transponder and the downlink transponder in the first satellite 305 (E RTN which can be represented by), and a part of the return channel between the first satellite 305 and the terrestrial system 307 (C RTN which can be represented by) can be estimated. When the first satellite receives a direct signal component, the terrestrial system can also estimate a part of the return channel (A RTN which can be represented by) between the radiator 301 and the first satellite 305.

[0059] In some examples, the terrestrial system 307 estimates the channel (A1 RTN ) between the radiator and the second satellite 303 based on interpolating signals transmitted by known transmitters in the vicinity of the set of geographical areas being monitored. Then, based on the reference signals transmitted from known transmitters within the set of geographical areas being monitored, the channels (e.g., A2 RTN , E RTN , and C RTN ) between the second satellite 303 and the terrestrial system 307 are estimated. In other examples, the components of the channel are estimated individually. For example, the channel (A2 RTN ) between the second satellite 303 and the first satellite 305 can be estimated (e.g., by the first satellite 305) based on the reference signals transmitted between the second satellite 303 and the first satellite 305. The return channel (E RTN ) of the transponder of the first satellite can also be estimated by the first satellite 305. The first satellite 305 can indicate the estimated channel to the terrestrial system 307. Also, the channel (C RTN ) between the first satellite 305 and the terrestrial system 307 can be estimated (e.g., by the terrestrial system 307) based on the reference signals transmitted between the first satellite 305 and the terrestrial system 307.

[0060] In block 335, the terrestrial system 307 can estimate the covariance associated with the return channel, for example, based on the estimated return channel / constituent of the estimated return channel. The covariance can provide information regarding interference between the transmission of signal components detected in different geographic regions to the terrestrial system 307 and interference from other communications with the terrestrial system 307. In some examples, the interference between signal components from different geographic regions can be [Number] represented by. Also, the interference between J users can be [Number] represented by. And the combined covariance can be [Number] represented by.

[0061] In block 340, the terrestrial system 307 can use the estimated return channel and the estimated return covariance to determine the beam coefficients to be applied to the signals received from the first satellite 305. In some examples, the beam coefficients may be represented by matrix B RTN , where B RTN is sometimes equal to (R RTN -1 H RTN ) H . In some examples, the beam coefficients and the return channel are determined based on the same period, and the signals received to estimate the channel may also be used to determine the beam coefficients. In some examples, the terrestrial system 307 can constantly (e.g., every millisecond) update the estimated return channel and the beam coefficients based on the received signals. For example, the terrestrial system 307 can 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.

[0062] In block 345, the terrestrial system 307 may apply beam coefficients to the signals received from the first satellite 305 to obtain one or more beam signals corresponding to one or more geographic regions. In some examples, the one or more beam signals correspond to representatives of one or more signals radiated in the geographic region. The one or more beam signals can include beam signals that are representatives of signals radiated by the radiator 301 within the geographic region. In some examples, when digital beamforming is used, applying the beam coefficients can include applying the beam coefficients to the digital representation of the signal, for example, by multiplying a beam coefficient matrix and a matrix representing the signal. In other examples, applying the beam coefficients can include combining components of the analog signal received at the terrestrial system 307 to obtain an analog beam signal.

[0063] In block 350, the terrestrial system 307 can process (e.g., filter, analyze, demodulate, decode) one or more beam signals to determine whether a signal has been detected within the geographic region of interest. In some examples, the terrestrial system 307 determines the type of signal (e.g., communication signal, signal related to a rocket, etc.) detected in the geographic region of interest.

[0064] As described above, the order of operations in process flow 300 may be changed. In some examples, operations for determining beam coefficients may be performed by the terrestrial system 307 to estimate the return channel and covariance related to the return channel before the representative of the signal radiated by the radiator 301 is received from the first satellite 305.

[0065] In some examples, the operations of process flow 300 may be performed by different devices. For example, the operations for estimating the return channel and the covariance associated with the return channel, determining the beam coefficients, and applying the beam coefficients may be performed by a first satellite 305 (e.g., if the first satellite is configured to perform OBBF). In such a case, the first satellite 305 may transmit one or more beam signals corresponding to the signals radiated by the radiator 301 to the ground system 307. Also, the ground system 307 can process the one or more received beam signals as described herein.

[0066] Although described in the context of using the second satellite 303 to detect signals via a return channel related to a geographic area within the coverage area of the first satellite 305, similar operations may be performed to estimate a forward channel related to the geographic area and relay signals to user devices within the geographic area using the second satellite 303.

[0067] FIG. 4 shows an example of a satellite layout diagram for assisting the lens effect using a low earth orbit repeater according to an example disclosed herein. The satellite layout diagram 400 shows a set of second satellites (e.g., LEO satellites, MEO satellites, relay satellites 115, etc. in FIG. 1) that can be used in combination with a first satellite (e.g., a GEO satellite, the first satellite 105 in FIG. 1, etc.) to enhance the detection resolution of the first satellite for detecting signals within the coverage area (in some examples, effectively increasing the aperture). In some examples, the coverage area of the second satellite 415 can correspond to each of the focused coverage areas 205 described in FIG. 2.

[0068] The satellite layout diagram 400 may include S second satellites 415, and S may be equal to 9. The set of second satellites 415 may be arranged on different orbital planes 405 (for example, K orbital planes). In some examples, the second satellites 415 are dispersed among three orbital planes 405. The first orbital plane 405-1 may have an inclination of negative 5 (-5) degrees, the second orbital plane 405-2 may have an inclination of 0 degrees, and the third orbital plane 405-3 may have an inclination of 5 (5) degrees. In some examples, the second satellites 415 may be evenly dispersed among the three orbital planes 405 such that three of the second satellites 415 are included in each orbital plane. In some examples, the second satellites 415 included in the same orbital plane 405 can be separated from each other based on the separation degree. For example, the separation degree between the second satellites 415 included in the same orbital plane 405 may be equal to 5 degrees (or approximately 5 degrees).

[0069] FIG. 5 shows a block diagram of a signal analyzer that uses a low Earth orbit repeater to assist with the lens effect, according to an example disclosed herein. The signal analyzer 520 can be an example of an aspect of a first satellite or a ground station as described with reference to FIG. 1A. The signal analyzer 520 or its various components can be an example of means for performing various aspects of the lens effect using the low Earth orbit repeater described herein. For example, the signal analyzer 520 can include a channel estimator 525, a beamformer 530, a signal manager 535, a covariance estimator 540, a demodulator 545, a decoder 550, or any combination thereof. Each of these components can communicate directly or indirectly with each other (for example, via one or more buses).

[0070] The signal analyzer 520 can assist in communication according to the examples disclosed herein. The beamformer 530 may be configured as means for obtaining beam coefficients of a beam related to a geographic area, or otherwise assist in obtaining means, based at least in part on an estimated return channel including a first channel element between the geographic area and a plurality of second satellites and a second channel element between the plurality of second satellites and the first satellite. Also, it may be configured as means for forming a beam associated with the geographic area, or otherwise assist in forming means, for obtaining a beam signal based at least in part on beam coefficients and a plurality of signal components of a signal originating from the geographic area and relayed by the plurality of second satellites to the first satellite.

[0071] In some examples, the channel estimator 525 can be configured as means for estimating a return channel from a geographic area, or otherwise assist in estimating means, where the return channel includes a first channel element between the first satellite and a plurality of second satellites and a second channel element between the plurality of second satellites and the geographic area. In some examples, to assist in estimating the return channel of the geographic area, the channel estimator 525 can be configured as means for determining a plurality of return channels based at least in part on one or more other signals received from known geographic locations, or otherwise assist in determining means. In some examples, the one or more other signals include one or more reference signals transmitted by a transmitter at a known geographic location. In some examples, to assist in estimating the return channel of the geographic area, the channel estimator 525 can be configured as means for interpolating the characteristics of a plurality of return channels to estimate the characteristics of the return channel, or otherwise assist in interpolating means.

[0072] In some examples, the signal manager 535 can be configured as, or otherwise assist in, means for obtaining a representative of a plurality of signal components relayed by a plurality of second satellites and a representative of a direct signal component of a signal received by the first satellite from a geographical area, and the beam signal is determined at least in part based on the representative of the plurality of signal components and the representative of the direct signal component.

[0073] In some examples, the covariance estimator 540 can be configured as, or otherwise assist in, means for estimating a return covariance associated with a geographical area based at least in part on a return channel. In some examples, the beamformer 530 is configured as, or otherwise assist in, means for determining beam coefficients of a beam based at least in part on the return channel and the return covariance.

[0074] In some examples, to assist in obtaining a beam signal, the beamformer 530 can be configured as, or otherwise assist in, means for applying the beam coefficients of a beam to a representative of a plurality of signal components of a signal to obtain one or more beam signals.

[0075] In some examples, the channel estimator 525 can be configured as means for estimating a plurality of return channels from a plurality of geographical regions or, alternatively, can assist means for estimating, where the plurality of return channels includes a return channel and a plurality of geographical regions including the geographical regions. In some examples, the covariance estimator 540 can be configured as means for estimating a return covariance based at least in part on the plurality of return channels or, alternatively, can assist means for estimating. In some examples, the beamformer 530 is configured as 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 or, alternatively, can assist means for determining.

[0076] In some examples, the beamformer 530 is configured as means for applying a plurality of beam coefficients of a plurality of beams to representatives of a plurality of signal components associated with a plurality of signals originating from a plurality of geographical regions to obtain one or more beam signals or, alternatively, can assist means for applying, where the one or more beam signals includes beam signals.

[0077] In some examples, the demodulator 545 is configured as means for demodulating a beam signal or, alternatively, can assist means for demodulating. In some examples, the decoder 550 is configured as means for decoding a demodulated beam signal or, alternatively, can assist means for decoding.

[0078] FIG. 6 shows a diagram of a communication device that uses a low Earth orbit repeater to assist with a lensing effect, according to an example disclosed herein. The communication device 605 can be, or can include, an example of a component of the first satellite 105 (e.g., a geostationary satellite that assists with on-board beamforming) or the terrestrial system 130 described herein. The communication device 605 can include components for processing signals, such as an input / output (I / O) controller 610, a transceiver 615, an antenna 625, a signal analyzer 620, a memory 630, a code 635, and a processor 640. These components can be connected (e.g., operably, communicably, functionally, electronically, electrically) either by electronic communication or via one or more buses (e.g., bus 645).

[0079] The I / O controller 610 can manage the input and output signals of the communication device 605. The I / O controller 610 can also manage peripheral devices that are not integrated into the communication device 605. In some cases, the I / O controller 610 can represent a physical connection or port to an external peripheral device. In some cases, the I / O controller 610 can utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS / 2®, UNIX®, LINUX®, or another known operating system. In addition or alternatively, the I / O controller 610 can represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I / O controller 610 can be implemented as part of a processor such as the processor 640. In some cases, a user can interact with the communication device 605 via the I / O controller 610 or via hardware components controlled by the I / O controller 610.

[0080] In some cases, the antenna 625 may be a single antenna. In some other cases, the antenna 625 may include a plurality of antennas (or antenna elements) capable of simultaneously transmitting or receiving multiple wireless transmissions. The transceiver 615 can communicate bidirectionally with a wired or wireless link via one or more antennas 625, as described herein. For example, the transceiver 615 may represent a wireless transceiver and may communicate bidirectionally with another wireless transceiver. The transceiver 615 can also include a modem for modulating packets and providing the modulated packets to one or more antennas 625 for transmission, and for demodulating packets received from one or more antennas 625.

[0081] The memory 630 can include a random access memory (RAM) and a read-only memory (ROM). The memory 630 can store the code 635. The code 635 can be computer-readable and computer-executable code and, when executed by the processor 640, can include instructions for causing the communication device 605 to perform various functions described herein. The code 635 may be stored in a non-transitory computer-readable medium such as a system memory or another type of memory. In some cases, the code 635 may not be directly executable by the processor 640 but can cause a computer to perform the functions described herein (e.g., when compiled and executed). In some cases, the memory 630 can include, among other things, a basic input / output system (BIOS) capable of controlling basic hardware or software operations such as interactions with peripheral components or devices.

[0082] Processor 640 can include an intelligent hardware device (e.g., a general-purpose processor, DSP, CPU, microcontroller, ASIC, FPGA, programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, processor 640 may be configured to operate a memory array using a memory controller. In some other cases, the memory controller may be integrated with processor 640. Processor 640 can be configured to execute computer-readable instructions stored in a memory (e.g., memory 630) to cause communication device 605 to perform various functions (e.g., functions or tasks that assist in reporting angle offsets over a frequency range). For example, communication device 605 or components of communication device 605 can include processor 640 and memory 630 connected to processor 640, and processor 640 and memory 630 are configured to perform the various functions described herein. Processor 640 can include (or be an example of) ground station processor 153 or on-board processor 187.

[0083] Signal analyzer 620 can assist in signal analysis at a first satellite (e.g., a geostationary satellite) or a ground station, according to the examples disclosed herein. For example, signal analyzer 620 can be configured as, or assist in configuring as, means for obtaining beam coefficients of a beam associated with a geographic area, based at least in part on an estimated return channel that includes a first channel element between the geographic area and a plurality of second satellites and a second channel element between the plurality of second satellites and the first satellite. Signal analyzer 620 can be configured as, or assist in configuring as, means for forming a beam associated with a geographic area to obtain a beam signal, based at least in part on beam coefficients and a plurality of signal components of signals originating from the geographic area and relayed by the plurality of second satellites to the first satellite.

[0084] In some examples, the signal analyzer 620 can be configured to perform various operations (e.g., receive, monitor, transmit) using, or otherwise in cooperation with, the transceiver 615, one or more antennas 625, or any combination thereof. Although the signal analyzer 620 is shown as a separate component, in some examples, one or more functions described with reference to the signal analyzer 620 can be assisted or performed by the processor 640, the memory 630, the code 635, or any combination thereof. For example, the code 635 can include instructions executable by the processor 640 to cause the communication device 605 to perform various aspects of reporting angular offsets over a frequency range as described herein, or the processor 640 and the memory 630 can be configured to perform or assist in performing such operations.

[0085] FIG. 7 is a flowchart illustrating a method of assisting a lens effect using a low Earth orbit repeater, according to an embodiment disclosed herein. The operations of the method can be implemented by components of a first satellite (e.g., a geostationary satellite that assists on-board beamforming) or a ground station, as described herein. In some examples, the first satellite or the ground station can execute a set of instructions for controlling the functional elements of the first satellite or the ground station to perform the described functions. Additionally or alternatively, the first satellite or the ground station can use dedicated hardware to perform aspects of the described functions.

[0086] At 705, the method can include obtaining beam coefficients of a beam associated with a geographic region, based at least in part on an estimated return channel that includes a first channel element between the geographic region and a plurality of second satellites and a second channel element between the plurality of second satellites and the first satellite. The operations at 705 can be performed according to the examples disclosed herein. In some examples, aspects of the operations at 705 can be performed by the channel estimator 525, as described with reference to FIG. 5.

[0087] At 710, the method may include forming a beam associated with a geographic area to obtain a beam signal based at least in part on beam coefficients and a plurality of signal components of signals relayed from the geographic area to the first satellite by a plurality of second satellites. The operations of 710 can be performed according to the examples disclosed herein. In some examples, aspects of the operations of 710 may be performed by beamformer 530 as described with reference to FIG. 5.

[0088] In some examples, the apparatus described herein may be capable of performing a method (s) such as method 700. The apparatus includes features, circuitry, logic, means, or instructions (e.g., non - transitory computer - readable media 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 including channel elements between the geographic area and a plurality of second satellites, and for forming a beam associated with the geographic area to obtain a beam signal based at least in part on beam coefficients and a plurality of signal components associated with signals originating from the geographic area.

[0089] Some examples of method 700 and apparatus described herein may further include operations, features, means, or instructions for receiving a representative of a plurality of signal components, and the beam signal is obtained based at least in part on applying beam coefficients of the beam to the representative of the plurality of signal components.

[0090] Some examples of method 700 and apparatus described herein may further include operations, features, means, or instructions for estimating a return channel from a geographic area, the return channel including a first channel element between the first satellite and a plurality of second satellites and a second channel element between the plurality of second satellites and the geographic area.

[0091] In some examples of the method 700 and apparatus described herein, estimating the return channel of a geographic region may include operations, features, circuits, 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 operations, features, circuits, logic, means, or instructions for interpolating the characteristics of the plurality of return channels to estimate the characteristics of the return channel.

[0092] In some examples of the method 700 and apparatus described herein, the one or more other signals include one or more reference signals transmitted by a transmitter at a known geographic location.

[0093] Some examples of the method 700 and apparatus described herein may further include operations, features, means, or instructions for obtaining a representative of a plurality of signal components relayed by a plurality of second satellites and a representative of a direct signal component of a signal received by a first satellite from a geographic region, and the beam signal is determined based at least in part on the representative of the plurality of signal components and the representative of the direct signal component.

[0094] Some examples of the method 700 and apparatus described herein may further include operations, features, means, or instructions for estimating a return covariance associated with a geographic region based at least in part on the return channel and determining a beam coefficient of a beam based at least in part on the return channel and the return covariance.

[0095] In some examples of the method 700 and apparatus described herein, obtaining a beam signal may include operations, features, circuits, logic, means, or instructions for applying the beam coefficient of the beam to a representative of a plurality of signal components of the signal to obtain one or more beam signals.

[0096] Some examples of the method 700 and apparatus described herein can further include operations, features, means, or instructions for estimating a plurality of return channels from a plurality of geographic regions, where the plurality of return channels includes a return channel and a plurality of geographic regions including the geographic region, and for estimating a return covariance based at least in part on the plurality of return channels, and 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.

[0097] Some examples of the method 700 and apparatus described herein can be configured as means for applying a plurality of beam coefficients of a plurality of beams to a representative of a plurality of signal components associated with a plurality of signals derived from a plurality of geographic regions to obtain one or more beam signals, or can alternatively further include operations, features, means, or instructions for applying, where the one or more beam signals can include beam signals.

[0098] A system for communication is described. The system can include a first satellite in a first orbit and a plurality of second satellites in a second orbit lower than the first orbit, where the plurality of second satellites are configured to detect respective signal components of signals derived from a geographic region and relay each signal component to the first satellite, and a beamformer configured to form a beam associated with the geographic region for obtaining a beam signal based at least in part on each signal component and an estimated return channel, where the estimated return channel includes channel elements between the geographic region and the plurality of second satellites.

[0099] In some examples of the system, the first satellite can include a plurality of transponders, where each transponder of the plurality of transponders can be configured to receive respective signal components relayed by the plurality of second satellites and transmit a representative of each signal component to a ground system for transmitting a representative of the signal to the ground system.

[0100] In some examples of the system, each of the plurality of second satellites includes at least one repeater, and the repeaters of the plurality of second satellites may be configured to amplify each detected signal component and transmit each amplified signal component to the first satellite in order to relay each signal component to the first satellite. In some examples of the system, at least one repeater may be a non-processing repeater.

[0101] In some examples of the system, the repeaters of the plurality of second satellites can be configured to transmit each amplified signal component at the same frequency as each signal component detected by the repeater.

[0102] In some examples of the system, the repeaters of the plurality of second satellites can be configured to transmit each amplified signal component at a frequency different from each signal component detected by the repeater.

[0103] In some examples of the system, each of the repeaters of the plurality of second satellites can be configured to transmit each amplified signal component at each of a plurality of frequencies.

[0104] In some examples of the system, each signal component detected by the plurality of second satellites can be detected via a first channel between the plurality of second satellites and a geographic region, and each signal component can be relayed to the first satellite via a second channel between the plurality of second satellites and the first satellite, and the first satellite can be configured to transmit a representative of each signal component to the terrestrial system via a third channel between the first satellite and the terrestrial system.

[0105] In some examples of the system, the beamformer may further be configured to estimate the return covariance associated with the estimated return channel, determine the 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 a beam signal.

[0106] In some examples, the system can include a terrestrial system comprising a plurality of gateways configured to receive representatives of the respective signal components and a beamformer, the beamformer being connected to the plurality of gateways and configurable to apply the beam coefficients of the beam to the representatives of the respective signal components to obtain a beam signal.

[0107] In some examples of the system, the first satellite can include a beamformer and can further be configured to transmit a beam signal to a terrestrial system.

[0108] In some examples of the system, a plurality of second satellites may be configured to detect the respective signal components of a plurality of signals originating from a plurality of geographical regions, the plurality of signals can include a signal and a plurality of geographical regions including the geographical region, and the beamformer may be configured to form a plurality of beams associated with the plurality of geographical regions to obtain a plurality of beam signals based at least in part on the plurality of respective signal components and the plurality of estimated return channels, and the plurality of estimated return channels can include an estimated return channel.

[0109] In some examples of the system, the beamformer may further be configured to estimate the return covariance associated with the plurality of geographical regions, determine the beam coefficients of the beam based at least in part on the estimated return channel and the return covariance, and apply the beam coefficients of the beam to the respective signal components of the plurality to obtain a plurality of beam signals.

[0110] In some examples of the system, the first satellite may be configured to detect a direct signal component of a signal.

[0111] In some examples of the system, the beamformer may be further configured to obtain a beam signal based at least in part on the direct signal component.

[0112] In some examples of the system, the beamformer can be further configured to estimate an estimated return channel based at least in part on other signals received from one or more other geographical regions. In some examples of the system, the other signals include one or more reference signals transmitted by a transmitter at a known location.

[0113] In some examples of the system, the plurality of second satellites includes a first set of satellites in a first orbital plane of a second orbit. In some examples of the system, the plurality of second satellites includes a second set of satellites in a second orbital plane of the second orbit.

[0114] In some examples, the system includes a processor configured to demodulate a beam signal. In some examples, the system includes a processor that includes a beamformer. In some examples of the system, the first orbit can be a geostationary orbit.

[0115] A communication device is described. The communication device can include a processor and a memory connected to the processor and including instructions executable by the processor, the instructions may cause the communication device to estimate a return channel from a geographical region, the return channel can include a first channel element between the first satellite and the plurality of second satellites and a second channel element between the plurality of second satellites and the geographical region, and may cause to obtain a beam signal based at least in part on a plurality of signal components associated with a signal originating from the geographical region, the plurality of signal components can be relayed by respective second satellites of the plurality of second satellites.

[0116] In some examples of a communication device, instructions for estimating a return channel may be further executable by a processor to determine a plurality of return channels based at least in part on one or more other signals received from a known geographic location and to interpolate the characteristics of the plurality of return channels to estimate the characteristics of the return channel.

[0117] In some examples of a communication device, instructions may be further executable by a processor to obtain a representative of a plurality of signal components relayed by a plurality of second satellites and a representative of a direct signal component of a signal received by a first satellite from a geographic region, and a beam signal can be determined based at least in part on the representative of the plurality of signal components and the representative of the direct signal component.

[0118] In some examples of a communication device, instructions may be further executable by a processor to estimate a return covariance associated with a geographic region based at least in part on a return channel and to determine beam coefficients of a beam based at least in part on the return channel and the return covariance.

[0119] In some examples of a communication device, instructions for obtaining a beam signal may be further executable by a processor to apply beam coefficients of a beam to a representative of a plurality of signal components of a signal to obtain one or more beam signals.

[0120] In some examples of a communication device, instructions may be further executable by a processor to estimate a plurality of return channels from a plurality of geographic regions, the plurality of return channels including a return channel and a plurality of geographic regions including the geographic region, to estimate a return covariance based at least in part on the plurality of return channels, and to 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.

[0121] In some examples of a communication device, the instructions may be further executable by a processor to apply a plurality of beam coefficients of a plurality of beams to representatives of a plurality of signal components associated with a plurality of signals from a plurality of geographic regions so as to obtain one or more beam signals, and the one or more beam signals may include beam signals.

[0122] Note that these methods illustrate examples of implementations, and the operations and steps can be reconfigured or otherwise modified so that other implementations are possible. In some examples, aspects from two or more methods can be combined. For example, aspects of each method can include steps or aspects of other methods, or other steps or techniques described herein.

[0123] The information and signals described herein can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0124] The various exemplary blocks and modules described in connection with the disclosure herein can be implemented or executed in any combination of a general-purpose processor, DSP, ASIC, FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or combinations of any of these designed to perform the functions described herein. The general-purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices (e.g., a digital signal processor (DSP) and one or more microprocessors in combination with a microprocessor, multiple microprocessors, DSP cores, or any other such configuration).

[0125] The functions described in this specification can be implemented in hardware, software executed by a processor, firmware, or any combination thereof. When implemented in software executed by a processor, the functions can be stored or transmitted as one or more instructions or codes on a computer-readable medium. Other examples and embodiments are within the scope of the present disclosure and the appended claims. For example, due to the nature of software, the functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. The features implementing the functions may also be physically disposed at various locations, including being distributed such that parts of the functions are implemented at different physical locations.

[0126] A computer-readable medium includes both a non-transitory computer storage medium and a communication medium including any medium that facilitates transfer of a computer program from one location to another. The non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can include RAM, ROM, electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc 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 store or execute 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. Also, any connection is properly termed a computer-readable medium. For example, if software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, microwave are included in the definition of the medium. As used herein, Disk and Disc includes CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically, while discs reproduce data optically using a laser. Combinations of the above are also included within the scope of computer-readable media.

[0127] As used herein, including in the claims, "or" as used in a list of items (e.g., a list of items beginning with phrases such as "at least one of" or "one or more of") indicates an inclusive list, such that, for example, a list of at least one of A, B, or C means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" should not be construed as referring to a set of exclusive conditions. For example, an exemplary step described as "based on condition A" can be based on both condition A and condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase "based on" shall be construed in the same manner as the phrase "based at least in part on".

[0128] In the accompanying drawings, like components or features may have the same reference label. Further, various components of the same type can be distinguished by appending a dash after the reference label and attaching a second label to distinguish similar components. If only the first reference label is used herein, the description is applicable to any of the similar components having the same first reference label, regardless of the second reference label or any subsequent reference labels.

[0129] The description set forth herein, in connection with the accompanying drawings, describes exemplary configurations and is not intended to represent all examples that can be implemented or that are within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration" and does not mean "preferred" or "advantageous over other examples". The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, these technologies can be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0130] The description in this specification is provided so that those skilled in the art can make or use the present disclosure. Various modifications to the present disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other variations without departing from the scope of the present disclosure. Accordingly, the present disclosure is not intended to be limited to the embodiments and designs described herein, but should be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A system for communication, comprising: a first satellite (105) in a first orbit; a plurality of second satellites (115) in a second orbit lower than the first orbit, each of the plurality of second satellites (115) having an antenna for irradiating a respective part of a geographical area (140), detecting a respective signal component (125) of a signal originating from the geographical area (140), and transmitting a respective relayed signal component (110) obtained from the respective signal component (125) to the first satellite (105); a beamformer (155, 190) located in a ground system (130) or the first satellite (105), the beamformer (155, 190) being configured to form a beam associated with the geographical area (140) and obtain a beam signal based at least in part on the respective relayed signal components (110) and an estimated return channel, the estimated return channel including channel elements between the geographical area (140) and the plurality of second satellites (115); A system for communication.

2. The beamformer (155) is located in the ground system (130), and the first satellite (105) includes: a plurality of transponders (175), each transponder (175) of the plurality of transponders (175) being configured to receive the respective relayed signal components (110) transmitted by the plurality of second satellites (115) and transmit a representative of the respective relayed signal components (110) to the ground system (130); The system according to claim 1, wherein the beamformer (155) is further configured to form the beam signal based at least in part on the respective relayed signal components (110) and at least in part on the representative of the respective relayed signal components (110).

3. Each satellite of the plurality of second satellites (115) includes at least one repeater (160). To transmit the respective relayed signal components (110) to the first satellite (105), the repeaters (160) of the plurality of second satellites (115) are configured to amplify the respective signal components (125) detected to obtain the respective relayed signal components (110). The system according to claim 1 or 2.

4. The system according to claim 3, wherein the at least one repeater (160) is a non-processing repeater.

5. The system according to claim 3 or 4, wherein the repeaters (160) of the plurality of second satellites (115) are configured to transmit the respective relayed signal components (110) at the same frequency as the respective signal components (125) detected by the repeaters (160).

6. The system according to claim 3 or 4, wherein the repeaters (160) of the plurality of second satellites (115) are configured to transmit the respective relayed signal components (110) at a frequency different from the respective signal components (125) detected by the repeaters (160).

7. The system according to any one of claims 3 to 6, wherein each of the repeaters (160) of the plurality of second satellites (115) is configured to transmit the respective relayed signal components at each of a plurality of frequencies.

8. The beamformer (155) is located in the terrestrial system (130). The respective signal components (125) detected by the plurality of second satellites (115) are detected via a first channel between the plurality of second satellites (115) and the geographical area (140). The respective relayed signal components (110) are transmitted to the first satellite (105) via a second channel between the plurality of second satellites (115) and the first satellite (105). The first satellite (105) is configured to transmit a representative of the respective relayed signal components (110) to the terrestrial system (130) via a third channel between the first satellite (105) and the terrestrial system (130). The beamformer (155) is configured to form the beam signal based at least in part on the representative of each of the relayed signal components (110), which is based at least in part on each of the relayed signal components (110), according to any one of claims 1 or 4 to 7.

9. The beamformer (155, 190) estimates a return covariance associated with the estimated return channel, and determines beam coefficients of the beam based at least in part on the estimated return channel and the return covariance. The system according to any one of claims 1 to 8, further configured as such.

10. The beamformer (155) is located in the terrestrial system (130), and the system further includes the terrestrial system (130). The terrestrial system (130) includes at least one gateway (135) configured to receive a representative of each of the relayed signal components (110), and the beamformer (155), which is connected to the at least one gateway (135) and is configured to apply beam coefficients of the beam to the representative of each of the relayed signal components (110) to obtain the beam signal. The representative of each of the relayed signal components (110) is based at least in part on each of the relayed signal components (110). The system according to claim 1, 4 to 7, or 9.

11. The beamformer (190) is located in the first satellite (105), and estimates a return covariance associated with the estimated return channel, determines beam coefficients of the beam based at least in part on the estimated return channel and the return covariance, and is further configured to apply the beam coefficients to each of the relayed signal components (125) to obtain the beam signal. The system according to claim 1.

12. The first satellite (105) is configured to transmit the beam signal to the terrestrial system (130). The system according to claim 11.

13. The beamformer (190) is located in the first satellite (105), The plurality of second satellites (115) are configured to detect respective signal components (125) of a plurality of signals from a plurality of geographic regions (140), and to transmit respective relayed signal components (110) obtained from the respective signal components (125) to the first satellite (105), the plurality of signals including the signal, the plurality of geographic regions (140) including the geographic region (140), The beamformer (190) is configured to form a plurality of beams associated with the plurality of geographic regions (140) in order to obtain a plurality of beam signals based at least in part on the plurality of respective relayed signal components (110) and a plurality of estimated return channels, the plurality of beams including the beam, the plurality of beam signals including the beam signal, the plurality of estimated return channels including the estimated return channel, the system of claim 1.

14. The beamformer (155, 190) is, estimating a return covariance associated with the plurality of geographic regions (140), determining beam coefficients of the beam based at least in part on the estimated return channel and the return covariance The system of claim 13, further configured as such.

15. The first satellite (105) is configured to detect a direct signal component (120) of the signal. The system according to any one of claims 1 to 14.

16. The beamformer (155, 190) is, The system of claim 15, further configured to obtain the beam signal based at least in part on the direct signal component (120).

17. The beamformer (155, 190) is, The system according to any one of claims 1 to 16, further configured to determine an estimated return channel based at least in part on other signals received from one or more other geographic regions (140).

18. The system of claim 17, wherein the other signals include one or more reference signals transmitted by a transmitter at a known location.

19. The plurality of second satellites (115) are, The system according to any one of claims 1 to 18, including a first set of satellites in a first orbital plane (405-1) of the second orbit.

20. The plurality of second satellites (115) The system of claim 19, further comprising a second set of satellites in a second orbital plane (405-2) of the second orbit. **Claim 21** The system according to any one of claims 1 to 20, further comprising a processor (153, 187) configured to demodulate the beam signal. **Claim 22** The system according to any one of claims 1 to 21, further comprising a processor (153, 187) including the beamformer (155, 190). **Claim 23** The system according to any one of claims 1 to 22, wherein the first orbit is a geostationary orbit. **Claim 24** A method for communication, comprising: Obtaining beam coefficients of a beam associated with the geographical area (140) based at least in part on an estimated return channel including a first channel element between the geographical area (140) and a plurality of second satellites (115) and a second channel element between the plurality of second satellites (115) and a first satellite (105), wherein the plurality of second satellites are in a second orbit lower than a first orbit of the first satellite (105), and each has an antenna for irradiating a respective part of the geographical area (140); Forming a beam associated with the geographical area (140) by a beamformer (155, 190) disposed on a ground system (130) or the first satellite (105), and obtaining a beam signal based at least in part on the beam coefficients and respective relayed signal components (110) obtained from a plurality of signal components (125) of a signal originating from the geographical area (140), wherein each of the respective relayed signal components (110) is obtained from the plurality of signal components (125) by a respective second satellite of the plurality of second satellites (115) and transmitted by the respective second satellite of the plurality of second satellites (115) to the first satellite (105); A method for communication, including the above. **Claim 25** The beamformer (190) is located on the first satellite (105), and the method includes: Receiving the respective relayed signal components (110) from the plurality of second satellites (115), wherein the beam signal is obtained based at least in part on applying the beam coefficients to the respective relayed signal components (110). The method according to claim 24, further comprising **Claim 26** wherein the beamformer (155) is located in the terrestrial system (130), and the method comprises: receiving, by the first satellite (105), each of the relayed signal components (110) from the plurality of second satellites (115); transmitting a representative of each of the relayed signal components (110) to the terrestrial system (130), wherein the beamformer (155) forms the beam at least partially based on the representative of each of the relayed signal components (110) that is at least partially based on each of the relayed signal components (110); The method according to claim 24, further comprising **Claim 27** The method according to claim 24, further comprising receiving each of the relayed signal components (110) from the plurality of second satellites (115). **Claim 28** The method according to claim 27, wherein each of the relayed signal components (110) is received from the plurality of second satellites (115) at the same frequency at which the signal from the geographical area (140) was detected by the plurality of second satellites (115). **Claim 29** The method according to claim 27, wherein each of the relayed signal components (110) is received from the plurality of second satellites (115) at one or more frequencies different from the frequency at which the signal from the geographical area (140) was detected by the plurality of second satellites (115). **Claim 30** The method according to any one of claims 24 to 29, further comprising estimating the return channel from the geographical area (140) to obtain the estimated return channel. **Claim 31** Estimating the return channel of the geographical area (140) comprises: determining a plurality of return channels at least partially based on one or more other signals received from known geographical locations; interpolating the characteristics of the plurality of return channels to estimate the characteristics of the return channel; The method according to claim 30, comprising **Claim 32** The method according to claim 31, wherein the one or more other signals comprise one or more reference signals transmitted by a transmitter at the known geographical location. **Claim 33** wherein the beamformer (155) is located in the terrestrial system (130), and the method comprises Obtaining a representative of each of the relayed signal components (110) transmitted by the plurality of second satellites (115) and a representative of the direct signal component (120) of the signal received by the first satellite (105) from the geographical area (140), wherein the beamformer (155) is based at least in part on the respective relayed signal components (110), the representative of the respective relayed signal components (110), and at least in part on the direct signal component (120), the representative of the direct signal component (120), to form the beam The method according to any one of claims 24 or 27 to 29, further comprising.

34. Estimating a return covariance associated with the geographical area (140) based at least in part on the return channel; The method according to any one of claims 24 to 33, further comprising determining the beam coefficients of the beam based at least in part on the return channel and the return covariance.

35. Obtaining the beam signal includes applying the beam coefficients of the beam to the representative of each of the relayed signal components (110) of the signal to obtain the beam signal, according to the method of claim 26.

36. Estimating a plurality of return channels from a plurality of geographical areas (140), the plurality of return channels including the return channel, and the plurality of geographical areas (140) including the geographical area (140); The method according to any one of claims 24 to 35, further comprising estimating a return covariance based at least in part on the plurality of return channels.

37. The beamformer is located in the terrestrial system (130), and the method includes: Estimating a plurality of return channels from a plurality of geographical areas (140), the plurality of return channels including the return channel, and the plurality of geographical areas (140) including the geographical area (140); Estimating a return covariance based at least in part on the plurality of return channels; 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, wherein the plurality of beam coefficients includes the beam coefficients and the plurality of beams includes the beams; Applying the plurality of beam coefficients of the plurality of beams to representatives of respective relayed signal components (110) associated with signals from the plurality of geographic regions (140) to obtain one or more beam signals, wherein the one or more beam signals includes the beam signals and the representatives of the respective relayed signal components (110) are based at least in part on the respective relayed signal components (110); The method according to claim 24, further comprising.

38. A terrestrial system (130), Comprising a beamformer (155), The beamformer (155) obtains beam coefficients of a beam associated with a geographic region (140) based at least in part on an estimated return channel including a first channel element between the geographic region (140) and a plurality of second satellites (115) and a second channel element between the plurality of second satellites (115) and a first satellite (105), wherein the plurality of second satellites are in a second orbit lower than a first orbit of the first satellite (105) and each has an antenna for irradiating a respective part of the geographic region (140); Configured to form a beam associated with the geographic region (140) and obtain a beam signal based at least in part on the beam coefficients and respective relayed signal components (110) obtained from a plurality of signal components (125) of a signal from the geographic region (140), wherein the respective relayed signal components (110) are obtained from the plurality of signal components (125) by respective second satellites of the plurality of second satellites (115) and transmitted by the respective second satellites of the plurality of second satellites (115) to the first satellite (105), the terrestrial system (130).

39. A first satellite (105), Comprising a beamformer (190), The beamformer (190) obtains beam coefficients of a beam related to the geographical area (140) based at least in part on an estimated return channel including a first channel element between the geographical area (140) and a plurality of second satellites (115) and a second channel element between the plurality of second satellites (115) and the first satellite (105). The plurality of second satellites are in a second orbit lower than a first orbit of the first satellite (105) and each have an antenna for irradiating a respective part of the geographical area (140). It is configured to form a beam related to the geographical area (140) and obtain a beam signal based at least in part on the beam coefficients and respective relayed signal components (110) obtained from a plurality of signal components (125) of a signal derived from the geographical area (140). Each of the relayed signal components (110) is obtained from the plurality of signal components (125) by a respective second satellite of the plurality of second satellites (115) and transmitted to the first satellite (105) by the respective second satellite of the plurality of second satellites (115).

40. The terrestrial system (130) is configured to receive a representative of each of the relayed signal components (110) from the first satellite (105), and the beamformer (155) is further configured to form the beam signal based at least in part on the representative of each of the relayed signal components (110) based at least in part on the relayed signal components (110). The terrestrial system (130) according to claim 38.

41. further comprising a transponder (175), wherein the transponder (175) is configured to receive the respective relayed signal components (110) from the plurality of second satellites (115). The first satellite (105) according to claim 39.

42. The transponder (175) is further configured to receive the respective relayed signal components (110) from the plurality of second satellites (115) at one or more frequencies different from those at which the signals derived from the geographical area (140) were detected by the plurality of second satellites (115). The first satellite (105) according to claim 41.

43. The transponder (175) is further configured to receive, from the plurality of second satellites (115), each of the relayed signal components (110) at the same frequency at which the signal derived from the geographical area (140) was detected by the plurality of second satellites (115), the first satellite (105) according to claim 41.

44. The beamformer (155) is further configured to estimate the return channel from the geographical area (140) in order to obtain the estimated return channel, the terrestrial system (130) according to claim 38 or 40.

45. To estimate the return channel, the beamformer (155) is determining a plurality of return channels based at least in part on one or more other signals received from known geographical locations, further configured to interpolate the characteristics of the plurality of return channels to estimate the characteristics of the return channel, the terrestrial system (130) according to claim 44.

46. The beamformer (155) is further configured to obtain a representative of each of the relayed signal components (110) transmitted by the plurality of second satellites (115) and a representative of the direct signal component (120) of the signal received at the first satellite (105) from the geographical area (140), the beamformer (155) being at least in part based on each of the relayed signal components (110), the representative of each of the relayed signal components (110) and at least in part based on the direct signal component (120), the representative of the direct signal component (120), further configured to form the beam signal, the terrestrial system (130) according to claim 38.

47. The beamformer (155) is estimating a return covariance associated with the geographical area (140) based at least in part on the return channel, further configured to determine the beam coefficients based at least in part on the return channel and the return covariance, the terrestrial system (130) according to any one of claims 38, 40 or 44 to 46.

48. The beamformer (155) is The terrestrial system (130) according to claim 40, further configured to apply the beam coefficients to the representation of each of the relayed signal components (110) of the signal in order to obtain the beam signal.

49. The beamformer (155) estimates a plurality of return channels from a plurality of geographic regions (140), where the plurality of return channels includes the return channel, and the plurality of geographic regions (140) includes the geographic region (140), estimates a return covariance based at least in part on the plurality of return channels, and is further configured to determine a plurality of beam coefficients for a plurality of beams based at least in part on the plurality of return channels and the return covariance, where the plurality of beam coefficients includes the beam coefficients, and the plurality of beams includes the beam. The terrestrial system (130) according to any one of claims 38, 40 or 44 to 48.

50. The beamformer (155) is further configured to apply the plurality of beam coefficients to a representation of each of the relayed signal components (110) associated with a plurality of signals derived from the plurality of geographic regions (140) to obtain one or more beam signals, where the one or more beam signals includes the beam signal. The terrestrial system (130) according to claim 49.

51. further comprising a transponder (175), where the transponder (175) is configured to receive each of the relayed signal components (110) from the plurality of second satellites (115), and the beam signal is obtained based at least in part on applying the beam coefficients to each of the relayed signal components (110). The first satellite (105) according to claim 39.

52. The beamformer (190) is further configured to estimate the return channel from the geographic region (140) in order to obtain the estimated return channel. The terrestrial system (130) according to claim 38 or 40.

53. To estimate the return channel, the beamformer (190) determines a plurality of return channels based at least in part on one or more other signals received from known geographic locations. The first satellite (105) according to any one of claims 39, 41 to 43, or 51, configured to interpolate the characteristics of the plurality of return channels in order to estimate the characteristics of the return channels.

54. The beamformer (190) estimates a return covariance associated with the geographical area (140) based at least in part on the return channel, and is further configured to determine the beam coefficients based at least in part on the return channel and the return covariance, the first satellite (105) according to any one of claims 39, 41 to 43, 51 or 53.

55. The beamformer (190) estimates a plurality of return channels from a plurality of geographical areas (140), where the plurality of return channels includes the return channel, and the plurality of geographical areas (140) includes the geographical area (140), and is configured to estimate a return covariance based at least in part on the plurality of return channels, the first satellite (105) according to any one of claims 39, 41 to 43, 51, 53 or 54.

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