Radar with End-to-End Relay

Abstract

A multistatic synthetic aperture radar using beamforming processing is described. A receiver processing system can process feed element signals (e.g., from a feed element on a satellite or from an access node terminal in an end-to-end relay system) according to multiple beam weight sets, each corresponding to a beam coverage pattern including one or more radar image pixel beams, to generate a set of beam signals. The feed element signals can represent signal energy from a reflected illumination signal (e.g., a beacon signal, a communication signal) or passively received signal energy (e.g., without a corresponding illumination signal). The multiple sets of beam signals obtained from processing the feed element signals are then processed to obtain image pixel values, which can be combined to obtain an image. The multiple sets of feed element signals (e.g., each corresponding to a time period) can be processed and combined to form an image.

Description

[Background technology]

[0001] The following relates generally to beamformed antenna systems, and more specifically to multistatic synthetic aperture radar. In some beamformed antenna systems, such as satellite communication systems, a receiving device may include an antenna configured to receive signals at each of a set of feed elements of a feed array. The set of feed element signals may be processed according to a receive beamforming configuration, which may include applying a phase shift or amplitude scaling to each of the feed element signals. The processing may involve, in some examples, generating spot beam signals corresponding to different spot beam coverage areas, which may support different allocations of communication resources across the service coverage areas of the antennas. Summary of the Invention

[0002] The described techniques relate to improved methods, systems, devices, and apparatuses supporting multistatic synthetic aperture radar. In some examples, the antenna may be included in a vehicle, such as a satellite, an airplane, an unmanned aerial vehicle (UAV), or some other type of device supporting communication services or other reception capabilities over a service coverage area. The antenna may include a feed array having a set of feed elements, each of which may be associated with a feed element signal corresponding to the energy received at the respective feed element. Alternatively, the device may relay a signal received at the feed array through a corresponding feed array (e.g., the same or different feed array). A ground system (e.g., multiple access node terminals) may receive the relayed signal. A receive processing system may receive the signal (e.g., a feed element signal or an access node signal), or other related signaling, and perform various beamforming techniques to support directional reception.

[0003] To support real-time communications, the receive processing system can process received signaling, such as the feed element signals, in accordance with the first beamforming configuration to generate one or more spot beam signals, each of which can correspond to a respective spot beam of the antenna and, in some examples, can include communications scheduled for a respective spot beam of a plurality of spot beams (e.g., a spot beam coverage area).

[0004] To support multistatic synthetic aperture radar, the receiver processing system can process the feed element signals according to multiple beam weight sets (e.g., for a duration), each corresponding to a beam coverage pattern including one or more radar image pixel beams, to generate a set of beam signals. The feed element signals can represent signal energy from reflected illumination signals (e.g., beacon signals, communication signals) or passively received signal energy (e.g., without a corresponding illumination signal). The multiple sets of beam signals obtained from processing the feed element signals can then be processed to obtain image pixel values, which can be combined to obtain an image. The processing of the feed element signals can take into account the illumination source, which can be the same as the receiver or relay of the feed element signals, or in some cases, a different transmitter. In some cases, multiple sets of feed element signals (e.g., each corresponding to a duration) can be processed and combined to form an image. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1A shows a diagram of a communication system supporting a multistatic synthetic aperture radar according to an example disclosed herein. FIG. 1B shows an antenna assembly of a satellite supporting a multistatic synthetic aperture radar according to an example disclosed herein. FIG. 1C shows a feed array assembly of an antenna assembly supporting a multistatic synthetic aperture radar according to an example disclosed herein. [Diagram 2] 2A-2D show example antenna characteristics of an antenna assembly having a feed array assembly supporting a multistatic synthetic aperture radar according to examples disclosed herein. [Diagram 3] 3A and 3B illustrate an example of beamforming to form a spot beam coverage area over a native antenna pattern coverage area according to examples disclosed herein. [Figure 4] FIG. 4 illustrates an example of a receiver processing system supporting a multistatic synthetic aperture radar according to examples disclosed herein. [Diagram 5] FIG. 5 illustrates an example of a composite beam coverage pattern supporting a multistatic synthetic aperture radar according to examples disclosed herein. [Figure 6] FIG. 6 illustrates a diagram of a system including devices supporting techniques for multistatic synthetic aperture radar according to examples disclosed herein. [Figure 7] FIG. 7 illustrates a process flow supporting techniques for multistatic synthetic aperture radar according to examples disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] A system according to the techniques described herein may support various examples of multistatic synthetic aperture radar. For example, a feed array antenna may be included in a vehicle such as a satellite, an airplane, an unmanned aerial vehicle (UAV), or some other type of device supporting communication services or other reception capabilities over a service coverage area. The antenna may include a feed array having a set of feed elements, and to support signal reception, each of the feed elements may be associated with a feed element signal corresponding to the energy received at the respective feed element. Alternatively, the device may relay a signal received at the feed array through a corresponding feed array (e.g., the same or different feed array). A ground system (e.g., multiple access node terminals) may receive the relayed signal. A receiver processing system may receive the signal (e.g., a feed element signal or an access node terminal signal) and perform various beamforming techniques to support directional reception. Components of the receiver processing system may be included in one or more ground stations or may be included in a satellite or other vehicle, which may or may not include an antenna associated with the feed element signal being processed. In some examples, components of the receiver processing system may be distributed among two or more devices, including components distributed between the vehicle and ground segments.

[0007] According to various aspects described herein, multiple feed signals or access node terminal signals may be processed according to multiple beam weight sets to obtain different sets of image points within an imaging region. The feed signals or access node terminal signals may include reflections of actively transmitted signals (e.g., reflected beacon signals, reflected communication signals) or passively collected signals (e.g., emissions or reflections of other communication signals, thermal emissions, or other signals). The sets of image points may be combined into a multistatic synthetic aperture radar image.

[0008] This specification provides various examples of techniques for multistatic synthetic aperture radar, and such examples are not intended to limit the scope, applicability, or configuration of the examples according to the principles described herein. Rather, the following description will provide those skilled in the art with an enabling description for implementing embodiments of the principles described herein. Various changes may be made in the function and arrangement of elements.

[0009] Thus, various embodiments according to the examples disclosed herein may omit, substitute, or add various procedures or components, as appropriate. For example, it should be understood that the methods may be performed in an order different from that described, and that various steps may be added, omitted, or combined. Also, aspects and elements described with respect to particular examples may be combined in various other examples. Also, it should be understood that the following systems, methods, devices, and software, individually or collectively, may be components of larger systems, and that other procedures may take precedence over or otherwise modify their application.

[0010] 1A shows a diagram of a satellite system 100 supporting a multistatic synthetic aperture radar according to examples disclosed herein. The satellite system 100 can use several network architectures including a space segment 101 and a ground segment 102. The space segment 101 can include one or more satellites 120. The ground segment 102 can include one or more access node terminals 130 (e.g., gateway terminals, ground stations), and network devices 141 such as a network operations center (NOC) or other central processing center or device, and satellite and gateway terminal command center. In some examples, the ground segment 102 can also include user terminals 150 that receive communication services via the satellites 120.

[0011] In various examples, satellite 120 may be configured to support wireless communication between one or more access node terminals 130 and / or various user terminals 150 located within its service coverage area, which may be a primary task or mission of satellite 120 in some examples. In some examples, satellite 120 may be configured for intelligence gathering and may include various sensors for detecting the geographic distribution of electromagnetic, optical, thermal, or other data (e.g., in a data gathering or receiving mission). In some examples, satellite 120 may be deployed in a geostationary orbit such that its orbital position relative to ground devices is relatively fixed or fixed within an operating tolerance or other orbital window (e.g., within an orbital slot). In other examples, satellite 120 may operate in any suitable orbit (e.g., low earth orbit (LEO), medium earth orbit (MEO), etc.).

[0012] The satellite 120 may use an antenna assembly 121, such as a phased array antenna assembly (e.g., a direct radiating array (DRA)), a phased array fed reflector (PAFR) antenna, or any other mechanism known in the art for receiving or transmitting signals (e.g., for communication or broadcast services, or data collection services). When supporting communication services, the satellite 120 may receive forward uplink signals 132 from one or more access node terminals 130 and provide corresponding forward downlink signals 172 to one or more user terminals 150. The satellite 120 may also receive return uplink signals 173 from one or more user terminals 150 and forward corresponding return downlink signals 133 to one or more access node terminals 130. Various physical layer transmit modulation and coding techniques (e.g., adaptive coding and modulation (ACM)) may be used by the satellite 120 for communication of signals between the access node terminals 130 or user terminals 150.

[0013] The antenna assembly 121 may support communication or other signal reception via one or more beamformed spot beams 125, which may be referred to as a service beam, a satellite beam, or any other suitable terminology. Signals may pass through the antenna assembly 121 according to the spatial electromagnetic radiation pattern of the spot beam 125. When supporting a communication service, the spot beam 125 may use a single carrier, such as one frequency or a continuous frequency range, which may also be associated with a single polarization. In some examples, the spot beam 125 may be configured to support only the user terminal 150, in which case the spot beam 125 may be referred to as a user spot beam or user beam (e.g., user spot beam 125-a). For example, the user spot beam 125-a may be configured to support one or more forward downlink signals 172 and / or one or more return uplink signals 173 between the satellite 120 and the user terminal 150. In some examples, the spot beam 125 may be configured to support only the access node terminal 130, in which case the spot beam 125 may be referred to as an access node spot beam, an access node beam, or a gateway beam (e.g., access node spot beam 125-b). For example, the access node spot beam 125-b may be configured to support one or more forward uplink signals 132 and / or one or more return downlink signals 133 between the satellite 120 and the access node terminal 130. In other examples, the spot beam 125 may be configured to serve both the user terminal 150 and the access node terminal 130, and thus the spot beam 125 may support any combination of the forward downlink signal 172, the return uplink signal 173, the forward uplink signal 132, and / or the return downlink signal 133 between the satellite 120, the user terminal 150, and the access node terminal 130.

[0014] The spot beams 125 may support communication services or other signal reception between target devices (e.g., user terminals 150 and / or access node terminals 130) within a spot beam coverage area 126. The spot beam coverage area 126 may be defined by an area of ​​the electromagnetic radiation pattern of the associated spot beam 125, as projected onto the ground or some other reference surface, that has a signal power, signal-to-noise ratio (SNR), or signal-to-interference-plus-noise ratio (SINR) of the spot beam 125 above a threshold. The spot beam coverage area 126 may cover any suitable service area (e.g., circular, elliptical, hexagonal, local, regional, national, etc.) and may support communication services with any number of target devices located within the spot beam coverage area 126. In various examples, a target device, such as an airborne or underwater target device, may be located within the spot beam 125 but may not be located on a reference surface of the spot beam coverage area 126 (e.g., reference surface 160, which may be the surface of the earth, the surface of a land, the surface of a body of water such as a lake or ocean, or a reference surface at an altitude or elevation).

[0015] Beamforming for a communication link may be performed by adjusting the signal phase (or time delay), and sometimes the signal amplitude, of signals transmitted and / or received by multiple feed elements of one or more antenna assemblies 121 having overlapping native feed element patterns. In some examples, some or all of the feed elements may be arranged as an array of constituent receive and / or transmit feed elements that cooperate to enable various instances of on-board beamforming (OBBF), ground-based beamforming (GBBF), end-to-end beamforming, or other types of beamforming.

[0016] The satellite 120 may support multiple beamformed spot beams 125 covering respective spot beam coverage areas 126, each of which may or may not overlap with adjacent spot beam coverage areas 126. For example, the satellite 120 may support a service coverage area (e.g., a regional coverage area, a national coverage area, a hemispheric coverage area) formed by a combination of any number (e.g., tens, hundreds, thousands) of spot beam coverage areas 126. The satellite 120 may support communication services through one or more frequency bands and any number of sub-bands thereof. For example, the satellite 120 may support operation in the International Telecommunications Union (ITU) Ku, K, or Ka bands, C band, X band, S band, L band, V band, etc.

[0017] In some examples, a service coverage area may be defined as a coverage area from which and / or to which either a terrestrial transmitting source or a terrestrial receiver may participate (e.g., transmit and / or receive signals associated therewith) in a communication service via satellite 120, and may be defined by a number of spot beam coverage areas 126. In some systems, the service coverage area of ​​each communication link (e.g., forward uplink coverage area, forward downlink coverage area, return uplink coverage area, and / or return downlink coverage area) may be different. Although a service coverage area may only be active when satellite 120 is in service (e.g., in a service orbit), satellite 120 may have (e.g., may be designed or configured to have) a native antenna pattern based on the physical components of antenna assembly 121 and their relative positions. The native antenna pattern of a satellite 120 may refer to the distribution of energy relative to the satellite's antenna assembly 121 (eg, energy transmitted from and / or received by the antenna assembly 121).

[0018] In some service coverage areas, adjacent spot beam coverage areas 126 may have some degree of overlap. In some examples, multi-color (e.g., two-color, three-color, or four-color reuse patterns) may be used, with "color" referring to a combination of orthogonal communication resources (e.g., frequency resources, polarization, etc.). In one example of a four-color pattern, overlapping spot beam coverage areas 126 may each be assigned one of four colors, with each color being assigned a unique combination of frequencies (e.g., one or more frequency ranges, one or more channels) and / or signal polarizations (e.g., right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), etc.), or otherwise orthogonal resources. Assigning different colors to each spot beam coverage area 126 having overlapping regions may reduce or eliminate interference between spot beams 125 associated with those overlapping spot beam coverage areas 126 (e.g., by scheduling transmissions corresponding to each spot beam according to the respective colors, filtering transmissions corresponding to each spot beam according to the respective colors). These combinations of frequencies and antenna polarizations can thus be reused in repeating non-overlapping "four-color" reuse patterns. In some examples, communication services can be provided by using more or fewer colors. Additionally or alternatively, time division between spot beams 125 and / or other interference mitigation techniques can be used. For example, spot beams 125 can use the same resources (same polarization and frequency range) simultaneously, with interference mitigated using mitigation techniques such as ACM, interference cancellation, space-time coding, etc.

[0019] In some examples, the satellite 120 may be configured as a "bent pipe" satellite. In a bent pipe configuration, the satellite 120 may perform frequency and polarization conversion of received carrier signals before retransmitting the signals to their destination. In some examples, the satellite 120 may support a non-processing bent pipe architecture with a phased array antenna used to generate relatively small spot beams 125 (e.g., by GBBF). The satellite 120 may support K general purpose paths, each of which may be allocated as a forward path or a return path at any instant. A relatively large reflector may be illuminated by a phased array of antenna feed elements, supporting the ability to create various patterns of spot beams 125 within constraints set by the size of the reflector and the number and placement of the antenna feed elements. A phased array feed reflector may be employed for both receiving uplink signals 132, 173, or both, and transmitting downlink signals 133, 172, or both.

[0020] The satellite 120 may operate in a multiple spot beam mode, transmitting or receiving according to multiple relatively narrow spot beams 125 directed to different regions of the Earth. This may allow separation of the user terminals 150 into the various narrow spot beams 125 or otherwise support spatial separation of the transmitted or received signals. In some examples, a beamforming network (BFN) associated with the receive (Rx) or transmit (Tx) phased array may be dynamic, allowing movement of the position of the Tx spot beam 125 (e.g., downlink spot beam 125) and the Rx spot beam 125 (e.g., uplink spot beam 125).

[0021] User terminals 150 may include a variety of devices configured to communicate signals with satellites 120, which may include fixed terminals (e.g., ground-based fixed terminals) or mobile terminals, such as terminals of boats, aircraft, ground-based vehicles, etc. User terminals 150 may communicate data and information via satellites 120, which may include communication via access node terminals 130 to a destination device, such as a network device 141 or some other device associated with network 140 or a distributed server. User terminals 150 may communicate signals according to a variety of physical layer transmission modulation and coding techniques, including, for example, cellular communication protocols, such as Digital Video Broadcasting-Satellite-2nd Generation (DVB-S2), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE) or Fifth Generation (5G) protocols, or those defined by the Data Over Cable Service Interface Specification (DOCSIS) standard.

[0022] The access node terminal 130 can service forward uplink signals 132 and return downlink signals 133 to and from the satellite 120. The access node terminal 130 may also be known as a ground station, a gateway, a gateway terminal, or a hub. The access node terminal 130 may include an access node terminal antenna system 131 and an access node receiver 135. The access node terminal antenna system 131 is capable of bidirectional communication and may be designed with appropriate transmit power and receive sensitivity to reliably communicate with the satellite 120. In some examples, the access node terminal antenna system 131 may include a parabolic reflector with high directivity in the direction of the satellite 120 and low directivity in other directions. The access node terminal antenna system 131 may include various alternative configurations and may include features such as high isolation between orthogonal polarizations, high efficiency in the operating frequency band, low noise, etc.

[0023] In supporting communication services, the access node terminal 130 may schedule traffic to the user terminal 150. Alternatively, such scheduling may be performed in other parts of the satellite system 100 (e.g., in one or more network devices 141, which may include a network operations center (NOC) and / or a gateway command center). Although one access node terminal 130 is shown in FIG. 1A, examples according to the present disclosure may be implemented in a communication system having multiple access node terminals 130, each of which may be coupled to each other and / or to one or more networks 140.

[0024] The satellite 120 may communicate with the access node terminal 130 by transmitting return downlink signals 133 and / or receiving forward uplink signals 132 via one or more spot beams 125 (e.g., access node spot beams 125-b that may be associated with respective access node spot beam coverage areas 126-b). The access node spot beams 125-b may support, for example, communication services for one or more user terminals 150 (e.g., relayed by the satellite 120) or any other communication between the satellite 120 and the access node terminal 130.

[0025] The access node terminals 130 may provide an interface between the network 140 and the satellites 120, and in some examples may be configured to receive data and information sent between the network 140 and one or more user terminals 150. The access node terminals 130 may format the data and information for delivery to the respective user terminals 150. Similarly, the access node terminals 130 may be configured to receive signals from the satellites 120 (e.g., originating from one or more user terminals 150 and directed to a destination accessible via the network 140). The access node terminals 130 may also format received signals for transmission over the network 140.

[0026] Network 140 may be any type of network, including, for example, the Internet, an Internet Protocol (IP) network, an intranet, a wide area network (WAN), a metropolitan area network (MAN), a local area network (LAN), a virtual private network (VPN), a virtual LAN (VLAN), a fiber optic network, a hybrid fiber optic coaxial network, a cable network, a public switched telephone network (PSTN), a public switched data network (PSDN), a public land mobile network, and / or any other type of network supporting communication between devices as described herein. Network 140 may include both wired and wireless connections as well as optical links. Network 140 may connect access node terminal 130 with other access node terminals that may communicate with the same satellite 120 or different satellites 120 or other vehicles.

[0027] One or more network devices 141 may be coupled to the access node terminal 130 and may control aspects of the satellite system 100. In various examples, the network devices 141 may be co-located with or otherwise near the access node terminal 130, or may be remote installations that communicate with the access node terminal 130 and / or the network 140 via wired and / or wireless communication links.

[0028] The satellite system 100 may be configured according to various techniques to support multistatic synthetic aperture radar. For example, multiple feed signals (e.g., signals received at the antenna assembly 121) or access node terminal signals (e.g., signals received at the access node terminal antenna system 131) may be processed according to multiple beam weight sets to obtain different sets of image points within an imaging region. In some cases, the feed signals or access node terminal signals may include reflections of actively transmitted signals. For example, the satellite 120 may transmit an illumination signal 145 over one or more of the spot beam coverage areas 126. In some cases, the illumination signal 145 may be transmitted as a broad beacon signal over an area including each of the spot beam coverage areas 126. For example, the illumination signal 145 may be a beacon signal used by terminals (e.g., user terminals, access node terminals) for signal acquisition and timing synchronization. Additionally or alternatively, the illumination signal 145 may be transmitted by one or more different satellites. For example, satellite 120 may be a GEO satellite, and illumination signal 145 may be transmitted by one or more LEO satellites 122. Thus, an aperture for imaging the received signal may be defined by the illumination area and the relative movement of LEO satellite 122 with respect to GEO satellite 120.

[0029] Additionally or alternatively, the forward downlink signal 172 may be used as an illumination signal. The illumination signal 145 or the forward downlink signal 172 may be reflected by terrain or objects (e.g., ground-based or airborne objects) and received in the feed signal or the access node terminal signal (e.g., as an auxiliary signal in the return uplink signal 173 or the return downlink signal 132). Additionally or alternatively, the feed signal or the access node terminal signal may include incidental signals (e.g., emissions or reflections of other communication signals, thermal emissions, or other signals). The set of image points may be combined into a multistatic synthetic aperture radar image.

[0030] 1B illustrates an antenna assembly 121 of a satellite 120 supporting a multistatic synthetic aperture radar according to examples disclosed herein. As shown in FIG. 1B, the antenna assembly 121 can include a feed array assembly 127 and a reflector 122 shaped to have a focal region 123 at which an electromagnetic signal (e.g., an inbound electromagnetic signal 180) is focused when received from a remote source. Similarly, a signal emitted by the feed array assembly 127 located at the focal region 123 is reflected by the reflector 122 into an outgoing plane wave (e.g., an outbound electromagnetic signal 180). The feed array assembly 127 and the reflector 122 can be associated with a native antenna pattern formed by a composite of native feed element patterns for each of a plurality of feed elements 128 of the feed array assembly 127.

[0031] The satellite 120 may operate according to a native antenna pattern of the antenna assembly 121 when the satellite 120 is in a service orbit, as described herein. The native antenna pattern may be based at least in part on the pattern of feeding elements 128 of the feeding array assembly 127, the relative position of the feeding array assembly 127 with respect to the reflector 122 (e.g., focal offset distance 129, or lack thereof at focal position), and the like. The native antenna pattern may be associated with a native antenna pattern coverage area. The antenna assembly 121 described herein may be designed to support a particular service coverage area with the native antenna pattern coverage area of ​​the antenna assembly 121, and various design characteristics may be computationally determined (e.g., by analysis or simulation) and / or experimentally measured (e.g., on an antenna test range or in actual use).

[0032] 1B, the feed array assembly 127 of the antenna assembly 121 is disposed between the reflector 122 and the focal region 123 of the reflector 122. Specifically, the feed array assembly 127 is disposed at a focal offset distance 129 from the focal region 123. Thus, the feed array assembly 127 of the antenna assembly 121 may be disposed in a defocused position relative to the reflector 122. Although shown in FIG. 1B as a direct offset fed array assembly 127, other types of configurations may be used, including a front fed array assembly 127, as well as the use of a secondary reflector (e.g., a Cassegrain antenna, etc.), or a configuration without a reflector 122 (e.g., a DRA).

[0033] 1C illustrates a feed array assembly 127 of an antenna assembly 121 supporting a multistatic synthetic aperture radar according to examples disclosed herein. As illustrated in FIG. 1C, the feed array assembly 127 may have multiple feed elements 128 for communicating signals (e.g., signals associated with communication services, signals associated with configuration or control of the satellite 120, received signals for data collection or sensor placement).

[0034] As used herein, the supply element 128 may refer to a receiving antenna element, a transmitting antenna element, or an antenna element configured to support both transmission and reception (e.g., a transceiver element). A receiving antenna element may include a physical transducer (e.g., a radio frequency (RF) transducer) that converts an electromagnetic signal into an electrical signal, and a transmitting antenna element may include a physical transducer that emits an electromagnetic signal when excited by an electrical signal. In some cases, the same physical transducer may be used for transmission and reception.

[0035] Each of the feed elements 128 may include, for example, a feed horn, a polarization transducer (e.g., a septum-polarized horn that can function as two combined elements with different polarizations), a multi-port multi-band horn (e.g., dual-band 20 GHz / 30 GHz with dual-polarized LHCP / RHCP), a cavity-slot, an inverted-F, a slotted waveguide, a Vivaldi, a helical, a loop, a patch, or any other configuration of antenna elements or combinations of interconnected sub-elements. Each of the feed elements 128 may also include or be otherwise coupled to an RF signal transducer, a low noise amplifier (LNA), or a power amplifier (PA), and may be coupled to a transponder within the satellite 120 that may perform other signal processing such as frequency conversion, beamforming processing, etc.

[0036] The reflector 122 may be configured to reflect signals between the feed array assembly 127 and one or more target devices (e.g., user terminal 150, access node terminal 130) or objects (e.g., terrain features, vehicles, buildings, airborne objects). Each feed element 128 of the feed array assembly 127 may be associated with a respective native feed element pattern, which may be associated with a projected native feed element pattern coverage area (e.g., projected onto a ground surface, plane, or volume after reflection from the reflector 122). The collection of native feed element pattern coverage areas for a multi-feed antenna may be referred to as a native antenna pattern. The feed array assembly 127 may include any number (e.g., tens, hundreds, thousands, etc.) of feed elements 128, which may be arranged in any suitable arrangement (e.g., linear array, arcuate array, planar array, honeycomb array, polyhedral array, spherical array, ellipsoidal array, or combinations thereof). The supply element 128 can have ports or openings having a variety of shapes, such as circular, oval, square, rectangular, hexagonal, and so forth.

[0037] 2A-2D show example antenna characteristics of an antenna assembly 121-a having a feed array assembly 127-a supporting a multistatic synthetic aperture radar, according to examples disclosed herein. The antenna assembly 121-a may be operating in a state in which it spreads a received transmission from a given location to multiple feed elements 128-a, or spreads the transmitted power from the feed elements 128-a over a relatively large area, or both.

[0038] 2A shows a drawing 201 of a native feed element pattern 210-a associated with a feed element 128-a of the feed array assembly 127-a. Specifically, the drawing 201 shows native feed element patterns 210-a-1, 210-a-2, and 210-a-3 associated with feed elements 128-a-1, 128-a-2, and 128-a-3, respectively. The native feed element pattern 210-a may represent a spatial radiation pattern associated with each of the respective feed elements 128. For example, when the feed element 128-a-2 is transmitting, the transmitted electromagnetic signal may be reflected from the reflector 122-a and propagate in a generally conical native feed element pattern 210-a-2 (although other shapes are possible depending on the characteristics of the feed element 128 and / or the reflector 122). Although three native feed element patterns 210-a are shown for antenna assembly 121-a, each of the feed elements 128 of antenna assembly 121 is associated with a respective native feed element pattern 210. The combination of native feed element patterns 210-a associated with antenna assembly 121-a (e.g., native feed element patterns 210-a-1, 210-a-2, 210-a-2, and other native feed element patterns 210-a not shown) may be referred to as native antenna pattern 220-a.

[0039] Each of the feed elements 128-a may also be associated with a native feed element pattern coverage area 211-a (e.g., native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3 associated with feed elements 128-a-1, 128-a-2, and 128-a-3, respectively) that represents a projection of the native feed element pattern 210-a onto a reference surface (e.g., ground or water surface, a reference surface at an elevation, or some other reference plane or surface). The native feed element pattern coverage area 211 may represent an area where various devices (e.g., access node terminal 130 and / or user terminal 150) may receive signals transmitted by the respective feed element 128. Additionally or alternatively, the native feed element pattern coverage area 211 may represent an area where transmissions from various devices may be received by the respective feed element 128. For example, a device located in area of ​​interest 230-a located within native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3 may receive signals transmitted by feed elements 128-a-1, 128-a-2, and 128-a-3, and may have transmissions received by feed elements 128-a-1, 128-a-2, and 128-3-a. The composite of native feed element pattern coverage areas 211-a associated with antenna assembly 121-a (e.g., native feed element pattern coverage areas 211-a-1, 211-a-2, 211-a-2, and other native feed element pattern coverage areas 211-a not shown) may be referred to as native antenna pattern coverage area 221-a.

[0040] The feed array assembly 127-a may be operating in a defocused position relative to the reflector 122-a such that the native feed element patterns 210-a, and thus the native feed element pattern coverage areas 211-a, substantially overlap. Thus, each location in the native antenna pattern coverage area 221-a may be associated with multiple feed elements 128 such that transmission to or reception from a point of interest may employ multiple feed elements 128. It should be understood that the drawing 201 is not drawn to scale and that the native feed element pattern coverage areas 211 are generally each much larger than the reflector 122-a.

[0041] 2B shows a diagram 202 illustrating the antenna assembly 121-a's signal reception of a transmission 240-a from a point of interest 230-a. The transmission 240-a from the point of interest 230-a may illuminate the entire reflector 122-a or a portion of the reflector 122-a and then be focused and directed towards the feed array assembly 127-a according to the shape of the reflector 122-a and the angle of incidence of the transmission 240 on the reflector 122-a. The feed array assembly 127-a may operate in a defocused position relative to the reflector 122-a such that the transmission 240-a may be focused onto multiple feed elements 128 (e.g., feed elements 128-a-1, 128-a-2, and 128-a-3 associated with native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3, each of which includes the point of interest 230-b).

[0042] 2C shows a drawing 203 of native feed element pattern gain profiles 250-a associated with three feed elements 128-a of the feed array assembly 127-a, with reference to angles measured from the zero offset angle 235-a. For example, native feed element pattern gain profiles 250-a-1, 250-a-2, and 250-a-3 may be associated with feed elements 128-a-1, 128-a-2, and 128-a-3, respectively, and thus may represent the gain profiles of native feed element patterns 210-a-1, 210-a-2, and 210-a-3. As shown in drawing 203, the gain of each native feed element pattern gain profile 250 may decay at angles offset in either direction from the peak gain. In drawing 203, the beam contour level 255-a may represent a desired gain level (e.g., to provide a desired information rate) for supporting communication services or other receiving or transmitting services via the antenna assembly 121-a, and thus may be used to define the boundaries of each native feed element pattern coverage area 211-a (e.g., native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3). The beam contour level 255-a may represent, for example, a -1 dB, -2 dB, or -3 dB attenuation from a peak gain, or may be defined by an absolute signal strength, SNR level, or SINR level. Although three native feed element pattern gain profiles 250-a are shown, other native feed element pattern gain profiles 250-a may be associated with other feed elements 128-a.

[0043] As shown in drawing 203, each of the native feed element pattern gain profiles 250-a may intersect with another native feed element pattern gain profile 250-a for a substantial portion of the gain profile above the beam contour level 255-a. Thus, drawing 203 illustrates a configuration of native feed element pattern gain profiles 250 in which multiple feed elements 128 of the feed array assembly 127 may support signal communication at a particular angle (e.g., at a particular direction of the native antenna pattern 220-a). In some examples, this condition may be referred to as the feed elements 128 of the feed array assembly 127, or the native feed element pattern coverage areas 211, having a high degree of overlap.

[0044] 2D shows a drawing 204 illustrating a two-dimensional array of idealized native feed element pattern coverage areas 211 of a plurality of feed elements 128 of a feed array assembly 127-a (e.g., including feed elements 128-a-1, 128-a-2, and 128-a-3). The native feed element pattern coverage area 211 may be shown relative to a reference surface (e.g., a plane at a distance from a communications satellite, a plane at a distance from the ground, a spherical surface at an altitude, the ground, etc.) and may further include a volume adjacent to the reference surface (e.g., a substantially conical volume between the reference surface and the communications satellite, a volume below the reference surface, etc.). The plurality of native feed element pattern coverage areas 211-a may collectively form a native antenna pattern coverage area 221-a. Although eight native supply element pattern coverage areas 211-a are shown, the supply array assembly 127 may have any number of supply elements 128 (e.g., less than eight or more than eight) each associated with a native supply element pattern coverage area 211.

[0045] The boundaries of each native feed element pattern coverage area 211 may correspond to a respective native feed element pattern 210 at the beam contour level 255-a, and the peak gain of each native feed element pattern coverage area 211 may have a position designated by "x" (e.g., a nominal alignment or axis of the respective native feed element pattern 210 or native feed element pattern coverage area 211). The native feed element pattern coverage areas 211a-1, 211-a-2, and 211-a-3 may correspond to projections of native feed element patterns associated with native feed element pattern gain profiles 250-a-1, 250-a-2, and 250-a-3, respectively, and drawing 203 shows the native feed element pattern gain profile 250 along cross section 260-a of drawing 204.

[0046] The native supply element pattern coverage areas 211 are referred to herein as idealized because the coverage areas are shown as circular for simplicity. However, in various examples, the native supply element pattern coverage areas 211 may be some shape other than circular (e.g., oval, hexagon, rectangle, etc.). Thus, the tiled native supply element pattern coverage areas 211 may have more overlap with each other than shown in drawing 204 (e.g., in some cases, more than three native supply element pattern coverage areas 211 may overlap).

[0047] In the drawing 204, which may represent a state in which the feed array assembly 127-a is disposed in a defocused position relative to the reflector 122-a, a substantial portion (e.g., a majority) of each native feed element pattern coverage area 211 overlaps with an adjacent native feed element pattern coverage area 211. A location within a service coverage area (e.g., the total coverage area of ​​the multiple spot beams of the antenna assembly 121) may be disposed within the native feed element pattern coverage areas 211 of two or more feed elements 128. For example, the antenna assembly 121-a may be configured such that the area of ​​overlap of three or more native feed element pattern coverage areas 211 is maximized. In some examples, this condition may also be referred to as the feed elements 128 of the feed array assembly 127, or the native feed element pattern coverage areas 211, having a high degree of overlap. Although eight native feed element pattern coverage areas 211 are shown, the feed array assembly 127 may have any number of feed elements 128 similarly associated with native feed element pattern coverage areas 211 .

[0048] In some cases, a single antenna assembly 121 may be used to transmit and receive signals between the user terminal 150 or the access node terminal 130. In other examples, the satellite 120 may include separate antenna assemblies 121 for receiving signals and transmitting signals. The receiving antenna assembly 121 of the satellite 120 may be directed to the same or similar service coverage area as the transmitting antenna assembly 121 of the satellite 120. Thus, some native feed element pattern coverage areas 211 for antenna feed elements 128 configured for receiving may naturally correspond to native feed element pattern coverage areas 211 for feed elements 128 configured for transmitting. In these cases, the receiving feed elements 128 may be mapped in a similar manner to their corresponding transmitting feed elements 128 (e.g., with similar array patterns of different feed array assemblies 127, with similar wiring and / or circuit connections to signal processing hardware, similar software configurations and / or algorithms, etc.), resulting in similar signal paths and processing for the transmitting and receiving native feed element pattern coverage areas 211. However, in some cases it may be advantageous to map the receive and transmit feed elements 128 differently.

[0049] Multiple native feed element patterns 210 with a high degree of overlap may be combined by beamforming to provide one or more spot beams 125. Beamforming of the spot beams 125 may be performed by adjusting the signal phase or time delay, and / or signal amplitude, of signals transmitted and / or received by multiple feed elements 128 of one or more feed array assemblies 127 with overlapping native feed element pattern coverage areas 211. Such phase and / or amplitude adjustment may be referred to as applying beam weights (e.g., beamforming coefficients) to the feed element signals. In the case of transmission (e.g., from a transmitting feed element 128 of a feed array assembly 127), the relative phase, and sometimes the amplitude, of the transmitted signals are adjusted so that the energy transmitted by the feed elements 128 constructively overlaps at a desired location (e.g., at the location of the spot beam coverage area 126). For reception (e.g., by receiving feed elements 128 of the feed array assembly 127), the relative phase, and sometimes the amplitude, of the received signals are adjusted (e.g., by applying the same or different beam weights) so that the energy received by the feed elements 128 from a desired location (e.g., at the location of the spot beam coverage area 126) superimposes constructively for a given spot beam coverage area 126.

[0050] The term beamforming may be used to refer to the application of beam weights, whether for transmission, reception, or both. Computing beam weights or coefficients may involve direct or indirect discovery of communication channel characteristics. The processes of beam weight computation and beam weight application may be performed in the same or different system components. An adaptive beamformer may include functionality that supports dynamically computing beam weights or coefficients.

[0051] The spot beams 125 may be steered, selectively shaped, and / or otherwise reconfigured by applying different beam weights. For example, the amount of active native feed element patterns 210 or spot beam coverage areas 126, the size of the shape of the spot beams 125, the relative gain of the native feed element patterns 210 and / or spot beams 125, and other parameters may change over time. The antenna assembly 121 may apply beamforming to form relatively narrow spot beams 125, and may be capable of forming spot beams 125 with improved gain characteristics. The narrow spot beams 125 may allow signals transmitted on one beam to be differentiated from signals transmitted on other spot beams 125, for example, to avoid interference between transmitted and received signals, or to identify spatial separation of received signals.

[0052] In some examples, narrow spot beams 125 may allow for greater reuse of frequency and polarization than when larger spot beams 125 are formed. For example, narrowly formed spot beams 125 may support signal communication through non-overlapping, discontinuous spot beam coverage areas 126, while overlapping spot beams 125 may be orthogonal in frequency, polarization, or time. In some examples, greater reuse through the use of smaller spot beams 125 may increase the amount of data transmitted and / or received. Additionally or alternatively, beamforming may be used to provide sharper gain roll-off at the beam edges, which may allow for higher beam gains through larger portions of the spot beams 125. Thus, beamforming techniques may be capable of providing higher frequency reuse and / or greater system capacity for a given amount of system bandwidth.

[0053] Some satellites 120 may use OBBF to electronically steer signals transmitted and / or received via the array of feeding elements 128 (e.g., apply beam weights to feeding element signals at the satellite 120). For example, the satellite 120 may have phased array multiple feed per beam (MFPB) on-board beamforming capability. In some examples, the beam weights may be calculated at a ground-based computing center (e.g., at the access node terminal 130, at the network device 141, at the communication services manager) and then transmitted to the satellite 120. In some examples, the beam weights may be pre-configured or otherwise determined at the satellite 120 for on-board applications.

[0054] In some cases, significant processing power may be involved in the satellite 120 to control the phase and gain of each feed element 128 used to form the spot beam 125. Such processing power may increase the complexity of the satellite 120. Thus, in some cases, the satellite 120 may operate at GBBF to reduce the complexity of the satellite 120 while still providing the advantage of electronically forming the narrow spot beam 125. In some examples, the beam weights or coefficients may be applied in the ground segment 102 (e.g., in one or more ground stations) before transmitting associated signaling to the satellite 120, which may include multiplexing the feed element signals in the ground segment 102 according to various time, frequency, or spatial multiplexing techniques, among other signal processing. Thus, the satellite 120 may receive such signaling, possibly demultiplex, and transmit the associated feed element signals via the respective antenna feed elements 128 to form the transmit spot beam 125 based at least in part on the beam weights applied in the ground segment 102. In some examples, the satellites 120 may receive feed element signals via their respective antenna feed elements 128 and transmit the received feed element signals to the ground segment 102 (e.g., one or more ground stations), which may include multiplexing the feed element signals at the satellite 120 according to various time, frequency, or spatial multiplexing techniques, among other signal processing. The ground segment 102 may thus receive and possibly demultiplex such signaling, and apply beam weights to the received feed element signals to generate spot beam signals corresponding to each spot beam 125.

[0055] In another example, the satellite system 100 according to the present disclosure may support various end-to-end beamforming techniques, which may involve forming an end-to-end spot beam 125 via a satellite 120 or other vehicle operating as an end-to-end relay. For example, the satellite 120 may include multiple receive / transmit signal paths (e.g., transponders), each coupled between a receive feed element and a transmit feed element. In an end-to-end beamforming system, beam weights may be calculated in a central processing system (CPS) of the ground segment 102, and the end-to-end beam weights may be applied in the ground segment 102, rather than at the satellite 120. Signals in the end-to-end spot beam 125 may be transmitted and received at an array of access node terminals 130, which may be satellite access nodes (SANs). Any suitable type of end-to-end relay may be used in the end-to-end beamforming system, and different types of access node terminals 130 may be used to communicate with different types of end-to-end relays.

[0056] The end-to-end beamformer in the CPS can calculate one set of end-to-end beam weights that considers: (1) the wireless signal uplink path to the end-to-end relay, (2) the receive / transmit signal path through the end-to-end relay, and (3) the wireless signal downlink path from the end-to-end relay. The beam weights can be mathematically represented as a matrix. In some examples, OBBF and GBBF satellite systems can have a beam weight vector dimension set by the number of feed elements 128 on the antenna assembly 121. In contrast, the end-to-end beam weight vector can have a dimension set by the number of access node terminals 130, rather than the number of feed elements 128 on the end-to-end relay. In general, the number of access node terminals 130 is not the same as the number of feed elements 128 on the end-to-end relay. Furthermore, the formed end-to-end spot beam 125 is not terminated at either the transmit or receive feed elements 128 of the end-to-end relay. Rather, the formed end-to-end spot beam 125 may be effectively relayed because the end-to-end spot beam 125 may have an uplink signal path, a relay signal path (via the satellite 120 or other suitable end-to-end relay), and a downlink signal path.

[0057] Because the end-to-end beamforming system can take into account both the user link and the feeder link, as well as the end-to-end relay, only a single set of beam weights is needed to form a desired end-to-end spot beam 125 (e.g., forward spot beam 125 or return spot beam 125) in a particular direction. Thus, one set of end-to-end forward beam weights results in signals transmitted from the access node terminal 130 via the forward uplink, via the end-to-end relay, and via the forward downlink that are combined to form the end-to-end forward spot beam 125. Conversely, signals transmitted from the return user via the return uplink, end-to-end relay, and return downlink have end-to-end return beam weights applied to form the end-to-end return spot beam 125. Under some conditions, it may be difficult or impossible to distinguish between the characteristics of the uplink and the downlink. Thus, shaped feeder link spot beams 125, shaped spot beam directivity, and individual uplink and downlink carrier-to-interference ratios (C / I) may no longer have their traditional role in system design, although the concepts of uplink and downlink signal-to-noise ratios (Es / No) and end-to-end C / I may still be relevant.

[0058] 3A and 3B show an example of beamforming to form spot beam coverage areas 126 on a native antenna pattern coverage area 221-b according to examples disclosed herein. In FIG. 3A, a drawing 300 shows a native antenna pattern coverage area 221-b including a plurality of native feed element pattern coverage areas 211 that may be provided by a defocused multi-feed antenna assembly 121. Each of the native feed element pattern coverage areas 211 may be associated with a respective feed element 128 of a feed array assembly 127 of the antenna assembly 121. In FIG. 3B, a drawing 350 shows a pattern of spot beam coverage areas 126 across a service coverage area 310 of the North American continent. The spot beam coverage area 126 may be provided by applying beamforming coefficients to signals carried through the feed elements 128 associated with the plurality of native feed element pattern coverage areas 211 of FIG. 3A.

[0059] Each of the spot beam coverage areas 126 may have an associated spot beam 125, which may be based on a predefined beamforming configuration configured to support communication services or other primary or real-time missions within the respective spot beam coverage area 126 in some examples. Each of the spot beams 125 may be formed from a composite of signals carried over multiple feed elements 128 for the native feed element pattern coverage area 211 that includes the respective spot beam coverage area 126. For example, the spot beam 125 associated with the spot beam coverage area 126-c shown in FIG. 3B may be a composite of signals over eight feed elements 128 associated with the native feed element pattern coverage area 211-b shown in FIG. 3A with solid black lines. In various examples, the spot beams 125 with overlapping spot beam coverage areas 126 may be orthogonal in frequency, polarization, and / or time, while the non-overlapping spot beams 125 may be non-orthogonal to one another (e.g., tiled frequency reuse patterns). In other examples, the non-orthogonal spot beams 125 may have varying degrees of overlap, with interference mitigation techniques such as ACM, interference cancellation, or space-time coding used to manage inter-beam interference.

[0060] Beamforming may be applied to signals transmitted or received via a satellite using OBBF, GBBF, or end-to-end beamforming receive / transmit signal paths. Thus, the service provided over the spot beam coverage area 126 shown in FIG. 3B may be based on the native antenna pattern coverage area 221-b of the antenna assembly 121 as well as the applied beam weights. Although the service coverage area 310 is shown as being provided through a substantially uniform pattern of spot beam coverage areas 126 (e.g., having equal or substantially equal beam coverage area sizes and amounts of overlap), in some examples, the spot beam coverage areas 126 for the service coverage area 310 may be non-uniform. For example, a densely populated area may be provided with communication services using relatively small spot beams 125, while a less densely populated area may be provided with communication services using relatively large spot beams 125.

[0061] A satellite system according to examples disclosed herein may employ various beamforming techniques to support multistatic synthetic aperture radar. For example, multiple feed signals (e.g., signals received at feed elements 128) or access node terminal signals (e.g., signals received at access node terminal antenna system 131) may be processed according to multiple beam weight sets to obtain different sets of image points within an imaging region (e.g., within native antenna pattern coverage area 221). The feed signals or access node terminal signals may include reflections of actively transmitted or passively collected signals. The sets of image points may be combined to obtain a multistatic synthetic aperture radar image.

[0062] 4 illustrates an example of a receiver processing system 400 supporting a multistatic synthetic aperture radar according to examples disclosed herein. The example receiver processing system 400 includes a feed element signal receiver 410, a beamforming processor 420, a beam weight set manager 430, a beam signal processor 440, and an image processor 450.

[0063] The feeding element signal receiver 410 may be configured to receive feeding element signals 405 associated with an antenna assembly 121 having a feeding array assembly 127. In some examples, the feeding element signal receiver 410 may refer to a satellite 120 coupled to an antenna assembly, or other vehicle component including such an antenna assembly 121. For example, the satellite 120 may support OBBF and may perform beamforming for received signals and transmission of beam signals to a ground segment.

[0064] In some examples, such as a GBBF system, the feeding element signal receiver 410 may refer to a component of the ground segment 102 that is separate from the device including such antenna assembly 121, but in communication with such device (e.g., via a wireless communication link such as the return link 133) to support reception of the feeding element signal 405. For example, the feeding element signal receiver 410 may refer to a return channel feeder link downconverter of the ground segment 102, which may be a component configured to receive feeding element signals 405 or other signaling for constructing a receiving spot beam 125 from one or more satellites 120. In some examples, the feeding element signal receiver 410 may receive feeding element signals by the return link 133 via one or more ground stations, and the feeding element signals 405 may be multiplexed according to various techniques, such as frequency division multiplexing, time division multiplexing, polarization multiplexing, spatial multiplexing, or other techniques. Thus, the feeding element signal receiver 410 may be configured to demultiplex or demodulate various signaling to receive or process the feeding element signals 405.

[0065] In some examples, the feed element signals 405 may be received as raw signals from the transducers of the respective feed elements 128. In some examples, the feed element signals 405 may be received as filtered or otherwise processed signals, which may include filtering, combining, or other processing at the satellite 120 or ground segment 102 components. The feed element signal receiver 410 may provide the feed element signals 415 to the beamforming processor 420. In some examples, to generate the feed element signals 415, the feed element signals 405 may be filtered or otherwise processed to support frequency bands associated with multistatic synthetic aperture radar. For example, the feed element signals 405 may include frequency bands used for communications in addition to frequency bands of interest for radar applications. To generate the feed element signal 415, the feed element signal receiver 410 may be configured to filter the feed element signal 405 according to a range of frequencies of interest for the radar application, or the feed element signal receiver 410 may be configured to perform other processing of the feed element signal 405 (e.g., frequency conversion, oversampling, downsampling).

[0066] In yet other cases, the feed element signals 405 may correspond to access node terminal signals of the end-to-end beamforming system (e.g., signals received at the access node terminal antenna system 131). Thus, each of the feed element signals may represent a composite of return uplink signals received at one or more receiving feeds of the end-to-end relay and relayed to one of the access node terminals via a corresponding one or more transmitting feeds of the end-to-end relay.

[0067] The source element signal 405 may represent signal energy from a reflected illumination signal (e.g., a beacon signal, a communication signal) or passively received signal energy (e.g., without a corresponding illumination signal transmitted by the satellite system 100 due to reflection).

[0068] In some examples, the feed element signals 405 may include multiple signals corresponding to each of multiple polarizations, and a multistatic synthetic aperture radar application may be configured to use different polarizations. The feed element signal receiver 410 may combine or otherwise process the feed element signals 405 to obtain feed element signals 415 corresponding to the same feed element 128, or two or more feed elements 128 sharing a common port or aperture associated with different polarizations. The feed element signal receiver 410 may provide the feed element signals 415 to a beamforming processor 420. The feed element signal receiver 410 may also be configured to sample and store the feed element signals 405 or other related signaling for later processing.

[0069] The beamforming processor 420 may be configured to process the feed element signals 415 by applying beam weights or coefficients to generate target spot beam signals associated with a multistatic synthetic aperture radar. The spot beams 125 formed by the beamforming processor 420 may correspond to radar image pixel beams. The beamforming processor 420 may apply multiple beam weight sets 433, with each beam weight set 434 corresponding to one or more radar image pixel beams. Each beam weight set 434 may have a first dimension corresponding to the number of feed element signals. For example, the first dimension may be equal to the number of feeders for an OBBF or GBBF system, or the number of access node terminals for a system employing end-to-end relays. The beam weight sets 434 may have a second dimension that is the same for each beam weight set, or some beam weight sets may have different sizes for the second dimension. For example, the second dimension may correspond to the number of beam signals generated from the beam weight sets 434, and each of the beam weight sets 434 may generate the same number of beam signals, or some of the beam weight sets 434 may generate different numbers of beam signals. Each coefficient of the beam weight set 434 may be a complex beam weight (e.g., including an amplitude component and a phase component). The beamforming processor 420 may receive the feed element signal 415 corresponding to the duration and process the feed element signal 415 according to each of the plurality of beam weight sets 433. For each of the plurality of beam weight sets 433, the beamforming processor 420 may generate a set of beam signals 425 (e.g., radar image pixel beams) corresponding to a beam coverage pattern.

[0070] In one example, the feeding element signal 415 may correspond to a return downlink signal received at a satellite access node (e.g., from an end-to-end relay). The return downlink signal may be a composite of return uplink signals received by a satellite via an antenna illuminating a geographic region. Processing the feeding element signal 415 may include processing a first set of signal data of the return downlink signal corresponding to a first duration of the return downlink signal according to a plurality of beam weight sets. In some cases, the processing includes processing the first set of signal data according to a first beam weight set to obtain a first subset of the plurality of beam signals corresponding to a first beam coverage pattern, and processing the first set of signal data according to a second beam weight set to obtain a second subset of the plurality of beam signals 425 corresponding to a second beam coverage pattern. The processing may include processing the first set of signal data according to an additional beam weight set to obtain an additional subset of the plurality of beam signals 425.

[0071] The beam signal processor 440 can generate image pixel values ​​corresponding to the beam signals 425. Image pixel values ​​may be generated for each radar image pixel beam (e.g., based on the signal levels associated with the radar image pixel beam). For each set of beam signals 425, the beam signal processor 440 can assign image components (e.g., brightness, color) to various signal levels detected in the set of beam signals 425. In addition, the beam signal processor 440 can receive beam position information 432 (e.g., according to corresponding beam coverage patterns from the beam weight set 433) and assign image values ​​to pixel positions based on the corresponding beam position information. For example, if a second beam coverage pattern corresponding to a second beam weight set is offset from a first beam coverage pattern corresponding to the second beam weight set, the beam signal processor 440 can determine an image signal value 445 based at least in part on the offset.

[0072] In some examples, processing the set of beam signals 425 may be based on the illumination signals. For example, if the feed element signals 405 include reflected energy from illumination signals (e.g., transmitted by a satellite or different satellites), the beam signal processor 440 may determine each image value based on a correlation between the corresponding beam signal and the illumination signal (e.g., amplitude and / or phase coherence between the illumination signal and the corresponding beam signal). Additionally, the beam signal processor 440 may apply external information to determine the image values. The external information may include information about known terrain features (e.g., elevation, buildings, surface composition) obtained from other sources (e.g., satellite imagery, elevation data, object databases) that is used to inform the determination of the image values. For example, the elevation data may be used to calibrate the phase relationship of the beam signals to the illumination signals. In some aspects, the illumination signals may be communication signals and different locations may be associated with different communication signals (e.g., illumination may be a forward downlink signal 172 that may be different in different spot beams). The beam signal processor 440 may receive beam information 455 that may be used in determining the image values. For example, beam information 455 may include beam signals (e.g., modulated data signals, symbol information) and other beam parameters (e.g., beam gain over a beam coverage area) for spot beam 125. Thus, beam signal processor 440 can evaluate the determined beam signals based on the transmit signals and beam gains at locations corresponding to the image pixel beams to determine image values. Beam signal processor 440 can output a set of image signal values ​​445 (e.g., each set of image signal values ​​corresponding to a set of beam signals 425) to image processor 450.

[0073] In some cases, the beam signal processor 440 may filter beam signals generated from different sets of feed element signals (e.g., corresponding to different durations). For example, the beamforming processor 420 may process a second set of signal data of the return downlink signal corresponding to a second duration of the return downlink signal according to a second plurality of beam weight sets, which may be the same or different from the plurality of beam weight sets used for the first set of signal data. In some cases, each of the plurality of beam weight sets and the second plurality of beam weight sets may be configured to provide substantially the same or overlapping beam coverage patterns. For example, processing the second set of signal data may include processing the second set of signal data corresponding to the second duration of the return downlink signal according to a third beam weight set to obtain a third subset of the plurality of beam signals corresponding to the first beam coverage pattern, and processing the second set of signal data according to a fourth beam weight set to obtain a fourth subset of the plurality of beam signals corresponding to the second beam coverage pattern. That is, the first beam weight set and the third beam weight set may be determined to provide a beam coverage pattern having at least some substantially overlapping image pixel beams.

[0074] The beam signal processor 440 can filter the subsets of the beam signals to obtain a filtered subset of the beam signals. For example, the beam signal processor 440 can apply a filtering function to the beam signals associated with the processed feed element signals corresponding to different dime durations to obtain a filtered subset of the beam signals. The filtering function can be, for example, averaging or other finite impulse response (FIR) or infinite impulse response (IIR) filters. Thus, the beam signal processor 440 can generate image signal values ​​445 from the filtered beam signals.

[0075] The image processor 450 can receive each set of image signal values ​​445 and process the set of image signal values ​​445 to generate the image 460. That is, the image processor 450 can combine sets of image signal values ​​445 for multiple sets of beam signals 425 to generate the image 460. In addition to or instead of the filtering performed by the beam signal processor 440, the image processor 450 can filter the image signal values ​​445 to generate the image 460. For example, the image processor 450 may combine multiple sets of image signal values ​​(e.g., corresponding to the same pixel location) to obtain the image 460. The filtering can include averaging or other FIR or IIR filtering. In some examples, the imaging values ​​associated with each radar image pixel beam can be transformed into three-dimensional (3D) space, and thus the image processor 450 can generate a set of voxels or a 3D representation of the imaging region.

[0076] In some examples, the beamforming processor 420 can process the feed element signals using multiple beam weight sets 433 for each of multiple frequency ranges or polarizations, and the beam signal processor 440 and image processor 450 can combine values ​​of radar image pixel beams from different frequency ranges or polarizations to generate one or more images. For example, a first set of radar image pixel beams may correspond to radar image pixel beams associated with passive detection of (e.g., incidental) signal energy, and a second set of radar image pixel beams may correspond to signal energy reflected from an illumination source (e.g., from a satellite or one or more different satellites). Such combined data can, for example, overlay information related to thermal emissions with the reflected signal energy to provide additional information about the imaged area.

[0077] Additionally or alternatively, the beamforming processor 420 can process multiple sets of feeding element signals corresponding to different time periods, and the image processor 440 can combine the beam signals 425 corresponding to the different time periods. For example, the feeding element signals 405 can correspond to feeding element signals of a GEO satellite, or access node terminal signals relayed by a GEO end-to-end relay, and the illumination signals can be transmitted by one or more LEO satellites. A synthetic aperture given an illumination angle of the LEO satellite can be provided by processing multiple time periods corresponding to different positions of the LEO satellite. Thus, each set of feeding element signals corresponding to one of the multiple time periods can be processed according to multiple beam weight sets and positions of the illumination source (e.g., LEO satellite) to obtain multiple sets of beam signals, and the multiple sets of beam signals can be combined to obtain a composite set of beam signals corresponding to the time period. Additional composite sets of beam signals can be obtained for different time periods and combined to obtain a synthetic aperture corresponding to an angular range of illumination for one or more illumination sources.

[0078] In some cases, the receiver processing system 400 may be configured to support real-time or primary missions, such as communication services or data collection services. For example, the beamforming processor 420 (or a different beamforming processor in some cases) may be configured to process the feed element signals 415 by applying beam weights or coefficients to generate spot beam signals. The spot beams 125 formed by the beamforming processor 420 may point to predefined beams having substantially non-overlapping spot beam coverage areas 126 and may use different frequency bands, polarizations, or both for a given location. The generated spot beam signals may be processed through the beam signal processor 440 (or a different beam signal processor) and passed to a modem (not shown) for demodulation to support various return link communications (e.g., to obtain data signals transmitted by the user terminal 150). In some cases, the beam weight set applied to support return link communications may be different from the multiple beam weight sets used to obtain the multiple sets of beam signals for the radar image pixel beams (e.g., the radar image pixel beams may be different from the spot beams used for return link communications), or the beam weight set applied to support return link communications may be a portion of the multiple beam weight sets.

[0079] In some cases, the source element signal receiver 410 may be configured to perform signal cancellation or suppression of the signal associated with the return link communication to obtain the source element signal 415 .

[0080] 5 illustrates an example of a composite beam coverage pattern 500 supporting a multistatic synthetic aperture radar according to examples disclosed herein. The composite beam coverage pattern 500 can include a set of beam coverage patterns 512, where each beam coverage pattern 512 in the set of beam coverage patterns 510 corresponds to a different beam weight set. In the illustrated example, the composite beam coverage pattern 500 includes nine beam coverage patterns 510, including beam coverage patterns 510-a, 510-b, 510-c, 510-d, 510-e, 510-f, 510-g, 510-h, and 510-i. Each of the beam coverage patterns can be offset from one another (e.g., offset in one dimension, offset in more than one dimension). For example, the first beam coverage pattern 510-a may be offset from the second beam coverage pattern 510-b by an offset 520. Thus, according to the exemplary composite beam coverage pattern 500, the set of data of the feed element signal 415 may be processed nine times, each with a different set of beam weights, to obtain nine sets of beam signals corresponding to each beam coverage pattern. However, the composite beam coverage pattern 500 is only an example, and composite beam coverage patterns may be generated for any number of beam coverage patterns. Each set of beam signals may include one or more beam signals, each corresponding to a position within the composite beam coverage pattern 500. Each beam signal may then be assigned an image value (e.g., corresponding to a signal value of an incident or reflected signal within the beam signal).

[0081] Although each beam coverage pattern 510 is shown as not overlapping with other beam coverage patterns, it should be understood that each beam coverage pattern may represent signal power received from one or more spatial directions and portions of the beam coverage patterns may overlap with each other. A beam coverage pattern may represent spatial information assigned to a given beam weight set and may generally be centered around each region of received beamforming signal energy. That is, the beam gain pattern (e.g., given by a gain contour such as 3 dB) for a given beam coverage area 515 may be circular or of various shapes depending on the satellite's orbit or terrain characteristics and the beam weight set applied, with the beam signal being assigned a location based on the center of gravity (e.g., of the beam contour such as 1 dB or 3 dB contour) or the location of the highest beamforming gain of the beam coverage area 515.

[0082] 6 illustrates a diagram of a system 600 including a device 605 supporting techniques for multistatic synthetic aperture radar, according to examples disclosed herein. The device 605 may be or include an example of components of a receiver processing system described herein. The device 605 may include components for bidirectional data communication, including components for transmitting and receiving communications, including a multistatic beamforming system 610, an I / O controller 615, a database controller 620, a memory 625, a processor 630, and a database 635. These components may be in electronic communication via one or more buses (e.g., bus 640).

[0083] The multistatic beamforming system 610 may be an example of a receive processing system 400 as described herein. In some cases, the multistatic beamforming system 610 may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. For example, the multistatic beamforming system 610 may receive feeding element signals (e.g., via an I / O controller 615) and process the feeding element signals to generate a multistatic synthetic radar aperture image. The feeding element signals may correspond to feeding element signals received at a feeding element of a beamforming satellite (e.g., an OBBF or GBBF system) or may be access node terminal signals for a system employing an end-to-end relay. The multistatic beamforming system 610 may process the feeding element signals according to multiple beam weight sets, each beam weight set may correspond to a pattern of radar image pixel beams. The multistatic beamforming system 610 may generate a set of image pixel values ​​for each set of radar image pixel beams, and may combine the sets of image pixel values ​​to generate one or more images. The multistatic beamforming system 610 may output the image in an output signal 650 via the I / O controller 615 (e.g., for display on a display device or storage on a storage medium).

[0084] The I / O controller 615 can manage input signals 645 and output signals 650 for the device 605. The I / O controller 615 can also manage peripherals that are not integrated into the device 605. In some cases, the I / O controller 615 can represent a physical connection or port to an external peripheral. In some cases, the I / O controller 615 may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS / 2®, UNIX®, LINUX®, or another known operating system. In other cases, the I / O controller 615 can represent or interact with a modem, keyboard, mouse, touch screen, or similar device. In some cases, the I / O controller 615 can be implemented as part of a processor. In some cases, a user can interact with the device 605 through the I / O controller 615 or through hardware components controlled by the I / O controller 615.

[0085] The database controller 620 can manage data storage and processing in the database 635. In some cases, a user can interact with the database controller 620. In other cases, the database controller 620 can operate automatically without user interaction. The database 635 can be an example of a single database, a distributed database, multiple distributed databases, a data store, a data lake, or an emergency backup database. The database 635 can store, for example, multiple beam weight sets for use by the multistatic beamforming system 610.

[0086] The memory 625 may include random access memory (RAM) and read only memory (ROM). The memory 625 may store computer-readable, computer-executable software that includes instructions that, when executed (e.g., by the processor 630), cause the processor to perform various functions described herein. For example, the memory 625 may store instructions for operation of the multistatic beamforming system 610 described herein. In some cases, the memory 625 may include a basic input / output system (BIOS) that may control basic hardware or software operations, such as interaction with peripheral components or devices, among other things.

[0087] The processor 630 may include intelligent hardware devices (e.g., a general purpose processor, a DSP, a central processing unit (CPU), a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 630 may be configured to operate a memory array using a memory controller. In other cases, the memory controller may be integrated into the processor 630. The processor 630 may be configured to execute computer-readable instructions stored in the memory 625 to perform various functions.

[0088] 7 illustrates a process flow 700 that supports techniques for multistatic synthetic aperture radar according to examples disclosed herein. The process flow 700 may be implemented, for example, by the receiver processing system 400 of FIG. 4 or the multistatic beamforming system 610 of FIG. 6.

[0089] Process flow 700 may represent a process for forming a multistatic synthetic aperture radar image from a system that supports beamforming of received signals (e.g., an OBBF system, a GBBF system, an end-to-end beamforming system).

[0090] At 705, the system can receive a supply element signal associated with a satellite having an antenna that irradiates a geographical area. For example, the supply element signal may correspond to a supply element signal received at a supply element of a beamforming satellite (e.g., an OBBF or GBBF system), or may be an access node terminal signal for a system employing end-to-end relay. The received supply element signal may correspond to a certain period. For example, the supply element signal may be processed according to a frame timing corresponding to the duration of a communication system (e.g., a communication symbol or frame).

[0091] At 710, the system can obtain I sets of beam weights corresponding to I beam coverage patterns. For example, each of the I sets of beam weights may be associated with one or more radar image pixel beams associated with the geographical location of the geographical area. The associated geographical location may be, for example, the geographical center (e.g., the centroid) or the point of maximum gain of the radar image pixel beam.

[0092] At 715, the system can process the supply element signal according to the i-th set of beam weights to obtain the i-th set of beam signals.

[0093] At 720, the system can determine whether there is an additional set of beam weights for the processing of the supply element signal. For example, if i < I (where i ∈ {1...I}), the system may increment i and return to 715 to process the supply element signal according to the next set of beam weights. When the I sets of beam weights have been processed at 720, the system proceeds to 725 and can process the set of beam signals.

[0094] At 720, the system may process the set of beam signals to obtain an image of the illuminated geographic area. For example, the system may assign a pixel image value to each of the beam signals. In some cases, the assignment of pixel image values ​​to each of the beam signals may take into account whether the supply element signal includes signal information related to incident or passive radiation or to reflections of the illumination source. The illumination source may be, for example, a broad beam signal (e.g., a single beam covering the illuminated geographic area, such as from a beacon signal) or a multi-beam signal (e.g., user beams for communication via a multi-beam satellite). In the case of illumination using a multi-beam signal, the system may determine a pixel image value based on the beam signal and characteristics of the corresponding beam signal at a location associated with the beam signal. For example, a first beam signal may be associated with a center of the user beam and a second beam signal may be associated with an edge of the user beam. The system may determine the pixel image value by scaling the beam signal by the incident energy of the user beam at the location of the beam signal. That is, the first beam signal and the second beam signal may be normalized by the gain pattern of the user beam.

[0095] Thus, the system may obtain multiple sets of pixel image values ​​corresponding to the set of beam signals. The system may then combine the multiple sets of pixel image values ​​to obtain an image of at least a portion of the illuminated geographic area. As described above, the system may perform beam weight set processing for multiple frequency bands or polarizations to obtain multiple pixel image values ​​for each pixel location of the image, and may combine the multiple pixel image values ​​(e.g., by pixel brightness or hue) to obtain each final pixel image value for the image.

[0096] It should be noted that the described techniques refer to possible implementations, and that operations and components may be rearranged or otherwise modified, and other implementations are possible. Further portions from two or more methods or devices may be combined.

[0097] The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, the data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0098] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed using a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration).

[0099] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored or transmitted as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of this disclosure and the appended claims. For example, due to the nature of software, the functions described herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Features that implement the functions may also be physically located in various locations, including being distributed such that parts of the functions are implemented in different physical locations.

[0100] Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available medium accessible by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general purpose or special purpose computer, or a general purpose or special purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within the definition of media. Disk and disc, as used herein, include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0101] As used herein, including the claims, "or" used in a list of items (e.g., a list of items prefaced by a phrase such as "at least one" or "one or more") indicates an inclusive list, such as, 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 a reference to a closed set of conditions. For example, an exemplary step described as "based on condition A" may 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" is to be interpreted in the same manner as the phrase "based at least in part on."

[0102] In the accompanying drawings, similar components or features may have the same reference label. Furthermore, various components of the same type may be distinguished by following the reference label with a dash and a second label that distinguishes among the similar components. If only a first reference label is used herein, the description is applicable to any one of the similar components having the same first reference label, regardless of the second reference label, or any other subsequent reference label.

[0103] The description set forth herein with reference to the accompanying drawings describes exemplary configurations and does not necessarily represent all examples that may be implemented or fall within the scope of the claims. As used herein, the term "exemplary" means "serving as an example, instance, or illustration" and not "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 may 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.

[0104] The description herein is provided to enable any person skilled in the art to 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 may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure is not limited to the examples and designs described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for imaging using a satellite (120), comprising: receiving at a satellite access node (130) a return downlink signal (133), the return downlink signal (133) comprising a composite of return uplink signals (173) received by a plurality of return uplink feeds (128) of an antenna array (127) of the satellite illuminating a geographic region; and processing the return downlink signal (133) according to a plurality of beam weight sets (433) to obtain a plurality of beam signals (425), the plurality of beam weight sets (433) corresponding to a respective plurality of beam coverage patterns (512), and processing the return downlink signal (133) includes processing a first set of signal data of the return downlink signal (133) corresponding to a first duration of the return downlink signal (133) by applying a first beam weight set (434) to the first set of signal data corresponding to the first duration, and processing a first subset of the plurality of beam signals (425) corresponding to a second beam coverage pattern (510). processing the first set of signal data corresponding to the first duration by applying a second set of beam weights (434) to the first set of signal data to obtain a second subset of the plurality of beam signals (425) corresponding to a first beam coverage pattern (510), the first beam coverage pattern (510) comprising a first plurality of beam coverage areas (515) associated with a first polarization and a first frequency range, the second beam coverage pattern (510) comprising a second plurality of beam coverage areas (515) associated with the first polarization and the first frequency range, the second plurality of beam coverage areas (515) being offset (520) from the first plurality of beam coverage areas (515); and processing the multiple beam signals (425) to obtain an image (460) of the illuminated geographic area including image pixel values ​​corresponding to the multiple beam signals (425).

2. 2. The method of claim 1, wherein each beam coverage area (515) of the second plurality of beam coverage areas (515) partially overlaps with a corresponding beam coverage area (515) of the first plurality of beam coverage areas (515).

3. Processing the plurality of beam signals (425) to obtain the image (460) of the illuminated geographic area includes: generating a first set of image data points from the first subset of the plurality of beam signals; generating a second set of image data points from the second subset of the plurality of beam signals (425); 2. The method of claim 1, further comprising: combining the first set of image data points and the second set of image data points according to the offset (520) between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515) by assigning the image pixel values ​​to pixel positions based on beam position information of the first plurality of beam coverage areas (515) and the second plurality of beam coverage areas (515).

4. Processing the return downlink signal (133) in accordance with the plurality of beam weight sets (434) comprises: processing a second set of signal data corresponding to a second duration of the return downlink signal (133) according to a third beam weight set (434) to obtain a third subset of the plurality of beam signals (425) corresponding to the first beam coverage pattern (510); and processing the second set of signal data according to a fourth set of beam weights (434) to obtain a fourth subset of the plurality of beam signals (425) corresponding to the second beam coverage pattern (510).

5. Processing the plurality of beam signals (425) to obtain the image (460) of the illuminated geographic area includes: filtering the first and third subsets of the plurality of beam signals (425) to obtain a first filtered subset of beam signals; generating a first set of image data points from the first filtered subset of the beam signals; filtering the second and fourth subsets of the plurality of beam signals (425) to obtain a second filtered subset of beam signals; generating a second set of image data points from a second filtered subset of the beam signals; and combining the first set of image data points and the second set of image data points according to the offset between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515).

6. Processing the plurality of beam signals (425) to obtain the image of the illuminated geographic area includes: generating a third set of image data points from the third subset of the plurality of beam signals (425); generating a fourth set of image data points from the fourth subset of the plurality of beam signals (425); filtering the first and third sets of image data points to obtain a first filtered set of image data points; filtering the second and fourth sets of image data points to obtain a second filtered set of image data points; and combining the first filtered set of image data points and the second filtered set of image data points according to the offset (520) between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515).

7. 7. The method of claim 1, wherein the return downlink signal (133) comprises a plurality of return downlink signals (133), each of the plurality of return downlink signals (133) corresponding to a return uplink signal (173) received by a feeder (128) of the antenna array (127) of the satellite (120).

8. Receiving the return downlink signal (133) 7. The method of claim 1, comprising receiving a plurality of return downlink signals (133) at a respective plurality of satellite access nodes (130), each of the plurality of return downlink signals (133) comprising a composite of one or more of the return uplink signals (173).

9. The method of any one of claims 1 to 8, wherein each of the plurality of beam coverage patterns (510) comprises a plurality of beam coverage areas (515).

10. The method of any one of claims 1 to 9, wherein the satellite transmits a beacon signal and relays respective reflections of the beacon signal received at a plurality of feeders (128) of the antenna array (127) of the satellite (120), and the return downlink signal (133) includes the respective relayed reflections.

11. 10. The method of claim 1, wherein the satellite access node (130) transmits a forward uplink signal (132), the satellite (120) repeats the forward uplink signal (132) via a plurality of forward downlink feeds (128) of the antenna array (127) of the satellite (120), the satellite (120) repeats respective reflections of the repeated forward link signal received at a plurality of return uplink feeds (128) of the antenna array (127), and the return downlink signal (133) includes the respective repeated reflections.

12. 12. The method of claim 11, wherein the forward uplink signal (133) comprises a plurality of forward user data streams for transmission to a plurality of user terminals (150) within the geographic region.

13. 10. The method of claim 1, wherein the satellite (120) is a first satellite (120) and one or more second satellites (122) transmit respective illumination signals (145) across the geographic region, the first satellite (120) relays respective reflections of the illumination signals (145) received at a plurality of return uplink feeds (128) of the antenna array (127) of the first satellite (120), and the return downlink signal (133) includes the respective relayed reflections.

14. 14. The method of claim 13, wherein the first satellite (120) is a geostationary (GEO) satellite and each of the one or more second satellites (122) is a low earth orbit (LEO) satellite W.

15. An imaging system for imaging using a satellite (120), comprising: a satellite access node (130) configured to receive a return downlink signal (133), the return downlink signal (133) comprising a composite of return uplink signals (173) received by a plurality of return uplink feeds (128) of an antenna array (127) of the satellite illuminating a geographical area; At least one processor (630), the at least one processor (630) and processing the return downlink signal (133) according to a plurality of beam weight sets (433) to obtain a plurality of beam signals (425), the plurality of beam weight sets (433) corresponding to a respective plurality of beam coverage patterns (512), and processing the return downlink signal (133) includes processing a first set of signal data of the return downlink signal (133) corresponding to a first duration of the return downlink signal (133) by applying a first beam weight set (434) to the first set of signal data corresponding to the first duration, and processing a first subset of the plurality of beam signals (425) corresponding to a second beam coverage pattern (510). processing the first set of signal data corresponding to the first duration by applying a second set of beam weights (434) to the first set of signal data to obtain a second subset of the plurality of beam signals (425) corresponding to a first beam coverage pattern (510), the first beam coverage pattern (510) comprising a first plurality of beam coverage areas (515) associated with a first polarization and a first frequency range, the second beam coverage pattern (510) comprising a second plurality of beam coverage areas (515) associated with the first polarization and the first frequency range, the second plurality of beam coverage areas (515) being offset (520) from the first plurality of beam coverage areas (515); and processing the multiple beam signals (425) to obtain an image (460) of the illuminated geographical area including image pixel values ​​corresponding to the multiple beam signals (425).

16. 16. The imaging system of claim 15, wherein each beam coverage area (515) of the second plurality of beam coverage areas (515) partially overlaps with a corresponding beam coverage area (515) of the first plurality of beam coverage areas (515).

17. Processing the plurality of beam signals (425) to obtain the image (460) of the illuminated geographic area includes: generating a first set of image data points from the first subset of the plurality of beam signals; generating a second set of image data points from the second subset of the plurality of beam signals (425); 16. The imaging system of claim 15, further comprising: combining the first set of image data points and the second set of image data points according to the offset (520) between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515) by assigning the image pixel values ​​to pixel positions based on beam position information of the first plurality of beam coverage areas (515) and the second plurality of beam coverage areas (515).

18. Processing the return downlink signal (133) in accordance with the plurality of beam weight sets (433) comprises: processing a second set of signal data corresponding to a second duration of the return downlink signal (133) according to a third beam weight set (434) to obtain a third subset of the plurality of beam signals (425) corresponding to the first beam coverage pattern (510); and processing the second set of signal data according to a fourth beam weight set (434) to obtain a fourth subset of the plurality of beam signals (425) corresponding to the second beam coverage pattern (510).

19. Processing the plurality of beam signals (425) to obtain the image of the illuminated geographic area includes: filtering the first and third subsets of the plurality of beam signals (425) to obtain a first filtered subset of beam signals (425); generating a first set of image data points from a first filtered subset of the beam signals (425); filtering the second and fourth subsets of the plurality of beam signals (425) to obtain a second filtered subset of beam signals (425); generating a second set of image data points from a second filtered subset of the beam signals (425); and combining the first set of image data points and the second set of image data points according to the offset (520) between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515).

20. Processing the plurality of beam signals (425) to obtain the image (460) of the illuminated geographic area includes: generating a third set of image data points from the third subset of the plurality of beam signals (425); generating a fourth set of image data points from the fourth subset of the plurality of beam signals (425); filtering the first and third sets of image data points to obtain a first filtered set of image data points; filtering the second and fourth sets of image data points to obtain a second filtered set of image data points; and combining the first filtered set of image data points and the second filtered set of image data points according to the offset (520) between the second plurality of beam coverage areas (515) and the first plurality of beam coverage areas (515).

21. The imaging system of any one of claims 15 to 20, wherein the return downlink signal (133) includes a plurality of return downlink signals (133), each of the plurality of return downlink signals (133) corresponding to a return uplink signal (173) received by a feeder (128) of the antenna array (127) of the satellite (120).

22. Receiving the return downlink signal (133) 21. The imaging system of claim 15, further comprising receiving a plurality of return downlink signals (133) at a respective plurality of satellite access nodes (130), each of the plurality of return downlink signals (133) including a composite of one or more of the return uplink signals (173).

23. The imaging system of any one of claims 15 to 22, wherein each of the plurality of beam coverage patterns (510) includes a plurality of beam coverage areas (515).

24. The imaging system of any one of claims 15 to 20, wherein the satellite transmits a beacon signal and relays respective reflections of the beacon signal received at a plurality of feeders (128) of the antenna array (127) of the satellite (120), and the return downlink signal (133) includes the respective relayed reflections.

25. 24. The imaging system of claim 15, wherein the satellite access node (130) transmits a forward uplink signal (132), the satellite (120) relays the forward uplink signal (132) via a plurality of forward downlink feeds (128) of the antenna array (127) of the satellite (120), the satellite (120) relays respective reflections of the relayed forward link signal received at a plurality of return uplink feeds (128) of the antenna array (127), and the return downlink signal (133) includes the respective relayed reflections.

26. 26. The imaging system of claim 25, wherein the forward uplink signal (132) comprises a plurality of forward user data streams for transmission to a plurality of user terminals (150) within the geographic region.

27. The imaging system of any one of claims 15 to 23, wherein the satellite (120) is a first satellite (120) and one or more second satellites (122) transmit respective illumination signals (145) across the geographic region, the first satellite (120) relays respective reflections of the illumination signals (145) received at a plurality of return uplink feeds (128) of the antenna array (127) of the first satellite (120), and the return downlink signal (133) includes the respective relayed reflections.

28. 30. The imaging system of claim 27, wherein the first satellite (120) is a geostationary (GEO) satellite and each of the one or more second satellites (122) is a low earth orbit (LEO) satellite.

Images