Past event signal tracking

Abstract

Methods, systems, and devices for past-event signal tracking are described. In some examples, a system can receive feed element signals corresponding to multiple feed elements of an antenna. To support a primary or real-time mission, the system can process the feed element signals according to a first beamforming configuration to generate spot beam signals, where the spot beam signals can include communications scheduled for the respective spot beams. To support retrospective or search missions, the system can also store the feed element signals for a period of time. Based on a determination to search for a target signal from a target location within the coverage area of ​​the antenna, the system can process the stored feed element signals according to a second beamforming configuration to generate target spot beam signals corresponding to the target location and evaluate the target spot beam signals for the presence of the target signal.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 834,912, filed April 16, 2019, entitled "PAST EVENT SIGNAL TRACKER (PEST)" by Hancharik, which application is assigned to the assignee of this document and is expressly incorporated by reference in its entirety herein. Summary of the Invention [Problem to be solved by the invention]

[0002] The following relates generally to beamforming antenna systems, and more specifically to past event signal tracking. In some beamforming antenna systems, such as satellite communication systems, a receiving device may include an antenna configured to receive signals at each of a plurality of feed elements of a feed array. The plurality 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 be associated with generating spot beam signals corresponding to different spot beam coverage areas, which in some examples may support different allocations of communication resources across the service coverage areas of the antenna.

[0003] The described technology relates to improved methods, systems, devices, and apparatuses that support past event signal tracking for remote sensing. In some examples, the antenna may be included in a mobile object, such as a satellite, an airplane, an unmanned aerial vehicle (UAV), or any other type of device that supports communication services or other reception capabilities over a service coverage area. The antenna may include a feed array having multiple feed elements, and each feed element may be associated with a feed element signal that corresponds to energy received at the respective feed element. A receiver processing system receives the feed element signals or other related signals and may perform various beamforming techniques to support directional reception.

[0004] To support a primary or real-time mission or task (e.g., real-time communications), the receive processing system can process received signals, such as feed element signals, according to 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 scheduled communications for each of multiple spot beams (e.g., spot beam coverage areas).

[0005] To support finding or searching missions or tasks, such as past event signal tracking, the receiver processing system may additionally or alternatively store received signals, such as feed element signals, for some period of time (e.g., in a rolling buffer). Based on a decision to search for a target signal at a target location within the service coverage area, at some point during the feed element signal storage period, the receiver processing system may process the stored signals according to a second beamforming configuration to generate a target spot beam signal corresponding to the target location. The receiver processing system may evaluate the target spot beam signal for the presence of the target signal. The generation of the target spot beam and the evaluation of the presence of the target signal may be repeated, such as repeated searches at different locations over the same period of time, or path following at different locations and different periods of time, or a priori evaluation with different signal characteristic hypotheses. Thus, the receiver processing system according to the embodiments disclosed herein may assist in performing retrospective or repeated evaluation of stored signals, such as feed element signals, to identify various signal sources, which may be beneficial in applications such as search and rescue missions, asset recovery, surveillance, criminal investigations, downed pilot location, or Internet of Things applications, among other applications. [Brief description of the drawings]

[0006] [Figure 1A] FIG. 1A illustrates a diagram of a communication system supporting past event signal tracking according to an embodiment disclosed herein.

[0007] [Figure 1B] FIG. 1B illustrates an antenna assembly of a satellite supporting past event signal tracking according to an embodiment disclosed herein.

[0008] [Figure 1C] FIG. 1C illustrates a feed array assembly of an antenna assembly supporting past event signal tracking according to an embodiment disclosed herein.

[0009] [Figure 2A] FIG. 2A illustrates an example of antenna characteristics of an antenna assembly having a feed array assembly supporting past event signal tracking, according to an embodiment disclosed herein. [Figure 2B] FIG. 2B illustrates an example of antenna characteristics of an antenna assembly having a feed array assembly supporting past event signal tracking, according to embodiments disclosed herein. [Figure 2C] FIG. 2C illustrates an example of antenna characteristics of an antenna assembly having a feed array assembly supporting past event signal tracking, according to an embodiment disclosed herein. [Figure 2D] FIG. 2D illustrates an example of antenna characteristics of an antenna assembly having a feed array assembly supporting past event signal tracking, according to embodiments disclosed herein.

[0010] [Figure 3A] FIG. 3A illustrates an example of beamforming to form a spot beam coverage area on a native antenna pattern coverage area according to embodiments disclosed herein. [Figure 3B] FIG. 3B illustrates an example of beamforming to form a spot beam coverage area on a native antenna pattern coverage area according to embodiments disclosed herein.

[0011] [Figure 4] FIG. 4 illustrates an example receiver processing system that supports past event signal tracking according to embodiments disclosed herein.

[0012] [Diagram 5] FIG. 5 illustrates an example of a search process to support past event signal tracking, according to embodiments disclosed herein.

[0013] [Figure 6]FIG. 6 illustrates an example of past event signal tracking according to embodiments disclosed herein.

[0014] [Figure 7] FIG. 7 illustrates a block diagram of a receiver processing system that supports past event signal tracking according to an embodiment disclosed herein.

[0015] [Figure 8] FIG. 8 is a flow chart illustrating a method for supporting past event signal tracking according to embodiments disclosed herein. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Systems according to the techniques described herein can support various implementations of past event signal tracking. For example, a feed array antenna can be included in a mobile body such as a satellite, an airplane, an unmanned aerial vehicle (UAV), or any other type of device that supports communication services or other reception capabilities through a service coverage area. The antenna can include a feed array with multiple feed elements, and to support signal reception, each feed element can be associated with a feed element signal corresponding to the energy received at the respective feed element. A receiver processing system can receive the feed element signals or other related signals and perform various beamforming techniques to support directional reception. Components of the receiver processing system can be included in one or more ground stations or in a satellite or other mobile body, 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 can be distributed across two or more devices, including components distributed across mobile bodies and ground segments.

[0017] To support a primary or real-time mission or task (e.g., real-time communications), the receive processing system can process received signals, such as 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 each of the multiple spot beams (e.g., scheduled for a respective spot beam coverage area).

[0018] To support retroactive or searching missions or tasks, such as past event signal tracking, the receiver processing system may additionally or alternatively store received signals, such as feed element signals, for some period of time (e.g., in a rolling buffer). Based on a decision to search for a target signal at a target location within the service coverage area, at some point within the signal storage period, the receiver processing system may process the stored signals according to a second beamforming configuration to generate a target spot beam signal corresponding to the target location, and evaluate the target spot beam signal for the presence of the target signal. Thus, the receiver processing system according to the embodiments disclosed herein may assist in performing retroactive evaluation of stored signals to identify various signal sources, which may be beneficial in applications such as search and rescue missions, high value asset recovery, surveillance, criminal investigation, downed pilot location, or Internet of Things applications, among others. In some examples, such techniques may be performed in parallel or simultaneously with a primary or real-time mission.

[0019] This description provides various examples of techniques for past event signal tracking, and such examples are not intended to limit the scope, applicability, or configuration of examples in accordance with the principles described herein. Rather, the description that follows is intended to provide one of ordinary skill in the art with an enabling illustration for implementing embodiments of the principles described herein. Various changes may be made in the function and arrangement of each element.

[0020] 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. It should also be understood that the following systems, methods, apparatus, and software, separately or collectively, may be components of a larger system, and that other procedures may take precedence or be modified in their application.

[0021] 1A illustrates a diagram of a communication system 100 supporting past event signal tracking according to embodiments disclosed herein. The communication system 100 can use several network architectures including a space segment 101 and a ground segment 102. The space segment 101 may 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, as well as satellite and gateway terminal command centers. In some examples, the ground segment 102 can also include user terminals 150 to which communication services are provided via the satellites 120.

[0022] In various examples, the 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 a service coverage area. This wireless communication may be the primary task or mission of the satellite 120 in some examples. In some examples, the satellite 120 may be configured for information gathering (e.g., in a data gathering or receiving mission) and may include various sensors to detect the geographic distribution of electromagnetic, optical, thermal, or other data. In some examples, the satellite 120 may be deployed in a geostationary orbit such that its orbital position with respect to a ground device is fixed relatively or within an operating tolerance or other orbital window (e.g., within an orbital slot). In other examples, the satellite 120 may be operated in any suitable orbit (e.g., low earth orbit (LEO), medium earth orbit (MEO), etc.).

[0023] 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 feed 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 transmission modulation and coding techniques may be used by the satellite 120 for communication of signals between the access node terminals 130 or user terminals 150 (e.g., adaptive coding and modulation (ACM)).

[0024] The antenna assembly 121 may support communication or other signal reception via one or more beamforming spot beams 125, which may otherwise be referred to as service beams, satellite beams, 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 a single frequency or a contiguous frequency range 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 forward downlink signals 172, return uplink signals 173, forward uplink signals 132, and / or return downlink signals 133 between the satellite 120 and the user terminal 150 and the access node terminal 130.

[0025] The spot beam 125 may support communication services or other signal reception between target devices (e.g., user terminals 150 and / or access node terminals 130) within the 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 projected onto the Earth or some other reference plane having a signal power, signal-to-noise ratio (SNR), or signal-to-interference-plus-noise ratio (SINR) that exceeds a threshold for the spot beam 125. The spot beam coverage area 126 may cover any suitable service area (e.g., circular, elliptical, hexagonal, local, regional, national) 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 not in a reference plane (e.g., reference plane 160, which may be the surface of the Earth, the surface of a body of water such as a lake or ocean, or a reference plane at an elevation or altitude) of the spot beam coverage area 126.

[0026] Beamforming for a communication link can be achieved 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 component receive and / or transmit feed elements that cooperate to enable various examples of on-board beamforming (OBBF), ground-based beamforming (GBBF), end-to-end beamforming, or other types of beamforming.

[0027] The satellite 120 may support multiple beamforming 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 bands, X bands, S bands, L bands, V bands, etc.

[0028] In some examples, a service coverage area may be defined as a coverage area in which either a terrestrial transmitting source or a terrestrial receiver may participate in a communication service (e.g., transmission and reception of signals associated therewith) via the 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 the satellite 120 is in service (e.g., in a service orbit), the satellite 120 may have (e.g., designed or configured to have) a native antenna pattern based on the physical components of the antenna assembly 121 and their relative positions. The native antenna pattern of the communications satellite 120 may depend on the distribution of energy (e.g., energy transmitted from and / or received by the antenna assembly 121) relative to the satellite's antenna assembly 121.

[0029] In some service coverage areas, adjacent spot beam coverage areas 126 may have some degree of overlap. In some examples, multiple colors (e.g., 2, 3, or 4 color reuse patterns) may be used, with "color" referring to a combination of orthogonal communication resources (e.g., frequency resources, polarization, etc.). In an example of a 4-color pattern, several overlapping spot beam coverage areas 126 may each be assigned to one of four colors, with each color assigned to a unique combination of frequencies (e.g., one or more frequency ranges, one or more channels, etc.) and / or signal polarizations (e.g., right-hand circular polarization (RHCP), left-hand circular polarization (LHCP), etc.), or orthogonal resources. By assigning different colors to each spot beam coverage area 126 having overlapping regions, interference between spot beams 125 associated with those overlapping spot beam coverage areas 126 may be reduced or eliminated (e.g., by filtering transmissions corresponding to each spot beam according to its respective color or by scheduling transmissions corresponding to each spot beam according to its respective color). These combinations of frequencies and antenna polarizations can be reused accordingly in non-overlapping "four-color" reuse patterns. In some examples, desired communication services can be provided by using more or fewer colors. Additionally or alternatively, time sharing between spot beams 125 and / or other interference mitigation techniques can be used. For example, spot beams 125 can simultaneously use the same resources (same polarization and frequency range) with interference mitigation using interference mitigation techniques such as ACM, interference cancellation, space-time coding, etc.

[0030] In some examples, the communications satellite 120 can be configured as a "bent pipe" satellite. In a bent pipe configuration, the communications satellite 120 can perform frequency and polarization conversion of received carrier signals before retransmitting the signals to their destinations. In some examples, the communications satellite 120 can support a raw bent pipe architecture, where a phased array antenna is used to form relatively small spot beams 125 (e.g., by ground based beamforming (GBBF)). The communications satellite 120 may support K general paths, which can be assigned as forward or return paths at any time. A relatively large reflector can be illuminated by a phased array of antenna feed elements, aiding in the ability to form various patterns of spot beams 125 within constraints set by the size of the reflector and the number and placement of antenna feed elements. The phased array feed reflector can be utilized for both receiving uplink signals 132, 173, or both, and transmitting downlink signals 133, 172, or both.

[0031] The communications satellite 120 may operate in a multiple spot beam mode and may transmit or receive corresponding to multiple relatively narrow spot beams 125 directed to different regions of the Earth. This may allow the user terminals 150 to be separated into various narrow spot beams 125 or may support spatial separation of the transmitted or received signals. In some embodiments, a beamforming network (BFN) associated with the receive (Rx) or transmit (Tx) phased array may be dynamic, allowing for movement of the location of the Tx spot beam 125 (e.g., downlink spot beam 125) and the Rx spot beam 125 (e.g., uplink spot beam 125).

[0032] User terminal 150 may include various devices configured to communicate signals with satellite 120, which may include fixed terminals (e.g., terrestrial stationary terminals) or mobile terminals, such as terminals located on ships, aircraft, ground vehicles, etc. User terminal 150 may communicate data and information via satellite 120, which may include communication via access node terminal 130 to a destination device, such as network device 141 or some other device associated with network 140 or a distributed server. User terminal 150 may communicate signals according to various physical layer transmission modulation and coding techniques, including, for example, cellular communication protocols such as Digital Video Broadcasting-Satellite-Second 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.

[0033] The access node terminal 130 can service forward uplink signals 132 to and return downlink signals 133 from the communications satellite 120. The access node terminal 130 is also known as a ground station, gateway, gateway terminal, or hub. The access node terminal 130 can include an access node terminal antenna system 131 and an access node receiver 135. The access node terminal antenna system 131 can be bidirectional and is designed to reliably communicate with the communications satellite 120 with appropriate transmit power and receive sensitivity. In some examples, the access node terminal antenna system 131 can include a parabolic reflector with high directivity in the direction of the communications satellite 120 and low directivity in other directions. The access node terminal antenna system 131 can include a variety of alternative configurations and operational characteristics such as high isolation between orthogonal polarizations, high efficiency in the operating frequency band, low noise, etc.

[0034] When supporting a communication service, 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 communications 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, embodiments consistent with the present disclosure may be implemented in a communications system having multiple access node terminals 130, each connected to each other and / or to one or more networks 140.

[0035] 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.

[0036] The access node terminals 130 may provide an interface between the network 140 and the satellite 120 and, in some examples, may be configured to receive data and information intended for propagation between the network 140 and one or more user terminals 150. The access node terminals 130 may format the data and information for transmission to the respective user terminals 150. Similarly, the access node terminals 130 may be configured to receive signals from the communications satellite 120 (e.g., from one or more user terminals 150) intended for destinations accessible via the network 140. The access node terminals 130 may also format the received signals for transmission over the network 140.

[0037] The network 140 may be any type of network and may include, 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 optical-coaxial network, a cable network, a public switched telephone network (PSTN), a public switched telephone network (PSDN), a public mobile telephone network (PLMN), and / or any other type of network supporting communication between devices as described herein. The network 140 may include both wired and wireless connections as well as optical links. The network 140 may connect the access node terminal 130 with other access node terminals that may communicate with the same satellite 120 or different satellites 120 or other mobile entities.

[0038] One or more network devices 141 may be coupled to the access node terminals 130 and may control aspects of the satellite communications system 100. In various examples, the network devices 141 may be co-located with or near the access node terminals 130, or may be remote locations that communicate with the access node terminals 130 and / or the network 140 via wired and / or wireless communications links.

[0039] The communications system 100 may be configured according to various techniques to support past event signal tracking, which may be separate from the primary or real-time tasks or missions of the communications system 100. For example, one or more components of the communications system 100 may be configured to store received feed element signals, or other signals supporting the formation of spot beams 125 or spot beam signals, for some period of time (e.g., in a rolling buffer) and process the stored signals according to a search or discovery beamforming configuration to generate a target spot beam signal corresponding to a target location associated with some past event or potential past event. The components of the communications system 100 may evaluate the target spot beam signal for the presence of a target signal according to various signal hypotheses.

[0040] The generation of the search or discovery spot beam 125 and evaluation for the presence of a target signal may be repeated by repeated searching at different locations over the same time period, or path following at potentially different locations and different time periods, or a priori evaluation with different signal characteristic hypotheses, etc. Thus, the communication system 100 may support performing retrospective or repeated evaluation of stored signals to identify various signal sources, which may be beneficial in applications such as search and rescue missions, asset recovery, surveillance, criminal investigations, downed pilot location, or Internet of Things applications, among other applications.

[0041] 1B illustrates an antenna assembly 121 of a satellite 120 supporting past event signal tracking according to an embodiment 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 focus region 123 where an electromagnetic signal (e.g., an inbound electromagnetic signal 180) is focused when received from a distant source. Similarly, a signal radiated by the feed array assembly 127 positioned at the focus region 123 is reflected by the reflector 122 into an outwardly directed 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.

[0042] 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 the feed elements 128 of the feed array assembly 127, the relative position of the feed array assembly 127 with respect to the reflector 122 (e.g., focus offset distance 129, or the absence of focus offset distance at the focus 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 that comprises the native antenna pattern coverage area of ​​the antenna assembly 121, and various design characteristics may be determined computationally (e.g., by analysis or simulation) and / or measured experimentally (e.g., at an antenna test range or in actual use).

[0043] As shown in Figure 1B, the feed array assembly 127 of the antenna assembly 121 is disposed between the reflector 122 and the focus region 123 of the reflector 122. Specifically, the feed array assembly 127 is disposed at a focus offset distance 129 from the focus region 123. Thus, the feed array assembly 127 of the antenna assembly 121 may be disposed in a defocused position with respect to the reflector 122. Although shown in Figure 1B as a direct offset type feed array assembly 127, other types of configurations may be used, including configurations using a front feed array assembly 127 as well as a subreflector (e.g., a Cassegrain antenna, etc.) or configurations without a reflector 122 (e.g., a DRA).

[0044] 1C illustrates a feed array assembly 127 of an antenna assembly 121 supporting past event signal tracking according to an embodiment disclosed herein. As shown in FIG. 1C, the feed array assembly 127 can have multiple feed elements 128 for communication of signals (e.g., signals associated with communication services, signals associated with configuration or control of the communication satellite 120, received signals for data collection or sensor placement).

[0045] As used herein, feed 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 transmit / receive 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 radiates an electromagnetic signal when excited by an electrical signal. In some cases, the same physical transducer may be used for transmission and reception.

[0046] Each of the feed elements 128 may include, for example, a feed horn, a polarization transducer (e.g., a bulkhead-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 polarization 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 connected to an RF signal transducer, a low noise amplifier (LNA) or a power amplifier (PA), and may be connected to a transponder within the communications satellite 120, which may perform other signal processing, such as frequency conversion, beamforming processing, etc.

[0047] 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). Each feed element 128 of the feed array assembly 127 may be associated with a respective native feed element pattern, which may further be associated with a native feed element pattern, a projected native feed element pattern coverage area (e.g., as projected from the reflector 122 onto the Earth's surface, plane, or volume after reflection). 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 of feed elements 128 (e.g., tens, hundreds, thousands, etc.) arranged in any suitable configuration (e.g., linear array, arcuate array, planar array, honeycomb array, polyhedral array, spherical array, elliptical array, or combinations thereof). The feed elements 128 may have ports or openings having various shapes, such as circular, elliptical, square, rectangular, hexagonal, and others.

[0048] 2A-2D show example antenna characteristics of an antenna assembly 121-a having a feed array assembly 127-a supporting past-event signal tracking according to embodiments disclosed herein. The antenna assembly 121-a can operate in a manner that spreads transmissions received from a given location across multiple feed elements 128-a, or spreads power transmitted from the feed elements 128-a over a relatively wide area, or both.

[0049] 2A illustrates a schematic diagram 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 schematic diagram 201 illustrates 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 respective feed element 128. For example, when feed element 128-a-2 is transmitting, the transmitted electromagnetic signal is reflected by reflector 122-a and propagates 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 reflector 122). Three native feed element patterns 210-a are shown for antenna assembly 121-a, with each of the feed elements 128 of antenna assembly 121 associated with a respective native feed element pattern 210. The combination of the 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-3, and other native feed element patterns 210-a not shown) may be referred to as native antenna pattern 220-a.

[0050] 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), which represents a projection of the native feed element pattern 210-a onto a reference plane (e.g., ground or water level, a reference plane at altitude, or any reference plane or surface). The native feed element pattern coverage area 211 represents 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 represents an area where transmissions from various devices may be received by the respective feed element 128. For example, a device located in coverage area 230-a located within native feed element pattern coverage 211-a-1, 211-a-2, and 211-a-3 can receive signals transmitted by feed elements 128-a-1, 128-a-2, and 128-a-3, and have the transmissions received by feed elements 128-a-1, 128-a-2, and 128-a-3. The combination 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) can be referred to as native antenna pattern coverage area 221-a.

[0051] The feed array assembly 127a may be operated in a defocused position relative to the reflector 122a such that the native feed element patterns 210a, i.e., the native feed element pattern coverage areas 211a, substantially overlap. Thus, each location within the native antenna pattern coverage area 221a may be associated with multiple feed elements 128, such that multiple feed elements 128 may be used to transmit to or receive from a point of interest. It should be understood that the schematic diagram 201 is not drawn to scale, and that the native feed element pattern coverage areas 211 are each typically much larger than the reflector 122-a.

[0052] 2B shows a schematic diagram 202 illustrating the antenna assembly 121-a's signal reception for a transmission 240-a from a point of interest 230-a. The transmission 240-a from the point of interest 230-a can 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 at the reflector 122-a. The feed array assembly 127-a can operate in a defocused position relative to the reflector 122-a, thereby focusing the transmission 240-a 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).

[0053] 2C shows a diagram 203 of native feed element pattern gain profiles 250-a associated with three feed elements 128-a of the feed array assembly 127-a, relative to an angle 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 represent the gain profiles of native feed element patterns 210-a-1, 210-a-2, and 210-a-3 as they are associated with feed elements 128-a-1, 128-a-2, and 128-a-3, respectively. As shown in diagram 203, the gain of each native feed element pattern gain profile 250 decays at angles offset in either direction from the peak gain. In diagram 203, beam boundary levels 255-a represent required gain levels to support communication services or other receiving or transmitting services via antenna assembly 121-a (e.g., to provide a desired information rate, etc.) and can therefore be used to define 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). Beam boundary levels 255-a can represent, for example, -1 dB, -2 dB, or -3 dB attenuation from a peak gain, or can be defined by 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 can be associated with other feed elements 128-a.

[0054] As shown in diagram 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 significant portion of the gain profile above the beam boundary level 255-a. Thus, diagram 203 illustrates an arrangement of native feed element pattern gain profiles 250 where multiple feed elements 128 of a feed array assembly 127 can support signal communication at a particular angle (e.g., a particular direction of the native antenna pattern 220-a). In some examples, this condition can be expressed as having a large degree of overlap between the feed elements 128 of the feed array assembly 127 or the native feed element pattern coverage areas 211.

[0055] 2D shows a diagram 204 illustrating a two-dimensional array of idealized native feed element pattern coverage areas 211 of several feed elements 128 (e.g., including feed elements 128-a-1, 128-a-2, and 128-a-3) of the feed array assembly 127-a. The native feed element pattern coverage area 211 can be illustrated relative to a reference plane (e.g., a plane at a distance from a communications satellite, a plane at a distance from the ground, a spherical surface at a certain altitude, the ground, etc.) and can further include a volume adjacent to the reference plane (e.g., a substantially conical volume between the reference plane and the communications satellite, a volume below the reference plane, etc.). The multiple native feed element pattern coverage areas 211-a collectively form a native antenna pattern coverage area 221-a. Although eight native feed element pattern coverage areas 211-a are shown, the feed array assembly 127 may have any number of feed elements 128 each associated with a native feed element pattern coverage area 211 (e.g., less than seven or more than nine).

[0056] A boundary of each native feed element pattern coverage area 211 corresponds to a respective native feed element pattern 210 at beam boundary level 255-b, and a peak gain of each native feed element pattern coverage area 211 has a position indicated 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). Native feed element pattern coverage areas 211-a-1, 211-a-2, and 211-a-3 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, where diagram 203 illustrates native feed element pattern gain profile 250 along cross-sectional plane 260-a of diagram 204.

[0057] Native feed element pattern coverage areas 211 are referred to as idealized herein because the coverage areas are shown as circular for simplicity. However, in various examples, native feed element pattern coverage areas 211 may be some shape other than circular (e.g., oval, hexagon, rectangle, etc.). Thus, tiled native feed element pattern coverage areas 211 can have more overlap than is shown in diagram 204 (e.g., in some cases, four or more native feed element pattern coverage areas 211 may overlap).

[0058] In diagram 204, which may represent a condition in which feed array assembly 127-a is placed in a defocused position relative to reflector 122-a, a significant portion (e.g., a majority) of each native feed element pattern coverage area 211 overlaps with adjacent native feed element pattern coverage areas 211. A location within the service coverage area (e.g., the total coverage area of ​​the multiple spot beams of antenna assembly 121) may fall within the native feed element pattern coverage areas 211 of two or more feed elements 128. For example, antenna assembly 121-a may be configured to maximize the area of ​​overlap of three or more native feed element pattern coverage areas 211. In some examples, this condition may also be expressed as having feed elements 128 or native feed element pattern coverage areas 211 of feed array assembly 127 with a large degree of overlap. Although eight native feed element pattern coverage areas 211 are shown, feed array assembly 127 may have any number of feed elements 128 associated with native feed element pattern coverage areas 211 in a similar manner.

[0059] In some cases, a single antenna assembly 121 may be used for transmitting and receiving signals between user terminals 150 or access node terminals 130. In other examples, a 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 feed elements 128 configured for receiving may directly correspond to native feed element pattern coverage areas 211 for antenna feed elements 128 configured for transmitting. In these cases, the receiving feed elements 128 may be mapped in a similar manner as their corresponding transmitting feed elements 128 (e.g., by having a similar array pattern of a different feed array assembly 127, having similar wired and / or circuit connections to signal processing hardware, having similar software configurations and / or algorithms, etc.) and form similar signal paths and processes toward the native feed element pattern coverage areas 211 for transmitting and receiving. However, in some cases it may be advantageous to map the receiving and transmitting feed elements 128 differently.

[0060] In some examples, multiple overlapping native feed element patterns 210 can be combined by beamforming to provide one or more spot beams 125. Beamforming for a spot beam 125 can 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 having overlapping native feed element pattern coverage areas 211. Such phase and / or amplitude adjustment can be referred to as applying beam weights (e.g., beamforming coefficients) to the feed element signals. For transmission (e.g., from a transmitting feed element 128 of a feed array assembly 127), the relative phase and possibly 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). Upon reception (e.g., by receiving antenna feed elements 128 of feed array assembly 127), the relative phase and possibly amplitude of the received signals are adjusted (e.g., by applying the same or different beam weights) so that energy received by feed elements 128 at a desired location (e.g., the location of a spot beam coverage area 126) is constructively overlapped for a given spot beam coverage area 126.

[0061] The term beamforming may be used to refer to the application of beam weights for transmission, reception, or both. The calculation of beam weights or coefficients may involve directly or indirectly discovering communication channel characteristics. The processes of beam weight calculation and beam weight application may be performed in the same or different system components. An adaptive beamformer may include the capability to dynamically calculate beam weights or coefficients.

[0062] The spot beams 125 can be steered, selectively formed, and / or otherwise reconfigured by applying different beam weights. For example, the quantity of active native feed element patterns 210 or spot beam coverage areas 126, the size of the spot beams 125 shapes, the relative gains of the native feed element patterns 210 and / or spot beams 125, and other parameters can change over time. The antenna assembly 121 can apply beamforming to form relatively narrow spot beams 125, and can form spot beams 125 with improved gain characteristics. The narrow spot beams 125 can, for example, distinguish signals transmitted in one beam from signals transmitted in other spot beams 125, avoid interference between transmitted or received signals, or identify spatial separation of received signals.

[0063] In some examples, narrow spot beams 125 can reuse frequencies and polarizations better than when wider spot beams 125 are formed. For example, narrowly formed spot beams 125 can support signal communication over non-overlapping, non-contiguous spot beam coverage areas 126, while overlapping spot beams 125 can be orthogonal in frequency, polarization, or time. In some examples, the amount of data transmitted and / or received can be increased by using smaller spot beams 125 to provide more reuse. Additionally or alternatively, beamforming can be used to provide sharper gain roll-off at the beam edges, thereby allowing for larger beam gains over the majority of the spot beams 125. Thus, beamforming techniques can provide higher frequency reuse and / or greater system capacity for a given amount of system bandwidth.

[0064] Some satellites 120 may use OBBF to electronically steer signals transmitted and / or received via the array of feed elements 128 (e.g., apply beam weights to the feed element signals at the satellite 120). For example, the communications satellite 120 may have phased array multi-feed-per-beam (MFPB) on-board beamforming capabilities. In some embodiments, the beam weights may be calculated at a terrestrial computing center (e.g., at the access node terminal 130, at the network device 141, at the communications services manager) and then transmitted to the satellite 120. In some embodiments, the beam weights may be pre-configured or determined at the satellite 120 for on-board application.

[0065] In some cases, significant processing power is required at 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 with GBBF to reduce the complexity of the satellite 120, but still provide the advantage of electronically forming the narrow spot beam 125. In some examples, beam weights or coefficients may be applied at the ground segment 102 (e.g., at one or more ground stations) before transmitting associated signals to the satellite 120, which may include multiplexing feed element signals at the ground segment 102 according to various time, frequency, or spatial multiplexing techniques, among other signal processing. Thus, the satellite 120 may receive and possibly demultiplex such signals, and transmit associated feed element signals via respective antenna feed elements 128 to form a transmit spot beam 125 based at least in part on the beam weights applied to the ground segment 102. In some examples, the satellites 120 can 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 can 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 can thus receive and possibly demultiplex such signals and apply beam weights to the received feed element signals to generate spot beam signals corresponding to each spot beam 125.

[0066] In another example, the communication system 100 according to the present disclosure can support various end-to-end beamforming techniques associated with forming end-to-end spot beams 125 via satellites 120 or other mobile bodies acting as end-to-end relays. For example, in an end-to-end beamforming system, beam weights can be calculated in a central processing system (CPS) of the ground segment 102, and the end-to-end beam weights can be applied to the ground segment 102, rather than the satellite 120. Signals in the end-to-end spot beams 125 may be transmitted and received at an array of access node terminals 130, which can be satellite access nodes (SANs). Any suitable type of end-to-end relay can be used in the end-to-end beamforming system, and different types of access node terminals 130 can be used to communicate with different types of end-to-end relays.

[0067] The end-to-end beamformer in the CPS can calculate multiple end-to-end beam weights for (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 embodiments, the 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 may 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 can be efficiently relayed. This is because an end-to-end spot beam 125 may have an uplink signal path, a relay signal path (via a satellite 120 or other suitable end-to-end relay), and a downlink signal path.

[0068] Since the end-to-end beamforming system can take into account 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-the 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 through the forward uplink, through the end-to-end relay, and through the forward downlink, which are combined to form the end-to-end forward spot beam 125. Conversely, signals transmitted from the return user through the return uplink, through the end-to-end relay, and through the 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 the characteristics of the uplink and downlink. Thus, the shaped feeder link spot beams 125, the shaped spot beam directionality, and the individual uplink and downlink carrier-to-interference ratios (C / I) may no longer have their traditional role in system design, but concepts such as uplink and downlink signal-to-noise ratios (Es / No) and end-to-end C / I are still important.

[0069] A communication system according to embodiments disclosed herein can use various beamforming techniques to support a primary or real-time mission, such as real-time communication or data collection, and a secondary or retrospective mission, such as past event signal tracking or other search mission. In some examples, the satellite 120 can include an on-board beamformer configured to support the real-time mission, and the same or a different on-board beamformer of the satellite 120 can be configured to support past event signal tracking (e.g., based on feed element signals stored on the satellite 120). In some examples, the ground station of the ground segment 102 can include a ground-based beamformer configured to support the real-time mission, and the same or a different ground-based beamformer of the ground segment 102 can be configured to support past event signal tracking (e.g., based on feed element signals stored on the ground segment 102). In some examples, the satellite 120 may include an on-board beamformer configured to support real-time missions, and the ground station may include a ground-based beamformer that is configurable to support past event signal tracking (e.g., based on feed element signals stored on the satellite 120 or ground segment). In some examples, the communication system may apply end-to-end beamforming for both the primary or real-time mission and past event signal tracking or other search missions. Thus, these and other configurations may be used to support various examples of the described techniques for past event signal tracking, which may include storing various received signals in a manner that supports retroactively or repeatedly forming target spot beams 125 or spot beam signals to search for signals of interest or associated devices.

[0070] 3A and 3B show examples of beamforming to form spot beam coverage areas 126 on a native antenna pattern coverage area 221-b according to embodiments disclosed herein. In FIG. 3A, a schematic diagram 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 schematic diagram 350 shows a pattern of spot beam coverage areas 126 across a service coverage area 310 in the continental United States. The spot beam coverage areas 126 may be provided by applying beamforming coefficients to signals carried via feed elements 128 associated with the plurality of native feed element pattern coverage areas 211 of FIG. 3A.

[0071] Each of the spot beam coverage areas 126 can have an associated spot beam 125, which in some examples can 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. Each of the spot beams 125 can be formed by combining signals carried by 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 can be a combination of signals via eight feed elements 128 associated with the native feed element pattern coverage area 211-b shown in FIG. 3A with a thick solid line. In various examples, the spot beams 125 of overlapping spot beam coverage areas 126 can be orthogonal in frequency, polarization, and / or time, while non-overlapping spot beams 125 can be non-orthogonal to one another (e.g., slanted frequency reuse patterns). In other examples, the non-orthogonal spot beams 125 may have varying degrees of overlap, and interference mitigation techniques such as ACM, interference cancellation, or space-time coding are used to manage inter-beam interference.

[0072] 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 to 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 the spot beam coverage areas 126 of a substantially uniform pattern (e.g., equal or substantially equal beam coverage area size and overlap amount), in some embodiments, 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 service using relatively small spot beams 125, while a sparsely populated area may be provided with communication service using relatively large spot beams 125.

[0073] The communication system may also be configured to support past event signal tracking over the native antenna pattern coverage area 121-b of the antenna assembly 221, which may be separate from the primary or real-time task or mission over the native antenna pattern coverage area 221-b. For example, one or more components of the receiver processing system may be configured to store received feed element signals for a predetermined period of time (e.g., in a rolling buffer corresponding to each of the native feed element pattern coverage areas 211), or, in a system that applies end-to-end beamforming, one or more components of the receiver processing system may be configured to store signals received at multiple access node terminals 130 (e.g., as relayed by satellites 120 or other mobile bodies). The receiver processing system may process the stored feed element signals or access node terminal signals according to a search or discovery beamforming configuration to generate target spot beam signals corresponding to target locations associated with some past event or potential past event. The receiver processing system components may evaluate the target spot beam signals for the presence of a target signal according to various signal hypotheses. The generation of the search or discovery spot beam 125 and the evaluation of the presence of the target signal may be repeated by repeated searching at different locations of the native antenna pattern coverage area 221-b over the same period of time, or by path following at different locations and for different periods of time in the native antenna pattern coverage area 221-b, or by a priori evaluation with different signal characteristic hypotheses, etc.

[0074] 4 illustrates an example of a receiver processing system 400 that supports past event signal tracking according to embodiments disclosed herein. The receiver processing system 400 includes a feed element signal receiver 410, a real-time processing component 420, a feed element signal storage component 430, and a post-time processing component 440.

[0075] The feed element signal receiver 410 may be configured to receive feed element signals 405 associated with an antenna assembly 121 having a feed array assembly 127. In some examples, the feed element signal receiver 410 may refer to a component of a satellite 120 connected with an antenna assembly, or a component of another mobile body including such an antenna assembly 121. In some examples, the feed 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 communicates with such device (e.g., via a wireless communication link, such as the return link 133) to support reception of the feed element signals 405. For example, the feed 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 feed element signals 405 or other signals from one or more satellites 120 to construct a receive spot beam 125. In some examples, the feed element signal receiver 410 may receive the feed element signals over the return link 133 via one or more ground stations, and the feed 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 feed element signal receiver 410 may be configured to demultiplex or demodulate various signals to receive or process the feed element signals 405.

[0076] In some examples, the feed element signals 405 may be received as raw signals from 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-a to a real-time processing component 420 and the feed element signals 415-b to a feed element signal storage component 430. In some examples, the feed element signals 415-a and 415-b may be the same as each other and may or may not be the same as the feed element signal 405. In some examples, to generate the feed element signal 415-a, the feed element signal 405 may be filtered or otherwise processed for real-time processing, which may include filtering or other processing to support frequency bands associated with a primary mission, such as communication services (e.g., filtering according to communication frequency bands). In some examples, to generate feed element signal 415-b, feed element signal 405 may be filtered or otherwise processed for post-time processing, which may include filtering or other processing that differs from the primary mission. For example, to generate feed element signal 415-b, feed element signal receiver 410 may be configured to filter feed element signal 405 according to a wider band to support a wider range of signal discovery, or feed element signal receiver 410 may be configured to oversample feed element signal 415 as compared to the sampling used to generate feed element signal 405-a.

[0077] In some examples, the post-time search may be configured to not search for signals according to different polarizations, so that the feed element signal 415-b may be generated by combining certain ones of the feed element signals 405 corresponding to the same feed element 128, or two or more feed elements 128 that share a common port or opening associated with different polarizations. In such examples, the feed element signals 415-a may maintain polarization separation, which may maintain the communications signal multiplexing used by the real-time processing component 420, for example.

[0078] The real-time processing components 420 can be configured to support a real-time or primary mission of the receive processing system 400, such as communication services or data collection services. In the example receive processing system 400, the real-time processing components 420 include a return beamforming network 421, a channelizer 422, and a modem termination system 423, which can collectively be configured to support communication with or using a satellite 120 or other mobile entity including an antenna assembly 121 associated with a feed element signal 405.

[0079] In some examples, the real-time processing component 420 may refer to a component of the ground segment 102 separate from the satellite 120, including the antenna assembly 121, and receives the feed element signal 415-a from the feed element signal receiver 410 of the ground segment 102 or the feed element signal receiver 410 of the satellite. For example, the return beamforming network 421 may be an example of a terrestrial or end-to-end beamformer. In some examples, the real-time processing component 420 may refer to a component of the satellite 120 connected with the antenna assembly 121, or a component of another mobile body including such an antenna assembly 121. For example, the return beamforming network may be an example of an on-board beamformer connected with the feed element signal receiver 410 of the satellite 120 and configured to receive the feed element signal 415-a via the signal path of the satellite 120.

[0080] The return beamforming network 421 may be configured to process the feed element signals 415-a by applying beam weights or coefficients to generate spot beam signals. The spot beams 125 formed by the return beamforming network 421 may point to predetermined 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 a channelizer 422 and a modem termination system 423 to support various return link communications.

[0081] In addition to supporting the operation of the real-time processing component 420 (e.g., primary mission), the receiving processing system 400 may also be configured to sample and store the feed element signal 405 or other related signals for later processing (e.g., beam reconstruction for past event searching). For example, the feed element signal storage component 430 may be configured to receive the feed element signal 415-b, optionally process the received signal using a quantizer 431, and store the feed element signal 415-b in a first-in-first-out (FIFO) component 432. The FIFO component 432 may include a physical storage component configured to store the feed element signal 415-b for a period of time that supports a desired lookback window or period. The feed element signal storage component 430 may be configured to provide the stored feed element signal 435 to a post-time processing component 440, which may support various operations performed in parallel (e.g., without interrupting the real-time processing component 420) or simultaneously with the operations performed by the real-time processing component 420.

[0082] In one example, the FIFO component 432 may be configured to support a 30-day lookback window for a feed element signal 405 sampled at a bandwidth of 34.0 MHz. If an oversampling factor of 6 is applied (e.g., at the feed element signal receiver 410 or the quantizer 431), the sampling rate of the data stored in the FIFO component 432 may be 204 million samples per second. If the feed element signal 405 corresponds to a feed array assembly 127 having 145 feed elements 128 and quantization of 4 bits per sample, the FIFO component 432 may support an input speed or rate of 118.32 Gbps. Thus, to support a 30-day lookback window, the FIFO component 432 would include at least 35.56 terabytes of storage capacity.

[0083] The post-time processing component 440 may be configured to support a search or discovery mission of the receive processing system 400, such as iteratively searching for a signal of interest within the service coverage area 310 or native antenna pattern coverage area 221 corresponding to the feed element signal 405 or feed element signal 415-b, or the stored feed element signal 435. According to various techniques, the post-time processing component 440 can support iterative processing to perform a spatial search for any signal feature from the perspective of the corresponding antenna assembly 121. With the assistance of the feed element signal storage component 430, the detected signal (e.g., stored in the feed element signal storage component 430 or held in the cache 441) can be iteratively demodulated and decoded. In the example receive processing system 400, the post-time processing component 440 includes the cache 441, the beamforming network 442, and the search component 443.

[0084] In some examples, the post-time processing component 440 may refer to a component of the ground segment 102 separate from the satellite 120 including the antenna assembly 121, which receives the stored feed element signal 435 of the same component of the ground segment 102, or one or more other components of the ground segment 102. For example, the beamforming network 442 may be an example of a ground-based beamformer or an end-to-end beamformer (e.g., a ground-based hub or feeder station). In some examples, the post-time processing component 440 may refer to a component of the satellite 120 or other mobile body including the antenna assembly 121 associated with the feed element signal 415-b. For example, the beamforming network 442 may be an example of an on-board beamformer.

[0085] The beamforming network 442 can be configured to process the stored (e.g., transferred and maintained in the cache 441) feed element signals 435 by applying beam weights or coefficients to generate targeted spot beam signals associated with an iterative search or signal discovery. The spot beams 125 formed by the beamforming network 442 can refer to speculative or hypothetical spot beams 125 and can be based on a predicted location or path of a device associated with the signal of interest, or can be based on random or repetitive location scanning (e.g., when location or path information is not known). The generated spot beam signals can be processed through a search component 443 configured to perform various evaluations of the presence or absence of a signal of interest.

[0086] The beamforming network 442 can support the formation of any spot beam 125 possible with the stored feed element signals 435, and thus may not be limited to the spot beam configuration of the return beamforming network 421. For example, the beamforming network 442 can be configured to generate smaller spot beams 125 for greater directivity or position resolution, or spot beams 125 with higher gain to support distinguishing signals from one another. The operation of the beamforming network 442 can be performed without affecting the primary mission (e.g., without interrupting the operation of the return beamforming network 421), and can assist in going back in time at different locations and with different granularity. In some examples, the spot beams 125 generated by the beamforming network 442 can have different locations or different shapes than the spot beams 125 generated by the return beamforming network 421, and the beamforming network 442 can be configured to support sweeping the spot beams 125 through a given location in a given time window of the stored feed element signals 435. The search component 443 can support various functions for detecting, characterizing, demodulating, and decoding the spot beam signals generated by the beamforming network 442 over a post-time search window.

[0087] Although certain techniques for past-event signal tracking have been described in the context of storing and processing feed element signals, the described techniques may be applied to any signal that supports post-event reconstruction of a target spot beam 125 or a corresponding spot beam signal. For example, in an end-to-end beamforming configuration, return uplink signals associated with a quantity of spot beam coverage areas 126 may be received according to an array of receive / transmit signal paths, each corresponding to a respective receive feed element 128 and a respective transmit feed element 128 of a relay device. The return uplink signals are transmitted by the transmit feed elements 128 of the relay device, and the transmit signals of at least a subset of the transmit feed elements 128 are received at each of a plurality of access node terminals 130. Each return uplink signal received at the plurality of access node terminals 130 may be forwarded to a CPS of the end-to-end beamforming system and processed (e.g., by applying a beam weight matrix to the received signals) to generate a spot beam signal corresponding to the spot beam coverage area 126. Thus, each return uplink signal of the end-to-end beamforming system, when received at each access node terminal 130 or received at a CPS, can support both a primary or real-time mission and a post-event or other search mission. This is true even if such signals are not split or multiplexed according to the signal of one of the feed elements 128. In other words, the described techniques for post-event signal tracking are not limited to receiving and storing signals each corresponding to a single feed element 128. Rather, the described techniques for post-event signal tracking can implement any signal that is stored and later processed to construct a spot beam 125 or a corresponding spot beam signal.

[0088] 5 illustrates an example of a search process 500 supporting past-event signal tracking according to embodiments disclosed herein. The search process 500 may be performed by one or more components of a post-time processing component, such as the post-time processing component 440 described with reference to FIG. 4. The search process 500 illustrates an example of an iterative process supporting a spatial search of any signal feature within the service coverage area of ​​one or more antenna assemblies 121.

[0089] At 505, a search process 500 can be initiated. In various examples, the search process 500 can be initiated based on user initiation or intervention, or based on an event trigger initiation (e.g., loss of expected signal, movement of target device out of threshold range, location, or path, alarm trigger initiation). In some examples, the search process 500 can be initiated as part of a search and rescue operation, a recovery operation, a surveillance operation, or a criminal investigation operation, among others.

[0090] At 510, the search process 500 can include defining a signal of interest. In some examples, characteristics of the signal of interest are known to a user and can be provided as input to the search process 500. In some examples, aspects of the signal of interest may be known to a component of the receiver processing system performing the search process 500, which includes information stored in a look-up table or other reference resource and searched from there. The signal of interest can have characteristics such as a modulation scheme, a symbol rate, an identifier, among others, and such characteristics may be known prior to initiating the search process 500 or may be expected to be known or one of multiple possibilities prior to initiating the search process 500.

[0091] At 520, the search process 500 can include beamforming (e.g., receiving beamforming) a plurality of stored feed element signals into a position hypothesis, which can be associated with generating a target spot beam signal based at least in part on the beamforming. The stored feed element signals can be received from a single antenna assembly 121 or from two or more antenna assemblies 121 (e.g., from multiple satellites 120). In some examples, the initial position hypothesis can be based at least in part on a predicted location of a device associated with the signal of interest. For example, the initial position hypothesis can be based on a last known location of a device associated with the signal of interest or based on a known or predicted path of a device associated with the signal of interest. The beamforming at 520 can be performed by a beamforming network, such as the beamforming network 442 of the post-time processing component 440, which can be the same or different as the beamforming network used in the primary mission (e.g., the return beamforming network 421 of the real-time processing component 420). Additionally, the beamforming at 520 can include spot beams 125 having the same or different characteristics as the spot beams 125 associated with the real-time mission. For example, the beamforming at 520 can include spot beams 125 having a wider or narrower spot beam coverage area 126, or spot beams 125 having a different target location (e.g., the spot beam center or axis may or may not be aligned with a location hypothesis) than the spot beams 125 of the real-time mission.

[0092] At 521, the search process 500 may include evaluating whether signal energy is present in the spot beam signal associated with the location hypothesis. The evaluation at 521 may include evaluation of signal energy at an expected frequency or frequency range for the target signal, or based on an expected polarization for the target signal, or various combinations thereof. If signal energy is present, the search process 500 may proceed to 530, and if signal energy is not present, the search process 500 may proceed to 522, where the search process 500 may include evaluating whether all target locations within the service coverage area have been examined. If all locations have not been examined, the search process 500 may return to 520 to beamform for the next location hypothesis (e.g., generate a new target spot beam signal for the next location hypothesis), and if all target locations have been examined, the search process 500 may proceed to 570, terminating the search process.

[0093] At 530, the search process 500 may include testing modulation hypotheses. In some examples, the initial modulation hypotheses may include an expected modulation scheme for the signal of interest, such as one of binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), or some other modulation scheme. In some examples, the particular modulation scheme may not be known or expected, and the initial modulation hypotheses may be selected randomly or according to a defined repeating sequence. Testing the modulation hypotheses may include various evaluations of the target spot beam signal (e.g., as generated at 520), such as evaluations of frequency, amplitude, or phase characteristics of the target spot beam signal against characteristics expected for the hypothetical modulation scheme. In some examples, such evaluations may be performed based on pilot signals identified in the target spot beam signal.

[0094] At 531, the search process 500 may include evaluating whether the virtual modulation scheme is present in the target spot beam signal. The evaluation at 531 may include evaluating whether the frequency, amplitude, and / or phase of the spot beam signal matches one or more points or patterns of a constellation of modulation symbols associated with the virtual modulation scheme. If the modulation scheme is present, the search process 500 may proceed to 540, and if the modulation scheme is not present, the search process 500 may proceed to 532, where the search process 500 may include evaluating whether all modulation schemes of a plurality of possibilities have been examined. At 532, if all modulation schemes have not been examined, the search process 500 may return to 530 to evaluate the next modulation scheme, and if all modulation schemes have been examined, the search process 500 may return to 522 to evaluate whether to beamform in the next location hypothesis (e.g., to generate a new target spot beam signal for the next location hypothesis).

[0095] At 540, the search process 500 can include testing a symbol rate hypothesis. In some examples, the initial symbol rate hypothesis can include an expected symbol rate for the target signal, which can be related to a communication bandwidth or signal bandwidth supported by a device associated with the target signal. In some embodiments, the particular symbol rate may not be known or expected, and the initial symbol rate may be selected randomly or according to a defined repeating sequence. Testing the symbol rate can include various evaluations of the target spot beam signal (e.g., as generated at 520), such as evaluating how frequently the amplitude or phase characteristics of the target spot beam signal change (e.g., how often new modulation symbols are rendered) for characteristics expected for the virtual symbol rate, or adjusting the signal processing to the virtual symbol rate.

[0096] At 541, the search process 500 may include evaluating whether a symbol rate is present in the target spot beam signal. The evaluation at 541 may include evaluating whether a rate of phase and / or amplitude changes or transitions matches the hypothesized symbol rate or evaluating whether decoding at the hypothesized symbol rate is successful. If the symbol rate is present, the search process 500 may proceed to 550, and if the symbol rate is not present, the search process 500 may proceed to 542, where the search process 500 may include evaluating whether all of the multiple possible symbol rates have been examined. At 542, if all symbol rates have not been examined, the search process 500 may return to 540 to evaluate the next symbol rate, and if all symbol rates have been examined, the search process 500 may return to 532 to evaluate whether to test another modulation hypothesis.

[0097] At 550, the search process 500 can include adjusting to the identifier hypothesis. In some examples, the initial identifier hypothesis can include an expected identifier for the signal of interest, which may be associated with an identifier of a device associated with the signal of interest, such as a device identifier, a mobile identifier, a device signature, or an address, among others. For example, the targeted spot beam signal can be evaluated for confirmation that the received signal includes a transmission made by a targeted device associated with the signal of interest. In some examples, the particular identifier may be unknown or unexpected, and the initial identifier may be selected randomly or according to a defined repeating sequence. Testing the identifier can include various evaluations of the targeted spot beam signal (e.g., as generated at 520). Such evaluations can include evaluating pilot signals or symbols, demodulating or decoding the targeted spot beam signal for signals of control or other information, among other evaluations for expected identifier characteristics for the identifier hypothesis, and the like.

[0098] At 551, the search process 500 may include evaluating whether an identifier is present in the target spot beam signal. The evaluation at 551 may include evaluating whether the detected identifier matches a hypothesized identifier. If the identifier is present, the search process 500 may proceed to 560, and if the identifier is not present, the search process 500 may proceed to 552, where the search process 500 may include evaluating whether all identifiers of a plurality of possibilities have been examined. If all identifiers have not been examined, the search process 500 may return to 550 to evaluate the next identifier, and if all identifiers have been examined, the search process 500 may return to 542 to evaluate whether to test another symbol rate hypothesis.

[0099] At 560, the search process 500 may include demodulating and / or decoding the processed signal (e.g., the targeted spot beam signal generated at 520). The demodulation and / or decoding may support extraction of information from the targeted spot beam signal, including information relevant to a target device associated with the signal of interest. For example, the operations at 560 may include demodulating or decoding information related to positioning information, operational information, or diagnostic information, among others. After the operations of 560, the search process may proceed to 570 and end. In some examples, the operation of 560 may be omitted and the search process 500 may proceed from 550 to 570 without demodulating or decoding the processed signal.

[0100] At 570, the search process 500 may terminate. In some examples, terminating the search process 500 may include an indication that the signal of interest was not found, and the search process 500 may or may not be run again with a revised definition of the signal of interest. In some examples, terminating the search process 500 may include confirmation that the signal of interest, or a device associated with the signal of interest, was found in a location hypothesis. In some examples, terminating the search process 500 may include outputting the demodulated or decoded information at 560, which may be associated with various search operations, such as search and rescue operations, asset recovery operations, surveillance operations, or criminal investigation operations, among others.

[0101] 6 illustrates an example of past event signal tracking 600 according to embodiments disclosed herein. The past event signal tracking 600 may illustrate an example where an aircraft was intended to follow a virtual path 605 but lost communication connectivity. To identify possible locations of the disabled aircraft, the past event signal tracking 600 may reference a post-event analysis including aspects of the search process 500 according to multiple target spot beam coverage areas 126-d.

[0102] The targeted spot beam coverage areas 126-d may refer to respective areas, and signal energy received over these areas may be separated from other areas by post-event receive beamforming (e.g., using the beamforming network 442). For example, each of the targeted spot beam coverage areas 126-d may be associated with a respective spot beam 125 formed from stored feed element signals 435, which may correspond to multiple native feed element patterns 210 of the native feed element pattern coverage area 221 that includes the area indicated by the targeted spot beam coverage area 126-d. The stored feed element signals 435 may be associated with feed element signals (e.g., feed element signals 405) that also support real-time missions, such as providing Internet connectivity via the service coverage area 310. In some examples, the targeted spot beam coverage areas 126-d may be the same as or similar to the spot beam coverage areas 126 associated with the real-time missions. In some examples, the target spot beam coverage area 126-d may be different from the spot beam coverage area 126 associated with the real-time mission, which may include a target spot beam coverage area 126-d having a smaller or larger size (e.g., diameter), a different location, a different number of beams, or a different gain than the spot beam coverage area 126 of the primary mission.

[0103] A post-time mission request in such a scenario may include a request to locate the target aircraft or identify information signals from the target aircraft. To support such a mission, a search process 500 may be used to form high gain target spot beams 125 (e.g., each corresponding to a respective target spot beam coverage area 126-d) from feed element signals 435 stored in a storage component (e.g., feed element signal storage component 430) for later analysis. In various examples, the target aircraft may or may not be engaged in communication with an associated satellite communication system. Rather, a process such as the search process 500 may be performed even if the target aircraft is not participating in communication via a feed element associated with a feed element signal used in the search process of past event signal tracking 600.

[0104] Performing a search process in past event signal tracking 600, such as search process 500, can be based on a virtual path 605 (e.g., including the target spot beam coverage area 126-d that overlaps with the virtual path 605), but can also include the surrounding target spot beam coverage area 126-d to evaluate whether the aircraft has deviated from the virtual path 605. For example, the search process can start with an initial spot beam 126-d-1 (e.g., a target location hypothesis or last known position) and a first time window. If a target signal is detected in a stored signal (e.g., a feed element signal, an access node terminal signal) during the first time window using a beamforming weight corresponding to the initial spot beam 126-d-1, the search process can continue by searching for the target signal in adjacent spot beams (e.g., including spot beams 126-d-2 and 126-d-3) in a second time window following the first time window. For example, each of the spot beams 126-d-2 and 126-d-3 can correspond to a different set of beamforming weights applied to the stored signal. In the illustrated example, a target signal was found in spot beam 126-d-3 during the second time window.

[0105] The search process continues, and as a result, a detected path 610 can be determined (e.g., based on detection of a signal in a target spot beam coverage area 126-d, shown solid, among multiple searched spot beam coverage areas 126-d, including spot beam coverage area 126-d shown dashed), which can provide an estimate of the target aircraft's location versus time, or an identification of the last target spot beam coverage area 126-d where a signal was detected (e.g., identifying a possible downed aircraft within target spot beam coverage area 126-d-n). In some examples, results of the search process (e.g., based on demodulating or decoding the target spot beam signal or the search process) can include identifying engine telemetry of the aircraft, determining the actual path of the aircraft, demodulating the telemetry information, and possibly identifying the cause of the aircraft failure. While performing the search process for past event signal tracking 600, real-time missions supported by the feed elements that provided the stored information are not affected, and feed element signal recording can continue.

[0106] While the described techniques for past event signal tracking are applicable to electromagnetic signals via antenna assembly 121, in some examples the described techniques for past event searching can also be applied to optical signals. For example, imaging information from multiple cameras or optical sensors may be stored separately, but may also be combined according to various optical focusing or other processing techniques. In one example, a phased array optical sensor may be used, where individual element data is stored and later used to focus the image using post-time processing techniques similar to those described herein with respect to antenna and electromagnetic signal processing.

[0107] FIG. 7 illustrates a block diagram 700 of a receiver processing system 705 supporting past event signal tracking according to embodiments disclosed herein. The receiver processing system 705 may be an example of an aspect of a communication system or receiver processing system described with reference to FIGS. 1A-5. The receiver processing system 705 may include a feed element signal receiver 710, a real-time beamforming processor 715, a storage component 720, a past event search manager 725, a past event beamforming processor 730, and a past event evaluation component 735. Each of these modules may be in direct or indirect communication with each other (e.g., via one or more buses). In some examples, the receiver processing system 705 may refer to or otherwise include components of a ground segment 102 of the communication system 100, or the receiver processing system 705 may refer to or otherwise include components of a satellite 120 of the communication system 100. In some examples, components of the receive processing system 705 may be distributed between the ground segment 102 and the space segment 101, or in other antenna systems (e.g., overhead antenna systems such as antenna systems on an aircraft or UAV) that support beamforming reception and feed element signal storage.

[0108] The feed element signal receiver 710 can be configured to receive a plurality of feed element signals. In some examples, each of the plurality of feed element signals can correspond to a respective one of a plurality of feed elements 128 of the feed array assembly 127 of the antenna assembly 121, where the antenna assembly can be associated with the service coverage area 310 or the native antenna pattern coverage area 221. In some examples, the feed element signal receiver 710 can be configured to receive a second set of feed element signals, where each of the second set of feed element signals corresponds to a respective one of the second set of feed elements 128 of the feed array assembly 127 of the second antenna assembly 121 (e.g., a different antenna), where the second antenna assembly is associated with the second service coverage area 310 or the second native antenna pattern coverage area 221. In various examples, the first antenna assembly 121 and the second antenna assembly 121 can be components of the same device or different devices (e.g., different satellites 120, different mobile bodies).

[0109] In some examples, the feed element signal receiver 710 may be a component of a ground station of the ground segment 102, or features of the feed element signal receiver 710 may be distributed across multiple ground stations of the ground segment 102. For example, the receive processing system 705 may be configured to receive multiple feed element signals at or otherwise using multiple ground stations of the ground segment 102. In some examples, the feed element signal receiver 710 may include a component of a network device 141 or other central processing component of the ground segment 102. In some examples, the feed element signal receiver 710 may reference or otherwise be associated with components of one or more satellites 120.

[0110] The real-time beamforming processor 715 can be configured to process the multiple feed element signals according to a first beamforming configuration (e.g., a primary beamforming configuration associated with the multiple spot beams 125, a real-time beamforming configuration associated with the multiple spot beams 125) to generate one or more spot beam signals. Each of the spot beam signals can correspond to a respective spot beam 125 (e.g., of the antenna assembly 121) and can include communications scheduled for transmission or reception via each of the multiple spot beams 125. In various examples, the real-time beamforming processor 715 can include a component of the ground segment 102 (e.g., the access node terminal 130 or the network device 141 to support ground-based beamforming of a primary or real-time mission or task), or the real-time beamforming processor 715 can include a component of a satellite 120 (e.g., to support on-board beamforming of a primary or real-time mission or task), which may or may not be the same satellite 120 that includes the antenna assembly 121 associated with the feed element 128 of the feed element signal.

[0111] The storage component 720 can store the feed element signals for a period of time. In some examples, the storage component 720 can include a FIFO buffer that stores the feed element signals for a moving time window (e.g., a period of hours, days, weeks, months, etc.). In some examples, the storage component 720 can oversample the received feed element signals relative to the bandwidth of the received feed element signals. In some examples, the storage component 720 can include a component of a ground station of the ground segment 102, or the features of the storage component 720 can be distributed across multiple ground stations of the ground segment 102. For example, the receiving processing system 705 can be configured to store the feed element signals at or otherwise using multiple ground stations of the ground segment 102. In some examples, the storage component 720 can be a component of the network device 141 or other central processing component of the ground segment 102. Additionally or alternatively, in some examples, the storage component 720 can refer to a component of one or more satellites 120 or other mobile bodies that locally stores the feed element signals.

[0112] Past events searching manager 725 can be configured to determine to search in a first time window within a predetermined period (e.g., related to the duration of storage of the feed element signal) for a target signal from a location within the service coverage area 310 or native antenna pattern coverage area 221. In various examples, such a determination can be made by past events searching manager 725 based on initiation or input from a user or operator, based on a starting or triggering event, or based on an operating state or mode.

[0113] In some examples, the past events search manager 725 may be configured to perform an iterative search, such as the search process 500 described with reference to FIG. 5. For example, the past events search manager 725 may be configured to search for the target signal from different locations within the service coverage area (e.g., in the same or different time windows that are within the storage period of the feed element signal) based on an evaluation of the target spot beam signal indicating an absence of the target signal. In some examples, the past events search manager 725 may be configured to determine or receive route hypotheses (e.g., from a user, from a lookup resource, from a route prediction model) for a device associated with the target signal. In some examples, the past events search manager 725 may be configured to determine one or more search locations over various time windows based on the route hypotheses for the device.

[0114] In some examples, the past event searching manager 725 can be configured to determine or receive (e.g., from a user, from a lookup resource, from a frequency prediction model) a target frequency hypothesis for the target signal. To evaluate the target spot beam signal for the presence of the target signal, the past event searching manager 725 can be configured to evaluate the target spot beam signal according to such target frequency hypothesis.

[0115] In some examples, the past event searching manager 725 can be configured to determine or receive (e.g., from a user, from a lookup resource, from a modulation prediction model) a target modulation scheme hypothesis for the target signal. To evaluate the target spot beam signal for the presence of the target signal, the past event searching manager 725 can be configured to evaluate the target spot beam signal according to such target modulation scheme hypothesis.

[0116] In some examples, the past event searching manager 725 can be configured to determine or receive (e.g., from a user, from a lookup resource, from a symbol rate prediction model) a target symbol rate hypothesis for the target signal. To evaluate the target spot beam signal for the presence of the target signal, the past event searching manager 725 can be configured to evaluate the target spot beam signal according to such target symbol rate hypothesis.

[0117] In some examples, the past event searching manager 725 can be configured to determine or receive (e.g., from a user, from a lookup resource, from a symbol rate prediction model) a target identifier hypothesis for the target signal. To evaluate the target spot beam signal for the presence of the target signal, the past event searching manager 725 can be configured to evaluate the target spot beam signal according to such target identifier hypothesis.

[0118] The past event beamforming processor 730 can be configured to process the stored feed element signals during the first time window according to a second beamforming configuration (e.g., different from the primary beamforming configuration or the real-time beamforming configuration) to generate a target spot beam signal corresponding to the location. In some examples, the past event beamforming processor 730 can be configured to process the stored feed element signals according to a target spot beam 125 different from each of the spot beams 125 associated with the first beamforming configuration (e.g., different location, different size, different gain). In some examples, generating the target spot beam signal corresponding to the location includes processing the stored second set of feed element signals (e.g., from an antenna assembly 121 different from the antenna assembly associated with the first set of feed element signals) during the first time window according to a third beamforming configuration.

[0119] In some examples, the past event beamforming processor 730 can be configured to process the stored plurality of feed element signals during the first time window according to a third beamforming configuration to generate a second targeted spot beam signal corresponding to the second location. In some examples, the past event beamforming processor 730 can be configured to process the stored plurality of feed element signals during the second time window according to a fourth beamforming configuration to generate a third targeted spot beam signal corresponding to the second location.

[0120] In various examples, the past event beamforming processor 730 may include a component of the ground segment 102 (e.g., an access node terminal 130 or a network device 141 to support ground-based beamforming of a past event tracking mission or task), or the past event beamforming processor 730 may include a component of a satellite 120 (e.g., to support on-board beamforming of an event tracking mission or task), which may or may not be the same satellite 120 that includes the antenna assembly 121 associated with the feed element 128 of the feed element signal. In various examples, the past event beamforming processor 730 may or may not be associated with the same device as the real-time beamforming processor 715. In some examples, the past event beamforming processor 730 may be the same processor as the real-time beamforming processor 715 or may share one or more components with the real-time beamforming processor 715.

[0121] The past event evaluation component 735 can be configured to evaluate the target spot beam signal for the presence of a target signal. In various examples, such evaluation may be based at least in part on hypotheses such as a target frequency hypothesis, a target modulation scheme hypothesis, a target symbol rate hypothesis, a target identifier hypothesis, etc. In various examples, the past event evaluation component 735 can include a component of the ground segment 102 (e.g., an access node terminal 130 or a network device 141 to support ground-based evaluation of the spot beam signal), or the past event evaluation component 735 can include a component of the satellite 120 (e.g., to support on-board evaluation of the spot beam signal). In various examples, the past event evaluation component 735 may or may not be included in the same device as the past event beamforming processor 730 or may be otherwise associated with it.

[0122] 8 is a flow chart illustrating a method 800 for supporting past event signal tracking, according to embodiments disclosed herein. The operations of method 800 may be performed by a receiving processing system or components thereof, as described herein. For example, the operations of method 800 may be performed by a receiving processing system such as those described with reference to FIG. 4 or FIG. 7. In some examples, the receiving processing system may execute a set of instructions to control functional elements of the receiving processing system to perform the described functions. Additionally or alternatively, the receiving processing system may use dedicated hardware to perform aspects of the described functions.

[0123] At 805, a receive processing system can receive a plurality of feed element signals. Each of the plurality of feed element signals can correspond to a respective one of a plurality of feed elements of a feed array of an antenna having a service coverage area. The operations of 805 can be performed in accordance with techniques described herein. In some examples, aspects of the operations of 805 can be performed by a feed element signal receiver as described with reference to FIG. 7.

[0124] At 810, the receive processing system may process the received feed element signals according to a first beamforming configuration (e.g., associated with a set of spot beams of the antenna) to generate one or more spot beam signals corresponding to each spot beam. In some examples, the one or more spot beam signals may include communications scheduled for transmission or reception via each of the plurality of spot beams. In some examples, the processing at 810 may be associated with a primary or real-time mission supported by the receive processing system. The operations of 810 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 810 may be performed by a real-time beamforming processor as described with reference to FIG. 7.

[0125] At 815, the receiving processing system can store the received feed element signals for a predetermined period of time. The operations of 815 can be performed in accordance with techniques described herein. In some examples, aspects of the operations of 815 can be performed by a storage component such as described with reference to FIG.

[0126] At 820, the receiving processing system may determine to search for a target signal from a location within the service coverage area in a first time window within a predetermined period. In some examples, the processing at 820 may be associated with a secondary mission or past event search or past event tracking function supported by the receiving processing system, which is triggered or initiated by a user command or instruction, an initiating event, or an operational mode. The operations at 820 may be performed in accordance with techniques described herein. In some examples, aspects of the operations at 820 may be performed by a past event search manager, as described with reference to FIG. 7.

[0127] At 825, the receive processing system may process the stored plurality of feed element signals during the first time window according to a second beamforming configuration (e.g., associated with a searcher spot beam of the antenna) to generate a target spot beam signal corresponding to the location. The operations of 825 may be performed according to techniques described herein. In some examples, aspects of the operations of 825 may be performed by a past event beamforming processor, as described with reference to FIG. 7.

[0128] At 830, the receiver processing system may evaluate the target spot beam signal for the presence of a target signal. The operations of 830 may be performed in accordance with techniques described herein. In some examples, aspects of the operations of 830 may be performed by a past event evaluation component such as described with reference to FIG.

[0129] In some examples, an apparatus described herein can perform a method, such as method 800. The apparatus can include features, components, means, or instructions (e.g., a non-transitory computer-readable medium storing instructions executable by a processor) for receiving a plurality of feed element signals (e.g., corresponding to feed elements of a feed array of an antenna having a service coverage area), processing the received plurality of feed element signals according to a first beamforming configuration to generate one or more spot beam signals corresponding to each spot beam, storing the received plurality of feed element signals for a predetermined period of time, determining to search for a target signal from a location within the service coverage area in a first time window within the predetermined period of time, processing the stored plurality of feed element signals according to a second beamforming configuration during the first window to generate a target spot beam signal corresponding to the location, and evaluating the target spot beam signal for the presence of a target signal.

[0130] Some examples of the method 800 and apparatus described herein may further include operations, features, components, means, or instructions for determining, based on evaluation of the target spot beam signal indicating an absence of the target signal, to search for a target signal from a second location within the service coverage area in a first time window within a predetermined period of time; processing the stored plurality of feed element signals during the first time window according to a third beamforming configuration (e.g., associated with another search spot beam of the antenna) to generate a second target spot beam signal corresponding to the second location; and evaluating the second target spot beam signal for the presence of the target signal.

[0131] Some examples of the methods 800 and apparatus described herein may further include operations, features, components, means, or instructions for determining a route hypothesis for a device associated with the target signal and determining a location based on the route hypothesis for the device.

[0132] Some examples of the methods 800 and apparatus described herein may include operations, features, components, means, or instructions for determining, based on a path hypothesis for the device, to search for a target signal from a second location within the service coverage area in a second time window within the period of time, processing the stored plurality of feed element signals during the second time window according to a fourth beamforming configuration (e.g., associated with another search spot beam of the antenna) to generate a third target spot beam signal corresponding to the second location, and evaluating the third target spot beam signal for the presence of the target signal.

[0133] In some examples of the methods 800 and apparatus described herein, processing according to the second beamforming configuration may include operations, features, components, means, or instructions for processing the set of stored feed element signals according to a target spot beam that is different from each of the plurality of spot beams associated with the first beamforming configuration. For example, the target spot beam may have a different size, a different orientation, a different coverage area size or location, a different set of phase or amplitude gains or coefficients, or other differences, as compared to the spot beams of the first beamforming configuration. For example, a target spot beam for speculative or hypothetical signal search may be different from a spot beam used for a primary mission or a real-time mission.

[0134] Some examples of methods 800 and apparatuses described herein may further include operations, features, components, means, or instructions for receiving a second set of feed element signals, each feed element signal of the second set corresponding to a respective feed element of the second set of a feed array of a second antenna (e.g., having a second service coverage area), and for storing the received second set of feed element signals for a second time period. In some examples, generating a target spot beam signal corresponding to the location may include operations, features, components, means, or instructions for processing the second set of stored feed element signals during the first time window according to a fifth beamforming configuration (e.g., associated with a search spot beam of the second antenna).

[0135] In some example methods 800 and apparatus described herein, storing the set of received feed element signals may include operations, features, components, means, or instructions for oversampling the received feed element signals relative to a bandwidth of the received feed element signals.

[0136] Some examples of the methods 800 and apparatus described herein may further include operations, features, components, means, or instructions for determining a target frequency hypothesis for the target signal, and the step of evaluating the target spot beam signal for the presence of the target signal may include evaluating the target spot beam signal according to the determined target frequency hypothesis.

[0137] Some examples of the methods 800 and apparatus described herein may further include operations, features, components, means, or instructions for determining a target modulation scheme hypothesis for the target signal, and the step of evaluating the target spot beam signal for the presence of the target signal may include evaluating the target spot beam signal according to the determined target modulation scheme hypothesis.

[0138] Some examples of the methods 800 and apparatus described herein may further include operations, features, components, means, or instructions for determining a target symbol rate hypothesis for the target signal, and the step of evaluating the target spot beam signal for the presence of the target signal may include evaluating the target spot beam signal according to the determined target symbol rate hypothesis.

[0139] Some examples of the methods 800 and devices described herein may further include operations, features, components, means, or instructions for determining a target identifier hypothesis for the target signal, and the step of evaluating the target spot beam signal for the presence of the target signal may include evaluating the target spot beam signal according to the determined target identifier hypothesis.

[0140] In some example methods 800 and apparatus described herein, processing the received plurality of feed element signals according to the first beamforming configuration may include operations, features, components, means, or instructions for processing at the ground segment.

[0141] In some example methods 800 and apparatus described herein, processing the received plurality of feed element signals according to the first beamforming configuration may include operations, features, components, means, or instructions for processing at a satellite including an antenna.

[0142] In some example methods 800 and apparatus described herein, receiving the multiple feed element signals may include operations, features, components, means, or instructions for receiving the multiple feed element signals at ground stations of multiple ground segments.

[0143] In some example methods 800 and apparatus described herein, processing the stored plurality of feed element signals in accordance with the second beamforming configuration may include operations, features, components, means, or instructions for processing at the ground segment.

[0144] 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.

[0145] 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.

[0146] The various example blocks and modules described in connection with the disclosure herein may be implemented or performed with 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 conjunction with a DSP core, or any other such configuration).

[0147] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. When implemented in software executed by a processor, the functions may be stored or transmitted as one or more instructions or codes 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 the software, the functions herein may be implemented using software executed by a processor, hardware, firmware, hardwiring, or any combination thereof. Also, features implementing the functions may be physically located in various locations, including being distributed such that some of the functions are implemented in different physical locations.

[0148] 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 that can be accessed 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), compact disk (CD) ROM or other optical disk storage, magnetic disk storage, or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code 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. Any connection is also 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, microwave, etc., the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, microwave, etc., are included within the definition of media. As used herein, Disk and Disc include CDs, laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where discs typically reproduce data magnetically while discs reproduce data optically using lasers. Combinations of the above are also included within the scope of computer readable media.

[0149] As used herein, including the claims, "or" when used in a list of items (e.g., a list of items preceded by phrases such as "at least one of" or "one or more of") indicates an inclusive list, so that, for example, "at least one of A, B, or C" means A or B or C, or AB or AC or BC, or ABC (i.e., A and B and C). Also, as used herein, the phrase "based on" should not be construed as referring to an exclusive set of conditions. For example, an exemplary process 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 construed in the same manner as the phrase "based at least in part on."

[0150] 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 symbol and a second label that distinguishes between the similar components. If only a first reference number is used herein, the description is applicable to any one of the similar components having the same first reference number, regardless of the second reference number or other subsequent reference numbers.

[0151] The description set forth herein describes exemplary configurations in conjunction with the accompanying drawings and does not represent every example that may be implemented or fall within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration" and does not mean "preferred" or "advantageous over other examples." The detailed description includes specific details for the purpose of providing an understanding of the described technology. However, these techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form to avoid obscuring the concepts of the described embodiments.

[0152] 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 generic principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Thus, the present disclosure should not be 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. 1. A method comprising: receiving a plurality of feed element signals (405), each of the plurality of feed element signals corresponding to a respective one of a plurality of feed elements (128) of a feed array (127) of an antenna (121) having a service coverage area (310); processing the received feed element signals (405) according to a first beamforming configuration associated with a plurality of spot beams (125) to generate one or more spot beam signals each corresponding to a respective spot beam (125) of the antenna (121), the one or more spot beam signals including a communication scheduled for transmission via each of the plurality of spot beams (125); storing the received feed element signals (405) for a predetermined period of time; determining to search for a target signal from a location within the service coverage area (310) during a first time window within the period; processing the stored plurality of feed element signals (435) during the first time window according to a second beamforming configuration to generate a target spot beam signal corresponding to the location; evaluating the target spot beam signal for the presence of the target signal; Including, the first beamforming configuration is used to form the plurality of spot beams (125), each configured to support a communication service within a spot beam coverage area; The method of claim 1, wherein the second beamforming configuration is used to generate the target spot beam signal for searching for the target signal after the first beamforming configuration.

2. determining a path hypothesis for a device associated with the target signal; determining the location based at least in part on the route hypotheses for the device; and The method of claim 1 further comprising:

3. determining, based at least in part on the route hypothesis for the device, to search for the target signal from a second location within the service coverage area (310) over a second time window within the period; processing the stored plurality of feed element signals (435) during the second time window according to a fourth beamforming configuration to generate a third target spot beam signal corresponding to the second location; evaluating the third target spot beam signal for the presence of the target signal; Further comprising: The method of claim 2 , wherein the fourth beamforming configuration is used to generate the third target spot beam signal for searching for the target signal after the first beamforming configuration.

4. receiving a second plurality of feed element signals (405), each of the second plurality of feed element signals corresponding to a respective one of a second plurality of feed elements (128) of a feed array (127) of a second antenna (121) having a second service coverage area (310); storing the received second plurality of feed element signals (405) for a second period of time; generating the target spot beam signal corresponding to the location includes processing the stored second plurality of feed element signals (435) during the first time window according to a third beamforming configuration; The method according to any one of claims 1 to 3, wherein the third beamforming configuration is used to generate the target spot beam signal for searching for the target signal after the first beamforming configuration.

5. Storing the received feed element signals (405) includes: Oversampling the received plurality of feed element signals (405) relative to a bandwidth of the received plurality of feed element signals (405). The method according to any one of claims 1 to 4, comprising:

6. 6. The method of claim 1, further comprising determining a target frequency hypothesis for the target signal, and wherein evaluating the target spot beam signal for the presence of the target signal comprises evaluating the target spot beam signal in accordance with the determined target frequency hypothesis.

7. 7. The method of claim 1, further comprising determining a target modulation scheme hypothesis for the target signal, and wherein evaluating the target spot beam signal for the presence of the target signal comprises evaluating the target spot beam signal according to the determined target modulation scheme hypothesis.

8. 8. The method of claim 1, further comprising determining a target symbol rate hypothesis for the target signal, and wherein evaluating the target spot beam signal for the presence of the target signal comprises evaluating the target spot beam signal in accordance with the determined target symbol rate hypothesis.

9. The method of any one of claims 1 to 8, further comprising determining a target identifier hypothesis for the target signal, and wherein evaluating the target spot beam signal for the presence of the target signal comprises evaluating the target spot beam signal in accordance with the determined target identifier hypothesis.

10. determining to search for the target signal from a second location within the service coverage area (310) during the first time window within the period based at least in part on an evaluation of the target spot beam signal indicating an absence of the target signal; processing the stored plurality of feed element signals (435) during the first time window according to a third beamforming configuration to generate a second target spot beam signal corresponding to the second location; evaluating the second target spot beam signal for the presence of the target signal; Further comprising: The method according to any one of claims 1 to 9, wherein the third beamforming configuration is used to generate the second target spot beam signal for searching for the target signal after the first beamforming configuration.

11. Processing in accordance with the second beamforming configuration includes: processing the stored feed element signals according to a target spot beam distinct from each of the spot beams associated with the first beamforming configuration; The method according to any one of claims 1 to 10, comprising:

12. The method of any one of claims 1 to 11, wherein processing the stored plurality of feed element signals (435) in accordance with the second beamforming configuration comprises processing at a ground segment (102).

13. The method of any one of claims 1 to 12, wherein receiving the plurality of feed element signals (405) comprises receiving the plurality of feed element signals (435) at a plurality of ground stations of a ground segment (102).

14. The method of any one of claims 1 to 13, wherein processing the received multiple feed element signals (405) in accordance with the first beamforming configuration comprises processing at a ground segment (102).

15. 14. The method of claim 1, wherein processing the received multiple feed element signals (405) in accordance with the first beamforming configuration comprises processing at a satellite (120) including the antenna (121).

16. An apparatus comprising: A processor; memory in electronic communication with said processor; and instructions stored in the memory and executable by the processor, the instructions causing the apparatus to: receiving a plurality of feed element signals (405), each of the plurality of feed element signals corresponding to a respective one of a plurality of feed elements (128) of a feed array (127) of an antenna (121) having a service coverage area (310); processing the received feed element signals (405) according to a first beamforming configuration associated with a plurality of spot beams (125) to generate one or more spot beam signals each corresponding to a respective spot beam (125) of the antenna (121), wherein the one or more spot beam signals include a communication scheduled for transmission via each of the plurality of spot beams (125); storing the received plurality of feed element signals for a predetermined period of time; determining to search for a target signal from a location within the service coverage area (310) during a first time window within the period; processing the stored plurality of feed element signals (435) during the first time window according to a second beamforming configuration to generate a target spot beam signal corresponding to the location; evaluating the target spot beam signal for the presence of the target signal; the first beamforming configuration is used to form the plurality of spot beams (125), each configured to support a communication service within a spot beam coverage area; The apparatus, wherein the second beamforming configuration is used to generate the target spot beam signal for searching for the target signal after the first beamforming configuration.

17. The instructions are sent by the processor to the device: determining a path hypothesis for a device associated with the target signal; determining the location based at least in part on the route hypotheses for the device; The apparatus of claim 16 further operable to:

18. The instructions are sent by the processor to the device: determining, based at least in part on the route hypothesis for the device, to search for the target signal from a second location within the service coverage area (310) over a second time window within the period; processing the stored plurality of feed element signals (435) during the second time window according to a fourth beamforming configuration to generate a third target spot beam signal corresponding to the second location; evaluating the third target spot beam signal for the presence of the target signal. It is further possible to 20. The apparatus of claim 17, wherein the fourth beamforming configuration is used to generate the third target spot beam signal for searching for the target signal after the first beamforming configuration.

19. The instructions are sent by the processor to the device: receiving a second plurality of feed element signals (405), where each of the second plurality of feed element signals corresponds to a respective one of a second plurality of feed elements (128) of a feed array (127) of a second antenna (121) having a second service coverage area (310); storing the received second plurality of feed element signals (405) for a second period of time; It is further possible to The instructions for generating the target spot beam signal corresponding to the location are executable by the processor to cause the device to process the stored second plurality of feed element signals (435) during the first time window according to a third beamforming configuration; The apparatus of any one of claims 16 to 18, wherein the third beamforming configuration is used to generate the target spot beam signal for searching for the target signal after the first beamforming configuration.

20. The instructions to store the received feed element signals (405) include instructions to the processor to the device to: oversampling the received feed element signals relative to a bandwidth of the received feed element signals The apparatus according to any one of claims 16 to 19, wherein the apparatus is operable to:

21. The instructions are sent by the processor to the device: An apparatus as described in any one of claims 16 to 20, further executable to determine a target frequency hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to cause the apparatus to evaluate the target spot beam signal in accordance with the determined target frequency hypothesis.

22. The instructions are sent by the processor to the device:

22. The apparatus of claim 16, further executable to determine a target modulation scheme hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to cause the apparatus to evaluate the target spot beam signal in accordance with the determined target modulation scheme hypothesis.

23. The instructions are sent by the processor to the device: The apparatus of any one of claims 16 to 22, further executable to determine a target symbol rate hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to cause the apparatus to evaluate the target spot beam signal in accordance with the determined target symbol rate hypothesis.

24. The instructions are sent by the processor to the device: An apparatus as described in any one of claims 16 to 23, further executable to determine a target identifier hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to cause the apparatus to evaluate the target spot beam signal in accordance with the determined target identifier hypothesis.

25. The instructions are sent by the processor to the device: determining, based at least in part on an evaluation of the target spot beam signal indicating an absence of the target signal, to search for the target signal from a second location within the service coverage area (310) during the first time window within the period; processing the stored plurality of feed element signals (435) during the first time window according to a third beamforming configuration to generate a second target spot beam signal corresponding to the second location; evaluating the second target spot beam signal for the presence of the target signal. It is further possible to The device of any one of claims 16 to 24, wherein the third beamforming configuration is used to generate the second target spot beam signal for searching for the target signal after the first beamforming configuration.

26. The instructions to process according to the second beamforming configuration may be sent by the processor to the device: causing the stored feed element signals to be processed according to a target spot beam that is distinct from each of the spot beams associated with the first beamforming configuration. The apparatus according to any one of claims 16 to 25, wherein the apparatus is operable to:

27. 27. The apparatus of claim 16, wherein the instructions for processing the stored plurality of feed element signals (435) according to the second beamforming configuration are executable by the processor to cause the apparatus to process at a ground segment (102).

28. 28. The apparatus of claim 16, wherein the instructions for receiving the plurality of feed element signals (405) are executable by the processor to cause the apparatus to receive the plurality of feed element signals (405) at a plurality of ground stations of a ground segment (102).

29. The apparatus of any one of claims 16 to 28, wherein the apparatus is a ground segment component of a satellite communication system (100).

30. The device according to any one of claims 16 to 26, wherein the device is a satellite (120) of a satellite communication system (100).

31. A non-transitory computer readable medium storing code, the code including instructions for executing, by a processor: receiving a plurality of feed element signals (405), where each of the plurality of feed element signals corresponds to a respective one of a plurality of feed elements (128) of a feed array (127) of an antenna (121) having a service coverage area (310); processing the received feed element signals (405) according to a first beamforming configuration associated with a plurality of spot beams (125) to generate one or more spot beam signals each corresponding to a respective spot beam (125) of the antenna (121), wherein the one or more spot beam signals include communications scheduled for transmission via each of the plurality of spot beams (125); storing the received feed element signals (405) over a period of time; determining to search for a target signal from a location within the service coverage area (310) during a first time window within the period; processing the stored plurality of feed element signals (435) during the first time window according to a second beamforming configuration to generate a target spot beam signal corresponding to the location; Evaluate the target spot beam signal for the presence of the target signal It is possible to do so, the first beamforming configuration is used to form the plurality of spot beams (125), each configured to support a communication service within a spot beam coverage area; The second beamforming configuration is used to generate the target spot beam signal searching for the target signal after the first beamforming configuration.

32. The instructions are further configured to: determining a path hypothesis for a device associated with the target signal; determining the location based at least in part on the route hypotheses for the device; 32. The non-transitory computer-readable medium of claim 31 , further operable to:

33. The instructions are further configured to: determining to search for the target signal from a second location within the service coverage area (310) over a second time window within the period based at least in part on the route hypothesis for the device; processing the stored plurality of feed element signals (435) during the second time window according to a fourth beamforming configuration to generate a third target spot beam signal corresponding to the second location; Evaluating the third target spot beam signal for the presence of the target signal. It is further possible to 33. The non-transitory computer-readable medium of claim 32, wherein the fourth beamforming configuration is used to generate the third target spot beam signal searching for the target signal after the first beamforming configuration.

34. The instructions are further configured to: receiving a second plurality of feed element signals (405), where each of the second plurality of feed element signals corresponds to a respective one of a second plurality of feed elements (128) of a feed array (127) of a second antenna (121) having a second service coverage area (310); storing the received second plurality of feed element signals (405) for a second period of time; It is further possible to The instructions for generating the target spot beam signal corresponding to the location are executable by the processor to process the stored second plurality of feed element signals (435) during the first time window according to a third beamforming configuration; 34. The non-transitory computer-readable medium of claim 31, wherein the third beamforming configuration is used to generate the target spot beam signal for searching for the target signal after the first beamforming configuration.

35. The instructions to store the received feed element signals (405) include, by the processor: Oversampling the received feed element signals (405) relative to a bandwidth of the received feed element signals (405). The non-transitory computer-readable medium of any one of claims 31 to 34, operable to:

36. The instructions are further configured to: A non-transitory computer readable medium as described in any one of claims 31 to 35, further executable to determine a target frequency hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to evaluate the target spot beam signal in accordance with the determined target frequency hypothesis.

37. The instructions are further configured to:

37. A non-transitory computer readable medium as claimed in any one of claims 31 to 36, further executable to determine a target modulation scheme hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to evaluate the target spot beam signal according to the determined target modulation scheme hypothesis.

38. The instructions are further configured to: A non-transitory computer readable medium as described in any one of claims 31 to 37, further executable to determine a target symbol rate hypothesis for the target signal, and wherein the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to evaluate the target spot beam signal in accordance with the determined target symbol rate hypothesis.

39. The instructions are further configured to: A non-transitory computer readable medium as described in any one of claims 31 to 38, further executable to determine a target identifier hypothesis for the target signal, and the instructions for evaluating the target spot beam signal for the presence of the target signal are executable by the processor to evaluate the target spot beam signal in accordance with the determined target identifier hypothesis.

40. The instructions are further configured to: determining to search for the target signal from a second location within the service coverage area (310) during the first time window within the time period based at least in part on evaluating the target spot beam signal indicating an absence of the target signal; processing the stored plurality of feed element signals (435) during the first time window according to a third beamforming configuration to generate a second target spot beam signal corresponding to the second location; Evaluating the second target spot beam signal for the presence of the target signal. It is further possible to 40. The non-transitory computer-readable medium of any one of claims 31 to 39, wherein the third beamforming configuration is used to generate the second target spot beam signal that searches for the target signal after the first beamforming configuration.

41. The instructions to process in accordance with the second beamforming configuration may include, by the processor: Processing the stored feed element signals according to a target spot beam distinct from each of the spot beams associated with the first beamforming configuration. The non-transitory computer-readable medium of any one of claims 31 to 40, operable to:

42. The non-transitory computer readable medium of any one of claims 31 to 41, wherein the instructions are executable by the processor of a ground segment (102) of a satellite communications system (100).

43. The non-transitory computer readable medium of any one of claims 31 to 41, wherein the instructions are executable by a processor of a satellite (120) of a satellite communications system (100).

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