IL301899A - RF Systems for Flying Vehicles - Google Patents

Description

SYSTEMS FOR ELECTRONIC WARFARE AND COMMUNICATION FIELD OF THE INVENTION The present disclosure is in the field of satellite communication and signaling.

BACKGROUND OF THE INVENTION Miniature satellites are satellites of low mass and size, usually under 500 kg. Reducing satellite size and mass can provide various advantages including reduced costs, which are achieved thanks to cheaper design and manufacturing and the launch of many satellites in one launcher to form a constellation of satellites. These satellites may be used, for example, as low earth orbit (LEO) satellites and may be applied in many systems and methods. SUMMARY OF THE INVENTIONAn aspect of the present disclosure concerns a flying object, e.g. a low earth orbit (LEO) satellite that is configured to transmit a desired RF signal at a desired geographical area and at desired time. This can be applied to disrupt detection of radars, e.g. ground/air radars or self-navigating ammunitions that comprise radars. Therefore, an aspect of the present disclosure provides a flying object. The flying object includes an electromagnetic signal receiver configured to receive operational data carried by the electromagnetic signal. The operational data comprises data indicative of (i) time of interest, (ii) geographical area of interest and (iii) characteristics of RF signal of interest. In other words, the operational data comprises data for executing an RF signal pattern at a desired geographical coverage at a desired time. The time of interest can be a real-time indication, namely a demand for executing the desired RF signal immediately. In some other embodiments, the time of interest may be an expected time, namely an absolute time, e.g. an hour, or a demand to execute the signal at a time-delayed indication, e.g. in a minute, an hour, etc. A control unit of the flying object is configured and operable for receiving the operational data and generate signal execution data based thereon.

An RF transmitter of the flying object is configured to receive the signal execution data and transmit an action RF signal based thereon that has the characteristics of the RF signal of interest, such that the action RF signal passes through at least of a portion of said geographical area of interest at the time of interest. The signal can pass through the area in various orientations, e.g. incident angles and/or polarizations. In some embodiments the flying object is being a satellite, an airborne vehicle or an air ammunition. In some embodiments, the satellite is a LEO satellite. In some embodiments of the flying object, the control unit is configured and operable to generate trajectory data based on the operational data. The trajectory data is configured to be received by a navigation unit comprised within the high-altitude flying object, and the navigation unit navigates the high-altitude flying object based on the navigation data to bring the high-altitude flying object to a position which the desired action RF signal can be executed and pass through the desired geographical area at the desired time. In some embodiments of the flying object, the data indicative of the time of interest comprises a starting time and an ending time, namely a time period for executing the desired action RF signal. During this time period, the RF signal may be transmitted continuously or periodically, e.g. every 10, 50 or 100 millisecond. In some embodiments of the system, the data indicative of the geographical area comprises at least a 2-dimensional area. The 2-dimensional area may be a plane through which the action RF signal passes through at the desired time. In some embodiments the geographical area may be a 3-dimensional area and the requirement on the RF signal may be such that it needs to pass at least a predetermined distance at the 3-dimenstional area. In some embodiments of the flying object, the data indicative of the RF signal of interest comprises at least one of one or more frequencies, intensity and polarization. In some embodiments of the flying object, the action RF signal is characterized by one or more frequency bands and/or polarization and other signal characteristics matching to at least one second signal that is identified in said geographical area. The second signal may be a signal of ground, aircraft or ammunition radar. In other words, the action signal is configured to mimic signals of radars in the geographical area of interest to interrupt their functionality.

In some embodiments of the flying object, the second signal is identified by a signal identifier unit configured to identify electromagnetic signals from said geographical area. In some embodiments of the system, the action RF signal is characterized by one or more frequency bands matching to an electromagnetic background noise of said geographical area. The background noise may be derived from a terrestrial, or man-made electromagnetic noise. In some embodiments of the flying object the electromagnetic background noise is identified by a signal identifier unit that is configured to identify electromagnetic signals from said geographical area. It may be desired to transmit the action RF signal for a long period of time. This may require a plurality of high-altitude flying objects that work together to execute a continuous action RF signal for the desired time. Therefore, an aspect of the present disclosure provides a constellation comprising one or more high-altitude flying objects of the present disclosure. In some embodiments, the action RF signal is configured to have corresponding characteristics to an interrogating signal of a defense system in said geographical area for blocking or jamming said defense system. In other words, the action RF signal is configured to be transmitted towards the defense system such that it appears as false target(s). In some embodiments, the action RF signal is configured to trigger operation of a defense system by having characteristics of electromagnetic signal of threats or targets of the defense system. For example, the action RF signal may appear to the defense system as an air combat fighter that may result in triggering irradiation of electromagnetic radiation of the defense system, as part of its defense mechanism, and eventually the defense system is being revealed. In some embodiments, the action RF signal is configured to disrupt operation of enemy's air ammunition. The action RF signal may have characteristics of operative signals of a missile, e.g. a semi-active missile, and the action RF signal may appear to the missile as its own directing signal and as a result thereof the air ammunition is diverted from its original target, which may be a friendly flying object, e.g. an aircraft. Thus, in some embodiments, the action RF signal is characterized by matching properties of that operating the enemy's air ammunition, e.g. a semi-active radar homing based missile (or abbreviated as semi-active missile).

A plurality of any one of the embodiments of the flying objects described above may be operated in a constellation, in which all the flying objects operate in synchronization with one another. Another aspect of the present disclosure provides a system for locating an object, e.g. an airborne vehicle, a flying missile, etc. The system may be a ground or an airborne system installed in an aircraft, air ammunition, a satellite, etc. The location of the object is determined by receiving a first signal originated in a transmitting source. The first signal is a direct signal from the source that is received in the system and indicating a start of time frame for receiving relevant signals that are indicative of a location of the object. A second signal that hits the object, reflects towards the system, and received thereby. The reception of the second signal by the system indicates that there is an object/target at the direction from which the second signal is received. By knowing the source location and the time differences between the reception of the first and second signals, a more accurate location may be derived. To avoid false detection of static object, the system filters out signals that are below a threshold of a Doppler shift with respect to the first signal. In other words, objects with a certain radial velocity with respect to the signal of the source are being detected and their location is determined. Therefore, this aspect of the present disclosure provides a system for locating a position of an object. The system includes an RF receiving unit configured to receive a first and second signals of a predetermined RF frequency band and generate a first and second signal data, respectively, based thereon. The first and second signals data are indicative of at least the direction of at least one of the signals, wherein the first and second signal originated by a single source. A control unit configured to (i) receive the first and second signal data, (ii) extract reception direction of the first and second signals from the first and second signal data, and (iii) generate location data indicative of the location of the object. In some embodiments of the system, the first signal is a direct transmission of an RF signal from a transmitting source, which may be a high-altitude flying object, e.g. a satellite or more specifically, a LEO satellite.

In some embodiments of the system, the second signal is a reflection of the signal from the object. Namely, the second signal first hits the object and a portion of the reflection of the signal is receive by the system and being the second signal. In some embodiments of the system, the first and second signal data comprises data indicative of reception time, and the control unit is configured to extract reception time stamps of the reception time of the first and second signal. Based on at least one of (i) relation between the reception time stamps, and (ii) relation between the reception directions of the first and second signals, the control unit generates the location data, which is indicative of the location of the object. In some embodiments of the system, the second signal is characterized by a Doppler shift of a predetermined threshold with respect to the first signal. In some embodiments, the system comprises two or more RF receiving units, and the location data generated by the control unit is indicative of 3-dimensional location of the object. In some embodiments, the flying object, in which the system is installed, is an airborne vehicle or an air ammunition. There also may be a constellation of two or more flying objects comprising the system for locating a position of an object as described above. Another aspect of the present disclosure provides a system for locating a position of an object, wherein the system is being installed in a flying object. The system includes an RF receiving unit configured to receive an electromagnetic signal of a predetermined RF frequency band and generate a signal data based thereon, being indicative of location of at least one of the signals; a control unit configured to analyze the signal data and generate location data indicative of the location of the object. In some embodiments, the electromagnetic signal is a reflected signal from the object. In some embodiments, the flying object is an airborne vehicle or an air ammunition. There is also provided a constellation of two or more flying objects comprising the system for locating a position of an object as described above. In some embodiments of the constellation, at least one of the flying objects is configured to receive the location data generated by the system of one or more of the other flying objects, the control unit of the at least one of the flying objects is configured for processing all the location data to obtain the location of the object. In some embodiments of the constellation, the processing of the control unit comprises the use of Time of Arrival techniques, Differential Time of Arrival techniques or Differential Doppler techniques. Another aspect of the present disclosure provides a system for determining location of a flying object. The system is configured as a multi-static array in which there are a plurality of RF emitting sources and a single receiving unit that may be installed in a flying object, e.g. an airborne vehicle, or an air ammunition. The receiving unit is configured to receive reflecting signals of the emitting sources from the object and determine its location based thereon. Therefore, the present disclosure provides a system for determining location of an object. The system includes an RF receiving unit configured to receive two or more different and discernable interrogating electromagnetic signals, each signal is originated from a different emitting source, and generate a signal data corresponding to each received electromagnetic signal. The signal data is indicative of at least one of (i) a time of arrival of the signal, (ii) the frequency shift of the signal with respect to the original emitted signal from the emitter and (iii) a receiving direction from which the signal is received by the RF receiving unit. A control unit of the system is configured to process all signal data and determine the location of the object based thereon. In some embodiments, the RF receiving unit is configured to receive three or more different interrogating electromagnetic signals, which are sufficient to determine an accurate 3-dimensional location of the flying object. In some embodiments, the system is being installed in a flying object, wherein the flying object may be an airborne vehicle or an air ammunition. In some embodiments, the two or more interrogating electromagnetic signals are reflections from the object. In some embodiments, the RF receiving unit if further configured to receive direct transmission of interrogating signals that are transmitted from the emitting sources, and the control unit is configured to generate corresponding signal data based on the direct interrogating signals. By receiving a direct transmission and a reflected transmission from a single emitting source, the control unit may be configured to determine the difference in the time of arrival of these two signals and determine based thereon data that is indicative of the location of the flying object. In some embodiments, the interrogating signals are time synchronized, namely the signals are being emitted from the emitting source at the same time. The control unit is configured to determine the location based thereon. In some embodiments, the emitting sources are a friendly Low Earth Orbit (LEO) satellite, an airborne vehicle or air ammunition which are synchronized with the system, e.g. time synchronized. In some embodiments, the control unit is configured to analyze the signal data and to determine the self-position of the system based thereon. Based on the signal data, the real-time position of the system may be determine which may be facilitate the determination of the position of the flying object. In some embodiments, the control unit is configured to process the signal data by using at least one of Time of Arrival techniques, Differential Time of Arrival techniques or Differential Doppler techniques. Another aspect of the present disclosure provides a Low Earth Orbit (LEO) satellite configured for communication with airborne objects, the satellite comprising: a control unit configured to receive operational data indicative of location of at least one airborne object with respect to a target and generate execution data based thereon; a transmitting unit configured to receive the execution data and to transmit an execution signal, based on the execution data, to the at least one airborne object. In addition to the above features, the method according to this aspect of the present disclosure can include one or more of features (xix) to (xxiv) listed below, in any desired combination or permutation which is technically possible: (xix) the execution signal is indicative of at least a trajectory plan of the at least one airborne object to be executed thereby. (xx) the execution signal is indicative of at least one of a location of the at least one airborne object, a velocity of the at least one airborne object, a desired destination of the at least one airborne object, a desired heading of the at least one airborne object. (xxi) the receiving of the operational data being from an external source. (xxii) a total time interval from the receiving of the operational data being from the external source to arrival of the first communication information at the at least one airborne object being less than 50 milliseconds. (xxiii) the at least one airborne object is one of an airplane, an Unmanned Aerial Vehicle (UAV) and a missile. (xxiv) the target being at least one of a ground target, a sea target and an air target. Another aspect of the present disclosure concerns a system configured for artificially increasing the thermal noise of a detecting defense system. In other words, the system is configured to transmit signal profile such that over time the signals are detected by the defense system and appears as an inherent thermal noise, which may result in a decrease of its range of detection. For obtaining this result, the system is configured to emit signal profile that appears in the defense system over time as a constant, relatively low, signal. Thus, towards the main lobe of the defense system, a relatively low signal is transmitted and towards the side lobes of the defense system, a relatively high signal is transmitted. Thus, the present disclosure provides a system that is being installed in a flying object. The system comprises an RF receiving unit configured to receive interrogating electromagnetic signals of an emitting source. The system further includes a control unit configured and operable for (i) analyzing said electromagnetic signals to identify their intensity profile; and (ii) generate signal execution data based thereon. An RF transmitter of the system is configured to receive the signal execution data and transmit action RF signals based thereon. The action RF signals are characterized by (a) that at least a portion thereof is directed to the source of the interrogating electromagnetic signal, e.g. a defense system, and (b) having a corresponding profile to the identified intensity profile, wherein the corresponding profile is such that facilitate that the action RF signals appear in the defense system as a thermal noise. In some embodiments, the interrogating electromagnetic signals are radar RF signals emitted from a defense system. In some embodiments of the system, the control unit is further configured to identify the direction of the emitting source. Namely, the location of the emitting source is identified and the action RF signal is being directed towards the emitting source based thereon. In some embodiments, the intensity profile corresponds to the state of the emitting source with respect to the flying object. The state of the emitting source indicates the relation between its main lobe and the flying object, namely whether the main lobe faces to the flying object or whether its side lobes. This is important for determining the intensity of the signal to be transmitted by the system. Towards the main lobe a low intensity signal is transmitted and towards the side lobes a relatively high intensity signal is transmitted. Therefore, in some embodiments, the action RF signals are inversed proportioned with respect to the intensity of the interrogating signals. In some embodiments, the high-altitude flying object is being a Low Earth Orbit (LEO) satellite, an unmanned aerial vehicle, an airborne vehicle or an air ammunition. In some embodiments, the action RF signals are configured to appear as a thermal noise in the emitting source. In some embodiments, the systems are configured to facilitate reducing detection capabilities of enemy's detection system. There is also provided a constellation comprising two or more flying objects comprising the systems for increasing the noise levels of an enemy's defense system as described above. In some embodiments, the two or more flying objects of the constellation are configured for synchronizing the execution of the action RF signals to obtain a desired continues transmission of action RF signals for a predetermined period of time. In other words, the flying objects may be synchronized such that when the first seizes from transmitting an action RF signal, the second immediately initiate the transmission of an action RF signal such that it appears in the enemy's defense system as a single continuous signal. Another aspect of the present disclosure concerns a system for directing or homing a friendly air ammunition to a target, e.g. a static ground target or a moving air target. The system is configured to transmit operating signals from an operating unit at one side to an air ammunition at the other side, wherein there is no direct line of sight between the operating unit and the air ammunition.

Therefore, the present disclosure provides a system for directing an air ammunition to a target. The system includes a first communication unit, being installed on a first flying object. The firs communication unit comprises an RF receiving unit configured to receive operative signals indicative operative commands of the air ammunition and generate transmission data based thereon. The communication unit further comprises an RF transmitting unit configured for transmitting said transmission data to the air ammunition. In some embodiments, the first flying object is a satellite, e.g. a LEO satellite, an airborne aircraft or an air ammunition. In some embodiments, the system further includes an operating unit configured for at least one of (i) detecting the target's real-time location and transmit operating signal indicative thereof; and (ii) transmitting operating signal of operative commands indicative of desired trajectory of the air ammunition. In some embodiments, the system includes the air ammunition that is being directed, wherein the air ammunition is configured to receive the transmission data and navigate to the target in response to the transmission data. In some embodiments, the process of directing the air ammunition is less than milliseconds. Namely, the process from the transmission of the operating signals until the reception of the transmission data in the air ammunition is less than milliseconds. In some embodiments, the first communication unit transmits in a frequency-hopping spread spectrum technique. In some embodiments, a second communication unit is installed in a second flying object. The second communication unit comprises an RF receiving unit configured to receive operating signals indicative of the air ammunition trajectory and generate transmission data based thereon, and an RF transmitting unit configured for transmitting said transmission data to the first communication unit. In some embodiments, the second flying object is a satellite, e.g. a LEO satellite, an airborne aircraft or an air ammunition. BRIEF DESCRIPTION OF THE DRAWINGSIn order to understand the invention and to see how it may be carried out in practice, some specific embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of a non-limiting example of an embodiment of a system for artificially increase the thermal noise of an enemy's defense system according to an aspect of the present disclosure; Fig. 2 is a block diagram of a non-limiting example of a constellation of satellite as described in the embodiment of Fig. 1 according to an aspect of the present disclosure. Figs. 3A-3B are block diagrams of non-limiting examples of different embodiments of a high-altitude flying object of the present disclosure. Fig. 4 is a block diagram of a non-limiting example of a constellation comprising a plurality of satellites according to an aspect of the present disclosure. Figs. 5A-5Bare block diagrams of non-limiting examples of embodiments of a system for determining the location of an object according to an aspect of the present disclosure. Fig. 6,is a generalized illustration of a satellite capable of transmitting a signal, according to examples of the presently disclosed subject matter. Fig. 7is a block diagram of a non-limiting example of an embodiment of a system for determining the location of a flying object according to an aspect of the present disclosure. Figs. 8A-8Bare block diagrams of non-limiting examples of embodiments of a system for directing an air ammunition according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE INVENTIONAs used herein, the phrase "for example," "such as" and variants thereof describing exemplary implementations of the present invention are exemplary in nature and not limiting. As used herein the terms "one or more" and "at least one" aim to include one as well any number greater than one e.g. two, three, four, etc. The term "airborne vehicle" throughout the application refers to any flying vehicle such as any kind of aircraft, manned or unmanned. The term "air ammunition" throughout the application refers to any flying ammunition, namely ground-to-ground, ground-to-air, air-to-air and air-to-ground ammunition that propagates through the air to reach the target from it launching location.

When referring to a satellite throughout the application, it should be understood as a Low Earth Orbit (LEO) satellite. The term "defense system" throughout the application refers to any defense system that includes an RF emitting unit for the operation thereof. The term "coupled" throughout the application refers to any connection of data between two components, namely a one/two ways of exchange of data. The connection may be physically, e.g. wired connection, or a wireless connection. In the application, when it is referred to a system that includes a control unit that is coupled/in data communication with another component, e.g. an RF transmitter, it is to be noted that the operation of the control unit may be divided between an independent control unit and a local control unit of the component. Therefore, the control unit of a system refers to a general entity that is capable of performing processing of data and controlling components of a system. Furthermore, it is to be noted that a system with a separate RF transmitter and receiver may be also realized with a transceiver. It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. While the invention has been shown and described with respect to particular embodiments, it is not thus limited. Figs. 1-7illustrate a schematic of the system architecture in accordance with embodiments of the invention. Elements in Figs. 1-7 can be made up of any combination of software and hardware and/or firmware that performs the functions as defined and explained herein. According to other examples of the presently disclosed subject matter, the system may comprise fewer, more and or different elements than those shown in Figs. 1-7 . Fig. 1is a block diagram of a non-limiting example of an embodiment of a flying object, e.g. a satellite, according to an aspect of the present disclosure. The satellite 150has an RF receiving unit 152that is configured to detect emitted signals, namely interrogating electromagnetic signals IES of an emitting defense system 151of an enemy. The defense system may be radar-based detection system for detecting flying objects that emits electromagnetic signals and detecting their reflections.

The RF receiving unit 152 generates received signal data RSD and communicate it to a control unit 154that is configured to process the received signal data RSDto identify the characteristics of the interrogating electromagnetic signals IESthat are emitted from the defense system 151 . The control unit 154is configured to identify one or more of the frequency of the signals, their intensity and polarization. By identifying these characteristics over time, a real-time state of the defense system 151may be determined, namely its scanning heading position. In other words, by identifying the real-time characteristics of the signals, the control unit may determine the direction to which the main and side lobes and of the defense system 151 are directed. Based on the process of the received signal data RSD , the control unit is configured to generate signal execution data SEDthat is indicative of the desired signal to be executed towards the defense system 151 such that the signal that is being transmitted is considered by the defense system 151as noise, e.g. thermal noise that is higher than the standard noise without the emission of such signal. Therefore, when the signal is executed towards the main lobe of the defense system 151 , the signal has a relatively low intensity, and when the signal is executed towards the side lobes of the defense system 151 , the signal has a relatively high intensity. By applying this signal profile, the defense system 151receives a constant signal over time, irrespective to where it is facing. This constant signal appears to the defense system 151as thermal noise and its detection threshold of targets rises, namely the detection of targets occurs in a shorter range. An RF transmitting unit 158is configured to receive the signal execution data SED from the control unit 154 and transmit an action RF signal AS based thereon towards the defense system 151 . Fig. 2 is a block diagram of a non-limiting example of a constellation of satellites similar to the one exemplified in Fig. 1 . The constellation 190of satellites 150A, 150Band 150C(the number of satellites is not limited to three and can be a great number according to the desired application) are controlled by a centralized control system 192 that is configured to plan such that a continuous signal is transmitted towards the defense system, which may be each moment from a different satellite to artificially increase the thermal noise of the defense system. Reference is now being made to Fig. 6,showing a generalized illustration of a satellite capable of transmitting a signal, according to examples of the presently disclosed subject matter. In some examples, a Low Earth Orbit (LEO) satellite 605 is configured for communication with airborne objects. Such a satellite includes, in some examples, a control unit 615 configured to receive operational data indicative of location of one or more airborne objects 645 with respect to a target and generate execution data based thereon. The satellite may also include a transmitting unit 6configured to receive the execution data and to transmit an execution signal, based on the execution data, to the airborne object. Non-limiting examples of the airborne object 645 are an airplane, an Unmanned Aerial Vehicle (UAV) and a missile. In some examples, the execution signal is indicative of at least a trajectory plan of the airborne object 645, to be executed thereby. In some examples, the execution signal is indicative of at least one of: the location of the airborne object 645, the velocity of the airborne object, the desired destination of the airborne object, the desired heading of the airborne object. In some examples, the communications system of the satellite is further configured to receiving of the operational data being from an external source 635. This external source could be, for example, a ground station. The transmission from the satellite 605 to the airborne object 645 may be done in near-real time, in some examples. In some examples, communication from an LEO satellite to the airborne object is fast enough, such that the total time interval from receiving of the operational data being from the external source 635, to arrival of the first communication information at airborne object 645, are less than 80 milliseconds (ms). In some examples, this time interval is less than 60 ms. In some examples, this time interval is less than 50 ms. On example scenario is that on-board spatial positioning systems of the airborne object are not functioning properly, and thus the object does not know its position/location nor its heading. Similarly, in some cases communication from a ground station to the airborne object has been lost, and the airborne object does not know its updated flight destination. Fig. 3A-3B are block diagrams of non-limiting examples of different embodiments of a flying object, e.g. a satellite, which is configured to carry out an aspect of the present disclosure. Fig. 3A shows a satellite 350 , typically a LEO satellite that has a receiver 352for receiving electromagnetic signal. The receiver is configured to receive an operational data ODthat is carried by an electromagnetic signal ES that is transmitted from an external system 356 , e.g. a centralized ground control unit that plans a mission and desires to use the operational means that may be provided by the satellite. The operational data ODcomprises data indicative of (i) time of interest, (ii) geographical area of interest and (iii) RF signal of interest and is communicated to a control unit 354 , which generates signal execution data SED based on the operation data OD . The signal execution data SEDis communicated to an RF transmitter 358 which executes the signal execution data SEDto generate an action RF signal ARSthat is transmitted to pass through at least a portion of an area of interest 360 . The action RF signal may serve several operational needs, for example: 1. Blocking or jamming an enemy's defense system, e.g. a radar, at a predetermined sequence, which may characterized by a periodical or non-periodical profile. Since this RF signal is transmitted from a satellite, which is beyond the range of detection of the defense system, no target is being detected by the enemy from the jamming direction, even with the assistance of other detection systems that are not jammed or blocked. Therefore, the credibility of the detection of the defense system may decrease in time that may result in operative advantage. 2. Disrupting operation of air ammunition, specifically semi-active missiles. By transmitting a matching signal to that of the missile or its homing system, the missile can be diverted from its planned trajectory towards a friendly flying object and miss its target. 3. Transmitting a triggering signal towards a defense system, or estimated location thereof, that is under a secrecy state, e.g. camouflaged or is in a passive-none transmitting state, which imitates a hostile transmission towards the defense system. This hostile transmission may trigger the defense system to activate its defense systems and irradiate electromagnetic signals that reveal its true identity and/or location.

Fig. 3Bdiffers from Fig. 3Aby showing that the satellite 350further includes a navigation unit 362 that is configured to navigate the satellite to a desired trajectory. The control unit 354 is configured to analyze the operational data and generate a navigation data ND indicative of a desired trajectory of the satellite. The navigation data NDis communicated to the navigation unit 362to navigate the satellite such that the RF action signal ARSis transmitted to the area of interest 360at the desired time frame.

Furthermore, an optional signal identifier 364 may identify the signals of interest in the area of interest 360 , such that the operational data ODis generated based on data that is derived from the signal identifier 364 . The signal identifier 364may identify signal of radars that are operative within the area 360 , e.g. ground or airborne radars, or signals of electromagnetic background noise. For example, the desired signal may be an amplification of the electromagnetic background noise such it raises the threshold of detection of targets of radars in the area of interest. Fig. 4 is a block diagram of a non-limiting example of a constellation comprising a plurality of satellites of this aspect of the present disclosure. The constellation 365includes satellites 350A, 350B, 350C, 350D … which are operated together to support a relatively long period of transmitting time of the desired signal. Figs. 5A-5Bare block diagrams of non-limiting examples of embodiments of a system for determining the location of an object, which is another aspect of the present disclosure. The system 370includes RF receiving units 372i(where i=the number of receiving units) configured to receive signals of a predetermined frequency band. The frequency band is determined based on the transmission frequency band of a transmitting source 376 , such that the transmitting signals of the source 376 are receivable by the RF receiving units 372i . Therefore, the receiving units 372i are configured to receive a first signal, which is a direct signal DSithat is derived from the source 376 . This signal is received first in the RF receiving unit 372and the signals that are received after the direct signal DSiare suspected to be related to an object. Thus, a second signal that is received in the RF receiving units 372iis recognized as being a reflected signal RSithat is derived from an object 378 . The RF receiving unit 372may include a Doppler filter 380that filters out signals with a low Doppler shift which are correlated with static elements, which are of low or no interest. The RF receiving units 372i generates direct signal data DSDi and reflected signal data RSDi based on the reception of the direct signal DSiand the reflected signal RSi , respectively. The direct signal data DSDiand reflected signal data RSDiare communicated to a control unit 374that extracts reception direction of the direct signal DSiand reflected signal RSifrom the signal data DSDi and reflected signal data RSDi , and generate location data indicative of the location of the object based thereon. The signal data DSDiand reflected signal data RSDimay carry data indicative of reception time of the signals. In some embodiments, the control unit 374 is configured to extract reception time stamps of the direct signal DSiand reflected signal RSi . Based on at least one of (i) relation between the reception time stamps, and (ii) relation between the reception directions of the first and second signals, the control unit 374 generates the location data that is indicative of the location of the object. The location data LDmay be transmitted to other external systems 382 . The control unit 374may use one of the following techniques for determining the location data: • Time of Arrival; • Differential Time of Arrival; or • Differential Doppler techniques.

Fig. 5Bdiffers from Fig. 5Aby that the system 370is configured to determine the location of the object only based on the reflected signals RSi from the object. By using sufficient number of receiving units 372i , a 3-dimensional location of the object 378may be determined, typically 3 or 4 and above. It is to be noted that the receiving units 372i in both Figs. 5A-5B , are embedded on different platforms, namely different flying objects. The receiving unit may be installed in an airborne vehicle or an air ammunition. It is to be noted that the receiving units 372i in both Figs. 5A-5B , Reference is now made to Figs. 7A-7B , which are block diagrams of non-limiting examples of an antenna made of pliable material. Fig. 7Ashows an antenna 790that is formed of a pliable material 792 , which functions as a substrate that carries a conductive material 794printed thereon. The conductive material 794is printed in a desired pattern on the pliable material to form the antenna element(s) capable of transmitting/receiving electromagnetic signals. The pliable material 792is configured to be deployed from a first, non-deployed state, to a second, deployed state. Once deployed, the pliable material 792 , together with the conductive material 794printed thereon, from an antenna that is configured to transmit and/or receive electromagnetic signals. For example, at the first state, the pliable material is folded to a compact formation, e.g. during a launch of a satellite. Once the satellite reaches to a certain position of its trajectory, the pliable material is unfolded to form the antenna.

Claims (10)

1.CLAIMS: 1. A system for directing an air ammunition to a target, the system comprising: a first communication unit, being installed on a first flying object, that comprises an RF receiving unit configured to receive operating signals indicative of operative commands for the air ammunition and generate transmission data based thereon, and an RF transmitting unit configured for transmitting said transmission data to the air ammunition.

2. The system of claim 1, wherein the first flying object is a satellite, an airborne aircraft or an air ammunition.

3. The system of claim 1 or 2, wherein the first flying object is a low earth orbit satellite.

4. The system of any one of claim 1-3, comprising an operating unit configured for at least one of (i) detecting the target's real-time location and transmit the operating signal indicative thereof; and (ii) transmitting operating signal of operative commands indicative of desired trajectory of the air ammunition.

5. The system of any one of claims 1-4, comprising the air ammunition, wherein the air ammunition is configured to receive the transmission data and navigate to the target in response to said transmission data.

6. The system of any one of claims 1-5, wherein the process of directing the air ammunition is less than 50 milliseconds.

7. The system of any one of claims 1-6, wherein the first communication unit transmits in a frequency-hopping spread spectrum technique.

8. The system of any one of claims 1-7, comprising a second communication unit being installed on a second flying object, wherein the second communication unit comprises an RF receiving unit configured to receive operating signals indicative of operative commands of the air ammunition and generate transmission data based thereon, and an RF transmitting unit configured for transmitting said transmission data to the first communication unit.

9. The system of claim 8, wherein the second flying object is a satellite, an airborne aircraft or an air ammunition.

10. The system of claim 8 or 9, wherein the second flying object is a low earth orbit satellite.