Patent Description:
Radars are known in the art and are employed to detect targets and provide information relating to the position thereof. Reference is now made to <FIG>, which is a schematic illustration of a scenario generally reference <NUM> which is known in the art, of a vehicle <NUM>, such as an aircraft, moving along a trajectory <NUM>. Trajectory <NUM> may be defined within a three-dimensional (3D) coordinate system <NUM>. The term 'trajectory' relates herein at least to a path of aircraft <NUM>, the velocities and accelerations of aircraft <NUM> over time. A radar <NUM> located on the ground (e.g., the XY plane of coordinate system <NUM>) detects aircraft <NUM> and provides information relating to the position of aircraft <NUM>. Typically, radar <NUM> provides the information relating to the position of aircraft <NUM> in terms of an azimuth, φ, relative to a reference direction <NUM> (e.g., the north), an elevation, ϕ, relative to a reference plane (e.g., the XY plane of coordinate system <NUM>) and the range, R, from radar <NUM>. The projection of the range, R, on the XY plane of coordinate system <NUM> is referred to herein as R'.

Training a radar operator or calibrating a radar requires simulating a target. Known in the art techniques for simulating a target of a radar such as radar <NUM> includes moving a mock vehicle (e.g., a drone, a pulled glider) in the actual trajectory being simulated. Alternatively, a stationary transceiver or transceivers are placed around the radar at known locations relative to the radar. Such a transceiver receives the radar signal, delays the signal at a delay corresponding to the distance of the simulated target from the radar and transmits the delayed signal.

According to another known in the art technique, an RF target simulator is connected instead of the radar antenna. Such an RF target simulator receives from the radar transmitter the transmitted radar signal as well as the radar beam direction. The RF target simulator generates an RF signal simulating a return signal from a target at a simulated direction and distance. The radar receiver receives this simulated RF signal and displays a representation of the target on the radar display. According to a further known in the art technique for training a radar operator is generating a computer simulation of targets on a display.

Patent No. <CIT>entitled "Methods and Systems for Generating Virtual Radar Targets" directs to a system and method, which employs reflections from a radome encasing the radar antenna. The system directed to by Sarafian, incudes a transceiver, located within the radome, which receives reflections from the radome. The transceiver re-transmits a signal toward the radome, at a delay corresponding to the simulated distance. The re-transmitted signal is reflected from the radome back toward the radar antenna.

Patent Application Publication No. <CIT>, directs to a target simulation device which includes a vertical antenna array positioned on or near a radar. The simulation device transmits signals, in response to received signals from the radar, that simulate a reflection signal of one or more targets of particular azimuths, elevations and distances. The simulation device can be rotated about the radar to simulate the azimuth of a target. The simulation device controls transmission from the vertical antenna array to simulating the elevation of the target, based on the received signal from the radar. The simulation device controls the delay of the transmitted signal to simulate the distance of the target.

International Publication Number <CIT> published under the Patent Cooperation Treaty (PCT) is directed at a method for controlled radar stimulation and a radar stimulator aircraft configured to stimulate a radar system. The radar stimulator aircraft receives information for causing it to stimulate a radar system in a user specific manner by simulation of at least one radar target from a perspective of the radar system. The radar stimulator aircraft monitors a position of an onboard unit relative to at least one antenna of the radar system and based on the received information and the monitored position of the onboard unit, the radar stimulator aircraft controls its flight and the emission of synthetic radar echoes by the radar stimulator aircraft thereby stimulating the radar system with at least one simulated radar target. The method operates according to the same principles.

European Patent Application No. <CIT> is directed at a method and a system for testing radar systems' capability to detect and track remote non-linear moving targets. The system includes a computing device, a drone, and a radar repeater. The computing device is programmed to define a first non-linear trajectory that includes a sequence of first positions of a non-linear moving target to be simulated, and to compute, based on the first non-linear trajectory, a second non-linear trajectory that includes a sequence of second positions that are each associated with a corresponding first position that is defined with respect to the antenna of the radar system under test. The drone includes an on-board antenna, and an automatic flight management system operable to fly the drone. The drone follows the second non-linear trajectory, and its on-board antenna receives radar signals transmitted by the antenna of a radar system under test. The radar repeater, which is connected to the on-board antenna, is operative to receive incoming radar signals transmitted by the antenna of the radar system under test and when the drone is located at one of the second positions, the radar repeater processes incoming radar signal received by the on-board antenna so as to generate a processed radar signal simulating a radar echo from the non-linear moving target located at the corresponding first position associated with the second position. The radar repeater transmits the processed radar signal by the on-board antenna from the second position towards the antenna of the radar system under test.

European Patent Application No. <CIT> is directed at methods, systems and a device for calibrating and/or testing radars or antennas embedded on an aerial vehicle. The device includes a receiver, a processing unit, an emitter, and a memory. The receiver includes at least one antenna. The receiver receives at least one electromagnetic (EM) signal emitted by one or more radars. The processing unit applies a delay to incoming EM signals to the emitter, which in turn transmits back the delayed EM signals to the radar. The processor modulates the EM signals after and/or before the delaying. The memory stores data representative of the delays and/or modulations to be applied to the EM signals. The processor controls the delay according to at least one delay value. Each delay value simulates a virtual range of the device or of the aerial vehicle with respect to the radar antenna receiving the transmitted EM signal, where the virtual range is different from an actual range of the device or of the aerial vehicle with respect to the radar or antenna.

It is an object of the disclosed technique to provide a novel method and system for simulating a trajectory of a radar target. In accordance with the disclosed technique, there is thus provided a method for simulating a trajectory of a radar target. The method includes the procedures of determining a simulated trajectory of the simulated target and determining a simulating vehicle trajectory for a simulating vehicle. The simulating vehicle trajectory is defined according to a simulation profile. The simulation profile at least includes a spatial simulation profile and a signal delay profile. The spatial simulation profile includes an azimuth simulation profile and an elevation simulation profile. The method further includes the procedures of maneuvering the simulating vehicle according the spatial simulation profile, receiving a radar signal by the simulating vehicle and re-transmitting a signal toward the radar at least according to the signal delay profile.

In accordance with another aspect of the disclosed technique, there is thus provided a system for simulating a trajectory of a radar simulated target. The system includes a simulating vehicle which includes a receiving transducer, a receiver, a position detector, a transmitter, a transmitting transducer and a processor. The processor at least includes a signal delay and is coupled with the receiver and with the transmitter. The receiver is further coupled with the receiving transducer and the transmitter is further coupled with the transmitting transducer. The receiving transducer receives signals from the radar and transforms the received signal to an electric received signal. The receiver receives the electric received signal and at least samples the electric received signal to produce a sampled received signal. The position detector determines the current position of the simulating vehicle. The transmitter converts a re-transmission signal to an analog signal. The transmitting transducer transforms the analog signal into a transmitted signal. The processor receives the sampled received signal and produces the re-transmission signal at a delay defined by a signal delay profile. The processor further determines motion characteristics of the simulating vehicle according to a spatial simulation profile and the current position of the simulating vehicle. The spatial simulation profile defines the trajectory of the simulating vehicle. The spatial simulation profile includes an azimuth simulation profile and an elevation simulation profile.

The disclosed technique overcomes the disadvantages of the prior art by providing a system and a method for simulating a trajectory of a simulated target for radar operator training, radar calibration and/or testing. According to the disclosed technique, a simulating vehicle (e.g., an un-manned vehicle such as a remote controlled drone) maneuvers according to a simulating vehicle trajectory, which simulate an actual trajectory of a target. The simulating vehicle trajectory is defined according to a simulation profile. The simulation profile at least includes a spatial simulation profile, a signal delay profile and may further include a signal characteristics profile (e.g., signal amplitude, Doppler shift and the like). The spatial simulation profile defines the trajectory of the simulating vehicle in space. The spatial trajectory profile includes, for example, at least one of an azimuth simulation profile and an elevation simulation profile. The azimuth simulation profile defines an azimuthal trajectory for the simulating vehicle. The elevation simulation profile defines an elevation trajectory for the simulating vehicle. The spatial simulation profile may alternatively include a list of coordinates and elevations in a reference coordinate system. The signal delay profile defines the delays employed before re-transmitting a received radar signal, thus simulating the distance of the target. The signal characteristics profile defines the signal characteristics of the re-transmitted signal. It is noted that the term 'distance' and the term 'range' are employed herein interchangeably.

According to the disclosed technique, the simulating vehicle maneuvers within the "radar blind zone". The term "radar blind zone" relates to a space around the radar where the radar does not detect targets. For example, the radar blind zone relates to the distance from the radar defined according to the duration in which the radar transmits a signal and does not receive signals, times the propagation speed of the signal in the medium (e.g., air, free space, water). This duration, in which the radar transmits a signal and does not receive signals, times the propagation speed of the signal in the medium defines a sphere around the radar in which the radar does not detect objects. This sphere is the radar blind zone. The radar blind zone is also referred to herein as the radar minimum detection range. It is noted that the simulating vehicle may operate outside the radar blind zone. However, this may result in a representation of the simulating vehicle appearing on the radar. Such a representation should typically be accounted for when training, calibrating and/or testing the radar (e.g., ignored or employed as an additional target).

For the purpose of the explanations brought forth herein, the simulating vehicle is exemplified as a drone and the simulating vehicle trajectory is defined at least according to a spatial simulation profile and signal delay. However, it is noted that the simulated target may be any land, air or sea vehicle (e.g., a car, an air plane, a ship and the like) and the simulating vehicle may be a corresponding unmanned vehicle (e.g., a remote controlled drone, a remote controlled car, a remote controlled boat and the like). Furthermore, the spatial simulation profile includes at least one of an azimuth simulation profile and an elevation simulation profile. The simulating vehicle trajectory may include any combination of at least one of an azimuthal simulation trajectory, elevation simulation trajectory and signal delay characteristics. For example, when simulating a vessel, only an azimuthal simulation trajectory and simulation delays are required to define a simulating vehicle trajectory (i.e., elevation profile is regarded as including only a constant value). For simulating a vehicle moving in a straight line toward and away from the radar, only simulation delays are required (i.e., the azimuth and elevation profiles are regarded as including only respective single constant values). Furthermore, the term 'radar' employed herein relates to a system that determines the range and direction of an object according to time-of-flight of a return signal which, the signal being, for example, radio frequency (RF) signals, sonic (e.g., ultrasound or sonar) signals or light signals.

Reference is now made to <FIG>, which are schematic illustrations of a simulating vehicle trajectory, generally referenced <NUM>, in accordance with an embodiment of the disclosed technique. The simulating vehicle trajectory in <FIG> simulate an actual trajectory <NUM> (i.e., the simulated trajectory) for training an operator of a radar <NUM> or for calibrating and testing radar <NUM>. Radar <NUM> is located on the ground <NUM>. Drone <NUM> is flying at a maneuvering distance from radar <NUM>, which is smaller than the minimum detection range <NUM> of radar <NUM> (i.e., drone <NUM> is not detected by radar <NUM>) according a simulating vehicle trajectory. <FIG> and <FIG> depict an azimuthal simulation trajectory and <FIG> and <FIG> depict an elevation simulation trajectory. To simulate a target at a simulated distance R, drone <NUM> receives a signal transmitted by radar <NUM>, and re-transmits the received signal at a respective delay (i.e., according to the signal delay profile) and optionally with respective amplitude corresponding a simulated range and Doppler shift corresponding to the changes in the simulated range (i.e., both according to a signal characteristics profile), thereby simulating the actual distance and the change thereof of drone <NUM> from radar <NUM>. Re-transmitting the received signal at respective amplitude simulates the attenuation the radar signal undergoes as it propagates through the medium toward the simulated target and back to radar <NUM> at the simulated distance. Re-transmitting the received signal with respective signal characteristics is also referred to herein as 'signal characterization'. According to the simulating vehicle trajectory, drone <NUM> maneuvers from point <NUM><NUM> to point <NUM><NUM>. Radar <NUM> receives signals simulating a target maneuvering from point <NUM><NUM> to point <NUM><NUM>, corresponding to points <NUM><NUM> and <NUM><NUM> respectively.

With reference to <FIG> and <FIG>, a drone <NUM> is maneuvering according to an azimuthal simulation trajectory <NUM> around radar <NUM>. As mentioned above, according to the simulating vehicle trajectory, drone <NUM> maneuvers from a point <NUM><NUM> to a point <NUM><NUM>. At point <NUM><NUM> drone <NUM> is at an azimuthal angle φ<NUM> (i.e., relative to a reference direction <NUM>) indicated by the double ark. At point <NUM><NUM> drone <NUM> is at an azimuthal angle φ<NUM>. When drone <NUM> maneuvers from point <NUM><NUM> to point <NUM><NUM>, drone <NUM> changes the azimuth angle thereof by Δφ. The actual distance between point <NUM><NUM> and point <NUM><NUM> is d. Since drone <NUM> also employs signal delay and signal characterization to simulate distance and target characteristics, radar <NUM> receives signals simulating a target maneuvering from point <NUM><NUM> to point <NUM><NUM>, corresponding to points <NUM><NUM> and <NUM><NUM> respectively. The distance between point <NUM><NUM> and point <NUM><NUM>, is D.

With reference to <FIG> and <FIG>, drone <NUM> is maneuvering according to an elevation simulation trajectory116. At point <NUM><NUM> drone <NUM> is at an elevation angle of ϕ<NUM>. At point <NUM><NUM> drone <NUM> is at an elevation angle of ϕ<NUM>. When drone <NUM> maneuvers from point <NUM><NUM> to point <NUM><NUM>, drone <NUM> changes the elevation angle thereof by Δϕ. At point <NUM><NUM>, the actual elevation, h, of drone <NUM>, corresponds to an elevation angle of ϕ<NUM> at distance r'. Since drone <NUM> also employs signal delay and signal characterization to simulate distance and target characteristics, radar <NUM> receives signals simulating a target at point <NUM><NUM> and elevation H. At point <NUM><NUM>, the actual elevation h+Δh of drone <NUM> corresponding to an elevation angle of ϕ<NUM> (indicated by the double arc) at distance r'. Since drone <NUM> also employs signal delay and signal characterization to simulate distance, radar <NUM> receives signals simulating a target at points <NUM><NUM> and elevation H+ΔH. In other words the change Δh in the elevation of drone <NUM> corresponds to a change ΔH in the elevation of the simulated target for a specific signal delay.

A simulating vehicle trajectory according to the disclosed technique simulates a trajectory of a target. The simulated trajectory of the target may be defined in terms of the azimuth of the target relative to a reference direction, the distance of the target from the radar and the elevation of the target above a reference plane. As a further example, the simulated trajectory may be defined by a set of coordinates in a reference coordinate system. According to yet another example, the simulated trajectory may be defined as a set of accelerations and directions relative to a start position in a reference coordinate system. The reference coordinate system may be a global coordinate system (e.g., WSG <NUM>, ETRS89) or a local coordinate system, for example, a coordinate system defined by the radar location and a reference direction (e.g., the location of the radar is defined as the [<NUM>;<NUM>;<NUM>] location and the reference direction defines one of the axis of the coordinate system).

As mentioned above, the simulating vehicle trajectory is defined according to a simulation profile. The simulation profile at least includes a spatial simulation profile and delay simulation profile. The simulation profile may further include a signal characteristics profile (e.g., signal amplitude, Doppler shift profile). The spatial simulation profile may define list of coordinates and elevations or a list of location and elevation changes in the reference coordinate system. As mentioned above, the spatial simulation profile may alternatively include at least one of an azimuth simulation profile and an elevation simulation profile. The azimuth simulation profile defines an azimuthal trajectory for the simulating vehicle. The elevation simulation profile defines an elevation trajectory for the simulating vehicle. Signal delay profile defines the duration that transceiver of the simulating vehicle should delay the signal re-transmission and the signal. The signal characteristics profile defines the signal characteristics of the re-transmitted signal. The simulating vehicle maneuvers according to the azimuth and elevation simulation profiles and delays the re-transmission of the received signal according to the signal delay profile, thus maneuvering according to the simulating vehicle trajectory and simulating the target trajectory.

To determine the simulation profile, the maneuvering distance of the simulating vehicle (e.g., a drone) from the radar is determined. For example, the maneuvering distance of the simulating vehicle may be determined to be at a range from the radar, smaller than the minimum detection range of the radar. Referring back to <FIG> and <FIG>, the maneuvering distance is denoted r'. Reference is now made to <FIG>, which are schematic illustrations of an exemplary azimuth simulation profile generally referenced <NUM>, an exemplary elevation simulation profile generally referenced <NUM>, an exemplary signal delay profile <NUM> and an exemplary signal characteristics profile generally reference <NUM>, all in accordance with another embodiment of the disclosed technique. With reference to <FIG>, azimuth simulation profile <NUM> defines the simulation azimuthal trajectory (i.e., the azimuths of the simulating vehicle over time). The azimuths defined by azimuth simulation profile <NUM> correspond to the azimuths of the simulated trajectory. Thus, these azimuths also define the azimuths of the simulating vehicle, when maneuvering according to the simulation profile. According to another example, the azimuth simulation profile may define the locations of the simulating vehicle in a reference coordinate system, over time. These locations are determined, for example, according to the location of the radar in the reference coordinate system, the azimuths (i.e., relative to a reference direction) and the maneuvering distance of the simulating vehicle from the radar. It is noted that the derivative of the azimuth simulation profile defines the rotational velocity of the simulating vehicle around the radar (e.g., with reference to <FIG>, the rotational velocity of simulating vehicle <NUM> around radar <NUM> on azimuthal simulation trajectory <NUM>).

With reference to <FIG>, elevation simulation profile <NUM> defines the simulation elevation trajectory (i.e., the elevations of the simulating vehicle over time). To determine the elevation simulation profile, the elevation angles of the simulated trajectory are determined according the elevations and distances of the simulated trajectory (e.g., by employing known trigonometric identities). From these elevation angels and maneuvering distance, the elevations of the simulating vehicle, when maneuvering according to the simulation profile, are determined.

With reference to <FIG>, signal delay profile <NUM> defines the durations the drone should delay the received radar signal before re-transmitting, over time. The distances of the simulated target are determined according to the difference between the actual distance of the simulating vehicle and the simulated distance from the radar. The actual distance of the simulating vehicle is determined according to the maneuvering distance and the actual elevations. The difference between the actual distance of the simulating vehicle and the simulated distance from the radar, and the propagation speed of the signal in the medium, define the delays that the drone should delay the received radar signal before re-transmitting. Signal delay profile <NUM> is determined according to these delays.

With reference to <FIG>, signal characteristics profile <NUM> is exemplified with an amplitude profile <NUM> (depicted with a solid line) and a Doppler shift profile <NUM> (depicted with a dashed doubled-dotted line), which defines the amplitudes at which the drone re-transmits the received radar signal over time. The amplitudes of the re-transmitted signal simulates the attenuation the signal undergoes in the medium when propagating toward the simulated target and back to the radar. The amplitude of the re-transmitted signal may also simulate losses due to transmitter imperfections, Free Space Path Loss (FSPL) or wave dispersion. The amplitude of the re-transmitted signal may further simulate effects that specific target characteristics such as Radar Cross Section may have on the amplitude of the signal received by the radar. Doppler shift profile <NUM> defines the Doppler shift in the frequency of the re-transmitted signal, caused by change in the simulated distance from the radar. In general, the Doppler shift is related to the rate of change (i.e., derivative) of the range of the simulated target from the radar. However, since the signal delay is proportional to this simulated distance, the Doppler shift is related to the rate of change of the signal delay as well.

Reference is now made to <FIG>, which is a schematic illustration of a system, generally referenced <NUM>, for simulating a trajectory of radar target, constructed and operative in accordance with a further embodiment of the disclosed technique. System <NUM> is located on a simulating vehicle <NUM> such as a drone <NUM>. System <NUM> includes a receiving transducer <NUM>, a transmitting transducer <NUM>, a receiver <NUM>, a transmitter <NUM>, a processor <NUM>, a memory <NUM>, a position detector <NUM> and a vehicle maneuver detector <NUM>. Processor <NUM> includes a signal delay <NUM> and a signal characterizer <NUM>. Receiver <NUM> optionally includes an attenuator <NUM>. Processor <NUM> is coupled with receiver <NUM>, with transmitter <NUM> with memory <NUM> with position detector <NUM> and with vehicle maneuver controller <NUM>. Receiver <NUM> is further coupled with receiving transducer <NUM>. Transmitter <NUM> is further coupled with transmitting transducer <NUM>.

Receiving transducer <NUM> may be an RF transducer (i.e., an antenna) an optical transducer (e.g., a photodiode, a light-dependent resistor (LDR), and the like) or a sonic transducer (e.g., piezo electric transducer, a capacitive transducer, magnetorestrictive transducers and the like), corresponding to the type of signal employed by the radar. Similarly, transmitting transducer <NUM> may be an RF transducer, an optical transducer, or a sonic transducer, corresponding to the type of signal employed by the radar. Processor <NUM> may be a general purpose processor, a digital signal processor or a special purpose processor implemented with field-programmable gate arrays (FPGA)s or application specific integrated circuit (ASIC) or with discrete components. Position detector <NUM> is for example a Global Positioning System (GPS) receiver determining the location of system <NUM> in a reference coordinate system (e.g., WSG <NUM>, ETRS89, or a coordinate system defined by the radar location and a reference direction). Position detector may alternatively or additionally include an inertial measurement unit (IMU) that measures the linear and angular accelerations of simulating vehicle <NUM> thus providing information relating to the location and orientation of simulating vehicle <NUM> relative to a reference location and orientation. Position detector <NUM> may also be a receiver receiving information relating to the position (i.e., location and orientation) of simulating vehicle <NUM> from a remote station and providing this information to processor <NUM> (e.g., according to a standard navigational data transmission protocol such as NMEA <NUM> or UBX). Memory <NUM> at least stores the azimuth simulation profile, the elevation simulation profile and the signal characteristics profile corresponding to the simulated trajectory.

Receiving transducer <NUM> receives a signal from the radar and transforms this received signal to an electric received signal. Receiving transducer <NUM> provides the electric received signal to receiver <NUM>. Receiver <NUM> at least samples the electric received signal to produce a sampled received signal. Receiver <NUM> may further filter the electric down convert and demodulate the electric received signal. Receiver <NUM> provides the sampled received signal to processor <NUM>. When the radar employs RF signals (i.e., an RF radar) or sonic signals (i.e., a sonic radar) receiver <NUM> includes attenuator <NUM>, which attenuates the signals received from receiving transducer <NUM>. When simulating vehicle <NUM> operates at ranges from the radar which is smaller than the radar minimum detection range, system <NUM> may receive the side lobes produced by the radar as well as the main lobe. Attenuator <NUM> attenuates the signals received by receiving transducer <NUM> such that receiver <NUM> samples only electric received signals corresponding to the main lobe of the radar (i.e., otherwise, it might be difficult to determine the time of arrival of a signal received from the main lobe of the radar and thus difficult to determine when to re-transmit the radar signal).

Processor <NUM> produces a re-transmission signal according to signal delay profile and optionally according to the signal characteristics profile. The re-transmission signal exhibits, for example, the amplitude defined by the signal characteristics profile (i.e., when the signal characteristics profile include an amplitude profile). Processor <NUM> provides the re-transmission signal to transmitter <NUM> at a delay corresponding to the delay defined by the signal delay profile, relative to the time of arrival of the signal. Transmitter <NUM> converts the re-transmission signal to an analog signal and optionally amplifies and filters the analog signal and provides the analog signal to transmitting transducer <NUM>. Transmitting transducer transforms the analog signal into a transmitted signal, the transmitted signal being in the signal type employed by the radar (e.g., an RF signal, a light signal or a sonic signal).

Furthermore, processor <NUM> employs the spatial simulation profile to determine the motion characteristics of simulating vehicle <NUM>. The motion characteristics at least include direction of motion and acceleration for simulating vehicle <NUM>. To that end, processor <NUM> receives the current position of simulating vehicle <NUM> from position detector <NUM> and determines the required motion characteristics for simulating vehicle <NUM> to comply with the spatial simulation profile. Processor <NUM> provides the required motion characteristics to vehicle maneuvering controller <NUM>. Vehicle maneuvering controller <NUM> determines the required motion control commands to the vehicle maneuvering system. For example, when simulating vehicle <NUM> is a quadcopter, vehicle maneuvering controller <NUM> determines the required rotational velocities or each rotor required to achieve the required motion characteristics. As a further example, when simulating vehicle is a remote control car, vehicle maneuvering controller <NUM> determines the requires steering angle and motor revolutions rate to achieve the required motion characteristics.

Reference is now made to <FIG>, which is a schematic illustration of a method for simulating a trajectory of radar target, operative in accordance with another embodiment of the disclosed technique. In procedure <NUM>, the location of the radar in a reference coordinate system is determined. The reference coordinate system is, for example, WSG <NUM>, ETRS89 or a coordinate system defined by the radar location and a reference direction.

In procedure <NUM>, a simulated trajectory of a target is determined. This simulated target trajectory is the trajectory which is to be simulated by the simulating vehicle. The simulated trajectory may be defined in terms of the azimuth of the target relative to a reference direction, the distance of the target from the radar and the elevation of the target above a reference plane. As a further example, the simulated trajectory may be defined by a set of coordinates in the reference coordinate system. According to yet another example, the simulated trajectory may be defined as a set of accelerations and directions relative to a start position in the reference coordinate system.

In procedure <NUM>, a simulating vehicle trajectory is determined for a simulating vehicle. The simulating vehicle trajectory is defined according to a simulation profile. The simulation profile includes a spatial simulation profile and a signal delay profile. The simulation profile may further include a signal characteristics profile (e.g., an amplitude profile). The spatial simulation profile may define list of coordinates and elevations or a list of location and elevation changes in the reference coordinate system. As mentioned above, the spatial simulation profile may alternatively include at least one of an azimuth simulation profile and an elevation simulation profile. The azimuth simulation profile defines an azimuthal trajectory for the simulating vehicle. The elevation simulation profile defines an elevation trajectory for the simulating vehicle. Signal delay profile defines the duration that transceiver of the simulating vehicle should delay the signal re-transmission and the signal. Signal characteristics profile define the signal characteristics of the re-transmitted signal. From procedure <NUM>, the method proceeds to procedures <NUM> and <NUM>.

In procedure <NUM>, the simulating vehicle is maneuvered according the spatial simulation profile. Maneuvering the simulating vehicle according to the spatial simulation profile includes determining the motion characteristics of the simulating vehicle and determining motion control commands to the simulating vehicle. With reference to <FIG>, processor <NUM> determines the motion characteristics of the simulating vehicle according to the spatial simulation profile. Processor <NUM> provides these motion characteristics to vehicle maneuvering controller which determines the motion control commands to the vehicle maneuvering system.

In procedure <NUM>, a radar signal is received by the simulating vehicle. With reference to <FIG> receiving transducer <NUM> receives a radar signal, transforms the received into an electric received signal and provides the electric received signal to receiver <NUM>. Receiver <NUM> at least samples the electric received signal and provides the electric received signal to processor <NUM>.

In procedure <NUM>, a signal is re-transmitted toward the radar at least according to the signal delay profile and optionally according to the signal characteristics profile. Accordingly, the simulating vehicle delays the transmission of the re-transmitted signal according to the signal delay profile. As described above, the simulation profile may further include a signal characteristics (e.g., amplitudes) profile. The simulating vehicle may further characterize the re-transmitted signal according to the signal characteristics profile. With reference to <FIG>, processor <NUM> produces a re-transmission signal according to the signal characteristics profile and provides the re-transmission signal to transmitter <NUM> at a delay corresponding to the delay defined by the signal delay profile, relative to the time of arrival of the signal. Transmitter <NUM> converts the re-transmission signal to an analog signal provides the analog signal to transmitting transducer <NUM> which transforms the analog signal into the signal type employed by the radar.

Claim 1:
A method (<NUM>) for training an operator of a radar (<NUM>) by simulating a trajectory (<NUM>) of a simulated radar target moving along a simulated trajectory, the method comprising the procedures of:
determining (<NUM>) said simulated trajectory of said simulated radar target;
determining (<NUM>) a simulating vehicle trajectory for a simulating vehicle (<NUM>), said simulating vehicle trajectory being defined in space according to a simulation profile, said simulation profile including at least a spatial simulation profile and a signal delay profile (<NUM>), said spatial simulation profile including an azimuth simulation profile (<NUM>) and an elevation simulation profile (<NUM>);
maneuvering (<NUM>) said simulating vehicle in space according to said spatial simulation profile;
receiving (<NUM>) by said simulating vehicle, a radar signal from said radar; and
re-transmitting (<NUM>) by said simulating vehicle, a signal toward said radar at least according to said signal delay profile,
wherein said simulating vehicle trajectory is at a range from said radar smaller than a radar minimum detection range (<NUM>),
wherein said simulation profile includes a signal characteristics profile (<NUM>) that includes a Doppler shift profile (<NUM>) that defines a Doppler shift of the frequency of the re-transmitted signal.