Patent ID: 12259494

DETAILED DESCRIPTION

Embodiments of the systems and methods described herein may be used to generate a rotating range profile reduced-order radar model (RRP-ROM) for use in high-speed, closed-loop radar sensor system and autonomous vehicle simulation. An RRP-ROM may provide radar signature characteristics of an electrically large target (such as an automobile at 77 GHz) over a range of prescribed aspect angles, and over a finite range measured about its center rotation axis. These models may include the key interaction effects of extended road, ground, ceiling, wall and other continuous environment interaction effects.

Through use of RRP-ROM models, an accurate target simulation model may be derived through offline simulation for a target and its interaction with an extended environment in order to capture, within a prescribed localization range, the target and its environment interaction effects. A typical target's distributed radar signature will vary depending on the aspect angle. In order to account for this variance, a target radar signature is stored in the RRP-ROM model for a descritized range of aspect angles.

The resulting RRP-ROM target simulation model may be combined in large-scale environment simulations with other such target simulation models that are accessed, for example, as lookup tables. The high-fidelity but localized target simulation model provided by a RRP-ROM may, for example, be applied to a large-scale closed-loop safety system or autonomous vehicle simulation by identifying the indicated target's direction and orientation, and reading back the radar response using a data lookup table (scaling for range, position of the target within the antenna's radiation pattern, and radar transmit power levels.) In this way, RRP-ROM models may enable high-speed simulation of accurate radar responses to a prescribed target so that automotive safety and autonomous control scenarios may be evaluated at speeds that significantly exceed real-time.

FIG.1is a block diagram illustrating an example system100for generating a RRP-ROM. The system100includes a radar system simulation module102that generates a frequency domain range profile104for a target object based on CAD models106,108for the target object and one or more environment objects, a prescribed target reference distance (Rtgt)110, and a target aspect angle (α)112. The system100further includes a frequency-to-time conversion module114that converts the frequency domain range profile104into a time domain range profile116, and a target aspect angle incrementation module118that varies the target aspect angle (α)112in discrete increments to generate a 360° range of target profiles. The target range profiles are stored in memory120, and are accumulated into a RRP-ROM122by an accumulation module124.

The radar simulation module102creates a simulation model composed of a model of the radar system (at origin), the target simulation model106, and the environment simulation model108. The target object defined by the target simulation model106is configured within the simulation model based on the prescribed target reference distance (Rtgt)110and target aspect angle (α)112, such that the target object is positioned with its center at the prescribed reference distance (Rtgt)110from the radar and is rotated about its center axis of rotation by the target aspect angle (α)112. Using the simulation model, the radar simulation module102performs a full-physics electromagnetic simulation of the radar scattering from the radar transmit antenna, for example using a shooting and bouncing rays (SBR) simulation technique. An illustration of an example SBR simulation200being performed on a simulation model is shown inFIG.2.

The example SBR simulation200illustrated inFIG.2is performed on a simulation model composed of the radar model, a target CAD model of a vehicle202, and an environment CAD model of a road204. In the illustrated example, the target aspect angle (α) is 180°, causing the target vehicle202to be rotated 180° about its center axis of rotation (i.e., facing away from the radar.) The target reference distance (Rtgt) is the distance from the center of the target vehicle202to the radar system antennas206,208.

In operation, the SBR simulation200uses a single linear frequency modulated (LFM) pulse (chirp) simulation210to generate a frequency domain range profile of the target202at the prescribed target aspect angle (α) and reference distance (Rtgt). As shown inFIG.2, the simulation200analyzes an LFM pulse210that is transmitted from a radar transmit antenna206, bounced off of the target vehicle202(including any interaction effects from the environment204), and received by a radar receive antenna208. Each radar antenna may have a unique radiation pattern that describes the manner in which energy is distributed or collected by the antenna. Using an antenna-to-antenna coupling simulation, the SBR technique is made to yield scattering parameter (S-parameter) data representing the coupling between the transmit and receive antennas. S-parameters from the SBR technique are separated into incident field parameters (coupling with no scattering geometry) and scattered field parameters (coupling due to currents stimulated on the target and environment.) The scattered S-parameters may be extracted using a swept-frequency analysis, and are used to represent a full transmit-environment-receive loop in the frequency domain range profile104. In embodiments, the SBR simulation200may, for example, be performed using the HRSS SBR+ advanced antenna performance simulation software sold by Ansys, Inc. headquartered in Canonsburg, Pennsylvania.

With reference again toFIG.1, the frequency domain range profile104is processed by the frequency-to-time conversion module114using an inverse Fast-Fourier Transform (FFT) to generate a time domain range profile116at the prescribed target aspect angle (α) and reference distance (Rtgt). More specifically, the result of performing an inverse FFT on the frequency domain range profile104is a radar time profile that represents the radar waveform echo from the environment as observed at the terminals of the receive antenna (in square-root voltage complex samples.) The radar time profile is multiplied by the speed of light to generate the time domain range profile116, which is stored in memory120.

Examples of the frequency domain range profile104and the time domain range profile116are shown inFIGS.3and4, respectively. Specifically,FIG.3illustrates an example frequency domain range profile300that includes scattered S-parameters extracted using a swept-frequency analysis of a single pulse frequency sweep, as explained above with reference toFIG.2. As shown, the frequency domain range profile300is a complex voltage that includes both the real (Scat (Real)) and imaginary (Scat (Imag)) components of the scattered S-parameters. The target return strength (complex voltage) in the frequency domain range profile300is a function of range (e.g., a window around the target body center) and the target aspect angle (α). The resolution of the range may be set by the bandwidth of the radar waveform used in the radar model.

FIG.4illustrates an example time domain range profile400for a target vehicle at a −90° target aspect angle and having a 0.75 m range resolution. As shown, the time domain range profile400identifies the radar return strength (dBW) over a range margin from the target center. The range margin captures the radar profile over the extents of the target body plus an additional margin (e.g., target extent +/−50%). The time domain range profile400is illustrated inFIG.4in the form of a graph with a picture of a target vehicle overlaid to help illustrate the range resolution and target aspect angle. It should be understood, however, that the overlaid picture of the target vehicle is not part of the time domain range profile.

With reference again toFIG.1, after creation of the time domain profile116, the target aspect angle (α) is incremented by the target aspect angle incrementation module118, and the simulation process is repeated for the new target aspect angle (α)112. This continues until time domain range profiles116have been generated and stored to memory120for each aspect angle (α) within a 360° rotation of the target. In the illustrated example, the target aspect angle (α) is shown being incremented by 1 (i.e., αN+1) at each iteration of the 360° rotation. It should be understood, however, that different increment amounts may be utilized, depending on the desired resolution of the resultant RRP-ROM122.

Once time domain range profiles116have been generated and stored for each aspect angle (α) in the 360° target rotation, the resultant set of time domain range profiles are accumulated124to generate the RRP-ROM122. The RRP-ROM122includes a matrix of radar returns which may, for example, be indexed by range bins on one axis and target aspect angles on the other axis. Examples of a RRP-ROM matrix122for a target vehicle are illustrated inFIGS.5and6for different radar waveforms.

FIG.5shows an example RRP-ROM matrix500for a target vehicle in an environment that includes a road surface. The illustrated RRP-ROM matrix500shows the radar return strengths (dBW) from the target in the form of a heat map on a graph, where the y-axis of the graph represents the target aspect angle (α), the x-axis represents the range margin from the target center, and the radar return strength is represented on the graph by a graduated heat index (e.g., by a color gradient). Using the illustrated RRP-ROM matrix500, the radar return strength may be determined at each target aspect angle (α) at any distance within the range margin. For example, the illustrated RRP-ROM matrix500shows a radar return strength of approximately −85 dBW at the point labeled “A” on the graph, which corresponds to a target aspect angle (α) of zero and a range of approximately 0.75 meters—uprange of target center.

Also shown to the left of the graph inFIG.5are pictures of the target vehicle at various aspect angles to help visualize the aspect angles included in the graph. In the illustrated examples (FIGS.5and6), a target aspect angle of 0 corresponds to a broadside position of the vehicle, with the target aspect angle increasing as the vehicle rotates in a counter-clockwise fashion according to the right-hand rule. The RRP-ROM matrix500illustrated inFIG.5utilizes a heat map type representation to further help the reader visualize the data that is indexed within the matrix. It should be understood, however, that an RRP-ROM matrix generated by the systems and methods described herein may be in other forms, such as a look-up table of radar returns indexed by range bins on one axis and target aspect angles on another axis.

The example RRP-ROM matrix500shown inFIG.5is based on a radar system simulation of a pickup truck (5.8 m×2.25 m) on a road surface at a target reference distance (Rtgt) of 30 m. The radar model used to generate the illustrated RRP-ROM matrix500utilizes a radar waveform having a 350 MHz bandwidth and providing a range resolution of 0.43 m.FIG.6illustrates an example of how the resultant RRP-ROM matrix may vary by changing the parameters of the radar model.

FIG.6shows an example RRP-ROM matrix600that is generated from the same target vehicle environment as used to generate the example inFIG.5. In this example, however, the radar model used for the simulation is varied by lowering the bandwidth of the radar waveform to 100 MHZ, resulting in a range resolution of 1.5 m. ComparingFIGS.5and6, it can be seen that modifications to the parameters of the simulation model can significantly affect the accuracy, quality and resolution of the resultant RRP-ROM matrix. Embodiments of the disclosed system and method therefore enable user modification and refinement of one or more of the various parameters that are used to create the simulation model, for example as shown inFIG.7.

FIG.7is a block diagram illustrating another example of a system700for generating a RRP-ROM. Like the example system described above with reference toFIG.1, the radar simulation module102in the illustrated system700creates a simulation model composed of a model of the radar system702, a target simulation model106, and an environment simulation model108, where the target106is configured within the simulation model based on a prescribed target reference distance (Rtgt)110and target aspect angle (α)112, such that the target106is positioned with its center at the prescribed reference distance (Rtgt)110from the radar and is rotated about its center axis of rotation by the target aspect angle (α)112. The example system700shown inFIG.7further illustrates how the parameters and models used by the radar system simulation module102may be generated and/or varied to create the desired simulation model.

As illustrated, the target simulation model106and environment simulation model(s)108utilized by the radar system simulation module102may be created using one or more computer-aided design (CAD) tools704. The target CAD model106may be created using physical parameters706that are based on one or more real-world observations708of a target object, such as an automobile, truck, bicycle, pedestrian, etc. These real-world observations708may include the shape (i.e., physical dimensions) of the target object, the desired scale of the model, the conductivity of the target object, and/or the target object's dielectric properties. The conductivity and/or dielectric properties of the target object may be included to take into account the target object's material composition. These properties may, for example, account for lossy materials in objects such as pedestrians. In other examples, the conductivity and/or dielectric properties may default to the characteristics of an ideal metal composition.

Similarly, the environment CAD model(s)108may be created using physical parameters710of an environment around the target that are based on one or more real-world observations708, such as the shape (i.e., physical dimensions) of the environment object, the desired scale of the model, and/or the target object's dielectric properties. In this way, one or more environment CAD models704may be developed to provide a continuous cross-section of the environment in the direction of radar propagation that incorporates parameters such as the dielectric properties of environmental objects, such as a road surface, fences, guardrail structures, tunnel-walls and ceiling, curbs, etc.

In addition, parameters of the radar model702, such as the radar channel radiation pattern714and radar waveform716, may be set and/or adjusted to provide the desired radar characteristics for the simulation model. For instance, the radar waveform parameters716may be adjusted by modifying the waveform frequency and/or bandwidth718. The characteristics of the radar channel radiation pattern714may, for example, be measured, simulated, or approximated720based upon the radar manufacturer's specification of radar cone coverage. These parameters720may, for example, be used to achieve a pattern covering the full sphere surrounding the radar, which is desirable in order to capture sidelobe effects from the extended environment.

As detailed above with reference toFIG.1, the resultant simulation model is used by the radar system simulation module102to generate a frequency domain range profile104, which is converted into a time domain range profile116by a frequency-to-time conversion module114and stored to a memory120for accumulation124into a RRP-ROM matrix122. As detailed above, the RRP-ROM matrix122is created by varying (118) the target aspect angle (α)112in discrete increments to generate a 360° range of target profiles.

FIG.8is a flow diagram illustrating an example method800for converting a frequency domain range profile into a time domain range profile. The method800illustrated inFIG.8may, for example, be utilized in the frequency-to-time conversion module114shown inFIGS.1and7. The method800begins with the time domain range profile802which, as explained above, may include scattered S-parameter (Sscattered) data extracted using a swept-frequency analysis of the results of a SBR radar-target-environment interaction simulation. At804, the frequency data802may be zero-padded in order to reach a convenient power-of-two sample size for use in Fast-Fourier Transforms (FFT) and inverse Fast-Fourier transforms, and to provide additional definition to the time domain range profile. An inverse Fast-Fourier Transform (invFFT) is applied at806to convert the data into the time domain. One or more time domain filtering window functions, such as a Rectangular, Hamming, Hann, Blackman-Harris, or other popular windowing function may be applied at808to further help reduce time domain sidelobes.

The result of steps804,806and808is a radar time profile810, which represents the radar waveform echo from the environment as observed at the terminals of the receive antenna (in square-root voltage complex samples.) The time-domain range profile812is created by multiplying the radar time profile810by the speed of light at814, and normalizing the range distance to the center of the target body at816. The range distance may be normalized to the center of the target body by subtracting the prescribed target reference distance (Rtgt) from the time-domain range profile812range values. This process816normalizes the time-domain range profile812to the center of the target body's center axis of rotation.

FIG.9is a diagram illustrating an example of a time-domain range profile900in which the range distance has been normalized to the center of the target body. To help visualize the range distance normalization, a target vehicle902is superimposed over the time-domain range profile900, and circle904is superimposed over the target vehicle902to show the location of the radar system in the foreground, facing the target vehicle902but at a reference distance Rtgt in front of it. The range distances indicated on the horizontal axis show radar returns about the center of the vehicle; negative distances indicate returns from uprange of the target center, and positive distances indicate returns from downrange of the target center. Uprange radar returns come from features on the target that are between the radar and the target center, and downrange radar returns come from target features that are beyond the target center. In the time-domain range profile900the leading return at 3 meters comes from the front of the target, and the final peak at 5 meters comes from a feature on the back end of the target. The target was originally placed at a reference distance Rtgt from the radar, the range profiles for the radar returns extracted, and the value of Rtgt subtracted from the range values so that the distances are expressed with origin at the target center.

FIGS.10-12illustrate another example in which a RRP-ROM matrix is created from a target consisting only of a vehicle bumper. The example shown inFIGS.10-12may, for example, be created using the systems described above with reference toFIGS.1and7, and illustrates that the systems and methods described herein may also be utilized to create range profiles for portions of an object, such as a vehicle bumper.

FIG.10shows an example of a time-domain range profile1000for a vehicle bumper1010. The illustrated range profile1000may, for example, be generated by modifying the target simulation model106shown inFIGS.1and7to include only a portion of the target vehicle (e.g., the bumper.) As shown, the target center may still be calculated relative to radar position1020based on one or more dimensions of the entire object so that the target object portion1010better reflects its position within a real-world environment. For example, in the illustrated example, the radar1020is positioned in front of the target object1010at a reference distance of Rtgt at the appropriate height for the radar system above a road environment to take into consideration the height dimension of the entire vehicle.

FIGS.11and12illustrate examples of a RRP-ROM matrix generated from the target object portion1010shown inFIG.10. Specifically,FIG.11is an example RRP-ROM matrix1100generated using the systems and methods described herein at a target reference distance (Rtgt) of 150 m, and utilizing a radar waveform having a 100 MHz bandwidth and providing a range resolution of 1.5 m.FIG.12is an example RRP-ROM matrix1200generated using the systems and methods described herein at a target reference distance (Rtgt) of 30 m and utilizing a radar waveform having a 350 MHz bandwidth and providing a range resolution of 0.429 mm.

Like the example described above with reference toFIG.5, the illustrated RRP-ROM matrices1100,1200show the radar return strengths (dBW) from the target in the form of a heat map on a graph, where the y-axis of the graph represents the target aspect angle (α), the x-axis represents the range margin from the target center, and the radar return strength is represented on the graph by a graduated heat index (e.g., by a color gradient). It should be understood, however, that an RRP-ROM matrix generated by the systems and methods described herein may be in other forms, such as a look-up table of radar returns indexed by range bins on one axis and target aspect angles on another axis.

Using the systems and methods described herein, RRP-ROM models may be captured and resampled to enable simulation of automotive radar systems with multiple radar types, and to enable very fast radar system simulation scenarios involving high-fidelity target simulation models that are based upon full-physics modeling. As described above, RRP-ROM matrices generated by the disclosed systems and methods may provide range profiles of the subject target at various aspect angles to the radar source, which include radar signature effects of the environment. These RRP-ROM matrices may, for example, be used in subsequent radar scene simulations involving multiple such targets. Examples illustrating the use of RRP matrices for multiple target radar sensor simulations are shown inFIGS.13and14, and an example system for generating multiple target radar sensor simulations is illustrated inFIG.15.

FIG.13illustrates an example1300in which three pre-generated RRP-ROM matrices1310,1320,1330are used in a closed-loop radar sensor simulation. The three pre-generated RRP-ROM matrices1310,1320,1330may, for example, be generated using the systems described above with reference toFIGS.1and7for three different objects within the environment. Specifically, in the illustrated example, RRP-ROM matrices are generated for a truck1340and two automobiles1350,1360on a road surface environment1370, each providing radar return strengths from a common radar system1380. To perform the closed-loop radar sensor simulation, the target vehicles1340,1350,1360are positioned within the simulation environment at desired distances and offsets from the radar system1380. The pre-generated RRP-ROM matrices1310,1320,1330may then be used to provide radar return values for each of the target objects1340,1350,1360, for example using a simple lookup table operation based on the target aspect angle (α) of the target object within the closed-loop simulation environment. The resultant radar return value for each target object may then be scaled for range and location within the antenna radiation patterns to account for the target object's position within the closed-loop simulation environment.

A radar return value from an RRP-ROM matrix may, for example, be scaled for range by multiplying the radar return value by a scaling factor that reflects the difference between the target range (Rtgt) used to create the RRP-ROM matrix and the target range within the closed-loop simulation. One or more target return values in the closed-loop simulation may also be scaled to account for any necessary gain variations due, for example, to the target being off-beam in the transmit or receive radiation pattern (e.g., such as target1360in the illustrated example).

FIG.14illustrates another example1400of how multiple pre-generated RRP-ROM matrices may be used in a closed-loop radar sensor simulation. In this example RRP-ROM matrices (not shown) have been pre-generated for three different target objects1410,1420,1430, for example using the systems described above with reference toFIGS.1and7. Specifically, a first RRP-ROM matrix has been pre-generated for Target A1410comprising a vehicle in an environment that includes a road surface and an adjacent guardrail. A second RRP-ROM matrix has been pre-generated for Target B1420comprising a tree in an environment that includes a road surface adjacent to the tree. A third RRP-ROM matrix has been generated for Target C1430for a manhole cover in an environment that includes a road surface surrounding the manhole cover.

As illustrated, a closed-loop simulation may be setup by defining the range and aspect angle (α) of each target object1410,1420,1430relative to the radar system antenna source1440. The closed-loop simulation may then use the pre-generated RRP-ROM matrices to identify radar return values for each target object1410,1420,1430based on the target aspect angles (a), for example using a lookup-table operation. The radar return value for each target object may then be scaled for range to account for the target object's position within the closed-loop simulation environment, and may also be scaled to account for any necessary gain reduction due to the target being off-beam in the transmit or receive radiation pattern of the antenna system1440.

FIG.15is a block diagram of an example system1500for performing a closed-loop radar sensor simulation using pre-generated RRP-ROM matrices. The system1500includes a range profile repository1510for storing a plurality of pre-generated RRP-ROM matrices. To perform the closed-loop radar sensor simulation, one or more of the pre-generated RRP-ROM matrices1520are retrieved from the profile repository1510by a profile accesser1530based on a simulation definition1540. The simulation definition1530may, for example, identify one or more target objects for simulation and the locations of the target objects within the simulation environment.

Based on the simulation definition1540, a range/angle determination engine1550may be used to determine the range and aspect angle (α)1560of each target object relative to the radar system antennas, for example as illustrated inFIG.14. Using the target object aspect angles (a), a profile row selector and scaler1570may determine a radar return value for each target object by performing a database operation, such as a lookup table operation, using the pre-generated RRP-ROM matrix1520for the target object. The profile row selector and scaler1570may then generate simulated radar returns1580by scaling the radar return value for each target object, if necessary, to account for the target object's position within the closed-loop simulation environment, and also to account for any necessary gain reduction due to the target being off-beam in the transmit or receive radiation pattern of the antenna system. A composite simulated radar return can be developed by combining the returns of each of the individual targets, thus capturing a first-order radar return from a complex environment composed of multiple targets in an extended environment. The simulated radar returns may, for example, be used to test and/or debug the control logic in a vehicle control or advance driver assistance system (ADAS) for incorporation or update to systems in a real-world physical vehicle.

FIG.16is a flow diagram of an example method1600for generating a radar model for a target object. The example method1600depicted inFIG.16may, for example, be employed by the systems shown inFIGS.1and7. At1610, a target simulation model is received that identifies one or more physical aspects of a target object. At1620, an environment simulation model is received that identifies one or more physical aspects of an environment object. A target distance parameter is received at1630that identifies a reference distance between the target object and a radar system to be simulated. Also received at1630are the waveform characteristics of the radar system to be simulated.

At1640, a simulation model is generated based, at least in part, on the target simulation model, the environment simulation model, the target reference distance and the waveform characteristics of the radar. The simulation model is further based on a target aspect angle that identifies an angular position of the target object in relation to the radar system. Interaction of the radar system with the target object and the environment object is then simulated at1650using the simulation model. The simulation is used at1660to generate a range profile for the target object at the target aspect angle, wherein the range profile identifies a radar return strength for the target distance.

The target aspect angle is incremented at1670, and operations1650-1660are repeated until range profiles are generated for the target object at a plurality of target angles amounting to a 360 degree rotation of the target object. The range profiles at the plurality of target angles are accumulated at1680to generate the radar model for the target object.

It should be understood that the method1600shown inFIG.16may be repeated for different combinations of radar systems (e.g., different radar waveform characteristics) and targets that a user may wish to simulate.

FIG.17is a flow diagram illustrating an example method of performing a closed-loop radar sensor simulation. At1710, a plurality of radar models are received for target objects within a simulation environment. The plurality of radar models may be generated using the method of set forth inFIG.16. At1720, for each target object within the simulation environment, a target aspect angle is identified relative to a radar sensor within the simulation environment. At1730, for each target object within the simulation environment, the target aspect angle is used to identify a corresponding radar return strength from the radar model for the target object. At1740, for each target object within the simulation environment, the radar return strength is scaled based on a position of the target object within the simulation environment relative to the radar sensor to generate a simulated radar return value.

FIG.18is a block diagram depicting an additional example of system1800for generating a RRP-ROM1802. The example system1800illustrated inFIG.18is similar to the example systems shown inFIGS.1and7, except that the ROM models are kept in the frequency domain.

Like the example systems described above with reference toFIGS.1and7, the radar simulation module102in the illustrated system1800creates a simulation model composed of a model of the radar system702, a target simulation model106, and an environment simulation model108, where the target106is configured within the simulation model based on a prescribed target reference distance (Rtgt)110and target aspect angle (α)112, such that the target106is positioned with its center at the prescribed reference distance (Rtgt)110from the radar and is rotated about its center axis of rotation by the target aspect angle (α)112. The parameters and models used by the radar system simulation module102may, for example, be generated and/or varied to create the desired simulation model in the same way as described above with reference toFIG.7.

As detailed above with reference toFIGS.1and2, the resultant simulation model is used by the radar system simulation module102to generate a frequency domain range profile1804. For instance, an SBR antenna-to-antenna coupling simulation may be used to yield scattering parameter (S-parameter) data representing the coupling between the transmit and receive antennas, which is separated into incident field parameters (coupling with no scattering geometry) and scattered field parameters (coupling due to currents stimulated on the target and environment.) The scattered S-parameters are extracted using a swept-frequency analysis, and are stored in memory1806with reference to the prescribed target aspect angle (α) and reference distance (Rtgt). The target aspect angle (α) is then incremented by the target aspect angle incrementation module118, and the simulation process is repeated for the new target aspect angle (α)112. Simulation continues until frequency domain range profiles1804have been generated and stored to memory1806for each aspect angle (α) within a 360° rotation of the target. The stored frequency domain simulation data (e.g., a table of complex frequency samples vs. target aspect angles) is then exported by accumulation module1808to generate the RRP-ROM1802.

FIG.19is a block diagram illustrating another example of a system1900for generating a RRP-ROM1902. The example illustrated inFIG.19is similar toFIG.18, except that the frequency domain range profile1804is converted to the time domain for filtering and then converted back into the frequency domain for storage and RRP-ROM creation.

The radar simulation module102in the illustrated system1900creates a simulation model, for example as described above with reference toFIGS.1and7, and the resultant simulation model is used by the radar system simulation module102to generate a frequency domain range profile1804. The frequency domain range profile1804is converted into the time domain by a frequency-to-time conversion module1904, for example using an inverse Fast-Fourier Transform (FFT) as described above with reference toFIG.1. A time domain windowing filter1906is then applied to the time domain range profile. The time domain windowing filter1906may, for example, utilize one or more time domain filtering window functions, such as a Rectangular, Hamming, Hann, Blackman-Harris, or other windowing function. The filtered time domain profile is then converted back into the frequency domain by a time-to-frequency conversion module1910to generate a filtered frequency domain range profile1912, which is stored in memory1806.

The target aspect angle (α) is then incremented by the target aspect angle incrementation module118, and the simulation process is repeated for the new target aspect angle (α)112. Simulation continues until filtered frequency domain range profiles1912have been generated and stored to memory1806for each aspect angle (α) within a 360° rotation of the target. The stored filtered frequency domain simulation data (e.g., a table of complex frequency samples vs. target aspect angles) is then exported by accumulation module1808to generate the RRP-ROM1902.

FIG.20is a flow diagram of an example method2000for generating a radar model for a target object. The example method2000depicted inFIG.20may, for example, be employed by the system shown inFIG.18. At2010, a target simulation model is received that identifies one or more physical aspects of a target object. At2020, an environment simulation model is received that identifies one or more physical aspects of an environment object. A target distance parameter is received at2030that identifies a reference distance between the target object and a radar system to be simulated. Also received at2030are the waveform characteristics of the radar system to be simulated.

At2040, a simulation model is generated based, at least in part, on the target simulation model, the environment simulation model, the target reference distance and the waveform characteristics of the radar. The simulation model is further based on a target aspect angle that identifies an angular position of the target object in relation to the radar system. Interaction of the radar system with the target object and the environment object is then simulated at2050using the simulation model. The simulation is used at2060to generate and store a frequency-domain range profile for the target object at the target aspect angle, wherein the stored frequency-domain range profile includes scattered S-parameters that are stored with reference to the prescribed target aspect angle (α) and reference distance (Rtgt).

The target aspect angle is incremented at2070, and operations2050-2060are repeated until range profiles are generated for the target object at a plurality of target angles amounting to a 360 degree rotation of the target object. The frequency-domain range profiles at the plurality of target angles are exported at2080to generate the radar model for the target object.

FIG.21is a flow diagram of another example method2100for generating a radar model for a target object. The example method2100depicted inFIG.21may, for example, be employed by the system shown inFIG.19. At2110, a target simulation model is received that identifies one or more physical aspects of a target object. At2115, an environment simulation model is received that identifies one or more physical aspects of an environment object. A target distance parameter is received at2120that identifies a reference distance between the target object and a radar system to be simulated. Also received at2120are the waveform characteristics of the radar system to be simulated.

At2130, a simulation model is generated based, at least in part, on the target simulation model, the environment simulation model, the target reference distance and the waveform characteristics of the radar. The simulation model is further based on a target aspect angle that identifies an angular position of the target object in relation to the radar system. Interaction of the radar system with the target object and the environment object is then simulated at2130using the simulation model, and the scattered S-parameters are saved as a frequency-domain range profile for the target object at the target aspect angle and reference distance (Rtgt).

The frequency-domain range profile is converted into the time domain at2135, for example using inverse Fast-Fourier Transform (FFT) as described above with reference toFIG.1. A time domain windowing filter is then applied to the time domain range profile at2140, for example utilizing one or more time domain filtering window functions, such as a Rectangular, Hamming, Hann, Blackman-Harris, or other windowing function. The filtered time domain profile is then converted back into the frequency domain at2145to generate a filtered frequency domain range profile, which is stored in memory at2150.

The target aspect angle is incremented at2155, and operations2230-2155are repeated until range profiles are generated for the target object at a plurality of target angles amounting to a 360 degree rotation of the target object. The frequency-domain range profiles at the plurality of target angles are exported at2160to generate the radar model for the target object.

It should be understood that the methods2000,2100shown inFIGS.20and21may be repeated for different combinations of radar systems (e.g., different radar waveform characteristics) and targets that a user may wish to simulate.

FIG.22is a flow diagram illustrating an example method2200of performing a closed-loop radar sensor simulation. At2210, a multi-target scene is constructed for a radar pulse in the closed-loop radar sensor simulation, for example as described below with reference toFIG.23. A RRP-ROM model is then received at2220for each target in the multi-target scene. The RRP-ROM models received at2220may, for example, be generated using one or more of the systems described herein, and may be received from an input mechanism or retrieved from one or more computer-readable storage medium. At2330the RRP-ROM contributions for each target in the multi-target scene are summed, accounting for the distance and angle of each target. The result of step2230is a summation of radar signal content at each sample frequency for all of the targets in the multi-target scene. The summation data is then transformed into the time domain at2240, for example using an inverse Fourier Transform. The result of step2240is a composite range profile, also known as a single pulse “fast time” response.

As illustrated by the dotted box inFIG.22, operations2210-2240may be repeated to generate a simulated radar return2250for multiple radar pulses, channels and frames within the closed-loop radar simulation.

FIG.23is a flow diagram of an example method2300for generating a multi-target scene for a closed-loop radar simulation. The method2300may, for example, be used at step2210ofFIG.22described above. The example method2300is described with reference to the example multi-target scene illustrated inFIG.24.

At2310, coordinates are located for the ground truth location of the center of each target in the scene. With reference to the example shown inFIG.24, two targets are illustrated (Target 1 and Target 2). In the illustrated example, the ground truth location of the center of Target 1 is located at a distance R1from the radar transmitter, and the ground truth location of the center of Target 2 is located at a distance R2from the radar transmitter. With reference again toFIG.23, at step2320, the aspect angle is determined for each target, and the aspect angle is used to look up the associated frequency sweep data (RRPn(θ)).

At2330, the RRPn(θ) frequency sweep data for each target is scaled in phase to obtain the appropriate electrical distance from the target to the reference location for the RRP ROM. Phase scaling may be accomplished by multiplying a factor of ej2k(RREF−∥R1∥), where k is the wave number (2π/λ) at the center frequency, R1is a vector from the radar origin to the target RRP ROM origin, and RREFis the reference distance for the RRP ROM. The factor of 2 accounts for round-trip phase distance. Phase is added (positive) when RREF−∥R1∥>0, and subtracted when RREF−∥R1∥<0.

At2340, if the bearing angle to the target is non-zero, the response is scaled by the reduction from peak gain at the bearing angle for the transmit radiation pattern (Ψt(θ)) and the receive radiation pattern (Ψr(θ)). Examples of the transmit radiation pattern (Ψt(θ)) and the receive radiation pattern (Ψr(θ)) for a radar transmitter are depicted in the example shown inFIG.24.

InFIG.24, the radar pulse/chirp response for the illustrated closed-loop radar simulation may be expressed as:
IFFT{RRP1(θ1)*A1*e2jk(−)+RRP2(θ2)*A2*ψt(Θ2)*e2jk(−)},
where

k=2⁢πλ=2⁢π⁢fc,
f is the center frequency, λ is the center frequency wavelength, c is the speed of light, A is the magnitude scaling relative to distance change from RREFfor each ROM, Ψt(θ) is the transmit antenna radiation pattern at angle θ, and Ψr(θ) is the receive antenna radiation pattern at angle θ.

The methods and systems described herein may be implemented on many different types of processing devices by program code comprising program instructions that are executable by the device processing subsystem. The software program instructions may include source code, object code, machine code, or any other stored data that is operable to cause a processing system to perform the methods and operations described herein and may be provided in any suitable language such as C, C++, JAVA, for example, or any other suitable programming language. Other implementations may also be used, however, such as firmware or even appropriately designed hardware configured to carry out the methods and systems described herein.

The systems' and methods' data (e.g., associations, mappings, data input, data output, intermediate data results, final data results, etc.) may be stored and implemented in one or more different types of computer-implemented data stores, such as different types of storage devices and programming constructs (e.g., RAM, ROM, Flash memory, flat files, databases, programming data structures, programming variables, IF-THEN (or similar type) statement constructs, etc.). It is noted that data structures describe formats for use in organizing and storing data in databases, programs, memory, or other computer-readable media for use by a computer program.

The computer components, software modules, functions, data stores and data structures described herein may be connected directly or indirectly to each other in order to allow the flow of data needed for their operations. It is also noted that a module or processor includes but is not limited to a unit of code that performs a software operation, and can be implemented for example as a subroutine unit of code, or as a software function unit of code, or as an object (as in an object-oriented paradigm), or as an applet, or in a computer script language, or as another type of computer code. The software components and/or functionality may be located on a single computer or distributed across multiple computers depending upon the situation at hand.

The methods and systems described herein may be implemented using any suitable processing system with any suitable combination of hardware, software and/or firmware, such as described below with reference to the non-limiting examples ofFIGS.25,26A,26B and26C.

FIG.25depicts at4000a computer-implemented environment wherein users4002can interact with a system4004hosted on one or more servers4006through a network4008. The system4004contains software operations or routines. The users4002can interact with the system4004through a number of ways, such as over one or more networks4008. One or more servers4006accessible through the network(s)4008can host system4004. It should be understood that the system4004could also be provided on a stand-alone computer for access by a user.

FIGS.26A,26B, and26Cdepict example systems for use in implementing a system. For example,FIG.26Adepicts an exemplary system5000that includes a standalone computer architecture where a processing system5002(e.g., one or more computer processors) includes a system5004being executed on it. The processing system5002has access to a non-transitory computer-readable memory5006in addition to one or more data stores5008. The one or more data stores5008may contain first data5010as well as second data5012.

FIG.26Bdepicts a system5020that includes a client server architecture. One or more user PCs5022accesses one or more servers5024running a system5026on a processing system5027via one or more networks5028. The one or more servers5024may access a non-transitory computer readable memory5030as well as one or more data stores5032. The one or more data stores5032may contain first data5034as well as second data5036.

FIG.26Cshows a block diagram of exemplary hardware for a standalone computer architecture5050, such as the architecture depicted inFIG.26A, that may be used to contain and/or implement the program instructions of system embodiments of the present disclosure. A bus5052may serve as the information highway interconnecting the other illustrated components of the hardware. A processing system5054labeled CPU (central processing unit) (e.g., one or more computer processors), may perform calculations and logic operations required to execute a program. A non-transitory computer-readable storage medium, such as read only memory (ROM)5056and random access memory (RAM)5058, may be in communication with the processing system5054and may contain one or more programming instructions. Program instructions may be stored on a non-transitory computer-readable storage medium such as magnetic disk, optical disk, recordable memory device, flash memory, or other physical storage medium. Computer instructions may also be communicated via a communications signal, or a modulated carrier wave, e.g., such that the instructions may then be stored on a non-transitory computer-readable storage medium.

A disk controller5060interfaces one or more disk drives to the system bus5052. These disk drives may be external or internal floppy disk drives such as5062, external or internal CD-ROM, CD-R, CD-RW or DVD drives such as5064, or external or internal hard drives5066.

Each of the element managers, real-time data buffer, conveyors, file input processor, database index shared access memory loader, reference data buffer and data managers may include a software application stored in one or more of the disk drives connected to the disk controller5060, the ROM5056and/or the RAM5058. Preferably, the processor5054may access each component as required.

A display interface5068may permit information from the bus5056to be displayed on a display5070in audio, graphic, or alphanumeric formal. Communication with external devices may occur using various communication ports5078.

In addition to the standard computer-type components, the hardware may also include data input devices, such as a keyboard5072, or other input device5074, such as a microphone, remote control, pointer, mouse and/or joystick.

While the disclosure has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope of the embodiments. Thus, it is intended that the present disclosure cover the modifications and variations of this disclosure provided they come within the scope of the appended claims and their equivalents.