Patent Description:
The use of radio frequency (RF) scene representations in missile <NUM>-Degree of Freedom (6DoF) simulations has grown in recent years as computing hardware has become powerful enough to complete the simulation calculations in reasonable times. These RF scenes included targets, weather effects, and static clutter. At the same time, models that simulate ocean surface physics and their interactions with surface vessels have been developed for use in similar 6DoF simulations. Because of the time precision required by RF scene generation, simulating moving ocean surface scattering effects for such an application was computationally intractable.

Thus, there are general needs for improved systems and methods that integrate a moving maritime surface into an RF scene.

<NPL>, discloses low-velocity small target detection with doppler-guided retrospective filter in high-resolution radar at fast scan mode.

<NPL>, discloses modelling the spectral structure of ducted sea clutter.

The present invention is set forth in the appended set of claims.

The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them.

Initial attempts to model ocean surfaces in RF scenes lead to static surface models which reduced realism and limited thorough analysis. These models would represent the ocean as a flat surface or waves frozen in time. Further implementations of a moving maritime surface into RF scene-generation were accomplished by updating the ocean surface at the radar's pulse repetition frequency which is orders of magnitude greater than the desired ocean surface update rate. This caused the 6DoF simulations to require many additional hours of run time to reach completion.

In order to reduce the run-time of a simulation that integrates both RF scene-generation and a moving maritime surface, embodiments disclosed herein disconnect the ocean surface update rate from the radar PRF. This is accomplished at the wrapper level by evolving the maritime surface at an optimal rate for the use case and passing a pointer to the surface object to the RF scene-generator. The RF scene model accesses current and previous maritime surfaces then interpolates the surface facet properties to the time required by the radar. If a radar dwell takes place over two or more maritime surface updates, the simulated radar returns are treated as separate sub-dwells by the RF scene generator and are stitched back together by the wrapper when the dwell is complete. This process may reduce typical simulation runtime by a factor of two.

In some embodiments, each model is driven separately as individual an object which allows independent time evolution. In some embodiments, the maritime surface owns its surface parameters which are available to the RF scene-generator for use. In some embodiments, RF system performance analysis in maritime environments is now feasible.

Embodiments are directed to simulating a radio frequency (RF) scene associated with a moving maritime surface. Some embodiments are directed to a non-transitory computer-readable storage medium that stores instructions for execution by processing circuitry. The instructions may configure the processing circuitry to simulate an RF scene associated with a moving maritime surface.

According to the invention, an RF scene is generated using an RF scene generation model and a moving maritime surface is generated using a maritime surface model and the RF scene is integrated with the moving maritime surface.

<FIG> illustrates maritime surface model updating in accordance with some embodiments. According to the invention, the RF scene generation model is configured to apply a radar model to generate and update the RF scene based on simulated radar returns at a radar pulse repetition frequency (PRF). The maritime surface model is configured to update the moving maritime surface at a maritime surface update rate, access previous and current maritime surfaces, and interpolate surface facet properties to pulse times of the radar model. The maritime surface model is configured to update the moving maritime surface once every subdwell <NUM> of a plurality of subdwells <NUM> comprising a radar dwell time. Each subdwell <NUM> comprises a plurality of simulated radar pulses <NUM>.

In some embodiments, the maritime surface update rate may be a fixed rate (e.g., once every second). In some embodiments, the maritime surface update rate may comprise a predetermined number of radar pulses <NUM> (i.e., several hundred to several thousand), although the scope of the embodiments is not limited in this respect.

In some embodiments, for a radar dwell that takes place over two or more maritime surface updates, the simulated radar returns may be treated as separate sub-dwells by the RF scene generation model to allow phase histories of the simulated radar returns to be concatenated (at time <NUM>) based on pulse index when the radar dwell is complete, although the scope of the embodiments is not limited in this respect. In these embodiments, a driver (e.g., driver software) may implement a wrapper around the RF scene generation model and the maritime surface model allowing the phase histories of the simulated radar returns to be concatenated together.

In some embodiments, the RF scene generation model and the maritime surface model are driven separately as individual software objects to allow for independent time evolution to allow the maritime surface model to be updated per subdwell, although the scope of the embodiments is not limited in this respect. These embodiments allow for the maritime surface model to be updated at a per-subdwell <NUM> rate rather than at the radar pulse repetition rate.

In some embodiments, the instructions may be configured for integration in a system performance suite (i.e., a system hardware test environment) comprising a six degrees-of-freedom (6DOF) system simulation, although the scope of the embodiments is not limited in this respect.

In some embodiments, prior to interpolation of the surface facet properties, the maritime surface model may be configured to update the moving maritime surface a predetermined number of times, although the scope of the embodiments is not limited in this respect. In some embodiments, at least three maritime surface updates may be needed prior to interpolation, although the scope of the embodiments is not limited in this respect.

In some embodiments, to interpolate the surface facet properties for an update of the moving maritime surface, the maritime surface model may be configured to perform a logarithmic interpolation of white water/whitecap properties of surface facets, perform a quadradic interpolation of height and/or position properties of the surface facets, and perform a linear interpolation of velocity properties of the surface facets, although the scope of the embodiments is not limited in this respect. In these embodiments, a facet may be viewed as a small patch of ocean and the facets which are interpolated to represent the sea surface.

The RF scene generation model is configured to interpolate the surface facet properties per radar pulse <NUM>.

In some embodiments, when any of the radar pulses <NUM> of the radar dwell remain un-simulated by the RF scene generation model, the RF scene generation model may be configured to interpolate the surface facet properties per pulse for each of the remaining un-simulated pulses. The RF scene generation model may be configured to refrain from concatenation of the phase histories of the simulated radar returns until all radar pulses <NUM> of the radar dwell are simulated, although the scope of the embodiments is not limited in this respect.

In some embodiments, a phase history may be generated for each subdwell, and the phase histories of the subdwells <NUM> may be concatenated to generate a dwell phase history <NUM> for the radar dwell. The dwell phase history may be passed on to a RF seeker simulator for additional signal processing for a full radar dwell, although the scope of the embodiments is not limited in this respect. In some embodiments, the additional signal processing comprises one or more of performance of motion compensation, range compression, and Doppler compression, although the scope of the embodiments is not limited in this respect. In some embodiments, the processing circuitry may be configured to store the phase history for each subdwell <NUM> in memory.

In some embodiments, the processing circuitry may calculate a maximum number of pulses before a next maritime surface update and update other dwell parameters.

<FIG> illustrates a process for simulating an RF scene in accordance with some embodiments. As illustrated in <FIG>, in some embodiments, a simulation driver <NUM> may perform master simulation loop comprising operations <NUM>, <NUM>, <NUM><NUM>, <NUM> and <NUM> in response to a dwell command until no pulses remain un-simulated. Operations <NUM> and <NUM> are configured to evolve the maritime surface each subdwell based on update interval (m) between the maritime surface and the RF scene generator updates. Once all pulses of a dwell are simulated, phase histories of the subdwells are concatenated in operation <NUM> and returned in operation <NUM>.

Embodiments disclosed herein make use of a high-fidelity, moving, maritime surface model with RF scene generation feasible in a performance simulation environment, where the ocean surface evolves throughout the simulation run with multiple active radar dwells commanded. Some embodiments may be suitable for simulating missile behavior and performance for missiles using RF seekers in a maritime environment, although the scope of the embodiment is not limited in this respect.

Some embodiments leverage interpolation between two or more ocean surfaces in time to allow the maritime surface simulation to be driven independently of the RF scene generator, which may reduce computation time and frees the maritime surface to be able to drive vehicle 6DoF data in a performance simulation environment. The reduction of surface updates may be by a factor on the order of (PRF/Surface update frequency) which is often on the order of 800x. Instead of updating the ocean surface to the specific time a pulse occurs, which is computationally intense, each facet's properties may be interpolated to that point in time between past and future surface states and those facet properties may be used for the RF reflections for the given pulse.

Some embodiments may be implemented in a prototype standalone driver. Some embodiments may be integrated into the RF scene generation driver.

<FIG> illustrates a block diagram of an example machine <NUM> upon which any one or more of the techniques (e.g., methodologies) discussed herein may be performed. The machine <NUM> may be system simulator (configured to perform the operations described above and illustrated in <FIG>), a personal computer (PC), a tablet PC, a set-top box (STB), a personal digital assistant (PDA), a mobile telephone, a smart phone, a web appliance, a network router, switch or bridge, or any machine capable of executing instructions (sequential or otherwise) that specify actions to be taken by that machine.

In an example, the software may reside on a non-transitory computer-readable storage medium. In some embodiments, the non-transitory computer-readable storage medium may store instructions for execution by one or more processors or processing circuitry, to perform the operations described herein. In some embodiments, the instructions may configure the processing circuitry to simulated a radio frequency (RF) scene associated with a moving maritime surface.

Machine (e.g., computer system) <NUM> may include processing circuitry such as a hardware processor <NUM> (e.g., a central processing unit (CPU), a graphics processing unit (GPU), a hardware processor core, or any combination thereof), a main memory <NUM> and a static memory <NUM>, some or all of which may communicate with each other via an interlink (e.g., bus) <NUM>.

Claim 1:
A non-transitory computer-readable storage medium that stores instructions for execution by processing circuitry, the instructions to configure the processing circuitry to simulate a radio frequency ,RF, scene associated with a moving maritime surface,
wherein instructions configure the processing circuitry to:
generate an RF scene using an RF scene generation model;
generate the moving maritime surface using a maritime surface model; and
integrate the RF scene and the moving maritime surface,
wherein the RF scene generation model is configured to apply a radar model to generate and update the RF scene based on simulated radar returns at a radar pulse repetition frequency ,PRF, characterised in that
the maritime surface model is configured to update the moving maritime surface at a maritime surface update rate, access previous and current maritime surfaces, and interpolate surface facet properties to pulse times of the radar model, and
in that the maritime surface model is configured to update the moving maritime surface once every subdwell (<NUM>) of a plurality of subdwells (<NUM>) comprising a radar dwell time, each subdwell (<NUM>) comprising a plurality of simulated radar pulses (<NUM>).