Accurate and efficient electromagnetic response for a sensor simulator
This document describes techniques and systems for accurate and efficient electromagnetic response for a sensor simulator. Target information and sensor parameters for an electromagnetic sensor are simulated in an environment that includes a ground plane. Electromagnetic rays that may be detected by the sensor or an image of the sensor are launched from the simulated sensor toward the target and an image of the target about the ground plane to determine a complex electromagnetic response of the target. A ray-tracing algorithm is applied to trace the forward wave propagation of electromagnetic rays in the environment that considers rays bouncing between the target and the image of the target. An electromagnetic response can be modeled based on the congregation of the electromagnetic response of all backward paths of all bounces of all rays. In this manner, an efficient and accurate electromagnetic response model may be approximated.
1. A method comprising:
receiving target information for a target and sensor parameters for an electromagnetic sensor that are simulated in an environment with a ground plane;
determining, based on the target information and the sensor parameters, electromagnetic rays interacting with the target, the electromagnetic rays having forward propagation paths to the target and backward propagation paths from the target; and
modeling an electromagnetic response by approximating, based on determining the electromagnetic rays interacting with the target, electromagnetic energy reflected by the target alone or in combination with the ground plane,
wherein determining the electromagnetic rays interacting with the target comprises:
determining a target image for the target that mirrors the target about the ground plane;
determining an electromagnetic sensor image that mirrors the electromagnetic sensor about the ground plane;
launching initial electromagnetic rays from the electromagnetic sensor at the target and the target image, the initial electromagnetic rays having the same spatial ray density relative to the target and the target image;
performing ray tracing to determine reflected electromagnetic rays from the target and the target image; and
evaluating, based on equivalent surface currents, scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image.
2. The method of claim 1 , wherein evaluating scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image further comprises:
responsive to a respective ray of the initial electromagnetic rays being reflected by the target or crossing the ground plane, calculating dielectric Fresnel reflection coefficients for the target and the ground plane; and
multiplying the scattered fields and respective incident fields by the dielectric Fresnel reflection coefficients.
3. The method of claim 2 , wherein evaluating the scattered fields of the reflected electromagnetic rays comprises:
computing the incident fields of the electromagnetic rays on the target using geometrical optics; and
computing the equivalent surface currents on the target and the scattered fields of the reflected electromagnetic rays using physical optics.
4. The method of claim 1 , wherein image theory is used to model the electromagnetic response for the simulated target.
5. The method of claim 1 , wherein a shooting and bouncing rays method is used to approximate the electromagnetic energy propagated to the target and reflected by the target.
6. The method of claim 1 , wherein approximating the electromagnetic energy reflected by the target includes multipath reflections from the ground plane.
7. The method of claim 1 , wherein approximating the electromagnetic energy reflected by the target excludes reflections determined to be occluded by physical characteristics of the target.
8. The method of claim 1 , wherein the target information comprises:
position of the target;
orientation of the target; and
speed of the target.
9. The method of claim 1 , wherein the parameters of the electromagnetic sensor comprise:
position of the electromagnetic sensor;
orientation of the electromagnetic sensor;
field-of-view of the electromagnetic sensor; and
operating frequency of the electromagnetic sensor.
10. A system comprising:
at least one processor configured to:
receive target information for a target and sensor parameters for an electromagnetic sensor that are simulated in an environment with a ground plane;
determine, based on the target information and the sensor parameters, electromagnetic rays interacting with the target, the electromagnetic rays having forward propagation paths to the target and backward propagation paths from the target; and
model an electromagnetic response by approximating, based on determining the electromagnetic rays interacting with the target, electromagnetic energy reflected by the target alone or in combination with the ground plane,
wherein the at least one processor is configured to determine the electromagnetic rays associated with the target by at least:
determining a target image for the target that mirrors the target about the ground plane;
determining an electromagnetic sensor image that mirrors the electromagnetic sensor about the ground plane;
launching initial electromagnetic rays from the electromagnetic sensor at the target and the target image, the initial electromagnetic rays having the same spatial ray density relative to the target and the target image;
performing ray tracing to determine reflected electromagnetic rays from the target and the target image; and
evaluating, based on equivalent surface currents, scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image.
11. The system of claim 10 , wherein the at least one processor is configured to evaluate the scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image by at least:
responsive to a respective ray of the initial electromagnetic rays being reflected by the target or crossing the ground plane, calculating dielectric Fresnel reflection coefficients for the target and the ground plane;
multiplying the scattered fields and respective incident fields by the dielectric Fresnel reflection coefficients;
computing, using ray tracing and geometrical optics, the incident fields of the electromagnetic rays on the target; and
computing, using physical optics, the equivalent surface currents on the target and the scattered fields of the reflected electromagnetic rays.
12. The system of claim 10 , wherein the at least one processor is configured to approximate the electromagnetic energy reflected by the target by including multipath reflections from the ground plane.
13. The system of claim 10 , wherein the at least one processor is configured to approximate the electromagnetic energy reflected by the target by excluding reflections determined to be occluded by physical characteristics of the target.
14. A non-transitory computer-readable storage media comprising instructions that, when executed, cause at least one processor to:
receive target information for a target and sensor parameters for an electromagnetic sensor that are simulated in an environment with a ground plane;
determine, based on the target information and the sensor parameters, electromagnetic rays interacting with the target, the electromagnetic rays having forward propagation paths to the target and backward propagation paths from the target; and
model an electromagnetic response by approximating, based on determining the electromagnetic rays interacting with the target, electromagnetic energy reflected by the target alone or in combination with the ground plane,
wherein the instructions, when executed, further cause the at least one processor to determine the electromagnetic rays interacting with the target by at least:
determining a target image for the target that mirrors the target about the ground plane;
determining an electromagnetic sensor image that mirrors the electromagnetic sensor about the ground plane;
launching initial electromagnetic rays from the electromagnetic sensor at the target and the target image, the initial electromagnetic rays having the same spatial ray density relative to the target and the target image;
performing ray tracing to determine reflected electromagnetic rays from the target and the target image; and
evaluating, based on equivalent surface currents, scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image.
15. The non-transitory computer-readable storage media of claim 14 , wherein the instructions, when executed, further cause the at least one processor to evaluate the scattered fields of the reflected electromagnetic rays received by the electromagnetic sensor and the electromagnetic sensor image by at least:
responsive to a respective ray of the initial electromagnetic rays being reflected by the target or crossing the ground plane, calculating dielectric Fresnel reflection coefficients for the target and the ground plane;
multiplying the scattered fields and respective incident fields by the dielectric Fresnel reflection coefficients;
computing, using ray tracing and geometrical optics, the incident fields of the electromagnetic rays on the target; and
computing, using physical optics, the equivalent surface currents on the target and the scattered fields of the reflected electromagnetic rays.
16. The non-transitory computer-readable storage media of claim 14 , wherein the instructions, when executed, cause the at least one processor to approximate the electromagnetic energy reflected by the target by including multipath reflections from the ground plane.
17. The non-transitory computer-readable storage media of claim 14 , wherein the instructions, when executed, cause the at least one processor to approximate the electromagnetic energy reflected by the target by excluding reflections determined to be occluded by physical characteristics of the target.