Geometric Optics with Uniform Asymptotic Physical Optics for Ray Tracing of Compound GRIN Lens Systems

In this paper, a compound Gradient-Refractive Index (GRIN) lens simulation method using hybrid Geometrical Optics and Uniform Asymptotic Physical Optics is proposed. The ray distributions of the compound lens structure are analyzed and seven major regions are described in detail with an example showing diffracted fields of both lenses. To improve the accuracy, a ray tracing design flowchart is given with an iterative ray-launching procedure to ensure proper ray spacing in the radiating aperture. An impedance-matched compound GRIN lens structure is simulated with the proposed numerical method (requiring only 2.5 minutes) and compared with a full-wave simulator (requiring about 3 hours). The hybrid ray tracing has a gain error of 0.2dB, a sidelobe level error of 4.7dB and a 3dB beamwidth error of 0.1 degrees.