Numerical Analysis of mm-wave Antenna with Dielectric Cover Based on Ray Tracing and NF-FF Transformation Techniques

Abstract

Ray tracing and near field to far field transformation (NF-FF) techniques are applied for efficient electromagnetic analysis of millimeter wave antennas with electrically large dielectric structures. When electrically large structures, such as vehicle bumper and mobile phone housing, are placed around an antenna system, it requires extremely high computational time and large memory resource to analyze the antenna systems. This is especially true if the analysis software is based on full wave algorithms, such as finite difference time domain (FDTD), finite element method (FEM), method of moments (MoM), whose complexity is dependent on the electrical size of the structure to be analyzed. In this thesis, ray tracing and near field to far field transformation techniques are considered for decreasing computation time and required memory resources. Dielectric covers which protect the antenna physically are usually located in front of the antenna and the radiated far field is obtained considering a transmission through the cover. In the proposed analysis procedure, electric field transmitting from the antenna through the dielectric cover is determined using ray tracing technique and radiated far field is obtained using near field to far field transformation technique. An array of patch antenna which is used as a source is characterized by equivalent dipole model technique. Non-uniform rational B-spline (NURBS) is used to represent the surrounding cover structure and conjugated gradient method (CGM) is applied to determine the optical path of rays on the cover model. Dielectric constant is calculated using Nicolson-Ross-Weir (NRW) method. The proposed method is validated through a comparison with measurements. With regard to the measurements, a patch array antenna, which is frequently used in millimeter wave application, was used as an antenna, and a commercial automotive radar cover was located at the front. In 76.5 GHz, the proposed method took less time compared to the commercial EM simulation program based on MoM, and the errors were less than 3 dB over the field of view (FOV) of the automotive radar. This work can be beneficial to efficient prediction of the effects of dielectric cover in mm-wave applications.