Time Domain Characteristic Mode Theory for Transmission and Coupling Problems

Characteristic mode analysis (CMA) is applied mostly in the frequency domain. In this paper, a time domain CMA is proposed based on the data of modal self-and mutual-admittance in the frequency domain. An algorithm is developed to compute the time domain CMA using IFFT, extrapolation and Hilbert Transformation. This time domain CMA is suitable for transmission and coupling problems, in which it represents the modal unit impulse response on specified ports. A parallel line and dipole antennas are computed for verification. For parallel line, time domain CMA is similar as the common and differential modes. For dipole antennas, the results are interesting to observe. The presented theory expands the areas of traditional CMA.