Finite-difference time-domain method for high-frequency and long-slot antennas

A study is presented of the characteristics of antennas used in the high-frequency (HF) communication band (2-30 MHz) and leaky-wave slot antennas used in the X band (8.2-12.4 GHz) region. The leaky-wave long slot antennas are constructed by cutting a slot into the broadwall of a rectangular waveguide. The HF antennas analyzed are the "towel bar" and "inverted-L" elements used in military helicopter communication systems. The finite-difference time-domain (FDTD) method is used to model the radiation of electromagnetic energy from these antenna elements. Limitations of the FDTD method for use on these electrically large (leaky-wave long slot antennas) and electrically small antennas (HF antennas) are overcome by implementing a new, more accurate grid truncation and also by implementing the FDTD code on a massively parallel computing platform. The antenna parameters to be examined include far-field radiation patterns, input impedance, gain, efficiency, and induced surface current densities.; The FDTD method discretizes Maxwell's curl equations explicitly using central differences in time and space. The equations are then solved in a leap-frog time-stepping manner on an interlaced grid of electric and magnetic field components. Far-field radiation is determined by applying the equivalence principle and the Sommerfeld radiation condition over a general surface. The computational space is truncated by implementing the Berenger Perfectly Matched Layer (PML) absorbing boundary condition on the six faces of the three-dimensional computational space. Near-field wideband characteristics of the antenna systems are computed by exciting the system with a pulse, detecting the time-domain voltages and currents of interest and performing FFTs to obtain wide-band frequency response of the antenna characteristics of interest.