The role of resistance in broadband, pulse-distortionless antennas

Radars that use baseband pulses, such as ground penetrating radars, require antennas that can radiate and receive temporally short, wide-bandwidth pulses. A variety of antennas have been proposed for this purpose. Usually these antennas incorporate resistive material to reduce reflections from discontinuities, such as the ends of a dipole antenna or at the open end of a transverse electromagnetic (TEM) horn antenna. The authors discuss two contributions resistance can make to the performance of these antennas: the aforementioned reduction of reflections along the structure and the preservation of the incident pulse shape on radiation. A simple canonical model is used: an open-ended parallel plate waveguide with a resistive (lossy) wall over a portion of its length. This structure is analyzed using finite-difference time-domain methodology.<>