Modification of Sinuous Antenna Arms for UWB Radar Applications

The sinuous antenna is modified to improve its performance for ultrawideband (UWB) radar applications. The radiated waveforms in the time domain of typical sinuous antennas contain a long ringing tail after the chirp-like main pulse when excited by a temporally short pulse. The ringing is due to resonances that are set up on the antenna arms and are essentially eliminated by modifying the shape of the arms. The first modification removes the sharp ends where the arms terminate, and the second changes the shape of the arms where they bend. These modifications are also shown to improve the gain flatness of the antennas. Three representative sinuous antennas are fabricated, tested, and demonstrated in a monostatic radar experiment. The measured results clearly show the advantages of the improved antenna.