Broad band spiral and sinuous antennas

摘要

The outer turns (3) of a spiral antenna are radially modulated to extend the low-frequency response. The modulation amplitude increases progressively with spiral angle. The unmodulated region may consist of equally-spaced inner turns (1), and outer turns (2) whose spacing increases with angle. The track width of the outer turns may progressively decrease. Alternatively the track width of the outer unmodulated region may increase, the width of the modulated turns then progressively decreasing. Similar modulation may be applied to the outer ends of the arms of sinuous antennas. <IMAGE>