Tilted- and axial-beam formation by a single-arm rectangular spiral antenna with compact dielectric substrate and conducting plane

A single-arm rectangular spiral antenna is analyzed using the finite-difference time-domain method. The spiral is printed on a finite-size dielectric substrate backed by a finite-size conducting plane. Both the substrate and conducting planes are square with a side length L of less than 0.6/spl lambda//sub 0/ (/spl lambda//sub 0/: wavelength in free space). The radiation pattern is dependent on the outermost arm peripheral length C. The spiral whose peripheral length is within 2/spl lambda//sub g/