Circularly polarized spiral antenna using a double negative property

A design process to realize a low-profile spiral antenna with an antenna height of approximately 1/100 wavelength is presented, where a negative phase constant for the current on the spiral arms is used. For circularly polarized radiation, frequency f
_N
, called the N frequency, is located between the lower bound frequency f
_L
for a fast wave and a transition frequency f
_TR
. The antenna characteristics, including the radiation pattern, gain, and input performance (VSWR) are presented and discussed.