TWO-ARM ARCHIMEDEAN SPIRAL HELICAL ANTENNA WITH WRAPAROUND ABSORBER

A method was presented to miniaturize a spiral antenna, without sacrificing performance at lower frequencies. A two-arm spiral antenna, with reduced size, whose diameter is 4.4 inches, but has gain and return loss across the desired band of at least the Archimedian antenna is build. The 6-inch diameter two-arm Archimedean spiral antenna with a ground plane placed 2.6 inches has r1 = 0.05'' and r2 = 3.0'' as the initial and final radius, respectively. W = 0.04'' is the width of the spiral arm and S = 0.06'' is the gap between turns. To improve the gain at the low frequencies, two helices are added such that they connect the two spiral arms to the ground plane. FEKO optimization is used to determine the loss tangent (tan ) and the thickness of the absorber. An optimization routine is set up with the goal of reaching the gain and maximizing the return loss at 500 MHz. FEM, being a field solver needed far more computation time and memory than MoM (FEKO).