A meander spiral antenna

A spiral antenna is a radiation element that radiates a circularly polarized (CP) wave over a wide frequency bandwidth. The spiral is often backed by a conducting plane to change the inherently bidirectional beam to a unidirectional one. The radiation pattern has been qualitatively and quantitatively investigated (Nakano, H. 1987; Nakano et al., 1988). These investigations show that, as the distance between the spiral and the conducting plane decreases, the capability of the antenna to form a CP beam deteriorates. This paper presents a technique to overcome this deterioration in the formation of the CP beam. The technique is based on modifying the spiral arm into a meander. For analysis of such a spiral antenna, first, a method of moments (MoM) solution to an integral equation for an arbitrarily shaped thin wire printed on a dielectric substrate is presented. Next, the integral equation is applied to a meander printed spiral antenna, which radiates first-mode radiation. The axial ratio is evaluated as a function of the number of meander cells.