ANALYSIS OF RESISTIVELY LOADED, PRINTED SPIRAL ANTENNAS

A method of moments formulation for the current on arbitrarily shaped planar conductors in layered media is utilized to study the characteri stics of printed spiral antennas. This algorithm permits the use of di stributed and lumped impedance loads on the conductor. Also, it takes advantage of the discrete rotational symmetry exhibited by certain str uctures, thus reducing the matrix storage requirements. Numerical resu lts are presented for two-arm and four-arm spiral antennas. Resistive loading along the outer portions of the spiral is used to eliminate re flected current contributions. For conductor-backed printed spirals, t he presence of the ground plane reduces the amount of mode 1 radiation , allowing for the radiation of higher order spiral modes. Increasing the number of the spiral arms is shown to alleviate this problem by in creasing the order of the first contributing higher order mode.