A series-fed loop array antenna radiating a circularly polarised wave

Abstract

A loop antenna can radiate a circularly polarised (CP) wave when two perturbation segments are used. We investigate a novel loop array antenna radiating a CP wave. The loops are linearly arrayed, and excited by a continuous feed line. The array belongs to a class of cascaded array antennas that are characterised by their simple feed. The loop array antenna is numerically investigated to form a CP beam. The method of moments is used to analyse the current distribution along the loops and feed line, and the radiation characteristics of the array antenna are evaluated using the determined current distribution. The CP beam is formed in the direction normal to the antenna plane. The guided wavelength of the current is estimated to realise the broadside beam. Using the estimated guided wavelength, the loop configuration and feed line length are appropriately chosen for radiation of a CP wave. The frequency response of the radiation characteristics, including the radiation pattern, axial ratio, and gain, are also presented and discussed.