A miniaturized, ultra-wideband, circularly polarized spiral antenna

A low-profile and compact, ground-plane backed spiral antenna with an ultra-wideband circularly-polarized response is presented. This antenna system is a multilayer structure composed of a center-fed modified Archimedean spiral antenna that includes a novel loading structure, a ring shaped absorber, a feeding network, and a 180° power splitter. The loading structure possesses both inductive and capacitive characteristics, which increase the equivalent electrical length of the antenna while maintaining its maximum dimensions. Using this structure, a compact spiral antenna with a diameter of 0.20λ_min is obtained (λ_min is the wavelength at the lowest frequency of operation of the antenna). This antenna is integrated into the multilayer structure along with a feeding network. An optimized ring shape absorber is used to reduce the ground effects on the performance of the antenna. The peak gain of the antenna with the feeding network is 3.94 dBic. The 3-dB axial ratio (CP) bandwidth is 155%. The VSWR <; 3 bandwidth is 137%. The size of the antenna with the feeding network is 0.20λ_min× 0.20λ_min × 0.08λ_min. The design and simulation results of the antenna are presented and discussed in this paper.