Characteristic mode-based design and analysis of an electrically small planar spiral antenna with omnidirectional pattern

The antenna under consideration is a five-turn Archimedean rectangular two-arm wire spiral antenna, which is 46 x 15.7cm in size is presented in this paper. It is placed in the x-y plane. There are two ports (one per arm) located at the center. Normally, a two-arm spiral antenna cannot practically radiate spiral mode 2, as it requires the two-ports at the center to be excited in phase (i.e. an unbalanced feed), but it can be simulated using a method of moments code (MoM) without any problems. All simulation results are obtained using an MoM code. The goal is to produce the best possible horizontally polarized omnidirectional pattern. The reader should note that all gain values cited in this section do not include mismatch losses. Absolute gain, which includes matching networks, will be presented at the conference.