Two stacked orthogonally wound spirals with connected arms

The lowest frequency in the bandwidth of a spiral antennas is limited by the size of the antenna. Horizontal connections between spiral arms of opposite polarization have been devised in linear arrays in order to reduce the lowest frequency in the bandwidth. This paper shows the reflection coefficient (|S₁₁|) and axial ratio (AR) are greatly enhanced at the low end of the frequency bandwidth by connecting the arms of two stacked, orthogonally wound spiral antennas.