There is disclosed an antenna exhibiting resonance over a broad frequency band
or over a plurality of closely-spaced frequency bands, comprising a ground plane,
a non-driven element affixed substantially perpendicular to the ground plane, a
driven element affixed substantially perpendicular to the ground plane and a horizontal
conductor electrically connected between the driven and the non-driven elements
and disposed substantially parallel to the ground plane. The non-driven and the
driven elements further comprise periodic slow wave structures. The periodic slow
wave structures are configured to provide a substantially constant propagation
factor with respect to the applied signal frequency, such that the antenna exhibits
broad resonance characteristics.