Bandwidth-Enhanced Electrically Small Printed Folded Dipoles

This letter presents a wire folding scheme to enhance the bandwidth of an electrically small resonant microstrip antenna. As an example, meandered two-wire slow-wave lines spread on both sides of a dielectric slab short-circuited at both ends form a vertically folded printed dipole. It is found that the radiation resistance increases by about a factor of 4, and the energy storage increases by about a factor of 2, using a folded dipole. It is shown through both measurement and simulation that the Q-factor is reduced by about 50% through antenna folding. A 0.14 ¿-long folded dipole resonant at 2.43 GHz shows a bandwidth of about 4.8%. The proposed folding method facilitates planar antenna miniaturization with sufficient bandwidth.