Low-Profile Broadband and Dual-Frequency Two-Strip Planar Monopole Antennas

A novel type of low-profile broadband and dual-frequency monopole antennas is developed for wireless applications. The broadband monopole consists of an S-strip and a folded T-strip which are separately printed on the two sides of a thin planar substrate. No via process is involved in the fabrication. The two-strip planar monopole can achieve a bandwidth (VSWR<2) of ~35% with a height of 0.056lambda
₀
. The dual-frequency operation of the broadband monopole antenna is realized by adding a short T-strip to the S-strip and a couple of inverted-L strips to the folded T-strip. The dual-frequency monopole can accomplish a bandwidth of ~40% at a lower-frequency band and ~10% at a higher-frequency with a total height of 0.08lambda
₀