Compact Wideband Filtering Monopole Antenna Using Characteristic Mode Analysis

A compact wideband filtering monopole antenna is presented using characteristic mode analysis (CMA). The antenna integrates a ‐shaped monopole arm and a folded monopole arm on a common ground plane. The ‐shaped monopole supports a /4 mode, whereas the folded monopole compresses a 3/4 mode towards a /4 mode. The antenna yields a trimode response. Mode decomposition of the antenna modes onto substructure modes shows that two /4 modes and a 3/4 mode produce radiation nulls in the lower and upper bands, enabling intrinsic filtering without external structures. The prototype achieves a 48.3% impedance bandwidth ( −10 dB). The antenna has a compact size of 0.354 0.049, making it suitable for space‐constrained wireless platforms.