A Quad-Band Branched Monopole Antenna with Filters Suppressing Higher-Order Modes

A novel quad-band branched monopole antenna with filters is proposed. The proposed antenna consists of a mast, two branch-elements for low-band, and two branch-elements for high-band. Lumped-element filters are loaded at the roots of the low-band elements to suppress higher-mode currents at the high-band. It is clarified by simulations that desirable VSWR characteristic can be achieved at all bands of interest if band-pass filters with an appropriate Q-factor are loaded.