Designs of Compact, Planar, Wideband, Monopole Filtennas with Near-Field Resonant Parasitic Elements

Two planar efficient wideband, electrically small monopole filtennas are presented. The first one directly evolves from a common planar capacitively loaded loop (CLL)-based filter possessing a flat realized gain response within the operational band and good band-edge selectivity. The second filtenna consists of a driven element augmented with a CLL structure and with slots etched into its ground plane. It expands the fractional impedance bandwidth of the first case from 6.28 percent up to 7.9 percent. It also has a gain response that remains flat over its operational bandwidth and even higher band-edge selectivity. Both filtennas are electrically small with ka less than 1. The experimental results, which are in good agreement with their simulated values, demonstrate that both filtennas exhibit excellent impedance matching, high radiation efficiency, flat gain response, and steep skirts at both band edges. Moreover, they produce monopole radiation patterns that are uniform and nearly omnidirectional in their H-planes.