Wideband, Compact Antennas With Interdigitated Magnetic-Based Near-Field Resonant Parasitic Elements

Wideband, compact antennas based on interdigitated magnetic-based near-field resonant parasitic (NFRP) elements are presented. The interdigitated NFRP elements, driven with coax-fed monopole antennas, facilitate the realization of two adjacent resonant modes whose combination yields the enhanced bandwidth. The resulting wideband compact antennas exhibit broadside radiation performance. Linearly polarized (LP) and circularly polarized (CP) prototypes based on this interdigitated NFRP element concept were designed, simulated, fabricated, and measured. The measured and simulated results are in good agreement. The NFRP radiating element of the LP antenna is electrically small with
$ka = 0.921$
and yields a wide, 17.4%, −10 dB impedance bandwidth with a stable realized gain, ~5.5 dBi, over its entire operational bandwidth. The NFRP radiating element of the CP antenna is also electrically small with
$ka = 0.923$
and exhibits a wide, 8.6%, 3 dB axial ratio bandwidth. Stable realized gain, ~5.2 dBi, and uniform radiation patterns along with relatively high radiation efficiency, RE > 88%, are achieved over its entire operational bandwidth.