Mutual Coupling Reduction in Airborne Co-Sited Blade Antennas Through Size-Constrained Vertical Soft Surfaces

In this letter, the mutual coupling reduction in airborne co-sited blade antennas is addressed. To suppress the interference between nearby radiators over a wideband, an innovative coplanar printed isolating device is designed by exploiting an extension of the soft surface concept. As a proof of the effectiveness of the proposed approach, a system working in the aircraft
L
-band is designed that yields a high isolation (with mutual scattering coefficient
$S_{12}\leq -\text{30.8}$
dB) over a fractional bandwidth of 23.4% without significantly impacting the radiation performance.