Reducing the Q Lower Bound for Electrically Small Antennas Using Dispersive Tuning

By tuning with dispersive permittivity or permeability, the quality factors and thus the Chu lower bound for lossy magnetic- or electric-dipole antennas at isolated resonances or antiresonances can be reduced by a factor of one-half (bandwidth doubled) for input-impedance bandwidth power drops of about −24 dB with radiation efficiencies of about 50%. Further reductions in quality factor (greater increases in bandwidth) for less restrictive power drops can be obtained with lower efficiencies.