Radiation Efficiency Cost of Resonance Tuning

Existing optimization methods are used to calculate the upper bounds on radiation efficiency with and without the constraint on self-resonance. These bounds are used for the design and assessment of small electric-dipole-type antennas. We demonstrate that the assumption of lossless, lumped, and external tuning skews the true nature of radiation efficiency bounds when practical material characteristics are used in the tuning network. A major result is that, when realistic (e.g., finite conductivity) materials are used, small antenna systems exhibit dissipation factors which scale as (ka)^-4, rather than (ka)^-2 as previously predicted under the assumption of lossless external tuning.