Nonresonant Magnetic Flux Control Enabling Low‐Loss Epsilon‐Near‐Zero Cavity Antennas

Epsilon‐near‐zero (ENZ) media enable unconventional electromagnetic‐wave manipulation through quasi‐uniform field distributions and geometry‐independent responses. Photonic doping extends ENZ functionality by enabling permeability engineering through embedded inclusions while preserving the near‐zero permittivity condition. Although recent developments have expanded photonic doping to resonant metallic, optical, and non‐Hermitian platforms, the perfectly conducting (PEC) limit has remained largely unexplored for radiating ENZ structures. Here, the PEC limit is systematically developed as a passive, nonresonant approach for permeability engineering in waveguide‐based ENZ cavities with radiating apertures. Analytical derivations and full‐wave simulations show that a solid metallic inclusion suppresses the magnetic field within its volume, yielding an effective permeability governed by the ratio between the excluded and cavity cross‐sectional areas. The resulting response is invariant with respect to inclusion geometry, position, and multiplicity, provided the total excluded area remains unchanged. The proposed implementation reproduces the impedance‐matching and radiation characteristics of dielectric and resonant photonic dopants while achieving higher radiation efficiency without resonant energy storage or engineered capacitive loading. These results demonstrate that dielectric, resonant metallic, and PEC inclusions represent different implementations of the same photonic‐doping framework, establishing the PEC limit as a practical low‐loss methodology for designing efficient ENZ cavities and antennas.