Fundamental limitations for antenna radiation efficiency

Abstract

Small volume, finite conductivity and high frequencies are major imperatives in the design of communications infrastructure. The radiation efficiency ${\eta }_r$ impacts on the optimal gain, quality factor, and bandwidth. The current efficiency limit applies to structures confined to a radian sphere $ka$ ($k$ is the wave number, $a$ is the radius). Here we present new absolute limits to ${\eta }_r$ for arbitrary antenna shapes based on $k^{2}S$ where $S$ is the conductor surface area. For a dipole with an electrical length of $10^{-5}$ our result is four orders of magnitude closer to the analytical solution when compared with previous bounds on the efficiency. The improved bound on ${\eta }_r$ is more accurate, more general, and easier to calculate than other limits. The efficiency of an antenna cannot be larger than the case where the surface of the antenna is 'peeled' off and assembled into a planar sheet with area $S$, and a uniform current is excited along the surface of this sheet.

Minor edits 8 pages, 8 figures, 1 appendix, Accepted in IEEE TAP

References in corpus (5)

• Fundamental Efficiency Limits for Small Metallic Antennas
• Optimal Currents on Arbitrarily Shaped Surfaces
• The impact of reduced conductivity on the performance of wire antennas
• Stored energies in electric and magnetic current densities for small antennas
• Lower Bounds on Q for Finite Size Antennas of Arbitrary Shape

Cited by in corpus (9)

• Trade-off Between Antenna Efficiency and Q-Factor
• Upper bounds on absorption and scattering
• Global $\mathbb{T}$ operator bounds on electromagnetic scattering: Upper bounds on far-field cross sections
• Optimal Planar Electric Dipole Antenna
• Densifying MIMO: Channel Modeling, Physical Constraints, and Performance Evaluation for Holographic Communications
• Harnessing superdirectivity in dielectric spherical multilayer antennas
• The Radiation Efficiency Cost of Resonance Tuning
• Trade-offs in absorption and scattering by nanophotonic structures
• Dissipation Factors of Spherical Current Modes on Multiple Spherical Layers