Open AccessOvercoming the Chu lower bound on antenna Q with highly dispersive lossy material
Author(s) -
Yaghjian Arthur D.
Publication year - 2018
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2017.0648
Subject(s) - lossy compression , antenna (radio) , mathematics , upper and lower bounds , optics , materials science , physics , telecommunications , computer science , mathematical analysis , statistics
Beginning with a brief overview of the history of lower bounds on the quality factor Q of antennas and the fundamental relationships between the impedance, bandwidth, and Q of antennas, it is demonstrated by means of RLC circuit models of electrically small antennas that their isolated‐resonance quality factors obtained from the ‘ Q ‐energy’ predicts their bandwidths with greater accuracy than the ‘equivalent‐circuit’ energies or the ‘electrodynamic’ energies. A generalisation is obtained for quasi‐static fields of antennas that facilitate the evaluation of the expressions for the Q ‐energy. It is verified that the Q‐energy cannot be considered stored energy in the highly dispersive lossy material. Nonetheless, using tuning elements containing highly dispersive lossy material, the bandwidth of fifty‐per cent (for example) efficient electrically small dipole antennas can be designed with twice the bandwidth predicted by the Chu lower bound for the quality factor of fifty‐per cent efficient antennas.