Efficiency-based approach to quantifying ‘tuneability’ performance in frequency-agile narrowband antennas

摘要

Many communications systems require reconfigurable band access in compact form factors. Contemporary literature routinely reports 'tuneability' (or frequency agility) in input response terms (S-11), yet repeatable efficiency data were reported in <40% of cases surveyed. Despite the low efficiencies associated with many tuneable narrowband antennas, e.g. electrically small antennas (ESAs), reference methods to quantify tuneability in terms of a tuned range of realised antenna efficiency, average efficiency in the band and integrated efficiency-bandwidth product do not exist and thus have not been widely adopted. Here, these metrics have been formulated for general application to efficiency-based tuneability assessment of narrowband antennas. Application to a set of fixed-frequency/varactor-tuned ESAs (ka = 0.19-0.31) in the ultra-high frequency band is demonstrated. Tuning range of 10% or 25% realised efficiency was found to be several times narrower than S-11 < -6 dB tuning range for antennas in this study and in the literature, highlighting the need for a shift to efficiency-based tuneability reporting in support of RF system design analysis. The integrated efficiency-bandwidth product has been demonstrated for combined efficiency and reconfigurability comparison of tuneable antennas, providing a platform for future performance grading of a diverse range of antenna tuning technologies.