Efficiency-Based Approach to Quantifying “Tuneability"Performance in Frequency-Agile Narrowband Antennas

Oliver James, Geoff Hilton, Mark Beach

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Many communications systems require reconfigurable band access in compact form factors. Contemporary literatureroutinely reports “tuneability” (or frequency agility) in input response terms (S11), yet repeatable efficiency data were reported in less than 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 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 UHF frequency band is demonstrated. Tuning range of 10% or 25% realised efficiency were found to be several times narrower than S11 < -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.
Original languageEnglish
Pages (from-to)120-131
Number of pages12
JournalIET Microwaves, Antennas & Propagation Journal
Issue number1
Early online date18 Sept 2019
Publication statusPublished - 8 Jan 2020


  • varactors
  • antennas
  • integrated efficiency-bandwidth product
  • RF system design analysis
  • tuneability performance quantification
  • contemporary literature
  • electrically small antennas
  • efficiency-based tuneability assessment
  • efficiency-based approach
  • reconfigurability comparison
  • reconfigurable band access
  • communications systems
  • antenna tuning technologies
  • compact form factors
  • fixed-frequency-varactor-tuned ESA
  • frequency-agile narrowband antennas
  • single antennas
  • junction and barrier diodes
  • capacitors


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