Frequency-agile, efficient, near-field resonant parasitic monopole antenna

Ming Chun Tang, Richard W. Ziolkowski, Shaoqiu Xiao, Mei Li, Junrui Zhang

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


A simple, frequency-agile, efficient, near-field resonant parasitic (NFRP) monopole antenna is presented. The NFRP element is a capacitively-loaded loop (CLL) augmented with a varactor diode to achieve the frequency tunability. The numerical and experimental studies agree reasonably well. The experimental results demonstrate that this frequency-agile antenna exhibits a 5.56% 10-dB fractional impedance bandwidth, which is more than four times larger than the 1.33% value of the original fixed-capacitor passive system. Good impedance matching (${\vert{\rm S}-{11}\vert}-{\min}\leq-$ 20 dB), relatively high radiation efficiency ($ RE>$76%), stable and uniform radiation patterns, and peak gain values between 3.57-4.05 dBi were measured over this frequency-agile range.

Original languageEnglish (US)
Article number6685875
Pages (from-to)1479-1483
Number of pages5
JournalIEEE Transactions on Antennas and Propagation
Issue number3
StatePublished - Mar 2014


  • Frequency agile
  • impedance bandwidth
  • monopole antenna
  • radiation efficiency
  • varactor diode

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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