A Miniature Actively Matched Antenna for Power-Efficient and Bandwidth-Enhanced Operation at Low VHF

Active matching techniques with non-Foster reactive elements have been introduced to overcome fundamental performance limits on electrically small passive antennas. While several experimental studies have demonstrated successful bandwidth enhancement with active matching applied to small unmatched passive antennas, their radiation performance against similar-sized, efficient, resonant antennas alone (and/or applied to active matching) has not yet been confirmed to assess their effectiveness for practical wireless communications applications. Beginning with a highly miniaturized efficient resonant antenna (λ ₀ /50 in height), we design an active matching network derived from an antenna impedance model. We conduct an extensive simulation analysis to address challenging issues associated with the design arising from a tradeoff between degree of bandwidth enhancement and stability of the matching network. Based on experimental performance assessment, the effective 3 dB bandwidth of the proposed actively matched antenna is improved by more than three times compared with the passive version and improved in efficiency by more than 10 dB relative to cases that apply active matching techniques to similar-sized, unmatched passive antennas.