Development of Electrically Small, Bandwidth Enhanced, Vertically Polarized Filtennas

Abstract

Electrically small, bandwidth enhanced, vertically polarized, omnidirectional and endfire-radiated filtennas are presented. They are enabled with two hybrid λ/4 open-circuit stubs that not only produce radiation nulls at the stopband to enhance the frequency skirt, but they also introduce an additional in-band resonance which has no influence on the original radiating mode. The operational bandwidth is improved significantly by the presence and overlapping of these two resonant modes. The tested values are well consistent with the simulated ones and demonstrate the omnidirectional filtenna exhibited a fractional bandwidth (FBW) of 11.3%, a 3.01 dBi highest gain and an electrically small size with ka = 0.73. The endfire filtenna, which is electrically small with ka = 0.93, attained a 12.8% FBW and a 6.09 dBi highest gain.