Title :
Realization of dual-frequency and wide-band VSWR performances using normal-model helical and inverted-F antennas
Author :
Nakano, Hisamatsu ; Ikeda, Noriaki ; Wu, Yu-Yuan ; Suzuki, Ryota ; Mimaki, Hiroaki ; Yamauchi, Junji
Author_Institution :
Coll. of Eng., Hosei Univ., Koganei, Japan
fDate :
6/1/1998 12:00:00 AM
Abstract :
The effects of parasitic elements on the voltage standing wave ratios (VSWR´s) of two antennas are investigated. First, a parasitic monopole is used for a normal-mode helical antenna. The VSWR investigation shows that dual-frequency operation is obtained by the parasitic element effects. The dual-frequency operation is revealed as a function of monopole position above a ground plane (monopole height). As the monopole height decreases, the separation of a higher resonance frequency fH from a lower resonance frequency fL increases. For a monopole length of LMP≈0.4λHX , where λHX is the resonance wavelength of the helix, the frequency bandwidth for a VSWR=2 criterion is 12.5% in the lower frequency fL region and 5.2% in the higher frequency f H region, with a frequency separation ratio of fH/fL=2.14. Secondly, L-figured parasitic elements are used for an inverted-F antenna (IFA). The parasitic elements improve the VSWR performance. The frequency bandwidth for a VSWR=2 criterion is approximately two times as wide as that of the single IFA. It is also found that bending the horizontal sections of the IFA and parasitic elements contributes to reducing the antenna size while not significantly deteriorating the VSWR bandwidth. The radiation patterns are also presented and discussed
Keywords :
antenna radiation patterns; helical antennas; land mobile radio; monopole antennas; L-figured parasitic elements; antenna size; bending; dual-frequency operation; frequency bandwidth; frequency separation ratio; helical antennas; higher resonance frequency; horizontal sections; inverted-F antennas; lower resonance frequency; monopole height; monopole length; monopole position; normal-mode helical antenna; parasitic elements; parasitic monopole; radiation patterns; voltage standing wave ratios; wide-band VSWR performance; Antenna radiation patterns; Bandwidth; Broadband antennas; Current distribution; Helical antennas; Multifrequency antennas; Resonance; Resonant frequency; Voltage; Wideband;
Journal_Title :
Antennas and Propagation, IEEE Transactions on