Low-Profile Tri-band Inverted-F Antenna for Vehicular Applications in HF and VHF Bands

Abstract

A low-profile tri-band inverted-F antenna (TIFA) is proposed for narrowband vehicle-based applications in upper HF and lower VHF ranges. A driven element, engineered as an inverted-F antenna, operates at the lowest frequency of 27 MHz, while two parasitic elements, built as inverted-L monopoles, enable resonances at 49 and 53 MHz. The standalone antenna height over a ground plane is ${\lambda }/{2}$ 5 at the lowest band. When mounted on a vehicle and bent to follow its profile, TIFA maintains similar performance with only ${\lambda }/{44}$ height above the vehicle’s roof. To eliminate the need for external matching network, the driven element is offset fed. The ${\bf VSWR} \leq {2}:{1}$ bandwidth of the first band is greater than 1%, whereas the bandwidths of the two VHF bands are narrower and do not exceed 0.4%. To mitigate possible detuning and enable full utilization of the FCC approved bandwidths, a simple approach for tuning the resonance is outlined. Scaled models of TIFA and vehicle are built and impedance and pattern measurements are conducted. Obtained results confirm the proposed antenna is a viable candidate for (among other applications) communication with remotely controlled ground and flying vehicles/toys.