Low-Profile VHF Antenna Based on Quarter-Mode Substrate-Integrated Waveguide Structure

Featured Application Low-profile antenna for terrestrial wireless communication. A traditional whip antenna is suitable for terrestrial wireless communication due to its omnidirectional radiation pattern which is capable of transmitting and receiving signals from all directions. However, the length of a whip antenna is long for the very high frequency (VHF) band applications; for example, the ideal length is 80 cm at 90 MHz, which restrains the mobility when mounted on a vehicle. Many studies have been conducted to develop a low-profile antenna that can substitute a whip antenna but most of them are for relatively high frequency (GHz) applications. In this paper, a planar low-profile antenna operating in the VHF band is proposed. The height of the antenna is only 9 cm by utilizing a quarter-mode substrate-integrated waveguide (QMSIW) structure with shorting pins at the edges. The latter promotes omnidirectional radiations despite its short height. The antenna design was optimized by 3D full-wave simulation software. Subsequently, an antenna prototype was fabricated and tested. The results demonstrated that the antenna resonated at 86 MHz with a maximum gain of 1.7 dB along the azimuth direction.