Highly miniaturized low-VHF folded dipole antenna for compact, mobile communication applications

For short range communications in the complex environments such as caves, urban and indoor settings, the main concern is to achieve reliable communication over wireless links since large number of scatterers in the communication channel at the conventional microwave radio bands lead to excessive signal attenuation and fast fading. One solution to mitigate such adverse effects is to use radios at much lower frequencies (e.g. HF and Low-VHF) since the signal can penetrate significantly through manmade and natural obstacles while reflection, scattering, and diffraction are far less than those observed at higher frequencies. In order to realize compact, mobile communication systems operating at the low frequencies, however, several challenges, especially in terms of antenna size, are encountered. One issue pertains to design of antennas with small form factors that can provide moderate radiation efficiency and bandwidth. It is noted that antennas with lower gain (efficiency) are tolerable as such drop in gain can easily be more than compensated for by the reduction in the path loss.