Low-profile top loaded monopole antenna for VHF applications

A low-profile top loaded folded monopole antenna with wide band omnidirectional radiation patterns is presented in this letter. The antenna is designed using a short vertical monopole element placed on a metallic reflector plane (MRP). The antenna impedance bandwidth is enlarged by adding vertical shorting pins at appropriate locations between the loading circuit and the MRP. The proposed antenna was studied numerically in the VHF frequency range. To meet with our measurement facilities, the antenna prototype was realized and fully characterized around 2.1 GHz. The experimental results are in good agreement with the numerical simulations. The antenna radiation patterns are omnidirectional with high radiation efficiency (> 90%) in a relatively large frequency band (11.5% bandwidth).