Loop Antenna Over a Conducting Cone With a Spherical Cap

A composite antenna structure consisting of a conducting cone loaded with a spherical cap is designed and analysed, considering all eigenmodes in the antenna structure. The configuration is used to enhance the impedance match to a loop antenna located above the cone tip. Matching characteristics to the loop are examined over a wide range of loop radius and loop location. It is found that the matching to the loop can be significantly enhanced over a wide range of parameter values, yielding a greater flexibility in design than the loop-around-the-cone structure presented earlier with the conducting cone body inside the loop. The structure also enables placement of the loop at a greater height than the loop-around-the-cone configuration, potentially improving the efficiency of signal transmission/reception or reducing scattering from the vehicular body. The mutual coupling effect of a parasitic loop placed adjacent to the primary loop is also analysed. The radiation characteristics are also evaluated.