The transformation of a single turn loop to a circular half-loop is analogous to the transformation of the dipole to the monopole, where a ground plane is inserted at the image plane of the antenna. The circular half loop antenna consists of a single wire bent into a half circle and mounted on a ground plane. The antenna is fed through the ground plane at one end while the other end is terminated on the ground plane.
The circular half loop is a linearly polarized, low gain antenna with a moderate impedance bandwidth.Typical total 3D radiation pattern at the center frequency. Typical S11 performance of the antenna.