A cavity-backed quadrifilar-curl antenna

A quadrifilar-curl antenna is numerically analyzed in the presence of a flat circular reflector and a circular cavity. Wire grid method is used to simulate the conducting surfaces. The current distribution along the antenna structure is determined by using the moment method. The radiation pattern, polarization pattern, axial ratio, input impedance, VSWR, and the antenna gain of quadrifilar-curl antenna backed by a circular reflector and by a cavity is calculated using theoretically determined current distribution. The circular plate and the cavity enhance the antenna gain (8.17 dB for plate and 8.45 dB for cavity). The circular cavity improves the axial ratio in all planes around the antenna.