New type of planar antenna of microwaves appropriate for operating in linear or circular polarization, free of welds and floating potentials, and therefore free of electrostatic discharges and problems related to passive intermodulation products, whose application is of particular interest in aircraft and space technologies. Said antenna consists in the interconnection of a microstrip radiator with a spiral antenna of wires. For certain applications wherein said radiators are arranged in a same plane, the radiating effect of the patch may reduce the size of the spiral, whereby the radiator object of this invention degenerates into a circular slit in the ground plane of the supply line and wherein the helically arranged wires provide for the electric contact between the edges of the slit.