A micros-strip ring patch antenna with ultra wide band characteristics is presented. The proposed antenna is designed by a modified form of the annular ring patch antenna with modified microstrip feedline. The designed antenna gives 5.6GHz bandwidth with regular radiation pattern from 4.4GHz to 12.0GHz for -10dE return loss or VSWR of less than 2.0 in simulation, which is also excellently agreed with the measured data.