The ultra wide band (UWB) circular microstrip antennas are devoloped and simulated for wide band communication applications.In these a circular radiating aperture is made available for broad band characteristics.The proposed antennas consists of the vertical and horizontal elements of L-type probe fixed at front and back portion of the substrate respectively.These antennas are excited by a microstrip line which is connected to a vertical component of the L-type probe and electromagnetically couples the signal to the horizontal component of the L-type probe.This new concept of placing a couple of triangular slots at the top of the antenna is proposed to enhance the bandwidth from 83.1% to 99.15% is achieved.