Abstract: In this paper, a novel wideband microstrip-fed monopole antenna with a size of only 24 mm×31.7 mm×1.6 mm is studied by the method of moment based on the two-level hi-conjugate gradient-fast Fourier transform method. The antenna has a wide bandwidth ranging from 3.1 GHz to 11 GHz for Sn₁₁〈-10dB (S₁₁ denotes the return losses). Details of the proposed antenna design approach and measured results are presented and discussed, which can be used for Ultra-wideband applications in the area of breast cancer imaging.