Abstract: A novel half-patch broadband circular microstrip antenna with two pairs of slots is proposed in this paper. Basedon the full patch microstrip antenna which has broadband excellent bandwidth for embedding a pair of double circular slots placedclose to the non-radiating edges of the patch, the half patch antenna is obtained by cutting away the half patch. The half patchantenna has the similar impedance bandwidth compared with the full patch antenna. The measured bandwidth of 12% is achievedwith small size, and the good radiation characteristics for operating frequencies within the impedance bandwidth are also observed.