In this paper, an annular-ring microstrip patch antenna is designed and simulated using IE3D (electromagnetic simulation and optimization simulator based on MoM). The antenna is designed for dualband operation in frequency range from 4.5GHz to 9.2GHz. By introducing slots on a circular patch, a multiband antenna can be defined. The performance parameters of proposed annular-ring microstrip patch antenna such as return loss, gain, radiation pattern, bandwidth etc. are examined and a comparison is made with conventional circular microstrip patch antenna. The proposed antenna shows dual band behavior with return loss less than -19dB, VSWR <1.5 and good directivity.