A Synthetic Aperture-based UWB imaging system is proposed for medical imaging applications. According to the desired resolution requirements, SAR array parameters as well as the frequency range of the system are derived. Discussion is made upon maintaining the balance between performance and complexity of the ultimate design. As image reconstruction algorithm, a hybrid semi-adaptive method consisting of the conventional Delay and Sum together with adaptive Coherence Weighting is applied. Simulation results corresponding to a 3D breast model with homogenous breast tissue are provided to demonstrate the efficiency of the proposed imaging system. The integration of UWB concept with SAR principle is proved to have a high potential for practical medical imaging purposes.