Channel estimation and synchronization are crucial problems in coherent ultra wideband (UWB) receiver designs. A joint maximum-likelihood (ML) and minimum-mean-square-error (MMSE) channel estimation scheme was developed for more precise channel estimates based on the assumption of exponential multipath decay. The performance improvement was analyzed theoretically with a computer simulation using IEEE 802.15.3a ultra-wideband channel models. Theoretical and simulation results show that the scheme further improves the estimation performance of channel gains and multipath delays compared with the traditional ML channel estimator.