The main feature of ultra wideband (UWB) communication systems is the high resolution of multipath arrivals, which is due to its large transmission bandwidth. Thus, the received signal has many replicas of the transmitted signal, and serious inter-symbol interference (ISI) effects can be made. Conventionally, rake receivers are applied to achieve the multipath diversity of the desired signal. However, ISI effects are usually not taken into account in the design of rake receivers. Therefore, the performance can be poor. To deal with this problem in such a dense multipath environment, we design the coefficients under two criterions, i.e., minimum mean-squared error (MMSE) and maximum ratio combining (MRC). Also, we can derive the closed-form of bit-error rate (BER) analysis for chip-rate sampled rake receivers in direct-sequence ultra wideband (DS-UWB) systems. From simulations, we conclude that ISI can be suppressed efficiently by the developed coefficients.