In this paper, the rate-2 pcu STF coding schemes that can be efficiently implemented for use in multiband UWB-MIMO systems has been presented. These proposed STF codes are constructed based on the multi-dimensional constellation precoding so that the rotated version of the information symbols are spread across adjacent subcarriers and sent over t M transmit antennas and b M time periods, allowing effective exploitation of space, time and frequency diversity. The performance of these STF codes with two transmit antennas over the IEEE 802.15.SG3a channel models are compared at the same spectral efficiency. It is shown that our proposed codes outperform well known schemes found in the literature such as rate-1 SF codes, which guarantee full diversity. In addition, we devise a random interleaving method to incorporate into the proposed codes and the simulation results show that further gains can be achieved depending on the level of SNR.