In this paper, we combine both of phase hopping and differential space-time block coding in our novel Phase hopping differential space-time block codes (PH-DSTBC) scheme. This scheme could not only provide higher coding gain by introducing redundancy using a trellis coding method, but also provide full diversity with phase hopping technology. At the same time, PH-DSTBC uses the Maximum likelihood (ML) for decoding which will result to a similar performance with Viterbi algorithm, but has much lower complexity. Simulation results confirm that the scheme performs a 1.5dB better than conventional DSTBC scheme. Moreover, the phase hopping technology, similar to interleaving, reduces the depth of interleaving.