Abstract : In this paper, we introduce further our recently designed family of L2 orthogonal Space-Time codes for CPM. With their advantage of maintaining both the constant envelope properties of CPM, the diversity of Space-Time codes and moreover orthogonality, and thus reduced decoding complexity, these codes are also full rate, even for more than two transmitting antennas. The issue of power efﬁciency for these codes is ﬁrst dealt with by proving that the inherent increase in bandwidth in these systems is quite moderate. It is then detailed how the initial state of the code inﬂuences the coding gain and has to be optimized. For the two and three antennas case, we determine the optimal values by computer simulations and show how the coding gain and therewith the bit error performance are signiﬁcantly improved by this optimization.