  In this paper we present an alternative separable implementation of
L2-orthogonal space-time codes (STC) for continuous phase modulation (CPM). In
this approach, we split the STC CPM transmitter into a single conventional CPM
modulator and a correction filter bank. While the CPM modulator is common to
all transmit antennas, the correction filter bank applies different correction
units to each antenna. Thereby desirable code properties as orthogonality and
full diversity are achievable with just a slightly larger bandwidth demand.
This new representation has three main advantages. First, it allows to easily
generalize the orthogonality condition to any arbitrary number of transmit
antennas. Second, for a quite general set of correction functions that we
detail, it can be proved that full diversity is achieved. Third, by separating
the modulation and correction steps inside the receiver, a simpler receiver can
be designed as a bank of data independent inverse correction filters followed
by a single CPM demodulator. Therefore, in this implementation, only one
correlation filter bank for the detection of all transmitted signals is
necessary. The decoding effort grows only linearly with the number of transmit
antennas.
