Described herein is a method and apparatus for transmission that provides
the performance of space time spreading (STS) or orthogonal transmit diversity
(OTD) and the backwards compatibility of phase sweep transmit diversity (PSTD)
without degrading performance of either STS or PSTD using a symmetric sweep PSTD
transmission architecture. In one embodiment, a pair of signals s1 and
s2 are split into signals s1(a) and s1(b) and
signals s2(a) and s2(b), respectively. Signal s1 comprises
a first STS/OTD signal belonging to an STS/OTD pair, and signal s2 comprises
a second STS/OTD signal belonging to the STS/OTD pair. Signals s1(b)
and s2(b) are phase swept using a pair of phase sweep frequency signals
that would cancel out any self induced interference. For example, the pair of phase
sweep frequency signals utilize a same phase sweep frequency with one of the phase
sweep frequency signals rotating in the opposite direction plus an offset of
relative to the other phase sweep frequency signal. The resultant phase swept signals
s1(b) and s2(b) are added to signals s2(a) and
s1(a) before being amplified and transmitted.
