hi all,can some one plz tell me that how phase coherent summation works in
polyphase filters? ?Here is some stuff i found in a paper but its not very
clear..can anyone he;lp
"The alias terms in each path of the M-path filter exhibit
unique phase profiles due to their distinct center frequencies and
the time offsets of the different down-sampled time series delivered
to each port. These time offset are, in fact, the input delays
shown in Fig. 22 and (18). Each of the aliased center frequency
experiences a phase shift shown in (18) equal to the product of
its center frequency and the path time delay.
(18)
The phase shifters of the DFT perform phase coherent
summation, very much like that performed in narrow-band
beam forming, extracting from the myriad of aliased time
series, the alias with the particular matching phase profile.
This phase-sensitive summation aligns contributions from the
desired alias to realize the processing gain of the coherent
sum while the remaining alias terms, which exhibit rotation
rates corresponding to the M roots of unity, are destructively
canceled in the summation."
