[Discuss-gnuradio] Frequency Xlating FIR filter: bug in gr_rotator

[Sérgio Rui Silva]

I have been using the "GrFreqXlatingFIRfilterSCF" and I notice
that its output slowly increases in amplitude (or diminishes,
depending on the frequency setting). I found that this is due to
the "gr_rotator" class. If the absolute value of the
"gr_rotator"s "phase"
variable is printed during the processing cycle one can see that
its value starts with 1.0, as it should, and then augments
slowly. I think this is because the recursive multiplication
used causes a precision error to increase in one direction. I
solved this by
not using the gr_rotator class but the gr_nco class instead.
This solution is not as elegant as the one with the gr_rotator
class, but it does the trick by now... Any ideas one how to
solve this correclty?

Sérgio Rui Silva

************************************************************
 Faculdade de Engenharia da Universidade do Porto, Portugal

                   http://www.fe.up.pt

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GrFreqXlatingFIRfilterSCF.cc
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GrFreqXlatingFIRfilterSCF.h
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