Need omnivorous carrier recovery method
in [DSP]
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From: mtr on 21 Jul 2010 16:20 > > >mtr wrote: >>> >>>Eric Jacobsen wrote: >>> >>> >>>>I'm still trying to wrap my head around "omnivorous" carrier recovery. >>>>I'm not sure whether the methods I've used previously are carnivorous >>>>or vegetarian or what. >>>>As mentioned by others, there is no universal method. IF, and it's a >>>>significant IF, you can assume that there are no signals in adjacent >>>>spectrum you can just take the power difference in both halves of the >>>>extended baseband channel. If one side has more power than the >>>>other, and the spectrum is symmetric, then there's an offset. >>> >>>This is essentially a discriminator; the output is going to be something >>>like a centroid of the signal + noise in the bandwidth. >>> >>> >>>>That'll work with most modulation methods, but it's generally not >>>>accurate enough for fine tuning. It won't work if there's an >>>>adjacent channel within the ambiguity range. It won't work if the >>>>spectrum isn't symmetric. >>> >>>1. Perform the FFT in the sliding window of one symbol. >>>2. Interpolate the FFT to get fractional bins. >>>3. Perform N-th power operation for each fractional bin. >>>4. Perform a long FFT on the result. >>> >>>Pretty heavy, but it works for any single- or multi-carrier signal. >> >> It's interesting, but how does it work in presence of ISI and raised root >> cosine filter? The phase of base band signal through the symbol length >> window would change significantly. > >It works very well, if you don't ask too much. If you need something >better, we can talk about that. This is going to be some other place >then here, and not for free. > > >Vladimir Vassilevsky >DSP and Mixed Signal Design Consultant >http://www.abvolt.com > > > > Thank you anyway :)
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