Hi Jonathan
I wrote down the problem and immediately see the problem with inversion.
So I retract my earlier comment about straightforward inversion being
possible.
Since all methods are approximate to a greater or lesser degree, I'd be
interested to try a simple PFB would handle the inversion. Take the same
PFB algorithm you already have and apply it a second time without
change. After the FFT, you will have to swap the output array end for
end (mirror) to get the right time ordering.
Intuitively, the errors upon inversion will be only 2x the error in the
output of the original PFB. Is that good enough?
Gerry
On 08-Dec-14 10:15 AM, Jonathan Weintroub wrote:
Hi Gerry,
I am glad someone is interested in this. To be clear we have a need for an
inverse PFB, but have not developed one ourselves—no where near to ready to
publish. ;) Our take was the “step by step” was needed, inverse FFT followed
by FIR, and that probably it would not be entirely trivial. While inverse FFT
itself is rather simple.
I put the question to the list serve in the hope someone has already worked on
this. I hereby bump this up, perhaps this is a better time to do so, compared
to Friday afternoon.
Jona
On Dec 5, 2014, at 7:12 PM, Gerry Harp <gh...@seti.org> wrote:
Hi Jonathan
This is interesting. Is an inverse PFB is just a PFB using an inverse FFT?
That should be very close by possibly not bit-perfect inversion.
Or are you considering a step-by-step inverse of the PFB algorithm? I'm
interested because there are traps. Small numerical errors are magnified when
you compute the inverse FIR filter on the data after inverse FFT. At least I
think so.
I'd be interested in your implementation of the inverse PFB. You should publish
it.
Thanks
Gerry
The reason I'm asking is that if you lose any
On 05-Dec-14 01:36 PM, Jonathan Weintroub wrote:
Hello CASPERites,
Has anyone implemented an _inverse_ PFB? That is a block taking channelized
PFB data and reproducing the original time series.
If so, is the code/mdl/yellow block available?
Thanks,
Jonathan
--
Gerald R Harp, Ph.D.
Senior Scientist
SETI Institute
189 Bernardo Ave, Ste. 100
Mountain View, CA
