Re: [casper] inverse PFB

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

Re: [casper] inverse PFB

I think the PFB FIR is not a reversible process. It sums samples and decimates, so that you have fundamentally lost the information that would be required to recover the input time series. However, as Gerry points out, it is possible to invert just the FFT component, leaving what is essentially

Re: [casper] inverse PFB

hi Aaron, I think this depends on what you use for the filter coefficients. In theory there are pairs of analysis and synthesis filters that let you exactly reconstruct the original input signal. In practice I think errors caused by quantization, overflow, etc are probably the main source

Re: [casper] inverse PFB

Hi Jonathan, I thought that I sent some replies to the Casper mailing list, but it turns out I accidentally only sent them only to Gerry Hart. So, I resend them here. - (originally sent Dec 5) Hi Jonathan, Even discounting small numerical errors in any implantation, one cannot get

Re: [casper] inverse PFB

Hi, I thought I'd comment as this is a problem we've been having to deal with recently for some VLBI observations. Fortunately we've had some success with an offline least-squares inversion of the PFB. This is probably not the scheme that you want, as it essentially operates on the whole PFB'd