Thanks for clarifying Aaron, I will go through the block carefully tonight and see if I can trace down the "cross-coupling." Glenn
On Thu, Sep 18, 2008 at 6:12 PM, Aaron Parsons <[email protected] > wrote: > Your description of what the FFT block *should* do for n_inputs = 2^0 > is correct. Assuming the output has been correctly descrambled into > to separate the spectra of the two inputs, one input should not > influence the other's spectrum in any way. This has been tested > extensively in the library as I left it last summer. If this is not > the behavior that you are seeing, then I suspect an error in one of > the mask scripts has been introduced during this massive code > migration. > > As for the PFB FIR, it is correct that in "biplex mode" it simply > makes two copies of the same polyphase filter. > > On Thu, Sep 18, 2008 at 8:19 PM, G Jones <[email protected]> wrote: > > Hello, > > I am trying to use the green FFT block with number of simultaneous inputs > > set to 0. My understanding was that this makes a biplex fft that > processes > > two independant data streams in parallel, thus the pol0 input should have > x0 > > x1 x2... and pol1 should have y0 y1 y2 and then the pol0 output will just > > have frequencies related to pol0. However, when I simulate this, I find > that > > the two inputs are interacting. If I set one input to a constant, the > output > > is significantly different than if I connect the two inputs together (in > > which case I should get two identical copies at the output. > > I did notice in the packetized correlator iBOB design (using pink blocks) > > the pfb_fir block preceeding the fft is set to biplex mode, but I had > > assumed this didn't change the functionality of the block since a biplex > > pfb_fir block should be equivalent two single input pfb_fir blocks. > > Can someone more clearly explain the functionality of the FFT block? > > Thank you, > > Glenn > > > > > > -- > Aaron Parsons > > 510-406-4322 (cell) > 787-878-2612 x329 (arecibo office) > 787-721-3991 (home) >
