And just in case you didn't get my images, I've uploaded them here for your convenience:
http://tinypic.com/a/3e8if/4 Thank you for your help! Best, Ali On Sun, Mar 1, 2015 at 4:49 PM, Ali Riaz <ari...@hawk.iit.edu> wrote: > Hello everyone, > > Hope you're all doing well. I have a grc design related question, and it > deals with the polyphase channelizer. I've tried looking into the > documentation as had been previously suggested to see how everything works, > and I got things working to an extent, but I'm confused as to the result > that I'm getting. Here's what I have so far: > > I want to divide the input spectrum into 8 equal channels using the > channelizer, so the mapping should be as follows correct: (4 - 5 - 6 - 7 - > 0 -1 - 2 - 3 - 4)? > > And I'm sending the 4th channel to a null sink, and working with the > remaining 7 channels with a channel mapping of [0,1,2,3,5,6,7,4]. To see if > I was doing things correctly, I decided to use the WX GUI Scope Sink. The > end result that I get is somewhat confusing as you'll see in a moment. I'm > attaching the pictures for your reference. > > 1) Firstly, the channels are not being divided equally, is it perhaps > because of the taps of the prototype filter? The way I'm calculating them > was actually suggested by a really helpful person at the USRP-Discussion > group, so I've also attached a picture for that as well for your > convenience. Would you suggest something else? > > 2) Sometimes, when I'm comparing the individual channels with the spectrum > of the combined channels, there seems to be this phase delay. Do you think > it's a hardware issue (because of all the computations and processing going > on) or does this usually happen when using the channelizer? > > Just an fyi, this is not an optimized version of my design (Thus, the > number of blocks lol); but I'm pretty sure some sort of vectorization can > be done to optimize the code and reduce the total amount of blocks. But > will get to that once I figure out why I'm not getting the desired output. > > P.S My apologies if this is a redundant email, I just realized that I > hadn't subscribed to the mailing list earlier, so sending it again just in > case you didn't receive it. > > Thank you in advance for your help. > > Best, > Ali Riaz > > On Thu, Feb 19, 2015 at 2:42 PM, Ali Riaz <ari...@hawk.iit.edu> wrote: > >> Awesome, thank you so much, both of you! I'll take a look into the >> documentation and Tom's blog, and will come back if I face any problems. >> [?] >> >> Best Regards, >> Ali >> >> On Tue, Feb 17, 2015 at 8:31 AM, Tom Rondeau <t...@trondeau.com> wrote: >> >>> On Tue, Feb 17, 2015 at 7:22 AM, sreeraj r <rsree...@gmail.com> wrote: >>> >>>> Hi, >>>> >>>> You can also look into Tom's blog on channelizers [1]. Some of the grc >>>> files in the blog might not work out of the box (especially those ones with >>>> QT-GUI frequency sink + bus ports). You can simply toggle the busports >>>> and connect it properly and make it work. >>>> >>>> [1] http://www.trondeau.com/examples/2014/1/23/pfb-channelizers >>>> -and-synthesizers.html >>>> >>>> Regards >>>> Sreeraj Rajendran >>>> >>>> >>>> On Mon, Feb 16, 2015 at 11:02 PM, Marcus D. Leech <mle...@ripnet.com> >>>> wrote: >>>> >>>>> On 02/16/2015 04:54 PM, Ali Riaz wrote: >>>>> >>>>>> Hi Marcus, >>>>>> >>>>>> I was the one who posted a question on the usrp-mailing list >>>>>> regarding the gnuradio companion channelizer a couple of days back, and >>>>>> was >>>>>> wondering if you could help me on something. I tried using the filter as >>>>>> you suggested, but I get a very strange result. I tried to get two >>>>>> partitioned channels, but they're being partitioned in a very strange >>>>>> manner. I've attached a photo for a visual for what I'm getting as a >>>>>> result. Any idea why that's happening? >>>>>> >>>>>> P.S My apologies, I know you pointed me to the GNUradio discussion >>>>>> mailing list, but it's been a while, and nobody has responded yet, and so >>>>>> far all I have is your clue to go on. >>>>>> >>>>>> Thank you so much for all your help, really appreciate it. >>>>>> >>>>>> Best, >>>>>> Ali >>>>>> >>>>>> This is very squarely in the domain of the discuss-gnuradio mailing >>>>> list. >>>>> >>>>> My understanding is that the polyphase channelizer behaves that way >>>>> for even-numbers of channels. Tom Rondeau on the discuss-gnuradio mailing >>>>> list >>>>> is the best person, probably, to explain this. I've copied that >>>>> list. >>>>> >>>> >>> Also, look at the documentation for the block: >>> >>> >>> http://gnuradio.org/doc/doxygen/classgr_1_1filter_1_1pfb__channelizer__ccf.html >>> >>> Specifically, the set_channel_map function. It shows the mapping of the >>> channels. With an even number of channels, the N/2 channel wraps around >>> fs/2 and -fs/2 while channel 0 spans 0 Hz. You just have to set up your >>> input bandwidth, sample rate, and tuning to account for this. >>> >>> Tom >>> >>> >> > > >
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