Re: [Discuss-gnuradio] [USRP-users] USRP, GNURadio Companion, Polyphase Channelizer Issue

[Tom Rondeau]

On Tue, Feb 17, 2015 at 7:22 AM, sreeraj r <address@hidden> 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 <mleech@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