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Re: [Discuss-gnuradio] Poly phase channelizing in Blade Or USRP

From: Garver, Paul W
Subject: Re: [Discuss-gnuradio] Poly phase channelizing in Blade Or USRP
Date: Tue, 27 Sep 2016 00:04:26 +0000

I'm a bit confused by your calculation. Nyquist for complex data is equal to the analog bandwidth so you only need a sample rate of 25.6 MSPS as stated. USB 3.0 will handle this without a problem on the B200. If you use short (16 bit integers) IQ then you have 4 bytes/complex sample so ~100MB/sec. 

I think solving your USB 3.0 woes and using GR on a general purpose processor will save you significant development time over FPGA implementations. 

Paul Garver

On Sep 26, 2016, at 7:53 PM, "address@hidden" <address@hidden> wrote:

duane> It seems like a perfect fit for a poly phase filter - however
this is
duane> something that I believe needs to be done in hardware (128
channels *
duane> 200khz = about 60mhz sample rate this will not go over a USB
cable, and
duane> I doubt I can get this bandwidth into a laptop PC.

sylvain> !?!?

sylvain> 128 channels of 200 kHz = 25.6 MHz of bandwidth. You can
totally get
sylvain> that to a laptop.

Nyquest requires 2x samples = 51.2mhz sample rate
Assuming I/Q data 2x bytes =  102.4mbyte/second
At 8bit bytes = 819.6 mbits per second is the bit rate.

thats about 17% of the bandwidth of USB 3 (5gbit) however that does not
account for framing overhead, and other related things.
Figure another 10% loss for signaling over head.

You are correct it is possible

sylvian> B2xx or BladeRF will do that without issues given a
sufficiently good laptop.

You mean a USB 3 based solution possibly - but I have had very limited
success with USB 3 - they always seem to fall back to USB 2 speeds,
and/or - the data rate is not there - perhaps my experience is flawed
due to cheap data sources {ie: hard drives}

sylvian> If the transmission are "infrequent" you can even use the same
sylvian> that researchers used a while back to listen to all of
bluetooth and
sylvian> deliberately alias the signal to fold the spectrum over itself.

I understand that, after 'unfolding' I need to get the actual channel
number. that's not possible if I do what you describe.

duane> Am I going to have to do FPGA work on my own?

sylvian> Very likely.

duane> Or - is there some existing cook book solution with the FPGA
duane> configuration pre-cooked?

sylvian> Very unlikely to find something "all done".
sylvian> Especially that if you don't want to ship the samples, a PFB is
sylvian> all you need. You'd need demod for each channel in the hardware
sylvian> well.

That is well understood.

duane> What I am looking for is the FPGA channelizer solution...
hopefully an
duane> existing one I could start with?

sylvian> There is an embryon of one in the ettus rfnoc repo and AFAIK
sylvian> might also replace it with another version soon.

sylvian> But it's written for RFNoC and Series-7 Xilinx fpga. It'll need
sylvian> some adaptation to run on anything else.
sylvian> Also, AFAIU, it's incomplete and non-tested currently so ...

Thanks for the pointer.


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