Re: [Discuss-gnuradio] Transients at burst rising edge

[madengr]

How are you generating the bursts at baseband?  I fill a vector source with
(1+1j)*(numpy.ones() + numpy.zeros()) at the appropriate length for the
sample rate, then let that repeat.  I'm getting nice, clean rising edges on
my pulses (run into an oscilloscope).  Maybe the first pulse is distorted,
but once the filters have been filled up, everything should be clean.
Lou



Lakshay Narula wrote
> Hello all,
> 
> I have been trying to perform ranging between nodes using time-of-arrival
> of signals. To this end, I am trying to transmit an accurately timed pulse
> using the USRP. My initial experiment simply sends out a 100 ms burst
> every
> 1 sec. I am then recording this signal using NI PXIe-5663 front end for
> analysis. Everything is working out fine, except that I am seeing some
> wild
> transients at the beginning of the burst for several nanoseconds.
> 
> I am attaching some plots that show this behavior at
> http://imgur.com/a/C0Ynq. The falling edges of the burst are very sharp. I
> would like to get something like that on the rising edge too.
> 
> In another post on the list (
> https://lists.gnu.org/archive/html/discuss-gnuradio/2012-06/msg00312.html),
> Josh said that "*If you are seeing transients at the beginning of a burst,
> thats probably the half band filters. They are implemented in block ram
> and
> don't clear **between bursts.*"
> 
> Is this the reason I am seeing these transients? Is there anything I could
> do to correct this?
> 
> Thanks,
> Lakshay.
> 
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