On 10/16/2018 07:23 PM, Ryan Marlow via USRP-users wrote:
Hey Brian,
Thanks for the suggestion. I think that idea should work for me. Is
there anywhere that documents the X300 TX ramp up time?
Best,
Ryan
Part of that time is in the digital domain, so, "easy" to characterize,
and part of it is in the analog domain, which will depend on
the vagaries of analog bits and pieces, which will depend on the
particular daughterboard, revision number, manufacturing batch,
etc, etc.
Every transmitter that has every been built has some non-zero ramp-up
time, even in the era before SDRs and DSP radios.
On Tue, Oct 16, 2018 at 6:28 PM, Brian Padalino <bpadal...@gmail.com
<mailto:bpadal...@gmail.com>> wrote:
Maybe ramp up time for the transmitter?
If you send 2.5us worth of 0's before your 1000 samples, do you
see the appropriate number of pulse burst length?
This method would be a compromise between the two methods you
described. Does that work for you?
Brian
On Tue, Oct 16, 2018 at 6:19 PM Ryan Marlow via USRP-users
<usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
wrote:
Hey All,
I am trying to transmit a series of pulses with the X300 and
am seeing some odd behavior. I want to transmit a set number
of samples in a pulse, let's say 1000. At 200 MSPS (the tx
rate in the radio core) I would expect this burst to last
approximately 5us. Yet, when I receive the data, I see a burst
that is shorter by half, approx 2.5 us. To send these bursts,
I am sending a timed burst of 1000 samples to the Radio with
significant space in between. Odder still, when I increase my
pulse to 2000 samples, expecting a pulse of 10 us, it is
shortened again by 2.5 us, making the pulse 7.5 us. I can
confirm with an ILA that the Radio core is receiving all
pulsed samples and they are passed to the daughterboard
interface. Is there an obvious explanation for this behavior
that I am overlooking?
One solution I have devised is generating a constant stream of
data in place of the gaps between pulses that contain zero'd
data. So it would look like this
Data x 1000 -> zeroes in place of gaps -> repeat.
In my original method, the transmitter is only active during
the pulses. In the alternative solution, the transmitter is
active the whole time.
This solution gives me the behavior that I want but I am
curious as to why the pulses are shortened.
Thanks,
Ryan Marlow
--
Ryan L. Marlow
R L Marlow Consulting LLC
rlmarlow.com <http://rlmarlow.com>
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Ryan L. Marlow
R L Marlow Consulting LLC
rlmarlow.com <http://rlmarlow.com>
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