I have a block that does what you need.
https://github.com/drmpeg/gr-iqlevels
Ron
On 3/17/19 08:09, John Ackermann N8UR
wrote:
I'm
working on a flowgraph that generates an output waveform about 375
kHz wide with very high peak-to-average power -- at least 20 dB.
This is sent into a USRP1 with BasicTX board to generate an output
at 29 MHz. I'd like to show in the flowgraph GUI the peak
instantaneous output level, to help in setting the gain.
It's painfully clear on a spectrum analyzer when the gain is too
high. The attached shows (a) single CW carrier at max output
(orange); (b) output without clipping (yellow); and (c) output
with occasional clipping (blue). These are max-hold plots so the
clipping is caught even though it happens only very infrequently.
Is there a probe or other function that can capture and hold the
maximum instantaneous value of a complex stream? If not, is there
a way to create that capability out of other blocks?
And, am I barking up the wrong tree -- is the distortion likely
caused by the complex output being driven into digital clipping
when enough vectors add up, or is this a function of the analog
conversion in the USRP? i.e., is the problem likely to be on the
input or output side of the DAC?
Thanks,
John
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