On 03/14/2018 05:36 AM, Lucas Val Terrón via USRP-users wrote:
Hi all,
Working with the example "tx_waveforms.cpp" provided in the uhd, i
found myself with two problems trying to set the sample rate and the
tx bandwith of the USRP B210 (UHD_3.11.0).
./tx_waveforms --rate 61440000 --freq 2350000000 --wave-type SINE
--wave-freq 1000000 --gain 40 --bw 50000000 (with sc16 format)
1. The first thing I realized is that despite the sample rate was the
maximum available, the bandwidth is limited to 40 MHz. Furthermore,
the following warning appears:
[WARNING] [AD936X] Selected Tx bandwidth (61.44 MHz) exceeds
So, it seems that somewhere inside the code tries to set the Tx
bandwith to the same value as the sample rate...
./tx_waveforms --rate 500000000 --freq 2350000000 --wave-type SINE
--wave-freq 1000000 --gain 40 --bw 50000000 (with sc16 format)
2. With sample rates greater tham 40 MHz, I get continuous underflows
in transmission. Does anybody knows what's happening? Is there any
limit in the maximum sample rate transmitting only in one channel?
Thanks in advance!!
Lucas
Underflows happen because your computer isn't keeping up with the
radio. The radio is perfectly capable of taking in the specified
sample-rate, but
the computer has to be able to "keep up". You might try playing
with the USB buffering:
https://files.ettus.com/manual/page_transport.html#transport_usb_params
I regards to the bandwidth setting, it's generally a poor idea to have
the analog bandwidth exceed 80% of the sample rate.
If you could share the exact invocation you used, and the complete error
message/log output, that would be helpful.
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