Dear USRP Mailing List Members,
I have two questions regarding power constraints of X440:
1. I set the master clock rate to 360 MHz and made sure that the converter
rate becomes 2.88 GSps instead of 1.44 GSps. I used an UHD example called
"tx_waveforms" to verify the maximum output power. To compare the results with
the specification sheet, a constant ('CONST') wave of 500 MHz frequency with an
amplitude of 1 is used. While expecting a single tone whose power is around -2
dBm (according to this graph given for 2.94912 GSps
https://www.ni.com/docs/de-DE/bundle/ettus-usrp-x440-specs/page/specs.html#:~:text=Figure%202.%20TX%20Maximum%20Output%20Power%3A%200%20dBFS%20CW%2C%202.94912%20GSps%20Converter%20Rate%2C%200%20Hz%20Waveform%20Frequency),
it is around -5 dBm. Does the output power vary that much between the
converter rates of 2.94912 GSps and 2.88 GSps?
1. I will use another X440 to capture the single tone (and the aliases due
to RF sampling) and analyze the ADC spurs. On the front panel, maximum receiver
input power is stated as 10 dBm. This is further elaborated down to the
operational frequency in this webpage
(https://www.ni.com/docs/de-DE/bundle/ettus-usrp-x440-specs/page/specs.html#:~:text=Maximum%20input%20power%2C%20damage%20level).
On the other hand, in the loop back configuration, >30dB attenuation between
ports were recommended.
What is the difference between connecting the Tx port of one X440 to the Rx
port of another X440 and connecting Tx&Rx ports of different daughter boards of
the same X440? Why does the maximum receiver power requirement change? The
maximum one can transmit from a Tx port of X440 is 0 dBm. According to my
understanding, it should be safe to connect Tx and Rx ports (of either same or
different X440s) to each other as long as I am working with a constant waveform
with a PAPR of 0 dB.
I am grateful for your time and effort. If anything is unclear and you are
willing to help, I can provide further details.
Best regards,
Altug KAYA
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