Hi community,
We are wondering if there is any documentation for amplifiers on the XTRX board (both TX and RX).
We are trying to set the gains for these amplifiers (eGainTypes in LimeSuiteNG), however, there is no tutorials or references for this, and it is hard to find the proper values for each amplifier at different center frequency.
Can anyone give some hints on this?
Thank you!
It doesn’t have any, at least not external to the LMS7002M RFIC. But maybe this is what you mean?
Ah, I see, you do mean LMS7002M. Tagging @ricardas for comment.
This is a wonderful question.
There is some information in the Programming and Calibration Guide part of the LMS7002M datasheet. Register map and block diagrams gives overall understanding on how stages are linked together, but it is hard to tell what values should be for a desired output power.
What I also wonder, is how universal the gain values across different LimeSDR’s are. As in, if the same stage configuration is used for XTRX and Mini, is it expected to have the same output power from the SDR, or do they need to be calibrated individually.
They all use the same LMS7002M RFIC and none have an any sort of driver or PA, with the exception of LimeSDR X3 (only available via integrated systems) and LimeSDR XTRX with the PCIe adapter board (the latter adds drivers). So this leaves two things:
These may vary with different boards, providing different performance at different frequencies. Though I haven’t checked and couldn’t say for certain.
Settings may be different between classic Lime Suite and Lime Suite NG, but otherwise I think behaviour should be the same across boards, noting (1) above and assuming there are not some board-specific settings. @ricardas if you could please confirm.
The gain controls that represent individual LMS7002M registers for each gain is controlled the same way in LimeSuite and LimeSuiteNG, the “generic” gain calculations might be different.
As far as the LMS7002M chip gain settings are concened, they will be set identical on all boards, so should produce the same output. But the final output power is affected by RF matching networks and other external factors, which are outside of software control.
On the topic of how to find the best gain values, I can’t really help, it’s beyond software area. The LMS7002M gains are not absolute values, so I suspect you need external tools to measure the power that you get on various frequencies.