RX/TX calibration using the RLT-SDR

Discussions related to schematic capture, PCB layout, signal integrity, and RF development

Moderator: robert.ghilduta

Post Reply
OskarM
Posts: 19
Joined: Sun Dec 09, 2018 3:02 pm

RX/TX calibration using the RLT-SDR

Post by OskarM » Sat Jan 19, 2019 11:52 am

Hi,
I use RTL-SDR as a spectrum analyzer for TX calibration, using oscmocom_siggen.

I managed to get DC spike and IQ quite low - what to do with the results I got in osmocom_siggen? I am playing with gnuradio companion - as for now I split IQ and "add const" for DC offset and then I use block of "IQ bal fix" to implement IQ corr values - is that correct approach? Can I apply this somehow though bladeRF-cli to skip additional blocks in gnuradio?
bladeRF> cal lms

LPF tuning module: 23

TX LPF I filter: 30
TX LPF Q filter: 39

RX LPF I filter: 30
RX LPF Q filter: 33

RX VGA2 DC reference module: 25
RX VGA2 stage 1, I channel: 29
RX VGA2 stage 1, Q channel: 37
RX VGA2 stage 2, I channel: 41
RX VGA2 stage 2, Q channel: 25


Are these values in bladerf-cli direct DAC settings (ie. the full swing of DAC is +/- 2048)? In the gnuradio DC offset example the step is set to 1.0/2048.0 so I'd need to convert that back if it's the case.

thanks,
best regards

robert.ghilduta
Posts: 61
Joined: Thu Feb 28, 2013 11:14 pm

Re: RX/TX calibration using the RLT-SDR

Post by robert.ghilduta » Sun Jan 20, 2019 10:29 pm

The `cal lms` values can be stored into a file that is autoloaded every time you use your bladeRF 1.0. Please take a look at https://github.com/Nuand/bladeRF/wiki/D ... fset_table

Post Reply