Loopback mode and RF transmission

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polidel
Posts: 1
Joined: Mon Dec 14, 2015 1:57 am

Loopback mode and RF transmission

Post by polidel »

HI, I am new with the bladeRF and I am having some troubles with the IQ data that I receive in the Loopback mode and RF transmission also.
I am working with the x40 model and CLI in Windows and Matlab.
The first problem faced is the diferent amount of data samples that i receive, are not the same amount that the ones that i send which is the up part of the attached image.
In one hand, when running the CLI and sending samples in CSV format after runing the TX it doesn't say that the file is being converted to the native language of the DACS, so I wonder if there is any way to solve that in order to send the right data to the board in order to don't have to deal with raw binary data.
I would be grateful if anyone could help me out with this problem,
Thans in Advance,
:roll:
Paulo.

https://www.icloud.com/sharedalbum/es-e ... FssfG0HkYd
jynik
Posts: 455
Joined: Thu Jun 06, 2013 8:15 pm

Re: Loopback mode and RF transmission

Post by jynik »

Hi Paulo,

If you haven't already, I would suggest you take a look at Figure 3.1: Loop back and test options in the LMS6002D programming manual (page 30). This gives you a clear picture of where the TX path is connected to the RX path for each of the various options. It looks like you're using the RF_LNA2 loopback option, implying that your TX path through the AUXPA connects to the output of (the powered down) RX LNA2.

With all of the LMS6 loopback modes, you're passing samples through analog components. As such, the values you receive will not be exactly what you transmit. There's a firmware loopback option for that, and I am working on getting an FPGA loopback option ("digital loopback") integrated into the codebase for this purpose. If you want to minimize non-idealities, I'd recommend one of the baseband loopback options, prefixed with "BB."

With respect to the CSV format -- it looks like you're missing the format=csv argument on your TX side. However, I see you do include this on the RX side.

Best regards,
Jon

P.S. - Since I see you're using MATLAB, I just wanted to let you know that improved MATLAB support is on the way. It's currently merged into bladeRF master and I'm tying up some loose ends before we do another release and installer. I've been working with it quite a bit, and am much happier with the result.
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