AnsweredAssumed Answered

inverted values

Question asked by Daniel_Camara on Aug 11, 2015
Latest reply on Aug 17, 2015 by Daniel_Camara



I am perceiving an behavior that, at least for me, is a little bit odd.  Sometimes, not always, the signals of the I and Q get inverted. I mean I build my wave format, like this:



and after I receive it, the half sinusoids that were supposed to be, for example, positive shows up negative and vice versa, maybe showing the RX is easier.  What I receive is something like this:


These are the raw values of I and Q I am receiving.... no treatment nothing,  and if you flip these, they are much closer to the original data sent! Well OK, compare the flipped version below with the first graph!

I mean I don't know if this is an expected behavior (I hope not) or if it is something that I messed up with my configuration.. or there is an option somewhere... I don't know. The thing is that it does not do that always, sometimes it goes as I am expecting and I manage to decode!


Main configuration (FMCOMMS4):

  - Ensm mode: FDD

  - Frequency: 2.4GHz

  - Gain:  Manual : 30 db

  - Sampling frequency: 2MHz

  - TX attenuation: 0

  - Calibration mode: auto


This happens in all three configurations I have tested:

        a. loopback cable between RX and TX

        b. over the air loopback between the same board RX and TX

        c. From board A to board B over the air


  Any ideas are welcome!!!