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problem in fagc setting in fmcomms 4

Question asked by rahulram on May 8, 2017

hi,

     i am using zc706 board along with fmcomms 4 board to transmit and receive ofdm modulated packets. from the reference design i have created a modem which transmits as well as decodes received ofdm signals and all seems to be working fine , i have two setups with two boards and two rf cards one for transmitting and one for receiving the signal , now my problem is that i run my design in fagc mode and it works fine for normal conditions, now to check the receiver i change the attenuation at the tx side in no os driver software form 0 db onward .  now when i make the attenuation at the tx side to  50 db then i notice that my receiver fails to decode majority of data that it is receiving. on investigating further i noticed that a sine wave appears in 50 db attenuation in fagc in place of a linear line ie noise and so my packet detection module is failing , this happens only in the range close to 50 db and works fine above 60 db again , i am not understanding why this happens , and is there a setting in fagc which can help me avoid this . i have attached the image of the iioscope in receiver side which explains my problem , pls help

thanks 

regards

rahul    

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