AnsweredAssumed Answered

Tuning Rx Lo independently than Tx LO AD9364

Question asked by bhatnagar.vaibhav81 on Oct 14, 2015
Latest reply on Mar 9, 2016 by bhatnagar.vaibhav81




I am using a customized DRF with aD9364 chip on it. This DRF is connected to an FPGA platofrm that holds an OFMD modem chain.

I would like to verify my CFO correction algorithm at demodulator side hence I perform an external loopback on DRF card.

My algorithm is working in internal loopback/ external loopback tx/rx lo tuned at 2.4GHz.

The problem is that when I tune both TX/RX at different frequencies in FDD mode with some offset from 1Khz to 10Khz, i observe that my algorithm has to correct 5 times more than the offset.



For example, if tx_lo is tuned at 2.4Ghz, and rx_lo is tuned at 2.4Ghz + 1 khz, my algorithm detects an offset CFO of ~=5 khz that is not normal.



My questions are :



Is it recommended to tune tx/rx lo independently in FDD mode on AD9364?

Is there any other possibility at rx chain that could increase this offset or the pll is not precise?



The parameters in main.c are :



//2399999000UL, //rx_synthesizer_frequency_hz *** adi,rx-synthesizer-frequency-hz

//2400020000UL, //rx_synthesizer_frequency_hz *** adi,rx-synthesizer-frequency-hz

{1280000000,  80000000, 40000000, 20000000,  10000000, 10000000}, tx chain

{1280000000,  80000000, 40000000, 20000000,  10000000, 10000000}, rx chain



Please let me know if there is any clue.



Thank in advance.



Best regards,