AnsweredAssumed Answered

Abnormal behaviour of Rx FIR in AD9361

Question asked by aslam on Jun 8, 2018
Latest reply on Jun 20, 2018 by xiji


I am using ad9361 chip. I used the internal FIR filter to filter 2 MHz signal. I employed ad9361 filter wizard (Matlab reference software )to design a filter. The following figure shows the desired filter parameters.



AD9361_RXFIRConfig rx_fir_config = {
3, // rx
0, // rx_gain
1, // rx_dec
{6,4,-10,9,4,-25,33,-11,-38,81,-70,-14,133,-192,110,109,-334,374,-116,-348,712,-637,7,888,-1427,1014,454,-2293,3248,-1897,-3255,20058,20058,-3255,-1897,3248,-2293,454,1014,-1427,888,7,-637,712,-348,-116,374,-334,109,110,-192,133,-14,-70,81,-38,-11,33,-25,4,9,-10,4,6,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, // rx_coef[128]
64, // rx_coef_size
{1024000000,64000000,32000000,16000000,8000000,8000000}, // rx_path_clks[6]
6724137 // rx_bandwidth

 AD9361_RXFIRConfig tx_fir_config = {........}


ad9361_set_tx_fir_config(rf_front_end, tx_fir_config);
ad9361_set_rx_fir_config(rf_front_end, rx_fir_config);
ad9361_set_trx_fir_en_dis (rf_front_end, 1);


However, when I applied this filter on ad9361 chip and captured ADC outputs, I got the following response


This figure contains only noise. Ideally, I am supposed to get only signal within 2 MHz and rest of the signal should be filtered. However, I am also getting the out-of-band signals (indicated by red lines in the figure).


Could you please tell me if I am missing something?