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AD9371 EVM external rxlo spectrum inversion issue

Question asked by C_Lee on Feb 8, 2018
Latest reply on Feb 13, 2018 by Vinod

Hello,

Let me explain my setup first.  

AD9371 EVM  Rx channel 1 using external rxlo at 1.96608GHz (measured actual signal is 3.93216GHz at 3dBm at rxlo SMA).  The RF input and lo are provided by sig gen.  Data is captured into fpga and ported to matlab.  

 

The problem:

The following is a diagram comparing the Sig Gen data with captured RX data from two different startups.  In case 1, the Q data is negated compare to case 2, the I data is negated. In both case, the spectrum is inverted.  Searching through UG992, I can't find related information regarding spectrum inversion.   Is there any way to disable spectrum inversion? 

 

 

My second question is regarding the initialization code for ad9371. 

 

In myk.c around line 347

static mykonosRxSettings_t rxSettings =
{
&rxProfile, /* Rx datapath profile, 3dB corner frequencies, and digital filter enables*/
&rxFramer, /* Rx JESD204b framer configuration structure*/
&rxGainControl, /* Rx Gain control settings structure*/
&rxAgcConfig, /* Rx AGC control settings structure*/
RX1_RX2, /* The desired Rx Channels to enable during initialization*/
1, /* Internal LO = 0, external LO*2 = 1*/
1966080000U, /* Rx PLL LO Frequency (internal or external LO)*/
0 /* Flag to choose if complex baseband or real IF data are selected for Rx and ObsRx paths. Where, if > 0 = real IF data, '0' = zero IF (IQ) data*/
};

 

The value of rxpll lo frequency should be entered as twice the intended lo frequency (in my case 3.93216GHz) when configured for external lo or the same as the intended carrier frequency (1.96608GHz)?

 

 Your help is greatly appreciated.  Thank you.

 

 

Li 

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