Re: [Discuss-gnuradio] DBSRX coherent problem (Phase Noise)

[tom_wgs]

Steven Clark-2 wrote:
> 
>>
>> The second image shows the plot of the two real components of the same
>> 128
>> samples.
>> The phase shift is so large it is visible in the plot.  I
>> I noticed that the tuned frequency is about 12 kHz off target, but this
>> is
>> within the expected spec. of the system.
>>
>>
>> http://old.nabble.com/file/p30200932/Real-RXa_Real_RXb.jpg
>>
>>
>>
> Can you copy and paste the section of code where you issue tuning commands
> to your daughtercards? This looks similar to something I was seeing
> earlier,
> with 2 WBX cards, which was due to a mistype in my tuning commands.
> 
> -Steven
> 
> below is a snippet of the code that sets up the usrp and the functions 
> that set freq and gain.
> 
> //snippet
> 
>   mux = 0x00003210;
>   d_which = 0;
>   fpga_filename="std_2rxhb_2tx_dig.rbf";
>   d_usrp_s = usrp_make_source_s(d_which, d_decim, 
>                                                     2, mux, 0, 0, 0, 
>                                                    
> fpga_filename.c_str());
>   d_usrp_s->set_nchannels(2);
>   d_spec  = str_to_subdev("A:0");
>   d_spec2 = str_to_subdev("B:0");
>   d_subdev  = d_usrp_s->selected_subdev(d_spec);
>   d_subdev2 = d_usrp_s->selected_subdev(d_spec2);
> 
>     // Set Gain
>     float gain_min = d_subdev->gain_min();
>     float gain_max = d_subdev->gain_max();
>     if(d_gain == -1) {
>     d_gain = (gain_min + gain_max)/2.0;
>     }
> 
>   // Set the USRP/dboard Gain
>   usrp_phaser_gain(d_gain);
>   // Set the USRP/dboard frequency
>   usrp_phaser_tune(freq);
> 
>   d_my_gpio = wgs_gpio_make_stream_ss();
>   connect(d_src, 0, d_my_gpio, 0);
> 
> 
> 
> int usrp_phaser::usrp_phaser_tune( double freq)
> {
>   usrp_tune_result r;
>   bool ok;
>   char tmp_str[256];
> 
>   ok = d_usrp_s->tune(0, d_subdev, freq, &r);
>   if(!ok)
>   {
>     sprintf (tmp_str, "Could not set frequency for (%s).\n",  
>                    d_subdev->side_and_name().c_str());
>     printf("%s", tmp_str);
>     return(1);
>   }
>   else
>   {
>     printf("Tune Results: DC-Freq=%g, DDC-Freq=%g,Residual=%g,
> Inverted+=%d\n",
>                   r.baseband_freq,r.dxc_freq,r.residual_freq,r.inverted);
>   }
> 
>   // Set the USRP/dboard 2 frequency
>   ok = d_usrp_s->tune(1, d_subdev2, freq, &r);
>   if(!ok)
>   {
>     sprintf (tmp_str, "Could not set frequency for (%s).\n",
>                  d_subdev2->side_and_name().c_str());
>     printf("%s", tmp_str);
>     return(1);
>   }
>   else
>   {
>     printf("Tune Results: DC-Freq=%g, DDC-Freq=%g,Residual=%g,
> Inverted+=%d\n",
>                r.baseband_freq,r.dxc_freq,r.residual_freq,r.inverted);
>   }
>   return(0);
> }
> 
> int usrp_phaser::usrp_phaser_gain( int gain )
> {
>   usrp_tune_result r;
>   bool ok;
> 
>   // Set the USRP/dboard 1 gain
>   ok = d_subdev->set_gain(gain);
>   if(!ok)
>   {
>     sprintf (tmp_str, "Could not set gain (%d) for (%s).\n", 
>                     gain, d_subdev->side_and_name().c_str());
>     printf("%s", tmp_str);
>     return(1);
>   }
>   else
>   {
>     printf("Gain A set to %d\n", gain);
>   }
> 
>   // Set the USRP/dboard 2 gain
>   ok = d_subdev2->set_gain(gain);
>   if(!ok)
>   {
>     sprintf (tmp_str, "Could not set gain (%d) for (%s).\n", 
>            gain, d_subdev2->side_and_name().c_str());
>     printf("%s", tmp_str);
>     return(1);
>   }
>   else
>   {
>     printf("Gain B set to %d\n", gain);
>   }
>   return(0);
> }
> 
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> 

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