RE: [Discuss-gnuradio] Impulse response USRP DAC<->ADC

[Per Zetterberg]

When I changed the base-band frequency of the digital up/down-conversion
from zero to 4MHz the hole disappeared.
  

> -----Original Message-----
> From: Matt Ettus [mailto:address@hidden 
> Sent: den 24 mars 2008 20:18
> To: Per Zetterberg
> Cc: address@hidden
> Subject: Re: [Discuss-gnuradio] Impulse response USRP DAC<->ADC
> 
> Per Zetterberg wrote:
> > Hi All,
> >
> > I connected the DAC of the USRP directly to the ADC (basic 
> db, 50ohm 
> > cable), 2MHz sample-rate. The impulse responses I get are:
> >
> > 
> h1=[0,-2,2,-7,8,-6,314,479,-47,-161,-124,-103,-79,-63,-50,-39,-29,-23,
> > -17,-1
> > 4,-13,-9,-7,-5,-4,-3,-3,-2,-1,-3,-3];
> > 
> h2=[0,-1,-1,0,-2,2,22,274,208,-77,-79,-71,-53,-46,-36,-28,-23,-17,-15,
> > -12,-1
> > 0,-7,-5,-4,-4,-3,-4,-2,-2,-2,-1,-2];
> >
> > Where h1 is with "set_adc_buffer_bypass" and h2 without it. 
> Does this 
> > make sense ?
> >
> >   
> 
> Yes, this looks reasonable.  You are seeing a hole at DC 
> because of the low frequency cutoff of the transformers.  If 
> you used the LFRX and LFTX instead of the BasicRX and 
> BasicTX, you wouldn't see the hole there.
> 
> Matt
> 
>