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Re: [Discuss-gnuradio] USRP DDC usage
From: |
Krzysztof Kamieniecki |
Subject: |
Re: [Discuss-gnuradio] USRP DDC usage |
Date: |
Thu, 26 May 2005 16:33:15 -0400 |
User-agent: |
Internet Messaging Program (IMP) 3.2.2 |
Quoting Achilleas Anastasopoulos <address@hidden>:
>
> Quoting Achilleas Anastasopoulos <address@hidden>:
>
> >> I have a question/observation on this issue:
> >>
> >> Since the DDC multiplication is complex and since the internal DDC
> >> oscilator is noncoherent, I do not see a difference between the MUX
> >> settings: 0x33221100 and 0xf3f2f1f0.
> >>
>
> >Is the difference between them a phase shift of 45 degrees and a gain
> >ratio of
> >sqrt(2)?
>
> Yes about the sqrt(2), but I guess the 45 degrees are irelevant here
> since the operation is noncoherent so we cannt resolve the phase.
> (see also comment below)
>
>
> >> Similarly, with the setting 0x00003210 you will never be able to
> >> separate the two channels coming from ADC0/ADC1 and ADC2/ADC3.
> >>
>
> >You can seperate ADC0/ADC1 and ADC2/ADC3 if you set the DDC frequency
> >to zero (I think you also have to never have set it to a non-zero
> value >after powerup, since you can't reset the DDC phase)
>
> Even if you set the frequency to 0, there is a "random" initial phase
> that is unknown, and thus you cannot separate the two channels.
>
> If x0(t) and x1(t) are the two inputs from ADC0 and ADC1 respect, then
> the output is
>
> [x0(t)+j x1(t)] exp(j w_cordic t + phi),
> where phi is unknown...
>
>
I can't find the message, but I though that Matt Ettus stated that "phi" is zero
at powerup, but it cannot be accessed thru software.
Matt?
> >> Is this right?
> >>
> >> Thanks
> >> Achilleas
>
- [Discuss-gnuradio] USRP DDC usage, Philip Balister, 2005/05/25
- Re: [Discuss-gnuradio] USRP DDC usage, Achilleas Anastasopoulos, 2005/05/26
- Re: [Discuss-gnuradio] USRP DDC usage, Achilleas Anastasopoulos, 2005/05/26
- Re: [Discuss-gnuradio] USRP DDC usage,
Krzysztof Kamieniecki <=
- Re: [Discuss-gnuradio] USRP DDC usage, Eric Blossom, 2005/05/26
- [Discuss-gnuradio] Delta 44, Bob McGwier N4HY, 2005/05/26
- Re: [Discuss-gnuradio] Delta 44, Eric Blossom, 2005/05/27
- Re: [Discuss-gnuradio] Delta 44, n4hy, 2005/05/27
- Re: [Discuss-gnuradio] Delta 44, Matt Ettus, 2005/05/27
- Re: [Discuss-gnuradio] Delta 44, n4hy, 2005/05/27
- Re: [Discuss-gnuradio] Delta 44, James Cooley, 2005/05/27
- Re: [Discuss-gnuradio] Delta 44, Eric Blossom, 2005/05/28
Re: [Discuss-gnuradio] USRP DDC usage, Krzysztof Kamieniecki, 2005/05/26
Re: [Discuss-gnuradio] USRP DDC usage, Matt Ettus, 2005/05/26