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Re: [Discuss-gnuradio] USRP DDC usage
From: |
Achilleas Anastasopoulos |
Subject: |
Re: [Discuss-gnuradio] USRP DDC usage |
Date: |
Thu, 26 May 2005 16:10:46 -0400 |
User-agent: |
Mozilla Thunderbird 1.0.2 (Windows/20050317) |
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...
>> 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 <=
- Re: [Discuss-gnuradio] USRP DDC usage, Krzysztof Kamieniecki, 2005/05/26
- 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