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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 21:25:06 -0400
User-agent: Mozilla Thunderbird 1.0.2 (Windows/20050317)

Dear all,

although I agree that in the SPECIAL case when the CORDIC
frequency is set to 0 it is meaningful to assume a known
phase (set to 0 at power up or otherwise set externally to 0),
I think it is a bad engineering practice to design receivers that assume a known phase (ie, a coherent operation) when the CORDIC frequency is NON-ZERO. I wonder if you share this reservation with me.


Matt Ettus wrote:
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.

The initial phase is always 0 at power up.  If you never set the
frequency to something other than 0, it will always stay that way.  Its
a simple change to make the phase go back to zero.  Patches welcome...


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