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Re: [Discuss-gnuradio] TVRX module questions

From: Sebastiaan Heunis
Subject: Re: [Discuss-gnuradio] TVRX module questions
Date: Tue, 26 Aug 2008 22:54:24 +0200


My DSPing is a bit rusty.  With the TVRX card, we send -20MHz to the
DDC.  Is this because of 44-64 MHz?  The code where the actual FPGA
register gets written is in usrp_standard.cc?  Here is a function
called compute_fpga_freq_control_word which takes the -20MHz and
returns 2952790016 which is 10110000000000000000000000000000 in
binary.  So for a DDC value of -20MHz, is that the value that gets
written to the FR_RX_FREQ_0 register?  What gets written to
FR_RX_PHASE_0?  Just zero?  I'm just trying to figure out how the
cordic and phase accumulator parts are implemented.

Thanks a lot.


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