Ok, that makes sense. Looking back at this site (http://www.nd.edu/~jnl/sdr/docs/tutorials/4.html#tth_sEc2.1) I see that the DDC is combining the I and Q inputs to do complex multiplication. I originally thought it was multiplying the I and Q components separately, so that no input to Q would mean zero output for Q also.
Thanks so much! -Ian Larsen On 7/18/07, Johnathan Corgan <[EMAIL PROTECTED]> wrote:
Ian Larsen wrote: > I assume this also true for the BasicRX daughterboard? (Doesn't do > downconversion, but does do analog multiplication to get I and Q?) Almost. The boards don't do anything with the signal, but have separate I and Q inputs that go to the ADCs as is. On the FPGA, however, there are digital mixers that you can use to convert a center frequency down to baseband, so you get a complex I and Q signal out of that, even if you only supply a signal to the I input. That is what is actually happening when you "tune" a BasicRX or LFRX board. -- Johnathan Corgan Corgan Enterprises LLC http://corganenterprises.com
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