Re: [Discuss-gnuradio] adding a DC offset to the output of a LFTX

On 08/31/2010 07:50 AM, William Cox wrote:
> I'm trying to add a DC offset to the output of my LFTX driven from a
> USRP 1. Is this possible progromatically? I edited my GRC block diagram
> to include adding a constant value to my complex stream, before
> inputting into the USRP sink block. I have a scope output at the same
> point, which shows adding a constant value to the signal, but the output
> of the USRP doesn't match. What am I missing? I've tried adding both a
> constant real value, and a complex constant with equal parts I and Q -
> neither work.
> Thanks.
> -William

If you have a non-zero frequency set on the USRP then your DC offset
will be mixed to that frequency. If you really want DC offset then you
can not use the DUC, or you can use the registers in the AD9862 to add
DC offset after the upconversion. The registers will only give you a
limited range, however.

Matt

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