Undersampling IF software

Hi,

I'm looking for a software to compute the frequency sampling for
undersampling an IF radio spectrum.

For example, if I have a IF of 455 kHz with 80 kHz bandwith, I can
sample at 200 kHz and the second IF would be 55 kHz.

I have try to compute with software designed for RF mixer but it
doesn't work because, in my example, the second IF is : ABS (
2=2Efreq_sampling - freq_IF ) and without the absolute op=E9rator, the
second frequency is negative and so the software for mixer doesn't
compute this frequency.

Thanks

>Hi,
>
>I'm looking for a software to compute the frequency sampling for
>undersampling an IF radio spectrum.
>
>For example, if I have a IF of 455 kHz with 80 kHz bandwith, I can
>sample at 200 kHz and the second IF would be 55 kHz.
>
>I have try to compute with software designed for RF mixer but it
>doesn't work because, in my example, the second IF is : ABS (
>2=2Efreq_sampling - freq_IF ) and without the absolute op=E9rator, the
>second frequency is negative and so the software for mixer doesn't
>compute this frequency.
>
>Thanks
>
>

Is there some reason that a sketch of the spectrum won�t work?  

Go out to at least the 3rd harmonic of the sample clk.  It�ll become
obvious real quick if you�re going to have filtering problems. 

Just remember any folding eats into your Dyn Range.