Re: [Discuss-gnuradio] RFX2400 intermediate frequency

[adib_sairi]

John Orlando wrote:
> 
> 
> The DDCs are only used if the front-end RF can't tune to the exact
> frequency requested by the user.  The DDCs are capable of doing a
> final digital mixing (from a low IF, typically) to center the
> bandwidth of interest at DC, but these aren't used with all
> daughterboards.
> 
> So, in the case of RF daughterboards that employ quadrature
> downconversion, and are able to tune to the exact frequency of
> interest (i.e., downconvert the RF bandwidth to center it at DC),
> there is no IF.  The A/D converters are simply digitizing the baseband
> signal, with one A/D digitizing the I channel, and one digitizing the
> Q channel.  Google for "zero IF receiver" and you'll find more
> details.
> 
> The 20 MHz low-pass filters are there to reduce wideband noise, and to
> help with anti-aliasing.  They don't imply that there is a mandated 20
> MHz IF.
> 
> -- 
> John Orlando
> CEO/System Architect
> Epiq Solutions
> www.epiq-solutions.com
> 
> 
> 

oh thank you John for the explanation. thats mean the AD8347 will convert
the signal to the baseband and output the I/Q signal to the ADC. then ADC
will convert the signal to the digital domain. in this case the DDC is only
for decreasing the frequency of the digital sample so that it can be
transfer trough usb 2.0 which have the bottleneck at 32Mhz am i correct? 


-----
Mohd Adib Sarijari
Universiti Teknologi Malaysia
www.fke.utm.my
www.utm.my
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