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Hi Alberto,
I'm quite familiar with digital
signal processing (I work in the embedded SW
area for a big manufacturer of telecommunications equipments
and digital streams of several Gbit/s are common on our boards), nevertheless I
know that analog conditioning of signals (before they become "numbers") is at
least as important as the digital treatment, unless you accept to sample
meaningless information (noise) at the ADC :-) Anyway I'm sure this is dealt
with perfectly in SDR's so I think we can stop here this
discussion.
Thank you for
clarifications.
Cheers
D,
----- Original Message -----
Sent: Tuesday, April 27, 2010 1:32
AM
Subject: Re: LF: Probably not a new
question...
On 4/27/2010 12:50 AM, Daniele Tincani wrote:
Hi Alberto,
thank you very much for
clarification. I was misled by the softrock example :-)
Anyway, a doubt persists...I read
on the frontpanel of the R&S SDR that it is a "digital wideband
receiver"...Well, in my "prejudice", "wideband" does not match with
"high-quality", unless the radio contain several different "narrow band"
receivers. Is this (apparent)
conflict solved at the digital signal processing level?
Regards
D HI Daniele,
yes, it is a prejudice, as a matter of
facts.... why "wideband" should be not compatible with "high quality" ? This
stems probably from the
old analog world, where you had to face conflicting
requirements... in a SDR, "wideband" can mean e.g. that an ADC does directly
sample the
incoming RF spectrum at a rate of 150 MHz (there are ADCs
capable of this), thus providing information up to the Nyquist frequency of 75
MHz.
Then you have just numbers, and with numbers you can perform miracles,
if correctly handled (ask to an accountant, if you don't believe me...
:-)
When you have the digitized stream of numbers that represents the
75 MHz chunk of spectrum, you can, if you need to, analyze those
75 MHz
with a resolution of 0.001 Hz, yes, one millihertz... changing on-the-fly
where that millihertz is placed on the spectrum, or even its
bandwidth...
try that with an old, analog "high quality" radio.... :-)
Of course,
you need both the mathematical background in digital signal processing and
coding ability to do that, and these are skills not very
familiar to
analog RF engineers that hence look suspiciously to the new world of SDRs. But
this does not mean that it can't be done....
73 Alberto
I2PHD
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