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<DIV>There are also intermodulation distortion products generated by the ADC.
The levels are never specified for audio ADCs and only occasioally
specified for high-speed ADCs. The IMD levels are always higher
than the quantitization noise and are critical if most of the
filtering is done via DSP.</DIV>
<DIV> </DIV>
<DIV>73,</DIV>
<DIV> </DIV>
<DIV>John</DIV>
<DIV>KD6OZH</DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=KA2WEU@aol.com href="mailto:KA2WEU@aol.com">KA2WEU@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=hpsdr@hpsdr.org
href="mailto:hpsdr@hpsdr.org">hpsdr@hpsdr.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, August 08, 2006 18:19
UTC</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [hpsdr] hpsdr] About the Dynamic
Range of Receivers</DIV>
<DIV><BR></DIV>***** High Performance Software Defined Radio Discussion List
*****<BR><BR>
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<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>About
the Dynamic Range of Receivers<BR><BR>It has nothing to do with the
instantaneous dynamic range, which is<BR>defining<BR>the radio's capabilty
to discern a weak signal (near the noise floor) in<BR>the<BR>presence of a
much larger signal. The maximum possible ratio of the two<BR>signal's
levels is called instantaneous dynamic range).<BR>The overall instantaneous
dynamic range of the receiver is not limited by<BR>the nyquist dynamic range
of the 16-Bit ADC (about 95 dB).<BR><BR>N1UL:</FONT></BLOCKQUOTE>
<DIV> </DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>Please
note ADC's quantization noise having a part in the receiver's<BR>overall
noise figure (NF): At the ADC input the thermal noise from the<BR>front end
and the quantization noise will add up. To keep the ADC's part in<BR>overall
NF as low as possible (<1dB), the gain from antenna to ADC should<BR>be
set so that for the front end noise will dominate the quantization
noise<BR>from ADC by about 10 dB. This will further reduce the overall
instantaneous<BR>dynamic range of the receiver !<BR><BR>DSP is decimating
the ADC sampling rate from 100 kS/sec down to rates<BR>appropriate to the
actual<BR>CW / SSB signal bandwidths of (50)300 ... 3100(4500) Hz
(meaning Fs=<BR>781.25 / 1.5625 / 3.125 / 6.25 / 12.5
kS/sec)./N1UL</FONT></BLOCKQUOTE>
<DIV> </DIV>
<BLOCKQUOTE
style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue 2px solid"><FONT
style="BACKGROUND-COLOR: transparent" face=Arial color=#000000 size=2>Noise
coming from ADC (including the quantization noise) is reduced
by<BR>just<BR>the ratio of ADC's nyquist bandwidth (=50 kHz) to the
signals bandwidth,<BR>thus<BR>giving a corresponding gain in dynamic
range of ... ><BR>>
_______________________________________________<BR></FONT></BLOCKQUOTE>
<DIV></DIV>
<DIV> </DIV></FONT>
<P>
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