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<DIV>This is correct. ( Friees formula)</DIV>
<DIV> </DIV>
<DIV>73 de Ulrich N1UL</DIV>
<DIV> </DIV>
<DIV>
<DIV>In a message dated 3/28/2011 8:06:57 A.M. Eastern Daylight Time,
h-hartfuss@t-online.de writes:</DIV>
<BLOCKQUOTE style="PADDING-LEFT: 0px; MARGIN-LEFT: 0px"><FONT style="BACKGROUND-COLOR: transparent" color=#000000 size=2 face=Arial>*****
High Performance Software Defined Radio Discussion List *****<BR><BR>Hi Edson,
<BR><BR>If the noise figure of the ADC is dominated by quantization noise,
it's<BR>noise figure Fadc is given by<BR>Fadc=((DV)^2)/(6kTRfs)<BR>with DV the
voltage quantization step and fs the sampling frequency (see<BR>for example
Frerking's book "Digital Signal Processing in
Communication<BR>Systems").<BR>So only by reducing the quantization step size
(more bits) or by<BR>increasing the sampling rate fs you can reduce the noise
figure of the<BR>ADC. You cannot improve this figure with measures in the
signal<BR>processing pass.<BR><BR>In the Mercury case the effect of increasing
the sampling rate and/or<BR>the number of bits will, however, be very small
since a preamp is<BR>involved which has 20dB gain.<BR><BR>Generally, when
cascading stages characterized by noise figures F1 and<BR>F2 the overall total
noise figure Ftot is always:<BR>Ftot= F1 + (1/G)(F2-1)<BR>where G is the gain
of the first stage. The noise figure F1 of the first<BR>stage dominates the
overall behavior and that the more the higher its<BR>gain G is. <BR>It is
completely independent of what you are cascading.<BR><BR>73, Hans,
DL2MDQ.<BR><BR>PS: In this context my paper on Mercury noise temperature
measurements<BR>in TAPR / psr109 might be interest for
you.<BR><BR><BR><BR><BR>-----Original Message-----<BR>Date: Mon, 28 Mar 2011
01:06:16 +0200<BR>Subject: Re: [hpsdr] DDC Noise Figure<BR>From: Edson Pereira
<ewpereira@gmail.com><BR>To: KA2WEU@aol.com<BR><BR>***** High
Performance Software Defined Radio Discussion List
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