And further, the clip point is simply the point where a signal is too
large for the A/D converter. So if you have 65536 values in 16 bits,
you divide the real dynamic range of the A/D by 65536 and use this as
your step size when designing the A/D.
Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com
On 9/11/2016 5:40 PM, Carl Moreschi wrote:
There's no law that says the step size has to be 1 mv. It can be
whatever the design allows.
Carl Moreschi N4PY
58 Hogwood Rd
Louisburg, NC 27549
www.n4py.com
On 9/11/2016 5:04 PM, Gary J FollettDukes HiFi wrote:
I understand and appreciate this discussion of NOISE dynamic range.
This does not explain how one can get SIGNAL dynamic range higher than
~96 dB with 16 bits. These are different quantities.
If the A to D has say, 1 mV per bit response, then the largest input
signal this 16 bit A to D can measure should be ~65,000 mV. That’s
about 96 dB. Please tell me what I am missing here…
Is the input amplifier compressing the RF input signal dynamic range
range to make this work? This was done on Vinyl records to compress
the roughly 120 dB dynamic range of an orchestra down to the 70 dB or
so that Vinyl records could carry.
Gary
On Sep 11, 2016, at 6:49 AM, shristov<shristov@ptt.rs> wrote:
Gary J FollettDukes HiFi wrote:
How is it that a 16 bit A to D can now handle a
dynamic range of 132 dB (in band)?
A perfect 16-bit ADC would have a difference of 97.8 dB
between the average noise level and the level of the full-scale
sinusoid. This is a basic fact, and it is NOT violated by ADCs
used in SDR receivers. In fact, a real-life 16-bit RF ADC
has substantially less than 97.8 dB.
Under certain conditions, not very difficult to fulfill,
ADC noise spectrum density is uniform, i.e., there is
the same average noise level in each Hz of the ADC output.
Now, if the ADC output goes through a filter with
the bandwidth smaller than half of the sampling
frequency, the average noise power AFTER the filter
will be decreased in proportion to bandwidth reduction.
For example, if the bandwidth gets reduced from 50 MHz
to 500 Hz, i.e. 100,000 times, the resulting average noise
level will be decreased by 50 dB.
So, one might say that the ADC dynamic range got increased
from 97.8 dB to 147.8 dB (minus imperfections).
Such an interpretation would not be correct if the essential
factor of bandwidth reduction is omitted.
73,
Sinisa YT1NT, VE3EA
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|