[hpsdr] sampling

[jeff millar]

Lawrence D. Lopez wrote:
> i was under the impression that sdr over sampled using low precision
> a/d converters in order to gain higher a/d accuracy.
> 
> For instrance:
> 
> a 16 bit a/d with .1 volt full scale has a resolution of 1.5 micro volts.
> Which is pretty useless.

An A/D has two significant sources of noise, quantization noise and
either internal noise or an external source of "dither".

Each sample quantizes the true input to within +/- 1/2 the sample
interval.  In the frequency domain, this noise spreads evenly across
the band from from 0 to 1/2 the clock rate.  So, the total noise
within any given sub-band drops at the sample rate goes up.

In other words, the higher sample rate allows a digital filter
to average several samples in a row to reduce noise.

"attaining higher accuracy" equates to lower noise.

jeff, wa1hco

 1177264391.0