[time-nuts] WWVB BPSK Receiver Project?

Azelio Boriani azelio.boriani at screen.it
Thu Mar 15 23:01:44 UTC 2012


PHK,
I'm interested in your circular averaging buffer: suppose 1K long, the 1st
sample goes into position 0, the 2nd into 1 ... the 1000th into 999 or, the
1st gets scaled and then summed with that already present in position 0
then the result back in position 0? And so on, of course, for position 1, 2
...

On Thu, Mar 15, 2012 at 11:48 PM, Chris Albertson <albertson.chris at gmail.com
> wrote:

> On Thu, Mar 15, 2012 at 3:13 PM, Poul-Henning Kamp <phk at phk.freebsd.dk>
> wrote:
> > In message <20120315152620.8347488e049854218aed4aa6 at kinali.ch>, Attila
> Kinali w
> > rites:
> >
> >>> Do you need 16 bits or can you get by with a 12 bit ADC?
> >
> > In general: The more the merrier, for a digital dude like me, having
> > more bits is easier than getting AGC working correctly :-)
> >
> >>> Have you considered using an FPGA for signal processing? It seems
> >> you need a fairly serious CPU to handle that much data.
>
>
> "That much data" we are talking about 192K samples per second.   I can
> routinely record multiple tracks of 192K audio and do processing in
> real time and the CPU meter hardly moves  the bottom.    Even a
> gigabit per second Ethernet port is not "a lot of data" on a modern
> computer.
>
> FPGAs and DSP come into play if you are talking about tens of millions
> of samples per second with data rates above say 200Mb/Sec  But the
> rate from an audio interface running 192K and 24-bits is still under
> one megabyte per second.    An interesting ratio is the number of CPU
> cycles available to process one sample.  On my Apple iMac that would
> be about roughly  200,000 operations per data sample.
>
> In real life SDR receivers even an older CPU can process the I and Q
> channels and maintain a large graphic screen and send and receive data
> over a network and still not be "maxed out"
>
>
> Chris Albertson
> Redondo Beach, California
>
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