On 12 May 2010 at 19:09, Olin Lathrop wrote:

> Richard Prosser wrote:
> > Thanks, I hadn't realised that the data slicer averaged over such a
> > short time interval. I'd assumed it was at least 8 to 10 bits and
> > likely to be more.  Looks like I'd definately get an improvement if I
> > went to manchester type encoding.
> 
> There are many ways to do a data slicer.  In one of the receivers of the
> system I mentioned earlier, I fed the analog output of the two receivers
> directly into a dsPIC and did everything from there on in firmware.  That
> included the data slicing.  The dsPIC sampled sampled the analog signals at
> 100KHz and the manchester data rate was 10KHz.  The firmware data slicer was
> faster and performed better than the all analog data slicer in the previous
> model.

Likewise I once used PIC firmware to improve on the performance of the built in 
data slicer in a receiver module. The PIC does 4x digital oversampling of the "data" 
output of the receiver module. If 3 or more 1's in 4 consecutive samples then data = 
1, else if 3 or more 0's then data = 0. Crude (compared to other methods such as 
analog sampling above, or modifying the actual data slicer circuit on the receiver so 
it better suited the signal being received) but it hugely the improved data error rate 
and operating distance.

-- 
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  brent.brown@clear.net.nz


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