Serial Data Quality Comparator Ideas

[Joe Leikhim]

Thanks Pete:

At the onset I should have clarified that the data is coming from an FM 
discriminator and is 2 level FSK modulation of the FM carrier. So 
amplitude should not be a concern as it is limited and levels will be 
carefully set post FM demod. As far as phase shift. as this is a VHF/UHF 
scenario the long paths in mutipath will be reflections that might add a 
few tens of microseconds between the direct and incident signals, there 
will also be Doppler at UHF.

Mostly, the signals will have varying degrees of channel noise on them 
unless the receiver is fully quieted. This noise will cause uncertainty 
of the rising edge, so there will be an indirect but real influence on 
the jitter.

I am hoping that the simple application of a PLL and extraction of the 
combined effects of jitter plus noise/signal from the loop could be 
measured to yield a crude but effective signal quality measurement.  In 
some instances only one receiver will be active, or it could be two, 
three or four.

Making direct comparison of the bits or bytes in the data streams would 
be very subjective, especially if there are only two streams of data 
(which one is bad?).  So I think this approach might be just as good 
maybe better.

-- 
Joe