[time-nuts] IRIG-B audio decoder circuits and ICs sought

[Joseph Gwinn]

I'm studying up on how IRIG-B decoder circuits work.  What are the good 
approaches, the bad approaches, especially in the presence of noise?  
(I asked on the NTP group, with little result beyond the C/C++ decoder 
software written for the audio channel of a 1990s Sun workstation, 
which it ate alive: 50% cpu load.)

Are there decoder ICs available?

The closest to a decoder IC I've found is some FPGA code from a partner 
of Microsemi (nee Symmetricom):

..<http://www.microsemi.com/products/fpga-soc/design-resources/partners/semquest>

All marketing and little technical information.  I'll have to find out 
the details.


I find very little, though I did find one intriguing idea using a 
Costas Loop to lock to the 1 KHz carrier, and a posting suggesting 
squaring the input signal and phase-locking to the 2 KHz result.  Most 
recent articles on IRIG decoders come from Chinese sources, mostly in 
the AC power industry.

Joe Gwinn