Sample IRIG Timing Signal

Thread Starter

lindula

Joined Sep 23, 2016
82
Hello, I need to find out how to sample an IRIG Timing Signal. Does anyone know the data period of a IRIG data stream? I have seen some design in which they used a 1Msps ADC but I need to learn more about the signal.
If anyone can help please share your comments.

Thank you
 
IRIG is a really old 1960 time-code prototcol from the US Army, used today in the electric power industry like substations and power plants, and some airports, for precise time-stamping of events and data logs.

It has formats- AM modulated 1kHz carrier and unmodulated and Manchester. These are so you can pipe the time-code through long cables. Of course, everyone modified the standard here and there, so it is a bit hairy to decode.
OP, you can consider buying the latest standard or search for IRIG-B. https://www.itsamerica.com/assets/publications/TN-102_IRIG-B.pdf
GPS and a NMEA packet with 1pps pulse is much easier to work with, but everyone generates IRIG using a GPS receiver.
 

Thread Starter

lindula

Joined Sep 23, 2016
82
I found some information on the web:
IRIG.jpg
I should be able to a sample any one of the formats with a 1Msps A/D Converter.

Comments please?

Thank you
 

jpanhalt

Joined Jan 18, 2008
11,088
Why do you need an A/D converter? WWVB is amplitude modulated similarly and is easily read without an A/D converter. As for the other modes, they look like digital will work.

1607694708732.png
 

Thread Starter

lindula

Joined Sep 23, 2016
82
Why do you need an A/D converter? WWVB is amplitude modulated similarly and is easily read without an A/D converter. As for the other modes, they look like digital will work.

View attachment 224620
Hello, thank you for responding to my message. I believe I will be receiving the IRIG-B120 signal. My understanding is that I must find the edges by the amplitude. What would you suggest? I found this on the web:
https://www.microsemi.com/product-directory/intellectual-property-partners/5180-semquest
Look for Figure 2.

I wonder if a parallel ADC would be better than an SPI ADC?

Thank you
 

jpanhalt

Joined Jan 18, 2008
11,088
There are several circuits for receiving and decoding WWVB. This is a circuit I followed (with mods): https://www.burningimage.net/clock/sensitive-60khz-receiver/

In your case, you probably do not need the sensitive RF section, but the sequence after that is rectify, low-pass filter, and comparator to get the AM envelope. The fourth paragraph from the bottom describes the relevant receiver sections.

You can also search for AM envelope detection and probably find many more circuits. Here's a lead on Wikipedia: https://en.wikipedia.org/wiki/Envelope_detector#:~:text=An envelope detector is an,called as a peak detector.
 
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Thread Starter

lindula

Joined Sep 23, 2016
82
Thank you very much. I was thinking about using a 2Msps ADC that has a SPI interface. I am planning of using a FPGA for the decoding. I will look into your recommendation. Thank you very much.

Joe
 
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