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IRIG-B clock time-stamps digital delay generator data

Posted: 16 Feb 2005 ?? ?Print Version ?Bookmark and Share

Keywords:interface technology? iti? ddg200? ddg400? digital delay generator plug-in?

In a recent eeProductCenter review we looked at Interface Technology Inc.'s (ITI) DDG200 and DDG400 table-driven digital delay generator plug-ins. On the heels of that product rollout, ITI is now announcing immediate availability of its IRIG-B Real Time Clock option for the DDG200 and DDG400.

The DDG200 and DDG400 provide both dynamically variable delay and dynamically variable pulse-width parameters for triggering an RF generator or synthesizer. The goal is to accurately simulate multiple radar targets having moving ranges. As such, these instruments could sequence through a table of timing parameterseither automatically or when triggeredand provide dynamic timing control for multiple RF pulses.

Adding a timestamp
With the new IRIG-B Real Time Clock option, both the DDG200 and the DDG400 are now able to time-stamp data using the IRIG-B (Inter-Range Instrumentation Group Time Code Format B) time code.

Standardization of time codes permits equipment to be synchronized to a known reference time. This also lets facilities at geographically disparate locations to synchronize to a known time code source. To do this, some labs are equipped with devices that create IRIG time code from GPS (Global Positioning System) satellite time. These labs distribute the GPS-derived time code to other devices for syncing.

Communication systems, data handling systems, missile and spacecraft tracking systems, and telemetry systems also require time-of-day information for data correlation with time. There are many formats and several modulation schemes, but they're typically amplitude modulated on an audio sinewave carrier. The most common version is IRIG-B, which encodes day of year, hour, minute, and second data on a 1-kHz carrier, with an update rate once per second.

Time in a FIFO
The IRIG-B Real Time clock is for correlating the output of a DDG plug-in with other instruments within a test system. When the IRIG-B option is enabled, each time the DDG receives a trigger to sequence to the next timing table vector, the current time is stored in a FIFO. Stored along with this time is information denoting which channel table has been incremented.

This information can then be used to determine which DDG timing parameters were active at any instant, providing both a direct and precise time correlation with the activity of other IRIG-B capable instruments.

- Alex Mendelsohn

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