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Session D3: Application/Impact of PNT Technologies in the Homeland Critical Infrastructure

The Time Interval Counter Kit (TICK) for Distributed Persistent Surveillance of IRIG Signals in Timing Networks
Wil Myrick, Charlie Vines, ENSCO, Inc.; James Patterson, US Space Force
Location: Ballroom D
Date/Time: Tuesday, Jun. 13, 8:55 a.m.

Persistent monitoring of Inter-range Instrumentation Group (IRIG) timecode signals in timing networks can be difficult and costly using conventional commercial-off-the-shelf (COTS) Time Interval Counters (TICs) with advance continuous (gap-free) timing measurements that are normally only found as an advance feature in COTS TICs. We present the Time Interval Counter Kit (TICK) that minimizes the Size, Weight, Power, and Cost (SWaP-C) normally associated with COTS TICs while incorporating the advance continuous (gap-free) timing measurement methodology to reveal timing irregularities potentially caused by intentional or unintentional interference on IRIG signals. The TICK is designed to support a distributed persistent surveillance network to monitor IRIG signals across a timing network to help detect anomalies and minimize timing outages or disturbances associated with IRIG signals.

The TICK approximates a continuous (gap-free) timing measurement of zero-crossings associated with IRIG signals. The TICK tracks multiple zero-crossing signatures associated with the IRIG signal to detect anomalies. We plan to present the TICK design and demonstrate timing measurements provided by the device leveraging IRIG signals from a variety of sources. The TICK is developed to learn a particular pattern of what is considered normal signal characteristics associated with IRIG signals. A discussion of the zero-crossing signature tracking associated with a typical IRIG signal will be presented as well as ways to monitor this signature for anomaly detection.

We plan to present early prototypes of the TICK and how this can be implemented to support persistent surveillance based on pattern recognition to support anomaly detection. The TICK is based on a Raspberry Pi Pico microcontroller with built in charging capabilities to provide mobility. The Raspberry Pi Pico (RPi Pico) is ~ 5$ microcontroller RP2040 microcontroller that has an innovative Programmable I/O (PIO) architecture that facilitates collecting and analyzing timing measurements for a variety of timing signals. This presentation focuses on transforming the RPi Pico into a TICK for analyzing jitter across a timing network with a focus on low frequency timing signals like IRIG. The low SWaP-C operating point of the TICK facilitates persistent monitoring across a variety of nodes within a timing network. An array of TICKs can function as a “trip-alarm” if the timing network exceeds some predetermined performance bound.

We explore the timing application of a network of TICKs monitoring IRIG timing signals across a timing network to support persistent situational awareness. We also plan to explore how the TICK could be used to consume higher precision measurements (PPS and 10 MHz signals) associated with the same timing network. Open-source software and hardware designs that were leveraged to develop the TICK will also be discussed.
A discussion about several persistent frequencies extracted by the TICK associated with the IRIG signal will be presented. Two of these persistent frequencies being tracked over time from the TICK are attributed to the IRIG carrier frequency and the modulated symbol rate associated with the embedded timing information providing a way to characterize jitter associated with these frequencies. Exploration of the TICK as a “frequency demodulator” with the strongest signal intermittently being capturing by the TICK to reveal the persistent frequencies associated with the IRIG signals will be discussed. It will be shown that these persistent frequencies provide insight into the jitter and signal anomalies potentially caused by interference or other sources of noise on the timing network.

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