Development and Analysis of an Accurate Timing Reference

Precise Position, Navigation, and Timing (PNT) is necessary for the functioning of many critical infrastructure sectors relied upon by millions every day. Specifically, precise timing is primarily provided through the Global Positioning System (GPS) and its system of satellites that each house multiple atomic clocks. Without precise timing, utilities such as the internet, the power grid, navigational systems, and financial systems would cease operation. Because oscillator devices experience frequency drift during operation, many systems rely on the precise time provided by GPS to maintain synchronization across the globe. However, GPS signals are particularly susceptible to disruption – both intentional and unintentional – due to their space-based, low-power, and unencrypted nature. It is for these reasons that there is a need to develop a system that can provide an accurate timing reference – one disciplined by a GPS signal – and can also maintain its nominal frequency in scenarios of intermittent GPS availability. This project considers an accurate timing reference deployed via Field Programmable Gate Array (FPGA) and disciplined by a GPS module. The objective is to implement a timing reference on a DE10-Lite FPGA disciplined by the 1 Pulse-Per-Second (PPS) output of an MTK3333 GPS module. When a signal lock is achieved with GPS, the MTK3333 delivers a pulse input to the FPGA on the leading edge of every second. The FPGA aligns a digital oscillator to this PPS reference, providing a disciplined output signal at a 10 MHz frequency that is maintained in events of intermittent GPS availability. The developed solution is evaluated using a frequency counter disciplined by an atomic clock in addition to an oscilloscope. The findings deem the software solution acceptable with more work needed to debug the hardware solution