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Session D4: Anti-Jam and Anti-Spoofing Technologies 2

Improving GNSS Jamming and Spoofing Resilience Through Low SWaP-C Precision MEMS Timing
Ron Rotstein, Tyler Hohman, SiTime
Location: Room 1-3
Date/Time: Monday, Jun. 1, 4:25 p.m.

Position, Navigation, and Timing (PNT) systems are increasingly required to operate in GNSS jammed and spoofed environments while simultaneously meeting aggressive size, weight, power, and cost (SWaP-C) constraints. The proliferation of autonomy and unmanned systems are driving PNT architectures to be lower SWaP-C and operate across all domains (land, air, sea, space). A critical component to these PNT architectures is the local oscillator. This paper investigates how improvements in local oscillator performance can add jamming and spoofing resilience by enabling tighter GNSS tracking loop designs and offering longer holdover without sacrificing SWaP-C or limiting domain operation. Using models, simulations, and customer testimonials, we demonstrate how rugged and precise local timing can improve a GNSS receiver’s ability to detect and mitigate spoofed signals while maintaining reliable time holdover during jamming events. This analysis focuses on how resiliency can be gained using low SWaP-C timing solutions that are available today, making the techniques applicable across a wide range of PNT architectures, applications, and domains.
A key function of GNSS spoofing resilience is the receiver’s carrier and code tracking loops which depend on the local oscillator. Oscillator stability influences loop bandwidth selection, phase noise performance, and frequency uncertainty, all of which affect a receiver’s sensitivity to spoofed signals. More stable local timing allows tracking loops to be narrowed without sacrificing dynamic response, increasing observability of subtle signal anomalies such as inconsistent Doppler dynamics, phase transients, and correlation distortions associated with spoofing. MATLAB-based simulations are presented to quantify the relationship between oscillator stability, loop bandwidth, and spoofing detection metrics under representative threat scenarios. These results demonstrate that improved timing stability enhances a receiver’s ability to detect and reject spoofed signals. To ensure applicability to real-world systems and cross domains, this discussion focuses on a low SWaP-C local oscillator that is available today. Simulation results are corroborated with industry partners who have deployed optimized tracking loop designs enabled through the local oscillator to improve jamming and spoofing resilience.
The paper also examines resilience to GNSS jamming through improved holdover performance. While precision timing cannot overcome signal denial, it enables PNT systems to maintain accurate local time during outages by minimizing time error, retrace, and reacquisition learning periods. We present holdover analysis showing that the same low SWaP-C oscillators can sustain up to 8 hours of operation with less than 1.5 microsecond of accumulated timing error, enabling continued mission execution when GNSS is degraded or denied. Holdover performance plots compare uncompensated operation to implementations using aging compensation algorithms. This demonstrates that relatively straightforward compensation techniques can double holdover duration compared to uncompensated designs. Finally, we will share holdover plots under constant temperature and under more realistic temperature profiles with temperate variations of 10°C and beyond.
In conclusion, MEMS-based oscillators by SiTime add resilience against GNSS jamming and spoofing today without compromising SWaP-C requirements. These devices will support the evolution of PNT architectures for autonomous platforms across all operational domains. With frequency stability as low as ±20 ppb over temperature, an operating range from ?55°C to +125°C, ultra-low acceleration sensitivity of 0.004 ppb/g, and shock survivability exceeding 100,000 g, these MEMS oscillators are well suited to enhance both precision and robustness in PNT systems. When combined with a compact 5032 package, power consumption below 22 mW, and unit costs under $100 , these performance characteristics collectively enable a critical building block for modular and scalable PNT architectures that deliver improved jamming and spoofing resilience using technology available today.

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