Enabling Assured PNT Beyond GNSS
How SiTime oscillators help maximize the performance of the Iridium PNT ASIC
1. A new moment for resilient PNT
Positioning, navigation, and timing (PNT) has become an invisible piece of today’s critical infrastructure. It coordinates telecom networks, synchronizes financial transactions, supports power grid operations, enables transportation systems, guides autonomous platforms and provides the timing foundation behind countless defense and industrial systems. For decades, GPS and other global navigation satellite systems (GNSS) have delivered that capability at global scale. But the world has changed. GNSS signals are weak by the time they reach the earth, and operational environments increasingly include jamming, spoofing, meaconing, dense urban multipath and obstructions, indoor operation and contested electromagnetic conditions.
The result is a growing design requirement: critical systems can no longer assume that GNSS will always be available, trustworthy or sufficient. Resilient PNT now requires diversity. System designers need complementary sources of time and position that are independent from traditional GNSS, difficult to manipulate and practical to integrate into compact products. Iridium PNT and SiTime® Precision Timing solutions each offer capabilities that can help system designers address that challenge.
Iridium brings a unique global low-earth-orbit satellite network and a growing PNT service portfolio. The newly available Iridium PNT ASIC moves that capability directly into a miniature chip designed for broad integration into end equipment. SiTime brings silicon MEMS Precision Timing solutions engineered for small size, low power, high reliability and environmental resilience. These complementary capabilities can help equipment manufacturers build PNT systems that are compact, trusted and more resilient in real-world operating conditions.
2. What the Iridium PNT ASIC is built to do
The Iridium PNT ASIC is an application-specific integrated circuit designed to provide alternative PNT capability through the Iridium satellite network. It gives designers a practical way to diversify PNT at the device level. The compact chip that can operate as a standalone Iridium PNT receiver or as part of a hybrid Iridium plus GNSS architecture.
At the integration level, the ASIC is intended to look familiar to developers already accustomed to GNSS receiver hardware. It is designed in an 8 mm by 8 mm package, supports standard-style interfaces, includes built-in RF and power regulation functions and provides configurable one-pulse-per-second outputs. The device accepts external reference clocks such as a TCXO or OCXO at common reference frequencies. That reference clock matters, because the oscillator directly influences the time base that the PNT ASIC uses to translate satellite-derived information into stable, system-level timing and positioning outputs.
The end applications are broad. In commercial markets, the Iridium PNT ASIC can support telecom timing, data center synchronization, financial timing infrastructure, power grid operations, transportation systems, maritime applications, aviation systems and precision agriculture. In industrial markets, it can support autonomous equipment, robotics, remote infrastructure, energy assets and systems that must continue operating through degraded GNSS conditions. In military and government applications, it can support assured PNT receivers, autonomous systems, tactical communications, electronic warfare support equipment, mounted and dismounted navigation systems, unmanned platforms, maritime systems and other mission-critical electronics that must operate when GNSS is contested.
The common thread across these markets is trust. Modern systems need more than a position or time stamp. They need confidence that the position and time are valid. During jamming, a receiver may lose the signal it depends on. During spoofing, a receiver may be presented with false signals that appear legitimate. During urban or indoor operation, multipath and attenuation can degrade availability. The Iridium PNT ASIC addresses these factors by delivering an independent PNT signal path from the Iridium network and enabling developers to embed alternative PNT directly into systems that depend on it.
Design implication: PNT resilience is no longer only a system architecture topic. With the Iridium PNT ASIC, resilience can be designed directly into compact devices. The quality of the local oscillator determines how much of that capability is preserved under real operating stress.
3. Why the reference oscillator determines system-level performance
Every PNT receiver depends on timing. The receiver must measure signal arrival times, maintain synchronization, support tracking loops, generate stable outputs and hold time when external references are unavailable. The oscillator is therefore not a commodity support component. It is the heartbeat of the PNT system.
In a benign laboratory environment, many oscillators can appear adequate. The real test is what happens when the system is exposed to vibration, shock, airflow changes, rapid temperature transitions, power supply variation, aging and GNSS interruptions. These conditions do not always create immediate hardware failure. More often, they create small frequency shifts that accumulate into time error, tracking instability, longer reacquisition time, reduced confidence, degraded synchronization margin and lower system availability.
For the Iridium PNT ASIC, the reference oscillator is especially important because the ASIC supports timing and position outputs that may be used when GNSS is unavailable or untrusted. A better oscillator helps preserve the time base between updates, reduces dynamic frequency error during thermal transitions, improves phase noise behavior under vibration and supports accurate signal measurements. At the system level, that can translate into faster acquisition, better holdover, more stable 1PPS outputs, improved synchronization and higher confidence in the PNT solution.
This is where SiTime’s Precision Timing oscillators are differentiated. SiTime MEMS oscillators are small and lightweight, over 1,000X smaller than quartz, which reduces sensitivity to mechanical shock and vibration. The silicon resonator’s extremely high tensile strength and stiffness add to that resilience. SiTime’s Super-TCXO® and OCXO devices have two resonators inside, one to drive frequency stability and one to measure temperature. This integrated temperature sensing allows for temperature measurements over 10,000 times per second which enables the oscillator to respond to rapid thermal changes. Low aging and low frequency drift help preserve system performance over long service life. And low SWaP-C gives developers more flexibility to integrate resilient PNT into space-, weight-, power- and cost-constrained equipment. A silicon-based manufacturing process enables scalability, repeatability and high reliability.
4. How SiTime oscillators add resilience to the Iridium PNT ASIC
SiTime oscillators help the Iridium PNT ASIC in five practical ways:
Frequency stability over temperature: Frequency stability limits how far the oscillator can drift as the operating temperature changes. Better stability gives the PNT ASIC a cleaner time base, especially in platforms exposed to altitude changes, airflow, solar loading, electronics self-heating and rapid thermal transients.
Low dF/dT: The frequency slope versus temperature can be more important than static stability in dynamic environments. Low dF/dT means the oscillator changes frequency slowly and predictably as temperature changes, reducing abrupt time-base disturbances that can affect tracking and synchronization.
Low aging: Aging determines how the oscillator drifts over months and years. Lower aging reduces recalibration burden and helps long-life systems preserve PNT performance over the service interval.
Shock and vibration insensitivity: PNT systems are often mounted on vehicles, aircraft, drones, industrial machinery, munitions or infrastructure exposed to mechanical stress. Low g-sensitivity helps maintain stable frequency and phase noise when the platform is vibrating or accelerating.
Small SWaP-C: Compact, low-power oscillators make resilient PNT practical in smaller end products. Lower size, weight, power and cost help extend Iridium PNT ASIC adoption from large infrastructure systems into compact commercial, industrial and defense platforms.
The system-level benefit is cumulative. A low-noise, low-drift, low-aging oscillator helps the PNT ASIC maintain a more stable local time base. A low-g-sensitivity oscillator helps preserve performance during vibration and acceleration. A low-SWaP oscillator makes the total solution easier to integrate. Together, these characteristics preserve the end user's trust in the PNT output when operating in challenging environments.
For commercial customers, this means keeping a telecom network synchronized during GNSS interference or maintaining reliable timing for financial infrastructure. For industrial customers, it means keeping autonomous equipment or remote infrastructure operational when GNSS signals are obstructed. For military customers, it preserves timing and navigation confidence on vehicles, unmanned systems, radios and assured PNT devices operating in contested environments. In each case, Precision Timing enables the Iridium PNT ASIC to deliver its full resilient PNT value at the system level.
5. Recommended SiTime oscillators for the Iridium PNT ASIC
The following table provides recommended oscillator options for Iridium PNT ASIC integrations.
| Highest Resiliency Part Number | Stability Over Temperature | Size, Weight and Power | Frequency Slope (ΔF/ΔT) | Recommended End Application and Commercial Part Alternatives |
|---|---|---|---|---|
Endura™ Highest Performance OCXO | ±0.5 to ±5 ppb; -40°C to +95°C; 10 to 250 MHz | 9.0 x 7.0 x 3.6 mm; 3 g; 420 mW (3.3 V) | ±0.01 ppb/°C | Highest-performance designed for long holdover use cases including telecom, power grid, financial timing, assured-PNT hubs for land/air and LEO satellites. |
Endura Ultra-Stable Super-TCXO | ±5 to ±10 ppb; -40°C to +95°C; 1 to 60 MHz | 7.0 x 5.0 x 2.2 mm; 2 g; 135 mW (2.5 V) | ±0.16 ppb/°C | High performance in low SWaP best for designs requiring medium holdover such as vehicle mounted PNT systems, manpack radios and critical infrastructure. |
Endura Ultra-Stable Super-TCXO | ±0.1 to ±0.2 ppm; -40°C to +105°C; 1 to 220 MHz | 5.0 x 3.2 x 1.1 mm; 1 g; 145 mW (2.5 V) | ±1.0 ppb/°C | General purpose TCXO great for applications requiring good performance and frequency slope without stringent power or size considerations. |
Endura Low-Power Super-TCXO | ±20 to ±500 ppb; -55°C to +125°C; 1 to 105 MHz | 5.0 x 3.2 x 1.1 mm; 1 g; 21 mW (1.8 V) | ±2.5 ppb/°C | Low-power PNT receivers, unmanned systems, tactical radios, compact A&D or industrial platforms where low power and performance are priorities. |
Endura Low-Power, Small-Size Super-TCXO | ±50 to ±300 ppb; -55°C to +125°C; 1 to 105 MHz | 3.2 x 2.5 x 0.9 mm; <1 g; 21 mW (1.8 V) | ±3.0 ppb/°C | Smallest form-factor ASIC integrations, industrial IoT, compact GNSS/Iridium hybrid modules, handheld systems and space-constrained commercial products. |
6. From component performance to real-world resilience
A resilient PNT architecture is only as strong as its weakest timing assumption. If the local oscillator drifts too quickly during a GNSS outage, the system may lose timing accuracy. If vibration creates phase noise or frequency modulation, tracking loops may degrade. If temperature changes cause abrupt frequency shifts, the receiver may need more time to reacquire or can accumulate more uncertainty. If aging is high, the system may require more frequent calibration or wider design margins. These are not component-level inconveniences. They are system-level failure modes.
The Iridium PNT ASIC gives developers a new way to add trusted PNT diversity. SiTime MEMS oscillators help ensure that this new source of trusted PNT is built on a stable, rugged and reliable timing foundation. That combination is powerful because it addresses both sides of the resilience problem: the external PNT source and the internal time base. Iridium provides independent, authenticated satellite-derived PNT. SiTime helps the end system preserve, distribute and act on that trusted timing information under the operating conditions the real world imposes.
For designers, the takeaway is straightforward: oscillator selection should happen early in the Iridium PNT ASIC design process. It should be treated as a system-level architectural decision, not a last-minute component choice. The right oscillator can reduce time error accumulation, preserve synchronization margin, improve holdover, simplify mechanical design, support harsher environments and make resilient PNT practical in smaller platforms.
Building resilient PNT for what's next
GNSS disruptions are no longer a hypothetical risk. The world needs PNT architectures that are diverse, trusted, compact and resilient enough to operate beyond the assumptions of the past.
Iridium and SiTime are aligned around that mission. Iridium is bringing alternative PNT into silicon through a compact ASIC that can be integrated across a wide range of systems. SiTime is providing Precision Timing solutions that help that ASIC perform in real-world environments. Both of these technologies help equipment manufacturers build resilient PNT into the products and infrastructure that modern life depends on.
The future of assured PNT will not be defined by any single signal, component or architecture, but rather by trusted layers working together. The Iridium PNT ASIC adds a powerful new layer of alternative PNT. SiTime oscillators help turn that layer into dependable system performance. Equipment manufacturers can draw on these complementary capabilities to address real-world PNT challenges and build systems that operate when GNSS alone is not enough.