Model GF-102/103/105S/105G

• NEW

The GF-100 Series offers a range of Dual-Band GNSS Disciplined Oscillators that integrate a Dual-Band GNSS receiver, a high-precision oscillator and control circuitry into a single module.
They output an accurate time pulse (1PPS) synchronized to UTC as well as a highly stable reference frequency (10 MHz). By simply integrating them into your system, you can achieve high-quality time synchronization with built-in countermeasures against GNSS vulnerabilities.
Based on Furuno’s expertise as a GNSS receiver manufacturer, the GF-100 Series features a proprietary design that eliminates the need for an external CPU. This helps reduce design workload and shorten time to market.

Our legacy GF-880x Series has delivered high timing accuracy using the L1 band. The GF-100 Series now supports dual-band with the addition of the L5 band.

By receiving two frequency bands simultaneously, the GF-100 Series corrects propagation delays caused by the ionosphere, further improving time accuracy.

The GF-100 Series supports multi-GNSS reception, including GPS (L1 + L5), Galileo (E1 + E5), Beidou (B1I /B1C, B2a), NavIC (L5) and QZSS (L1 + L5). By utilizing signals from multiple satellite systems, it helps improve reception stability in a wide range of operating environments.
For details on the role of the L5 band in countermeasures against GNSS vulnerabilities, please refer to the Defense-in-Depth section.

In urban areas, near windows, and other environments where multipath is likely to occur, reflected GNSS signals can degrade time accuracy.
The GF-100 Series features Dynamic Satellite Selection™*, which evaluates the quality of received satellite signals in real time and dynamically selects satellites with higher signal quality. This helps minimize degradation in timing performance, even in challenging reception environments.

The L1 band of GNSS signals — 1575.42 MHz — is widely used, but it is also a common target for jamming interference.
The GF-100 Series adopts a dual-band design that receives not only L1 but also L5 — 1176.45 MHz. It also supports fully independent L5 search, allowing satellites to be acquired using the L5 band alone, without relying on L1. Even if the L1 band is affected by jamming, the GF-100 Series can continue time synchronization using L5.
The GF-100 Series also includes a function to detect and monitor the frequency and level of jamming signals, helping support root-cause analysis.

Satellite signal quality can deteriorate for various reasons, including satellite malfunctions, atmospheric anomalies, and residual reflected signals. If low-quality signals are used without proper evaluation, time synchronization accuracy may be degraded.
The GF-100 Series features T-RAIM — Timing Receiver Autonomous Integrity Monitoring. It continuously evaluates the reliability of received satellite signals and automatically excludes abnormal signals that are inconsistent with other observations. By using only valid satellite signals, the GF-100 Series ensures accurate time synchronization.

Malicious spoofing signals can intentionally mislead the time calculated by a GNSS receiver.
The GF-100 Series supports Galileo OSNMA — Open Service Navigation Message Authentication — and QZSS QZNMA. Using authentication information transmitted from satellites, the GF-100 Series verifies that received signals are genuine. Signals that fail authentication are identified as spoofed and excluded.

Even in the unlikely event that a threat passes through all four defense lines described above, the GF-100 Series keeps precise time output running.
When the GF-100 Series detects the effects of jamming or spoofing on all bands, Proactive Holdover automatically disengages from GNSS signals and switches to holdover using the built-in oscillator.
This is fundamentally different from conventional holdover. Conventional holdover typically starts running only after GNSS reception is lost. In contrast, Proactive Holdover actively disengages from GNSS when abnormal conditions are detected.
Furuno’s proprietary oscillator control technology predicts and compensates for oscillator behavior. The GF-105S / GF-105G achieves holdover performance of ±1.5 µs over 24 hours.

The GF-100 Series ensures hardware compatibility with the GF-880x Series across all models. It can replace existing products without requiring changes to board layout or connector placement.

The GF-100 Series lineup includes the Short form factor (GF-102 / GF-103 / GF-105S) for applications that prioritize compact size, and the Grande form factor (GF-105G) for direct replacement of the GF-8804/8805. Customers can choose the model that best fits their design requirements.

In the GF-880x Series, holdover performance of ±1.5 µs over 24 hours was available only in the Grande form factor — GF-8805.
With the GF-100 series, the GF-105S achieves the same level of performance in a Short form factor — 34 × 27 × 15.5 mm. It delivers top-level holdover performance while reducing the required mounting area by approximately 80%.

The GF-100 Series includes four models with different holdover performance levels and form factors. GNSS vulnerability countermeasures, including Defense in Depth, are common across all models. Customers can select the optimal model according to system requirements.

These models provide the core functions of the GF-100 Series, including Defense in Depth, at a lower cost. They are suitable for systems deployed over wide areas in large numbers, such as professional radio base stations and private 5G networks.

These models deliver the highest holdover performance in the series — ±1.5 µs over 24 hours. They are suitable for critical infrastructure applications that require high time accuracy and robustness, including telecommunications, power utilities, finance, and broadcasting.

The phase relationship between the frequency output and time pulse output is always constant — coherent and jitter-free.

The GF-100 Series can output frequency and time pulse signals while tracking only one satellite, excluding mobile positioning mode.

The GF-100 Series can synchronize to an external time pulse. This capability can be used for synchronization to time information acquired via a network, such as IEEE 1588 or SyncE, helping improve overall system robustness.

Antenna selection is also important to fully utilize the Defense-in-Depth performance of the GF-100 Series.

The Defense-in-Depth capability of the GF-100 Series has been developed not only based on catalog specifications, but also through verification in real-world jamming and spoofing environments.

In this white paper, a FURUNO engineer specializing in GNSS timing explains how OSNMA and QZNMA should be used in real-world applications, with practical insights provided in about 20 pages.

"What GNSS spoofing is and why it matters today"
"Key concepts of OSNMA and QZNMA"
"Operational considerations"
"How to use authentication functions in FURUNO GNSS receivers"