APX-GTS500 Advanced GNSS Timing Reference

The APX-GTS500 Advanced GNSS Timing Reference is a high-precision GNSS-disciplined timing and frequency reference designed for applications requiring stable, accurate, and reliable time and frequency signals.

The system combines a high-performance rubidium atomic clock with a precision GNSS timing receiver and advanced frequency measurement and disciplining technology. The internal rubidium oscillator is continuously measured and disciplined against the GNSS reference, achieving frequency stability down to 5 × 10⁻¹⁴ at 10,000 seconds.

In addition to providing a high-stability frequency reference, the APX-GTS500 generates a reconstructed UTC time reference. Its 10 MHz reference is divided down to generate the 1PPS signal, reducing the impact of short-term variations in satellite pulse timing and providing a more stable timing output for precision measurement and synchronization applications.

The APX-GTS500 also incorporates intelligent learning and reference management functions. During the disciplining process, the system learns the frequency drift characteristics of the internal rubidium oscillator and stores the relevant parameters in onboard memory. When the primary GNSS reference becomes unstable or unavailable, the system can automatically switch to an external reference or enter holdover mode based on historical performance parameters.

This architecture enables the APX-GTS500 to continue providing reliable time and frequency reference signals during temporary loss of external synchronization.

Key Features

• High-precision GNSS synchronization with timing accuracy better than 20 ns RMS

• Integrated rubidium atomic clock for high-stability frequency reference

• Frequency stability down to 5 × 10⁻¹⁴ at 10,000 s

• GNSS-disciplined rubidium oscillator with intelligent drift learning

• Automatic transition between disciplining and holdover modes

• Stable operation after temporary loss or removal of the GNSS antenna

• Support for external frequency and time references

• Manual selection between internal and external timing references

• Multiple frequency outputs including 10 MHz, 10.23 MHz, and 100 MHz

• Configurable pulse outputs with adjustable phase

• Optional NTP and PTP timing outputs

• 19-inch 2U rack-mount platform for laboratory and infrastructure applications

Precision Timing and Frequency Architecture

The APX-GTS500 uses GNSS as the primary long-term timing reference while the internal rubidium oscillator provides the short-term stability required for precision applications.

The disciplined 10 MHz output is divided by 10,000,000 to generate the 1PPS signal. This architecture provides a stable time reference while reducing the influence of short-term random variations in satellite pulse timing.

The system can also accept external frequency and time references. Reference sources can be selected according to application requirements, allowing the APX-GTS500 to operate as a centralized timing and frequency reference for multiple measurement and synchronization systems.

GNSS Reference Input

The GNSS receiver supports multi-system satellite timing operation and provides the reference required for disciplining the internal rubidium oscillator.

External Timing Reference Inputs

The APX-GTS500 supports external reference inputs for applications requiring integration with an existing timing infrastructure.

• 1 × External Frequency Reference Input

• 1 × External Time Reference Input

• Optional BDS B3 input

• Optional PTP input

• Optional B/IN input

• Optional TOD input

The internal and external references can be selected according to system requirements. When the external references are unavailable, the unit can automatically enter holdover operation.

Frequency Outputs

The APX-GTS500 provides high-stability frequency outputs for precision measurement, communications, instrumentation, and synchronization systems.

Standard Frequency Outputs

Supported frequency outputs include:

• 10 MHz

• 10.23 MHz

• 100 MHz

Optional outputs include:

• 1 MHz

• 5 MHz

• 20 MHz

• 40 MHz

Frequency Output Specifications

The high-stability frequency reference is suitable for systems requiring a common frequency standard across multiple instruments or measurement channels.

Rubidium Timing Performance

The integrated rubidium oscillator provides the stability required for precision holdover and frequency reference applications.

The intelligent disciplining algorithm continuously learns the oscillator's frequency drift characteristics and stores the relevant parameters in onboard memory. This allows the system to maintain improved holdover performance when the external GNSS reference is temporarily unavailable.

1PPS Timing Output

The APX-GTS500 generates a stable pulse-per-second reference derived from the disciplined internal frequency standard.

* Holdover specification is stated for a 30-day synchronized condition followed by 24 hours of holdover, according to the source product specification.

Optional pulse outputs include:

• 20PPS

• PPM

• PPH

• PPD

The configurable pulse output can be used as a precise trigger or synchronization signal for measurement and ranging systems.

Intelligent Reference Management

The APX-GTS500 provides automatic reference management for high-reliability timing applications.

The system can:

1. Use GNSS as the primary timing reference.

2. Monitor the stability and availability of the active reference.

3. Switch to an external frequency or time reference when required.

4. Enter holdover mode when external references are unavailable.

5. Use stored oscillator performance parameters to maintain timing and frequency output during holdover.

This architecture supports applications where continuous timing availability is required even during temporary interruptions of the primary reference source.

Optional Network Timing Outputs

For applications requiring network-based synchronization, the APX-GTS500 can be configured with:

• NTP timing output

• PTP timing output

These options allow the precision timing reference to serve as a timing source for networked equipment and synchronization systems.

Applications

The APX-GTS500 is designed for precision timing and frequency reference applications, including:

• Scientific research and laboratories

• Astronomy and precision observation

• Physics experiments

• Satellite communication systems

• Precision measurement systems

• Time and frequency metrology

• Ranging and measurement systems

• Distributed data acquisition

• RF and communications test systems

• Instrument synchronization

• High-precision timing reference networks

Physical and Environmental Specifications

Standard Configuration

The standard APX-GTS500 package includes:

• APX-GTS500 timing and frequency reference unit — 1

• Coaxial cable — 1

• GNSS antenna — 1 set

• Mounting bracket — 1 set

• Power cable — 1

• Product documentation — 1

• Certificate and warranty documentation — 1

• Test report — 1

• Instrument case — 1 set