APX-GTS400 Portable GNSS Rubidium Timing Reference
High-Precision GNSS-Disciplined Rubidium Timing Reference
The APX-GTS400 Portable GNSS Rubidium Timing Reference is a high-precision timing and frequency reference designed for applications requiring stable frequency standards and accurate UTC time synchronization.
The system combines a high-stability rubidium atomic clock with a high-precision GPS/BeiDou timing receiver. Through precision frequency measurement and disciplining technology, the rubidium oscillator is continuously synchronized to the GNSS reference, providing a highly stable frequency reference with an accuracy better than 1E-12 under the specified conditions.
In addition to a precision frequency standard, APX-GTS400 provides a reproducible UTC time reference and multiple timing and frequency outputs, including 10 MHz, 1PPS, programmable PPS, IRIG-B, and 1PPS + TOD.
Its portable enclosure, integrated battery system, automatic reference selection, and holdover capability make it suitable for communication systems, satellite-related applications, precision measurement, scientific research, and other timing-sensitive systems.
Key Features
GNSS-Disciplined Rubidium Atomic Clock
APX-GTS400 integrates a high-stability rubidium atomic clock with a GPS/BeiDou timing receiver. The internal rubidium oscillator is disciplined against the GNSS reference to provide a stable and precise frequency standard.
Frequency Accuracy Better Than 1E-12
The system uses precision frequency measurement and calibration technology to synchronize the rubidium oscillator to the GPS or BeiDou reference. Under the specified satellite-lock and averaging conditions, the output frequency accuracy can reach better than 1E-12.
GPS and BeiDou Support
The timing receiver supports:
- GPS L1
- BeiDou B1
- GPS-only positioning
- BeiDou-only positioning
- GPS + BeiDou combined positioning
The receiver provides 32 channels and supports automatic reference selection according to the configured operating mode.
10 MHz Precision Frequency Output
APX-GTS400 provides a stable 10 MHz TTL frequency reference through a BNC interface.
The 10 MHz output can be used as a precision frequency standard for timing-sensitive measurement and synchronization equipment.
High-Precision 1PPS Output
The system provides a 1PPS timing output through a BNC interface.
The specified synchronization output accuracy is up to 100 ns.
Programmable PPS Outputs
Four programmable PPS outputs are available, allowing users to configure the output period from 1 to 5 seconds and set the required timing parameters through the system interface.
IRIG-B Time Code Output
APX-GTS400 provides an IRIG-B AC time code output through BNC, supporting integration with timing and synchronization equipment requiring IRIG-B references.
1PPS + TOD Output
The system provides time-of-day information through an RJ45 interface using a 1PPS + TOD signal interface.
Supported message formats include:
Automatic Reference Selection
APX-GTS400 can be configured with GPS, BeiDou, or combined GPS/BeiDou operation. The system can monitor the stability of the available GNSS reference sources and switch between configured primary and backup references.
Holdover Operation
When the GNSS reference becomes temporarily unavailable, the rubidium oscillator continues to provide a stable frequency and timing reference based on its stored operating characteristics.
This allows the system to maintain timing and frequency outputs during temporary loss of satellite reference.
Built-In Battery System
The system includes a removable lithium battery system and supports operation without continuous external power for a specified period.
The battery system is designed as an integrated and replaceable module to facilitate maintenance and transportation.
Portable Design
The equipment uses a compact enclosure with integrated carrying handles, making it suitable for transportation and deployment in environments where a portable precision timing reference is required.
Precision Timing Architecture
APX-GTS400 combines three major timing functions:
GNSS Reference → Rubidium Frequency Discipline → Precision Timing & Frequency Outputs
The GNSS receiver provides the external reference.
The rubidium atomic clock provides a highly stable local frequency reference.
The internal disciplining system continuously measures and adjusts the rubidium oscillator so that the local frequency remains synchronized with the GNSS reference.
The resulting timing reference can then be distributed through multiple outputs, including:
10 MHz → Frequency Reference
1PPS → Precise Timing Reference
Programmable PPS → Configurable Timing Output
IRIG-B → Time Code Reference
TOD → Time-of-Day Information
Applications
Telecom & Communication Systems
APX-GTS400 can provide a stable frequency and timing reference for communication systems requiring high-precision synchronization.
Typical applications include timing reference generation, synchronization testing, and communication equipment calibration.
Satellite Communication
The combination of GNSS synchronization and a rubidium frequency reference makes APX-GTS400 suitable for satellite communication systems requiring stable frequency and accurate time references.
Precision Measurement
The 10 MHz, 1PPS and other timing outputs can be used as reference signals for precision measurement and test equipment.
Scientific Research
APX-GTS400 can provide a stable frequency and UTC-related timing reference for scientific and laboratory applications requiring precise time and frequency synchronization.
Timing System Testing
The portable design and multiple timing outputs make APX-GTS400 suitable for field testing, timing system verification, and synchronization equipment evaluation.
Frequency Reference Systems
The rubidium-based architecture provides a high-stability local frequency source for systems requiring a precision 10 MHz reference.
Technical Specifications
Timing & Frequency Outputs
| Parameter | Specification |
|---|
| 10 MHz Output | 1 × BNC, TTL, 50 Ω |
| 10 MHz Accuracy | Better than 1E-12, satellite locked, 24-hour average |
| 1PPS Output | 1 × BNC, 5 V TTL, 50 Ω |
| 1PPS Synchronization Accuracy | ≤100 ns |
| 1PPS Pulse Width | 10 μs |
| 1PPS Rising Edge | <10 ns=""> |
| Loss-of-Reference Holdover Accuracy | 10 μs / 24 h |
| Programmable PPS | 4 × BNC, 5 V TTL, 50 Ω |
| Programmable PPS Period | 1–5 s |
| IRIG-B | 1 × BNC, AC mode, 1 kHz |
| TOD Output | 1 × RJ45, 1PPS + TOD |
| TOD Electrical Level | RS-422 |
| TOD Formats | SYS / GGA / RMC |
| Serial Interface | 1 × DB9 Female, RS232 |
GNSS Receiver
| Parameter | Specification |
|---|
| GNSS Systems | GPS / BeiDou |
| GPS Frequency | L1 |
| BeiDou Frequency | B1 |
| Operating Modes | GPS / BeiDou / GPS + BeiDou |
| Channels | 32 |
| Cold Start | <120 s=""> |
| Hot Start | <1 s=""> |
| Positioning Accuracy | 10 m RMS |
GNSS Antenna
| Parameter | Specification |
|---|
| Antenna Type | GPS/BeiDou Dual-System Antenna |
| GPS Band | 1570–1580 MHz |
| BeiDou Band | 1556–1566 MHz |
| Polarization | Right-hand circular polarization |
| Noise Figure | ≤1.5 dB |
| Supply Voltage | 4–6 V DC |
| Gain | 38 dBi |
| Impedance | 50 Ω |
| Antenna Size | 114 × 116 mm |
| Connector | NK |
Physical & Environmental
| Parameter | Specification |
|---|
| Dimensions | 247 × 180 × 103 mm |
| Weight | <5 kg=""> |
| AC Input | 130–240 V AC |
| Operating Temperature | -10°C to +50°C |
| Storage Temperature | -40°C to +85°C |
| Relative Humidity | 95%, non-condensing |
| Power Consumption | 20 W |
Rubidium Holdover
The integrated rubidium atomic clock provides a stable local frequency reference when the GNSS reference is temporarily unavailable.
The system stores relevant operating characteristics and supports automatic operating-mode switching, allowing it to continue providing timing and frequency reference signals during temporary loss of the primary GNSS reference.
Redundant Synchronization & Backup Operation
APX-GTS400 supports redundant timing reference operation.
GPS and BeiDou can be configured as primary and backup references. When the primary reference becomes unstable or unavailable, the system can automatically switch to the configured backup reference.
If both primary and backup GNSS references become unavailable, the system can enter holdover operation based on the internal rubidium frequency reference.
This architecture helps improve the continuity and reliability of timing and frequency outputs in demanding synchronization environments.
Portable Timing Reference for Field Applications
With its integrated battery system, carrying handles, protective enclosure and multiple timing/frequency interfaces, APX-GTS400 is designed for applications where a precision timing reference needs to be transported and deployed at different locations.
The removable battery design also simplifies maintenance, replacement and transportation.
Typical System Configuration
A typical APX-GTS400 deployment can include:
GPS / BeiDou Satellite Signals
↓
GNSS Timing Receiver
↓
Rubidium Atomic Clock
↓
Frequency Discipline & Timing Processing
↓
10 MHz / 1PPS / PPS / IRIG-B / TOD Outputs
↓
Communication / Measurement / Synchronization Equipment
Product Applications
- Telecom Synchronization
- Satellite Communication
- Precision Frequency Reference
- Timing System Testing
- Measurement & Instrumentation
- Scientific Research
- Network Synchronization
- GNSS Timing Systems
- Frequency Standard Applications
- Field Timing Calibration
OEM & Custom Timing Solutions
APEX provides timing and synchronization products for system integrators, communication equipment manufacturers and project-based applications.
APX-GTS400 can be integrated into customized timing architectures according to project requirements, including different timing output configurations, GNSS reference configurations, frequency reference requirements and system integration requirements.
For application-specific requirements, please contact the APEX technical team for configuration and engineering support.
