Time Synchronization System

Customer

A developer of communication and navigation systems.

Task

To design a time synchronization system that receives GPS/GLONASS signals and transmits the info on the exact time to the users (hardware and software systems). 

The system should be designed for the industrial applications, communication centers, control points and other facilities that require accurate information on the current time (bank systems, broadcasting stations, etc.).

 

The system should operate as a time server in an Ethernet network via NTP and PTP protocols. The configuration and monitoring of the device should be performed in the terminal mode or via a web interface.

Accuracy: scale departure is ±300 msec after three days of autonomous operation.    

The designed device should have the following features:

  • Generation of user’s time scale which is synchronized with the UTC (SU) and UTC (USNO) scales.
  • Storage of user’s time scale with specified accuracy during the worsening conditions of signal reception from the GPS / GLONASS satellites.
  • Positioning of stationary and moving objects.
  • Identification of the speed and the course of moving objects.
  • The function of a primary clock and control of a secondary clock in form of digital time displays and analog clocks.
  • Safety of control programs and current settings in case of power failure, including information on the current time.

Basic technical parameters:

  • Maximum time scale synchronization standard error in auto control mode, based on GNSS signals, is ≤ 1 microsecond.
  • The amplification coefficient of the GLONASS/GPS antenna amplifier: ≥ 25 dB.
  • Power consumption at the max number of connected secondary clocks: ≤ 100 W.
  • A unified enclosure 1U high, designed to be mounted into a 19-inch rack.

Operational conditions:

  • Operational temperature of the time synchronization block is – 10 … + 55 °С.
  • The degree of protection is ≥ IP20.

Solution

1. Concept

For high-accuracy offline storage of the time scale, the following system architecture was developed and applied:

The central node of the architecture: FPGA with an implemented algorithm for digital correction of the temperature-compensated crystal oscillator (TCXO), based on PPS tags from a GLONASS/GPS receiver.

2. Circuit Design

The circuit design is based on AT91SAM9260, an inexpensive and easily available ARM microcontroller by Atmel, for which the manufacturer provides a developer board with Linux support.

The board implements the option of installing one of two popular GLONASS/GPS receivers, NAVIOR-24S by Navis or GeoS-1М by GeoStar.

The product’s back panel implements digital correction algorithm calibration signals, 1 PPS and 10 MHz.

The unified design of the rear wall enables installation of various combinations of adapter modules, which act as an amplifier/transmitter of second/minute tag output signals.

3. Software

The product’s software is based on the Linux kernel version 2.6.34.3. A web interface is developed to control and monitor the system:

The system was tested for its claimed characteristics at the National Metrological Institute Test Center.

The customer successfully completed the product’s certification process at the Institute of Defense and Security Metrology Test Center and received a patent for a utility model thanks to Promwad engineers’ development.

Advantages

The developed time synchronization system has a number of advantages compared to its analogs:

  • Support for two satellite positioning systems, GPS and GLONASS.
  • FPGA features an algorithm for TCXO oscillator digital correction.
  • Configuration and monitoring of the system operation through a web interface.
  • Linux software platform.
  • A much lower cost compared to analogs on the European market.
  • The product’s unified enclosure makes it possible to mount the device in a 19-inch rack.