RTD Embedded Technologies, Inc.
AS9100 and ISO 9001 Certified
1
Introduction
1.1
Product Overview
The SYNC25104HR/SYNC35104HR is a GPS disciplined oscillator board which is designed to provide high accuracy frequency and time
reference signals to PC/104 systems and external devices. This board utilizes the u-blox LEA-M8F GPS Receiver which locks the output signal
of a low noise, high precision oven-controlled crystal oscillator (OCXO) to the GNSS satellites. The 10MHz signal from the OCXO is available
on the SyncBus connector, two MMCX connectors and is fed into a low noise synthesizer (SI5395). The synthesizer can generate signals up to
the gigahertz range. The board connects to the CPU via USB. An additional RS232 serial port is also provided to the GPS receiver which can
be used for synchronizing the CPU clock the GNSS. This module can p3.3V to active antennas or can be used with passive antennas.
1.2
Timing Accuracy Information
The board provides time and frequency reference which are based on the GNSS system. When the system is powered up, the board
synchronizes itself to the GNSS. Note that the receiver is only functional, when the normal 5V is available, ie. it is not powered from 5V standby
or other power source (eg. battery). After the synchronization process is complete (this may take minutes) the time and frequency accuracy will
be within the specs below. If GNSS signals are lost, the board enters into holdover mode. In this mode, the internal OCXO provides reference
signal to the receiver, therefore the accuracy will be determined by the OCXO. Table 1 summarizes the accuracy of time and frequency outputs
of SYNC25104HR/SYNC35104HR.
Table 1: Accuracy
Parameter
Condition
Value
Time pulse accuracy
clear sky
≤20ns
Indoor
≤500ns
Frequency accuracy
GNSS locked
≤5ppb
hold-over (-20 to 70C°)
±10ppb
OCXO short term stability (Alan variance)
2×10
-10
1/s
OCXO aging
Daily
±1ppb
First year
±100ppb
10-years
±500ppb