User's Manual

USER
MANUAL
MPD-1611291-A
EXACT-V2 High End Rack Modulator / Exciter
3/10/2017
MPD-1611291-A
Page 32/94
2.8 Clock and Synchronization
The clock and synchronization function is responsible for synthesizing the required
temporal signals and data rates. A high-stability 10 MHz OCXO provides the internal
clock reference.
However, if synchronization with other equipment is required, an external 10 MHz clock
signal can be chosen as a reference together with external 1PPS. The user shall
configure the signal reference edge (rising or falling edge). An internal 1 PPS signal is
generated from the external signal in order to maintain synchronized the output signal
as long as possible in case of external signal failure.
The modulator clock reference (10MHz) source can be configured as:
o Locked on the external 10 MHz signal reference (by default),
o Derived from the 1PPS source (either on-board GPS or external 1PPS)
o Internal.
The module delivers a 10 MHz clock reference output signal and can also provide 1PPS
if the user configures the “1PPS IN/OUT” connector as an output. For VX20-x0x2 (with
on-board GPS), the 1PPS output is derived from the on-board GPS.
2.8.1 GPS and clock management for VX20-x0x2
For VX20-x0x2, the on-board GPS block gives the possibility to directly receive an
incoming GPS or Glonass signal. Please refer to Appendix C for GPS installation
recommendations and Appendix D for GPS antenna recommendations.
Up to four satellite signal levels may be displayed (Note: In case of GPS/Glonass, the
four strongest levels are chosen amongst the eight total signals available.) Signal
level is normally positive. If it is zero, this means that no satellite lock has been
acquired yet. If it is negative, then that satellite is not being locked. The absolute
value of a signal level field is the last known signal level of that satellite.
Note: The GPS configuration parameters (location & time) is kept in the memory
for faster synchronization after reset or ON/OFF.