DOC 6511_Release K
ATS-6511A/B/C Users Guide
45
The fiber inputs A and B are monitored for signal presence and their time code, frequency and 1
PPS are extracted. If both signals are present, the unit will begin steering the OCXO to fiber input
A’s frequency. Once the OCXO frequency is within 1e-10 of the fiber input frequency, the
software propagates the fiber 1 PPS signal through the unit and the front panel indicator “OSC
LOCK” will illuminate green. The software then begins using the system 1 PPS vs. fiber 1 PPS
measurements to steer the phase of the system. The 10MHz frequency reference measurements
are made on the internal OCXO source. The internal OCXO is generally warm and operational
within 10 minutes. Once the phase has been steered to within 10 ns of the fiber 1 PPS, the outputs
are enabled. The software will continue to steer the OCXO phase to keep the phase within 100 ps
of the ATS-6501 1 PPS.
The Time Code generator uses 10 MHz, 1 PPS, and system time to generate the IRIG/NASA36
signals. As a result, it is the final step in the startup procedure. The Time Code generator uses
the 10MHz as its frequency reference and the PPS to indicate the start of the second. These two
signals serve as the time base for the Time Codes. System time is sent by the CPU to the Time
Code generator to indicate what time is associated with the received PPS signal. This information
is then used to produce the user/factory defined time codes.
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