Jackson Labs RSR GNSS Transcoder, Руководство пользователя

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RSR GNSS Transcoder™ User Manual
64 © 2017 Jackson Labs Technologies, Inc.
4.7.6 SYNChronization:TINTerval?
This query returns the difference or timing shift between the RSR GNSS Transcoder™ internal
oscillator 1PPS phase and the externally-supplied 1PPS reference phase. The resolution is 1E-010
seconds.
4.7.7 SYNChronization:TINTerval:THReshold [50,2000]
This command selects the oscillator 1PPS phase-offset threshold as compared to the reference 1PPS
at which point the unit will initiate a counter-reset (jam-sync) aligning the oscillator generated 1PPS
with the reference 1PPS phase. The oscillator phase is slowly and continuously adjusted toward 0ns
offset to the externally-supplied reference 1PPS phase as long as the phase difference is less than the
THReshold phase limit. The oscillator generated 1PPS phase is allowed to drift up to this threshold
before a jam-sync is initiated. The default setting is 220ns, allowing a drift of up to +/-220ns.
Reaching this selected threshold will cause a jam-sync phase-normalization to be initiated, which
will reset the counter phase that generates the internal 1PPS output, it will also cause the
SYNC:HEALTH? Status to indicate 0x200, and the lock status to be “unlocked”. By selecting larger
phase windows the user can prevent these phase resets (jam-syncs) of the output 1PPS from
happening too frequently in environments where airflow or thermal changes are expected, especially
on units without the CSAC option.
4.7.8 SYNChronization:IMMEdiate
This command initiates a near-instantaneous alignment of the GNSS 1PPS and Receiver output 1PPS
phases. To be effective, this command has to be issued while the unit is not in holdover.
4.7.9 SYNChronization:FEEstimate?
This query returns the Frequency Error Estimate, similar to the Allan Variance using a 1000s
measurement interval by comparing the internal 1PPS to GNSS 1PPS phase offset.
Values less than 1E-012 are below the noise floor, and are not significant.
4.7.10 SYNChronization:LOCKed?
This query returns the lock state (0=OFF, 1=ON) of the PLL controlling the TCXO.
4.7.11 SYNChronization:OUTput:1PPS:RESET [ON|OFF]
This command allows the generation of the 1PPS output pulse upon power-on without an external
GNSS receiver being connected to the unit. By default the unit does not generate a 1PPS pulse until
the GNSS receiver has locked onto the Satellites. With the command SYNC:OUT:1PPS:RESET ON
the unit can now be configured to generate an asynchronous 1PPS output after power-on even if a
GNSS antenna is not connected to the unit. The ON setting will also allow the NMEA output strings
to be generated in the absence of an externally-provided 1PPS reference input. Once the GNSS
receiver locks, the 1PPS pulse will align itself to UTC by stepping in 10 equally spaced steps toward
UTC alignment. The default setting is OFF which means the 1PPS pulse is disabled until proper