__________________________________________________________________________ 2 Connectors
PolaRx3e Product Family Hardware Manual v1.1.0
8
Use this input to synchronize the internal receiver time to an external time source. For proper
operation, the PPS IN input should be used in combination with the REF IN input. REF IN provides
the receiver with a precise external frequency reference, and PPS IN provides a precise time reference.
It is important that the PPS input signal and the 10 MHz reference be generated from the same external
clock. It is also necessary that these two external signals be present from the start-up of the receiver.
Plugging in a PPS input signal when the receiver is already operating will lead to erroneous
measurements.
If the PPS input option is permitted, the receiver will synchronize its measurement latching with the
first low-to-high transition it detects on the PPS IN connector. There is no command to enter. Once
this initial time synchronization is done, the signal on the PPS IN connector is ignored: the receiver
simply integrates its frequency reference to keep track of the time. If the PPS input signal originates
from the same clock as the 10MHz reference signal, the receiver time will stay in sync with the
external clock time.
The delay between a low-to-high transition on the PPS input connector and the latching of the
measurements in the receiver depends on the phase relationship between the 10 MHz frequency
reference and the PPS input signal and can take a value from 178.4 to 211.7 ns (+/-2 ns). This delay is
insensitive to powering off and on the receiver.
In order to measure the delay between the PPS input pulse and the measurement latching, it is possible
to synchronize the PPS OUT signal with the measurement latching epoch. This is done by the
following command:
setPPSParameters,sec1,low2high,0,RxClock
After this command, the low-to-high transition at the PPS OUT connector is synchronized with the
internal measurement latching.
2.1.5
REF OUT (BNC)
This connector provides a 10 MHz output signal synchronized with the frequency reference used by
the receiver (be it internal or external). It is a sinusoidal signal with an unloaded peak-to-peak
amplitude of 0.7V (-5dBm in a 50
load).