Keysight E8267D User Manual page 259

GPS Modulation (Option 409)
Real Time GPS
Figure 8-4 Subframe Structures
The TLM word is 30-bits long, with an 8-bit preamble, 16 reserve bits (bits 9 to
24, all set to zero), and 6 parity bits (bits 25 to 30).
The HOW word is 30-bits long, with the first 17 bits used for an incrementing
time-of-week (TOW), bits 23 and 24 used for parity computation, and bits 25
to 30 used for parity bits.
During a GPS signal transmission, a pulse signal is generated every 6 seconds
at the
EVENT 1 rear panel connector. This pulse coincides with the beginning of each
subframe starting with the second subframe and is synchronized to the RF
output to compensate for any internal signal delay.
Chip Clock Reference
The GPS reference clock (chip clock) is adjustable using the GPS Ref (f0)
softkey. The factory-set value is 10.23 Mcps (the GPS standard). You can use
the internal chip clock or an external source to provide the reference. To use an
external reference, connect the external source to the DATA CLOCK input
connector.
If you use an external source to provide the chip clock reference, the
NOTE
frequency of the external source must match the PSG's reference clock
frequency. Press the GPS Ref (f0) softkey then use the numeric keypad to
enter the reference clock frequency.
Keysight E8357D/67D & E8663D PSG User's Guide 245