Viavi T-BERD 5800, Руководство пользователя

Страница: 39 / 100

Chapter 3 High Accuracy Timing
Basic timing principles
T-BERD/MTS/SC Timing Expansion Module User Manual
July 2017 22112315, Rev. 004 Page 23
Voltage
When you configure the TEM module, you can select the voltage used by the
connected antenna (3.3V or 5V), or select 0V. If you select 3.3V or 5V, the module will
report antenna faults due to low voltage that indicates an antenna may be discon-
nected, damaged, or defective.
Delay bias
The TEM Module ships with a default Antenna Bias value of 28, which is the optimal
value for the Viavi supplied antenna. If you are using a different antenna, you should
calculate the
cumulative delay introduced by 1) the antenna, 2) the antenna’s cable,
and if applicable, 3) any in-line splitter or amplifier, then change the Antenna Bias value
on the GNSS setup tab. The value that you specify will be retained when you power
cycle the module.
The specified bias setting may also be used to adjust the absolute timing of the TEM to
match other system components or standards. To determine the delay value introduced
by each item, refer to supporting vendor specifications. For instructions on specifying
the bias value, see
“Specifying GNSS settings” on page 30 .
Available survey modes
When you configure the TEM Module to use GNSS timing, you must either specify a
survey mode or manually specify the latitude, longitude, altitude, and survey position
accuracy for the test instrument.
If you configure the module to generate accurate coordinates by surveying a GNSS
constellation, you select a survey mode or manually specify survey settings based on
1) the minimum duration of the survey, and 2) the survey accuracy requirement, in
meters, representing the maximum allowed standard deviation of the position data
collected throughout the survey. The survey will run until both conditions are satisfied.
Surveys conducted for a longer period of time will provide more data points, observe
more satellite orbits, and as a result, yield more accurate coordinates.
If you are conducting surveys in areas with poor satellite visibility, you can configure the
module to use SBAS to optimize availability of the satellites during the survey.
The survey will not begin until you select the Start Survey action button provided on
either the Location setup tab, or the bottom of the Timing Module tab on the Main
screen. After the survey is complete, you can save the generated coordinates with a
specific location name; this allows you to retrieve the coordinates in the future if you
return to conduct additional tests.
NOTE:
If you configure a manual survey with a position accuracy of less than one
meter (without providing an accurate fixed location), the survey will take a
very long time to complete.