Trigger Signal - Agilent Technologies 89410A Operator's Manual

Note
TIP
Main length is set to 16 slots. Without a
trigger signal, the analyzer may begin the
measurement using any slot. In this
example, slot 2 is the first slot in the
measurement (as shown by the shaded
portion).
Main length is again set to 16 slots. This
example uses a trigger signal with trigger
delay to make slot 1 the first slot in the
measurement. The trigger delay ensures
that the trigger point occurs before the
LMS in slot 16.
Wideband CDMA Concepts (Options B73, B79, and 080)

Trigger Signal

If you use a trigger signal, the first slot in the measurement is the slot after the first
complete LMS (Long-Code Masked Symbol) for trial 1998 signals or the slot with
the first SCS (Search Code Symbol) for ARIB 1.0-1.2 signals, or the slot with the
first PSCH (Primary Sync Channel) for 3GPP signals.
For trial 1998 signals, LMS is at the end of the slot; for ARIB 1.0-1.2 signals, SCS is
at the beginning of the slot; for 3GPP signals, PSCH is at the beginning of the slot.
Setting up a trigger for ARIB 1.0-1.2 and 3GPP signals is different than setting up a
trigger for trial 1998 signals. For ARIB 1.0-1.2 and 3GPP signals, if you trigger at the
beginning of a slot, that slot becomes the first slot in the measurement (because the
SCS or PSCH is at the beginning of the slot). For trial 1998 signals, the slot
immediately following that slot becomes the first slot in the measurement (because
the LMS is at the end of the slot).
The following illustration shows you how to use trigger delay to select the first slot
in a measurement for trial 1998 signals.
For trial 1998 signals, to make slot 1 the first slot in the measurement when you
trigger at the start of a frame, set a pre-trigger delay (negative trigger delay) such
that the signal sampling begins before the LMS preceeding slot 1. For a 4.096 MHz
system, the duration of the LMS is –625µs. In this case, slot 1 will be the first slot in
the measurement if you trigger at the start of the frame (the start of slot 1) and set
the trigger delay to –625µs.
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