Trigger Mode

This topic describes the trigger mode and synchronization for the instrument.

The instrument’s frame synchronization method depends on the trigger mode selected:

Single Trigger

The frame timing is adjusted at the first trigger. All triggers, except the first one are ignored and not used for instrument frame timing.

Continuous Trigger

All external triggers are used to adjust the instrument’s frame timing.

Figure 1 , Figure 2 and Figure 3 describe the triggering modes and synchronization patterns.

Figure 1 Trigger Mode and Synchronization

Single Frame Synchronization

Figure 3 illustrates the single synchronization mode behavior, when the instrument is in E4438C compatible mode. Refer to your instrument's documentation at www.keysight.com for the correct instrument SCPI commands. For the N7600C W-CDMA/HSPA+ specific SCPI commands, refer to SCPI.

The software was set for a single frame synchronization mode measurement:

  1. Instrument is armed (Refer to instrument's display). The RF signal is set automatically set to CW.

  2. The first trigger occurs. The MXG/EXG responds to the trigger signal (Pattern Trigger in 1) and initiates the trigger delay count to align the frame timing with the trigger timing.

    • For the DPCH mode, the trigger delay value is: 1024 chip + Timing Offset + Timeslot Offset + SFN-CFN Offset + External Delay Time

    • After the delay count is completed, the instrument stops the CW signal output and starts the W-CDMA modulated signal output.

  3. At this point, if a second trigger occurs, the MXG/EXG ignores the second trigger, because after the first trigger, the instrument has already aligned with the timing at “2”.

  4. Customer  executes the “Apply” operation. The generated IQ/RF signal is unstable for a short time, and frame timing aligned at “2" is interrupted. The W-CDMA application is ready to receive a trigger signal.

  5. The trigger state is armed. But, there is no front panel indication of the instrument being armed. At this step, the output signal is W-CDMA modulated, but the modulated signal is uncorrected.

  6. Customer executes a trigger signal. MXG/EXG responds to the trigger signal (Pattern Trigger in 1) and starts the trigger delay count to align the frame timing with the trigger timing.

  7. The trigger delay count has been completed. The MXG/EXG adjusts its power level.

    The trigger delay time shown at this point includes the following: trigger detection and the (trigger delay + sync marker frame cycle (W-CDMA default is 80 ms).

  8. MXG/EXG starts a newly synched frame generation. The trigger signal has aligned at "7", so additional trigger signals will be ignored, until the W-CDMA real-time is toggled (On/Off) or software's "Apply" is executed.

Figure 2 E4438C Compatible Mode – Single Frame Synchronization Mode Behavior

For the following timing diagrams, the transmission time interval (TTI) can be set to 10 ms, 20 ms, 40 ms, or 80 ms.

Figure 3 Baseband Initial Triggering and Frame Synchronization for Early and Late Continuous Triggers

The instrument checks the timing difference between the external trigger and the internal frame timing whenever an external trigger is received. If the single trigger mode is selected, the instrument checks the timing difference between the external trigger and the internal frame timing when the first trigger is received. If continuous trigger mode is selected, timing is checked at each trigger signal.