User`s guide

Chapter 15 433
W-CDMA Uplink Digital Modulation for Receiver Test
W-CDMA Uplink Concepts
Transition between Normal Frame and Compressed Frame
In a dedicated physical channel (DPCH), an RF notch exists at the transition between a
normal frame and a compressed frame (see Figure 15-56). In a CW signal, the notch measures
approximately five microseconds in length and approximately seven decibels in depth (peak
compressed mode to peak normal mode).
Figure 15-56 RF Notch with Compressed Mode Transitions
Settling Time during User Event for DPCH Compressed Mode
Some user events, such as changing the amplitude or frequency, will cause the signal to jump
to an unexpected amplitude for a short period of time before it settles to expected parameters.
This transition period is approximately 200 milliseconds (see Figure 15-57). It is, therefore,
important to allow for this time when you make changes to signal characteristics. If you make
changes using remote SCPI commands, insert wait instructions into the program. The
following events can cause this unstable transition time:
• amplitude and frequency changes
• RF switched on and off
• modulation switched on and off
• ALC switched on and off
• saving or recalling states
Figure 15-57 DPCH Compressed Mode Signal after a Change in Amplitude