Chapter 16 463
W-CDMA Uplink Digital Modulation for Receiver Test
Generating a Single PRACH Signal
4. Press Mode Setup to return to the top-level real-time W-CDMA menu.
A default PRACH signal output has a single preamble and a message part with a 20 ms transmission time
interval (TTI). Setting the trigger output to occur on the PRACH pulse lets the spectrum analyzer or other
measuring equipment that is externally triggered, start its sweep at the beginning of the PRACH signal.
Generating the Baseband Signal
Press W-CDMA Off On to On.
Setting Up the E4440A PSA for the PRACH Signal
This procedure guides you through setting up the PSA for making a time domain measurement. Refer to
Figure 16-1 on page 447 for connecting the ESG to the E4440A PSA. Figure 16-12 on page 464 shows the
ESG output signal on the PSA display.
1. Preset the spectrum analyzer.
2. Select the W-CDMA mode.
Press
Mode > W-CDMA.
3. Set the center frequency.
Press
Frequency Channel > Center Freq > 1.95 > GHz.
4. Select the time domain measurement mode.
Press
Measure > More 1 of 2 > Waveform (Time Domain).
5. Set a sweep time that shows the components of the PRACH transmission.
Press
Meas Setup > Sweep Time > 50 > ms.
This sets 5 ms as the vertical time divisor (10 divisions x 5 ms = 50 ms)
6. Set the resolution bandwidth for a quick response time that captures the bursting nature of the PRACH
components.
Press
Res BW > 500 > kHz.
7. Trigger the spectrum analyzer from the rear trigger input using the ESG’s PRACH pulse trigger signal.
Press
Trig Source > Ext Rear.
8. Zoom in on the RF Envelope display.
Press
Zoom.
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