Example Of Using Scpi Commands; Optimizing Ccdf Measurements - Keysight X Series Manual

Making WLAN Measurements
Making Power Stat CCDF Measurements

Example of Using SCPI Commands

Select WLAN mode
Select the Power Stat CCDF measurement
Get the measurement result unprocessed I/Q trace data, as a series of trace
point values in volts.

Optimizing CCDF Measurements

To accurately perform a useful CCDF measurement of a device such as a power
amplifier (PA), the measurement must be made on the data portion of the
OFDM burst. In an 802.11g ERP-OFDM signal, the burst includes training
symbols (the first 16 µs of the burst) followed by the signal field, and then the
data field.
In order to accurately characterize the PA, only the signal and data portions of
the burst should be measured. This can be done by adjusting the trigger
parameters within the CCDF measurement.
OFDM bursts are variable in length. Therefore, the first task is to identify the
total length of the burst. This can be done using the Power vs Time
measurement.
The total length of the burst can be found using markers. Place a marker on
the left edge of the burst, to indicate the start of that burst. Then place a delta
marker at the end of the same burst. Read the marker value to get the total
length of burst.
In the measurement shown below, the burst is 180 µs long. the training portion
of the OFDM burst occupied the first 16 µs. Therefore, the CCDF measurement
should only analyze the portion of the burst between 16 µs and 180 µs, for a
total length of 164 µs.
The total trigger offset that will be set for the CCDF measurement includes two
parts: the hardware-caused trigger delay (25 µs) plus the training portion of
the OFDM burst (16 µs). The user can read the hardware-caused trigger delay
using marker function.
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INST WLAN
CONF:PST
READ:PST[0]?
Keysight WLAN Measurement Guide