Chapter 13 285
Troubleshooting
No Modulation at the RF Output
DC bias is removed and the I/Q signal is reapplied to the I/Q modulator.
The RMS voltage value can be found in the waveform header (Refer to Chapter 3,
“Basic Digital Operation.”) The RMS voltage value can be set by the user or
calculated by the signal generator.
NOTE The ARB RMS softkey is only available when the internal Arb is enabled.
Fixed During Fixed, the Power Search Reference is set fixed RMS reference level and is used
to bias the I/Q modulator.
Manual RMS During the Manual RMS, the user selects a DC bias level (0 to 1.414 Vrms) as a
Power Search Reference to be applied to the I/Q modulator during the power search.
Modulated During the Modulated power search, the
Power Search Reference is set to Modulated,
the actual modulating signal is used to provide the AC bias on the I/Q modulator.
Modulated can be used with either internally generated or externally supplied I/Q
modulation.
CAUTION Due to the time varying nature of the I/Q data, a modulated reference search can take
longer to settle and be less accurate than the other reference bias types. The modulated
search reference bias type is not recommended for use with low symbol rate modulated
formats.
The modulated power search reference cannot be used with a bursted signal.
No Modulation at the RF Output
Check the MOD ON/OFF annunciator on the display. If it reads MOD OFF, press Mod On/Off to toggle the
modulation on.
Although you can set up and enable various modulations, the RF carrier is modulated only when you
have also set
Mod On/Off to On.
On the E8267D, for digital modulation, make sure that
I/Q Off On is set to On.
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