Instrument Function
R&S
®
SMU200A
287Operating Manual 1007.9845.32 ─ 15
The crest factor gives the difference in level between the peak envelope power (PEP)
and average power value (RMS) in dB.
This value is necessary to allow the correct output power to be generated at the RF output.
When the set output power is generated, the R&S Signal Generator uses this value to
compensate the average power which is lower compared to the peak power.
The maximum input voltage at the I/Q input is equated to the peak power and is used as
the "reference" for setting the level of the output signal. Since the signal does not usually
supply the peak power at a constant level and instead supplies a lower average power,
the crest factor specifies how many dB have to be added internally so that the correct
output power is achieved.
Note: The crest factor of vector modulation for an external signal that is fed into the
baseband path is entered in the "Baseband Input" menu ("BB Input block", option R&S
SMU-B17).
See also chapter 5.9, "External Baseband Signal - Baseband Input", on page 436.
SCPI command:
[:SOURce<hw>]:IQ:CREStfactor on page 723
Baseband Gain-Gain - I/Q Mod
Optimizes the modulation of the I/Q modulator for any measurement requirement.
The modulation is determined by selecting the gain.
Note:
The remote-control commands to be used depend on the selected I/Q input signal
(SOURce:IQ:SOURce ANALog | BASeband).
●
For the Analog Wideband I/Q input signal, the commands of system
SOURce:IQ:GAIN are valid.
●
For the internal or external Baseband I/Q input signal (SOURce:IQ:SOURce
BASeband), the commands of system SOURce:BB:IQGain are valid.
"Auto"
(digital baseband signal only)
With this setting, the modulation is automatically optimized for the inter-
nally set baseband signal.
"- 3dB (Low Dis-
tortion)"
Activates -3 dB gain. With this setting, signal distortions are minimized.
"0 dB (Stand-
ard)"
Activates 0 dB gain
"3 dB (High
3GPP ACLR)"
Activates 3 dB gain. This setting is recommended for 3GPP signals with
very high adjacent channel power ratio (ACPR).
"6dB (Low
Noise)"
Activates 6 dB gain. With this setting, signal noise is minimized.
SCPI command:
[:SOURce<hw>]:IQ:GAIN on page 724 (for analog I/Q signal)
[:SOURce<hw>]:BB:IQGain on page 727 (for digital I/Q signal)
I/Q Modulation - I/Q Mod Block
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