Applying I/Q Vector Modulation
R&S
®
SMW200A
420User Manual 1175.6632.02 ─ 16
I/Q Wideband
Setting mode for wideband modulation signals (higher I/Q modulation bandwidth).
The modulation frequency response of the R&S SMW in the useful bandwidth is
improved at the expense of poorer harmonic suppression. This is achieved by shifting
the switching frequencies of the lowpass filters in the output section.
Remote command:
[:SOURce<hw>]:IQ:WBSTate on page 1051
Crest Factor
Sets the crest factor of the externally supplied analog signal.
The crest factor gives the difference in level between the peak envelope power (PEP)
and the average power value (RMS) in dB. The R&S SMW uses this value for the cal-
culation of the RF output power. For more information, refer to Chapter 3.3.4, "Impor-
tant Signal Parameters and Interface's Characteristics", on page 133
Note: To set the crest factor of an externally supplied digital signal, use the parameter
"BB Input > Input Level > Crest Factor" (see "Crest Factor" on page 176).
See also "To apply an external analog signal directly to the I/Q modulator"
on page 217.
Remote command:
[:SOURce<hw>]:IQ:CREStfactor on page 1050
(Baseband) Gain
Optimizes the modulation of the I/Q modulator for a subset of measurement require-
ment. Provided is a dynamic range of 16 dB divided into 2 dB steps. The optimization
is a trade-off between signal distortion and signal-to-noise ratio (SNR).
In instruments equipped with one of the High frequency options and for "Freq > 19.5
GHz", this parameter is disabled.
See also Chapter 6.5, "How to Adjust the I/Q Modulator to Optimize Performance",
on page 424.
"-4 dB/- 2 dB (Low Distortion)"
Activates -4 dB or -2 dB gain.
Baseband signal is internally attenuated to minimize signal distor-
tions; the intermodulation characteristics of signal are optimized, the
SNR however decreases.
"0 dB"
No changes on the baseband signal; optimization is not applied.
"+2 dB/ +4 dB/ + 6dB (Low Noise)"
Activates a 2 dB, 4 dB or 6 dB gain
Baseband signal is internally boosted to maximize the SNR; signal
noise is minimized, the signal distortions however increase.
These values are suitable for 3GPP signals with high adjacent chan-
nel power ratio (ACPR).
"Auto"
The gain value is retrieved form the connected R&S SZU. The I/Q
modulator is configured automatically.
I/Q Modulator Settings
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