Applying I/Q Vector Modulation
R&S
®
SMW200A
452User Manual 1175.6632.02 ─ 30
IS2000 = the RF signal s(t) is derived from the baseband I/Q signal as s(t)=i(t)cos(2*pi*f
c
t) +
q(t)sin(2*pi*f
c
t)
R&S SMW = the RF signal s(t) is based on the definition s(t)=i(t)cos(2*pi*f
c
t) - q(t)sin(2*pi*f
c
t)
See also:
●
Description "CDMA2000
®
incl. EV-DV Digital Standard for R&S SMW"
●
Description "1xEV-DO Rev. A, Rev. B Digital Standard for R&S SMW"
"Off"
I/Q control is normal.
"On"
The modulation sidebands are inverted by swapping the I and Q sig-
nals (the Q-part of the signal is inverted).
The generated baseband signal is according to CDMA200 and 1xEV-
DO standards.
An I/Q modulator defined according to these standards can cope with
the RF signal generated by the R&S SMW.
Remote command:
[:SOURce<hw>]:IQ:SWAP[:STATe] on page 1138
I/Q Wideband
Activates/deactivates optimization for wideband modulation signals (higher I/Q modula-
tion bandwidth).
The modulation frequency response of the R&S SMW in the useful bandwidth is
improved at the expense of poorer harmonic suppression. This improvement is ach-
ieved by shifting the switching frequencies of the lowpass filters in the output section.
Remote command:
[:SOURce<hw>]:IQ:WBSTate on page 1138
Crest Factor
If "Source = Analog Wideband I/Q Input", 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 4.3.5, "Impor-
tant Signal Parameters and Interface's Characteristics", on page 119
Note:
To set the crest factor of an externally supplied digital signal, use the parameter:
●
"BB Input > Input Level" > Crest Factor.
●
"BB Input > Input Level" > Crest Factor.
See also "To apply an external analog signal directly to the I/Q modulator"
on page 213.
Remote command:
[:SOURce<hw>]:IQ:CREStfactor on page 1138
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).
I/Q Modulator Settings
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