R&S SMJ100A, Operating Manual

Page: 302 / 874

Instrument Function
R&S
®
SMJ100A
286 Operating Manual 1403.7458.32 ─ 14
The I/Q modulator defined in the IS2000 standard differs from the definition in the
R&S
SMJ. The definition on which the R&S SMJ is based is used by virtually all digital
communication standards (except IS95 and IS2000).
In the final step, the filtered I/Q signal is modulated to the desired RF in a different way
in the I/Q modulator:
Figure 5-12: Definition of I/Q modulator in IS2000 and R&S SMJ f
According to IS2000, the RF signal s(t) is derived from the baseband I/Q signal as fol-
lows:
s(t)=i(t)cos(2pif
c
t) + q(t)sin(2pif
c
t)
The instrument family is based on the following definition:
s(t)=i(t)cos(2pif
c
t) - q(t)sin(2pif
c
t)
"I/Q Swap" must now be set to "On" so that an I/Q modulator defined according to
IS2000 can cope with the RF signal generated by the R&S
SMJ.
"Off" I/Q control is normal.
"On" The I and Q signals are swapped.
Remote command:
[:SOURce<hw>]:IQ:SWAP[:STATe]
on page 727
I/Q-Wideband - I/Q Mod
Optimized setting for wideband modulation signals (>5 MHz). Optimized setting for
wideband modulation signals (>5 MHz).
The modulation frequency response is decreased at the expense of poorer harmonic
suppression. This is achieved by shifting the switching frequencies of the lowpass fil-
ters in the output section.
Remote command:
[:SOURce<hw>]:IQ:WBSTate
on page 727
I/Q Modulation - I/Q Mod Block