Modulation Analysis
R&S
®
Cable Rider ZPH
287
User Manual 1321.0950.02 ─ 07
Display mode
Description
The modulation depth diagram displays the mod-
ulation depth of the signal.
The modulation depth indicates the amplitude
drop during low state amplitudes (binary 1 = high
state or modulated signal, binary 0 = low state or
unmodulated signal).
The high state amplitude is normarlized to 100%.
The modulation depth is the amount that the
amplitude drops during the low state in %. The
modulation depth is therefore a value < 100 %.
Another way to express the amplitude variations
of an ASK modulated signal is the modulation
index. The R&S Cable Rider ZPH displays the
modulation index as a numeric result in the mea-
surement result view.
The modulation deviation diagram shows the fre-
quency shift of the FSK signal. The frequency
shift (or frequency deviation) is the frequency dif-
ference between the mark (binary 1) and space
(binary 0) frequencies representing the binary dig-
its.
The modulation error diagram shows the modula-
tion error over time (% for ASK and Hz for FSK).
The modulation error shows the deviation of the
measured symbols from the ideal symbol loca-
tions. The ideal symbol locations are defined in a
reference signal.
12.2.1
Measurement Configuration
A digital modulation system needs a transmit filter to limit the bandwidth of the trans-
mitted signal. The receiver needs to know the characteristics of that filter to demodu-
late the signal. Sometimes, an additional receive filter is necessary for proper demodu-
lation. Other demodulation parameters like the symbol rate, roll factor of the filter and
frequency deviation in the case for FSK modulated signal are also required for a proper
demodulation of the signal. Demodulation parameters like oversampling factor, refer-
Digital Demodulation
