Measurement Principles
R&S
®
RT-ZD40
39
User Manual 1410.5363.02 ─ 05
5.2.1.2
Input Capacitance C
dm
The input capacitance C
dm
causes the input impedance to decrease in the
medium-frequency range (100 kHz to 1.0 GHz). It affects the settling time of the
input voltage in the case of fast transients.
5.2.1.3
RF Resistance R
RF
The RF resistance R
RF
determines the minimum input impedance and thus the
maximum loading at very high frequencies above 1.0 GHz. Thus, the measure-
ment result depends on the source impedance of the DUT. The RF resistance R
RF
prevents the input voltage from rising immediately to its final value in the case of
fast transients.
The resulting loading of a step signal at the input of the probe is shown in
.
Figure 5-7: Signal loading caused by the R&S
RT-ZD40 probe
Signal Loading of the Input Signal
