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R&S
RT-ZZ80
Fig. 4-6: Step response of the R&S RT-ZZ80 with a type 3 connection
4.2
Signal Loading of the Input Signal
The previous section dealt with the transfer function and step response of the
probe. This section describes how the probe influences the input signal.
4.2.1
Transmission Line Probes
Traditional passive probes have a high input impedance at DC (typically from
1 MΩ to 10 MΩ) that quickly decreases with rising frequency. For DC, the load of
the DUT is usually negligible, but high-frequency signals are loaded all the more.
On the contrary, transmission line probes have a very low input impedance at DC,
typically from a few 100 Ω to 1 kΩ. This results in a significant higher load of the
DUT at DC than the load caused by a traditional passive probe and can lead to a
malfunction of the circuit.
User Manual 1409.7689.02 ─ 02
Measurement Principles
Signal Loading of the Input Signal
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