It is important for oscilloscope users to note the difference in the concept of channel in oscilloscope and network analyzer.
In network analyzer, channel is referred to the window for displaying traces. Because a channel corresponds to a window, it is called a channel window.
On the other hand, the points on the front panel of network analyzer where cables and DUTs are connected are called test ports. These test ports are not channels and do not directly associate with channel windows.
The E5071C, for example allows you to use up to 160 channels (when the number of traces is up to 9) to perform measurement under 160 different stimulus conditions.
For each channel, up to 4, 6, 9, 12 or 16 traces (measurement parameters) can be displayed. Because multiple traces can be displayed for each channel, no feature is provided to link the stimulus conditions between channels, and each channel is always independent of the others. In other words, for the E5071C, you need to set the measurement conditions and execute calibration for each channel you use for measurement.
To learn more about setting the channel and traces in E5071C, refer to Setting Channels and Traces.
Enhanced Time Domain Analysis option allows you to use channel 1 only. Up to 16 traces can be displayed in this option (when Differential 2-Port DUT topology and all T or all S traces are selected).
Refer to the technical overview (http://literature.cdn.keysight.com/litweb/pdf/5990-5237EN.pdf) for maximum DUT lengths
To convert from DUT length in seconds to distance in free space, multiply the value in time by c, the speed of light in free space. To calculate the actual physical length, multiply this value in free space by Vf, the relative velocity of propagation in the transmission medium. (Most cables have a relative velocity of 0.66 for a polyethylene dielectric or 0.7 for a PTFE dielectric.)
DUT length (m) = DUT length (s) × c × Vf
Caution is required when measuring AC coupled (DC cut) DUTs.
The response after the capacitor cannot be measured correctly, because the capacitor response overlaps the response from the input and may cause measurement errors.
When measuring AC coupled devices, make sure that the following two conditions are satisfied for proper measurements.
Capacitance should be equal to or greater than 10 nF
DUT length should be equal to or less than 6.25 nsec (1.25 meters at ε=2.25)
DUT length is an actual length of DUT, not "DUT Length" in the Setup Tab in the TDR GUI.
When the above conditions are not satisfied, either:
Short circuit the capacitor
Provide open termination at one end of the capacitor and measure from the opposite side.
Using high quality cables to connect the DUT is recommended in order to minimize measurement degradation. The cables should have low loss, low reflections, and minimum performance variation when flexed.
Refer to the technical overview (http://literature.cdn.keysight.com/litweb/pdf/5990-5237EN.pdf) for maximum test cable lengths.