What are differential TDR measurements?
Differential TDR measurements are useful when characterizing differential transmission lines, or for characterization of crosstalk, or when TDR measurement device ground is not easily accessible or not well defined (click here for further details). In that case, the two TDR outputs can be set to provide signals of the same amplitude and opposite polarity. The advantage of these measurements is that if the DUT is symmetric, a virtual ground plane is created, allowing easy characterization of self-capacitance, inductance and impedance of the interconnects, as well as the crosstalk characteristics for the adjacent interconnect. Ensure that the differential signals arrive at the DUT at the same time; if this condition is not met, the differential measurement will not be accurate.
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