Drift reduction of the incident signal in time domain reflectometry

Modification of a 1811A Hewlett–Packard time domain reflectometry (TDR) system is described for long-time drift reduction. Triggering methods for single-channel as well as dual-channel TDR systems are discussed. It is shown that the long-time drift of the 1024-point incident signal is reduced to less than one discrete point over a period of several hours. This modification extends the upper frequency limit of a TDR system to about 10 GHz for precision permittivity measurements.