Low frequency suppression circuit for a time domain reflectometer

摘要

An improved time domain reflectometer (TDR) includes a capacitor coupled in series between a transmission medium under test and the TDR receiver input. A switch, operating under microprocessor control, selectively couples and uncouples the capacitor to a voltage reference, such as ground. During the generation of interrogating pulses from the TDR and the acquisition of data from the transmission medium under test, the capacitor is uncoupled from the voltage reference and acts as a DC blocking capacitor. During periods of non-TDR activity, the capacitor is coupled to voltage reference and acts as a load for low frequency interference appearing on the transmission medium. The capacitor-switch operation blocks low frequency interference signals from the receiver input of the TDR.