Balanced two-conductor time domain reflectometer

A method of digitizing a waveform transmitted through a medium, which comprises:

• (a) launching a fast-transitioning differential waveform onto a proximal end of a two-conductor transmission line that passes through the medium to an open distal end of the transmission line;
• (b) receiving resultant waveforms from the two conductors using latching comparators at the proximal end of the transmission line, wherein the resultant waveforms contain signal components reflected from the open distal end of the transmission line;
• and
• (c) digitizing the resultant waveforms by generating timing strobes to latch the latching comparators at a programmed point in time and to measure an amplitude by a successive approximation process, wherein the digitizing comprises:
• (c1) providing a programmable time offset for generation of a precisely-timed sampling strobe offset from the launching of the fast-transitioning differential waveform to sample an amplitude of the resultant waveforms at the latching comparators;
• (c2) using the latching comparators to compare the resultant waveforms to a programmable voltage reference;
• (c3) launching a multiplicity of the fast-transitioning differential waveform onto the two-conductor transmission line and adjusting the programmable voltage reference using the successive approximation process until an amplitude representative of a composite of resultant waveforms at a point in time has been acquired;
• and
• (c4) incrementing the programmable time offset and repeating steps (c1) through (c3) to acquire another amplitude representative of a multiplicity of resultant waveforms until the waveform has been digitized, and
• wherein propagation time of the fast-transitioning differential waveform through the medium is calculated from the fast-transitioning differential waveform by a method that comprises:
• differentiating the fast-transitioning differential waveform to locate a local maximum in a second derivative that is followed by a sustained positive value in a first derivative to establish an approximate time of an incident wave and an approximate time of a reflected wave;
• and
• recalculating the time of the first derivative and the time of the second derivative of the fast-transitioning differential waveform using minimal increments of the programmable time offset respectively from the approximate time of the incident wave and the approximate time of the reflected wave to determine a precise time of the incident wave and a precise time of the reflected wave.