Interesting project but I wonder if this is mostly academic. Wheatstone bridges are very sensitive to tampering. While the reflectometry is pretty cool I wonder if for practical purposes the extra sensitivity is needed for physical intrusion detection. While 10€ may not be much for securing a payment terminal a wheatstone bridge is a lot cheaper.

Enjoyed the paper, thanks.

While there was brief discussion about environmental influence due to temperature and environmental EMI, it would be nice to get an idea of how this approach compares with regards to radiated emissions.

Fast edges and their wide spectral content are one of the earliest things to minimise/eliminate as part of compliance testing - other approaches aren't as active of an aggressor so getting to production may not be as easy given the stated goals for low cost/effort implementation.

The frequency domain data from the MXA shows the output during edge measurement, but there's no discussion about measuring how much these tones leak...

Very interesting! Thanks for sharing.

It’s very frustrating that the tried and true method of sampling comparators has become prohibitively expensive due to niche parts.

I suspected that the ST HRTIMER would be a good candidate for replacing the delay line components, with the benefit of synchronisation for free. Good to see it works!

The diode bridge sampling and verification is the “hard part”. My motivation was for wanting to make a TDR was lack of equipment required to measure the signals required. Ironically, it’s the very equipment you need decent equipment to verify a TDR is working correctly. Most existing designs attempt to replicate old sampling bridges that use exotic unobtainable diodes. If you stray from the tried path, it’s up to you to verify performance, so there is some valuable insight here.

I liked reconstructing the signal using a spectrum analyser, very clever idea.