Hi, Please ask me to stop in whatever words you like, with a reference to this request, if I talk about anything other than this. I'd like to make a cheap device for taking ongoing measurements of the effectiveness of a shielded enclosure. Would you be willing to briefly review my first prototype theory, and _concisely_ offer any _concise_ problems or _concise_ better ideas you can think of?

Noise source emits EM signal noise function, which at the receiver is present as Rn(t). This signal oscillates in what is roughly a square wave, for example with a relay.

During inactive time, receiver receives only Rb(t) the background signal.

During active time, receiver receives Rb(t) + Rn(t) = Rr(t).

When the signal is weak, heuristics can't differentiate between active and inactive time periods. So, we separate the problem of keeping the receiver in sync with the emitter from that of measuring the signal, and compare the probability distributions of the active and inactive timeperiods to discern the strength of Rn(t). Now, summation over time can be used to increase sensitivity if the signal is very weak.

First, estimate the probability distribution of Rn(t) from our observations of the probability distributions of Rr(t) and Rb(t), possibly using e.g. the convolution theorem for the sum of two independent random variables, which is not complex.

Then, discern mean electromagnetic properties such as relative power by solving from the distribution of Rn(t).

I've started pursuing this algorithm and goal a couple times over the years, and I'd like to try again. Step 1 is to identify in software the precise oscillation period of such a waveform, similar to implementing a van eck phreaking attack. I imagine while exploring step 1, plotting the accumulated shape of a single cycle visually, as if an oscilloscope had a trigger set for it. Each time point in the plot would be a fully colored column, like in a spectrogram, but of the frequency of occurrences of different signal powers, rather than spectral decomposition. I think such a plot would be worthwhile because it would help move towards both this goal, and other goals in electromagnetic security, of quickly reviewing the details of a repeating signal. Such signals are common in clocked digital electronic systems.