Common characteristics in the phenomenon

[mustefa ubram]

hi
I study the time I was researching on different circuits lrls.Almost all of them had one thing in common .If the source a frequency placed in the range of phenomenon Change Amplitude - frequency - phase.I think with study on one of these three characteristics can reveal buried metals.I think it is very effective as the antennas use ferrite Because of the high permeability
What do you think about this design?