A method for detecting and analyzing an object in a monitored area, comprising: emitting an electromagnetic/microwave, EM/MW, signal via at least one transmitter through the monitored area, said signal transmitting through any object along a path directed towards at least one receiver located at a distance opposite of said one transmitter for receiving said signal, said path having an optical path length, said receiver detecting an amplitude and a phase as a complex amplitude of a received EM/MW signal transmitted through the monitored area, said receiver further performing a first processing of said received signal to determine whether said amplitude is above a preset amplitude threshold, said receiver further performing a second processing of said received signal if said preset amplitude threshold is met, said second processing comprising determining a shift in the optical path length due to said EM/MW signal transmitting through said object, compared to the optical path length when the same signal is emitted through a free space in the absence of said object within the monitored area, wherein the shift in the optical path length is calculated by a Fourier transform of a relation between the signal's complex amplitude in the presence of the object within the monitored area and the signal's complex amplitude in the absence of the object within the monitored area, sending data regarding said shift to a processor, measuring a thickness t of said object and sending data regarding said thickness to said processor, said processor further calculating a dielectric permittivity value ε of said object via a relationship of said shift equating to t* ε − 1, said processor comparing said dielectric permittivity value to a database of reference dielectric permittivity values forming preselected groups of objects, so as to determine to which preselected group of objects the object belongs and whether the object belongs to a preselected group of dangerous objects. emitting an electromagnetic/microwave, EM/MW, signal via at least one transmitter through the monitored area, said signal transmitting through any object along a path directed towards at least one receiver located at a distance opposite of said one transmitter for receiving said signal, said path having an optical path length, said receiver detecting an amplitude and a phase as a complex amplitude of a received EM/MW signal transmitted through the monitored area, said receiver further performing a first processing of said received signal to determine whether said amplitude is above a preset amplitude threshold, said receiver further performing a second processing of said received signal if said preset amplitude threshold is met, said second processing comprising determining a shift in the optical path length due to said EM/MW signal transmitting through said object, compared to the optical path length when the same signal is emitted through a free space in the absence of said object within the monitored area, wherein the shift in the optical path length is calculated by a Fourier transform of a relation between the signal's complex amplitude in the presence of the object within the monitored area and the signal's complex amplitude in the absence of the object within the monitored area, sending data regarding said shift to a processor, measuring a thickness t of said object and sending data regarding said thickness to said processor, said processor further calculating a dielectric permittivity value ε of said object via a relationship of said shift equating to t* ε − 1, said processor comparing said dielectric permittivity value to a database of reference dielectric permittivity values forming preselected groups of objects, so as to determine to which preselected group of objects the object belongs and whether the object belongs to a preselected group of dangerous objects.