Abstract: In a method for generating a transillumination signal of a section of the subsurface, an HPEM radiation source radiates an electromagnetic pulse into the section for the purpose of exciting electromagnetically reactive structures to emit an electromagnetic response signal. For the pulse, a pulse duration of at most 500 ns, a center frequency in the range between 10 MHz and 10 GHz, and a bandwidth in the range from 10% to 150% of the center frequency is set. The transillumination signal is formed as the sum of response signals received at a measuring location. In a method for detecting a cavity in the subsurface, the above method is carried out, and the structures are detected from the transillumination signal with the aid of a detection method, and the cavity is detected if the structures satisfy a detection criterion.

Abstract: In a method for generating a transillumination signal of a section of the subsurface, an HPEM radiation source radiates an electromagnetic pulse into the section for the purpose of exciting electromagnetically reactive structures to emit an electromagnetic response signal. For the pulse, a pulse duration of at most 500 ns, a center frequency in the range between 10 MHz and 10 GHz, and a bandwidth in the range from 10% to 150% of the center frequency is set. The transillumination signal is formed as the sum of response signals received at a measuring location. In a method for detecting a cavity in the subsurface, the above method is carried out, and the structures are detected from the transillumination signal with the aid of a detection method, and the cavity is detected if the structures satisfy a detection criterion.

Abstract: A microwave generator (11) has a parallel connection of series connections of uncontrolled discharge spark gaps (13) and charge storage means (12) which are charged up by way of charging resistors (17) and an inductor (19) common to all parallel connections, from a high voltage generator (26), until the respective spark gaps (13) short-circuit by way of arcs and the storage means (12) are discharged again by way of the inductor (19). The oscillating short-circuit currents which thus occur in stochastic steep-edged manner and which are superimposed on each other in the inductor (19) are emitted by way of an antenna (21) connected in single-pole manner thereto in the form of a high-energy microwave spectrum which is wide-band in accordance with the arc switching speed, with a spectral key point which is determined by the inductor (19).

Abstract: A very compact interference frequency generator (11) which emits with an extremely wide band width and extremely powerfully is afforded by the combination of a mechanical pulse generator (25) with two piezoelectric pillars (13) which are disposed axially in succession and which can be axially acted upon by the pulse generator (25) and which are electrically connected in series in opposite relationship and which are electrically conductively connected with their mutually remote ends (18) to electrodes (34) which extend parallel to the piezoelectric pillars (13) to an electrically conductive coupling portion (15) between the piezoelectric pillars (13) where they end as electrodes (36) of an axial spark gap and at the same time spark gaps (37) which are oriented inclinedly radially towards the coupling portion (15).

Abstract: For a compact microwave generator (11) with powerfully wide-band microwave radiation in which there is a marked resonance increase whose frequency center of gravity is variable in order to be able to adapt the power center in respect of the radiated wavelengths to the geometrical structure of a circuit configuration to be disturbed, a conductor (29) which coaxially surrounds the spark gap (13) between the electrodes (14-15) is electrically connected to one of the two electrodes (15) mechanically adjustably in its effective length as a variable resonator.

Abstract: A microwave generator (11) has a parallel connection of series connections of uncontrolled discharge spark gaps (13) and charge storage means (12) which are charged up by way of charging resistors (17) and an inductor (19) common to all parallel connections, from a high voltage generator (26), until the respective spark gaps (13) short-circuit by way of arcs and the storage means (12) are discharged again by way of the inductor (19). The oscillating short-circuit currents which thus occur in stochastic steep-edged manner and which are superimposed on each other in the inductor (19) are emitted by way of an antenna (21) connected in single-pole manner thereto in the form of a high-energy microwave spectrum which is wide-band in accordance with the arc switching speed, with a spectral key point which is determined by the inductor (19).

Abstract: For a compact microwave generator (11) with powerfully wide-band microwave radiation in which there is a marked resonance increase whose frequency centre of gravity is variable in order to be able to adapt the power centre in respect of the radiated wavelengths to the geometrical structure of a circuit configuration to be disturbed, a conductor (29) which coaxially surrounds the spark gap (13) between the electrodes (14-15) is electrically connected to one of the two electrodes (15) mechanically adjustably in its effective length as a variable resonator.