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Vilnius, Lithuania

Asmontas S.,Lithuanian Academy of Sciences | Kiprijanovic O.,Lithuanian Academy of Sciences | Levitas B.,Geozondas UAB | Matuzas J.,Geozondas UAB | Naidionova I.,Geozondas UAB
Medziagotyra | Year: 2014

Pulsed excitation of a horn antenna for generating large B wideband electromagnetic pulses was used. The antenna was excited by electrical pulses with rise time of 200 ps and pulse voltage of 15 V. The spectral properties of the electromagnetic pulses were investigated using different wide band antennas and (0 - 18) GHz passband sampling oscilloscope. It was found that the signal spectra is wide and ranges from 0.3 GHz to higher than 12 GHz. Hollow cylinders made from opaque for visible light materials were used to hide other cylinders with certain electrical properties. To reveal their presence we employ the electromagnetic pulses. Transmitted through and reflected from investigated objects pulses were received by several antennas having different frequency ranges and detected to obtain needed information. The experiments show that analyzing this information leads to conclusions about the presence of the object and its electrical properties. This methodic supposedly can be employed to disclose electrical properties of objects having complex electrical properties if broadband amplifiers and digital oscilloscopes are used. Source


Asmontas S.,Lithuanian Academy of Sciences | Kiprijanovic O.,Lithuanian Academy of Sciences | Levitas B.,Geozondas UAB | Matuzas J.,Geozondas UAB | Naidionova I.,Geozondas UAB
Medziagotyra | Year: 2014

Pulsed excitation of small size monopole antennas for generating wideband electromagnetic pulses was used. The monopoles were excited by electrical pulses having rise times of 600 ps, 200 ps, 70 ps and voltages 100 V, 15 V, and 0.4 V respectively. Antennas spanning (0.3 - 26) GHz bandwidth, including broadband horns with coaxial outputs, were employed to receive signals, which were investigated using (0 - 26) GHz passband sampling oscilloscope. It was found that waveforms of signals, received by the antennas, mostly depend on the pulse rise time and on the details of geometry of monopoles. The electromagnetic pulses have relatively long duration of about 30 ns and spectral harmonics up to 22 GHz. Therefore they can be attributed to pulses with large base. The results show that the upper frequencies of the spectrum most probably are cut off by existing arrangement. Usage of such pulses can find wide practical application when they are received after transmission trough different media by a number of antennas having different operational frequency ranges, followed by digital signal processing. Source

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