Near-field subsurface tomography and holography based on bistatic measurements with variable base

Microwave Near-Field Dynamical Tomography of Thorax at Pulmonary and Cardiovascular Activity

“…In our experiments, we used the equipment that includes processing, a transceiver system with two identical bow-tie antennas with the length of arms 3.8 cm and the width of 5.4 cm that were used in [ 28 , 29 , 30 , 33 ], an oscilloscope GZ10E, broadband (0.05–5 GHz) pulse generators GZ1120ME-01,03 with the pulse time 50 ns at 1024 sweep points (a resolution of about 0.05 ns) and a repetition time of 10 μs, and the control computer for recording signals. The pickup time added up to 10 s (500 pulses).…”

“…In our studies of the near-field subsurface microwave diagnostics, it was first used in passive radiothermometry [ 23 , 24 ] (for details see [ 25 ]) and later in various methods of the active microwave tomography of subsurface dielectric inhomogeneities [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. In these papers, methods of tomography and holography (for solid targets) of 3D subsurface inhomogeneities of permittivity were worked out and studied experimentally [ 26 , 27 , 28 , 29 , 30 , 31 , 33 ]. Additionally, methods of profiling 1D inhomogeneities were developed in papers [ 30 , 31 ].…”

“…Additionally, methods of profiling 1D inhomogeneities were developed in papers [ 30 , 31 ]. Unlike far-field radar measurements, where the depth of a scattering element is determined by the signal time or phase delay, the depth sensitivity of near-field methods is provided by other parameters, such as frequencies of harmonic signals [ 27 , 28 , 29 , 30 ] (in multifrequency methods); probe aperture sizes [ 24 , 25 , 26 ] or source-receiver offset [ 33 ] (in multi-aperture methods); probe altitudes above the surface [ 28 , 33 ] (in multilevel scanning); and pulse spectrum [ 31 ] (in the ultra-wideband pulse sounding).…”

“…The sharp localization of currents on the emitting antenna produces a broad k -space spectrum of the probing field that provides a high-depth resolution of subsurface inhomogeneities in the near zone (see Figure A1 in Appendix A ). The same antennas were used in our previous studies on the near-field subsurface diagnostics [ 28 , 29 , 30 , 31 , 33 ].…”

Dynamic near-field microwave diagnostics of lungs.

“…Данный подход позволяет реализовать субволновую разрешающую способность, что особенно важно в сильнопоглощающих средах -таких, как живые ткани, где невозможно использование в зондировании более коротких длин волн из-за сильного поглощения на высоких частотах. Исследования в области дистанционной СВЧ диагностики процессов дыхания и работы сердца сначала получили развитие в приложении к задачам радиолокационного обнаружения людей за препятствиями, в частности, для их поиска под завалами или снежными лавинами [10][11]. В этих работах диагностика состояла в визуализации вариаций сигнала, принимаемого в дальней зоне, которые определялись главным образом отражением от поверхности тела и отображали в основном ее механические колебания в процессах дыхания и работы сердца.…”