A new promising architecture of microwave personnel screening system is analyzed in this paper with numerical simulations. This architecture is based on the concept of inverse aperture synthesis applied to a naturally moving person. The extent of the synthetic aperture is formed by a stationary vertical linear antenna array and by a length of subject’s trajectory as he moves in the vicinity of this antenna array. The coherent radar signal processing is achieved by a synchronous 3D video-sensor whose data are used to track the subject. The advantages of the proposed system architecture over currently existing systems are analyzed. Synthesized radar images are obtained by numerical simulations with a human torso model with concealed objects. Various aspects of the system architecture are considered, including: advantages of using sparse antenna arrays to decrease the number of antenna elements, the influence of positioning errors of body surface due to outer clothing. It was shown that detailed radar images of concealed objects can be obtained with a narrow-band signal due to the depth information available from the 3D video sensor. The considered ISAR architecture is considered perspective to be used on infrastructure objects owing to its superior qualities: highest throughput, small footprint, simple design of the radar sub-system, non-required co-operation of the subject.
The paper summarizes results of step-frequency radars application in medicine. Remote and non-contact control of physiological parameters with modern bioradars provides a wide range of possibilities for non-contact remote monitoring of a human psycho-emotional state and physiological condition. The paper provides information about technical characteristics of bioradars designed at Bauman Moscow State Technical University and experiments using them. Results of verification experiment showed that bioradars of BioRASCAN type may be used for simultaneous remote measurements of breathing and heart rate parameters. In addition, bioradar assisted experiments for detecting of different sleep disorders are described. Their results proved that method of bioradiolocation allows correct estimation of obstructive sleep apnea severity compared to the polysomnography method, which satisfies standard medical recommendations.
The paper contains feasibility study of a method for bioradar monitoring of small laboratory animals loco-motor activity improved by using a corner reflector. It presents results of mathematical simulation of bioradar signal reflection from the animal with the help of finite-difference time-domain method. It was proved both by theoretical and experimental results that a corner reflector usage during monitoring of small laboratory animals loco-motor activity improved the effectiveness of the method by reducing the dependency of the power flux density level from the distance between antennas block and the object.
This paper describes the architecture of a microwave radar system intended for imaging concealed objects under clothing as a subject walks through the inspection area. The system uses the principle of inverse aperture which is achieved by a person’s movement past a stationary microwave sensor array. In the system, the vertical resolution is achieved by arranging microwave sensors vertically while the horizontal resolution is due to the subject’s horizontal motion. The positioning of the objects is achieved by employing a synchronous video sensor that allows coherent radar signal processing. A possible radar signal processing technique based on signal accumulation is described. Numerical experiments are conducted with the described object trajectory model. The influence of positioning errors attributed to the video positioning system is also modeled numerically. An experimental setup is designed and proposed to evaluate the suggested signal processing techniques on real data with an electro-mechanical scanner and single transceiver. It is suggested that the signal acquisition with the system can be accomplished using the stop motion technique, in which a series of changing stationary scenes is sampled and processed. Experimental radar images are demonstrated for stationary objects with concealed items and considered as reference images. Further development of the system is suggested.
In this paper, microwave holography is considered as a tool to obtain high resolution images of shallowly buried objects. Signal acquisition is performed at multiple frequencies on a grid using a two-dimensional mechanical scanner moving a single transceiver over an area of interest in close proximity to the surface. The described FFT-based reconstruction technique is used to obtain a stack of plan view images each using only one selected frequency from the operating waveband of the radar. The extent of a synthetically-formed aperture and the signal wavelength define the plan view resolution, which at sounding frequencies near 7 GHz amounts to 2 cm. The system has a short depth of focus which allows easy selection of proper focusing plane. The small distance from the buried objects to the antenna does not prevent recording of clean images due to multiple reflections (as happens with impulse radars). The description of the system hardware and signal processing technique is illustrated using experiments conducted in dry sand. The microwave images of inert anti-personnel mines are demonstrated as examples. The images allow target discrimination based on the same visually-discernible small features that a human observer would employ. The demonstrated technology shows promise for modification to meet the specific practical needs required for humanitarian demining or in multi-sensor survey systems.
A system for mine detection in aerial images is considered as an interactive system in which the operator is responsible
for making iterative queries to the database of images and analyzing the results. Preliminary, each image undergoes
formal decomposition into a set of feature vectors. Each feature vector is calculated for every irregularity found at a
scale-invariant salient point detection stage where a blob detector is used. Assuming that every small object in the image
can be described by a single invariant feature vector calculated on a patch around the salient point, formalization of
search algorithms is feasible. While the template-based search is straightforward in the terms of one object - one feature
vector, we focus on another important option when searching for mines - similar object search. For similar object search
a hierarchical clustering algorithm is considered. The mentioned steps of image processing as well as similar object
search are illustrated by performing on aerial mine field images taken by an electronic camera from a height of 27
meters. Encouraging preliminary results lead to the formulated plan for future research. The developed algorithms are
planned to be used in an image search engine allowing the operator to interactively search for mines in a database of
aerial images in humanitarian de-mining operations.
Experiments have been carried out to evaluate holographic subsurface radar (RASCAN) for non-destructive
evaluation (NDE) of subnominal bond conditions between the Space Shuttle Thermal Protection System tiles and
the aluminum substrate. Initial results have shown detection of small voids and spots of moisture between Space
Shuttle thermal protection tiles and underlying aluminum substrate. The characteristic feature of this device is the
ability to obtain one-sided radar soundings/images with high sensitivity (detecting of wire of 20 micron and less in
diameter), and high resolution (2 cm lateral resolution) in the frequency band of 3.6-4.0 GHz. JPL's advanced
high-speed image processing and pattern recognition algorithms can be used to process the data generated by the
holographic radar and automatically detect and measure the defects. Combining JPL's technologies with the
briefcase size, portable RASCAN system will produce a simple and fully automated scanner capable of inspecting
dielectric heat shielding materials or other spacecraft structures for cracks, voids, inclusions, delamination,
debonding, etc.. We believe this technology holds promise to significantly enhance the safety of the Space Shuttle
and the future CEV and other space exploration missions.
In this paper the mathematical models and results on processing the experimental single-frequency microwave holograms received by scanning subsurface radar with sine wave signal are submitted. The holograms reconstruction method with the use of support functions, which take into account the near field of the aperture antenna with round cylindrical waveguide, is analysed. The models consider both known and unknown phase shift of the signal reflected from the point object. It is theoretically and experimentally shown that single- frequency holograms reconstruction allows to estimate depth of shallowly buried objects and improve the resolution on the probing surface with the growth of objects depths.
In this paper we describe a method of minefield reconnaissance with the use of the multi-frequency ground-penetrating radar (GPR) combined with a metal detector. This method allows the mine images in the soil to be obtained in the band of the mine detector sensors. An experimental installation with remote control and scanning sensors has been designed and built. A mine detector of this kind can be used in peacekeeping and humanitarian operations.
The purpose of our investigation is to develop sounding radar for non-destructive inspection of buildings and structures designed for different uses, which can obtain high resolution radio-images representing the interior structure, objects and heterogeneities in load bearing and protecting construction. Our primary goal is to resolve problems dealing with the determination of strength of structures in service, repair and renovation of buildings.