The paper represents the development of a vehicle based array of GPR sensor for the detection of anti-personnel mines.

In this paper the nonlinear iterative algorithm, the so-called Extended Contrast Source Inversion is applied to subsurface sensing problem where the number of measured data are very limited and the unknown objects/layers are illuminated from only one side. Some numerical results obtained from synthetic and real data are presented to illustrate the strengths and the weakness of the method.

This paper presents activities concerning optical detection of landmines at FOI, former FOA. The work is focused on the understanding of the origin of detectable optical signatures for choosing the most favorable conditions for detection. Measurements in test beds and calculations using a thermodynamic FEM model with conditions similar to those of the measurements are compared and interpreted in order to explain the behavior of the contrast. Examples will be given on modeling of buried landmines in soil. The heat flow as well as moisture flow has been taken into consideration. The diurnal heat exchange between the soil surface and the atmosphere generates the contrasts in the infrared images. Calculated temperature differences between the background and the surface above the buried object are compared to measured data from experiments. Results are presented and show how the temperature differences can vary over a 24-hour period. The variation depends on the weather at the time as well as the weather before the measurements started. Results from processing and analysis of temporal variations of optical signals from buried landmines and backgrounds are presented as well as their relation to weather parameters. A detection approach including the Likelihood Ratio Test (LRT) is presented. Some of the work has been carried out in an international cooperation project, Airborne Minefield Area Reduction (ARC). The objective is to develop, demonstrate and promote a new system for performing the UN Level 2 surveys allowing a quick reduction of suspected mine polluted areas and post cleaning quality control.

Detection and classification of anti-tank (AT) mines, buried in fine-grained dry sand, have been carried out using a hand held ground penetrating radar. Real AT mine bodies of types M47 and TMA4 are used with the explosive replaced by a surrogate. Interspaced metal rods and cylinder shaped bodies make false alarm objects. The sensor system consists of a horn-type antenna mounted on a swinging arm and fed by a stepped frequency radar emitter. An angular rate counter, ensuring records with reasonably accurate positions, monitors the arm deflection. A number of B-scans result in data sequences containing 75 measurements, each with 55 frequency samples in the 0.3-3 GHz band. The classification of targets relies on the shape of radar echoes returned as sampled waveforms. Given a certain control of the position of the sensor, a sequence of waveforms coming from different measurement points enhances the classification quality. Two classification methods have been used in parallel based on 2D matched filters. The first method uses 2D templates extracted from background subtracted B-scans known to contain prototype mines. These templates are matched to full B-scans using normalized correlation in the time domain. The second method uses time-frequency maps based on the pseudo Wigner-Ville transform. Here, the matching to data sequences is done by direct comparison of selected features. The results show that, combining both methods, perfect recognition is achieved for two different AT mines with very good discrimination against the non-mine objects.

Polarization measurements in the IR region are useful for the detection of man-made objects in natural environment. Surface laid landmines are examples of man-made objects that are difficult to detect, especially when a certain time have elapsed. As time goes by, both IR signature and degree of polarization are reduced, due to the dust coverage and the grass that has grown around the mines. Polarization measurements are useful when detecting Trip Wires. This article reports the results of IR polarization measurements compared to the measurements without a polarizing element. To simulate the dust and grasses that can cover the mines, a series of controlled covers are constructed. Measurements on this series are performed, and the results are shown in a diagram of relative Degree of Linear Polarization, (DoLP) as a function of coverage. The same is done for the case without a polarizer but here the relative radiance is shown. By comparing the two diagrams a measure is achieved of how effective the polarization measurements are with respect to the case without a polarizer. A simple parameter model of the coverage has been made and has been compared with the measurements. Measurements indicate that detection of trip wire is improved when using polarization measurements.

This paper describes scene simulation in passive millimeter wave imaging. The appearance of flat metal and plastic objects is simulated, as viewed from a grazing incidence angle, using a passive millimeter wave imager. The assumptions and essential physics behind the simulation are reviewed. The simulations are made in the atmospheric window at 90 GHz. Experimental data taken at 35 GHz is presented for comparison. It is demonstrated that metal objects have generally low radiation temperatures in relation to their environments. Plastics on the other hand can have higher or lower radiation temperatures than their backgrounds, dependent on the polarization, the type of earth, its condition and the amount of water present. In the cases demonstrated in this paper the simulations agree well the experimental data.

Determining slope stability in a mining operation is an important task. This is especially true when the mine workings are close to a potentially unstable slope. A common technique to determine slope stability is to monitor the small precursory movements, which occur prior to collapse. The slope stability radar has been developed to remotely scan a rock slope to continuously monitor the spatial deformation of the face. Using differential radar interferometry, the system can detect deformation movements of a rough wall with sub-millimeter accuracy, and with high spatial and temporal resolution. The effects of atmospheric variations and spurious signals can be reduced via signal processing means. The advantage of radar over other monitoring techniques is that it provides full area coverage without the need for mounted reflectors or equipment on the wall. In addition, the radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, twenty-four hours a day. The system has been trialed at three open-cut coal mines in Australia, which demonstrated the potential for real-time monitoring of slope stability during active mining operations.

This paper presents the first results on multistatic ultra wideband (UWB) ground penetrating radar (GPR) interferometry. It has been known that phase data may contain subtle information of the physical and geometrical properties. Most GPR antennas are used in near-field and/or Fresnel regions; the energy scattered from randomly rough surfaces appears diffusely and merely depends on the wavelength of the incident radiation and the incident angles. The random nature makes it a difficult task to determine the profile of the surfaces. Furthermore it is too time-consuming to solve this kind of three-dimensional inhomogeneous problems by using pure electromagnetic approaches, especially when real time applications are required. Therefore we initiated the research on near-field UWB GPR interferometry to profile randomly inhomogeneous rough surfaces as well as their shallow layers in three-dimensional space. In this paper we discuss the first results based on practically measured multistatic UWB phase data scattered from curved objects. An initial algorithm that was developed for image reconstruction in the surface height domain (SHD) has been applied to the measured data. The image patterns show good agreement with the geometries of the practical curved objects. The results demonstrate the applicability of the phase information to characterization of the curved objects.

Six experiments on remote sensing of soil moisture and surface roughness were carried out over bare fields with a microwave scatterometer at a frequency of 5.3 GHz during February 1998 and January-April 2000. Other two experiments in May and June 2001 were conducted under controlled field condition for putting in evidence the radar response sensitivity to soil moisture. Data analysis indicates that a clear dependence of backscattering coefficients on soil moisture variations, with an average sensitivity of 0.25 dB/gr/cm³, when other parameters as roughness and incidence angle remain constant. Regarding surface roughness, a rougher field shows more suitable characteristics for inversion purposes. In fact, backscattering coefficients retain a good sensibility on soil moisture content, after the removal of incidence angle effects. These remote-sensing campaigns are part of an extensive activity where angular and polarization microwave signatures for airborne and ground based radars are collected on bare soils in different soil moisture and roughness conditions.

In this paper we describe a directional borehole radar system. We first present the simulation and design of the antenna system. The antennas are positioned in a bistatic setup. In order to obtain a focused radiation pattern the transmitting and receiving dipoles are each shielded with a curved reflector. The radiation pattern of this scattered wavefield is computed by solving the integral equation for the unknown electric surface current at the conducting surface. Based on these numerical simulations, a prototype has been built. The radiation pattern measured in the plane perpendicular to the antenna is in good agreement with the computed pattern. Subsequently, we discuss a three-dimensional imaging method for this borehole radar. The computed radiation pattern is used in such a way that deconvolution for the angular radiation pattern can be applied. Some preliminary imaging results will be presented.

The generation and recording of electromagnetic waves by typical ground-penetrating radar (GPR) sounding systems is complex and the effects of the antennas on the recorded data are not well understood. To address this problem, we present a versatile and efficient GPR system simulation tool. This algorithm is based on a finite-difference time-domain (FDTD) approximation of Maxwell's equations and allows us to model realistically the radiation characteristics of a wide variety of typical surface GPR antenna systems. The accuracy of the algorithm is benchmarked and validated with respect to extensive laboratory measurements for comparable antenna systems. Given the flexibility of this GPR modeling software, we anticipate that it will be useful not only for the design and interpretation of GPR surveys, but also for the design of novel GPR sounding systems.

Migration is a common name for processing techniques that try to reconstruct, from the dat recorded at the surface, the reflecting structures in the sub-surface. Most of the existing migration techniques do not take into account the characteristics of the acquisition system and the ground characteristics. We propose a novel migration method, applicable on Ground Penetrating Radar (GPR) images, that integrates the time domain model of the GPR in the migration scheme. We calculate by forward modeling a synthetic 3D point spread function of the GPR, i.e. a synthetic C-scan of a small point scatterer. The 3D point spread function, containing system characteristics like the waveform of the excitation source, the combined antenna footprint and the impulse response (IR) of the antennas, is then used to deconvolve the recorded data. Results of this migration method on real data obtained by an ultra-wideband GPR system show that the migration method is able to reconstruct the top contour of small targets like AP mines, in some cases even the correct dimensions. The method is also capable of migrating oblique targets into their true position. The migration scheme is not computational intensive and can easily be implemented in real time.

A family of spectral estimation techniques, termed the PDFT algorithm, is applied to subsurface imaging. We compare various schemes to suppress the surface reflection in subsurface detection. For each scheme we investigate methods of incorporating information about the target and the background medium. The PDFT algorithm is used to extrapolate the target spectrum and provide sufficient resolution to identify buried objects. From experimental data we illustrate the performance of the PDFT algorithm as a superresolution imaging method, and assess its usefulness for subsurface imaging applications.

A group of algorithms of increasing complexity for the processing of bi-static fixed-offset Ground Penetrating Radar (GPR) data is considered, ranging from a simple Synthetic Aperture Radar (SAR) imaging to linearized effective and full-scale inversion. We consider only two-dimensional algorithms and discuss their applicability to real-life three-dimensional objects. A multi-stage interactive algorithm is proposed, which utilizes a filtered SAR-type imaging routine and a linearized inversion on a rough non-equispaced interactively constructed grid. The algorithm is tested on the experimental data obtained by the third party.

Designing optimized survey layouts for DC resistivity data is a difficult task. This is primarily due to the non-linear relationship between observed data and the subsurface resistivity structure. A possible solution is provided by real-time experimental design, a novel approach for acquiring geophysical data. Technical realization of real-time experimental design requires versatile recording facilities. We have developed a new multi-electrode system, that offers the necessary flexibility. Furthermore, our concept of distributed acquisition units with a digital layout enables the recording of high quality data.

In a composite board factory, the continuous permittivity monitoring of large-sized particle boards was to be solved using a microwave on-line sensor system. The method described below is based on a free-space / double transmission/ reflection type two-parameter (complex vector) measurement. A short description of the measurement set-up, the system-design and the design of the basic microwave elements are included. Using low cost MMICs, self-designed microstrip antennas and passive detectors/ modulated-backscatterers combined with modern digital spread-spectrum techniques made the realization of the concept possible.

Many theoretical studies have been reported on applications of ground penetrating radar (GPR) system to detect the permittivity and thickness of subsurface layers. However, to develop a GPR system that can accurately measure the thickness and the permittivity simultaneously is not a straightforward task. The main difficulty of quantitative thickness measurement is that the reflected wave from the subsurface interface is very weak compared to the directly coupled waves. The reflected signal may be completely submerged into the strong direct waves. Secondly, the inversion computation from measured data is very noise sensitive. In this paper, we present the development of a frequency-modulated-continuous-wave (FMCW) radar for quantitative layer thickness measurement. A new mathematical model for the calculation of depth and permittivity from the measured electromagnetic data is presented. The new model is based on the time delay between the direct wave and the reflected wave recorded by a bistatic radar. The data inversion algorithm considers the influences from air-ground interface. It is found that neglecting the air layer effects as the case applied in seismic analysis, the inversion will not be correct. This is because the electromagnetic rays from the GPR take different propagation path from straight or curved ray in seismic-like analysis. Ray path searching must be included in the calculation algorithm. With the consideration of wave path, the experimental results agree well with the actual values either in field test of in laboratory test.

Blades, knives, handguns and vehicles are similar targets for magnetic tracking purposes, and their differences can be described parametrically. These parameters can be used for classification, and to model the performance of a sensor node being used for a proposed application. The scaling laws that relate these parameters to actual performance will be reviewed and applied to a real world example. This computed noise limit will be contrasted with the practical limit observed in those measurements.

The objective of the presented research program is to design and develop a prototype system for measuring the length of a moving log in an outdoor environment. Investigations on different sensor concepts proved the suitability of certain radar and optical solutions. The two systems, one applying microwaves and evaluating the Doppler-shift, the other using digital image processing are described in detail.

A method is presented by which a complicated space-time domain electromagnetic wavefield in a lossless configuration may afterwards be transformed into the space-time domain field of a lossy configuration with a prescribed quality factor Q. The method is applicable to inhomogeneous and anisotropic media. Moreover, it may be employed to fields in 1D, 2D and 3D spatial configurations. The first step is the introduction of a specific loss model into the lossless Maxwell's equations. Two loss models will be presented. These are generalizations to the electromagnetic case of the elastodyanmic Scott-Blair stress-strain law and the elastodynamic Power Law, which yield a quality factor Q that is (nearly) constant over a long frequency range. Both loss models introduce fractional time derivatives in Maxwell's equations. The second step of the method relates the lossless and the lossy time domain Green's tensors by means of the similarity transformation technique. This approach has the benefit that an existing time domain wavefield for a lossless but otherwise intricate medium can be converted to the relevant lossy situation by a simple postprocessing step. Next, numerical results for both loss models will be shown. These will be compared with the results for a third loss model that is guaranteed to yield the correct arrival time. It is observed that the former two loss models cause deviations from the exact arrival time. However, these deviations are small except for high losses. As far as the shape of the time evolution of the fields is concerned, both loss models perform equally well, even in case of high losses.

A 3-D code has been designed to reconstruct the three-dimensional conductivity distribution in beds surrounding a wellbore from electromagnetic field data measured on the well axis. An arbitrarily oriented point magnetic dipole located on the well axis is considered as a source of electromagnetic radiation, where the well is parallel or normal to bed boundaries. In the specific case the solution to the vector Helmholtz equation for layered medium including the well and invasion zones is used to determine the background field E₀. The order/size of the finite-difference operator of Helmholtz equation for the secondary field E, which arises from the 3D properties of the geological medium that differ from the background medium, is reduced by the thinning method. Formal application of the method produces a set of equations that connect the measured secondary field values on the axis with the unknown conductivity model. A biconjugate gradient method and simple iterative updates on the conductivity model are used to find the solution to the thinned system of equations, where the solution to the equations for the conductivity perturbation is sought by traditional regularization functional minimization. Specific examples are presented, which illustrate the possibilities of the method. It is shown that the use of the thinning method allows for a significant reduction in computational expenditure, without appreciable loss in the quality of the conductivity reconstruction.

In medical diagnostics, non invasive optical techniques will become common at a variety of applications because they contribute to objectivity and precision. The spectral properties of human tissue are an important field of interest. They offer opportunities of detection of skin diseases and of evaluation of chronic wounds. In the visible range, the hemoglobin absorption corresponds to blood microcirculation and the melanin absorption to the skin-type. Two types of diode-array equipment will be described: a combined VIS-NIR spectrometer system from J&M Aalen/Germany (400 nm to 1600 nm) and a stand-alone spectrometer from COLOUR CONTROL Farbmesstechnik Chemnitz/Germany (400 nm to 1000 nm). Non-contacting sensing is essential for investigating chronic wounds (no disturbances of blood microcirculation by contact pressure). The spectroscopic VIS-NIR readings of chronic wounds mainly depend on the absorption of hemoglobin and water. Multivariate analysis was applied for an objective spectral classification of eight different wound scores. Some results regarding spectral measurements of wounds and skin will be discussed. The spectrometer of COLOUR CONTROL was tested in dental surgery. To select dentures, its color has to be determined exactly to meet beauty culture demands. Color determination by dentist is not sufficient enough because of possible metameric effects of illumination. Results of spectral evaluation of denture material and human teeth will be given. Medical examination requires portable and ease equipment suitable for precise measurements. This is solved by a modular measurement system comprising microcomputer, display, light source, fiber probe, and diode-array spectrometer. It is efficient to process primary spectral data to appropriate medical interpretations.

We have developed an excitation wavelength tunable Raman system which consists of a spectrometer, a CCD detector and an electronically tuned Ti:sapphire (ETT) laser. All those components are controlled with a single computer. This system is useful for Raman excitation profile measurements. A new technique was developed to calibrate deviation of wavelengths of ETT laser from that of Raman spectrometer within +/- 1.5cm^-1 of error. Obtained Raman spectra of hemoglobin measured with various excitation wavelengths in 700-860 nm range showed characteristic change of their intensities in some of Raman bands. Assignments of Raman bands were carried out sufficiently in help with change in intensity of the bands which reflect symmetric character of the responsible vibrational modes with the change in excitation wavelength.

The advanced methods of fiber optical vibrational spectroscopy (FOVS) has been developed in conjunction with interferometer and low-loss, flexible, and nontoxic optical fibers, sensors, and probes. The combination of optical fibers and sensors with Fourier Transform (FT) spectrometer has been used in the range from 2.5 to 12micrometers . This technique serves as an ideal diagnostic tool for surface analysis of numerous and various diverse materials such as complex structured materials, fluids, coatings, implants, living cells, plants, and tissue. Such surfaces as well as living tissue or plants are very difficult to investigate in vivo by traditional FT infrared or Raman spectroscopy methods. The FOVS technique is nondestructive, noninvasive, fast (15 sec) and capable of operating in remote sampling regime (up to a fiber length of 3m). Fourier transform infrared (FTIR) and Raman fiber optic spectroscopy operating with optical fibers has been suggested as a new powerful tool. These techniques are highly sensitive techniques for structural studies in material research and various applications during process analysis to determine molecular composition, chemical bonds, and molecular conformations. These techniques could be developed as a new tool for quality control of numerous materials as well as noninvasive biopsy.

The field of microtechnology is an important industrial and scientific resource for the 21st century. There is a great interest in spectroscopic sensors in the near and middle infrared (NIR-MIR) wavelength regions (1 - 2.5 micrometers ; 2.5 - 4.5 micrometers ; 4 - 6 micrometers ). The potential for cheap and small devices for nondestructive, remote sensing techniques at a molecular level has stimulated the design and development of more compact analyzer systems. Therefore we will try to build analyzers using micro optical components such as micromirrors and embossed micro gratings optimized for the above mentioned spectral ranges. Potentially, infrared sensors can be used for rapid nondestructive diagnostics of surfaces, liquids, gases, polymers and complex biological systems including proteins, blood, cells and cellular debris as well as body tissue. Furthermore, NIR-MIR microsensing spectroscopy will be utilized to monitor the chemical composition of petrochemical products like gasoline and diesel. In addition, miniature analyzers will be used for rapid measuring of food, in particular oil, starch and meat. In this paper we will present an overview of several new approaches for subsurface and surface sensing technologies based on the integration of optical micro devices, the most promising sensors for biomedical, environmental and industrial applications, data processing and evaluation algorithms for classification of the results. Both scientific and industrial applications will be discussed.

Acute Lymphoblastic Leukemia (ALL) accounts for majority of the childhood leukemia. Outcome of children with ALL treatment has improved dramatically. Sensitive techniques are available today for detection of minimal residual disease in children with ALL, which provide insight into the effective cytotoxic treatment. Here, we present a case study, where lymphocytes isolated from two children before and after the treatment were characterized using microscopic Fourier Transform Infrared spectroscopy. Significant changes in the absorbance and spectral pattern in the wavenumber region between 800-1800 cm^-1 were found after the treatment. Preliminary analysis of the spectra revealed that the protein content decreased in the T-lymphoma patient before the treatment in comparison to the age matched controls. The chemotherapy treatment resulted in decreased nucleic acids, total carbohydrates and cholesterol contents to a remarkable extent in both B and T lymphoma patients.

A variety of progress concerned with an electronically tuned Ti:sapphire laser with an acousto-optic tunable filter for the purpose of spectroscopic applications are described. The major advances are that fast and random access tuning can be achieved in a tuning range of 690-1056 nm by computer control without any mechanical changes of cavity. The access speed reached to 250 microsecond(s) . The Ti:sapphire laser also provided tunable dual-wavelength operation in a single laser cavity with introducing two different radio frequencies at same time. The operation was promising as a pumping source of difference-frequency generation. Difference-frequency generation of non-mechanical tuning was realized from 6.0 to 7.1 micrometers , from 6.8 to 8.6 micrometers , and from 8.5 to 11.3 micrometers for the phase-matching angle at 58, 53, and 46 deg, respectively, using the dual-wavelength laser. Furthermore, the electronic tuning by acousto-optic tunable filter achieved broad tunable picosecond pulse generation with only computer control.

New applications for the Fiberoptic Evanescent Wave Fourier Transform (FEW-FTIR) method have been developed for the diagnostics of skin surfaces. Our technique allows for the detection of functional groups in the molecular structure of skin tissue noninvasively and in vivo. The FEW-FTIR spectroscopic method is direct, nondestructive, and fast. Our optical fibers for the middle infrared (MIR) range are nontoxic, nonhygroscopic, flexible, and characterized by extremely low losses. This combination of traditional FTIR spectroscopy and advanced fiber technology has enabled us to noninvasively investigate normal skin tissue in vivo in the range of 900 to 4000 cm^-1. The second derivative spectra of the baseline-corrected and normalized data have been calculated to determine the peak positions. We have obtained for the first time a more detailed understanding of normal skin tissue fusing FTIR spectroscopy. Despite the complex nature of human skin tissue, the MIR spectra of normal human skin surface tissue has some basic characteristics seen in all cases. The results of our surface analysis of skin tissue are discussed in terms of spectral parameters, band assignments, and molecular structural similarities and differences. Our results have revealed that our spectral parameters can be separated into four distinct classes, providing us with a preliminary model of normal human skin tissue.

In this paper, a nondestructive method for the non-contact characterization of non-planar dielectric objects is presented. Traditionally, this kind of measurements is achieved by using spot-focused antennas associated to a vector automatic network analyzer. In this study, we propose a free space measurement system, fitted out with a classical horn antenna, which demonstrates its usefulness in many practical cases. The permittivity is computed from the reflection coefficient of metal-backed samples of different shapes at 2.45 GHz.

This paper compares our proposed new method to the former methods for density-independent moisture measurement using microwave free-space technique. The measurement setups and the published results of the two methods are summarized and compared. The methods are compared in the aspects of accuracy and moisture range based on the measurements for the same samples of green tea and timber. It is shown that the accuracy by the new method is better than that by the former method for both materials in the moisture range from 2 to 30%. The results also indicates that the new method has the feature to be able to measure wide moisture range. The new method measures moisture content up to 42% for green tea, in contrast to the former method, by which the maximum measurable moisture content is approximately 30%.

As part of a study using GPR to quantitatively determine Volumetric Moisture Content (VMC) spatially for hillslope hydrology and water leak detection applications, a series of controlled laboratory experiments were conducted to investigate material-specific GPR response to different VMC conditions. Using a specially developed GPR-soil hydrology test facility, six materials were tested with incremented moisture from dry to saturation. A number of directly derived GPR trace parameters acquired using Reflection Profiling Mode were used to develop and test VMC-GPR relationships to enable GPR measurement of soil moisture and to determine the effect of different material properties on hydraulic characteristics and how this is manifested in GPR response. Data was analyzed in both the time and frequency domains as a depth-average and at specific depths beneath the subsurface. The most consistent parameter investigated used was the mean instantaneous amplitude. A strong textural dependence related to how the water interacted with the host material suggests that individual models can be combined to form a moisture response model for GPR based on the particle size distribution of a material. This only works for well-structured materials and where there is a relatively simple subsurface structure and where other system interference is low.

Microwave remote sensing is a good tool for topsoil moisture monitoring due to the large difference between dielectric properties of dry soil and water. The aim of this work is to exploit microwave remote sensing techniques to collect data on soil water content of large areas rapidly and without direct soil samples analysis. To this purpose, a frequency modulated - continuous wave C-band microwave polarimetric radar has been built. The device has two transmitting channels that illuminate the soil with orthogonal linearly polarized electromagnetic waves. Two receiving channels detect the linearly polarized waves backscattered from the same target. This scatterometer can measure the module of the soil electromagnetic scattering matrix elements. The knowledge of this matrix permits the computation of all the possible polarization combinations of backscattering normalized Radar Cross Section (RCS) through a polarization synthesis approach. A Fourier analysis of this signal extracts the scattering matrix values of different-in-range resolution cells. The height and the incidence angle of this microwave sensor can be varied within large intervals; this allows the measurements of the RCS in various configurations that should give insights on soil moisture parameter extraction under different conditions.

Two broadband methods for simultaneously measuring the complex values of the permittivity and permeability of film-shaped materials are presented. The complex properties of these materials are calculated from S-parameter measurements of coplanar or microstrip cells propagating the quasi-TEM dominant mode. The S-parameter measurements are easy to be implement. They are carried out from a network analyzer and on-wafer systems allowing different sizes of cell and covering 0.05-40 GHz. In the case of the coplanar, the dispersion is very low for a cell shape such as h>W+2S. Thus, a fast extraction method of the coplanar substrate properties ((epsilon) _r,(mu) _r ) has been developed from analytical relationships. It is faster than the microstrip extraction method, which requires a numerical method for a rigorous analysis of the microstrip cell in order to take into account the quasi-TEM mode dispersion. Measured (epsilon) _r and (mu) _r data for several materials are presented in the 0.05 GHz to 40 GHz frequency range. These methods show good agreement between measured and predicted values.

In this paper a two-port slot sensor for measuring the moisture content of sheetlike materials is proposed and analyzed. The sensor is of the resonant type and it mainly consists on a section of a slot-line interacting with the material under test (MUT) by means of radiative near fields. The most important design aspects of the sensor are discussed in relation to the dispersive behavior of the slot line and its radiative interaction with the MUT. The article deals with the full-wave numerical modeling of the interaction between the sensor and a moist felt, chosen as reference MUT. The parametric sensitivity to the distance between the slot radiating aperture and the MUT surface is also analyzed, since in the industrial environment the monitoring of the moisture content is usually performed by linearly scanning the sensor over the material surface. Finally, a calibration and measuring procedure based on the use of a neural artificial network is suggested and its accuracy is numerically evaluated.

This paper addresses the task of automatic detection and characterization of the signatures of solid reflecting targets in ground-penetrating radar data. The images generated by ground-penetrating radar are of a much lower resolution than conventional images, due to the ratio of the wavelength of the radiation and the physical dimensions of the target, and hence do not correspond to the geometrical representation of the targets. For the class of target under consideration, namely localized or extended linear reflecting targets such as land-mines, pipes or cables, the reflections exhibit a broad hyperbolic anomaly in the region of the target. Detection and characterization of these distinctive signatures yields information about the location of the targets as well as the surrounding medium. Edge enhancement and edge processing techniques are developed to trace the envelope of the reflected wavefronts. By fitting hyperbolae to these detected edges, the location of the targets and the relative permittivity of the medium are estimated. This estimate enables the effective elimination of the background clutter that leads to spurious non-hyperbolic reflections. Thus automatic target detection and mapping is achieved without the heavy computational demands of techniques such as synthetic aperture radar processing, enabling on-site data interpretation.

A linear spectral estimator, referred to as the PDFT was previously used to reconstruct a target in a homogeneous background. More typically, a target will have other objects or noise around it. We address this problem for the general case of having several targets embedded in clutter and apply the PDFT to each target sequentially. We show that in such cases the regularization process and the choice of what prior knowledge is included in the reconstruction algorithm play key roles in obtaining a good image.

In this paper a high-speed procedure for motion tracking of endocardium is presented. If a contour is available in the first frame of a sequence, the contours on the subsequent frames are segmented. Deformable active contours is a technique that combine geometry, physics and approximation theory to solve problems with fundamental important into medical image analysis like segmentation, representation and matching of shapes, and tracking of objects in movement. The procedure was implemented on a DSP processor (TMS320C6701) using its hardware characteristics massively. The results are illustrated on a sequence of four-chambers apical images.

Surface acoustic wave (SAW) devices, used as filters or diplexers, are well established components in communications applications like in mobile handsets or television sets. The characteristics of SAW devices make them also well suitable for the application of wireless sensors or wireless identification tags. A great advantage of SAW sensors is their completely passive operation without the need for additional power supplies. SAW sensors can be designed to sense several physical or chemical quantities like temperature, pressure, stress, or gas concentration. During operation of the wireless sensor the energy delivered from an RF pulse sent by an interrogation unit is picked up by the antenna, stored in the surface acoustic wave, modified by the sensor effect and is finally transmitted back to the interrogation unit. In this paper the basic operating principles of SAW devices are reviewed and two applications, a state-of-the-art tire pressure sensor and a moisture sensor, are presented.

This problem involves magnetic induction methods to locate and determine the depth of a subsurface line source of magnetic field. The origin of the field may be self- generated or induced by a surface transmitter. The experimental method requires measuring the horizontal gradient of either the vertical or horizontal component of the field rather than the field itself so as to increase signal to noise ratio. A mathematical outline is presented and experimental results are discussed.

Loss of water from urban water supplies is becoming an increasingly significant problem. Standard procedures for identifying and repairing a mains water leak can be time- consuming, disruptive and expensive. In association with Thames Water Utilities Ltd. the potential of GPR to accurately and efficiently detect mains water leaks has been investigated. The approach adopted here is to measure subsurface moisture conditions using GPR and from this locate the source of the leak. Common Mid-point velocity analyses for moisture measurement cannot be used since they are time-consuming. More direct methods have been employed utilizing GPR parameters (such as trace mean, maximum and minimum amplitudes, amplitude and phase spectra and other waveform characteristics) measured in Reflection Profiling Mode. Knowledge of the effects of subsurface leakage moisture on the GPR return was used to map the location of a number of mains water leaks. A combination of amplitude techniques in time and frequency domains was successful but is limited by substantial impact of other system components on the returned responses and by the depth of investigation. This necessitates field calibration to correctly quantify soil moisture, otherwise the technique becomes a relative measure in which some dielectric patterns are not associated with the leak itself.

Historically, the communities of engineers and scientists who image objects under the ground, under the ocean, inside the body, and inside the cell, have had relatively little contact, despite dealing with similar issues and often using similar mathematical models and algorithms. CenSSIS, the Center for Subsurface Sensing and Imaging Systems, is an NSF Engineering Research Center, developed to bring these seemingly disparate fields together. Conceived at Northeastern University, the Center now has four university partners, four affiliates, and a growing number of corporate and government sponsors. CenSSIS was established to solve real--world problems in these and other fields, to spark revolutionary advances by developing a unified framework for subsurface sensing and imaging systems, and to immerse students and researchers in a multi--disciplinary teaching and learning environment. Already this effort has begun to bear fruit. Here we report on the first full year of activity as an Engineering Research Center.

Diffusive optical tomography provides a technique for imaging the human body using modulated laser light. The modulation of the light allows measurement of the amplitude and phase of the modulation, which improves the spatial resolution over that which could be obtained with unmodulated light. Diffusive optical tomography is normally described by a diffusion equation for photon density. An alternative description considers the propagation of an optical carrier and two sidebands, and the diffusive wave is the mathematical result of the slight differences among the carrier and sidebands, the result being described as a wave at the difference frequency. This suggested that the use of multiple, closely spaced frequencies might be advantageous in other subsurface imaging. Here we discuss an application to landmine detection under a rough surface.