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A low-cost 1 kHz–400 kHz operating frequency fully-active electrode bioimpedance measurement module, based on Howland current source, is presented in this paper. It includes a buffered positive feedback Howland current source, implemented with operational amplifiers, as well as an AD8421 instrumentation amplifier, for the differential voltage measurements. Each active electrode module can be connected to others, assembling a wearable active electrode module array. From this array, 2 electrodes can be selected to be driven from a THS413 fully differential amplifier, activating a mirrored Howland current source. This work performs a complete circuit analysis, verified with MATLAB and SPICE simulations of the current source’s transconductance and output impedance over the frequency range between 1 kHz and 1 MHz. Resistors’ tolerances, possible mismatches, and the operational amplifiers’ non-idealities are considered in both the analysis and simulations. A comparison study between four selected operational amplifiers (ADA4622, OPA2210, AD8034, and AD8672) is additionally performed. The module is also hardware-implemented and tested in the lab for all four operational amplifiers and the transconductance is measured for load resistors of 150 Ω, 660 Ω, and 1200 Ω. Measurements showed that, using the AD8034 operational amplifier, the current source’s transconductance remains constant for frequencies up to 400 KHz for a 150 Ω load and 250 kHz for a 1200 Ω load, while lower performance is achieved with the other 3 operational amplifiers. Finally, transient simulations and measurements are performed at the AD8421 output for bipolar measurements on the 3 aforementioned load resistor values.

An impedance surface is presented that reduces the dispersion experienced upon propagation of broadband pulses within rectangular waveguides. The surface impedance is selected so that, within a frequency range, the transverse resonance condition is satisfied for longitudinal wavenumber that varies linearly with frequency. A synthesis procedure for practical surface topologies consisting of periodic dipole arrays is described. An example involving a finite structure is employed to illustrate the reduced dispersion. Numerical simulation results obtained from in-house mode-matching method as well as HFSS are presented. A prototype is fabricated and tested experimentally validating the theoretical predictions.

Accurate and timely detection of leaks in water supply pipes is a significant environmental issue. Development of efficient non-invasive methods would lead into significant water saving and prevention of health hazards introduced by water leakage. This paper shows the ability to use a High Resolution Ground Penetrating Imaging Radar (GPIR), to be used as an instrument for water pipeline rehabilitation situations, parallel to the existing industrial equipment. In the framework of the European research initiative WATERPIPE, a Decision Support System (DSS) for the rehabilitation management of the underground water pipelines has been developed, parallel to the implementation of the GPIR. This paper briefly presents the system design, the basic principles of the algorithms' implementation and some indicative results from the initial use of the GPIR system.

The Virtual Cathode Oscillator (Vircator) is a high power microwave tube with simple design principles, ease in operation, low maintenance and capability of operating in a wide range of vacuum conditions. The effect of residual gas pressure on the output of a low-voltage, vertical extraction Vircator is examined. It can be experimentally observed that a rough vacuum, in the order of 10−3 Torr, can still be adequate for normal Vircator operation. Higher pressures result in significant reduction of the power and duration of the microwave pulses. Deterioration on the output is rapid and microwaves cease for pressures over 10−2 Torr.

This research presents the development and testing procedures for an experimental phased-array cylindrical-antenna transmitting system, operating at 10 GHz. The antenna-element excitation phases are set at the intermediate-frequency stage, and are determined by using a least-squares radiation-pattern synthesis technique. The antenna-element excitation amplitudes are taken to be equal and fixed. The system provides steerable main lobes and nulls at predefined directions, including control of the sidelobes at specified levels. It can be used for communications and radar applications with interference-rejection requirements.

This paper investigates the data association problem for a multiple target tracker, in dense clutter environment, using multiple bistatic range and range-rate measurements from a number of bistatic radars, composing a multistatic radar. Special emphasis is given to the initialization procedures, where a multiple hypothesis logic is adopted to resolve 'ghost'-targets, frequently generated by range-only multisensor systems. The contribution of the paper is twofold. First, the development and implementation of the multiple target tracker algorithm is presented, including filtering, association and track management. The proposed algorithm includes: (i) global nearest neighbor (GNN) based on auction algorithm combined with a heuristic multiple hypothesis logic for new track initialization; (ii) interacting multiple model algorithm combined with iterated unscented Kalman filter (IMM-I-UKF); (iii) and a rule-based track management. Second, a set of performance metrics is chosen to evaluate the performance of the algorithm presented. Monte Carlo simulation demonstrates the track accuracy, probability of correct association, robustness and computational complexity for numerous scenarios of multiple targets (crossing track patterns, closely spaced or manoeuvring targets), for different values of clutter density and probability of detection. Finally, comparisons with other widely used methods prove the superiority of the proposed algorithm.

The fundamental concept of coupled-resonator optical waveguides (CROWs) is for the first time taken a step farther to propose the more complicated case of coupled-resonator directional couplers, by analyzing the phenomenon of propagation in two parallel chains of microring resonators. Using the method of transfer matrices it is shown that the infinite coupler supports even and odd supermodes that satisfy frequency-shifted replicas of the familiar CROW dispersion equation as well as modified periodic Floquet conditions. Depending on the relative coupling strengths between neighboring resonators in the same chain and between the two chains, the frequency bands of the supermodes can overlap or be completely separated, resulting, in the latter case, to a complete bandgap around the central resonance frequency of the microrings. Three frequency windows, corresponding to totally different properties of directional coupling, are defined through this band-overlap mechanism along the increased total bandwidth of the coupler. These predictions are fully confirmed in the response of the realistic finite-length version of the considered coupler which is also analyzed.

The key technology of the future will be the use of low-cost sensor networks in order to replace large aperture antennas. The proposed multistatic radar system is composed of a transmitter, a number of receivers, dispersed in a lower altitude area, and a central processing station. Each receiver extracts the targets bistatic range and range-rate information, while estimating their azimuth angle. The receiver bistatic measurements, after local data processing, are sent to a central processing station, where three dimensional multiple target tracking is conducted. The main objective of the proposed multistatic radar system is to increase the detection probability of targets with low monostatic RCS, taking advantage of the Bistatic Radar Cross Section (BRCS) and the low operating frequency (low UHF band). Furthermore, the transmitter is only charged with the operation of emitting a Frequency Modulated Continuous Wave (FMCW) signal and an appropriate synchronization beacon, while the receiver performs a totally passive function. The main design objective is the use of a low cost radar sensor which performs an unsophisticated operation, while the main system functionality is accumulated in the central processing station.

As the result of a collaboration between the Detector and Imaging Group of Thomas Jefferson National Accelerator Facility (US), the Institute of Radioisotopes and Radiodiagnostic Products (IRRP) of N.C.S.R. ldquoDemokritosrdquo and the Biomedical Simulations and Imaging Applications Laboratory (BIOSIM) of National Technical University of Athens (Greece), a mouse sized camera optimized for Tc99m imaging was developed. The detector was built in Jefferson Lab and transferred to Greece, where it was evaluated with phantoms and small animals. The system will be used initially for planar dynamic studies in small animals, in order to assess the performance of new radiolabeled biomolecules for oncological studies. The active area of the detector is approximately 48 mm times 96 mm. It is based on two flat-panel Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT), a pixelated NaI(Tl) scintillator and a high resolution lead parallel-hole collimator. The system was developed to optimize both sensitivity and resolution for in vivo imaging of small animals injected with technetium compounds. The results of system evaluation in planar mode with phantoms are reported. Results are presented for in vivo dynamic studies of mice injected with > 100 muCi of two conventional and novel radiopharmaceuticals, namely Tc99m-MDP and Tc99m -Bombesin.

A mouse sized camera has been built in terms of collaboration between the presenting institutions. The system is used for the performance of dynamic studies in small animals, in order to evaluate novel radiopharmaceuticals. The active area of the detector is approximately 48×96 mm allowing depiction of the entire mouse in a single view. The system is based on two flat-panel Hamamatsu H8500 position sensitive photomultiplier tubes (PSPMT), a pixellated NaI(Tl) scintillator and a copper–beryllium (CuBe) parallel-hole collimator. In this work, the evaluation results of the system are presented, using phantoms and small animals injected with conventional radiophrmaceuticals. Average resolution was ∼1.6 mm on the collimator surface and increased to ∼4.1 mm in 12 cm distance from the detector. The average energy resolution was measured and found to be ∼15.6% for Tc99m. Results from imaging thin capillaries demonstrated system's high resolution and sensitivity in activity variations was shown. Initial dynamic studies have been carried out in small animals injected with Tc99m-DTPA and Tc99m-MDP. The results show system's ability to perform kinetic imaging in small animals.

The radiation properties of a hemispherical dielectric resonator, consisting of a monopole antenna placed in a dielectric hemisphere is theoretically examined. A method based on the combination of Green's function theory, in conjunction with the Method of Auxiliary Sources (MAS), is used to solve analytically and calculate the electromagnetic field at any arbitrary point of the structure. The Green's function theory is used to calculate the response of the hemisphere to an excitation consisting of an elementary dipole placed inside its volume. The Method of Auxiliary Sources (MAS) is applied by distributing a set of elementary dipoles along the axis of the antenna probe. A number of matching points, lying on the surface of the cylindrical antenna, are used to calculate the dipole moments of the auxiliary sources, by imposing appropriate boundary conditions. Additionally, the input impedance and the current distribution on the antenna are also derived through application of the above-mentioned methodology....

Two novel Marconi-Franklin type printed antenna arrays, each consisting of three radiating elements arranged in a cascade configuration, are investigated. Both antennas are printed on a single high permittivity dielectric substrate and fed by SMA connectors, although coplanar waveguide (CPW) feed could easily be applied to further allow easier integration into an RF chip module. Two constructed prototypes, suitable for local-multipoint-distribution service operation in the 26-GHz band (25.5-26.5 GHz), are demonstrated. The constructed prototypes show an impedance bandwidth of about 1 GHz and a maximum gain of more than 5 dBi, with small variations (

This paper presents an experimental Phased Array Antenna System operating at 10 GHz. Geometry of the antenna array is cylindrical. Antenna element excitation phases are adjusted at the intermediate frequency stage. Antenna element excitation amplitudes are taken to be constant. A least squares technique is used for phase computation and radiation pattern synthesis. The obtained radiation patterns provide steerable main lobes and nulls at predefined directions including control of the side lobes at specified levels. Units of the system are presented in detail and their architecture is explained. A phase calibration is used to compensate the system. Measurements of radiation patterns are presented and are compared with calculated patterns.

Electromagnetic wave propagation at the microwave region, when a weakly disturbed sea surface is covered with a tropospheric duct, is analyzed theoretically and studied experimentally. A layered medium field solution using a perturbative approach to account for the reflection on the sea surface is used while reasonable approximations are used to compute the “channel response” of the tropospheric medium. Numerical results are computed for several cases of propagation media which show qualitative match to experimental measurements. Finally, the developed “channel response” model is utilized to extract valuable conclusions on the effects of environmental parameters to the detection performance of L and S band surveillance radars operating under anomalous propagation conditions.

The switching operation of a nonlinear dual-core photonic crystal fiber (PCF) coupler, based on a highly nonlinear As2Se3 chalcogenide glass, is numerically studied for the first time. Combining the standard coupled-mode formulation with a full-vectorial integral equation analysis of the PCF geometry, we show that the device parameters can be tailored to achieve switching power requirement ∼1 W at a coupler length of only few centimeters. The dispersion results show that efficient switching can be attained for pulsewidths greater than ∼2 ps.

The multistatic radar proposed in this paper is composed of a transmitter, placed in a high altitude site, at least four receivers distributed in a low altitude area and a central processing station. The transmitter emits a FMCW signal in the air which is reflected by the natural environment and the targets inside the radar's coverage area. The line of sight signal and the collected signal scattered from the surrounding objects are collected from each receiver and a processing algorithm is applied to measure range/doppler and separate the moving air vehicles from the stationary targets (clutter). The targets' range/doppler measurements from every receiver are sent to a central processing station where data fusion of the distributed measurements is performed. A list of the existing tracks is maintained, updated and managed, while deghosting is also applied to remove the pseudo-targets generated from geometrical ambiguities. The main goal of this multistatic radar system is to take advantage of the bistatic...

Focused microwave radiometry, aiming mainly in clinical applications at measuring temperature distributions inside the human body, may provide the capability of detecting electrical conductivity variations at microwave frequencies of excitable cell clusters, such as in the case of brain tissues. A novel microwave radiometric system, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed for the imaging of biological tissues via contactless measurements. The measurement is realized by placing the human head in the region of the first focus and collecting the radiation converged at the second by an almost isotropic dipole antenna connected to a sensitive radiometer operating at 3.5 GHz. In order to compute the focusing properties of the ellipsoidal reflector, an accurate electromagnetic numerical analysis is developed using a semianalytical method. The experimental part of this study focuses on measurements of activation of the primary somatosensory (SI) brain area, elicited during the application of the cold pressor test, a standard experimental condition inducing pain. Analysis of the measured data from 16 healthy subjects suggests that this methodology may be able to pick up activation of the SI during the pain conditions as compared with the nonpainful control conditions. Future research is needed in order to elucidate all the interacting factors involved in the interpretation of the presented results. Finally, potential limitations to the generalization of our results and strategies to improve the system's response are discussed.

This paper shows the ability to use a continuous wave (CW) radar as an instrument to search for trapped alive persons in demolished buildings and ruins. The utilized operation principle is the detection of the Doppler frequency shift of the E/M wave when it is reflected by a slightly moving part of a living human body. The presented system has gone through several prototype development phases. Many parameters and alternative implementations have been tested in both real and simulated sites. A system analysis is carried out and presented followed by a presentation of the signal processing techniques. The inherent difficulties for the realization and practical exploitation of such a system are discussed. Results from tests of the system are also presented.

The coupling between a finite-length dipole antenna and a three-layer lossy dielectric sphere, representing a simplified model of the human head, is analyzed theoretically in this paper. The proposed technique is based on the theory of Green's functions in conjunction with the method of auxiliary sources (MAS). The Green's function of the three-layer sphere can be calculated as the response of this object to the excitation generated by an elementary dipole of unit dipole moment. The MAS is then applied to model the dipole antenna by distributing a set of auxiliary current sources on a virtual surface lying inside the antenna physical surface. By imposing appropriate boundary conditions at a finite number of points on the real surface of the antenna, the unknown auxiliary sources coefficients can be calculated and, hence, the electric field at any point in space can be easily obtained. Numerical results concerning the specific absorption rate inside the head, the total power absorbed by the head, the input impedance, and the radiation pattern of the antenna are presented for homogeneous and layered head models exposed to the near-field radiation of half-wavelength dipoles at 900 and 1710 MHz. The developed method can serve as a reliable platform for the assessment of purely numerical electromagnetic methods. The method can also provide an efficient tool for accurate testing and comparison of different antenna designs since generalizations required to treat more complex antenna configurations are straightforward.

A rigorous full-wave analysis is employed to analyze a shielded microstrip T-junction. A method of moments technique is employed on the T-junction apertures of microstrip lines. A multi-step Green's function approach is employed to determine the integral equations related to aperture fields. In this context the Green's function of the T-junction enclosed inside a shielded microstrip is determined by applying semi-analytic techniques. The scattering parameters of the T-junction are computed for various cases and are presented for a wide range of frequencies. The importance of shielding box modes is investigated.

The propagation characteristics of multiple coupled rectangular dielectric waveguides are investigated through an integral equation analysis. In contrast with the widely used subdomain-basis Galerkin's method, in this work a novel set of entire-domain basis functions is introduced. This set consists of plane wave functions that satisfy Maxwell's equations in each guiding region, therefore representing a proper expansion system. The simple form of the basis functions employed enables the accurate numerical evaluation of the spectral integrals, by means of an efficient asymptotic extraction technique. It is found that the computed dispersion curves presented for various single and coupled waveguides compare very favorably to published results of other methods. Finally, leakage effects in lossy waveguides are numerically treated for the first time, in view of mode transitions from leaky to bound regime. The technique presented in this paper is accurate, though conceptually simple, and can deal with a wide variety of integrated circuits and multilayered substrate configurations. It is also demonstrated that its main advantage is superior computational efficiency, since very satisfactory results are obtained with only a few expansion terms.

Microstrip asymmetric step discontinuities are analyzed using a mode-matching technique, leading to the frequency-dependent characteristics of the structure. On both sides of the discontinuity the fields are expanded in terms of the normal even and odd hybrid modes of shielded microstrip lines, taking into account not only the propagating modes but also higher-order even and odd modes, which are evanescent-type waves. The propagation constants of the even and odd hybrid modes are computed using a previously developed method. Then a mode-matching technique is applied in order to obtain the reflection and transmission coefficients of the discontinuity. Numerical results are given for several asymmetric step discontinuities. >

Many EU cities are experiencing increasing problems with their water pipeline infrastructure. The cost of replacing these old, worn-out systems, if left to deteriorate beyond repair, is astronomical and clearly beyond the resources of many communities. Replacement, however, is not the only choice as many of these systems can be rehabilitated at 30 to 70 percent of the cost of replacement. Accordingly, resources are now increasingly being allocated to address pipeline rehabilitation management issues. Due to the emphasis on sustainable management, risk-based approaches for the rehabilitation management of the water supply network need to be developed. Rehabilitation decisions should be based, interalia, on inspection and evaluation of the pipeline conditions. Yet, utilities cannot locate a number of their old pipes and current inspection technologies typically do not provide the needed detailed information on pipeline damage. The objectives of this book are to describe the research work carried out in the framework of WATERPIPE project aiming: This title belongs to European Water Research Series . ISBN: 9781843393719 (Print) ISBN: 9781780401560 (eBook)

Radiation from a monopole antenna placed over an infinite size perfect conductivity ground plane and covered by a finite height dielectric cylinder is examined. The axial symmetry of the structure and of the excitation simplifies the analysis. A two step approach is applied to determine the radiation properties of the monopole antenna. In the first place, the radiation from an elementary annular current source embedded inside the finite height dielectric cylinder is determined. After determining the Green's function, in the second step, an integral equation on the monopole antenna source is solved by Galerkin's technique to compute the current distribution. Input impedances and radiation patterns are derived in terms of the current distribution on the monopole antenna. Numerical results are presented for several cases.

We demonstrate recent advances towards the development of a novel 2-D THz imaging system for brain imaging applications both at macroscopic and at biomolecule level. A frequency synthesized THz source based on difference frequency generation between optical wavelengths is presented, utilizing supercontinuum generation in a highly-nonlinear optical fiber with subsequent spectral carving by means of a fiber Fabry-Perot filter. Experimental results confirm the successful generation of THz radiation in the range of 0.2-2 THz, verifying the enhanced frequency tunability properties of the proposed system. Finally, the roadmap towards capturing functional brain information by exploiting THz imaging technologies is discussed, outlining the unique advantages offered by THz frequencies and their complementarity with existing brain imaging techniques.

The pole and zero matching method has been applied for the dispersion analysis of waveguides loaded with metamaterial surfaces. Very good agreement with commercial software packages has been observed. This allows to produce a synthesis procedure, where the admittance characteristics of the metasurface are designed to meet the dispersion requirements. A matched finite structure has been designed and fabricated. Preliminary experimental results suggest successful matching of the structure.

Integrated circuit packages employed in high-speed digital systems are studied theoretically by employing an equivalent circuit in terms of lumped elements. Each package track is modelled as an isolated lossless transmission line. The identification of the parameters used in this model is performed by employing electromagnetic field theory concepts. Pulse transmission through package tracks is examined.

In this analysis, the excitation is taken to be either (1) the lowest-order transverse electric (TE) or the lowest-order transverse magnetic (TM) (i.e. transverse electromagnetic) waves, or (2) a uniform, E- or H-polarized, incident plane wave. As a result of the anisotropy, cross-polarization effects are observed. The formulation of the boundary-value problem is carried out in the Fourier transform domain. Considerable contraction results by using previously developed matrix analysis techniques. In this way, a fruitful integral representation of the tangential components of the magnetic field is first derived in terms of the tangential components of the electric field at the excitation aperture. Next, and after imposing the boundary conditions at the aperture boundary surface, this representation is used as the starting point for a solution on the basis of a moment method (MM) approach using the eigenmodes as basis and weighting functions. Numerical results related to the reflection and coupling coefficients as well as the directive diagrams of the structure are presented in graphical form for various cases. >

The radiation properties of linear log-periodic dipole array antennas placed near a finite conductivity earth is investigated analytically. A method of moment solution is developed to solve the integral equation associated with the log periodic antenna array. The effect of finite ground conductivity is taken into account by using the appropriate Green's function which is derived from the well known Sommerfeld solution of the finite conductivity semi-infinite space. Piecewise sinusoidal pulse functions are employed as describing and testing functions. In computing the mutual impedance matrix elements, Sommerfeld type integrals are encountered which are computed by applying a numerically efficient technique. After computing the current distributions on the dipole elements of the log-periodic array the far field of the antenna is computed by employing the stationary phase integration technique. Several type log-periodic dipole arrays placed near a finite conductivity ground are computed. The effects of condu...

The capability of detecting electrical conductivity variations using focused microwave radiometry, a method used in clinical applications for temperature distribution imaging of subcutaneous tissues, is discussed in the present study. A novel microwave radiometric system operating at 3.5 GHz, including an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing, is developed. The system is capable of providing distribution measurements of the product of conductivity and temperature of any object being at a temperature above the absolute zero. The implemented experimental procedure is based on the results of an electromagnetic numerical analysis using a semianalytical method which was developed in order to compute the focusing properties of the ellipsoidal reflector. Each measurement is realized by placing the region of interest in the area of the first focus of the cavity and collecting the radiation converged at the second by an almost isotropic dipole antenna connected to a sensitive radiometer. Experimental data from cylindrical shaped saline or de-ionized water filled tank phantoms in which saline solutions of different concentrations were infused, provide promising results concerning the system's ability of detecting conductivity variations. Future research is needed in order to elucidate the potential of the proposed methodology to be used for brain conductivity measurements.

The scattering by a linear chain of spherical dielectric inclusions, embedded along the axis of an optical fiber, is analyzed using a rigorous integral equation formulation, based on the dyadic Green's function theory. The coupled electric field integral equations are solved by applying the Galerkin technique with Mie-type expansion of the field inside the spheres in terms of spherical waves. The analysis extends the previously studied case of a single spherical inhomogeneity inside a fiber to the multisphere-scattering case, by utilizing the classic translational addition theorems for spherical waves in order to analytically extract the direct-intersphere-coupling coefficients. Results for the transmitted and reflected power, on incidence of the fundamental HE(11) mode, are presented for several cases.

Aim of this study is the improvement of the focusing properties of a microwave radiometry tomography system, used for the imaging of the product of temperature and conductivity in biological tissues via contactless measurements. The operation principle of the device in question is based on an ellipsoidal conductive wall cavity, which provides the required beamforming and focusing. The biological tissue under measurement is placed on one of the two focal points whereas on the other one, a dipole antenna measures the black body type radiation emitted from the head's tissue. In the framework of the present research several approaches are followed in order to improve and optimize the system's focusing properties on the tissue area of interest. Extensive simulations using a commercial FEM tool are performed in a wide range of operation frequencies. Dielectric spheres of various electromagnetic characteristics are placed either around the source (human head model) or the receiver (dipole antenna) in order to improve the matching on the head-air interface. The ability of focusing the electromagnetic energy in specific areas inside the human head is herein investigated in detail and further discussed.

A rigorous integral equation analysis of the coupling between a fiber waveguide and an adjacent spherical particle is developed. The solution is obtained by applying the entire-domain Galerkin technique, based on Mie-type spherical wave expansion of the field in the sphere and the use of dyadic Green's function of the fiber waveguide. The conversion between cylindrical and spherical wave functions is done through classic analytical formulas. The analysis is applied to numerically investigate transmission through silica wires of subwavelength diameter in the presence of particles of comparable size. The results show the possibility of sensing microparticles through the reduction of transmitted power, which is maximum for certain critical values of the fiber diameter.

The radiation properties of microstrip dipole antennas are investigated. Input and mutual impedance calculations are performed by employing the variational principle. Also, the radiation field is determined by employing the stationary phase method.

In this paper the fundamental properties of printed circuit antennas on cylindrical substrates are investigated. Examples are given in terms of printed strip dipoles. A Pocklington type integral equation is solved numerically for the antenna current distribution and a variety of results is presented for input impedance computations with parameters of importance being cylinder size, substrate thickness and substrate permittivity. The radiated field is also computed via steepest descent methods taking into consideration the substrate surface wave effects.

The purpose of this study was to investigate in a randomized way the clinical benefit of addition of intracavitary hyperthermia (ICHT) to a conventional chemoradiotherapy schedule in patients with T2-T3N0M0 anal cancer.Patients were randomly assigned to undergo chemotherapy with 5-fluorouracil (5-FU) and mitomycin-C combined with radiotherapy with (arm A: 24 patients) or without ICHT (arm B: 25 patients). A microwave applicator operating at 433 MHz inserted into the anal-rectal cavity was used for ICHT. Patients in both arms received 1000 mg/m2 per day of 5-FU on days 1-4 and days 28-31 plus 15 mg/m mitomycin-C on day 1. Radiotherapy was administered with a dose of 41.4 Gy (1.8 Gy per fraction) plus a booster dose of 14 Gy (2 Gy per fraction).One patient from group A developed severe mucositis, whereas no severe morbidity was noted in the rest of the patients in both groups. The incidence of lower-intestine acute reactions was higher in the ICHT arm. After a 5-year follow up in the hyperthermia arm, 23 of 24 patients (95.8%) preserved their anorectal function and avoided permanent colostomy, whereas in the second arm, 17 of 25 (68.0%) had sphincter preservation. Local recurrence-free survival time was significantly higher in the ICHT arm (P = 0.0107, log rank test), whereas no significant difference in overall survival was noted.The addition of ICHT to the chemoradiotherapy schedule of anal cancer seems to offer a new effective and safe therapeutic modality. The preservation of anorectal function seems to be the significant clinical benefit of adjuvant ICHT.

A novel printed antenna array has been designed and simulated for the needs of a node antenna for point-to-multipoint, PMP, radio links, operating at 26GHz. The antenna array elements are derived from the concept of the Marconi-Franklin collinear array. Each array element is being fed by two parallel transmission lines via an under ground plane of approximately 3/spl lambda//sub 26GHz//2 /spl times/ 3/spl lambda//sub 26GHz//2 mm/sup 2/. Following extensive simulations the radiation pattern of each array element was extracted concluding in an almost 8dB directivity with a 75% efficiency.

A system consisting of millimeter wavelength ferroelectric substrate components has been simulated in order to be used to excite a phased array antenna at 26 GHz. This system is used as a beamformer for a point-to-multipoint radio link at the frequency range of 25.5 - 26.5 GHz. The system analysis, simulations and optimizations aim to examine the tolerances of each microwave component and to extract their optimum characteristics in order to achieve the desired excitation currents for the phased array antenna. The present work shows the analysis and simulation steps, in order to prove that such systems are able to produce the desired radiation pattern of the whole array.

The results of studies conducted with a small field of view tomographic gamma camera based on a Position Sensitive Photomultiplier Tube are reported. The system has been used for the evaluation of radiopharmaceuticals in small animals. Phantom studies have shown a spatial resolution of 2 mm in planar and 2–3 mm in tomographic imaging. Imaging studies in mice have been carried out both in 2D and 3D. Conventional radiopharmaceuticals have been used and the results have been compared with images from a clinically used system. r 2003 Elsevier Science Ltd. All rights reserved.

An efficient numerical method is developed in analyzing antenna elements of a cylindrically shaped conformal array system based on microstrip antennas, by taking into account curved surfaces and various substrate materials. In order to optimize the design parameters of such an antenna to achieve the desired directivity and input impedance, a three-dimensional electromagnetic code based on the method of auxiliary sources is developed. The validity of the method is checked and numerical results are presented. Both near field and far field calculations are made and presented in the paper.

The necessity of developing a high performance human life detector system, to support rescue operations after an earthquake disaster, is addressed by using CW Doppler radar. Various configurations are examined, regarding the transmitted frequency, antenna type and signal processing techniques. The major problem that hinders the performance of such a system is the high attenuation of electromagnetic waves through ruin materials, especially concrete.

The radiation properties of a spiral antenna above a double-dielectric loaded ground plane are investigated analytically. The electromagnetic field components in the far field region are derived by using the Green's function formulation, while an appropriate model for the surface current distribution on the spiral antenna is used. This type of antenna has been found to be convenient for mobile telecommunication applications, since it is a wideband, circular-polarized, and omnidirectional one, with no radiation at the vertical and the horizontal axes, no side lobes, and a main lobe at an elevation angle that corresponds to a large region of latitudes. For a central operating frequency at 1.6 GHz, the antenna has been found to be significantly compact and therefore easily mounted on a car ceiling, without causing noticeable modifications to its appearance. >

Summary form only given. We consider the problem of imaging of radar targets using parabolic reflectors. The radar target is represented as a summation of point sources of appropriate strength and polarization. Using traditional vector electromagnetic (EM) field theory, the EM field produced by these sources in the vicinity of the parabolic reflector (far field) is calculated. Subsequently, the electric current distribution induced on the parabolic reflector surface is calculated by using the physical optics (PO) approximation. Finally, the electric field distribution (image) along the focal plane of the reflector is calculated through conventional EM vector field theory. For this purpose, an integration of the induced reflector currents over its paraboloid surface is necessary, and this calculation is performed by using paraboloidal coordinates. We perform this calculation in various ways, such as direct analytical and numerical integration, or through the method of stationary phase (SPM), for comparison purposes. Simple analytical formulae concerning the electric field distribution along the focal plane (image) are derived for the case that the sources' 'center of mass' lies on the principal axis of the reflector, and when their polarization is assumed linear. Then, even though our presentation begins with very general arguments and assumptions, it yields very simple analytical results for several special cases of target description.

Summary form only given. Considerable research efforts have been devoted to the study of the interaction between the human head and various types of handset antennas used in mobile communications equipment. Such studies are necessary for evaluating possible health hazards as well as for assessing the effect of the human head on the antenna performance. Most published works dealing with the interaction between canonical head models and handset antennas are based on the assumption that the current along the antenna has a predetermined distribution. Consequently, the effect of the presence of the head in the current distribution is not taken into account. In this paper, a semianalytical technique based on the use of the dyadic Green's function theory and the method of moments (Green/MoM) is presented with the aim of evaluating the interaction between a three-layer dielectric sphere head model and a radiating helical antenna. The method can be used in order to evaluate the antenna input impedance and radiation pattern as well as the electric field distribution inside the head model.

Summary form only given. The problem of filtering is becoming increasingly important to satisfy present-day requirements of broadband and long-haul fiber optics communication based on the wavelength division multiplexing (WDM). Fiber Bragg gratings serving as narrow-band filters successfully bring into play this function. The demands of contemporary fiber optics communication are directed to the substantial growth of the number of informative channels, i.e. to the dense wavelength division multiplexing (DWDM). Apodized fiber Bragg gratings are the best choice for this purpose. Apodization means that the amplitude of permittivity modulation varies along the length of the Bragg grating. By applying the non-traditional method a comparative analysis of uniform and nonuniform gratings with different apodization law has been performed.

A set of FDTD numerical experiments is presented for a homogeneous spherical head and a simple dipole, in order to quantitatively assess the effect of antenna numerical representation and absorbing boundary conditions on simulated parameters of interest, referring to both dosimetric and antenna performance studies. A semi-analytical technique based on the theory of dyadic Green's function in conjunction with the method of auxiliary sources is used for further validation and comparison of the FDTD results.

Monolithic Microwave Integrated Circuits (MMICs) and Microstrip Antennas (MSA) technologies are used in the design and development of a cylindrically shaped conformal array system as presented in Kanno er al (1)(4)(6) operating at X-band to be used for mobile communications, as well as remote sensing - radar applications. A novel hybrid Method of Moments and Method of Auxiliary Sources technique is employed to design the printed antenna array on the curved surfaces. MMICs are designed for the QPSK modulator/demodulator using the F20 GaAs foundry process of GEC-Marconi as described in (15) in the framework of the EUROPRACTICE Action. Low noise and power amplifier as well as the diplexer filters and the circulator have been designed based on MIC technology on TEFLON R4003 substrates. An IF band signal processing is employed for phase shifting of the array elements, without using amplitude control at the first stage.

A holographic technique based on the method of auxiliary sources (MAS) for microwave and ultrasonic imaging is presented. The essence of the method is the visualization of the scattered field singularities (SFS). The idea is that any discontinuity of the electromagnetic characteristics of the investigated media causes remission of the incident field and represents the SFS of the scattered field. The proposed imaging method is sensitive to such singularities and gives the possibility to visualize and detect the insertions in the area under investigation.

In this study, the physical layer (PHY) of the upcoming vehicular communication standard IEEE 802.11p has been simulated in vehicle-to-vehicle situation through two different scenarios. IEEE 802.11p wireless access in vehicular environment defines modifications to IEEE 802.11 to support intelligent transportation systems applications. The standard is being considered as a promising wireless technology for enhancing transportation safety and provides safety-related services like collision avoidance and emergency breaking. At first, this includes data exchange between high-speed vehicles and between the vehicles and the roadside infrastructure in the licensed ITS band of 5.9 GHz. Performance analysis of PHY model has been evaluated into different propagation conditions (AWGN, Ricean and Rayleigh fading). In particular, bit error rate (BER) and signal to noise ratio for all the data rates have been estimated. Simulation results reveal that our system can efficiently mitigate inter-symbol interference and inter-carrier interference introduced by multi-path delay spread in our high mobility environment but against frequency-selective fading BER values are on to increase. To overcome this problem, the authors propose to use a different value of guard interval (3.2 s). Our initial results indicate that the performance with the larger cyclic prefix outperforms the performance of the initial value in our mobile channel profiles. Moreover, the authors investigated in which way the Doppler spread affects the performance with regard to the transmission distance.