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International audience; Objectives: High rates of clinical acute rejection after kidney transplantation have been reported in people living with HIV (PLHIV), probably as a consequence of drug interactions. We therefore investigated the incidence of acute rejection within 6 months of transplantation in HIV-infected recipients treated with a protease-inhibitor-free raltegravir-based regimen.Methods: The Agence Nationale de Recherche sur le Sida et les Hépatites Virales (ANRS) 153 TREVE (NCT01453192) study was a prospective multicentre single-arm trial in adult PLHIV awaiting kidney transplantation, with viral load < 50 HIV-1 RNA copies/mL, CD4 T-cell count > 200 cells/μL, and HIV-1 strains sensitive to raltegravir, aiming to demonstrate 6-month clinical acute rejection rates < 30%. Time to transplantation was compared with that for uninfected subjects matched for age, sex and registration date.Results: In total, 61 participants were enrolled in the study, and 26 underwent kidney transplantation. Two participants experienced clinical acute rejection, corresponding to an estimated clinical acute rejection rate of 8% [95% confidence interval (CI) 2-24%] at 6 and 12 months post-transplantation. HIV infection remained under control in all but one participant, who temporarily stopped antiretroviral treatment. Median time to transplantation was longer in PLHIV than in controls (4.3 versus 2.8 years, respectively; P = 0.002) and was not influenced by blood group.Conclusions: Acute rejection rates were low after kidney transplantation in PLHIV treated with a raltegravir-based regimen. However, PLHIV have poorer access to transplantation than HIV-uninfected individuals after registration on the waiting list.

Background and importance Since 2011, the French drug agency has sponsored an expanded access programme to make Malacef (artesunate) available for the treatment of severe malaria. This drug has not yet been approved by European and US pharmaceutical agencies, while it is available in China and several African countries. Aim and objectives The aim of this study was to assess the efficiency and real life safety of intravenous artesunate (IA) for the treatment of severe malaria. Material and methods We performed a retrospective, monocentric, observational study. All patients who received IA from January 2016 to September 2019 were included. Data were collected from the pharmacy service computerised system, patient records and nominative expanded access authorisation forms. The primary endpoint was efficiency, assessed by the microscopic negativation of the parasitaemia. The secondary endpoint was safety, assessed by monitoring haemoglobin, transaminases, blood platelets, kaliaemia and creatinaemia. Results Sixty-nine patients were treated with IA in our hospital. Among all patients, 59 patients (86%) had not received chemoprophylaxis. The average time between leaving the infected zone and hospital admission was 11±7 days. Patients received 3.1±0.7 doses of IA. Sixty-five patients presented at least one criterion requiring the use of IA (the most common was >4% hyperparasitaemia in 39 patients). Forty-six (67%) patients had a microscopic negativation of their parasitaemia after 3 days of treatment and 100% at day 7. Regarding tolerance, only 52% had a decrease in their haemoglobin level of >2 g/L during the whole hospitalisation. Platelets and transaminase values were normal (184–440 G/L and Conclusion and relevance The IA treatment was effective and well tolerated in all patients. These results seem to be in favour of a broader and ease of use of IA. References and/or acknowledgements No conflict of interest.

Background and importance There are few data on the use of herbal medicines and the potential risks of herbal drug interactions (HDI) with oral anticancer drugs (OACD), even though their consumption is increasing. Aim and objectives The aim of this study was to collect data on consumption of medicinal plants by patients on OACD and to assess the potential HDI and their knowledge among patients and physicians. Material and methods This was an observational study conducted within a hospital outpatient pharmacy for 6 weeks. Patient interviews were carried out using a questionnaire on the following themes: phytotherapy products consumed, point of purchase, consumption objectives and awareness of health professionals. Potential HDI were evaluated using the MSKCC and Hedrine databases. A targeted questionnaire was sent to haematologists and physicians to assess their knowledge and needs. Results Among the 59 included patients receiving OACD, 17% (n=10) were using phytotherapy. Of these 10 patients, 4 were taking herbal medicine as a complement to their anticancer treatment and the other 6 for another purpose (well being, cough, cold). The majority (70%) consumed on a regular basis on average of 2.4 different products. Four (40%) had informed a professional of their consumption. The products were mainly purchased in organic product shops (40%) and in pharmacies (20%), on the advice of a member of the family and friends (50%) or a health professional (40%). Five interactions were found. These were HDI at risk of hyperkalaemia, increased risk of bleeding and toxicity of OACD by reduced metabolism. Among the 21 physicians who answered the survey, a difference in practice between general practitioners and haematologists was highlighted. All doctors were seeking training in complementary medicine. Conclusion and relevance The consumption of herbal medicines in patients treated with OACD is not negligible. Patients appear to be poorly or not informed about HDI, as well as doctors. The pharmacist has a major role to play in this context. Distribution of a recommendation guide could reduce the risk of HDI. References and/or acknowledgements 1. Boiteux-Jurain M, Gerard B, Perrin-Bonnot, et al. Interactions between phytotherapy and oral anticancer drugs: development of a tool to assist in pharmaceutical analysis. Hosp Pharm Clin 2017;52(1). No conflict of interest.

In order to reduce the use of fossil energies, the development of new technologies, such as those concerning fuel cells, is required. However, fuel cells currently involve issues of storing and generating hydrogen. Borohydride materials, like ammonia borane (NH3BH3), seem to present an interesting solution to these problems. In fact, NH3BH3 contains 19.6 wt.% of hydrogen, of which a high percentage can easily be released by moderate heating. Understanding and controlling the behaviour of ammonia borane would allow the development of a safe, lightweight and compact hydrogen storage system. The final purpose would consist in having a device that is able to be integrated in nomad applications such as GSM, PDA; or in thermal accumulators. The present study reports on thermal decompositions of ammonia borane doped with various percentages of NH4NO3. Differential scanning calorimetry (DSC) permitted an understanding of the thermal behaviour of the material, and the detection of released hydrogen was examined by evolved gas analysis on a thermo-gravimetric analyser (TGA) coupled to a mass spectrometer (MS). Finally, in order to avoid fuel cell malfunctioning due to pollutant gases, an identification of the decomposition products was carried out.

The bistatic scattering by perfectly conducting higher order polyhedral reflectors of large dimensions with respect to the wavelength, is studied. These particular faceted polyhedra, composed of several identical trihedral corner reflectors (TCR), are expected to exhibit a large RCS over a wide angular range with specific properties in terms of directivity and depolarization. Since numerical methods can not be applied to these complex structures (owing to the number of unknowns involved), an asymptotic method based on the physical optics combined with the geometrical optics approximations and the method of equivalent currents, recently developed for a single TCR, is used. The validity of the extended method is discussed and results for higher order (first-, second- and fourth-order) octahedral reflectors and icosahedral reflectors are also studied, in particular in terms of depolarization.

The transient hot-wire technique is widely used for measurements of the thermal conductivity of most fluids. However, for some particular liquids such as concentrated nitric acid solutions or similar nitric mixtures, for which the thermal properties are important for industrial or security applications, this technique can be difficult to use, which is essentially due to incompatibility between measurement probe materials and highly electrically conducting and corrosive liquids. Moreover, the possible highly energetic (explosive) character of these liquids requires minimum volume liquid samples, and safety measurement devices and processes. It is the purpose of this paper to report on a new patented instrument, based on tantalum short-hot-wire probe technology, which responds to the above requirements and allows safe automated thermal-conductivity measurements of concentrated acid nitric solutions and similar nitric mixtures for liquid samples less than 2 cm3, with uncertainties better than 5%.

Poly(para-phenylene)s (PPPs) are an interesting class of rigid-rod polymers that have excellent thermal and mechanical properties. Because of their high degree of crystallinity and lower permeability to methanol, PPPs are insoluble and infusible. A number of methods have been developed to synthesize substituted sulfonated PPPs bearing lateral chains to improve their solubility. In this work, a comparison of the physicochemical properties of three PPP-based polymers is made with respect to Nafion membranes. One of these polymers was prepared with the postsulfonation method, and the other two were made with a new method of grafting developed in the Commissariat a l'Energie Atomique laboratory (a grafted sulfonated PPP polymer and a grafted perfluorinated sulfonated polymer). The sulfonated PPP polymers were examined for their mechanical properties, small-angle X-ray scattering, water absorption, proton conductivity, and methanol permeability. Relations between structures and properties were also investigated. Performances in fuel-cell tests were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 944–952, 2006

Many modulated communication signals exhibit a cyclostationarity (or periodic correlation) property, corresponding to the underlying periodicity arising from carrier frequencies or baud rates. By exploiting cyclostationarity, the signal direction of arrival (DOA) estimation can be significantly improved. We propose two new direction finding beamformer algorithms that exploit cyclostationarity. These algorithms show very attractive estimation performance over conventional beamforming methods, as depicted by simulation results.

The mean polarimetric behavior of the sea surface, on a time-averaged measurement, can be described by its averaged Mueller matrix. A method for the calculation of this matrix has already been proposed: it consists of an extension of the small perturbations technique to the vectorial case, from a two-scale sea surface model. In this article a backscattering model is shown, which is representative of a single instantaneous measurement instead of a time-average of measurements. For this purpose, the polarimetric response is characterized by the sea surface "polarization fork," described by the five Euler parameters. A minimal polarimetric descriptor is defined, the Euler vector, characterizing a "frozen" sea state, and whose components are the averaged values of the Euler parameters. The main interest of such a polarimetric signature of the sea surface is that the component of this new descriptor can be linked with the observation parameters (incidence of the illumination, azimuthal direction of the observa...

In many situations, the process representation in terms of poles and zeros may provide a more appropriate description than other widely used representations. This paper deals with time-varying process. A weighted Functional Series Modelling for system's poles and zeros is proposed. The approach is based on the Gauss-Newton recursive prediction error method with an exact expression for the gradient.

The polarimetric signature of the sea surface is calculated, by using the small perturbation method, from a two-scale sea surface model. This signature is formalized by the Mueller matrix, whose coefficients are functions of the speed of the wind, the incidence of illumination and the azimuthal direction of the wave with respect to the direction of the wind. The polarimetric signature of the ocean is then described by the nine Huynen coefficients. In this paper, the cross-correlation between these coefficients is shown; a reduction of the polarimetric information to a Huynen vector whose dimension is minimal (five) is proposed. From this defined vector a Bayesian estimator (a maximum likelihood ratio test) is built, making it possible to estimate the wind direction and speed from polarimetric measurements of the sea backscattering.

In this paper, we propose an adaptive polarimetric system which allows the minimization of the contribution of stationary clutter by adapting the polarization state of the receiving antenna to the polarimetric signature of the environment by using the minimum power criterion. From the knowledge of the polarimetric signature of the environment and by applying the least square criterion, we can detect the presence of targets and estimate their polarimetric parameters. Some results of simulation are presented, in order to show the feasibility of the system and the robustness against the spread of clutter variation.

In this paper, we present an evolution of the IPO method to compute RCS of targets, taking into account edges' diffractions in the resolution of the MFIE. The equivalent currents method is used to compute the diffracted fields.

Few fast asymptotic models have been developed on stacks of rough interfaces. Nevertheless, the specific case of very rough surfaces comparatively to the incident wavelength has not been treated before, which is the context of this paper. The model starts from the iteration of the Kirchhoff approximation to calculate the fields scattered by a rough layer, and is reduced to the high-frequency limit in order to fast obtain numerical results. The shadowing effect, important under grazing angles, is taken into account. The model can be applied to any given slope statistics. It is validated by comparison with a reference numerical method based on the method of moments, in the high- frequency limit for lossless and lossy inner media separating ID surfaces. Then, the model is extended to 2D surfaces.

This study aims at achieving an automatic classification of geometrical targets in order to simplify the interpretation which is necessary to read an image. The algorithms which have been developed, are applied to real geometrical scattering objects measured during an X-pol radar campaign. Very high resolution images were taken. Specific measurements and a sharp analysis of this set of images provided the interpretation and the decomposition of many scattering effects, as, for example, double bounces, diffractions by edges.. .. The principle of the classification techniques requires a training step. In order to do so, a reference set of scattering effects has to be defined. Therefore, several classification techniques were applied to the different parameters. One of the methods involved is a multidata analysis called PCA (Principal Components Analysis). An algorithm of neural networks provides other interesting results to the classification problem. The results about classification of geometrical scattering objects described in this paper show the interest of polarimetric parameters as well as the main advantages of neural networks for this particular application.

High-resolution electromagnetic radar imaging is a process allowing the discrimination of a radar target by studying the location of its scatterers. It is well known that the knowledge of a simple scalar number is not adequate to obtain a satisfactory radar image. The authors propose a polarimetry concept in the radar imaging domain for improving the discrimination of radar targets. Using this concept, it is possible to determine, without acting physically on the antennas, the optimal transmitted and received polarization vector to obtain an optimal radar image, thus allowing better radar target discrimination. >

The authors examine the quantization problems in the array weights and in the signals which are present on the array elements. The two method generally used to achieve complex weights are considered. In the rectangular method, the signals are separated in quadrature components and then weighted with real quantities. In the polar method, an attenuator and a phasor with linear control are used. The rectangular solution is shown to be a better solution for the complex weights implementation. A precision of eight bits is sufficient to place a -40-dB null in the direction of a jammer with a two-element array. A precision of six bits is sufficient to compute the optimum weights. >

A digital receiver associated with an adaptive combiner and a two-antenna array is described. The following processing is done. The complex signals are weighted and added to build the adaptive array output. The data are estimated by a MSK demodulator which generates a reference signal. Then, a least mean square algorithm computes new weights for the array. Simulations and experiments to evaluate the receiver performance are discussed. >

The design of a space diversity microwave combiner which is used to measure different parameters of mobile radio channels and to test algorithms in diversity is described. The transmission equipment uses a carrier at 890.2 MHz in a 6 W amplifier. The receiver and measuring equipment are mounted in a mobile van. Source test measurement results are plotted. >

In many applications the practical usefulness of adaptive antennas depends on both the convergence rate and noise rejection that can be achieved. Adaptive antenna systems lead generally to very complicated and high cost implementations. An inexpensive hardware prototype is suggested for a real-time processing solution. The emphasis is on its flexibility for the use of various discrete adaptive algorithms. >

Reference signal generation is a fundamental problem for the design of a least mean square adaptive array algorithm. A reference signal generated using a demodulator is discussed. A study of reference signal generation shows that the carrier frequency estimator and the bit error rate are very important. A reference signal generator model, gives good results with coherent jammers and multipath with some limits. Comprehensive simulation results are presented. >

A transmitting-receiving array antenna of angular beam steering and polarization agility is proposed. The controls of beam steering and those of polarization agility are totally independent for this system. The principle advantage of this system is that it can improve the performances of radar systems by adapting the polarimetric state of the transmitting and receiving antenna to the environment and at the same time by using the successful experiences of the technique of angular beam steering. A way to obtain any desired polarization state by using realistic shifters and amplifiers or attenuators is also proposed. >

To demonstrate the performance of the constant modulus amplitude array in a typical application, a computer simulation was performed. The transmitting signals are modulated by minimum shift keying (MSK). Two signals, direct and delayed, are generated. The array uses two antenna elements. The influence of the signals correlation, of initial weights, desired output array and the signals incidence are studied. The ratio between the delayed signal and direct signal after adaptation is computed and plotted. >

Wave scattering from rough surface is important in many diverse areas, including radio communications, microwave remote sensing, underwater acoustics. The recent interest in bistatic radar, or the study of radio links above the sea surface, has led to the need for information concerning bistatic reflectivity of clutter viewed by such systems, particularly for near grazing incidence. The problem of developing a model for a rough surface is very difficult since at best /spl sigma/ is dependent upon (at least) radar frequency, geometrical parameters, physical parameters, incident and observation angles, and polarization. Therefore, it is necessary to restrict the areas of applicability of such models. A first major new consideration in this paper is to study the domain of validity of the Kirchhoff and small-perturbation rough surface scattering models (in the bistatic case). Comparisons between the numerical calculations and the models are presented for various surface rms height and correlation length both normalized to the incident wave number (denoted by k/spl sigma/ and kL, respectively). These two parameters form a two-dimensional space, into which the approximate regions of validity are established. The second new major consideration is the development of the theoretical composite model describing bistatic reflectivity. One application is implemented for the ocean surface case. Numerical results for the cross sections are compared to those found using Kirchhoff approximation (Physical Optics), small-perturbation model, and the phase perturbation technique.

At the present time in microwave remote sensing the power of the backscattered wave is used. The electromagnetic wave backscattered by a target is a vectorial measurement which contains polarimetric information about the target; therefore knowledge of the polarimetric signature of the sea surface allows some observational parameters to be estimated, ie speed and direction of the wind, dielectric permittivity of the seawater. The polarimetric signature of the ocean as a function of the observation conditions can be formalized by different methods. In this article different types of signatures are proposed and calculated from a classical two-scale surface as sea surface model. >

In many situations, the plant representation in terms of poles and zeros may provide a more appropriate description of a process than other widely used representations. We propose an autocorrelation-based zero tracking algorithm (ZTA) to deals with stationary process. For the time varying process, a weighted functional series modelling (FSM) of a time varying system's poles and zeros is proposed. This approach is based on the Gauss-Newton recursive prediction error method with an exact expression for the gradient. >

Measuring scattering depolarisation ratio of a surface is one powerful means from which randomly rough dielectric surfaces can be effectively detected. Until now, theoretical models available to deal with the surface scattering topic are treated as a scalar problem. However, it is possible to extend these methods to the vectorial case to obtain the polarimetric signature of the ocean surface. To do this one must compute the backscattered and bistatic scattering coefficient for a sea surface and it is necessary to provide the calculation of dispersion properties of the sea water complex dielectric permittivity and its dependence on physical parameters: temperature T and salinity S. In order to describe the scattering of an electromagnetic wave, an appropriate theory has to be chosen. Existing theories may be classified in two mains groups: Kirchhoff approximation, small-perturbation approximation. Numerical results, of the RCS for the two groups are presented. Salinity effects are only visible for low frequencies. >

It is shown that in a situation where a radar target is distant enough from the radar and is included in a natural or artificial clutter environment in such a manner that the conventional detection methods fail, it is possible to improve the radar detection performance by using appropriate signal processing on two orthogonal polarization states. A CFAR (constant false alarm rate) polarimetric detection system based on the study of the polarization difference between clutter and target is proposed. Since the polarization state of the clutter echoes fluctuates slowly from cell to cell, an autoregressive model can be applied to the components of the polarization vector to predict the detection thresholds needed to follow the polarization state variation. The detection thresholds are determined to maintain a false alarm probability equal to 10/sup -6/. The presence of a target registers as a significant variation of the estimation error of the polarization vector. Results obtained from measurements of simple and canonical targets with artificial clutter are presented, and these results validate the principle of polarimetric detection. >

The object of this article is to present two mathematical supports which allow a better knowledge of the target in a bistatic polarimetric radar configuration. These aids are firstly the nine bistatic target equations which link together the new sixteen bistatic target parameters, and secondly the bistatic polarisation fork which visualises the sixteen characteristic polarisation states of the target on the Poincare sphere.

This paper proposes an experimental study of a space-time diversity receiver for DS-CDMA systems. The objective is to obtain a trade-off between space (i.e. the number of antennas) and time (i.e. the length of the filters) diversity for particular signal scenarios. Single and multi-user scenarios are considered involving fading effects and co-channel interference. The antennas array is composed of three antennas and one monopole. The chip rate is equal to 12.5 M chips/s and the spreading factor is fixed at 31.

The problem of electromagnetic scattering from a randomly rough surface is analyzed using the Kirchhoff approximation (stationary phase, scalar approximation), the small perturbation model and the two-scales models. A first major new consideration in this paper is study of the domain of validity of the Kirchhoff and small-perturbation rough surface scattering models (in the bistatic case). Comparisons between the numerical calculations and the models are made for various of the surface rms height and correlation length both normalized to the incident wave number (denoted by k/spl sigma/ and kL, respectively). By using these two parameters to form a two-dimensional space, the approximate regions of validity are then established. The second major new consideration is the development of the composite model in the bistatic case. One application is made in the ocean surface case.

Summarizes the scattering properties of a rough surface as a function of observation parameters, physic and geometric characteristics of the surface. This study is applied to the oceanic surface. Results are presented in the form of polarimetric signature as a function of the transmitter location and receiver location for a bistatic radio-link over the rough sea surface. The like- and cross-polarized received power are directly calculated using the scattering coefficients, without calculating the Mueller matrix. The Kirchhoff model and the small perturbation method are applied to determine the scattering coefficients. The polarization states, obtained for the minima and maxima received power in order to increase the performance of a bistatic radio-link, or to improve the discrimination power of a radar target are investigated. It is observed that for a fixed transmitter location and receiver location it is possible to choose a polarization state minimizing the scattered power from a rough sea surface, independently of the sea state. An electromagnetic wave scattered from a target is a vectorial quantity containing polarimetric information. This information is a function of the target, and also depends on the observation parameters. The purpose of this paper is to present, the polarimetric signature of the rough sea surface in order to increase the performance of a bistatic radio link (decreasing fading effect, for example), or to improve the discrimination power of a radar target or to identify a target.

We propose a new high resolution method with polarization diversity for the characterization of the scattering centers of a radar target, using a stepped-frequency radar system. The proposed method is based on the polynomial rooting technique. It allows one to optimally use the information contained in the polarization of the received wave while keeping the calculation cost moderate. Moreover, it can estimate the range and the polarization parameters of each scattering center in only one step. Simulation results are presented to show the performance of the algorithm.

Based on sequencing data and results obtained from applying a tailored mismatch polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis, we report that the G allele of the mitochondrial DNA (mtDNA) polymorphism at nucleotide position 11719 is associated with the European mtDNA haplogroup cluster HV, and that 11719A is therefore the ancestral allele.

The authors propose two polarimetric techniques to evaluate the potential of full polarimetric SAR data to classify dry snowcover. These decomposition methods can be used to compare different images of a site in order to characterize polarimetric variations that are closely linked to properties of the observed medium.

This paper describes the design of a space diversity microwave combiner which is used to measure different parameters of mobile radio channels and to test algorithms in diversity. The transmission equipment uses a carrier at 890.2 MHz in a 6 Watt amplifier. The receiver and measuring equipments are mounted in a mobile van. Source test measurement results are presented to study and to analyze the different problems of mobile communication in rural and suburban areas (from the viewpoint of the short term signal, the fading caused by the multipaths). After a study of the elements position on the roof van using simulation, different array geometry are tried. The received signal envelope and phase characteristics are measured and discussed. The signals correlation is analyzed. To counter the effects of multipaths fading, modulation scheme in space diversity are presented. The performance study, using experimental measures, shows improvements obtained with different algorithms (LMS, CMA) compared to reception without diversity.

La modelisation des avions s’effectue couramment en remplacant l’appareil par un certain nombre de points brillantsconvenablement disposes. Dans le chapitre 1,les auteurs montrent qu’un diagramme de Section Efficace de Retrodiffusion (ser)peut etre exprime sous la forme d’une somme de diagrammes d’interference entre points brillants et que cette decomposition peut etre simplifiee dans de tres grandes proportions tout en decrivant de facon satisfaisante les phenomenes de retrodiffusion. Dans le chapitre 2,est envisagee l’extraction, a partir du diagramme deser,des parametres caracterisant les points brillants (position etserpropres). L’etude montre que la fonction d’interference d’un bipoint est representee par une combinaison de polynomes de Chebyshev de premiere et de seconde espece. Apres une translation et un changement de variables, la fonction bipoint se reduit a une fonction circulaire modulee en amplitude. Par analyse de Fourier de lasertransformee, nous avons acces aux caracteristiques du modele. Cette methode peut s’appliquer a l’etude de multipoints lineiques anisotropes.

The problem of electromagnetic scattering from a randomly rough surface is analyzed using the Kirchhoff approximation (stationary phase, scalar approximation), the small perturbation model and the two-scale model. The authors show that physical and geometrical optics approximations can be used for a rough sea surface. A small perturbation model gives a satisfactory solution. Unfortunately, it only applies to a smooth sea surface. Therefore, these methods have been shown to be limited in their regions of validity. Comparisons between the numerical calculations and the models are made for various surface rms heights and correlation lengths both normalized to the incident wave number (denoted by k/spl sigma/ and kL, respectively). The two-scale model proposed in this paper is the method which tries to conciliate the two previous aspects. One application is made in the ocean surface case. A set of experimental data, describing simultaneous bistatic radar cross section and forward radar cross section measurements of sea clutter taken with a moderately high resolution X-band scatterometer system operating near grazing incidence for both horizontal and vertical polarizations over a range of low grazing bistatic angles, is used but not presented in this paper to examine the applicability of bistatic scattering models.

The recent interest in bistatic and multistatic radar has led to a need for information concerning the bistatic reflectivity of clutter viewed by such systems. Unfortunately, little information is available describing calibration for a bistatic radar system. This paper presents a new calibration technique for bistatic scatterometers. This technique assumes perfect isolation between antenna ports. It is shown that all magnitudes and phases (relative to one of the similarly polarized linear polarization configurations) of the radar transfer function can be calibrated without knowledge of the scattering matrix of a reference target. Only the use of the direct path between the transmitter and receiver is required. The technique is particularly useful for calibrating a radar under field conditions, because it does not require a set of calibration targets.

In the case of optical approximation, when we process, in Chebyshev polynomial space, a record of diffracted power produced by a real structure formed by scatterers having isotropic RCS diagrams, in order to obtain its power spectrums, some new lines appear, which a previously proposed model (i.e. independent scatterers) ignored. In the letter we show that the principal explanation of the phenomena is the double reflection of an element of structure on another element.

By considering a linear target consisting of a finite number of isotropic scatterers, we can determine these scatterers from a partial knowledge of the RCS diagram. In the letter we estimate the minimum interval of viewing aspects required for a given wavelength.