RSLAB - Remote Sensing Research Group
http://hdl.handle.net/2117/1442
2017-02-27T19:10:21ZSelf-similar current distribution on fractal Sierpinski antenna verified with infrared thermograms
http://hdl.handle.net/2117/101406
Self-similar current distribution on fractal Sierpinski antenna verified with infrared thermograms
González Arbesú, José María; Puente Baliarda, Carles; Romeu Robert, Jordi; Aguasca Solé, Alberto
Experimental verification of the fractal Sierpinski antenna surface current distribution is presented. Measured data from an infrared camera agree with numerical data showing a self-similar behavior in the current density distribution over the fractal antenna surface. This result gives a better insight on the multiband behavior of the fractal-shape antenna.
2017-02-22T18:26:45ZGonzález Arbesú, José MaríaPuente Baliarda, CarlesRomeu Robert, JordiAguasca Solé, AlbertoExperimental verification of the fractal Sierpinski antenna surface current distribution is presented. Measured data from an infrared camera agree with numerical data showing a self-similar behavior in the current density distribution over the fractal antenna surface. This result gives a better insight on the multiband behavior of the fractal-shape antenna.Reduction of the model noise in non-linear reconstruction via an efficient calculation of the incident field: application to a 434 MHz Scanner
http://hdl.handle.net/2117/101405
Reduction of the model noise in non-linear reconstruction via an efficient calculation of the incident field: application to a 434 MHz Scanner
Geffrin, J M; Mallorquí Franquet, Jordi Joan; Joachimowicz, N; Redondo, R; Vall·Llossera, M; Vall-Llossera Ferran, Mercedes Magdalena; Franza, Joisel A; Bolomey, Jean Charles
Microwave tomography has been drastically boosted by the development of efficient reconstruction algorithms based on an iterative solution of the corresponding non-linear inverse problem. The accuracy of the electric field radiated by the antennas of a microwave scanner, inside the target area, has been shown to play a significant role on the overall image quality. Taking into account the antenna environment is of prime importance, especially when operating at low frequency. For instance, the wall of a 60 cm diameter whole-body microwave scanner cannot be neglected at 434 MHz, even when using the immersion technique consisting of putting the target in water. Indeed, at such a frequency, the attenuation introduced by water is not sufficient to avoid multiple reflections on the scanner boundary walls. Consequently, the method of calculating the incident field constitutes a key factor in iteratively solving non-linear inverse problems. The selected technique must accommodate high accuracy while maintaining acceptable calculation complexity. In this paper, three distinct techniques are analysed. They are based on the use of i) free-space and ii) non free-space Green's function, and iii) a FDTD approach. All these techniques have been firstly investigated for their 2D version, being used in 2D reconstruction algorithms. However, the scattered field data are collected in a 3D scanner. For assessing the validity of the previous 2D techniques, their results have been compared to both experimentally and 3D-FDTD results.
2017-02-22T18:22:10ZGeffrin, J MMallorquí Franquet, Jordi JoanJoachimowicz, NRedondo, RVall·Llossera, MVall-Llossera Ferran, Mercedes MagdalenaFranza, Joisel ABolomey, Jean CharlesMicrowave tomography has been drastically boosted by the development of efficient reconstruction algorithms based on an iterative solution of the corresponding non-linear inverse problem. The accuracy of the electric field radiated by the antennas of a microwave scanner, inside the target area, has been shown to play a significant role on the overall image quality. Taking into account the antenna environment is of prime importance, especially when operating at low frequency. For instance, the wall of a 60 cm diameter whole-body microwave scanner cannot be neglected at 434 MHz, even when using the immersion technique consisting of putting the target in water. Indeed, at such a frequency, the attenuation introduced by water is not sufficient to avoid multiple reflections on the scanner boundary walls. Consequently, the method of calculating the incident field constitutes a key factor in iteratively solving non-linear inverse problems. The selected technique must accommodate high accuracy while maintaining acceptable calculation complexity. In this paper, three distinct techniques are analysed. They are based on the use of i) free-space and ii) non free-space Green's function, and iii) a FDTD approach. All these techniques have been firstly investigated for their 2D version, being used in 2D reconstruction algorithms. However, the scattered field data are collected in a 3D scanner. For assessing the validity of the previous 2D techniques, their results have been compared to both experimentally and 3D-FDTD results.Vectorial waveguide reflectometer for dielectric characterisation of materials under power microwaves
http://hdl.handle.net/2117/101403
Vectorial waveguide reflectometer for dielectric characterisation of materials under power microwaves
Mallorquí Franquet, Jordi Joan; Aguasca Solé, Alberto; Ribó Vedrilla, Serni
The temperature rise in a material modifies its physical properties, particularly its dielectric permittivity. In many applications involving relatively high levels of power the electrical behavior of the different materials will change as they are heated by the radiation. For instance, the numerical codes that simulates the behavior of microwave heating processes in order to improve the design of the feeding antennas must take into account the load variations with temperature. The measurement of the changing dielectric characteristics of materials is of great interest for the industry. Previous works used completely filled waveguides near a shorting plate. The method supplied excellent results at low power levels, while the sample was not heated. When the power is risen, the field distribution of the TE/sub 10/ mode causes a non-uniform heating of the sample and the measured permittivity corresponds to an average value. In order to reduce this problem a method using a partially filled waveguide is presented. The reduced sample dimensions and its positioning into the waveguide assures a near homogeneous power distribution implying a uniform heating.
2017-02-22T18:16:57ZMallorquí Franquet, Jordi JoanAguasca Solé, AlbertoRibó Vedrilla, SerniThe temperature rise in a material modifies its physical properties, particularly its dielectric permittivity. In many applications involving relatively high levels of power the electrical behavior of the different materials will change as they are heated by the radiation. For instance, the numerical codes that simulates the behavior of microwave heating processes in order to improve the design of the feeding antennas must take into account the load variations with temperature. The measurement of the changing dielectric characteristics of materials is of great interest for the industry. Previous works used completely filled waveguides near a shorting plate. The method supplied excellent results at low power levels, while the sample was not heated. When the power is risen, the field distribution of the TE/sub 10/ mode causes a non-uniform heating of the sample and the measured permittivity corresponds to an average value. In order to reduce this problem a method using a partially filled waveguide is presented. The reduced sample dimensions and its positioning into the waveguide assures a near homogeneous power distribution implying a uniform heating.Application of the conjugate gradient method to a self-matching network for industrial microwave heating antennas
http://hdl.handle.net/2117/101401
Application of the conjugate gradient method to a self-matching network for industrial microwave heating antennas
Mallorquí Franquet, Jordi Joan; Aguasca Solé, Alberto; Cardama Aznar, Ángel; Pages, R; Haro, J M
One of the main problems regarding the efficiency in a heating industrial system using high power microwaves is related with the uncontrolled changes on the load. These changes can be caused both by the different kinds of materials to be processed in the same oven and by the temperature rise which modifies the material's physical properties, particularly its dielectric permittivity. Usually, the microwave generator is matched to the antenna feeding the oven by means of a waveguide matching system, typically a two, three or four capacitive-screw tuner empirically adjusted for a given load. Once the heating process is started, the temperature dependence of the complex permittivity usually changes the impedance seen by the generator, worsening the mismatch factor and reducing the efficiency of the heating process. A similar process happens when the load is inhomogeneous or discontinuous; it is not feasible to manually re-adjust the matching network for every different sample processed. Until now the solution has been simple but highly inefficient: to increase the incident power in order to overcome the mismatching effects.
2017-02-22T18:11:12ZMallorquí Franquet, Jordi JoanAguasca Solé, AlbertoCardama Aznar, ÁngelPages, RHaro, J MOne of the main problems regarding the efficiency in a heating industrial system using high power microwaves is related with the uncontrolled changes on the load. These changes can be caused both by the different kinds of materials to be processed in the same oven and by the temperature rise which modifies the material's physical properties, particularly its dielectric permittivity. Usually, the microwave generator is matched to the antenna feeding the oven by means of a waveguide matching system, typically a two, three or four capacitive-screw tuner empirically adjusted for a given load. Once the heating process is started, the temperature dependence of the complex permittivity usually changes the impedance seen by the generator, worsening the mismatch factor and reducing the efficiency of the heating process. A similar process happens when the load is inhomogeneous or discontinuous; it is not feasible to manually re-adjust the matching network for every different sample processed. Until now the solution has been simple but highly inefficient: to increase the incident power in order to overcome the mismatching effects.AIterative algorithm for microwave imaging using the cgm-fft and the pseudoinverse method
http://hdl.handle.net/2117/101397
AIterative algorithm for microwave imaging using the cgm-fft and the pseudoinverse method
Mallorquí Franquet, Jordi Joan; Llorens, V
Within biomedical microwave tomography, a spatial iterative method for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape from their scattered electric field is shown. Starting from the integral representation of the electric field and by means of the method of moments (MoM) and a first order linearization of the resulting expressions, the integral equations are converted into matrix equations building an iterative scheme. This technique has been developed for the bidimensional TM case with cylindrical geometry. The advantages and limitations of this algorithm are also discussed.
2017-02-22T17:32:33ZMallorquí Franquet, Jordi JoanLlorens, VWithin biomedical microwave tomography, a spatial iterative method for the reconstruction of the complex permittivity of inhomogeneous lossy dielectric objects with arbitrary shape from their scattered electric field is shown. Starting from the integral representation of the electric field and by means of the method of moments (MoM) and a first order linearization of the resulting expressions, the integral equations are converted into matrix equations building an iterative scheme. This technique has been developed for the bidimensional TM case with cylindrical geometry. The advantages and limitations of this algorithm are also discussed.The cgm and the fdtd for sar studies
http://hdl.handle.net/2117/101394
The cgm and the fdtd for sar studies
Pous Andrés, Rafael; Mallorquí Franquet, Jordi Joan; Bayonas, F
In the study of electromagnetic radiation effects over dielectric bodies, effective numerical methods are needed. At present, there is a lack of tools for measuring these effects and due to the huge growth of microwave devices, like cellular radio telephones working close to the human body, it is necessary to develop accurate numerical methods for evaluating those effects. Two of the most efficient and extensively used methods are the FFT-CGM (fast Fourier transform-conjugate gradient method) and the FDTD (finite difference time domain method). Since both methods use a rectangular grid, it is interesting to compare the two solutions in order to validate the results. Algorithms for solving the two-dimensional scattering of transversal magnetic (TM) polarized waves by a lossy dielectric objects are presented. At the same time, the SAR (specific absorption rate) of tissues is obtained from the diffracted fields.
2017-02-22T17:21:44ZPous Andrés, RafaelMallorquí Franquet, Jordi JoanBayonas, FIn the study of electromagnetic radiation effects over dielectric bodies, effective numerical methods are needed. At present, there is a lack of tools for measuring these effects and due to the huge growth of microwave devices, like cellular radio telephones working close to the human body, it is necessary to develop accurate numerical methods for evaluating those effects. Two of the most efficient and extensively used methods are the FFT-CGM (fast Fourier transform-conjugate gradient method) and the FDTD (finite difference time domain method). Since both methods use a rectangular grid, it is interesting to compare the two solutions in order to validate the results. Algorithms for solving the two-dimensional scattering of transversal magnetic (TM) polarized waves by a lossy dielectric objects are presented. At the same time, the SAR (specific absorption rate) of tissues is obtained from the diffracted fields.Study of RFI signals in protected GNSS bands generated by common electronic devices: effects on GNSS-R measurements
http://hdl.handle.net/2117/101292
Study of RFI signals in protected GNSS bands generated by common electronic devices: effects on GNSS-R measurements
Querol Borràs, Jorge; Forte Veliz, Giuseppe Francesco; Camps Carmona, Adriano José
RFI (Radio Frequency Interference) signals are a threat for GNSS-R (Global Navigation Satellite Systems - Reflectometry) due to the very low power of the navigation signals. Interference signals coming from computers or high-speed buses may affect GNSS-R measurements introducing a bias or even corrupting them completely. These RFI may be in-band or near-band and can desensitize GNSS and GNSS-R receivers. A number of techniques are currently under development to mitigate the effect of RFI signals.
2017-02-21T11:00:14ZQuerol Borràs, JorgeForte Veliz, Giuseppe FrancescoCamps Carmona, Adriano JoséRFI (Radio Frequency Interference) signals are a threat for GNSS-R (Global Navigation Satellite Systems - Reflectometry) due to the very low power of the navigation signals. Interference signals coming from computers or high-speed buses may affect GNSS-R measurements introducing a bias or even corrupting them completely. These RFI may be in-band or near-band and can desensitize GNSS and GNSS-R receivers. A number of techniques are currently under development to mitigate the effect of RFI signals.Application of the boundary elements method to 3-d radiation problem
http://hdl.handle.net/2117/100985
Application of the boundary elements method to 3-d radiation problem
Abad, J.; Duffo Ubeda, Núria; Rius Casals, Juan Manuel; Cruellas Ibarz, Juan Carlos
In order to analyze the electromagnetic fields generated by perfectly conducting bodies composed by interconnected wires and solid objects, whichever its geometry, the Boundary Element Method is applied. The basic formulation and the associated items are commented. Results of problems of radiation are given and compared with available analytic solutions.
2017-02-14T13:40:02ZAbad, J.Duffo Ubeda, NúriaRius Casals, Juan ManuelCruellas Ibarz, Juan CarlosIn order to analyze the electromagnetic fields generated by perfectly conducting bodies composed by interconnected wires and solid objects, whichever its geometry, the Boundary Element Method is applied. The basic formulation and the associated items are commented. Results of problems of radiation are given and compared with available analytic solutions.Bidimensional scattering of tm and te polarized waves by dielectric
http://hdl.handle.net/2117/100982
Bidimensional scattering of tm and te polarized waves by dielectric
Mallorquí Franquet, Jordi Joan; Vaquer Bonnin, Miguel; Cardama Aznar, Ángel; Jofre Roca, Lluís
In the study of electromagnetic radiation effects over dielectric bodies, effective numerical methods are needed. At present, there is a lack of tools for measuring this effects and due to the huge growth of microwave devices, like cellular radio telephones working close to the human body, it is necessary to develop accurate numerical methods for evaluating those effects. One of the most efficient and extensively used method is the FFT-CGM (Fast-Fourier-Transform Conjugate Gradient Method). In this paper, algorithms for solving the two-dimensional scattering of transversal magnetic (TM) and transversal electric (TE) polarized waves by a lossy dielectric and metallic objects are presented. At the same time, the SAR (Specific Absorption Rate) of tissues and the modified radiation diagrams when the body is present are obtained from the diffracted fields.
2017-02-14T13:22:39ZMallorquí Franquet, Jordi JoanVaquer Bonnin, MiguelCardama Aznar, ÁngelJofre Roca, LluísIn the study of electromagnetic radiation effects over dielectric bodies, effective numerical methods are needed. At present, there is a lack of tools for measuring this effects and due to the huge growth of microwave devices, like cellular radio telephones working close to the human body, it is necessary to develop accurate numerical methods for evaluating those effects. One of the most efficient and extensively used method is the FFT-CGM (Fast-Fourier-Transform Conjugate Gradient Method). In this paper, algorithms for solving the two-dimensional scattering of transversal magnetic (TM) and transversal electric (TE) polarized waves by a lossy dielectric and metallic objects are presented. At the same time, the SAR (Specific Absorption Rate) of tissues and the modified radiation diagrams when the body is present are obtained from the diffracted fields.SNR and standard deviation of cGNSS-R and iGNSS-R scatterometric measurements
http://hdl.handle.net/2117/100968
SNR and standard deviation of cGNSS-R and iGNSS-R scatterometric measurements
Alonso Arroyo, Alberto; Querol Borràs, Jorge; López Martínez, Carlos; Zavorotny, Valery U.; Hyuk, Park; Pascual Biosca, Daniel; Onrubia Ibáñez, Raúl; Camps Carmona, Adriano José
This work addresses the accuracy of the Global Navigation Satellite Systems (GNSS)-Reflectometry (GNSS-R) scatterometric measurements considering the presence of both coherent and incoherent scattered components, for both conventional GNSS-R (cGNSS-R) and interferometric GNSS-R (iGNSS-R) techniques. The coherent component is present for some type of surfaces, and it has been neglected until now because it vanishes for the sea surface scattering case. Taking into account the presence of both scattering components, the estimated Signal-to-Noise Ratio (SNR) for both techniques is computed based on the detectability criterion, as it is done in conventional GNSS applications. The non-coherent averaging operation is considered from a general point of view, taking into account that thermal noise contributions can be reduced by an extra factor of 0.88 dB when using partially overlapped or partially correlated samples. After the SNRs are derived, the received waveform’s peak variability is computed, which determines the system’s capability to measure geophysical parameters. This theoretical derivations are applied to the United Kingdom (UK) TechDemoSat-1 (UK TDS-1) and to the future GNSS REflectometry, Radio Occultation and Scatterometry on board the International Space Station (ISS) (GEROS-ISS) scenarios, in order to estimate the expected scatterometric performance of both missions.
2017-02-14T12:08:43ZAlonso Arroyo, AlbertoQuerol Borràs, JorgeLópez Martínez, CarlosZavorotny, Valery U.Hyuk, ParkPascual Biosca, DanielOnrubia Ibáñez, RaúlCamps Carmona, Adriano JoséThis work addresses the accuracy of the Global Navigation Satellite Systems (GNSS)-Reflectometry (GNSS-R) scatterometric measurements considering the presence of both coherent and incoherent scattered components, for both conventional GNSS-R (cGNSS-R) and interferometric GNSS-R (iGNSS-R) techniques. The coherent component is present for some type of surfaces, and it has been neglected until now because it vanishes for the sea surface scattering case. Taking into account the presence of both scattering components, the estimated Signal-to-Noise Ratio (SNR) for both techniques is computed based on the detectability criterion, as it is done in conventional GNSS applications. The non-coherent averaging operation is considered from a general point of view, taking into account that thermal noise contributions can be reduced by an extra factor of 0.88 dB when using partially overlapped or partially correlated samples. After the SNRs are derived, the received waveform’s peak variability is computed, which determines the system’s capability to measure geophysical parameters. This theoretical derivations are applied to the United Kingdom (UK) TechDemoSat-1 (UK TDS-1) and to the future GNSS REflectometry, Radio Occultation and Scatterometry on board the International Space Station (ISS) (GEROS-ISS) scenarios, in order to estimate the expected scatterometric performance of both missions.