Marco Azpurua

Publications

• AN INTERPOLATION METHOD TO CALIBRATE ELECTROMAGNETIC PROBES IN SEMIANECHOIC CHAMBERS

  C. Tremola, M. A. Azpúrua, E. Páez, D. Ormeno, A. Rebolledo

  Progress In Electromagnetics Research B. 03/2012; 39:355-371.

  Based upon the standard IEEE 1309, a new calibration method for electromagnetic (EM) probes is proposed. The aforementioned method compares the electric field strength measured with the EM probe subject to calibration with the E-field intensity calculated through a linear interpolation of the correc... [more] Based upon the standard IEEE 1309, a new calibration method for electromagnetic (EM) probes is proposed. The aforementioned method compares the electric field strength measured with the EM probe subject to calibration with the E-field intensity calculated through a linear interpolation of the corrected measurement using a reference EM probe. The corrected measurement results are computed by means of the calibration factors stated in the calibration certificate of the reference EM probe. The conditions and criteria under which it is possible to calibrate EM probes inside semi-anechoic chambers in the frequency range of 80 MHz to 1 GHz, are presented. The results shows that the calibration method proposed in this paper is characterized by deviations of less than 1 dB in almost all the frequencies considered, verifying the reliability of the method. The proposed approach is very useful for registering the measurement drift of EM probes used in EMC testing laboratories.

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• A semi-analytical method for the design of coil-systems for homogeneous magnetostatic field generation

  M. A. Azpúrua

  Progress In Electromagnetics Research B. 01/2012; 37:171-189.

  This paper proposes a simple semi-analytical method for designing coil-systems for homogeneous magnetostatic field generation. The homogeneity of the magnetic field and the average magnitude of the magnetic flux density inside of the volume of interest are the objective functions chosen for the sele... [more] This paper proposes a simple semi-analytical method for designing coil-systems for homogeneous magnetostatic field generation. The homogeneity of the magnetic field and the average magnitude of the magnetic flux density inside of the volume of interest are the objective functions chosen for the selection of the coil-system geometry (size and location), number of coils and the number of turns of each winding. The spatial distribution of the magnetostatic field is estimated superposing the magnetic induction numerically computed from the analytical expression of the magnetic field generated by each coil, obtained using the Biot-Savart’s law and the current filament method. The homogeneous magnetic field is synthesized using an iterative algorithm based on TABU search with geometric constraints, which varies the design parameters of the windings to meet the requirements. The number of turns of each coil and gauge of wire used for the windings is adjusted automatically in order to achieve the target average magnitude of the magnetic induction under the constraints imposed by power consumption. This method was used to design a coil arrangement that can generate up to 10 mT within a volume 0.5 m × 0.5 m × 1 m with 99% of spatial homogeneity, with square loops of length less than or equal to 1.5 m, and with a power dissipated by Joule effect less than or equal to 1 W per coil. The synthesized magnetic field distribution was validated using Finite Element Method simulation, showing a good correspondence between the objective values and the simulated fields. This method is an alternative to design magnetic field exposure systems over large volumes such as those used in bioelectromagnetics applications

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• Comparison of the GUM and Monte Carlo Methods for the Uncertainty Estimation In Electromagnetic Compatibility Testing

  M.A. Azpúrua, C. Tremola, E. Páez

  Progress In Electromagnetics Research B. 01/2011; 34:125-144.

  The rigorous uncertainty estimation in Electromagnetic Compatibility (EMC) testing is a complex task that has been addressed through a simplified approach that typically assumes that all the contributions are uncorrelated and symmetric, and combine them in a linear or linearized model using the erro... [more] The rigorous uncertainty estimation in Electromagnetic Compatibility (EMC) testing is a complex task that has been addressed through a simplified approach that typically assumes that all the contributions are uncorrelated and symmetric, and combine them in a linear or linearized model using the error propagation law. These assumptions may affect the reliability of test results, and therefore, it is advisable to use alternative methods, such as Monte Carlo Method (MCM), for the calculation and validation of measurement uncertainty. This paper presents the results of the estimation of uncertainty for some of the most common EMC tests, such as: the measurement of radiated and conducted emissions according to CISPR 22 and radiated (IEC 61000-4-3) and conducted (IEC 61000-4-6) immunity, using both the conventional techniques of the Guide to the Expression of Uncertainty in Measurement (GUM) and the Monte Carlo Method. The results show no significant differences between the uncertainty estimated using the aforementioned methods, and it was observed that the GUM uncertainty framework slightly overestimates the overall uncertainty for the cases evaluated here. Although the GUM Uncertainty Framework proves to be adequate for the particular EMC tests that were considered, generally the Monte Carlo Method has features that avoid the assumptions and the limitations of the GUM Uncertainty Framework.

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• A Proposed Method for Quantifying Uncertainty in RF Immunity Testing Due to EUT Presence

  M. A. Azpúrua, E. Páez, C. Tremola

  Progress In Electromagnetics Research B. 01/2011; 29:175-190.

  Throughout the performance of a RF immunity test according IEC 61000-4-3 there are several factors that should be taken into account to ensure the quality and to estimate the uncertainty associated to the results. One phenomenon that should be considered to calculate uncertainty is the disturbing ef... [more] Throughout the performance of a RF immunity test according IEC 61000-4-3 there are several factors that should be taken into account to ensure the quality and to estimate the uncertainty associated to the results. One phenomenon that should be considered to calculate uncertainty is the disturbing effect produced by the EUT over the electric field generated within the calibrated uniform field area; nevertheless the mentioned effect is not easily quantifiable because the measuring process using additional antennas or field probes inside the semianechoic chamber could also alter the electric field distribution. An experimental method for quantifying the mentioned uncertainty contribution is presented. The method is based upon the fact that antenna-EUT coupling and reflection effects could be measured through changes in the input impedance of the field generation antenna. A validation procedure for the proposed method is also described. Hence, a relationship between the reflection coefficient at the antenna input port and the electric field strength is derived. The uncertainty contribution is calculated through the maximum relative change in the E-field intensity magnitude for the frequency range of 80-1000 MHz, considering the worst case for several EUT positions.

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• Evaluación de la compatibilidad electromagnética en ambientes hospitalarios

  C. Tremola, M. A. Azpurúa, E. Páez

  Revista de Bioingenería y Física Médica Cubana. 01/2011; 12:15-21.

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• A Comparison of Spatial Interpolation Methods for Estimation of Average Electromagnetic Field Magnitude

  M.A. Azpúrua, K. Dos Ramos

  Progress In Electromagnetics Research M. 01/2010; 14:135-145.

  Several georeferenced measurements of electric field were done in a pilot area of Caracas, Venezuela, to verify that the magnitude of radio frequency electromagnetic fields is below the human exposure limits, recommended by the International Commission on Non-Ionizing Radiation Protection. The colle... [more] Several georeferenced measurements of electric field were done in a pilot area of Caracas, Venezuela, to verify that the magnitude of radio frequency electromagnetic fields is below the human exposure limits, recommended by the International Commission on Non-Ionizing Radiation Protection. The collected data were analyzed using geographical information systems, with the objective of using interpolation techniques to estimate the average electromagnetic field magnitude, to obtain a continuous dataset that could be represented over a map of the entire pilot area. This paper reviews the three methods of interpolation used: SPLINE, Inverse Distance Weighting (IDW) and KRIGING. A statistical assessment of the resultant continuous surfaces indicates that there is substantial difference between the estimating ability of the three interpolation methods and IDW performing better overall.

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• Validation testing of a direct-to-home (DTH) satellite television receiver in the Ku band

  M. Azpurua, E. Paez, C. Tremola, V. Velasquez

  Latin America Transactions, IEEE (Revista IEEE America Latina). 9:798-803.

  The aim of this study was to establish the necessary setups for the measurement of the basic parameters of a commercial DTH receiver based on the standardized measurement techniques in order to provide the Venezuelan state a system of quality management to ensure well-functioning of equipment being ... [more] The aim of this study was to establish the necessary setups for the measurement of the basic parameters of a commercial DTH receiver based on the standardized measurement techniques in order to provide the Venezuelan state a system of quality management to ensure well-functioning of equipment being procured to provide the end user, the digital satellite television service. The tests were done by measuring the variables of interest from the three major subsystems that make DTH system: internal unit, low noise block and the antenna system.

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