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Papers by Antoni Josep Canós Marín
IEEE Transactions on Instrumentation and Measurement, 2019
This paper reports the development of a stand-alone and portable instrument designed to measure t... more This paper reports the development of a stand-alone and portable instrument designed to measure the complex permittivity of dielectric materials at microwave frequencies. The equipment consists of an in-house singleport vectorial reflectometer and a resonant coaxial bi-reentrant microwave cavity where the material under test is placed inside a Pyrex vial, making the device appropriate for measuring liquids, semi-solids, powders and granular materials. The relation between the dielectric properties of the involved materials and the cavity resonance has been solved by numerical methods based on mode-matching and circuit analysis. In order to increase the measurement range, so that low to high loss materials can be characterized in the same cavity, the effect of the coupling network is de-embedded from the resonance measurements. The performance of the newly devised instrument is evaluated by error/uncertainty analysis and comparative studies with other wellestablished instruments and methods. Errors lower than 2% in the dielectric constant, and 5% in the loss factor, are found. This simple, portable, affordable and robust device could help non-specialized personnel to accurately measure dielectric properties of materials used in a wide range of microwave applications.
IEEE Transactions on Microwave Theory and Techniques, 2018
A novel dielectrometer to measure the complex permittivity of high loss liquids is presented. The... more A novel dielectrometer to measure the complex permittivity of high loss liquids is presented. The geometry consists of a reentrant cavity with insertion holes where the holder filled with liquid can be introduced readily. Radii of the insertion holes are large enough for a convenient pouring of the liquid. The electromagnetic analysis has been performed by a mixed modematching and circuit technique with the purpose of taking the high accuracy and fast convergence of the mode-matching and the flexibility and versatility of the circuit method. The convergence of the method is studied, and a procedure to estimate the result for an infinite number of modes is proposed. A calibration procedure is presented to minimize the error introduced by the numerical method. Mode charts are shown to analyze the behavior of resonant parameters for every mode. Some reference liquids are measured at different resonant frequencies and results are compared with those provided by other models of the literature.
IEEE Transactions on Microwave Theory and Techniques, 2015
A microwave cavity and heating system for microwave processing and in situ dynamic measurements o... more A microwave cavity and heating system for microwave processing and in situ dynamic measurements of the complex permittivity of dielectric materials at high temperatures (1000 C) has been developed. The method is based on a dual-mode cylindrical cavity where heating and testing are performed by two different swept frequency microwave sources. A cross-coupling filter isolates the signals coming from both sources. By adjusting the frequency bandwidth of the heating source and the level of coupling to the cavity, an automatic procedure allows for the establishment of a desirable level of heating rate to the dielectric sample to reach high temperatures in short cycles. Dielectric properties of materials as a function of temperature are calculated by an improved cavity perturbation method during heating. Accuracy of complex permittivity results has been evaluated and an error lower than 5% with respect to a rigorous analysis of the cavity has been achieved. The functionality of the microwave dielectric measurement system has been demonstrated by heating and measuring glass and ceramic samples up to 1000 C. The correlation of the complex permittivity with the heating rate, temperature, absorbed power, and other processing parameters can help to better understand the interactions that take place during microwave heating of materials at high temperatures compared to conventional heating.
International Journal of RF and Microwave Computer-Aided Engineering, 2015
This paper proposes the use of APM (Argument Principle Method) method to find all complex resonan... more This paper proposes the use of APM (Argument Principle Method) method to find all complex resonant frequencies in a three layer cylindrical cavity. APM guarantees that no root is lost and frequencies can be associated with the resonant mode. The roots can be used to find permittivity of a material inside a cavity.
Measurement Science and Technology, 2012
A microwave sensor system has been developed for monitoring adhesives curing processes. The syste... more A microwave sensor system has been developed for monitoring adhesives curing processes. The system provides continuous, real-time information about the curing progress without interfering with the reaction. An open-coaxial resonator is used as the sensor head, and measurements of its resonance frequency and quality factor are performed during cure to follow the reaction progress. Additionally, the system provides other interesting parameters such as reaction rate or cure time. The adhesive dielectric properties can be also computed off-line, which gives additional information about the process. The results given by the system correlate very well to conventional measurement techniques such as Differential Scanning Calorimetry, combining accuracy and rate with simplicity and an affordable cost.
IEEE Transactions on Microwave Theory and Techniques, 2012
In this paper, a full-wave method for the electromagnetic analysis of dielectric-loaded cylindric... more In this paper, a full-wave method for the electromagnetic analysis of dielectric-loaded cylindrical and coaxial waveguides and cavities is developed. For this purpose, a new 4-port ring network is proposed, and the mode-matching method is applied to calculate the Generalized Admittance Matrix (GAM) of this new structure. A number of analyses on dielectric-loaded waveguide structures and cavities have been conducted in order to validate and to assess the accuracy of the new approach. The results have been compared with theoretical values, numerical modeling from the literature, and data from commercial electromagnetic simulators. The method has been also applied to the accurate determination of dielectric properties, and we provide an example of these measurements as another way to validate this new method.
IEEE Transactions on Microwave Theory and Techniques, 2013
ABSTRACT An improvement of the accuracy of dielectric measurements of the open-ended coaxial reso... more ABSTRACT An improvement of the accuracy of dielectric measurements of the open-ended coaxial resonator method is described. The technique is based on an empirical technique for de-embedding the coupling network excited by electric probes. By this procedure, the influence of the coupling structure on the resonance can be precisely eliminated independently of the coupling conditions, which guarantees a high accuracy in the permittivity determination of materials by open-ended coaxial resonators. The technique is applicable to materials with a wide range of dielectric constants and losses. The results of dielectric measurements are compared with those obtained using other standard methods.
IEEE Sensors Journal, 2011
Both high temperature phases and microstructure transformations of stoneware products microwave a... more Both high temperature phases and microstructure transformations of stoneware products microwave and conventionally (gas and electric) fired are investigated aiming at a better understanding of factors affecting their mechanical and aesthetic properties. The microstructure of microwave fired stoneware has similar characteristics to those of conventionally fired samples, microwave firing requiring lower temperatures to achieve a similar structure. X-Ray diffraction and scanning electron micrographs show that the most relevant transformations are complete for lower temperatures when using microwave heating. Microwave radiation is presented as an alternative heating technology for stoneware firing, leading to similar, or even better, mechanical properties and similar microstructural characteristics, requiring lower firing temperatures and shorter processing times.
IEEE Transactions on Instrumentation and Measurement, 2019
This paper reports the development of a stand-alone and portable instrument designed to measure t... more This paper reports the development of a stand-alone and portable instrument designed to measure the complex permittivity of dielectric materials at microwave frequencies. The equipment consists of an in-house singleport vectorial reflectometer and a resonant coaxial bi-reentrant microwave cavity where the material under test is placed inside a Pyrex vial, making the device appropriate for measuring liquids, semi-solids, powders and granular materials. The relation between the dielectric properties of the involved materials and the cavity resonance has been solved by numerical methods based on mode-matching and circuit analysis. In order to increase the measurement range, so that low to high loss materials can be characterized in the same cavity, the effect of the coupling network is de-embedded from the resonance measurements. The performance of the newly devised instrument is evaluated by error/uncertainty analysis and comparative studies with other wellestablished instruments and methods. Errors lower than 2% in the dielectric constant, and 5% in the loss factor, are found. This simple, portable, affordable and robust device could help non-specialized personnel to accurately measure dielectric properties of materials used in a wide range of microwave applications.
IEEE Transactions on Microwave Theory and Techniques, 2018
A novel dielectrometer to measure the complex permittivity of high loss liquids is presented. The... more A novel dielectrometer to measure the complex permittivity of high loss liquids is presented. The geometry consists of a reentrant cavity with insertion holes where the holder filled with liquid can be introduced readily. Radii of the insertion holes are large enough for a convenient pouring of the liquid. The electromagnetic analysis has been performed by a mixed modematching and circuit technique with the purpose of taking the high accuracy and fast convergence of the mode-matching and the flexibility and versatility of the circuit method. The convergence of the method is studied, and a procedure to estimate the result for an infinite number of modes is proposed. A calibration procedure is presented to minimize the error introduced by the numerical method. Mode charts are shown to analyze the behavior of resonant parameters for every mode. Some reference liquids are measured at different resonant frequencies and results are compared with those provided by other models of the literature.
IEEE Transactions on Microwave Theory and Techniques, 2015
A microwave cavity and heating system for microwave processing and in situ dynamic measurements o... more A microwave cavity and heating system for microwave processing and in situ dynamic measurements of the complex permittivity of dielectric materials at high temperatures (1000 C) has been developed. The method is based on a dual-mode cylindrical cavity where heating and testing are performed by two different swept frequency microwave sources. A cross-coupling filter isolates the signals coming from both sources. By adjusting the frequency bandwidth of the heating source and the level of coupling to the cavity, an automatic procedure allows for the establishment of a desirable level of heating rate to the dielectric sample to reach high temperatures in short cycles. Dielectric properties of materials as a function of temperature are calculated by an improved cavity perturbation method during heating. Accuracy of complex permittivity results has been evaluated and an error lower than 5% with respect to a rigorous analysis of the cavity has been achieved. The functionality of the microwave dielectric measurement system has been demonstrated by heating and measuring glass and ceramic samples up to 1000 C. The correlation of the complex permittivity with the heating rate, temperature, absorbed power, and other processing parameters can help to better understand the interactions that take place during microwave heating of materials at high temperatures compared to conventional heating.
International Journal of RF and Microwave Computer-Aided Engineering, 2015
This paper proposes the use of APM (Argument Principle Method) method to find all complex resonan... more This paper proposes the use of APM (Argument Principle Method) method to find all complex resonant frequencies in a three layer cylindrical cavity. APM guarantees that no root is lost and frequencies can be associated with the resonant mode. The roots can be used to find permittivity of a material inside a cavity.
Measurement Science and Technology, 2012
A microwave sensor system has been developed for monitoring adhesives curing processes. The syste... more A microwave sensor system has been developed for monitoring adhesives curing processes. The system provides continuous, real-time information about the curing progress without interfering with the reaction. An open-coaxial resonator is used as the sensor head, and measurements of its resonance frequency and quality factor are performed during cure to follow the reaction progress. Additionally, the system provides other interesting parameters such as reaction rate or cure time. The adhesive dielectric properties can be also computed off-line, which gives additional information about the process. The results given by the system correlate very well to conventional measurement techniques such as Differential Scanning Calorimetry, combining accuracy and rate with simplicity and an affordable cost.
IEEE Transactions on Microwave Theory and Techniques, 2012
In this paper, a full-wave method for the electromagnetic analysis of dielectric-loaded cylindric... more In this paper, a full-wave method for the electromagnetic analysis of dielectric-loaded cylindrical and coaxial waveguides and cavities is developed. For this purpose, a new 4-port ring network is proposed, and the mode-matching method is applied to calculate the Generalized Admittance Matrix (GAM) of this new structure. A number of analyses on dielectric-loaded waveguide structures and cavities have been conducted in order to validate and to assess the accuracy of the new approach. The results have been compared with theoretical values, numerical modeling from the literature, and data from commercial electromagnetic simulators. The method has been also applied to the accurate determination of dielectric properties, and we provide an example of these measurements as another way to validate this new method.
IEEE Transactions on Microwave Theory and Techniques, 2013
ABSTRACT An improvement of the accuracy of dielectric measurements of the open-ended coaxial reso... more ABSTRACT An improvement of the accuracy of dielectric measurements of the open-ended coaxial resonator method is described. The technique is based on an empirical technique for de-embedding the coupling network excited by electric probes. By this procedure, the influence of the coupling structure on the resonance can be precisely eliminated independently of the coupling conditions, which guarantees a high accuracy in the permittivity determination of materials by open-ended coaxial resonators. The technique is applicable to materials with a wide range of dielectric constants and losses. The results of dielectric measurements are compared with those obtained using other standard methods.
IEEE Sensors Journal, 2011
Both high temperature phases and microstructure transformations of stoneware products microwave a... more Both high temperature phases and microstructure transformations of stoneware products microwave and conventionally (gas and electric) fired are investigated aiming at a better understanding of factors affecting their mechanical and aesthetic properties. The microstructure of microwave fired stoneware has similar characteristics to those of conventionally fired samples, microwave firing requiring lower temperatures to achieve a similar structure. X-Ray diffraction and scanning electron micrographs show that the most relevant transformations are complete for lower temperatures when using microwave heating. Microwave radiation is presented as an alternative heating technology for stoneware firing, leading to similar, or even better, mechanical properties and similar microstructural characteristics, requiring lower firing temperatures and shorter processing times.