Alfonso J Zozaya | Universidad Tecnologica Metropolitana (original) (raw)
A. J. Zozaya (ORCID: 0000-0003-3357-3887) received his B.Sc. degree in Electronic Engineering from the Instituto Universitario Politécnico de las Fuerzas Armadas Nacionales (I.U.P.F.A.N.), Venezuela, in 1991, and his Ph.D. degree in Signal Theory and Communications from the Universidad Politécnica de Cataluña (UPC), Spain, in 2002. He has been a professor at the Universidad de Carabobo, Valencia, Venezuela, since 1994.
From September 2014 to September 2015, and again from August 2016 to August 2017, he served as a senior researcher at the Instituto Espacial Ecuatoriano (IEE) in Quito, Ecuador, where he focused on synthetic aperture radar systems. Currently, he is a full professor in the Department of Electricity at the Universidad Tecnológica Metropolitana del Estado de Chile (UTEM), Santiago, Chile.
His research interests include applied electromagnetics, computational electromagnetics, digital signal processing, RF circuit design, antenna engineering, synthetic aperture radar, and UWB radar technology.
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Papers by Alfonso J Zozaya
SoftwareX, 2025
This manuscript introduces a synthetic aperture radar (SAR) simulator and presents the applicatio... more This manuscript introduces a synthetic aperture radar (SAR) simulator and presents the application of the Range-Doppler Algorithm (RDA) to process the simulated SAR data. The simulator efficiently generates raw data by considering various radar parameters and point targets within a specified probing area. The RDA is used to perform range focusing, range cell migration correction (RCMC), and azimuth focusing on the raw data. The resulting SAR image is presented as an outcome of this process, providing valuable insights into SAR system design and algorithm validation.
The Cartesian feedback technique is an extended solution for reducing the distortions generated b... more The Cartesian feedback technique is an extended solution for reducing the distortions generated by the nonlinearities of power RF amplifiers, being its restrictions of use related to the stability margins of the lineariser loop. Here, considerations are given to its use in the Ka-band, where the small wavelengths lead to critical times and phase unbalances which produce misadjustments of the feedback loop parameters. Results are obtained from the simulation of a Cartesian feedback lineariser applied to a commercial 28 GHz power amplifier.
Revista INGENIERÍA UC, 2018
En el presente artículo se recrea, para fines didácticos, un ejercicio clásico de adaptación de u... more En el presente artículo se recrea, para fines didácticos, un ejercicio clásico de adaptación de una línea de transmisión con un stub en paralelo acompañado de dos programas escritos en GNU Octave, los cuales paulatinamente trazan una Carta de Smith ad hoc simplificada y sobre esta las curvas, círculos y puntos de interés del procedimiento de adaptación. La red de adaptación que se obtiene de este procedimiento se simula usando QucsStudio y se comprueba la exactitud de los resultados.
AIP Advances, 2022
In this paper, we revisit the impulse response of a perfectly conducting sphere from a short puls... more In this paper, we revisit the impulse response of a perfectly conducting sphere from a short pulse excitation. From the basics associated with that response, we assess a novel late response turn-on time criterion that we investigate by means of simulation. In this way, we determine a better late response turn-on time criterion compared to the well-established one used in natural resonance estimation algorithms in the literature so far. The results obtained are in agreement with those expected from the theory.
Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 2022
Characterization of a physical system is an important issue to approach some applied physics and ... more Characterization of a physical system is an important issue to approach some applied physics and engineering problems. The complex natural resonance frequencies of the system which are included in its impulsive response are characteristic of such system and are part of its description. Few works written in English language show a comparisson among discrete methods that extract natural complex frequencies from a system impulsive response. Much less common is to find works written in Spanish language about this important research topic. Given this situation, important discrete numeric methods to estimate the complex natural resonance frecuencies of a system through its impulsive response are described, tested and compared in different simulation scenarios in this document. According to the obtained results, the matrix pencil method with a SVD filter is the less sensitive method to the noise, while the Prony method and its different versions are the fastest ones. Scenarios that could be more suitable for each method are discussed.
En el presente reporte técnico se documentan los resultados del análisis del radar de onda conti... more En el presente reporte técnico se documentan los resultados del análisis del radar de
onda continua con modulación líneal de frecuencia del MIT en el contexto del proyecto titulado Implementación de un prototipo de sensor de radar para la observación remota de la tierra. Este análisis constituye el punto de partida del proyecto y es fundamental en el desarrollo del mismo. El reporte consta de dos capítulos.
En el Capítulo 1 se describe detalladamente el diagrama de bloques del radar, se identifican las distintas señales de interés y se describe su principio de funcionamiento. En este capítulo se analiza exhaustivamente la señal de video del radar y se bosqueja una estrategia de enfoque. Se incluye, también, un inventario de los principales componentes del radar y las descripciones de los sistemas de antenas y de alimentación.
En el Capítulo 2 se analizan los diferentes presupuestos de potencia, a saber: de radiofrecuencia y de DC. El presupuesto de potencia incluye tanto el interno del radar así
como el de espacio libre. En este capítulo se analiza también el ruido en la cadena de
recepción del radar. Finalmente, se estiman los siguientes parámetros de desempeño del
radar: alcance, coeficiente de retrodispersión equivalente de ruido, resolución en distancia y resolución en acimut.
In this document some aspects of the Range Cell Migration Correction process within the range-DO... more In this document some aspects of the Range Cell Migration Correction process within
the range-DOPPLER algorithm are described.
Advanced Electromagnetics, Nov 8, 2017
Progress In Electromagnetics Research M, 2009
Abstract—In classical antenna books, the field radiated by a filamentary antenna is calculated by... more Abstract—In classical antenna books, the field radiated by a filamentary antenna is calculated by integrating the electrical current induced over the wires as if it is a primary (impressed) source. This is not technically incorrect, but is not rigorous. In this paper some formal steps are added to the classical procedure to do it more rigorously. 1.
This work deals on the estimation of the radar cross section (RCS) of five three-dimensional cond... more This work deals on the estimation of the radar cross section (RCS) of five three-dimensional conductive objects: the metallic sphere, NASA almond, single ogive, double ogive and conesphere, using the Moment Method. The Rao-Wilton-Glisson (RWG) basis functions were used to expand the surface current of targets inside the Electric Field Integral Equation (EFIE). Triangular domains of RWG basis functions were constructed using MATLAB tessellation capabilities and a MATLAB code was developed and run to solve the electromagnetic scattering problem. As a result five RCS graphs, one for each target, were obtained. The accuracy of the program was validated by comparing the obtained results with those reported in the Literature.
Orthogonal Frequency Division Multiplexing (OFDM) is the modulation scheme most widely used in mo... more Orthogonal Frequency Division Multiplexing (OFDM) is the modulation scheme most widely used in modern telecommunication systems. In this article the basics of such technique are described. A simplified simulation model of an OFDM system is used for this purpose.
Revista Ingeniería UC, 2016
The design of a synthetic aperture radar (SAR) is an engineering problem with many degrees of fre... more The design of a synthetic aperture radar (SAR) is an engineering problem with many degrees of freedom, and there is not an unique way to undertake it. This document deals with a description of a series of design decisions of a basic SAR. All these reasoning steps together constitute a conceptual and general guide for designing a synthetic aperture radar. In order to illustrate the proposed procedure a validation numerical example is provided.
Revista Ingenieria Uc, 2013
La técnica de Multiplexación por División de Frecuencias Ortogonales (OFDM) es el esquema de modu... more La técnica de Multiplexación por División de Frecuencias Ortogonales (OFDM) es el esquema de modulación más ampliamente usado en los sistemas de comunicaciones modernos. En este artículo se describen los principios básicos de funcionamiento de ésta técnica mediante la simulación de un sistema OFDM simplificado.
Field theory is used to analyze a simple circuit and to deduce the conditions for nonradiative an... more Field theory is used to analyze a simple circuit and to deduce the conditions for nonradiative and quasistatic fields. From the condition for quasistatic fields, which is the more stringent of the two, Kirchhoff's voltage equation and its range of validity are deduced. These conditions for the validity of circuit theory are not treated appropriately in the undergraduate curricula. A simple numerical problem is given to illustrate these ideas.
DYNA, 2020
This paper deals with the design of two identical 1 × 4 patch antenna arrays for a linear frequen... more This paper deals with the design of two identical 1 × 4 patch antenna arrays for a linear frequency modulated (LFM) continuous wave (CW) synthetic aperture radar (SAR) prototype. The theoretical design is carried out by using the empirical equations available in the literature, while the design optimization is performed by numerical methods using two commercial full wave simulators. Once the antennas are built they are experimentally characterized and incorporated into a radar prototype implemented at the Ecuadorian Space Institute. The radar is tested in a probing polygon and the horizontal resolution is estimated. A measured azimuthal resolution value very close to the theoretical one is achieved.
Journal of Aerospace Technology and Management, 2020
This paper deals with the implementation of a version of the MIT LFM-CW radar at the Ecuadorian S... more This paper deals with the implementation of a version of the MIT LFM-CW radar at the Ecuadorian Space Institute. The effects of near and very near ranges, and free space loss in the performance of the image processing is theoretically revised. Subsequently, the implemented radar is tested in an imaging campaign on a small probing polygon, and very congruent results are obtained.
SoftwareX, 2025
This manuscript introduces a synthetic aperture radar (SAR) simulator and presents the applicatio... more This manuscript introduces a synthetic aperture radar (SAR) simulator and presents the application of the Range-Doppler Algorithm (RDA) to process the simulated SAR data. The simulator efficiently generates raw data by considering various radar parameters and point targets within a specified probing area. The RDA is used to perform range focusing, range cell migration correction (RCMC), and azimuth focusing on the raw data. The resulting SAR image is presented as an outcome of this process, providing valuable insights into SAR system design and algorithm validation.
The Cartesian feedback technique is an extended solution for reducing the distortions generated b... more The Cartesian feedback technique is an extended solution for reducing the distortions generated by the nonlinearities of power RF amplifiers, being its restrictions of use related to the stability margins of the lineariser loop. Here, considerations are given to its use in the Ka-band, where the small wavelengths lead to critical times and phase unbalances which produce misadjustments of the feedback loop parameters. Results are obtained from the simulation of a Cartesian feedback lineariser applied to a commercial 28 GHz power amplifier.
Revista INGENIERÍA UC, 2018
En el presente artículo se recrea, para fines didácticos, un ejercicio clásico de adaptación de u... more En el presente artículo se recrea, para fines didácticos, un ejercicio clásico de adaptación de una línea de transmisión con un stub en paralelo acompañado de dos programas escritos en GNU Octave, los cuales paulatinamente trazan una Carta de Smith ad hoc simplificada y sobre esta las curvas, círculos y puntos de interés del procedimiento de adaptación. La red de adaptación que se obtiene de este procedimiento se simula usando QucsStudio y se comprueba la exactitud de los resultados.
AIP Advances, 2022
In this paper, we revisit the impulse response of a perfectly conducting sphere from a short puls... more In this paper, we revisit the impulse response of a perfectly conducting sphere from a short pulse excitation. From the basics associated with that response, we assess a novel late response turn-on time criterion that we investigate by means of simulation. In this way, we determine a better late response turn-on time criterion compared to the well-established one used in natural resonance estimation algorithms in the literature so far. The results obtained are in agreement with those expected from the theory.
Revista Internacional de Métodos Numéricos para Cálculo y Diseño en Ingeniería, 2022
Characterization of a physical system is an important issue to approach some applied physics and ... more Characterization of a physical system is an important issue to approach some applied physics and engineering problems. The complex natural resonance frequencies of the system which are included in its impulsive response are characteristic of such system and are part of its description. Few works written in English language show a comparisson among discrete methods that extract natural complex frequencies from a system impulsive response. Much less common is to find works written in Spanish language about this important research topic. Given this situation, important discrete numeric methods to estimate the complex natural resonance frecuencies of a system through its impulsive response are described, tested and compared in different simulation scenarios in this document. According to the obtained results, the matrix pencil method with a SVD filter is the less sensitive method to the noise, while the Prony method and its different versions are the fastest ones. Scenarios that could be more suitable for each method are discussed.
En el presente reporte técnico se documentan los resultados del análisis del radar de onda conti... more En el presente reporte técnico se documentan los resultados del análisis del radar de
onda continua con modulación líneal de frecuencia del MIT en el contexto del proyecto titulado Implementación de un prototipo de sensor de radar para la observación remota de la tierra. Este análisis constituye el punto de partida del proyecto y es fundamental en el desarrollo del mismo. El reporte consta de dos capítulos.
En el Capítulo 1 se describe detalladamente el diagrama de bloques del radar, se identifican las distintas señales de interés y se describe su principio de funcionamiento. En este capítulo se analiza exhaustivamente la señal de video del radar y se bosqueja una estrategia de enfoque. Se incluye, también, un inventario de los principales componentes del radar y las descripciones de los sistemas de antenas y de alimentación.
En el Capítulo 2 se analizan los diferentes presupuestos de potencia, a saber: de radiofrecuencia y de DC. El presupuesto de potencia incluye tanto el interno del radar así
como el de espacio libre. En este capítulo se analiza también el ruido en la cadena de
recepción del radar. Finalmente, se estiman los siguientes parámetros de desempeño del
radar: alcance, coeficiente de retrodispersión equivalente de ruido, resolución en distancia y resolución en acimut.
In this document some aspects of the Range Cell Migration Correction process within the range-DO... more In this document some aspects of the Range Cell Migration Correction process within
the range-DOPPLER algorithm are described.
Advanced Electromagnetics, Nov 8, 2017
Progress In Electromagnetics Research M, 2009
Abstract—In classical antenna books, the field radiated by a filamentary antenna is calculated by... more Abstract—In classical antenna books, the field radiated by a filamentary antenna is calculated by integrating the electrical current induced over the wires as if it is a primary (impressed) source. This is not technically incorrect, but is not rigorous. In this paper some formal steps are added to the classical procedure to do it more rigorously. 1.
This work deals on the estimation of the radar cross section (RCS) of five three-dimensional cond... more This work deals on the estimation of the radar cross section (RCS) of five three-dimensional conductive objects: the metallic sphere, NASA almond, single ogive, double ogive and conesphere, using the Moment Method. The Rao-Wilton-Glisson (RWG) basis functions were used to expand the surface current of targets inside the Electric Field Integral Equation (EFIE). Triangular domains of RWG basis functions were constructed using MATLAB tessellation capabilities and a MATLAB code was developed and run to solve the electromagnetic scattering problem. As a result five RCS graphs, one for each target, were obtained. The accuracy of the program was validated by comparing the obtained results with those reported in the Literature.
Orthogonal Frequency Division Multiplexing (OFDM) is the modulation scheme most widely used in mo... more Orthogonal Frequency Division Multiplexing (OFDM) is the modulation scheme most widely used in modern telecommunication systems. In this article the basics of such technique are described. A simplified simulation model of an OFDM system is used for this purpose.
Revista Ingeniería UC, 2016
The design of a synthetic aperture radar (SAR) is an engineering problem with many degrees of fre... more The design of a synthetic aperture radar (SAR) is an engineering problem with many degrees of freedom, and there is not an unique way to undertake it. This document deals with a description of a series of design decisions of a basic SAR. All these reasoning steps together constitute a conceptual and general guide for designing a synthetic aperture radar. In order to illustrate the proposed procedure a validation numerical example is provided.
Revista Ingenieria Uc, 2013
La técnica de Multiplexación por División de Frecuencias Ortogonales (OFDM) es el esquema de modu... more La técnica de Multiplexación por División de Frecuencias Ortogonales (OFDM) es el esquema de modulación más ampliamente usado en los sistemas de comunicaciones modernos. En este artículo se describen los principios básicos de funcionamiento de ésta técnica mediante la simulación de un sistema OFDM simplificado.
Field theory is used to analyze a simple circuit and to deduce the conditions for nonradiative an... more Field theory is used to analyze a simple circuit and to deduce the conditions for nonradiative and quasistatic fields. From the condition for quasistatic fields, which is the more stringent of the two, Kirchhoff's voltage equation and its range of validity are deduced. These conditions for the validity of circuit theory are not treated appropriately in the undergraduate curricula. A simple numerical problem is given to illustrate these ideas.
DYNA, 2020
This paper deals with the design of two identical 1 × 4 patch antenna arrays for a linear frequen... more This paper deals with the design of two identical 1 × 4 patch antenna arrays for a linear frequency modulated (LFM) continuous wave (CW) synthetic aperture radar (SAR) prototype. The theoretical design is carried out by using the empirical equations available in the literature, while the design optimization is performed by numerical methods using two commercial full wave simulators. Once the antennas are built they are experimentally characterized and incorporated into a radar prototype implemented at the Ecuadorian Space Institute. The radar is tested in a probing polygon and the horizontal resolution is estimated. A measured azimuthal resolution value very close to the theoretical one is achieved.
Journal of Aerospace Technology and Management, 2020
This paper deals with the implementation of a version of the MIT LFM-CW radar at the Ecuadorian S... more This paper deals with the implementation of a version of the MIT LFM-CW radar at the Ecuadorian Space Institute. The effects of near and very near ranges, and free space loss in the performance of the image processing is theoretically revised. Subsequently, the implemented radar is tested in an imaging campaign on a small probing polygon, and very congruent results are obtained.
LIBRO DE INVESTIGACIÓN APROPIACIÓN, GENERACIÓN Y USO EDIFICADOR DEL CONOCIMIENTO EN CIENCIAS DE INGENIERÍAS. ISBN: 978-1-945570-91-9, 2018
Resumen La Teoría de Circuitos es un componente fundamental del currículo de la carrera de ingeni... more Resumen La Teoría de Circuitos es un componente fundamental del currículo de la carrera de ingeniería eléctrica/electrónica. La validez de esta teoría, sin embargo, está supe-ditada al cumplimiento de ciertas premisas físicas que muchas veces se suelen sosla-yar en los cursos de circuitos y electromagnetismo básicos. En este artículo derivamos las ecuaciones principales de la Teoría de Circuitos a partir de la Teoría Electromag-nética con el propósito de facilitar la comprensión de sus limitaciones y de proveer una visión más precisa de su significado físico. Abstract Circuit Theory is a fundamental component of the electrical and electronic engineering career curricula. The validity of this theory, however, is subjected to the fulfillment of certain physical premises that are often ignored in basic circuit and electromagnetism courses. In this article we deduce the main equations of the Circuit Theory from the Electromagnetic Theory with the purpose of facilitating the understanding of its limitations and of providing a more precise vision of its physical meaning.
Estos Apuntes de Teoría Electromagnética son el resultado de mi experiencia como profesor de las ... more Estos Apuntes de Teoría Electromagnética son el resultado de mi experiencia como profesor de las cátedras de Teoría Electromagnética I y II de los currículos de Ingeniería Eléctrica e Ingeniería en Telecomunicaciones de la Universidad de Carabobo, Valencia, Venezuela, desde 1994 hasta la fecha de hoy. Recogen los principales conceptos y formulaciones matemáticas desarrollados en clase y constituyen un importante material de apoyo en el estudio concienzudo de las asignaturas Teoría Electromagnética I y II mencionadas. Con todo, como siempre hemos recomendado los libros clásicos del área como las mejores fuentes del conocimiento, estos apuntes han de servir de acompañamiento en el proceso de aprendizaje del estudiante.
Este libro consta de 11 capítulos. En el primer capítulo se hace una revisión de los conceptos principales del Análisis Vectorial, el cual constituye un elegante cuerpo de las matemáticas apropiadamente natural para describir el electromagnetismo. En los siguientes 6 capítulos (capítulos del 2 al 7) se desarrollan, siguiendo el método inductivo, yendo de lo particular a lo general, los conceptos de campo electrostático, problemas con valores en la frontera, corriente eléctrica, magnetostática, del campo eléctrico al magnético a través de la relatividad especial y campos variables en el tiempo. El Capítulo 8 está dedicado a las Ecuaciones de Maxwell y a su solución en el dominio de la frecuencia. En los capítulos subsiguientes (capítulos del 9 al 11) se sigue un método deductivo y se desarrollan algunas aplicaciones de las Ecuaciones de Maxwell en el dominio de la frecuencia, a saber: ondas planas, principios de radiación y ondas guiadas.