<?xml version="1.0" encoding="ISO-8859-1"?><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<front>
<journal-meta>
<journal-id>1815-5928</journal-id>
<journal-title><![CDATA[Ingeniería Electrónica, Automática y Comunicaciones]]></journal-title>
<abbrev-journal-title><![CDATA[EAC]]></abbrev-journal-title>
<issn>1815-5928</issn>
<publisher>
<publisher-name><![CDATA[Universidad Tecnológica de La Habana José Antonio Echeverría, Cujae]]></publisher-name>
</publisher>
</journal-meta>
<article-meta>
<article-id>S1815-59282020000300041</article-id>
<title-group>
<article-title xml:lang="en"><![CDATA[RF modulator upgrading for an NMR spectrometer]]></article-title>
<article-title xml:lang="es"><![CDATA[Modernización de un modulador de RF para un espectrómetro de RMN]]></article-title>
</title-group>
<contrib-group>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Hing Batista]]></surname>
<given-names><![CDATA[Joaquin Enrique]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Bordelois Boizán]]></surname>
<given-names><![CDATA[Alejandro]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
<contrib contrib-type="author">
<name>
<surname><![CDATA[Noda Guerra]]></surname>
<given-names><![CDATA[Manuel Ernesto]]></given-names>
</name>
<xref ref-type="aff" rid="Aff"/>
</contrib>
</contrib-group>
<aff id="Af1">
<institution><![CDATA[,Universidad de Oriente  ]]></institution>
<addr-line><![CDATA[ Santiago de Cuba]]></addr-line>
<country>Cuba</country>
</aff>
<pub-date pub-type="pub">
<day>00</day>
<month>12</month>
<year>2020</year>
</pub-date>
<pub-date pub-type="epub">
<day>00</day>
<month>12</month>
<year>2020</year>
</pub-date>
<volume>41</volume>
<numero>3</numero>
<fpage>41</fpage>
<lpage>52</lpage>
<copyright-statement/>
<copyright-year/>
<self-uri xlink:href="http://scielo.sld.cu/scielo.php?script=sci_arttext&amp;pid=S1815-59282020000300041&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://scielo.sld.cu/scielo.php?script=sci_abstract&amp;pid=S1815-59282020000300041&amp;lng=en&amp;nrm=iso"></self-uri><self-uri xlink:href="http://scielo.sld.cu/scielo.php?script=sci_pdf&amp;pid=S1815-59282020000300041&amp;lng=en&amp;nrm=iso"></self-uri><abstract abstract-type="short" xml:lang="en"><p><![CDATA[ABSTRACT Low field magnetic resonance (MR) for the study of chemical compounds is a very common and important area of research. However, the greater the intensity of the magnetic field, the better the signal-to-noise ratio of the signal obtained from the substance under study and, therefore, the greater the possibilities of identifying the different chemical compounds. To conduct these studies, an MR spectrometer was built at the Centro de Biofísica Médica (Biophysics and Medical Physics Center), the parts of which were taken from other equipment in the laboratory or modified, such as the radio frequency (RF) modulator. This paper describes the changes and improvements made to the RF modulator that allowed the spectrometer to function correctly at the new 1.5 T field. The aforementioned changes included: changing the modulator's working frequencies to make it work well at the new 64 MHz, change of frequency, changing the RF switch to achieve better attenuation of the non-desired RF signal, designing and implementing a RF switch control circuit and designing and implementing a new 64 MHz passband filter. The performance of the upgraded modulator was demonstrated by measuring harmonic suppression, sideband rejection and conversion loss. Finally, the modulator fitted into the spectrometer was validated by carrying out a complete experiment that ended with the acquisition of an MR signal.]]></p></abstract>
<abstract abstract-type="short" xml:lang="es"><p><![CDATA[RESUMEN La Resonancia Magnética (RM) de bajos campos para el estudio de compuestos químicos es un área muy importante y común de la investigación. Sin embargo, mientras mayor es la intensidad del campo magnético, mejor es la relación señal a ruido de la señal que se obtiene de la sustancia en estudio y, por lo tanto, mayores las posibilidades de identificación de los diferentes compuestos químicos. Para realizar estos estudios se construyó en el Centro de Biofísica Médica un espectrómetro de RM cuyas partes se adquirieron de otros equipos en el laboratorio o se modificaron, como por ejemplo, el modulador de radio frecuencia (RF). En este trabajo se describen los cambios y mejoras realizadas al modulador de RF que permitieron al espectrómetro funcionar correctamente en el nuevo campo de 1,5 T. Los cambios anteriores incluyeron: cambio de las frecuencias de trabajo del modulador para poder operar bien a la nueva frecuencia de 64 MHz, cambio del interruptor de RF para lograr una mejor atenuación de la señal de RF no deseada, diseño e implementación de un circuito controlador del interruptor de RF y diseño e implementación de un nuevo filtro pasabanda a 64 MHz. El rendimiento del modulador modernizado se demostró midiendo la supresión armónica, el rechazo de la banda lateral y la pérdida de conversión. Finalmente se validó el modulador incorporado al espectrómetro mediante la realización de un experimento completo que culminó con la adquisición de una señal de RM.]]></p></abstract>
<kwd-group>
<kwd lng="en"><![CDATA[Magnetic Resonance]]></kwd>
<kwd lng="en"><![CDATA[modulator]]></kwd>
<kwd lng="en"><![CDATA[NMR spectrometer]]></kwd>
<kwd lng="en"><![CDATA[switch]]></kwd>
<kwd lng="en"><![CDATA[filter]]></kwd>
<kwd lng="es"><![CDATA[Resonancia Magnética]]></kwd>
<kwd lng="es"><![CDATA[modulador]]></kwd>
<kwd lng="es"><![CDATA[espectrómetro de RMN]]></kwd>
<kwd lng="es"><![CDATA[interruptor]]></kwd>
<kwd lng="es"><![CDATA[filtro]]></kwd>
</kwd-group>
</article-meta>
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<person-group person-group-type="author">
<name>
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<given-names><![CDATA[V]]></given-names>
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<name>
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<given-names><![CDATA[AA]]></given-names>
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<article-title xml:lang=""><![CDATA[Proton NMR chemical shifts and coupling constants for brain metabolites]]></article-title>
<source><![CDATA[NMR in Biomedicine]]></source>
<year>2000</year>
<volume>13</volume>
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