New paper about Dielectric Kit for Vials (DKV)

IEEE_Trans_On_Instrum_and_MeasA recent work about the Dielectric Kit for Vials (DKV) developed by Microwave Division has been published in the IEEE Transactions on Instrumentation and Measurement Journal.

Dielectric materials have many applications ranging from microwave components and subsystems to industrial and manufacturing processes. Often in these applications, a successful design greatly depends on an accurate knowledge of the complex permittivity of the materials at these frequencies.

DKV is a simple, portable, affordable, and robust device intended to help both specialized metrologists and nonspecialized personnel to accurately measure the dielectric properties of materials used in a wide range of microwave applications around the 2.45GHz ISM frequency. The device is specifically appropriate for measuring liquids, semisolids, powders, and granular materials, but it can also be used for solids, if properly machined to fit into the container.


Dielectric Kit for Vials

The measurement process consists of placing a 1 mL Pyrex vial containing the sample inside a microwave cavity and measuring the resonant parameters of the cavity without the need of additional calibration measurements of reference materials, simplifying the measurement procedure and minimizing the measurement uncertainty.

The paper describes the DKV design and electromagnetic modelling, and provides dielectric properties of several materials in a wide range of dielectric constant and loss factor values, including uncertainty and a comparative study with other well-established instruments and methods. It provides an accuracy of 1.5% in the dielectric constant and 5% in the loss factor, which is particularly relevant since the losses of materials considered in the paper spread throughout four orders of magnitude (from 10−3 to 10).

You will find additional information about the technical specifications of DKV here, and several practical examples:



The Microwave Division of ITACA has participated in the 38th annual symposium of the IEEE Geoscience and Remote Sensing Society (GRSS) [IGARSSS 2018] held in Valencia from July 22nd to 27th, 2018.

Dimas has published a paper in collaboration with ARAMCO SERVICES COMPANY in Houston (Texas-USA) that shows the permittivity of Shale at different frequencies from 1 GHz to 3.5 GHz with a Dimas equipement based on a resonant TM0np cavity and measurements performed at different harmonics.

The method has been validated with Rexolite values with an excellent match.

Paper at the European Microwave Week

Dimas group participated in the European Microwave Week that was held in Nuremberg in October 2017, with the paper entitled “Analysis of an Overmoded Re-Entrant Cavity“. It was authored by David Marques-Villarroya, Felipe Penaranda-Foix, Beatriz Garcia-Banos, Jose Manuel Catala-Civera, Jose Daniel Gutierrez-Cano.

The paper deals with the well knows reentrant cavity, but taking into account the complete set of modes and presenting a chart to fully charaterize the cavity. It is based on the Circuit Analisys Method, being developed in the Microwave Division of ITACA Research Institute since some years ago.

The paper was selected for a short video presentation that can be found here and also in this YouTube link:

New paper published at IEEE MTT

DIMAS has published in April 2017 a new research paper at IEEE Transactions on Microwave Theory and Techniques. It is entitled “Enhanced Full-Wave Circuit Analysis for Modeling of a Split Cylinder Resonator” and presents another way of analysing the split resonator by circuit analysis. Circuit analysis applied to electromagnetic strutures is a technique that DIMAS has been developing last years, with several publications and applications specially in the field of dielectric characterization of material (dielectrometry).


2017-04-04-Imagen articulo MTT-David-v01

Split cavity and circuit analysis

In this case the improvement consists of using higher modes in the circuit characterization of all the simple networks that appear when the original structure is segmented into smallest and simplest ones. Then, not only the TM0np modes can be analysed but also all the set of TE and TM resonant modes that appear in the split cavity resonator.
The main application will be the possibility of using more resonant modes to characterize planar materials and to increase the frequency band where the permittivuity is calculated.
This paper is a part of the research work performed by David Marqués-Villarroya in his way to get the PhD in Electrical Engineering, and is the result of an extension of the original paper published in the International Microwave Symposium (IMS) held in San Francisco (USA) in May 2016.

New research paper in the “Journal of Food Engineering”

DIMAS has published a new research paper in early 2017 in the Journal of Food Engineering. The paper is entitled: “Dynamic measurement of dielectric properties of food snack pellets during microwave expansion“.

This is the result of a collaboration between PepsiCo R&D and DIMAS.


Calorimeter facility at DIMAS laboratory

The papers presents in situ dielectric properties measurements of a starch-based foodfood pellet during microwave expansion. To do this, a dual-mode cylindrical cavity that allowed simultaneous microwave heating and dielectric measurements of a single pellet inside a quartz tube was used, ensuring uniform heating during microwave processing.
This systemm in shown in the figure. It is a DIMAS facility that included additional measurement devices to correlate the dielectric properties with the main parameters of the expansion process, such as temperature, expansion time, pellet volume
and absorbed power.

DIMAS participates in COSMIC european project

DIMAS is participating in the COSMIC (European Training Network for Continuous Sonication and Microwave Reactors) european project.
The kick-off of the project was held in Leuven (Belgium) in March 2017, where all the 12 partners (beneficiaries and partner organizations) participated and exchanged discussions about the future of the project.
All the 15 students that will be devolping their PhD in the frame of this project also participated in the kick-off meeting and also discussed with the host partners the activity to be done during their visits along the duration of the project.
DIMAS will host four of these students: two of them will arrive from KU Leuven (Belgium), one from UCL (UK) and the last one from Universidad de Zaragoza (Spain).
The student hosted by DIMAS will perform experiments with the microwave facilities available at DIMAS laboratory.

The project science and technology objectives are to develop:

1.-Resource-efficient multiphase reactions in the fields of organic synthesis (C–H, C=C and C=C bond activation) and nanoparticle synthesis (for use in catalysis and health applications);
2.-Intensified reactors that efficiently integrate milliflow technology with ultrasound and/or microwave actuation;
3.-Knowledge-based assessment and decision methodologies to evaluate and select process-intensification technologies.

2017-04-04-Imagen de COSMIC-v02

Group photo during the kick-off meeting in Leuven

DIMAS participation in BRAVO EIP

Logo_BavoBRAVO is a European Innovation Partnership focused on advanced metal recovery, with the following objectives:

  • To boost the innovation capacity of the aluminum value chain with respect to secondary raw materials recovery
  • The creation of new value chains for the recovered raw materials from by-products of the manufacturing process
  • To test the viability of solutions and holistic processing concepts
  • To increase the impact of research , innovations and achieve technology transfer
  • To promote socially acceptable, environmentally responsible and economically viable technologies
  • Waste as a resource: generation of a more valuable waste which can be processed to recover critical raw materials

DIMAS contributes with a wide expertise in the development of low and high temperature continuous-flow processing of rotary1materials with electromagnetic energy. This can be applied in the following BRAVO key areas:

  • Al-Source: Microwave technology for aluminium extraction from bauxite.
  • Al-Ore: Microwave-assisted extraction of iron and high added value metallic concentrates.
  • Al-Build: Microwave technology for artificial aggregate manufacturing and ceramic based materials.

You can find more information at the DIMAS profile within the BRAVO site.

Dielectric Kit for Materials Characterization at Microwave Frequencies

Dielectric materials have many applications ranging from microwave components and subsystems to industrial and manufacturing processes. Often in these applications, a successful design greatly depends on an accurate knowledge of the complex permittivity of the materials at these frequencies.

The Dielectric Kit for Vials is a new instrument developed by the Microwave Division of the institute ITACA to determine the complex permittivity (dielectric constant and loss factor) of a wide range of liquid, granular or powdered materials around the ISM frequency of 2.45 GHz. It is a complete solution which includes all necessary components to perform the generation, control and analysis of microwave signals, calculation of dielectric properties and display of results.

Two versions of the Dielectric Kit for Vials have been designed depending on the sample volume (with standard vials of 1mL or 8 mL). The measurement probe dimensions have been optimized in each case to provide repeatability and high accuracy in the determination of materials dielectric properties. Unlike other available equipment, calibration and adjustment with reference liquids is not necessary, and measurement of sample dielectric properties is fast and convenient.


The equipment comprises a source (PLL Microwave Synthesizer), which generates the microwave stimulus, a set of directional couplers to separate reflected and transmitted signals, a microwave receiver based on the AD-8302 integrated circuit for magnitude and phase detection and a measurement probe, where the material to be measured is placed. A control unit (Microprocessor System) is connected through a USB link to a personal computer which includes all the required processing to determine dielectric properties from the measurements and to transform the outputs into the desired representation.

The dielectric probe is designed as a microwave resonator where the interaction of the signals with the material takes place. Vials containing the material under test are introduced in the microwave resonator though a hole at the top of the probe. After sample insertion, the probe response (resonant frequency and quality factor) is shifted depending on the sample dielectric properties. From the measurement of the new response, the complex permittivity of the sample is calculated by using the electromagnetic model of the structure by a numerical procedure.

The Vials Dielectric Kit is fully controlled by a Labview-based software, which has been developed to perform all the necessary functions with a user-friendly interface.


This equipment is specially designed for liquid, granular or powdered materials. Solid materials might be measured if machined in rod shape with the inner vial dimensions. The following table shows some measurements of common materials. Comparisons with other measurement methods or published data are also included.


  • Frequency range: 1.5GHz to 2.6GHz (nominal, limited by MUT properties)
  • Dielectric constant: ε′<100
  • Loss factor: 0.001<ε′′<15
  • Accuracy: About 1% in dielectric constant and 2-5 % in the loss factor
  • Repeatability and Linearity 0.2%
  • Material under test assumptions:  (Minimum sample volume required :1mL (vial external diameter 4.1 mm) or 8 mL (vial external diameter 5.1mm), non-magnetic, isotropic, homogeneous (uniform composition). For granular materials (particle diameter < 2 mm) measurement repeatability is dependent on density variation.
  • Calibration: No calibration is needed
  • Microwave output: 0 dBm
  • Communication with PC: USB
  • Probe Materials: Aluminum
  • Dimensions: 190mm x 230mm x 85mm
  • Operating Temperature: 22-50 °C
  • Required OS: Windows XP/Vista/7

Dielectric Properties at Temperatures up to 350ºC with Dielectric Kit for Vials

The use of microwaves in fields as communications, radar, medicine, biology, agriculture and industrial processes demands accurate knowledge of the dielectric properties of materials and its variations with respect to many factors.

In particular, monitoring variations of materials dielectric properties with temperature is crucial for many applications, in which it is important to predict the materials performance over the whole working temperature range.

In order to provide a suitable technique, the Dielectric Kit for Vials has been equipped with viales_con_temperatura_v01the necessary components for the dielectric characterization of materials up to 350ºC. It allows for continuous verification of the sample complex permittivity and temperature conditions, maintaining its advantages with respect to other methods: accuracy, convenience, and easiness of use.

To illustrate this application, several tests have been performed with different materials placed in 1mL vials, and heated from room temperature to 350ºC. The figures illustrate the variation of the dielectric properties of cross-linked polystyrene (left) and silicon carbide (right) with the temperature. As figures show, this variation can be followed by simple inspection of the dielectric properties given by the Dielectric Kit during the cooling process of the samples.


DIMAS at ECerS Conference 2015


The Microwave Division of ITACA will participate as an exhibitor in ECerS 2015 Conference that will be held in Toledo, Spain from the 21st to the 25th of June.

Organized every two years, the ECerS Conference is the place to be for scientists, students and industrialists willing to have a direct access to one of the largest community of international experts of ceramic science and technology.

In our booth, people will be able to see:

  • Innovative microwave equipment for processing and synthesis of high-tech ceramics with advanced and unique properties.
  • Advanced technology for testing and characterization of electromagnetic properties of materials from room to high temperatures (>1000ºC).
  • Equipment for real-time combination of different testing techniques (i.e. simultaneous dielectric and Raman spectroscopy) during microwave processing, allowing a fine-tuning control and a deeper understanding of microwave-matter interaction.
  • Our expertise in electromagnetic modeling and design of microwave equipment for emerging challenges and novel applications.

Some recent results about ceramics processing and characterization obtained with our technology will be presented in the conference as well:

  • Julian Jiménez Reinosa, Beatriz García-Baños, Jose M. Catalá-Civera, Jose Francisco Fernández Lozano, “Microwave sintering processes for ceramic: microwave kinetic effect”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).
  • Rut Benavente, María D. Salvador, Ana Martínez-Amesti, Felipe Peñaranda-Foix, Adolfo Fernández, Amparo Borrell, “Effect of microcracking evolution on the thermal stability of β-eucryptite materials obtained by conventional and microwave methods”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).
  • Álvaro Presenda, María Dolores Salvador, Pedro J. Plaza-Gonzalez, Eliria Pallone, Julieta Ferreira, Amparo Borrell, “Effect of Microwave Sintering on Hydrothermal Degradation of Zirconia-Toughened-Alumina (ZTA) Composites”, 14th International Conference of European Ceramic Society, June 2015, Toledo (Spain).