Reliable inverse imaging of source currents in rat’s brain requires accurate models of fields and... more Reliable inverse imaging of source currents in rat’s brain requires accurate models of fields and interfaces. Accuracy of field models can be influenced by a proper representation of electrodes used for sensing potentials. In the paper, we study the effect of realistic modelling of electrodes on the distribution of electric field intensity in the head. Fields are evaluated for three commonly used configurations of electrodes using a three-dimensional finite element model of rat’s head comprising the brain, the cerebrospinal fluid, and the skull. Simulations show a lower amplitude of electric field intensity if realistic models of electrodes are considered. Moreover, electric field intensity near electrode models is shown to be slightly influenced. Therefore, realistic modelling of electrodes can improve the accuracy of an inverse imaging, and consequently make the localization of current sources in rat’s brain more accurate.
The contribution is focused on the comparison of the accuracy of the solution obtain from the Fie... more The contribution is focused on the comparison of the accuracy of the solution obtain from the FieldTrip-Simbio and the CST EM Studio. It is showed that the solution from FieldTrip-Simbio can have higher inaccuracy due to either exploitation of the St. Venant's approach for dipole approximation, or not considering the displacement current.
In the paper, we introduce a novel neural estimator of seats occupied by passengers in a vehicle.... more In the paper, we introduce a novel neural estimator of seats occupied by passengers in a vehicle. The estimator is built from the radial basis function (RBF) neural network. Occupied seats in a vehicle are estimated from transmissions between antennas operating at 60 GHz.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
In this paper, a 2 × 2 antenna array operating at 5.8 GHz is presented for vital signs acquisitio... more In this paper, a 2 × 2 antenna array operating at 5.8 GHz is presented for vital signs acquisition using a radar-based system, also known as bio-radar. Since these non-contact systems have multiple applications, their front-end design should take into account the monitoring environment of each specific application. In this sense, the antenna design has a crucial role to guarantee the proper integration of the full system, considering different materials. In this work, the antennas were made using textile materials, in order to integrate the bio-radar system in a car seat cover. This work presents the design of the antenna and the results achieved through measures in the anechoic chamber. Furthermore, respiratory signals were also acquired with the manufactured antennas and they are herein presented for validation purposes.
Reliable inverse imaging of source currents in rat's brain requires sufficiently accurate and... more Reliable inverse imaging of source currents in rat's brain requires sufficiently accurate and CPU-time moderate forward models of fields to calibrate inverse solvers. In this paper, we compare different mathematical formulations of electromagnetic problem related to the analysis of brain waves (static, quasi-static, full-wave) and various meshes differing in density, type and geometrical accuracy. Comparison of results indicates the necessary accuracy of the model to calibrate the imaging procedure properly.
In the paper, we describe the design and simulation of a button-like antenna for wireless body ar... more In the paper, we describe the design and simulation of a button-like antenna for wireless body area network (WBAN) communication operating in the 61 GHz ISM frequency band. We developed a disc-like concept of an antenna. Instead of a direct connection between a circular disc and a feeding pin, the electromagnetic coupling is used. This concept enables us to obtain broadband characteristics with omnidirectional radiation pattern and polarization properties optimized for a body-centric communication. Impedance properties and radiation of the antenna were studied in free space and on a tissue-equivalent phantom representing the human body. The antenna was designed considering a single-layer technology and a substrate integrated waveguide (SIW) technology. We show that the antenna is matched from 59 GHz to 64 GHz. When simulated on a body, the antenna exhibited efficiency 60% and the maximum gain 8.8 dBi.
The paper discusses possible ways of building a wireless link along an inner part of a roof of a ... more The paper discusses possible ways of building a wireless link along an inner part of a roof of a car at 60 GHz. The investigation is mainly based on experimental measurements. A vector network analyzer, horn antennas integrated into substrate and open-ended rectangular waveguide antennas are key components of measurement setup. For an appropriate positioning of the antennas and an adjustment of used materials, suggested mechanical equipment was designed to improve repeatability of measuring the transmission coefficient.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
The paper deals with the relative permittivity measurement of the selected types of 3D-knitted fa... more The paper deals with the relative permittivity measurement of the selected types of 3D-knitted fabrics by the two-line method combined with the matrix-pencil method and by the transmission/reflection method. The measured relative permittivity of the fabrics is in the range from 1.17 to 1.23. Further, the fabrics exhibit slight anisotropic behavior. The obtained results can be used for the design of the microwave devices where the 3D knitted fabrics play the role of the substrate.
In this paper, we present the design and implementation of a 1H/19F volume coil for mouse body ma... more In this paper, we present the design and implementation of a 1H/19F volume coil for mouse body magnetic resonance (MR) imaging and spectroscopy using a high magnetic field (4.7 T). By changing the geometry of the coil rungs to include both nuclei for MR experiments, this innovative coil can be tuned over an extremely wide range of frequency. The coil, 45 mm in diameter and 55 mm in length, consists of a 12-rung birdcage-like structure. Using two types of tuning, the coil can generate a sufficiently homogeneous B1+ electromagnetic field within a working volume optimized for laboratory mouse. The first tuning involves changing the resonance frequency over a large frequency range. The electrical capacitance between the wires can be adjusted to reflect changes in the length of the coil. The second tuning comprises a habitual tuning transformer for precise detection in a narrow band. In contrast to widely used multinuclear coils, the coil presented here features only one resonance peak and can be manipulated according to the Larmor frequencies given for 1H and 19F. The coil was successfully tested using full-wave simulations of magnetic and electric field distributions under in vivo MR conditions.
For the numerical design of on-body communication components, accurate and reliable models of a c... more For the numerical design of on-body communication components, accurate and reliable models of a communication channel of a wireless body area network (WBAN) are needed. Whereas numerical models (volume-pixel ones, layered ones) can be very detailed, experimental models consist of a single layer of an agar gelatin usually. In the paper, an analytical model based on Norton surface waves is used to describe the surface wave propagating along the interface between the agar phantom and environment. For the frequency band of interest, electrical parameters of the analytical model of the agar phantom are optimized so that the propagation properties of the phantom can agree with properties computed by numerical layered models, volume-pixel models, or experiments.
In this paper, we compare three different concepts of compact antenna arrays fed by substrate int... more In this paper, we compare three different concepts of compact antenna arrays fed by substrate integrated waveguides (SIW). Antenna concepts differ in the type of radiators. Slots represent magnetic linear radiators, patches are electric surface radiators, and Vivaldi slots belong to travelling-wave antennas. Hence, the SIW feeders have to exploit different mechanisms of exciting antenna elements. Impedance and radiation properties of studied antenna arrays have been related to the normalized frequency. Antenna arrays have been mutually compared to show fundamental dependencies of final parameters of the designed antennas on state variables of antennas, on SIW feeder architectures and on related implementation details.
Iet Microwaves Antennas & Propagation, Feb 1, 2016
This study deals with a design procedure and achieved parameters of a microstrip patch antenna ar... more This study deals with a design procedure and achieved parameters of a microstrip patch antenna array fed by a substrate integrated waveguide (SIW) operating at V-band. The antenna array consists of 6 × 8 microstrip patch antennas which are aperture coupled with an SIW-based feeding network. The antenna design is performed in a full-wave electromagnetic solver (ANSYS HFSS) for the operation frequency 60 GHz. The design procedure of the proposed antenna array comprises the analysis of an isolated radiating element, the synthesis of a linear array, and the development of an SIW-based power divider. At the operation frequency 60 GHz, a fabricated prototype has an impedance bandwidth of 1.8% for a reflection coefficient lower than -10 dB, a gain of 21.6 dBi, and a low sidelobe level below -23 dB in the E-plane and H-plane.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
The paper summarizes experience with the development of high-frequency electronic components whic... more The paper summarizes experience with the development of high-frequency electronic components which are manufactured on a three-dimensional knitted material instead of a conventional microwave substrate. Attention is turned to specific aspects of the design, manufacturing and integration of components to applications. Technological problems, which have not been solved yet, are discussed.
Reliable inverse imaging of source currents in rat’s brain requires accurate models of fields and... more Reliable inverse imaging of source currents in rat’s brain requires accurate models of fields and interfaces. Accuracy of field models can be influenced by a proper representation of electrodes used for sensing potentials. In the paper, we study the effect of realistic modelling of electrodes on the distribution of electric field intensity in the head. Fields are evaluated for three commonly used configurations of electrodes using a three-dimensional finite element model of rat’s head comprising the brain, the cerebrospinal fluid, and the skull. Simulations show a lower amplitude of electric field intensity if realistic models of electrodes are considered. Moreover, electric field intensity near electrode models is shown to be slightly influenced. Therefore, realistic modelling of electrodes can improve the accuracy of an inverse imaging, and consequently make the localization of current sources in rat’s brain more accurate.
The contribution is focused on the comparison of the accuracy of the solution obtain from the Fie... more The contribution is focused on the comparison of the accuracy of the solution obtain from the FieldTrip-Simbio and the CST EM Studio. It is showed that the solution from FieldTrip-Simbio can have higher inaccuracy due to either exploitation of the St. Venant's approach for dipole approximation, or not considering the displacement current.
In the paper, we introduce a novel neural estimator of seats occupied by passengers in a vehicle.... more In the paper, we introduce a novel neural estimator of seats occupied by passengers in a vehicle. The estimator is built from the radial basis function (RBF) neural network. Occupied seats in a vehicle are estimated from transmissions between antennas operating at 60 GHz.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
In this paper, a 2 × 2 antenna array operating at 5.8 GHz is presented for vital signs acquisitio... more In this paper, a 2 × 2 antenna array operating at 5.8 GHz is presented for vital signs acquisition using a radar-based system, also known as bio-radar. Since these non-contact systems have multiple applications, their front-end design should take into account the monitoring environment of each specific application. In this sense, the antenna design has a crucial role to guarantee the proper integration of the full system, considering different materials. In this work, the antennas were made using textile materials, in order to integrate the bio-radar system in a car seat cover. This work presents the design of the antenna and the results achieved through measures in the anechoic chamber. Furthermore, respiratory signals were also acquired with the manufactured antennas and they are herein presented for validation purposes.
Reliable inverse imaging of source currents in rat's brain requires sufficiently accurate and... more Reliable inverse imaging of source currents in rat's brain requires sufficiently accurate and CPU-time moderate forward models of fields to calibrate inverse solvers. In this paper, we compare different mathematical formulations of electromagnetic problem related to the analysis of brain waves (static, quasi-static, full-wave) and various meshes differing in density, type and geometrical accuracy. Comparison of results indicates the necessary accuracy of the model to calibrate the imaging procedure properly.
In the paper, we describe the design and simulation of a button-like antenna for wireless body ar... more In the paper, we describe the design and simulation of a button-like antenna for wireless body area network (WBAN) communication operating in the 61 GHz ISM frequency band. We developed a disc-like concept of an antenna. Instead of a direct connection between a circular disc and a feeding pin, the electromagnetic coupling is used. This concept enables us to obtain broadband characteristics with omnidirectional radiation pattern and polarization properties optimized for a body-centric communication. Impedance properties and radiation of the antenna were studied in free space and on a tissue-equivalent phantom representing the human body. The antenna was designed considering a single-layer technology and a substrate integrated waveguide (SIW) technology. We show that the antenna is matched from 59 GHz to 64 GHz. When simulated on a body, the antenna exhibited efficiency 60% and the maximum gain 8.8 dBi.
The paper discusses possible ways of building a wireless link along an inner part of a roof of a ... more The paper discusses possible ways of building a wireless link along an inner part of a roof of a car at 60 GHz. The investigation is mainly based on experimental measurements. A vector network analyzer, horn antennas integrated into substrate and open-ended rectangular waveguide antennas are key components of measurement setup. For an appropriate positioning of the antennas and an adjustment of used materials, suggested mechanical equipment was designed to improve repeatability of measuring the transmission coefficient.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
The paper deals with the relative permittivity measurement of the selected types of 3D-knitted fa... more The paper deals with the relative permittivity measurement of the selected types of 3D-knitted fabrics by the two-line method combined with the matrix-pencil method and by the transmission/reflection method. The measured relative permittivity of the fabrics is in the range from 1.17 to 1.23. Further, the fabrics exhibit slight anisotropic behavior. The obtained results can be used for the design of the microwave devices where the 3D knitted fabrics play the role of the substrate.
In this paper, we present the design and implementation of a 1H/19F volume coil for mouse body ma... more In this paper, we present the design and implementation of a 1H/19F volume coil for mouse body magnetic resonance (MR) imaging and spectroscopy using a high magnetic field (4.7 T). By changing the geometry of the coil rungs to include both nuclei for MR experiments, this innovative coil can be tuned over an extremely wide range of frequency. The coil, 45 mm in diameter and 55 mm in length, consists of a 12-rung birdcage-like structure. Using two types of tuning, the coil can generate a sufficiently homogeneous B1+ electromagnetic field within a working volume optimized for laboratory mouse. The first tuning involves changing the resonance frequency over a large frequency range. The electrical capacitance between the wires can be adjusted to reflect changes in the length of the coil. The second tuning comprises a habitual tuning transformer for precise detection in a narrow band. In contrast to widely used multinuclear coils, the coil presented here features only one resonance peak and can be manipulated according to the Larmor frequencies given for 1H and 19F. The coil was successfully tested using full-wave simulations of magnetic and electric field distributions under in vivo MR conditions.
For the numerical design of on-body communication components, accurate and reliable models of a c... more For the numerical design of on-body communication components, accurate and reliable models of a communication channel of a wireless body area network (WBAN) are needed. Whereas numerical models (volume-pixel ones, layered ones) can be very detailed, experimental models consist of a single layer of an agar gelatin usually. In the paper, an analytical model based on Norton surface waves is used to describe the surface wave propagating along the interface between the agar phantom and environment. For the frequency band of interest, electrical parameters of the analytical model of the agar phantom are optimized so that the propagation properties of the phantom can agree with properties computed by numerical layered models, volume-pixel models, or experiments.
In this paper, we compare three different concepts of compact antenna arrays fed by substrate int... more In this paper, we compare three different concepts of compact antenna arrays fed by substrate integrated waveguides (SIW). Antenna concepts differ in the type of radiators. Slots represent magnetic linear radiators, patches are electric surface radiators, and Vivaldi slots belong to travelling-wave antennas. Hence, the SIW feeders have to exploit different mechanisms of exciting antenna elements. Impedance and radiation properties of studied antenna arrays have been related to the normalized frequency. Antenna arrays have been mutually compared to show fundamental dependencies of final parameters of the designed antennas on state variables of antennas, on SIW feeder architectures and on related implementation details.
Iet Microwaves Antennas & Propagation, Feb 1, 2016
This study deals with a design procedure and achieved parameters of a microstrip patch antenna ar... more This study deals with a design procedure and achieved parameters of a microstrip patch antenna array fed by a substrate integrated waveguide (SIW) operating at V-band. The antenna array consists of 6 × 8 microstrip patch antennas which are aperture coupled with an SIW-based feeding network. The antenna design is performed in a full-wave electromagnetic solver (ANSYS HFSS) for the operation frequency 60 GHz. The design procedure of the proposed antenna array comprises the analysis of an isolated radiating element, the synthesis of a linear array, and the development of an SIW-based power divider. At the operation frequency 60 GHz, a fabricated prototype has an impedance bandwidth of 1.8% for a reflection coefficient lower than -10 dB, a gain of 21.6 dBi, and a low sidelobe level below -23 dB in the E-plane and H-plane.
2020 23rd International Microwave and Radar Conference (MIKON), Oct 5, 2020
The paper summarizes experience with the development of high-frequency electronic components whic... more The paper summarizes experience with the development of high-frequency electronic components which are manufactured on a three-dimensional knitted material instead of a conventional microwave substrate. Attention is turned to specific aspects of the design, manufacturing and integration of components to applications. Technological problems, which have not been solved yet, are discussed.
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Papers by Zbyněk Raida