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"Valderas, Daniel"
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Low-Profile FSS Design Methodology to Increase Isolation between Vehicle-Borne Multifrequency Antennas
The present work describes a new approach for the design of a Frequency-Selective Surface (FSS) in the context of frequency filters to increase isolation between two vehicle-borne antennas. A compact FSS design based on nested square meandered resonators is optimized for multifrequency operation. Furthermore, a design workflow is proposed. In general, the measurement of low-profile FSS does not correspond to simulation through Floquet modes based on periodic boundary conditions due to the lack of uniformity of mutual coupling among the FSS unit cells. The proposed method demonstrates the agreement between the infinite simulation and the measurement of the finite prototype once a convenient scale factor is applied, which facilitates the design workflow. In this case, an FSS is used as an efficient filter to increase the isolation between antennas by 6 dB in three representative bands (3GPP, WiFI I and II). In this way, multifrequency antennas can be placed at approximately half their actual distance with the same performance in spatial-constrained vehicular environments.
Journal Article
Minimum Representative Human Body Model Size Determination for Link Budget Calculation in Implanted Medical Devices
In this work, the optimum homogeneous phantom size for an equivalent whole-body electromagnetic (EM) modeling is calculated. This will enable the simple characterization of plane wave EM attenuation and far-field link budgets in Active Medical Implant (AMI) applications in the core region of the body for Industrial, Scientific, Medical and MedRadio frequency bands. A computational analysis is done to determine the optimum size in which a minimum phantom size reliably represents a whole-body situation for the corresponding frequency of operation, saving computer and laboratory resources. After the definition of a converge criterion, the computed minimum phantom size for subcutaneous applications, 0–10 mm insertion depth, is 355 × 160 × 255 mm3 for 402 MHz and 868 MHz and a cube with a side of 100 mm and 50 mm for 2.45 GHz and 5.8 GHz, respectively. For deep AMI applications, 10–50 mm insertion depth, the dimensions are 355 × 260 × 255 mm3 for 402 MHz and 868 MHz, and a cube with a side of 200 mm and 150 mm for 2.45 GHz and 5.8 GHz, respectively. A significant reduction in both computational and manufacturing resources for phantom development is thereby achieved. The verification of the model is performed by field measurements in phantoms made by aqueous solutions with sugar.
Journal Article
Ultrawideband antennas
Ultrawideband (UWB) technology, positioned as the cutting edge of research and development, paves the way to meet the emerging demands set by broadband wireless applications, such as high-speed data transmission, medical imaging, short-range radars, electromagnetic testing, etc.
eBook
Classification of UWB Antennas
The following sections are included:
Helical Antennas
Frequency-independent Antennas
Spiral antennas
Biconical antennas
3D biconical antennas
2D biconical antennas
Log-periodic Antennas
Horn Antennas
3D horn antennas
2D horn antennas
UWB Antennas Derived from Resonant Antennas
3D monopoles
Modifications to the geometry
Euclidean shapes
Computer optimisation
Partial variation on a Euclidean shape
Changes in current distribution
Use of parasitic elements
Use of a short-circuit pin
Asymmetric feed
Double feed
2D resonant antennas
Full 2D monopoles
Slot antennas
Conclusions
Book Chapter
Revolution Monopole Antennas
The following sections are included:
Introduction
Current distribution in an RMA
TLM applied to an RMA
Case study: Maximising RMA impedance bandwidth
Design
Simulation and measurements
Impedance bandwidth
Uniformity
Gain stability
Transfer function stability
Group delay stability
Design options and conclusions
Book Chapter
UWB Monopole Antenna Bandwidth Synthesis
The following sections are included:
Introduction
Defining the Lower Limit of the Frequency Band
Obtaining the Upper Frequency with Staircase Profile in TLM
One step in a PMA's profile according to TLM
Two steps in a PMA's profile according to TLM
Analytical estimate of the upper limit of the band for a rectangular staircase monopole
Obtaining the Upper Frequency through Slot Etching
Case Study 1
Design
Simulation and measurements
Impedance bandwidth
Radiation patterns at representative frequencies
Case Study 2
Design
Simulation and measurements
Case Study 3
Design
Simulation and measurements
Discussion: Impedance matching and transfer function
Book Chapter
UWB Monopole Antenna Bandwidth Maximisation
The following sections are included:
Introduction
Modifying the profile of the edge of the PMA closest to the ground plane
Applying TLM: Changing the characteristic impedance
Case Study: Maximising AMP Impedance Bandwidth
Lower frequency limit of the band: Initial L,W and p parameters
Adjusting the width
Changing the height p over the ground plane
Implementing a bevelled cut
Changing the profile close to the feed
Simulation and measurements
Impedance bandwidth
Radiation patterns at representative frequencies
Discussion of Spectral Efficiency in Broadband Antennas
Book Chapter