Diego Caratelli

Terahertz electromagnetic field propagation in human tissues: A study on communication capabilities

A Body Area Nano-NETwork represents a system of biomedical nano-devices that, equipped with sensing, computing, and communication capabilities, can be implanted, ingested, or worn by humans for collecting diagnostic information and tuning medical treatments. The communication among these nano-devices can be enabled by graphene-based nano-antennas, which generate electromagnetic waves in the Terahertz band. However, from a perspective of the electromagnetic field propagation, human tissues generally introduce high losses that significantly impair the communication process, thus limiting communication ranges. In this context, the aim of this contribution is to study the communication capabilities of a Body Area Nano-NETwork, by carefully taking into account the inhomogeneous and disordered structure offered by biological tissues. To this end, the propagation of Pulsed Electric Fields in a stratified media stack made up by stratum corneum, epidermis, dermis, and fat has been carefully modeled. First, electric and magnetic fields, as well as the Poynting vector, have been calculated through an accurate Finite-Difference Time-Domain dispersive modeling based on the fractional derivative operator. Second, path loss and molecular absorption noise temperature have been evaluated. Finally, channel capacity and the related transmission ranges have been estimated by using some baseline physical interfaces. Moreover, the comparison with respect to reference values already available in the literature is presented too. Obtained results clearly highlight that new research efforts are needed to ensure the considered communications due to the severe impairment suffered by electromagnetic waves.

Fractional-calculus-based FDTD method for solving pulse propagation problems

In this paper, an accurate finite-difference time-domain (FDTD) scheme for modeling the electromagnetic pulse propagation in arbitrary dispersive media is presented. The main mathematical drawbacks encountered while solving this class of problems by means of the FDTD technique is the approximation of the fractional derivatives appearing in the time-domain permittivity response pertaining such materials. In order to overcome this issue, the proposed scheme solves the Maxwells equations directly in the time-domain by using the Riemann-Liouville fractional derivative operator. The feasibility of the proposed method is demonstrated by simulating the ultra-wideband wave propagation in general stratified Raicu dispersive media displaying multiple relaxation times response.

Fractional–Calculus–Based FDTD Algorithm for Ultra–Wideband Electromagnetic Pulse Propagation in Complex Layered Havriliak–Negami Media

A novel finite–difference time–domain algorithm for modeling ultra–wideband electromagnetic pulse propagation in layered multi–relaxed Havriliak–Negami media is presented. The proposed scheme is based on a general, yet computationally efficient, series representation of the fractional derivative operator associated with the permittivity function describing the frequency dispersion properties of the dielectric material. Dedicated uniaxial perfectly matched layer boundary conditions are derived and implemented in combination with the basic time–marching scheme. Moreover, a total field/scattered field formulation is adopted in order to analyze the material response under plane–wave excitation. Compared to alternative numerical methodologies available in the scientific literature, the proposed technique features a significantly enhanced robustness and accuracy which are essential for solving complex electromagnetic propagation problems typically encountered in bio–engineering applications.

Super-elliptical waveguide technology for reactively loaded antenna arrays

The aim of this paper is to introduce a novel super-elliptical waveguide technology for the design of reactively loaded antenna arrays. The benefits arising from the application of the proposed waveguide geometry based on Lame equation are described and discussed in detail, with a special focus on the possibility of controlling parasitic coupling level between adjacent waveguiding structures by changing the relevant cross section. This gives us an additional degree of freedom in the design process of reactively loaded arrays.

Bandwidth enhancement of a supershape patch antenna using multiple feeding technique

The technique of multiple points feeding in order to achieve improved bandwidth performance is here exploited and used to feed a supershape structured radiator. The achieved operating bandwidth, is an important advancement compared to the performance of the usual, single fed and regularly shaped patch antennas. The proposed antenna operates from 2.5 to 3.9 GHz with linear polarization and its behavior is investigated in terms of Return Loss, VSWR, input impedance, radiation pattern, electric field and efficiency.

Gain enhancement of reactively loaded aperture antennas

The goal of this paper is to show that a reactively loaded antenna is able to provide maximum directivity similar to the one featured by a uniformly excited array featuring the same physical aperture. In particular, it is shown that the superdirectivity behavior of such an antenna can be achieved without compromising the relevant radiation efficiency.

Spherical Harmonic Solution of the Robin Problem for the Laplace Equation in Supershaped Shells

The Robin problem for the Laplace equation in normal-polar shells is addressed by using a suitable spherical harmonic expansion technique. Attention is in particular focused on the wide class of domains whose boundaries are defined by a generalized version of the so-called “superformula” introduced by Gielis. A dedicated numerical procedure based on the computer algebra system Mathematica(^{copyright }) is developed in order to validate the proposed methodology. In this way, highly accurate approximations of the solution, featuring properties similar to the classical ones, are obtained.

On a Geometric Model of Bodies with “Complex” Configuration and Some Movements

Aim of this chapter is analytical representation of one wide class of geometric figures (lines, surfaces and bodies) and their complicated displacements. The accurate estimation of physical characteristics (such as volume, surface area, length, or other specific parameters) relevant to human organs is of fundamental importance in medicine. One central idea of this article is, in this respect, to provide a general methodology for the evaluation, as a function of time, of the volume and center of gravity featured by moving of one class of bodies used of describe different human organs.

Reactively loaded arrays based on overlapping sub-arrays with flat-top radiation pattern

The design of reactively-loaded antenna arrays featuring a pulse-shaped radiation pattern for limited scan-angle applications is presented. The use of the reactive loading allows reducing the complexity of the feeding structure, eliminating the need for complex overlapping beam-forming networks and permitting a drastic reduction in the number of control points.

Design and full-wave characterization of supershaped printed monopole antennas

Novel printed monopole antennas having supershaped profile are studied. The proposed class of radiating structures shows ultrawideband behavior in terms of input impedance matching, radiation patterns, and polarization. The considered antennas can potentially find application in multi-protocol wireless communication systems with demanding requirements in terms of high data rate, reduced power consumption, and low cost.