Nikolay Atanasov

Complex Permittivity and Permeability Studies Viewing Antenna Applications of NBR-Based Composites Comprising Conductive Fillers

The work presents studies on the complex permittivity and permeability of composites based on acrylonitrile butadiene rubber containing combinations of conductive fillers which include carbon black and nickel powder. The properties of those composites, containing each of the fillers at the same amount were compared. The permittivity and permeability values of the composites are influenced remarkably by their morphology and structure as well as by the morphological and structural specifics of both fillers. As electron scanning microscopy studies confirm, those parameters are predetermined by the nature of the composites studied—particle size, particles arrangement in the matrix and their tendency to clustering. Last but not least matrix-filler interface phenomena also impact the characteristics in question. The possibilities for applications of the composites in antennae have been studied, in particular, as substrates and insulating layers in flexible antennae for body centric communications (BCCs). The research results allow the conclusion that these materials can find such applications indeed. Composites of higher conductivity can be used where surface waves are generated to provide on-body communications, while composites of lower conductivity may be used for antennae that will be on the body of a person and will transmit to and receive from other antennas that are not on the body of the same person (off-body communications). It is clear that one can engineer the properties of antennae substrates at microwave frequencies by adjusting the filler content and the type of filler and thus control and tailor the antenna performance specific for a particular application.

A FLEXIBLE PLANAR ANTENNA ON MULTILAYER RUBBER COMPOSITE FOR WEARABLE DEVICES

This paper presents the design of a flexible antenna using planar dipole with a reflector to achieve optimal radiation efficiency and low specific absorption rate (SAR) when the antenna is placed directly over the skin of body model. The antenna is designed for the 2.45 GHz frequency band. The parametric analysis of the proposed antenna is carried out. The proposed antenna achieves stable onbody performance: |S11| varies from −16.05 dB (on skin) at 2.47 GHz resonant frequency to −16.40 dB (in free space) at 2.44 GHz resonant frequency. It was found that the maximum 1g average SAR value is only 0.23 W/kg for an input power of 100 mW when the antenna is placed directly over the skin of a three-layer body model, and radiation efficiency is 20.5%. The measured results are presented to demonstrate the validity of the proposed antenna.

Flexible and small wearable antenna for wireless body area network applications

Abstract In this paper, we present design and simulation of the compact planar dipole antenna on fully flexible nitrile butadiene rubber polymer composite for body area network applications. A three-layer human tissue model is used to numerically analyse the performance of the antenna, including the human body effect. The proposed antenna achieves stable on-body performance: |S11| varies from −19.45 dB (in free space) at 2.46 GHz resonant frequency to −20.62 dB (on the skin) at 2.44 GHz resonant frequency. Additionally, the specific absorption rate (SAR) of the proposed antenna is evaluated. It was found that the maximum 1 g average SAR value is only 0.20 W/kg for an input power of 100 mW at a distance 2 mm away from tissue model. Simulated and measured results are presented to demonstrate the validity of the proposed antenna. Furthermore, the proposed antenna offer advantages of being compact, of low profile, cheap and easy to fabricate.