טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentTal Nikolay
SubjectNumeric and Analytic Optimization Methods of Antennas for
Magnetic Induction Communication and Inductive
Power Transfer
DepartmentDepartment of Electrical Engineering
Supervisor Assistant Professor Yoash Levron
Full Thesis textFull thesis text - English Version


Abstract

Magnetic Induction (MI) communication is a promising alternative communication scheme for wide variety of applications, in which it is superior to communication based on classic EM waves. These applications include Body Area Networks (BAN), underground and underwater communication for land sliding and earthquake monitoring, oil reservoirs and pipelines leakage, and more. In such applications, the conductivity of earth and water requires low frequencies operation to compensate for the high path loss in the medium, which is proportional to square root of frequency. This in turn requires large antennas. In underground environment, an additional problem is rapid changes in channel conditions due to changing nature of the terrain, which poses significant challenges.

MI communication systems utilize low frequency near magnetic field to transmit data between the transmitter and the receiver. This technique is weakly affected by the communication medium, as the operation frequency is low, and so the attenuation in conducting medium, and the magnetic permeability of most natural materials is unity. The transmitting coil need not to be an efficient radiator, hence, its size is much smaller than wavelength, enabling practical antenna size at low frequencies.

This work focuses on four subjects regarding optimal design of MI communication systems and inductive power transfer. At the first part of the work we consider sensitivity increase of magnetic induction antenna. In published works, the receiver sensitivity optimization is typically approached at better electronics and matching design, while in this work, a fundamental constraint, which is the coil self-resonance frequency, is addressed.

The second part focuses on the design of transmitting coils in weakly coupled magnetic induction communication systems. We propose several optimization methods that reduce the active, reactive and apparent power consumption of the coil. These problems are formulated as minimization problems, with the constraint of providing a required magnetic field at the receiver location. We develop efficient numeric and analytic methods to solve the resulting problems, which are of high dimension, and in certain cases non-convex. The proposed criteria are novel, and the results obtained allow reduced power consumption and increased performances in magnetic induction communication systems.

The third part of the work considers increase of channel capacity in magnetic induction communication systems by means of an antenna array, in which a central challenge is low intra-array coupling along with high gain. Published works proposed using quadrupole magnetic dipoles to achieve this property, while in this work we propose a method to employ magnetic dipoles, with significantly higher gain.

At the last part of the work, we propose an optimization method to improve the efficiency of air core inductors, which are frequently employed in MI communication and wireless power transfer. We propose a modification to the PEEC based method, coupled to a hybrid 2D-3D computation. The proposed method allows significantly faster optimization of the air core inductors compared to the published works.

The results obtained in this research can contribute to more efficient MI communication systems, with increased communication range, reduced size and cost, higher data rates, and increased efficiency.