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Near-Field Based Communication and Electrical Systems

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  • PhD Defenses
When Apr 17, 2013
from 02:00 PM to 04:00 PM
Where Engr. IV Bldg. Maxwell Rm. 57-124
Contact Name
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Umar Azad

Advisor: Professor Yuanxun Ethan Wang



Inductively coupled near-field based systems have been used or proposed in many application areas such as contactless power and information transmission in drill machines, telemetric powering of difficult-to-access sensor systems especially bio-medical implants, RFID allowing tagged items to be individually identified by a reader, health monitoring by allowing short range connectivity between health monitoring devices and mobile terminals, seamless coverage of littoral mine warfare operations in shallow water, and under-ground communications.

In this talk, we present a power transfer equation for an inductively coupled near-field system, derived based on the equivalent circuit model of the coupled resonant loops. Experimental results show that the proposed near-field coupling equation is trustworthy as it correctly predicts the transferred power versus distance relationship for different values of loaded quality factors at the transmitter and the receiver. We will also discuss the capacity performance of near-field communication (NFC) links based on information theory. The analytical results provide guidelines for design of inductively coupled antenna systems, as the power and capacity budget of the link is carried out. However, in a conventional setup of NFC link, the power coupled through and the bandwidth must be traded off. Direct Antenna Modulation (DAM) is a feasible scheme to break this dilemma. With DAM utilized in NFC link, the power-bandwidth product limit in a high Q system can be circumvented because the non-linear/time-varying nature of the operation allows high speed modulations decoupled from the charging and discharging process of the high-Q resonator. In this talk, the theory of NFC link with DAM on the transmitter is presented and validated with an experimental setup. Improvement in reception of the high-speed modulation information is observed in the experiment, implying that a superior capacity performance of a NFC link is achieved through DAM versus the traditional scheme.



Umar Azad received the B.E. degree in Electrical Engineering from National University of Sciences and Technology, Pakistan, and M.S. degree from University of California, Los Angeles, in 2007 and 2010, respectively. He is currently a Ph.D. candidate in the Electrical Engineering Department at UCLA. His research interests include electrically small antennas, wireless power transfer systems and near-field based communication systems.

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