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This study documents the design of an electromagnetic energy transducer, which is used to convert ambient vibration into electrical energy. The response of the designed energy transducer is theoretically and experimentally analysed using a simple equivalent circuit model and magnetic field simulator in low-acceleration environments. For an electromagnetic energy transducer in ambient vibration, an approximate analytical expression is derived for the extracted power across a load. The energy transducer consists of four magnets (NdFeB, N35), two I-shaped magnetic cores, two U-shaped cores made of soft ferrite material, and a coil for induced voltage. The two U-shaped magnetic cores are surrounded by a coil with an approximate 3000 turn. The energy transducer is theoretically modelled using the commercial tool, COMSOL, and is experimentally validated through electrical measurements. The relation between the acceleration of vibration and the maximum average power that can be extracted at the optimal load was also studied. The size of the electromagnetic energy transducer is 43 × 37 × 80 mm3. The energy transducer has a maximum average power of 3.24 mW at a frequency of 28 Hz and an acceleration of 0.4g, and has a maximum average power of 3.83 mW at a frequency of 31 Hz and an acceleration of 0.5g. [ABSTRACT FROM AUTHOR]

This paper studies the magnetic coupling between two adjacent loop antennas that are parallel to each other in a plane and presents a new practical method to avoid the resulting magnetic coupling interference. The study focuses on the high frequency radio-frequency identification (RFID) system for casino applications, where several loop antennas are closely built into a game table to monitor gaming chips. In this case, neighboring loop antennas may severely interfere with each other by magnetic coupling, which leads to the malfunction of the RFID system. In this paper, we present a practical loop antenna with a new loop switch circuit for avoiding magnetic coupling. The loop switch circuit is integrated with a matching circuit and automatically operated by using an interrogating signal from a reader. We verified the validity of the proposed design by showing that an RFID reader with the proposed antenna can exactly and separately read the gaming chips placed on the different betting zones of a game table. [ABSTRACT FROM AUTHOR]

In this paper, we present a demodulation structure suitable for a reader baseband receiver in a passive radio frequency identification (RFID) environment. In a passive RFID configuration, an undesirable DC-offset phenomenon may appear in the baseband of the reader receiver, which can severely degrade the performance of the extraction of valid information from the received tag signal. To eliminate this DC-offset phenomenon, the primary feature of the proposed demodulation structures for the received FM0 and Miller subcarrier signals is to reconstruct the signal corrupted by the DC-offset phenomenon by creating peak signals from the corrupted signal. It is shown that the proposed method can successfully detect valid data, even when the received baseband signal is distorted by the DC-offset phenomenon. [ABSTRACT FROM AUTHOR]

A UHF band near-field antenna using microstrip lines and stubs for tagging stacked tags in a smart table is presented. It is shown that a suitable near-field reader antenna can be designed from signal lines, ground lines, and several stubs to generate coupled electric and magnetic fields. The proposed near-field reader antenna satisfactorily operates in a UHF radio frequency identification (RFID) smart table, and the measurements show that the antenna is capable of detecting 200 stacked tags in a reading area of 200 mm × 190 mm and achieves a detection rate of 97% when the tags are stacked in a smart table. The proposed UHF RFID smart table is successfully implemented for casino chip management. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1116–1119, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25115 [ABSTRACT FROM AUTHOR]