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A magnetic resonant loop antenna enhancing the operating distance by improving the wireless power transfer efficiency of 13.56MHz RFID system was proposed. The proposed resonant antenna consists of resonant coils arranged between source coil and device coil coupled to each of them. The effects of resonant coils were measured using a 13.56MHz RFID reader and tag system in addition to simulation using RF simulator. The measurement results from RFID reader and tag show that the maximum operating distance is increased by approximately 96% and amplitude of receiving voltage on the RFID tag antenna is increased by 18% thanks to the magnetic resonance loop antenna.

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We propose a way of achieving maximum power and power-transfer efficiency from thermoelectric generators by optimized selection of maximum-powerpoint-tracking (MPPT) circuits composed of a boost-cascaded-with-buck converter. We investigated the effect of switch resistance on the MPPT performance of thermoelectric generators. The on-resistances of the switches affect the decrease in the conversion gain and reduce the maximum output power obtainable. Although the incremental values of the switch resistances are small, the resulting difference in the maximum duty ratio between the input and output powers is significant. For an MPPT controller composed of a boost converter with a practical nonideal switch, we need to monitor the output power instead of the input power to track the maximum power point of the thermoelectric generator. We provide a design strategy for MPPT controllers by considering the compromise in which a decrease in switch resistance causes an increase in the parasitic capacitance of the switch. List of symbolsD Duty ratio D maxjGain Duty cycle of the peak voltage conversion gain D maxjPin Duty cycle of the maximum input power D maxjPout Duty cycle of the maximum output power D MPPT Duty cycle for achieving maximum power point DT Temperature difference g Power transfer efficiency IGBT Insulated gate bipolar mode transistor I in Input current of boost converter MOSFET Metal oxide semiconductor field effect transistor MPP Maximum power point MPPT Maximum power point tracking P MAX Maximum output power from the TEG P injmax Peak input power P outjmax Peak output power PWM Pulse width modulation R L Load resistance R SW On-resistance of switch R TEG Internal resistance of TEG S Seebeck coefficient SW Switch SPICE Simulation program with integrated circuit emphasis TEG Thermoelectric generator V in Input voltage of boost converter V out Output voltage of boost converter V out =V Sjmax Peak gain of boost converter V S Open circuit voltage of TEG Subscripts (practical SW) Practical switch (ideal SW) Ideal switch