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High frequency metrology for intracardiac ablation: in-vivo results

100%

Rouane A. , Bru P.

2012

tom Vol. 19, nr 3

603-610

Cardiac Radiofrequency (RF) ablation is a commonly used clinical procedure for treating many cardiac arrhythmias. However, the efficacy of RF ablation may be limited by two factors: small ventricular lesions and impedance rise, leading to coagulum formation and desiccation of tissue. In this paper, a high frequency (HF) energy ablation system operating at 27.12 MHz based on an automated load matching system was developed. A HF energy matched probe associated to the automated impedance matching device ensures optimal transfer of the energy to the load. The aim of this study was to evaluate this energy for catheter ablation of the atrioventricular junction. In vivo studies were performed using 10 sheep to characterize the lesions created with the impedance matching system. No cardiac perforation was noted. No thrombus was observed at the catheter tip. Acute lesions ranged from 3 to 45 mm in diameter (mean šSD = 10.3š10) and from 1 to 15 mm in depth (6.7š3.9), exhibiting a close relationship between HF delivered power level and lesion size. Catheter ablation using HF current is feasible and appears effective in producing a stable AV block when applied at the AV junction and large myocardial lesions at ventricular sites.

Impedance matching of the inverter for induction heating

75%

Kobos W.

tom R. 94, nr 4

71--74

The impedance matching of source and load has influences on the ability to transfer power. In induction heating processes, the electrical parameters of the induction heating system can significantly differ. In the paper the comparison of sensitivity of power sources with different resonant systems on the changing the load impedance are presented. The possibility of increasing the elasticity of the inverter with LLC resonant circuit has been analyzed. The solution combining the controlled LLC circuit with a suitable algorithm has been proposed to automatically correct the substitute impedance of the load by the power source system.

Dopasowanie impedancyjne źródła i obciążenia decyduje o możliwość przekazywania mocy do obciążenia. Przy nagrzewaniu indukcyjnym parametry elektryczne indukcyjnego układu grzejnego mogą się znacząco różnić. W artykule porównano wrażliwość źródeł zasilania z różnymi układami rezonansowymi na zmianę impedancji obciążenia. Przeanalizowano możliwości zwiększenia elastyczności impedancyjnej źródła z układem rezonansowym LLC poprzez połączenie sterowanego układu LLC z odpowiednim algorytmem pozwalającym na samoczynne korygowanie przez źródło zasilania zastępczej impedancji obciążenia.

Automatic tuning of a resonant circuit in wireless power supply systems for biomedical sensors

63%

Blakiewicz G. , Jakusz J. , Jendernalik W. , Szczepański S.

tom Vol. 64, nr 3

641--646

In this paper, a tuning method of a resonant circuit suited for wireless powering of miniature endoscopic capsules is presented and discussed. The method allows for an automatic tuning of the resonant frequency and matching impedance of a full wave rectifier loading the resonant circuit. Thereby, the receiver tunes so as to obtain the highest power efficiency under given conditions of transmission. A prototype receiver for wireless power reception, fabricated in in AMS CMOS 0.35 μm technology, was used to verify correct operation of the proposed tuning. The prototype system produces a stable supply voltage, adjustable in the range of 1.2–1.8 V at a maximum output current of 100–67 mA, which is sufficient to power a typical endoscopic capsule.