Output impedance

About: Output impedance is a research topic. Over the lifetime, 11185 publications have been published within this topic receiving 134949 citations.

Range-Adaptive Wireless Power Transfer Using Multiloop and Tunable Matching Techniques

Abstract: In this paper, a range-adaptive wireless power transfer (WPT) system is proposed to achieve high efficiency over a wide range of distances by using tunable impedance matching techniques. A multiloop topology is employed to greatly reduce the variation in the input impedance of the WPT system with respect to the distance, where one of the four loops with a different size is selected, depending on the distance. It enables the design of a simple tunable matching circuit using a single variable capacitor. An algorithm is written to find the optimum loop and capacitance in the matching network, based on the measured input return loss using a directional coupler and rectifiers. The fabricated WPT system shows a range-adaptive operation with high efficiency over a wide range of distances. It attains 48% efficiency at a distance of 100 cm with a maximum efficiency of 92% at a distance of 10 cm.

Multilayer Substrate Integrated Waveguide Four-Way Out-of-Phase Power Divider

Abstract: In this paper, a multilayer substrate integrated waveguide (SIW) four-way out-of-phase power divider is investigated. In a previous research (Eom , 2009), the four-way power division was studied by a 3-D mode coupling method, which was achieved by a vertical Y-junction as well as a lateral Y-junction of half mode substrate integrated waveguides (HMSIW) using a multilayer substrate. In this research, resistive coupling slots, for obtaining good isolation between four output ports and impedance matching at all the ports, are realized on the lateral HMSIW Y-junctions and the vertical HMSIW Y-junctions using isolation resistors. From the measurement results, excellent performances of insertion loss, isolation, impedance matching, and amplitude balancing were simultaneously achieved for the X-band range. It is expected that the proposed design of a multilayer substrate integrated waveguide (ML-SIW) power divider will play an important role in the future integration of compact multiway SIW circuits and systems.

Method and device for stable impedance plethysmography

Abstract: A method and device for impedance plethysmography, with relative immunity to skin electrode contact resistance drift are provided. The method comprises placing first and second measurement electrodes (100, 102) on a biological object; first and second reference electrodes (103, 105) on opposite sides of the first measurement electrode (100); and third and fourth reference electrodes (104, 106) on opposite sides of the second measurement electrode (102), so as to define a measurement electrical circuit (100, 102, 200, 300), six reference electrical circuits (200, 300), and one of (100, 103) or (100, 105) or (103, 105) or (102, 104) or (102, 106) or (104, 106); measuring a first electrical impedance of the measurement circuit; a second, third and fourth electrical impedances of three reference circuits which include the first measurement electrode, the first reference electrode, and the second reference electrode; a fifth, sixth and seventh electrical impedances of three reference circuits which include the second measurement electrode, the third reference electrode and the fourth reference electrode; calculating the skin electrode resistance drift of the first measurement electrode based on the second, third and fourth electrical impedances; the skin electrode resistance drift of the second measurement electrode based on the fifth, sixth and seventh electrical impedances; and calculating the internal impedance of the biological object by subtracting the skin electrode resistance drifts of the first and second measurement electrodes from the first electrical impedance.

ARC generation in a fluid medium

Abstract: An electrosurgical generator is disclosed. The generator includes a radio frequency output stage configured to generate a frequency waveform to an active electrode of an electrosurgical instrument when the active electrode is disposed in a fluid medium. The generator also includes a sensor circuit configured to measure tissue impedance and a controller configured to increase power of the radio frequency waveform to a predetermined electrical arcing level in response to the tissue impedance being within an open circuit impedance range and tissue contact impedance range. The controller is further configured to lower the power of the radio frequency waveform to a lower level when the tissue impedance is outside the open circuit impedance range and the tissue contact impedance range.

An Improved Design of Current Controller for LCL -Type Grid-Connected Converter to Reduce Negative Effect of PLL in Weak Grid

Abstract: For three-phase LCL -type grid-connected converter, when it is attached to weak grid, current control interacts with phase-locked loop (PLL) via point of common coupling voltage. Consequently, PLL dynamic might deteriorate grid current control and even result in system instability. However, the conventional design method of current controller neglects the impact of PLL, and therefore, it is hard for the current controller to mitigate the negative effect of PLL. In this paper, an improved design of current controller, i.e., proportional–integral controller and capacitor-current-feedback active damping, is proposed to reduce the negative effect of PLL on current control. First, a small-signal impedance model is developed to analyze the impact of PLL on current control. Then, the effect of current controller parameters on the converter output impedance is analyzed, and a design guideline to improve the current controller parameters is presented. With the improved parameters, in precondition of satisfying system stability margin under both stiff and weak grid, the negative effect of PLL on current control can be effectively mitigated without employing additional control strategies. Furthermore, the current control has a strong robustness against wide-range variation of grid impedance. Finally, the experiment demonstrates the effectiveness of the proposed design method.