Electrical impedance

About: Electrical impedance is a research topic. Over the lifetime, 36015 publications have been published within this topic receiving 371891 citations. The topic is also known as: electrical impedance & complex impedance.

Radio frequency coil for open magnetic resonance imaging system

Abstract: A quadrature coil suitable for use with an open frame MRI system provides crossing pairs of arrays of parallel conductor elements, respectively. Compact configuration is provided through use of an isolating circuit for incorporating parasitic capacitances at the resonance frequency of the coil into a blocking parallel resonance. Termination of the parallel conductor elements may be accomplished by equal impedance node connectors formed from branching pairs of conductors or a triangular least resistance connection form. RF shields are provided by pairs of conductive sheets containing eddy current reducing slots aligned with the parallel conductors elements of the coil.

De-tuning in wireless power reception

Abstract: Exemplary embodiments are directed to wireless power transfer. A receiver (820) with a receive antenna (L2) couples with near field radiation in a coupling mode region. The receiver generates an RF signal at a resonant frequency responsive to the near field radiation. A de-tuning circuit (860) generates a variable impedance responsive to a control signal to modify the RF signal to a smaller amplitude or to a different resonant frequency. A rectifier (840) converts the modified RF signal to a DC signal. A comparator (850) creates a feedback loop by generating the control signal responsive to comparing the DC signal to a reference voltage (Vref). The de- tuning circuit may operate in digital mode or in linear mode with the feedback. An impedance element (Rl) may be coupled to the de- tuning circuit to generate a voltage proportional to a current through the de-tuning circuit. The proportional voltage is rectified to a receive signal (1430) with information sent from a transmitter.

Interconnect module with reduced power distribution impedance

Abstract: An interconnect module for an integrated circuit chip incorporates a thin, high dielectric constant embedded capacitor structure to provide reduced power distribution impedance, and thereby promote higher frequency operation. The interconnect module is capable of reliably attaching an integrated circuit chip to a printed wiring board via solder ball connections, while providing reduced power distribution impedance of less than or equal to approximately 0.60 ohms at operating frequencies in excess of 1.0 gigahertz.

Sensorless Battery Internal Temperature Estimation Using a Kalman Filter With Impedance Measurement

Abstract: This study presents a method of estimating battery- cell core and surface temperature using a thermal model coupled with electrical impedance measurement, rather than using direct surface temperature measurements. This is advantageous over previous methods of estimating temperature from impedance, which only estimate the average internal temperature. The performance of the method is demonstrated experimentally on a 2.3-Ah lithium-ion iron phosphate cell fitted with surface and core thermocouples for validation. An extended Kalman filter (EKF), consisting of a reduced-order thermal model coupled with current, voltage, and impedance measurements, is shown to accurately predict core and surface temperatures for a current excitation profile based on a vehicle drive cycle. A dual-extended Kalman filter (DEKF) based on the same thermal model and impedance measurement input is capable of estimating the convection coefficient at the cell surface when the latter is unknown. The performance of the DEKF using impedance as the measurement input is comparable to an equivalent dual Kalman filter (DKF) using a conventional surface temperature sensor as measurement input.

Microfabricated AC impedance sensor

Abstract: A microfabricated instrument for detecting and identifying cells and other particles based on alternating current (AC) impedance measurements. The microfabricated AC impedance sensor includes two critical elements: 1) a microfluidic chip, preferably of glass substrates, having at least one microchannel therein and with electrodes patterned on both substrates, and 2) electrical circuits that connect to the electrodes on the microfluidic chip and detect signals associated with particles traveling down the microchannels. These circuits enable multiple AC impedance measurements of individual particles at high throughput rates with sufficient resolution to identify different particle and cell types as appropriate for environmental detection and clinical diagnostic applications.