Variable capacitor

Abstract: A wireless power system includes a power source, power receiver, and components thereof. The system can also include a parasitic antenna that can improve the coupling to the power source in various modes. The antenna can have both a variable capacitor and a variable inductor, and both of those can be changed in order to change characteristics of the matching.

Abstract: In a wireless power transfer (WPT) system via the magnetic resonant coupling, one of the most challenging design issues is to maintain a reasonable level of power transfer efficiency (PTE), even when the distance between the transmitter and the receiver changes When the distance varies, the PTE drastically decreases due to the impedance mismatch between the resonator of the transmitter and that of the receiver This paper presents a novel serial/parallel capacitor matrix in the transmitter, where the impedance can be automatically reconfigured to track the optimum impedance-matching point in the case of varying distances The dynamic WPT matching system is enabled by changing the combination of serial and parallel capacitors in the capacitor matrix An interesting observation in the proposed capacitor matrix is that the resonant frequency is not shifted, even with capacitor-matrix tuning In order to quickly find the best capacitor combination that achieves maximum power transfer, a window-prediction-based search algorithm is also presented in this paper The proposed resonance WPT system is implemented using a resonant frequency of 1356 MHz, and the experimental results with 1W power transfer show that the transfer efficiency increases up to 88 % when the distance changes from 0 to 12 m

Abstract: A wireless power infrastructure for delivering wireless power from a wireless network to mobile devices. The infrastructure includes a plurality of power transmission hubs, each hub having: a first capacitor for transmitting a signature frequency for a defined range; and a set of second capacitors, each for transmitting resonant wireless power within the defined range at a selectable frequency. A mobile device for obtaining wireless resonant the plurality of power transmission hubs is also described, and includes: a first variable capacitor for detecting a signature frequency associated with a proximately located power transmission hub; a second variable capacitor for receiving wireless resonant capacitor from the proximately located power transmission hub; and a synchronization system for setting the second variable capacitor to a frequency that is synchronized with a wireless resonant power transmission of the proximately located power transmission hub.

Abstract: A wireless, surgically implantable pressure transducer for measuring pressure of fluid or tissue in a body chamber such as brain ventricle of a patient suffering hydrocephalus or a severe head injury. The transducer includes a coaxial variable capacitor electrically connected across an inductor to form a parallel resonant L-C circuit. Alternatively, a coaxially variable inductor may be connected across a capacitor to form the L-C circuit. A bellows is mechanically connected to the variable component to vary the value of capacitance or inductance and hence the resonant frequency of the L-C circuit in response to pressure changes of the fluid in which the bellows is immersed. The transducer is electromagnetically coupled to an external source of variable-frequency oscillatory energy such as a grid-dip oscillator which enables external detection of the transducer resonant frequency which is in turn indicative of the level of fluid pressure being sensed.