420 results about "Impedance variation" patented technology

A near field RF communicator (100) has an inductive coupler (102) and a first signal provider (109, 110, 111) to cause the inductive coupler to provide a first signal that when inductively coupled to the inductive coupler of another near field RF communicator in near field range is insufficient to cause initiation of communication with that other near field RF communicator. A sensor (116) senses a change in an impedance of the inductive coupler (102) due to inductive coupling of the first signal between the inductive couplers of the said near field RF communicator and a said other near field RF communicator in near field range. A controller (107) determines whether or not another near field RF communicator is in near field range on the basis of any change in impedance sensed by the sensor and, if another near field RF communicator is determined to be in near field range, causes a second signal to be inductively coupled to the other near field RF communicator to initiate communication between the two near field RF communicators. The sensor may use a phase detector (118) to enable a change in impedance to be sensed by detecting a change in a current-voltage phase relationship resulting from a change in impedance.

The invention relates to a device that can be used to monitor the penetration of a penetration member into anatomical structures and, in particular, bone structures of a living body, the structures having at least two different electrical impedance areas. The device is characterized in that it comprises: at least one impedance meter which can be connected to at least two electrodes, at least one of the electrodes being located at a distal end of the penetration member; and at least one alert device which can produce an alert signal if the impedance meter detects an impedance variation. The invention also relates to a penetration member for the device and to an electronic board for the device.

An improved electrical connector is provided by compensating for skew in signal conductors of a differential pair while ensuring a uniform impedance along the differential pair. Skew is equalized by regions of lower dielectric constant preferentially positioned adjacent the longer conductor of each pair. Impedance along the length of the signal conductor is equalized by a compensation portion in the first conductor that offsets for a change in impedance associated with the change in dielectric constant adjacent the longer conductor. The compensation portion may be a widening in the first conductive element relative to a nominal width of the conductive element. The skew compensation portion may be along a longer edge of the longer conductor and the impedance compensation portion may be along the shorter edge of the longer conductor.

A focused ultrasound system includes a transducer array, a controller for providing drive signals to the transducer array, and a switch. The transducer array includes a plurality of “n” transducer elements, and the controller includes a plurality of “m” output channels providing sets of drive signals having respective phase shift values, “m” being less than “n.” The switch is coupled to the output channels of the controller and to the transducer elements, and is configured for connecting the output channels to respective transducer elements. The controller may assign the transducer elements to respective output channels based upon a size and/or shape of a desired focal zone within the target region, to steer or otherwise move a location of the focal zone, and/or to compensate for tissue aberrations caused by tissue between the transducer array and the focal zone, geometric tolerances and/or impedance variations of the transducer elements.

To maintain consistency in different environments with different impedances, a high voltage current driver may be used as a signal generator to output a tactile signal with a constant current. The constant current ensures that the voltage between the user's finger and the object's surface or electrode remains the same even if impedances in the electrical path change. Specifically, the current driver includes a current sensing circuit that determines the average current being generated. Using a feedback loop, the measured current is compared to a reference current to determine if the correct tactile sensation is perceived by the user. As the impedance changes, the current driver detects the resulting change in the signal's current and adjusts the voltage amplitude of the generated tactile signal in order to match the measured current to the reference current.

Inductive position sensors and circuit configurations are disclosed for the measurement of linear, rotary, or curved position along a motion axis. The simplified sensor structures combine one or two parts of a movable core element with a simple planar substrate having first and second inductances connected in series. Movement of the core element in parallel to the planar substrate causing the impedance of at least one of the inductances to change. Simple circuit configurations are taught by which the impedance change is converted into a useful output signal that indicates position along the motion axis.

A system and method of detecting changes in the impedance of a segment of medium voltage power line is provided. In one embodiment, the method comprises receiving voltage data comprising data of the voltage of the power lines at locations at a plurality of different points in time, receiving current data that comprises data of the current flowing between adjacent locations at the plurality of points in time, intermittently determining an impedance of the power lines between adjacent locations based on the voltage data and current data, monitoring the impedance of the power lines between adjacent locations over time, and providing a notification of a change in the impedance of a power line between adjacent locations upon detection of a change in the impedance beyond a threshold change.

According to the general concept disclosed herein, a circuit for adaptive matching of a load impedance to a predetermined load-line impedance of a load-line connected to a power amplifier output includes a fixed matching network between the power transistor and an adaptive matching network, whereby the fixed matching network acts as an impedance inverter which results in a relatively low insertion loss at high power. Results indicate that the impedance-inverting network can be used over more than a factor of 10 in impedance variation. Further, the usage of the fixed matching network, close to the power transistor, allows for the implementation of transmission zeros and/or for a well defined load impedance at a predetermined harmonic frequency, independent of the (variable) load impedance at the fundamental frequency.

The invention provides a foreign body detection method and system based on an impedance characteristic. The method comprises the steps that a detection coil is laid in an area to be detected, wherein the detection coil is connected with a capacitor element to form a resonant circuit, and a high frequency carrier signal is loaded on the resonant circuit; a resonant current signal on the resonant circuit is collected; other induction signals outside the frequency band of the high frequency carrier signal are filtered out; and finally, amplitude and phase analysis is carried out on the filtered resonant current signal to determine whether a foreign body is in the area to be detected. The method has the advantages that the impedance change of the detection coil is correspondingly acquired by detecting the change of the phase and amplitude of the resonant current signal, so as to judge whether a foreign matter exists. The method has the advantages of low cost and good effect. The original system is changed less. Especially for a wireless power transmission system, without affecting the efficiency of the original system, the method and system can be well adapted to foreign body detection in a variety of magnetic fields to improve the safety of the wireless power transmission system.

The present invention relates to a system for measuring the impedance of a skin/electrode interface and selectively modifying the system gain of the monitoring circuit to compensate for errors introduced by variations in the skin/electrode impedance. More particularly, a simplified, low-cost method for measuring and compensating for skin/electrode impedance variations is provided. The skin/electrode impedance measuring circuit and determines a system gain correction factor which may be applied to the measured signal using a software algorithm, thereby eliminating the need to change the circuit topology with a programmable gain amplifier or programmable resistor network.

A portable electronic device is provided for sending and receiving a communication signal to and from a target, respectively. Among other components, the portable electronic device includes an antenna, a transceiver, a signal processing system and control circuitry. The signal processing system determines a distance between the target and the portable electronic device. There are various ways to determine the relative distance between the target and the device. One such methodology is to use a change in a signal that is transmitted from the transceiver and reflected from the target back to the transceiver. The change can be a frequency shift, a phase shift, a capacitive coupling change, an impedance change, or any other change which notes the presence of a target relative to the transceiver. The control circuitry may be used to change the amount of power applied to the antenna and/or to change at least one security measure of the device depending on the distance detected between the target and the device.

A calibration circuit block includes a first resistor network, a second resistor network, and a feedback loop. The first resistor network includes a set of transistors and receives a constant current from a constant current source. The second resistor network receives a tracking current from a tracking current source. The impedance of the second resistor network changes with temperature and process variations on the integrated circuit. The tracking current source compensates for variations in the impedance of the second resistor network that are caused by process and temperature variations to maintain a constant reference voltage at the second resistor network. The feedback loop generates calibration control signals for controlling the conductive states of the transistors in the first resistor network. The feedback loop adjusts the calibration control signals to maintain a constant impedance in the first resistor network.

The invention discloses a distributed generator islanding detection method based on impedance measurement, the principle utilizes the feature that a great change of system equivalent impedance occurs in DG synchronization and isolated network states, high-frequency voltage signals are injected at a synchronization contact point, and impedance change can be reflected by measuring voltage change, thus judging whether the system is connected with a large grid at present. In theory, the method is not influenced by load, has nothing to do with characteristics of a DG synchronization inverter, the DG number in the island in an islanding state and the topological state of a power grid, has easy realization of self-adaption setting and does not need coordination relationships. Experiment results show that the principle has excellent sensitivity, selectivity and rapidity.

The invention discloses a power grid impedance self-adaption based LC type grid-connected inverter dual-mode control method. According to the invention, a power grid impedance boundary value of mutual switching between a current source grid-connected mode and a voltage source grid-connected mode of an inverter is determined at first, the inverter adopts a current source grid-connected mode control method when the power grid impedance boundary value is less than a switching boundary value, and the inverter adopts a voltage source grid-connected mode control method when the power grid impedance boundary value is greater than the switching boundary value; and an impedance hysteresis loop based switching mode is adopted in order to improve the stability in switching. The method disclosed by the invention solves a defect that the inverter can only operate stably within a small power grid impedance variation range when adopting a single current source or voltage source grid-connected mode under different power grid impedance conditions, and stable operations of the inverter within a large power grid impedance variation range are realized through mutual switching between the current source power-grid mode and the voltage source grid-connected mode.

The invention provides a load detecting system comprising a core (83) of magnetostrictive material, a coil (85) disposed in the vicinity of the core, and a load detecting circuit (10) connected to the coil (85) for detecting the magnitude of a load acting on the core (83). The load detecting circuit (10) comprises an exciting circuit (102) for passing an a.c. detecting current through the coil (85), a pulse current generating circuit (103) for passing through the coil a detection preparing current having a current value greater than the maximum value of the detecting current, a change-over circuit (104) for effecting a change-over between the exciting circuit (102) and the pulse current generating circuit (103) to pass the detecting current through the coil after passing the detection preparing current therethrough, and a microcomputer (100) for deriving the magnitude of the load acting on the magnetostrictive element based on an impedance variation produced in the coil during the period of passage of the detecting current through the coil.