852 results about "Common mode noise" patented technology

A low cost, two-dimensional, fingerprint sensor includes a pixel array, each pixel including a switch and a pixel electrode for forming a capacitance with a fingertip. One or more active transmission electrodes are spaced from a selected row of the pixel array, and transmit a carrier signal into the finger without direct coupling into the selected pixels. Signals sensed by the pixel array are coupled to an independent integrated circuit, and connections between the IC and the pixel array are reduced by demultiplexing row select lines, and by multiplexing sensed column data. Differential sensing may be used to improve common mode noise rejection. The fingerprint sensor may be conveniently incorporated within a conventional touchpad LCD panel, and can mimic the performance of lower density touchpad pixels.

The invention discloses a balance feed differential slot antenna for restraining common-mode noise. Based on a planar substrate integrated waveguide structure, the slot antenna is adopted as a radiating unit; due to different electric field distributions in the substrate integrated waveguide under different stimulation modes, energy can be effectively radiated under the different-mode signal stimulation, and most of energy is reflected under the common-mode signal stimulation. Due to the adoption of the antenna of the structure, different-mode signals can be effectively transmitted and received, meanwhile, common-mode signals are restrained from being transmitted and received, and therefore the function of restraining common-mode noise is achieved.

Image sensing apparatus includes an image pickup plate disposed generally orthogonally with respect to an expected direction of movement of an object, such as a finger, multiple image drive plates in spaced relation to the image pickup plate to define sensor gaps between respective image drive plates and the image pickup plate, and a reference plate disposed substantially parallel to the image pickup plate. The reference plate is spaced from the image pickup plate to permit common mode noise and coupling to be cancelled and is spaced from the image drive plates to permit a differential image signal to develop between the image pickup plate and the reference plate. A differential amplifier coupled to the image pickup plate and the reference plate provides noise cancellation. The apparatus may further include a comb plate spaced from the reference plate and coupled to a reference potential, such as ground.

In order to overcome problems when using an adaptive filter for cancellation of common-mode noise in digital subscriber loops, caused by a portion of the differential signal being converted to common mode, which degrades the performance of the filter, a noise cancellation technique is proposed which compensates for this cross-coupled signal energy. In particular, a digital noise detector is used to detect one or more noisy frequency bands of the common mode signal and pass only the digitized common mode signal in those detected frequency bands through the adaptive filter to produce a digital common mode noise estimate signal. A control unit adjusts coefficients of the adaptive filter to reduce correlation between the differential signal and common mode signal. It is also proposed to compensate for the effects of stray capacitive coupling across the usual hybrid device by including an equivalent capacitive component in a common mode noise estimation circuit.

Image sensing apparatus includes an image pickup plate disposed generally orthogonally with respect to an expected direction of movement of an object, such as a finger, multiple image drive plates in spaced relation to the image pickup plate to define sensor gaps between respective image drive plates and the image pickup plate, and a reference plate disposed substantially parallel to the image pickup plate. The reference plate is spaced from the image pickup plate to permit common mode noise and coupling to be cancelled and is spaced from the image drive plates to permit a differential image signal to develop between the image pickup plate and the reference plate. A differential amplifier coupled to the image pickup plate and the reference plate provides noise cancellation. The apparatus may further include a comb plate spaced from the reference plate and coupled to a reference potential, such as ground.

A bridgeless power factor correction converter that can reduce common-mode noise and enhance power density is made up of a boost inductor coupled to an input end, a bidirectional switch connected in series with the boost inductor, a first series rectifying circuit having a junction node connected between the boost inductor and the bi-directional switch, a second series rectifying circuit connected in parallel with the first series rectifying circuit and having a junction node coupled to the bi-directional switch, and an output capacitor connected in parallel with the second series rectifying circuit, in which the second series rectifying circuit is made up of slow-recovery diodes and the first series rectifying circuit is made up of fast-recovery diodes.

The LC VCO includes an LC oscillator module with first and second tank nodes and a control module with positive and negative input voltage terminals. The control module includes four voltage dependent capacitive elements which are configured to be biased for operation as voltage dependent variable capacitances. The voltage dependent capacitive elements are interconnected such that the effect of a common mode input voltage is to increase the capacitance of two of the voltage dependent capacitive elements, while simultaneously decreasing the capacitance of two of the other voltage dependent capacitive elements by a substantially similar amount, such that a differential voltage applied across the positive and negative input voltage terminals is operable to change the capacitance of the voltage dependent capacitive elements, and thereby the frequency of the LC oscillator module, while effects on the output frequency of the oscillator caused by a common mode voltage tend to cancel. Accordingly, a fully differential signal path in phase locked loops employing LC oscillators, with improved noise rejection, substantial suppression of common mode noise, and a minimal increase in complexity over a single-ended control design can be achieved. Additional supply voltages need not be employed.

A noise cancellation system configured to isolate and process a common mode noise signal to generate a cancellation signal. The cancellation signal is combined with a differential signal to cancel unwanted differential mode noise that coupled onto the differential signal. In one embodiment a multi-channel communication system utilizes two or more channels that are in close proximity to other alien channels. A common mode signal isolation unit is configured to isolate common mode noise. The common mode noise signal is processed with a filter or other means to generate a cancellation signal. The cancellation signal is combined with the differential signal to thereby cancel noise that coupled onto the differential signal. The processed common mode noise signal may be made to approximate the differential mode noise signal. The common mode signal may be obtained from a center tap of a transformer, or a sensing winding of a three winding transformer.

A bridgeless power factor correction converter that can reduce common-mode noise and enhance power density is made up of a boost inductor coupled to an input end, a bidirectional switch connected in series with the boost inductor, a first series rectifying circuit having a junction node connected between the boost inductor and the bi-directional switch, a second series rectifying circuit connected in parallel with the first series rectifying circuit and having a junction node coupled to the bi-directional switch, and an output capacitor connected in parallel with the second series rectifying circuit, in which the second series rectifying circuit is made up of slow-recovery diodes and the first series rectifying circuit is made up of fast-recovery diodes.

An optical sensing system uses light scattered from a sensing fibre to sense conditions along the fibre, and has a receiver with a frequency to amplitude converter to obtain a frequency of a Brillouin component of the received scattered light, to deduce the conditions. This converter can avoid time consuming scanning of frequencies to obtain the Brillouin frequency spectrum, and avoids the heavy processing load of deducing a peak or average frequency from the spectrum. The converter can be implemented in the optical domain using a grating or interferometer, or in the electrical domain using a diplexer or electrical interferometer. It can generate complementary signals, having opposite signs, a ratio of these signals representing the frequency. This can avoid sensitivity to amplitude changes in the received scattered signals and provide common mode rejection of noise.

An intelligent electronic device (IED), e.g., an electrical power meter, having circuitry for an input structure of an analog-to-digital converter (ADC) that reduces noise of a signal from a sensor in the device, resulting in a highly accurate power measurement, is provided. The circuitry includes a first single-ended analog-to-digital converter with an input from a voltage signal and a second single-ended analog-to-digital converter with an input that is the reference voltage used by the voltage signal. A programmable device subtracts the digital output of the second single-ended analog-to-digital converter from the digital output of the first single-ended analog-to-digital converter to produce a digital result of the voltage signal that is free from common-mode noise.

In an adaptive filter for cancelling common-mode noise in digital subscriber loops, a narrowband noise estimator is used to detect one or more noisy frequency bands of the common mode signal and derive therefrom a first noise estimation signal. A wideband noise estimator derives from the remainder of the common mode signal a second noise estimation signal. The first and second noise estimation signals are subtracted from the differential signal, The wideband noise estimator comprises a bandstop filter for removing the frequencies detected by the narrowband noise estimator, an analog-to-digital converter for digitizing the bandstopped signal, and an adaptive filter for deriving the second noise estimation signal from the digitized bandstopped signal and, in the process, compensating for phase and gain differences, especially attributable to the interference being injected at different points along the length of the channel.

A double reference wave modulation scheme for filterless power amplifiers is disclosed for reducing EMI and common mode voltages. In the filterless power amplifier, differential outputs for driving load impedance are feedback and corrected based on input audio signals. Reference wave generators generate reference waves. A control logic results pulses in the pair of differential outputs in response to a clock signal or a reference voltage and a cross relationship between the input audio signal and the first and second reference waves. Pulses of one of the differential outputs are not overlapped with pulses of the other of the differential outputs for eliminating common mode noises of the power amplifier.

In an adaptive filter for cancelling common-mode noise in digital subscriber loops, a narrowband noise estimator is used to detect one or more noisy frequency bands of the common mode signal and derive therefrom a first noise estimation signal. A wideband noise estimator derives from the remainder of the common mode signal a second noise estimation signal. The first and second noise estimation signals are subtracted from the differential signal, The wideband noise estimator comprises a bandstop filter for removing the frequencies detected by the narrowband noise estimator, an analog-to-digital converter for digitizing the bandstopped signal, and an adaptive filter for deriving the second noise estimation signal from the digitized bandstopped signal and, in the process, compensating for phase and gain differences, especially attributable to the interference being injected at different points along the length of the channel.

A noise suppression circuit for a communications channel (10) comprises a hybrid device (11) coupled to the channel for providing a differential output signal corresponding to a received signal. A delay unit (12) delays the differential signal by a suitable amount to allow for the generation and subtraction of a noise estimate. A summing device (13) extracts a digital common mode signal from the channel, and a noise estimation unit (16) provides a common mode noise estimate signal in dependence upon a history of the common mode signal over a predetermined period of time and over a plurality of frequency bands. The common mode noise estimate signal is combined subtractively (19) with the delayed differential signal to cancel common mode noise elements of the delayed differential signal. The noise estimation unit may comprise an analysis filter bank (20) for producing a plurality of subband signals (S1-SM), each at a different one of a plurality of different frequencies, a plurality of noise detection circuits (231-23M), each for processing a respective one of the plurality of subband signals to provide a component of the common mode noise estimate signal, and a synthesis filter bank (24) for processing the common mode noise signal components to provide the noise estimate signal.

A motor drive system control provides global closed loop feedback to cooperatively operate system components to adaptively reduce noise and provide noise cancellation feedback. An active EMI filter reduces differential and common mode noise on an input and provides a noise level indication to a system controller. Power switches in both a power converter and power inverter are cooperatively controlled with dynamic dv / dt control to reduce switching noise according to a profile specified by the controller. The dv / dt control is provided as an analog signal to a high voltage IC and codified as a pulse width for a level shifting circuit supplying control signals to the high voltage gate drive. A noise extraction circuit and technique obtain fast noise sampling to permit noise cancellation and adaptive noise reduction.

The present invention provides an improved column readout circuitry and method of operation which minimizes substrate and other common mode noise during a read out operation. The circuit improves the consistency of the pixel to pixel output of the pixel array and increases the dynamic range of the pixel output. This is accomplished by obtaining a differential readout of the reset signal and integrated charge signal from a desired pixel along with the reset signal and charge signal from a reference circuit. In this manner common mode noise can be minimized by a combination of signals from the desired and reference pixels in the sample and hold aspect of the column circuitry. In one exemplary embodiment of the invention, a 3T pixel arrangement is used. In another exemplary embodiment, a 4T arrangement is used. Additional exemplary embodiments provide differential column readout circuitry that can be used with any two signal sources.

The present invention provides a ferrite core which has a structure in that plating is prevented from elongating, which can maintain insulation resistance between electrodes and can prevent short-circuit between a conductor wire and the electrode without damaging adhesion properties while mounted and, moreover, which can stabilize a Q value (loss characteristic) of a product. The ferrite core includes a wound core and flanges integrally formed at both ends of the wound core, and each of the flanges includes a plurality of legs provided so as to rise from one surface of the wound core and having a top surface to be formed with electrode, and each leg is tapered off toward the top surface and an vertical corner portion formed between adjacent side faces thereof has a curved surface.

A double reference wave modulation scheme for filterless power amplifiers is disclosed for reducing EMI and common mode voltages. In the filterless power amplifier, differential outputs for driving load impedance are feedback and corrected based on input audio signals. Reference wave generators generate reference waves. A control logic results pulses in the pair of differential outputs in response to a clock signal or a reference voltage and a cross relationship between the input audio signal and the first and second reference waves. Pulses of one of the differential outputs are not overlapped with pulses of the other of the differential outputs for eliminating common mode noises of the power amplifier.

In a filter circuit (1), a common mode choke (2) and a normal mode choke (3) have extremely high and low impedances, respectively, for common mode signals received through two input terminals (1a and 1b). The chokes have the opposite impedance characteristics for differential signals. In particular, the difference in impedance is large. Furthermore, the normal mode choke (3) is installed as a previous stage of the common mode choke (2). Accordingly, common mode noises which enter the two input terminals (1a and 1b) penetrate the normal mode choke (3), but neither penetrate the common mode choke (2) nor are reflected from the common mode choke (2). In particular, common mode currents flow through the normal mode choke (3) but do not flow through the common mode choke (2).

A method and apparatus for reducing common mode noise in a three phase pulse width modulated (PWM) system the method comprising the steps of receiving modulating waveforms, identifying a first of the modulating waveforms that is instantaneously the maximum of the modulating waveforms, identifying a second of the modulating waveforms that is instantaneously the minimum of the modulating waveforms, for a first phase associated with at least one of the first and second identified waveforms, substituting a first substitute waveform for the one of the first and second waveforms, for the first phase, modifying at least one of the first substituted waveform and duty cycle signals generated by comparing the first substituted waveform with the carrier signal as a function of a first rule set to substantially minimize the effects of turn on delays and for at least one of the second and third phases, modifying at least one of the associated modulating waveform and duty cycle signals generated by comparing the modulating waveform with the carrier signal as a function of a second rule set to substantially eliminate the effects of turn on delays where the second rule set is different than the first rule set.

An intelligent electronic device (IED), e.g., an electrical power meter, having circuitry for an input structure of an analog-to-digital converter (ADC) that reduces noise of a signal from a sensor in the device, resulting in a highly accurate power measurement, is provided. The circuitry includes a first single-ended analog-to-digital converter with an input from a voltage signal and a second single-ended analog-to-digital converter with an input that is the reference voltage used by the voltage signal. A programmable device subtracts the digital output of the second single-ended analog-to-digital converter from the digital output of the first single-ended analog-to-digital converter to produce a digital result of the voltage signal that is free from common-mode noise.

A power conversion apparatus, comprising: a power conversion circuit comprising an AC source; a power conversion unit with DC terminals and AC terminals; a filter inductor unit including first and second terminals, the first terminals of the filter inductor unit being connected to the AC source, the second terminals of the filter inductor unit being connected to the AC terminals of the power conversion unit; a common mode noise suppression circuit comprising a capacitive impedance network including first and second terminals; an impedance balancing network including first and second terminals; the second terminals of the capacitive impedance network are connected to the first terminals of the impedance balancing network, the first terminals of the capacitive impedance network are connected to the first terminals of the filter inductor unit, and the second terminals of the impedance balancing network are connected to the DC terminals of the power conversion unit.

A fail-safe circuit for a differential receiver can tolerate noise. A latch is enabled when both differential inputs V+, V- rise above a reference voltage that is close to Vcc. The latch, once enabled, is set by an offset amplifier, signaling the fail-safe condition. The offset amplifier sets the latch when V+ is above or equal to V-. The differential amplifier has a small offset voltage to allow the latch to remain set when V+ and V- are equal in voltage. An output from a differential amplifier receiving V+ and V- can be blocked by a gate when the fail-safe condition is latched. Pullup resistors pull V+, V- to Vcc when an open failure occurs. The latch remains set when common-mode noise occurs on V+, V-, preventing noise from prematurely disabling the fail-safe condition. Such noise coupled into a broken cable is usually common-mode.

The invention is a bridge-free power factor correction (PFC) converter able to reduce common code noises and increase power density, comprising: boost inductor coupled to input end; two-way switch connected in series with the boost inductor and having junction node coupled between the boost inductor and two-way switch; second series rectifier circuit, having junction node coupled to the two-way switch; and output capacitor connected in parallel with the second series rectifier circuit; where the second series rectifier circuit is composed of slow recovery diode and the first series rectifier circuit is composed of fast recovery diode. Thus, the invention can reduce common mode noises in the converter and increase the power density of the converter.

A power factor correction (PFC) power converter, particularly of a multiphase totem-pole or other topology presenting a switching bridge that can potentially provide bi-directional power transfer control, reduces a nominal switching frequency and achieves zero voltage switching over an increased portion of a half line cycle by providing positive or inverse coupling of inductors in an inductor structure that can be formed of a multi-layer printed circuit board such that at least three different inductances are presented during each half line cycle period; allowing increased switching frequency and simplifying EMI filtering arrangements. Parasitic capacitances can be balanced with additional coupled windings to reduce differential mode and common mode noise. The PFC power converter is particularly applicable to provide bi-directional power control from an on-board battery charger in an electrically powered vehicle.

An efficient system (10) for measuring target characteristics via a torsion mode beam of electromagnetic energy. The system (10) includes a first mechanism (34, 38, 40, 42, 16) for transmitting the torsion mode beam toward a target (12). A second mechanism (16, 18, 20) receives the resulting target return beam and provides a first signal in response thereto. A third mechanism (26, 28) employs the first signal to determine rotational characteristics of the target (12). In a specific embodiment, the system (10) further includes a fourth mechanism (20, 26) that reduces or eliminates noise in the return beam based on common mode noise rejection. A fifth mechanism (32) identifies the type of the target based on the target rotational characteristics via comparison to predetermined target rotational signatures (36). An additional mechanism (24, 40, 42) selectively switches the mode of the beam between a first mode and a second mode. The first mechanism (34, 38, 40, 42, 16) and second mechanisms (16, 18, 20) employ a laser transceiver (16) having a transmit chain (34, 38, 40, 42, 16) and a receive chain (16, 18, 20). The transmit chain includes a time-division multiplexer (34) or a spatial multiplexer (34, 62) for selectively transmitting the beam of electromagnetic energy or for selectively transmitting first and second spatially separated beams characterized by the first and second modes, respectively. The receive chain (16, 18, 20) includes a corresponding time-division demultiplexer (20, 26) or spatial demultiplexer (16, 64, 66, 26), respectively, for providing the first signal. In a more specific embodiment, the first mode is a left-handed Laguerre-Gaussian torsion mode, and the second mode is a right-handed Laguerre-Gaussian torsion mode. The third mechanism (26, 28) determines rotational Doppler due to reflection of the beam of electromagnetic energy from the target.

The present invention discloses a power converter with low common mode noise. The power converter having a primary side and a secondary side, comprises a transformer having a primary winding and a secondary winding, and at least one electrostatic shield disposed between the primary winding and the secondary winding, wherein the electrostatic shield is configured with partial first region of the primary winding and partial second region of the secondary winding such that the electrostatic shield partially shields with the primary winding and the secondary winding to reach the purpose of suppressing the common mode noise. In addition, another method can be used to reduce the common mode noise of a power converter having primary side and secondary side, which is adding some additional impedance between the static points and jump points of the primary side and secondary side.

A differential method has been developed which determines displacement from the midpoint of optical transmission (±45°) and utilizes the coupled nature of the two signals for common mode noise rejection to enhance the detection of chiral species. A beam of light is modulated, applied to the chiral mixture, and then split into a first beam and a related orthogonal beam by a polarizer or prism. The first beam and orthogonal beam are converted into electrical signals before a differential comparison of the signals is performed to detect a desired chiral species within the chiral mixture.

An apparatus or method can be configured to receive first information indicative of respiratory effort of a subject from a first piezoelectric film sensor and second information indicative of respiratory effort of the subject from a second piezoelectric film sensor, and to process the received first and second information to produce an electronic signal output indicative of respiratory effort of the subject, the processing including averaging the received first information using a first differential amplifier and signal integrator with resistive reset to reduce differential noise and to attenuate common-mode noise, and averaging the received second information using a second differential amplifier and signal integrator with resistive reset to reduce differential noise and to attenuate common-mode noise.