208 results about "Ac components" patented technology

An image encoding apparatus includes a converter 1 for receiving an image signal, and for converting the image signal of individual blocks to DC components and AC components by orthogonal transformation of the individual blocks of an image frame; a predicted reference value generator 2 for receiving the image signal, and for generating a predicted reference value of each image frame from DC components resulting from the orthogonal transformation of left-edge blocks of the image frame; and a differential unit 3 for obtaining difference values between the DC components output from the converter 1 and the predicted reference value generated by the predicted reference value generator 2. The image encoding apparatus outputs a bit stream by quantizing and variable-length encoding the AC components and difference values obtained by the differential unit 3, and by quantizing and variable-length encoding the predicted reference value to be added to a header.

A resonant power converter draws current from a source that provides a supply current. Multiple quasi-resonant converters are interleaved and each quasi-resonant converter receives the supply current and forms a phase-shifted current according to drive signals supplied by a controller. Each phase-shifted current includes a dead-time delay and is phase-shifted relative to the other phase-shifted currents. The dead-time delay is determined as a time value within a calculated dead-time delay range having a dead-time delay minimum and a dead-time delay maximum. The outputs of each quasi-resonant converter are added together thereby reducing the AC components of current. Two, three, or four quasi-resonant power converters can be interleaved, each forming phase-shifted currents that are phase-shifted relative to the other phase-shifted currents.

In an apparatus for determining a concentration of a light absorbing substance in blood, a plurality of photo emitters are adapted to emit light beams having different wavelengths toward a living tissue including a blood vessel. A photo receiver is adapted to receive the light beams which have been transmitted through or reflected from the living tissue. A driver inputs driving currents for causing the respective photo emitters to emit the light beams. An optimizer obtains values of AC components of the light beams received by the photo receiver, and adjusts values of the driving currents such that the values of the AC components fall within a predetermined range.

A demodulation circuit for an Amplitude Shift Keyed (ASK) modulated signal includes an envelope detector, an alternating voltage amplifier, a differentiator circuit, and a comparator having a hysteresis connected in series. The envelope detector produces an envelope signal from the received ASK signal. The amplifier blocks the DC component of the envelope signal and amplifies AC components of the envelope signal to obtain a steeper slope of the rising and falling edges. The differentiator circuit then processes the transition edges to provide a differentiated signal having positive and negative electrical pulses. The comparator converts the pulses into a binary data stream which corresponds to the transmitted data stream. The combination of the differentiated signal and comparator having a hysteresis enables better stability and sensitivity of the ASK demodulation circuit.

A self-contained and encapsulated AC to Voltage supplying module containing a complete set of AC circuitry components therein and directly connecting the components to the AC voltage source, an inrush protection circuit, a DC-DC converter and power control circuits which enable the encapsulation of AC and DC components within a module being directly mountable and DC electrically connected to a printed circuit board assembly.

An RF power amplifier system adjusts the supply voltage to the power amplifier based upon an amplitude correction signal indicating the amplitude difference between the amplitude of the RF input signal and an attenuated amplitude of the RF output signal of the power amplifier. A variable gain amplifier (VGA) adjusts the amplitude of the RF input signal, thus providing a second means of adjusting the amplitude of the output of the power amplifier. The gain of the VGA or the supply voltage to the power amplifier is controlled based on the AC components of the amplitude correction signal, while the DC components of the amplitude correction signal are blocked from controlling the VGA or the supply voltage to the power amplifier. The DC level of the gain control of the VGA, the average supply voltage to the power amplifier, or the closed loop gain of the overall amplitude correction loop is controlled separately by a compression control signal.

The invention pertains to the technical field of laser application, the method provided by the invention includes the following procedures that the laser tube arranged in a longitudinal magnetic field is turned on and preheated, 1/4 clockwise and counterclockwise circularly polarized lights emitted from the laser tube preliminarily separated by a wave-plate and a polarized light splitter to achieve two orthogonal linear polarized light beams; a low-excursion high-frequency photoelectric detector is used to convert the linear polarized light beams into electric signals and measure the amplitude values of the DC and AC components, so as to accurately separate and measure the optical powers P L and PR of the two circularly polarized light beams; the current value of the electric-heating apparatus wound around the laser tube is adjusted, and the temperature of the laser tube and the length of the resonant cavity are changed to adjust the optical power difference PL-PR to zero, and both polarized optical frequencies are stabilized; the device provided by the invention comprises an optical-power precise separating and measuring circuit used to gain the optical-power DC component and AC component; the invention is characterized in that the low-excursion high-frequency photoelectric detector can simultaneously measure the optical powers of two laser beams (with different frequencies) mixed in the linear polarized light, as a result, the stability of the frequency of a frequency-stabilized LASER is improved.

A device and method for detecting and analyzing faults in a generator stator are disclosed. The device and method include measuring a direct current component of a neutral ground current in a generator stator grounding conductor, analyzing the direct current flow and comparing it with other ground fault indicators, and providing diagnosis and recommended actions based on the analysis. The direct current flow is measured by a sensitive direct current sensor that may also measure AC components via oscillations in the current measurement, such as a Hall Effect sensor, placed on the generator stator grounding conductor. The analysis of the direct current signal includes consideration of the generator operating conditions and environmental conditions, and also includes comparison to historical data representing both normal and abnormal operation of the generator. Alarms and advisories are provided when generator faults are detected or predicted.

The invention relates to an excitation control method and device used in the starting process of an aeronautical tertiary brushless AC synchronous motor. When the motor stops, a controller can output the maximum AC excitation quantity for an exciter to excite; when the motor rotates at a certain speed, the AC excitation quantity starts to decrease linearly, meanwhile, a PI (Proportion Integration) regulator regulates and intervenes DC excitation quantity, and the regulation upper limit is comprehensively determined by the magnitude of AC excitation component and the bus voltage of the controller. When the AC component decreases to zero, the exciter enters the DC excitation mode. When the excitation control method is used for starting the tertiary brushless AC synchronous motor, flux linkage fluctuation of a main generator rotor, caused when the exciter directly switches the excitation mode, is avoided, and the running stability of a unit which conducts excitation switching in the starting process is effectively improved.

The invention provides a method of detecting inverter AC and DC-side grounding through a single grounding insulation impedance detection network. The method comprises steps: a grounding insulation impedance detection network is only added to the input side of a solar array, and waveforms of the DC-side array positive electrode grounding voltage VPV+PE and the negative electrode grounding voltage VPV-PE are detected; or, the grounding insulation impedance detection network is only added to the AC output side to detect waveforms of AC-side three-phase grounding voltage VA-PE, VB-PE and VC-PE; and as for the former, AC components in the waveforms are extracted to judge the AC-side grounding condition, and as for the latter, DC components in the waveforms are extracted to judge the DC-side grounding condition. The method has the advantages that an AC/DC-side grounding detection method is brought forward, on the basis of adding the grounding insulation impedance detection network only at the input side/output side, the grounding fault of the AC output side/DC side can be judged, the detection circuit is saved, and the system composition is simplified.

Methods and apparatus are provided for separating DC and AC components of a composite signal Is=Idc+Iac from a current source, e.g., a photodiode current source. Four current mirrors CM-1 . . . CM-4 are used with common branches and overlap. CM-1 through CM-3 mirror Is and CM-4 mirrors Idc where lac has been removed by a frequency selective branch. Outputs of the Cm-3 and Cm-4 are combined at a node to provide a signal proportional substantially only to Iac. Complementary devices are used where Cm-1 and Cm-4 are of one type and Cm-2 and Cm-3 are of opposite type. The arrangement allows detection of AC signals (e.g., pulses) that are orders of magnitude smaller than the DC background. An I-to-V converter with a large feedback resistance is used at the output to produce a comparatively large voltage output proportional to lac.

The invention discloses an orthogonal fundamental mode fluxgate sensor. The sensor includes a cobalt-based amorphous wire, an excitation current source, an induction coil, a clock source, a preamplifier, a band-pass filter, a phase-sensitive detector, a low-pass filter and a feedback channel. The cobalt-based amorphous wire, the excitation current source and the clock source constitute an excitation circuit of the sensor. The induction coil, the preamplifier, the band-pass filter, the phase-sensitive detector, the low-pass filter, the feedback channel and the clock source constitute a measurement circuit of the sensor. The excitation current source is a biased alternating current source, namely, the excitation current source contains both DC components and AC components. The DC amplitude is greater than the AC amplitude, which makes the excitation current source in a mono-polar state. Compared with the traditional bipolar current source, the biased current source can significantly suppress the Barkhausen noise of the magnetic core. Compared with the prior art, the orthogonal fundamental mode fluxgate sensor of the invention has such advantages as small size, low noise, low nonlinear error, wide frequency band and large measurement range.

A device for measuring impedance of biological tissue may include electrodes and a voltage-to-current converter coupled to the electrodes to drive an alternating current (AC) through the tissue and sense an AC voltage. The converter may include an amplifier having first and second inputs and an output, a first voltage divider coupled to the first input, a second voltage divider coupled to the second input, a filter capacitor coupled between the output and the second voltage divider, a current limiting resistor coupled between the second input the second voltage divider, and a bypass capacitor coupled to the second input of the amplifier and in parallel with the resistor. A single-ended amplitude modulation (AM) demodulator may demodulate the AC voltage and generate a corresponding baseband voltage representing the impedance. The device may also include an output circuit to generate output signals representative of DC and AC components of the baseband voltage.

The invention discloses an electromagnetic torque jitter elimination method for a doubly-fed induction wind driven generator. According to the method, a rotor reference current instruction under a forward rotation synchronous speed coordinate system comprises an average active current instruction, an average reactive current instruction, a negative sequence, a fifth-order harmonic current component and a seventh-order harmonic component. A current controller can simultaneously realize the accurate and rapid adjustment of a direct current component, a frequency-doubled alternating current component and a frequency-sextupled alternating current component to effectively suppress frequency doubling and frequency sextupling jitter of the electromagnetic torque of the generator when a power grid has a voltage unbalance fault or a harmonic distortion fault and particularly when the two faults of the power grid coexist, so that the safe and reliable running of parts such as a gear box and a bearing of the generator is ensured, and the fault-ride-through capability of the doubly-fed induction wind driven generator is improved.

The watermark insertion section divides the quantized DCT coefficients into at least two data streams, and modifies values of AC components of the data streams, so as to embed the watermark information in each block of the image information with the DCT coefficients quantized. The modification is performed as follows. The sum of a plurality of data of each data stream (or the sum of a plurality of data of a prescribed portion of each data stream) is divided by 2. Then, a value of an AC component of each data stream is modified such that the value of each remainder (the value of the LSB) has a prescribed relationship with (for example, is equal to) the value of the watermark information. Specifically, the value of the first non-zero AC component, from the trailing end of each data stream, is processed by addition of 1 or subtraction of 1.

A chopper-stabilized amplifier includes a main signal path having first and second chopping circuits at the inputs and outputs of a transconductance amplifier, and an auto-correction feedback loop. The feedback loop includes a transconductance amplifier connected to amplify the chopped output from the main signal path, a third chopping circuit which chops the amplified output, a filter which filters the chopped output to substantially reduce any offset voltage-induced AC component present in the signal being filtered, and a transconductance amplifier which receives the filtered output and produces an output which is coupled back into the main signal path. When properly arranged, the auto-correction feedback loop operates to suppress transconductance amplifier-related offset voltages and offset voltage-induced ripple that might otherwise be present in the amplifier's output.

Image processing is carried out by transforming image data to image data having spatial frequency components, by judging whether the absolute values of the coefficients of the predetermined frequency components of the transformed image data are equal to or more than a predetermined value, by modifying the coefficients of the AC components of the image data depending on the result of the judgment, by inversely transforming the image data having the modified coefficients to image data having spatial coordinate components, by comparing the gray levels of the inversely transformed image data with predetermined values, and by transforming the gray levels to quantized levels corresponding to the result of the comparison. By carrying out proper image processing corresponding to the characteristics of the image, the number of gray levels of the image can be decreased while the characteristic portions of the original image are maintained properly.