433 results about "Zero frequency" patented technology

A waveform adaptive transmitter that conditions and/or modulates the phase, frequency, bandwidth, amplitude and/or attenuation of ultra-wideband (UWB) pulses. The transmitter confines or band-limits UWB signals within spectral limits for use in communication, positioning, and/or radar applications. One embodiment comprises a low-level UWB source (e.g., an impulse generator or time-gated oscillator (fixed or voltage-controlled)), a waveform adapter (e.g., digital or analog filter, pulse shaper, and/or voltage variable attenuator), a power amplifier, and an antenna to radiate a band-limited and/or modulated UWB or wideband signals. In a special case where the oscillator has zero frequency and outputs a DC bias, a low-level impulse generator impulse-excites a bandpass filter to produce an UWB signal having an adjustable center frequency and desired bandwidth based on a characteristic of the filter. In another embodiment, a low-level impulse signal is approximated by a time-gated continuous-wave oscillator to produce an extremely wide bandwidth pulse with deterministic center frequency and bandwidth characteristics. The UWB signal may be modulated to carry multi-megabit per second digital data, or may be used in object detection or for ranging applications. Activation of the power amplifier may be time-gated in cadence with the UWB source thereby to reduce inter-pulse power consumption. The UWB transmitter is capable of extremely high pulse repetition frequencies (PRFs) and data rates in the hundreds of megabits per second or more, frequency agility on a pulse-to-pulse basis allowing frequency hopping if desired, and extensibility from below HF to millimeter wave frequencies.

The invention is directed to a method and system for supporting multiple time division duplexed (TDD) based wireless services or frequency division duplexed (FDD) wireless services on a Distributed Antenna System (DAS). A DAS can support a many wireless services, including voice and data services using the same physical equipment. TDD based services use a common clock signal to synchronize the components of the DAS for transmission and reception of TDD signals. In accordance with the invention, the DAS can include a GPS receiver which can extract a timing signal (such as a 1 pps signal) from a GPS signal and distribute the timing signal to any and all components of the DAS to enable synchronization of the components for transmitting and receiving TDD signals. The GPS receiver can be part of the interface that connects a TDD based service to the DAS or separate component of the DAS. In accordance with the invention, the DAS can distribute a reference clock signal to all of the components of the DAS in order to maintain zero frequency shift while manipulating with the carrier frequencies of the various wireless services carried by the DAS. In addition, and in accordance with the invention, two analog architectures for better integration between the services sources (BTS) and the DAS are disclosed.

Systems and methods for parallel stream item counting are disclosed. A data stream is partitioned into portions and the portions are assigned to a plurality of processing cores. A sequential kernel is executed at each processing core to compute a local count for items in an assigned portion of the data stream for that processing core. The counts are aggregated for all the processing cores to determine a final count for the items in the data stream. A frequency-aware counting method (FCM) for data streams includes dynamically capturing relative frequency phases of items from a data stream and placing the items in a sketch structure using a plurality of hash functions where a number of hash functions is based on the frequency phase of the item. A zero-frequency table is provided to reduce errors due to absent items.

Loss of optical signal is detected in a synchronous communications system by detecting features of a monitor signal occurring at a detection frequency corresponding to the frame rate. Since the frame rate is substantially less than the bit rate, monitoring and detection can be performed at a lower bandwidth than the bit rate. An auto-correlation circuit utilises delays which are an integral multiple of the frame rate and produces a detection value which is compared with a threshold value. Alternatively, detection may be based on a power measurement of a band pass filtered monitor signal by setting the lower bandwidth limit above zero frequency and normalizing the measurement of power relative to an average power measurement. A loss of signal may then be detected by a change in power measurement relative to a threshold and can be used for asynchronous systems as well as synchronous systems. Loss of signal detection may be utilised to control an optical switch to re-route optical signals and generate alarm signals. The use of such detection in all optical networks avoids the requirement for electronic processing at the bit rate as a means of detection of loss of signal.

The invention relates to a self-adaption zero-frequency compensation circuit in a low-voltage difference linear voltage regulator. The output end of a transconductance amplifier is connected with a voltage regulation pipe by a voltage bumper, a current detection circuit is connected with the voltage bumper and the common end of the voltage regulation pipe, and the other end is connected with a variable-resistance circuit connected with the compensation end of the transconductance amplifier. In the invention, when a load is higher and current is lower, the current detection circuit can detect the load and the current and the load and the current act on the variable-resistance circuit at the moment to ensure that the resistance is enlarged, and the zero position is also relatively lower; on the contrary, when the load is reduced and the current is enlarged, the resistance value of the variable-resistance circuit is reduced, and the zero position is higher. Therefore, the self-adaption zero can change along with the change of a pole so that the compensation circuit takes the effect of compensation and effectively ensures the stable state of system operation. The compensation circuit successfully solves the problem of poor stability of a low-voltage difference linear voltage regulator so that a load capacitance equivalent series resistance is not really important to the influence on system stability, transient response and ripple waves.

The invention discloses a novel method for realizing spectral combination amplification based on the frequency division multiplexing technology, which comprises the following steps of: (a), pre-amplifying and broadening laser pulse generated by an ultra-short pulse oscillator; (b), segmenting the frequency spectrum of a super-continuous broad-band spectrum into multiplex optical pulses with different central wavelengths; (c), amplifying each optical pulse, outputting a part of amplified seed light to a self-reference zero-frequency detection device by using a splitting slice, and taking a beat frequency signal output by the self-reference zero-frequency detection device as the driving frequency of an acousto-optic frequency shifter after filtering and amplifying; (d), coherently synthesizing amplification pulses output by various multi-stage optical fibre amplifiers through a wavelength division multiplexing beam combiner; and (e), carrying out dispersion compensation and pulse width compression of coherently synthesized pulses by using a compressor so as to obtain ultra-short pulse output with high peak power. According to the invention, the frequency division multiplexing technology and the coherent synthesizing technology are organically combined; therefore, the pulse synchronization problem and the spectrum coherent problem in the ultra-short pulse optical fibre laser coherent synthesizing process are solved.

Methods and apparatus for power-efficiently and reliably transmitting high-level quadrature amplitude modulation (QAM) optical signals using binary drive signals. Even though binary signals are used to drive a QAM modulator directly, without digital-to-analog conversion, the methods and apparatus disclosed allow the transmission of pilot symbol sequences having near optimal properties, such as a constant power profile in the time domain; a mean power that is approximately the same as the mean power of the data symbols; and roughly uniform amplitude in the frequency domain for non-zero frequency components of the pilot symbol sequence. The binary drive signals can be processed so that the modulated optical signals are selectively constrained to a subset of points of the QAM constellation to form a QAM constellation with reduced size and a mean power that is approximately the same as the mean power of the original QAM constellation.

A method for responding to an existing or incipient surge condition of a turbocharger coupled to an engine of a motor vehicle is provided. The method comprises receiving a signal responsive to an operating condition of the turbocharger and adjusting one or more operating parameters of the motor vehicle when a power of the signal, integrated over a pre-selected range of non-zero frequencies, exceeds a pre-selected threshold. Other embodiments provide related systems for responding to an existing or incipient surge condition of a turbocharger.

A control method of a net-side rectifier of a double-fed asynchronous wind power generator designed by the invention can realize zero steady-state error tracking of zero frequency and frequency-doubled component in an input signal of a forward channel as well as the complete attenuation of zero frequency and frequency-doubled interference by changing a traditional PI adjustor to a PIR adjustor and setting a set frequency Omega[c] in the PIR adjustor to a double synchronous rotation angular speed Omega[s], thus relieving the influence caused by harmonic generated due to unbalanced network voltage. Only through the replacement of the adjustor, the method realizes the control over the net-side rectifier of the generator under the condition of unbalanced network voltage, is simple in modification and obvious in effect, does not relate to the design of complicated parts and is easy for implementation.

A low voltage differential linear regulator utilizes an embedded compensation network in an amplifier to improve performance, which embeds a compensation network composed of resistances and capacitances into an amplifier to increase one or a plurality of pole-zero pairs with their pole-zero frequency lower than pole frequency in a transfer function of a feedback loop without changing static operating point of the amplifier and increasing static current. Frequency of the pole-zero pairs can be accurately confirmed to enhance stability of the feedback loop of the low voltage differential linear regulator, expand loop unit gain bandwidth and increase phase margin and DC and low-frequency gain of the loop, thus enhancing performance of the low voltage differential linear regulator.

A fully-integrated continuous-time active complex bandpass IF filter that may contain transmission zeros yielding much sharper roll-off than that of an all-pole filter is implemented using transconductors and capacitors only. Each of the filter second-Order sections realizes a pair of complex poles and a may realize a double imaginary axis zero. Since the transconductors are electronically tunable the positions of filter zeros and poles are adjustable using an automatic tuning system. In each filter section the value of different transconductors are modified to separately change the pole frequency, its Q-factor and the zero frequency. Each pole and zero are separately tuned, which achieves a higher level of tuning accuracy than in case where all poles and zeros were adjusted simultaneously.

In a modular multi-level power converter, additional switching states are interleaved between main switching states that control output voltage or waveform. The additional switching states provide current from a DC-link to charge capacitors in respective modules or cells to an offset voltage from which the capacitor voltages are controlled toward a reference voltage during each switching cycle rather than being allowed to build up over a period of an output waveform of variable line frequency, possibly including zero frequency. Since the switching cycle is much shorter than the duration of a line frequency cycle and the capacitor voltages are balanced during each switching cycle, output voltage ripple can be limited as desired with a capacitor of much smaller value and size than would otherwise be required.

The invention discloses a low-voltage traversing control method for a double-fed wind power generation system. The method comprises the following steps of: 1) detecting zero frequency transient flux component of a motor; 2) when the motor has zero frequency transient flux component outburst, controlling a rotor current transformer and a network current transformer, and attenuating the zero frequency transient flux components of the current transformers; and 3) controlling torque current and power grid reactive compensation current to inhibit the growth of harmful voltage and prevent the formation of harmful current. The method can really realize the elimination of the transient flux caused by sudden decline and sudden rise of a stator voltage and inhibit negative sequence current so as to avoid offline of the fan power generation system at the same time of protecting the rotor current transformer and the network current transformer; meanwhile, by the method, double times ultrahigh dangerous voltage of rotor induction caused by zero frequency transient flux superposition when the voltage is recovered can be prevented, and power grid-friendly intelligent low-voltage traversing is realized.

The present invention provides a pulse Doppler radar polarization anti-jamming method under a complicated interference environment. By utilizing the method of the present invention, the inhibition capability aiming at various interference, such as chaffs, active suppression, cheat, etc., can be improved substantially, and the targets can be detected effectively. The method is realized by the following technical scheme of inputting a radar dual polarization echo signal, determining whether the active suppression-type interference exists, when the suppression-type interference exists, carrying out the polarization cancellation; then calculating the target signal walking time between the front and back pulses, and carrying out the range walking correction on a pulse sequence; and then carrying out the phase-coherent accumulation on a dual polarization channel, shifting the zero to a frequency spectrum center in a frequency shift manner, identifying the channel number of a target in a Doppler-range two-dimensional matrix, setting a two dimensional tracking gate of the target, and carrying out the two dimensional constant false alarm detection in the tracking gate; finally, carrying out the target polarization ratio detection determination, and outputting a signal passing the detection determination as a target signal after the interference inhibition, thereby improving the correct detection probability of the target.

This invention relates to systems and methods for increasing image compression. The systems and methods are improvements applicable to encoder/decoders which compress images by, inter alia, transforming non-overlapping independent blocks of pixels into a frequency domain and then quantizing the resulting frequency domain coefficients. The invention achieves increased compression by predicting low frequency coefficients of a block from, preferably, the average intensities, or zero frequency coefficients, of the block and its adjacent blocks. In an encoder, the low frequency coefficients are predicted, are then subtracted from the actual transform coefficients, and the difference coefficients are transmitted to a decoder. In the decoder, the low frequency coefficients are again predicted, are added to the received difference coefficients, and the resulting actual transform coefficients are used to reconstruct an image.

An input feature vector is computed from an input text record, the input feature vector comprising one or more features, each feature including a subsequence of characters and a frequency of occurrence of the associated subsequence. A input fingerprint is generated out of the input feature vector by choosing one or more features with non-zero frequencies and alphabetizing the features chosen. One or more input indices are generated by alphabetizing features in the input fingerprint and concatenating features occurring in subsequent locations of the input fingerprint. The input text record is matched against a target text record if (1) one or more of the input indices match a target index corresponding to the target text record and (2) the corresponding input fingerprint matches a target fingerprint corresponding to the target text record. The target text record is outputted as a search result if it matches the input text record.

In a direct conversion receiver with zero-frequency intermediate frequency (IF) signal, the DC offset and 1/f noise of the IF signal is compensated by means of double-sampling. The first period of the doubling-sampling is a calibration phase, which stores the DC offset and the 1/f noise. The second period is a signal flow phase during which the stored DC offset and 1/f noise is connected in opposition with the IF signal to cancel the DC offset and 1/f noise.

A source-measure unit (SMU) may be implemented with respective digital control loops for output voltage and output current. The output voltage and output current may be measured with dedicated ADCs (analog-to-digital converters). The readings obtained by the ADCs may be compared to a setpoint, which may be set in a digital loop controller. The digital loop controller may be used to produce an output to drive a DAC (digital-to-analog converter) until the output voltage and/or output current and/or a function thereof reach the respective desired levels. The digital loop controller may implement respective integrating functions for the respective digital control loops, and may also implement a compensation function featuring pole-zero pairs to stabilize the respective current/voltage outputs. Coefficients of the compensation function may be calculated based on user programmable parameters corresponding to the gain bandwidth product, compensation frequency, and ratio of the added pole-zero frequencies.

The invention relates to a rapid broadband frequency domain beamforming method based on an acoustic vector sensor uniform linear array. The method comprises the following steps of: firstly, receiving spatial signals through the acoustic vector sensor uniform linear array to obtain time domain signals of all array elements, wherein the time domain signals comprise time domain acoustic pressure signals and time domain vibration velocity signals, and performing Fourier transform on snapshot data needed to be processed so as to obtain a corresponding frequency domain signal; secondly, performing zero fill on the acoustic pressure signals and the vibration velocity signals of all the array elements in a space domain according to a frequency band range needed to be processed, performing fast Fourier transform (FFT) on the signals in the space domain, and transferring a zero frequency component of the transform result to a spectrum center; thirdly, performing alignment correction and corresponding linear addition on beam and space domain Fourier results at each frequency point of bandwidth needed to be processed according to a frequency-beam grid corresponding to the acoustic pressure signals and the vibration velocity signals so as to obtain beamforming results of different frequency points; and finally, synthesizing beamforming results of different frequencies to obtain power output of a linear array spatially.

The invention discloses an unsmooth dynamic compensation method for an ultralow-frequency horizontal vibration table guide rail. The unsmooth dynamic compensation method comprises the following steps: measuring unsmooth dynamic characteristics of the ultralow-frequency horizontal vibration table guide rail and output uori t of a calibrated acceleration sensor in real time by taking a horizontal direction as reference; constructing a guide rail unsmoothness dynamic compensation system, and removing a gravitational acceleration component in the output of the calibrated sensor generated by pitching of a sliding table from the original output of the calibrated sensor in real time in the vibration calibration process; calibrating a calibrated acceleration sensor by adopting the compensated output ucomt of the calibrated sensor, calculating to obtain a compensated amplitude-frequency curve, and finishing vibration calibration of the calibrated sensor. The unsmooth dynamic compensation method has the advantages that the calibration result deviation of the acceleration sensor with zero frequency response caused by guide rail unsmoothness based on the ultralow-frequency horizontal vibration table can be compensated in real time in the vibration calibration process, so that the precision of ultralow-frequency vibration calibration is improved.

A random-bit sequence generator includes a biasing circuit, a source of a noisy voltage signal biased by the biasing circuit, an amplification stage generating an amplified signal representative of the sole non-zero-frequency (AC) component of the noisy voltage signal and an output stage electrically in cascade to the amplification stage that generates a random bit sequence in function of the amplified signal. The generator also filters the undesired low-frequency disturbance components because the amplification stage comprises an input low-pass filter that feeds the zero- (DC) component of the noisy voltage signal to one of the inputs of a differential amplifier, to another input of which is fed the non-filtered noisy voltage signal.