589 results about "Linear phase" patented technology

A prefilter (5) for an audio system comprising a loudspeaker (1) in a room (2), which corrects both amplitude and phase errors due to the loudspeaker (1) by a linear phase correction filter response and corrects the amplitude response of the room (2) whilst introducing the minimum possible amount of extra phase distortion by employing a minimum phase correction filter stage. A test signal generator (8) generates a signal comprising a periodic frequency sweep with a greater phase repetition period than the frequency repetition period. A microphone (7) positioned at various points in the room (2) measures the audio signal processed by the room (2) and loudspeaker (1), and a coefficient calculator (6) (e.g. a digital signal processor device) derives the signal response of the room and thereby a requisite minimum phase correction to be cascaded with the linear phase correction already calculated for the loudspeaker (1). Filter (5) may comprise the same digital signal processor as the coefficient calculator (6). Applications in high fidelity audio reproduction, and in car stereo reproduction.

A millimeter wave (MMW) antenna array includes a continuous transverse stub (CTS) radiating aperture comprising a set of spaced continuous transverse stubs, each having a longitudinal extent. A series feed system is coupled to an excitation source for exciting the stubs with MMW electromagnetic energy having a linear phase progression along the longitudinal extent of the stubs to produce an array beam which can be scanned over a beam scan range by changing the excitation frequency.

A novel interpolating phase detector for use in a multiphase PLL is described comprising an array of individual phase comparators, all operating at essentially the same operating point which permits the circuits to be designed simultaneously for high speed and for low power consumption. Two adjacent phase outputs of a multi-phase VCO may be selected and interpolated in between, by selectively attaching a variable number of phase comparators to each phase output and summing their phase error outputs. By varying the number of phase comparators attached to each phase output, interpolation can be achieved with high linearity.

Disclosed is a generalized reconstruction method that corrects for non-linear phase errors based on least-squares estimation. An approximation of the least squares estimate utilizes refocusing reconstruction in which high-resolution data is multiplied by the phase conjugate of a navigator in image-space. The multiplication rephases the unaliased signal in the high-resolution data. The high-resolution data can then be added together coherently. The multiplication can be effected in k-space as a convolution using a gridding reconstruction of the high-resolution data using the low resolution navigator.

In a QAM demodulator including an adaptive equalizer, a method of carrier tracking comprising the following steps is disclosed: (A) sampling a QAM signal received from a transmission channel; (B) recovering a symbol clock function from the sampled QAM signal; (C) applying the sampled QAM signal to the adaptive equalizer in order to obtain a QAM equalized signal in a Blind Equalization (BE) mode; (D) using a slicer to locate a nearest plant point for the QAM Blind equalized signal for each recovered symbol clock; (E) using a complex conjugate multiplier to obtain an instantaneous inphase component and an instantaneous quadrature component of a phase angle error signal; (F) using a linear phase detector to obtain an instantaneous phase angle error for each symbol clock; (G) averaging the instantaneous phase angle error signal by using a carrier loop filter; (H) using a complex multiplier to insert an inverse of the averaged phase angle error signal into the QAM Blind equalized signal to compensate for the carrier phase angle error; and (I) repeating the steps (D-H) to close a carrier frequency loop.

A cycle slip detector interfaces with a phase/frequency detector (PFD), such as might be used in a phase-locked loop circuit (PLL), and indicates when cycle slips occur in the PFD. Typically, the PFD generates output control signals as a function of the phase difference between first and second input signals, with the first input signal usually serving as a reference signal against which the PLL adjusts the second input signal. The PFD provides linear phase comparison between its input signals, provided their relative phase difference does not exceed ±2π radians. If one of the two signals leads or lags the other by more than that amount, a cycle slip occurs, and the PFD responds nonlinearly. The cycle slip detector provides logic for detecting and indicating leading and lagging cycle slips as they occur in the PDF, and is typically implemented as a minimal arrangement of logic gates and flip-flops.

A digital signal processor (DSP) comprises an input terminal configured to receive an input, an adaptive nonlinear phase filter coupled to the input terminal, the adaptive nonlinear phase filter having a time-varying phase response, and an adaptive nonlinear amplitude filter coupled to the input terminal, the adaptive nonlinear amplitude filter having a time-varying amplitude response.

A method of processing a signal comprises receiving the signal, sending the signal to an adaptive nonlinear phase filter, the adaptive nonlinear phase filter having a time-varying phase response, and sending the signal to an adaptive nonlinear amplitude filter, the adaptive nonlinear amplitude filter having a time-varying amplitude response.

A method for accelerating data acquisition in MRI with N-dimensional spatial encoding has a first method step in which a transverse magnetization within an imaged object volume is prepared having a non-linear phase distribution. Primary spatial encoding is thereby effected through application of switched magnetic fields. Two or more RF receivers are used to simultaneously record MR signals originating from the imaged object volume, wherein, for each RF receiver, an N-dimensional data matrix is recorded which is undersampled by a factor R_i per selected k-space direction. Data points belonging to a k-space matrix which were not recoded by a selected acquisition schema are reconstructed using a parallel imaging method, wherein reference information concerning receiver coil sensitivities is extracted from a phase-scrambled reconstruction of the undersampled data matrix. The method generates a high-resolution image free of artifacts in a time-efficient manner by improving data sampling efficiency and thereby reducing overall data acquisition time.

A timing error compensation system in an OFMD/CDMA communication system includes an analog-to-digital converter for converting an OFDM signal, comprised of a data symbol stream in which a pilot symbol is inserted at intervals of a prescribed number of data symbols, received from a transmitter, to a digital OFDM symbol stream by prescribed sampling synchronization, a guard interval remover for removing a guard interval inserted in the OFDM symbol by prescribed frame synchronization, and a fast Fourier transform (FFT) device for performing fast Fourier transform on the guard interval-removed OFDM symbol and outputting a data symbol stream. In the time error compensation system, a pilot symbol detector receives the data symbol stream and detects the pilot symbols inserted in the data symbol stream at prescribed intervals. A timing compensator determines a linear phase difference line for the detected pilot symbol, generates a timing error estimation signal according to the determined linear phase difference line, and provides the timing error estimation signal to the analog-to-digital converter and the guard interval remover so as to determine the sampling synchronization and the frame synchronization.

An all fiber optic laser based scanning system for real time terrain mapping under degraded visual conditions is disclosed. A laser output is modulated to achieve a desired pulse width and pulse repetition frequency (PRF) and the modulated signal is amplified. The amplified optical signals are split into N channels that correspond to N elements of an optically phased array that steers light by modulating the phase of light entering and exiting the optical system. By applying a linear phase shift across the beam's wave front, the light propagating along the system's optical axis is steered to an off-axis angle. A real time map of an underlying terrain is accomplished by sweeping the N channel array across the terrain while collecting range information from each scan grid.

In a filter coefficient calculation device according to the present invention, a gain correction characteristic calculation section calculates impulse responses corresponding to a linear-phase filter having an inverse characteristic of a gain characteristic of a reproduction system, and calculates, as a gain correction characteristic, a frequency characteristic of continuous-time impulse responses that include a peak value, the continuous-time impulse responses being impulse responses, clipped from the calculated impulse responses, whose number is identical to the preset number of filter taps. Moreover, a phase correction characteristic calculation section calculates a phase correction characteristic by normalizing, from an inverse characteristic of a frequency characteristic of the reproduction system, a gain characteristic of the inverse characteristic, and a filter coefficient calculation section calculates, as filter coefficients of the reproduction characteristic correction filter, filter coefficients of a filter having a synthetic correction characteristic obtained by combining the gain correction characteristic with the phase correction characteristic. This makes it possible to correct acoustic characteristics with high accuracy even in cases where the number of taps is limited.

The invention discloses a digital locked ring device to realize clock phase smooth conversion, which is characterized by the following: the reference source processes the selected reference clock according to master spare pattern; the time digital converses the reference clock and phase difference from local clock of frequency divider into the corresponding coded digital code to realize phase demodulation and phase difference digitalization to be transmitted to CPU filter and locked processing unit the proceed linear phase disposal, low-pass digital filter disposal, locked disposal, which outputs the digital phased error signal to the digifax converser as corresponding analog voltage-controlled value, in order to control the corresponding vibrating frequency output by voltage-controlled crystal oscillator; the frequency is processed by frequency divider to transmit the local clock with the same frequency as reference frequency to time digital converter. The invention realizes high-precision error control of main spare systems, which is convenient to integrate chip with high reliability and integration level.

A method of inspecting the steam inlet sleeves on high pressure outer cylinders and the nozzle chamber to cylinder welds on the high pressure steam turbines using linear phased array ultrasonic transducers. The transducers are supported on the surface of the component to be monitored. The transducers are then move axially while monitoring the transducer's output to identify the location to be monitored. The axial extent of the transducers are then fixed and the transducers are moved circumferentially around the surface of the component at least 360° while noting outputs of the transducers indicative of fatigue-induced flaws. The transducers are then routed to the location on the wall of the component where the most significant flaw was noted. Then the transducers are successively focused at different depths in the wall where the most significant flaw was identified to further characterize the depth and size of the flaw.

The present invention relates to an apparatus and method for estimating and compensating for a time offset and a carrier frequency offset in a Multiple Input Multiple Output (MIMO) communication system that supports Orthogonal Frequency Division Multiplexing (OFDM) or Orthogonal Frequency Division Multiplexing Access (OFDMA). According to the present invention, a phase difference of pilot signals of the same transmitting antenna, which are received through receiving antennas, is calculated. An arc tangent operation is then carried out on the phase difference of the pilot signals to calculate a time offset linear phase and/or a carrier frequency offset linear phase. Further, a time offset compensation value and/or a carrier frequency offset compensation value are found by employing the time offset linear phase and/or the carrier frequency offset linear phase. A time offset and/or a carrier frequency offset with respect to pilots and data are compensated for by employing the time offset compensation value and/or the carrier frequency offset compensation value.

Ultrasound probes that transmits/receives ultrasound pulses with frequencies both in a low frequency (LF) and a high frequency (HF) band, where the radiation surfaces of said HF and LF bands at least have a common region. Several solutions for transmission (and reception) of LF and HF pulses through the same radiation surface are given. The arrays and elements can be of a general type, for example linear phased or switched arrays, or annular arrays or elements with division in both azimuth and elevation direction, like a 1.5D, a 1.75D and a full 2D array. The LF and HF element division and array apertures can also be different.

For suppression of continuous wave interferers at, e.g., up to four interferer frequencies (f₁, f₂, f₃, f₄) in a GNSS receiver base band circuit a raw digital signal is, in a band stop unit (21), shifted, by a first mixer (31a), by the negative of the first interferer frequency (f₁) in the frequency domain whereupon the continuous wave interferer is suppressed by a band stop filter (30a), a linear phase FIR filter with a suppression band centered at zero, e.g., a filter subtracting a mean over previous subsequent signal values from the actual signal value. After further shifting of the shifted digital signal by the negative of the difference between the second interferer frequency (f₂) and the first interferer frequency (f₁) the shifted digital signal is again filtered by an identical band stop filter (30b) and so on. After the last filtering step the shifted digital signal is shifted back to its original position in the frequency domain to provide a filtered digital signal which corresponds to the raw digital signal with narrow interferer bands centered at the interferer frequencies (f₁, f₂, f₃, f₄) suppressed.

Apparatus for inserting transmit diversity into an RF signal for transmission, comprises: an RF splitter for splitting the RF signal to be transmitted into two signal parts, and a non-linear phase modulator which applies a non-linear phase modulation to one of the two signal parts, thereby to provide transmit diversity between the first signal part and the second signal part. One of the ways of inserting a non-linear phase modulation into the RF signal is to use a spinning disc with tracks of different dielectric strength. The apparatus is useful in cellular telephony for supplying repeaters and base station extensions with diversity capability.

Provided are a system and method of estimating channels for a plurality of multicarrier signals in a wireless receiver. A receiver accepts a plurality of multicarrier signals, transmitted simultaneously from a plurality of transmitters, with overlapping carrier frequencies and nominally orthogonal reference signals. For each multicarrier signal, a reference signal is recovered including a plurality of adjacent subcarrier frequencies carrying predetermined symbols. A channel estimate is found across the plurality of adjacent subcarrier frequencies, for each multicarrier signal channel, by compensating for a loss of orthogonality between reference signals, in response to assuming a linear phase rotation for each channel across the plurality of adjacent reference signal subcarriers, and a constant amplitude for each channel across the plurality of adjacent reference signal subcarriers. More explicitly, the assumption of linear phase rotation and constant amplitude permits a Direction of Arrival (DoA) algorithm to be used.

It is an adaptive optics system based on the linear phase inversion recovery technique, comprising the imaging sensor, the linear phase inversion recovery algorithm, the real-time control algorithm, the wave-front correction and drive circuit, and the reference light source. During the system running, the imaging sensor measures the residual aberration far-field image after the compensation of the wave-front correction device, and subtracting with the benchmark image to obtain the image difference vector. In advance, using the reference light source to calibrate the imaging sensor to obtain the benchmark image, and according to the corresponding relations between the wave-front correction device and the imaging sensor, obtaining the recovery matrix between the image difference vector and control voltage. Multiply the image difference vector and the recovery matrix to obtain the corresponding control voltage of the residual wave-front, and use real-time control algorithms, such as proportional integral, to obtain the control voltage of the wave-front correction device, making the wave-front aberration to be corrected. Compared the adaptive optics system based on the linear phase inversion recovery technique and the conventional adaptive optical technology, it has simple structure, high optical energy efficiency, and other advantages.

A variable differential phase shifter including an isolation element providing good isolation between output ports, good return loss and reduced reflections. In one embodiment a Wilkinson divider is incorporated in the wiper arm of a wiper type variable differential phase shifter. In another embodiment a linear phase shifter incorporates a Wilkinson divider. Multistage embodiments are also disclosed. The variable differential phase shifter may be used in combination with a hybrid coupler to provide an isolated variable power divider. The variable differential phase shifter may be utilized in a variety of feed networks and antenna arrays to vary beam tilt, beam azimuth and beam width. Antennas incorporating the phase shifter exhibit low variation of half power beam width with frequency and reduced side lobes.

Consistent with the present disclosure, a method and system for estimating chromatic dispersion of an optical signal in a coherent receiver is provided that is insensitive to polarization mode dispersion (PMD) and other polarization effects in the optical communication system. The effects of chromatic dispersion in the optical system are estimated by first calculating a phase shift between a pair of related frequency domain data outputs of a Fourier transform circuit. The calculated phase shift includes a linear phase component that is proportional to the chromatic dispersion, a DC constant phase component, and a data spectrum component. The calculated phase shift is then averaged over a number of clock cycles to remove the data spectrum components. The time averaged result is used to normalize any effects of PMD from the received signal. A slope of the linear phase component as a function of frequency is then calculated and used to estimate the value for chromatic dispersion. The chromatic dispersion estimate is then used to determine a number of coefficients of an inverse frequency response of the chromatic dispersion in the system, and is used to compensate for the chromatic dispersion.