65 results about "Fractional delay filter" patented technology

A method for holographic storage data recovery in a holographic storage system is presented. One exemplary method includes detecting a stored image at a detector such that the image is oversampled. A relationship is determined between a location of the detected image and a location of the source image. Pixel information associated with the source image may be obtained from the detected image based on a fractional delay filter. In one example, the image may be oversampled by magnifying the detected image at the detector and / or having a detector with pixel sizes and spacing less than the image pixel size. Further, coefficients of the fractional delay filter may be determined, at least in part, on magnification and shift information of the image based on known registration marks.

The invention discloses a joint estimation and real-time correction method for channel error of a time-interleaved ADC (TIADC) system. The method for implementing joint estimation comprises the steps of: sampling a single-tone signal with input frequency of f0 to obtain a sampling sequence xk(n) of various channels of the system, wherein k=0, 1, L M-1; performing fast Fourier transform (FFT) on sampling data x(n) which is reduced into a single-tone signal after the split joint; and in an FFT result, selecting a value FAk at the position where the frequency is 1fs / M+ / -f0,1=0, 1L M-1 and selecting a value FBk at the position where the frequency is 1fs / M,1=0, 1L M-1 to perform inverse fast Fourier transform (IFFT) to obtain M complex numbers, namely IAk and IBk, and finally, obtaining the joint estimation on time error delta tk, gain error gk, and offset error ok, k=0, 1, L M-1 through phase angle extraction and a modulus operation algorithm module. The method for implementing real-time correction comprises the step of: utilizing a comprehensive correction mechanism formed by a subtractor, a divider and a fractional delay filter to correct the offset error, the gain error and the time error existing in the sampling data of the channels respectively. By the method, joint estimation is performed on the three errors, SFDR of the sampling sequence is improved through the real-time correction, and a filter coefficient is not required to be updated or a correction module is not required to be redesigned even if channel errors are changed, so the aim of the real-time correction is fulfilled.

A multicarrier receiver that receives N carrier frequencies therein comprises N A / D converters each of which analog-digital converts a receive signal at a sample rate fs for each carrier, N quadrature detectors which receive outputs sent from the N A / D converters therein and digitally quadrature-detect the outputs, respectively, 2N LPFs which allow only desire bands of outputs of the N quadrature detectors to pass therethrough, and N delay time correcting means each of which corrects a processing delay time deviation for each carrier inside the multicarrier receiver in a time unit of less than 1 / fs using a fractional delay filter. The delay time correcting means has, for example, an M-stage shift register which operates at fs and generates a delay of M / fs, and a fractional delay filter which operates at fs and includes an even number of tap coefficients and which generates a delay different from M / fs by 0.5 / fs.

The equipment comprises two microphones, sampling means, and de-noising means. The de-noising means are non-frequency noise reduction means comprising a combiner having an adaptive filter performing an iterative search seeking to cancel the noise picked up by one of the microphones on the basis of a noise reference given by the other microphone sensor. The adaptive filter is a fractional delay filter modeling a delay that is shorter than the sampling period. The equipment also has voice activity detector means delivering a signal representative of the presence or the absence of speech from the user of the equipment. The adaptive filter receives this signal as input so as to enable it to act selectively: i) either to perform an adaptive search for the parameters of the filter in the absence of speech; ii) or else to “freeze” those parameters of the filter in the presence of speech.

The present invention refers to a method and apparatus for reconstruction of a nonuniformly sampled bandlimited analog signal xa(t), said nonuniformly sampled signal comprising N subsequences xk(m), k=0, 1, . . . , N-1, N>=2, obtained through sampling at a sampling rate of 1 / (MT) according to xk(m)=xa(nMT+tk), where M is an integer, and tk=kMT / N+DELTAtk, DELTAtk being different from zero. The invention comprises forming a new sequence y(n) from said N subsequences xk(m) such that y(n) at least contains the same information as x(n)=xa(nT), i.e. xa(t) sampled with a sampling rate of 1 / T, in a frequency region lower than omega0, omega0 being a predetermined limit frequency, by means of (i) upsampling each of said N subsequences xk(m), k=0, 1, . . . , N-1, by a factor M, M being a positive integer; (ii) filtering each of said upsampled N subsequences xk(m), k=0, 1, . . . , N-1, by a respective digital filter; and (iii) adding said N digitally filtered subsequences to form y(n). The respective digital filter is preferably a fractional delay filter and has preferably a frequency response Gk=ake(-jomegasT), k=0, 1, . . . , N-1, in the frequency band |omegaT|<=omega0T, ak being a constant and s=d+tk, d being an integer.

The invention discloses a wideband digital wave beam forming method based on an all-pass type variable fractional delay filter. The problem that a needed filter in the prior art is large in order number and high in complexity is solved. The method comprises the steps that (1) according to radar system parameters, sampling rate fs and sampling time ts are determined; (2) according to the radar array geometric structure and the sampling time ts, a propagation time delay tau of each array element relative to a reference array element is calculated; (3) according to the sampling rate fs, an AD chip is selected to digitize analog signals received by the array elements; (4) according to the propagation time delay tau and the digitized received analog signals, the all-pass type variable fractional delay filter is designed; (5) the digitized received signals are filtered; (6) phase delay of the filtered signals is compensated for; (7) a window function is selected to conduct weighted summation on the filtered compensated signals to obtain a wave beam forming result. The wideband digital wave beam forming method can achieve wideband digital beam forming, saves hardware resources, improves instantaneity and can be used for wideband digital array radar.

The invention discloses a magnetic suspension rotor harmonic current suppression method based on an FIR filter and a fractional-order repetitive controller. The method comprises the steps: firstly, a magnetic suspension rotor dynamic model containing mass unbalance and sensor harmonic wave is established; then, the FIR filter is a low-pass filter with the linear phase characteristic, and the fractional-order repetitive controller can be obtained through approximation of a fractional delay filter. The method provided by the invention can achieve harmonic current suppression in a constant rotation speed through online updating of the fractional delay filter and is suitable for harmonic current suppression of a magnetic suspension rotor with mass unbalance and sensor harmonic wave; the FIR low-pass filter and the fractional-order repetitive controller are combined and used, and the harmonic current suppression can be achieved through the linear phase characteristic of the FIR filter and the online updating of the fractional-order repetitive controller.

The invention discloses a magnetic suspension rotor harmonic current suppression method based on a frequency self-adaptive fractional compensation repetition controller. The method comprises the steps that a magnetic suspension rotor dynamic model with unbalanced mass and sensor harmonics is established; after high-band signal amplitude attenuation and phase lag, which are caused by a low-pass filter Q (s), are considered, the disturbance suppression ability of a system is reduced; the low-pass filter Q (s) is moved to the branch of the repetition controller from the inside feedback loop; a fractional order compensation link is replaced by a fractional delay filter; and through online updating of the coefficients of the fractional delay filter, precise harmonic current suspension at any frequency can be realized. According to the invention, precise harmonic current suspension of a magnetic suspension flywheel or a magnetic suspension gyroscope at any rated speed can be realized, and the method is suitable for current suppression of magnetic suspension rotor harmonics with mass imbalance and sensor harmonics.

Systems and methods are provided for aligning amplitude and phase signals in a polar receiver. A receiver generates digital amplitude and phase signals representing the amplitude and phase of a modulated input signal. At least one of the digital signals is filtered using a fractional delay filter with a variable delay. The delay of the fractional delay filter is adjusted to align the amplitude and phase signals. In some embodiments, an error vector magnitude is determined by comparing in-phase and quadrature values of the signal with values corresponding to a constellation point, and the delay is adjusted based on the error vector magnitude. The fractional delay filter may be a finite impulse response filter with coefficients stored in a lookup table that correspond to different delays.

The invention discloses a magnetic suspension rotor harmonic current suppression method based on SDMRC (second order dual mode repetitive control). Firstly, a magnetic suspension rotor dynamic model with mass unbalance and sensor harmonic waves is built. Secondly, the magnetic suspension rotor harmonic current suppression method based on SDMRC is adopted, wherein SDMRC belongs to high order RC, and frequency fluctuation robustness of a system can be effectively improved. SDMRC is of a dual mode structure, odd and even harmonic components can be independently suppressed, and response rapidity of the system can be improved. Besides, a fractional delay filter is added into the structure, and suppression precision of the system under a fixed sampling rate can be greatly improved. By the control method, slight rotation speed fluctuation robustness and the current suppression dynamic performance of the system and suppression precision of a rotor at an optional rotation speed can be improved.The harmonic components of magnetic bearing coil current in the magnetic suspension rotor can be suppressed, and the method is applicable to harmonic current suppression of the magnetic suspension rotor system with mass unbalance and the sensor harmonic waves.

The invention discloses a TIADC system error estimation and compensation method based on sine wave fitting. The TIADC system error estimation and compensation method comprises steps that a low frequency sinusoidal signal of a provided frequency is input in the TIADC, and estimated values of three parameters are solved, and amplitudes and offsets of sinusoidal outputs of various channels are calculated; the gain mismatches and the offset mismatches of the residual channels are acquired, and are calculated to complete compensation; a high frequency sinusoidal signal of a provided frequency is input in the TIADC, and after the three parameters are acquired, the amplitude values and the phase values of the sinusoidal outputs of the time-skew errors and the bandwidth mismatches of the various channels are calculated; the channel bandwidths, the phase values caused by the bandwidth mismatches, and the phase values caused by the time-skew errors are estimated; phase adjustment is carried outby adopting a variable delay line and a fractional delay filter to compensate the phase errors caused by the time-skew errors and the bandwidth mismatches. The accurate estimation and the accurate compensation of the errors caused by the various mismatches of the TIADC are realized without being limited by the number of channels, and therefore good effectiveness, wide application, and practicability are realized.

The invention discloses a near field time domain beam forming method suitable for a wideband signal. According to the index requirements of a desired beam pattern, under the far field assumed condition, the existing far field beam forming technology is utilized to design and obtain the far field beam weight coefficient wm', and the time domain implementation structure is determined; according to the distance r of a near field signal source to a basic matrix center, the far field beam weight coefficient wm' is modified for obtaining the near field beam weight wm; the accurate time delay quantity needed by the modified weight coefficient in the near field beam forming is determined; the window minimum mean square error is adopted to design a finite impulse response fractional delay filter bank, so as to realize the accurate time delay needed in the near field beam forming; the fractional delay filter bank designed at the step (d) is added into a time domain beam former determined at the step (a), so the implementation structure of the near field time domain beam former is obtained. The invention is simple and effective, and is suitable for real time coefficient renovation and the wideband signal, thereby the complexity and the feasibility of the design can be improved greatly.

The invention discloses a method for restraining a magnetic levitation rotor harmonic current by connecting a harmonic oscillator and a fractional order repetitive controller in parallel. The method comprises the following steps: firstly, building a magnetic levitation rotor system dynamic model including imbalance mass and a sensor harmonic wave; secondly, shifting a low-pass filter Q(s) from a feedback circuit of a repetitive controller to a branch circuit which is in series connection with the repetitive controller due to the lowering of disturbance restraining performance of the system since the low-pass filter Q(s) has an amplitude value attenuation and phase lag in high-frequency section, thirdly, substituting a fractional delay filter for a fractional compensation loop, increasing the convergence speed of restraining the harmonic current by connecting the harmonic oscillator in parallel. By adopting the method, accurate restraining for the harmonic current can be realized for amagnetic levitation flywheel or a magnetic levitation gyroscope at any rated rotation speed, high current restraining-converging speed can be kept, the method is applied to harmonic current restraining of the magnetic levitation rotor having the imbalance mass and the sensor harmonic wave.

Systems and methods are provided in which a wireless receiver can be configured to digitally synchronize a receive sampling rate to a transmit sampling rate, and may include a digital interpolator controlled by a timing control unit with a timing offset estimator. The timing control unit can be configured to calculate and output parameters to the digital interpolator. The digital interpolator can include a sample buffer followed by a fractional delay filter. Output parameters to the digital interpolator can include a fractional delay timing offset signal of the receiver relative to a transmitter timing signal and a buffer pointer control signal to control a position of the read pointer relative to a write pointer to compensate for subsample timing offset. The timing offset estimator can be configured to calculate and provide to the timing control unit a sampling period ratio control word and an instantaneous timing offset control word.

A system for time aligning widely frequency spaced signals includes a digital predistortion (DPD) processor and a power amplifier coupled to the DPD processor and operable to provide a transmit signal at a power amplifier output. The system also includes a feedback loop coupled to the power amplifier output. The feedback loop comprises an adaptive fractional delay filter, a delay estimator coupled to the adaptive fractional delay filter, and a DPD coefficient estimator coupled to the delay estimator.

Systems and methods are provided for aligning amplitude and phase signals in a polar receiver. A receiver generates digital amplitude and phase signals representing the amplitude and phase of a modulated input signal. At least one of the digital signals is filtered using a fractional delay filter with a variable delay. The delay of the fractional delay filter is adjusted to align the amplitude and phase signals. In some embodiments, an error vector magnitude is determined by comparing in-phase and quadrature values of the signal with values corresponding to a constellation point, and the delay is adjusted based on the error vector magnitude. The fractional delay filter may be a finite impulse response filter with coefficients stored in a lookup table that correspond to different delays.

The invention discloses a time synchronization algorithm based on a loosely coupled IMU array navigation system. An error model of an IMU array navigation system is established, a system equation containing a time synchronization error is established based on the model, and a time synchronization error as a state variable is introduced into a state space model to serve as a state estimation amount; with a fractional delay filter, time displacement is performed on the time synchronization error, interpolation is performed on amplitude and phase responses of the fractional delay filter by usingthe Lagrange's interpolation to obtain displacement of the inertial sensor data so as to ensure time synchronization of the inertial sensor; and carrying out error compensation on the delayed inertialsensor data, inputting the inertial sensor data after time displacement and error compensation into a navigation equation of the inertial navigation system, and carrying out navigation calculation toobtain actual navigation parameters. According to the disclosed method, no extra hardware is needed; and the computation load of the navigation system is reduced.

The equipment comprises two microphones, sampling means, and de-noising means. The de-noising means are non-frequency noise reduction means comprising a combiner having an adaptive filter performing an iterative search seeking to cancel the noise picked up by one of the microphones on the basis of a noise reference given by the other microphone sensor. The adaptive filter is a fractional delay filter modeling a delay that is shorter than the sampling period. The equipment also has voice activity detector means delivering a signal representative of the presence or the absence of speech from the user of the equipment. The adaptive filter receives this signal as input so as to enable it to act selectively: i) either to perform an adaptive search for the parameters of the filter in the absence of speech; ii) or else to “freeze” those parameters of the filter in the presence of speech.

The invention belongs to the technical field of digital filter design and in particular relates to an interference canceling method based on an improved all-pass fractional delay filter. The interference canceling method comprises the specific steps of utilizing a minimum mean square error criterion to construct a mathematic model of the all-pass fractional delay filter, utilizing a particle swarm optimization method based on natural selection to solve the mathematic model of the all-pass fractional delay filter and further construct the all-pass fractional delay filter, obtaining reference signals, utilizing the constructed all-pass fractional delay filter to filter the reference signals and carrying out interference canceling process on the filtered signals and signals received by a radar. The interference canceling method uses a natural-selection particle swarm algorithm, guarantees the solving convergence of the filter, quickens the convergence speed, avoids complex numeric calculation, guarantees the solving numerical stability of the all-pass fractional delay filter and enables design of the variable fractional delay filter to be more flexible.

The present invention refers to a method and apparatus for reconstruction of a nonuniformly sampled bandlimited analog signal xa(t), said nonuniformly sampled signal comprising N subsequences xk(m), k=0, 1, . . . , N-1, N>=2, obtained through sampling at a sampling rate of 1 / (MT) according to xk(m)=xa(nMT+tk), where M is an integer, and tk=kMT / N+DELTAtk, DELTAtk being different from zero. The invention comprises forming a new sequence y(n) from said N subsequences xk(m) such that y(n) at least contains the same information as x(n)=xa(nT), i.e. xa(t) sampled with a sampling rate of 1 / T, in a frequency region lower than omega0, omega0 being a predetermined limit frequency, by means of (i) upsampling each of said N subsequences xk(m), k=0, 1, . . . , N-1, by a factor M, M being a positive integer; (ii) filtering each of said upsampled N subsequences xk(m), k=0, 1, . . . , N-1, by a respective digital filter; and (iii) adding said N digitally filtered subsequences to form y(n). The respective digital filter is preferably a fractional delay filter and has preferably a frequency response Gk=ak e(-jomegasT), k=0, 1, . . . , N-1, in the frequency band |omegaT|<=omega0T, ak being a constant and s=d+tk, d being an integer.

A beamforming apparatus is provided for improving beamforming accuracy by employing fractional delay filters in an interpolation process and reducing hardware complexity by using post-filtering technique. The beamforming apparatus of the present invention includes a post-filtering means implemented with fractional delay filters that combines block data, on the respective channels, supposed to be fractionally delayed and obtains a delay value of fractional part from the combined data. The post-filtering means collects the block data of the channels assigned identical coefficients and performs a filtering process simultaneously.

A fractional delay optimization method applicable to multiple Nyquist regions and an implementation structure thereof belong to the field of digital signal processing. First, fractional delay processing is carried out on an input data sequence to get a first output data sequence, and multiplication operation and Hilbert transformation are carried out on the input data sequence to get a second output data sequence. Then, the second output data sequence is subtracted from the first output data sequence to get an output data sequence after fractional delay applicable to multiple Nyquist regions. The multiplication operation is to multiply the input data sequence by a zoom factor A=(-1)<NZ>*ceil[(NZ-1) / 2]*2 Pai D, wherein NZ represents a Nyquist region where the frequency f(in) of the input data sequence is located relative to the sampling frequency f(s), ceil refers to rounding up (NZ-1) / 2 to an integer, and D represents the delay of a fractional delay filter. The application band range of the traditional fractional delay filter can be extended to a high Nyquist region to realize the fractional delay of multiple Nyquist regions. The structure is simple, and the method is easy to implement.

A multi-carrier receiver receiving N carrier frequencies, including N A / D converters, each A / D converter performs analog-to-digital conversion on the received signal of each carrier at a sampling rate fs; N quadrature detection 2N LPFs, which only allow the required frequency bands output by N quadrature detectors to pass through; and N delay correction devices, Each correcting device uses a fractional delay filter to correct the processing delay deviation of each carrier in the multi-carrier receiver, and the corrected time unit is less than 1 / fs. The delay correction device has, for example, an M-stage shift register that operates at fs and produces a delay of M / fs; and a fractional delay filter that operates at fs and includes an even number of tap coefficients that produces a delay that differs from M / fs 0.5 / fs.

The invention discloses a TIADC system frequency response non-consistency error correction method based on a sampling reconstruction filter bank, and the method comprises the steps: firstly measuringthe frequency response of each ADC of a TIADC system, determining an ideal frequency response function, and calculating the frequency response of a sampling reconstruction filter through the ideal frequency response and the frequency response of each ADC; obtaining amplitude-frequency response and group delay according to the frequency response of the sampling reconstruction filter; designing a first-stage linear phase amplitude-frequency compensation filter bank according to amplitude-frequency, designing a second-stage all-pass filter bank and a third-stage fractional delay filter bank according to group delay, and calculating integral integer delay to form a sampling reconstruction filter bank by the three stages of filter banks; enabling actual sampling data to pass through a samplingreconstruction filter bank; determining the reconstructed sampling sequence corresponding to the actual sampling sequence according to the overall time delay, and finally calculating the corrected sampling sequence according to the actual sampling sequence and the reconstructed sampling sequence, so that the problem of frequency response non-consistency error correction of the TIADC system under large frequency response difference is solved.

The invention discloses an optimized design method of a broadband digital array radar reception channel. The relative positions of an extraction module and a fractional delay filter of a broadband digital array radar reception channel are changed, an anti-aliasing filter in a back stage extraction structure is prepositioned, a variable fractional delay filter is arranged before the extraction module to obtain an equivalent multistage filter, and thus people can design a target function and constraint conditions to obtain an optimized design according to the transmission band inner ripple waves, stop band inner ripple waves, transmission band cut-off frequency, and stop band cut-off frequency requirements of the equivalent multistage filter. The provided method can effectively reduce the orders of filters and the system complexity and power consumption are reduced therefore.

The invention discloses a delay performance test method and a test device for a fractional delay filter. The delay performance test method comprises the following steps: providing two test signals between which a delay precision value exists; respectively transmitting the two test signals into two fractional delay filters to be tested with delay values respectively set to be zero and equal to the delay precision value, to form two output signals; comparing the two output signals; subtracting the two output signals, and judging and estimating the delay performance of the fractional delay filters to be tested according to a difference, or estimating the delay performance by implementing a relevant function method on the two output signals; changing the delay value into an integral multiple of the delay precision value or change frequency values of the two test signals, and repeating the above steps. The invention further discloses a delay performance test device for the fractional delay filter by adopting the method, another delay performance test method for the fractional delay filter and a delay performance test device for the fractional delay filter by adopting the another delay performance test method.

A system for time aligning widely frequency spaced signals includes a digital predistortion (DPD) processor and a power amplifier coupled to the DPD processor and operable to provide a transmit signal at a power amplifier output. The system also includes a feedback loop coupled to the power amplifier output. The feedback loop comprises an adaptive fractional delay filter, a delay estimator coupled to the adaptive fractional delay filter, and a DPD coefficient estimator coupled to the delay estimator

The invention discloses a high-precision multichannel synchronous high-speed data acquisition and processing system and method, and the system comprises a clock distribution calibration source, an ADC data acquisition module, and an ADC data receiving module, an FIFO data caching module, a fractional delay filtering module and a programmable control module in an FPGA, wherein the clock distribution calibration source generates a multi-channel synchronous signal and a synchronous clock, the multi-channel synchronous signal and the synchronous clock are distributed to the ADC data acquisition module for sampling, and the sampled data are sent to the FIFO data caching module through the ADC data receiving module; the programmable control module performs FFT operation according to the sampling data, extracts the phase difference between each channel and the reference channel through a CORDIC algorithm, then calculates the time delay between each channel and the reference channel, and solves the integer and fractional multiple of the sampling period; and the FIFO data caching module and the fractional delay filter sequentially complete integral multiple and fractional multiple movement of a sampling period, and finally a multi-channel synchronization sequence is obtained. According to the invention, high-precision multi-channel synchronous high-speed data acquisition and processing are realized.