148 results about "Unit impulse response" patented technology

An OFDM communication system performs time domain channel estimation responsive to received symbols before the symbols are processed by a fast Fourier transform. The communication system generates virtual pilots from actual pilots to improve the stability and quality of channel estimation. The system generates a reference signal from the actual and virtual pilots and correlates the resulting reference signal with a signal responsive to the received symbol to generate an initial channel impulse response (CIR) and to determine statistics about the channel. In some circumstances, the resulting reference signal is correlated with a modified symbol in which the actual and virtual pilot locations are emphasized and the data locations are deemphasized. Time domain channel estimation iteratively improves on the initial CIR. The system determines channel estimates for data only symbols through averaging such as interpolation.

The invention discloses a training sequence reconstruction-based channel estimation method and a training sequence reconstruction-based channel estimation system. The method comprises the following steps: acquiring a known channel estimation result; according to the known channel estimation result, constructing linear convolution of former frame transmitted data and a channel and the linear convolution of a transmitted training sequence and a channel impulse response; eliminating inter-block interference of data on a training sequence; obtaining a cyclic convolution, of the training sequence and the channel impulse response, serving as a reconstruction item; according to the reconstruction item, reconstructing the training sequence; and performing channel estimation by utilizing the reconstructed training sequence, and updating a channel estimation result. The method and the system of the invention can ensure that a TDS-OFDM system can also obtain relatively accurate channel estimation when maximum delay extension of the channel exceeds the guard space length of the training sequence, simultaneously improves the accuracy of the channel estimation and improves the spectrum utilization ratio and the mobility performance of the system.

We disclose an opto-electronic circuit having an optical modulator and a driver circuit configured to generate a plurality of electrical drive signals for the optical modulator in a manner that causes the opto-electronic circuit to operate as a finite-impulse-response (FIR) filter. Different electrical drive signals generated by the driver circuit represent different taps of the FIR filter and are individually applied to different respective electrodes in the optical modulator without first being combined with one another prior to said individual application. The optical modulator represents an adder of the FIR filter and is configured to use the applied electrical drive signals to perform signal summation in the optical domain, thereby alleviating some of the limitations associated with the electrical RF circuitry used in the driver circuit. The opto-electronic circuit can be employed in optical transceivers and equalizers and be configured to implement signal pre-emphasis, feed-forward equalization, or decision-feedback equalization.

The invention discloses a construction method of a frequency-selecting filter and a construction method for realizing FIR-type and IIR-type filters by adopting the same, relates to the technical field of information, solves the problems of fussy conventional manual design of the filter and low efficiency and low accuracy of the manual design and also provides a rapid and accurate output function which can directly use an output file in the design of an embedded system. The method comprises the following steps of: through set parameters, budgeting and regulating corresponding parameters according to the parameters to construct a filter and generate an amplitude-frequency characteristic diagram, a log magnitude-frequency characteristics diagram, a frequency-phase characteristic diagram, a unit step response diagram, a unit impulse response diagram, a group delay characteristic diagram and a zero-pole point distribution diagram; if the construction requirement is not met, returning to reset the parameters; and if the construction requirement is met, outputting the constructed filter. The invention is suitable for construction of the filters.

The invention relates to a sparse deconvolution method for impact load identification of a mechanical structure. The method is used for solving the ill-posed nature of the impact load identification inverse problem and comprises steps as follows: 1) a frequency response function between an impact load acting point and a response measurement point of the mechanical structure is measured with a hammering method, a unit impulse response function is obtained through inverse fast fourier transform, discretization is further performed, and a transfer matrix is obtained; 2) an acceleration signal generated by impact load of the mechanical structure is measured with an acceleration sensor; 3) an L1-norm-based sparse deconvolution convex optimization model for impact load identification is established; 4) the sparse deconvolution optimization model is resolved with a primal-dual interior point method, and a sparse deconvolution solution, namely, a to-be-identified impact load, is obtained. The sparse deconvolution method is suitable for identifying the impact load acting on the mechanical structure. Compared with conventional Tikhonov regularization methods based on an L2 norm, the sparse deconvolution method has the advantages of high identification accuracy, high computation efficiency and high stability.

The invention relates to a precompensation method for in-band group delay fluctuation of a satellite navigation signal generating system, which comprises the following steps: (1) measuring a combined S parameter of a modulator, a filter and an amplifier in the satellite navigation signal generating system, and determining amplitude-frequency and group delay characteristic of the combination of the three devices; (2) counting the group delay characteristic of a precompensation filter according to the combined group delay characteristic; (3) obtaining the phase-frequency characteristic of the precompensation filter; (4) setting the phase-frequency characteristic of the precompensation filter to be an inverse Sinc function; (5) obtaining a system function of the precompensation filter according to the amplitude-frequency characteristic and phase-frequency characteristic of the precompensation filter; (6) obtaining a unit impulse response function of the precompensation filter; (7) setting a threshold value, and setting the quantity in the unit impulse response function, which is smaller than the threshold value, to be zero to be as a coefficient of the precompensation filter; and (8) realizing the precompensaiton filter in a digital standalone of the satellite navigation signal generating system by using the coefficient of the precompensation filter, so as to compensate the group delay fluctuation of the satellite navigation signal generating system.

The invention discloses a multivariable time-lag parameter estimation method based on FIR (Finite Impulse Response) model identification, comprising the following steps of: step 101, collecting the input and output data of a system; step 102, carrying out the FIR model identification on the collected data to obtain a system step response coefficient and a step response curve; step 103, selecting threshold to be delta%(infinity); step 104, judging whether the fluctuation of a time-lag phase in the step response curve is in the threshold range or not; if the fluctuation does not exceed the threshold range, carrying out the step 105; otherwise, carrying out the step 103 to reselect a threshold; step 105, obtaining the first intersected point between the threshold and the step response curve; step 106, if t is judged to be larger than t1 and smaller than t2, carrying out a step 107 to obtain corresponding time-lag estimation value; otherwise, if the horizontal coordinator value t indicated by the intersected point is arranged on a sampling point t1 or t2, judging that the time-lag parameter estimation value zeta to be the sampling point t1 or t2; and step 107, obtaining the time-lag parameter estimation value zeta=t1. The invention has good applicability and high precision.

The present application a digital self-interference residual cancellation method that adjusts a magnitude of a sampled transmit signal based on compared magnitude and phases associated with tones. The digital self-interference residual cancellation method may follow an analog carrier cancellation stage where the digital self-interference residual cancellation is based on a determination of the channel circuit response used to control an infinite impulse response filter which can compensate using both poles and zeroes.

System and method for digitally equalizing a data channel having wide channel impulse response for clock recovery of heavily ISI-induced received signals operating at one sample per symbol, according to which the received signal is pre-processed to provide a received signal with modified constellation, which is pre-processed for the decision process of signal with Inter-Symbol Interference by introducing controlled ISI to the received signal. The decision process is performed, based on a higher order vocabulary according to the introduced controlled ISI.

A receiver is disclosed that includes a slicer having an input to receive a sequence of symbols exhibiting inter-symbol-interference (ISI). The slicer determines a state associated with each symbol based on a threshold. A feedback equalization unit is coupled to the slicer to apply equalization to the symbol fed to the slicer input based on prior detected symbol states. A Least-Mean-Square (LMS) unit cooperates with the slicer and feedback equalization unit to estimate a channel impulse response based on the equalized symbols. The LMS unit feeds the estimated channel impulse response to a Maximum-Likelihood-Sequence-Estimation (MLSE) unit to generate an estimated sequence of bits based on the estimated channel impulse response.

The invention discloses a wireless multipath fading channel simulating method and a channel simulator. The method comprises the following steps: measuring a channel between a transmitting antenna and a receiving antenna in actual environment, and measuring the frequency response of an actual measurement channel through frequency sweep; performing fourier inverse transform on the frequency response of the actual measurement channel so as to obtain the unit impulse response of the actual measurement channel; separating parameters in the unit impulse response of the actual measurement channel, and performing modeling so as to obtain a parameter model; storing the parameters of the model into a database; reading the parameters of the model, and generating the unit impulse response of a simulating channel; calculating a bit error ratio by utilizing Monte-Carlo simulation so as to complete channel simulation under the actual environment. The simulator comprises a channel measuring module, a module for extracting the unit impulse response of the actual measurement channel, a model building module, a model parameter extracting module and a simulating channel generating and verifying module. According to the wireless multipath fading channel simulating method and the channel simulator, disclosed by the invention, data can be measured in an actual manner, the model can be established, the bit error properties in different communication processes can be analyzed, and the channel obtained through simulation more conforms to the actual environment.

A mixed signal processing circuit includes an analog to PWM converting circuit and a finite impulse response (FIR) filter having a multiple output tapped delay line and a summing and integration circuit. The mixed signal processing circuit converts an input analog signal to a PWM signal, forms a multi-level PWM signal from the PWM signal and one or more delayed versions of the PWM signal, and converts the multi-level PWM signal to an output analog signal. The analog to PWM converting circuit is implemented using a triangle waveform generator and a comparator. The FIR filter is implement using a resistive network to apply scaling coefficients of the FIR filter. The mixed signal processing circuit can be implemented within a noise cancellation headphone to generate a noise cancelling signal or generally in applications that would be benefitted from the combination of analog input/output and digital filter techniques.

The invention provides an estimation method for channel impulse response, which is used in mobile communication system and including the following steps: (a) the channel impulse response is estimated initially h(i), i is equal to 0...N-1, (b) the energy of the N paths of the channel impulse response is calculated. The energy maximum is En Max and energy threshold value is En Max/T. T is more than 1. If the path energy in the channel impulse response is less than the energy threshold value, the path is set as a noise path and the channel impulse response value corresponding to the path is cleared, (c) channel impulse response estimation value h(i){i is equal to 0, ...L-1} is gotten to estimate noise variance according to different channel impulse response orders L. L ranges from Lstart to N. Lstart is an integer less than or equal to N, (d) the L value corresponding to the smallest noise variance is taken as the dispersion length M of the channel. The channel impulse response value from path M+1 to path N is cleared. Compared with the traditional method, the invention can inhibit the influence of noise on channel impulse response estimation and consequently improve balanced demodulation performance.

The invention discloses a FIR filter design method based on particle swarm optimization. The method is characterized by using the unit impulse response of a FIR filter as the particle position vector of the particle swarm optimization; designing the fitness function of the particle swarm optimization on the basis of a signal-to-noise ratio of a signal filtered by the FIR filter and the mean square error of the FIR filter and obtaining the FIR filter by iteration. The method designs the fitness function of the particle swarm optimization based on minimized signal-to-noise ratio and mean square error, and designs the FIR filter based on particle swarm optimization so as to achieve the FIR filter taking account of signal-to-noise ratio performance.

Embodiments of systems and methods for improved measurement of transient thermal responses in electronic systems are described herein. Embodiments of the disclosure use the known thermal transfer function of an electronic system to generate an equivalent resistor-capacitor (RC) network having a dynamic response that is identical to a given power excitation as the actual electronic system would have to that power excitation. Using the analogy between thermal and electrical systems, a Foster RC network is constructed, comprising a plurality of RC stages in which resistors and capacitors are connected in parallel. Subsequently, the analog thermal RC network is converted into an infinite impulse response (IIR) digital filter, whose coefficients can be obtained the Z-transform of the analog thermal RC network. This IIR digital filter establishes the recursive relationship between temperature output at the current time step and measured power input at the previous time step. Using this IIR digital filter, temperature response subject to arbitrary time-dependent power can be calculated in very small amount of time compared with prior art methods.

The invention relates to a mechanical structure dynamic load identification method based on a cubic b-spline scaling function. The method comprises the steps of (1) measuring a frequency-response function between a mechanical structure position point bearing a dynamic load and a mechanical structure response measurement point with the hammering method, obtaining a unit impulse response function through rapid Fourier inversion, and then obtaining a transfer matrix through deconvolution; (2) measuring an acceleration signal of the response point generated by the structure dynamic load through an accelerator sensor; (3) establishing scaling function matrixes, dual matrixes and coefficient matrixes of the cubic b-spline scaling function under different layer numbers, and selecting a coefficient matrix with the minimum conditional number; (4) calculating the weight coefficient of the cubic b-spline scaling function under the regularized layer number by means of an acceleration response and coefficient matrix; (5) obtaining a regularized mechanical structure dynamic load to be identified by multiplying the weight coefficient by the corresponding scaling function matrix.

The invention discloses a power line communication channel estimation method. The power line communication channel estimation method comprises the steps of receiving signal conversion; selecting pilot frequency; conducting estimation by using a compressed sensing signal recovery algorithm. Aiming at the disadvantages that the channel estimation performance of the traditional estimation algorithm based on a least square method and a minimum mean square error is reduced with pilot frequency number, the estimation accuracy is reduced, the calculation complexity is high and the like, power line channel estimation is conducted by using the feature that power line channels have sparsity and by adopting a compressed sensing method, unit impulse responses of the channels are obtained through the known pilot frequency information by using a matching tracking algorithm, the pilot frequency number is reduced, the calculation complexity is decreased and the transmission efficiency and communication quality are improved. By adopting irregular pilot frequency distribution and designing pilot frequency distribution according to channel and noise conditions, a typical strategy is to interpose pilot frequency reference information at frequency points with small channel attenuation or larger signal-to-noise ratio to improve the accuracy of channel estimation.

An analog circuit fault diagnosis method based on echo state network dynamic classification relates to an analog circuit fault diagnosis method. It solves the problem of low diagnostic accuracy of analog circuit fault diagnosis using traditional neural network. Its method: use the unit pulse signal to excite the analog circuit to work, obtain the response signal of the circuit to be diagnosed; collect the unit pulse response output signal of the analog circuit, and use the unit pulse response output signal as the fault data sample; input the fault data sample to the echo Training is carried out in the state network, and an analog circuit fault diagnosis model is established according to the training results; the obtained circuit to-be-diagnosed response signal is used as fault data, and input into the analog circuit fault diagnosis model, and the fault diagnosis result is obtained and output. The invention is suitable for analog circuit fault diagnosis.

The invention discloses an online clustering equivalent modeling method of photovoltaic power plant. The method comprises the following steps: building photovoltaic power generation unit models with active and reactive power control links and low voltage crossing control links, and then building a photovoltaic power plant model with multiple photovoltaic units; according to the various types of photovoltaic power generation unit models of the photovoltaic power plant model, inferring and calculating the unit impulse curves corresponding to the model; using the distances among the unit impulse responding curves as clustering indexes; and utilizing the K-means algorithm to conduct online clustering to the photovoltaic power plant model so as to obtain the clustering result of the active and reactive power control links of an inverter; according to the actual output of each photovoltaic unit in the photovoltaic power plant model, calculating the equivalent parameters of each equalizer; and establishing an online clustering equivalent model of a photovoltaic power plant. In the invention, the clustering result bears no relationship with the output of the photovoltaic units and is solely determined by the control parameters of the inverter. Therefore, it is not necessary to establish a parameter sensitivity database offline, which greatly reduces the computational complexity.

Various embodiments of the present invention provide apparatuses and methods for filtering a digital signal with a Nyquist constrained digital finite impulse response filter. For example, an apparatus for filtering digital data is disclosed that includes a digital finite impulse response filter having a plurality of taps. The apparatus also includes a tap weight controller connected to the digital finite impulse response filter, operable to adjust a tap weight for each of a subset of the taps such that a magnitude of a Nyquist response of the digital finite impulse response filter remains within a constraint range.