126 results about "Prototype filter" patented technology

The present invention proposes a new method and apparatus for the improvement of digital filterbanks, by a complex extension of cosine modulated digital filterbanks. The invention employs complex-exponential modulation of a low-pass prototype filter and a new method for optimizing the characteristics of this filter. The invention substantially reduces artifacts due to aliasing emerging from independent modifications of subband signals, for example when using a filterbank as an spectral equalizer. The invention is preferably implemented in software, running on a standard PC or a digital signal processor (DSP), but can also be hardcoded on a custom chip. The invention offers essential improvements for various types of digital equalizers, adaptive filters, multiband companders and spectral envelope adjusting filterbanks used in high frequency reconstruction (HFR) systems.

The invention discloses a broadband sub-matrix adaptive beamforming method based on sub-band decomposition, which mainly resolves the problem that computation burden in the prior art is high, and broadband interference signals cannot be processed and suppressed adaptively. The implementation process of the broadband sub-matrix adaptive beamforming method includes steps: 1) dividing a total matrix into a plurality of sub-matrixes, leading the sub-matrixes to be aligned with local beam pointing by the aid of microwave synthesis of a phase shifter, and obtaining sub-matrix synthesis data; 2) selecting a prototype filter and obtaining corrected analyzing and comprehensive filter banks via a cosinusoidal modulation filter bank; 3) under-sampling the sub-matrix synthesis data after the sub-matrix synthesis data pass through the analyzing filter banks, solving an adaptive weight in a narrow band and performing sub-band beamforming in the narrow band; and 4) up-sampling signals after sub-band beamforming, leading the up-sampling signals to pass through the comprehensive filter banks, and summating data of the comprehensive filter banks to obtain data after broadband adaptive beamforming. The broadband sub-matrix adaptive beamforming method has the advantages that the dimension of hardware is small, computation burden is low and broadband interference signals can be suppressed adaptively. In addition, the broadband sub-matrix adaptive beamforming method can be used for adaptive beamforming of a broadband phased array radar.

An apparatus having a band-separating filter bank for separating a digital signal into a plurality of sub-band signals, to be processed or transmitted, and a band-combining filter bank for subsequently combining the resultant sub-band signals into a single digital signal, wherein each of the band-separating filter bank and band-combining filter bank incorporates a FIR low pass filter having an asymmetric impulse response, as the prototype filter of the filter bank. A significant reduction can thereby be achieved in the amount of overall group delay that results from the processing performed by these filter banks.

A system includes at least a transmitter having a serial-to-parallel converter, an iFFT block and a frequency de-spreader device that applies each signal that results from multiplying a data sample by one of the predetermined frequency coefficients of the prototype filter of a synthesis filter bank to one of the inputs of the iFFT block presenting a size that is strictly greater than the number of subchannels. Also described is a system including at least one receiver including a serial-to-parallel converter, a FFT block presenting a size that is strictly greater than the number of subchannels of the system, and a frequency de-spreader device that multiplies the signal from each output of the FFT block by one of predetermined frequency coefficients of the prototype filter of an analysis filter bank and sums the results of these multiplications to deliver at least a portion of the output signal from the receiver.

A digital signal processing system for multiplexing/demultiplexing a large number of closely spaced FDM channels in which sub-band definition filtering divides the FDM spectral band comprised of "N" channels into "K" sub-bands in order to reduce the dimension of the polyphase filter fast Fourier transform structure required to complete the multiplexing/demultiplexing. This reduces the order of the required prototype filter by a factor proportional to K. The number of sub-bands K is chosen so that it is large enough to ensure the polyphase filter, fast Fourier transform structure for each sub-band is realizable within a finite word length, fixed point arithmetic implementation compatible with a low power consumption. To facilitate efficient sub-band definition filtering, the real basebanded composite signal is inputted at a spectral offset from DC equal to one quarter the FDM channel bandwidth for the N channels and the signal is sampled at a frequency 50% greater than the applicable Nyquist rate. The quarter band spectral offset and oversampling by 50% above the theoretical Nyquist rate facilitate the use of computationally efficient bandshift and symmetric half-band Finite Impulse Response (FIR) filtering.

An actively tunable waveguide-based iris filter having a first part including a first portion of a deformable iris filter cavity having an inlet and an outlet; a second part operatively coupled with the first part and including a second portion of the deformable iris filter cavity having a deformable membrane operatively coupled with the first portion of a deformable iris filter cavity; the first portion and the second portion together forming the deformable iris filter cavity of the tunable waveguide-based iris filter; and means for moving the deformable membrane, whereby movement of the deformable membrane changes the geometry of the deformable iris filter cavity for causing a change in the frequency of a signal being filtered by the filter. The tunable filter is fabricated using a MEMS-based process including a plastic micro embossing process and a gold electroplating process. Prototype filters were fabricated and measured with bandwidth of 4.05 GHz centered at 94.79 GHz with a minimum insertion loss of 2.37 dB and return loss better than 15 dB. A total of 2.59 GHz center frequency shift was achieved when membranes deflected from −50 μm to +150 μm.

The invention discloses a digital channelizing method and circuit, relating to the technical field of broadband reception. The method comprises the following steps of: S1, determining a channel number 2M of a part to be analyzed and an FFT (Fast Fourier Transform Algorithm) point number of a corresponding integrated part during signal reconstruction; S2, determining a multi-phase filter order L after extraction according to a prototype filter order N and the channel number 2M of the part to be analyzed; S3, determining a coefficient of a multi-phase filter group; S4, performing multi-phase filtering on the part to be analyzed; S5, performing Fourier transformation on filtered signals to obtain yA; S6, judging whether the signals distribute in a cross-channel manner or not, if not, executing a step S7, and if so, executing a step S8; S7, performing baseband processing on the obtained signal yA and then outputting a signal yA'; S8, performing Fourier transformation on the signal yA to obtain yS; S9, leading the signal ys to a multi-phase filter group CS in the integrated part for filtering to obtain yf; and S10, interpolating 0 into the obtained signal yf and performing delayed addition to obtain a system output yout. According to the invention, the adaptability to signal reception can be enhanced, and the computation amount is reduced at the same time.

The invention provides a filter bank multicarrier modulation system and a design method thereof. According to the design requirement of the system, a prototype filter is determined, the prototype filter shifts on an angular frequency axis to obtain an integrated filter bank of a sending terminal, and an analysis filter bank of a receiving terminal satisfies a time domain complete reconstruction condition. Compared with the traditional frequency domain design, according to the system and method, a constraint condition that an integrated filter bank is the conjugate transpose of an analysis filter bank in the traditional filter bank multicarrier modulator is abandoned, and the integrated filter bank can be freely designed according to the design requirement of the system. According to the multicarrier modulator in the invention, while the reconstruction condition is completely satisfied, the modulator still has a very high frequency resolution and is especially suitable for being applied in a communication system with a strict frequency resolution requirement.

A multirate spectral analyzer receives a data sequence through a tapped delay line (510) onto a plurality of filter channels, each of which includes a first decimator (520), a polyphase filter (530), and a second decimator (540). Each filter channel is coupled to a transform processor (550) which modulates the frequency response of the polyphase filters to a plurality of identical bandpass filters spaced evenly at 2πk/M intervals, where k=1, 2, . . . , M−1, and M is the number of filter channels. The transform processor (550) outputs a plurality of time series representative of the frequency component for each of the corresponding filter channels. By choosing a prototype filter order to be much larger than the number of filter channels, the effects of aliasing in the output are greatly reduced. The reduction in aliasing further allows, by prudent selection of the two decimators, for fractional temporal overlap to be implemented in the spectral estimates.

FBMC (Filter Bank Multicarrier) is a special carrier communication mode. Being different from OFDM (Orthogonal frequency division multiplexing), subcarriers of the FBMC are not orthogonal to one another, so that intersymbol interference and inter-carrier interference naturally exist. A traditional OFDM channel estimation method is built on the basis of no intersymbol interference and inter-carrier interference, thereof, to carry out accurate channel estimation, the interference of surrounding symbols to a pilot symbol must be eliminated, and surrounding interference factors are definite under a certain filter bank structure and a prototype filter design. An auxiliary pilot method is such a method that an auxiliary pilot is placed nearby the position of an actual pilot, the value of the auxiliary pilot is determined by virtue of the values of the surrounding symbols and the corresponding interference factors, and the interference of the surrounding symbols to the pilot position is eliminated by virtue of the auxiliary pilot, so as to carry out accurate channel estimation.

The invention discloses a method for optimally designing graph filter banks on the basis of a two-step process. The method includes converting requirements on reconstruction characteristics and frequency characteristics of the filter banks into functions related to coefficients of prototype filters; converting design problems of the graph filter banks into a constrained optimization problem according to design requirements; ultimately solving the optimal coefficients of the prototype filters by the aid of the two-step process. The method has the advantages that optimization ideas are introduced into designs of the graph filter banks for the first time, and the reconstruction characteristics and the frequency characteristics of the graph filter banks are taken into consideration by the aid of factor regulating modes; the reconstruction characteristics and the frequency characteristics of the filter banks can be taken into consideration by optimization paths as compared with existing methods on the basis of polynomial decomposition; compromising effects can be realized between the reconstruction characteristics and the frequency characteristics by means of regulating parameters epsilon r under the condition of given lengths of graph filters.

A method is provided for receiving an OQAM multi-carrier signal, which implements a step of estimating, in the time domain, at least one time, phase, and/or frequency shift of the multi-carrier signal. The estimation step implements at least one estimator in order to estimate the time shift, referred to as a time estimator, and/or at least one estimator for estimating the phase shift, referred to as a phase estimator, and/or at least one estimator for estimating the frequency shift, referred to as a frequency estimator. The multi-carrier signal includes at least one preamble, and at least one of the estimators takes into account coefficients of a prototype filter used in transmission in order to shape at least one preamble inserted into the multi-carrier signal.

The invention provides a method for realizing a high-order FIR filter based on an FPGA, used for solving the technical problem of excessive occupation of the high-order FIR filter to logic units in the FPGA in the existing method for realizing high-order FIR multiphase filtering. The method comprises the following steps: selecting parameters of a prototype filter; designing the prototype filter h (n); performing multiphase decomposition on the prototype filter h (n) to obtain multiphase filters; performing module division on each multiphase filter; storing coefficients of the multiphase filters in a module ROM; reading the coefficients of the multiphase filters in the module ROM; caching and reading input data by read-write enable, a write address control signal and a read address control signal of a module RAM obtained by system clock control; and performing multiplication and addition operations on the coefficients of the multiphase filters and the input data by using a multiplication accumulation module, and outputting an operation result. The method provided by the invention is little in occupation of the logic units in the FPGA, simple, efficient and is easy to realize.

The invention belongs to the technical field of communication, relates to an implementation method for a digital channelized filter bank and provides a digital channelized filter bank implementation technology based on low computation burden, low resource consumption and high adaptability of a multi-channel filter and application thereof in implementation of digital channelization. When the required frequency resolution is changed, only coefficient of a lowpass prototype filter needs to be calculated again, and a new filter coefficient is reallocated into a multi-channel filter bank of the original structure according to multi-phase decomposition and multichannel filter theories, and an expression and an implementation structure do not need to be deduced again, so that the implementation method provided by the invention is applicable to platforms such as FPGA and DSP, and digital channelization processing is realized.

The invention relates to a satellite-borne reconfigurable broadband digital channelizing switching method, belonging to the technical field of satellite communication. The method comprises the following steps of: carrying out secondary sampling to uplink signals of the satellite so as to obtain digital signals; constructing perfect reconfigurable prototype filtering module and obtain a complex-exponential modulation perfect reconfigurable filter group module by complex-exponential modulation; carrying out filtering to the secondary sampling signals so as to obtain baseband signals of subchannels; carrying switching to the separated baseband signals of the subchannels according to switching information set by the satellite so as to obtain switched data; carrying combination to the switched data so as to obtain the downlink signals of the satellite. The method is not independent physical layer concrete setting, is not relevant to the wave form of the signals to be processed, and has good adaptability; the method is suitable for uniform bandwidth channel switching scenes and is also suitable for non-uniform bandwidth channel switching scenes; all the control is realized by control signaling with flexible reconfigurability; and the method supports functions of broadcast and multicast simultaneously.

The invention discloses a method for realizing multicarrier VDE system modulation and demodulation of a ship VDES system. According to the method, the modulation and demodulation of multicarrier VDE system information are realized by adopting fast Fourier transform (FFT) and fast Fourier inverse transform (IFFT), this modulation and demodulation realization mode can ensure complete orthogonality between subcarriers, and thus good modulation and demodulation performance and reliable transmission of signals are realized. By adoption of the method disclosed by the invention, the problems of resource strain and complex control caused by the adoption of multiple carrier numerically controlled oscillators (NCO) in parallel in the case of numerous subcarriers are solved. In addition, the intervals between the subcarriers are greater than a signal bandwidth is realized in a manner of combining multicarrier modulation and demodulation with a narrowband prototype filter, the harsh requirements of a demodulation terminal for frequency difference, code synchronization and other synchronization information in multipath and other serious communication environments of the system are reduced, and the complexity of realizing the VDE system modulation and demodulation is greatly reduced.

The document relates to modulated sub-sampled digital filter banks, as well as to methods and systems for the design of such filter banks. In particular, the present document proposes a method and apparatus for the improvement of low delay modulated digital filter banks. The method employs modulation of an asymmetric low-pass prototype filter and a new method for optimizing the coefficients of this filter. Further, a specific design for a (64) channel filter bank using a prototype filter length of (640) coefficients and a system delay of (319) samples is given. The method substantially reduces artifacts due to aliasing emerging from independent modifications of subband signals, for example when using a filter bank as a spectral equalizer. The method is preferably implemented in software, running on a standard PC or a digital signal processor (DSP), but can also be hardcoded on a custom chip. The method offers improvements for various types of digital equalizers, adaptive filters, multiband companders and spectral envelope adjusting filterbanks used in high frequency reconstruction (HFR) or parametric stereo systems.

The invention discloses a rapid design method of a DFT modulated filter bank. The rapid design method comprises the following steps: firstly, initializing an analysis prototype filter h0 according to the design requirements; obtaining a time domain condition free of transfer distortion or aliasing distortion according to a frequency domain condition free of transfer distortion or aliasing distortion; summarizing the design into an optimization problem free of constraint on the basis of the time domain frequency, wherein the target function is the weighted sum of transfer distortion, aliasing distortion and stopband energy of the prototype filter; rapidly solving an analysis prototype filter h and a comprehensive prototype filter g by a double iterative algorithm based on a matrix inversion equivalent condition according to the initialized analysis prototype filter h0; and modulating by the obtained prototype filter to obtain an overall filter bank. According to the rapid design method, the reconstruction error of the filter bank is relatively small; the overall performance of the filter tank is improved; the rapid design method is suitable for the conditions of overlarge number of filter bank channels and overlong sub-band filters; and the computation complexity is relatively low.

This disclosure relates to a 5G or pre-5G communication system to be provided for supporting higher data transfer rate following a 4G communication system such as LTE. To accomplish the objective mentioned above, a method for transmitting and receiving a signal at a terminal in the mobile communication system according to one embodiment of the present application comprises the steps of: receiving, from a base station, a reference signal generated on the basis of a first filter; determining channel information on the basis of the received reference signal; transmitting the determined channel information to the base station; receiving, from the base station, information related to a second filter determined on the basis of the channel information; and receiving, from the base station, a data signal on the basis of the second filter. According to an embodiment of the present application, it is possible to maximize the signal-to-interference-plus-noise ratio (SINR) while minimizing spectral interference in the event of multiuser connection, by using a prototype filter application method and system structure.

The invention discloses a design method of a two-dimensional double prototype completely-oversampled DFT (discrete Fourier transform) modulated filter bank. The design of the completely-oversampled DFT modulated filter bank is realized under the condition of near perfect reconstruction. The design problem of two prototype filters is resolved into an unconstrained optimization problem, wherein an objective function is overall distortion of the filter bank, namely, a weighted sum of transmission distortion, aliasing distortion and stopband energy of the prototype filters, and the optimization problem is solved through a double-iteration mechanism according to gradient vectors of the objective function. The computation complexity is remarkably reduced according to equivalent conditions of matrix inversion and a fast algorithm of Toeplitz matrix inversion in single-step iteration. With the adoption of the method, the filter bank with better overall performance can be obtained, the computation complexity is greatly reduced, and the large-scale two-dimensional filter banks can be rapidly designed.

The invention discloses a multi-phase structure of a two-channel orthogonal mirror image filter bank and a coefficient design method of thereof. At present, most known two-channel QFMB design methodsare optimization design of prototype filter coefficients, and do not pay much attention to reduction of hardware implementation complexity of a QMFB structure. The multi-phase structure of the two-channel orthogonal mirror image filter bank comprises an H0 module, an M (z) module, q modules, a module connecting part, a main input port Input, a main output port Output0 and a main output port Output1. According to the multi-phase structure of the two-channel QMFB analysis filter bank part provided by the invention, a traditional QMFB prototype filter coefficient is converted into a form of an extrapolation pulse response filter, and LU decomposition is adopted, so that more 0 and 1 exist in the coefficient, and multiplier and adder resources are saved.

The invention provides a multiple access method (F-BFDM) and a system thereof applicable to multiple application scene signals in wireless communication. The method comprises the following steps of: firstly performing a fast Fourier transform (FFT) change to each path of signals at a transmitting end to configure the signals to the allocated frequency bands, then pre-filtering to reduce the peak-to-average power ratio (PAPR) of a modulated signal, modulating the filtered signal onto a subcarrier by a cyclic Fourier transform (CCIDFT), combining the modulated signals of each path, and transmitting the combined signals to a channel together with a cyclic prefix (CP). The signal of each path in the invention corresponds to an application scenario, the complete reconstruction of the system iscompleted by the CCDFT at the receiving end, and the CCDFT is implemented by a bi-orthogonal filter bank. By freely designing a prototype filter, the interference of multiple application scene signalsfor multiple accessing can be minimized, so that the signal of each path can be accessed without interference under the situation that no isolation band exists, and the spectral efficiency can be maximized.