43 results about "Filter impulse response" patented technology

A filter compressor for generating compressed subband filter impulse responses from input subband filter impulse responses corresponding to subbands, which include filter impulse response values at filter taps, includes a processor for examining the filter impulse response values from at least two input subband filter input responses to find filter impulse response values having higher values and at least one filter impulse response value having a value being lower than the higher values, and a filter impulse response constructor for constructing the compressed subband filter impulse responses using the filter impulse response values having the higher values, wherein the compressed subband filter impulse responses do not include filter impulse response values corresponding to filter taps of the at least one filter impulse response value having the lower value or include zero-valued values corresponding to filter taps of the at least one filter impulse response value having the lower value.

The present invention provides a method of characterizing a frequency response of a transmission channel between a transceiver and a subscriber unit. The method includes once per predetermined interval of time, the transceiver transmitting a signal including multiple carriers, a plurality of the carriers including training symbols, a plurality of the carriers including information symbols. The subscriber unit generates frequency response estimates at the frequencies of the carriers including training symbols, each interval of time. The frequency response estimates are converted into a time domain response generating an impulse response once per interval of time. The impulse responses are filtered over a plurality of intervals of time. A channel profile is determined from the filtered impulse responses. The channel profile is converted to the frequency domain generating a channel interpolator. The characterized frequency response is generated from the channel interpolator and the frequency response estimates. The filtering can include averaging the impulse responses over a plurality of intervals of time, accumulating the impulse responses over a plurality of intervals of time, or weighted averaging of the impulse responses over a plurality of intervals of time. The weighted averaging can be dependent upon a phase error between the impulse responses, and/or an amplitude error between the impulse responses.

A receiver is operable to detect a synchronisation position for recovering data from a set of received signal samples. The receiver comprises a filter having an impulse response matched to a predetermined characteristic of the received signal and is operable to produce an output signal which is representative of the convolution of the impulse response and the received signal samples. The receiver includes a synchronisation detector operable to detect the synchronisation position from the filter output signal, and a data detector operable to detect and recover data from the set of received signal samples from the synchronisation position provided by the synchronisation detector. The synchronisation detector is operable to represent each of the received signal samples as a positive or negative constant in dependence upon the relative sign of the signal sample, and to represent the samples of the filter impulse response as a positive or negative constant in dependence upon the relative sign of the impulse response samples, and the filter is operable to convolve the impulse response with the received signal samples by logically combining the representation of the received signal samples and the impulse response to produce the output signal. The receiver is therefore provided with a facility for detecting a synchronisation position from an output of the filter matched to a characteristic of the received signal. The output signal of the matched filter is formed by logically combining the filter impulse response and the received signal samples to form a representation of a convolution but with a substantially reduced number of computations.

A Multi-mode Loop Frequency modulator (10) for modulating a carrier signal according to various modulation pulse shapings and data signal to provide a modulated output signal (VCOout), comprises a waveform generator (12) and two multiplexors (14,38) to perform various pulse shaping filtering and or predistord the pulse shaping filter impulse response for either a dual port modulation or for a single port modulation. The waveform generator (12) can also provide interpolation to input frequency deviation and also provide scaling for various reference frequency clock provided by the crystal (30) and the reference divider (28). The low pass filter (22) is used for providing the PLL loop filtering and also as the smoothing filter for the high port DAC (18).

The invention provides a channel estimation method and device for an MIMO (multiple input multiple output) OFDM (orthogonal frequency division multiplexing) system. The method comprises the following steps of: determining the channel response of a multipath channel between a receiving antenna and a transmitting antenna based on the signal received by the receiving antenna; performing inverse Fourier transform on the determined channel response to obtain the impulse response of the multipath channel; performing iterative time-variable filtering on the impulse response of the multipath channel; and performing Fourier transform on the filtered impulse response. The invention solves the problem of lower estimation precision resulted from that the factors are not considered in the relevant technologies, thus improving the channel estimation precision.

A method of operation of a communication system includes: generating a filter impulse response and a filter time-domain data with a shortening filter; generating a filter frequency response based on the filter impulse response with a filter frequency response calculator; generating a filter frequency-domain data based on the filter time-domain data with a first process unit; and generating a raw channel impulse response with a filter frequency removal unit for removing the filter frequency response from the filter frequency-domain data.

A data processing method is provided to enable a calculation based signal analyzer, such as an FFT based spectrum analyzer, to produce results corresponding to a swept spectrum analyzer employing a video bandwidth (VBW) filter. Once a spectrum is produced the frequency axis is replace by a corresponding time axis, so that a time domain filter, such as a video bandwidth (VBW) filter can be applied. In a first example, the filter characteristics are applied by performing an FFT on display spectrum data, which has had its frequency axis replaced by a corresponding time axis, produce frequency domain data, multiplying by the frequency response to produce a filtered version, performing an inverse FFT and replacing the time axis with the original frequency axis to produce a filtered version of the display spectrum data. In another example, a filter impulse response is computed based upon the desired filter characteristics, a convolution integral of the display spectrum data, which has had its frequency axis replaced by a corresponding time axis, and the filter impulse response is conducted, and the time axis is replace by the original frequency axis to produce filtered display spectrum data.

Systems and methods for orbital angular momentum (OAM)-based multidimensional signaling with multiple-input-multiple-output (MIMO). The wireless communication is achieved using a transmitter including a plurality of orthogonal pulse shapers of a multidimensional modulator, the plurality of orthogonal pulse shapers generating a multidimensional modulated signal by imposing one or more data sequences on corresponding mutually orthogonal filter impulse responses derived from multiple orthogonal basis functions including Slepian sequences. An OAM antenna array including OAM antenna elements is used such that each of the OAM antenna elements includes an azimuthal phase shifter for shifting an azimuthal phase term of a wavefront generated by an antenna element such that the OAM antenna elements impose the multidimensional modulated signal on pre-determined OAM modes of a carrier signal corresponding to the azimuthal phase term.

A numerical string consisting of a ratio of “−1, m, −1” or “1, m, 1” is subjected to a predetermined moving average calculation n times. A numerical string thus obtained is used as filter coefficients of a basic filter and at least one basic filter is combined in an arbitrary way for cascade connection, thereby calculating the filter coefficients of the digital filter to be obtained. This significantly reduces the number of taps and the number of multipliers used as compared to the conventional FIR filter. Moreover, by using the numerical strings “−1, m, −1” and “1, m, 1” so that the filter impulse response becomes a finite-base function, it is possible to obtain a preferable frequency characteristic having no discretization error and having a great attenuation amount out of band.

A system and method for signal peak reduction in a spread spectrum communication system of the type including a filter for limiting signal bandwidth of symbols transmitted from the system. A signal peak reduction unit is provided before the filter that includes a filter predictor that predicts the effect of the filter on input symbols by using filter coefficient values corresponding to the filter impulse response function. Input symbols that are predicted to cause the output signal to exceed a predetermined peak limit value are adjusted. Several examples of suitable algorithms for calculating the necessary peak reduction to be applied to the input symbols are disclosed. The peak reduction unit provides adjusted symbols to the filter for processing and communication system output.

The invention discloses a strictly band-limited efficient modulating system based on impact filter forming. An emitting end of the system comprises a molding filter which is used for realizing a strictly band-limited communication system and improving spectrum efficiency of the system signal by reducing signal bandwidth, wherein the molding filter is an impact filter; a receiving end of the system adopts an optimal receiver which takes a pre-stored impact waveform sample sequence obtained by an expanded jumping part of the molding filter as a correlation operation template or matching filter impulse response to respectively perform matched filtering with a MPPSK receiving signal of an existing code element received by the receiving end to demodulate a corresponding sending code element after sliding fixed step length to an impact appearing position of the code elements [1,2, ...., M]; the system sending end sufficiently applies an resonance effect of the impact filter, so that the interference effect between the strictly band-limited system codes is small, the structure is simple, the complexity is low, the frequency efficiency is high and the demodulating performance is good.

Mechanisms for operating a wireless user equipment device, to determine the state of data scheduling activity. Such activity state (and other information such as measurements of signal interference and/or channel condition) may be used to dynamically control the selection of a high-power high-performance receiver vs. a low-power basic receiver. A first mechanism involves transitioning to a high activity state and starting a timer upon each occurrence of scheduled subframe. A transition to the low activity state occurs whenever the timer expires. A second mechanism involves filtering a sequence of binary-valued indicators corresponding respectively to a sequence of time intervals. Each indicator indicates whether a subframe is scheduled during the corresponding time interval. The filter output is compared to a threshold to determine high/low activity state. The temporal width of the filter impulse response may be increased to support fast initial response without harming the accuracy of activity-state determination in the steady state.

The invention discloses an SOCP (Second Order Conic Programming) based broadband transmission DBF (Digital Beam Formation) interference design method. The principle though of the method is as follows:determining a uniform linear array including M array elements and broadband digital signals, branching the broadband digital signals to obtain M channels of broadband digital signals; obtaining M FIRs (Filter Impulse Responses); performing FIR filtering on each channel of the broadband digital signals through a corresponding FIR to obtain M channels of broadband digital signals subjected to FIR filtering; performing digital-to-analog conversion, up-conversion, RF filtering and amplification on each channel of broadband digital signals subjected to FIR filtering, and obtaining M channels of broadband signals subjected to amplitude and phase processing; obtaining broadband interference beams after transmitting each channel of broadband signals subjected to amplitude and phase processing tothe air through corresponding array elements, the broadband interference beams being a SOCP based broadband transmission DBF interference design result.

This disclosure relates to a peak reduction unit (100) and method for reducing peaks by identifying peak sample values exceeding a pre-set threshold value in an aggregated baseband carrier signal anddetermining a maximum peak sample by detecting its maximum peak absolute value and phase. A search is performed a pre-determined search length (L) beyond an identified peak to retrieve close sub-peaksor local extrema. A stored, predetermined filter impulse response based on the carrier passband configuration is retrieved and its amplitude and phase of the predetermined filter impulse response isadjusted by means of the phase and absolute value of the determined maximum peak sample. Finally, the aggregated baseband carrier signal and the adjusted predetermined filter impulse response are combined by synchronizing their maximum peaks and their opposite phase values for adjusting the aggregated baseband carrier signal to said pre-set threshold value.