171 results about "Feedforward filter" patented technology

A method of controlling a feedforward filter of an equalizer includes the steps of generating a complex representation of an output of the feedforward filter and generating a representation of a decision from an output of the equalizer. The complex representation and the decision representation are correlated to obtain a phase error estimate. A phase correction value is generated based on the phase error estimate and used to adjust the phase of the output of the feedforward filter.

The present invention is a method and apparatus for compressing and decompressing data. In particular, the present invention provides for (de-)compressing naturalistic color-image and moving-image data, including high-precision and high-definition formats, with zero information loss, one-sample latency and in faster than real time on common computing platforms, resulting in doubled transmission, storage, and playback speed and doubled transmission bandwidth and storage capacity, and hence in doubled throughput for non-CPU-bound image-editing tasks in comparison with uncompressed formats. The present invention uses a nearly symmetrical compression-decompression scheme that provides temporal, spatial, and spectral compression, using a reversible condensing / decondensing filter, context reducer, and encoder / decoder. In the preferred embodiment of the invention, the compression filter is implemented as a cascade of quasilinear feedforward filters, with temporal, multidimensional spatial, and spectral stages, where appropriate, in that order, whose support consists of adjacent causal samples of the respective image. The decompressor cascades quasilinear feedback inverse filters in the reverse order. The filters can be implemented with mere integer addition, subtraction, and either one-dimensional table lookup or constant multiplication and binary shifting, depending on the computing environment Tables permit the data precision to be constrained throughout to that of the image samples. The encoder uses a table of prefix codes roughly inversely proportional in length to their probability, while the decoder uses chunked decode tables for accelerated lookup. In the fastest and simplest mode, the code tables are context-independent. For greater power, at the cost of a reduction in speed, the code tables are based on the temporal, multidimensional spatial, and spectral adjacent causal residue samples, where contexts with similar probability distributions are incoherently collapsed by a context reducer using one-dimensional lookup tables followed by implicitly multidimensional lookup tables, to minimize the overall table size. The invention's minimal resource requirements makes it ideal for implementation in either hardware or software.

In a waveform equalizer for a communication apparatus, a magnetic recording apparatus, or an optical recording / reproducing apparatus, a feed-forward filter (FFF) is provided and, at a subsequent stage, a decision feedback equalizer (DFE) or a fixed delay tree search / decision feedback equalizer (FDTS / DFE) employing FDTS for a determination unit is provided. Partial response (PR) is performed on only a first portion of inter-symbol interference (ISI) of a waveform equalized by the FFF and equalization that does not consider subsequent response (i.e., trailing-edge ISI) is performed. A feed-back filter (FBF) generates a response for the trailing-edge ISI and the DFE structure subtracts the generated response from a response provided by the FFF so that a result becomes a partial response.

Methods and apparatus are provided for performing equalization of communication channels. In an embodiment of the invention, at least one tap can be selected from a set of feedforward taps of feedforward filter circuitry, where each tap of the selected at least one tap has a magnitude that is greater than or substantially equal to a magnitude of any tap of the set of feedforward taps that is not in the selected at least one tap. In addition, at least one tap can be added to a set of taps of feedback filter circuitry in communication with the feedforward filter circuitry. The invention advantageously allows for more efficient and reliable equalization of communication channels.

The invention discloses a self-adaptive active noise reduction method for an error-free microphone. According to the method, only one reference microphone is used for achieving active noise reduction;the method comprises the steps that firstly, transfer functions of a main channel and a secondary channel are estimated in advance, an error signal of a target noise-reduction point is estimated in real time by utilizing a received reference signal, and then weight coefficient vectors of a feedforward filter and a feedback filter are updated by using the error signal; the output of the feedforward filter and the output of the feedback filter are superimposed to obtain the output of an infrasound source. By means of the method, an error microphone required in a traditional self-adaptive activenoise reduction method is not needed, the problems of insufficient algorithm stability, complicated earphone structure and the like generally existing in traditional self-adaptive active noise reduction can be solved, and therefore the applicability and stability of the self-adaptive active noise reduction algorithm are greatly improved.

The invention discloses an equalizer, which comprises a feed-forward filter, a first adder, a feedback filter, a second adder and a filter tap coefficient determination unit, wherein the feed-forward filter carried out feed-forward filtering on an underwater acoustic communication training sequence; the first adder adds the underwater acoustic communication training sequence subjected to feed-forward filtering and an output of the feedback filter together and outputs an adding result to the feedback filter; the second adder adds the output of the first adder and an expected output d(n) of the equalizer together; and the filter tap coefficient determination unit determines tap coefficients of the feed-forward filter and the feedback filter according to the output of the second adder. According to the equalizer and the feedback equalization method, a channel model is simplified, the calculated amount for design of the equalizer is reduced and the rate of convergence of an algorithm is improved, so that the algorithm can be converged at a smaller convergence residual, the computational complex is reduced and the equalization performance is improved.

Outputs from respective elements of an array antenna 21 are demodulated, and the demodulated outputs are stored in storage means 29. The demodulated outputs are multiplied by tap coefficients of adaptive array antenna, then the multiplied outputs are combined by combining means 28, and the combined output is provided via a feed forward filter 22 to an adaptive equalizer 23, wherein it is equalized to obtain a decision symbol. During reception of a training signal the tap coefficients of adaptive array antenna and tap coefficients of the adaptive equalizer 23 are subjected to convergence processing by tap coefficient calculating means 24 so that an error signal becomes small, and then tap coefficients of the feed forward filter 22 and the adaptive equalizer 23 are subjected to convergence processing by tap coefficient calculating means 25 so that an error signal becomes small. Thereafter, the convergence processing by the means 24 and 25 is repeated, during which a training signal stored in storage means 29 is used, results of the immediately preceding convergence processing are used as initial values, and it is decided by receiving quality estimating means 26 whether the error signal has become sufficiently small relative to the received signal power.