Sub-band Analysis Patents (Class 379/406.14)
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Patent number: 6771772Abstract: The present invention is a method and apparatus for estimating the bulk delay and span associated with an echo signal on a telephone line carrying a proximal signal and an echo signal. A baseline solution is to use the echo canceller itself to estimate the bulk-delay. After achieving a reasonable level of echo cancellation, the bulk-delay and the echo-span are estimated from the adaptive coefficients, followed by an enhanced mode of operation using the estimated parameters. Alternatively, for longer, unknown bulk delays, a subband adaptive system is used to estimate the bulk-delay and echo-span. The subband adaptive echo canceller outputs the set of subband adaptive coefficients to a full-band echo canceller after achieving a reasonable level of convergence.Type: GrantFiled: July 9, 1999Date of Patent: August 3, 2004Inventor: Oguz Tanrikulu
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Patent number: 6757385Abstract: Processing complexity in an acoustic echo canceller can be reduced by partitioning the input near-end and far-end signals into respective pluralities of frequency subband signals. Also, due to the complex conjugate symmetry of conventional Discrete Fourier Transform matrices, not all of the subband signals of each plurality need be subjected to echo cancellation processing. The subband signals that would have otherwise been produced by echo cancellation processing are instead provided by producing complex conjugates of selected ones of the subband signals that have been subjected to echo cancellation processing.Type: GrantFiled: May 18, 2000Date of Patent: June 29, 2004Assignee: Telefonaktiebolaget LM Ericsson (Publ)Inventors: Fredrik Ehrenstråle, Patrik Grundström
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Patent number: 6744884Abstract: A speaker-phone that is operable to perform system change detection, double-talk detection and if desired, optimal step-size control. The invention differentiates between system change and double-talk and is operable to these two situations differently. The invention does not rely solely on the energy measurements that are employed by conventional speaker-phones. Highly reliable system change detection is offered when compared to conventional speaker-phones. The direction and the amplitude of the system change is measured with very good detection probability in the invention. For double-talk detection, the invention does not rely on assumptions that the far-end echoes are of lower amplitude that the near-end signal in performing double-talk detection. The invention performs double-talk detection within a large diversity of echo-paths and background noise levels. A designer may tune the speaker-phone system to ensure proper double-talk detection near low levels of the near-end signal.Type: GrantFiled: September 29, 2000Date of Patent: June 1, 2004Assignee: Skyworks Solutions, Inc.Inventor: Elias Bjarnason
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Patent number: 6735304Abstract: An adaptive filter allowing rapid adaptation to a sudden and great change in a system to be estimated is disclosed A memory stores position information indicative of a signal block connected to each of M filter circuits and power information obtained from K filter coefficients generated by each of the M filter circuits. A valid/invalid block selector selects one as an invalid block from the M signal blocks connected to the M filter circuits and determines position information indicative of a selected signal block as an invalid block and a corresponding filter circuit that has been connected to the selected signal block. The position information indicative of the selected signal block is appended to a queue of a shift register and position information is output from a head of the queue. Based on the corresponding filter circuit and the position information received from the shift register, a matrix switch connecting M filter circuits and M signal blocks is controlled.Type: GrantFiled: March 2, 2001Date of Patent: May 11, 2004Assignee: NEC CorporationInventor: Atsushi Hasegawa
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Publication number: 20040071284Abstract: A method and system for processing subband signals using adaptive filters is provided. The system is implemented on an oversampled WOLA filterbank. Inputs signals are oversampled. The system includes an adaptive filter for each subband, and the functionality of improving the convergence properties of the adaptive filter. For example, the convergence property is improved by whitening the spectra of the oversampled subband signals and/or affine projection algorithm. The system is applicable to echo and/or noise cancellation. Adaptive step size control, adaptation process control using Double-Talk detector may be implemented. The system may further implement a non-adaptive processing for reducing uncorrelated noise and/or cross-talk resistant adaptive noise cancellation.Type: ApplicationFiled: August 18, 2003Publication date: April 15, 2004Inventors: Hamid Reza Abutalebi, Robert L. Brennan, Hamid Sheikhzadeh-Nadjar, Dequn Sun
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Patent number: 6690791Abstract: Echo compensator with a plurality of sub-bands, whereby a complete FIR filter (FIR1) is employed in only one sub-band and shortened FIR filters (FIR2) that are respectively connected in series with an adjustable delay element (Z) are provided in the other sub-bands.Type: GrantFiled: November 8, 2000Date of Patent: February 10, 2004Assignee: Siemens AktiengesellschaftInventors: Horst-Jürgen Kratschmann, Konrad Bertignoll
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Patent number: 6661895Abstract: A zero-delay structure to be used in sub-band echo cancellation systems. In telecommunications, a delay is usually introduced in sub-band decomposition and/or sub-band reconstruction. This invention will help remove this. This structure not only removes the delay but does not sacrifice the performance of the echo canceller. It is to be used in combination with any sub-band-based echo canceller or wavelet echo canceller.Type: GrantFiled: October 7, 1999Date of Patent: December 9, 2003Assignee: Zarlink Semiconductor Inc.Inventors: Qu Jin, Kon Max Wong, Qiang Wu, Philippe Wu, Gordon J. Reesor
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Patent number: 6628781Abstract: In methods and apparatus for echo cancellation using sub-band adaptive filtering, the bandwidth of each of a number of sub-band analysis filters, as well as the bandwidth of each of a number of synthesis filters, is increased as compared to a corresponding bandwidth in a conventional system. More specifically, the −3 dB bandwidths of adjacent filters in an analysis or synthesis filter bank according to the invention are designed to overlap one another. For example, each of M (an integer) sub-band filters in an analysis or synthesis filter bank according to the invention can include a −3 dB bandwidth somewhat greater than 1/M times a total bandwidth of interest. The increase in bandwidth tends to cancel aliasing effects resulting from sub-band down-sampling, and an echo canceling device according to the invention can therefore provide superior output signal reconstruction as compared to conventional devices.Type: GrantFiled: June 3, 1999Date of Patent: September 30, 2003Assignee: Telefonaktiebolaget LM Ericsson (publ)Inventors: Patrik Grundström, Fredrik Ehrenstråle
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Patent number: 6618481Abstract: A method for improving acoustic sidetone suppression in hands-free telephones, in particular for use in motor vehicles, is described. The telephone has a level discriminator and a plurality of adaptive echo compensation filters each processing a subband. In at least one subband, a further adaptive filter (a shadow filter) of a lower order is connected in parallel with the adaptive echo compensation filter. Spatial changes are detected with the aid of a combined evaluation of a correlation analysis and a residual error comparison of the two competing, adaptive filters.Type: GrantFiled: August 14, 2000Date of Patent: September 9, 2003Assignee: Infineon Technologies AGInventor: Gerhard Schmidt
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Patent number: 6608898Abstract: A complementary comb filter includes a plurality of band pass filters and a plurality of notch filters, wherein the notch filters have the same center frequencies as the band pass filters or the same center frequencies as the dead bands defined by the band pass filters. Phase distortion by the notch filters occurs primarily in the notch, thereby eliminating distortion of the signal.Type: GrantFiled: October 6, 1999Date of Patent: August 19, 2003Assignee: Acoustic Technologies, Inc.Inventors: Kendall G. Moore, Samuel L. Thomasson
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Patent number: 6580795Abstract: An echo canceller (110) for a full-duplex communication system (100) such as a speakerphone determines a gain factor to be used in sub-band adapter coefficient updates by using both time domain and sub-band signals to determine the state of the system (100). In one embodiment a gain factor controller (120) uses the sampled time domain signal to determine if the system (100) is in the silence state, and if not uses the sub-band signals to determine whether the system (100) is in the talk, double-talk, or listen state. The gain factor controller (120) selectively changes the gain factor and selectively performs coefficient updating based on the state. In another embodiment the gain factor controller (120) determines the state and selectively updates coefficients using state information developed on a band-by-band basis.Type: GrantFiled: October 14, 1999Date of Patent: June 17, 2003Assignee: Motorola, Inc.Inventors: Zhao Li, John E. Lane
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Patent number: 6574336Abstract: The invention relates to an acoustic echo suppressor and a non-linear processor for an echo canceller in a 4-wire data transmission network. An echo canceller is typically controlled by comparing the power levels of the near-end and far-end signals. The transfer function of an acoustic echo path is usually very non-uniform. According to the invention, the spectrum of the far-end signal is treated, before the signal power level is calculated, with a weighted filter, which models the effect of the transfer function of acoustic echo. As a result, the double talk dynamics is improved, since high-energy vowels of far-end speech, which normally cause low-energy vowels of near-end speech to be clipped in an echo suppresseor, will be attenuated.Type: GrantFiled: December 2, 1998Date of Patent: June 3, 2003Assignee: Nokia Telecommunications OyInventor: Olli Kirla
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Patent number: 6570985Abstract: The Least Mean Square (LMS) and Normalized LMS (NLMS) algorithms commonly employed in adaptive filters of echo cancelers are further optimized. Finite impulse response (FIR) filters are used to estimate a transfer function of an echo channel in a communications link. The LMS and NLMS algorithms are used to adapt the filter coefficients of the estimated transfer functions. By including the echo channel energy gain in the LMS or NLMS update equation, adaptation speed is increased by making adaptation responsive to the channel energy gain. An algorithm for estimating the echo channel energy gain adapts the estimate based on measured system parameters, such as a measured instantaneous channel gain and a near-end voice level. By considering in the NLMS algorithm, the average energy of either the microphone signal or the error signal, as well as the standard reference signal, a higher nominal update gain can be used. With a higher nominal update gain, the NLMS algorithm will converge more quickly.Type: GrantFiled: September 17, 1998Date of Patent: May 27, 2003Assignee: Ericsson Inc.Inventor: Eric Douglas Romesburg
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Patent number: 6522747Abstract: In a method of processing an input signal, the input signal is divided into a plurality of subbands with the aid of bank of complex valued, single-sided subband filters. The single-sided frequency spectra of the resulting subbands make aliasing negligible at near twice the critical downsampling rates.Type: GrantFiled: November 23, 1999Date of Patent: February 18, 2003Assignee: Zarlink Semiconductor Inc.Inventors: James Reilly, Nima Ahmadvad, Mike Seibert, Gordon Reesor
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Patent number: 6507653Abstract: A hybrid echo suppresser and associated methods of use provide echo suppression in a bi-directional communications system, while minimizing desired-voice signal disruption. The hybrid echo suppresser includes a linear echo canceller (LEC), a non-linear processor (NLP), and a control circuit. The LEC operates on an echo-causing signal to produce an estimated-echo signal, which is subtracted from an input echo-containing signal, thereby producing an echo-cancelled signal. The NLP operates on this echo-cancelled signal to eliminate residual echo arising from system non-linearities. The control circuit repeatedly compares the echo-containing signal and the estimated-echo signal to determine if the echo-containing signal includes a desired-voice component. If not, the control circuit operates the NLP in an echo-voice mode having substantial signal attenuation.Type: GrantFiled: April 14, 2000Date of Patent: January 14, 2003Assignee: Ericsson Inc.Inventor: Eric Douglas Romesburg
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Patent number: 6498850Abstract: A compander circuit (20) for echo cancellation in telecommunications apparatus with an estimator module (21) for estimating an echo coupling and a delay of a line echo and a characteristic module (23) with an associated multiplier (24) for controlling the short-time output level of zout(k) as a function of the short-time input level of zin(k) is characterized in that at all inputs and outputs of the compander circuit (20), a plurality of N communications channels are applied and outputted, respectively, at an N-fold clock rate as compared with a single communications channel; that all memory units in the compander circuit (20) are designed as multiplexer-buffer-demultiplexer (MBD) units (30); and that a modulo-N counter (26) is provided which controls all MBD units (30) so that in each of the MBD units (30), always the same memory cell (351, 352, 35N) assigned to a particular communications channel is addressed.Type: GrantFiled: March 31, 1999Date of Patent: December 24, 2002Assignee: AlcatelInventors: Michael Walker, Hans Jürgen Matt, Armin Mann, Fritz Weinschenk, Holger Söhnle
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Patent number: 6493448Abstract: A process for suppressing total echoes comprising a plurality of partial echoes in telecommunications (TK) equipment such as terminals, transmission systems, or switching equipment by means of adaptive FIR (=Finite Impulse Response) filters that simulate the total echo and subtract it from the echo-affected useful signal transmitted to the respective TK equipment, whereby n partial FIR filters are provided, which respectively simulate a partial echo, is characterized in that m parallel, mutually independent TK channels are provided with an echo suppression function and that for this purpose a variable sub-quantity of the partial FIR filters is assigned to a TK channel to be operated, respectively, as required depending on the number of partial echoes and the size of the occurring delay times between signal and echo.Type: GrantFiled: January 15, 1999Date of Patent: December 10, 2002Assignee: AlcatelInventors: Armin Mann, Hans Jürgen Matt, Michael Walker
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Patent number: 6456650Abstract: In a splitterless Digital Subscriber Line (DSL) modem 30, a receiver architecture (100) that permits monitoring of harmonics within the upstream channel of a DSL connection. The receiver (100) can detect the harmonics by monitoring the harmonics in some empty tones or specified tones. A threshold can be set to differ the normal noise power and harmonics power in those empty or specified tones. When a POTS device (10) coupled to same wire line pair (20) as the DSL modem (30) goes off-hook, the DSL modem (30) can switch from the normal state to an off-hook state in which the harmonics are reduced to minimum by transmitting only the upper sub-band tones of the upstream transmission channel at reduced power levels.Type: GrantFiled: February 4, 1999Date of Patent: September 24, 2002Assignee: Texas Instruments IncorporatedInventors: Yaqi Cheng, Adam M. Chellali, Michael O. Polley
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Patent number: 6442274Abstract: An echo canceling apparatus suitable for multiplexed transmission lines is provided that achieves a short convergence time and a small number of arithmetic operations. Adaptive filters are located in respective transmission lines. Each adaptive filter adaptively controls tap positions such that tap coefficients are located in dispersive regions which are obtained by removing fixed delays from the impulse response in an echo path. A controller receives tap position information from the adaptive filters to mutually compare the convergence degrees among the adaptive filters. Thus, the controller respectively supplies coefficient update control signals to the adaptive filters so as to suppress coefficient adaptation of an adaptive filter whose convergence is leading compared with the others.Type: GrantFiled: September 7, 1999Date of Patent: August 27, 2002Assignee: NEC CorporationInventor: Akihiko Sugiyama
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Patent number: 6442275Abstract: Residual echo components resulting from an adaptive echo canceler are minimized by employing a subband echo suppressor. The residual echo components are minimized by individually, controllably adjusting the echo suppressor attenuation level in each of the subbands to gradually attenuate echo peaks having a magnitude lower than a clipping threshold with the magnitude of the attenuation increasing for residual echoes of decreasing magnitude. Additionally, the threshold of suppression engagement is dynamically matched to the signal gain in the echo path for each subband. If the signal gain in a subband is high (strong echo), the suppressor must attenuate residual echo peaks in the subband of higher energy to maintain a constant quality of service.Type: GrantFiled: September 17, 1998Date of Patent: August 27, 2002Assignee: Lucent Technologies Inc.Inventor: Eric J. Diethorn
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Patent number: 6438225Abstract: A system and method for detecting and controlling severe echo. The system includes an echo canceller having an adaptive filter responsive to a set of coefficients, a first memory storing a software program operative to evaluate these coefficients to determine the severity of echo existing in the system, and a second memory accessible by the echo canceller and the first memory which stores the coefficients. Upon evaluating the coefficients, the system and method enables the proper mode of echo cancellation in the echo canceller.Type: GrantFiled: January 13, 2000Date of Patent: August 20, 2002Assignee: Motorola, Inc.Inventor: Mansour Tahernezhaadi