Nortel Networks Corporation

National Research Council of Canada

Northern Telecom Limited

Heping Ding

Ryan Griffin

Ye Tao

Scott McClennon

David Dal Farra

Zhiyi Zhang

Shoude Chang

Salima Alem

Frank Lau

George Xiao

Scott Mcclennon

A DC-DC converter for converting a low voltage DC input to a higher voltage DC output, the DC-DC converter comprising: an oscillator comprising a first relatively voltage sensitive and relatively low power transistor and a second relatively voltage insensitive and relatively high power transistor, the oscillator producing an AC signal from the low voltage DC input; a first transformer for converting the AC signal produced by the oscillator to a higher voltage AC signal; an autonomous, synchronous voltage-doubling rectification circuit for converting the higher voltage AC signal to the higher voltage DC output, wherein the autonomous, synchronous voltage-doubling rectification circuit comprises a second transformer, a first shunt switch and a second shunt switch; and wherein current through the second transformer controls the synchronous rectification.

Synchronous rectification to improve efficiency of electricity conversion for harvesting energy from low voltage sources

A DC-DC converter and method are provided for converting a low voltage DC input to a higher voltage DC output. The DC-DC converter has an oscillator with a first relatively voltage sensitive and relatively low power transistor and a second relatively voltage insensitive and relatively high power transistor, the oscillator producing an AC signal from the low voltage DC input. The inclusion of the voltage sensitive transistor allows the oscillator to turn on at a relatively low voltage. The inclusion of the higher power transistor allows the oscillator to operate at a higher power once it turns on. The DC-DC converter can be used for converting energy harvested from low voltage sources.

Efficient electricity conversion for harvesting energy from low voltage sources

Methods are provided for fabricating photodetector arrays using passive matrix addressing technology. The photodetector arrays use a pair of switching diode and photo diode to overcome crosstalk issues within the passive matrix. The switching diode and the photo diode of each pixel may be connected using a cathode-to-cathode connection, or an anode-to-anode connection. The photodetector arrays are fabricated by assembling on a first substrate, an array of photodetector pixels comprising a switching diode and a photo diode, providing conductive lines for each row of the array and conductive lines for each column of the array, and attaching a second substrate to the first substrate. The photodetector array may also be fabricated by assembling on a first substrate an array of switching diodes, and assembling on a second substrate an array of photo diodes, and bonding the first and second substrates together.

Methods of manufacturing printable photodetector array panels

A voltage and current triggered switch that turns on when a voltage across the switch reaches a turn-on voltage and that turns off when a current through the switch drops below a holding current. The switch features a Zener diode having a breakdown voltage. The Zener diode is connected to set the turn-on voltage of the switch to be the breakdown voltage of the Zener diode. Also provided is a step-down DC-DC converter comprising such a switch. Also provided is a system that has a tribo-electricity source or a piezo-electricity source, the provided step-down DC-DC converter and a load connected to an output of the stepdown DC-DC converter.

Voltage and current triggered switch, and step-down DC-DC converters containing such a switch

A method of adaptive filtering using fast affine projection (FAP) that allows for direct solution of the projected error vector from the autocorrelation matrix using a backward and forward recursion technique or LDLfactorization of the autocorrelation matrix followed by forward substitution, scaling and backward substitution. The method results in less computational complexity in the implementation, while still having good stability and fast convergence.

Adaptive filtering using fast affine projection adaptation

Methods and apparatus are provided for communicating an audio stream. A perceptual mask is estimated for an audio stream, based on the perceptual threshold of the human auditory system. A hidden sub-channel is dynamically allocated substantially below the estimated perceptual mask based on the characteristics of the audio stream, in which additional payload is transmitted. The additional payload can be related to components of the audio stream that would not otherwise be transmitted in a narrowband signal, or to concurrent services that can be accessed while the audio stream is being transmitted. A suitable receiver can recover the additional payload, whereas the audio stream will be virtually unaffected from a human auditory standpoint when received by a traditional receiver. A coding scheme is also provided in which a portion of a codec is used to code an upper-band portion of an audio stream, while the narrowband portion is left uncoded.

Method and apparatus for transmitting an audio stream having additional payload in a hidden sub-channel

A Fast Affine Projection (FAP) adaptive filter and method of adaptive filtering are disclosed, which reduce instability associated with FAP filters caused by error accumulation in the process of inversion of an autocorrelation matrix. The method provides updating of the adaptive filter coefficients by solving at least one system of linear equations whose coefficients are the autocorrelation matrix coefficients, by using a descending iterative method with intrinsic feedback. The results of the solution are used to update the adaptive filter coefficients. The approach is applicable for a normalized step size ranging from zero to unity, and allows either direct determination of updated filter coefficients without determining an inverse autocorrelation matrix, or, determining the inverse autocorrelation matrix by a descending iterative method. In some embodiments, a normalized step size is set close to unity, and the system of linear equations is solved by steepest descent or conjugate gradients methods. In other embodiments, a normalized step size is substantially less than unity, e.g. less than about 0.7. Accumulation of inevitable numerical errors is avoided and the stable adaptive filter and method are suitable for various DSP platforms, e.g. 16 and 24 bit, fixed-point and floating-point platforms.

Stable adaptive filter and method

Stable adaptive filter and method are disclosed. The invention solves a problem of instability associated with Fast Affine Projection adaptive filters caused by error accumulation in an inversion process of an auto-correlation matrix. The Stable FAP uses a simplification of setting a normalized step size close to unity and reduces a problem of the matrix inversion to solving a system of linear equations whose solution coincides with a first column of the inverse auto-correlation matrix. The system of linear equations is then solved by one of descending iterative methods which provide inherent stability of operation due to intrinsic feedback adjustment. As a result, inevitable numerical errors are not accumulated, being corrected as the process goes on. In first and second embodiments of the invention the system of linear equation is solved by steepest descent and conjugate gradient methods respectively. Being immune to numerical errors, the invented method and filter are suitable for various DSP platforms, e.g., 16 and 24 bit fixed-point as well as floating point platform.

An adaptive filter having a hybrid structure and capable of operating in a tri-mode regime is disclosed. The tri-mode adaptive filter includes three sub-filters which operate in a fast convergence mode, a slow convergence mode, and a freezing mode respectively. The adaptive filter further comprises a quality detector which measures non-convergence and a near-end signal of the tri-mode filter and generates a feedback signal which is sent to a switching means. In response to the feedback signal, the switching means provides switching between the sub-filters so that one of the sub-filters operates at a time, providing adaptive filtering in accordance with its corresponding filtering method. In the embodiment of the invention the sub-filters operating in fast, slow and freezing mode are represented by Conjugate Gradient Fast Affine Projection (CGFAP) adaptive filter, Normalized Least Mean Square (NLMS) adaptive filter and Freezing adaptive filter respectively, wherein the Freezing filter operates with constant adaptive filter coefficients, i.e. without updating the filter coefficients, thereby providing convolution without adaptation. Corresponding method of adaptive filtering is also provided.

Tri-mode adaptive filter and method

The invention provides an adaptive echo canceller and method for detecting double talk (DT) and echo path change (EPC) conditions and for distinguishing therebetween. DT and EPC conditions are detected by comparing a generated echo return loss enhancement (ERLE) signal with a selected ERLE threshold level. Similarly, the energy level of the echo canceller incoming signal is compared with a second threshold level. If the level of the ERLE signal is below its threshold and the level of the incoming signal is above the second threshold, a DT or EPC condition is deemed to exist and a predetermined signal is generated. Responsive to this signal, an orthogonality monitor recognizes the predetermined signal as representing either a DT or EPC condition. The determination is obtained by comparing the absolute value of cross-correlation between the output signal to be transmitted from the echo canceller and the echo estimate signal generated by the adaptive filter of the echo canceller to the product of a predetermined EPC threshold level and an average amplitude estimate of the product of the output signal to be transmitted from the echo canceller and the echo estimate signal generated by the adaptive filter of the echo canceller.

Method of distinguishing between echo path change and double talk conditions in an echo canceller

An improved echo canceller capable of reducing a magnitude of an echo signal propagating in a return channel of a communication device. The echo canceller includes an adaptive filter that models the echo path to generate an estimate of the echo. That estimate is subtracted from the echo-corrupted signal. The residual echo signal (error-signal) is then attenuated in a switching loss device. The switching loss device manifests a variable attenuation level selected in accordance with certain characteristics of the residual echo signal. These characteristics are the strength of the residual echo signal and its duration. For residual echo signals of very short duration, the attenuation level is set lower because those signals are perceived by the human ear as being weaker. For signals having a longer duration, the attenuation level is raised to inhibit the residual echo to acceptable levels.

Method and apparatus for inhibiting echo in a channel of a communication system

The invention provides an audio subsystem for use in a telephone terminal operable in handsfree mode and comprises a receive path including a receive transducer for generating audio signals from a received signal and a transmit path including a transmit transducer for converting audio signals to electrical signals for transmission to a far-end user. An acoustic echo canceller is communicatively coupled between the receive path and the transmit path and includes a subtractor circuit connected serially with the transmit transducer. The echo canceller is responsive to control signals for controlling the subtractor circuit. The subsystem comprises means for detecting a near-end talking condition including first circuit means for measuring the level of the total energy of the out-of-telephony-band components in the signal from the transmit transducer and circuit means for comparing the energy level represented by an output signal from the first measurement circuit to a first predetermined threshold. If the measured energy level exceeds the predetermined threshold, near-end talking activity is deemed to exist. There is also provided a second measurement circuit for measuring the level of the signal on the receive path and for comparing it to a second predetermined threshold whereby if the latter is exceeded, far-end talking activity is determined to exist. Thus, if both measured signals exceed their respective threshold, a double talk situation is deemed to exist.

Circuit and method of double talk detection for use in handsfree

A telephone terminal having handsfree functionality is provided with an audio system which controls echo return loss while permitting virtual full-duplex operation. The system, which has a variolosser in both the transmit and receive path and an acoustic echo canceller, also has a complementary variolosser which introduces additional echo return loss only when required and as a function of the state of the system.

Method and system for controlling echo return loss using a complementary

A system and method for dynamically optimizing the analog gain for a microphone in a telephone terminal operable in handsfree mode. The system makes use of a process whereby a relatively inexpensive analog to digital converter is used to meet gain requirements so as to accommodate the loudest echo through transmit path while maintaining an acceptable signal to noise ratio for the quietest talker. The system digital signal processor in conjunction with speech activity detection means is used to provide an optimum microphone gain under all circumstances.

Growing community of inventors

Ottawa, Canada

Heping Ding