Abstract: In training a SERDES, a Common Electrical Interface (CEI) training frame, having certain bits of information embedded therein, is transmitted over a path which comprises transmitter, channel, and receiver components. The present invention analyzes the resulting received signal and determines the effective aggregate channel impulse response of these three components. The invention then determines an estimate of the inverse of this aggregate channel and uses this determination to reduce distortions that have been introduced into a signal that has been transmitted over the path.

Abstract: A system for improving the attenuation of an undesired signal found in a differential signal path through the use of inductive coupling. The system includes a primary inductor, a secondary inductor, and a filter. The primary inductor and the secondary inductor operably couple an input differential signal pair to an output differential signal pair, and the filter attenuates an undesired signal in the output differential signal pair.

Abstract: The present invention utilizes a parallel sampled multi stage decimated digital loop filter for clock and data recovery function. In particular, the present invention provides multiple sampling clocks, with these clocks having sampling clock phases separated in time. These clocks are used in conjunction with multiple data detectors and phase detectors to efficiently process received analog signals in a decimated loop filter system.

Abstract: The invention is a method and apparatus for ensuring synchronization for digital communication between a transmitting and a receiving device, particularly when the clock and/or frame synchronization is sourced from a different location than the transmit data.

Abstract: An ADSL front end is implemented with an adaptive AM interference canceller to cancel out either a carrier signal of an interfering AM radio signal, or a carrier signal and its sidebands of an interfering AM radio signal, from a received ADSL signal. By canceling an interfering AM radio signal rather than simply filtering out the relevant interfered with frequency band, the interfered with frequency band remains useable for ADSL transmission. In one embodiment, a reference AM radio receiver is either fixedly or adaptively tuned to the carrier frequency of an interfering AM radio station, and the received signal in the frequency band surrounding that carrier frequency is digitized and provided to an adaptive interference canceller. The adaptive interference canceller adaptively adjusts a time delay and phase of the generated AM interference signal to optimize cancellation at a hybrid of the same AM radio signal received as interference over a subscriber line.

Abstract: The present invention provides a low power method and apparatus for detecting a signaling tone. The apparatus comprises a resonator which can be configured to resonate at a specified frequency, a controller for configuring the resonator, and a comparator for comparing the output of the resonator as configured by the controller. The method comprises configuring the resonator to resonate at a first frequency to generate an output, configuring the resonator to resonate at a second frequency to generate an output, comparing the outputs, and indicating the presence of a signal if the output of the resonator configured to resonate at a first frequency exceeds the output of the resonator configured to resonate at a second frequency by a predefined amount.

Abstract: A method and apparatus for a telephone line interface or data access arrangement (DAA) which includes a shunt regulator in series with a line modulator and a sense resistor. A shunt regulator is placed in series between the sense resistor and the line modulator. The shunt regulator draws power from the telephone line, and the sense resistor senses the amount of current being drawn. The voltage across the sense resistor is fed back to the line modulator. The line modulator is thus capable of adjusting the AC modulation and the DC termination presented to the telephone line based upon the sensed current draw from the telephone line. The telephone line interface can also place an information signal on the telephone line.

Abstract: A method and apparatus for a telephone line interface or data access arrangement (DAA) which includes a shunt regulator in series with a line modulator. A sense resistor is placed in series between the shunt regulator and the line modulator to provide a measurement of the amount of current distortion in the DAA. The line modulator contains a Darlington pair which reduces the amount of current drawn by the line modulator, allowing the sense resistor to sense a majority of the system current. The voltage across the sense resistor is fed back to the line modulator. The line modulator is capable of adjusting the AC modulation and the DC termination presented to the telephone line. The method includes drawing power from the telephone line using a shunt regulator, modulating the telephone line in series with the shunt regulator, sensing a level of distortion in the DAA, and feeding the sensed level of distortion to the line modulator.

Abstract: A telephone line interface or data access arrangement (DAA) is provided which draws power for the customer premises equipment from the telephone line. The DAA includes a shunt regulator as the power source drawing power from the telephone line, and a line modulator in series with the shunt regulator. A sense resistor is placed in series between the line modulator and shunt regulator to sense the line current. Accordingly, DC termination and AC modulation characteristics as presented by the DM to the telephone line can be adjusted by variation of an AC signal with DC offset input to the amplifier driving the line modulator without requiring a different DAA for use in regions or countries having various DC termination and AC modulation requirements. The differential feedback from a sense resistor reduces the noise induced in the circuit from the shunt regulator.

Abstract: A method and apparatus for a data access arrangement (DAA) which includes a line modulator containing capacitive elements to increase system stability. The invention provides improved stability during system startup and normal system operation. The line modulator is capable of adjusting the AC modulation and the DC termination presented to the telephone line. Capacitive elements are added to the modulator to provide enhanced system stability. The method includes drawing power from the telephone line, modulating the telephone line, sensing a level of distortion through the line modulator, feeding the sensed level of distortion to the line modulator, and using capacitive circuits to provide additional system stability.

Abstract: The digital-to-analog converter includes an output line, and a plurality of converters receiving control signals representative of digital data. Each converter selectively connects the output line to a voltage in response to a respective one of the control signals. Optionally, the digital-to-analog converter further includes a reset circuit for resetting the voltage on the output line to a reset voltage between portions of the analog waveform representing a digital data symbol.

Abstract: A digital device for controlling the DC line current on a telephone line which includes a digital device that utilizes a digital filter for setting the DC line current. By controlling the DC line current digitally, software can be used to set the DC line current in accordance with predefined characteristics. Predefined characteristics can be set to accommodate varying country specifications instead of using switches to control resistors and capacitors. In addition, changes in a country's requirements can be accomplished through software, instead of changing components or redesigning a circuit board. The device also incorporates a method for maintaining DC current level during changes in digital filter characteristics. The use of software results in increased flexibility by allowing an infinite number of settings via software or software updates, and allowing changes to be made quickly and easily throughout the world.

Abstract: A circuit provides a modulation signal to an input terminal of a line modulator which places a line current modulated in accordance with the modulation signal on a telephone line. An amplifier of the circuit amplifies an analog input signal to provide the modulation signal at an output terminal. A first resistor and a first capacitor are coupled in series between a first input terminal of the amplifier and the line, and a second resistor and a second capacitor are coupled in series between a second input terminal of the amplifier and the line. First and second precharge amplifiers are used to precharge the first and second capacitors, respectively, to reduce DC setup time.

Abstract: The digital-to-analog converter includes an output line, and a plurality of converters receiving control signals representative of digital data. Each converter selectively connects the output line to a voltage in response to a respective one of the control signals. Optionally, the digital-to-analog converter further includes a reset circuit for resetting the voltage on the output line to a reset voltage between portions of the analog waveform representing a digital data symbol.

Abstract: A method and apparatus for controlling the DC line current on a telephone line and reducing the amount of error introduced to the system. The error is reduced by compensating for a DC error term introduced by an analog to digital converter having a DC offset. The DC offset is controlled digitally, allowing software to be used to limit the DC error in accordance with predefined parameters. Predefined parameters can be set to accommodate varying country specifications instead of using switches to control resistors and capacitors. In addition, changes in a country's requirements can be accomplished through software, instead of changing components or redesigning a circuit board. The use of software results in increased flexibility by allowing an infinite number of settings via software or software updates, allowing changes to be made quickly and easily throughout the world, and allowing error terms to be accommodated digitally.

Abstract: A method and apparatus which compensates for the effect of DC components due to imperfections in analog circuits used in a coder/decoder (CODEC) by adding a compensation value to an outgoing signal prior to the DC components being introduced. The method includes the steps of determining a compensation value to compensate for the effect of the DC components due to imperfections in analog circuits in a CODEC and adding the compensation value to a path within the CODEC. The apparatus includes an adder coupled in at least one outgoing path of the CODEC, the adder having an input for coupling to a DSP, wherein the DSP determines a DC compensation value to compensate for the effect of the DC components and the adder adds the DC compensation value to the outgoing path.

Abstract: A telephone line interface or data access arrangement (DAA) is provided which draws power for the customer premises equipment from the telephone line. The DAA includes a shunt regulator as the power source drawing power from the telephone line, and a line modulator in series with the shunt regulator. A sense resistor is placed in series between the line modulator and shunt regulator to sense the line current. Accordingly, DC termination and AC modulation characteristics as presented by the DM to the telephone line can be adjusted by variation of an AC signal with DC offset input to the amplifier driving the line modulator without requiring a different DAA for use in regions or countries having various DC termination and AC modulation requirements. The differential feedback from a sense resistor reduces the noise induced in the circuit from the shunt regulator.

Abstract: The present invention provides a low power method and apparatus for detecting a signaling tone. The apparatus comprises a resonator which can be configured to resonate at a specified frequency, a controller for configuring the resonator, and a comparator for comparing the output of the resonator as configured by the controller. The method comprises configuring the resonator to resonate at a first frequency to generate an output, configuring the resonator to resonate at a second frequency to generate an output, comparing the outputs, and indicating the presence of a signal if the output of the resonator configured to resonate at a first frequency exceeds the output of the resonator configured to resonate at a second frequency by a predefined amount.

Abstract: A method and apparatus which compensates for the effect of DC components due to imperfections in analog circuits used in a coder/decoder (CODEC) by adding a compensation value to an outgoing signal prior to the DC components being introduced. The method includes the steps of determining a compensation value to compensate for the effect of the DC components due to imperfections in analog circuits in a CODEC and adding the compensation value to a path within the CODEC. The apparatus includes an adder coupled in at least one outgoing path of the CODEC, the adder having an input for coupling to a DSP, wherein the DSP determines a DC compensation value to compensate for the effect of the DC components and the adder adds the DC compensation value to the outgoing path.

Abstract: The invention is a method and apparatus for ensuring synchronization for digital communication between a transmitting and a receiving device, particularly when the clock and/or frame synchronization is sourced from a different location than the transmit data. In accordance with the first aspect of the invention, the transmitting device employs a look ahead algorithm to begin transmitting data before actual receipt of the frame synchronization signal.