Lucent Technologies Inc.

Lsi Corporation

Other

Avago Technologies General IP (singapore) Pte. Ltd.

Avaya Technology LLC

Legerity, Inc.

Robert K Chen

Dewayne Alan Spires

John C Gammel

James Arthur Bailey

Richard T Kaul

Apurba Roy

Dieter J H Knollman

Paul W Frazier

Andrew J Marsh

Various embodiments of the present invention provide systems and methods for data filter tuning. As an example, a method for filter tuning is disclosed that includes: providing a tunable filter having an operation filter and a calibration filter; applying a low frequency test input to the operation filter in place of an input signal to yield a first filter output; calculating a low frequency magnitude value corresponding to the first filter output; applying a high frequency test input to the operation filter in place of an input signal to yield a second filter output; calculating a high frequency magnitude value corresponding to the second filter output; modifying a tuning factor of the calibration filter when a ratio of the high frequency magnitude value and the low frequency magnitude value is outside of a defined range; and storing the tuning factor of the calibration filter when the ratio of the high frequency magnitude value and the low frequency magnitude value is within the defined range.

Systems and methods for filter initialization and tuning

Various embodiments of the present invention provide tunable filter circuits and methods for using such. As an example, a tunable biquad filter is disclosed that includes a tunable biquad circuit, a mixer circuit and a low pass filter. The tunable biquad circuit exhibits a cutoff frequency corresponding to an adjustment value, and is operable to receive an filter input and to provide a filter output. The mixer circuit is operable to provide a product of the filter input and the filter output. The product includes a time dependent component and a static component. The low pass filter is operable to receive the product and to provide the static component.

Tunable biquad filter circuit including phase shift detection and methods for using such

An impedance warping circuit (IWC) and technique for compensating the effect of a blocking capacitor within a transformer of an interface circuit for passing plain old telephone service (POTS) band and asynchronous digital subscriber line (ADSL) band signals on signals having frequencies in the POTS band. The IWC does not significantly affect the performance of the interface circuit in the ADSL band. The IWC synthesizes impedance to compensate the frequency-dependent deviation in the termination impedance across the tip/ring lines. The resulting termination impedance may be designed to conform to the Telcordia Standard of 900 &#x3a9;+2.16 &#x3bc;F or other telecommunication standards throughout the entire POTS band.

Frequency-dependent impedance synthesis for DSL interface circuits

A dual-supply line-interface circuit (,) uses a &minus;48V power supply (V,) to drive long subscriber loops (,) and uses a &minus;28V power supply (V,) to drive short subscriber loops. For intermediate-length loops, a dual-slope current-feed profile (FIG.,) is employed to limit the line-circuit's power dissipation. The line-interface circuit operates in an apparent constant-current mode, generating about 40 mA of differential line current using the low power supply, up to a threshold line voltage of about 25V, which is equal to the low power supply voltage minus required overhead. For longer loops, the line-interface circuit switches to a second constant-current mode, generating about 22 mA of differential current using the high power supply, which maintains the loop current constant until it drops to the 48V resistive-feed value.

Dual-slope current battery-feed circuit

A line circuit whose circuit components are selectively controllable by a microprocessor/DSP to provide normal BORSCHT functions or to be selectively tested without need for an electromechanical relay to isolate the line circuit from the loop conductors. The conventional line transformer is advantageously replaced by a loop current feed resistor network and either a high voltage or a lower voltage battery may be connected to provide loop current to the resistor network through a current regulator circuit and battery switch circuit. In normal operation, an ac feedback path, which includes the line receive amplifier, increases the terminating impedance above the dc value of the feed resistors so the loop termination resistor network may match the characteristic impedance of the loop at the audio frequencies employed. In the testing mode, the microprocessor/DSP selectively applies or denies power to the line driving and receive amplifiers as well as to a level shifting circuit interposed between the codec analog output and the input to isolate or include these components or to provide a codec loop-back path. The condition of the dc feed resistors and protective fuses, the condition of the loop closure detector and of the ringing generator are reported to the microprocessor/DSP over the same terminal normally used for reporting the on-hook and off-hook status of the loop.

Self-monitoring line interface circuit

A line circuit provides BORSCHT functions and supplies the customer loop through a feed resistor network and current limiter either from a high voltage battery to provide for maximum signaling range or from a lower voltage battery to conserve power. The current limiter operates under the control of a microprocessor/DSP which selectively applies or denies power to isolate or include components for testing and controls the switching in and out of transistors to control the scaling factor between the channel width-to-length ratios of the current mirror's input and output FET transistors according to the type of test or operating condition dictated by the microprocessor while the input reference current to the current mirror is maintained constant.

Dual voltage, self-monitoring line circuit

A subscriber line circuit which truly implements all of the BORSCHT functions and which does not rely on an external ringing generator to provide the ringing voltage when needed is disclosed. This implementation is achieved by recognizing that supervisory and ringing signals occur in some sort of sequence and, therefore, do not have to be generated simultaneously. Based on this recognition, we provide a circuit which truly implements all of the BORSCHT functions and includes a power section that generates each of the supervisory signals, e.g., -48 volts and -24 volts, and alerting signal, e.g., ringing signal, in turn and as required.

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North Andover, MA, United States of America

Robert K Chen