Abstract: This invention provides a simplified communication system that transmits voice and SDSL signals between customer premise equipment (“CPE”) on a single twisted-pair line. The system preferably includes at least one combiner for combining voice and SDSL signals into a combined voice/SDSL signal that can be transmitted to the CPE on a single twisted pair of wires, preferably a pair of wires currently being used to transmit the voice signal to the CPE. One combiner is ideally located at a common wiring closet of the building where the CPE is located. The combiner is ideally coupled to the existing pair of wires for the voice signal. This eliminates the need to add another set of wires between the common wiring closet and the CPE for the SDSL signal. A second combiner, normally located at or near the CPE separates the combined voice/SDSL signal into the separate voice and SDSL signals for processing by the CPE.

Abstract: An ADSL receiver HPF architecture 300 that reduces the number of Op Amps below that required for known ADSL receiver HPFs. The ADSL receiver HPF 300 is implemented as an active RC filter to provide a single fifth-order Elliptic filter instead of the more conventional pair of third-order Elliptic filters. Since the HPF Elliptic filter stage having the lowest Q factor is reduced as the order of an Elliptic filter transfer function is increased, a single fifth-order Elliptic filter suitable for use as an ADSL receiver HPF can be implemented using only one Op Amp in the second 2nd-order HPF stage 308. A notch (imaginary zero) is provided by summing of output signals associated with active RC structure state variables. This structure minimizes the number of capacitors while preserving the capability to provide a high Q factor for the first 2nd-order HPF stage 304.

Abstract: A filter circuit with two 2nd order stages cascaded in sequence. The first stage is implemented with high quality (Q) factor, and the second stage is implemented with a low Q factor and an imaginary zero. The first stage is designed to further eliminate the unwanted frequency components. The imaginary zero in the second stage eliminates the noise present in the output of the first stage due to the requirement of high Q in the first stage. Any additional noise introduced by the second stage is minimal due to the low Q of the second stage. Each stage may be implemented using only a single operational amplifier when the first stage generates a differential output signal.

Abstract: A hybrid circuit models a plurality of attributes of a communication system including a subscriber line coupled to a line interface circuit. The plurality of attributes includes subscriber line impedance, and impedance of a coupling transformer. The attributes are based on other factors, such as whether or not bridge taps exist at or near the line interface circuit on the subscriber line. The plurality of attributes are modeled by a specific arrangement of resistive and capacitive elements to substantially duplicate the collective transforming effects of the attributes on a transmission signal being sent out on the subscriber line. The transmission signal is transformed and provided to an output, where it is subtracted from a composite signal representing a combination of the actual transformed transmission signal and a receive signal. The subtraction yields an isolated receive signal, which is later processed to recover the full receive signal.

Abstract: This invention provides a simplified communication system that transmits voice and SDSL signals between customer premise equipment (“CPE”) on a single twisted-pair line. The system preferably includes at least one combiner for combining voice and SDSL signals into a combined voice/SDSL signal that can be transmitted to the CPE on a single twisted pair of wires, preferably a pair of wires currently being used to transmit the voice signal to the CPE. One combiner is ideally located at a common wiring closet of the building where the CPE is located. The combiner is ideally coupled to the existing pair of wires for the voice signal. This eliminates the need to add another set of wires between the common wiring closet and the CPE for the SDSL signal. A second combiner, normally located at or near the CPE separates the combined voice/SDSL signal into the separate voice and SDSL signals for processing by the CPE.

Abstract: A hybrid circuit models a plurality of attributes of a communication system including a subscriber line coupled to a line interface circuit. The plurality of attributes includes subscriber line impedance, and impedance of a coupling transformer. The attributes are based on other factors, such as whether or not bridge taps exist at or near the line interface circuit on the subscriber line. The plurality of attributes are modeled by a specific arrangement of resistive and capacitive elements to substantially duplicate the collective transformative effects of the attributes on a transmission signal being sent out on the subscriber line. The transmission signal is transformed and provided to an output, where it is subtracted from a composite signal representing a combination of the actual transformed transmission signal and a receive signal. The subtraction yields an isolated receive signal, which is later processed to recover the full receive signal.

Abstract: A filter circuit with two 2nd order stages cascaded in sequence. The first stage is implemented with high quality (Q) factor, and the second stage is implemented with a low Q factor and an imaginary zero. The first stage is designed to further eliminate the unwanted frequency components. The imaginary zero in the second stage eliminates the noise present in the output of the first stage due to the requirement of high Q in the first stage. Any additional noise introduced by the second stage is minimal due to the low Q of the second stage. Each stage may be implemented using only a single operational amplifier when the first stage generates a differential output signal.

Abstract: An ADSL subscriber loop equalizer architecture 100 employs a circuit having a capacitor 102 connected to ground as a basic building block; where the capacitor 102 is much smaller than equivalent capacitors that must be employed using known ADSL CP subscriber loop equalizer architectures. The ADSL subscriber loop equalizer is adaptive to provide different levels of equalization in response to a selector switch setting.

Abstract: This invention provides a simplified communication system that transmits voice and SDSL signals between customer premise equipment (“CPE”) on a single twisted-pair line. The system preferably includes at least one combiner for combining voice and SDSL signals into a combined voice/SDSL signal that can be transmitted to the CPE on a single twisted pair of wires, preferably a pair of wires currently being used to transmit the voice signal to the CPE. One combiner is ideally located at a common wiring closet of the building where the CPE is located. The combiner is ideally coupled to the existing pair of wires for the voice signal. This eliminates the need to add another set of wires between the common wiring closet and the CPE for the SDSL signal. A second combiner, normally located at or near the CPE, separates the combined voice/SDSL signal into the separate voice and SDSL signals for processing by the CPE.

Abstract: A stop band second order active RC filter architecture that does not use a non-inverting input to receive an input signal, and that employs both positive and negative feedback to provide an RC transfer function having an imaginary zero.

Abstract: An ADSL receiver HPF architecture 300 that reduces the number of Op Amps below that required for known ADSL receiver HPFs. The ADSL receiver HPF 300 is implemented as an active RC filter to provide a single fifth-order Elliptic filter instead of the more conventional pair of third-order Elliptic filters. Since the HPF Elliptic filter stage having the lowest Q factor is reduced as the order of an Elliptic filter transfer function is increased, a single fifth-order Elliptic filter suitable for use as an ADSL receiver HPF can be implemented using only one Op Amp in the second 2nd-order HPF stage 308. A notch (imaginary zero) is provided by summing of output signals associated with active RC structure state variables. This structure minimizes the number of capacitors while preserving the capability to provide a high Q factor for the first 2nd-order HPF stage 304.

Abstract: A stop band second order active RC filter architecture that does not use a non-inverting input to receive an input signal, and that employs both positive and negative feedback to provide an RC transfer function having an imaginary zero.

Abstract: A T-network containing three impedances is provided between two terminating ends connected to a non-fixed voltage level. Two impedances are connected in series between the two terminating ends. A third impedance is connected between the junction of the first two impedances and a fixed voltage. Switches may be used to trim the third impedance, thus obtaining a desired voltage between the two terminating ends. A terminal of any switches used for trimming can be connected to the fixed voltage node, thereby ensuring that the impedance introduced by the switches does not change substantially during different operating situations.

Abstract: A T-network containing three impedance is provided between two terminating ends not connected to ground. Two impedances may be connected in series between the two terminating ends. A third impedance may be connected between the junction of the first two impedances and a fixed voltage (e.g., ground). Switches may be used to trim the third voltage, thus obtaining a desired voltage between the two terminating ends. A terminal of any switches used for trimming can be connected to the fixed voltage node, thereby ensuring that the impedance introduced by the switches does not change substantially during different operating situations.

Abstract: A line interface apparatus includes a line coupling transformer having first and second windings, and an impedance matching circuit connected to the first winding. The impedance matching circuit includes a first section characterized by a first impedance, a second section characterized by a second impedance, and a switch circuit, connected to the first and second sections and to the first winding of the line coupling transformer, for switching either the first or the second section in series with the first winding of the line coupling transformer. An echo of a transmitted signal is replicated and subtracted from a composite signal comprising a received signal and the echo of the transmitted signal. The result of the subtraction is compared to a threshold value to indicate whether a loop connected to the second winding of the line coupling transformer has an impedance about equal to a first impedance or about equal to a second impedance.

Abstract: A plurality of electrical circuit components having capacitance, e.g. ceramic capacitors, are tested simultaneously in a corresponding plurality of test channels. They are stressed by a variable voltage source that can produce an electrical potential selected from a wide range from low potential to high potential. For example the range of selectable potentials can be 1000 volts with a resolution of 1 volt. The charge current by which a component accumulates a charge is controlled to a selected linear rate by a current controller. Voltage sensors and current sensors measure accumulated charges and leakage current, respectively. The current sensor can be selectively sensitized to a plurality of anticipated leakage current ranges. In addition, the selected potentials can each be applied to the components in a single step or can be applied over time in ramp fashion.

Abstract: A circuit for processing related signal components, such as in-phase and quadrature signal components generated within a modulator, in which a first filter and a second filter are matched such that the gain of each such filter is nearly identical. A modulator is provided having matched filters in accordance with the present invention in which the gain "K" of each filter is equal to 1. By using a filter which has a gain of 1, the gain is removed from consideration when attempting to match the filter response of one filter to another. Furthermore, each filter is relatively simple to implement, having only four resistors, two capacitors, and two operational amplifiers.

Abstract: A phase-locked loop frequency modulation circuit that compensates for the inability of a phase-locked loop to pass low-frequency content of an input modulation signal, and that may be utilized with existing communication apparatus, such as a cellular telephone voice radio, for accurate data transmission without having to modify such apparatus, includes a compensation circuit for processing an input modulation signal to provide a compensation signal that is added to a loop filter output signal by processing the input modulation signal to provide the same effect as adding the input modulation signal to an integrated input modulation signal that is filtered by a filter having the same transfer function as the loop filter to provide the compensation signal.