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US 4,351,060 AGranted
Automatic, digitally synthesized matching line terminating impedance
AssigneeInternational Telephone and Telegraph Corporation
InventorRobert Treiber
Life of this patent
Estimating the term…
Abstract
A circuit for automatically digitally synthesizing an output impedance, which may be a matching line terminating impedance, is provided. The means for establishing the desired output impedance characteristic is accomplished using a simplified recursive digital filter arrangement. In addition, means are provided for eliminating the effects of incidental undesirable shunting impedances.
Claims15
A circuit for automatically digitally synthesizing an output matching line terminating impedance comprising:
- analog to digital conversion means for converting negative feedback analog communication signals occurring at circuit output terminals to negative feedback digital signals;
- means for summing said negative feedback digital signals with input digital communication signals providing a composite digital signal input;
- digital filter means having said composite digital signal input coupled thereto for directly establishing a predetermined output impedance characteristic, said digital filter having filter coefficients, and having a digital signal output;
- means for selectively altering said filter coefficients;
- digital to analog conversion means for converting said digital signal output to an analog voltage signal;
- and
- means for converting said analog voltage signal to an analog current having a high output impedance characteristic compared to the matched line and to the synthesized impedance such that said analog current is coupled to said circuit output terminals and to said analog to digital conversion means.
4 more elements
A circuit for digitally synthesizing a line matching impedance comprising:
- analog-to-digital conversion means for converting negative feedback input analog signals to negative feedback digital signals;
- means for summing said negative feedback digital signals with additional digital signals to derive a combined signal output;
- recursive digital filter means having said combined signal output coupled thereto, and having filter coefficients;
- means for programmably altering said filter coefficients such that the processing of said combined signal output by said digital filter establishes a controllable line matching impedance characteristic of said circuit with respect to said digital filter transfer characteristics;
- digital-to-analog conversion means for converting the output of said digital filter to an analog voltage signal;
- and
- transconductance amplifier means for converting said analog voltage signal to an analog current having a high output impedance characteristic with respect to the impedance at the output of said converting means, said analog current also being coupled to said analog-to-digital conversion means.
4 more elements
Dependencies are inferred from the claim text.