Programmable Impedance Synthesis for DSL POTS Filters

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Solution Overview

Problem

Existing filter devices for passing telephony signals in DSL transmission systems face challenges in designing and manufacturing splitters that meet specific complex impedance requirements for different countries, while also needing cost and space-efficient solutions for adequate low-pass filtering of POTS signals.

Innovation Solution

A filter device with a real impedance low pass filter and a digital signal processor to synthesize complex impedance, allowing for the creation of different complex impedances without changing hardware, using a 3rd order filter with double wound inductors and shunt capacitors, and optionally additional capacitors, integrated into a POTS line card for efficient impedance matching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a complex impedance filter is designed to meet specific country requirements, then the impedance matching is improved, but the device complexity and manufacturing variety increases

Engineering Contradiction:

Improveimpedance matchingVSAvoidhardware variants

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent changes the electrical parameters of the filter by using programmable gain amplifiers and variable resistors to adjust the impedance characteristics. This allows a single hardware design to adapt to different country-specific impedance requirements by modifying circuit parameters through programming rather than manufacturing different hardware variants.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The filter device is designed with multi-functionality to serve multiple countries and impedance requirements using a single hardware platform. The programmable components enable the same physical device to be configured for different national standards, eliminating the need for country-specific hardware variants.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Manufacturing precision

If multiple hardware variants are manufactured for different countries, then the impedance matching is improved, but the manufacturing cost and inventory complexity increases

Engineering Contradiction:

Improveimpedance matchingVSAvoidmanufacturing cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

A single universal hardware design is created that can be programmed to meet different country-specific impedance requirements. This eliminates the need to manufacture, store, and distribute multiple country-specific hardware variants, significantly reducing manufacturing costs and inventory complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

Instead of manufacturing different physical hardware variants for each country, the patent uses software programming to create virtual copies of the impedance characteristics. The same physical hardware can be programmed to replicate the electrical behavior required for different national standards.

Inventive Principle:

Principle #26Copying

3Ease of manufacture

If a real impedance filter is used, then the manufacturing is simplified, but the complex impedance requirement is not met

Engineering Contradiction:

Improvefilter manufacturingVSAvoidimpedance matching

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent introduces programmable gain amplifiers and variable resistors as intermediary components between the real impedance filter and the line. These intermediaries transform the real impedance output of the simple filter into the required complex impedance by adding controllable reactive components through programming.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent replaces the need for complex physical filter designs with a simpler real impedance filter combined with electronically controlled impedance transformation. Instead of manufacturing complex passive filters, the system uses active electronic components programmed to provide the required impedance characteristics.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution allows for the synthesis of required complex impedances, reducing the need for multiple hardware variants, achieving efficient and cost-effective filtering with improved impedance transparency and stopband rejection, suitable for various markets and applications.

Implementation Method 1

The LPF 1 passes low frequency telephone signals to the POTS line card 2 and blocks the higher frequency DSL signals

Methodology Applied

Scientific EffectLow pass filtering: Filter (electronic)

Implementation Method 2

means to synthesize a complex impedance coupled to the low pass filter, said means creating a complex impedance at the input port

Methodology Applied

Scientific EffectImpedance synthesis:

Data Source

PatentEP1898663B1A filter device for passing telephony signals

Publication Date: 2011.11.02 ALCATEL LUCENT SA

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AI summary

A filter device for passing telephony signals. Communication traffic containing telephony signals and other signals in a higher frequency band are received at an input port (P1) and a low pass filter (10) is coupled to the input port (P1). The filter device includes means to synthesize a complex impedance (22) coupled to the low pass filter (10) by using a digital signal processor. A method of producing a filter device is also provided.