Spread Spectrum TDR for Live Circuit Fault Detection

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Solution Overview

Problem

Existing electrical testing methods, such as TDR and VNA, are limited by their inability to perform live circuit testing, are prone to noise issues, and are expensive, making it difficult to detect intermittent faults and requiring circuit disconnection, which is problematic for applications like power distribution networks.

Innovation Solution

The implementation of Spread Spectrum Time Domain Reflectometry (S/SSTDR) methods that allow for simultaneous multi-port testing on live circuits, using pseudo noise codes and curve fitting algorithms to improve measurement resolution and accuracy, enabling the detection of resistance, inductance, capacitance, and impedance changes without interfering with existing signals.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If TDR or VNA methods are used for circuit testing, then measurement capability is provided, but circuit disconnection is required and live testing is not possible

Engineering Contradiction:

Improvelive circuit testing capabilityVSAvoiddetection of intermittent faults

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent transforms the test signal parameters by using spread spectrum modulation techniques, spreading the test signal across a wide frequency band. This allows the test signal to be injected into live circuits without interfering with normal operation, enabling live testing while maintaining measurement capability through correlation processing of the spread spectrum signal

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary spread spectrum test signal that acts as a carrier for measurement information. This test signal is injected into the live circuit and its reflections are extracted through correlation processing, serving as an intermediary that enables measurement without direct disruption to the circuit under test

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If multi-port VNA devices are used for circuit testing, then comprehensive measurements are obtained, but noise problems increase and testing becomes more complex

Engineering Contradiction:

Improvecircuit parameter measurement accuracyVSAvoidmulti-port testing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the multi-port measurement process by independently injecting spread spectrum test signals at each port and processing reflections separately through correlation. This segmentation allows comprehensive multi-port measurements while maintaining simplicity, as each port can be tested independently without the noise and complexity issues of traditional multi-port VNA devices

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If TDR methods are used with higher bandwidth, then measurement resolution is improved, but sampling speed requirements increase and processing circuitry becomes more sophisticated

Engineering Contradiction:

Improvetime domain measurement resolutionVSAvoidsampling and processing circuitry

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent replaces the mechanical/electronic sampling system with a signal processing approach. Instead of requiring fast sampling circuitry to capture high bandwidth signals, the system uses spread spectrum modulation and correlation processing to achieve high resolution measurements. The correlation process inherently filters and integrates the signal, providing high resolution without the need for sophisticated fast sampling circuitry

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Measurement precision

If VNA methods are used with higher frequencies, then frequency domain coverage is improved, but sine wave generation and reception become more difficult

Engineering Contradiction:

Improvefrequency domain measurement rangeVSAvoidhigh frequency signal generation

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent changes the signal generation approach from traditional sine waves to spread spectrum modulated signals. This allows wide frequency band coverage to be achieved through modulation rather than direct high frequency generation. The spread spectrum signal inherently occupies a wide frequency band, and correlation processing extracts the measurement information, avoiding the difficulties of precise high frequency sine wave generation and reception

Inventive Principle:

Principle #35Parameter changes

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

S/SSTDR enables efficient, accurate, and cost-effective testing of circuits under live conditions, allowing for the detection of faults and impedance changes, reducing testing time and improving fault localization, particularly suitable for complex systems like power converters and PV systems.

Implementation Method 1

a transmit/receive circuitry configured to send a spread spectrum test signal through a transmission line and detect reflected signals

Methodology Applied

Scientific EffectReflection: Reflection

Data Source

PatentUS9970977B2Systems and methods for implementing S/SSTDR measurements

Publication Date: 2018.05.15 UNIV OF UTAH RES FOUND

AI summary

Systems and methods which utilize spread spectrum sensing on live circuits to obtain information regarding a circuit under test are provided. In some embodiments S/SSTDR testing may be utilized to obtain R, L, C and Z measurements from circuit components. In yet further embodiments, these measurements may be utilized to monitor the output of sensors on a circuit.