Computer-implemented method for checking and correcting of TDR impedance profiles

The technology includes software algorithms and methods for the precise analysis and correction of impedance profiles in the field of time-domain reflectometry.

Challenge

Time domain reflectometry (TDR) is the process of sending an input signal into an object to be studied (e.g. an electrical conductor) and detecting its specific reflections. If the object under investigation has an uniform impedance and a correct electrical termination, no reflection will occur, and the input signal will be absorbed in the electrical termination. Impedance variations result in reflections of the input signal. The impedance variations or discontinuities can be quantified by the amplitude of the reflected signal, the position of the discontinuity over the running length. In the application, kinks or changes in the diameter of a cable or cable to be examined can be detected. However, in the application, often only an initial reflection of the measurement signal can be resolved well. Further reflections are distorted or superimposed by multiple reflections. The frequency dependence of the object properties can lead to changes in the reflection signal that are not resolved.

Our Solution

Received reflection signals are based on the interaction of the input signal with the object to be examined, which has one or more interference points and therefore partially reflects the input signal. In the present technology, these reflection signals are used to create a simulation signal to which a Fourier transform is applied. Based on this transformed signal, a simulation of the object to be examined in the frequency domain is created. By applying the simulation signal to the object simulation, a comparison between the simulation signal and the reflection signal can now take place, so that an evaluation of the simulation signal can be performed. If the deviation is correspondingly small, it can be assumed that the object simulation was sufficiently good, and that the type and position of the faults were thus determined sufficiently well. If there is too much deviation, further iterations can be carried out until a satisfactory result is achieved. Figure 1 shows schematically how different properties of the cable sections A1, A2 and A3 in a microstrip line lead to reflections at the transitions. While it is well known that multiple reflections can hinder the evaluation, the initial resolution of the signals can be achieved with the available technology. The technology also offers special algorithms to control, expand and optimize known TDR sub-processes such as the formation of differences, difference evaluation and modeling algorithms.

Figure 1: Exemplary application of the present technology in combination with a microstrip line (source: Prof. Hampe, Ostfalia University of Applied Sciences).

Advantages

• Precise determination of the properties of electrical conductors and similar objects to be examined
• Efficient elimination of the interfering influence of multiple reflections
• Determination of dispersion possible
• Extended and optimized algorithms for known TDR sub-processes

Applications

• Implementation in commercial measuring instruments (e.g. TDR devices) for quality checks of circuit boards or similar
• Inspection of data transmission systems (for example high-frequency boards for fast data transmission)

Development Status

The software and the process have been successfully developed and tested. The technology is being used in the research sector. Prototypes are available.

Patent Status

German patent applications:
DE102021114651A1
DE102024113020.2
Patent holder: Ostfalia University of Applied Sciences - University Braunschweig/ Wolfenbüttel, Public Law Foundation

Contact

Dr. Mirza Mackovic
Patent & Innovation Manager Technology
E-Mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
Phone: +49 551 30724 153
Reference: MM-2275-FHBW and CPA-2510-FHBW

Tags: IT and Software, Measurement and analysis technology, Physics and Technology & Software