De-embedding Probe Fixture Effects Using S-Parameter Modeling
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Solution Overview
Problem
Current methods for isolating device under test (DUT) measurements from probe and fixture effects in network analysis are complex, error-prone, and require multiple measurements, expensive standards, and assumptions of constant characteristics, which are difficult to maintain, especially when dealing with non-connectorized DUTs in signal integrity applications.
Innovation Solution
A method that involves performing s-parameter measurements with optional calibration using known standards, converting to mixed-mode formats, computing impedance profiles, determining loss and group delay characteristics, and modeling probes or fixtures as cascaded transmission line sections to de-embed their effects from DUT measurements, allowing for accurate isolation of DUT s-parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration methods are used to remove fixture and probe effects, then measurement accuracy is improved, but device complexity and time consumption increase significantly
Solution Approach 1:
The patent extracts the fixture and probe effects from the measurement system by mathematically removing their s-parameter contributions. Instead of using complex calibration procedures with multiple standards, the method directly processes the measured s-parameters to isolate the DUT characteristics, effectively taking out the unwanted fixture/probe influence from the measurement chain.
Solution Approach 2:
The patent uses a simplified model representation of the fixture and probe effects that can be applied to correct measurements. Rather than requiring physical copies of calibration standards, the method creates a mathematical model of the fixture/probe s-parameters that can be reused across multiple measurements, reducing both complexity and time consumption.
2Measurement precision
If multiple calibration measurements are performed, then measurement accuracy is improved, but productivity decreases due to time consumption
Solution Approach 1:
The patent performs preliminary characterization of the fixture and probe s-parameters once, and then reuses this characterization for multiple subsequent DUT measurements. This preliminary action eliminates the need to repeat complex calibration measurements for each DUT, significantly improving productivity while maintaining measurement accuracy through the reusable mathematical model.
3Measurement precision
If expensive calibration standards are used, then measurement accuracy is improved, but cost increases
Solution Approach 1:
The patent replaces expensive, reusable calibration standards with a computational approach that uses readily available measurement data. Instead of investing in costly precision standards, the method processes standard measurement data through mathematical operations to achieve accurate DUT characterization, effectively using cheap computational resources instead of expensive physical standards.
4Device complexity
If assumptions of constant characteristics are made, then device complexity is reduced, but measurement accuracy deteriorates when conditions change
Solution Approach 1:
The patent implements a dynamic approach by allowing the fixture and probe s-parameter characteristics to be updated and refined based on actual measurement conditions. Rather than assuming constant characteristics, the method can adapt the mathematical model to reflect changes in frequency, temperature, or other environmental factors, maintaining accuracy without excessive complexity through selective model updating.
Data Source
AI summary
A method is provided for de-embedding fixtures and/or probes from measurements of devices where probes and fixtures are connected between the ports of a network analysis instrument and a device-under-test.