Probe Equalization Filter for Non-50 Ohm Source Impedance
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Solution Overview
Problem
Existing signal acquisition systems, such as oscilloscopes, face measurement errors due to probe tip loading when the device under test (DUT) has a source impedance other than 50 ohms, leading to inaccurate waveform representation.
Innovation Solution
A test and measurement system that allows users to input the nominal source impedance of the DUT, using stored probe parameters to calculate an equalization filter that compensates for probe loading, thereby providing a more accurate representation of the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If equalization filters are designed for 50 ohm source impedance, then measurement accuracy is improved for 50 ohm DUTs, but measurement accuracy deteriorates for DUTs with non-50 ohm source impedance
Solution Approach 1:
The system dynamically adjusts the equalization filter based on the detected source impedance of the DUT. Instead of using a fixed 50 ohm-designed filter, the system calculates and applies a customized equalization filter that matches the actual source impedance, allowing optimal performance across varying impedance conditions
Solution Approach 2:
The system changes the parameters of the equalization filter based on the source impedance detection. By detecting the actual source impedance and recalculating the equalization filter parameters accordingly, the system adapts to different DUT configurations while maintaining measurement accuracy
2Measurement precision
If probe tip loading is reduced, then waveform accuracy is improved, but probe bandwidth is limited
Solution Approach 1:
The system introduces an intermediary processing step - the equalization filter - that compensates for the probe tip loading effect. By detecting the source impedance and applying a customized equalization filter, the system mathematically corrects the waveform distortion caused by probe loading, effectively decoupling the probe design from the loading constraint
Data Source
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AI summary
A test and measurement system including a test and measurement instrument, a probe connected to the test and measurement instrument, a device under test connected to the probe, at least one memory configured to store parameters for characterizing the probe, a user interface and a processor. The user interface is configured to receive a nominal source impedance of the device under test. The processor is configured to receive the parameters for characterizing the probe from the memory and the nominal source impedance of the device under test from the user interface and to calculate an equalization filter using the parameters for characterizing the probe and nominal source impedance from the user interface.