Signal Analysis Probe Calibration via Equalization Filters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Signal analysis systems face measurement errors due to probe tip loading and signal path transmission errors, particularly when multiple probes are used, leading to inaccurate representations of circuit voltages.
Innovation Solution
A method is introduced to calibrate signal paths by characterizing transfer parameters and calculating open circuit voltages in the spectral domain, followed by the computation of equalization filters to compensate for loading effects, allowing for accurate representation of circuit voltages before probe attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple probes are coupled to the device under test, then signal acquisition capability is improved, but measurement accuracy deteriorates due to probe loading effects
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements before actual signal acquisition. The system measures the device under test with different known impedance loads connected, characterizes the transfer parameters in advance, and computes equalization filters beforehand. This preliminary characterization allows the system to later compensate for probe loading effects during normal operation, enabling accurate measurements even with multiple probes connected.
Solution Approach 2:
The patent utilizes parameter changes by varying the impedance load connected to the device under test during calibration. The system measures the device with at least two different known impedance loads, thereby changing the loading conditions to characterize how the device responds to different loads. This parameter variation enables the computation of equalization filters that can compensate for probe loading effects across different operating conditions.
2Speed
If probe impedance is reduced to increase bandwidth, then signal frequency response is improved, but probe loading effect on the circuit worsens
Solution Approach 1:
The patent implements feedback by using the measured transfer parameters to compute equalization filters that compensate for probe loading effects. The system measures the device under test with known impedance loads, characterizes the loading effects through transfer parameter measurements, and then uses this information to generate correction filters. These filters are applied to subsequent measurements to remove the harmful loading effects, creating a feedback loop that eliminates the adverse impact of low probe impedance on circuit loading.
Data Source
AI summary
A method and apparatus adapted to calibrate signal path of a signal analysis system such that loading effects of additional probes are substantially removed from the measurement. A signal under test from a device under test is coupled to a test probe and used with selectable impedance loads in the test probe to acquires sets of samples for characterizing transfer parameters of the device under test and compute open circuit voltages at the test probe. Other probes are coupled to the device under test and a set of measurement samples are acquired via the test probe. An equalization filter in either the frequency or time domain is computed from the open circuit voltage and measurement samples for reducing signal errors attributable to the measurement loading of the device under test by the test probe and other probes.