Signal Analysis Probe Calibration for Loading Error Compensation
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Solution Overview
Problem
Signal analysis systems face measurement errors due to probe tip loading and signal path transmission errors, particularly because typical probes have impedance that varies with frequency, causing inaccuracies in representing the voltage of circuits under test.
Innovation Solution
A system and method that calibrate the signal path using a controllable impedance device and memory to store transfer parameters, allowing for the adaptation of the probe's input impedance and de-embedding signal degrading effects, utilizing two-port S or T parameter representations to normalize impedance and filter parameters, thereby compensating for loading and transmission errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a probe with frequency-varying impedance is used for signal acquisition, then the probe can operate across a wide bandwidth, but the probe loading effect on the circuit under test increases significantly
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the input impedance of the probe to match the output impedance of the device under test across different frequency ranges. This is achieved through impedance transformation circuits that modify the probe's input impedance parameters, allowing the probe to maintain high bandwidth while minimizing loading effects on the circuit under test by adapting its electrical parameters to the specific measurement conditions.
2Measurement precision
If the probe impedance is increased to reduce loading effect, then the circuit loading is reduced, but the signal acquisition capability at high frequencies deteriorates
Solution Approach 1:
The patent implements dynamics by making the probe's input impedance a dynamic parameter that automatically adjusts with frequency. Rather than using a fixed high impedance that would limit bandwidth, the system employs frequency-dependent impedance transformation that maintains optimal impedance matching across the entire operating bandwidth. This dynamic adaptation allows the probe to reduce loading effects at low frequencies while maintaining signal acquisition capability at high frequencies.
3Measurement precision
If a calibration system with controllable impedance device is implemented, then measurement accuracy is improved, but the system complexity increases
Solution Approach 1:
The patent applies self-service by implementing an automated calibration system where the controllable impedance device and controller work together to automatically perform calibration procedures without requiring manual intervention. The system self-adjusts impedance parameters, automatically compares measurements against reference standards, and dynamically modifies probe characteristics based on real-time feedback. This automation reduces the operational complexity despite the added hardware components, as the calibration process becomes self-executing rather than manually controlled.
Data Source
AI summary
A method and apparatus adapted to calibrate a signal path of a signal analysis system such that loading effects of the system are substantially removed from measurements of a device under test. A signal under test from the device under test is coupled to a test probe in the signal path and used with selectable impedance loads in the test probe to characterize transfer parameters of the device under test. An equalization filter in either the frequency or time domain is computed from the device under test transfer parameters for reducing in signal error attributable to the measurement loading of the device under test.