Isolated Test Probe Thermal Drift Correction
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Solution Overview
Problem
Existing isolated test and measurement probes face challenges in accurately correcting for thermal drift-induced gain and offset errors, particularly in high-frequency signals, due to the integration of optical components like DFB lasers and monitor diodes, which are prone to thermally induced variations.
Innovation Solution
The implementation of a pilot tone to separately sense gain variations, differential signaling to separate and cancel offset errors, and the use of an external photodiode to decouple the laser and monitor diode thermally, along with silicon photonics substrates for local thermal feedback, enables independent correction of gain and offset errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If optical components (DFB laser, monitor diode) are integrated into the probe for galvanic isolation, then galvanic isolation and high bandwidth performance are achieved, but thermal drift-induced gain and offset errors increase
Solution Approach 1:
The patent segments the error correction process into two independent parts: offset error correction using differential signaling and gain error correction using pilot tone injection. This allows each type of error to be corrected separately, improving overall measurement precision while maintaining galvanic isolation through optical components.
Solution Approach 2:
The patent implements feedback mechanisms where the monitor diode continuously monitors the laser output and feeds back correction signals. Additionally, pilot tone injection provides a reference signal that enables continuous gain error correction, compensating for thermal drift in real-time and maintaining measurement accuracy.
2Measurement precision
If traditional differential probing is used for high voltage differential signals, then common mode rejection is achieved, but high frequency performance and measurement accuracy deteriorate
Solution Approach 1:
The patent replaces traditional electrical differential probing with optical probing for galvanic isolation. The optical system substitutes electrical fields with optical fields, enabling high bandwidth performance while maintaining common mode rejection through the inherent isolation properties of optical components.
Solution Approach 2:
The patent uses composite probing technology combining optical components (DFB laser, optical fiber, photodiode) with electronic components. This composite approach enables both galvanic isolation for common mode rejection and high bandwidth performance by leveraging the strengths of both optical and electrical systems.
3Measurement precision
If calibration routines are implemented to correct drift errors, then measurement accuracy is improved, but operational complexity and time consumption increase
Solution Approach 1:
The probe performs self-calibration through automatic pilot tone injection and monitor diode feedback. The system continuously corrects its own gain and offset errors without requiring user intervention or external calibration equipment, maintaining high measurement precision while simplifying operation.
Solution Approach 2:
The patent implements continuous error correction through ongoing pilot tone injection and monitor diode monitoring. Instead of periodic calibration routines, the system continuously compensates for drift errors, maintaining accuracy throughout operation without interrupting the measurement process.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
These approaches enhance the accuracy of signal measurements by effectively addressing thermal drift issues, improving the separation and correction of gain and offset errors, especially in high-frequency signals, and reducing thermally induced errors in optically isolated probes.
Implementation Method 1
an electrical to optical (E/O) converter coupled to the input to convert the input electrical signal to an optical signal
Implementation Method 2
an optical splitter separate from the E/O converter to divide the optical signal into a feedback portion of the optical signal and a remaining portion of the optical signal
Implementation Method 3
an optical to electrical (O/E) converter to convert the optical signal to an electrical signal
Data Source
AI summary
A test and measurement accessory has an input to receive an input signal from a device under test (DUT), a pilot signal generator to generate a pilot signal, an E/O converter to convert the input signal and the pilot signal to a combined optical signal, an O/E converter to convert the combined optical signal to a combined electrical signal, a signal separator to separate the pilot signal from the combined electrical signal, an amplitude detector to determine amplitude of the separated pilot signal, and circuitry to adjust a gain of a signal path using the amplitude. A test and measurement accessory has an input to receive an input signal from a DUT, an E/O converter to produce an optical signal, an optical splitter to split the optical signal into a feedback portion and a remaining portion, a feedback photodiode to produce a feedback electrical signal to adjust the optical signal.