Terahertz On-Wafer S Parameter Calibration with Crosstalk Correction
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Solution Overview
Problem
Conventional error models fail to accurately represent crosstalk errors at higher frequencies in on-wafer S parameter testing, leading to low accuracy in S parameter measurements due to increased leakage between probes.
Innovation Solution
A calibration method that acquires eight error models and uses these to establish mathematical models with parallel and series crosstalk terms between probes, allowing for the determination of the Z parameter and subsequent accurate S parameter measurement by incorporating two crosstalk corrections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional error models (12 or 8 error models) are used for calibration, then the calibration process is simple and can be performed at low frequencies, but the measurement precision deteriorates at high frequencies due to inability to represent crosstalk error amount
Solution Approach 1:
The patent changes the mathematical parameters of the error model by introducing crosstalk error terms (S21 for parallel crosstalk and S12 for series crosstalk) to the conventional 8-error-model. This parameter enhancement allows the model to represent high-frequency crosstalk effects while maintaining the calibration process framework, thereby improving measurement precision without excessive complexity increase
Solution Approach 2:
The patent introduces calibration pieces (through piece, open piece, short piece) as intermediaries to measure and characterize crosstalk errors. These calibration pieces serve as mediators that enable the system to quantify crosstalk effects at high frequencies, which are then used to correct measurement data without requiring a complete redesign of the calibration methodology
2Speed
If on-wafer test frequency is increased to achieve higher bandwidth testing, then the testing capability is improved, but the measurement precision deteriorates due to increased crosstalk signal between probes
Solution Approach 1:
The patent implements a feedback mechanism where crosstalk errors are first measured using calibration pieces at the desired high frequency, then these measured error values are used to correct subsequent measurement data. This feedback loop allows the system to maintain high-frequency testing capability while compensating for the deteriorating precision caused by crosstalk
Solution Approach 2:
The patent converts the harmful crosstalk signal into a useful correction factor. By deliberately measuring the crosstalk effect using calibration pieces and then applying this information as a correction to the actual device under test measurements, the previously harmful high-frequency crosstalk becomes a quantifiable and correctable parameter, enabling both high bandwidth and high precision
Data Source
AI summary
A calibration method includes: acquiring eight error models obtained after a preliminary calibration of a Terahertz frequency band system; based on the eight error models, determining a first mathematical model according to a first S parameter related to a first calibration piece, the first mathematical model comprising parallel crosstalk terms between probes, and determining a second mathematical model according to a second S parameter related to a second calibration piece, the second mathematical model comprising series crosstalk terms between the probes; determining a third mathematical model according to a third S parameter related to a measured piece; and solving and obtaining a Z parameter of the measured piece based on the first mathematical model, the second mathematical model and the third mathematical model, and acquiring an S parameter of the measured piece according to the Z parameter of the measured piece.