S-Parameter Extraction Using Virtual Substrate Division
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Solution Overview
Problem
Conventional frequency characteristic measurement methods require multiple substrates for calibration, leading to high costs and lengthy calibration operations.
Innovation Solution
A frequency characteristic measurement apparatus that performs SOLT calibration and uses a computer program to extract DUT S-parameters by assuming symmetrical or asymmetrical reflection and transmission characteristics of virtually divided substrates, reducing the need for multiple substrates and simplifying the measurement process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional SOLT calibration method is used with multiple substrates, then measurement accuracy is improved, but cost and calibration time increase significantly
Solution Approach 1:
The invention extracts and removes the fixture components from the measurement equation through mathematical operations. By measuring the fixture's S-parameters separately and subtracting them from the total measurement, only the DUT's pure frequency characteristics remain, eliminating the need for multiple calibration substrates while maintaining measurement accuracy
Solution Approach 2:
A single substrate with multiple connectors can serve multiple functions: it acts as both the test substrate for DUT measurement and the reference substrate for fixture characterization. The same substrate is used to measure both the combined (fixture+DUT) and separate (fixture only) S-parameters, replacing the need for multiple specialized calibration substrates
2Measurement precision
If conventional SOLT calibration method is used with multiple substrates, then measurement accuracy is improved, but manufacturing cost increases
Solution Approach 1:
A single substrate with multiple connectors serves multiple functions: it acts as both the test substrate for DUT measurement and the reference substrate for fixture characterization. The same substrate is used to measure both the combined (fixture+DUT) and separate (fixture only) S-parameters, replacing the need for multiple specialized calibration substrates
Solution Approach 2:
The fixture's S-parameters are measured and stored as a reference copy. This copied data is then used in mathematical operations to remove the fixture's influence from subsequent measurements, eliminating the need for physical copies of calibration substrates
3Measurement precision
If conventional SOLT calibration method is used, then pure DUT frequency characteristics can be obtained, but device complexity increases
Solution Approach 1:
The invention extracts and removes the fixture components from the measurement equation through mathematical operations. By measuring the fixture's S-parameters separately and subtracting them from the total measurement, only the DUT's pure frequency characteristics remain, eliminating the need for multiple calibration substrates while maintaining measurement accuracy
Solution Approach 2:
The measurement process is segmented into distinct steps: first measuring the fixture's S-parameters, then measuring the combined (fixture+DUT) S-parameters, and finally performing mathematical separation. This segmentation simplifies the overall process by breaking down the complex calibration into manageable, sequential operations
Data Source
AI summary
A frequency characteristic measurement apparatus includes a calibration circuit configured to perform a SOLT calibration on cable end surfaces, a first measurement circuit measuring S-parameters of a first substrate provided with a DUT, after the SOLT calibration by the calibration circuit, a second measurement circuit measuring S-parameters of a second substrate after the SOLT calibration by the calibration circuit, and an extraction circuit performing a vector operation of a measurement result of the first measurement circuit and a measurement result of the second measurement circuit to extract S-parameters of the DUT. The extraction circuit assumes that a reflection of each of first second fixtures obtained by virtually dividing the second substrate into two parts at the center, on an end surface of the second substrate is equal to or smaller than a reflection on an end surface of the second substrate without the virtual division at the center.