Linear Multiport VNA Measurement Using Power Ratios
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Solution Overview
Problem
Conventional Vector Network Analyzers (VNAs) face challenges in measuring high-frequency signal amplitude ratios and phase differences due to the need for high component accuracy and difficulty in generating intermediate frequencies, especially with heterodyne type VNAs, and require complex calculations for system parameter determination.
Innovation Solution
A method using a linear multiport with specific power measurement steps and equations to calculate system parameters H3_11, H4_11, and H5_11, H3_12, H4_12, and H5_12, allowing for the measurement of amplitude ratios and phase differences using power measurements, reducing the complexity of calculations and hardware requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heterodyne type VNA is used for measuring amplitude ratios and phase differences, then measurement capability is provided, but high component accuracy is required which increases device cost and makes high frequency measurement difficult
Solution Approach 1:
The patent changes the measurement parameter from complex voltage/phase measurement to power measurement. By measuring power ratios instead of direct voltage amplitudes and phase differences, the system avoids the need for high-precision voltage measurement components and frequency mixing, thereby reducing device complexity and cost while maintaining measurement capability
Solution Approach 2:
The patent replaces the heterodyne frequency mixing mechanism with a power measurement-based system. Instead of using local oscillators and mixers to down-convert frequencies, the system directly measures power at the measurement frequency point, eliminating complex frequency conversion hardware and associated precision requirements
2Measurement precision
If conventional homodyne method is used to obtain system parameter T, then S-parameters can be obtained, but large amount of calculation is required and three circular intersections cannot always be obtained
Solution Approach 1:
The patent extracts the essential measurement information directly from power ratio measurements without requiring the intermediate step of calculating system parameter T through circular intersections. By formulating a direct relationship between power measurements and S-parameters, the complex calculation process is eliminated while preserving measurement accuracy
Solution Approach 2:
Instead of following the conventional approach of measuring power values, calculating system parameter T through circular intersections, and then deriving S-parameters, the patent inverts the process by directly calculating S-parameters from power ratio measurements using a simplified mathematical relationship, thereby avoiding the complex intermediate calculation step
Data Source
AI summary
The present invention provides a novel measurement method for system parameters of a 5-port junction used in a VNA (Vector Network Analyzer). A VNA is a device for measuring amplitude ratios and phase differences (S-parameters: scattering matrix elements) between incident waves and reflected waves of a DUT (Device Under Test), or between input waves and transmitted waves. What has been newly discovered is that for 5 ports, S-parameters can be expressed by a linear coupling using H and power difference ratios ({P(S)/P(0)}−1). It is possible to easily calculate parameter H using a minimum of three already known standards, and amount of calculation can be reduced compared to conventionally.