Mixed Mode Vector Network Analyzer for Balanced DUTs
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Solution Overview
Problem
Traditional Vector Network Analyzers (VNAs) are costly and inefficient for characterizing balanced Device Under Test (DUTs) with multiple ports, especially when the DUTs have a frequency range below 10 GHz, as they require complex fixtures and high bandwidth, making large-scale characterization expensive and inconvenient, especially for dual-ended DUTs where synchronization of two VNAs is necessary.
Innovation Solution
A mixed mode vector network analyzer system that includes differential transmitters, reflectometers, receivers, DC measurement circuits, and coupling capacitors to measure S-parameters and DC parameters of differential DUTs, using in-phase and 180° out-phase excitation signals to calculate common and differential mode S-parameters, and DC parameters, while blocking RF signals to prevent interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional VNAs are used to characterize balanced DUTs with multiple ports, then measurement capability is provided, but cost and device complexity increase rapidly
Solution Approach 1:
The system segments the measurement functions by using separate reflectometers for common-mode and differential-mode measurements, and distinct measurement circuits for S-parameters and DC parameters. This modular segmentation allows each component to be optimized independently while maintaining overall measurement capability, reducing the complexity of a single monolithic VNA system.
Solution Approach 2:
The measurement system is designed to perform multiple functions using a unified architecture that can measure both S-parameters and DC parameters, characterize single-ended and differential modes, and test both common-mode and differential-mode signals. This multi-functionality eliminates the need for multiple specialized instruments, reducing overall system complexity and cost.
2Measurement precision
If traditional VNAs are used for balanced DUTs with frequency range below 10 GHz, then measurement accuracy is maintained, but bandwidth requirements and cost increase
Solution Approach 1:
The system applies local quality optimization by using coupling capacitors with specific impedance characteristics matched to the measurement frequency range. The capacitors are selected to provide appropriate AC coupling for signals below 10 GHz while blocking DC components, ensuring measurement accuracy is maintained only at the required frequency range without paying the penalty of high-bandwidth VNA requirements.
3Measurement precision
If two VNAs are used for dual-ended DUT characterization, then complete characterization is achieved, but synchronization complexity and cost increase
Solution Approach 1:
The system merges the measurement functions for both ends of the DUT into a single integrated measurement platform. By combining common-mode and differential-mode reflectometers with unified DC measurement circuits, the system achieves complete dual-ended characterization without requiring two separate VNA systems, thereby eliminating synchronization complexity and reducing overall system cost.
4Measurement precision
If complex test fixtures are used to connect balanced DUTs to traditional VNAs, then measurement capability is provided, but fixture complexity and measurement time increase
Solution Approach 1:
The system extracts the DC measurement capability from the RF VNA measurement path by implementing separate DC measurement circuits that directly measure voltage and current at the DUT terminals. This extraction eliminates the need for complex RF test fixtures that would be required to measure DC parameters, allowing simple direct connections while maintaining measurement capability for both RF and DC parameters.
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
Enables accurate, simple, and cost-effective characterization of balanced DUTs by providing a cost-effective solution for measuring S-parameters and DC parameters without the need for high-bandwidth VNAs, suitable for multi-port and dual-ended DUTs, improving noise immunity and reducing the complexity of test fixtures.
Implementation Method 1
The coupling capacitor is configured to block RF signals from the DC measurement circuit
Implementation Method 2
a first reflectometer and a second reflectometer, the first reflectometer being coupled to the first transmitter port and the second reflectometer being coupled to the second transmitter port
Data Source
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AI summary
A mixed mode vector network analyzer (VNA) system to measure S- parameters and DC parameters of a differential device under test (DUT) is provided. The mixed mode VNA system measures mixed mode S-parameter measurements (i.e., AC measurements) using an independent resistive reflectometer bridge connected to each of the two ports of the differential DUT. The mixed mode VNA system further measures DC parameters of the differential DUT without impacting the measurement of S-parameters. In one embodiment, the mixed mode VNA system is used to measure multi-port differential DUT. Coupling capacitors provide low enough impedance to even the smallest RF frequency of AC measurement (i.e., measurement of S-parameters).