Differential Signal Termination Block for Single-Ended Test Equipment
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Solution Overview
Problem
Current test equipment designed for single-ended signal protocols is inadequate for characterizing differential signal protocols, leading to signal degradation and distortion due to mismatched impedance and common-mode voltage issues when connecting differential signal devices to single-ended devices.
Innovation Solution
A termination block with a housing supporting coaxial connectors and passive circuit elements that provide balanced load and matched impedance, maintaining symmetry and phase-matching in differential signal paths to ensure high signal quality by using a combination of resistors and dielectric insulating material to achieve 100 ohm differential and 50 ohm single-ended impedance matching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If single-ended connectors with 50 ohm termination to ground are used in test equipment, then the equipment is suitable for single-ended signal protocols, but the differential signal impedance matching deteriorates causing signal degradation and distortion
Solution Approach 1:
The patent introduces a termination block as an intermediary device between differential signal sources and single-ended test equipment. This block contains a differential-to-single-ended converter that transforms the differential signal into a single-ended signal compatible with standard 50 ohm test equipment, while maintaining proper impedance matching through its internal resistor network configuration
Solution Approach 2:
The termination block changes the impedance parameters by providing 100 ohm differential impedance matching at the differential input ports and 50 ohm single-ended impedance matching at the single-ended output port. This parameter transformation allows seamless interfacing between differential and single-ended systems without signal degradation
2Reliability
If differential signal protocols consider only the differential portion and suppress the common-mode portion, then the serial link performance is improved, but the impedance match for common-mode signals deteriorates
Solution Approach 1:
The termination block extracts and processes the common-mode signal component separately from the differential component. By providing dedicated common-mode termination resistors connected to ground, the device properly terminates common-mode signals while maintaining high-impedance differential signaling, thus resolving the impedance mismatch issue without compromising serial link performance
3Device complexity
If asymmetric termination is used in test equipment, then the device complexity is reduced, but the signal quality and symmetry in differential paths deteriorates
Solution Approach 1:
The termination block intentionally employs asymmetric termination structures where the common-mode resistors are connected to ground while the differential resistors are configured between the differential pairs. This controlled asymmetry simplifies the circuit design and grounding scheme while maintaining proper signal integrity through the deliberate imbalance that favors common-mode termination
Data Source
AI summary
A termination block provides a pair of coaxial connectors for a differential signal source and a pair of coaxial connectors for connection to a single ended coaxial input. Passive electrical components provide impedance matching while maintaining phase-matched true and complement signal paths for the differential signal.