Automated TDR Testing for High-Frequency Cable Assembly

The testing system is designed with universal interfaces and fixtures that can accommodate different cable types (coaxial, twisted pair, multi-core) through standardized connection mechanisms. The TDR measuring device with multiple channels can simultaneously test various cable configurations, eliminating the need for separate manual testing procedures for each cable type while maintaining automation capability.

A fixture serves as an intermediary component between the automated testing system and the cable under test. This fixture provides standardized interfaces for both the TDR measuring device and the cable, enabling automated high-frequency testing while adapting to different cable types. The fixture acts as a mediator that translates between the automated system requirements and the diverse cable configurations.

The system replaces traditional mechanical/current-based testing methods with TDR (Time Domain Reflectometry) technology. Instead of using physical current injection and measurement, the system uses electromagnetic signal transmission and reflection analysis to detect cable characteristics. This substitution enables high-frequency measurements of reflection, impedance, and propagation time that cannot be achieved with conventional current testing methods.

The testing system changes the measurement parameter from DC current characteristics to high-frequency electromagnetic signal characteristics. By using TDR technology with rise times of less than 100 ps and measurement bandwidths exceeding 5 GHz, the system can measure high-frequency parameters such as signal reflection, characteristic impedance, and propagation time, providing comprehensive cable characterization beyond basic continuity testing.

The measuring device is divided into multiple independent measurement channels, each capable of testing individual conductors or conductor pairs within a cable. This segmentation allows the system to handle multi-core cables by assigning different channels to different conductors, enabling simultaneous or sequential measurement of all conductors while maintaining a modular and manageable device architecture.

The system transitions from single-ended measurement (one-dimensional testing against ground) to differential mode measurement (two-dimensional testing between conductors). By implementing both single-ended and differential measurement capabilities across multiple channels, the system can effectively test multi-core cables by measuring voltage differences between various conductor pairs, adding a new dimension to the measurement capability.

The cable is pre-positioned in a fixture that holds it in a measured state before testing begins. The fixture is designed to maintain known geometric relationships between connection points, so the physical length and test configuration are established in advance. This preliminary positioning eliminates the need for manual cable laying and measurement during the testing process, significantly improving productivity while maintaining measurement accuracy through precise fixture design.

Instead of physically measuring the cable length by manual laying, the system uses TDR to create an electrical copy or representation of the cable's electrical characteristics. The TDR measurement provides a virtual model of the cable's length and impedance profile based on signal propagation time, eliminating the need for physical manipulation while maintaining measurement accuracy through electromagnetic field analysis.