Test & measurement


Fig. 1: Example of signal transmission loss: The eye pattern at the receiver is closed but equalization filters can recover signal information


EMULATING SIGNAL LOSS AND EQUALIZATION


When developing designs with data interfaces such as USB 3.2, PCI Express or HDMI, signal integrity must be verified on both the transmitter and receiver sides. The R&S RTP164B 16 GHz oscilloscope provides a range of new possibilities – for example, adding signal loss caused by signal channels and using filtering to equalize losses to the signal at the receiver. Guido Schulze, Johannes Ganzert and Francisco Javier Garcia Gomez, all Rohde & Schwarz, investigate...


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SIGNAL LOSS FROM TRANSMISSION LINES


The design of the transmission channel is a major challenge when developing applications with fast data interfaces. In addition to correct dimensioning of transmission bandwidth, the control of the impedance, especially at the transitions, is also crucial as is protection against crosstalk from other signals.


The problems and limitations of the transmission channel appear as signal distortion, known as intersymbol interference. Parts of neighboring signal symbols overlap due to the attenuation of high-frequency signal components and the “blurring” of the symbol energy. Reflections caused by impedance mismatches can also cause signal symbols to overlap. In the worst


Fig. 2: Definition of a cascade of trans- mitter pre-distortion (TX FFE), embedding of additional transmission paths and RX equalization filter


April 2025 Instrumentation Monthly


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