Design

Signal integrity in high-speed designs

18th February 2020
Alex Lynn

Ensuring signal integrity is one of the main challenges in high-speed designs. Digital transmission in the range of several Gbps is characterised by the introduction of jitter and noise into the signal. What appears at the receiving end does not match the intent at the transmission end when there is any degree of jitter and noise.

This applies to amplitude, frequency and phase. Therefore, developers of high-speed connectivity systems have to analyse the signal quality, i.e. what happens on the receiver side, to ensure robust and error-free data links. To support designers on these needs Inova Semiconductor provides the APIX3 PHY Monitor tool, combining a powerful Eye Tracer algorithm with a user-friendly GUI.

Jitter arises from the combination of interference among symbols, crosstalk, reflections, thermal effects and various random phenomena that are omnipresent in electronic systems. For a jitter- and noise-free digital pulse, an ideal receiver samples the data at the centre of the incoming pulse. In the presence of jitter and noise, the rising and falling edges can move along the time axis, and the voltage level can move along the amplitude axis.

If the signal’s edges are too far off, the correct bit detection conditions may not be satisfied, resulting in a bit error. Eye diagram is a preferred tool to evaluate channel noise and jitter. It is the superposition of transmitting signal viewed within a particular interval.

Traditional eye diagram is measured by connecting the signal (output from transceiver TX) to an oscilloscope, giving results at the pins of the device. With the APIX3 PHY monitor, customers can print the real time eye of the signal inside the receiver (RX). The colour coding of the eye diagram (different colours for all hit, no hit and the ranges between) provides a convenient and fast way to check the signal quality. Finally, the PHY Monitor enables a more intuitive view that how the signal quality is inside the receiver device.

In addition to scan an eye diagram of the receiver in real time user can read the status of some relevant registers for calibration and can configure the FIR filter (amplitude and delay) of the transmitter. Other functions provided by the tool is the generation of test patterns, enable/disable upstream, get/set replica gain and the check of bit errors (of internal and external source).

The APIX3 PHY Monitor tool consists of two parts: GUI and the eye diagram algorithm. The GUI will be provided by Inova to its customers so that they are able to install it on their own PC. The Eye Tracer algorithm is already implemented into the latest version of the device. Thus, customers just connect the board with their PC, open the GUI and start with the signal analysis.

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