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Data Mining 12-Port S-Parameters Application Note 1 Introduction 12-port differential S-parameters contain the complete behavior of up to three independent differential channels in a high-speed serial interconnect. Though there are 78 unique elements, when including magnitude and phase information, single-ended and differential forms, and the frequency and time domain descriptions, there are more than 400 different elements. This application note puts into perspective the most important terms and the valuable information that can be extracted about the interconnect performance of these measurements. In particular, we will show how the information about coupling regions can be mined from 12-port measurements. High-Speed Serial Links High-speed serial links proliferate in data centers between servers, in backplanes and the Bandwidth Of between plug-in cards and between devices on a board. Each protocol, such as Infiniband, PCI-express and SATA, undergoes generational advances, with Interconnects typically a factor of two increase in bit rate per channel. For example, Infiniband was introduced at 2.5 Gbps, with a second generation announced as double data rate (DDR) at 5 Gbps, and a quad data rate (QDR) at 10 Gbps. The bandwidth of the signal components that make up the bit stream is difficult to quantify because it changes as it propagates down the channel. The signal with the highest bit transition density looks like a clock with a clock frequency of half the data rate. If the rise time of the signal were about 7% of the clock period, the bandwidth of this bit pattern would be the fifth harmonic, or 5 x 0.5 x bit rate or 2.5 x the bit rate. While this might be the bandwidth of the signal at the transmitter, as it propagates down the interconnect, high frequencies are attenuated and the bandwidth reduces. In the typical case of a lossy line, only the first harmonic is left and the bandwidth is close to the clock frequency, or 0.5 x the bit rate at the receiver. This is why the bandwidth of a serial data stream is typically reported as anywhere between 0.5 and 2.5 times the bit rate. This is a factor of five