Stub termination

摘要

Figure 1 illustrates the channel insertion loss of a 30-in. differential channel with differential vias at each end. Using short vias with no stubs (green, top trace), the response rolls off smoothly to -13 dB at 5 GHz. Thick backplane vias with long stubs (red) create unwanted resonances in the channel insertion loss, whereas vias with short or no stubs do not. If these resonances occur near the Nyquist frequency of the bit rate, they will devastate the eye opening at the receiver.