The impact of high-speed de-emphasis and multi-stage passive rc equalization on the radiated EMI and signal integrity performances of a 5Gbs microstrip channel

De-emphasis is a well-known signal conditioning technique that overdrives the rising and falling edges of the signal to compensate for the expected attenuation that these edges will incur as they propagate through long transmission lines. On the other hand, equalization is a different signal conditioning technique that can be used to extend the transmission bandwidth. Passive equalization, such as RC high-pass filtering in a single stage, attempts to extend the transmission bandwidth at the expense of its insertion loss, and has been discussed in the literature [1]. However, the required resistive values disclosed for this application at high speeds, derived from simulations, tend to exceed the practical limitations for implementing the single-stage RC equalizer with such resistive values [1]. It is of interest to understand the impact of splitting the single stage RC equalizer into multiple stages, in which each stage contains low resistive values that are available with off-the-shelf RC equalizers, and that are characterized with low parasitic effects. This paper discusses the application of de-emphasis and multi-stage RC equalization on a 5.0Gbs signal that propagates along a differential microstrip with a bandwidth of 600MHz. The values of R and C for the equalizers are chosen to maximize the eye opening at the output of the multi-stage equalizer. The mathematical modelling of this scenario demonstrates that the nearly closed received eye patterns without de-emphasis or equalization can be significantly improved with de-emphasis at a level of about 1.6dB and RC equalization in two identical stages, with R=45.0O̅ and C=6.1pF. In addition, it is shown that the associated maximum radiated EMI is about 51.0dBμV/m along the differential microstrip.