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NOVEMBER 2018 I DESIGN007 MAGAZINE 87 als for comparison. The analysis is conducted using the 2DEM solver in Keysight ADS. For both case studies, analysis of differen- tial insertion loss, mode conversion, intra-pair skew, and eye diagram at the receiver are con- ducted. Results of the analysis are presented and discussed in the next section. Analysis and Results Case Study 1 A simulation of s-parameter with topology shown in Figure 2 is performed to study the impact of non-homogeneous substrate seg- ment length on signal transmission. The 4-port single-mode insertion loss was converted to differential mode (i.e., Sdd21) using the math function in ADS. The plots of Sdd21 for microstrip and stripline are shown in Figures 3a and 3b. These plots indicate that resonance frequency or channel bandwidth gets lower when the overall non-homogeneous segment becomes longer for both microstrip and stripline models. The plots of mode conversion from differ- ential to common (i.e., Scd21) for microstrip and stripline are shown in Figures 4a and 4b. A smaller absolute magnitude of Scd21 in dB indicates more easily differential is converted to common mode, which is encountered by Figure 2: Simulation topology of an s-parameter. Figure 3a: Sdd21 for microstrip. Figure 3b: Sdd21 for stripline.