254 www.xilinx.com Virtex-4 RocketIO MGT User GuideUG076 (v4.1) November 2, 2008Chapter 11: Design of Transitions RFigure 11-16 shows that phase mismatch is reduced to 0.75° with jog-outs and 0.3° withjog-outs and plane cutouts.Figure 11-17 shows test cases without (left side) and with (right side) jog-outs. There arefour pairs of 45° turns — i.e., four 90° mitered turns in each structure.The left side of Figure 11-18 are the results of a differential TDR measurement showing theP/N mismatch of about 33 ps of down-and-back delay from the structure without the jog-outs. The P/N mismatch is one-half of 33 ps, and with four mitered corners, the mismatchfor each corner is therefore about 4.125 ps, which agrees well with the model. On the rightside are the measured TDR results for the structure with the jog-outs where the P/N skewhas been decreased substantially.Figure 11-16: Simulated Phase Response of 45 Degree Bends with Jog-OutsFigure 11-17: 90° Mitered Turns without and with Jog-Outs-75-76-774.95 Frequency, GHz 5.00Single-Ended Insertion Phase (degrees)UG072_c3_38_050206Outer signalInner trace with jog-outInner trace with both jog-out and cut-outsUG076_ch11_17_050406
