Q & A on Cross talk

Questions and Answers

Q1. Which of the following does not reduce cross talk

A. Increasing the separation between the traces.
B. Increasing the width of trace
C. Reducing the separation between trace and ground plane.


Q2. Which of the following is not true about Near End Cross talk (NEXT)

A. Near end cross talk amplitude saturates when the parallel length of the transmission line exceeds half the rise time of the signal.
B. Near end cross talk increases in proportional to the length of the parallelism if the length of parallel traces is less than one half of the signal rise time.
C. Increasing the length of parallelism beyond half the rise time increases the duration of the NEXT and not its amplitude.
D. The Near End Cross Talk can not be reduced by separating the traces farther away.


Q3. Which of the following will NOT lead to reduction in cross talk level

A. Reducing separation between traces
B. Using stripline in place of microstrip.
C. Reducing separation between the traces and the ground/power plane.
D. Reducing the dielectric constant of the medium.


Q4. Assume a ramp signal of 0 to 100 % rise time of Tr is incident on a transmission line of length equivalent to propagation delay of Tp. Tp is much greater than tr. Which one best describes the duration of the backward cross talk signal.

A. Tp
B. 2Tp
C. 2Tp+2Tr
D. Tp+Tr


Q5. The shape of the forward cross talk is

A. Same as the shape of the incident signal
B. Same as the first derivative of the incident signal
C. Same as the shape of the incident signal, except that it is inverted in sign.
D. None of the above.


Q6. Consider a pair of microstrip traces spaced at distance D apart. The separation from the ground plane is H. Which of these cases generates greatest amount of cross talk.

A. D = 4 mils , H = 8 mils
B. D = 6 mils, H = 8 mils
C. D = 8 mils, H = 4 mils
D. D = 8 mils, H = 6 mils


Q7. Consider guard traces inserted in between two traces between a pair of microstrip. Which one of the following cases is not true.

A. The effectiveness of guard traces increase if they are grounded.
B. The guard traces do not reduce the cross talk at all.
C. Guard traces show more promising improvement in case of microstrip than in case of stripline.


Answer and Explanations

1.B
2.D
3. D
4. C
5. B
6. A Lower the D/H ratio, more is the crosstalk.
7. B

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