By Jonathan Coup
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Crosstalk is the transfer of
energy between adjacent
conductors due to either
capacitive or inductive
coupling.
In order for crosstalk to
occur, there must be an
active and passive line in
close proximity to each
other.
Clock and periodic signals
are usually the aggressor
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Crosstalk has become a more crucial factor in
performance due to:
◦ As speed increases so does the edge rate of the signal,
more energy at higher frequencies, therefore increased
crosstalk
◦ As bandwidth requirements increase and I/O pins on a
board increases, the pressure to reduce number of
power and ground signals on chip. As a result crosstalk
management for these I/O signals becomes a challenge
due to minimal ground pin access.
◦ Smaller form factor and lower design costs are forcing
tighter spacing between signal traces so then crosstalk
between them increases.
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The loops inserts a notch in the frequency
response of the crosstalk transfer function.
The notch frequency and the level of attenuation
depends on the perimeter of the loop and
distance between loop and victim line
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This technique has no
negative affects on the
signal trace unlike other
filter and shielding
techniques in use today
The smaller the perimeter
of the loop the higher in
frequency the notch will
occur.
Here is an example of the
frequency response for a
single loop.
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For additional reduction, more than one open
loop resonator can be placed
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Uses nonlinear capacitors which have a
voltage-dependent capacitance at each stage
of the line.
The capacitors mitigate the mutual
inductance effect and reduce data-dependent
signal fluctuation
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Here is the depiction of
how the non-linear
caps are placed
This shows the addition
of grounded orthogonal
grids to further
decrease the affects of
crosstalk
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The yellow trace
indicates the input
square pulse with a 600
mV peak to peak
amplitude.
The green trace is the
victim line being
affected by crosstalk
due to the aggressor
with the peak to peak
voltage listed in the
figures.
3 GHz, 5 stage line.
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Takiri, M., Masoumi, N., Mehri, M., & Koozenhkanani, Z.
(2008). Crosstalk reduction using open-loop resonators for
printed circuit board traces. Manuscript submitted for
publication, Dept of Electrical Engineering, University of Tehran,
Tehran, Iran.
Ye, X. (2011). Intentional and un-intentional far end crosstalk
cancellation in high speed differential link.IEEE, 791-796. doi:
10.1109/ISEMC.2011.6038416
Li, H., Guo, C., & Zhang, Y. (2010). Research of crosstalk
reduction between microstrip lines based on high-speed
pcbs. IEEE, 994-997. doi: 10.1109/ISAPE.2010.5696641
Kim, J., Ni, W., & Kan, E. (2006). Crosstalk reduction with
nonlinear transmission lines for high-speed vlsi system.IEEE,