By Jonathan Coup

 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

 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.

 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

 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.

 For additional reduction, more than one open loop resonator can be placed

 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

 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

 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.

 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, doi: /ISEMC  Li, H., Guo, C., & Zhang, Y. (2010). Research of crosstalk reduction between microstrip lines based on high-speed pcbs. IEEE, doi: /ISAPE  Kim, J., Ni, W., & Kan, E. (2006). Crosstalk reduction with nonlinear transmission lines for high-speed vlsi system.IEEE,