Direct measurement of crosstalk between integrated differential circuits

Silicon integrated-circuit test structures have been fabricated that allow direct measurement of crosstalk between differential transmission lines and between single-ended transmission lines in the presence of metal ground plane. The differential test structures are characterized with mixed-mode scattering parameters (common mode, differential mode, and mode conversion), as measured with the pure-mode vector network analyzer. Comparisons with simulation show good agreement for differential-mode crosstalk, and the dependence of crosstalk on transmission-line separation is presented. Difficulties in simulating crosstalk fur even simple structures illustrate the utility of direct measurement of crosstalk.