Printed-circuit impedance control using skewed reference mesh
View Patent ↗A printed circuit laminate is provided comprising at least one conductor trace for carrying forward electrical signals in a first direction of signal propagation. The printed circuit laminate also comprises a mesh reference plane, spaced from the at least one conductor trace, for carrying return electrical signals in a second direction. The mesh reference plane defines a plurality of cells. Each cell of the plurality of cells includes at least one axis of repetition. The plurality of cells are configured so that all of the axes of repetition of each cell are different from the first direction of signal propagation. Furthermore, the frequency of cell repetition along the first direction of signal propagation is chosen to reduce differences in transmission line impedance between any two conductors on the same laminate or any two conductors on different laminates.
1. A printed circuit laminate comprising:
at least one conductor trace, for carrying forward electrical signals in a first direction of signal propagation; and
a mesh reference plane, spaced from the at least one conductor trace, for carrying return electrical signals in a second direction, the mesh reference plane defining a plurality of cells,
wherein each cell of the plurality of cells includes at least one axis of repetition and the plurality of cells are configured so that all of the axes of repetition of each cell are different from the first direction of signal propagation, and
the at least one axis of repetition is skewed from the first direction of the at least one conductor trace by an angle determined from the rise time of the electrical signals and the period of impedance of the electrical signals along the at least one conductor trace.
2. A printed circuit laminate according to claim 1 , wherein the difference between each of the axes of repetition of each cell and the first direction of signal propagation is defined by an angle in the range of greater than 0 degrees and less than 90 degrees.
3. A printed circuit laminate according to claim 1 , wherein the difference between each of the axes of repetition of each cell and the first direction of signal propagation is defined by an angle in the range of about 1 degree to about 89 degrees.
4. A printed circuit laminate according to claim 1 , wherein the difference between each of the axes of repetition of each cell and the first direction of signal propagation is defined by an angle in the range of about 2 degrees to about 10 degrees.
5. A printed circuit laminate according to claim 1 , wherein the difference between each of the axes of repetition of each cell and the first direction of signal propagation is defined by an angle in the range of about 3 degrees to about 5 degrees.
6. A printed circuit laminate according to claim 1 , wherein each cell includes at least one feature for carrying the return electrical signals and the mesh reference plane is configured so that the at least one conductor trace is equally spaced from all of the features of the mesh reference plane over a predetermined length of the at least one conductor trace.
7. A printed circuit laminate according to claim 1 , wherein the mesh reference plane is configured so that the impedances of each signal along each of the at least one conductor trace is substantially equal over a predetermined length of each of the at least one conductor trace when the signals are propagated along the at least one conductor trace.
8. A printed circuit laminate according to claim 1 , comprising at least two conductor traces, for carrying forward electrical signals in a first direction of signal propagation, wherein the at least two conductor traces are substantially parallel to each other.
9. A printed circuit laminate according to claim 1 , wherein the printed circuit laminate is substantially rigid.
10. A printed circuit laminate according to claim 1 , wherein the printed circuit laminate is substantially flexible.