Technique for increasing the range of impedances for circuit board

Abstract

A shielded flexible cable includes a first shielding grid having conductive elements formed as squares. A second shielding grid is also formed as squares. The two shielding grids are positioned with respect to each other so that the vertices of the squares of the two grids are respectively offset from each other in each of two directions by one-half the diagonal distance between the vertices of the squares. Electrical signal conductors are positioned between the two grids along lines extending between the vertices of the squares to maintain a controlled impedance of the signal lines. A circuit board includes a reference plane configured as a grid having conductive elements formed as squares. Electrical signal conductors are positioned in a plane adjacent said grid. The decreased percent copper used to construct the grid increases the characteristic impedance of the signal conductors without increasing the thickness of the circuit board, without decreasing the width or thickness of the conductors and without using nonhomogeneous or nonstandard dielectrics. The circuit board provides the use of an increased range of impedance in signal conductors that permits the transfer of signals without degradation of the signal quality or loss of signal density, while providing an acceptable shielding capability.