planes as illustrated in fig3 and 5 this invention will not reduce the unwanted reflected signals to zero or even to an absolute minimum it is inherently impossible to exactly match the real dielectric constant of the non absorbent dielectric material to the complex dielectric constant of the absorbent material furthermore the reflection from the interface between the non absorbent and absorbent materials is a function of the angle of incidence of the wave the essence of this invention however is based on the fact that appropriate absorbent material reduces reflections this is of considerable benefit despite the fact that the reflections are not reduced to zero there are other ways to incorporate absorbent materials other than at the perimeter of the circuit board fig9 a and 9b respectively illustrate a circuit board scheme in which most of the dielectric material between two reference planes 41 consists of highly absorbent material 45 low loss dielectric material 46 is placed only in the immediate vicinity of vias 42 and strip lines 43 respectively this scheme has the advantage of providing more lossy material and tends to attenuate radial waves that will be launched from the vias before they reach the perimeter of the circuit board this approach therefore reduces the interaction between vias before reflection from the perimeter even occurs it is important to not bring the highly absorbent material too close to the strip lines 43 or the vias 42 else absorbent material will also attenuate the desired signals as they travel along the strip line interconnections a rough guide is to not allow the highly absorbent material 45 to approach by a distance that is closer than three times the width of the lines 43 and vias 42.