HIGH-FREQUENCY ELECTRICAL CIRCUITS ON A PLANAR LIGHTWAVE CIRCUIT PLATFORM

We investigated the propagation losses and the characteristic impedanc es Z(L) of coplanar waveguides (CPW's) and microstrip lines (MSL's) on a planar lightwave circuit (PLC)-platform formed on a silica /silicon substrate. The loss of the CPW's was 2.7 dB/cm at 10 GHz on the PLC-p latform with 30 mu m thick silica layer. Thus, a cm-order circuit of t his CPW is difficult to fabricate in the 10 Gb/s module. This is becau se the silicon substrate has a large loss tangent (tan delta). On the other hand, the loss of the MSL's, where a ground plane shielded the h igh loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz w ith 30 mu m thick polyimide. These lower loss MSL's on a PLC-platform can he applied to module operation at 10 Gb/s. Furthermore they have t he advantage that they are suitable for application to array device ci rcuits or circuits in a module where several devices are integrated be cause unlike CPW's the ground planes are not divided by signal lines o r DC bias lines. The structure of CPW's and MSL's on a PLC-platform wi th a Z(L) of 50 Omega was also studied in detail.