Slotted ground transmission line

Here a method to design transmission lines with controlled characteristic impedance in the highly dense design requirement is presented. In this method a transmission line is designed as a slow-wave synthetic line by repeatedly disturbing either the signal or the return current by adding slots in the grounds over or under the line of interest. To verify the method we have designed and fabricated transmission lines with slots in groundplane and compared them with a typical coplanar strip line in the same process. Both types of transmission lines are having same width and length in same metal layer. However unlike the typical design, the slotted-ground transmission requires no additional metal layer. From the measurement results, the slotted transmission lines reached the targeted impedance of approximately 50 Ohm and shows same level of loss of 0.8 dB and cross coupling to a common microstrip line of -78 dB at 2 GHz as of the typical design.