Novel on-chip high performance slow wave structure using discontinuous microstrip lines and multi-layer ground for compact millimeter wave applications

In this paper, a novel on chip slow wave structure is developed. It is built with discontinuous microstrip steps, the discontinuous line is made by placing a wide and short line and a narrow and short line in turn and the step discontinuity provides with additional inductance and capacitance. The slow wave transmission line structures were achieved through IBM 45 nm technology with multi-layer metals. Simulated and measured results for slow wave transmission line are provided in the paper for design with different characteristics impedances. Results have shown that the inductance per unit length and capacitance per unit length of the line increased about 50% compared with the conventional transmission line structure. In addition, the length effect of the wide and narrow signal sections is thoroughly studied and results have shown that the smaller the pitch, the better the slow wave effect which agrees with very well. A 75 GHz Branchline coupler built with the slow wave transmission lines has also been designed, and the coupler is 70% smaller than the conventional design.