Design and Performance of Slow-wave Microstrip Lines in BiCMOS Technology

In this article, we present an innovative slow-wave line concept based on a recently published idea that we have simplified. This concept relies on the use of microstrip lines, making it highly suitable for the implementation of mixed microstrip and slow-wave circuits. Different configurations of layers in the considered CMOS technology have been investigated for better performance of the proposed slow-wave microstrip line. A slow-wave factor of 1.4 can be achieved, translating to length reduction factor of 40%. The width of the strips, for the same characteristic impedance of 50 Ω, is reduced by approximately a factor of 3, allowing for more aggressive meandering, leading to more compact layouts. The quality factor is about half of a conventional microstrip line having the same characteristic impedance, but remains significant beyond 100 GHz.