Comparison of Microstrip, Coplanar, and SIW Interconnects on the Same 50µm-thick GaAs Chip

The design of interconnects is critical for the performance of mm-wave integrated circuits, especially for operations above 110GHz. However, a direct comparison of transmission lines by the same technology on the same substrate has been absent from the literature. This work presents the first comprehensive analysis of microstrip, grounded coplanar waveguide (GCPW), and substrate integrated waveguide (SIW) interconnects fabricated by the WIN PP10-20 technology on the same 50µm GaAs chip. We show that up to 200GHz, although the SIW exhibits the lowest loss per millimeter, the microstrip line has a lower loss per guided wavelength. This implies that the microstrip line may be better for compact impedance-matching networks while the SIW may be better for high-quality passives like power combiners, filters, and duplexers. These results help guide the design of next-generation transceivers at the D-band and higher frequencies.