Full-wave analyses of composite-metal multidielectric lossy microstrips

The full-wave mode-matching method is extended to analyze composite-metal multidielectric microstrips commonly used in monolithic microwave integrated circuits (MMICs). The theoretical data obtained by the present approach agree favorably with the available experimental data for GaAs-SiN-Ti-Au finite-width, composite-metal, and multidielectric microstrips. Specifically, the case of a microstrip line with composite-metal Ti-Au configuration on multidielectric GaAs-SiN layers, where ground plane conductor loss is also considered, is analyzed. The effect of the thickness of the Ti layer (t/sub 2/) on the dominant-mode complex propagation constant is plotted against a fixed-thickness SiN layer (d/sub 1/) of 2000 AA at 1 GHz and 70 GHz, and 50 GHz, respectively. The results of the total loss alpha computed using a simplified analysis technique are compared to results of the full-wave analysis. It is noted that as the frequency is increased to 50 GHz or even higher, the simplified analysis overestimates the total loss alpha because the currents on the edges of Ti and Au metal layers can no longer be neglected.<>