Limited Conduction Band Thickness Of The Microstrip Line Electromagnetic Characteristics

Microstrip line is one of the most popular planar transmission lines in monolithic microwave integrated circuits and millimeter-wave integrated circuits. It's valuable for microwave circuit design to investigate the electromagnetic properties of microstrip lines with different structural parameters and working frequencies, for the propagation characteristics of microstip lines would behave differently under different conditions. Most research done before about its characteristics were based on the assumption that the strip has in finite thickness. Actually, the strip thickness can't be zero and would indeed influence the characteristics of a microstrip line, especially when the thickness is comparable to the skin depth. Hence, to analysis the effect of strip thickness has considerable value.Spectral-domain approach(SDA) is adopted in this paper to analyze the propagation characteristics of microstrip lines with finite conductor strip thickness after the comparasion between different analysis methods. First, a set of spectral Green's functions for multilayer structures is derived by SDI. Then, we use the modified SDA to get the governing equations of propagation constant. After that, two approximate models are proposed by considering the different current distribution in different frequency band. Finally, some examples of microstrip structures are analyzed to demonstrate the validity of the theory mentioned in this paper by compared with the simulation results in HFSS.