Modeling of shielded, suspended and inverted, microstrip lines

Electromagnetic simulation and modeling of suspended-substrate microstrip lines have an important role in designing microwave and millimeter- wave integrated circuits. Suspended- substrate microstrip lines are sometimes manufactured and placed in a shield to reduce performance degradation from external influences. In this paper, we will illustrate modeling of shielded, suspended-substrate, microstrip lines using the finite element method(FEM). We specifically determine the capacitance per unit length, inductance per unit length, and characteristic impedance of shielded, suspended, microstrip lines. We compared our results with those obtained by other methods and found them to be in agreement. We extended the modeling by designing our own model of shielded, inverted, microstrip lines and compared it with shielded, suspended, microstrip lines. We found them to be very close.

1. Introduction

During recent years, simulation of high performance systems such as in microwave integrated circuit packaging design, based on numerical methods in calculating the capacitance, inductance, and characteristic impedance has been essential in the electromagnetic field technology. Advances in integrated circuit technology have caused renewed interest in the computation of capacitance, inductance, or characteristic impedance of microstrip lines. Therefore, their computation has become important for designers. In this work, we focus on designing and modeling the transmission media of shielded, suspended and inverted, microstrip lines. We use finite-element method (FEM) in modeling the quasi-TEM mode analysis of microstrip transmission lines structure, because FEM is especially suitable for the computation of electric and electromagnetic fields in strongly inhomogeneous media. Also, it has high computation accuracy and fast computation speed.