Microwave Modes

Microwave Modes of a Microstrip Line

Modes of Microwave Waveguides

FIMMWAVE can be used to solve the modes around electrical contacts even at microwave and RF frequencies. Results from these simulations can be used to calibrate our traveling wave electrode model found in circuit simulator PICWave for high speed modulators found in silicon, TFLN, III-V and more.

Electric field of fundamental mode for alumina substrate at a frequency of 1GHz.

Validation

In this example, the modes of various metalic microstrip lines are calculated with FIMMWAVE's complex mode solvers for frequencies ranging from 1 to 20GHz.

The geometry of the microstrip line is shown below.

The modes of the structure were calculated for three different kinds of substrate: alumina, gallium-arsenide and silicon. The dimensions of the structure are given in the following table.

Substrate	Alumina	Gallium Arsenide	Silicon
strip width (mm)	0.8698	0.664	0.7232
strip thickness (mm)	0.05	0.05	0.05
substrate thickness (mm)	0.9	0.9	0.9
substrate relative permittivity	9.9	12.9	11.9

The Ex (horizontal) and Ey (vertical) field profiles for the alumina waveguide at 1GHz are shown below.

Ex and Ey field profiles for the alumina-substrate microstrip line at a frequency of 1GHz.

Fundamental mode’s effective index spectrum for silicon substratestructure. Dataset highlighted in blue is the result computed in FIMMWAVE. Other results are taken from [1].

FIMMWAVE allows you to characterise the dispersion of the structure, and the evolution of the effective permittivity for the fundamental mode of the microstrip with frequency is plotted below. The data matches published values with very good accuracy [1].

Reference

[1] S. K. Sable, P. Gour, "Dispersion Analysis of a Microstrip Line at Higher Frequencies by using Sonnet and Matlab", 2011 International Confernece on Communication Systems and Network Technologies