A Spectral-Domain Analysis of Periodically Nonuniform Microstrip Lines

Periodically nonuniform microstrip lines are analyzed on the basis of a numerical field calculation. Floquet´s theorem is used to express all field quantities in terms of their spatial harmonics, so that the problem can be treated similarly to the uniform microstrip line. The boundary-value problem for the microstrip line in an enclosure is formulated in a rigorous way and then solved using Galerkin´s method in the Fourier-transform domain. Numerical and experimental results are presented for a sinusoidal and a zigzag-shaped microstrip line.