Finline Basics

This page covers Finline basics and provide advantages and disadvantages of Finline.


Finline supports combination of both TE and TM modes instead of quasi TEM mode. Due to less dispersion, wider bandwidth and high Quality factor can be achieved compare to microstrip lines.

It operates from 25 to 100GHz with loss of about 0.1 dB /wavelength. The finline construction is shown in the figure. It offers higher characteristic impedance on the order of about 20 to 400 Ohm. The higher losses can be compensated by using ridged waveguide of same size as of finline.

There are two variants of finline, viz. bilateral finline and antipodal finline.

Advantages of finline

•  Low dispersion
•  Broader bandwidth
•  compatible with standard devices and waveguides
•  moderate attenuation
•  As it produces circular fields, it can be used for isolator and circulator design
•  guide wavelength in finline is greater than guide wavelength in microstrip line.

Disadvantages of finline

•  assembly is relatively complex.
•  fabrication is costlier.


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