Finline Basics: Advantages and Disadvantages

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

Finline supports a combination of both TE and TM modes instead of just a quasi-TEM mode. Due to less dispersion, a wider bandwidth and high Quality factor can be achieved compared to microstrip lines. It typically operates from 25 to 100GHz, with a loss of about 0.1 dB/wavelength. The finline construction is shown in the figure above.

It offers a higher characteristic impedance, on the order of about 20 to 400 Ohms. Higher losses can be compensated for by using a ridged waveguide of the same size as the finline. There are two main variants of finline: 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
• The guide wavelength in finline is greater than the guide wavelength in microstrip line.

Disadvantages of Finline

• Assembly is relatively complex.
• Fabrication is costlier.