Existence of a leaky dominant mode on microstrip line with an isotropic substrate: theory and measurement

The authors have found that a leaky dominant mode is present at higher frequencies on conventional microstrip line with an isotropic substrate. They have confirmed its existence both theoretically and experimentally. The leaky mode exists independently of, and in addition to, the customary bound dominant mode. This new mode leaks power away from the line into the TM/sub 0/ surface wave supported by the surrounding grounded substrate, and may be responsible for spurious microstrip performance at higher frequencies. This could have important implications for millimeter-wave circuits.<>