Types of Leaky Dominant Modes and Spectral Gaps on Printed-Circuit Lines
Not long ago it was generally believed that the dominant mode on open printed-circuit transmission lines would be purely bound at all frequencies. Now we know that, for most such lines, the dominant mode is purely bound at low frequencies, in agreement with common perception, but becomes leaky above a critical frequency. For certain lines, however, the behavior is different; for example, the dominant mode on conductor-backed slot line or coplanar waveguide of infinite width is leaky at all frequencies, whereas for microstrip line there is an additional dominant mode, which is leaky at high frequencies but nonphysical at low frequencies. It is important to know when leakage may occur because the presence of leakage can lead to power loss, crosstalk, and package effects which would deteriorate circuit performance.
KeywordsSurface Wave Dispersion Curve Dominant Mode Strip Width Microstrip Line
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