The Residual-Wave Current Excited on a Printed-Circuit Line: A Source of Spurious Effects

The excitation of a new type of current wave on printed-circuit lines by a practical source, such as a delta-gap source, is examined. This new type of current wave is called a residual-wave current, and corresponds to that portion of the continuous-spectrum current that is separate from the leaky-mode currents. A source on a printed-circuit line will excite bound modes, leaky modes, and one or more residual-wave currents. The residual-wave currents may be responsible for spurious transmissions effects. This is demonstrated by numerical calculations on stripline and microstrip, which account for the delta-gap source.