An SEM analysis of the voltage induced upon a printed strip antennaby a transient plane wave

The singularity expansion method (SEM) is applied to study the interaction of a transient electromagnetic plane wave with a printed strip antenna. In SEM, the time-domain response of the element is separated into excitation-independent natural resonances and modes, which have considerable physical significance, and closed-form coupling terms which can be rapidly evaluated as the geometric or temporal properties of the source change. The SEM is demonstrated as applied to the transient microstrip problem, and the effect of varying the properties of the printed circuit substrate over a range of values typically found in microstrip antenna applications is studied. The transient response due to a step and Gaussian excitation is studied. It is found that the level of transient signal induced on a printed element increases with increasing substrate permittivity. The shape of the induced voltage or current waveform is highly dependent on the geometric and temporal properties of the source for elements printed on relatively thin substrates, while, for elements printed on thicker substrates, the shape of the induced waveform is much less sensitive to the form of the excitation, and resembles the oscillation of the fundamental resonance of the antenna