Transient coupling analysis using the singularity expansion method

The problem of electromagnetic coupling between objects has been extensively studied within the context of continuous-wave (CW) signals. The problem of coupling between objects for transient excitation has not received as much attention. This paper addresses the problem of transient coupling using the singularity expansion method (SEM). Specifically, the proper physical interpretation of the SEM modes of a system of objects is discussed within the context of observed transient surface currents and scattered fields. It is seen that the SEM modes of the system of objects are global quantities and hence have no clear physical interpretation prior to times when global modes can be established. It is also apparent that the early-time response of the system can be expressed using the SEM modes of the individual objects for some time periods. These observations are important for the effective use of target identification schemes based on natural resonance phenomena in multiple target situations as well as the proper use of SEM in EMC coupling analyses.