IDEALIZED ELECTRIC- AND MAGNETIC-FIELD SENSORS BASED ON SPHERICAL SHEET IMPEDANCES
Carl E. Baum · Electromagnetics · 1989
This paper considers the response of electric- and magnetic-field sensors in terms of spherical modal expansions to identify the electric-and magnetic-dipole terms which are associated with the ideal angular response to an incident plane wave. Considering an idealized spherical resistive sheet sensor, the dipole surface current densities are computed and bandwidth and figure of merit determined to optimize the choice of Rs. For practical sensors the response in general includes various multipole terms besides the desired dipole terms. Expanding the response in terms of spherical harmonics allows one to identify the dipole term and from this gives one a definition of upper frequency response. In addition a norm over the unit sphere of the difference between the actual response and the ideal response gives another way to define upper frequency response. An example of a magnetic -sensor design which approximates the resistive-sheet sphere is also considered.