  We develop two inverse scattering schemes for locating multiple
electromagnetic (EM) scatterers by the electric far-field measurement
corresponding to a single incident/detecting plane wave. The first scheme is
for locating scatterers of small size compared to the wavelength of the
detecting plane wave. The multiple scatterers could be extremely general with
an unknown number of components, and each scatterer component could be either
an impenetrable perfectly conducting obstacle or a penetrable inhomogeneous
medium with an unknown content. The second scheme is for locating multiple
perfectly conducting obstacles of regular size compared to the detecting EM
wavelength. The number of the obstacle components is not required to be known
in advance, but the shape of each component must be from a certain known
admissible class. The admissible class may consist of multiple different
reference obstacles. The second scheme could also be extended to include the
medium components if a certain generic condition is satisfied. Both schemes are
based on some novel indicator functions whose indicating behaviors could be
used to locate the scatterers. No inversion will be involved in calculating the
indicator functions, and the proposed methods are every efficient and robust to
noise. Rigorous mathematical justifications are provided and extensive
numerical experiments are conducted to illustrate the effectiveness of the
imaging schemes.
