  We propose a sampling type method to image scatterer in an electromagnetic
waveguide. The waveguide terminates at one end and the measurements are on the
other end and in the far field. The imaging function is based on integrating
the measurements and a known function over the measurement surface directly.
The design and analysis of such imaging function are based on a factorization
of a data operator given by the measurements. We show by analysis that the
imaging function peaks inside the scatterer, where the coercivity of the
factorized operator and the design of the known function play a central role.
Finally, numerical examples are provided to demonstrate the performance of the
imaging method.
