  A phase shift and sum (PSAS) algorithm to image objects in dispersive media
is presented. The algorithm compensates the phase shift of the scattered field
from the receiver to the source for each frequency component in an
ultrawideband (UWB) and then integrates all the frequency responses. This
method resolves the multispeed and multipath issue when UWB signals propagate
in dispersive media. In addition, a multipath effect due to refraction on a
curved boundary is also explored. By collecting data using a customized
microwave measurement system of two different objects placed in a plastic
graduated cylinder filled with glycerin, along the measured dielectric
parameters of glycerin (a dispersive medium), highquality reconstructed images
are formed using PSAS. Quantitative and qualitative comparisons with two other
traditional time-shift radar-based microwave imaging algorithms for the same
objects under test demonstrate the advantages of PSAS.
