  Multilayered structures consisting of alternating negative-permittivity and
dielectric layers are explored to obtain high-resolution imaging of
subwavelength objects. The peaks with the smallest |ky| (ky is the transverse
wave vector) on the transmission curves, which come from the guided modes of
the multilayered structures, can not be completely damped by material loss.
This makes the amplitudes of the evanescent waves around these peaks
inappropriate after transmitted through the imaging structures, and the imaging
quality is not good. To solve such a problem, the permittivity of the
dielectric layers is appropriately chosen to make these sharp peaks merge with
their neighboring peaks. Wide flat upheavals are then generated on the
transmission curves so that evanescent waves in a large range are transmitted
through the structures with appropriate amplitudes. In addition, it is found
that the sharp peaks with the smallest |ky| can be eliminated by adding
appropriate coating layers and wide flat upheavals can also be obtained.
