A microwave filter has resonator comprised of a cylindrical structure
having conductive walls filled with a dielectric material where the
cylindrical structure is recessed inside a multi-layered substrate. First
and second conductive coupling arms are disposed on a top layer of the
substrate for coupling signals to the cylindrical structure. The
conductive coupling arms are separated by a dielectric layer. The first
and second conductive coupling arms extend away from the center of the
cylindrical structure to form a microstrip line. The cylindrical
structure further comprises a bottom portion having a solid conductive
bottom plate perpendicular to the axis of the cylinder and a bottom
conductive ground layer separated from the conductive bottom plate by a
second dielectric layer.