Description of the Related Art [0004] A typical lumped filter is now described with reference to FIGS. 14A and 14D. [0005]FIGS. 14A and 14B are a plan view and an equivalent circuit diagram of a lumped filter, respectively. [0006]FIG. 14A illustrates an alumina substrate 1, an input terminal 2, an output terminal 3, a ground electrode 4, spiral inductors 5 and 6, interdigital capacitors 7 to 11, a