A resonator, a filter, and a duplexer are provided which are capable of
very effectively suppressing the power loss caused by the edge effect, and
which allow a great reduction in the overall size to be achieved. Also, a
communication device including the above-mentioned filter or duplexer is
provided. A ground electrode is formed over the bottom surface of a
dielectric substrate, and a multiple spiral line pattern is formed on the
top surface thereof. A radial line pattern is further formed on this
surface with an insulation layer interposed therebetween. By thus
disposing the radial pattern adjacently to the multiple spiral resonator
constituted of the above-mentioned multiple spiral line, an electrostatic
capacitance is added to the multiple spiral resonator. This reduces the
occupation area of the resonator on the substrate, and improves the loss
reduction effect.
