PURPOSE: To ensure the coupling with a circuit and to reduce the influence of an inductive reactance when the desired part of a circuit composed of a microstrip line is connected to ground with a metallic wire by providing a capacitance element provided on a ground conductor and inserted in series between a conductor wire and the ground conductor electrically to the resonator.

CONSTITUTION: A microstrip capacitor 30 is mounted on a ground conductor face 10 in the vicinity of the ground terminal of a microstrip resonator 24 so that one terminal of the capacitor 30 is connected electrically to the ground conductor 10. The other terminal of the microstrip capacitor 30 and a ground terminal of the microstrip resonator 24 are connected with a metallic wire 22. A coupling position 28 with other circuit element is decided in the vicinity of the ground terminal of the microstrip resonator 24. Thus, the inductive reactance by the metallic wire 22 is cancelled by the capacitive reactance of the chip capacitor 30 and the impedance at the coupling position 28 is brought into a state close to the short-circuit state.