A conventional bandpass filter will be described. The conventional bandpass filter as shown in FIG. 12 is formed of ring resonator 5a and ring resonator 5b disposed on a substrate (not shown). Ring resonator 5a is made up of pattern inductor 1a, resonance capacitor 2a connected in parallel with pattern inductor 1a, and input/output terminal 4a connected with the pattern inductor 1a via coupling capacitor 3a. Ring resonator 5b is made up of pattern inductor 1b, resonance capacitor 2b connected in parallel with pattern inductor 1b, and input/output terminal 4b connected with pattern inductor 1b via coupling capacitor 3b. 
In order to obtain electromagnetic coupling between ring resonator 5a and ring resonator 5b, a portion of pattern inductor 1a and a portion of pattern inductor 1b are arranged to oppose each other, whereby a bandpass filter is provided. As the first resonance capacitor 2a and the second resonance capacitor 2b, chip capacitors mounted on the substrate have so far been used.
In bandpass filters formed of ring resonators as described above, the resonance line, in general, is not grounded. Therefore, it is not possible for them to induce stray inductances and therefore have merit in that their circuits provide enhanced stability. Further, it is possible to provide attenuation poles on both sides of the center frequency so that greater attenuation can be obtained in the vicinity of the passband. Further, the insertion loss caused by the filter can be reduced as compared with that of a quarter-wave filter or a combline filter, which has its resonance line grounded.
However, in the bandpass filter configured as described above, the center frequency of passband deviates, due to variations of resonance chip capacitors 2a, 2b. For example, in a bandpass filter having a passband of 6 MHz, the center frequency of passband deviates approximately 50 MHz against the 6 MHz passband. When such a bandpass filter is to be applied, for example, to an intermediate frequency circuit in a tuner, it has been necessary to reduce the variations of the resonance capacitors prior to the mounting of the capacitors on a filter substrate. Therefore, it has been necessary to provide equipment and expense for sorting out of the resonance capacitors.