Patent ID: 7495531

Claim:
A filter containing plural resonators adjacent to each other, comprising: a first resonator and a second resonator which are arranged in proximity to each other in a first direction and each of which is fabricated on a substrate having a first region and a second region which are adjacent to each other in a second direction perpendicular to the first direction, the first region having a first width and the second region having a second width smaller than the first width, each of the first resonator and the second resonator comprising: a pair of first microstrip lines formed on the first region having the first width larger than the second width and juxtaposed in the first direction, each of the first microstrip lines having an open end and an other end, and a sum of widths of the first microstrip lines and a distance between the first microstrip lines being equal to the first width; and a second microstrip line formed on the second region having the second width smaller than the first width and connected between other ends of the pair of first microstrip lines, the second microstrip line having the second width smaller than the first width of the first region, wherein a minimum distance between one of the first microstrip lines of the first resonator adjacent to the second resonator in the first direction and one of the first microstrip lines of the second resonator that is adjacent to the one of the first microstrip lines is set at a value smaller than a minimum distance between the second microstrip line of the first resonator and the second microstrip line of the second resonator that is adjacent to the second microstrip line of the first resonator.