Patent ID: 7619491

Claim:
An elastic wave duplexer comprising: a transmission filter unit including an elastic wave filter; a reception filter unit including an elastic wave filter; a common connection end commonly connecting one end of the transmission filter unit to one end of the reception filter unit; an impedance matching circuit unit disposed between the common connection end and a ground potential; a laminated board; a transmission filter chip flip-chip bonded onto the laminated board using a face-down method, the transmission filter chip including the transmission filter unit; and a reception filter chip flip-chip bonded onto the laminated board using a face-down method, the reception filter chip including the reception filter unit; wherein the transmission filter chip is a ladder filter including a first piezoelectric substrate, and the transmission filter chip includes an input terminal and an output terminal; the reception filter chip is a longitudinally coupled resonator type filter including a second piezoelectric substrate, and the reception filter chip includes first and second reception terminals and a reception input terminal; the laminated board includes a plurality of insulating layers, an interconnection pattern, and a matching circuit pattern defining an impedance matching circuit unit; the interconnection pattern is provided on the laminated board and includes first and second electrode lands to which the output terminal of the transmission filter chip and the input terminal of the reception filter chip are connected, respectively, and an antenna electrode land; the laminated board includes a first edge, a second edge located opposite the first edge, the transmission filter chip being disposed on one side of a center line extending in a direction between the first and second edges of the laminated board and passing through an approximate center of the laminated board, and the reception filter being disposed on the other side of the center line; the matching circuit pattern includes a plurality of conductor patterns, via hole conductors to electrically connect the plurality of conductor patterns, and a coil-shaped line provided on the plurality of insulating layers, one end of the matching circuit pattern being connected to the antenna electrode land, and the other end of the matching circuit pattern being connected to a ground potential; and in plan view an approximate center of the coil-shaped line is located on a side of the center line of the elastic wave duplexer on which the reception filter chip is disposed.