Patent ID: 7924118

Claim:
A duplexer comprising: a transmission elastic wave filter; a reception elastic wave filter; and a laminated substrate on which the transmission elastic wave filter and the reception elastic wave filter are provided; wherein the transmission elastic wave filter includes a first piezoelectric substrate, a first filter unit provided on the first piezoelectric substrate, and a transmission output pad provided on a bottom surface of the first piezoelectric substrate and connected to the first filter unit; the reception elastic wave filter includes a second piezoelectric substrate, a second filter unit provided on the second piezoelectric substrate, an unbalanced pad, and first and second balanced pads, the unbalanced pad and the first and second balanced pads being provided on a bottom surface of the second piezoelectric substrate and connected to the second filter unit; the second filter unit comprises: a first longitudinally-coupled filter device including at least one first IDT having one end connected to the unbalanced pad, and a second longitudinally-coupled filter device including at least one second IDT having one end connected to the unbalanced pad, in which a phase of an output signal relative to an input signal is different by 180 degrees from the phase of an output signal relative to an input signal in the first filter device; a first ground pad to which another end of the at least one first IDT is connected; and a second ground pad to which another end of the at least one second IDT is connected; the laminated substrate comprises: first and second ground lands electrically connected to the first and second ground pads, respectively, a common land electrically connected to the transmission output pad and the unbalanced pad, and a common ground electrode to which the first and second ground lands are commonly connected; a first inductance component connected between the first ground land and the common ground electrode; a second inductance component connected between the second ground land and the common ground electrode; and a coil connected between the common land and the common ground electrode; and a distance between the second ground pad and the coil is greater than a distance between the first ground pad and the coil, and the second inductance component is less than the first inductance component.