Filter using film bulk acoustic resonator and transmission/reception switch

A duplexer comprising:

• a transmission port, reception port, and transmission/reception port;
• a transmission band filter which is connected between the transmission port and transmission/reception port and which includes a first circuit including a first series element constituted of a film bulk acoustic resonator and a first shunt element constituted of a film bulk acoustic resonator and which has a transmission frequency pass band;
• and
• a reception band filter which is connected between the reception port and transmission/reception port and which includes a second circuit including a second series element constituted of a film bulk acoustic resonator and a second shunt element constituted of a film bulk acoustic resonator and which has a reception frequency pass band,
• wherein the transmission port, reception port, transmission/reception port, transmission band filter, and reception band filter are formed using a common substrate, the substrate is a ceramic substrate and includes a patterned conductive film in at least an inner part, and a phase matching circuit formed using the patterned conductive film and connected to the port for transmission/reception, transmission band filter and reception band filter is disposed on the substrate.