Band-switchable surface acoustic wave antenna duplexer and mobile radio terminal

A surface acoustic wave antenna duplexer comprising a transmitter-line filter, a receiver-line filter and an antenna terminal, said transmitter-line filter and said receiver-line filter being connected in parallel with said antenna terminal as a common terminal;

• wherein at least one of said transmitter-line and receiver-line filters includes a top filter using the whole of a transmitter band or a receiver band as its pass band, a phase shift circuit, a surface acoustic wave resonator filter, and a transmitter or receiver terminal, said top filter, said phase shift circuit, said surface acoustic wave resonator filter and said transmitter or receiver terminal being disposed in this order viewed from said antenna terminal;
• and
• wherein said surface acoustic wave resonator filter includes at least one surface acoustic wave resonator and at least one additive capacitance or inductance, and a switching element is provided for varying a value of said capacitance or inductance so as to provide a function for varying a pass band frequency or an attenuation band frequency of said surface acoustic wave resonator filter;
• and
• wherein said phase shift circuit is constituted by at least one lumped-constant chip capacitance or coil inductance.