Interdigital transducer, surface acoustic wave filter, and radio communication apparatus

An interdigital transducer comprising:

• a plurality of one-wavelength basic units of a single phase unidirectional transducer each having three electrode fingers within one wavelength;
• and
• a plurality of one-wavelength basic units of a bidirectional electrode each having four electrode fingers within said one wavelength,
• wherein said one-wavelength basic units are properly arranged according to a desired filter characteristic, and
• one of the three electrode fingers of each one-wavelength basic unit of said single phase unidirectional transducer is wider than the two other electrode fingers, and
• of the four electrode fingers of each one-wavelength basic unit of said bidirectional electrode, one pair of two fingers is interdigitated to the other pair of two fingers, and
• an adjustment section is provided between the one-wavelength basic units of said single phase unidirectional transducer and the one-wavelength basic units of said bidirectional electrode, and
• a bus bar electrode of the one-wavelength basic units of said single phase unidirectional transducer is connected by said adjustment section to a bus bar electrode of the one-wavelength basic units of said bidirectional electrode.