Surface acoustic wave filter

The surface acoustic wave filter is provided with a distribution function and preferably a balance-unbalanced conversion function. Typically, in the three electrode vertical mode surface acoustic wave filter, a space between said second comb-like electrodes 305-1 provided with an outputting terminal of said first side interdigital transducer and said first comb-like electrodes 304-1 provided with an inputting terminal of said central interdigital transducer is different at one or odd number times of half wavelength ( lambda /2) from a space between said second comb-like electrodes 305-2 provided with an outputting terminal of said second side interdigital transducer and said first comb-like electrodes 304-1 provided with an inputting terminal of said central interdigital transducer, whereby one unbalanced input signal entering into said central interdigital transducer 304 is distributed through said side interdigital transducers into at least two output signals having balanced relation to each other with respect to phase.