Surface elastic wave filter having finger omitted transducers to eliminate side lobes

A surface elastic wave filter which can substantially eliminate side lobes, comprising:

• a plurality of input interdigital transducers connected in parallel to each other and disposed on a substrate for receiving in parallel a high-frequency input signal and in response to said high frequency input signal generating a surface elastic wave to be propagated along said substrate;
• a plurality of output interdigital transducers connected in parallel to each other and disposed on said substrate for respectively producing respective output signals derived from the surface elastic wave generated in response to said input signal, said respective output signals when combined having predetermined frequency characteristics;
• each of said plurality of input interdigital transducers and each of said plurality of output interdigital transducers comprising a pair of spaced apart connectors disposed on said substrate and facing each other, each connector having a plurality of spaced apart electrode fingers extending therefrom at predetermined positions, so that the electrode fingers from each respective pair of connectors are arranged in an interdigitated configuration;
• said plurality of input interdigital transducers including a plurality of finger-omitted input interdigital transducers with electrode fingers omitted therefrom at preselected ones of said predetermined positions, said preselected ones of said predetermined positions being different in at least two of said finger-omitted input interdigital transducers;
• and
• said plurality of output interdigital transducers including a plurality of finger-omitted output interdigital transducers with electrode fingers omitted therefrom at preselected ones of said predetermined positions, said preselected ones of said predetermined positions being different in at least two of said finger-omitted output interdigital transducers.

A surface elastic wave filter which can substantially eliminate side lobes, comprising:

• a plurality of input interdigital transducers connected in parallel to each other and disposed on a substrate for receiving in parallel a high-frequency input signal and in response to said high frequency input signal generating a surface elastic wave to be propagated along said substrate;
• a plurality of output interdigital transducers connected in parallel to each other and disposed on said substrate for respectively producing respective output signals derived from the surface elastic wave generated in response to said input signal, said respective output signals when combined having predetermined frequency characteristics;
• each of said plurality of input interdigital transducers and each of said plurality of output interdigital transducers comprising a pair of spaced apart connectors disposed on said substrate and facing each other, each connector having a plurality of spaced apart electrode fingers extending therefrom at predetermined positions, so that the electrode fingers from each respective pair of connectors are arranged in an interdigitated configuration;
• and
• said plurality of output interdigital transducers including a plurality of finger-omitted output interdigital with electrode fingers omitted therefrom at preselected ones of said predetermined positions, said preselected ones of said predetermined positions being different in at least two of said finger-omitted interdigital transducers.