Surface acoustic wave device and communication system using it

A signal receiver comprising:

• a circuit for receiving a modulated signal transmitted from a transmitter;
• a circuit for generating a reference signal;
• a surface acoustic wave device for outputting a convolution signal of the modulated signal and the reference signal;
• and
• a circuit for demodulating information, using the convolution signal output from the surface acoustic wave device;
• wherein said surface acoustic wave device comprises:
• a piezoelectric substrate having an anisotropy;
• first and second input transducers formed on said substrate and adapted for respectively generating surface acoustic waves corresponding to the modulated signal and the reference signal, each of said first and second input transducers being formed in an arcuate shape which causes an anisotropy in that propagation speeds of surface acoustic waves generated at respective portions of each of said arcuate first and second transducers differ from each other arcuate first and second transducers differ from each other due to the anisotropy of the piezoelectric substrate;
• an output transducer formed between said first and second input transducers on said substrate and adapted for obtaining a convolution signal of the modulated signal and the reference signal from a surface acoustic wave generated by nonlinear interaction of the surface acoustic waves generated by said first and second input transducers, said each of said first and second input transducers being concave toward said output transducer so that the surface acoustic waves generated by said arcuate first and second transducers are focused toward said output transducer;
• and
• a conductive film which is formed in at least one of between the output transducer and the first input transducer and between the output transducer and the second input transducer, on the substrate, for relieving the anisotropy of the propagation speeds of the surface acoustic waves generated by said input transducer.

A communication system comprising:

• a transmitter for transmitting a signal modulated according to information;
• a circuit for receiving the modulated signal transmitted from the transmitter;
• a circuit for generating a reference signal;
• a surface acoustic wave device for outputting a convolution signal of the modulated signal and the reference signal;
• and
• a circuit for demodulating the information, using the convolution signal output from the surface acoustic wave device;
• wherein said surface acoustic wave device comprises:
• a piezoelectric substrate having an anisotropy;
• first and second input transducers formed on said substrate and adapted for respectively generating surface acoustic waves corresponding to the modulated signal and the reference signal, each of said first and second input transducers being formed in an arcuate shape which causes an anisotropy in that propagation speeds of surface acoustic waves generated at respective portions of each of said arcuate first and second transducers differ from each other due to the anisotropy of the piezoelectric substrate;
• an output transducer formed between said first and second input transducers on said substrate and adapted for obtaining a convolution signal of the modulated signal and the reference signal from a surface acoustic wave generated by nonlinear interaction of the surface acoustic waves generated by said first and second input transducers, said each of said first and second input transducers being concave toward said output transducer so that the surface acoustic waves generated by said arcuate first and second transducers are focused toward said output transducer;
• and
• conductive films, one formed between the first input transducer and the output transducer and another between the second input transducer and the output transducer on said substrate, for relieving the anisotropy of the propagation speeds of the surface acoustic waves generated by said input transducer.

A method for obtaining a convolution signal, using a surface acoustic device comprising:

• a piezoelectric substrate having an anisotropy;
• first and second input transducers formed on said substrate and adapted for respectively generating surface acoustic waves corresponding to input signals, each of said first and second input transducers being formed in an arcuate shape which causes an anisotropy in that propagation speeds of surface acoustic waves generated at respective portions of each of said arcuate first and second transducers differ from each other due to the anisotropy of the piezoelectric substrate;
• an output transducer formed between said first and second input transducers on said substrate, said each of said first and second input transducers being concave toward said output transducer so that the surface acoustic waves generated by said arcuate first and second transducers are focused toward said output transducer;
• and
• a conductive film which is formed in at least one of between the output transducer and the first input transducer and between the output transducer and the second input transducer, on the substrate, for relieving the anisotropy of the propagation speeds of the surface acoustic waves generated by said input transducer;
• said method comprising steps of:
• inputting an input signal into each of the first and second input transducers;
• making the first and second input transducers respectively generate surface acoustic waves corresponding to the input signals;
• obtaining a convolution signal of said input signals from a surface acoustic wave generated by nonlinear interaction of the surface acoustic waves generated by said first and second input transducers;
• and
• outputting the convolution signal from the output transducer.

A method for performing communication, using a communication system comprising:

• a transmitter for transmitting a signal modulated according to information;
• a circuit for receiving the modulated signal transmitted from the transmitter;
• a circuit for generating a reference signal;
• a surface acoustic wave device for outputting a convolution signal of the modulated signal and the reference signal;
• and
• a demodulating circuit for demodulating the information, using the convolution signal output from the surface acoustic wave device;
• wherein said surface acoustic wave device comprises:
• a piezoelectric substrate having an anisotropy;
• first and second input transducers formed on said substrate and adapted for respectively generating surface acoustic waves corresponding to the modulated signal and the reference signal, each of said first and second input transducers being formed in an arcuate shape which causes an anisotropy in that propagation speeds of surface acoustic waves generated at respective portions of each of said arcuate first and second transducers differ from each other due to the anisotropy of the piezoelectric;
• an output transducer formed between said first and second input transducers on said substrate, said each of said first and second input transducers being concave toward said output transducer so that the surface acoustic waves generated by said arcuate first and second transducers are focused toward said output transducer;
• and
• a conductive film which is formed in at least one of between the output transducer and the first input transducer and between the output transducer and the second input transducer, on the substrate, for relieving the anisotropy of the propagation speeds of the surface acoustic waves generated by said input transducer;
• said method comprising steps of:
• transmitting a signal modulated according to information from the transmitter;
• receiving the modulated signal transmitted from the transmitter, by means of the receiving circuit;
• inputting the modulated signal received by the receiving circuit and the reference signal generated by the reference signal generating circuit into the first and second input transducers, respectively;
• obtaining a convolution signal of the modulated signal and the reference signal from a surface acoustic wave generated by nonlinear interaction of the surface acoustic waves generated by said first and second input transducers;
• outputting the convolution signal from the output transducer;
• and
• demodulating the information by the demodulating circuit from the convolution signal output from the output transducer.

A surface acoustic wave device comprising:

• a piezoelectric substrate having an anisotropy;
• an input transducer formed on said substrate and adapted for generating surface acoustic waves, said input transducer being formed in an arcuate shape which causes an anisotropy in that propagating speeds of surface acoustic waves generated at portions of said input transducer differ from each other due to the anisotropy of the piezoelectric substrate, said input transducer being concave toward a portion toward which the surface acoustic waves generated by said input transducer are focused;
• and
• a conductive film which is formed, on the substrate, a path through which the surface acoustic waves generated by said input transducer are focused, for relieving the anisotropy of the propagation speeds of the surface acoustic waves generated by said input transducer.