Surface acoustic wave device improved in convolution efficiency, receiver using it, communication system using it, and method for producing surface acoustic wave device improved in convoluting efficiency

A surface acoustic wave device, comprising:

• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• wherein said substrate has a roughness configuration on a back face thereof and said roughness configuration is formed by grinding said back face with an abradant of a grit number N satisfying the following relation:
• ##EQU6## where .lambda..sub.B is a wavelength of bulk waves of convolution output taken out of said output electrode.

A method for producing a surface acoustic wave device which comprises:

• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• said method having a step of forming a roughness configuration on a back face of said substrate so that a maximum depth of the roughness configuration is not less than a wavelength of bulk waves of convolution output taken out of said output electrode.

A method for producing a surface acoustic wave device which comprises:

• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• said method having a step of grinding a back face of said substrate with an abradant,
• wherein said grinding is carried out using the abradant of a grit number N satisfying the following relation:
• ##EQU7## where .lambda..sub.B is a wavelength of bulk waves of convolution output taken out of said output electrode.

A receiver for receiving a spread spectrum signal, comprising a surface acoustic wave device for obtaining a correlation output between a spread code signal and a reference spread code signal input thereinto, said surface acoustic wave device comprising:

• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• wherein said substrate has a roughness configuration on a back face thereof and a maximum depth of said roughness configuration is not less than a wavelength of bulk waves of convolution output taken out of said output electrode.

A receiver for receiving a spread spectrum signal, comprising a surface acoustic wave device for obtaining a correlation output between a spread code signal and a reference spread code signal input thereinto, said surface acoustic wave device comprising:

• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• wherein said substrate has a roughness configuration on a back face thereof and said roughness configuration is formed by grinding said back face with an abradant of a grit number N satisfying the following relation:
• ##EQU8## where .lambda..sub.B is a wavelength of bulk waves of convolution output taken out of said output electrode.

A communication system for communication using a spread spectrum signal, comprising:

• a transmitter for spectrum-spreading a signal to be transmitted and outputting the spread signal;
• and
• a receiver for receiving the spread spectrum signal, said receiver comprising a surface acoustic wave device for obtaining a correlation output between a spread code signal and a reference spread code signal input thereinto, said surface acoustic wave device comprising:
• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• wherein said substrate has a roughness configuration on a back face thereof and a maximum depth of said roughness configuration is not less than a wavelength of bulk waves of convolution output taken out of said output electrode.

A communication system for communication using a spread spectrum signal, comprising:

• a transmitter for spectrum-spreading a signal to be transmitted and outputting the spread signal;
• and
• a receiver for receiving the spread spectrum signal, said receiver comprising a surface acoustic wave device for obtaining a correlation output between a spread code signal and a reference spread code signal input thereinto, said surface acoustic wave device comprising:
• a substrate having piezoelectricity;
• at least two input electrodes, provided on said substrate, for exciting first and second surface acoustic waves;
• and
• an output electrode for taking a convolution signal of said two surface acoustic waves out;
• wherein said substrate has a roughness configuration on a back face thereof and said roughness configuration is formed by grinding said back face with an abradant of a grit number N satisfying the following relation:
• ##EQU9## where .lambda..sub.B is a wavelength of bulk waves of convolution output taken out of said output electrode.