# US 5,353,304 A · Surface acoustic wave device, and demodulating apparatus and communication system using the surface acoustic wave device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,353,304 A - Document ID: US5353304A - Status: Granted - Kind: A - Application number: 08/183,255 - Filed: 1994-01-19 - Granted: 1994-10-04 - Earliest claimed: 1992-05-08 - Assignees: Canon Kabushiki Kaisha - Inventors: Norihiro Mochizuki - Web page: https://patentgrep.com/patent/US5353304A ## CPC - H03H 9/6406: {Filters characterised by a particular frequency characteristic} - H03H 9/14502: {Surface acoustic wave [SAW] transducers for a particular purpose} - H04B 1/70712: {with demodulation by means of convolvers, e.g. of the SAW type (SAW convolvers in general G06G7/195)} - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - H04B: TRANSMISSION ## Abstract In a surface acoustic wave device, there are arranged a piezoelectric substrate, an input electrode and an output electrode. The input electrode is formed on the substrate, and generates a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal. The output electrode is also formed on the substrate, and converts the surface acoustic wave to an electric signal. One of the input and output electrodes includes a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave. The other one of the input and output electrodes may comprise a pair of taps arranged at a predetermined distance in the propagation direction. The electrode including a plurality of taps or the electrode including a pair of taps satifies a predetermined relation established among a length between the taps, a transmission speed of the input signal, a propagation velocity of the surface acoustic wave and so forth. According to such a structure, two bits of the signal can be processed without a delay circuit. A demodulating device and a communication system respectively include the surface acoustic wave device so that a circuit structure can be simplified and that data can be reproduced with a high signal quality. ## Claims ### Claim 1 A surface acoustic wave device, said device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; and wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave. ### Claim 2 (depends on 1) A surface acoustic wave device according to claim 1, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 3 (depends on 1) A surface acoustic wave device according to claim 1, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 4 (depends on 1) A surface acoustic wave device according to claim 1, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 5 A surface acoustic wave device, said device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; and wherein one of said input and output electrodes comprises first and second electrodes which are arranged along a direction perpendicular to a propagation direction of the surface acoustic wave, said first and second electrodes respectively comprise a 2N number of taps (N is a natural number) which are equidistantly arranged in the propagation direction of the surface acoustic wave, said first electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side, said second electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side, and said first and second electrodes respectively satisfy an equation L+.DELTA.l=2V/A where L is a length of each of said first and second electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave. ### Claim 6 (depends on 5) A surface acoustic wave device according to claim 5, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 7 A demodulating device comprising: (a) a surface acoustic wave device for supplying a correlation signal based on an input signal modulated in accordance with data, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (b) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (c) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 8 (depends on 7) A demodulating device according to claim 7, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 9 (depends on 7) A demodulating device according to claim 7, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 10 (depends on 7) A demodulating device according to claim 7, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 11 (depends on 7) A demodulating device according to claim 7, wherein the input signal is a spread spectrum signal. ### Claim 12 A demodulating device comprising: (a) a surface acoustic wave device for supplying a correlation signal based on an input signal modulated in accordance with data, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises first and second electrodes which are arranged along a direction perpendicular to a propagation direction of the surface acoustic wave, said first and second electrodes respectively comprise a 2N number of taps (N is a natural number) which are equidistantly arranged in the propagation direction of the surface acoustic wave, said first electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side, said second electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side, and said first and second electrodes respectively satisfy an equation L+.DELTA.l=2V/A where L is a length of each of said first and second electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (b) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (c) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 13 (depends on 12) A demodulating device according to claim 12, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 14 (depends on 12) A demodulating device according to claim 12, wherein the input signal is a spread spectrum signal. ### Claim 15 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a surface acoustic wave device for supplying a correlation signal based on the signal received by said receiver circuit, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the received signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (d) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (e) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 16 (depends on 15) A communication system according to claim 15, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 17 (depends on 15) A communication system according to claim 15, wherein one of said input and output electrodes comprises a 2N number of taps (N is a natural number) and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 18 (depends on 15) A communication system according to claim 15, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 19 (depends on 15) A communication system according to claim 15, wherein the input signal is a spread spectrum signal. ### Claim 20 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a surface acoustic wave device for supplying a correlation signal based on the signal received by said receiver circuit, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the received signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises first and second electrodes which are arranged along a direction perpendicular to a propagation direction of the surface acoustic wave, said first and second electrodes respectively comprise a 2N number of taps (N is a natural number) which are equidistantly arranged in the propagation direction of the surface acoustic wave, said first electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side, said second electrode is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side, and said first and second electrodes respectively satisfy an equation L+.DELTA.l=2V/A where L is a length of each of said first and second electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (d) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (e) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 21 (depends on 20) A communication system according to claim 20, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 22 (depends on 20) A communication system according to claim 20, wherein the input signal is a spread spectrum signal. ### Claim 23 A demodulating device comprising: (a) a branching device for dividing a signal modulated in accordance with data into first and second input signals; (b) a first surface acoustic wave device for supplying a first correlation signal based on the first input signal divided by said branching device, said first surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side, and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (c) a second surface acoustic wave device for supplying a second correlation signal based on the second input signal divided by said branching device, said second surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side, and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (d) a first detection circuit for envelope-detecting the first correlation signal supplied from said first surface acoustic wave device to supply an output; and (e) a second detection circuit for envelope-detecting the second correlation signal supplied from said second surface acoustic wave device to supply an output; and (f) a comparator circuit for comparing the outputs supplied from said first and second detection circuits. ### Claim 24 (depends on 23) A demodulating device according to claim 23, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 25 (depends on 23) A demodulating device according to claim 23, wherein the input signal is a spread spectrum signal. ### Claim 26 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a branching device for dividing the signal received by said receiver circuit into first and second input signals; (d) a first surface acoustic wave device for supplying a first correlation signal based on the first input signal divided by said branching device, said first surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a 2N number of taps (n is a natural number) equidistantly arranged in a propagation direction of the surface acoustic wave, is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side, and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (e) a second surface acoustic wave device for supplying a second correlation signal based on the second input signal divided by said branching device, said second surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, is structured so that a signal polarity corresponding to the tap, which is the i-th one (i=1, 2, . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side, and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave; (e) a first detection circuit for envelope-detecting the first correlation signal supplied from said first surface acoustic wave device to supply an output; and (f) a second detection circuit for envelope-detecting the second correlation signal supplied from said second surface acoustic wave device to supply an output; and (g) a comparator circuit for comparing the outputs supplied from said first and second detection circuits. ### Claim 27 (depends on 26) A communication system according to claim 26, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 28 (depends on 26) A communication system according to claim 26, wherein the input signal is a spread spectrum signal. ### Claim 29 A surface acoustic wave device, said device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; and wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction, and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer. ### Claim 30 (depends on 29) A surface acoustic wave device according to claim 29, a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to the second tap. ### Claim 31 (depends on 29) A surface acoustic wave device according to claim 29, a signal polarity corresponding to said first tap is opposite to a signal polarity corresponding to the second tap. ### Claim 32 (depends on 29) A surface acoustic wave device according to claim 29, wherein each of said taps of said one electrode, and said first and second taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 33 A surface acoustic wave device, said device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second electrodes arranged in a direction perpendicular to the propagation direction, said first electrode comprises first and second taps arranged at a predetermined distance in the propagation direction, said second electrode comprises third and fourth taps arranged at a predetermined distance in the propagation diraction, and said first and second electrodes respectively satisfy an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer. ### Claim 34 (depends on 33) A surface acoustic wave device according to claim 33, wherein each of said taps of said one electrode, and said first, second, third and fourth taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 35 A demodulating device comprising: (a) a surface acoustic wave device for supplying a correlation signal based on an input signal modulated in accordance with data, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction, and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (b) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (c) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 36 (depends on 35) A demodulating device according to claim 35, wherein a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to the second tap. ### Claim 37 (depends on 35) A demodulating device according to claim 35, a signal polarity corresponding to said first tap is opposite to a signal polarity corresponding to the second tap. ### Claim 38 (depends on 35) A demodulating device according to claim 35, wherein each of said taps of said one electrode, and said first and second taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 39 (depends on 35) A demodulating device according to claim 35, wherein the input signal is a spread spectrum signal. ### Claim 40 A demodulating device comprising: (a) a surface acoustic wave device for supplying a correlation signal based on an input signal modulated in accordance with data, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with an input signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second electrodes arranged in a direction perpendicular to the propagation direction, said first electrode comprises first and second taps arranged at a predetermined distance in the propagation direction, said second electrode comprises third and fourth taps arranged at a predetermined distance in the propagation diraction, and said first and second electrodes respectively satisfy an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (b) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (c) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 41 (depends on 40) A demodulating device according to claim 40, wherein each of said taps of said one electrode, and said first, second, third and fourth taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 42 (depends on 40) A demodulating device according to claim 40, wherein the input signal is a spread spectrum signal. ### Claim 43 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a surface acoustic wave device for supplying a correlation signal based on the signal received by said receiver circuit, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the received signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction, and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (d) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (e) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 44 (depends on 43) A communication system according to claim 43, wherein a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to the second tap. ### Claim 45 (depends on 43) A communication system according to claim 43, wherein, wherein a signal polarity corresponding to said first tap is opposite to a signal polarity corresponding to said second tap. ### Claim 46 (depends on 43) A communication system according to claim 43, wherein each of said taps of said one electrode, and said first and second taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 47 (depends on 43) A communication system according to claim 43, wherein the input signal is a spread spectrum signal. ### Claim 48 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a surface acoustic wave device for supplying a correlation signal based on the signal received by said receiver circuit, said surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the received signal, said input electrode being formed on said substrate; and an output electrode for receiving the surface acoustic wave and supplying the correlation signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second electrodes arranged in a direction perpendicular to the propagation direction, said first electrode comprises first and second taps arranged at a predetermined distance in the propagation direction, said second electrode comprises third and fourth taps arranged at a predetermined distance in the propagation diraction, and said first and second electrodes respectively satisfy an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (d) a detection circuit for envelope-detecting the correlation signal supplied from said surface acoustic wave device to supply an output; and (e) a data judging circuit for judging the data based on the output from said detection circuit. ### Claim 49 (depends on 48) A communication system according to claim 48, wherein each of said taps of said one electrode, and said first, second, third and fourth taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 50 (depends on 48) A communication system according to claim 48, wherein the input signal is a spread spectrum signal. ### Claim 51 A demodulating device comprising: (a) a branching device for dividing a signal modulated in accordance with data into first and second input signals; (b) a first surface acoustic wave device for supplying a first correlation signal based on the first input signal divided by said branching device, said first surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction, a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to said second tap, and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (c) a second surface acoustic wave device for supplying a second correlation signal based on the second input signal divided by said branching device, said second surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises third and fourth taps arranged at a predetermined distance in the propagation direction, a signal polarity corresponding to said third tap is opposite to a signal polarity corresponding to said fourth tap, and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said third and fourth taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (d) a first detection circuit for envelope-detecting the first correlation signal supplied from said first surface acoustic wave device to supply an output; and (e) a second detection circuit for envelope-detecting the second correlation signal supplied from said second surface acoustic wave device to supply an output; and (f) a comparator circuit for comparing the outputs supplied from said first and second detection circuits. ### Claim 52 (depends on 51) A demodulating device according to claim 51, wherein each of said taps of said one electrode, and said first, second, third and fourth taps comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 53 (depends on 51) A demodulating device according to claim 51, wherein the input signal is a spread spectrum signal. ### Claim 54 A communication system comprising: (a) a transmitter for transmitting a signal modulated in accordance with data; (b) a receiver circuit for receiving the signal transmitted from said transmitter; (c) a branching device for dividing the signal received by said receiver circuit into first and second input signals; (d) a first surface acoustic wave device for supplying a first correlation signal based on the first input signal divided by said branching device, said first surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction, a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to said second tap and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (e) a second surface acoustic wave device for supplying a second correlation signal based on the second input signal divided by said branching device, said second surface acoustic wave device comprising: a piezoelectric substrate; an input electrode for generating a surface acoustic wave propagated in a predetermined direction, in accordance with the input signal, said input electrode being formed on said substrate; and an output electrode for converting the surface acoustic wave to an electric signal, said output electrode being formed on said substrate; wherein one of said input and output electrodes comprises a plurality of taps equidistantly arranged in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises third and fourth taps arranged at a predetermined distance in the propagation direction, a signal polarity corresponding to said third tap is opposite to a signal polarity corresponding to said fourth tap and said the other electrode satisfies an equation D=nV/A where D is a distance between center lines of said third and fourth taps in the propagation direction, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer; (e) a first detection circuit for envelope-detecting the first correlation signal supplied from said first surface acoustic wave device to supply an output; and (f) a second detection circuit for envelope-detecting the second correlation signal supplied from said second surface acoustic wave device to supply an output; and (g) a comparator circuit for comparing the outputs supplied from said first and second detection circuits. ### Claim 55 (depends on 54) A communication system according to claim 54, wherein each of said taps of said one electrode, and said first, second, third and fourth taps respectively comprise a comb electrode which includes at least one pair of electrode digits. ### Claim 56 (depends on 54) A communication system according to claim 54, wherein the input signal is a spread spectrum signal. ### Claim 57 A method for demodulating data by using a surface acoustic wave device comprising a piezoelectric substrate, an input electrode for generating a surface acoustic wave propagated in a predetermined direction in accordance with an input signal, said input electrode being formed on said substrate, and an output electrode formed on said substrate, wherein one of said input and output electrodes comprises a plurality of taps arranged equidistantly in a propagation direction of the surface acoustic wave and satisfies an equation L+.DELTA.l=2V/A where L is a length of one of said input and output electrodes in the propagation direction of the surface acoustic wave, .DELTA.l is a length of a space between said taps, A is a transmission speed of the input signal and V is a propagation velocity of the surface acoustic wave, said method comprising the steps of: generating the surface acoustic wave by inputting the input signal modulated in accordance with the data; converting the surface acoustic wave to an electric signal by said output electrode; and demodulating the data from the electric signal. ### Claim 58 (depends on 57) A method for demodulating data according to claim 57, wherein the step for demodulating data comprises a step for envelope-detecting the electric signal and a step for judging the data from the envelope-detected signal. ### Claim 59 (depends on 57) A method for demodulating data according to claim 57, wherein the input signal is a spread spectrum signal. ### Claim 60 (depends on 57) A method for demodulating data according to claim 57, wherein the input signal is a differential phase-shifted keyed signal. ### Claim 61 (depends on 57) A method for demodulating data according to claim 57, wherein one of said input and output electrodes comprises 2N taps (N is a natural number), and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2 . . . , N) counted from one side, is the same as a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 62 (depends on 57) A method for demodulating data according to claim 57, wherein one of said input and output electrodes comprises 2N taps (N is a natural number), and a signal polarity corresponding to the tap, which is the i-th one (i=1, 2 . . . , N) counted from one side, is opposite to a signal polarity corresponding to the (N+i)-th tap counted from the same side. ### Claim 63 (depends on 57) A method for demodulating data according to claim 57, wherein each of said taps comprises a comb electrode which includes at least one pair of electrode digits. ### Claim 64 A method for demodulating data by using a surface acoustic wave device comprising a piezoelectric substrate, an input electrode for generating a surface acoustic wave propagated in a predetermined direction in accordance with an input signal, said input electrode being formed on said substrate, and an output electrode formed on said substrate, wherein one of said input and output electrodes comprises a plurality of taps arranged equidistantly in a propagation direction of the surface acoustic wave, the other one of said input and output electrodes comprises first and second taps arranged at a predetermined distance in the propagation direction of the surface acoustic wave, and the other one of said input and output electrodes satisfies an equation D=nV/A where D is a distance between center lines of said first and second taps in the propagation direction of the surface acoustic wave, A is a transmission speed of the input signal, V is a propagation velocity of the surface acoustic wave and n is a positive integer, said method comprising the steps of: generating the surface acoustic wave by inputting the input signal modulated in accordance with the data; converting the surface acoustic wave to an electric signal by said output electrode; and demodulating the data from the electric signal. ### Claim 65 (depends on 64) A method for demodulating data according to claim 64, wherein the step for demodulating the data comprises a step for envelope-detecting the electric signal and a step for judging the data from the envelope-detected signal. ### Claim 66 (depends on 64) A method for demodulating data according to claim 64, wherein the input signal is a spread spectrum signal. ### Claim 67 (depends on 64) A method for demodulating data according to claim 64, wherein the input signal is a differential phase-shifted keyed signal. ### Claim 68 (depends on 64) A method for demodulating data according to claim 64, wherein a signal polarity corresponding to said first tap is the same as a signal polarity corresponding to said second tap. ### Claim 69 (depends on 64) A method for demodulating data according to claim 64, wherein a signal polarity corresponding to said first tap is opposite to a signal polarity corresponding to said second tap. ### Claim 70 (depends on 64) A method for demodulating data according to claim 64, wherein each of said taps of said one electrode, and said first and second taps of the other electrode respectively comprise a comb electrode which includes at least one pair of electrode digits.