JPH08307202A - Surface acoustic wave device and communication equipment using it - Google Patents

Abstract

PURPOSE: To obtain the surface acoustic wave device easily detecting a convolution output signal by improving isolation between input and output. CONSTITUTION: The surface acoustic wave element has a surface acoustic wave element with input electrodes 2, 3 stimulating 1st and 2nd surface acoustic waves and an output electrode 5 extracting a convolution electric signal of two surface acoustic waves produced by the nonlinear effect on a piezoelectric substrate 1, input external circuits 10a-12b connecting to the input electrodes 2, 3 and output external circuits 13-15 connecting to the output electrode 5. The output external circuits 13-15 are arranged on a rear side opposite to a front side of the substrate 1 on which the input external circuits 10a-12b are arranged to isolate electrically and spatially the input external circuits 10a-12b and the output external circuits 13-15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses surface acoustic waves to
The present invention relates to a surface acoustic wave device that extracts a convolution output of two input signals as an electric signal, and a communication device using the same.

[0002]

2. Description of the Related Art A surface acoustic wave device using a surface acoustic wave convolver for extracting a convolution output of two input signals by using a surface acoustic wave signal has been increasing in importance in recent years and is being actively studied. .

FIG. 5 is a schematic view showing such a conventional surface acoustic wave device.

In the figure, 1 is a piezoelectric substrate, and 2 and 3 are piezoelectric substrates 1.
Of the comb-shaped input electrodes 4a and 4b formed on the surface of the piezoelectric substrate 1, the output electrode formed on the surface of the piezoelectric substrate 1, the output bonding wires 6a and 7a, 7
b is an input lead pin, 8 is an output lead pin, 9 is a package stem, 10a and 10b are input side matching circuits, 1
1a and 11b are input filters, 12a and 12b are input amplifiers, 13 is an output matching circuit, 14 is an output filter, 15 is an output amplifier, 16 is a mounting substrate, and 17a and 1a.
7b is an input terminal and 18 is an output terminal.

In the present invention, the part constituted by the part numbers 1 to 9 is a surface acoustic wave convolver.

In practice, the package stem 9 has a sealing cap and is used in a hermetically sealed state, but it is omitted in the drawing.

The input / output electrodes of the surface acoustic wave convolver are made of a conductive material such as aluminum, and are usually formed directly on the surface of the piezoelectric substrate 1 using a photolithography technique.

In the surface acoustic wave convolver having such a structure, when an electric signal of carrier frequency ω is input to the comb-shaped input electrode 2, the surface acoustic wave is excited by the piezoelectric effect of the substrate. Similarly, when an electric signal of carrier frequency ω is input to the comb-shaped input electrode 3, surface acoustic waves are excited.

These two surface acoustic waves propagate in the opposite directions on the piezoelectric substrate 1 while being confined in the output electrode by the output electrode 5 acting as a waveguide.

When these two surface acoustic waves overlap on the output electrode 5, the convolution of these two surface acoustic waves (frequency 2) is caused by the physical nonlinear effect of the piezoelectric substrate 1.
ω) occurs. The convolution thus generated is taken out from the output electrode 5 as an electric signal.

The mechanism of such convolution is described in detail, for example, in "Shibayama," Application of surface acoustic waves ", Television, 30, 457 (1976)".

When the surface acoustic wave convolver as described above is used as a single electric component as a circuit element, the impedance of the comb-shaped input electrode (or output electrode) is normally connected to the comb-shaped input electrode portion (or output electrode portion). Matching circuits 10a and 10b (or 13) for equalizing the impedance of the external peripheral circuit to be generated, and a filter 11a for removing unnecessary waves other than the input (or output) signal
And 11b (or 14), amplifiers 12a and 12b (or 1) for amplifying the input (or output) signal
5) are connected to the outside of the input and output electrodes of the surface acoustic wave convolver and used.

In the present specification, the input side (or output side) matching circuit and the filter amplifier are collectively referred to as an input side (or output side) external circuit.

The surface acoustic wave convolver, the input side external circuit, and the output side external circuit are formed on the same mounting substrate 16.

[0015]

However, in the above conventional example, the signal level of the convolution output that can be taken out as an electric signal is 10 ^-5 to 1 of the input signal level.
It is extremely low, about 0 ^-6 , so that a part of the signal propagating in the input side external circuit propagates in the air and directly reaches the output side external circuit And caused a decrease in the isolation (separation) between the input and the output.

FIG. 6 shows an example of a frequency spectrum of an output signal when an electric signal having a carrier frequency ω is input to each input of a conventional surface acoustic wave device.

In the figure, (1) is the convolution output component (carrier frequency 2ω), and (2) is the input signal component (carrier frequency ω) due to the wraparound. The signal level of the input component (2) due to the wraparound is about 10 dB higher than the signal level of the convolution output component (1).

Since the input signal component due to the wraparound increases the noise floor of the convolution waveform, it becomes difficult to detect the convolution output signal.

In addition, among the signal components sneaking into the external circuit on the input side, a component having the same carrier frequency (2ω) as the convolution output component is also included, and this causes a time variation in the convolution waveform. It becomes difficult to detect the volume output signal.

Further, a bandpass filter connected to the output electrode in order to suppress the input signal component due to the wraparound is inevitably required to have a high performance, and in order to meet this requirement, the filter is of a multistage type. This complicates the design and increases the number of parts.

There are some problems as described above.

It is an object of the present invention to provide a surface acoustic wave device in which the convolution output signal can be easily detected by improving the isolation (separation) between the input and the output.

[0023]

The above object is to provide two input electrodes for exciting first and second surface acoustic waves on a piezoelectric substrate and convolution of two surface acoustic waves generated by a non-linear effect with an electric signal. A surface acoustic wave element having an output electrode to be taken out as an input terminal, two input side external circuits connected to the input electrode of the surface acoustic wave element, and one output side external circuit connected to the output electrode. In the surface acoustic wave device according to the present invention, the two external circuits on the input side and the external circuit on the output side are electrically shielded from each other.

For that reason, the output side external circuit is
The surface acoustic wave device, which is arranged on the back surface opposite to the surface of the substrate on which the input side external circuit is arranged, is used as the means.

Further, by individually covering the input side external circuit and the output side external circuit with a conductive material, the input side external circuit and the output side external circuit are electrically shielded from each other. The surface acoustic wave device, which is characterized in that

Further, the surface acoustic wave device is characterized in that the input side external circuit and the output side external circuit are respectively arranged on different substrates.

[0027]

According to the above-mentioned means of the present invention, a component of the sneak into the output of the input signal in which a part of the signal propagating through the input side external circuit propagates through the air and directly reaches the output side external circuit. Is suppressed by being electrically shielded,
Since the signal level of the input component that wraps around can be suppressed to be smaller than the level of the output signal, it becomes easy to detect the convolution output signal.

Further, it is not necessary to use a filter having a higher performance than the conventional one, which is provided on the outside of the output electrode side, and the filter design becomes easier accordingly. Further, since the number of parts constituting the filter can be reduced, the device can be downsized.

[0029]

Embodiments of the present invention will be described below.

[Embodiment 1] FIG. 1 is a schematic perspective view showing a first embodiment of a surface acoustic wave device according to the present invention.

In the figure, 1 is a piezoelectric substrate such as lithium niobate, 2 and 3 are comb-shaped input electrodes formed on the surface of the piezoelectric substrate 1, 4a and 4b are input bonding wires, and 5 is on the surface of the piezoelectric substrate 1. Formed on the output electrode, 6 is an output bonding wire, 7a and 7b are input lead pins, 8 is an output lead pin, and 9 is a package stem, 10a and 10
b is an input side matching circuit, 11a and 11b are input side filters, 12a and 12b are input side amplifiers, 13 is an output side matching circuit, 14 is an output side filter, 15 is an output side amplifier, 1
6 is a mounting substrate, 17a and 17b are input terminals, and 18 is an output terminal.

In the figure, the part constituted by the part numbers 1 to 9 is a surface acoustic wave convolver.

Although the package stem 9 actually has a sealing cap and is used in a hermetically sealed state, it is omitted in the drawing.

In this embodiment, as shown in FIG. 1, input side external circuits 10a, 11a, 12a and 10b, 11 are provided.
b and 12b are arranged and formed on the same surface of the mounting substrate 16, the output side external circuits 13, 14 and 15 are formed.
Are arranged and formed on the opposite surface, which is the back surface of the mounting substrate 16 opposite to the surface on which the input side external circuit is arranged.

The input / output electrodes of the surface acoustic wave convolver are made of a conductive material such as aluminum and are usually formed directly on the surface of the piezoelectric substrate 1 by using a photolithography technique.

In the surface acoustic wave convolver having such a structure, when an electric signal of carrier frequency ω is input to the comb-shaped input electrode 2, the surface acoustic wave is excited by the piezoelectric effect of the substrate. Similarly, when an electric signal of carrier frequency ω is input to the comb-shaped input electrode 3, surface acoustic waves are excited.

These two surface acoustic waves propagate in the opposite directions on the piezoelectric substrate 1 while being confined in the output electrode by the output electrode 5 acting as a waveguide.

When these two surface acoustic waves overlap on the output electrode 5, the convolution of these two surface acoustic waves (frequency 2) is caused by the physical nonlinear effect of the piezoelectric substrate 1.
ω) occurs. The convolution thus generated is taken out from the output electrode 5 as an electric signal. The output electrode 5 is the bonding wire 6 and the output lead pin 8
Is connected to the output side external circuits 13, 14, and 15 through.

Here, in the input side external circuit, a part of the signal propagating through the circuit is radiated into the air, but the output side external circuit is the surface of the mounting substrate 16 on which the input side external circuit is arranged. Since it has a structure arranged on the opposite surface which is the back surface on the opposite side, the signal radiated from the input side external circuit does not reach the output side external circuit,
It is possible to suppress the "wrapping of the input signal to the output side external circuit" and improve the isolation between the input and the output.

FIG. 2 shows a frequency spectrum of an output signal when an electric signal of carrier frequency ω is input to each input electrode of the surface acoustic wave device according to the present invention.

In the figure, (1) is the convolution output component (carrier frequency 2ω), and (2) is the input signal component (carrier frequency ω) due to the aforementioned wraparound. As compared with the conventional example shown in FIG. 6, the signal level of (2) is suppressed by about 13 [dB].

In this way, the level of the input signal component due to the wraparound can be suppressed smaller than the level of the convolution output signal, so that the convolution output signal can be detected easily.

Further, it is not necessary to use a filter having a higher performance than the conventional one, which is provided on the outside of the output electrode side, and the filter design becomes easier accordingly. Further, since the number of parts constituting the filter can be reduced, the device can be downsized.

In this embodiment, the input side external circuit is arranged on the front surface of the mounting board, while the output side external circuit is arranged on the rear surface of the mounting board. Not limited to this example, the output side external circuit may be arranged on a surface opposite to the surface on which the input side external circuit is arranged.

In this embodiment, the piezoelectric substrate is made of lithium niobate, but other piezoelectric substrates such as quartz, lithium tantalate, piezoelectric ceramics and non-piezoelectric substrates are used. Other piezoelectric substrates such as a piezoelectric film may be used.

Further, although the elastic convolver is used in this embodiment, another convolver such as an AE convolver may be used.

Further, in the present embodiment, the structure in which the convolution output is taken out from one place of the output electrode is shown, but the structure in which the outputs are taken out from a plurality of places may be used.

Further, in the present embodiment, the two-layer board in which the circuit pattern is formed only on the front and back surfaces of the board is used as the mounting board. You may use the multilayer substrate in which the pattern layer was formed.

[Embodiment 2] FIG. 3 is a schematic perspective view showing a second embodiment of the surface acoustic wave device according to the present invention. In this figure, the same members as those in FIG. 1 are designated by the same reference numerals.

Numerals 19a and 19b are metal caps for covering the input side external circuit, and 20 is a metal cap for covering the output side external circuit.

In the figure, the metal caps 19a and 19b for covering the input side external circuit and the metal cap 20 for covering the output side external circuit are shown in perspective for easy understanding of this embodiment.

The package stem 9 is actually a sealing cap and is used in a hermetically sealed state, but it is omitted in the drawing.

In the present embodiment, the input side external circuit 10
a, 11a, 12a and 10b, 11b and 12b, and metal caps 19a, 19b and 20 that cover the output side external circuits 13, 14 and 15 respectively are provided.

Here, in the input side external circuit, a part of the propagating signal is radiated into the air, but since the input side external circuit is covered by the metal wall, the signal is electrically shielded. , Is not radiated to the outside of the metal wall. Further, since the output side external circuit is also covered with the metal wall, it is possible to prevent the input signal radiated in the air from reaching the output side external circuit and improve the isolation between the input and the output. be able to.

That is, also in the present embodiment, as in the first embodiment, the level of the input signal component due to the sneak can be suppressed to be smaller than the level of the convolution output signal, so that the convolution output signal can be easily detected. Become. Further, it is not necessary to use a filter having a higher performance than the conventional one provided on the outside of the output electrode side, which facilitates the design of the filter. Further, since the number of parts constituting the filter can be reduced, the device can be downsized.

Further, in this embodiment, since the output side external circuit is covered with the metal wall, it is possible to prevent unnecessary signals other than the input signal radiated in the air from reaching the output side external circuit. , It becomes easy to detect the convolution output signal.

In the present embodiment, the input side external circuit and the output side external circuit are covered with a metal cap, but the present invention is not limited to the metal cap. For example, a conductive resin mold or a conductive resin may be used. It may be covered with a conductive substance such as a film or a non-conductive cap coated with a conductive film.

As such a metallic cap,
There are iron, nickel, kovar (alloy of iron, nickel, cobalt), etc., and as the conductive resin mold, a substance having conductivity in an epoxy-based, phenol-based, polyester-based resin, for example, silver, carbon, There are those formed by diffusing graphite, copper, etc., and the conductive film includes, for example, copper foil, silver foil, aluminum foil or polyester film coated with the above conductive resin, and is coated with a conductive film. Examples of the non-conductive cap that has been applied include, for example, plastic, epoxy-based, phenol-based, polyester-based resin, or other insulating material, and a conductive foil such as copper foil or aluminum foil attached thereto, or the conductive resin described above. Can be used.

Further, in the present embodiment, an example in which the input side external circuit and the output side external circuit are arranged on the same surface of the mounting board is shown, but the arrangement is not limited to this example, and for example, in the first embodiment. Thus, the output side external circuit may be arranged on a surface opposite to the surface on which the input side external circuit is arranged.

Further, in this embodiment, an example in which lithium niobate is used as the piezoelectric substrate is shown, but other piezoelectric substrates such as quartz, lithium tantalate, piezoelectric ceramics and non-piezoelectric substrates are formed. Other piezoelectric substrates such as a piezoelectric film may be used.

Further, although the elastic convolver is used in this embodiment, another convolver such as an AE convolver may be used.

Further, in the present embodiment, the structure in which the convolution output is taken out from one place of the output electrode is shown, but the structure in which the convolution output is taken out from a plurality of places may be used.

Further, in the present embodiment, the two-layer board in which the circuit pattern is formed only on the front and back surfaces of the board is used as the mounting board. You may use the multilayer substrate in which the pattern layer was formed.

[Embodiment 3] FIG. 4 is a schematic perspective view showing a third embodiment of the surface acoustic wave device according to the present invention. In this figure, the same members as those in FIG. 1 are designated by the same reference numerals.

Reference numeral 21 is a mounting board different from 16.

The package stem 9 is actually a sealing cap and is used in a hermetically sealed state, but it is omitted in the drawing.

In the present embodiment, the input side external circuit 10
a, 11a, 12a and 10b, 11b, 12b are provided on the mounting board 21, the output side external circuits 13, 14, 15 are provided on the mounting board 16, and so on.

Furthermore, in the present embodiment, the input side external circuit and the output side external circuit are provided on different mounting boards to separate the grounds, thereby eliminating the influence of the fluctuations of the respective ground potentials and convolution. It becomes easier to detect the output signal. Also in this embodiment, the first
Similar to the embodiment, the level of the input signal component due to the wraparound can be suppressed smaller than the level of the convolution output signal, so that the convolution output signal can be detected easily. Further, it is not necessary to use a filter having a higher performance than the conventional one provided on the outside of the output electrode side, which facilitates the design of the filter. Further, since the number of parts constituting the filter can be reduced, the device can be downsized.

In this embodiment, the mounting board 21 on which the input side external circuit is arranged is formed on the main surface of the mounting board 16 on which the output side external circuit is arranged. Vice versa, that is, the mounting board on which the output external circuit is arranged may be formed on the main surface of the mounting board on which the input side external circuit is arranged, and the mounting on which the input side external circuit is arranged. The board and the mounting board on which the output side external circuit is arranged may be different boards.

In this embodiment, the example in which the piezoelectric substrate is made of lithium niobate is shown. However, it is formed on other piezoelectric substrates such as quartz, lithium tantalate, piezoelectric ceramics and non-piezoelectric substrates. Other piezoelectric substrates such as a piezoelectric film may be used.

Further, this embodiment may be used in combination with the second embodiment.

Further, although the elastic convolver is used in this embodiment, another convolver such as an AE convolver may be used.

In the present embodiment, the structure in which the convolution output is taken out from one place of the output electrode is shown, but the structure in which the convolution output is taken out from a plurality of places may be used.

Further, in this embodiment, the two-layer board in which the circuit pattern is formed only on the front and back surfaces of the board is used as the mounting board, but the present invention is not limited to this, and the circuit is formed inside the board in addition to the front and back surfaces. You may use the multilayer substrate in which the pattern layer was formed.

[Embodiment 4] FIG. 7 is a block diagram showing an example of a communication system using the surface acoustic wave device as described above. In the figure, 40 indicates a transmitter. This transmitter performs spread spectrum modulation on a signal to be transmitted using a spread code, and transmits the signal from an antenna 401. The transmitted signal is received by the receiver 41 and demodulated. Receiver 4
1 is an antenna 411, a high frequency signal processing unit 412, a synchronization circuit 413, a code generator 414, a spread demodulation circuit 415,
It is composed of a demodulation circuit 416. The reception signal received by the antenna 411 is appropriately filtered and amplified by the high-frequency signal processing unit 412, and is output as it is as a transmission frequency band signal or as an appropriate intermediate frequency band signal. The signal is input to the synchronizing circuit 413. The synchronization circuit 413 is a signal output from the surface acoustic wave device 4131 described in the embodiment of the present invention and a modulation circuit 4132 that modulates the reference spread code input from the code generator 414 and the surface acoustic wave device 4131. Of the output signal from the high frequency signal processing unit 412 and the modulation circuit 4132. The surface acoustic wave device 4131 includes a signal processing circuit 4133 for processing the transmission signal and the spread code synchronization signal and the clock synchronization signal for the transmission signal to the code generator 414. The input signal is input and the convolution operation of the two input signals is performed. Here, when the reference spreading code input from the code generator 414 to the modulation circuit 4132 is a code obtained by time-reversing the spreading code transmitted from the transmission side, the surface acoustic wave device 41.
In 31, the correlation peak is output when the synchronization-specific spreading code component and the reference spreading code included in the received signal match on the waveguide of the surface acoustic wave device 4131. In the signal processing circuit 4133, the correlation peak is detected from the signal input from the surface acoustic wave device 4131, the deviation amount of the code synchronization is calculated from the time from the code start of the reference spread code to the output of the correlation peak, and the code synchronization is performed. The signal and clock signal are output to the code generator 414. After the synchronization is established, the code generator 414 generates a spread code having the same clock and spread code phase as the spread code on the transmission side. This spread code is input to the spread demodulation circuit 415, and the signal before spread modulation is restored. Since the signal output from the spread modulation / demodulation circuit 415 is a signal modulated by a generally used modulation method such as so-called frequency modulation or phase modulation, data demodulation is performed by the demodulation circuit 416 known to those skilled in the art.

[Embodiment 5] FIGS. 8 and 9 are block diagrams showing an example of a transmitter and a receiver of a communication system using the surface acoustic wave device as described above.

In FIG. 8, 501 is a serial-parallel converter for converting data input in series into n pieces of parallel data, and 5
02-1 to n are multiplier groups for multiplying each parallelized data and n spread codes output from the spread code generator,
Reference numeral 503 is a spreading code generator that generates n different spreading codes and spreading codes dedicated to synchronization, and 504 is a spreading code dedicated to synchronization output from the spreading code generator 503 and n pieces of multiplier groups 502-1 to 502-1. 505 that adds the outputs of the
Is a high frequency stage for converting the output of the adder 504 into a transmission frequency signal, and 506 is a transmission antenna.

Further, in FIG. 9, 601 is a receiving antenna, 602 is a high frequency signal processing section, 603 is a synchronizing circuit for capturing and maintaining synchronization with the spreading code and clock on the transmitting side, and 604 is a code input from the synchronizing circuit 603. A spreading code generator that generates n + 1 spreading codes and a reference spreading code that are the same as the spreading code group on the transmission side according to the synchronization signal and the clock signal, and 605 is a carrier reproduction spreading code output from the spreading code generator 604. And high-frequency signal processing unit 60
A carrier reproduction circuit for reproducing a carrier signal from the output of 2.
Reference numeral 606 is a baseband demodulation circuit that performs demodulation in the baseband using the output of the carrier reproduction circuit 605, the output of the high frequency signal processing unit 602 and the output of the spread code generator 604, and 607 is baseband demodulation. Circuit 60
6 is a parallel-to-serial converter that performs parallel-to-serial conversion of n pieces of parallel demodulated data, which are the outputs of 6.

In the above structure, on the transmission side, the input data is first converted by the serial-parallel converter 501 into n parallel data equal to the number of code division multiplexes. On the other hand, the spreading code generator 503 generates n + 1 pieces of spreading codes PN0 to PNn having the same code period but different from each other. Of these, PN0 is dedicated to synchronization and carrier reproduction, and is directly input to the adder 504 without being modulated by the parallel data. The remaining n spread codes are modulated by n parallel data in the multiplier groups 502-1 to 502-1 and input to the adder 504. The adder 504 linearly adds the n + 1 input signals and outputs the added baseband signal to the high frequency stage 505. The baseband signal is subsequently fed to the high frequency stage 5
At 05, it is converted into a high frequency signal having an appropriate center frequency and transmitted from the transmitting antenna 506. On the receiving side,
The signal received by the reception antenna 601 is appropriately filtered and amplified by the high frequency signal processing unit 602, and is output as it is as a transmission frequency band signal or as an appropriate intermediate frequency band signal. The signal is input to the synchronizing circuit 603. The synchronization circuit 603 processes the signals output from the surface acoustic wave device 6031 and the modulation circuit 6032 for modulating the reference spread code input from the code generator 604 and the surface acoustic wave device 6031 described in the embodiment of the present invention. , A signal processing circuit 6033 for outputting a spread code synchronization signal and a clock synchronization signal for the transmission signal to a spread code generator 604. The surface acoustic wave element 6031 includes a high frequency signal processing unit 6
The output signal from 02 and the output signal from the modulation circuit 6032 are input, and the convolution operation of the two input signals is performed. Here, the modulation circuit 60 from the code generator 604
If the reference spreading code input to 32 is a code obtained by time-reversing the synchronization dedicated spreading code transmitted from the transmitting side, the surface acoustic wave device 6031 has the synchronization dedicated spreading code component and the reference spreading code included in the received signal. A correlation peak is output when the code matches the waveguide of the surface acoustic wave device 6031. In the signal processing circuit 6033, the surface acoustic wave device 6
The correlation peak is detected from the signal input from 031,
The code synchronization deviation amount is calculated from the time from the code start of the reference spreading code to the correlation peak output, and the code synchronization signal and the clock signal are output to the spreading code generator 604.
After the synchronization is established, the spreading code generator 604 generates a spreading code group in which the clock and the spreading code phase match the spreading code group on the transmitting side. Of these code groups, the spread code PN0 dedicated to synchronization is input to the carrier reproduction circuit 605. The carrier reproduction circuit 605 despreads the reception signal converted to the transmission frequency band or the intermediate frequency band which is the output of the high frequency signal processing unit 602 by the synchronization-dedicated spreading code PN0 and reproduces the carrier wave in the transmission frequency band or the intermediate frequency band. As the configuration of the carrier reproducing circuit 605, for example, a circuit using a phase locked loop is used. The received signal and the spread code for synchronization PN0 are multiplied by the multiplier. After the synchronization is established, the clock and code phase of the synchronization-specific spreading code in the received signal and the reference synchronization-specific spreading code match, and the synchronization-specific spreading code on the transmitting side is not modulated with data. It is despread and carrier components appear in its output.
The output is then input to a bandpass filter, and only the carrier component is extracted and output. The output is then input to a well-known phase locked loop composed of a phase detector, a loop filter and a voltage oscillator, and a signal whose phase is locked to a carrier component output from the band pass filter from the voltage controlled oscillator. Is output as a reproduced carrier wave. The reproduced carrier wave is input to the baseband demodulation circuit 606. In the baseband demodulation circuit, a baseband signal is generated from the reproduced carrier wave and the output of the high frequency signal processing unit 602. The baseband signal is divided into n pieces and despreaded for each code division channel by the spreading code groups PN1 to PNn which are the outputs of the spreading code generator 604, and then data demodulation is performed. The parallel-serial converter 607 converts the demodulated n pieces of parallel demodulated data into serial data and outputs the serial data.

In this embodiment, binary modulation is used, but other modulation methods such as quadrature modulation may be used.

[0081]

As described above, according to the present invention, the two input electrodes for exciting the first and second surface acoustic waves on the piezoelectric substrate and the two surface acoustic wave capacitors generated by the nonlinear effect are connected. A surface acoustic wave element having an output electrode for extracting a volute as an electric signal, two input side external circuits connected to the input electrode of the surface acoustic wave element, and one output side external circuit connected to the output electrode. In a surface acoustic wave device including a circuit, a signal propagating in the input side external circuit by electrically shielding between the two input side external circuits and the output side external circuit, respectively. Is suppressed by being electrically shielded from the component of the sneak into the output of the input signal that propagates through the air and reaches the output side external circuit directly. Since the signal level of the input component can be suppressed to writing, to facilitate detection of the convolution output signal.

Further, it is not necessary to use a filter having a higher performance than the conventional one, which is provided on the outside of the output electrode side, and the filter design becomes easier accordingly. Further, since the number of parts constituting the filter can be reduced, the device can be downsized.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing a first embodiment of a surface acoustic wave device according to the present invention.

FIG. 2 is a diagram showing a frequency spectrum of a convolution output signal extracted from an output terminal when a signal having a carrier frequency ω is input to each input terminal of the surface acoustic wave device according to the present invention.

FIG. 3 is a schematic perspective view showing a second embodiment of the surface acoustic wave device according to the present invention.

FIG. 4 is a schematic perspective view showing a third embodiment of the surface acoustic wave device according to the present invention.

FIG. 5 is a schematic perspective view showing a conventional surface acoustic wave device.

FIG. 6 is a diagram showing a frequency spectrum of a convolution output signal extracted from an output terminal when a signal having a carrier frequency ω is input to each input terminal of a conventional surface acoustic wave device.

FIG. 7 is a block diagram showing an example of a communication system using the surface acoustic wave device of the present invention.

FIG. 8 is a block diagram showing an example of a transmitter of a communication system using the surface acoustic wave device of the present invention.

FIG. 9 is a block diagram showing an example of a receiver of a communication system using the surface acoustic wave device of the present invention.

[Explanation of symbols]

1 piezoelectric substrate such as lithium niobate 2,3 comb-shaped input electrodes formed on the surface of the piezoelectric substrate 1 4a, 4b input bonding wire 5 output electrode formed on the surface of the piezoelectric substrate 1 output bonding wire 7a, 7b Input lead pin 8 Output lead pin 9 Package stem 10a, 10b Input side matching circuit 11a, 11b Input side filter 12a, 12b Input side amplifier 13 Output side matching circuit 14 Output side filter 15 Output side amplifier 16 Mounting board 17a, 17b Input terminal 18 Output Terminals 19a, 19b Metal Cap Covering Input-side External Circuit 20 Metal Cap Covering Output-side External Circuit 21 Mounting Board 40 Transmitter 401 Transmitting Antenna 41 Receiver 411 Receiving Antenna 412 High-frequency Signal Processor 413 Synchronous Circuit 414 Code Generator 41 Spreading demodulation circuit 416 Demodulation circuit 501 Serial-parallel converters 502-1 to n for converting data input in series to n parallel data 503 Spreading code generator 504 Adder 505 High frequency stage 506 Transmission antenna 601 Reception Antenna 602 High-frequency signal processing unit 603 Synchronization circuit 604 Spreading code generator 605 Carrier recovery circuit 606 Baseband demodulation circuit 607 Parallel-serial converter

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takahiro Hachisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akane Yokota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Tadashi Eguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (9)

[Claims] 1. A piezoelectric substrate having two input electrodes for exciting first and second surface acoustic waves and two generated by a non-linear effect.
A surface acoustic wave element having an output electrode for taking out the convolution of two surface acoustic waves as an electric signal, an input side external circuit connected to the input electrode, and an output side external circuit connected to the output electrode. In the surface acoustic wave device having the above structure, the input side external circuit and the output side external circuit are electrically shielded from each other. 2. The surface acoustic wave device according to claim 1, wherein a signal propagating through the air from the input side external circuit and directly reaching the output side external circuit is shielded. 3. The elastic surface according to claim 1, wherein the output side external circuit is arranged on a back surface opposite to a substrate surface on which the input side external circuit is arranged. Wave device. 4. The board according to claim 1, wherein the board on which the input side and output side external circuits are arranged is a multi-layer board and has at least one ground layer. The surface acoustic wave device according to item 1. 5. The input-side external circuit and the output-side external circuit are individually covered with a conductive material to electrically shield the input-side external circuit and the output-side external circuit from each other. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave device is provided. 6. The conductive material for covering the external circuits on the input side and the output side is a metal shield cap,
The surface acoustic wave device according to claim 5, wherein the surface acoustic wave device is at least one of a conductive resin mold, a conductive film, and a non-conductive cap coated with a conductive film. 7. The surface acoustic wave device according to claim 1, wherein the input-side external circuit and the output-side external circuit are arranged on different substrates, respectively. 8. The input side external circuit and the output side external circuit are configured by at least one of a matching circuit, a filter, an amplifier, or a combination thereof, according to any one of claims 1 to 7. The surface acoustic wave device according to item 1. 9. A communication device comprising the surface acoustic wave device according to claim 1. Description: