JPH0974331A - Surface acoustic wave device and communication system using the same - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To improve the convolution efficiency by suppressing a higher-order transverse mode component in the excitation intensity of an arc-shaped comb-shaped input electrode near the focus where surface acoustic waves excited from the arc-shaped comb-shaped input electrode are gathered. The purpose is to improve. A surface acoustic wave device having at least one substantially arc-shaped comb-shaped input electrode for exciting a surface acoustic wave on a main surface of a piezoelectric substrate and at least one output electrode,
An acoustic lens is provided in a region between the arc-shaped comb-shaped input electrode and the output electrode. Further, the crossing width of the electrode fingers of the arc-shaped comb-shaped input electrode is formed wider than the crossing width represented by the opening angle determined by the waveguide width. In addition, the shape of the acoustic lens is characterized in that it is formed in a concave shape with respect to the arc-shaped comb-shaped input electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention utilizes the physical non-linearity effect of a piezoelectric substrate or a substrate in which a piezoelectric material is formed on a non-piezoelectric material to extract the convolution of two input signals as an output signal. The present invention relates to a surface acoustic wave element in which characteristics are effectively improved in a surface acoustic wave convolver, and a communication system using the same.

[0002]

2. Description of the Related Art Currently, surface acoustic wave (SAW) devices have been variously applied and researched. Among them, the surface acoustic wave convolver is a spread spectrum (SS) which has been attracting attention as a next-generation communication technology. ) It is becoming more and more important as a key device for communication.

This surface acoustic wave (SAW) is a surface acoustic wave that propagates on the surface of a propagation medium such as a piezoelectric substrate, and its energy is mostly contained within about one wavelength from the surface, and even with a relatively small input power. High-density elastic energy can be easily obtained, and the nonlinear effect becomes larger than that of the bulk wave, and its application as a communication device is expected.

As the nonlinear effect of this surface acoustic wave, harmonic generation, parametric mixing effect, parametric oscillation, direct current effect, convolution (Convolutio)
n) Effects and others are known, especially using surface acoustic waves
A surface acoustic wave device using a surface acoustic wave convolver for extracting convolution outputs of two input signals is a spread spectrum communication system (SS: Spread Spectrum Communicat
In recent years, its importance has been increasing and is being actively studied for application to signal processing devices such as ion).

FIG. 4 is a schematic view showing a conventional surface acoustic wave convolver. In the figure, 41 is a piezoelectric substrate made of Y-cut (Z-propagation) lithium niobate or the like, and 42 is an arc-shaped comb-shaped input electrode (I) formed on the surface of the piezoelectric substrate 41.
DT: Interdigital Transducer) 43 is a waveguide (output electrode) formed on the surface of the piezoelectric substrate 41.

The arc-shaped comb-shaped input electrode 42 and the electrode of the waveguide 43 are made of a conductive material such as aluminum, and are usually formed directly on the surface of the piezoelectric substrate 41 by using a photolithography technique.

In the surface acoustic wave device having such a structure,
When an electric signal having the carrier angular frequency ω is input to the two comb-shaped input electrodes 42, the surface acoustic wave is excited by the piezoelectric effect of the piezoelectric substrate 41. These two surface acoustic waves propagate in opposite directions on the piezoelectric substrate 41 while being confined in the output electrode 43 by the output electrode 43 acting as a waveguide.

The two surface acoustic waves thus propagating while being confined and colliding with each other on the waveguide 43 are the piezoelectric substrate 4.
Due to the physical nonlinear effect of 1, a convolution signal (carrier angular frequency 2ω) of two input signals is taken out from the output electrode 43.

That is, two surface acoustic waves are

[0010]

[Equation 1] Then, on the piezoelectric substrate 41, the product is obtained by nonlinear interaction.

[0011]

[Equation 2] Surface acoustic wave is generated. This signal is integrated in the output electrode length region L by providing a uniform output electrode,

[0012]

(Equation 3) Is taken out as a signal represented by. Here, the integration range L is substantially ± when the interaction length is sufficiently larger than the signal length.
If ∞, and τ = t- (x / v),

[0013]

(Equation 4) And the signal is a convolution of two input signals.

The mechanism of convolution and bulk wave as described above is described, for example, in "Surface acoustic wave element technology handbook" edited by Japan Society for the Promotion of Science, 150th Committee, Surface acoustic wave element technology, Ohmsha, Ltd., (1991), p145. ~ P
205, p371-p374 and the like.

Further, the arc-shaped comb-shaped input electrode 42 used in the above-mentioned conventional example can focus the excited surface acoustic wave on the end face of the waveguide 43, and is compared with the one having a regular comb-shaped input electrode shape. The surface acoustic wave energy density can be increased. Therefore, convolution efficiency (ratio between power P1 and P2 of input signal and output signal POUT = POUT
/ P1 · P2) can be increased.

The fact that the comb-shaped input electrode 42 is formed in an arc shape in this way means that the surface acoustic waves excited there are focused on the end face of the waveguide 43, and the surface acoustic wave energy density can be increased. At the focal position where the surface acoustic waves gather, the excitation distribution of the surface acoustic wave has not only the peak at the focal position but also the peaks having high excitation intensity of the surface acoustic waves on both sides thereof.

FIG. 5 is a simulation result showing the excitation distribution of the surface acoustic wave on the end face of the output electrode. The surface acoustic wave is excited by, for example, an arcuate comb-shaped input electrode, and the level of excitation intensity can be observed at the position where the surface acoustic wave is focused.

It can be seen that the 0th-order mode (fundamental mode) is excited in the central portion, and the higher-order transverse modes at the excitation intensity of the comb electrodes are excited on the left and right sides thereof.

[0019]

However, the surface acoustic wave convolver using the arc-shaped comb-shaped input electrodes as shown in the above-mentioned conventional example has the following problems, and it is necessary to solve them. is there.

That is, at the focal position where the surface acoustic waves gather, the excitation distribution of the surface acoustic waves not only has a peak at the focal position, but also has a peak having a high surface acoustic wave excitation intensity on both sides thereof. This is because surface acoustic waves with the same intensity distribution are excited at the intersections of the electrode fingers of the arc-shaped comb-shaped input electrode, so that the surface acoustic waves collected by the arc-shaped comb-shaped input electrode have a step function of near the focal position. This is because the intensity distribution of the Fourier image is shown.

The higher-order transverse mode of the Fourier image is not coupled with the waveguide mode of the waveguide (output electrode), which causes the convolution efficiency to decrease.

In order to solve the above problems, since the excitation distribution of the surface acoustic wave is changed in the electrode finger portion of the conventional arc-shaped comb-shaped input electrode, the outer side (end) is formed at the intersection of the arc-shaped comb-shaped input electrodes. Weakens the excitation intensity of the surface acoustic wave of
On the contrary, the inventors of the present invention have devised a method of apotizing (weighting) such as increasing the excitation intensity at the central portion of the intersection of the arc-shaped comb-shaped input electrodes (JP-A-7-142956).

However, in order to widen the band in the frequency characteristic, the number of pairs of electrode fingers of the arc-shaped comb-shaped input electrode cannot be increased, so that the effect of apodization was not obtained so much.

As another method, the excitation distribution of the surface acoustic wave at the focus position where the surface acoustic waves gather can be obtained by increasing the width of intersection of the electrode fingers in the arc-shaped comb-shaped input electrode.
Conventionally, there was only a peak at the focal position, and a peak with a high excitation intensity of surface acoustic waves generated on both sides of it, that is, a higher-order transverse mode component in the excitation intensity of the arc-shaped comb input electrode, was less likely to occur. . But,
The 0th-order mode (fundamental mode) at the focus position does not couple with the guided mode on the waveguide, and therefore, even if it enters the waveguide, it goes out.

As another method, a frequency-dispersive comb-shaped input electrode (transducer) is provided in the vicinity of the end face of the waveguide, and the comb-shaped input electrode is arranged so as to match the waveguide mode of the surface acoustic wave excited in the waveguide. There is an example in which a higher-order transverse mode in the excitation intensity at the focus position of a surface acoustic wave excited from a comb-shaped input electrode is suppressed by devising the shape (JP-A-60-6538).
1, USP No. First, it is difficult to match the phase and intensity of the surface acoustic wave in the vicinity of the output electrode end face with respect to a wide frequency band. In particular, a piezoelectric substrate having anisotropy is used. When used, it is very difficult to design a comb-shaped input electrode.

Secondly, the provision of the comb-shaped input electrode near the end face of the waveguide requires that the cross width of the comb-shaped electrodes be made small, which increases the impedance and makes it difficult to adjust the matching. Will end up.

[0027]

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface acoustic wave convolver using arcuate comb-shaped input electrodes.
An object of the present invention is to improve the convolution efficiency by suppressing higher-order transverse mode components in the excitation intensity of the arc-shaped comb-shaped input electrode near the focal point where surface acoustic waves excited from the arc-shaped comb-shaped input electrode are gathered.

According to the present invention, in a surface acoustic wave convolver using an arc-shaped comb-shaped input electrode, the crossing width of the electrode fingers of the arc-shaped comb-shaped input electrode is widened, and the end face between the waveguide and the arc-shaped comb-shaped input electrode is widened. This can be achieved by providing an acoustic lens in the area.

Specifically, the first and second layers are formed on the main surface of a piezoelectric substrate or a substrate in which a piezoelectric substance is formed on a non-piezoelectric substance.
At least two substantially arcuate comb-shaped input electrodes that excite the surface acoustic wave of
In a surface acoustic wave device having a waveguide and an output electrode for taking out convolution signals of two surface acoustic waves, an acoustic lens is provided in a region between the arc-shaped comb-shaped input electrode and the output electrode. .

According to the above structure, in the surface acoustic wave convolver using the arcuate comb-shaped input electrodes having the wide crossing width of the electrode fingers, the surface acoustic waves excited from the arcuate comb-shaped input electrodes are elastically deformed by the acoustic lens. At the focal position where the surface waves gather, the higher-order transverse mode components in the excitation intensity can be suppressed, and the crossing width of the electrode fingers of the arc-shaped comb-shaped input electrode is expressed by the aperture angle determined by the conventional waveguide width. Even if the width is wider than the crossing width, the 0th-order mode (fundamental mode) is not coupled with the waveguide mode on the waveguide and does not go out of the waveguide, so that the convolution efficiency can be improved. .

[0031]

Embodiments of the present invention will now be described in detail with reference to the drawings along with the operation of each embodiment according to the present invention.

<< First Embodiment >> FIG. 1 is a schematic view showing a first embodiment of a surface acoustic wave convolver according to the present invention.
In the figure, 11 is a Y-cut (Z-propagation) lithium niobate piezoelectric substrate, 12 is an arc-shaped comb-shaped input electrode formed on the surface of the piezoelectric substrate 11, and 13 is formed on the surface of the piezoelectric substrate 11. The waveguides (output electrodes) 14 are acoustic lenses provided in a region between the arcuate comb-shaped input electrode 12 and the end face of the waveguide 13.

The arc-shaped comb-shaped input electrode 12, the electrode of the waveguide 13 and the acoustic lens are made of a conductive material such as aluminum, and are usually formed on the surface of the piezoelectric substrate 11 by photolithography. It is directly formed by vapor deposition, sputtering or the like.

Further, in this embodiment, the cross width of the electrode fingers of the arc-shaped comb-shaped input electrode 12 is formed wider than the cross width represented by the opening angle determined by the conventional waveguide width. The acoustic lens 14 provided between the arc-shaped comb-shaped input electrode 12 and the end face of the waveguide 13 is formed in a concave shape with respect to the arc-shaped comb-shaped input electrode 12.

In the surface acoustic wave device having such a structure,
When an electric signal having a carrier angular frequency ω is input to the arc-shaped comb-shaped input electrode 12, surface acoustic waves are excited by the piezoelectric effect of the substrate, and the output electrode 13 acts as a ΔV / V waveguide, and the waveguide (output electrode). While being confined inside, they propagate in opposite directions on the piezoelectric substrate 11. Then, the two waves collide with each other on the output electrode 13 and are extracted from the output electrode 13 as a 2ω convolution signal due to the physical nonlinear effect of the piezoelectric substrate 11.

Here, the ΔV / V waveguide is intended to confine the surface acoustic wave to the short-circuited portion by lowering the propagation velocity of the surface acoustic wave as compared with the free surface by electrically short-circuiting the substrate surface. .

FIG. 2 is a simulation result showing an excitation intensity distribution of an arc-shaped comb-shaped input electrode having a wide intersection width in the present invention. In the figure, the one having the highest excitation intensity in the central portion is the 0th mode (basic mode).

From the results of the simulation shown in FIG. 2, the higher-order transverse modes in the excitation intensity of the comb-shaped electrode, which were conventionally generated on both sides of the 0th-order mode (fundamental mode), are suppressed, and only the 0th-order mode component is left. You can see that

From this fact, an arc type having an opening angle larger than the opening angle determined by the conventional waveguide width such that the surface acoustic wave is coupled with the waveguide mode of the waveguide (wide crossing width of the electrode fingers). Even if the comb-shaped input electrode is used, it is possible to suppress higher-order transverse mode components in the excitation intensity of the comb-shaped electrode.

FIG. 3 is an enlarged view of FIG. 1 showing the relationship between the arcuate comb-shaped input electrode and the acoustic lens.

In the figure, 31 is a Y-cut (Z-propagation) lithium niobate piezoelectric substrate, 32 is an arcuate comb-shaped input electrode formed on the surface of the piezoelectric substrate 31, and 33 is the piezoelectric substrate 31.
One end of the waveguide (output electrode) formed on the surface of
Reference numeral 34 is an acoustic lens provided in a region between the arc-shaped comb-shaped input electrode 32 and the end face of the waveguide 33.

As described above, the arc-shaped comb-shaped input electrodes 32,
The electrodes of the waveguide 33 and the acoustic lens 34 are made of a conductive material such as aluminum, and are usually formed directly on the surface of the piezoelectric substrate 31 by vapor deposition, sputtering or the like using a photolithography technique. The point O is the center of the arc of the arc-shaped comb-shaped input electrode 32, and the acoustic lens 34 is arranged in the region between the point O and the waveguide 33.

From FIG. 3, the surface acoustic wave excited from the arc-shaped comb-shaped input electrode 32 propagates to the acoustic lens 34 formed in a concave shape with respect to the arc-shaped comb-shaped input electrode 32, and the acoustic lens 34. Has a function corresponding to an optical light wave lens, and with respect to the propagation of a surface acoustic wave, as shown by the chain line in FIG. 3, it is refracted at its concave surface and focused at the end surface of the waveguide 33.

As a result, the 0th-order mode (fundamental mode) of the surface acoustic wave propagates to the waveguide 33, and the conventional waveguide width determines that the surface acoustic wave is coupled to the waveguide mode of the waveguide 33. The zero-order mode (basic mode) of the surface acoustic wave is obtained even when the arc-shaped input electrode 32 having a crossing width wider than the crossing width of the electrode fingers represented by the aperture angle is used.
Can be coupled with the guided mode on the waveguide 33 and does not go out of the waveguide 33.

As described above, the conventional waveguide width in which the 0th order mode (fundamental mode) of the surface acoustic wave propagates to the waveguide 33 and the surface acoustic wave is coupled to the waveguide mode of the waveguide 33. The arc-shaped input electrode 32 having a crossing width wider than the crossing width of the electrode fingers represented by the opening angle determined by is used, and the acoustic lens 34 is provided in the region between the arc-shaped input electrode 32 and the end face of the waveguide 33. By providing the high-order transverse mode component in the excitation intensity of the comb-shaped electrode, the acoustic lens 34 propagates the surface acoustic wave to the end facet 33 of the waveguide, and the 0th-order mode (basic mode) of the surface acoustic wave.
Is coupled with the guided mode on the waveguide 33, so that effects such as convolution efficiency improvement can be obtained.

Further, in this case, since it is not necessary to increase the number of pairs of the arc-shaped comb-shaped input electrodes 32 as compared with the conventional one, the band in the frequency characteristic of the convolver can be widened and the electrode fingers of the arc-shaped comb-shaped input electrode 32 can be widened. The impedance can be suppressed to a low level as much as the width of intersection of .times. Becomes wider, so that impedance matching becomes easier. The design of the arc-shaped comb-shaped input electrode 32 is also the same as that of the conventional one, and is therefore preferable from the viewpoint of ease of design.

The concave shape of the acoustic lens 34 used in the above embodiments is not limited to this, and may be any shape as long as the surface acoustic wave excited from the comb-shaped input electrode focuses on the end face of the waveguide. .

The acoustic lens used in the above embodiments is formed of a conductive material. However, an acoustic lens in which a surface acoustic wave excited from a comb-shaped input electrode focuses on the end face of the waveguide is also used. Any material can be used so long as it plays a role of.

Although the arc-shaped comb-shaped input electrode having a wide crossing width is used in the above-mentioned embodiment, the effect as shown in this embodiment can be obtained even if the crossing width is narrow.

In the above embodiment, an example in which electric signals of the same carrier angular frequency ω are input to the respective comb-shaped input electrodes of the surface acoustic wave convolver has been shown, but the carrier frequencies do not have to be the same and different carrier angular frequencies are used. May be input, the output signal obtained from the output electrode at that time is
It is the sum of the carrier angular frequencies of the input signal. For example, when the respective input angular frequencies are ω1 and ω2, the output angular frequency has a component of (ω1 + ω2).

In the examples, the surface acoustic wave convolver is used as an example, but if an arc-shaped comb electrode is used,
With respect to other surface acoustic wave elements such as a surface acoustic wave filter, a resonator, a matched filter, etc., it is possible to maintain the input impedance as usual and to obtain the same effect as described above with a small loss of surface acoustic wave energy.

Although a single electrode is used as the arc-shaped comb-shaped electrode in the above-described embodiments, a unidirectional double electrode, a double electrode using additional mass, a floating electrode, an apodized electrode, etc. may be used. The same effects as those shown in the examples can be obtained by using other unidirectional electrodes.

Although the piezoelectric substrate shown in the above embodiment uses Y-cut (Z-propagation) lithium niobate, other piezoelectric materials such as quartz, lithium tantalate, lithium borate, and other cuts. Oriented piezoelectric material may be used.

Further, in the above-mentioned embodiment, the surface acoustic wave element is of the elastic type, but the AE type is not limited to the elastic type.

The piezoelectric substrate shown in the above embodiments is not limited to that originally, but a substrate in which a piezoelectric substance is formed on a non-piezoelectric substance other than the piezoelectric substrate may be used.

<Second Embodiment> FIG. 6 is a block diagram showing an example of a communication system used as a surface acoustic wave element as described above, particularly as a surface acoustic wave convolver. In the figure, reference numeral 40 denotes a transmitting device. The transmitter 40 spread-spectrum modulates a signal to be transmitted using a spread code and transmits the signal from an antenna 401. The transmitted signal is
The signal is received by the receiving device 410 and demodulated. Receiver 41
0 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 synchronizing circuit 413 includes the surface acoustic wave element 4131 shown in the first embodiment of the present invention, a modulation circuit 4132 for modulating the reference spread code input from the code generator 414, and an elastic circuit. The signal processing circuit 4133 processes the signal output from the surface acoustic wave element 4131 and outputs a spread code synchronization signal and a clock synchronization signal for the transmission signal to the code generator 414. Surface acoustic wave element 4131
The output signal from the high frequency signal processing unit 412 and the output signal from the modulation circuit 4132 are input to the surface acoustic wave element 4131, and the convolution operation of the two input signals is performed. Here, from the code generator 414, the modulation circuit 4132
Assuming that the reference spreading code input to is a code obtained by time-reversing the spreading code transmitted from the transmitting side, in the surface acoustic wave element 4131 using the surface acoustic wave convolver element, the synchronization dedicated spreading code included in the received signal is used. Component and modulation circuit 413
The reference spreading code from 2 is the surface acoustic wave element 4131.
When they coincide with each other on the waveguide of the output electrode, the correlation peak is output.

At this time, in the surface acoustic wave element 4131, since the acoustic lens is added to the arc-shaped comb-shaped input electrode on the piezoelectric substrate, the surface acoustic wave propagates to the output electrode in a concentrated manner without loss. The convolution efficiency generated in the output electrodes can be remarkably improved, a high correlation peak output level can be obtained, and the impedances of both input electrode portions are held, so that the power loss is small and the power efficiency can be improved.

Next, the signal processing circuit 4133 detects the correlation peak from the signal input from the surface acoustic wave element 4131, and shifts the code synchronization in the time from the code start of the reference spreading code to the correlation peak output. The amount is calculated, and the code synchronization signal and the clock signal are output to the code generator 414.

After the synchronization is established, the code generator 414 generates a spread code in which the clock and the spread code phase match the spread code on the transmission side. This spreading code is a spreading demodulation circuit 41.
The signal before being input to the signal 5 and subjected to spread modulation is restored.
Since the signal output from the spread modulation / demodulation circuit 415 is a signal that has been modulated by a modulation method such as so-called frequency modulation (FSK: Frequency Shift Keying) or phase modulation (PSK: Phase Shift Keying), the corresponding demodulation circuit 41
6, data demodulation is performed.

The surface acoustic wave convolver, which is the surface acoustic wave element 4131 used in this configuration, uses an acoustic lens having a predetermined shape on the piezoelectric substrate to efficiently transfer the energy of the surface acoustic wave propagating on the piezoelectric substrate. Since it can be well propagated to the output electrode, a large convolution signal can be obtained.

<Third Embodiment> FIGS. 7 and 8 are block diagrams showing an example of a transmitter and a receiver of a communication system using the surface acoustic wave device described in the first embodiment.

In FIG. 7 showing a block diagram of the transmitting apparatus, 501 is a serial-parallel converter for converting serially input data into n parallel data, and 502-1 to n are parallelized data and spread. A multiplier group for multiplying n spread codes output from the code generator, 503 is n different spread codes PN1 to PNn and a spread code PN dedicated to synchronization.
A spreading code generator for generating 0, 504 is an adder for adding the synchronization dedicated spreading code PN0 output from the spreading code generator 503 and n outputs of the multiplier groups 502-1 to 502-n, 50
Reference numeral 5 is a high frequency stage for converting the output of the adder 504 into a transmission frequency signal, and 506 is a transmission antenna.

In FIG. 8 showing a block diagram of the receiving apparatus, 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 Synchronization circuit 60
A spreading code generator for generating n + 1 spreading codes and a reference spreading code, which are the same as the spreading code group on the transmission side, according to the code synchronization signal and the clock signal input from the reference numeral 3, and 605 is output from the spreading code generator 604. A carrier reproducing circuit for reproducing a carrier signal from the carrier reproducing spread code PN0 and the output of the high frequency signal processing unit 602, and 606 is an output of the carrier reproducing circuit 605, an output of the high frequency signal processing unit 602 and an output of the spread code generator 604. Some n spreading codes P
A baseband demodulation circuit that demodulates the baseband using N1 to PNn, and a parallel-serial converter 607 that parallel-serial converts n parallel demodulated data output from the baseband demodulation circuit 606.

In the above structure, on the transmission side, the input data is first converted into n parallel data equal to the number of code division multiplexes by the serial-parallel converter 501. 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, is not modulated by the parallel data, and is directly input to the adder 504. The remaining n spread codes PN1 to PNn are modulated by n parallel data in the multiplier groups 502-1 to 50n and input to the adder 504. The adder 504 linearly adds the input n + 1 signals and outputs the added baseband signal to the high frequency stage 505. Subsequently, the baseband signal is converted into a high-frequency signal having an appropriate center frequency in the high-frequency stage 505 and transmitted from the transmission antenna 506.

Next, on the receiving side, the signal received by the receiving antenna 601 is appropriately filtered and amplified by the high frequency signal processing section 602, and is output as it is as a transmission frequency band signal or as an appropriate intermediate frequency band signal. It The signal is input to the synchronization circuit 603. The synchronizing circuit 603 is the surface acoustic wave device 6031 described in the first embodiment of the present invention.
A modulation circuit 6032 for modulating the reference spread code input from the code generator 604, and a surface acoustic wave element 6031.
The signal processing circuit 6033 processes the signal output from the signal processing unit and outputs the spread code synchronization signal and the clock synchronization signal for the transmission signal to the spread code generator 604.

As the surface acoustic wave element 6031, the surface acoustic wave convolver element shown in the first embodiment is used, and the output signal from the high frequency signal processing section 602 and the signal from the modulation circuit 6032 are input to the two input terminals. A signal convolution operation is performed.

Here, the modulation circuit 60 is supplied from the code generator 604.
If the code string of the reference spreading code input to 32 is a code string obtained by time-reversing the synchronization-dedicated spreading code transmitted from the transmission side, the surface acoustic wave element 6031 has the synchronization-dedicated spreading code included in the reception signal. A correlation peak is output when the code string of the component and the code string of the reference spreading code match on the waveguide of the output electrode of the surface acoustic wave element 6031.

Next, in the signal processing circuit 6033, the correlation peak is detected from the signal output from the surface acoustic wave element 6031, and the code synchronization shifts in the time from the code start of the reference spreading code to the correlation peak output. The amount is calculated, and the code synchronization signal and the clock signal are output to the spread code generator 604.

After the synchronization is established, the spread code generator 604 generates a spread code group in which the clock and the spread code phase match with the spread code group on the transmission 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. .

The carrier reproducing circuit 605 has a structure using a phase locked loop, for example. The received signal and the synchronization-dedicated spreading code 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-specific synchronization-specific spreading code PN0 match, and the transmission-side synchronization-specific spreading code is not modulated with data. Is despread at, and a carrier component appears at the 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 consisting of a phase detector, a loop filter and a voltage controlled oscillator, and a phase is applied to a carrier component output from the voltage controlled oscillator through a bandpass filter. The locked signal is output as a reproduced carrier wave.

The reproduced carrier wave is input to the baseband demodulation circuit 606. The baseband demodulation circuit 606 generates a baseband signal 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 output from the spreading code generator 604, and subsequently data demodulation is performed. The parallel demodulated n demodulated data is converted into serial data by the parallel-serial converter 607, and the signal input to the transmission device is output.

Although the present embodiment is a case of binary modulation, other modulation methods such as quadrature modulation may be used. Further, the present invention can be applied to any of the DS (direct spread) method, the FH (frequency hopping) method, and the TH (time hopping) method in a spread spectrum communication system.

Further, in the above embodiment, an example in which the transmission device and the reception device are separated into a communication system has been described.
Both devices can be stored in the same package as a communication device. Further, in the case of the communication device, mutual communication can be performed by changing the codes of the used code strings. In that case,
A transmitter and a receiver are provided in the same package, and the same carrier is used by differentiating the spreading code for synchronization, and the communication device has almost the same configuration and is capable of communicating with other communication devices. is there. Further, since the above-mentioned surface acoustic wave element is used for the receiving device, the establishment of synchronization can be achieved at high speed and reliably, which enables a highly reliable communication system.

[0075]

As described above, according to the present invention, at least two arc-shaped comb-shaped input electrodes for exciting the first and second surface acoustic waves are provided on the main surface of the piezoelectric substrate and the piezoelectric substrate. In a surface acoustic wave device having an output electrode for taking out the convolution signal of the two surface acoustic waves by utilizing nonlinearity, a 0th-order mode (fundamental mode) of the surface acoustic wave propagates to the waveguide, In addition, by using the arc-shaped input electrode having a crossing width wider than the crossing width of the electrode fingers, which is represented by the opening angle determined by the conventional waveguide width in which the surface acoustic wave is coupled with the waveguide mode of the waveguide, the comb-shaped electrode It is possible to suppress higher-order transverse mode components in the excitation intensity of, and by providing an acoustic lens in the region between the arc-shaped input electrode and the waveguide end face, the surface acoustic wave propagates to the waveguide end face, Zero-order mode of surface acoustic waves It can be obtained effects such as improvement of the convolution efficiency because the fundamental mode) is bonded to the waveguide mode in the waveguide path.

Since it is not necessary to increase the number of pairs of arc-shaped comb-shaped input electrodes, the band in the frequency characteristic of the convolver can be widened, and the impedance can be lowered by the increase in the cross width of the electrode fingers of the arc-shaped comb-shaped input electrode. Since it can be suppressed, impedance matching becomes easy.

Further, by using the above-mentioned surface acoustic wave element in a receiving device, a communication device, and a communication system, a correlation with a high convolution output level is obtained especially when a synchronization signal synchronized with a spread code in a spread spectrum communication system is obtained. Since the peak signal can be obtained, it is possible to quickly cope with the synchronization acquisition and perform stable and reliable communication.

[Brief description of drawings]

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

FIG. 2 is a simulation showing an excitation intensity distribution of an arc-shaped comb-shaped input electrode having a wide crossing width according to the present invention.

FIG. 3 is an enlarged view of FIG. 1 showing a relationship between an arc-shaped comb-shaped input electrode and an acoustic lens according to the present invention.

FIG. 4 is a schematic view showing a conventional surface acoustic wave convolver.

FIG. 5 is a simulation showing an excitation intensity distribution of a conventional arc-shaped comb-shaped input electrode.

FIG. 6 is a block diagram showing an example of a communication system using the surface acoustic wave device of the present invention.

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

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

[Explanation of symbols]

11, 31, 41 Piezoelectric substrate 12, 32, 42 Arc-shaped comb-shaped input electrode 13, 33, 43 Waveguide (output electrode) 14, 34 Acoustic lens 40 Transmitter 401 Transmitter antenna 410 Receiving device 411 Receiving antenna 412 High frequency Signal processing unit 413 Synchronization circuit 414 Code generator 415 Spreading demodulation circuit 416 Demodulation circuit 501 Serial / parallel converter 502-1 to n for converting data input in series into 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

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tadashi Eguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akira Torizawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Akane Yokota 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. A piezoelectric substrate or at least two substantially arc-shaped comb-shaped input electrodes for exciting first and second surface acoustic waves on a main surface of a substrate in which a piezoelectric substance is formed on a non-piezoelectric substance. A surface acoustic wave device having a waveguide and an output electrode for taking out convolution signals of the two surface acoustic waves by utilizing a nonlinear effect of the substrate, wherein a region between the arc-shaped comb-shaped input electrode and the output electrode A surface acoustic wave device characterized in that an acoustic lens is provided on the surface. 2. The intersecting width of the electrode fingers of the arc-shaped comb-shaped input electrode is formed wider than the intersecting width represented by the opening angle determined by the waveguide width of the waveguide. 1. The surface acoustic wave device according to item 1. 3. The surface acoustic wave device according to claim 1, wherein the acoustic lens has a concave shape. 4. The surface acoustic wave device according to claim 3, wherein the acoustic lens has a concave shape with respect to the arc-shaped comb-shaped input electrode. 5. The Y-cut lithium niobate piezoelectric substrate is used as the piezoelectric substrate.
5. The surface acoustic wave device according to any one of items 4 to 4. 6. A communication system using the surface acoustic wave device according to claim 1. Description: