JPH09270662A - Surface acoustic wave element, surface acoustic wave component and spread spectrum communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the surface acoustic wave element in which dispersion in correlation output signal levels from an output electrode without deteriorating a non-defective rate in the manufacture process. SOLUTION: The element is a surface acoustic wave element in which an input coding electrode 2 and plural 1st and 2nd output interdigital electrodes 3, 4 are formed on a piezoelectric substrate 1, and a single electrode is adopted for the input coding electrode 2 and a double electrode is adopted at least for the final stage 2nd output interdigital electrode 4 in the 1st and 2nd output interdigital electrodes 3, 4. Thus, dispersion in correlation output signal levels from the output electrode is reduced without deteriorating the non-defective rate in the manufacture process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave element for demodulating a spread spectrum modulated signal, a surface acoustic wave component using the surface acoustic wave element, and a spread spectrum communication device using the surface acoustic wave component.

[0002]

2. Description of the Related Art In recent years, a spread spectrum communication system (SS communication system) which is resistant to noise and excellent in confidentiality and confidentiality has attracted attention as a communication system for consumer use. In the SS communication system, a spectrum that becomes a transmission signal is obtained by performing spread spectrum modulation (SS modulation) on a carrier wave in which information to be transmitted is modulated with a carrier signal with a predetermined code sequence having a predetermined high chip rate. A spread modulation signal (SS modulation signal) is obtained. In this case, there are a pseudo-noise code sequence (PN code sequence) and a Barker code sequence (Barker code sequence) as the above-mentioned code sequences, and a direct spreading method (DS method) and a frequency hopping method (FH method) as SS modulation methods. There is.

In such an SS communication system, a demodulating device for demodulating the transmitted SS modulated signal is required on the receiver side. DS using PN code sequence
When SS modulation is performed by the method, the receiver side performs demodulation using the same PN code sequence as that on the transmitter side. The demodulation device used at this time is roughly classified into a demodulation device using an IC and a demodulation device using a surface acoustic wave element. The surface acoustic wave element used in the demodulator is attracting attention because it is inexpensive and simple to construct by using a photolithography technique, and thus the demodulator is inexpensive and simple to construct.

The surface acoustic wave device is classified into a surface acoustic wave matched filter and a surface acoustic wave convolver due to the difference in structure. The surface acoustic wave convolver is particularly suitable for applications where confidentiality and confidentiality are required because a PN code sequence for demodulation can be selected. In the surface acoustic wave matched filter, the PN code sequence used for demodulation is fixed, but the peripheral circuits can be easily configured, and the overall cost of the device can be reduced. Therefore, it is suitable for small-scale SS communication devices such as a local wireless LAN. Attention has been paid to the surface acoustic wave device used.

Conventionally, as the surface acoustic wave matched filter, the one described in Japanese Patent Laid-Open No. 3-77445 is known. FIG. 7 is a plan view showing a conventional surface acoustic wave matched filter and an SS communication demodulator using the surface acoustic wave matched filter. In FIG. 7, the piezoelectric substrate 5
1 is made of quartz, LiNbO _3, etc., the input encoding electrode 52 converts an electric signal into a surface acoustic wave, and the first and second output comb electrodes 53 and 54 convert a surface acoustic wave into an electric signal. The sound absorbing material 55 absorbs unnecessary surface acoustic waves, and the integrating circuit 56 integrates the output signals m and n of the first and second output comb electrodes 53 and 54. As can be seen from FIG. 7, the surface acoustic wave element is a portion excluding the integrating circuit 56.
By including 6, the SS communication demodulation device is configured.

Next, the pattern will be described. On the piezoelectric substrate 51, the input coding electrode 52, the first output comb-shaped electrode 53 separated from the input coding electrode 52 by a first predetermined distance, and further the first coding electrode 53 are provided. A second output comb electrode 54 is formed at a second predetermined distance from the first output comb electrode 53. When an i-bit PN code sequence is used as the code sequence, the input coding electrode 52 has i comb-shaped electrode pairs corresponding to the PN code sequence, and each comb-shaped electrode pair is separated by an interval corresponding to the chip rate. Has been formed. In addition, the input encoding electrode 52 and the first and second output comb-shaped electrodes 53 and 54.
A ground pattern (not shown) for reducing noise is formed around the area as necessary. Further, a sound absorbing material 55 is formed outside the input encoding electrode 52 and the second output comb-shaped electrode 54 for the purpose of absorbing unnecessary surface acoustic waves. In this case, the input coded electrode 52 and the first and second output comb-shaped electrodes 53 and 54 are reversely configured, that is, the comb-shaped electrode is used as the input electrode and the coded electrode is used as the output electrode. I don't care.

The operation of the SS communication demodulation device configured as described above will be briefly described. The SS modulation signal s input to the input encoding electrode 52 is output as a correlation output signal m from the first output comb electrode 53, and is output as a correlation output signal n from the second output comb electrode 54. , Is input to the integrating circuit 56. The correlation output signal n is
The correlation output signal m is delayed by a delay amount corresponding to the distance between the first output comb-shaped electrode 53 and the second output comb-shaped electrode 54, that is, one cycle of the information signal, and input to the integrating circuit 56. It The integrating circuit 56 integrates the correlation output signal m and the correlation output signal n delayed by a predetermined delay amount to obtain a demodulated signal.

By using the surface acoustic wave device having the structure shown in FIG. 7, the surface acoustic wave matched filter and the surface acoustic wave delay line can be integrated. That is, the input coding electrode 52 and the first output comb-shaped electrode 53 constitute a surface acoustic wave matched filter, and the first output comb-shaped electrode 53 and the second output comb-shaped electrode 54 form a surface acoustic wave. By configuring the delay line, an external amplifier is not required as compared with the case where the surface acoustic wave matched filter and the surface acoustic wave delay line are separately configured, and the configuration can be simplified. However, the publications describing the conventional surface acoustic wave device (for example, the above-mentioned publication) do not refer to the structures of the input encoding electrode 52 and the first and second output comb-shaped electrodes 53 and 54.

Here, the width of the electrode finger of each of the electrodes 52 to 54 is determined by the carrier frequency used and the velocity of the surface acoustic wave of the piezoelectric substrate 51. For example, the velocity of the surface acoustic wave is 315
When a carrier frequency is set to 286 MHz using an ST cut quartz substrate of 8 m / s, the width of the electrode finger is about 2.76 μm in the single electrode structure, and it is about 1.38 μm in the double electrode structure. Therefore, considering the non-defective product rate in the manufacturing process, the single electrode structure in which the width of the electrode finger is wide is preferable.

[0010]

However, in the conventional surface acoustic wave element, if each electrode has a single-electrode structure, the correlation output signal n from the second output comb-shaped electrode 54 depends on the input signal sequence. Although the level does not vary, the correlation output signal m from the first output comb electrode 53
Had the problem that its level would vary. For example, when the input signal s is “11110”, the ratio between the maximum output and the minimum output of the correlation output signal n (hereinafter, “maximum output ratio η”) is about 0.95, while The maximum / minimum output ratio η of the correlation output signal m is about 0.82. The variation in the level of the correlation output signal m leads to the variation in the level of the demodulation output signal from the integrating circuit 56, which deteriorates the error rate at the time of demodulating the information signal from the demodulation output signal, and thus the error rate of the SS communication device itself. It had a problem of deterioration.

This surface acoustic wave element is required not to deteriorate the error rate.

The present invention is a surface acoustic wave device capable of reducing variations in the level of correlated output signals from output electrodes without lowering the yield rate in the manufacturing process, and
Correlation from output electrodes without reducing the non-defective rate in the manufacturing process Surface acoustic wave components that can reduce variations in output signal levels, and correlation from output electrodes without reducing the non-defective rate in the manufacturing process An object of the present invention is to provide a spread spectrum communication device capable of reducing variations in output signal level.

[0013]

In order to solve this problem, a surface acoustic wave device of the present invention is a surface acoustic wave device in which an input electrode and a plurality of output electrodes are formed on a piezoelectric substrate. The input electrode is a single electrode, and at least the final output electrode of the plurality of output electrodes is a double electrode.

As a result, it is possible to obtain the surface acoustic wave device capable of reducing the variation in the level of the correlation output signal from the output electrode without lowering the non-defective rate in the manufacturing process.

The surface acoustic wave component of the present invention for solving this problem is configured so as to seal the surface acoustic wave element.

As a result, it is possible to obtain the surface acoustic wave component which can reduce the variation in the level of the correlated output signal from the output electrode without lowering the yield rate in the manufacturing process.

The spread spectrum communication device of the present invention for solving this problem is configured to have a signal demodulation section for demodulating a spread spectrum modulated signal using the surface acoustic wave component.

As a result, it is possible to obtain the spread spectrum communication device capable of reducing the variation in the level of the correlation output signal from the output electrode without reducing the non-defective rate in the manufacturing process.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention is a surface acoustic wave device in which an input electrode and a plurality of output electrodes are formed on a piezoelectric substrate. This is not an electrode, and at least the output electrode at the final stage of the plurality of output electrodes is a double electrode, and has an effect of suppressing variation in the level of the correlation output signal.

According to a second aspect of the present invention, the input coding electrode, the first output comb-shaped electrode spaced apart from the input coding electrode by a first predetermined distance, and the first output electrode are provided on the piezoelectric substrate. A surface acoustic wave device having a second output comb-shaped electrode spaced apart from the comb-shaped electrode by a second predetermined distance, wherein the input coding electrode is a single electrode, and the first and second output comb-shaped electrodes are provided. Among them, at least the second output comb-shaped electrode is formed as a double electrode, and the first output comb-shaped electrode has an effect of suppressing variation in the correlation output signal level.

According to a third aspect of the invention, in the invention according to the second aspect, the input encoding electrode has a comb-shaped electrode pair corresponding to each bit, and the electrode fingers of the comb-shaped electrode pair corresponding to each bit. The number of logarithms is more than one and the carrier frequency is less than or equal to the chip rate, which has the effect of efficiently converting an electrical signal into a surface acoustic wave.

The invention according to claim 4 is to seal the surface acoustic wave device according to claim 1, 2 or 3 and has an effect of stabilizing the operation of the surface acoustic wave device.

The invention described in claim 5 has a signal demodulation section for demodulating a spread spectrum modulation signal using the surface acoustic wave component according to claim 4, and an error at the time of demodulating an information signal is obtained. It has the effect that the rate does not deteriorate.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 (a) is a plan view showing a surface acoustic wave device according to Embodiment 1 of the present invention, and FIG. 1 (b) is an enlarged view of part A of FIG. 1 (a). In FIG. 1A,
The piezoelectric substrate 1 is made of crystal, LiNbO ₃ or the like, the input coding electrode 2 is made of Al, Au or the like, converts an electric signal into a surface acoustic wave, and outputs the first and second comb-shaped electrodes 3 and 4 for output. Is made of Al, Au, etc., and converts the surface acoustic waves into electric signals. The ground pattern 5 is made of Al, Au, etc., and the sound absorbing section 6 absorbs unnecessary surface acoustic waves.

Next, the pattern will be described. On the piezoelectric substrate 1, the input coding electrode 2 and the first output comb-shaped electrode 3 separated from the input coding electrode 2 by a first predetermined distance.
And a second output comb-shaped electrode 4 separated from the first output comb-shaped electrode 3 by a second predetermined distance. When an i-bit PN code sequence is used as the code sequence, the input coding electrode 2 has i comb-shaped electrode pairs corresponding to the PN code sequence, and each comb-shaped electrode pair is separated by an interval corresponding to the chip rate. Has been formed. Further, a ground pattern 5 for reducing noise is formed around the input encoding electrode 2, the first and second output comb-shaped electrodes 3 and 4. Further, a sound absorbing portion 6 is formed outside the input encoding electrode 2 and the second output comb-shaped electrode 4 for the purpose of absorbing unnecessary surface acoustic waves. Further, the input encoding electrode 2 has a single electrode structure, and as shown in FIG. 1B, the second output comb-shaped electrode 4 has a double electrode structure. Further, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit of the input encoding electrode 2 is more than one and less than or equal to the ratio of carrier frequency and chip rate (carrier frequency / chip rate) used. Thereby, an electric signal can be efficiently converted into a surface acoustic wave, and a highly efficient surface acoustic wave element can be obtained. In the present embodiment, the carrier frequency is 286 MHz and the chip rate is 11 MHz, so that the number of electrode finger pairs of the comb-shaped electrode pair corresponding to 1 bit can be selected from 2 to 26 pairs. In this embodiment, there are eight pairs as shown in FIG. As a result, the efficiency is improved by about 18 dB as compared with the case of the pair.

The greater the number of pairs of electrode fingers of the comb-shaped electrode pair, the higher the efficiency becomes, but the electrode area increases accordingly, so that the influence of dust and the like in the manufacturing process becomes large. In particular, if the input coded electrode 2 has a double electrode structure, the width of the electrode finger becomes narrower and the influence is further increased. Therefore, it is a manufacturing process that the input coded electrode 2 has a single electrode structure. Desirable from above.

Table 1 shows the structure of each electrode to be tested.

[0028]

[Table 1]

In Table 1, in Example a, the input coding electrode 2 is a single electrode, the first output comb-shaped electrode 3 is a single electrode, and the second output comb-shaped electrode 4 is a double electrode. In the example b, the input encoding electrode 2 is shown.
Is a single electrode, both the first and second output comb-shaped electrodes 3 and 4 are double electrodes, the comparative example is a double electrode, and the conventional example is a single electrode. The case where it is used as an electrode is shown.

FIG. 2 shows Example a, Example b, (Table 1),
In the comparative example and the conventional example, the input signal s is “1111”.
It is a characteristic graph figure which shows the relationship of the maximum and minimum output ratio (eta) of the 1st output comb-shaped electrode 3 at the time of "0" to carrier frequency.
As can be seen from FIG. 2, in Examples a and b, the maximum and minimum output ratio η = 0.95 at the carrier frequency of 286 MHz, which is superior to 0.82 of the conventional example. This is because the double electrode structure suppresses the surface acoustic wave reflected by the second output comb-shaped electrode 4 from adversely affecting the first output comb-shaped electrode 3. Further, in the comparative example, the maximum / minimum output ratio η vs. carrier frequency characteristic is the reverse of the characteristics in Examples a and b, and the maximum / minimum output ratio η at the carrier frequency 286 MHz used is 0.9. Is getting worse.

The first and second output comb electrodes 3, 4 are provided.
The electrode structure of is not particularly specified, and the same applies to the electrode structure in which the cross width is weighted like an apodized electrode in addition to the normal type electrodes (electrodes having the same cross width) shown in the present embodiment. Has the effect of. Further, the input encoding electrode 2 and the first and second input electrodes shown in the present embodiment are provided.
It is possible to use a configuration opposite to that of the output comb-shaped electrodes 3 and 4, that is, a comb-shaped electrode can be used as an input electrode and a coded electrode can be used as an output electrode. Since the coded electrode used as a double electrode has a double electrode structure, even if an excellent value can be obtained as the maximum and minimum output ratio η, the non-defective product rate is lowered in the manufacturing process.

As described above, according to the present embodiment, in the surface acoustic wave device in which the number of electrode finger pairs of the comb-shaped electrode pair of the input encoding electrode 2 is increased to make the efficiency high, the input encoding electrode 2 is By using a single electrode, it is possible to prevent a reduction in the yield rate in the manufacturing process, and by using at least the second output comb-shaped electrode 4 as a double electrode, it is possible to suppress the variation in the correlation output signal level and to reduce the maximum output ratio η. Can be maintained at a high value.

(Second Embodiment) FIG. 3 is a plan view showing a surface acoustic wave device according to a second embodiment of the present invention. In FIG. 3, the piezoelectric substrate 11 is made of crystal, LiNbO _3, etc., and the input coding electrodes 12, 15 are made of Al, Au, etc., which converts an electric signal into a surface acoustic wave and outputs the first and third outputs. The comb-shaped electrodes 13 and 16 and the second and fourth output comb-shaped electrodes 14 and 17 are made of Al, Au, or the like for converting surface acoustic waves into electric signals, and the ground pattern 18 is made of Al,
The sound absorbing portion 19 is made of Au or the like and absorbs unnecessary surface acoustic waves.

Next, the pattern will be described. On the piezoelectric substrate 11, the input coding electrode 12 and the first output comb-shaped electrode 13 separated from the input coding electrode 12 by a first predetermined distance are provided. A second output comb-shaped electrode 14 spaced from the first output comb-shaped electrode 13 by a second predetermined distance is formed.
Two surface acoustic wave elements are formed. Further, on the piezoelectric substrate 11, the input encoding electrode 15, the third output comb-shaped electrode 16 separated from the input encoding electrode 15 by a first predetermined distance, and the third output comb-shaped electrode 16 are provided. To the fourth output comb-shaped electrode 17 spaced apart from the second predetermined distance, and another surface acoustic wave element is formed. Further, a ground pattern 18 for reducing noise is formed around the input coded electrodes 12 and 15 and the first to fourth output comb-shaped electrodes 13, 14, 16 and 17 for input / output. The size of the electrodes 12 to 17 is reduced by using a common ground terminal and a ground pattern. Further, the input encoding electrodes 12 and 15, the second and fourth output comb electrodes 14,
A sound absorbing portion 19 is formed on the outside of 17 for the purpose of absorbing unnecessary surface acoustic waves.

Also in this embodiment, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit of the input encoding electrodes 12 and 15 is more than one, and the ratio between the carrier frequency and the chip rate used. (Carrier frequency / Chip rate)
By the following, an electric signal can be efficiently converted into a surface acoustic wave, and a highly efficient surface acoustic wave element can be obtained. At this time, the input encoding electrodes 12 and 15 are single electrodes, and at least the second and fourth output comb-shaped electrodes 1 are provided.
Embodiment 4 is realized by forming 4 and 17 as double electrodes.
The same effect can be obtained.

The first to fourth output comb electrodes 13,
The electrode structure of 14, 16 and 17 is not particularly specified except that the second and fourth output comb electrodes 14 and 17 are double electrodes, and other than the normal type electrodes shown in this embodiment. Also, the same effect can be obtained with a weighted electrode structure such as an apodized electrode. In addition, the distance between the first output comb-shaped electrode 13 and the second output comb-shaped electrode 14, and the third output comb-shaped electrode 16 and the fourth output comb-shaped electrode 1.
7 is used as a surface acoustic wave device for four-phase phase modulation, the input coding electrodes 12 and 15 are made to correspond to spread codes having different codes, and different chips are used. It is possible to have a free structure such as a structure corresponding to the rate. Furthermore, the input encoding electrodes 12 and 15 and the first to
It is possible to use a configuration opposite to that of the fourth output comb electrodes 13, 14, 16, 17; that is, a comb electrode can be used as an input electrode and a coded electrode can be used as an output electrode. In this case, the encoding electrode used as the output electrode has a double electrode structure, and even if an excellent value can be obtained as the maximum / minimum output ratio η, the non-defective rate in the manufacturing process is reduced.

As described above, according to the present embodiment, in the surface acoustic wave device having a high efficiency by increasing the number of electrode finger pairs of the comb-shaped electrode pairs of the input encoding electrodes 12 and 15, the input encoding electrodes are provided. By using 12 and 15 as a single electrode, it is possible to prevent the non-defective rate from decreasing in the manufacturing process, and by using at least the second and fourth output comb electrodes 14 and 17 as a double electrode, the correlation output signal level It is possible to suppress variations and maintain the maximum and minimum output ratio η at a high value.

(Third Embodiment) FIG. 4 is a plan view showing a surface acoustic wave device according to a third embodiment of the present invention. In FIG. 4, the piezoelectric substrate 21 is made of quartz, LiNbO _3, etc., and the input coding electrode 22 is made of Al, Au, etc., and converts an electric signal into a surface acoustic wave.
The fourth output comb-shaped electrodes 23, 24 and 25, 26 are A
l, Au, etc., which converts surface acoustic waves into electric signals,
The ground pattern 27 is made of Al, Au, etc.
8 and 29 absorb unnecessary surface acoustic waves.

Next, the pattern will be described. On the piezoelectric substrate 21, the input coded electrode 22 and the first output comb-shaped electrode 23 separated from the input coded electrode 22 by a first predetermined distance are provided. A second output comb-shaped electrode 24, which is separated from the first output comb-shaped electrode 23 by a second predetermined distance, is formed, and the first output comb-shaped electrode 23 is formed with respect to the input encoding electrode 22.
A third output comb-shaped electrode 25 that is separated from the input encoding electrode 22 by a first predetermined distance and a fourth output that is separated from the third output comb-shaped electrode 25 by a second predetermined distance in the opposite direction. And a comb-shaped electrode 26 are formed. Further, a ground pattern 27 for reducing noise is formed around the input encoding electrode 22 and the first to fourth output comb-shaped electrodes 23 to 26, and the second and fourth output comb-shaped electrodes are formed. A sound absorbing portion 28 is provided outside the electrodes 24 and 26 for the purpose of absorbing unnecessary surface acoustic waves.
29 are formed.

Further, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit of the input encoding electrode 22 is larger than one and is equal to or less than the ratio (carrier frequency / chip rate) of the carrier frequency to be used and the chip rate. By doing so, an electric signal can be efficiently converted into a surface acoustic wave, and a highly efficient surface acoustic wave element can be obtained. At this time, the same effect as in the first embodiment can be obtained by forming the input encoding electrode 22 as a single electrode and forming at least the second and fourth output comb-shaped electrodes 24, 26 as double electrodes.

The second and fourth output comb electrodes 24,
The electrode structure of 26 is not particularly specified except that it is a double electrode, and the same effect can be obtained by a weighted electrode structure such as an apodized electrode other than the normal type electrode shown in the present embodiment. is there. In addition, the distance between the first output comb-shaped electrode 23 and the second output comb-shaped electrode 24, and the third output comb-shaped electrode 25 and the fourth output comb-shaped electrode 26.
It is possible to have a free configuration, such as using a surface acoustic wave device for four-phase phase modulation with different values for the interval between them. Furthermore, the configuration opposite to the configuration of the input coding electrode 22 and the first to fourth output comb electrodes 23 to 26 shown in the present embodiment, that is, the comb electrode is used as the input electrode, Although it is possible to use a coded electrode as the electrode, in this case the coded electrode used as the output electrode has a double electrode structure, and an excellent value can be obtained as the maximum and minimum output ratio η. Even if it can be done, the non-defective rate will be reduced in the manufacturing process.

As described above, according to the present embodiment, in the surface acoustic wave device in which the number of electrode finger pairs of the comb-shaped electrode pair of the input encoding electrode 22 is increased to make the efficiency high, the input encoding electrode 22 is not used. By using a single electrode, it is possible to prevent a decrease in the yield rate in the manufacturing process.
By using the output comb-shaped electrodes 24 and 26 as double electrodes, it is possible to suppress variation in the correlation output signal level and maintain the maximum and minimum output ratio η at a high value.

(Fourth Embodiment) FIG. 5 is a sectional view showing a surface acoustic wave device according to a fourth embodiment of the present invention. FIG.
In the above, the surface acoustic wave element 31 is the element described in the first to third embodiments, the package base 32 is for holding and fixing the surface acoustic wave element 31 and hermetically sealing, and the lead pin 33 is the surface. The acoustic wave element 31 is connected to the input / output terminal and the ground terminal to lead the terminal out of the package, and the base 32 is provided in the number corresponding to the number of connections. The wire 34 is made of Au, Al or the like, and connects each terminal (the input / output terminal and the ground terminal) of the surface acoustic wave element 31 to the lead pin 33. The cap 35 is welded to the base 32 to hermetically seal the surface acoustic wave element 31. The base 32 and the cap 35 form a package. At the time of hermetically sealing the surface acoustic wave element 31, the inside of the package is filled with nitrogen gas or an inert gas.
With such a configuration, the surface acoustic wave device 3
No. 1 is shielded from the external environment, so that there are no problems such as changes in the surface acoustic wave propagation velocity, extra reflection, and short-circuiting of the comb-shaped electrodes, which are caused by foreign matter adhering to the surface of the surface acoustic wave element 31.

In the present embodiment, the structure in which the surface acoustic wave elements 31 in the can seal packages 32 and 35 are connected by wire bonding and sealed is described, but the sealing and mounting modes are limited. Not a thing, for example, a structure sealed with a ceramic package or a mold package, a flip chip, a TAB
(Tape Automated Bonding, automatic bonding using tape) or the like, the surface acoustic wave device may be mounted, or the like.

As described above, according to the present embodiment, since the surface acoustic wave element 31 is hermetically sealed, the surface acoustic wave element 31 itself described in the first to third embodiments has the following effects. The effect that the operation of the surface acoustic wave element 31 can be stabilized can be obtained.

(Fifth Embodiment) FIG. 6 is a block diagram showing a spread spectrum communication apparatus according to a fifth embodiment of the present invention. In FIG. 6, the SS modulation unit 41 converts the information signal to be transmitted into an SS modulation signal with a predetermined code sequence, and the transmission / reception frequency conversion unit 42 converts the frequency of the transmission / reception signal,
The SS demodulation unit 43 mounts the surface acoustic wave component shown in the fourth embodiment and demodulates the SS modulated signal into the original information signal, and the antenna 44 transmits and receives radio waves.

In FIG. 6, since the SS demodulation section 43 is constructed by using the surface acoustic wave component shown in the fourth embodiment, the variation in the correlation output signal level can be suppressed to a small level. It is also possible to suppress variations in the demodulation signal level output from the integrating circuit that integrates the output signals of the second or third and fourth output comb electrodes,
It is possible to suppress the deterioration of the error rate at the time of demodulating the information signal.

In the present embodiment, the configuration of one transceiver using one frequency conversion unit 42 integrated with transmission / reception has been described, but the present invention is not limited to this, and for example, the frequency conversion unit transmits and receives. It may be configured such that the transmitter and the receiver are separated from each other, or the transmitter and the receiver are separated from each other.

As described above, according to the present embodiment, since the SS demodulation section 43 is configured by using the surface acoustic wave component described in the fourth embodiment, the same effect as in the fourth embodiment is obtained. That is, it is possible to stabilize the operation of the surface acoustic wave element and thus the operation of the SS demodulation unit 43, and to reliably obtain the information signal as the demodulation signal.

[0050]

As described above, according to the surface acoustic wave device of the present invention, the single electrode is used as the input electrode to suppress the reduction of the non-defective product rate in the manufacturing process, and at least the final output electrode. Since the variation of the correlation output signal level can be suppressed by making the output electrodes of the stages double electrodes, the variation of the correlation output signal level from the output electrodes can be reduced without lowering the non-defective rate in the manufacturing process. The advantageous effect that it can be obtained is obtained. Further, in the input coding electrode, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit is set to be more than one and less than or equal to the carrier frequency vs. chip rate, so that the electric signal is efficiently converted into a surface acoustic wave. The advantageous effect that it can be obtained is obtained.

According to the surface acoustic wave component of the present invention,
By sealing the surface acoustic wave element, an advantageous effect that the operation of the surface acoustic wave element can be stabilized can be obtained.

Further, according to the spread spectrum communication device of the present invention, by having the signal demodulation section for demodulating the spread spectrum modulated signal by using the upper surface acoustic wave component, the variation of the correlation output signal level from the output electrode can be prevented. An advantageous effect that a small and stable demodulation operation can be obtained is obtained.

[Brief description of drawings]

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

FIG. 2 is a characteristic graph diagram showing the relationship between the maximum and minimum output ratio η and the carrier frequency in the first output comb-shaped electrode.

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

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

FIG. 5 is a sectional view showing a surface acoustic wave component according to a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a spread spectrum communication device according to a fifth embodiment of the present invention.

FIG. 7 is a plan view showing a conventional surface acoustic wave matched filter and an SS communication demodulator using the surface acoustic wave matched filter.

[Explanation of symbols]

 1, 11, 21 Piezoelectric substrate 2, 12, 15, 22 Input coding electrode 3, 13, 23 First output comb-shaped electrode 4, 14, 24 Second output comb-shaped electrode 16, 25 Third Output comb-shaped electrode 17,26 Fourth output comb-shaped electrode 5,18,27 Ground pattern 6,19,28,29 Sound absorption part 31 Surface acoustic wave device 32 Base 33 Lead pin 34 Wire 35 Cap 41 SS modulation part 42 Transmission / reception frequency Converter 43 SS demodulator 44 Antenna

Claims (5)

[Claims] 1. A surface acoustic wave device having an input electrode and a plurality of output electrodes formed on a piezoelectric substrate, wherein the input electrode is a single electrode and at least one of the plurality of output electrodes is provided. A surface acoustic wave device in which the final output electrode is a double electrode. 2. An input coded electrode, a first output comb-shaped electrode spaced from the input coded electrode by a first predetermined distance, and a second output comb-shaped electrode formed on a piezoelectric substrate. A surface acoustic wave device having a second output comb-shaped electrode separated by a predetermined distance, wherein the input coding electrode is a single electrode, and at least the first and second output comb-shaped electrodes are provided. A surface acoustic wave device in which the second output comb-shaped electrode is a double electrode. 3. The input encoding electrode has a comb-shaped electrode pair corresponding to each bit, the number of electrode finger pairs of the comb-shaped electrode pair corresponding to each bit is greater than one, and carrier frequency vs. chip rate ( 3. The surface acoustic wave device according to claim 2, wherein the carrier frequency / chip rate) or less. 4. A surface acoustic wave component in which the surface acoustic wave element according to claim 1, 2 or 3 is sealed. 5. A spread spectrum communication device having a signal demodulation unit for demodulating a spread spectrum modulated signal using the surface acoustic wave component according to claim 4.