JPH09284086A - Surface acoustic wave device and communication equipment using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wide pass band and to sufficiently ensure an out-band suppression degree with a limited chip size. SOLUTION: A weighted electrode 3 is adopted as one interdigital electrode of the surface acoustic wave device. An electrode finger cross width wider than a maximum electrode finger cross width d1 of an outermost side lobe 5 is provided to an electrode outermost end 9 at the outside of the outermost side lobe 5 at both sides of a main lobe 4 in existence in the weighted electrode 3. Thus, the pass band in the frequency-amplitude characteristic of the surface acoustic wave device is extended more. In this case, although an undesired projection characteristic is produced in the frequency-amplitude characteristic of the weighted electrode 3, the projection characteristic is attenuated around the zero frequency on the outside of the band of a regular electrode (not shown).

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 device capable of simultaneously obtaining a sufficient out-of-band suppression degree and a wide pass bandwidth with a small chip size, and a communication device using the same.

[0002]

2. Description of the Related Art FIG. 12 is a schematic view showing a general surface acoustic wave device, wherein 1 is a piezoelectric substrate, 2 is a normal type electrode, 3'is a weighting electrode, 4 is a main slope, and 5 is a main slope. Is a side slope, 6 is a sound absorbing material, 7 is a metal film, and 8 is an envelope.

In the figure, on a piezoelectric substrate 1 made of YX LiNbO3 rotated by 128 degrees, two input / output interdigital transducers in which every other electrode finger and another every other electrode finger intersect in a comb shape. The electrodes 2 and 3'are provided at a predetermined distance. One of the input / output interdigital interdigital electrodes 2 is a normal type electrode having a constant interdigital width, and the other input / output interdigital interdigital electrode 3'changes the interdigital width of the electrode fingers to form a space between the opposing electrode fingers. Is a weighting electrode with lobes representing the locus of Such lobes include a main rope 4 located at the center of the weighting electrode 3 ′ and a plurality of side lobes 5 arranged on both sides of the main rope 4, and the maximum cross width of the side lobes 5 is as shown by an envelope 8. In addition, the side lobes 5 on the end side of the weighting electrode 3 ′ become smaller. Here, only the side lobes at the outermost end are shown.

Further, a sound absorbing material 6 for suppressing a reflected wave from the end surface of the piezoelectric substrate 1 is applied to the end portion side of the input / output interdigital transducers 2 and 3'on the piezoelectric substrate 1. ,
A metal film 7 for suppressing a direct wave between the input / output interdigital transducers 2 and 3 ′ is formed between the input / output interdigital transducers 2 and 3 ′.

[0005]

Such a surface acoustic wave device obtains a desired frequency characteristic by utilizing the surface wave propagating between these input / output interdigital transducers 2 and 3 '. The out-of-band suppression degree of such a surface acoustic wave device is closely related to the pass band frequency. With conventional weighting electrodes, for example, "IEEE TRANSACTION ON MICROWAVE
THEORY AND TECHNIQUES "Volume. MTT-21 No.4, Apr
It is well known that widening the passband frequency within a limited number of impulses degrades the out-of-band suppression, as described in il 1973 pp.162-P.175. FIG.
3 schematically shows this, and when the narrow pass band A shown by the broken line is sufficient, the out-of-band suppression degree C can be taken, but as shown by the solid line, the wide pass band B is designed. The out-of-band suppression degree D is deteriorated.

Therefore, in the conventional weighting electrode, the number of impulses (the number between electrode fingers in the traveling direction of the surface acoustic wave) must be increased in order to widen the pass band frequency and secure the out-of-band suppression degree. However, there is a problem that the chip size becomes large as a result.

An object of the present invention is to solve such a problem and to obtain a sufficient out-of-band suppression degree with a chip size equal to or smaller than that of a conventional weighting electrode or to obtain a wide pass band width at the same time. An object of the present invention is to provide a surface acoustic wave device and a communication device using the same.

[0008]

In order to achieve the above object, the present invention provides an outermost end of an electrode outside a side lobe of a weighting electrode having a width greater than a maximum electrode finger crossing width of an outermost side lobe. Electrode fingers that intersect the electrode fingers are provided.

With this configuration, in the frequency-amplitude characteristics of the weighting electrode, both shoulders of the pass band can be further raised, and the pass band of the surface acoustic wave device can be further widened. In this case, the characteristics outside the band are not so affected as a whole, so that the out-of-band suppression degree is secured and a wider pass bandwidth is obtained.

Further, according to the present invention, the rising portion outside the band of the frequency amplitude characteristic of the weighting electrode is set near the zero frequency outside the band of the frequency amplitude characteristic of the interdigital transducer facing the weighting electrode.

When the frequency-amplitude characteristic of the weighting electrode is set so as to widen the pass band of the frequency-amplitude characteristic of the surface acoustic wave device, a swelling characteristic occurs outside the frequency-amplitude characteristic band of the weighting electrode. However, in the present invention, by setting this raised portion near the zero frequency of the frequency amplitude characteristic of the other interdigital transducer, this raised portion is greatly attenuated and a good degree of suppression can be obtained.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 is a configuration diagram showing a main part of a surface acoustic wave device according to the first embodiment of the present invention, that is, a weighting electrode, 3 is this weighting electrode, 9 is the outermost end of the electrode, and FIG. The same symbols are attached to the portions corresponding to.

In the figure, the outermost side lobes 5 do not reach the outermost electrode ends 9 on both sides of the weighting electrode 3, and a pair of electrode fingers are provided on these outermost electrode parts 9. The electrode finger crossing width d2 is set larger than the maximum electrode finger crossing width d1 in the outermost side lobe 5.

The first embodiment is the same as the surface acoustic wave device shown in FIG. 12, except that FIG.
The weighting electrode 3 having the structure shown in FIG.

FIG. 2 is a characteristic diagram showing the frequency amplitude characteristic of the first embodiment.

In the figure, the dotted line 10 is the frequency-amplitude characteristic 10 of the normal type electrode 2 shown in FIG. 12, which is a mountain-shaped characteristic in which both shoulders are attenuated in the pass band, and outside the band,
The mountain-shaped characteristic having a periodic zero-point frequency 12 is repeated. The envelope of the characteristic outside these bands is a curve that attenuates as it moves away from the pass band.

On the other hand, the broken line 11 shows the frequency amplitude characteristic 11 of the weighting electrode 3 shown in FIG. 1, and the weighting electrode 3 is constructed so that both shoulders of the pass band rise. Therefore, in the first embodiment, by combining these frequency amplitude characteristics 10 and 11, the attenuation of both shoulders in the pass band of the frequency amplitude characteristic 10 is caused by the swelling of both shoulders of the pass band of the frequency amplitude characteristic 11. Compensated, solid line 13
A wide pass band can be obtained with the overall frequency-amplitude characteristic shown by.

Of course, also in the weighting electrode 3'shown in FIG. 12, as shown by the solid line 14 in FIG. 2, both shoulders of the passband are raised to widen the passband of the overall frequency amplitude characteristic. can do. However, if an attempt is made to increase this rise to obtain a wider pass band, the out-of-band suppression degree deteriorates, as described with reference to FIG.

Therefore, in the first embodiment, the electrode finger crossing width d2 of a pair of electrode fingers at the electrode outermost ends 9 on both sides of the weighting electrode 3 is set to the electrode finger crossing of the outermost side lobe 5. It is made larger than the width d1. According to this, as shown in FIG. 2, both shoulders of the pass band in the frequency-amplitude characteristic 11 of the weighting electrode 3 can be raised, and this rise is the frequency of the conventional weighting electrode 3 ′ shown by the solid line 14. Even if the amplitude characteristic is increased, the out-of-band suppression degree is not significantly deteriorated by the conventional weighting electrode 3 ′.

However, when the above-mentioned electrode fingers are provided at the outermost end portion 9 of the electrode to widen the pass band in the total frequency amplitude characteristic of the surface acoustic wave device, as shown in FIG. If a swelling characteristic 15 that significantly deteriorates the out-of-band suppression degree is generated outside the band, and if both shoulders of the pass band of the frequency amplitude characteristic 11 of the weighting electrode 3 are further swelled, the swelling characteristic 15 outside this band is It gets more exciting. As a result, the out-of-band suppression degree is deteriorated.

Therefore, in the first embodiment, the swelling characteristic 15 outside the band of the frequency amplitude characteristic 11 of the weighting electrode 3 becomes a zero frequency 12 outside the band of the frequency amplitude characteristic 10 of the normal type electrode 2. The weighting electrodes 3 are configured to match. As a result, as shown in FIG. 2, the swelling characteristic 15 outside the band of the frequency amplitude characteristic 11 of the weighting electrode 3 is sufficiently attenuated, and the overall frequency amplitude characteristic 13 has a sufficient suppression degree even outside the band. Will be done.

In this way, in the first embodiment, even if the pass band is widened, the out-of-band suppression degree can be simultaneously increased.

FIG. 3 is a characteristic diagram showing the total frequency amplitude characteristic of this first embodiment with the same number of impulses and the conventional surface acoustic wave device as shown in FIG. 12, and the solid line 16 shows the first frequency. The total frequency amplitude characteristic of the above embodiment and the dotted line 17 are the total frequency amplitude characteristic of the conventional surface acoustic wave device. Further, the solid line 16 ′ is an enlarged view of the ± 5 dB portion of the total frequency amplitude characteristic 16 of the first embodiment, and the dotted line 1
7'denotes a total frequency amplitude characteristic of the conventional surface acoustic wave device 17
3 is an enlarged view of the ± 5 dB part of FIG.

As is apparent from FIG. 3, if the out-of-band suppression degrees are equal, the total frequency amplitude characteristic 1 of the first embodiment is obtained.
It can be seen that the pass band at 6 (16 ') can be made wider than the pass band at the total frequency amplitude characteristic 16 (16') of the conventional surface acoustic wave device.

FIG. 4 shows a second surface acoustic wave device according to the present invention.
It is a block diagram which shows the principal part of this embodiment, ie, a weighting electrode, The same code | symbol is attached | subjected to the part corresponding to FIG. 1, and the overlapping description is abbreviate | omitted.

In the second embodiment, in this second embodiment, the electrode finger crossing width d3 is defined by two pairs of electrode fingers at the electrode outermost ends 9 on both sides of the weighting electrode 3, and the maximum width of the side lobe 5 at the outermost end is obtained. The width is made larger than the electrode finger cross width d1.

In the second embodiment, both shoulders of the pass band in the frequency amplitude characteristic 11 shown in FIG. 2 can be made larger than those in the first embodiment shown in FIG. In order to obtain a good out-of-band suppression degree with a wide pass bandwidth similar to the embodiment shown in FIG. 1,
The design margin of the weighting electrode 3 is increased.

In the second embodiment, the number of electrode finger pairs at the electrode outermost end 9 may be 3 or more.

FIG. 5 shows a third surface acoustic wave device according to the present invention.
2 is a configuration diagram showing a main part of the embodiment, that is, a weighting electrode, and parts corresponding to those in FIG.

In the figure, in the third embodiment, the weighting electrode 3 is a so-called tilt type electrode in which the side lobes 5 on both sides of the main lobe 4 are arranged on the opposite sides with respect to the surface acoustic wave propagation central axis 18. To do.

If the surface acoustic wave propagation central axes of all the side lobes are made to coincide with each other as in the previous embodiment, the surface wave intensities on both sides of the central axis will be offset on the weighting electrode 3, and the weighting will be performed. The surface acoustic wave propagating on the electrode 3 is difficult to obtain a desired frequency amplitude characteristic due to the weighting loss. The tilt-type electrode is configured to prevent this, and the surface wave intensity can be uniformized in the propagation velocity of the surface acoustic wave in the opening direction of the weighting electrode 3, and the weighting loss can be improved.

And on top of that, the weighting electrode 3
With such a tilt-type electrode structure, as is apparent from FIG. 5, it is possible to increase the electrode crossing width d4 at the electrode outermost end 9 as compared with the first embodiment shown in FIG.
In order to obtain a wide pass band and a sufficient out-of-band suppression degree, the restriction on the electrode design is further relaxed.

Also in the third embodiment, as in the second embodiment shown in FIG. 4, the number of pairs of electrode fingers of the electrode outermost end portion 9 of the weighting electrode 3 can be two or more.

FIG. 6 shows a fourth surface acoustic wave device according to the present invention.
2 is a configuration diagram showing the embodiment of the present invention, and the same reference numerals are given to the portions corresponding to the previous drawings.

In the figure, the weighting electrode 3 is similar to that of the embodiment shown in FIGS. 1, 4 and 5, and in this fourth embodiment, the surface acoustic wave propagation center of the weighting electrode 3 is further added. The axis 16 and the surface acoustic wave propagation central axis 19 of the normal type electrode 2 are displaced from each other.

The piezoelectric substrate 1 has anisotropy of sound velocity, and the propagation velocity of surface acoustic waves varies depending on the propagation direction. Therefore, the weighting electrode 3 receives the surface acoustic waves having different propagation velocities from the normal type electrode 2. The frequency-amplitude characteristic of the weighting electrode 3 is also affected by the distribution of surface acoustic waves having different propagation velocities.

Therefore, in the fourth embodiment, the amount of deviation between the surface acoustic wave propagation central axis 16 of the weighting electrode 3 and the surface acoustic wave propagation central axis 19 of the normal type electrode 2 is set as appropriate so that It is possible to obtain a more excellent out-of-band suppression degree than each of the embodiments. In this case, the pass band is hardly affected by the shift amount of these axes 16 and 19. Therefore, as in the previous embodiment,
A wide pass band can be obtained.

There is also a tradeoff with the out-of-band suppression degree, but there is some restriction due to the out-of-band suppression degree.
It is also possible to improve ripple in the pass band. Therefore, the characteristics of the surface acoustic wave device can be improved by setting the deviation amounts of the axes 16 and 19 so that the out-of-band suppression degree and the improvement of the ripple in the pass band are the best. .

FIG. 7 shows a fifth surface acoustic wave device according to the present invention.
FIG. 2 is a configuration diagram showing the embodiment of FIG. 2, 2 ′ is an extraction electrode, and the same reference numerals are given to the portions corresponding to the above drawings.

In the figure, the weighting electrode 3 has the same structure as that of each of the previous embodiments. In the fifth embodiment, the normal type electrode is the extraction electrode 2'with electrode fingers partially removed. Also in this embodiment, the same effects as those of the first, second, and third embodiments can be obtained.

A structure in which some electrode fingers are thinned is called a sampling electrode. An electrode having such a structure generally has a higher degree of side lobe suppression than a normal type electrode.

The fifth embodiment uses the extraction electrode 2'as a normal type electrode, and the same effect as that of the previous embodiment can be obtained by this.

FIG. 8 shows a sixth surface acoustic wave device according to the present invention.
2 is a configuration diagram showing the embodiment of the present invention, and the same reference numerals are given to the portions corresponding to the previous drawings.

In the figure, one of the input / output interdigital interdigital electrodes is the weighting electrode 3 having the same structure as in the previous embodiments, but the other input / output interdigital interdigital electrode sandwiching the metal film 7 is shown in FIG. A conventional weighting electrode 3'as shown in 12 is used.

The frequency amplitude characteristic of the weighting electrode 3 is shown in FIG.
2 has the characteristics of the chain-broken line 11 and the frequency-amplitude characteristics of the conventional weighting electrode 3'is similar to this, but there is almost no raised portion 15 shown in FIG.

In the sixth embodiment, the zero-point frequency outside the band of the frequency-amplitude characteristic of the weighting electrode 3'and the zero frequency outside the band of the frequency-amplitude characteristic of the weighting electrode 3 are deviated so that the zero-frequency portions are mutually characteristic. Is attenuated, so that a sufficient out-of-band suppression degree can be obtained even if the conventional weighting electrode 3'is used instead of the normal type electrode.

Here, the pass band of the frequency amplitude characteristic of the conventional weighting electrode 3'is set as the characteristic 10 in FIG. 2, and the pass band of the frequency amplitude characteristic of the weighting electrode 3 is set as the characteristic 11 in FIG. Needless to say. This allows
A wide pass band can be obtained.

In the above embodiments, the piezoelectric substrate 1
Although it uses YX LiNbO3 rotated by 128 degrees, it is made of other materials, such as 112 degrees YX LiTaO3, LiNbO3, LiT.
The same effect can be obtained by using a piezoelectric substrate such as aO3 or quartz.

FIG. 9 is a block diagram showing a first embodiment of a communication device using a surface acoustic wave device according to the present invention, in which 20 is an antenna, 21 is a tuner section, 22 is an intermediate frequency filter, and 23 is demodulation. The parts 24 and 25 are output parts.

In the figure, in the first embodiment, the communication device is a television receiving device, and the surface acoustic wave device according to the present invention is used for the intermediate frequency filter 22.

The received television signal from the antenna 20 is converted into an intermediate frequency signal by the tuner section 21 and filtered by the intermediate frequency filter 22. The intermediate frequency signal from the intermediate frequency filter 22 is demodulated into a video signal and an audio signal by the demodulation section 23, and the video signal is output from the output section 24.
Audio signals are output from the output unit 25, respectively.

Since the surface acoustic wave device according to the present invention is used as the intermediate frequency filter 25,
As compared with the case of using the conventional surface acoustic wave device, the filtering of the intermediate frequency signal becomes better, and it is possible to realize a television receiver that can be made smaller and has excellent demodulation performance.

FIG. 10 is a block diagram showing a second embodiment of a communication device using a surface acoustic wave device according to the present invention, in which 26 is a parabolic antenna, 27 is an outdoor unit, and 2 is an outdoor unit.
8 is an indoor unit, 29 is a mixer, 30 is an oscillator, 31
Is an intermediate frequency filter, 32 is a demodulation unit, and 33 and 34 are output units.

In the figure, this second embodiment uses a satellite broadcasting receiver as the communication device, and uses the surface acoustic wave device according to the present invention as the intermediate frequency filter 22.

The satellite broadcast signal received by the parabolic antenna 26 is converted into a high frequency signal by the outdoor unit 27 and supplied to the indoor unit 28. In the indoor unit 28, this high frequency signal is combined with the output signal of the oscillator 30 by the mixer 29 and converted into an intermediate frequency signal. The intermediate frequency signal is filtered by the intermediate frequency filter 31 and demodulated by the demodulation unit 32 into a video signal and an audio signal.
This video signal is output from the output unit 33, and the audio signal is output from the output unit 34.
Are output respectively.

Since the surface acoustic wave device according to the present invention is used as the intermediate frequency filter 34,
As compared with the case of using the conventional surface acoustic wave device, the filtering of the intermediate frequency signal becomes better, and it is possible to realize a satellite broadcast receiver that can be further downsized and has excellent demodulation performance.

FIG. 11 is a block diagram showing a third embodiment of a communication device using the surface acoustic wave device according to the present invention. 35 is a cable terminal, 36 is a tuner section, 37 is an intermediate frequency filter, and 38 is Demodulation units 39 and 40 are output units.

In the figure, this third embodiment uses a CATV receiver as the communication device, and uses the surface acoustic wave device according to the present invention as the intermediate frequency filter 37.

The input signal from the cable terminal 35 is converted into an intermediate frequency signal by the tuner section 36 and filtered by the intermediate frequency filter 37. The intermediate frequency signal from the intermediate frequency filter 37 is demodulated by the demodulation unit 38 into a video signal and an audio signal, the video signal is output from the output unit 39, and the audio signal is output from the output unit 40.

Since the surface acoustic wave device according to the present invention is used as the intermediate frequency filter 37,
It is possible to realize a CATV receiver having better intermediate frequency signal filtering, smaller size, and excellent demodulation performance.

[0061]

As described above, according to the present invention,
In the surface acoustic wave device, the pass band can be widened and the out-of-band suppression degree can be increased without increasing the number of impulses, and good frequency-amplitude characteristics can be obtained with a limited chip size.

Further, according to the present invention, good demodulation performance can be realized in the communication device.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a weighting electrode in a first embodiment of a surface acoustic wave device according to the present invention.

FIG. 2 is a diagram showing a frequency amplitude characteristic in the first embodiment shown in FIG.

FIG. 3 is a characteristic diagram showing a comparison between the frequency amplitude characteristics of the first embodiment shown in FIG. 1 and the frequency amplitude characteristics of a conventional surface acoustic wave device.

FIG. 4 is a configuration diagram showing weighting electrodes in a second embodiment of the surface acoustic wave device according to the present invention.

FIG. 5 is a configuration diagram showing a weighting electrode in a third embodiment of the surface acoustic wave device according to the present invention.

FIG. 6 is a configuration diagram showing a fourth embodiment of a surface acoustic wave device according to the present invention.

FIG. 7 is a configuration diagram showing a fifth embodiment of a surface acoustic wave device according to the present invention.

FIG. 8 is a configuration diagram showing a sixth embodiment of a surface acoustic wave device according to the present invention.

FIG. 9 is a block diagram showing a first embodiment of a communication device using the surface acoustic wave device according to the present invention.

FIG. 10 is a block diagram showing a second embodiment of a communication device using the surface acoustic wave device according to the present invention.

FIG. 11 is a block diagram showing a third embodiment of a communication device using the surface acoustic wave device according to the present invention.

FIG. 12 is a configuration diagram showing an example of a conventional surface acoustic wave device.

FIG. 13 is a schematic diagram showing the relationship between the pass band and the out-of-band suppression degree in the conventional surface acoustic wave device.

[Explanation of symbols]

 1 Piezoelectric Substrate 2 Normal Type Electrode 2'Extraction Electrode 3 Weighting Electrode 4 Main Lobe 5 Sidelobe 6 Sound Absorbing Material 7 Metal Film 8 Envelope 9 Outermost Edge of Electrode 10 Frequency Amplitude Characteristic of Normal Type Electrode 11 Frequency Amplitude of Weighting Electrode Characteristic 12 Zero frequency 13 Total frequency amplitude characteristic 15 Raised part 20 Antenna 21 Tuner part 22 Intermediate frequency filter 23 Demodulation part 24, 25 Output part 26 Parabolic antenna 27 Outdoor unit 28 Indoor unit 26 Mixer 30 Oscillator 31 Intermediate frequency filter 32 Demodulation part 33, 34 output section 35 cable terminal 36 tuner section 37 intermediate frequency filter 38 demodulation section 39, 40 output section

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Yanagihara 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Prefecture Hitachi, Ltd. Multimedia Systems Development Division

Claims (6)

[Claims] 1. A comb-shaped electrode for input and a comb-shaped electrode for output are formed on a piezoelectric substrate, and at least one of the comb-shaped electrodes comprises a weighting electrode having a main lobe and one or more side lobes. In the surface acoustic wave device, the outermost end electrode finger crossing width outside the outermost end of the weighting electrode is formed larger than the maximum electrode finger crossing width of the outermost end sidelobe. A surface acoustic wave device. 2. The surface acoustic wave device according to claim 1, wherein a raised portion outside the band of the frequency amplitude characteristic of the weighting electrode is outside the band of the frequency amplitude characteristic of the interdigital electrode facing the weighting electrode. A surface acoustic wave device characterized by being set to near zero frequency in. 3. The surface acoustic wave device according to claim 1, wherein the interdigital transducer facing the weighting electrode is a regular electrode. 4. The surface acoustic wave device according to claim 1, wherein the interdigital transducer facing the weighting electrode is a sampling electrode. 5. The surface acoustic wave device according to claim 1, wherein the interdigital transducer facing the weighting electrode is a weighting electrode. 6. A communication device comprising the surface acoustic wave device according to claim 1, 2, 3, 4 or 5.