JPS62168409A - Overtone oscillating piezo-resonator utilizing higher order mode vibration - Google Patents

Abstract

PURPOSE:To easily generate an nth-order overtone by providing a multi-division energy confinement part of cut-off frequency f1 on a piezoelectric substrate, providing a part of cut-off frequency f2(f2>f1), also selecting each parameter, and diffusing an overtone of (n-2)th-order or below, to the whole surface of the piezoelectric substrate. CONSTITUTION:Two-split electrodes 2, 2' and 3, 3' are made to adhere to both faces of the center part of a piezoelectric substrate 1, and an excitation is executed. A cut-off frequency of the center part is set lower than a cut- frequency of the peripheral part, and a vibration of an asymmetrical (a0) mode of the lowest order is excited strongly. In case a desired overtone order number is (n), a parameter is selected so that a position of a coefficient of confinement of (n-2)th-order is in a position where an energy confinement rate of a mode curve is zero, namely, a confinement mode does not exist, and also, so that a position of a coefficient of confinement of nth-order is in a position where the confinement rate is large.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a piezoelectric resonator, particularly a piezoelectric resonator for overtone oscillation that enables oscillation at a desired overtone frequency without the need for a special oscillation circuit. Regarding resonators.

(Prior art) In recent years, demands for higher frequencies and ultra-miniaturization have become more severe in various electronic devices such as communication devices, but in order to meet these demands, crystal resonators, which have been commonly used In addition to the use of overtone vibration of piezoelectric resonators such as
Surface acoustic wave (SAW) resonators have become widely used.

However, the former method generally involves extracting the desired output through an LC tuning circuit that tunes to the desired overtone frequency, or inserting an LC tuning circuit into a part of the oscillation circuit so that the negative resistance of the circuit adjusts to the desired overtone frequency. They are designed to be sufficiently large only in the frequency domain, and both require a coil, which is extremely inconvenient in promoting the use of ICs for oscillation circuits.

On the other hand, as is well known, the oscillation frequency of a SAW resonator is uniquely determined by the material of the piezoelectric substrate and the pitch of the interdigital transducer (IDT) electrodes formed on its surface, so the resonator itself can be made smaller. Although there are no circuit problems as mentioned above, there is a flaw in that it is far inferior to an AT cut crystal resonator in terms of frequency and temperature characteristics.

(Objective of the Invention) The present invention has been made in view of the defects of conventional high-frequency resonators as described above, and has almost the same form as a conventional piezoelectric resonator, Therefore, it is possible to utilize high-order symmetrical or asymmetrical mode vibration to enable oscillation at a desired overtone frequency without substantially changing the manufacturing process or adding an LC tuning circuit or the like to the oscillation circuit. The object of the present invention is to provide a piezoelectric resonator for overtone oscillation.

(Summary of the Invention) In order to achieve the above objects, a resonator for overtone oscillation according to the present invention has the following configuration.

That is, the higher-order frequency f1 generated when the piezoelectric resonator is excited
A multi-divided energy confinement section (by attaching a multi-divided electrode to the negative part).

It strongly excites the vibrations, substantially confines the vibration energy of higher-order overtone vibrations higher than the n-order overtone among the vibrations of the relevant mode near the periphery of the multi-divided energy confinement section, and also confines the vibration energy of the n-2nd order or lower including fundamental wave vibrations. The size of the multi-divided portion (electron+li), the amount of plateback (f 2 -ft)/f 2 and the thickness of each substrate are selected so that the vibration energy of the overtone vibration is diffused over the entire surface of the substrate.

9. The inventor of the present application has already focused only on the vibration energy confinement mode of the lowest order symmetrical mode vibration in the patents (Patent Application No. 6O-77065) filed on April 1, 1985. A piezoelectric resonator for overtone oscillation, which confines the vibration energy of a desired overtone order in the vicinity of the center electrode, while leaking all the vibration energy of lower order overtone vibrations, including fundamental wave vibration, to the periphery of a piezoelectric substrate. However, it should be noted that the present invention extends this concept to the use of higher-order symmetrical or asymmetrical modes of vibration.

(Embodiments of the Invention) The present invention will now be described in detail based on the theory that led to the invention and the embodiments shown in the drawings.

Prior to explaining the embodiments, the theory of the present invention will be explained in some detail in order to facilitate understanding of the present invention.

First, if we enumerate all the facts that are the premise of the nine ideas of the present invention, they will be as follows.

(1) Shockley's energy confinement theory is a purely elastic analysis and analyzes SH waves as waves, but the vibration medium can be metal, crystal, lithium tantalate, lithium niobate, or piezoelectric ceramics. For general piezoelectric resonators using high-coupling materials such as
It is known that this theory can be applied to the qualitative behavior of all vibration modes such as thickness flat, thickness twist, thickness nine, etc., even if the vibration energy propagation direction and overtone order are different.

(2) According to Shockley's energy confinement theory, as shown in Figure 2 (al), if there is a part with a cutoff frequency f2 around a part with a cutoff frequency f1, vibration energy is transferred to the part with a small cutoff frequency (part fl). However, the degree of confinement is as shown in Figure 2 (bl).

The normalized resonant frequency is called the normalized resonant frequency by the formula: (Cf-f・)/(f2-f・), and the case of 1=1 means the case of f=f2. In other words, there is no influence of the cutoff frequency f1, which means that there is no core. In this case, the vibration energy is diffused over the entire surface of the substrate and no confinement occurs.

On the other hand, in the case of F=0, contrary to the above explanation, the cutoff frequency f
This means that the entire vibration energy is confined in one part.

Also, the parameter naJm/H on the horizontal axis is called a confinement coefficient and is the overtone order n1g! A cutoff frequency f1
It is defined by the size a and thickness H of the portion, and the amount of frequency reduction Δ.

By the way, considering Fig. 2 (bl?), if the confinement coefficient n a , /m/H is less than a certain value, the high-order symmetric mode (81,'82...) or the asymmetric mode (a
□.

It can be seen that there is no confined mode at all in the vibration of al,...). This property is the lowest symmetric mode (
Note that this property does not exist in So).

(3) If the confinement coefficients a, Jts, and H are appropriately fixed values, the degree of energy confinement increases as the overtone order n increases; The degree of energy confinement can be determined by the overtone order. The cutoff frequency f
1, which is the frequency reduction amount Δ due to the size of the part (generally the electrode attachment) and the addition of some mass.

However, when a highly coupled material such as quartz is used as a vibration medium, the effect of lowering the frequency due to its piezoelectricity becomes significant, and if the above-mentioned Δ cannot be sufficiently manipulated, the above-mentioned aQ
It is effective if you change it.

(5) Regarding vibrations in which energy is trapped, the equivalent resistance increases as the overtone order increases.

Furthermore, as is clear from the above-mentioned FIG.
If there is a portion that absorbs the leakage energy and converts it into heat excessively close to the portion where the cut-off frequency is low, the equivalent resistance to the vibration will increase.

Incidentally, in conventional crystal resonators, the difference in cutoff frequency can be increased by attaching a sufficiently thick electrode to the center of the crystal substrate.
Since the vibration energy of all overtone orders is confined in the core, it is easiest to oscillate at the fundamental frequency where the CI value is the minimum, and if you want to make this overtone oscillation, the oscillation circuit side As mentioned above, it requires some ingenuity.

(6) However, the properties of the higher-order symmetrical or asymmetrical modes shown in Figure 2 (bl) are the results of theoretical analysis on an infinite piezoelectric substrate, but if this property also applies to a finite substrate, If this were to be preserved, the energy of the vibrations diffused over the entire surface of the substrate would leak or be consumed from the holding portions at the edge of the substrate, so the equivalent resistance to these vibrations would be extremely small.

Considering the facts explained above, first of all, to what extent are the properties of higher-order symmetrical or asymmetric mode vibrations on an infinite substrate described in (2) and (3) maintained on a finite substrate? I will consider it.

Figure 3 (at has an infinite length in the χ direction and a finite width of 2b in two directions. This is a schematic cross-sectional view showing an energy confinement type resonator with an electrode having a width of 23 at the center of the substrate in the width direction. be.

As for the waves excited in such a resonator, it is only necessary to consider the SH wave having a displacement parallel to the χ axis, but the displacement U is as described in Umagami and Jumonji's "Analysis of Energy Confinement Type Piezoelectric Resonators" (1966). According to September IEICE Journal Vol. 48, No. 9), TJ = u @ωs(n”y;/H)1) exp(j
ωt ) ・−・−・−(1). However, the above U is u = f (Z'), and the propagation constant β is defined to always be a real number in each region (I), (03, and (4)) of the substrate shown in Figure 3 (a). It can be rewritten as follows using k and ni'Q.

u 1 = B Taste k' z C: k k ' z
(b≦2≦−a) ---・(21u, =A, □
IIkz (-a≦2≦a) ---
(31u, =B:lk'z+(, Jk'z (a≦
2≦b ) -・- (41 where A, B, and C are constants, and flt - natural resonance frequency of thickness shear vibration assuming that the electrode part (b) is infinitely wide + fz'it electrodeless part (
Assuming that Il and (2) are infinitely wide, and assuming that Il and (2) are the natural resonance frequencies of nine cases, each of the above regions (b) and (Il, C
For each propagation constant of I[l, ni' is "'=n"&(f/ft)2-1/H
・(sl"=n"V'1-(f/f2)2/H-・-・
-・(61.

In addition, in the double notation of Equations (2), (3), and (4), the upper part gives a symmetric vibration where the displacement U is an even function with respect to the origin, and the lower part gives an asymmetric vibration where the displacement U is an odd function. be.

In the above equations (1) to (6), the following frequency equation is obtained from the boundary conditions that 2=a and the displacement and stress are continuous, and z=±6 and the end face is free.

, t; m tuhk'(b-a)=ni/k ka ・-・
(71COS) Here, an approximation of equation (7) when f1 is slightly lower than f2 is calculated.

First, the observable force frequency when the substrate thickness is varied or electrodes are attached to region 0 in FIG. 3 (al) is defined as the resonant frequency f:f.

Next, two new standardization frequencies, δ and Δ, that satisfy the following equation are introduced.

f=(1+δ)fl −・・・・・・・(8) fx=(
1-Δ) f2 ・・・・・・・・・(9) From (5) and (8), (kH)2==(nr)22δ Hit-(1)
From (6) and (9), (k'H)2= (nr)2-2
(Δ−δ) ・(From Jυan and al k'H/
kH= J (,4?δ)/δ−・・・−・−a’a where δ/Δ=W ・・・・・・・・・・・・・・・
... Let's say αj.

k'/ni= , 7 (1-F)/F ・・・・・・・・・
・・・・・・・・・ From Il, Ql and (13), ka = nwaJ2A/H= nraJ 2Fth
/H-・・・・(15) Furthermore, (from lυ and u3, 'a = n7raV/2Δ(1-F) /H・−・−
-= (16) α4), (1!19 and (lt1917
Hc substitution f le,! =tanh n*aJ2Δ(1-F)
・(6/a-1)/H□- ”'v'(IF)/F nyraV/2F, =h/
H---------...-α乃cot This is a formula that shows the relationship between the normalized resonance frequency 1, which is the parameter b/a'jt, and the resonator dimension naJm/H, and it is expressed as the vibration energy on a finite plate. This is a general formula that gives a confinement state.

Therefore, the frequency spectra of higher-order symmetric and asymmetric mode vibrations in the case of b/a=4 were calculated using the above-mentioned surface formula, and the results were compared with those in an infinite substrate, as shown in Figure $3 (bl).

As is clear from this figure, the degree of energy confinement for vibrations in the lowest-order symmetrical mode varies greatly depending on the substrate dimensions, but for vibrations in higher-order symmetrical and asymmetrical modes, it is virtually constant for both infinite and finite substrates. It turned out that it is safe to consider them to be equivalent.

That is, (2) and (3) which are the prerequisites of the present invention described above
can be applied as is to finite substrates, and the slopes of other modes are steeper than the characteristics of the lowest-order symmetric (SO) mode, and the degree of this is more pronounced as the higher-order modes increase. Note in particular that it is held in a finite substrate.

As a result of the above analysis, once we consider all the facts (1) to (5) that are the premise of the idea of the present invention mentioned above, it is understood that by integrating these facts, we will arrive at the following idea. It will be.

That is, if the two-part electrodes 2, 2' and 3°3' are fully attached to both sides of the central part of the piezoelectric substrate 1, respectively, and are excited as shown in FIG. It is clear that it excites strongly.

Here, Opert-7, which is desired to oscillate with the above-mentioned vibrator,
When the orders are f and n, the confinement coefficient (n-2) of the (n-2) order on the horizontal axis of FIG. 3(b) is a Jw
The position of /H should be at the position where the energy confinement rate of the ao-f-de curve is zero, that is, the confinement mode does not exist, and the position of naJΔ/H should be at the position where the confinement rate of the a0 mode curve is as small as possible. If each parameter a and Δ are selected, as shown in FIG.
．． The vibrational energy of the overtone vibration of the (n-2) order or lower is confined near the periphery of the piezoelectric substrate 1 and is diffused to a considerable extent through the substrate holder that always exists at the periphery of the substrate 1. It will leak and be consumed.

On the other hand, as mentioned above, the higher the overtone order, the higher the equivalent resistance of the vibration energy of the overtone vibrations of the nth or higher order confined in the vicinity of the divided electrodes 2, 2' and 3, 3'. After all, the resonator configured in this manner should oscillate at the zero-order overtone frequency without requiring any special measures for its oscillation circuit.

Figure 1 fc) is a. This is a diagram showing the basic parameter selection procedure when trying to obtain a resonator for third-order overtone oscillation using vibration in the a0 mode. Since this is a case where the confinement coefficient naJ-ku/H is approximately 0.4 or less, aJ, h/H = 0.4 for fundamental wave (n = 1) vibration and third-order (n = 3) overtone vibration, respectively. , 3 av7
x lHHI32 fx Parameter a and Δ
All you have to do is decide.

Incidentally, the gap between the divided electrodes may be set to an appropriate value as long as a short circuit does not occur between adjacent electrodes.

However, it is well known that when this electrode gap is extremely small, the asymmetric mode vibration acoustically couples with the simultaneously excited symmetric mode vibration, resulting in two different resonance frequencies. In the resonator according to the present invention, it is only necessary to extract one of the resonance frequencies, that is, the resonant frequency due to the asymmetric mode vibration in the above example, so no particular problem occurs.

In addition, if you want to make full use of vibrations in higher-order modes, 9
For example, if you want to use S1 mode or a□ mode, 1! In that case, the frequency spectrum of each mode becomes steeper as the slope of the curve becomes higher order, as shown in Figure 3 (bl), so the desired zero-order overtone can be obtained. It is extremely advantageous to be able to set a large difference between the vibration energy confinement rate of vibration and that of the (n-2)th order or lower.

Although the two basic principles of the present invention have been described above, in reality, it is possible to obtain a resonator that exhibits the same effects even if these principles are slightly deviated.

In other words, in a two-oscillator circuit, the gain of the amplifier generally decreases as the frequency increases, and the negative resistance of the circuit also has the property of being inversely proportional to the square of the y frequency. This is because it cannot necessarily be asserted that oscillation at the −7 frequency is the easiest.

For example, the lowest order asymmetry (ao
) mode of vibration to manufacture a resonator for fifth-order overtone oscillation, all parameters were set so that the vibration energy confinement rates of the first-order (fundamental wave vibration) and third-order overtone vibration were both zero. Then, as shown in FIG. 4, the vibration energy confinement rate of the fifth-order overtone vibration may not be sufficiently large, and therefore, the equivalent resistance for the fifth-order overtone vibration may be higher than that for the seventh-order vibration.

Even in such a case, if the difference in equivalent resistance for 5th and 7th overtone oscillations is small, oscillation at the 5th overtone frequency is possible in relation to the characteristics of the rooting circuit described above. It is quite conceivable that if the difference in equivalent resistance for the fifth-order and seventh-order overtone vibrations is large, oscillation may occur at the seventh-order overtone frequency.

In order to avoid the above-mentioned instability, the vibration energy confinement rate of the third-order overtone vibration is increased slightly above zero, and the equivalent resistance for the desired fifth-order overtone vibration is made as small as possible than that of the third-order overtone vibration. Further, the vibration energy confinement rate of the fifth-order overtone vibration may be selected so as to be slightly higher than that of the first-order vibration.

Therefore, it should be noted that the present invention does not necessarily require that the vibration energy of overtone vibrations (including fundamental wave vibration whole tones) of orders lower than the overtone order for which oscillation is desired be made into a completely unconfined mode.

The above explanation was based on an example of using the vibration of the lowest order asymmetric (ao) mode, but the higher order asymmetric mode (a
1ea2+...) or higher-order symmetric mode (81,
82,...) When using vibration, the total 7°,
- A similar concept can be used to select each Huff meter a and Δ.

The nine basic concepts of the present invention have been fully explained above.Next, specific electrode configurations, wiring connections, etc. when manufacturing a resonator according to the present invention will be described in detail.

First, since the electrodes of a vibrator generally need to be arranged so that they can effectively draw out the charges generated by the displacement of the piezoelectric substrate, the resonator according to the present invention also depends on the number of peaks or troughs of charges generated by the vibration mode used. Needless to say, it is necessary to make the positions coincide with those of the divided electrodes and to connect the electrodes so that the charges generated in each electrode do not cancel each other out.

Therefore, for example, when using vibration in the lowest order asymmetric (AO) mode, two divided electrodes 2, 2' and 3, 3' are attached to the front and back of the piezoelectric substrate 1 as shown in Figure (a), and the curve 4 A charge of the level shown in the figure is generated, and this charge is expressed as shown in the figure (
Either connect them in series as shown in bl, or connect them in parallel as shown in cl. In this case, the impedance when connected in parallel is 1/4 of that when connected in series, so you want to reduce the equivalent resistance. In some cases a parallel connection may be advantageous.

Furthermore, when considering the spurious of a resonator using such split electrodes, it is necessary to consider that the vibration mode to be used is higher-order symmetric (81,
S2,...) mode, electrically asymmetric (ao, a□, a2...) modes are not excited, and when using higher-order asymmetric mode vibrations, On the contrary, the symmetric mode should not be excited, but in reality some other modes are excited due to errors in the manufacturing of the resonator.

Further, among the vibration modes used, modes having different orders, for example, the a2 mode for al, are essentially excited.

However, in the former case, the response is inherently extremely small, and in the latter case, the number of peaks or valleys in the generated charge pattern does not match the electrode division pattern, so the response is small. It doesn't reach the level where it becomes a problem.

For reference, the method of connecting three divided electrodes using the S1 mode is shown in FIGS. 6(a) and 6(bl).

Further, FIG. 7(a) shows an example of the wiring pattern to be formed on the piezoelectric substrate for the resonator of the two-divided electrode and the three-divided electrode.
(a) and (bl) are examples of series and parallel connection of two divided electrodes, respectively (9) and (C).

(dl is a perspective view showing an example of series and parallel connection of three divided electrodes, respectively, and when the wiring patterns 5, 5, etc. go around the edges of the piezoelectric substrate 1, the edges are also conductive. The front and back patterns may be connected by fully depositing the pattern or by applying conductive paint or adhesive.

By the way, the resonator according to the present invention leaks and diffuses the vibration energy of overtone vibrations of orders lower than the desired overtone order, including fundamental wave vibrations, over the entire surface of the piezoelectric substrate, but this leakage energy is transmitted without any loss. As described above, the dog portion of the cut-off frequency is entirely propagated and leaks from the resonator support portion that is always present at the end of the piezoelectric substrate.

However, it is important to consume this leakage energy more effectively in order to increase the total equivalent resistance to the vibration, so as shown in FIG. Vibration energy absorbing parts 6, 6 whose frequency f3 is extremely low. ...... will be established. By doing so, the amplitude of the leaked vibration energy can be increased in the core portion and converted into heat and consumed. In order to obtain such an effect, the energy absorbing portions 6, 6 . . . . The thickness of the piezoelectric substrate 1 itself may be made larger than other parts, or an appropriate mass such as a conductive film or a resin film may be attached.

Alternatively, as shown in tbl of the same figure, adhesives 7, 7.・・・・・・
A mass such as the following may be placed in the core.

Also, the value f3 of the cutoff frequency of the energy absorbing section 6 is also fl.
It may be equal to or less than , but it is desirable to increase or decrease it as necessary to minimize unnecessary vibration energy consumption in the core.

In order to further actively consume leakage energy, the same figure (c
) As shown in FIG.
may be attached and connected between the two through a suitable resistor 9.9.

The value of the resistor to be connected at this time is basically (2πfnCo ) And it is sufficient. However, if there are multiple vibration frequencies that should absorb energy, (2πf aC”)−1+ (2π
A number of different resistors may be attached, such as fbCo)-", -..., or f a + f b r...
The average value of ``tfm and 2πfmCo)−''
A resistance may be added.

However, the above-mentioned resistor does not necessarily have to be used in the construction of an electronic circuit, and may be made by applying a conductive adhesive for fixing the holding part of a general crystal resonator, for example. It would be convenient to implement it without any negative impact.

Now, the specific structures and obtained characteristics of two different embodiments of overtone oscillation resonators using the lowest order asymmetric (AO) mode vibration manufactured based on the principle explained above are as follows. Shown below.

Figure 9 (at is a plan view of a basic third-order overtone oscillation resonator without a vibration energy absorption part according to the present invention, in which a circular crystal substrate 1 is divided into two main electrodes 2 and 2 ′
The leads 5.5 drawn out from the front and back are used for parallel reading with the back main wire (not shown), which is the same on both sides.

In addition, FIG. 6B shows a structure in which a vibration energy absorbing portion 6.6 is provided on the outer periphery of the crystal substrate. As a result of measuring the characteristics of these two types of resonators, the CI values at the 3rd and 1st (fundamental wave) overtone frequencies for the former were 70, respectively.
Ω and 175Ω, and when a small amount of conductive adhesive was attached to the crystal substrate holder, these values became 72Ω and 380Ω, respectively, and the validity of the theory of the present invention was basically verified.

In addition, the CI values at the 3rd and 1st (fundamental wave) overtone frequencies where the vibration energy absorption part is heavily distributed are 65Ω and 250Ω, respectively, and these values are 65Ω and 250Ω, respectively, when a conductive adhesive is attached to the crystal substrate holding part. were 65Ω and 1330Ω, respectively, confirming the effectiveness of the vibration energy absorption section.

Furthermore, for the resonator shown in Fig. 9 fa), if the crystal substrate holding part is fixed with a conductive adhesive and the electrode film thickness is increased to ftf, the difference in CI value at the third-order and first-order Opart-7 frequencies is It decreased as shown in Figure 10 (at).

This means that, as described above in FIG. 7 (at), Δ changes depending on the 1j film thickness, and when confinement occurs in both the first-order and third-order overtone vibrations, the difference in CI values decreases. Therefore, it will be understood that it is necessary to set various parameters including the electrode film thickness so as to keep the difference between the CI values sufficiently large.

In addition, in a resonator having a vibration energy absorbing part shown in Figure 10 (bl is 'ij!) and Figure 9 (bl), the gap between the excitation electrode and the energy absorbing part is changed. This is a study of the change in CI value at tone frequency, and it was found that as the gap increases, the leaked vibration energy of the primary (fundamental wave) frequency is not sufficiently consumed in the energy absorption part, and the effect of providing the core part decreases. Therefore, it will be understood that when the entire energy absorption section is used, it is important to set the gap between this and the excitation electrode to an appropriate value.

The principles, basic configuration, and experimental results of the nine overtone oscillation resonators according to the present invention have been explained above. In order to meet this requirement, modifications may be made as shown in Figures 1) (a) to (dl).

That is, Fig. 1) (al) is a sectional view showing an embodiment in which resin films 7, 7 are attached to the vibration energy absorbing parts 6, 6 on the periphery of the piezoelectric substrate to lower the cutoff frequency of the core part, and Fig. In order to obtain a sufficient difference in cutoff frequency, the thickness of the substrate between the main electrodes 2 and 3 at the center of the substrate and the vibration energy absorbing portions 6 and 6 at the periphery is reduced using an etching method to increase the cutoff frequency at the core. The elevated version (C) in the same figure is the one in which electrodes 8, 8 are further attached to the vibration energy absorbing portion 6.6 in (b) above to enable electro-thermal conversion of the vibration energy as described above. can be,
Furthermore, in the same figure (dl is the thickness of the main electrode attached to the substrate in order to prevent the film thickness of the main electrodes 2, 2' and 3.3' from decreasing and increasing the electrical resistance when trying to obtain a high resonant frequency). Only that part is made thinner by etching or the like.

The above-described embodiments merely show some of the configurations that can be adopted by the resonator according to the present invention, and it goes without saying that these may be combined as appropriate.

Above 1. Overtone support according to the present invention.

For pendulums, the lowest-order asymmetry (
Although all examples have been explained in which the ao) mode vibration is used, the present invention is not limited to this, and can also be applied to higher-order asymmetric (a-work, a2...) modes and higher-order asymmetric vibrations. It will be easily understood that symmetrical (Sl, 82, . . . ) modes of vibration can also be utilized in the same manner without requiring further detailed explanation.

Furthermore, the vibration mode of the resonator shown as an experimental example is the lowest-order asymmetric mode with biaxial excitation of the crystal substrate, but it may also be excitation in the X-axis direction, and 1! in both the Z and X-axis directions. It may also be possible to divide the poles and excite vibration in both directions.

Furthermore, although the vibration energy absorbing portion-i is provided in the Z-axis direction in the 91g (bl), it may be provided in the X-axis direction, or may be provided over the entire circumference of the substrate, or a plurality of vibration energy absorbing portions may be provided. The vibration energy absorbing section may be divided into individual parts, because the effect of the vibration energy absorbing part is greater as the area surrounding the substrate periphery becomes more circular.

1. As stated at the beginning of the specification of the present invention, the present invention
It is applicable not only to thickness torsional vibration as shown in Figure (at) or (bl), but also to any type of vibration such as thickness longitudinal or thickness shear, and various piezoelectric materials can be used.

Furthermore, although not shown in the drawings, the resonator according to the present invention may be a two-boat resonator with a three-terminal electronic structure, and in this way it will be possible to easily oscillate in a high frequency band.
Furthermore, if applied to a monolithic crystal filter, it is expected that filter characteristics with less spurious will be obtained over a wide frequency range.

(Effects of the Invention) Since the present invention is configured as explained above, it does not require any special changes in the manufacturing process compared to conventional resonators, and moreover, it does not require special changes in the manufacturing process, and moreover, it does not require special circuits such as an LC tuning circuit in the oscillation circuit. Since it can easily oscillate at over -7 frequencies without adding any additional components, it is extremely effective when used as a frequency source for various electronic devices that have strict requirements for higher frequencies and higher circuit integration.

Furthermore, in the case of a normal piezoelectric resonator, especially a thickness vibration type resonator such as an AT-cut crystal resonator with good temperature characteristics, if a high frequency is to be obtained through fundamental wave vibration, the thickness of the piezoelectric substrate must be increased. However, according to the present invention, since the resonator itself is most easily excited at the overtone frequency, the thickness of the piezoelectric substrate can be set within a range that is easy to manufacture. This also has the effect of reducing the total manufacturing cost.

Question 9: Since the present invention utilizes higher-order symmetrical or asymmetrical mode vibrations in which the curve of the vibration energy confinement ratio against the confinement coefficient is steep, what is the lowest-order symmetrical mode according to the invention filed by the present inventor? It should be noted that this method is more effective in completely suppressing the vibration energy of orders lower than the desired overtone order and obtaining the desired oscillation frequency, compared to those that utilize the vibrations of the overtone order.

[Brief explanation of drawings]

Figure 1 (al is a cross-sectional view showing the basic configuration of the overtone oscillation resonator according to the present invention, bl is a diagram showing the vibration energy distribution of various vibration modes excited in the resonator, the same figure ( cl is an explanatory diagram showing the basic method for selecting various parameters of this resonator, and FIG. A diagram showing the vibration spectrum of
Figure 3 (at and (bl) are diagrams showing a schematic diagram of the board and the results of theoretical analysis, respectively, to prove that the vibration spectrum is valid even on a finite plate; Figure 4 is for overtone oscillation according to the present invention. An explanatory diagram showing another parameter setting method for configuring the entire resonator. Schematic diagram showing an example of parallel connection, Fig. 6 (a) and (bl
7 (al to (d)) are schematic diagrams showing series connection and parallel connection rows of electrodes of resonators that utilize Ss mode vibration, respectively.
8 is a perspective view showing an embodiment in which 2 divided electrodes are connected in series and in parallel, and 3 divided electrodes are connected in series and parallel, respectively. FIG. 9 is a cross-sectional view showing the structure of the resonator used in the confirmation experiment of the present invention, and FIG.
) is the one with a vibration energy absorption part, Fig. 10(a)
and (bl are diagrams of the experimental results showing the characteristics of the resonator shown in FIGS. 9 and 1, respectively). FIGS. 1...Piezoelectric substrate, 2.2' and 3.
．． 3'・・・・・・Multi-divided vibration energy confinement part (electrode). 6...... Vibration energy absorption section. 9・・・・・・・・・Resistance. Patent Applicant Toyo Tsushinki Co., Ltd. No. 2 Zuwani 7 E No. 8 Illustrated Notes // Drawing Procedure Amendment April 2, 1988 Patent Application No. 9756 No. 2, 1988
Title of the invention Piezoelectric resonator 3 for nine-overtone imaging using higher-order mode vibrations and correction Relationship to the case Applicant Postal code 253-01 Telephone 0467-74-1
) 31 (Representative) 753-4 Otari, Kanyo-cho, Koza-gun, Kanagawa Prefecture Date of procedural amendment order: March 25, 1985 5゜ Number of inventions to be increased by amendment: None 6, Subject of amendment
"Brief explanation of the drawings" column 7 Contents of amendment Original specification page 32, line 13 "...(a) to (d)..." was replaced with "...(a) to (C)...""..." is corrected.

Claims (3)

[Claims] (1) By providing a multi-divided energy confinement section with a cutoff frequency f_1 on the piezoelectric substrate and a section with a cutoff frequency f_2 (however, f_1<f_2) around it, high-order symmetrical or asymmetrical mode vibration is excited. Of the mode vibrations, the vibration energy of overtone vibrations of orders higher than or equal to the nth overtone vibration is almost confined near the periphery of the multi-divided energy confinement section, and the vibration energy of the n-2nd order or lower including the fundamental wave vibration of the vibration of the mode is approximately confined. The size of the multi-divided energy confinement section and the frequency reduction rate ((f_2-f_1)/f_
2) By selecting each parameter of the thickness of the piezoelectric substrate, at least the desired n-order overtone vibration is made easier to oscillate than the lower-order overtone vibration including fundamental wave vibration. A piezoelectric resonator for overtone oscillation that utilizes higher-order mode vibration. (2) The cutoff frequency f is placed at a suitable location near the outer periphery of the piezoelectric substrate.
By adding a vibration energy absorbing part with a smaller cut-off frequency than _2, the vibration energy of overtone vibrations lower than the n-2 order overtone vibration, including the fundamental wave vibration that is diffused over the entire surface of the substrate, can be effectively consumed. A piezoelectric resonator for overtone oscillation using higher-order mode vibration according to claim (1). (3) A patent characterized in that by connecting a resistor of an appropriate value between electrodes attached to both surfaces of the piezoelectric substrate at appropriate positions near the outer periphery of the substrate, consumption of vibration energy diffused over the entire surface of the substrate is increased. A piezoelectric resonator for overtone oscillation using higher-order mode vibration according to claim (1) or (2).