JP2903399B2 - Frequency adjustment method for piezoelectric filter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for adjusting the frequency of a monolithic piezoelectric filter.

2. Description of the Related Art With the development of an information-oriented society, communication devices have become increasingly popular. For this reason, there is an increasing demand for a filter that can pass or block a signal of a specific frequency. A crystal filter is known as a typical filter of this type. As a more functional crystal filter, a monolithic type is known. As shown in FIG. 7A, this monolithic quartz crystal filter (hereinafter sometimes abbreviated as “MCF”) is, for example, a quartz plate (a quartz plate usually called an AT plate) as a piezoelectric crystal piece. The first electrode 13 and the second electrode 1
5 and a third electrode 17 on the other surface. More specifically, the lead portions 13a, 15a, and 17a for the respective electrodes from the first to third electrodes to the edge of the quartz plate.
Are formed respectively, and these electrode lead-out portions 13 are formed.
The crystal plate 11 is fixed to the support 19 by fixing the terminals a to 17a to the respective terminals 19a to 19c of the support 19 called a base. Further, a cover (not shown) is mounted on the support 19 so as not to touch the quartz plate 11, and the cover is filled with, for example, an inert gas. In this MCF, it is necessary to perform frequency adjustment to obtain desired filter characteristics and frequency characteristics. To this end, as shown in FIG. 7B, the resonance frequency F ₁ of the crystal resonator formed between the first electrode 13 and the third electrode 17 and the second electrode 15 and the third electrode 17 The resonance frequency F of the crystal resonator formed between
_2, and the resonant frequency _{F a} in the constructed crystal resonator between the first electrode 13 and second electrode 15, first electrode 13 and the second
The electrode 15 is in a connected state, and the resonance frequency F _s of the crystal resonator formed between the electrode in this connected state and the third electrode 17.
And need to be adjusted respectively. And for that,
Conventionally, (1). F as ₁ and the F ₂ coincide or substantially coincide, selectively, for example, silver or aluminum on the first electrode 13 or the second electrode 15 is deposited. (2). Next, silver or aluminum is deposited on the third electrode 17 so that _Fa has a desired frequency. (3). Next, as F _s has a desired frequency, silver or aluminum is deposited on the third electrode 17. And _Fa
While keeping the range of the -F _{s, F s} is eventually predetermined value F
₀ so that a range of hand, the (1) process the coarse adjustment to (3), medium adjustment is continuously performed in steps of fine adjustment. However, the order of (2) and (3) may be reversed. Incidentally, the _{F 0} is the reference frequency of the MCF,
F _a -F _s is the bandwidth. Here, as shown in FIG. 7C, the actual operation for performing each of the frequency adjustments (1) to (3) is performed by the evaporation source 21, the shutter mechanisms 23 and 25, and the control unit 27. This is performed by the frequency adjusting device 29 provided. FIG.
In (C), each of 23a and 25a is one mask of a constituent component of each of the shutter mechanisms 23 and 25. This is a mask having a window for leading to such an electrode. Further, each of the shutters 23b, 25b, and 25c is one of the constituent components of the shutter mechanisms 23 and 25, and is a shutter that covers and opens the window of the mask 23a or 25a. At the time of adjustment by the frequency adjuster 29, (a). To adjust the frequencies F _1, as shown in FIG. 8 (A), connects the first electrode 13 and the third electrode 17 to the frequency adjustment device 29 (actually support that is connected to the first electrode 13 The body terminal 19a and the support terminal 19c connected to the first electrode 17 are connected (similarly in the following description), and the shutter 25c (see FIG. 7B) is opened and closed, so that the evaporation source 21 controlling the mass of aluminum or silver which adheres to the first electrode 13. (b). in order to adjust the frequency F _2, as shown in FIG. 8 (B), the second electrode 15 to the frequency adjusting device 29 And the third electrode 17, and a shutter 25b (FIG. 7).
(Refer to (B)) to open and close the second electrode 15 from the evaporation source 21.
Controls the mass of aluminum and silver adhering to the surface. After F ₁ and _{F 2} are identical, (c). To adjust the frequency _{F a,} as shown in FIG. 8 (C), connects the first electrode 13 and the second electrode 15 to the frequency adjusting device 29, and a shutter 23b (Figure 7
(Refer to (B)) to open and close the third electrode 17 from the evaporation source 21.
Controls the mass of aluminum and silver adhering to the surface. (D). To adjust the frequency F _s, as shown in FIG. 8 (D), the first electrode 13 and the second electrode 15 to a connected state the electrode and the frequency adjustment device and a third electrode 17 29
And the shutter 23a (see FIG. 7B) is opened and closed to control the mass of aluminum and silver adhering to the third electrode 17 from the evaporation source 21. In each of the above adjustments (a) to (d), it is necessary to drive (resonate) the crystal filter. Therefore, conventionally, an oscillation method or a transmission method has been used. The former method is MC
In this method, F is connected to the oscillation circuit in each of the connection states shown in FIGS. In the latter, the MCF is incorporated in a π circuit in each connection state of FIGS. 8A to 8D, and a signal whose frequency changes sequentially from a separately prepared reference oscillator whose frequency can be varied over a wide range ( This is referred to as a "frequency sweep signal.") Is applied to the π circuit, and the frequency from the reference oscillator when the phase difference between both ends of the π circuit becomes zero is defined as the resonance frequency of the resonator. Things. The former is simple, but has problems in that the sub-vibration is erroneously adjusted to the main vibration, and that it is difficult to produce an oscillation circuit at high frequencies. On the other hand, the latter has solved it.

However, in the conventional frequency adjustment method, even if the transmission method is used,
FIG. 8 shows the electrodes 13, 15, and 17 (actually, the terminals 19a to 19c of the support 19 shown in FIG. 7A) of the MCF.
In each of the states (A) to (D), there is a problem that the frequency needs to be adjusted by switching to and connecting to the frequency adjuster 29 as appropriate. For this reason, the frequency adjustment time increases due to the terminal switching time, and circuit and mechanical parts for terminal switching are required, which complicates the frequency adjuster, makes maintenance difficult and increases costs, and is expected to be improved. Was rare. SUMMARY OF THE INVENTION The present invention has been made in view of the foregoing, and an object of the present invention is to provide a method capable of adjusting the frequency of a monolithic piezoelectric filter more easily and faster than before.

In order to achieve this object, the inventor of the present application has diligently studied. as a result,
A first electrode and a second electrode on one surface of the piezoelectric material piece;
In order to selectively adjust the mass of the first electrode, the second electrode, and the third electrode of the monolithic piezoelectric filter having the third electrode on the other surface and adjust the frequency of the piezoelectric filter, As a result, the present invention has been completed. (I). As shown in FIG. 1A, one of the first electrode 13 and the second electrode 15, for example, the second electrode 15 and the third electrode 17 are connected to each other. When a frequency sweep signal according to the transmission method is applied to the other of the first and second electrodes (the first electrode 13 in this example), FIG. 1 (B) resulting from resonance with the sweep signal a frequency _{F s} and the level _{L s} information and the frequency _{F a} and the level _{L a} information shown is first noticed that obtained _(provided that F s _{<F s.).} (II). Further, the frequency F _{1 of the} vibrator formed between the first electrode 13 and the third electrode 17 (see FIG. 7B);
It found that the difference between the level L _s and L _a as the frequency F ₂ of the oscillator constituted between the second electrode 15 and third electrode 17 _(see FIG. 7 (B)) and match small Was. (III). Further, any one of the first electrode and the second electrode, for example, the second electrode 15 and the third electrode 17 are connected, and the electrode in the connected state is connected to the first and second electrodes.
When silver or the like is deposited on an appropriate side of the first electrode or the second electrode while a frequency sweep signal in the transmission method is applied between the other electrode (the first electrode in this example) of the electrodes, the difference between the level _{L s} and _{L a} can be reduced, and,
F _s has been found that the closer to the desired value _{F 0.} Therefore, according to the present invention, one of the first electrode and the second electrode is connected to the third electrode, and the electrode in the connected state is connected to the other of the first and second electrodes. A frequency sweep signal in the transmission method is applied between the electrode and the electrode, and the difference | L _s -L _a | between the levels is within _a predetermined range ΔL, and F _s is a predetermined range with respect to a predetermined frequency F _0. It is characterized in that the masses of the first to third electrodes are selectively adjusted so as to be within (however, F _s <F _a ). Here, the level is a value related to the resonance intensity, and may be, for example, a voltage. Adjusting the mass of each electrode means that, for example, silver or the like is added to a desired electrode (not limited to one) among the first to third electrodes by, for example, an evaporation method, Any part (partly in thickness) may be removed. Further, the predetermined range for a predetermined range ΔL and, F ₀ is a value determined by the specifications required for the MCF. Incidentally, it is of course to be adjusted to keep the value of F _a -F _s is required in MCF in the adjustment.

According to the present invention, the mass of the first to third electrodes can be selectively adjusted while the connection between the first to third electrodes and the frequency adjuster is kept constant. Further, in the conventional method, since the electrodes are connected in several modes as shown in FIG. 8, the mass adjustment has to be performed for only one electrode. On the other hand, in the present invention, it is even noted that | L _s −L _a | is within the predetermined range ΔL and that F _s is within the predetermined range with respect to the predetermined frequency F _0. With this arrangement, it is also possible to perform mass adjustment on a plurality of the first, second, and third electrodes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for adjusting the frequency of a piezoelectric filter according to the present invention will be described below with reference to the drawings. It is to be noted that the drawings used in the description are only schematically shown to the extent that the present invention can be understood. Also, among the components in the drawings used for the description, the same components as those of the prior art are denoted by the same reference numerals as those in the drawings referred to in the conventional description. In addition, the description of such constituent components will be repeated and may be omitted. FIG. 2 is a block diagram schematically illustrating a configuration of the control unit 27 of the frequency adjustment device 29 used in the embodiment. In FIG. 2, 27a
Is a π circuit, 27b is a gain phase analyzer, 27c
Is a sequencer. This gain phase analyzer 2
By 7b, the frequency sweep signal can applied to the MCF, moreover, information of the information and the frequency F _a at and level L _a frequency F _s and the level L _s from the resonance with the sweep signal is obtained, further, already the _{F 1} and _{F 2} as described can be measured. In addition, as the gain phase analyzer 27b,
In this case, HP8751 manufactured by Hewlett-Packard Company
OA was used. FIGS. 3A to 6B are views for explaining the experimental procedure performed in this example. In this embodiment, first, an AT-cut quartz plate 11 having a predetermined shape is used.
A pre-adjustment MCF having predetermined first to third electrodes 13, 15, 17 and having a frequency of about 58 MHz is prepared (see FIG. 3A ). Next, the first electrode 13 and the third electrode 1 of the MCF are connected to the π circuit of the control unit 27 of the frequency adjustment device 29.
7 (see FIG. 3B). However, FIG.
As shown (A), the same in connection to (the following description of the support pin 19c which is connected to the support pin 19a and the first electrode 17 which is connected to the first electrode 13 to the π circuit 27 a ) . Then, the resonant frequencies F ₁ at configured crystal resonator between the first electrode 13 and the third electrode 17 is measured by the gain phase analyzer 27b. Frequencies _{F 1} at that time was 58.149666MHz.
Next, the second electrode 15 and the third electrode 17 of the MCF are connected to the π circuit of the control unit 27 of the frequency adjusting device 29 ( see FIG. 3C ). Then, the resonant frequency F ₂ at constituted quartz resonator between the second electrodes 15 and the third electrode 17 is measured by the gain phase analyzer 27b. Frequency _{F 2} at that time 58.154500MHz
Met. Therefore, the MCF before this adjustment is F ₂ >
F ₁ a and MCF of the difference is approximately 4.8KHz between _{F 1} and _{F 2}
It is. Next, the second electrode 15 and the third electrode 17 of this MCF are connected, and the control unit 27 of the frequency adjustment device 29 is set.
The connected electrode and the first electrode 13 are connected to the π circuit (see FIG. 4A). Then, obtain a resonance spectra at constituted quartz resonator at this time by the gain phase analyzer 27 b. In this measurement, FIG.
A spectrum as shown in (B) was obtained. That is, the information of the frequency F _s and the level L _s information and the frequency F _a at and level L _a from the resonance between the frequency sweep signal is obtained respectively. Next, this time,
The first electrode 13 and the third electrode 17 are connected, and the π circuit 27 a of the frequency adjustment device 29 is connected to the third electrode 17 and the third electrode 17.
The two electrodes 15 are connected (see FIG. 5A). Then, obtain a resonance spectra at constituted quartz resonator at this time by the gain phase analyzer 27 b.
In this measurement, a spectrum as shown in FIG. 5B was obtained. That is, the information of the frequency F _s and the level L _s information and the frequency F _a at and level L _a from the resonance between the frequency sweep signal is obtained respectively. However, FIG.
Magnitude relationship between _{L s} and _{L a} are reversed compared to the case of (B).
However, FIG. 4 (A), the both cases the connection state of FIG. _{5 (A) | L s -L} a | = △ L was almost the same value. Therefore, the second electrode 15 (F
Silver was supplied from the evaporation source 21 (see FIG. 1A) to the electrode associated with the higher frequency side of F ₁ and F ₂ , and the mass was added to the second electrode 15. At this time, L _s and L _a
The difference between _| L s _-L a | is the mass adding so in this case approximately 3dB to fall within a predetermined range. That is,
The mass is added so that the spectrum obtained by the gain phase analyzer 27b becomes as shown in FIG. FIG. 6B shows a state in which the mass is added in this way and the spectrum is measured by the gain phase analyzer 27b in the connection state shown in FIG. 4A. FIG.
(A) and (B) in the spectrum of both _{L s} and _{L a}
It can be seen that | L _s -L _a | Furthermore, the MCF finishing such adjustment, in the connected state shown in FIG. 3 (B) measuring the F _1, also measuring the F ₂ in the connection state of FIG. 3 (C). As a result, the frequency difference _F 1 -F ₂ both have discovered that a 344Hz. As is apparent from this description, according to the method of the present invention, the frequency of the MCF can be adjusted by paying attention to | L _s -L _a | and performing mass adjustment so as to reduce this. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. For example, the range of | L _s −L _a | is changed according to the specifications of the MCF, and is not limited to the above example. Further, the piezoelectric material is not limited to quartz, but may be another material. In the above example, the mass adjustment of only one electrode was performed for the experiment of mass adjustment.
_s -L _a | a while small and so the _{F s} becomes a desired value _{F o,} is also _natural, while keeping the F a -F _s within a certain range, two or more among the first to third electrode Of course, the mass of the electrode may be adjusted. This is because the adjustment time can be further reduced. Further, the configuration of the frequency adjustment device is not limited to this, and can be arbitrary. Further, the adjusting device that can be used in the embodiment of the present invention is not limited to the example described with reference to FIGS. 1 and 2, and any other suitable device may be used.

As is apparent from the above description, according to the method for adjusting the frequency of the piezoelectric filter of the present invention, the first to the first are as follows.
The connection between the third electrode and the frequency adjuster remains constant,
Selective adjustment of the masses of the first to third electrodes can be performed. For this reason, the problem of switching the electrodes, which has been a problem in the related art, can be eliminated, so that the frequency adjustment time can be reduced, the frequency adjuster can be simplified and the cost can be reduced. In the conventional method,
Since the electrodes were connected in several modes as shown in FIG. 8, the mass adjustment had to be performed only for a limited number of electrodes. On the other hand, in the present invention, | L _s −L _a | is within the predetermined range ΔL, and F _s is set to the predetermined frequency F _0.
It is also possible to perform the mass adjustment for a plurality of the first, second and third electrodes, as long as it is kept within the predetermined range. Therefore,
Frequency adjustment time can be greatly reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining the principle of the present invention. FIG.

FIG. 2 is a block diagram schematically showing a configuration of a control unit of the frequency adjustment device used.

FIGS. 3A to 3C are explanatory diagrams of an experimental procedure in an example.

4 (A) to 4 (D) show the experimental procedure in the example in FIG.
FIG.

5 (A) and (B) show FIG. 4 of the experimental procedure in the example.
FIG.

6 (A) and (B) are explanatory diagrams following FIG. 5 of the experimental procedure in the example.

FIG. 7 is an explanatory view of a conventional and the present invention.

FIG. 8 is a diagram provided for explanation of a conventional adjustment method.

[Explanation of symbols]

11: Piezoelectric material piece (quartz plate) 13: First electrode 15: Second electrode 17: Third electrode 19: Support body 21: Evaporation source 23, 25: Shutter mechanism 23a, 25
a: Mask 23b, 25b, 25c: Shutter 27: Control unit 27a: π circuit 27b: Gain phase analyzer 27c: Sequencer 29: Frequency adjustment device

Claims (1)

(57) [Claims] 1. A monolithic piezoelectric filter, comprising a piezoelectric material piece having first and second electrodes on one surface and a third electrode on the other surface. When selectively adjusting the mass of the electrode and adjusting the frequency of the piezoelectric filter, one of the first electrode and the second electrode is connected to the third electrode, and the electrode in the connected state is connected to the third electrode. by applying a frequency sweep signal in the transmission method between the other electrode of said first and second electrodes, from a resonance with said sweep signal frequency F _s and the level L _s information and the frequency F _a in and for information of the level L _a, deer, difference of the level between _| L s _-L a | so falls within a predetermined range, and wherein F _s is the within a predetermined range for a given frequency F _o So that the selective mass adjustment is performed. Frequency adjustment method of the piezoelectric filter (however,
It is an _{F s} <F _a. ).