JPH03284007A - Compound longitudinal oscillation mechanical filter - Google Patents

Abstract

PURPOSE:To realize a satisfactory compound longitudinal oscillation mechanical filter without generating spurious outside area by providing a curvature part at a coupling member, and eliminating coupling between longitudinal oscillation sound pieces due to unrequired longitudinal oscillation. CONSTITUTION:A high frequency signal S4 is supplied from a signal source Osc to between input side piezoelectric ceramics 44a, 44b and an input side longitudinal oscillation sound piece 32, and an electric field in accordance with the signal S4 is generated. In the electric field, electrostriction is generated in directions of arrow heads mi and mo at the ceramics 44a, 44b, and the sound piece 32 resonates with frequency F4 setting length L4 as the half-wave length of a longitudinal wave. Such longitudinal oscillation is propagated by coupling mechanically with an output side longitudinal oscillation sound piece 34 via the coupling members 36, 38. The longitudinal oscillation propagating through couplers at the curvature parts provided at the members 36, 38 are reflected, and no coupling with an output side longitudinal oscillator occurs. Therefore, the members 36, 38 oscillate only by curvature oscillation, and the sound piece 34 resonates with the longitudinal oscillation. No coupling between input and output sound pieces by the longitudinal oscillation occurs in this compound longitudinal oscillation mechanical filter, and unrequired spurious response outside area can be eliminated.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a composite longitudinal vibration mechanical filter, which includes a longitudinal vibrating body (hereinafter referred to as a longitudinal vibrating vibrating element), a piezoelectric member, a coupling member, and a supporting member. In a composite longitudinal vibration mechanical filter consisting of a structure such as a holding member, a plurality of longitudinally vibrating sound bars are coupled by the bending vibration of the coupling member, and by providing a bending part etc. in the coupling member, unnecessary longitudinal vibration is prevented. This invention relates to a composite longitudinal vibration mechanical filter that suppresses coupling and improves characteristics.

(Background of the Invention) Recently, mechanical filters have been adopted in communication equipment and the like as intermediate characteristics between LC filters and crystal filters. This means that mechanical filters have a good Q
This is based on the fact that it has good selection characteristics based on the value of , has excellent stability against temperature changes, and can be miniaturized.

An example of this type of composite longitudinal vibration mechanical filter is shown in the third example.
As shown in the figure. As shown in the figure, the composite longitudinal vibration mechanical filter has an input side vertical vibration sound piece 2 and an output side longitudinal vibration sound piece 4, which are arranged on the same plane and made of a metal material or the like. The input side vertically vibrating sound piece 2 and the output side vertically vibrating sound piece 4 are integrally formed by constant elastic coupling members 6 and 8. In this case, supporting members 10 and 12 are provided in a protruding manner at the outer central portions of the input side vertically vibrating sound piece 2 and the output side vertically vibrating sound piece 4. A pair of input side piezoelectric ceramics 14a and 14b are superimposed and fixed to the input side longitudinal vibrating sound piece 2 using soldering or the like. The ends of the support members 10 and 12 are connected to the upright pieces 24a of the holding member 24.
and 24b is fixed to the upper center by laser welding or the like.

The composite longitudinal vibration mechanical system constructed in this way
Piezoelectric ceramics 14a on the input side of the filter.

14b and the upright piece 24a, a power supply line 18 for supplying an input signal and a ground line 18e are connected, while a lead-out line 20 for deriving an output signal and a ground p' 20e are connected.

According to the above configuration, the input side vertical vibration sound piece 2 and the output side vertical vibration sound piece 4, which are connected in series by the coupling members 6 and 8, can be arranged substantially in the air, and their longitudinal vibration etc. It is understood that the structure is formed in such a way that there is no problem. The composite longitudinal vibration mechanical filter is housed in a case (not shown), and then installed in an intermediate frequency amplification section of a communication device or the like to achieve its desired purpose.

In the composite longitudinal vibration mechanical filter configured as described above, a high frequency signal S from an oscillator Osc via a resistor R is attached between the feed line 18 and the ground line 18e on the input side piezoelectric ceramics 14a and 14b. This generates an electric field corresponding to a high frequency signal between the longitudinally vibrating sound piece 2 on the input side which is electrically grounded.

This electric field causes the input side piezoelectric ceramics 14a and 1 to
4b produces electrostriction in the directions indicated by Vm and Vn in the figure, and resonates at a frequency F where the length Ll of the input-side longitudinally vibrating resonator bar 2 is a half wavelength of the longitudinal wave. If the average propagation velocity of the longitudinal wave in the input side vertically vibrating acoustic bar 2 is V, the frequency F1 is given by the following equation.

F+=V/(2L+)...
(1) This longitudinal vibration at frequency F1 is mechanically coupled to the output side longitudinal vibration sound bar 4 at the coupling members 6 and 8, and the output side longitudinal vibration sound bar 4 resonates with the longitudinal vibration at frequency F2 due to the length L2. do. Similar to equation (1), this frequency F2 is calculated as follows, assuming that the average propagation speed of the longitudinal wave of the output longitudinally vibrating sound piece 4 is ■, then F2=V/(2L2)...
(2) becomes. Electrodes generated on the output side piezoelectric ceramics 16a and 16b due to the longitudinal vibration of the output side longitudinally vibrating sound piece 4 are derived as a high frequency signal S2 formed with a predetermined steep frequency characteristic between the lead wire 20 and the ground wire 20e. be done.

(Problem to be Solved by the Invention) By the way, in this type of composite longitudinal vibration mechanical filter, the coupling members 6 and 8 are connected to the input side longitudinal vibration sound piece 2.
It is coupled to the output side longitudinal vibration sound piece 4 by bending vibration that vibrates in the longitudinal vibration direction and propagates in a direction perpendicular to the longitudinal vibration direction, but the positions of the coupling members 6 and 8 are such that the input side longitudinal vibration sound When the ends of the piece 2 and the output side longitudinal vibration sound piece 4 are not opposite,
The input side vertical vibrating sound piece 2 not only vibrates in the longitudinal vibration direction at the position of the coupling members 6 and 8, but also contracts in a direction perpendicular to the longitudinal vibration direction, and this vibration causes the coupling members 6 and 8 to vibrate longitudinally. Since it is extracted as an output signal without being combined with the longitudinal vibration of the output side longitudinal vibration acoustic bar 4, it becomes an out-of-band spurious in the composite longitudinal vibration mechanical filter, revealing the disadvantage that the characteristics outside the filter's pass band are poor. do.

The present invention has been made to overcome the above-mentioned disadvantages, and the coupling member that connects a plurality of longitudinally vibrating sound pieces including an input side vertically vibrating sound piece and an output side longitudinally vibrating sound piece is caused by bending vibration. It is an object of the present invention to provide a composite longitudinal vibration mechanical filter having good characteristics inside and outside the passband, characterized in that the coupling member is provided with a bent portion or the like to prevent coupling due to unnecessary longitudinal vibration.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a composite longitudinal vibration mechanical filter that forms and derives a supplied high frequency signal into a predetermined frequency band. connecting a plurality of vibrating bodies including an output side, a piezoelectric member having an electrode plate for connecting a conductor superimposed on the input side vibrating body and the output side vibrating body, and the plurality of vibrating bodies; a plurality of coupling members, a support member formed to protrude from the input side vibration body and the output side vibration body, and the support member is attached to hold the plurality of vibration bodies including the input side vibration body and the output side vibration body. It is configured to include a holding member and a conductor for inputting or outputting a high frequency signal to the electrode plate of the piezoelectric body, and a plurality of vibrating bodies including an input side and an output side undergo longitudinal vibration near the filter passband. vibrates,
In addition, the coupling member that couples the longitudinal vibrating bodies is characterized in that the coupling member is provided with at least one bending portion or the like for coupling by bending vibration and preventing coupling due to unnecessary longitudinal vibration.

(Embodiment) Next, a preferred embodiment of the composite longitudinal vibration mechanical filter according to the present invention will be described, and the accompanying drawings (first
This will be explained in detail below with reference to FIG. In FIG. 1, reference numeral 30 indicates an embodiment of the composite longitudinal vibration mechanical filter according to the present invention, and the composite longitudinal vibration mechanical filter 30 includes an input longitudinal vibration acoustic bar 32 and an input side vibration acoustic bar 32. Output side longitudinal vibration sound piece 34 with the same shape
have. The input side and output side longitudinal vibration sound bars 32
and 34 are arranged on the same plane, and coupling members 36 and 38 are formed of thin, constant-elasticity material and have a bent portion in the center. Further, each of the input side longitudinal vibration sound piece 32 and the output side vertical vibration sound piece 34 has a support member 40 projecting from the center thereof.
and 42 are provided. The input side longitudinal vibration sound bar 3
2, a pair of input-side piezoelectric ceramics 44a, 44b are polymerized and fixed by soldering or the like. Similarly, the output side piezoelectric ceramics 46a, 46 are also used for the output side vertical vibrating sound piece 34.
b is polymerized and fixed. Input side piezoelectric ceramics 44
a, 44b and output side piezoelectric ceramics 46a, 46
Electrodes (not shown) such as metallization are formed in advance on the surfaces of b. And the support members 40 and 42
Each end portion of is attached to the inner end surface of the rectangular outer frame member 50. In this case, the outer frame member 50, the input-side vertically vibrating sound piece 32, and the output-side vertically vibrating sound piece 34 are on the same plane.

In addition, input side and output side piezoelectric ceramics 44a, 4
A power supply line 52 and a lead-out line 54 for feeding and deriving high-frequency signals to 4b, 46a, and 46b are wired, and ground wires 52e and 54e are also wired.

The composite longitudinal vibration mechanical filter 30 of the present invention is constructed as described above, and the operation thereof and the effects of this embodiment will be explained next.

First, a pair of input side piezoelectric ceramics 44a and 44
A high frequency signal S4 of 455 KHz, which can be generated from a frequency converter such as a super heterodyne receiver, is sent from a signal source Osc via a power supply line 52 and a ground line 52e between B and the input side longitudinally vibrating acoustic bar 32 via a resistor R. intermediate frequency signals are supplied.

As a result, the electrically grounded input longitudinal vibrating sound bar 3
input side piezoelectric ceramics 44a and 44b between
An electric field corresponding to the high frequency signal S4 is generated through the high frequency signal S4. This electric field causes the input side piezoelectric ceramics 44a and 44b to
produces electrostriction in the directions shown by arrows mi and mo in the figure,
The input-side longitudinally vibrating sound piece 32 resonates at a frequency F4 where the long L4 is a half wavelength of the longitudinal wave. When the average propagation velocity of the longitudinal wave in the input longitudinally vibrating sound bar 32 is V, the frequency F4 is given by the following equation.

F4=V/ (2La)... (3
) This longitudinal vibration is mechanically coupled to the output longitudinal vibrating sound piece 34 via the coupling members 36 and 38 having bent portions and propagated. At this time, the coupling members 36 and 38 are coupled to the output longitudinally vibrating sound piece 34 through bending vibration whose vibration direction is the direction of the vibration of the input longitudinally vibrating sound piece 32 and whose propagation direction is perpendicular to the longitudinal vibration direction. Since the input-side longitudinal vibration sound bar 32 is contracting in a direction perpendicular to the longitudinal vibration direction other than the longitudinal vibration direction, this vibration also propagates through the coupling members 36 and 38 as a longitudinal vibration. It's possible. However, the longitudinal vibration propagating through the coupler is reflected at the bent portions provided in the coupling members 36 and 38, and is not coupled to the output longitudinal vibrator.

Therefore, the coupling member vibrates only due to bending vibration from the input side longitudinal vibration sound piece 32, and the length and L of the 8 force side longitudinal vibration sound pieces 34
5 in vibrations of frequency F5, i.e.
Resonates with longitudinal vibration. Similar to equation (3), this frequency F5 is calculated as follows, assuming that the average propagation velocity of the longitudinal wave of the output longitudinally vibrating acoustic bar 34 is V, F5=V/ (2L5)... (4
). Due to the electrostriction of the longitudinal vibration of the output-side longitudinal vibration vibrating bar 34, a voltage is generated in the electrodes (not shown) of the a-side piezoelectric ceramics 46a and 46b, and a predetermined steep frequency characteristic is formed due to the transmission of the longitudinal vibration, etc. That is, an intermediate frequency signal of, for example, 455 KHz formed into a narrow band frequency characteristic is outputted from the lead lines 54 and 54e as the output signal s5.
It can be derived as

In the composite longitudinal vibration mechanical filter 30 formed in this way, the coupling members 36 and 38 are coupled to the 8-force side longitudinal vibration sound piece 34 by bending vibration, and unnecessary longitudinal vibrations are transmitted to the coupling members 36 and 38. Since it is reflected at the provided bend, there is no coupling between input and output sound pieces due to longitudinal vibration,
Eliminates unnecessary out-of-band spurious responses.

(Effects of the Invention) As explained above, by providing a bent portion in the coupling member, coupling between longitudinally vibrating sound pieces due to unnecessary longitudinal vibrations is eliminated, so that in a composite longitudinally vibrating mechanical filter,
This has the effect of realizing a good filter with no out-of-band spurious.

The above explanation is for a structure with only input and output sound pieces, but even when there are multiple longitudinal vibration sound pieces on the input and output sound pieces as shown in Fig. 2, the coupling member having a similar bending part can also be used. A similar effect can be obtained by configuring as follows.

[Brief explanation of drawings]

FIG. 3 is a perspective view showing the configuration of a composite longitudinal vibration mechanical filter according to the prior art, FIG. 1 is a perspective view of an example of a composite longitudinal vibration mechanical filter according to the present invention, and FIG. FIG. Reference numerals relating to embodiments of the invention. 32... Input side vertical vibration sound piece, 34... Output side longitudinal vibration sound piece, 36.38... Coupling member, 40° 42... Support member, 44a, 44b... Input side piezoelectric ceramics , 46a, 46b...output side piezoelectric ceramics, 50
4... Outer frame member, 52° 52e... High frequency power feeding conductor and grounding wire, 54.54e... High frequency derivation conducting wire and grounding wire.

Claims (1)

[Claims] In a composite longitudinal vibration mechanical filter that forms and derives a supplied high frequency signal into a predetermined frequency band, a plurality of vibrating bodies including an input side and an output side of the high frequency signal;
a piezoelectric member superimposed on the input-side vibrating body and the output-side vibrating body and provided with an electrode plate for conductor connection; a plurality of coupling members connecting the plurality of vibrating bodies; and the input-side vibrating body. and a support member formed to protrude from the output side vibrating body, a holding member to which the support member is attached and holds a plurality of vibrating bodies including the input side and output side, and an electrode plate of the piezoelectric body. and a conductor for inputting or outputting a high frequency signal, and a plurality of vibrating bodies including the input side and the output side vibrate with longitudinal vibration near the filter pass band, and 1. A composite longitudinal vibration mechanical filter, characterized in that the coupling member is provided with at least one bent portion or the like for coupling by bending vibration and preventing coupling due to unnecessary longitudinal vibration.