JPH10224176A - Multiple-unit ladder type piezoelectric filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multiple-unit ladder type piezoelectric filter in which each member is well arranged and contained, even though it has many sheets of resonance elements and its connecting form becomes complicated. SOLUTION: Inside a shallow bottom-shaped square case 10, each inner connection end 15a and 16a of an input terminal I and an output terminal O is exposed on two sides that face each other. Furthermore, an inner connection terminal 17a of a ground terminal E is exposed on another side that meets the sides at right angles, each terminal I, O and E is united with the case through insertion forming and each is extended to the outside the case, and also a purality of serial resonance elements S1 to S3 and parallel resonance elements P1 to P6 are vertically inserted between the ends 15a and 16a of the terminals I and O to constitute a required circuit. Moreover, a sitting fixed groove is formed along a center line on an inner bottom of the case 10, U-shaped connecting pieces 21 are interfittingly attached to a groove 20, and the required electrical connection is secured through the pieces 21.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a portable mobile radio,
The present invention relates to a ladder-type piezoelectric filter used in a filtering circuit of a wireless communication device such as a mobile phone, and more particularly to a ladder-type piezoelectric filter most suitable for digital communication.

[0002]

2. Description of the Related Art Conventionally, this kind of ladder type piezoelectric filter is
Unit filtering circuits each formed by connecting a series resonator and a parallel resonator in an L-shape are arranged in multiple stages between an input terminal, an output terminal, and a ground terminal. Then, the resonance frequency of the series resonator and the anti-resonance frequency of the parallel resonator are matched, and the difference between the resonance frequency and the anti-resonance frequency is kept constant. For example, the resonance frequency of three series resonators is about 455 kHz, the antiresonance frequency is about 477 kHz, and the difference Δf is set to 22 kHz. The resonance frequency of three parallel resonators is about 433 kHz. The anti-resonance frequency is set to about 455 kHz, and the difference Δf is set to be 22 kHz. By the way, this configuration has a problem that the flatness is poor in the group delay characteristic.

In order to improve the group delay characteristic, a series resonator inserted between an input terminal and an output terminal and two parallel resonators inserted adjacent to one side of the series resonator are used. There has been proposed a configuration in which a unit filtering circuit composed of a plurality of sub-elements is used as a basic division and two or more stages are connected.

[0004]

On the other hand, a conventional multi-element ladder-type piezoelectric filter has an opening on the side surface of a case, and a resonator and a terminal plate are parallel to the mounting surface (bottom surface) of the filter through the opening. Was to be inserted into. However,
The height of the piezoelectric filter is required to be reduced, and the height of the opening is correspondingly reduced, and insertion of the resonator and the terminal plate becomes troublesome.

Further, as described above, a multi-element ladder piezoelectric filter having a large number of resonators and a complicated structure is used, for example, two parallel resonators are used for one series resonator. Accordingly, the arrangement structure for configuring the predetermined circuit has become complicated, and the assembling work has become more troublesome. SUMMARY OF THE INVENTION An object of the present invention is to provide a multi-element ladder type piezoelectric filter which is easy to assemble and can easily construct a predetermined circuit.

[0006]

SUMMARY OF THE INVENTION The present invention is directed to a synthetic resin shallow rectangular case having an opening on the top surface of which a cover plate is attached, and an input terminal on two opposing sides inside the case. Exposing each internal connection end of the output terminal, further exposing the internal connection end of the ground terminal on the other side perpendicular to the side, integrating each terminal with the case by insert molding, and connecting each external connection end Are extended to the outer surface of the case, and a plurality of series resonators and a parallel resonator are vertically inserted between the internal connection ends of the input terminal and the output terminal, and are arranged in a superposed manner. Resonators are connected in series, one end of the row is connected to the internal connection end of the input terminal, the other end is connected to the internal connection end of the output terminal, and one electrode of the parallel resonator is connected to the series resonator, Connect the other electrode to the internal connection end of the earth terminal via the earth connection piece. A seating groove is formed on the inner bottom surface of the case along a center line orthogonal to a side where the internal connection ends of the input terminal and the output terminal are arranged, and a U-shaped connecting terminal piece is fitted into the seating groove. A multi-element ladder type piezoelectric filter characterized in that both protruding ends of the terminal piece are brought into contact with electrodes of a required resonator to make the electrodes the same potential.

In this configuration, since the opening is formed on the upper surface, a wide opening area can be secured without mounting the case to go down, and the mounting becomes easy. In addition, since the U-shaped connection connection piece is fitted in the seating groove formed at the center of the inner bottom surface of the case, the protruding end of the connection connection piece contacts the node position of the electrode of the resonator, and The vibration of the child is held without being hindered. In addition, since the connecting portion connecting the two protruding ends of the U-shaped connecting connecting piece is embedded in the seating groove, the connecting portion is located below the inner bottom surface,
For this reason, it does not come into contact with other electrodes, but can be brought into contact with only required electrodes via the connection connection pieces without fail, and these can be brought to the same potential.

On the other hand, the ground connection piece may be provided with a linear contact end that contacts a node position of an electrode of the resonator. Thus, the node position can be reliably contacted with the predetermined pressure, and the formation is easy. That is, in a configuration in which the center is bulged and the bulged end is brought into contact with the node position as in a conventional terminal plate, the contact pressure varies depending on the degree of bulging, or molding is troublesome. However, because of the linear contact end,
The thickness is defined by the material thickness and is always constant, a uniform contact pressure can be secured, stable filtering characteristics can be achieved, and no bulging is required.

In such a configuration, in order to improve the group delay characteristic, a series resonator inserted between an input terminal and an output terminal and two series resonators inserted adjacent to one side of the series resonator are provided. This is optimal for a circuit configuration in which a unit filtering circuit composed of the parallel resonators described above is used as a basic division and two or more stages are connected.

In this configuration, two adjacent parallel resonators are arranged between both protruding ends of the U-shaped connecting connection piece,
The protruding ends are located between the series resonator and the parallel resonator, respectively, and the adjacent series resonators and the electrodes of the parallel resonator are connected to each other through the protruding ends. There has been proposed a configuration in which a ground connection piece is inserted between parallel resonators, and the ground connection piece is connected to an internal connection end of a ground terminal. In the above-described circuit configuration, the number of resonators is large and the connection form is complicated. However, the above-described configuration allows the resonators to be integrated and housed in the case.

[0011]

FIG. 15 shows three series resonators S ₁ ,
S ₂ and S ₃ (see FIG. 8) are connected in series to an input / output line L ₁ connecting the input terminal I and the output terminal O, and the six parallel resonators P ₁ , P ₂ , P ₃ , P ₄ , P _5, in which P ₆ (see FIG. 9) shows a circuit diagram of a ladder type filter connected in parallel between the output line L ₁ and the earth line L _2.

That is, a series resonator S ₁ (S ₂ , S ₃ ) inserted between the input terminal I and the output terminal O, and _two series resonators S ₁ (S ₂ , S ₃ ) inserted adjacent to one side of the series resonator S _1. A unit filter circuit composed of a plurality of parallel resonators P ₁ and P ₂ (P ₃ , P ₄ , P ₅ , P ₆ ) is used as a basic division and is connected in three stages. As described above, in a configuration in which a unit filtering circuit in which two parallel resonators are connected to each series resonator is used as a basic section and two or more stages are connected, a conventional attenuation The group delay characteristics are greatly improved without substantially deteriorating the characteristics.

FIGS. 1 to 14 show an example in which the present invention is applied to a ladder-type filter having such a circuit configuration.

Here, the series resonators S ₁ , S ₂ , S ₃ are:
As shown in FIG. 8, it has a strip shape made of lead zirconate titanate or the like, and is formed by forming electrodes 2a and 2b on the front and back of a strip-shaped piezoelectric ceramic plate 1 having a predetermined thickness. As shown in FIG. 9, the parallel resonators P ₁ , P ₂ , P ₃ , P ₄ , P ₅ , and P ₆ are made of lead zirconate titanate, like the series resonators S ₁ , S ₂ , and S _3. The electrodes 5a and 5b are formed on the front and back sides of the strip-shaped piezoelectric ceramic plate 4 to reduce the thickness and increase the capacitance. Thus, by making the thickness of the parallel resonator thinner than that of the series resonator, the capacitance ratio between the two increases,
The amount of attenuation can be increased.

Next, a rectangular case 1 in which each resonator is housed
Numeral 0 is made of synthetic resin and has a shallow bottom shape. The rectangular case 10 has an opening 11 formed at an upper part thereof,
A locking step portion 12 is formed along the inner wall of the opening 11, and a lid plate 13 is attached to the opening 11, and the lid plate 13 is supported by the locking step portion 12. Further, inside the rectangular case 10, the input terminals I and the internal connection ends 15 a, 16 a of the output terminal O are disposed in an exposed state at the center of the inner surfaces of the two opposing sides. An internal connection end 17a of the ground terminal E is exposed on the upper surface of the locking step 12 at a side perpendicular to the side. The terminals I, O, and E are integrally inserted into the rectangular case 10 and assembled by insert molding in a process described later.

Insert molding of the rectangular case 10 and the terminals I, O, E can be performed with good mass productivity by the means shown in FIG. That is, first, the thickness is 0.08 mm
A long thin plate 40 in which phosphor bronze is subjected to PbSn plating is punched into a shape shown in FIG. Then, as shown by a position A, portions (see chain lines) corresponding to the internal connection ends 15a and 16a of the punched portion 41 formed at predetermined intervals are bent at a right angle in advance. Then, as shown by a position B, the rectangular case 10 is transferred intermittently to the molding die, and the internal connection ends 15a, 16a, 17a are positioned in the die as described above, and the rectangular case 10 is molded. Next, as shown by position c,
The terminals I, O and E are separated from the long thin plate 40 by cutting and bent at the same time as the terminals I and O so that the lower bottom ends 15 b and 16 b are located at the lower bottom of the rectangular case 10.
Both ends of the lower bottom ends 15b, 16b are bent at right angles, and folded along the outer side surfaces to be connected to the external connection ends 15c, 15b.
c and the external connection ends 16c, 16c. Further, the ground terminal E protrudes laterally from the internal connection end 17a and is folded along the side surface to form an external connection end 17c.
Further, the end portion is folded along the bottom surface to be a lower bottom end 17b.

Thus, the rectangular case 1 having a configuration in which the external connection ends 15c, 16c, 17c of the terminals I, O, E are exposed on the peripheral surface and the lower bottom ends 15b, 16b, 17b are exposed on the lower bottom.
0 is completed. As described later, when the ladder-type filter using the rectangular case 10 is mounted on a printed circuit board, the external connection terminals 15c, 16c, and 17c are connected to a required electric circuit on the printed circuit board. Become. In this configuration, the external connection terminals 15
Since c and 16c are arranged, connection to a required conductive path on the printed board is possible from any surface. In addition, you may make it connect with a required electric circuit by the lower bottom end 15b, 16b, 17b.

In this configuration, unlike the conventional configuration, the input terminal plate, the input / output terminal plate, and the ground terminal plate are separately inserted into the case, or after the insertion, the insert terminal plate, the input terminal plate, the input terminal plate, and the ground terminal plate are not bent. The square case 10 having the external connection ends 15c, 16c, and 17c exposed on the outer surface is formed by a series of processes up to the bending process, so that the assembling becomes easy.

As shown in FIGS. 5 and 6, on the inner bottom surface in the rectangular case 10, there are provided internal connection ends 15a, 15b, which are disposed opposite to the inner wall surfaces of the input terminal I and the output terminal O.
A seating groove 20 is formed between 16a along a center line orthogonal to the side where the internal connection ends 15a and 16a are arranged. As shown in FIG. 10, three U-shaped connecting connecting pieces 21, 21, 21 are fitted into the seating grooves 20, and both protruding ends 22, 22 of the connecting pieces are connected to a required resonator. , So that the electrodes have the same potential.

On the other hand, between the internal connection terminals 15a and 16a, a series resonator S is connected from the internal connection terminal 15a side in FIG.
₁ , S ₂ , and S ₃ are provided, and the connection piece 29 connects the electrode of the series resonator S _{1 to} the internal connection end 15 a and alternately with each series resonator S ₁ , S ₂ , and S _3. The U-shaped connection connecting pieces 21, 21 and 21 are connected in series, and the series resonator S ₃ is connected to the U-shaped connection connection piece 2.
1 and the internal connection end 15 via the metal spacers 24, 24.
a. Further, between the protruding ends 22 of the U-shaped connection connecting piece 21 located between the series resonators S ₁ and S ₂ , the parallel resonators P ₁ and P ₂ are connected with the series resonators S ₂ and S _3. Protruding ends 22, 22 of the U-shaped connecting connection piece 21 located between
Between the parallel resonators P ₃ and P ₄ , there are parallel resonators P ₅ and P ₆ between the protruding ends 22 of the U-shaped connection connecting piece 21 adjacent to the series resonator S _3. The parallel resonators P ₁ and P ₂ , the parallel resonators P ₃ and P ₄ and the parallel resonator P
_5, between P _6, respectively ground connection pieces 25a, 25b, 25
c is interposed.

Here, as shown in FIGS. 11 and 12, the ground connection pieces 25a and 25b have a linear contact end 26 that contacts the center of the adjacent parallel resonator and an internal connection end 17a of the ground terminal E. L-shaped linear contact end 27 for connecting to
And formed by punching or the like. The ground connection piece 25c has a linear contact end 26, and an internal connection end plate 28 extending from the side of the linear contact end 27 to the internal connection end 17a for surface contact is provided with a linear contact end. It protrudes laterally from end 27. And the earth connection piece 2
5a, 25b linear contact end 27, and ground connection piece 25
c is connected to the internal connection end 17 of the ground terminal E.
By contacting and soldering a, each ground connection piece 25a, 25b, 25c is connected to the internal connection end 17a of the ground terminal E.

Each of the connecting connection pieces 21, 21, 21 includes:
It is held in the settling groove 20 and located at the center, thereby contacting the node position at the center of each resonator. Therefore, the vibration is not inhibited.

Further, as shown in FIG. 13, the connecting portion 23 connecting the two protruding ends 22, 22 of the U-shaped connecting connecting pieces 21, 21, 21 is embedded in the seating groove 20. , The connection portion 23 is located below the inner bottom surface, so that contact with the ground connection pieces 25a, 25b, 25c is reliably avoided, and the series resonators S ₁ , S ₂ are connected via the connection connection piece 21. Only these electrodes are reliably connected, and these are set to the same potential and can be connected in series.

On the other hand, the ground connection pieces 25a, 25b,
The reference numeral 25c makes the linear contact end 27 contact the node position of the electrode of the resonator as described above. For this reason, it is possible to reliably contact almost only the node position. The ground connection pieces 25a, 25b, 25c are easily formed by punching a plate material. Therefore, the linear contact end 27
Is always uniform. Therefore, in a configuration in which the center is bulged and the bulged end is brought into contact with the node position as in a conventional terminal plate, the contact pressure varies depending on the degree of bulging, or molding is troublesome. However, since the thickness is defined by the material thickness, the thickness is always constant, a uniform contact pressure can be secured, and stable filtering characteristics can be achieved.

Thus, in the rectangular case 10, the parallel resonators P ₁ and P ₂ , the parallel resonators P ₃ and P ₄ and the parallel resonator P
_5, P _6, each series resonators one side electrode S _1, S _2, S ₃
And the other side electrode is connected to the ground, and while each is connected in parallel, each series resonator S ₁ , S
₂ and S ₃ are connected in series between the internal connection terminals 15 a and 16 a to form an input / output line L ₁ , and are a unit filtering circuit composed of one series resonator and two parallel resonators. Is a basic division, and the circuit of FIG.

In such a configuration, the connecting connection pieces 21 and
1 and 21 are held in the seating grooves 20. For this reason, each resonator is held by the protruding end portions 22, 22 of the connection connection pieces 21, 21, 21, and the arrangement thereof is stably held. In addition, since each member is mounted through the opening 11 that is widely opened on the upper surface of the rectangular case 10, the insertion is easy, and a required circuit configuration can be realized only by inserting each member. There is no need to connect each electrode or the like with a lead wire. Therefore, assembly becomes easy.

With this configuration, the piezoelectric filter F
Is an example of a planar square shape having a height of 1.8 mm and a side length of 5.0 mm, and a width of the seating groove 20 of 0.3 mm. In the above embodiment, the unit ladder circuit composed of one series resonator and two parallel resonators is used as a basic division, and a child ladder type piezoelectric filter in which three units are connected is described as an example. Dan,
The present invention can also be applied to a multi-element ladder type piezoelectric filter connected in four stages and multiple stages.

[0028]

As described above, according to the present invention, the inner connection ends of the input terminal and the output terminal are exposed on two opposing sides inside the shallow-bottom rectangular case. Exposing the internal connection end of the ground terminal to the other side, extending each terminal to the outer surface of the case integrally with the case by insert molding, and between the internal connection end of the input terminal and the output terminal, A plurality of series resonators and a parallel resonator are inserted in the vertical direction to form a required circuit, and on the inner bottom surface of the case, between the internal connection ends of the input terminal and the output terminal, along the center line. In this case, a U-shaped connecting connection piece is fitted in the positioning groove to secure required electrical connection via the connecting connection piece.

[0029] For this reason, since the opening is formed in the upper surface, a wide opening area can be ensured and mounting becomes easy without going against the reduction in height of the case. Further, since the U-shaped connecting connection piece is fitted into the seating groove formed on the inner bottom surface of the case, the connection connecting piece is restrained from moving in the width direction, and its protruding end is moved to the node position of the electrode of the resonator. And the resonator can be stably held without inhibiting the vibration of the resonator. Further, since the connecting portion connecting the two protruding ends of the U-shaped connecting connecting piece is buried in the seating groove, the connecting portion is located below the inner bottom surface, so that the other electrode Without contact with the electrodes, and only the required electrodes can be reliably contacted via the connection connection pieces to make them the same potential. For this reason, a configuration in which a large number of resonators are used, such as a unit configuration in which a unit filtering circuit in which two parallel resonators are connected to one series resonator is used as a basic division and two or more stages are connected. In this case, assembling becomes easy, and each member can be stored in the case in a cohesive manner. on the other hand,
When the ground connection piece is provided with a linear contact end that contacts the node position of the electrode of the resonator, the thickness is defined by the material thickness and is always constant, and a uniform contact pressure is obtained. As a result, stable filtering characteristics can be achieved.

[Brief description of the drawings]

FIG. 1 is a plan view of a multi-element ladder type piezoelectric filter of the present invention. In addition, only each resonator is shown in a cross section.

FIG. 2 is a bottom view of the multi-element ladder type piezoelectric filter of the present invention.

FIG. 3 is a rear view of the multi-element ladder type piezoelectric filter of the present invention.

4 is an exploded perspective view of the rectangular case 10. FIG.

5 is a plan view of the rectangular case 10. FIG.

6 is a sectional view taken along line AA of FIG.

FIG. 7 is a sectional view taken along line BB of FIG. 5;

FIG. 8 is a perspective view of series resonators S _{1 to} S ₃ .

FIG. 9 is a perspective view of parallel resonators P _{1 to} P ₆ .

FIG. 10 is a perspective view of a connection connecting piece 21.

FIG. 11 is a perspective view of ground connection pieces 25a and 25b.

FIG. 12 is a perspective view of a ground connection piece 25c.

FIG. 13 is a longitudinal sectional side view showing the operation of the connection connection pieces 21, 21, 21.

14 is a plan view of the long thin plate 40. FIG.

FIG. 15 is a circuit diagram of a piezoelectric filter according to the present embodiment.

[Explanation of symbols]

S _{1 to} S ₃ Series resonators P _{1 to} P ₆ Parallel resonators I Input terminal O Output terminal E Ground terminal 10 Square case 15a, 16a, 17a Internal connection terminal 15c, 16c, 17c External connection terminal 20 Seating groove 21 Connection Connection piece 22, 22 Protruding end 25a, 25b, 25c Ground connection piece 26 Linear contact end 40 Long thin plate

Claims (3)

[Claims] An inner connection end of an input terminal and an output terminal is provided on two opposing sides inside a shallow rectangular case made of synthetic resin having an opening on the upper surface of which a cover plate is attached. It is exposed, and further, the inner connection end of the ground terminal is exposed on the other side perpendicular to the side, and each terminal is integrated with the case by insert molding, and each external connection end extends to the outer surface of the case. Along with, between the internal connection ends of the input terminal and the output terminal, a plurality of series resonators and a parallel resonator are inserted in the vertical direction and arranged in a superposed manner, and each series resonator is connected in series, One end of the row is connected to the internal connection end of the input terminal, the other end is connected to the internal connection end of the output terminal, and one electrode of the parallel resonator is connected to the series resonator, and the other electrode is connected to the ground connection piece. To the internal connection terminal of the ground terminal via the A locating groove is formed along a center line orthogonal to a side where the internal connection end of the output terminal is arranged, and a U-shaped connecting terminal piece is fitted into the locating groove, and both ends of the terminal piece protrude. A multi-element ladder type piezoelectric filter characterized in that an end portion contacts an electrode of a required resonator to make the electrodes the same potential. 2. The multi-element ladder type piezoelectric filter according to claim 1, wherein the ground connection piece has a linear contact end that contacts a node position of an electrode of the resonator. 3. A unit comprising: a series resonator inserted between internal connection terminals of an input terminal and an output terminal; and two parallel resonators inserted adjacent to one side of the series resonator. In a circuit configuration in which a filtering circuit is used as a basic division and two or more stages are connected, two adjacent parallel resonators are arranged between both protruding ends of the U-shaped connecting connection piece, and the protruding end is provided. Parts are located between the series resonator and the parallel resonator, respectively, and the adjacent series resonator and the electrode of the parallel resonator are connected to each other through the protruding end, and the two parallel resonators are further connected. 2. The multi-element ladder type piezoelectric filter according to claim 1, wherein a ground connection piece is inserted between the ground connection pieces and the ground connection piece is connected to an internal connection end of a ground terminal.