KR20220104922A - Filter and multiplexer - Google Patents

Abstract

Provided are a filter capable of obtaining a high amount of attenuation in a wide frequency band and a multiplexer including the same. The filter comprises: a piezoelectric substrate (50); and a filter circuit (11) composed of a ladder-type filter circuit on the piezoelectric substrate (50). The filter circuit (11) comprises: an input pad (TPd) and an output pad (CPd); a plurality of series resonators (S1-S4) composed of surface acoustic wave resonators connected in series between the input pad (TPd) and the output pad (CPd); a plurality of parallel resonators (P1-P4) composed of surface acoustic wave resonators connected in parallel to each other between ground potential; and a plurality of ground pads (GPd) connected to the plurality of parallel resonators (P1-P4), respectively, wherein the plurality of ground pads (GPd) may be spaced apart from each other on the piezoelectric substrate (50).

Description

Filter and multiplexer

The present invention relates to a filter and a multiplexer to which it is applied.

As a filter for extracting a predetermined frequency component, a surface acoustic wave filter using a surface acoustic wave is conventionally known. In addition, surface acoustic wave branching using a surface acoustic wave in a demultiplexer such as a duplexer that simultaneously filters a transmission signal and a reception signal having different frequency bands in each frequency band, and prevents the signal from flowing from the transmission circuit to the reception circuit. Prayer is known from the past.

For example, in Japanese Patent Application Laid-Open No. 2003-347964 (Patent Document 1) and the like, there are various surface acoustic wave filters and the like as interstage filters and demultiplexers of high-frequency circuits in communication devices such as mobile phones. has been proposed

With the recent development of multi-band communication equipment, the surface acoustic wave filter is strongly required not only to reduce the insertion loss in the communication band, but also to improve the attenuation outside the communication band. For example, due to the deployment of 5G services, in the transmission filter of the duplexer, in addition to attenuation of harmonics of 2 times and 3 times the transmission frequency, high attenuation is required also in the frequency bands of n77 and n78.

Japanese Patent Laid-Open No. 2003-347964

However, as the size of surface acoustic wave devices progresses, it is not easy to obtain a high attenuation in a wide band reaching the frequency bands of n77 and n78 in addition to harmonics that are twice or three times the transmission frequency.

An object of the present invention is to provide a filter capable of obtaining a high attenuation in a wider frequency band and a multiplexer to which the filter is applied.

The filter of the present invention comprises a piezoelectric substrate,

and a ladder-type filter circuit formed on the piezoelectric substrate,

The ladder filter circuit comprises:

an input pad and an output pad;

a plurality of series resonators comprising a surface acoustic wave resonator connected in series between the input pad and the output pad;

a plurality of parallel resonators comprising a surface acoustic wave resonator connected in parallel between the plurality of series resonators and a ground potential;

a plurality of ground pads connected to each of the plurality of parallel resonators;

The plurality of ground pads are separated from each other on the piezoelectric substrate.

Each of the plurality of ground pads is connected to an electrode formed on a support substrate supporting the piezoelectric substrate through a bump.

Optionally, each of the plurality of ground pads may be configured to be connected to one end of a plurality of inductances each independently formed on the support body.

Preferably, the plurality of series resonators and the plurality of parallel resonators are arranged in a predetermined arrangement direction and extend in an intersecting direction intersecting in the arrangement direction,

The plurality of ground pads are arranged to be divided at both sides of an arrangement region of the plurality of series resonators and the plurality of parallel resonators in the crossing direction.

More preferably, the plurality of parallel resonators are two parallel resonators connected to the input pad side and the output pad side of a common series resonator, and are connected to a ground pad connected to one side of the two parallel resonators and the other side. The ground pad includes two parallel resonators disposed on opposite sides with respect to the arrangement area.

Preferably, the plurality of parallel resonators are each connected to the input pad side of a different series resonator,

A plurality of ground pads connected to the plurality of parallel resonators may be arranged alternately on opposite sides of the arrangement area in order from the input pad side.

In this case, it is possible to adopt a configuration in which the arrangement relationship in the cross direction of the parallel series resonators and the parallel resonators is alternately replaced in the arrangement direction. The two parallel resonators between adjacent rows in the arrangement direction may be arranged so as not to overlap in the arrangement direction.

The multiplexer of the present invention includes a common terminal, a first terminal and a second terminal;

a first filter connected between the first terminal and the common terminal;

a second filter connected between the second terminal and the common terminal;

The first filter is the filter,

The pass band of the second filter has a different pass band than that of the first filter.

Preferably, the first filter is a transmission filter formed on the piezoelectric substrate,

the second filter is a receive filter, and the first terminal is the input pad;

The common terminal is the output pad.

According to the present invention, according to the above configuration, a filter capable of obtaining a high attenuation in a wider frequency band and a multiplexer to which the filter is applied can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS It is a top view of the filter chip which comprises the reception filter and transmission filter of the duplexer in 1st Embodiment of this invention.
FIG. 2 is a circuit diagram of a transmission filter formed in the filter chip of FIG. 1 .
3 is a circuit diagram of a duplexer according to the first embodiment of the present invention.
4 is a cross-sectional view of the duplexer on which the filter chip of FIG. 1 is mounted.
Fig. 5 is a plan view of a filter chip constituting a reception filter and a transmission filter of the duplexer according to the second embodiment of the present invention.
6 is a circuit diagram of a transmission filter formed in the filter chip of FIG. 5 .
7 is a circuit diagram of a filter according to a third embodiment of the present invention.
It is a graph which shows the example of the attenuation amount characteristic of the filter of 1st Embodiment - 3rd embodiment, and a comparative example.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings. In addition, in this specification and drawings, the overlapping description is abbreviate|omitted by using the same code|symbol for the component which has substantially the same function.

first embodiment

1 is a plan view of a filter chip 2 constituting a reception filter and a transmission filter of a duplexer according to a first embodiment of the present invention, a circuit diagram of the reception filter in FIG. 2, and the filter chip of FIG. 1 is applied to FIG. A circuit diagram of the duplexer, Fig. 4 shows a cross-sectional view of the duplexer.

As shown in Fig. 3, in the duplexer 1, a transmission filter 10 described later is connected between an antenna terminal Ant as a common terminal and a transmission terminal Tx as a first terminal. The reception filter 200 is connected between the antenna terminal Ant and the reception terminal Rx as the second terminal. The transmission filter 10 passes a signal of a transmission band among the high frequency signals input from the transmission terminal Tx as a transmission signal to the antenna terminal Ant, and suppresses signals of other frequencies. The reception filter 200 passes a signal of a reception band different from the transmission band among the high frequency signals input from the antenna terminal Ant to the reception terminal Rx as a reception signal, and suppresses a signal of a different frequency. The transmission filter 10 and the reception filter 200 are formed by the filter chip 2 shown in FIG.

The filter chip 2 shown in FIG. 1 forms a piezoelectric substrate 50, a transmission filter circuit 11 forming a transmission filter 10 formed on the surface of the piezoelectric substrate 50, and a reception filter 200. and a receive filter circuit (201). The filter chip 2 constitutes the filter of the present invention.

The reception filter circuit 201 includes a plurality of surface acoustic wave resonators 202 to 204 formed on the piezoelectric substrate 50, a reception pad RPd functioning as a reception terminal Rx, and a plurality of ground pads ( GPd), a common pad CPd functioning as an antenna terminal Ant, and a wiring WR connecting these elements to each other. In addition, since the characteristic of the duplexer 1 of this embodiment is the transmission filter 10, the detailed description of the reception filter circuit 201 is abbreviate|omitted. In addition, dotted circles described on the reception pad RPd, each ground pad GPd, a transmission pad TPd to be described later, and each ground pad GPd indicate bumps Bp to be described later connected to them, respectively. represents In addition, in the following description, the receiving pad RPd, each ground pad GPd, a transmission pad TPd to be described later, and each ground pad GPd are also referred to as pads Pd.

The transmission filter 10 includes a transmission filter circuit 11 comprising a piezoelectric substrate 50 having a rectangular shape and a ladder filter circuit including a plurality of surface acoustic wave resonators formed on the surface of the piezoelectric substrate 50 . .

The transmission filter circuit 11 includes series resonators S1 to S4 and parallel resonators P1 to P4 as surface acoustic wave resonators, a transmission pad TPd as an input pad, a common pad CPd as an output pad, and these elements. and a wiring WR connecting them to each other.

As shown in Fig. 2, the plurality of series resonators S1 to S4 are connected in series between the transmission terminal Tx and the antenna terminal Ant.

The plurality of parallel resonators P1 to P4 are connected in parallel between the plurality of series resonators S1 to S4 and the ground potential.

1, the plurality of series resonators S1 to S4 and the plurality of parallel resonators P1 to P4 of the transmission filter circuit 11 are arranged in the longitudinal direction of the rectangular piezoelectric substrate 50 in the arrangement direction D1. are being arranged These series resonators S1 to S4 and parallel resonators P1 to P4 extend in an intersecting direction D2 (orthogonal direction in this embodiment) intersecting in the arrangement direction D1.

Although not shown, the series resonators S1 to S4 and the plurality of parallel resonators P1 to P4 composed of surface acoustic wave resonators have an IDT (Inter Digital Transducer) and reflectors disposed on both sides thereof. The IDT and reflector are patterned by a metal film formed directly on the piezoelectric substrate 50 . The surface acoustic wave resonator is formed of a metal material made of Al, Cu, Ag, or an alloy mainly comprising these.

The wiring WR and each pad Pd are integrated and are patterned with a metal film directly formed on the piezoelectric substrate 50 . These are formed of a metal material made of Al, Cu, Ag or an alloy mainly having these.

The piezoelectric substrate 50 is formed of a single crystal lithium tantalate (LiTaO ₃ ) substrate, a single crystal lithium niobate (LiNbO ₃ ) substrate, a single crystal quartz substrate, or a piezoelectric ceramic.

As can be seen from Figs. 1 and 2, the parallel resonators P1 to P4 are connected to the transmission terminal Tx (transmission pad TPd) side of the other series resonators S1 to S4, respectively. That is, the parallel resonator P1 is the series resonator S1, the parallel resonator P2 is the series resonator S2, the parallel resonator P3 is the series resonator S3, and the parallel resonator P4 is the series resonator S4. It is electrically connected to the transmission pad TPd side.

Each ground pad GPd connected to the parallel resonators P1 to P4 is separated from each other on the piezoelectric substrate 50 . That is, there is no connection relationship between the plurality of ground pads GPd on the piezoelectric substrate 50 .

The plurality of ground pads GPd are arranged to be divided at both sides of the arrangement region R of the plurality of series resonators S1 to S4 and the plurality of parallel resonators P1 to P4 in the crossing direction D2 .

Specifically, the plurality of parallel resonators P1 to P4 are alternately arranged on the opposite side to the arrangement region R in order from the side of the transmission pad TPd.

Further, the series resonator S1 and the parallel resonator P1, the series resonator S2 and the parallel resonator P2, the series resonator S3 and the parallel resonator P3, and the series resonator S4 and the parallel resonator P4 are parallel to each other in the intersecting direction D2. The arrangement of the series resonators S1 to S4 and the parallel resonators P1 to P4 in the crossing direction D2 is alternately changed in the arrangement direction D1. Two parallel resonators (P1, P2), two parallel resonators (P2, P3), and two parallel resonators (P3, P4) between adjacent columns in the arrangement direction (D1) are arranged such that they do not overlap in the arrangement direction (D1). is placed.

As shown in FIG. 4 , the filter chip 2 configured as described above is flip-chip mounted (face-down mounted) on the substrate 300 as a support body through bumps Bp. The bump Bp is, for example, a gold bump, a solder bump, or a copper bump. The bump Bp electrically connects the plurality of ground pads GPd, the common pad CPd, the reception pad RPd, and the transmission pad TPd to the plurality of electrodes 301 formed on the substrate 300 . . The substrate 300 is formed of, for example, ceramic, resin, or the like, and the filter chip 2 mounted on the substrate 300 is sealed by the encapsulation unit 400 . For example, it is formed of metals, such as soldering, or resin.

Wirings (not shown) are formed on the substrate 300 , and the ground pad GPd of the filter chip 2 is electrically connected to a reference potential (ground potential) through these wirings.

According to the present embodiment, by forming the plurality of ground pads GPd connected to the plurality of parallel resonators P1 to P4 separately from each other, compared with the case where the ground pads GPd are common, each of the parallel resonators P1 The inductance of the wiring connected to ~P4) becomes small. Accordingly, a plurality of attenuation pole frequency bands having the transmit filter circuit 11 can be set to a higher frequency band, and in addition to the frequency bands of two and three times the harmonics of a relatively low frequency band, for example, n77 It is possible to improve the attenuation characteristics of the filter in a relatively high frequency band such as , n78 and the like.

In the present embodiment, since the plurality of ground pads GPd connected to the plurality of parallel resonators P1 to P4 are formed separately from each other, the respective parallel resonators P1 to P4 and the wiring WR connected thereto are formed. Capacitive coupling by floating capacitance occurs between them. When the stray capacitance is large, there is a possibility that the attenuation characteristic of the filter is reduced, that is, the attenuation amount is deteriorated. To this end, in the present embodiment, by adopting the structure as described above, the generation of capacitive coupling between the plurality of parallel resonators P1 to P4 including the wiring WR is reduced by the plurality of ground pads GPd and the plurality of parallel resonators P1 to P4. The effect of capacitive coupling between P1~P4) is minimized. Specifically, the ground pad GPd of the parallel resonator P1 and the GPd of the parallel resonator P2 are disposed on opposite sides with the arrangement region R interposed therebetween, and the parallel resonator P1 is disposed in the crossing direction D2. Since it is disposed on one side and the parallel resonator P2 is disposed on the other side in the crossing direction D2, as shown in FIG. 2, capacitive coupling between the parallel resonator P1 and the parallel resonator P2 can be suppressed. . Since the distance on the circuit can be secured between the parallel resonator P1 and the parallel resonator P3, the influence of capacitive coupling between the parallel resonator P1 and the parallel resonator P3 can be suppressed. Similarly, the effect of capacitive coupling can be suppressed between the parallel resonator P3 and the parallel resonator P4 and between the parallel resonator P2 and the parallel resonator P4.

second embodiment

Fig. 5 is a plan view of a filter chip constituting a receiving filter and a transmitting filter of the duplexer according to the second embodiment of the present invention, and Fig. 6 shows a circuit diagram of the receiving filter formed in the filter chip of Fig. 5 .

The difference in this embodiment from the first embodiment is that, as shown in Fig. 5, in the filter chip 2B of the present embodiment, the ground pad GPd of the parallel resonator P2 and the parallel resonator P3 are The point is that only the ground pad GPd is disposed on the opposite side to the arrangement area R. That is, in the filter chip 2B of the present embodiment, the plurality of ground pads GPd are alternately arranged on the opposite side to the arrangement region R in order from the side of the transmission pad TPd in the crossing direction D2. there is not

Even in this structure, as can be seen from the transmission filter circuit 11B shown in Fig. 6, the distance on the circuit can be secured between the parallel resonator P2 and the parallel resonator P3, so that the effect of capacitive coupling is reduced. can be suppressed

third embodiment

7 shows a circuit diagram of a filter according to a third embodiment of the present invention. The transmission filter circuit 11C shown in FIG. 7 is formed by the filter chip 2C and inductance L1-L4 formed in the board|substrate 300 on which the filter chip 2C is flip-chip mounted. The inductances L1 to L4 are composed of wirings (not shown) formed on the substrate 300 .

The filter chip 2C may have the same structure as the transmission filter circuit 11 or the transmission filter circuit 11B described in the second embodiment. In addition, the filter chip 2C may be a ladder filter circuit having a different configuration in which a plurality of ground pads GPd of the transmission filter circuit 11C are separated from each other on the piezoelectric substrate 50 .

Each of the parallel resonators P1 to P4 of the transmission filter circuit 11C according to the present embodiment has one end connected to one end of the independent inductance L1 to L4 formed on the substrate 300 side, and the other end is commonly grounded. has been

By setting it as such a structure, the attenuation amount of the transmission filter circuit 11C can be enlarged so that it may mention later.

Example

Here, in FIG. 8, the attenuation characteristic example of the transmission filter circuit 11, 11B, 11C of the structures demonstrated in the above-mentioned 1st Embodiment - 3rd Embodiment, and the attenuation characteristic example of a comparative example are shown.

The graph 1 shows the attenuation characteristic of the transmission filter 11 of the structure demonstrated in 1st Embodiment. The graph (2) shows the attenuation characteristic of the transmission filter 11B of the structure demonstrated in 2nd Embodiment. The graph 3 shows the attenuation characteristic of the transmission filter 11C of the structure demonstrated in 3rd Embodiment.

Graph 4 is a comparative example, in which the filter is formed in a ladder-type filter circuit in which the ground pads of the parallel resonators formed on the piezoelectric substrate are in common and are not separated from each other.

As can be seen from FIG. 8 , in graphs (1) to (3), the attenuation is increased in a wider band than in graph (4).

In each of the above embodiments, the case in which four parallel resonators are used is exemplified, but it is not limited to this, and it can be less than this or more than this. .

Although the case of a transmission filter was illustrated as a filter of this invention in embodiment, it is not limited to this, This invention is applicable also to a reception filter.

Although the duplexer was exemplified as the multiplexer in the above embodiment, the present invention is not limited thereto, and the filter of the present invention can be applied to a triplexer or a quadplexer.

In the above embodiment, the transmission filter circuit and the reception filter circuit of the duplexer are formed on a common piezoelectric substrate, but the present invention is not limited thereto. It is also possible to form the transmit filter circuit and the receive filter circuit on separate piezoelectric substrates and combine separate filter chips.

In the above embodiment, the case in which the filter of the present invention is applied to a so-called CSP product is exemplified, but it is also applicable to a single unit filter used for a module use such as a wafer level package (WLP).

Although the case where the inductance is provided on the package side was exemplified in the third embodiment, the present invention is not limited thereto, and a configuration in which an inductance is not provided can be adopted.

As mentioned above, the embodiment of the present invention has been described above, but the present invention is not limited to this specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims.

1: Duplexer
2, 2B, 2C: filter chip
10: transmit filter
11, 11B, 11C: transmit filter circuit
50: piezoelectric substrate
200: receive filter
201: receive filter circuit
202-204: surface acoustic wave resonator
300: substrate (support substrate)
301: electrode
400: encapsulation part
Bp: bump
D1: Array direction
D2: cross direction
L1~L4 : Inductance
S1~S4 : series resonator
P1~P4 : Parallel resonator
R: Placement area
RPd: Receive Pad
TPd : Transmit Pad
CPd: common pad
GPd: Ground Pad
Pd: pad
Rx : Receive terminal
Tx: Transmitting terminal
Ant : Antenna terminal
WR: wiring

Claims (11)

a piezoelectric substrate;
and a ladder-type filter circuit formed on the piezoelectric substrate;
The ladder filter circuit comprises:
an input pad and an output pad;
a plurality of series resonators comprising a surface acoustic wave resonator connected in series between the input pad and the output pad;
a plurality of parallel resonators comprising a surface acoustic wave resonator connected in parallel between the plurality of series resonators and a ground potential;
a plurality of ground pads connected to each of the plurality of parallel resonators;
and the plurality of ground pads are separated from each other on the piezoelectric substrate. According to claim 1,
and each of the plurality of ground pads is connected to an electrode formed on a support base supporting the piezoelectric substrate through a bump. 3. The method of claim 2,
each of the plurality of ground pads is connected to one end of a plurality of inductances each independently formed in the support body. 4. The method according to any one of claims 1 to 3,
the plurality of series resonators and the plurality of parallel resonators are arranged in a predetermined arrangement direction, and extend in an intersecting direction intersecting in the arrangement direction;
and the plurality of ground pads are arranged to be divided on both sides of an arrangement region of the plurality of series resonators and the plurality of parallel resonators in the crossing direction. 5. The method of claim 4,
The plurality of parallel resonators are two parallel resonators connected to the input pad side and the output pad side of a common series resonator, and a ground pad connected to one side of the two parallel resonators and a ground pad connected to the other side of the two parallel resonators are arranged in the above arrangement. A filter comprising two parallel resonators disposed on opposite sides with respect to the region. 6. The method of claim 5,
the plurality of parallel resonators are respectively connected to the input pad side of a different series resonator,
a plurality of ground pads connected to the plurality of parallel resonators are arranged alternately on opposite sides of the arrangement region in order from the input pad side. 7. The method of claim 6,
two parallel resonators between adjacent columns in the arrangement direction are arranged so as not to overlap in the arrangement direction. 8. The method according to any one of claims 1 to 7,
A filter having four or more of the parallel resonators. a common terminal, a first terminal and a second terminal;
a first filter connected between the first terminal and the common terminal;
a second filter connected between the second terminal and the common terminal;
The first filter is the filter of any one of claims 1 to 9,
and the passband of the second filter has a different passband than the passband of the first filter. 10. The method of claim 9,
The first filter is a transmission filter formed on the piezoelectric substrate,
and the second filter is a receive filter. 12. The method of claim 10 or 11,
the first terminal is the input pad;
and the common terminal is the output pad.

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