JP2007150758A - Demultiplexer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small demultiplexer which exhibits a proper isolation property. <P>SOLUTION: The demultiplexer is provided with a surface acoustic wave filter 21 for transmission, and a surface acoustic wave filter 22 for reception which are flip chip mounted on the surface of a package 1, and a reception signal output terminal 13 which is separated from a common ground pattern 12 with which a grounding terminal 211 of the surface acoustic wave filter 21 for transmission and a grounding terminal 221 of the surface acoustic wave filter 22 for reception are connected on the back surface of the package 1. In this case, the reception signal output terminal 13 is arranged at approximately an equal distance from the grounding terminal 211 of the surface acoustic wave filter 21 for transmission and the grounding terminal 221 of the surface acoustic wave filter 22 for reception, when viewed from the direction perpendicular to the surface of the package 1. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a duplexer equipped with a surface acoustic wave filter.

  In recent years, with the development of mobile communication systems, mobile communication devices such as mobile phones and portable information terminals have rapidly spread, and because of the demand for miniaturization and high performance of these devices, components used in these devices However, miniaturization and high performance are required.

  In mobile phones, two types of analog and digital wireless communication systems are used, and the frequencies used range from 800 to 1000 MHz and 1.5 to 2.0 GHz. In these mobile communication devices, a duplexer is used as a component in an RF unit that branches and generates signals transmitted and received through an antenna.

  Conventionally, as an example of a duplexer having two surface acoustic wave filters having different frequency pass bands, a surface acoustic wave filter is mounted in a cavity portion of a package made of a ceramic substrate or the like, and an electrode terminal of the surface acoustic wave filter And a package electrode pad are electrically connected by a bonding wire such as gold (for example, see Patent Document 1).

Further, as another duplexer, a surface acoustic wave filter in which bumps such as gold are formed on electrode terminals is formed of a ceramic substrate or the like with an IDT electrode formed on the surface on which the surface acoustic wave propagates downward. A duplexer having a flip-chip mounting structure in which a cap is placed and fixed on a package by a flip-chip mounting method and a cap is sealed over the package is known (for example, see Patent Document 2).
Japanese Patent Application Laid-Open No. 2002-237739 WO2002 / 005424 publication

  Here, as an important characteristic of the above-described duplexer, there is an isolation characteristic between the transmission terminal and the reception terminal. This is evaluated as the signal strength leaking to the receiving terminal side in the transmission frequency band or the signal strength leaking to the transmitting terminal side in the receiving frequency band, and the strength of these leaked signals must be lower than a predetermined level. In general, the level required in the transmission frequency band is stricter.

  In order to improve the isolation characteristics, it is indispensable to provide sufficient amount of out-of-band attenuation of the surface acoustic wave filter, and in particular, it is necessary to increase the amount of attenuation in the transmission frequency band of the surface acoustic wave filter for reception that has strict requirements There is. This is adjusted by the characteristics of the resonator constituting the surface acoustic wave filter, and is formed in a package on which the surface acoustic wave filter is mounted, and connects the ground terminal of the surface acoustic wave filter and the ground (common ground pattern). It is adjusted by an inductance component such as a conductor pattern (via conductor).

However, there are factors other than the above that affect the isolation characteristics.
In the duplexer as described above, a common ground pattern as a potential reference surface is formed inside or on the back surface of the package, and at the same time, the common ground pattern is a reception signal output terminal for the purpose of stabilizing the signal. It is provided around. Here, in the operating state of the duplexer, since a large amount of current flows through the ground terminals of the surface acoustic wave filter for transmission and the surface acoustic wave filter for reception, the potential near the ground terminal of the surface acoustic wave filter increases. As a result, the common ground pattern connected to the ground terminal of the surface acoustic wave filter varies in potential around the ground terminal of the surface acoustic wave filter as viewed from the direction perpendicular to the surface of the package. When the potential of the common ground pattern fluctuates, the fluctuation propagates to the reception signal output terminal, and the potential of the reception signal output terminal also fluctuates. When the potential of the reception signal output terminal fluctuates, it means that energy is transmitted, and this results in deterioration of isolation characteristics.

  Such a variation in the potential of the common ground pattern is weak compared to the input signal, but such a weak variation in potential affects the attenuation level required for the duplexer. It is.

  Therefore, by arranging the received signal output terminal of the package away from the surface acoustic wave filter, the influence of the above-mentioned potential fluctuation can be reduced, but for this purpose, it is necessary to increase the area of the package. Cannot meet the demand for

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small duplexer with good isolation characteristics.

  As a result of diligent study to achieve the above object, the present inventor has found that the distance from the ground terminal of the surface acoustic wave filter for transmission to the reception signal output terminal of the package and the signal received from the ground terminal of the surface acoustic wave filter for reception to the package It has been found that the isolation characteristics are good when the distance to the output terminal is substantially equidistant, and the present invention has been achieved.

  That is, according to the present invention, a surface acoustic wave filter for transmission and a surface acoustic wave filter for reception in which an IDT electrode, an input terminal, an output terminal, and a ground terminal are formed on the surface of a piezoelectric substrate are flip-chip mounted on the surface of the package. And a duplexer in which a reception signal output terminal connected to the output terminal of the surface acoustic wave filter for reception is provided on the back surface of the package, from a direction perpendicular to the surface of the package As shown in the figure, the duplexer is characterized in that the reception signal output terminal is arranged at a substantially equal distance from the ground terminal of the surface acoustic wave filter for transmission and the ground terminal of the surface acoustic wave filter for reception. .

  In the present invention, a surface acoustic wave filter for transmission and a surface acoustic wave filter for reception, each of which includes an IDT electrode, an input terminal, an output terminal, and a ground terminal formed on the surface of a piezoelectric substrate, are mounted on the surface of the package. A grounding terminal of the credit surface acoustic wave filter and a first grounding pad provided on the surface of the package corresponding to the grounding terminal of the surface acoustic wave filter for transmission are connected by a bonding wire, and the receiving elasticity A grounding terminal of the surface wave filter and a second grounding pad provided on the surface of the package corresponding to the grounding terminal of the surface acoustic wave filter for reception are connected by a bonding wire, and the receiving surface is connected to the back surface of the package. A duplexer provided with a received signal output terminal connected to the output terminal of the surface acoustic wave filter for a package, the package When viewed from the direction perpendicular to the surface, a demultiplexer, wherein the reception signal output terminal to the position of the substantially equal distances from said first ground pad and the second ground pad is disposed.

  Although the potential fluctuation is large near the ground terminal of the surface acoustic wave filter for transmission and the surface acoustic wave filter for reception, the position of the received signal is at this position because the potential fluctuation is relatively weak at a position approximately equidistant from these. By arranging the output terminal, it is possible to suppress deterioration of the isolation characteristic.

  Here, in the duplexer, at least in the pass frequency band of the surface acoustic wave filter for transmission, current flows to the ground terminal of the surface acoustic wave filter for transmission and flows to the ground terminal of the surface acoustic wave filter for reception. It is preferable to have a frequency at which the current is substantially in antiphase.

  According to the present invention, since the received signal output terminal can be arranged at a location where the potential fluctuation is weak within a limited range, a duplexer that has a reduced size and suppresses deterioration of isolation characteristics is provided. Can be obtained.

An embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing an embodiment of the duplexer of the present invention, and FIG. 2 is a plan perspective view of the duplexer shown in FIG.

  The duplexer shown in FIG. 1 includes a surface acoustic wave filter for transmission 21 and a surface acoustic wave filter for reception 22 that are flip-chip mounted on the surface of the package 1 and a surface acoustic wave filter for reception 22 on the back surface of the package 1. The duplexer is provided with a reception signal output terminal 13 connected to the output terminal of the package, and is viewed from a direction perpendicular to the surface of the package 1. The reception signal output terminal 13 is arranged at a position substantially equidistant from the ground terminal 221 of the surface acoustic wave filter 22 for use.

  The surface acoustic wave filter for transmission 21 and the surface acoustic wave filter for reception 22 are formed of, for example, a lithium tantalate single crystal, a lanthanum-gallium-niobium single crystal having a langasite type crystal structure, a lithium tetraborate single crystal, or the like. A surface acoustic wave (SAW) element in which an IDT electrode, an input terminal, an output terminal, and ground terminals 211 and 221 are formed of silver, copper or the like on the surface of a piezoelectric substrate. In this embodiment, the transmission surface acoustic wave filter 21 and the reception surface acoustic wave filter 22 are formed separately, but they may be formed integrally.

  The package 1 includes a plurality of dielectric layers made of a dielectric material such as LTCC, and a conductor pattern (via conductor) 14 made of silver or copper formed on the surface and inside as a phase matching circuit or an inductance adjustment pattern. Composed. On the surface of the package 1, input pads and output pads (not shown) are formed corresponding to input terminals and output terminals (not shown) of the surface acoustic wave filter 21 for transmission and the surface acoustic wave filter 22 for reception. A first ground pad 111 is formed corresponding to the ground terminal 211, and a second ground pad 112 is formed corresponding to the ground terminal 221. A common ground pattern 12 connected to the first ground pad 111 and the second ground pad 112 on the front surface via a conductor pattern (via conductor) is formed on the back surface of the package 1, and the common ground pattern 12 is formed by a slit. A reception signal output terminal 13 is formed separately from the ground pattern 12. The reception signal output terminal 13 is electrically connected to the output terminal (not shown) of the surface acoustic wave filter 22 for reception via a conductor pattern (not shown) inside the package 1. The reception signal output terminal 13 is connected to a reception system circuit formed on the wiring board on which the duplexer 1 is mounted, and is a terminal for sending a reception signal from the package 1 to the reception system circuit. A signal is sent to the receiving system circuit via a transmission line composed of a line connected to the line and a ground adjacent to the line.

  In FIG. 1 and FIG. 2, these are separated by slits and formed on the same plane (the back surface of the package 1) so that the common ground pattern 12 surrounds the reception signal output terminal 13. In general, a relatively large current flows through the transmission signal input terminal and reception signal output terminal provided in the package, so a common ground pattern is placed around the input / output terminals to prevent interference between them. The electromagnetic field created by the current that flows through is prevented from spreading. Here, the common ground pattern 12 and the reception signal output terminal 13 do not necessarily have to be formed on the same plane. For example, as shown in FIG. 3, the reception signal output terminal 13 is provided on the back surface of the package 1. The common ground pattern 12 may be provided on substantially the entire surface above the back surface. In FIG. 3, the path connecting the output terminal of the surface acoustic wave filter for reception 22 and the reception signal output terminal 13 is secured by hollowing out a part of the common ground pattern 12 and providing a via conductor in this part. Has been. Further, as shown in FIG. 4, the common ground pattern 12 is not formed on the inside or the back surface of the package 1, but the common ground pattern 31 is formed on the wiring board 3 on which the duplexer of the present invention is mounted. Also good.

  The transmission surface acoustic wave filter 21 and the reception surface acoustic wave filter 22 are flip-chip mounted on the surface of the package 1 in a face-down state, and signals from the transmission surface acoustic wave filter 21 and the reception surface acoustic wave filter 22 are transmitted. The input / output terminals and the input / output pads (not shown) on the surface of the package 1 are connected by the solder bumps 5, and the ground terminal 221 of the surface acoustic wave filter 21 for transmission and the ground terminal 221 of the surface acoustic wave filter 22 for reception Corresponding to these, ground pads 111 and 112 formed on the surface of the package 1 are connected by solder bumps 5. In addition, structures not directly related to the present invention are omitted.

  As shown in FIGS. 1 and 2, the surface acoustic wave filter for transmission 21 and the surface acoustic wave filter for reception 22 include a ground terminal 211 of the surface acoustic wave filter for transmission 21 and a ground terminal 221 of the surface acoustic wave filter for reception 22. It is important that the line segment connecting with the line segment is positioned so that the intersection with the perpendicular line drawn from the center position of the reception signal output terminal 13 formed in the package 1 is located approximately in the middle of the line segment. is there. In other words, when viewed from a direction perpendicular to the surface of the package 1, the received signal is positioned at a substantially equal distance from the ground terminal 211 of the surface acoustic wave filter 21 for transmission and the ground terminal 221 of the surface acoustic wave filter 22 for reception. An output terminal 13 is arranged. The distance between the terminals is measured with the center (center of gravity) of each terminal. When the surface acoustic wave filter for transmission 21 has a plurality of ground terminals 211, the grounding terminal 211 located near the output terminal in the surface acoustic wave filter for transmission 21 is used as a target, and the elasticity for reception is obtained. When the surface acoustic wave filter 22 has a plurality of ground terminals 221, the ground terminal 221 located at a position close to the input terminal in the surface acoustic wave filter 22 for reception is a target. Furthermore, when there are multiple ground terminals that are close to the input terminal or output terminal (when there are multiple ground terminals at the same distance from the terminal), consider the smallest area that contains these ground terminals, Target the center of the region.

  The ground terminal 211 of the surface acoustic wave filter for transmission 21 and the ground terminal 221 of the surface acoustic wave filter for reception 22 have large potential fluctuations. Therefore, by disposing the reception signal output terminal 13 at this position, it is possible to suppress degradation of isolation characteristics. 5 will be described in detail based on the result of calculating the potential of the common ground pattern 12 by the PEEC (Partial Element Equivalent Circuits) method shown in FIGS. 6 and 7.

  The positional relationship of the ground terminal 211 of the surface acoustic wave filter 21 for transmission, the ground terminal 221 of the surface acoustic wave filter 22 for reception, and the reception signal output terminal 13 viewed from the stacking direction is as shown in FIG. In FIG. 5, the position where the reception signal output terminal 13 is disposed is the ground terminal 211 of the surface acoustic wave filter 21 for transmission and the surface acoustic wave filter for reception when viewed from the direction perpendicular to the surface of the package 1. The position is away from the position of approximately equal distance from the 22 ground terminals 221. In addition to the reception signal output terminal 13 in FIG. 5, there are terminals formed by being separated from the common ground pattern 12 by slits in the same manner as this, but these are terminals that do not affect the present invention, and the description thereof. Is omitted.

  As the potential of the ground terminal 211 of the surface acoustic wave filter for transmission 21 and the potential of the ground terminal 221 of the surface acoustic wave filter for reception 22 vary, the potential of the common ground pattern 12 varies with time, as shown in FIG. Contour lines indicate the magnitude of the amplitude. This shows that the high potential display portion has a large potential fluctuation amplitude and decreases toward the low potential display portion. Further, the graph in FIG. 7 calculates the intensity of the signal leaking to the reception signal output terminal 13 of the package 1 in the pass band (1.85 GHz to 1.91 GHz) of the surface acoustic wave filter 21 for transmission.

  From FIG. 6, the potential increases in the common ground pattern 12 immediately below the ground terminals 211 and 221 of the surface acoustic wave filter 21 for transmission and the surface acoustic wave filter 22 for reception, and the magnitude of the potential varies depending on the frequency. I understand that. The change with respect to this frequency largely depends on the characteristics of the surface acoustic wave filter. As described above, when the potential of the common ground pattern 12 varies, the potential of the reception-side output terminal 13 also varies due to the influence of the surroundings. Therefore, it is preferable that the reception signal output terminal 13 be as far as possible from the position where the potential of the common ground pattern 12 is high, that is, the ground terminals 211 and 221. However, at the present time when further miniaturization is required, it is necessary to arrange the reception signal output terminal 13 of the package 1 in the immediate vicinity of the surface acoustic wave filter when viewed from the direction perpendicular to the surface of the package 1. . Therefore, when viewed from a direction perpendicular to the surface of the package 1, a position (potential variation is at a substantially equal distance from the ground terminal 211 of the surface acoustic wave filter for transmission 21 and the ground terminal 221 of the surface acoustic wave filter for reception 22. By arranging the reception signal output terminal 13 at a relatively weak position), stable isolation characteristics can be secured within the pass band.

  FIG. 8 shows the calculated isolation characteristics when the receiving-side output terminal 13 of the package 1 is arranged directly below the receiving surface acoustic wave filter 22 which is a position deviated from the position shown in FIG. Compared with the results of FIG. 6, it can be seen that the isolation characteristics in the pass band of the surface acoustic wave filter for transmission 21 are degraded.

  On the other hand, FIG. 9 shows the position of the ground terminal 211 of the surface acoustic wave filter 21 for transmission in FIG. 7 as the distance from the ground terminal 211 of the surface acoustic wave filter 21 for transmission to the output terminal 13 on the receiving side of the package 1. This is an isolation characteristic when the distance from the ground terminal 221 of the surface acoustic wave filter 22 to the reception-side output terminal 13 is moved in a direction that is substantially equidistant when viewed from a direction perpendicular to the surface of the package 1. It can be seen that more stable characteristics are obtained compared to the characteristics shown in FIG.

  5 to 9, the fluctuation state of the potential of the common ground pattern 12 is described. However, the fluctuation of the common ground pattern 12 is caused by the fluctuation of the potentials of the ground terminal 211 and the ground terminal 221 being transmitted through the space. This affects the common ground pattern 12 directly below. Therefore, the relationship between the ground terminal 211 and the ground terminal 221 and the reception signal output terminal 13 is important, and even if the reception signal output terminal 13 is not surrounded by the common ground pattern 12 separated by the slit, the reception is possible. The signal output terminal 13 can be affected by the ground terminal 211 and the ground terminal 221. That is, an effect can be obtained even for a structure in which a gap larger than the slit is provided between the reception signal output terminal 13 and the common ground pattern 12.

  Such an effect is not limited to the case where the surface acoustic wave filter is mounted by flip-chip mounting, but can also be obtained when mounting by wire bonding.

Next, another embodiment of the present invention will be described with reference to the drawings.
FIG. 10 shows an example in which a surface acoustic wave filter is mounted on a package by a connection method using wire bonding.

  In this duplexer, a first ground pad 141 is provided on the surface of the package 1 corresponding to the ground terminal 211 of the surface acoustic wave filter 21 for transmission, and the ground terminal 221 of the surface acoustic wave filter 22 for reception is provided. Correspondingly, a second ground pad 142 is provided. The ground terminal 211 of the surface acoustic wave filter for transmission 21 and the first ground pad 141 are connected by the bonding wire 4, and the ground terminal 221 and the second ground pad 142 of the surface acoustic wave filter for reception 22 are connected to each other. Are connected by a bonding wire 4. Further, a reception signal output terminal 13 is provided on the back surface of the package 1 separately from the common ground pattern 12 to which the first ground pad 141 and the second ground pad 142 are connected. The output terminal 13 is configured to be disposed at a substantially equidistant position from the first ground pad 141 and the second ground pad 142 when viewed from the stacking direction.

  When such a connection form is adopted, the area of the package needs to be larger than that in the case of flip-chip connection. Therefore, the reception signal output terminal 13 of the package 1 is a surface acoustic wave for transmission and reception as viewed from the stacking direction. It is easy to keep away from the ground terminals 211 and 221 of the filters 21 and 22. However, when the reception signal output terminal 13 and the surface acoustic wave filters 21 and 22 for transmission or reception approach each other due to other design factors, the problem of deterioration of isolation characteristics must be considered. Therefore, when the reception signal output terminal 13 is arranged at a substantially equidistant position from the first ground pad 141 and the second ground pad 142 as viewed from the stacking direction, the same flip-chip mounting embodiment as that described above is used. An effect is obtained.

  Also in the connection form by the bonding wire 4, the common ground pattern 12 may be provided at the position as shown in FIGS. 3 and 4, and the common ground pattern 12 is provided inside or on the back surface of the package 1 as shown in FIG. The common ground pattern may be formed on the wiring board on which the duplexer is mounted.

  Furthermore, in the present invention, at least within the pass frequency band of the surface acoustic wave filter for transmission 21, the current flowing to the ground terminal 211 of the surface acoustic wave filter for transmission 21 and the current flowing to the ground terminal 221 of the surface acoustic wave filter for reception 22 It is preferable to have a frequency where and are substantially in opposite phases. The reception signal output terminal 13 is arranged at a position approximately equidistant from the ground terminal of each surface acoustic wave filter, and the current flowing to the ground terminal 211 of the transmission acoustic wave filter 21 and the ground terminal of the reception acoustic wave filter 22 are measured. This is because a higher effect can be obtained by making at least one frequency in the band that has an opposite phase to the current flowing to 221. That is, in such a situation where the phase is reversed, a frequency with a low potential appears at a position where the distance from the ground terminal of the surface acoustic wave filter for transmission is substantially equal to the distance from the ground terminal of the surface acoustic wave filter for reception. . This is because the oscillations of the respective potentials are in opposite phases and cancel each other. Therefore, particularly with respect to the strength of the leaked signal, it is possible to obtain better isolation characteristics by having a frequency that is substantially in reverse phase in a transmission frequency band where the required level is severe. In order to have a frequency having a substantially opposite phase in the transmission frequency band, it is achieved by adjusting the phase characteristics of the surface acoustic wave filter 21 for transmission and the surface acoustic wave filter 22 for reception.

It is a schematic sectional explanatory drawing of one Embodiment of the splitter of this invention. FIG. 2 is a plan perspective view of the duplexer shown in FIG. 1. It is a schematic cross-sectional explanatory drawing of other embodiment which changed the formation position of the common ground pattern 12 shown in FIG. FIG. 10 is a schematic cross-sectional explanatory diagram of still another embodiment in which the formation position of the common ground pattern 12 shown in FIG. 1 is changed. It is explanatory drawing of the splitter prepared for description of electric potential fluctuation | variation, (a) is a plane perspective view, (b) is a schematic sectional drawing. It is a figure which shows the electric potential distribution of the common ground pattern by simulation of the branching filter shown in FIG. It is a figure which shows the isolation characteristic by simulation of the duplexer shown in FIG. (A) is a plane perspective view of the form which changed the position of the received signal output terminal 13 of the duplexer shown in FIG. 5, (b) is a figure which shows the isolation characteristic by simulation in the form of (a). . (A) is a plane perspective view of the form which changed the position of the grounding terminal 211 of the surface acoustic wave filter 21 for transmission of the duplexer shown in FIG. 5, (b) is the isolation by the simulation in the form of (a). It is a figure which shows a characteristic. It is explanatory drawing of other embodiment of the splitter of this invention, Comprising: (a) is a schematic sectional drawing, (b) is a plane perspective view.

Explanation of symbols

1 ... package 111, 141 ... first ground pads 112, 142 ... second ground pads 12, 31 ... common ground pattern 13 ... received signal Output terminal 21... Transmission surface acoustic wave filter 22... Reception surface acoustic wave filters 211 and 221... Ground terminal 3. .... Bonding wire 5 ... Solder bump

Claims (3)

A surface acoustic wave filter for transmission and a surface acoustic wave filter for reception in which an IDT electrode, an input terminal, an output terminal, and a ground terminal are formed on the surface of the piezoelectric substrate are flip-chip mounted on the surface of the package,
A duplexer in which a reception signal output terminal connected to the output terminal of the surface acoustic wave filter for reception is provided on the back surface of the package;
The reception signal output terminal is disposed at a substantially equal distance from the ground terminal of the surface acoustic wave filter for transmission and the ground terminal of the surface acoustic wave filter for reception as viewed from a direction perpendicular to the surface of the package. A duplexer characterized by that. A surface acoustic wave filter for transmission and a surface acoustic wave filter for reception in which an IDT electrode, an input terminal, an output terminal, and a ground terminal are formed on the surface of the piezoelectric substrate are mounted on the surface of the package,
A ground terminal of the surface acoustic wave filter for transmission and a first ground pad provided on the surface of the package corresponding to the ground terminal of the surface acoustic wave filter for transmission are connected by a bonding wire, and the reception A grounding terminal of the surface acoustic wave filter for use and a second grounding pad provided on the surface of the package corresponding to the grounding terminal of the surface acoustic wave filter for reception are connected by a bonding wire;
A duplexer in which a reception signal output terminal connected to the output terminal of the surface acoustic wave filter for reception is provided on the back surface of the package;
The duplexer, wherein the reception signal output terminal is disposed at a substantially equidistant position from the first ground pad and the second ground pad when viewed from a direction perpendicular to the surface of the package. . A duplexer according to claim 1 or claim 2, wherein
The frequency at which the current flowing to the ground terminal of the surface acoustic wave filter for transmission and the current flowing to the ground terminal of the surface acoustic wave filter for reception are approximately in opposite phase at least within the pass frequency band of the surface acoustic wave filter for transmission The duplexer characterized by having.

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