JP5185057B2 - Duplexer - Google Patents

Description

  The present invention relates to a duplexer that transmits and receives transmission signals and reception signals having different frequencies via a common antenna.

  In a wireless communication system in which a communication terminal such as a mobile phone or the like having a bidirectional wireless communication function or a device of this type is used as a communication terminal, the frequency and reception of a transmission signal are received in order to transmit and receive signals using one antenna of the communication terminal. A difference is given to the frequency of the signal, and a transmission signal and a reception signal are separated by a duplexer (elastic wave duplexer) using this frequency difference.

FIG. 15 schematically shows a configuration example of a commonly used duplexer 100. In this example, the duplexer 100 performs filtering (frequency selection) on one common antenna port 2 and a signal of, for example, the center frequency f _R = 856 MHz received at the antenna port 2, and reception (not shown) in the apparatus. For example, a signal having a center frequency f _T = 911 MHz transmitted from a low-pass (reception side) filter 3 output to the processing unit and a transmission processing unit (not shown) in the apparatus is subjected to filter processing (frequency selection) to the antenna port 2. And a high frequency side (transmission side) filter 4 for input. A low-pass filter 3 and a high-pass filter 4 are connected in parallel to the antenna port 2, and a received signal and a transmitted signal pass through a low-pass filter port 6 and a high-pass filter port 7, respectively. Between the antenna port 2 and the apparatus. In addition, a phase shifter 5 is interposed between the antenna port 2 and the low-pass filter 3, and this phase shifter 5 prevents the transmission signal from flowing into the high-pass filter 4 side. Yes.

  As such filters 3 and 4, for example, ladder type filters such as SAW (Surface Acoustic Wave) resonators in which small and low loss acoustic wave resonators are connected in a ladder type are used. For example, the low-pass filter 3 connects four series arms 31a to 31d each made of an acoustic wave resonator in series, and parallel arms 32a to 32a made of an acoustic wave resonator are similarly connected between the series arms 31a to 31d. A T-type 7-stage ladder type filter is configured by connecting 32c in parallel to form a T-type circuit. The high-pass filter 4 constitutes a T-type five-stage filter in which series arms 41a to 41c and parallel arms 42a and 42b each made of an acoustic wave resonator are connected in series and in parallel. The parallel arms 32a to 32c, 42a, and 42b are grounded.

  Such serial arms 31a to 31d, 41a to 41c, and parallel arms 32a to 32c, 42a and 42b include, for example, a pair of parallel bus bars 81 and 81 and these bus bars 81 and 81, as shown in FIG. An elastic structure comprising an IDT electrode 83 comprising a large number of electrode fingers 82 extending alternately in a comb-tooth shape from one to the other bus bar 81, 81, and reflectors 84 disposed on both sides of the IDT electrode 83. Each of them is constituted by a wave resonator 85. The elastic wave resonator 85 is made of, for example, a metal film formed on a piezoelectric substrate, and the period unit d formed by the electrode fingers 82 is, for example, an elastic wave taken out by the elastic wave resonator 85. The wavelength is set to correspond to the center frequency. In the following description, the elastic wave resonator 85 is simplified as shown in FIG.

Conventionally, when mounting the above-described filters 3 and 4 on a substrate, the low-pass filter 3 and the high-pass filter 4 are formed on piezoelectric substrates, which are separate chips, and these chips are mounted on a common module substrate. I was trying to place it. On the other hand, with the recent miniaturization of cellular phones and the like, the duplexer 100 is also required to be further miniaturized, and a method for forming the low-pass filter 3 and the high-pass filter 4 in one chip is examined. Has been. FIG. 17 shows a configuration example of such a duplexer 100. In this example, on the piezoelectric substrate 10 having a relative dielectric constant of about 50 such as LiTaO ₃ , LiNbO ₃ or quartz, the right side in the longitudinal direction of the piezoelectric substrate 10 is shown. The filter 3 is disposed on the left side and the filter 4 is disposed on the left side.

  The series arms 31 a to 31 d and 41 a to 41 c are substantially parallel to the longitudinal direction of the piezoelectric substrate 10 so that the series arms 31 a to 31 d and 41 a to 41 c face each other at the center of the piezoelectric substrate 10. The parallel arms 32a to 32c, 42a, and 42b described above are arranged outside the series arms 31a to 31d and 41a to 41c (on the end side of the piezoelectric substrate 10). The series arms 31a to 31d and 41a to 41c are connected by signal paths 33 and 43, respectively. Therefore, the signal paths 33 and 43 are opposed to each other via the central region 15 extending in the direction orthogonal to the longitudinal direction of the piezoelectric substrate 10. The parallel arms 32a to 32c, 42a, and 42b are connected to the signal paths 33 and 43 by the parallel signal paths 34 and 44, and are connected to ground ports (not shown) formed on the module substrate 11, respectively. .

The piezoelectric substrate 10 on which the filters 3 and 4 are formed in this way is arranged on the module substrate 11 constituting the base of the chip, and one end side and the other end side of the signal paths 33 and 43 are arranged on the module substrate 11. Are connected to the antenna port 2 and the filter ports 6 and 7, respectively. The piezoelectric substrate 10 is formed so that the width dimension W is 2 mm, for example, and the depth dimension L is 1.6 mm, for example. The signal paths 33, 34, 43, and 44 are hatched for easy identification.
Here, in FIG. 17, the distance between the filters 3 and 4 on the piezoelectric substrate 10 (the width dimension of the central region 15) D is drawn narrow so that the configuration of the filters 3 and 4 can be easily identified. As described above, since the relative dielectric constant of the piezoelectric substrate 10 is about 50 and the frequency of the signal to be transmitted / received is about 1 GHz, this separation distance D is actually 1 mm as shown in FIG. Is set to The reason why the distance D is set to be larger than the lateral width W of the piezoelectric substrate 10 will be described below.

When transmission / reception is performed in the duplexer 100, a number of electric lines of force E ₁ , E ₂ , E ₃ ,. ,,, _{E n} is formed. When the signal paths 33 and 43 are close to each other, the potential of the signal paths 33 and 43 changes in a narrow region, so that the distribution of the electric lines of force E becomes dense. When the electric force lines E at this time are schematically shown in FIG. 19 showing a longitudinal sectional view of the piezoelectric substrate 10 along the line AA in FIG. 17, the distribution of the electric force lines E between the signal paths 33 and 43 is as follows. Since it becomes dense, many capacitive couplings C ₁ , C ₂ , C _3, ..., C _n are formed. In FIG. 19, the number of lines of electric force E and the number of capacitive couplings C are omitted.

  Here, the signal path 33 between each of the series arms 31 a to 31 d of the low-pass filter 3 is defined as signal paths 33 a, 33 b, and 33 c, and the signal path 33 in a portion connected to the low-pass filter port 6 is defined as the signal path 33. The signal path is 33d. Further, the signal path 43 between the series arms 41a to 41c of the high-pass filter 4 is defined as signal paths 43a and 43b, respectively, and the signal path 43 at the portion connected to the high-pass filter port 7 is defined as the signal path 43c. Then, the capacitive coupling C is formed in each region between the signal paths 33a to 33d and the signal paths 43a to 43c, as schematically shown in FIG. Therefore, the total amount of capacitive coupling C between the signal paths 33 and 43 becomes extremely large.

  FIGS. 21A, 21B, and 21C show the frequency characteristics of the high frequency side (transmission side) filter 4 and the frequency characteristics and isolating characteristics of the low frequency side (reception side) filter 3 in the arrangement structure shown in FIG. The solid line represents the ideal value when the capacitive coupling C does not exist, and the dotted line represents the value when the capacitive coupling C exists. This ideal value can be obtained by setting the distance D between the elastic wave resonators 85 facing each other to 1 mm or more. From FIG. 21, it can be seen that the isolation characteristic is deteriorated by the capacitive coupling C, and therefore the frequency characteristic of the filters 3 and 4 is deteriorated.

  By the way, if a space of 1 mm is provided between the filters 3 and 4 so that the capacitive coupling C is not formed, this space becomes a dead space, and the piezoelectric substrate 10 is enlarged. Therefore, for example, as shown in FIG. 22, a shield electrode 101 made of, for example, a metal film is formed between the filters 3, 4. There is known a duplexer 100 configured to be grounded. When the shield electrode 101 is formed in this way, a part of the capacitive coupling C between the signal paths 33 and 34 is formed via the shield electrode 101 as shown in FIG. The bond C can be reduced. The dotted lines in FIGS. 24A, 24B, and 24C indicate the frequency characteristics of the high-pass filter 4 and the low-pass filter when the separation distance D is set to 0.7 mm in the arrangement structure shown in FIG. 3 is a result of calculation with respect to the frequency characteristic and the isolation characteristic, and the solid line is the above-described ideal value. FIG. 24 shows that even when the separation distance D is reduced to, for example, 0.7 mm, deterioration of the isolation characteristics can be suppressed, and the frequency characteristics of the filters 3 and 4 are improved. However, such a shield electrode 101 is insufficient to further reduce the size of the duplexer 100 while maintaining or improving the isolation characteristics, and further improvement is required.

  Patent Document 1 describes such a shield electrode, but the dimensions of the gap between the filter and the shield electrode, the shape of the shield electrode, the arrangement method, the electrical characteristics of the shield electrode, and the like are studied. Not.

International Publication No. 2005/011114 (9th page, 15th line to 29th line, FIG. 1)

  The present invention has been made based on such circumstances, and the purpose of the present invention is to reduce the size of a duplexer having a transmission filter and a reception filter on the same piezoelectric substrate while obtaining good isolation characteristics. It is to provide a duplexer that can be realized.

The duplexer of the present invention is
A transmission-side filter and a reception-side filter are arranged on the piezoelectric substrate so as to be opposed to each other on the left and right sides. In a duplexer configured with connection,
A shield electrode is interposed between the transmission side filter and the reception side filter, and both side edges of the shield electrode are bent edges formed by the arrangement of signal paths and acoustic wave resonators in the transmission side filter and the reception side filter, respectively. It is bent along the line.
It is preferable that the left and right maximum width of the shield electrode is 150 μm to 480 μm.

  According to the present invention, the transmission-side filter and the reception-side filter are arranged on the piezoelectric substrate so as to oppose each other in the left-right direction, and these filters have a plurality of elastic wave resonators whose elastic waves propagate in the left-right direction. In a duplexer configured to be connected to a signal path via a signal path, a shield electrode is interposed between the transmission side filter and the reception side filter, and both side edges of the shield electrode are connected to signal paths in the transmission side filter and the reception side filter, respectively. And an elastic wave resonator are bent along a bent edge. Then, paying attention to the fact that a high-pass filter is constituted by this shield electrode, the gap dimension between the shield electrode and the transmission-side filter and the reception-side filter is set so that the pole of this bypass filter is located in the required frequency band. Selected. Therefore, it is possible to obtain a good isolation characteristic while reducing the separation distance between the transmission filter and the reception filter, and to reduce the size of the duplexer.

A duplexer (elastic wave duplexer) 1 according to an embodiment of the present invention will be described with reference to FIG. The duplexer 1 includes a common module substrate 11 whose planar shape is formed in a substantially rectangular shape. The approximate center position on the module substrate 11 is made of, for example, a piezoelectric material such as LiTaO ₃ , LiNbO _3, or quartz formed so that the width W is 2.0 mm, for example, and the depth L is 1.6 mm, for example. The piezoelectric substrate 10 is fixed, and in this example, the piezoelectric substrate 10 is arranged so that the longitudinal direction of the piezoelectric substrate 10 faces in the left-right direction in FIG. On the module substrate 11, the antenna port 2 is arranged at the center position on the back side when viewed from the piezoelectric substrate 10, and a low-pass (reception side) filter is provided at the right end on the front side of the piezoelectric substrate 10. A high frequency side (transmission side) filter port 7 is formed at the left end of the port 6.

On the piezoelectric substrate 10, on the right side is a low-pass (reception side) filter 3 that is a ladder-type filter configured in, for example, a T-type seven-stage, and on the left side is also a ladder-type filter similarly configured in a T-type five-stage, for example. A certain high frequency side (transmission side) filter 4 is arranged. These filters 3 and 4 respectively filter the received signal of f _R = 856 MHz (frequency selection) and output it to a reception processing unit (not shown) in the apparatus and a transmission processing unit (not shown) in the apparatus. For example, it is a filter that filters a transmission signal having a center frequency f _T = 911 MHz and inputs it to the antenna port 2.

  Since the configurations of the filters 3 and 4 are the same as the duplexer 100 shown in FIG. 17 described above, the series arms 31 a to 31 d and 41 a to 41 c are arranged at the center of the piezoelectric substrate 10. 10 are connected in series by signal paths 33 and 43 so as to oppose each other in a direction orthogonal to the longitudinal direction of the ten, and one end side of the parallel arms 32a to 32c, 42a and 42b is connected to the series arms 31a to 31d and 41a to 41c. The parallel signal paths 34 and 44 are connected in parallel to the signal paths 33 and 43 at the outer position (end side of the piezoelectric substrate 10). The other ends of the parallel arms 32a to 32c, 42a, 42b are illustrated on the module substrate 11 via wires (not shown) connected to the parallel signal paths 34, 44 extending from the other ends. Not connected to the ground port respectively.

Further, one end sides of the signal paths 33 and 43 are connected to the antenna port 2 by wires 51 and 51 so that the filters 3 and 4 are connected to the antenna port 2 in parallel. The other end side is connected to the low-pass filter port 6 and the high-pass filter port 7 by wires 52 and 52, respectively. A phase shifter (not shown) is interposed between the antenna port 2 and the low-pass filter 3.
Further, the serial arms 31a to 31d, 41a to 41c and the parallel arms 32a to 32c, 42a and 42b are each configured by an elastic wave resonator 85 including the IDT electrode 83 and the reflectors 84 and 84 shown in FIG. The signal paths 33 and 43 and the parallel signal paths 34 and 44 described above are connected across the width direction of the IDT electrode 83 of the acoustic wave resonator 85.

  Next, the shield electrode 60 that is the main part of the duplexer 1 of the present invention will be described. If a region extending in a direction orthogonal to the longitudinal direction of the piezoelectric substrate 10 between the signal paths 33 and 43 is a central region 15, the width of the central region 15, that is, the separation between the signal paths 33 and 43 on the piezoelectric substrate 10. The distance D is set to a dimension shorter than the duplexer 100 shown in FIG. 17 described above, for example, 200 to 500 μm. In the central region 15, a shield electrode 60 made of, for example, a metal film is formed. The shield electrode 60 is formed along the shape of the filters 3 and 4 facing the central region 15 side, that is, close to the signal paths 33 and 43 at portions where the signal paths 33 and 43 face each other. On the other hand, the portion where the reflector 84 is formed is formed so as to be recessed in a rectangular shape on the inner side (center region 15 side) in accordance with the shape of the reflector 84 so as not to contact the reflector 84. Therefore, the width D1 of the shield electrode 60 at the part where the signal paths 33 and 34 face each other is set to 150 to 482 μm, for example, and the filter 3 and 4 (the signal paths 33 and 43 or the reflector 84) and this The gap dimension D2 between the shield electrode 60 and the shield electrode 60 is set to 9 to 25 μm, for example. As shown in FIG. 2, the shield electrode 60 is grounded via, for example, a bump (not shown) formed on the shield electrode 60. The signal paths 33, 34, 43, and 44 are hatched for easy identification.

Next, the reason why the width dimension D1 and the gap dimension D2 are set as described above in the shield electrode 60 will be described in detail below together with the description of the operation of the duplexer 1.
In the duplexer 1, when transmission / reception is performed between the antenna port 2 and the low-pass filter 3 and between the antenna port 2 and the high-pass filter 4 based on the above-described principle, the signal paths 33 and 43 are transmitted. numerous electric flux lines _E 1 over the upper and lower regions of the respective piezoelectric substrate _{10, E 2, E 3 ,,,,,} E n is formed in the. As described above, since the separation distance D, which is the distance between the signal paths 33 and 43, is set shorter than the duplexer 100 of FIG. 17 described above, as shown in FIG. , 43 is densely distributed, so that a large number of capacitive couplings C ₁ , C ₂ , C _3, ... C _n are formed. At this time, since the shield electrode 60 is disposed in the central region 15, a part of the capacitive coupling C formed between the signal paths 33 and 43 is connected via the shield electrode 60.

Here, among the many capacitive couplings C, for example, only _six capacitive couplings C _{1 to} C ₆ from the lower side to the upper side of the piezoelectric substrate 10 are shown in FIG. The capacitive coupling C directly formed between the signal paths 33 and 43 is defined as capacitive couplings C ₁ and C ₆ on the outside, and the capacitive coupling C formed via the shield electrode 60 is defined as capacitive couplings C _{2 to} C ₅ on the inside. To do. At this time, since the shield electrode 60 is grounded via the bump as described above, it can be said that the bump and the shield electrode 60 itself have an inductance component. In FIG. 2 described above, this inductance component is indicated as “61” for convenience.

  When the equivalent circuit 62 of the capacitive coupling C and the inductance component 61 is schematically shown in FIG. 3, it can be said that the equivalent circuit 62 is a high-pass filter having a pass band in a high frequency region. With respect to the high-pass filter having such an equivalent circuit 62, the attenuation characteristics were calculated as described in the later-described examples. As shown schematically in FIG. It has been found that there is a maximum value at which the attenuation amount becomes extremely large on the side, that is, on the frequency side of the signal transmitted and received in the duplexer 1. Therefore, by designing the equivalent circuit 62 so that the maximum value is formed at a position close to the pass frequency band of the low-pass filter 3 in the duplexer 1, the separation distance D of the central region 15 is shortened as described above. Thus, even when the capacitive coupling C is formed between the signal paths 33 and 43, a large attenuation can be obtained, that is, a large insulation can be ensured, so that deterioration of isolation characteristics can be suppressed. It is considered possible. As shown in FIG. 20 described above, a large number of capacitive couplings C are formed between the signal paths 33 and 43. However, in order to simplify the illustration, in FIG. 3, between the series arms 31b and 31c. The capacitive coupling C between the signal path 33 and the signal path 43 between the series arms 41b and 41c is shown.

As a result of studying the high-pass filter constituted by the equivalent circuit 62, the position of the maximum value is shifted by changing the width dimension D1 and the gap dimension D2 of the shield electrode 60, as shown in an example described later. I understood. Specifically, as the gap dimension D2 is narrowed, the capacitive coupling C (C _{2 to} C ₅ ) formed between the signal paths 33 and 43 via the shield electrode 60 increases. As a result, it was found that the position of the maximum value of the high-pass filter shifted toward the low frequency side. Further, for example, when only the width dimension D1 is expanded without changing the gap dimension D2, the capacitive coupling C directly formed between the signal paths 33 and 43 without the shield electrode 60 decreases, and as a result, It was found that the position of the maximum value of the high-pass filter shifted to the high frequency side. However, in this example, in order to reduce the size of the duplexer 1, the width dimension D1 is set to the above value. Further, by changing the grounding method of the shield electrode 60 to a method other than the above-described method using the bump, for example, a method using a wire or a via hole formed in the piezoelectric substrate 10 or the module substrate 11, transmission to the ground is performed. It was found that the inductance component 61 is changed because the length, wire diameter, and resistance value of the line change, and therefore the characteristics of the high-pass filter change. Specifically, for example, in the case of wire connection, it has been found that the inductance component 61 increases and the position of the maximum value of the high-pass filter shifts to the low frequency side.

  Therefore, in this example, when the duplexer 1 is reduced in size by reducing the separation distance D, the width dimension D1, the gap dimension D2, and the grounding method of the shield electrode 60 are set as described above, so that the shield electrode 60 is configured. The position of the local maximum value of the high-pass filter is brought close to the pass frequency band of the low-pass filter 3, so that the influence of the capacitive coupling C formed between the signal paths 33 and 43 is suppressed to reduce the degradation of the isolation characteristics. I have to. With respect to the duplexer 1 designed in this way, the characteristics corresponding to the above-described FIG. 21 and FIG. 24 were calculated, and in the filters 3 and 4, the characteristics indicated by the dotted lines in FIGS. 5A and 5B were obtained. As for the isolation characteristics between the low-pass filter port 6 and the high-pass filter port 7, the characteristics indicated by the dotted line in FIG. The characteristic indicated by the solid line in FIG. 9 is a value obtained when the separation distance D of the central region 15 is made large by the above-described duplexer 100, that is, an ideal value. Therefore, in this duplexer 1, the separation distance D of the central region 15 is obtained. It can be seen that the isolation characteristic is the same level as the ideal value even if the value is narrowed.

  The position of the maximum value of the high-pass filter is not necessarily matched with the center frequency of the frequency band of the signal received by the low-pass filter 3, as will be described later in the embodiment. It has been found that such an effect can be obtained by bringing it close to.

  According to the above-described embodiment, the duplexer 1 including the low-pass filter 3 and the high-pass filter 4 on the same piezoelectric substrate 10 is disposed between the low-pass filter 3 and the high-pass filter 4. Focusing on the fact that a high-pass filter is constituted by the shield electrode 60 to be removed, the idea of setting the width dimension D1 of the shield electrode 60 to a uniform dimension is taken away, and the shape of the edge of the filters 3 and 4 is followed. In other words, the shield electrode 60 is configured to conform to the shapes of the edges of the signal paths 33 and 43 and the edge of the acoustic wave resonator 85, and the value of the gap dimension D2 between the shield electrode 60 and the filters 3 and 4 is set. Is selected so that the poles of the high-pass filter are located in the required frequency band. Therefore, good isolation characteristics can be obtained while the separation distance D of the filters 3 and 4 is reduced to, for example, about 150 to 480 μm, and the duplexer 1 can be downsized as shown in FIG. Further, the position of the maximum value of the high-pass filter is brought close to the frequency region received by the low-pass filter 3, but for example, it is made close to the frequency region of the signal transmitted by the high-pass filter 4. In other words, the position of the maximum value may be shifted to a position where the attenuation can be increased so that a desired isolation characteristic can be obtained in the frequency band transmitted and received by the duplexer 1.

  In this example, the duplexer 1 is reduced in size by reducing the separation distance D (width dimension D1). However, the filter 3 in the duplexer 100 shown in FIGS. 4, the shield electrode 60 of the present invention may be arranged to narrow the gap dimension D2. In this case, good isolation characteristics can be obtained.

  In the above example, the filters 3 and 4 are arranged so that the signal paths 33 and 43 are opposed to each other over the length direction of the central region 15, but for example, as shown in FIG. Without changing, the arrangement positions of the serial arms 31a to 31d (41a to 41c) and the arrangement positions of the parallel arms 32a to 32c (42a, 42b) may be partially reversed. In such a case, even when the separation distance D is narrowed as described above, the signal paths 33 and 43 are largely separated in the inversion region (in this example, the serial arm 31d). Although the influence is reduced, the influence of the capacitive coupling C is suppressed by the shield electrode 60 between the signal paths 33 and 43 facing each other across the central region 15 as described above. Therefore, it can be said that the present invention can be applied to the duplexer 1 in which at least a part of the signal paths 33 and 43 sandwich the central region 15 from both sides. In addition, the present invention can be applied to a configuration in which the transmission filter 4 and the reception filter 3 are disposed opposite to each other on a single substrate 10.

  Further, not only the structure of the duplexer 1 described above in which the filter for the reception signal is the low-pass filter 3 and the filter for the transmission signal is the high-pass filter 4, but the low-pass filter 3 is for the transmission signal. The duplexer may be configured by using the high-pass filter 4 for the received signal. Further, the acoustic wave resonator constituting the low-pass filter 3 is not limited to the SAW resonator, and for example, a resonator using a boundary acoustic wave may be used.

(Experiment 1)
A calculation for confirming how the position of the maximum value of the high-pass filter constituted by the shield electrode 60 is shifted by setting the above-described gap dimension D2 to various values as shown in the following calculation conditions. went. At this time, the width dimension D1 is constant between 150 μm and 480 μm under any condition, and the grounding method of the shield electrode 60 is performed via the bumps as described above. For this calculation, a two-dimensional circuit simulator (MDS (Microwave Design System) manufactured by Hewlett Packard (Agilent)) was used.

(Calculation condition)
Gap dimension D2: 25 μm, 20 μm, 15 μm, 12 μm, 9 μm
(Calculation result)
With respect to the position of the maximum value of the high-pass filter calculated under the above conditions, the calculation results when the gap dimension D2 is 25 μm, 20 μm, 15 μm, 12 μm, and 9 μm are shown by solid lines in FIGS. In addition, the result calculated about the shield electrode 101 of the above-described duplexer 100 of FIG. 22 is also shown by a dotted line.

  From the result of FIG. 8, the width dimension D1 and the gap dimension D2 are narrowed, and the shield electrode 60 is grounded by the bump, so that the shield is obtained at 1.6 GHz close to the frequency band of the signal received by the low-pass filter 3. The maximum value of the high-pass filter constituted by the electrode 60 was confirmed. Therefore, it was found that good isolation characteristics can be obtained at 1 GHz to 1.9 GHz. In the conventional example (FIG. 22) indicated by a dotted line in the figure, the shield electrode 101 is grounded, and this shield electrode 101 has an inductance component between the shield electrode 101 and the ground. 101 is considered to constitute a high-pass filter similarly to the shield electrode 60 of the present invention, but because the distance between the filter 3 (4) and the shield electrode 101 is greatly separated, is a maximum value formed? Alternatively, it is considered that a maximum value is formed on the higher frequency side than the range shown in this graph. Therefore, in this duplexer 100, it can be seen that the high-pass filter constituted by the shield electrode 101 cannot be expected to improve the isolation characteristics.

  Further, from the results of FIGS. 9 to 12, it was found that the position of the maximum value of the high-pass filter shifts to the low frequency side by narrowing the gap dimension D2. 9 to 12, good isolation characteristics are obtained at 0.8 GHz to 1.75 GHz, 0.7 GHz to 1.5 GHz, 0.6 GHz to 1.4 GHz, and 0.55 GHz to 1.25 GHz, respectively. be able to. Therefore, as described above, by appropriately changing the width dimension D1, the gap dimension D2 or the grounding method of the shield electrode 60, the distance D (duplexer 1) can be adjusted in accordance with the frequency band of the signal transmitted and received by the duplexer 1. It was found that the shift amount (maximum value position) of the maximum value position of the high-pass filter can be adjusted in accordance with the horizontal width dimension of the high pass filter.

(Experiment 2)
Next, the duplexer 1 of the present invention and the conventional duplexer 100 were actually manufactured, and the isolation characteristics of both were compared. The configurations of these duplexers 1 and 100 are shown in FIGS. 13 (a) and 13 (b), respectively. As can be seen from FIG. 13, in each duplexer 1, 100, only the shield electrodes 60, 101 are changed without changing the configuration of the filters 3, 4. Specifically, the width dimension D1 is 480 μm in all cases, and the gap dimension D2 is 10 μm in the duplexer 1 and 50 μm in the duplexer 100. Further, both duplexers 1 and 100 are grounded via bumps. In FIG. 13, 70 is a piezoelectric substrate, 71 is an elastic wave resonator, and 72 is a transmission path (signal path).

  The isolation characteristics obtained for the duplexers 1 and 100 are shown in FIGS. 14 (a) and 14 (b), respectively. As a result, it has been found that, for example, at 900 MHz to 940 MHz, the duplexer 1 can increase the attenuation by about 10 dB compared to the conventional duplexer 100.

It is the top view which showed the structural example of the duplexer which concerns on embodiment of this invention. It is a cross-sectional view schematically showing the duplexer. It is the top view which showed roughly the equivalent circuit about the shield electrode of said duplexer. It is the top view which showed roughly the characteristic of the high pass filter comprised by said shield electrode. It is the characteristic view which calculated the attenuation characteristic of said duplexer. It is the top view which showed the above-mentioned duplexer roughly. It is the top view which showed other embodiment of said duplexer. It is the characteristic view which calculated the attenuation characteristic of the shield electrode of said duplexer. It is the characteristic view which calculated the attenuation characteristic of the shield electrode of said duplexer. It is the characteristic view which calculated the attenuation characteristic of the shield electrode of said duplexer. It is the characteristic view which calculated the attenuation characteristic of the shield electrode of said duplexer. It is the characteristic view which calculated the attenuation characteristic of the shield electrode of said duplexer. It is the top view which showed the duplexer produced in the Example of this invention. It is the characteristic view which showed the attenuation | damping characteristic obtained about the duplexer produced in said Example. It is the schematic which showed the conventional duplexer. It is the top view which showed an example of the elastic wave resonator which comprises said conventional duplexer. It is the top view which showed an example of the conventional duplexer. It is the top view which showed the conventional duplexer typically. It is the longitudinal cross-sectional view which showed schematically an example of the conventional duplexer. It is the top view which showed typically the capacitive coupling formed in said conventional duplexer. It is the characteristic view which showed the attenuation | damping characteristic obtained with the conventional duplexer. It is a top view which shows an example of the conventional duplexer. It is the longitudinal cross-sectional view which showed schematically an example of the conventional duplexer. It is a characteristic view which shows the attenuation | damping characteristic obtained by said conventional duplexer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Duplexer 2 Antenna port 3 Low band side filter 4 High band side filter 6 Low band side filter port 7 High band side filter port 10 Piezoelectric board 11 Module board 15 Center area D Separation distance D1 Width dimension D2 Gap dimension E Electric force line W Width 31 Series arm 33 Signal path 41 Series arm 43 Signal path

Claims (2)

A transmission-side filter and a reception-side filter are arranged on the piezoelectric substrate so as to be opposed to each other on the left and right sides. In a duplexer configured with connection,
A shield electrode is interposed between the transmission side filter and the reception side filter, and both side edges of the shield electrode are bent edges formed by the arrangement of signal paths and acoustic wave resonators in the transmission side filter and the reception side filter, respectively. A duplexer characterized by being bent along.   The duplexer according to claim 1, wherein the left and right maximum widths of the shield electrode are 150 μm to 480 μm.

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