JP6286955B2 - Elastic wave device - Google Patents

Description

  The present invention relates to an acoustic wave device, and more particularly, to an acoustic wave device including a transmission side terminal and balanced first and second reception side terminals.

  Conventionally, a surface acoustic wave filter device has been proposed in which an element that is electromagnetically coupled to an antenna terminal is disposed between a parallel arm resonator of a transmission filter and a ground (for example, JP 2011-10317 A). Publication (refer patent document 1)).

JP 2011-10317 A

  FIG. 1G of the above document describes the arrangement of the transmission side signal terminal and the two reception side signal terminals on the circuit board. According to this description, there is a difference in the distance between the transmission-side signal terminal and one reception-side signal terminal and the distance between the transmission-side signal terminal and the other reception-side signal terminal. Therefore, there is a difference between the parasitic capacitance generated in the circuit from the transmission side signal terminal to one reception side signal terminal and the parasitic capacitance generated in the circuit from the transmission side signal terminal to the other reception side signal terminal. Become. Due to this difference in parasitic capacitance, the phase of the signal transmitted from the transmission side signal terminal to each of the two reception side signal terminals is shifted. In particular, there has been a problem that good differential mode isolation characteristics cannot be obtained due to a phase shift in the transmission frequency band.

  The present invention has been made in view of the above-described problems, and a main object thereof is to provide an acoustic wave device capable of obtaining good differential mode isolation characteristics.

  An acoustic wave device according to the present invention includes a piezoelectric substrate, a first filter element, a second filter element, a transmission side signal terminal, a first reception side signal terminal, and a second reception side signal terminal. Yes. The piezoelectric substrate has a main surface. The first filter element, the second filter element, the transmission side signal terminal, the first reception side signal terminal, and the second reception side signal terminal are provided on the main surface of the piezoelectric substrate. The transmission side signal terminal is electrically connected to the first filter element. The first reception side signal terminal and the second reception side signal terminal are provided in a balanced type and are electrically connected to the second filter element. The distance from the transmission side signal terminal to the first reception side signal terminal is equal to the distance from the transmission side signal terminal to the second reception side signal terminal.

  Here, in this specification, the equal distance is a concept including both a case where two distances coincide with each other and a case where the two distances are not completely the same but the difference between them is sufficiently small. Defined. That is, if one of the two distances is within a range of ± 5% of the other, the effects of the present invention to be described later can be obtained in the same manner, and therefore it is included in the scope of the present invention.

  Preferably, the acoustic wave device further includes an antenna terminal provided on the main surface. The antenna terminal is electrically connected to the first filter element and the second filter element. The distance from the antenna terminal to the first reception side signal terminal is equal to the distance from the antenna terminal to the second reception side signal terminal.

  Preferably, in the acoustic wave device, the transmission side signal terminal is disposed at a midpoint of a line segment connecting the first reception side signal terminal and the second reception side signal terminal.

  Preferably, in the acoustic wave device, the antenna terminal is disposed at a midpoint of a line segment connecting the first reception side signal terminal and the second reception side signal terminal.

  Preferably, in the acoustic wave device, the first filter element is a ladder-type element having a series arm resonator and an even number of parallel arm resonators. The parallel arm resonators are arranged in line symmetry with a straight line passing through a midpoint of a line connecting the first reception side signal terminal and the second reception side signal terminal as a target axis.

  According to the present invention, it is possible to realize an acoustic wave device that can obtain good differential mode isolation characteristics.

1 is a schematic plan view showing an acoustic wave device according to Embodiment 1. FIG. FIG. 3 is a schematic diagram showing the arrangement of terminals on the piezoelectric substrate of the first embodiment. 6 is a schematic plan view showing an acoustic wave device according to Embodiment 2. FIG. FIG. 6 is a schematic diagram showing the arrangement of terminals on the piezoelectric substrate of the second embodiment. 6 is a schematic plan view showing an acoustic wave device according to Embodiment 3. FIG. FIG. 6 is a schematic diagram showing the arrangement of terminals on the piezoelectric substrate of the third embodiment.

  Embodiments of the present invention will be described below with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated.

(Embodiment 1)
FIG. 1 is a schematic plan view showing an acoustic wave device 200 according to the first embodiment. In the following embodiment, a duplexer will be described as an example of the acoustic wave device 200. However, it should be noted that the duplexer is merely an example. That is, elastic wave device 200 may be, for example, a device having only one filter unit, or may be another duplexer such as a triplexer.

  An elastic wave device 200 shown in FIG. 1 is an elastic wave duplexer, and includes a piezoelectric substrate 100 having a main surface 101, an antenna terminal 4, a transmission side signal terminal 1, first and second reception side signal terminals 2, and the like. 3, a first filter element 5, and a second filter element 6. The transmission side signal terminal 1, the first and second reception side signal terminals 2 and 3, the antenna terminal 4, the first filter element 5, and the second filter element 6 are provided on the main surface 101 of the piezoelectric substrate 100. ing.

  The first filter element 5 in the present embodiment is a surface acoustic wave filter having a ladder-type circuit configuration, and has a function as a transmission filter. The first filter element 5 is disposed between the antenna terminal 4 and the transmission-side signal terminal 1, and is electrically connected to both the antenna terminal 4 and the transmission-side signal terminal 1.

  The first filter element 5 includes a series arm 60 connecting the antenna terminal 4 and the transmission side signal terminal 1, and a plurality of series arm resonators 63, 64, 65 provided on the series arm 60, It has an even number of parallel arm resonators 61 and 62 provided between the series arm 60 and the ground potential. A plurality of series arm resonators 63, 64, 65 are connected between the transmission-side signal terminal 1 and the antenna terminal 4. The parallel arm resonators 61 and 62 and the series arm resonators 63, 64, and 65 are each constituted by a 1-port surface acoustic wave resonator.

  The second filter element 6 constitutes a longitudinally coupled resonator type surface acoustic wave filter, and has a function as a reception filter. The second filter element 6 is arranged between one filter unit 6 a arranged between the antenna terminal 4 and the first reception side signal terminal 2, and between the antenna terminal 4 and the second reception side signal terminal 3. The other filter portion 6b is a balanced element. One filter unit 6 a is electrically connected to both the antenna terminal 4 and the first reception-side signal terminal 2. The other filter unit 6 b is electrically connected to both the antenna terminal 4 and the second reception side signal terminal 3.

  The second filter element 6 has a plurality of surface acoustic wave resonators 71, 72, 73, 74, 75, 76. The surface acoustic wave resonators 71, 72, 73 are included in one filter unit 6a. The surface acoustic wave resonators 74, 75, and 76 are included in the other filter unit 6b. One filter unit 6a and the other filter unit 6b constitute a 3IDT (InterDigital Transducer) type longitudinally coupled resonator type surface acoustic wave filter. However, in FIG. 1, the reflector which pinches | interposes three IDTs located in a line with the propagation direction of a surface acoustic wave is abbreviate | omitted and displayed. The surface acoustic wave resonators 71 and 73 are provided between the ground potential and the first reception-side signal terminal 2. The surface acoustic wave resonators 72 and 75 are provided between the antenna terminal 4 and the ground potential. The surface acoustic wave resonators 74 and 76 are provided between the ground potential and the second reception side signal terminal 3. As one modification of the 3IDT type longitudinally coupled resonator type surface acoustic wave filter, five IDTs may be arranged between the reflectors in the propagation direction of the surface acoustic wave.

  Both the first filter element 5 and the second filter element 6 constituting the acoustic wave device 200 of the present embodiment are produced on the main surface 101 of the piezoelectric substrate 100. By manufacturing the transmission filter and the reception filter on the same piezoelectric substrate 100, it is possible to avoid that the optimum inductance value differs due to manufacturing variations between the transmission filter and the reception filter. From the viewpoint of miniaturization, it is advantageous to form the transmission filter and the reception filter on the same piezoelectric substrate 100.

  The first filter element 5 is a filter in which both an input signal and an output signal are unbalanced signals. The second filter element 6 is a filter whose input signal is an unbalanced signal and whose output signal is a balanced signal. That is, the transmission side signal terminal 1 is an unbalanced signal terminal, and the first reception side signal terminal 2 and the second reception side signal terminal 3 are a pair of balanced signal terminals.

  The acoustic wave device 200 has a configuration in which a first filter element 5 as a transmission filter and a second filter element 6 as a reception filter are connected in parallel with the antenna terminal 4 as a common terminal. That is, the first filter element 5 and the second filter element 6 are connected to the antenna terminal 4 in common.

  FIG. 2 is a schematic diagram showing the arrangement of terminals in the piezoelectric substrate 100 of the first embodiment. 2 shows the piezoelectric substrate 100, the transmission-side signal terminal 1 formed on the piezoelectric substrate 100, and the first and second reception-side signal terminals 2 and 3 among the components of the acoustic wave device 200 shown in FIG. The antenna terminal 4 is shown. A straight line L indicated by a one-dot chain line in FIG. 2 indicates a straight line passing through the midpoint of the first and second reception side signal terminals 2 and 3 and the transmission side signal terminal 1. The straight line L passes through the midpoint of the line connecting the first and second receiving signal terminals 2 and 3 and extends perpendicularly to this line. That is, the straight line L is a vertical bisector connecting the first and second receiving signal terminals 2 and 3. In FIG. 2, one of the two-dot chain lengths of the two-dot chain line in FIG. 2 indicates the distance D1 from the transmission side signal terminal 1 to the first reception side signal terminal 2, and the other is the second side from the transmission side signal terminal 1. The distance D2 to the receiving side signal terminal 3 is shown. In the first filter element which is a ladder-type element including a plurality of series arm resonators and an even number of parallel arm resonators, all the series arm resonators are arranged on a straight line L, and the main surface of the piezoelectric substrate is straight. The same number of parallel arm resonators are arranged in each of the two regions divided by L. In FIG. 1, even-numbered parallel arm resonators are arranged in line-symmetric positions with the straight line L as the axis of symmetry.

  The transmission side signal terminal 1 and the first and second reception side signal terminals 2, 3 are the spatial distance between the transmission side signal terminal 1 and the first reception side signal terminal 2, and the transmission side signal terminal 1 It arrange | positions so that the spatial distance between the 2nd receiving side signal terminals 3 may become equal. The distance D1 and the distance D2 shown in FIG. 2 are the same, and the relationship of D1 = D2 is established. The transmission-side signal terminal 1 and the first and second reception-side signal terminals 2 and 3 are arranged so as to be substantially line-symmetric with respect to the straight line L shown in FIG.

  In the acoustic wave device 200 of the first embodiment having the above configuration, the transmission signal input to the transmission-side signal terminal 1 passes through the first filter element 5 and is output from the antenna terminal 4. That is, the traveling direction of the transmission signal passing through the first filter element 5 is the direction from the left side to the right side in FIG. On the other hand, the reception signal received at the antenna terminal 4 passes through the second filter element 6 and is output from the first and second reception-side signal terminals 2 and 3. That is, the traveling direction of the reception signal passing through the second filter element 6 is a direction from the left side to the right side in FIG.

  The characteristic of the signal transmitted through the path between the transmission side signal terminal 1 and the first and second reception side signal terminals 2 and 3 is called an isolation characteristic. The good isolation characteristic means that, among the transmission signals input to the transmission side signal terminal 1, leakage signals that leak to the reception filter side and reach the first and second reception side signal terminals 2 and 3 are present. It shows that it is suppressed. That is, the isolation characteristic is a characteristic that does not allow the transmission signal to pass through the first and second reception side signal terminals 2 and 3. In particular, the anti-phase component signal appearing between the first and second receiving side signal terminals 2 and 3 is referred to as differential mode isolation. As for the differential mode isolation, the closer the phase characteristics of the transmission frequency band are to the same phase, the better the characteristics are obtained.

  In the acoustic wave device 200 of the present embodiment, the distance D1 between the transmission side signal terminal 1 and the first reception side signal terminal 2 and the distance between the transmission side signal terminal 1 and the second reception side signal terminal 3. D2 is equal to each other, and the difference between the distances D1 and D2 is small. Therefore, the difference between the shape of the circuit from the transmission side signal terminal 1 to the first reception side signal terminal 2 and the shape of the circuit from the transmission side signal terminal 1 to the second reception side signal terminal 3 can be reduced. Thereby, the difference between the parasitic capacitance and the parasitic inductance generated in both circuits is reduced. As a result, a phase shift factor of a signal transmitted from the transmission-side signal terminal 1 to each of the two reception-side signal terminals 2 and 3 is reduced, so that the phase characteristic in the transmission frequency band becomes close to the same phase. Transmission / reception is performed because the difference in the influence of parasitic capacitance and parasitic inductance between the path from the transmission side signal terminal 1 to the reception side signal terminal 2 and the path from the transmission side signal terminal 1 to the reception side signal terminal 3 is small. Good differential mode isolation characteristics between terminals can be obtained.

  Among the surface acoustic wave resonators constituting the first filter element 5, the parallel arm resonators 61 and 62 are arranged in line symmetry with the straight line L as the symmetry axis. That is, the parallel arm resonators 61 and 62 are arranged in line symmetry along the traveling direction of the transmission signal passing through the first filter element 5. The parallel arm resonators 61 and 62 are arranged in line symmetry with a straight line passing through the midpoint of the line connecting the first and second receiving signal terminals 2 and 3 and perpendicular to the line as the axis of symmetry. In this way, the difference between the parasitic capacitance in the circuit from the transmission side signal terminal 1 to the first reception side signal terminal 2 and the parasitic capacitance in the circuit from the transmission side signal terminal 1 to the second reception side signal terminal 3 is calculated. Can be made even smaller. Therefore, better differential mode isolation characteristics can be obtained.

(Embodiment 2)
FIG. 3 is a schematic plan view showing the acoustic wave device 200 of the second embodiment. FIG. 4 is a schematic diagram showing the arrangement of terminals on the piezoelectric substrate 100 of the second embodiment. The elastic wave device 200 according to the second embodiment has a configuration basically similar to that of the first embodiment described above. However, the second embodiment is different from the first embodiment in that the antenna terminals 4 are arranged as shown in FIGS.

  Specifically, the antenna terminal 4 according to the second embodiment includes a midpoint between the first and second receiving signal terminals 2 and 3 and a transmitting signal terminal 1 indicated by a straight line L indicated by a one-dot chain line in FIG. It is arranged on a straight line passing through. A straight line L in FIG. 4 indicates a straight line connecting the transmission-side signal terminal 1 and the antenna terminal 4. In addition to the distances D1 and D2 described in the first embodiment, the lengths of the two-dot chain lines in FIG. 4 are the distance D3 from the antenna terminal 4 to the first reception side signal terminal 2, and the antenna terminal. 4 and a distance D4 between the second receiving side signal terminal 3 and FIG.

  The antenna terminal 4 and the first and second receiving signal terminals 2 and 3 are the spatial distance between the antenna terminal 4 and the first receiving signal terminal 2, and the antenna terminal 4 and the second receiving signal terminal. Are arranged so that the spatial distance between them is equal. The distance D3 and the distance D4 shown in FIG. 4 are the same, and the relationship of D3 = D4 is established. The antenna terminal 4 is disposed at the midpoint of the line segment connecting the first reception side signal terminal 2 and the second reception side signal terminal 3. The transmission-side signal terminal 1, the first and second reception-side signal terminals 2 and 3, and the antenna terminal 4 are arranged so as to be substantially line-symmetric with respect to the straight line L shown in FIG. As a result, the entire acoustic wave device 200 has a layout close to line symmetry about the straight line connecting the antenna terminal 4 and the transmission-side signal terminal 1, that is, the straight line L indicated by the one-dot chain line in FIG. .

  In the acoustic wave device 200 according to the second embodiment, the distances D1 and D2 are equal to each other as in the first embodiment, and therefore, between the transmission-side signal terminal 1 and the two reception-side signal terminals 2 and 3. The difference in parasitic capacitance is small. In addition, the distance D3 between the antenna terminal 4 and the first receiving signal terminal 2 and the distance D4 between the antenna terminal 4 and the second receiving signal terminal 3 are equal to each other, and the distance D3, The difference in D4 is small. Therefore, the difference between the parasitic capacitance in the circuit from the antenna terminal 4 to the first reception side signal terminal 2 and the parasitic capacitance in the circuit from the antenna terminal 4 to the second reception side signal terminal 3 is small.

  The difference in parasitic capacitance between the transmission side signal terminal 1 and the two reception side signal terminals 2 and 3 is small, and further, the difference in parasitic capacitance between the antenna terminal 4 and the two reception side signal terminals 2 and 3 is small. As a result, the phase of the transmission frequency band becomes close to the same phase, and a better differential mode isolation characteristic can be obtained. For the same reason, the amplitude difference between the signals in the reception frequency band is reduced, and a good balance characteristic can be obtained.

(Embodiment 3)
FIG. 5 is a schematic plan view showing the acoustic wave device 200 of the third embodiment. FIG. 6 is a schematic diagram showing the arrangement of terminals on the piezoelectric substrate 100 of the third embodiment. The elastic wave device 200 according to the third embodiment has a configuration basically similar to that of the second embodiment described above. However, the third embodiment is different from the second embodiment in that the two reception-side signal terminals 2 and 3 and the second filter element 6 are arranged as shown in FIGS.

  Specifically, as shown in FIG. 6, the two reception-side signal terminals 2 and 3 in the third embodiment are equidistant from a straight line L indicated by a dashed line connecting the transmission-side signal terminal 1 and the antenna terminal 4. They are arranged so as to be line-symmetric with respect to the straight line L as the symmetry axis. The two reception side signal terminals 2 and 3 are symmetrically arranged on both sides of the transmission side signal terminal 1 so as to sandwich the transmission side signal terminal 1 in the vertical direction in FIGS. In the figure, the first reception side signal terminal 2 is disposed above the transmission side signal terminal 1, and the second reception side signal terminal 3 is disposed below the transmission side signal terminal 1. The transmission side signal terminal 1 is disposed at the midpoint of the line segment connecting the first reception side signal terminal 2 and the second reception side signal terminal 3. 6 indicate the distances D1 and D2 described in the first embodiment and the distances D3 and D4 described in the second embodiment.

  One filter section 6a disposed between the antenna terminal 4 and the first reception side signal terminal 2 and the other filter section 6b disposed between the antenna terminal 4 and the second reception side signal terminal 3 These are disposed at positions separated from each other in the propagation direction of the surface acoustic wave (vertical direction in FIG. 5). One filter unit 6a and the other filter unit 6b are arranged with the first filter element 5 interposed therebetween. One filter unit 6a and the other filter unit 6b are arranged so as to be substantially line symmetric with respect to a straight line L shown in FIG. As a result, the entire acoustic wave device 200 has a layout close to line symmetry about the straight line connecting the antenna terminal 4 and the transmission-side signal terminal 1, that is, the straight line L indicated by the one-dot chain line in FIG. .

  In the elastic wave device 200 of the third embodiment, the distances D1 and D2 are the same, and the distances D3 and D4 are the same, as in the second embodiment. For this reason, the difference in parasitic capacitance between the transmission side signal terminal 1 and the two reception side signal terminals 2 and 3 is small, and further, the difference in parasitic capacitance between the antenna terminal 4 and the two reception side signal terminals 2 and 3. Becomes smaller. Therefore, good differential mode isolation characteristics and good balance characteristics can be obtained.

  Although the embodiment of the present invention has been described as above, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Transmission side signal terminal, 2 1st reception side signal terminal, 3 2nd reception side signal terminal, 4 Antenna terminal, 5 1st filter element, 6 2nd filter element, 6a One filter part, 6b The other filter Part, 60 series arm, 61, 62 parallel arm resonator, 63, 64, 65 series arm resonator, 71, 72, 73, 74, 75, 76 surface acoustic wave resonator, 100 piezoelectric substrate, 101 main surface, 200 Elastic wave device, D1, D2, D3, D4 distance, L straight line.

Claims (3)

A piezoelectric substrate having a main surface;
A first filter element provided on the main surface;
A second filter element provided on the main surface;
A transmission-side signal terminal provided on the main surface and electrically connected to the first filter element;
A balanced first receiving-side signal terminal and a second receiving-side signal terminal provided on the main surface and electrically connected to the second filter element;
Wherein the distance from the transmission-side signal terminal to the first reception signal terminal, the distance from the transmission-side signal terminal to the second reception-side signal terminal phase rather equal,
Further comprising an antenna terminal provided on the main surface,
The antenna terminal is electrically connected to the first filter element and the second filter element,
The distance from the antenna terminal to the first receiving signal terminal is equal to the distance from the antenna terminal to the second receiving signal terminal,
The transmission-side signal terminal is an acoustic wave device arranged at a midpoint of a line segment connecting the first reception-side signal terminal and the second reception-side signal terminal . A piezoelectric substrate having a main surface;
A first filter element provided on the main surface;
A second filter element provided on the main surface;
A transmission-side signal terminal provided on the main surface and electrically connected to the first filter element;
A balanced first receiving-side signal terminal and a second receiving-side signal terminal provided on the main surface and electrically connected to the second filter element;
The distance from the transmission side signal terminal to the first reception side signal terminal is equal to the distance from the transmission side signal terminal to the second reception side signal terminal,
Further comprising an antenna terminal provided on the main surface,
The antenna terminal is electrically connected to the first filter element and the second filter element,
The distance from the antenna terminal to the first receiving signal terminal is equal to the distance from the antenna terminal to the second receiving signal terminal,
The antenna terminal is an acoustic wave device arranged at a midpoint of a line segment connecting the first reception side signal terminal and the second reception side signal terminal. The first filter element is a ladder-type element having a series arm resonator and an even number of parallel arm resonators,
The parallel arm resonators are arranged symmetrically with respect to a straight line passing through a midpoint of a line segment connecting the first reception side signal terminal and the second reception side signal terminal and perpendicular to the line segment. The elastic wave device according to claim 1 or 2 .

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