JP4817875B2 - Duplexer and communication device - Google Patents

Description

  The present invention relates to a surface acoustic wave element used as a duplexer in a communication device such as a mobile communication device such as a mobile phone, and to a surface acoustic wave element that can be miniaturized while improving electrical characteristics. The present invention relates to a communication device used as a duplexer.

  In recent years, many surface acoustic wave elements have been used as constituent elements such as filters, delay lines, and oscillators of electronic devices that use radio waves. In particular, surface acoustic wave elements that are small and lightweight and have high steep cut-off performance as filters have come to be widely used as RF stage and IF stage filters for mobile terminal devices in the field of mobile communication. It is required to have low loss, to have high attenuation characteristics outside the passband, and to have a wide passband width.

  In addition, surface acoustic wave elements are also frequently used as a duplexer, which is a circuit directly under the antenna, and it is required that the insertion loss in the transmission band is small, and isolation between the transmission side and the reception side is required. Is also required to be high. In response to such market demands, improving the characteristics of the duplexer leads to an improvement in the quality of the mobile terminal device in the mobile communication field. Therefore, it is necessary to change the electrode structure of the duplexer. is there.

  8 and 9 are graphs showing pass characteristics when a surface acoustic wave element is used as a filter of a duplexer that passes the transmission band and the reception band, respectively. In this example, the frequency of the reception band is higher than the frequency of the transmission band.

  The amount of attenuation in the passband of the surface acoustic wave element is referred to as “insertion loss” or simply “loss”. Further, the attenuation characteristic of a signal outside the passband is referred to as “attenuation characteristic”. The amount that the signal of the transmission circuit leaks to the reception circuit is called “isolation”.

  In addition, in one type of surface acoustic wave element used for the duplexer, a plurality of surface acoustic wave resonators are disposed on a piezoelectric substrate, and the surface acoustic wave resonators are connected in series and in parallel to the signal line. A ladder-type surface acoustic wave filter connected in a ladder shape as a whole is known.

  This ladder type surface acoustic wave filter is small in size and low in loss, and can realize a filter with steep attenuation characteristics. Therefore, it is widely used as a surface acoustic wave filter for transmitting and receiving a duplexer such as a cellular phone. I'm starting.

  Conventionally, when a surface acoustic wave element is used as a branching filter, the comb teeth with respect to the pitch (period) P of electrode fingers of the surface acoustic wave resonator are used for the purpose of improving the accuracy of the fabrication process of the surface acoustic wave element. It has been studied to set the electrode finger width L ratio (L / P) to a value larger than 0.5 (for example, see Patent Document 1).

On the other hand, in order to obtain a good sharp cutoff performance, the ratio (L / P) of the electrode finger width L of the comb-shaped electrode to the pitch P of the electrode fingers of the surface acoustic wave resonator is a ratio smaller than 0.5 (For example, refer to Patent Document 2).
JP 2001-308671 A JP 2003-198317 A

  However, in the technique disclosed in Patent Document 1, by setting the L / P to a value larger than 0.5, the electrode finger width L becomes wide if the electrode finger pitch P is constant. The interval (P-L) is narrowed, thereby increasing the capacitance of the surface acoustic wave resonator, and as a result, the insertion loss of the surface acoustic wave element is increased.

  Since the transmission ladder type surface acoustic wave element of the duplexer is required to reduce the loss in the transmission frequency band, the technique disclosed in Patent Document 1 is a lossy duplexer. There was a problem of end.

  Further, in the technique disclosed in Patent Document 2, since the electrode finger width L is reduced by setting the L / P to a value smaller than 0.5, the electrode finger interval (P−L) is increased. As a result, the capacitance of the surface acoustic wave resonator is reduced, and as a result, the attenuation amount outside the pass band of the surface acoustic wave element, that is, the isolation is reduced.

  In the receiving ladder type surface acoustic wave element of the duplexer, in order to achieve high isolation characteristics, it is essential to improve the attenuation characteristics in the transmission frequency band. There is a problem that the duplexer has poor isolation characteristics.

  In order to make the insertion loss of the surface acoustic wave element low and make the attenuation characteristic steep, it can be adjusted by increasing the number of electrode fingers of the surface acoustic wave resonator or the electrode finger crossing width. Generally known. However, as the number of electrode fingers and the crossing width of electrode fingers increase, the size of the surface acoustic wave resonator increases, which makes it impossible to satisfy the market demand for miniaturization. was there.

  The present invention has been devised in view of the above-described problems in the prior art, and an object of the present invention is to achieve a surface acoustic wave element having a low loss and a high attenuation while achieving downsizing, and the surface acoustic wave element. It is another object of the present invention to provide a duplexer and a communication device.

The surface acoustic wave device according to the present invention is a surface acoustic wave device formed on a main surface of one or a plurality of piezoelectric substrates, and one or a plurality of transmission elastic surfaces connected in series to a transmission-side signal line. A ladder-type surface acoustic wave element for transmission including a wave resonator and one or more surface acoustic wave resonators for transmission connected in parallel to the transmission-side signal line, and connected in series to the reception-side signal line A receiving ladder type surface acoustic wave element including one or more receiving surface acoustic wave resonators and one or more receiving surface acoustic wave resonators connected in parallel to the receiving-side signal line. A ratio (LT / PT) of the electrode finger width LT of the comb-shaped electrode to the pitch PT of the electrode fingers adjacent to each other in the at least one surface acoustic wave resonator for transmission; Comb-shaped electricity in a surface acoustic wave resonator for reception The ratio of the electrode finger width LR of the comb-shaped electrodes to the pitch PR of the adjacent electrode fingers to each other and (LR / PR) satisfies the following equation.
(LT / PT) <(LR / PR)
In the surface acoustic wave device according to the present invention, in the above configuration, the ratio (LT / PT) in the surface acoustic wave resonator for transmission connected in series and the ratio in the surface acoustic wave resonator for reception connected in parallel are combined. (LR / PR) satisfies the above formula.

  The surface acoustic wave device according to the present invention has the above-described ratio (LT / PT) in all the surface acoustic wave resonators for transmission connected in series and parallel and all the elastic surfaces for reception connected in series and parallel. The ratio (LR / PR) in the wave resonator satisfies the above equation.

  In the surface acoustic wave element of the present invention, in the above configuration, the frequency of the pass band of the ladder-type surface acoustic wave element for reception is higher than the frequency of the pass band of the ladder-type surface acoustic wave element for transmission.

  In the surface acoustic wave device according to the present invention, the pitch P of the electrode fingers is substantially equal between the surface acoustic wave resonator for transmission and the surface acoustic wave resonator for reception.

In the surface acoustic wave device of the present invention, in the above configuration, the ratio (LT / PT) in the at least one surface acoustic wave resonator for transmission satisfies the following expression.
(LT / PT) <0.6
In the surface acoustic wave device of the present invention, in the above configuration, the ratio (LR / PR) in the at least one receiving surface acoustic wave resonator satisfies the following expression.
0.6 <(LR / PR)
The surface acoustic wave element according to the present invention is configured such that, in the above configuration, the transmission ladder-type surface acoustic wave element and the reception ladder-type surface acoustic wave element are respectively formed on main surfaces of different piezoelectric substrates.

  The duplexer of the present invention uses the surface acoustic wave element of the present invention as a filter.

  The communication device of the present invention is equipped with the duplexer of the present invention.

The surface acoustic wave device according to the present invention is a surface acoustic wave device formed on a main surface of one or a plurality of piezoelectric substrates, and one or a plurality of transmission elastic surfaces connected in series to a transmission-side signal line. A ladder-type surface acoustic wave element for transmission including a wave resonator and one or more surface acoustic wave resonators for transmission connected in parallel to the transmission-side signal line, and connected in series to the reception-side signal line A receiving ladder type surface acoustic wave element including one or more receiving surface acoustic wave resonators and one or more receiving surface acoustic wave resonators connected in parallel to the receiving-side signal line. The ratio (LT / PT) of the electrode finger width LT of the comb-shaped electrode to the pitch PT of the adjacent electrode fingers of the comb-shaped electrode in at least one of the surface acoustic wave resonators for transmission; Comb-shaped electricity in a surface acoustic wave resonator for reception The ratio of the electrode finger width LR of the comb-shaped electrodes to the pitch PR of the adjacent electrode fingers to each other and (LR / PR) satisfies the following equation.
(LT / PT) <(LR / PR)
According to the surface acoustic wave device having this configuration, by satisfying the above expression, the electrode finger width L is relatively narrowed in any of the surface acoustic wave resonators for transmission. ) Is widened, thereby reducing the electrostatic capacitance of the surface acoustic wave resonator and reducing the extra parasitic capacitance generated in the surface acoustic wave resonator. As a result, a ladder-type surface acoustic wave device for transmission And low loss characteristics can be obtained.

  In any of the surface acoustic wave resonators for reception, since the electrode finger width L is relatively wide, the electrode finger interval (P−L) can be narrowed, and thereby the surface acoustic wave resonator can be statically operated. The capacitance can be increased, and thereby the parasitic capacitance generated in the receiving ladder-type surface acoustic wave element can be increased. As a result, the ladder-type surface acoustic wave element for reception has high attenuation characteristics, and high isolation characteristics can be obtained in the transmission band.

  Further, the ratio (LT / PT) in any one of the surface acoustic wave resonators for transmission connected in series and the ratio (LR / PR) in any one of the surface acoustic wave resonators for reception connected in parallel. However, if the above equation is satisfied, the two requirements of low insertion loss and high isolation can be easily satisfied.

  Further, the ratio (LT / PT) in all surface acoustic wave resonators for transmission connected in series and parallel, and the ratio (LR / PR) in all surface acoustic wave resonators for reception connected in series and parallel. However, if the above equation is satisfied, the two requirements of low insertion loss and high isolation can be satisfied easily and reliably.

  Further, it is possible to obtain a surface acoustic wave element that can be suitably used for a small duplexer without increasing the size of the piezoelectric substrate necessary for forming the surface acoustic wave element.

It is preferable that the ratio (LT / PT) in the at least one surface acoustic wave resonator for transmission satisfies the following formula.
(LT / PT) <0.6
According to this configuration, the influence of the parasitic capacitance generated in the surface acoustic wave resonator for transmission can be reduced, and a low-loss characteristic can be obtained more easily. Therefore, it is possible to obtain a surface acoustic wave device with lower loss and higher isolation characteristics.

The ratio (LR / PR) in the at least one receiving surface acoustic wave resonator preferably satisfies the following equation.
0.6 <(LR / PR)
According to this configuration, it is possible to increase the parasitic capacitance necessary for out-of-band attenuation generated in the reception ladder-type surface acoustic wave element, and it is possible to easily obtain high attenuation characteristics.

  When the transmission ladder-type surface acoustic wave element and the reception ladder-type surface acoustic wave element are formed on the main surfaces of different piezoelectric substrates, the surface acoustic wave (SAW) or piezoelectric that propagates on the surface of the piezoelectric substrate is used. Since it is possible to eliminate the coupling between the transmission ladder-type surface acoustic wave element and the reception ladder-type surface acoustic wave element due to the bulk wave propagating in the substrate, it can be suitably used as a duplexer with more excellent isolation characteristics. A surface acoustic wave element can be obtained.

  Further, when the surface acoustic wave element of the present invention is used as a duplexer, the attenuation of the transmission signal is reduced, so that a communication device with low power consumption can be configured. In addition, since the transmission signal of the communication device does not return as a reception signal, it is possible to configure a communication device capable of high-quality communication with little reception noise.

  Hereinafter, the surface acoustic wave device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a circuit diagram showing an example of a surface acoustic wave element according to the present invention, and FIG. 2 is a diagram showing a pattern example of comb-like electrode fingers of a surface acoustic wave resonator. Note that FIG. 2 is only a diagram schematically showing the comb-shaped electrode fingers, and the shape and logarithm of the comb-shaped electrode fingers are not limited to those shown in this figure.

  As shown in FIG. 1, the surface acoustic wave element D1 of the present invention is used as a duplexer, and includes a transmission ladder type surface acoustic wave element T1 and a reception ladder type surface acoustic wave element R2. Preferably, a matching line M1 is further added.

  In the following example, it is assumed that the frequency of the passband of the ladder-type surface acoustic wave element R2 for reception is higher than the frequency of the passband of the ladder-type surface acoustic wave element T1 for transmission.

  A plurality of surface acoustic wave resonators S1 are connected in series and in parallel between the transmission input terminal 10 and the antenna terminal 20 of the surface acoustic wave element D1, thereby forming a transmission ladder type surface acoustic wave element T1. Yes.

  Also, a reception ladder type surface acoustic wave element R2 in which a plurality of surface acoustic wave resonators S2 are connected in series and in parallel is formed between the antenna terminal 20 and the reception output terminal 30 of the surface acoustic wave element D1. ing.

  A matching line M1 is added between the antenna terminal 20 and the receiving ladder-type surface acoustic wave element R2. The matching line M <b> 1 is configured by an electrode pattern formed on the piezoelectric substrate 9. The matching line M1 may be formed on a housing on which the piezoelectric substrate 9 is mounted, a ceramic substrate, a ceramic laminated substrate, or a substrate on which the surface acoustic wave element D1 is mounted.

  In place of the matching line M1, reactance components such as an inductance element and a capacitance element may be used as a substitute for the line.

The surface acoustic wave resonators S1 and S2 are formed on a main surface of a piezoelectric substrate 9 such as a LiTaO ₃ single crystal or a LiNbO ₃ single crystal by combining a pair of comb-like electrode fingers as shown in FIG. Further, reflector electrodes 2 and 4 are arranged on both sides of IDT (Inter Digital Transducer) electrodes 1 and 3, respectively.

  Here, in the transmission ladder type surface acoustic wave element T1 shown in FIG. 2, the line width ratio (LT) which is the ratio of the electrode finger width LT to the electrode finger pitch PT of the IDT electrode 1 of the surface acoustic wave resonator S1. / PT) is an important design parameter for improving the electrical characteristics of the surface acoustic wave resonator S1.

  The line width ratio (LR / PR), which is the ratio of the electrode finger width LR to the electrode finger pitch PR of the IDT electrode 3, of the ladder-type surface acoustic wave element R2 for reception is also similar to that for transmission. This is an important design parameter for improving the electrical characteristics of the resonator S2.

The surface acoustic wave element D1 is characterized in that the line width ratio (LT / PT) of any one of the surface acoustic wave resonators S1 of the transmission ladder type surface acoustic wave element T1 is the same as that of the ladder type surface acoustic wave element R2 for reception. Smaller than the line width ratio (LR / PR) of any one of the surface acoustic wave resonators S2,
(LT / PT) <(LR / PR)
It is in the relationship.

  For example, among the transmission ladder type surface acoustic wave element T1, the line width ratio (LT / PT) of the surface acoustic wave resonator S1 closest to the transmission input terminal 10 is calculated from the reception ladder type surface acoustic wave element R2. The line width ratio (LR / PR) of the surface acoustic wave resonator S2 closest to the reception output terminal 30 is made smaller.

  As described above, by making the line width ratio (LT / PT) of any one of the surface acoustic wave resonators S1 smaller than the line width ratio (LR / PR) of any one of the surface acoustic wave resonators S2, transmission is performed. Since extra parasitic capacitance generated in the ladder-type surface acoustic wave element T1 can be reduced, the transmission ladder-type surface acoustic wave element T1 can have low loss characteristics.

  Further, the isolation characteristic in the transmission band of the surface acoustic wave element D1 is greatly influenced by the attenuation amount of the ladder type surface acoustic wave element R2 for reception.

  In the conventional product, the reception ladder type surface acoustic wave element R2 is also reduced in the parasitic capacitance necessary for attenuation by reducing the line width ratio (LR / PR), similarly to the transmission ladder type surface acoustic wave element T1. For this reason, if the transmission ladder type surface acoustic wave element T1 has a low loss, the reception ladder type surface acoustic wave element R2 also has low isolation characteristics.

  However, in the surface acoustic wave device D1 of the present invention, the line width ratio (LR / PR) of the surface acoustic wave resonator S2 of the ladder type surface acoustic wave device R2 for reception is set to the ladder type surface acoustic wave device for transmission. It is made relatively larger than the line width ratio (LT / PT) of any one of the surface acoustic wave resonators S1 of T1. As a result, the parasitic capacitance required for the increase in attenuation generated in the reception ladder type surface acoustic wave element R2 can be increased, so that the reception ladder type surface acoustic wave element R2 can have high attenuation characteristics. Therefore, high isolation characteristics can be obtained.

In particular, the ratio (LT / PT) in the transmission surface acoustic wave resonator S1 connected in series in the transmission ladder-type surface acoustic wave element T1 and the reception elasticity connected in parallel in the reception ladder-type surface acoustic wave element R2. The ratio (LR / PR) in the surface wave resonator S2 is the above formula.
(LT / PT) <(LR / PR)
It is effective to satisfy the above.
The reason for this is that the series surface acoustic wave resonator of the ladder filter is designed at a higher frequency than the parallel surface acoustic wave resonator. It is possible to control the characteristics on the high frequency side. In addition, since parallel surface acoustic wave resonators are designed at a lower frequency than series surface acoustic wave resonators, the characteristics of the low frequency side of the passband are mainly achieved by designing parallel surface acoustic wave resonators. Can be controlled. Further, in a communication system in which the transmission band is arranged on the lower frequency side than the reception band, since the high frequency side of the transmission band is close to the reception band, characteristics with lower loss and higher attenuation are required. That is, the design of a serial surface acoustic wave resonator for transmission is important. Further, since the low frequency side of the reception band is close to the transmission band, characteristics with lower loss and higher attenuation are required. That is, the design of a parallel surface acoustic wave resonator for reception is important. For the above reasons, it is effective to satisfy the above equation for the serial surface acoustic wave resonator for transmission and the parallel surface acoustic wave resonator for reception.

In particular, the ratio (LT / PT) in all the transmission surface acoustic wave resonators S1 connected in series and parallel in the transmission ladder type surface acoustic wave element T1, and the series connection in parallel in the ladder type surface acoustic wave element R2 for reception. The ratio (LR / PR) in all the receiving surface acoustic wave resonators S2
(LT / PT) <(LR / PR)
It is more effective to satisfy the above.

  Here, FIG. 3 is a graph showing the relationship between the line width ratio (LT / PT) and the transmission side insertion loss when all the resonators satisfy the above equation.

  It can be seen that when the line width ratio (LT / PT) exceeds 0.6, the transmission-side insertion loss increases rapidly, and when it is less than 0.6, a stable transmission-side insertion loss with low loss can be obtained.

  Therefore, the line width ratio (LT / PT) of the surface acoustic wave resonator S1 of the ladder-type surface acoustic wave element T1 for transmission satisfies the expression (LT / PT) <0.6. The influence of the parasitic capacitance generated in the ladder-type surface acoustic wave element T1 can be reliably eliminated, and a more stable and low-loss characteristic can be obtained.

  FIG. 4 is a graph showing the relationship between the line width ratio (LR / PR) and transmission band isolation when all the resonators satisfy the above equation.

  It can be seen that when the line width ratio (LR / PR) is smaller than 0.6, the transmission band isolation is rapidly deteriorated. When the line width ratio (LR / PR) is greater than 0.6, a stable transmission band isolation is obtained.

  Therefore, by setting the line width ratio (LR / PR) of the surface acoustic wave resonator S2 of the ladder-type surface acoustic wave element R2 for reception to satisfy the equation 0.6 <(LR / PR), The parasitic capacitance required for the increase in attenuation generated in the ladder-type surface acoustic wave element R2 can be increased, and a more stable and highly attenuated characteristic can be obtained.

  Next, FIG. 5 is a circuit diagram showing a more preferred example of the surface acoustic wave element of the present invention.

  The surface acoustic wave element D2 in this example is characterized in that the surface acoustic wave resonator S1 of the ladder type surface acoustic wave element T1 for transmission and the surface acoustic wave resonator S2 of the ladder type surface acoustic wave element R2 for reception are different piezoelectric substrates. It is formed on the main surfaces of 9a and 9b.

  By forming the surface acoustic wave resonator S1 and the surface acoustic wave resonator S2 on the main surfaces of the different piezoelectric substrates 9a and 9b in this manner, the surface acoustic wave resonator S1 and the surface acoustic wave resonator S2 are formed. It is possible to prevent the deterioration of the isolation characteristics due to the coupling of the surface acoustic wave leaking to the surface.

  Further, since the electrode patterns of the surface acoustic wave resonator S1 and the surface acoustic wave resonator S2 are separated into different piezoelectric substrates 9a and 9b, the isolation characteristics are deteriorated due to the electrical and magnetic coupling between the resonators. Can be prevented.

  The IDT electrodes of the surface acoustic wave resonators S1 and S2 of the surface acoustic wave element D1 of the present invention are Al or Al alloys such as Al-Cu, Al-Ti, Al-Mg, and Al-Cu-Mg. Alternatively, it may be formed of a laminated film of different metals such as Al-Cu / Cu / Al-Cu, Ti / Al-Cu, Ti / Al-Cu / Ti.

  The IDT electrode may be formed by a thin film forming method such as a vapor deposition method, a sputtering method, or a CVD method.

  The number of comb-like electrode fingers of the IDT electrode is about 50 to 300, the line width L of the electrode fingers is about 0.1 to 10 μm, the pitch P between the electrode fingers is about 0.1 to 10 μm, As the surface acoustic wave resonators S1 and S2 or the surface acoustic wave elements D1 and D2, the opening width (crossing width) W is about 10 to 200 μm and the thickness of the electrode fingers is about 0.1 to 0.5 μm. It is suitable for obtaining desired characteristics.

As the piezoelectric substrate, 36 ° ± 10 ° Y cut-X propagation LiTaO ₃ single crystal, 64 ° ± 10 ° Y cut-X propagation LiNbO ₃ single crystal, 45 ° ± 10 ° X cut-Z propagation Li ₂ A B ₄ O ₇ single crystal or the like is preferable because it has a large electromechanical coupling coefficient and a small group delay time temperature coefficient. In particular, a 36 ° ± 10 ° Y-cut-X propagation LiTaO ₃ single crystal having a large electromechanical coupling coefficient and a small characteristic change due to temperature is preferable. The cut angle in the crystal Y-axis direction may be in the range of 36 ° ± 10 °, whereby sufficient piezoelectric characteristics can be obtained.

  The thickness of the piezoelectric substrate is preferably about 0.1 to 0.5 mm. If the thickness is less than 0.1 mm, the piezoelectric substrate becomes brittle, and if it exceeds 0.5 mm, the material cost increases.

  Moreover, in order to prevent the electrode destruction by the pyroelectric effect of a piezoelectric substrate, you may use the piezoelectric substrate which gave the reduction process.

  Moreover, in order to prevent the electrode destruction by the pyroelectric effect of a piezoelectric substrate, you may use the piezoelectric substrate to which Fe element was added.

  In addition, it is desirable that the line width ratios (LT / PT) of the plurality of surface acoustic wave resonators S1 constituting the transmission ladder type surface acoustic wave element T1 are approximately the same, but the number of electrode fingers and the number of electrode fingers Other numerical values such as the intersection width and the pitch of the electrode fingers may be different designs.

  Similarly, it is desirable that the line width ratios (LR / PR) of the plurality of surface acoustic wave resonators S2 constituting the ladder-type surface acoustic wave element R2 for reception are approximately equal to each other. Other numerical values such as the crossing width and the pitch of the electrode fingers may be different designs.

  The surface acoustic wave element of the present invention can be applied to a communication device.

  That is, in a communication apparatus including one or both of a receiving circuit and a transmitting circuit, a band pass filter or a duplexer using the surface acoustic wave element of the present invention can be mounted.

  The transmission circuit is a circuit that places a transmission signal on a carrier frequency with a mixer, attenuates an unnecessary signal with a band-pass filter, then amplifies the transmission signal with a power amplifier, and transmits it from an antenna through a duplexer. is there.

  The receiving circuit receives the received signal with an antenna, amplifies the received signal that has passed through the duplexer with a low noise amplifier, then attenuates unnecessary signals with a band-pass filter, and separates the signal from the carrier frequency with a mixer. This is a circuit for extracting this signal.

  A communication device having excellent characteristics can be realized by incorporating the duplexer and the bandpass filter into the communication device.

  Next, specific examples of the surface acoustic wave device of the present invention will be shown.

First, lithium tantalate (LiTaO ₃ ) was used as a piezoelectric substrate, a Ti thin film having a thickness of 6 nm was formed on the main surface, and an Al—Cu thin film having a thickness of 130 nm was formed thereon, and this was alternately formed. Three layers were laminated one by one to form a total of six Ti / Al—Cu laminated films.

  Next, a photoresist was applied to a thickness of about 0.5 μm using a resist coating apparatus.

  Next, the line width ratio (LT / PT) of the comb-like electrode fingers of the surface acoustic wave resonator S1 in the transmission ladder type surface acoustic wave element T1 shown in FIG. 2 is received by the reduction projection exposure apparatus (stepper). A photoresist pattern was formed so as to be smaller than the line width ratio (LR / PR) of the comb-like electrode fingers of the surface acoustic wave resonator S2 in the ladder type surface acoustic wave element R2.

  Next, an unnecessary portion of the photoresist was dissolved with an alkaline developer using a developing device, and an electrode pattern was formed using a RIE (Reactive Ion Etching) device.

Next, a protective film was formed on a predetermined region of the electrode pattern. That is, a SiO ₂ film having a thickness of about 0.02 μm was formed on the main surface of the electrode pattern and the piezoelectric substrate by a CVD (Chemical Vapor Deposition) apparatus.

  Next, the photoresist was patterned by photolithography, and the protective film of the flip chip electrode portion was etched by an RIE apparatus or the like.

  Next, using a sputtering apparatus, a laminated electrode made of Cr, Ni, Au was formed. The electrode film thickness at this time was about 1 μm.

  Next, the photoresist and the laminated electrode at unnecessary portions were simultaneously removed by a lift-off method to form pads for connecting flip-chip bumps.

  Next, the piezoelectric substrate was diced along dicing lines and divided into each surface acoustic wave element chip.

  Next, an electrode pattern made of solder was printed on the ceramic mounting substrate.

  Next, each chip was temporarily bonded onto the ceramic mounting substrate using a flip chip mounting apparatus with the electrode formation surface on the bottom surface.

Next, the chip was bonded to the ceramic mounting substrate by baking in an N ₂ atmosphere and melting the solder.

Next, a resin was applied to the ceramic mounting substrate to which the chip was bonded, and baked in an N ₂ atmosphere to seal the chip with resin.

  Next, the ceramic mounting substrate was diced along dicing lines and divided into individual pieces, thereby producing a duplexer using the surface acoustic wave device of the present invention. In addition, the ceramic mounting board | substrate divided | segmented into the piece used the thing of the laminated structure of 2.5 * 2.0mm.

  On the other hand, the matching line M1 is configured by reactance components of an inductance element and a capacitance element arranged on a ceramic mounting substrate on which the surface acoustic wave element is mounted.

  Thus, the surface acoustic wave element A of the present invention was produced. In the surface acoustic wave element A, the line width ratio (LT / PT) of each surface acoustic wave resonator S1 of the transmission ladder type surface acoustic wave element T1 is 0.60, and the ladder type surface acoustic wave element for reception is provided. The line width ratio (LR / PR) of each surface acoustic wave resonator S2 of R2 was 0.71.

  Further, as a comparative example, a conventional surface acoustic wave device B is manufactured in the same manner as described above, with the line width ratios (LT / PT) and (LR / PR) set to 0.65. did.

  The electrical characteristics of these surface acoustic wave elements A and B were measured with a network analyzer apparatus. The results are shown in FIGS.

  FIG. 6 is a diagram showing the insertion loss of the surface acoustic wave elements A and B. The horizontal axis represents the frequency (unit: MHz) and the vertical axis represents the insertion loss (unit: dB). Indicates the result of the surface acoustic wave element A, and the broken characteristic curve indicates the result of the surface acoustic wave element B.

  FIG. 7 is a diagram showing the isolation characteristics of the surface acoustic wave elements A and B. The horizontal axis represents the frequency (unit: MHz), and the vertical axis represents the isolation characteristic (unit: dB). The solid characteristic curve indicates the result of the surface acoustic wave element A, and the broken characteristic curve indicates the result of the surface acoustic wave element B.

  As shown in FIGS. 6 and 7, the surface acoustic wave device A of the embodiment of the present invention has an insertion loss of 2.0 dB and an isolation characteristic of 58 dB, whereas the surface acoustic wave device of the comparative example. In B, the insertion loss is 2.4 dB and the isolation characteristic is 54 dB. According to the embodiment of the present invention, both the insertion loss and the isolation characteristic can be greatly improved.

Further, according to the pattern shown in FIG. 2, the surface acoustic wave element C, in which the line width ratio (LT / PT) of the surface acoustic wave resonator S1 in the transmission ladder type surface acoustic wave element T1 is changed as shown below. D, E, and F were produced. The line width ratios (LT / PT) and (LR / PR) in the surface acoustic wave elements C, D, E, and F were as shown below.

  The electrical characteristics of the surface acoustic wave elements C, D, E, and F of these examples were measured with a network analyzer device. The measurement results are shown in a diagram in FIG.

  In FIG. 3, the horizontal axis represents the line width ratio (LT / PT), the vertical axis represents the transmission-side insertion loss (unit: dB), and the black circle plot and characteristic curve represent the line width ratio (LT / PT). The relationship with the transmission side insertion loss is shown.

  As shown in FIG. 3, the insertion loss increased as the line width ratio (LT / PT) of the surface acoustic wave resonator S1 in the transmission ladder type surface acoustic wave element T1 increased.

  As can be seen from this result, when the line width ratio (LT / PT) of the surface acoustic wave resonator S1 in the transmission ladder type surface acoustic wave element T1 is 0.6 or more, the transmission ladder type surface acoustic wave element Even if the line width ratio (LT / PT) of the surface acoustic wave resonator S1 at T1 is smaller than the line width ratio (LR / PR) of the surface acoustic wave resonator S2 in the ladder-type surface acoustic wave element R2 for reception. It was found that the loss increased.

  Therefore, it is preferable that (LT / PT) <0.6.

  Further, the line width ratio (LR / PR) of the surface acoustic wave resonator S2 in the ladder-type surface acoustic wave element R2 for reception was changed in accordance with the pattern of the comb-like electrode fingers shown in FIG. The surface acoustic wave elements G, H, I, J, and K of Examples were manufactured.

The electrical characteristics of the surface acoustic wave elements G, H, I, J, and K of these examples were similarly measured with a network analyzer device. The line width ratios (LT / PT) and (LR / PR) in the surface acoustic wave elements G, H, I, J, and K were as shown below.

  The electrical characteristics of the surface acoustic wave elements G, H, I, J, and K of these examples were similarly measured with a network analyzer device. The measurement results are shown as a diagram in FIG.

  In FIG. 4, the horizontal axis represents the line width ratio (LR / PR), the vertical axis represents the transmission side isolation (unit: dB), and the black circle plots and characteristic curves represent the line width ratio (LR / PR). The relationship with the transmission side isolation is shown.

  As shown in FIG. 4, the transmission-side isolation increased as the line width ratio (LR / PR) of the surface acoustic wave resonator S2 in the ladder-type surface acoustic wave element R2 for reception increased.

  As can be seen from this result, when the line width ratio (LR / PR) of the surface acoustic wave resonator S2 in the reception ladder type surface acoustic wave element R2 is 0.6 or less, the ladder type surface acoustic wave element for transmission is used. Even if the line width ratio (LT / PT) of the surface acoustic wave resonator S1 at T1 is smaller than the line width ratio (LR / PR) of the surface acoustic wave resonator S2 in the ladder-type surface acoustic wave element R2 for reception. It was found that the transmission side isolation decreased.

  Therefore, it is preferable that (LR / PR)> 0.6.

  From the above results, it was confirmed that the surface acoustic wave device of the present invention was a duplexer having good electrical characteristics.

  Note that the above are merely examples of the embodiments of the present invention, and the present invention is not limited to these embodiments, and various modifications and improvements may be added without departing from the scope of the present invention. . Moreover, you may combine the structure of the above-mentioned each claim arbitrarily.

  For example, the number of electrode fingers, the crossing width, and the like may be changed for each surface acoustic wave resonator. In this case, since the parasitic capacitance can be adjusted and the surface acoustic wave can be controlled by changing the number of electrode finger pairs, the crossing width, etc., it is possible to obtain a further low loss and high isolation characteristic.

In the above-described example, the passband frequency of the ladder-type surface acoustic wave element R2 for reception is higher than the frequency of the passband of the ladder-type surface acoustic wave element T1 for transmission. However, the reverse relationship, that is, a relationship in which the frequency of the passband of the reception ladder-type surface acoustic wave element R2 is lower than the frequency of the passband of the transmission ladder-type surface acoustic wave element T1. In this case, in particular, the parallel-connected surface acoustic wave resonator on the transmission side and the serial surface acoustic wave resonator on the reception side are expressed by the equation (LT / PT) <(LR / PR).
It is effective to satisfy the above. The reason is as follows.

  The series surface acoustic wave resonator of the ladder filter is designed at a higher frequency than that of the parallel surface acoustic wave resonator. Therefore, the design of the series surface acoustic wave resonator mainly improves the characteristics on the high-frequency side of the passband. Can be controlled. In addition, since parallel surface acoustic wave resonators are designed at a lower frequency than series surface acoustic wave resonators, the characteristics of the low frequency side of the passband are mainly achieved by designing parallel surface acoustic wave resonators. Can be controlled. Further, in a communication system in which the transmission band is arranged on the higher frequency side than the reception band, since the low frequency side of the transmission band is close to the reception band, characteristics with lower loss and higher attenuation are required. That is, the design of a parallel surface acoustic wave resonator for transmission is important. Further, since the high frequency side of the reception band is close to the transmission band, characteristics with lower loss and higher attenuation are required. In other words, it is important to design a series surface acoustic wave resonator for reception. For the above reasons, it is effective that the parallel surface acoustic wave resonator for transmission and the serial surface acoustic wave resonator for reception satisfy the above equation.

It is a circuit diagram which shows an example of embodiment of the surface acoustic wave element of this invention. It is a schematic pattern diagram which shows an example of the comb-tooth shaped electrode finger formed in the piezoelectric substrate. It is a diagram which shows the relationship between the line width ratio (LT / PT) of the ladder type surface acoustic wave element for transmission in the Example of the surface acoustic wave element of this invention, and insertion loss. It is a diagram which shows the relationship between the line | wire width ratio (LR / PR) of the ladder type surface acoustic wave element for reception in the Example of the surface acoustic wave element of this invention, and an isolation characteristic. It is a schematic pattern diagram which shows an example of the comb-tooth shaped electrode finger formed in the piezoelectric substrate. It is a diagram which shows the insertion loss of the surface acoustic wave element of the Example and comparative example of this invention. It is a diagram which shows the isolation characteristic of the surface acoustic wave element of the Example and comparative example of this invention. It is a diagram for demonstrating the definition of insertion loss. It is a diagram for demonstrating the definition of isolation.

Explanation of symbols

D1, D2: surface acoustic wave element T1: transmission ladder type surface acoustic wave element R2: reception ladder type surface acoustic wave element M1: matching line S1: surface acoustic wave resonator constituting a transmission ladder type surface acoustic wave element S2: Surface acoustic wave resonator constituting a ladder type surface acoustic wave element for reception 1: IDT electrode of surface acoustic wave resonator for transmission 2: Reflector of surface acoustic wave resonator for transmission 3: Surface acoustic wave resonance for reception IDT electrode of child 4: Reflector of surface acoustic wave resonator for reception 9: Piezoelectric substrate 10: Transmission input terminal 20: Antenna terminal 30: Reception output terminal

Claims (6)

A duplexer using a surface acoustic wave element formed on the main surface of one or more piezoelectric substrates as a filter ,
A transmission including one or more surface acoustic wave resonators for transmission connected in series to the signal line on the transmission side and one or more surface acoustic wave resonators for transmission connected in parallel to the signal line on the transmission side A credit ladder type surface acoustic wave element;
Reception including one or more receiving surface acoustic wave resonators connected in series to the receiving side signal line and one or more receiving surface acoustic wave resonators connected in parallel to the receiving side signal line Including a ladder-type surface acoustic wave device,
Ratio of electrode finger width LT of comb-shaped electrode to pitch PT of adjacent electrode fingers of comb-shaped electrode in at least one surface acoustic wave resonator for transmission included in the ladder-type surface acoustic wave element for transmission (LT / PT) and at least one of the reception surface acoustic wave resonators included in the reception ladder-type surface acoustic wave element , the comb-shaped electrode with respect to the pitch PR of the electrode fingers adjacent to each other of the comb-shaped electrode duplexer ratio of the electrode finger width LR (LR / PR) and satisfies the following expression.
(LT / PT) <0.6 <(LR / PR) The ratio (LT / PT) in the surface acoustic wave resonators for transmission connected in series is smaller than the ratio (LR / PR) in the surface acoustic wave resonators for reception connected in parallel. The duplexer described. The ratio (LT / PT) in all surface acoustic wave resonators for transmission connected in series and parallel is higher than the ratio (LR / PR) in all surface acoustic wave resonators for reception connected in series and parallel. The duplexer according to claim 1 or 2, which is small. 4. The duplexer according to claim 1, wherein the frequency of the passband of the ladder-type surface acoustic wave element for reception is higher than the frequency of the passband of the ladder-type surface acoustic wave element for transmission . 5. . 5. The transmission ladder-type surface acoustic wave element and the reception ladder-type surface acoustic wave element are respectively formed on main surfaces of different piezoelectric substrates. Duplexer . The communication apparatus carrying the duplexer as described in any one of Claims 1 thru | or 5.

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