JP3839866B2 - Surface acoustic wave filter and method of forming pass frequency band - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave filter. The present invention also relates to a method for forming a pass frequency band of a surface acoustic wave filter.
[0002]
[Prior art]
Surface acoustic wave filters are widely used in information communication equipment.
[0003]
A surface acoustic wave filter used for mobile communication such as an automobile telephone is a ladder type in which surface acoustic wave resonators are connected in a ladder shape, an IDT type in which a plurality of IDTs (Inter Digital Transducers) are arranged, and a reflector from both sides. A resonator type sandwiched between the two has been used. When out-of-band attenuation is emphasized, a two-port resonator type filter configuration is often adopted.
[0004]
FIG. 21 is a diagram schematically showing the structure of a two-port surface acoustic wave resonator type filter.
In this two-port resonator type filter, two resonator type filters are connected mirror-symmetrically in order to improve out-of-band attenuation.
The pad 1401 is connected to the input signal terminal, and the pads 1402 and 1403 are connected to the input side GND (reference potential). When an electric signal is input to the IDT 1404 by the pad 1401 and the pad 1403, a surface acoustic wave is generated on the piezoelectric substrate. The surface acoustic wave is received by the IDT 1405 and the IDT 1406 and converted into an electric signal again.
Surface acoustic waves are generated again by the IDT 1407 and IDT 1408, and the electrical signals are finally received by the IDT 1409 and converted into electrical signals, and then output to the output signal terminal via the pad 1410. The pads 1411 and 1412 are connected to the output side GND, and the input / output GNDs are connected to each other and have a common potential.
[0005]
FIG. 22 is a diagram illustrating frequency characteristics of the surface acoustic wave resonator type filter illustrated in FIG.
Such a surface acoustic wave filter is used for both reception and transmission, and each has a suppression band in the vicinity of the pass band, and a high attenuation is required as a frequency characteristic here. Particularly in applications such as mobile communication filters such as automobile telephones, there is a strong demand for downsizing and low power consumption of the system itself. The two-stage resonator filter described above has a good out-of-band attenuation, but has a problem of large insertion loss.
[0006]
On the other hand, as a surface acoustic wave filter realizing low-loss in-band characteristics, a ladder-type surface acoustic wave resonator is provided.
FIG. 23 is a diagram schematically showing the configuration of such a ladder-type surface acoustic wave filter 1600.
In the surface acoustic wave filter 1600, surface acoustic wave resonators 1602, 1603, and 1604 are formed in series between the input pad 1606 and the output pad 1607. A surface acoustic wave resonator 1604 is formed in parallel between the series surface acoustic wave resonator 1601 and the surface acoustic wave resonator 1602 and the reference potential 1608. Further, a surface acoustic wave resonator 1605 is formed in parallel between the output pad 1607 and the reference potential 1609. Here, when a section composed of the series surface acoustic wave resonator and the parallel surface acoustic wave resonator is defined as a unit section, the surface acoustic wave filter 1600 illustrated in FIG. It has a structure in which three unit sections are connected, such as a parallel section) -second unit section (parallel section-series section) -third unit section (series section-parallel section). In addition, the surface acoustic wave resonator 1604 formed over two unit sections includes a parallel kite resonator to be formed in the first unit section and a parallel kite resonator to be formed in the second unit section. The two surface acoustic wave resonators are synthesized (the aperture length or the logarithm is doubled), and the single surface acoustic wave resonator 1604 is substituted.
In the case of the surface acoustic wave filter having such a structure, the resonance frequency of the series surface acoustic wave resonator and the anti-resonance frequency of the parallel surface acoustic wave resonator form this frequency band. A frequency characteristic having a sharp high attenuation region (notch) at the anti-resonance frequency of the surface acoustic wave resonator and the resonance frequency of the parallel surface acoustic wave resonator can be obtained.
[0007]
FIG. 24 is a diagram illustrating frequency characteristics of the ladder-type surface acoustic wave filter illustrated in FIG. As can be seen from this frequency characteristic, it is easy to provide a sharp high attenuation region in the vicinity of the band in the ladder-type surface acoustic wave filter, but it is difficult to provide a high attenuation region over a wide frequency range. There is a disadvantage that the frequency characteristics are not good. In order to improve the out-of-band characteristics, there is a method of adding an inductance component to the resonators arranged in parallel by a bonding wire or the like. However, the addition of the inductance component by the bonding wire is greatly restricted by the envelope on which the element is mounted, and it goes against the miniaturization that has a strong demand in the market.
[0008]
In cellular phone systems and the like, dielectric filters and LC filters are often used. In such a case, unbalanced input / output is required as a filter specification for reasons of design of an amplifier connected to the filter input / output. It was common. Ladder type filters are used with unbalanced input / output, but recently, with the development of RF band ICs, the demand for filters used with balanced input / output is increasing.
[0009]
As a filter used for balanced input / output, there is a lattice type filter in which impedance elements are arranged in a symmetrical lattice type. FIG. 25 is a diagram schematically showing an example of the structure of such a lattice type surface acoustic wave filter, in which surface acoustic wave resonators 1801 and 1802 as impedance elements are connected in a symmetric lattice type.
[0010]
FIG. 26 is a diagram schematically showing an example of the structure of a surface acoustic wave resonator used as an impedance element constituting the lattice filter illustrated in FIG.
The lattice filter can obtain a high attenuation over a wide range outside the band, and can realize a filter with a small in-band loss.
However, when a mobile communication filter is configured using a symmetric lattice filter having such a surface acoustic wave resonator as a constituent element, the realizable pass bandwidth is the resonance frequency fr of the surface acoustic wave resonator to be used. It is determined by the difference from the antiresonance frequency far. Therefore, there is a problem that the degree of freedom in setting the frequency characteristics is small depending on the electromechanical coupling coefficient of the piezoelectric substrate constituting the surface acoustic wave resonator. In particular, the bandwidth of a system used in a mobile phone or the like tends to increase as the line capacity increases, and since it is portable, it is necessary to reduce the loss to reduce power consumption. In the lattice type filter, it is strongly desired to widen the pass band in order to cope with various mobile communication applications.
[0011]
[Problems to be solved by the invention]
The present invention has been made to solve such problems. That is, an object of the present invention is to provide a surface acoustic wave filter having a low-loss band characteristic over a wide frequency band and a good out-of-band characteristic.
[0012]
Another object of the present invention is to provide a method for forming a pass frequency band that has a low-loss band characteristic over a wide frequency band and also has a good out-of-band characteristic.
[0013]
[Means for Solving the Problems]
The surface acoustic wave filter according to the present invention is a surface acoustic wave filter in which impedance elements are arranged in a symmetrical lattice pattern between a plurality of input / output terminals, between the first input terminal and the first output terminal and 2 is inserted between the second input terminal and the second output terminal, and within a predetermined frequency band.
fr₁<Far₁<Fr_Three<Far_Three
A first impedance element including a surface acoustic wave resonator having a plurality of resonance frequencies fr and anti-resonance frequencies far, and between the first input terminal and the second output terminal and the second input Between the terminal and the first output terminal, and within the frequency band
fr₂<Far₂<Fr_Four<Far_Four
And almost
fr₂= Far₁, Fr_Four= Far_Three
And a second impedance element including a surface acoustic wave resonator having a plurality of resonance frequencies fr and anti-resonance frequencies far.
[0014]
The surface acoustic wave filter of the present invention is a surface acoustic wave filter in which impedance elements having resonance frequencies and anti-resonance frequencies alternately appearing in a predetermined frequency band between a plurality of input / output terminals are arranged in a symmetrical lattice type. A first impedance element including a surface acoustic wave resonator having an anti-resonance frequency at the first frequency and the second frequency, and an elasticity having a resonance point at the first frequency and the second frequency. And a second impedance element including a surface wave resonator.
[0015]
The surface acoustic wave filter of the present invention includes a first input terminal, a second input terminal, a first output terminal, a second output terminal, and a first input terminal and a first output terminal. And a first impedance element including a surface acoustic wave resonator having a plurality of resonance frequencies and anti-resonance frequencies interposed between the second input terminal and the second output terminal, and a first input terminal A plurality of portions that are inserted between the second output terminal and between the second input terminal and the first output terminal and that form a pass frequency band corresponding to the plurality of anti-resonance frequencies of the first impedance element. And a second impedance element including a surface acoustic wave resonator having a resonance frequency of.
[0016]
These impedance elements constituting the surface acoustic wave filter of the present invention may form an impedance hand by inductance or capacitance in addition to the surface acoustic wave resonator.
[0017]
Further, a composite mode surface acoustic wave resonator having a plurality of resonance frequencies and anti-resonance frequencies may be used as the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention. The composite mode surface acoustic wave resonator may use a transverse composite mode or a longitudinal composite mode.
[0018]
Further, as the surface acoustic wave resonator of the transverse composite mode or the longitudinal composite mode, for example, a surface acoustic wave resonator having comb-like electrodes arranged in a plurality of stages substantially perpendicular to the surface acoustic wave propagation direction is used. Alternatively, a surface acoustic wave resonator having comb-like electrodes arranged in a plurality of stages in a direction substantially parallel to the surface acoustic wave propagation direction may be used (longitudinal composite mode).
[0019]
In addition, a surface acoustic wave resonator including a comb-like electrode pair having a region partially meshed with a partial region of the opening may be used, and further, substantially parallel to the propagation direction of the surface acoustic wave. A surface acoustic wave resonator having a pair of comb-like electrodes arranged in plural directions and at least two pairs connected in parallel to each other may be used.
[0020]
A method of forming a pass frequency band according to the present invention includes a surface acoustic wave filter in which impedance elements having a resonance frequency and an anti-resonance frequency alternately appearing in a predetermined frequency band between a plurality of input / output terminals are arranged in a symmetrical lattice type. A plurality of anti-resonance frequencies of a first impedance element including a surface acoustic wave resonator having a plurality of resonance frequencies and anti-resonance frequencies; A plurality of resonance frequencies of the second impedance element including a surface acoustic wave resonator having a plurality of different resonance frequencies and anti-resonance frequencies are substantially matched.
[0021]
That is, the present invention provides a plurality of resonance frequencies fr in a symmetric grating type surface acoustic wave filter._iAnd anti-resonance frequency far_iThe impedance elements having the above are combined.
[0022]
FIG. 1 is a diagram schematically showing a configuration of a surface acoustic wave filter 100 of the present invention.
[0023]
A first impedance having a plurality of resonance frequencies and anti-resonance frequencies between the first input terminal 101a and the first output terminal 102a and between the second input terminal 101b and the second output terminal 102b. An element 103 is inserted and is different from the first impedance element between the first input terminal 101a and the second output terminal 102b and between the second input terminal 101b and the first output terminal 102a. A second impedance element 104 having a plurality of resonance frequencies and anti-resonance frequencies is inserted to form a symmetrical lattice type surface acoustic wave filter. The configuration of the surface acoustic wave filter of the present invention illustrated in FIG. 1 is an example, and a specific configuration such as the arrangement of impedance elements may be designed as necessary. A configuration equivalent to the surface acoustic wave filter illustrated in FIG. 1 is illustrated in FIG.
[0024]
FIG. 3 is a diagram schematically illustrating the frequency characteristics of the first impedance element 103, and FIG. 4 is a diagram schematically illustrating the frequency characteristics of the second impedance element 104. In FIG.
The first impedance element 103 is an impedance element in which a plurality of resonance frequencies fr and anti-resonance frequencies far appear alternately in a predetermined frequency band, that is, fr1 <far1 <fr3 <far3. Yes.
In the second impedance element 104, a plurality of resonance frequencies and anti-resonance frequencies different from those of the first impedance element appear alternately in this frequency band, that is, fr2 <far2 <fr4 <far4. Such an impedance element is used.
[0025]
The relationship between the resonance frequency and the antiresonance frequency of the first impedance element 103 and the second impedance element 104 is adjusted so as to satisfy fr1 <fr2 <fr3 <fr4. More preferably, the resonance frequency of the second impedance element 104 substantially matches the anti-resonance frequency of the first impedance element 103. That is, the resonance frequency and the anti-resonance frequency of the first and second impedance elements can be adjusted so that the anti-resonance frequency far1 and the resonance frequency fr2 and the anti-resonance frequency far3 and the resonance frequency fr4 substantially coincide with each other. It is preferable (see FIG. 5).
[0026]
Here, the description has been made so that the resonance frequency of the second impedance element 104 and the anti-resonance frequency of the first impedance element 103 are matched, but the resonance frequency of the first impedance element 103 and the second impedance element are the same. Even if the anti-resonance frequency 104 is made to coincide, the same is true.
[0027]
As such an impedance element, a surface acoustic wave resonator may be used, and a resistance R, an inductance L, and a capacitance C may be added to the surface acoustic wave resonator (necessarily R). , L, and C components are included).
[0028]
The resonance frequency and antiresonance frequency of the first impedance element and the second impedance element are based on the above-described resistance R, inductance L, capacitance C, etc. in addition to using the resonance frequency and antiresonance frequency of the surface acoustic wave resonator. The formed resonance frequency and anti-resonance frequency may be used. That is, the resonance frequency and antiresonance frequency of the impedance element of the surface acoustic wave filter of the present invention are not limited to the resonance frequency and antiresonance frequency of the surface acoustic wave resonator, and the impedance element has a plurality of resonance frequencies and antiresonance frequencies. If you do.
[0029]
As the surface acoustic wave resonator, a composite mode surface acoustic wave resonator may be used. The composite mode may be a vertical composite mode or a horizontal composite mode. By changing the film thickness, logarithm, arrangement, pitch, and the like of the comb-like electrodes of the surface acoustic wave resonator, the resonance frequency and antiresonance frequency of the surface acoustic wave resonator can be adjusted.
[0030]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 6 is a diagram showing an example of an electrode pattern of the composite mode surface acoustic wave resonator 600 constituting the surface acoustic wave filter of the present invention. In the surface acoustic wave resonator 600, two pairs of comb-shaped electrodes (hereinafter referred to as IDTs) 602 disposed so as to face each other are formed in a region sandwiched between two reflectors 601. A surface acoustic wave confined in a cavity formed by reflectors disposed on both sides of two pairs of IDTs has a plurality of modes having symmetric and semi-symmetric particle displacement distributions. FIG. 7 is a diagram schematically showing the particle displacement distribution in the AB direction of such a longitudinal mode surface acoustic wave resonator, taking a low-order two-mode as an example. In FIG. 7, (a) shows a symmetric mode (first order), and (b) shows an antisymmetric mode (second order).
[0031]
Such a surface acoustic wave resonator can have frequency characteristics having a plurality of resonance points. The IDT film thickness, logarithm, aperture length, IDT distance, IDT pitch, reflector pitch, and the like are changed to adjust a plurality of resonance frequencies and to match the impedance of an external circuit.
[0032]
8 and 9 are diagrams showing frequency characteristics of such a surface acoustic wave resonator. Hereinafter, the surface acoustic wave resonator shown in FIG. 8 is used as a first surface acoustic wave resonator (first impedance element), and the surface acoustic wave resonator shown in FIG. 9 is used as a second surface acoustic wave resonator (second impedance). Element).
[0033]
Resonant frequencies (resonance points) fr1, 801, fr3, and 803 of the first surface acoustic wave resonator illustrated in FIG. 8 are the frequencies indicated as (1) and (3) on the upper side of the figure. The resonance frequencies (resonance points) fr2, 802 and fr4, 804 of the second impedance element shown are frequencies indicated by (2), (4) on the upper side of the figure. The resonance frequencies of the first surface acoustic wave resonator and the second surface acoustic wave resonator satisfy fr1 <fr2 <fr3 <fr4 within the illustrated frequency band. Further, in both the first surface acoustic wave resonator and the second surface acoustic wave resonator, a plurality of resonance frequencies and anti-resonance frequencies appear alternately on the frequency.
[0034]
FIG. 10 is a diagram schematically showing the configuration of a surface acoustic wave filter 900 having a symmetric grating type configuration according to the present invention.
The surface acoustic wave filter 900 includes a first surface acoustic wave resonator 901 having the frequency characteristics illustrated in FIG. 8 and a second surface acoustic wave resonator 902 having the frequency characteristics illustrated in FIG. Connected to the mold.
[0035]
That is, the first surface acoustic wave resonator 901 is inserted between the first input terminal 903a and the first output terminal 904a and between the second input terminal 903b and the second output terminal 904b, A second surface acoustic wave resonator 902 is inserted between the first input terminal 903a and the second output terminal 904b and between the second input terminal 903b and the first output terminal 904a. Although two types of surface acoustic wave resonators having a plurality of resonance points and antiresonance points are used here, the resonance points of the first surface acoustic wave resonator 901 and the second surface acoustic wave resonator 902 are frequencies. It is set to appear alternately above.
[0036]
FIG. 11 is a diagram illustrating frequency characteristics of the surface acoustic wave filter 900 illustrated in FIG. Thus, in the surface acoustic wave filter of the present invention, a wide passband can be obtained corresponding to a plurality of resonance points of the composite mode surface acoustic wave resonator. In addition, by forming a lattice-type surface acoustic wave filter by combining impedance elements having a plurality of resonance frequencies and anti-resonance frequencies, the degree of freedom in forming a pass frequency band can be increased compared to a conventional lattice-type surface acoustic wave filter. Also, the frequency characteristics outside the band, which was a problem of the ladder type surface acoustic wave filter, are greatly improved. Further, since the insertion loss is small, the power consumption is small and it can be applied to a portable system such as mobile communication.
[0037]
FIG. 12 is a diagram showing another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention. This surface acoustic wave resonator 1200 is a transverse mode coupled surface acoustic wave resonator in which two stages of IDTs 1201 are arranged in parallel substantially perpendicular to the propagation direction of the surface acoustic wave. 1202 is a reflector.
FIG. 13 is a diagram schematically showing the particle displacement distribution in the CD direction in the low-order mode of such a transverse mode coupled surface acoustic wave resonator. In FIG. 13, (a) shows a symmetric mode and (b) shows an antisymmetric mode. That is, there are symmetric and antisymmetric modes in a direction perpendicular to the propagation direction of the surface acoustic wave.
As described above, the resonance frequency is adjusted by changing the IDT film thickness, logarithm, aperture length, IDT distance, IDT pitch, reflector pitch, etc., and matching with the impedance of the external circuit is performed. do it. A symmetric lattice type surface acoustic wave filter as illustrated in FIGS. 1, 2, and 10 may be configured using a transverse mode coupled surface acoustic wave resonator illustrated in FIG.
[0038]
14 to 20 are diagrams schematically showing another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
[0039]
FIG. 14 is a diagram schematically showing another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention. The surface acoustic wave resonator 1200b is a 1-port surface acoustic wave resonator having an IDT 1201b and a reflector 1202b disposed so as to sandwich the IDT 1201b from both sides. Then, by adjusting the opening length as described above, it is possible to combine the first and third transverse modes as shown in FIG. 15 in terms of the particle displacement distribution in the CD direction.
FIG. 16 is a diagram showing the frequency characteristics of the surface acoustic wave resonator 1201b at this time, and it can be seen that two resonance points fr1 and fr3 appear.
[0040]
FIG. 17 is a diagram schematically showing still another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention. The surface acoustic wave resonator 1200c is a one-port surface acoustic wave resonator having an IDT 1201c and a reflector 1202c disposed so as to sandwich the IDT 1201c from both sides. In the IDT 1201c, some of the comb-like electrodes have an electrode length that is a half of the opening length. The part to be used is a surface acoustic wave excitation part. That is, the IDT 1201c has a partially meshed region that excites a surface acoustic wave in a partial region of the opening. Of the electrodes constituting IDT 1201c, the oppositely meshed portions are portions that excite surface acoustic waves, and the portions that excite the surface acoustic waves are openings (regions between the bus bars of a pair of IDTs). It is a partial area. By providing such an IDT 1201c, the surface acoustic wave resonator 1200c can couple two primary and secondary transverse modes as shown in FIG. 18 in terms of the particle displacement distribution in the CD direction.
Also in this case, a frequency characteristic having two resonance points as exemplified in FIG. 16 can be obtained. Therefore, the surface acoustic wave filter of the present invention can be configured even if such a surface acoustic wave resonator is used.
[0041]
FIG. 19 is a diagram schematically showing still another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention. This surface acoustic wave resonator 1200d uses longitudinal mode coupling, and includes two IDTs 1201d and a reflector 1202d disposed between the two IDTs 1201d and sandwiching them from both sides. Two pairs of IDTs 1201d are connected in parallel. Three or more IDTs may be provided. In that case, at least two pairs of IDTs 1201d may be connected. Also. The arrangement position of the IDT may be adjusted.
[0042]
FIG. 20 is a diagram schematically showing the particle displacement distribution in the AB direction of the surface acoustic wave resonator 1200d illustrated in FIG. Thus, by combining the first and third longitudinal modes, the frequency characteristic having two resonance points as illustrated in FIG. 16 can be obtained. Therefore, the surface acoustic wave filter of the present invention can be configured even if such a surface acoustic wave resonator is used.
[0043]
In the example of FIG. 19, the reflector is inserted between the IDTs, but the floating electrode may be formed between a plurality of IDTs or inside one IDT.
[0044]
Although the example of the surface acoustic wave resonator that can constitute the surface acoustic wave filter of the present invention has been described above, the surface acoustic wave filter of the present invention may be, for example, FIG. 6, FIG. 12, FIG. 14, FIG. In addition to the surface acoustic wave resonator having the electrode pattern as exemplified in FIG. 19, a longitudinal mode, a transverse mode, or a surface acoustic wave resonator using a combination mode of these may be used.
[0045]
Although an example in which only a surface acoustic wave resonator is used as an impedance element constituting a symmetric lattice type surface acoustic wave filter has been described here, the surface acoustic wave filter is configured together with a resistor R, an inductance L, a capacitance C and the like as described above. You may make it do. For example, even when a resistance R, an inductance L, a capacitance C, and the like are attached due to wiring on a piezoelectric substrate, each impedance element has a plurality of resonance frequencies (resonance points) as described above. If the anti-resonance frequency (anti-resonance point) exists, the surface acoustic wave filter of the present invention can be configured by adjusting the resonance frequency and anti-resonance frequency of the surface acoustic wave resonator.
[0046]
【The invention's effect】
As described above, according to the surface acoustic wave filter of the present invention, a wide pass band can be obtained corresponding to a plurality of resonance points of the composite mode surface acoustic wave resonator. That is, by combining impedance elements having a plurality of resonance frequencies and anti-resonance frequencies, it is possible to obtain band characteristics with low loss over a wide frequency band. In addition, a pass frequency band can be formed without impairing the out-of-band characteristics like a ladder type surface acoustic wave filter.
[0047]
Furthermore, since the insertion loss is small, the power consumption is small, and it can be applied to portable systems such as mobile communication. Therefore, by applying to a mobile communication system such as a mobile phone, the pass frequency band can be expanded and the line capacity can be increased.
[0048]
Further, according to the method for forming a pass frequency band of the present invention, by combining a plurality of resonance frequencies and anti-resonance frequencies, the pass frequency band has low loss band characteristics over a wide frequency band and good out-of-band characteristics. Can be formed.
[0049]
Further, by forming a lattice-type surface acoustic wave filter by combining impedance elements having a plurality of resonance frequencies and anti-resonance frequencies, it is possible to increase the degree of freedom in forming the pass frequency band as compared with the conventional case.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a surface acoustic wave filter of the present invention.
FIG. 2 is a diagram schematically showing a configuration of a surface acoustic wave filter according to the present invention.
FIG. 3 is a diagram schematically illustrating frequency characteristics of a first impedance element.
FIG. 4 is a diagram schematically showing frequency characteristics of a second impedance element.
FIG. 5 is a diagram schematically illustrating a relationship between frequency characteristics of first and second impedance elements.
FIG. 6 is a diagram showing an example of an electrode pattern of a surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
FIG. 7 is a diagram schematically showing a particle displacement distribution in the AB direction of a surface acoustic wave resonator in a longitudinal mode.
FIG. 8 is a diagram illustrating frequency characteristics of a first surface acoustic wave resonator.
FIG. 9 is a diagram illustrating frequency characteristics of a second surface acoustic wave resonator.
FIG. 10 is a diagram schematically showing a configuration of a surface acoustic wave filter having a symmetrical lattice type configuration according to the present invention.
FIG. 11 is a diagram showing frequency characteristics of the surface acoustic wave filter of the present invention.
FIG. 12 is a diagram showing another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
FIG. 13 is a diagram schematically showing a particle displacement distribution in a CD direction of a surface acoustic wave resonator in a transverse mode.
FIG. 14 is a diagram schematically showing another example of an electrode pattern of a surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
15 is a diagram schematically showing a particle displacement distribution in the CD direction of the surface acoustic wave resonator shown in FIG.
FIG. 16 is a diagram schematically showing frequency characteristics of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
FIG. 17 is a diagram schematically showing still another example of the electrode pattern of the surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
18 is a diagram schematically showing a particle displacement distribution in a CD direction of the surface acoustic wave resonator shown in FIG.
FIG. 19 is a diagram schematically showing another example of an electrode pattern of a surface acoustic wave resonator constituting the surface acoustic wave filter of the present invention.
20 is a diagram schematically showing a particle displacement distribution in the AB direction of the surface acoustic wave resonator shown in FIG. 19;
FIG. 21 is a diagram schematically showing an example of a structure in which two filters of a two-port surface acoustic wave resonator type filter are continuously connected.
22 is a diagram showing frequency characteristics of the surface acoustic wave resonator type filter exemplified in FIG. 21;
FIG. 23 is a diagram schematically showing a configuration of a ladder-type surface acoustic wave filter.
24 is a diagram showing frequency characteristics of the ladder-type surface acoustic wave filter exemplified in FIG. 23;
FIG. 25 is a diagram schematically showing an example of the configuration of a lattice type surface acoustic wave filter.
26 is a diagram schematically showing an example of the structure of a surface acoustic wave resonator that constitutes the lattice type surface acoustic wave filter illustrated in FIG. 25;
[Explanation of symbols]
100: surface acoustic wave filter, 101a: first input terminal
101b: second input terminal, 102a: first output terminal
102b: second output terminal, 103: first impedance element
104 …… Second impedance element
600 …… Composite mode surface acoustic wave resonator, 601 …… Reflector
602 …… IDT
801 …… Resonance frequency fr1, 802 …… Resonance frequency fr2
803 …… Resonance frequency fr3, 804 …… Resonance frequency fr4
900: surface acoustic wave filter, 901: first surface acoustic wave resonator
902: second surface acoustic wave resonator, 903a: first input terminal
903b: second input terminal, 904a: first output terminal
904b ...... Second output terminal
1200 …… Composite mode surface acoustic wave resonator, 1201 …… IDT
1202 …… Reflector
1200b, 1200c, 1200d... Composite mode surface acoustic wave resonator
1201b, 1201c, 1201d ...... IDT
1202b, 1202c, 1202d .... Reflector

Claims (10)

A surface acoustic wave filter in which impedance elements are arranged in a symmetrical lattice pattern between a plurality of input / output terminals,
It is inserted between the first input terminal and the first output terminal and between the second input terminal and the second output terminal, and fr1 <far1 <fr3 <far3 within a predetermined frequency band.
A first impedance element including a composite mode surface acoustic wave resonator having a plurality of resonance frequencies fr and anti-resonance frequencies far such that
It is inserted between the first input terminal and the second output terminal and between the second input terminal and the first output terminal, and fr2 <far2 <fr4 <far4 within the frequency band.
And fr2 = far1 and fr4 = far3
A surface acoustic wave filter comprising: a second impedance element including a composite mode surface acoustic wave resonator having a plurality of resonance frequencies fr and anti-resonance frequencies far. A surface acoustic wave filter in which impedance elements having a resonance frequency and an anti-resonance frequency alternately appearing in a predetermined frequency band between a plurality of input / output terminals are arranged in a symmetric lattice type,
A first impedance element including a composite mode surface acoustic wave resonator having anti-resonance frequencies at a first frequency and a second frequency;
A surface acoustic wave filter comprising: a second impedance element including a composite mode surface acoustic wave resonator having resonance points at a first frequency and a second frequency. A first input terminal and a second input terminal;
A plurality of resonances are inserted between the first output terminal and the second output terminal, between the first input terminal and the first output terminal, and between the second input terminal and the second output terminal. A first impedance element including a composite mode surface acoustic wave resonator having a frequency and an anti-resonance frequency;
Inserted between the first input terminal and the second output terminal and between the second input terminal and the first output terminal, and passes in correspondence with the plurality of anti-resonance frequencies of the first impedance element. A surface acoustic wave filter comprising: a second impedance element including a composite mode surface acoustic wave resonator having a plurality of resonance frequencies forming a frequency band.   4. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonator is a composite mode surface acoustic wave resonator using a transverse composite mode.   4. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonator is a composite mode surface acoustic wave resonator using a longitudinal composite mode.   4. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonator includes a plurality of comb-like electrodes arranged in a direction substantially perpendicular to the surface acoustic wave propagation direction.   4. The surface acoustic wave filter according to claim 1, wherein the surface acoustic wave resonator includes a plurality of comb-like electrodes arranged in a direction substantially parallel to the surface acoustic wave propagation direction. .   4. The surface acoustic wave according to claim 1, wherein the surface acoustic wave resonator includes a comb-like electrode pair having a region partially meshed with a partial region of the opening. 5. filter.   The surface acoustic wave resonator includes a plurality of pairs arranged in a direction substantially parallel to the propagation direction of the surface acoustic wave, and at least two pairs of comb-like electrode pairs connected in parallel to each other. The surface acoustic wave filter according to claim 1. A method for forming a pass frequency band in a surface acoustic wave filter in which impedance elements having a resonance frequency and an anti-resonance frequency that alternately appear in a predetermined frequency band are arranged in a symmetrical lattice type between a plurality of input / output terminals. ,
A plurality of anti-resonance frequencies of the first impedance element including a composite mode surface acoustic wave resonator having a plurality of resonance frequencies and anti-resonance frequencies, and a plurality of resonance frequencies and anti-resonance frequencies different from the first impedance element A method for forming a pass frequency band, characterized in that a plurality of resonance frequencies of a second impedance element having a composite mode surface acoustic wave resonator having the same are substantially matched.

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