JP3939293B2 - Surface acoustic wave filter and duplexer - Google Patents
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- 238000010897 surface acoustic wave method Methods 0.000 title claims description 75
- 230000005540 biological transmission Effects 0.000 description 11
- 238000004891 communication Methods 0.000 description 8
- 238000010586 diagram Methods 0.000 description 7
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- 238000013016 damping Methods 0.000 description 1
- 238000010295 mobile communication Methods 0.000 description 1
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Description
本発明は、弾性表面波フィルタおよびデュプレクサに係り、特に、ラダー型弾性表面波フィルタにおいて通過帯域外の所望の周波数帯に良好な減衰域を形成するフィルタ構造に関する。 The present invention relates to a surface acoustic wave filter and a duplexer, and more particularly to a filter structure that forms a good attenuation region in a desired frequency band outside a pass band in a ladder-type surface acoustic wave filter.
近年、携帯電話機などの移動体通信機器のフィルタやアンテナデュプレクサとして小型軽量化に有利な弾性表面波フィルタ(以下、SAWフィルタという)が広く用いられている。このうち、SAW共振子を直列・並列に梯子型に多段接続したいわゆるラダー型SAWフィルタは、音響エネルギーと電気エネルギーの変換ロスが少ない設計であり、低挿入損失と広帯域幅を実現できる特徴を有する。 2. Description of the Related Art In recent years, surface acoustic wave filters (hereinafter referred to as SAW filters) that are advantageous in reducing size and weight have been widely used as filters and antenna duplexers for mobile communication devices such as mobile phones. Among these, a so-called ladder-type SAW filter in which SAW resonators are connected in multiple stages in series and in parallel in a ladder shape is designed to have low conversion loss between acoustic energy and electric energy, and has a feature that can realize low insertion loss and wide bandwidth. .
また、SAWフィルタを開示するものとして下記特許文献がある。 Further, there are the following patent documents disclosing SAW filters.
ところで、帯域通過フィルタは、一般に通過帯域における低い挿入損失とともに、通過帯域外での高い抑圧特性(高減衰量)が求められる。また、送受信の周波数帯域が比較的離れた通信方式(例えば次世代携帯電話の一通信方式として標準化が進められているW−CDMA等)では、送受信周波数が近いシステムに較べ、通過帯域から離れた周波数帯域においても十分な減衰量を確保する必要があり、減衰域を広域化する手段の提供が望まれる。 By the way, the band pass filter generally requires a high suppression characteristic (high attenuation) outside the pass band as well as a low insertion loss in the pass band. In addition, in a communication method in which the transmission / reception frequency band is relatively distant (for example, W-CDMA, which is being standardized as one communication method for next-generation mobile phones), it is farther from the pass band than a system with a close transmission / reception frequency. It is necessary to secure a sufficient amount of attenuation even in the frequency band, and provision of means for widening the attenuation range is desired.
しかしながら、従来提案されているSAWフィルタは、通過帯域外の減衰特性について、通過帯域近傍の特性改善を図るものはあるものの(例えば前記特許文献2)、通過帯域から離れた周波数領域の特性改善を図るものは必ずしも十分なものがなかった。 However, the SAW filters that have been proposed in the past have improved the characteristics in the vicinity of the passband with respect to the attenuation characteristics outside the passband (for example, Patent Document 2), but improved the characteristics in the frequency region far from the passband. There was not always enough to plan.
一方、減衰域に関するこのような要請に応えるため、フィルタにトラップを設けることも考えられる。例えば、共振周波数を順次ずらした複数のSAW共振子をフィルタに多段に接続し、当該フィルタの減衰域に対し広帯域に減衰を確保するのである。 On the other hand, it is conceivable to provide a filter with a trap in order to meet such a request regarding the attenuation region. For example, a plurality of SAW resonators whose resonance frequencies are sequentially shifted are connected to the filter in multiple stages, and attenuation is ensured in a wide band with respect to the attenuation region of the filter.
ところが、このような方法では、フィルタが大型化し、SAWフィルタが本来有する小型軽量という重要な特長を損なう難がある。なぜなら、トラップとして接続するSAW共振子は、急峻なインピーダンス特性を有することから、トラップ用共振子の接続に起因してリップルが生じやすく、これを抑制しつつ広帯域に減衰を確保するには共振子の接続段数を増さざるを得ないからである(周波数を少しずつずらした数多くの共振子を接続する必要がある)。 However, with such a method, there is a difficulty in impairing the important feature of the SAW filter, which is inherently small and light, because the filter is enlarged. This is because the SAW resonator connected as a trap has a steep impedance characteristic, so that a ripple is easily generated due to the connection of the trap resonator. This is because the number of connection stages must be increased (it is necessary to connect many resonators whose frequencies are shifted little by little).
したがって本発明が解決しようとする問題点は、従来のSAWフィルタ構造では、通過帯域から比較的離れた周波数帯において良好な(広くかつ平坦な)減衰特性を得ることが出来ない点にある。 Therefore, the problem to be solved by the present invention is that the conventional SAW filter structure cannot obtain a good (wide and flat) attenuation characteristic in a frequency band relatively far from the pass band.
このような課題を解決するため、本発明に係る弾性表面波フィルタは、直列腕に配した弾性表面波共振子、および並列腕に配した弾性表面波共振子を有して所定の通過帯域を形成可能なフィルタ本体部と、該フィルタ本体部の前段および後段のうちの少なくとも一方に接続した弾性表面波共振子とを備える弾性表面波フィルタであって、フィルタ本体部に接続する前記弾性表面波共振子として、互いに異なる共振周波数を有する2以上の弾性表面波共振子を備え、これらフィルタ本体部に接続した弾性表面波共振子は、前記フィルタ本体部の通過帯域から離れた減衰域に反共振点を生じさせるものであり、かつ、これらフィルタ本体部に接続した弾性表面波共振子のうちの1つ以上が、すだれ状電極と反射器とを有して、弾性表面波の波長をλとしたときに、該すだれ状電極と反射器と間の間隔を0.5λ以外の値に設定したものである。 To solve such problems, the surface acoustic wave filter of the present onset Ming, predetermined passband having a surface acoustic wave resonator arranged surface acoustic wave resonators arranged in series arms and parallel arms And a surface acoustic wave filter connected to at least one of a front stage and a rear stage of the filter main body, wherein the elastic surface is connected to the filter main body. As the wave resonator, two or more surface acoustic wave resonators having mutually different resonance frequencies are provided, and the surface acoustic wave resonator connected to the filter main body portion has an anti-damping region far from the pass band of the filter main body portion. a shall cause a resonance point, and one or more of the surface acoustic wave resonator connected thereto filter body portion, and a interdigital transducer and the reflector, the wavelength of the surface acoustic wave When a is obtained by setting the distance between the said interdigital electrodes and the reflectors to a value other than 0.5 [lambda.
本発明のSAW(弾性表面波)フィルタでは、通過帯域外の(通過帯域から離れた)減衰特性を改善したい所望の周波数帯に反共振点を有するSAW共振子を、通過帯域を形成するフィルタ本体部に接続することで当該周波数帯における減衰特性を改善するが、本発明ではさらに、当該フィルタ本体部に接続するSAW共振子(以下、減衰域用共振子という)として、すだれ状電極(IDT/Interdigital Transducer)と反射器との間隔を0.5λ以外の値(0.5λより大きい値または小さい値)としたものを使用する。 In the SAW (surface acoustic wave) filter of the present invention, a filter main body that forms a pass band with a SAW resonator having an anti-resonance point in a desired frequency band that is desired to improve attenuation characteristics outside the pass band (away from the pass band). In the present invention, an interdigital electrode (IDT / IDT) is further used as a SAW resonator (hereinafter referred to as an attenuation region resonator) connected to the filter main body. The distance between the interdigital transducer and the reflector is set to a value other than 0.5λ (a value larger or smaller than 0.5λ).
フィルタ本体部に接続する減衰域用共振子をこのような構成とすれば、当該減衰域用共振子の反共振点付近に新たな極を形成することができ、この極の形成によって新たな減衰が生じ、該共振子を接続したSAWフィルタの減衰帯域幅を拡大させることが可能となる。尚、この点については、図面を参照して実施形態とともに後にさらに詳しく説明する。 If the attenuation region resonator connected to the filter main body has such a configuration, a new pole can be formed in the vicinity of the antiresonance point of the attenuation region resonator. As a result, the attenuation bandwidth of the SAW filter to which the resonator is connected can be increased. This point will be described in more detail later with reference to the drawings together with the embodiment.
フィルタ本体部に接続する減衰域用共振子の数は、減衰帯域幅をより拡大させる観点からはその数を増やした方が良いが、要求される特性に応じ2個以上の範囲で接続数を適宜決定することが可能である(例えば3〜6個等)。 The number of attenuation range for resonators to connect the filter main body is better to increase the number of terms of further expanding the attenuation bandwidth, number of connections required response to the characteristic being Ji two or more ranges Can be determined as appropriate (for example, 3 to 6).
減衰域用共振子は、互いに異なる共振周波数を有するものとする。減衰帯域幅をより広くするためである。尚、減衰域用共振子の接続位置は、フィルタ本体部の前段としても良いし、後段、あるいは前段と後段の双方に設けることも可能である。 Attenuation band for resonator shall be the one having a different resonance frequency to each other physician. This is to make the attenuation bandwidth wider. Note that the connection position of the resonator for the attenuation region may be provided at the front stage of the filter main body, or may be provided at the rear stage or both the front stage and the rear stage.
フィルタ本体部は、SAW共振子を直列腕と並列腕とに配した従来のラダー型SAWフィルタと同様の構成とすれば良い。このとき、フィルタ本体部を構成するSAW共振子の接続段数は特に問わない。例えば直列腕に2個、並列腕に1個の共振子をそれぞれ有するものとしても良いし、さらに多くの共振子を直列腕または並列腕に設けることも可能である。 The filter main body may have the same configuration as a conventional ladder type SAW filter in which SAW resonators are arranged in series arms and parallel arms. At this time, the number of connection stages of the SAW resonator constituting the filter main body is not particularly limited. For example, two resonators may be provided on the series arm and one resonator may be provided on the parallel arm, or more resonators may be provided on the series arm or the parallel arm.
本発明のSAWフィルタは、例えば弾性表面波装置の一つであるデュプレクサ(アンテナ共用器)に使用することが可能であり、本発明に係るデュプレクサは、互いに異なる通過帯域を有する少なくとも2つの弾性表面波フィルタと、該フィルタが接続されるアンテナ接続用の共通端子と、該フィルタの入出力端子とを有するデュプレクサであって、該弾性表面波フィルタの少なくとも1つが前記本発明の弾性表面波フィルタである。 SAW filter of the present invention, for example, it is possible to use the duplexer is one of a surface acoustic wave device (antenna duplexer), duplexer service according to the present invention, at least two elastic having different pass bands from each other and surface acoustic wave filter, and a common terminal for antenna connection in which the filter is connected, a duplexer having an input and output terminal of the filter, at least one of the present onset bright surface acoustic wave of the elastic surface wave filter It is a filter.
また、該デュプレクサでは、前記互いに異なる通過帯域を有する弾性表面波フィルタのうちの低域側フィルタの中心周波数をf1、高域側フィルタの中心周波数をf2としたときに、これら両フィルタの中心周波数差(f2−f1)を両フィルタの中心周波数の平均値(f1+f2)/2で規格化した値である、(f2−f1)/{(f1+f2)/2}が0.05以上の場合がある。 In the duplexer, when the center frequency of the low-pass filter of the surface acoustic wave filters having different pass bands is f1, and the center frequency of the high-pass filter is f2, the center frequencies of both filters In some cases, (f2−f1) / {(f1 + f2) / 2}, which is a value obtained by normalizing the difference (f2−f1) by the average value (f1 + f2) / 2 of the center frequencies of both filters, is 0.05 or more. The
このような本発明のデュプレクサでは、従来に較べより少ない共振子の接続段数で広い減衰域を所望の周波数帯に形成することが可能となり、低域側フィルタと高域側フィルタとの周波数帯域が離れている場合にも、相手側フィルタの通過帯域における減衰特性を改善して平坦でかつ十分な減衰量を確保することが出来る。 In such a duplexer of the present invention, it is possible to form a wide attenuation region in a desired frequency band with a smaller number of connection stages of resonators than in the past, and the frequency band between the low-pass filter and the high-pass filter is reduced. Even when they are separated, the attenuation characteristics in the pass band of the counterpart filter can be improved to ensure a flat and sufficient amount of attenuation.
本発明によれば、通過帯域から離れた周波数帯において良好な(広くかつ平坦な)減衰特性を得ることが出来る。 According to the present invention, it is possible to obtain a good (wide and flat) attenuation characteristic in a frequency band far from the pass band.
本発明の他の特徴および利点は、以下の本発明の実施の形態の説明により明らかにする。 Other features and advantages of the present invention will become apparent from the following description of embodiments of the present invention.
以下、添付図面の図1から図7を参照しつつ本発明の実施の形態(以下、本実施形態という)を説明する。 Hereinafter, an embodiment of the present invention (hereinafter referred to as this embodiment) will be described with reference to FIGS. 1 to 7 of the accompanying drawings.
〔SAWフィルタ〕
図1は、本発明の一実施形態に係るSAWフィルタを示すものである。同図に示すようにこのSAWフィルタ11は、通過帯域を構成するラダー型SAWフィルタ12(フィルタ本体部)の前段および後段に、減衰特性を改善するためのSAW共振子13,14(減衰域用共振子)を接続したものである。減衰域用共振子13,14としては、入力端子15とフィルタ本体部12との間(フィルタ本体部前段)に4個の共振子13a〜13dを、またフィルタ本体部12と出力端子16との間(フィルタ本体部後段)に1個の共振子14aをそれぞれ直列に挿入してある。また、フィルタ本体部12は、直列腕と並列腕にそれぞれ2個ずつSAW共振子を設けてなる。尚、フィルタ本体部を構成する共振子の数、並びに減衰域用共振子の数は、これらの数に限定されるものではない。
[SAW filter]
FIG. 1 shows a SAW filter according to an embodiment of the present invention. As shown in the figure, this SAW filter 11 includes SAW resonators 13 and 14 (for an attenuation region) for improving the attenuation characteristics before and after the ladder-type SAW filter 12 (filter body portion) constituting the pass band. Resonator) is connected. As the attenuation region resonators 13 and 14, four resonators 13 a to 13 d are provided between the input terminal 15 and the filter main body 12 (preceding stage of the filter main body), and the filter main body 12 and the output terminal 16 are connected to each other. One resonator 14a is inserted in series between each other (after the filter main body). The filter main body 12 is provided with two SAW resonators on each of the series arm and the parallel arm. Note that the number of resonators constituting the filter body and the number of attenuation region resonators are not limited to these numbers.
減衰域用共振子13a〜13d,14aは、フィルタ本体部12を構成する共振子と共振周波数を異にするもので、フィルタ本体部12によって形成される通過帯域の外に(通過帯域から離れた減衰域に)反共振点を有するものである。また、各減衰域用共振子13a〜13d,14aは、互いに異なる共振周波数を有する。 The attenuation band resonators 13a to 13d and 14a have resonance frequencies different from those of the resonator constituting the filter main body 12, and are outside the pass band formed by the filter main body 12 (away from the pass band). It has an anti-resonance point (in the attenuation region). Each of the attenuation region resonators 13a to 13d and 14a has a different resonance frequency.
図6は図1の回路のSAWフィルタの周波数特性と共振子のインピーダンス特性との関係を示す図である。図中、実線はSAWフィルタの周波数特性、一点鎖線は通過帯域(フィルタ本体部12)を構成する共振子のインピーダンス特性、破線は減衰域用共振子のインピーダンス特性をそれぞれ示す。通過帯域を構成する共振子のインピーダンス特性はSAWフィルタの通過帯域から離れた周波数帯域の減衰と関係ないが、減衰域用共振子のインピーダンス特性の極とSAWフィルタの通過帯域から離れた周波数帯域の減衰とが一致しており、減衰域用共振子のインピーダンス特性の極とSAWフィルタの通過帯域から離れた周波数帯域の減衰とが関係を有していることがわかる。 FIG. 6 is a diagram showing the relationship between the frequency characteristics of the SAW filter of the circuit of FIG. 1 and the impedance characteristics of the resonator. In the figure, the solid line indicates the frequency characteristic of the SAW filter, the alternate long and short dash line indicates the impedance characteristic of the resonator constituting the pass band (filter body portion 12), and the broken line indicates the impedance characteristic of the attenuation band resonator. The impedance characteristics of the resonator constituting the pass band are not related to the attenuation of the frequency band away from the pass band of the SAW filter, but the impedance characteristic poles of the attenuation band resonator and the frequency band away from the pass band of the SAW filter are not related. It can be seen that the attenuation coincides with the impedance characteristic pole of the attenuation region resonator and the attenuation in the frequency band away from the pass band of the SAW filter.
図2は、共振周波数をずらした複数の(図の場合3個)共振子を直列に接続した場合のインピーダンス特性を示すものであるが、共振周波数(反共振点)をずらした複数の共振子を多段に接続することによって各共振子の極が合わさり、広帯域にわたり減衰を確保することができる。尚、各減衰域用共振子の共振周波数をずらすには、例えば各段の共振子について互いにIDT(すだれ状電極)の電極指のピッチ(間隔)を異ならせることにより行えば良く、これにより所望の周波数に反共振点を得ることが出来る。 FIG. 2 shows impedance characteristics when a plurality of (three in the figure) resonators whose resonance frequencies are shifted are connected in series, and a plurality of resonators whose resonance frequencies (antiresonance points) are shifted are shown. Are connected in multiple stages, the poles of the resonators are combined, and attenuation can be ensured over a wide band. In order to shift the resonance frequency of each attenuation region resonator, for example, the pitches (intervals) of electrode fingers of IDTs (interdigital electrodes) may be made different from each other for each stage of the resonator. An antiresonance point can be obtained at a frequency of.
本実施形態のフィルタ11では、かかる減衰域用共振子13a〜13d,14aについてさらに、IDTと反射器と間の間隔を0.5λ以外の値に設定する。すなわち、本実施形態で使用する減衰域用共振子は、図3(b)に示すようにIDT21の両側に反射器22を有するが、弾性表面波の波長をλとしたときに、IDT21と反射器22と間の間隔Grefを0.5λ以外の値に設定してある。尚、同図(a)は従来の一般的な反射器型のSAW共振子を示すもので、IDT21と反射器22と間の間隔Grefは0.5λにされている。 In the filter 11 of the present embodiment, the interval between the IDT and the reflector is further set to a value other than 0.5λ for the attenuation region resonators 13a to 13d and 14a. That is, the attenuation region resonator used in the present embodiment has the reflectors 22 on both sides of the IDT 21 as shown in FIG. 3B. However, when the wavelength of the surface acoustic wave is λ, The gap Gref between the two is set to a value other than 0.5λ. FIG. 2A shows a conventional general reflector type SAW resonator, and a gap Gref between the IDT 21 and the reflector 22 is set to 0.5λ.
図4は、SAW共振子の反共振点付近におけるインピーダンス特性を拡大して示す図であり、同図において実線(1)がGrefを0.5λ以外の値に設定した場合を、破線(2)がGrefを0.5λとした従来の共振子をそれぞれ示す。同図から明らかなように、Grefを0.5λ以外の値とすると、反共振点付近に新たな極P1が発生する。そして、この極P1の形成によって新たな減衰が生じ、減衰帯域を拡大することが可能となる。 FIG. 4 is an enlarged view of the impedance characteristics near the antiresonance point of the SAW resonator. In FIG. 4, the solid line (1) indicates the case where Gref is set to a value other than 0.5λ. Respectively show conventional resonators having Gref of 0.5λ. As can be seen from the figure, when Gref is set to a value other than 0.5λ, a new pole P1 is generated near the antiresonance point. The formation of the pole P1 causes new attenuation, and the attenuation band can be expanded.
さらに、図5は、前記図1に示した実施形態のSAWフィルタにおいて、Grefを0.5λ以外の値にしたSAW共振子を接続した場合のSAWフィルタの周波数特性を示すものである。同図(a)および図(a)中の一点鎖線で囲った部分の拡大図である(b)に示すように、減衰域用共振子(Gref=0.5λ以外の値)を有しない従来のフィルタ(図中細線(1)で示す)に較べ、本発明によるフィルタ(図中太線(2)で示す)は、減衰のピーク値は浅くなるものの、減衰域幅を拡大できることが分かる。 Further, FIG. 5 shows the frequency characteristics of the SAW filter when a SAW resonator having a value of Gref other than 0.5λ is connected in the SAW filter of the embodiment shown in FIG. As shown in FIG. 2A and FIG. 2B, which is an enlarged view of a portion surrounded by a one-dot chain line in FIG. 1A, a conventional resonator that does not have an attenuation region resonator (a value other than Gref = 0.5λ). It can be seen that the filter according to the present invention (indicated by the thick line (2) in the figure) has a shallower attenuation peak value but can expand the attenuation band width than the filter (indicated by the thin line (1) in the figure).
本実施形態によれば、通過帯域の挿入損失の増大を抑えつつ、通過帯域から離れた周波数域において広くかつ十分な減衰を得ることが出来る。したがって、本実施形態(本発明)のフィルタは、送受信の周波数帯が離れた通信方式に使用するデュプレクサを構成するのに好適である。 According to this embodiment, it is possible to obtain wide and sufficient attenuation in a frequency region away from the pass band while suppressing an increase in insertion loss of the pass band. Therefore, the filter of the present embodiment (the present invention) is suitable for configuring a duplexer used for a communication method in which transmission / reception frequency bands are separated.
〔デュプレクサ〕
図7は、本発明に係るデュプレクサの一例を示すものである。図に示すようにこのデュプレクサ31は、送信用フィルタ32と受信用フィルタ33とを備え、これらのフィルタ32,33として前記実施形態に係るSAWフィルタを使用する。送信側フィルタ32および受信側フィルタ33は、それぞれ送信信号が入力される送信端子Txと、受信信号が出力される受信端子Rxを有し、両フィルタ32,33はアンテナ接続用の共通端子Cに接続されている。
[Duplexer]
FIG. 7 shows an example of a duplexer according to the present invention. As shown in the figure, the duplexer 31 includes a transmission filter 32 and a reception filter 33, and the SAW filter according to the embodiment is used as the filters 32 and 33. The transmission-side filter 32 and the reception-side filter 33 each have a transmission terminal Tx to which a transmission signal is input and a reception terminal Rx to which a reception signal is output. Both filters 32 and 33 are connected to a common terminal C for antenna connection. It is connected.
また、下記表1は、携帯電話システムの代表的な通信方式における送受信周波数と、送受信の中心周波数差を送受信の中心周波数の平均値で規格化した値を示すものである。本実施形態に係るフィルタを使用した前記デュプレクサによれば、送受信周波数差の規格化値、(fr−ft)/{(ft+fr)/2}が0.05以上のこれらいずれの通信方式においても、従来のデュプレクサに較べ相手側フィルタの減衰域において良好な減衰特性を実現することができ、特に送受信の周波数差の大きい通信方式(例えばW−CDMA等)では大きなメリットを得ることが出来る。尚、表に示す以外の通信方式に対しても適用可能なことは勿論である。 Table 1 below shows values obtained by normalizing a transmission / reception frequency and a transmission / reception center frequency difference in a typical communication method of the mobile phone system by an average value of the transmission / reception center frequencies. According to the duplexer using the filter according to the present embodiment, the normalized value of the transmission / reception frequency difference, (fr−ft) / {(ft + fr) / 2} is 0.05 or more, Compared to a conventional duplexer, it is possible to realize a good attenuation characteristic in the attenuation region of the counterpart filter, and particularly in a communication system (for example, W-CDMA) having a large transmission / reception frequency difference, a great merit can be obtained. Of course, the present invention can be applied to communication methods other than those shown in the table.
以上、本発明の実施の形態について図面に基づいて説明したが、本発明はこれに限定されるものではなく、特許請求の範囲に記載の範囲内で種々の変更を行うことができることは当業者に明らかである。 The embodiments of the present invention have been described with reference to the drawings. However, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the claims. Is obvious.
例えば、前記実施形態では、通過帯域を構成するフィルタ本体部の前段および後段に合計5個の共振子を接続したが、2個から4個、あるいは6個以上の共振子を接続しても良い。また、IDTと反射器と間の間隔Grefを0.5λ以外の値とするのは、必ずしも減衰域用共振子のすべてについてでなくても良い。さらに、本発明のSAWフィルタおよびデュプレクサは、携帯電話機の送受信部に使用して好適なものであるが、これに限定されるものではなく、PHSや通信機能を備えたPDA、無線LANカードその他、様々な電子通信機器に適用することが可能である。 For example, in the above-described embodiment, a total of five resonators are connected to the front and rear stages of the filter main body constituting the passband. However, two to four, or six or more resonators may be connected. . In addition, the gap Gref between the IDT and the reflector is not necessarily set to a value other than 0.5λ for all of the attenuation region resonators. Furthermore, the SAW filter and duplexer of the present invention are suitable for use in a transmitting / receiving unit of a mobile phone, but are not limited thereto, and are not limited to this, a PDA having a PHS or a communication function, a wireless LAN card, etc. It can be applied to various electronic communication devices.
11 SAWフィルタ
12 フィルタ本体部
13,14 減衰域用共振子
15 入力端子
16 出力端子
21 IDT(すだれ状電極)
22 反射器
31 デュプレクサ
DESCRIPTION OF SYMBOLS 11 SAW filter 12 Filter main-body part 13 and 14 Resonator for attenuation regions 15 Input terminal 16 Output terminal 21 IDT (interdigital electrode)
22 Reflector 31 Duplexer
Claims (3)
該フィルタ本体部の前段および後段のうちの少なくとも一方に接続した弾性表面波共振子と、
を備える弾性表面波フィルタであって、
フィルタ本体部に接続する前記弾性表面波共振子として、互いに異なる共振周波数を有する2以上の弾性表面波共振子を備え、
これらフィルタ本体部に接続した弾性表面波共振子は、
前記フィルタ本体部の通過帯域から離れた減衰域に反共振点を生じさせるものであり、かつ
これらフィルタ本体部に接続した弾性表面波共振子のうちの1つ以上が、すだれ状電極と反射器とを有して、弾性表面波の波長をλとしたときに、該すだれ状電極と反射器と間の間隔を0.5λ以外の値に設定したものである
ことを特徴とする弾性表面波フィルタ。 A filter body having a surface acoustic wave resonator disposed on the series arm and a surface acoustic wave resonator disposed on the parallel arm and capable of forming a predetermined passband;
A surface acoustic wave resonator connected to at least one of a front stage and a rear stage of the filter main body,
A surface acoustic wave filter comprising:
The surface acoustic wave resonator connected to the filter body includes two or more surface acoustic wave resonators having different resonance frequencies.
These surface acoustic wave resonators connected to the filter body are
A shall cause the anti-resonance point in the attenuation band away from the pass band of the filter main body, and
When one or more of the surface acoustic wave resonators connected to the filter main body have an interdigital electrode and a reflector, and the wavelength of the surface acoustic wave is λ, the interdigital electrode and the reflective The surface acoustic wave filter is characterized in that the interval between them is set to a value other than 0.5λ.
該フィルタが接続されるアンテナ接続用の共通端子と、
該フィルタの入出力端子と、
を有するデュプレクサであって、
前記弾性表面波フィルタの少なくとも1つが請求項1に記載の弾性表面波フィルタである
ことを特徴とするデュプレクサ。 At least two surface acoustic wave filters having different passbands;
A common terminal for antenna connection to which the filter is connected;
An input / output terminal of the filter;
A duplexer having
The duplexer according to claim 1, wherein at least one of the surface acoustic wave filters is the surface acoustic wave filter according to claim 1 .
(f2−f1)/{(f1+f2)/2}
が0.05以上である
ことを特徴とする請求項2に記載のデュプレクサ。 Of the surface acoustic wave filters having different passbands, when the center frequency of the low-pass filter is f1, and the center frequency of the high-pass filter is f2, the difference between the center frequencies of these two filters (f2-f1) Is the value normalized by the average value (f1 + f2) / 2 of the center frequencies of both filters.
(F2−f1) / {(f1 + f2) / 2}
The duplexer according to claim 2 , wherein the duplexer is 0.05 or more.
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