JP4654879B2 - FSK modulator - Google Patents

FSK modulator Download PDF

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JP4654879B2
JP4654879B2 JP2005318025A JP2005318025A JP4654879B2 JP 4654879 B2 JP4654879 B2 JP 4654879B2 JP 2005318025 A JP2005318025 A JP 2005318025A JP 2005318025 A JP2005318025 A JP 2005318025A JP 4654879 B2 JP4654879 B2 JP 4654879B2
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idt
sub
fsk modulator
saw resonator
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JP2007129299A (en
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道明 ▲高▼木
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Seiko Epson Corp
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Description

本発明は、水晶等の安定な周波数を発生できる圧電体ＳＡＷ共振子を使用してＦＳＫ変調を直接に行うことができるＦＳＫ変調器に関する。   The present invention relates to an FSK modulator that can directly perform FSK modulation using a piezoelectric SAW resonator that can generate a stable frequency such as crystal.

従来、圧電気を有する水晶ＳＴカット基板（圧電体平板の一例）を用いて構成するＳＡＷ共振子は、その周波数温度特性が零温度係数をもち精度が良くかつ、所望の周波数を直接発振が可能であるために、各種無線系の圧電発振器に使用されているが、これはジッタが無く位相ノイズに優れた信号が高信頼性かつ低コストに容易に得られるという長所があるためである。   Conventionally, SAW resonators constructed using a quartz ST-cut substrate with piezoelectricity (an example of a piezoelectric flat plate) have a frequency temperature characteristic with a zero temperature coefficient and high accuracy, and can directly oscillate a desired frequency. Therefore, it is used in various types of wireless piezoelectric oscillators because it has an advantage that a signal having no jitter and excellent phase noise can be easily obtained with high reliability and low cost.

この理由から近年、乗用車のドアの自動開閉にはＳＡＷ共振子を用いた微弱無線機（キーレスエントリー装置）が多数使用されるに至っている。この微弱無線機には周波数可変できるＳＡＷ発振器を構成したＦＳＫ変調器が使われている。   For this reason, in recent years, many weak wireless devices (keyless entry devices) using SAW resonators have been used for automatic opening and closing of passenger car doors. This weak radio uses an FSK modulator that constitutes a SAW oscillator whose frequency can be varied.

しかしながら、前述の従来技術を使用したものはいずれもＦＳＫ変調するための２つの周波数の発生手段として、伸張コイルと切り換え電圧発生回路と可変容量ダイオード等の素子を付加して使用することが必要である（例えば、特許文献１参照）。このためこれら部品によりコストアップとなる他、周波数調整の際に各素子のバラツキが重なって生産上で歩留まりが低下するという不具合を生じることがあった。また最近になって、前記装置の小形化要請が強まりＦＳＫ変調器の小形化も必要になって来た。   However, any of those using the above-described conventional technology needs to use elements such as an expansion coil, a switching voltage generation circuit, and a variable capacitance diode as a means for generating two frequencies for FSK modulation. Yes (for example, see Patent Document 1). For this reason, in addition to an increase in cost due to these components, there is a problem in that variations in the elements overlap during frequency adjustment, resulting in a decrease in production yield. Recently, there has been an increasing demand for downsizing of the apparatus, and downsizing of the FSK modulator has become necessary.

本発明はかかる課題を解決するものでその目的とするところは、ＳＡＷ共振子のみで振幅変動の少ない２周波数信号の発生を実現することにより、外付け素子である伸張コイル，可変容量ダイオード等を無くして、低ジッタ，小形かつ低コストなＦＳＫ変調器を市場に提供することにある。   The present invention solves such a problem, and an object of the present invention is to realize an expansion coil, a variable capacitance diode, and the like as an external element by realizing generation of a two-frequency signal with small amplitude fluctuation using only a SAW resonator. The goal is to provide a low-jitter, small and low-cost FSK modulator on the market.

特開平１−２５２０１６号公報JP-A-1-252016

（１） 本発明のＦＳＫ変調器は、圧電体平板上に形成された２個の振動状態を有するＳＡＷ共振子と、増幅器とＳＷ回路からなるＦＳＫ変調器において、前記２個の振動状態を有するＳＡＷ共振子は、1個のＩＤＴを３つあるいは４つに分割して主ＩＤＴとゲイトＩＤＴおよび副ＩＤＴを構成し、その両側に1対の反射器を配置した１個の２ポート型のＳＡＷ共振子からなり、かつ前記主ＩＤＴと前記副ＩＤＴの極性を前記ＳＷ回路にて同符号として発振器の増幅器に接続して、第１の振動状態を励振して第１の発振周波数ｆＨを発生し、また、前記主ＩＤＴと前記副ＩＤＴの極性を前記のＳＷ回路にて逆符号として発振器の増幅器に接続して、第２の振動状態を励振して前記第１と若干異なる第２の発振周波数ｆＬを発生する構成としたことを特徴とする。 (1) An FSK modulator according to the present invention includes two SAW resonators formed on a piezoelectric plate and having two vibration states, an amplifier and an SW circuit, and the two vibration states. The SAW resonator is divided into three or four IDTs to form a main IDT, a gate IDT, and a sub-IDT, and one 2-port SAW in which a pair of reflectors are arranged on both sides thereof. The first oscillation frequency fH is generated by exciting the first vibration state by connecting to the amplifier of the oscillator having the same sign as the polarity of the main IDT and the sub IDT in the SW circuit. In addition, the polarity of the main IDT and the sub IDT is connected to the amplifier of the oscillator as the opposite sign in the SW circuit, the second oscillation state is excited and the second oscillation frequency slightly different from the first A configuration that generates fL It is characterized by.

この回路構成によれば、先出願技術は２個のＳＡＷ共振子を並列使用して２つのモードを発生していたものが、１個のＳＡＷ共振子内に形成したゲイトＩＤＴにより、ＩＤＴの総対数を少なくしても所望の２つの振動状態を発生させることが可能であるため、素子の小形化および生産性面において有利となるという効果がある。   According to this circuit configuration, in the prior application technology, two SAW resonators were used in parallel to generate two modes. However, the gate IDT formed in one SAW resonator allowed the total IDT. Even if the logarithm is reduced, it is possible to generate two desired vibration states, which is advantageous in terms of downsizing of the element and productivity.

（２）本発明のＦＳＫ変調器は、前記ＳＡＷ共振子が有する２個の振動状態が縦の対称モードＳ０および縦の斜対称モードＡ０からなる構成としても良い。 (2) The FSK modulator of the present invention may have a configuration in which the two vibration states of the SAW resonator include a vertical symmetric mode S0 and a vertical oblique symmetric mode A0.

上記（２）の構成であれば、２つの発生周波数差が１００ｐｐｍ程度に接近したＦＳＫ変調器を実現できる他、ＩＤＴの電極指交叉幅に制約が無いため２つの振動状態でのＳＡＷ共振子の等価回路定数をほぼ等しく設定することが可能であり、周波数の切り替え時において、発振回路系の負性抵抗マージンが同一に確保できる結果、ＦＳＫ変調器の出力信号の振幅の変化が軽減でき、ＡＭジッタの発生を抑制できるという効果がある。   With the configuration of (2) above, it is possible to realize an FSK modulator in which the difference between the two generated frequencies approaches 100 ppm, and since there is no restriction on the electrode finger crossing width of the IDT, the SAW resonator in two vibration states It is possible to set the equivalent circuit constants to be approximately equal, and as a result of ensuring the same negative resistance margin of the oscillation circuit system when switching the frequency, the change in the amplitude of the output signal of the FSK modulator can be reduced, and AM There is an effect that generation of jitter can be suppressed.

（３）本発明のＦＳＫ変調器は、前記２ポート型のＳＡＷ共振子が有する２個の振動状態が縦の対称モードＳ０および縦の斜対称モードＡ０からなり、副ＩＤＴに接続して配置したＩＤＴの正負極性を切り替えるＳＷ回路により発振モードを選択して２つの周波数を位相連続して出力可能とする構成であっても良い。 (3) In the FSK modulator of the present invention, the two vibration states of the two-port SAW resonator are composed of a vertical symmetric mode S0 and a vertical oblique symmetric mode A0, and are connected to the sub-IDT. The configuration may be such that the oscillation mode is selected by the SW circuit that switches the positive / negative polarity of the IDT, so that two frequencies can be continuously output in phase.

上記（３）の構成であれば、伸張コイル、可変容量ダイオード等の外付け素子を使わなくとも、直接に送信データ（ＮＲＺ信号）に対応してＳ０モード状態の発振周波数をｆＨ、Ａ０モード状態の発振周波数をｆＬを発生することが可能となりＦＳＫ変調信号を送出できるという効果がある。さらに、縦のＳ０とＡ０モードを使用するために、共振子を構成するＩＤＴの総対数Ｍを比較的少なくして２つの振動モードが発生できるという効果があり、小形化がはかれる。   With the configuration of (3) above, the oscillation frequency of the S0 mode state is directly set to the fH, A0 mode state corresponding to the transmission data (NRZ signal) without using an external element such as an extension coil or a variable capacitance diode. The oscillation frequency of fL can be generated and the FSK modulation signal can be transmitted. Furthermore, since the vertical S0 and A0 modes are used, the total logarithm M of the IDTs constituting the resonator can be relatively reduced, and two vibration modes can be generated, and the size can be reduced.

（４）本発明のＦＳＫ変調器は、前記２ポート型のＳＡＷ共振子が有する副ＩＤＴが１部に弾性表面波の励振に寄与しない浮き電極を有する構成であっても良い。 (4) The FSK modulator of the present invention may have a configuration in which the sub-IDT included in the two-port SAW resonator has a floating electrode that does not contribute to excitation of surface acoustic waves.

上記（４）の構成であれば、振動状態の切り替えに際して発生する出力信号振幅の変動を極力押さえることが可能となり、振幅変調成分の少ない安定なＦＳＫ変調信号を送出できるという効果がある。   With the configuration (4), it is possible to suppress the fluctuation of the output signal amplitude that occurs when switching the vibration state as much as possible, and there is an effect that a stable FSK modulation signal with a small amplitude modulation component can be transmitted.

以下本発明のＦＳＫ変調器の実施形態について、図２と図３によって具体的回路の実施例をブロック図にて説明した後、図１には本発明で使用される２固の振動状態が実現できる２モード型ＳＡＷ共振子の具体的な電極パターンの構成を図により説明し、さらに図４と図５図６をもちいてその動作状態を詳細に解説する。   The embodiment of the FSK modulator of the present invention will be described below with reference to a block diagram of a specific circuit example shown in FIGS. 2 and 3, and FIG. 1 realizes a dual vibration state used in the present invention. A specific electrode pattern configuration of the two-mode SAW resonator that can be formed will be described with reference to the drawings, and the operation state thereof will be described in detail with reference to FIGS.

図２は請求項１の本発明に係わるＦＳＫ変調器の一実施例について、その構成をブロック図にて図示したものである。   FIG. 2 is a block diagram showing the configuration of an embodiment of the FSK modulator according to the present invention.

図２中の各部位の名称は、２００は前記の２モード型ＳＡＷ共振子、２０１は増幅器、２０２と２０３はバイポーラあるいはＭＯＳトランジスタからなるＳＷ（スイッチ）回路、２０５はＦＳＫ変調器への入力データ信号端子、２０４はＦＳＫ変調器の出力信号端子である。さらに、２００の２モード型ＳＡＷ共振子は表面波が伝搬する１つのトラックからなり、２０１１が主ＩＤＴが形成された部分であり、２０１２は周波数切り替え制御側の副ＩＤＴが形成された部分である。副ＩＤＴへの正負極性の端子接続は、前記の切り替えＳＷ回路２０２と２０３およびＦＳＫ変調器への入力信号端子２０５へのＨ（＋１），Ｌ（０）信号により設定できる。例えば、入力信号がＨ（＋１）に状態においては、ＳＷ回路２０２と２０３はいずれも端子２の状態に接続する。この状態においては、主ＩＤＴ２０１１の位相と副ＩＤＴ２０１２は同一位相電圧が加えられて励振される。また、入力信号がＬ（０）の場合においては、ＳＷ回路２０２と２０３はいずれも端子１の状態に接続する。この状態においては、主ＩＤＴ２０１１の位相と副ＩＤＴ２０１２の位相は１８０°異なる位相にて増幅器２０1に接続されて励振される。   In FIG. 2, the names of the respective parts are as follows: 200 is the above-described two-mode SAW resonator, 201 is an amplifier, 202 and 203 are SW (switch) circuits composed of bipolar or MOS transistors, and 205 is input data to the FSK modulator. A signal terminal 204 is an output signal terminal of the FSK modulator. Furthermore, 200 two-mode SAW resonators are composed of one track on which surface waves propagate, 2011 is a portion where the main IDT is formed, and 2012 is a portion where the sub-IDT on the frequency switching control side is formed. . Positive and negative terminal connection to the sub-IDT can be set by the H (+1) and L (0) signals to the switching SW circuits 202 and 203 and the input signal terminal 205 to the FSK modulator. For example, when the input signal is in the H (+1) state, both the SW circuits 202 and 203 are connected to the state of the terminal 2. In this state, the phase of the main IDT 2011 and the sub IDT 2012 are excited by applying the same phase voltage. When the input signal is L (0), both the SW circuits 202 and 203 are connected to the state of the terminal 1. In this state, the phase of the main IDT 2011 and the phase of the sub IDT 2012 are connected to the amplifier 201 at a phase different by 180 ° and excited.

つぎに図２のブロック図が示す回路につき動作状態の説明を図３を用いて行う。図３は本発明の図２に対応したＦＳＫ変調器の動作波形を示すものである。横軸Ｔは、時間を意味する。図中の上段の３０１は入力信号端子２０５の電位である。中段の３０２は出力信号端子２０５の電位、下段の３０３は前記ＲＦ信号が有する発振周波数ｆの変化である。図２と図３の状態では入力信号データのＨ（＋１）に対応してＳ０モード（ｆＨ）が、０に対応してＡ０（ｆＬ）モードが動作する。   Next, the operation state of the circuit shown in the block diagram of FIG. 2 will be described with reference to FIG. FIG. 3 shows operation waveforms of the FSK modulator corresponding to FIG. 2 of the present invention. The horizontal axis T means time. The upper part 301 in the figure is the potential of the input signal terminal 205. The middle 302 is the potential of the output signal terminal 205, and the lower 303 is the change in the oscillation frequency f of the RF signal. 2 and 3, the S0 mode (fH) operates corresponding to H (+1) of the input signal data, and the A0 (fL) mode operates corresponding to 0.

つぎに、図２の２モード型ＳＡＷ共振子２００につき図１をもちいて説明する。図１は２モード型ＳＡＷ共振子２００の電極パーンの配置を示す平面図である。２モード型ＳＡＷ共振子２００に使用する圧電体平板（１００）を説明する。前圧電体平板１００は、例えば面内回転ＳＴカット水晶板でありレイリー型表面波で動作するもので、水晶結晶の基本軸である電気軸Ｘと光軸Ｚの２軸が作る面を主面とするＹ板を電気軸Ｘの回りに反時計方向にθ度（特に零温度係数が得られるθ＝３１度から４２度）回転した基板において、さらに前記基板の法線軸の回りに前記電気Ｘ軸からの面内の回転角Ψが±（４０〜４６）度である方位を弾性表面波の位相伝播方位軸としたものである。あるいはまた、前記の圧電体平板はＳＨ型表面波で動作する水晶基板であってもよい。つぎに前記圧電体平板の表面を鏡面研磨した後、レイリー型あるいはＳＨ型等の弾性表面波の位相伝搬方向軸に対して直交して、例えば金属アルミニウムからなる多数の平行導体の電極指を周期的に配置した少なくとも1個のＩＤＴ（すだれ状電極とも呼ぶ）を構成し、その両側に1対の反射器１０１、１０５を形成して１個のＳＡＷ共振子を構成することができる。   Next, the two-mode SAW resonator 200 shown in FIG. 2 will be described with reference to FIG. FIG. 1 is a plan view showing the arrangement of the electrode patterns of the two-mode SAW resonator 200. A piezoelectric flat plate (100) used for the two-mode SAW resonator 200 will be described. The front piezoelectric flat plate 100 is, for example, an in-plane rotating ST-cut quartz plate that operates with a Rayleigh type surface wave. The principal plane is a plane formed by two axes of an electric axis X and an optical axis Z, which are basic axes of a quartz crystal. In the substrate rotated Y degrees counterclockwise around the electric axis X (particularly θ = 31 degrees to 42 degrees at which a zero temperature coefficient is obtained), the electric X is further rotated around the normal axis of the substrate. The orientation in which the in-plane rotation angle Ψ from the axis is ± (40 to 46) degrees is the phase propagation azimuth axis of the surface acoustic wave. Alternatively, the piezoelectric plate may be a quartz substrate that operates with an SH type surface wave. Next, after the surface of the piezoelectric plate is mirror-polished, electrode fingers of a number of parallel conductors made of, for example, metal aluminum are periodically formed perpendicular to the phase propagation direction axis of the Rayleigh type or SH type surface acoustic wave. It is possible to configure at least one IDT (also referred to as a comb-shaped electrode) arranged in the same manner, and to form one SAW resonator by forming a pair of reflectors 101 and 105 on both sides thereof.

図１において、１００は前述の圧電体平板であり、１０１と１０５は反射器、１０２は主ＩＤＴ（主すだれ状電極）、１０４は副ＩＤＴ（副すだれ状電極）、１０３はゲイトＩＤＴ、１０６は主ＩＤＴへの正負極性の入力端子、１０７は副ＩＤＴへの入力端子である。またＩＤＴ領域中の斜線で形成された部位１１１はＩＤＴの正負極性からなる電極指群への給電導体部位であり、いずれも前述のアルミニウム電極等の金属で形成されている。１０１と１０２，１０３，１０４，１０５の全体で１個の２モード型ＳＡＷ共振子を構成している。   In FIG. 1, 100 is the above-described piezoelectric plate, 101 and 105 are reflectors, 102 is a main IDT (main interdigital electrode), 104 is a sub-IDT (sub-interdigital electrode), 103 is a gate IDT, and 106 is Positive and negative polarity input terminals to the main IDT, 107 is an input terminal to the sub-IDT. Further, a portion 111 formed by oblique lines in the IDT region is a feeding conductor portion to the electrode finger group having the positive / negative polarity of the IDT, and both are formed of the above-described metal such as an aluminum electrode. 101, 102, 103, 104, and 105 constitute one two-mode SAW resonator.

前記ＳＡＷ共振子は表面波にて動作して２つの定常振動を形つくるが、両者は１個のＳＡＷ共振子内において相互に弾性的に結合するように設計することが必要である。この状態を効果的に形成するために、１０３のゲイトＩＤＴが必要である。ＳＴカットの場合においては、このゲイトＩＤＴの電極周期長Ｐ（Ｘ）を、左右両側の主ＩＤＴ１０２と副ＩＤＴ１０４が有する電極周期長ＰＴ０のいずれにに対しても、大きく設定することにより振動の変位状態を制御して、対称モードＳ０と斜対称モードＡ０を効果的に発生させることができる。ちなみに、図１には記載しないが前記の電極周期長とは各ＩＤＴを構成する電極指の電極幅（ライン）と電極指導体間の距離（スペース）と通常定義されるものである。また、前記対称モードＳ０とは主電極領域の振動振幅の包絡線変位が副ＩＤＴ領域の振動振幅の包絡線変位と同位相の状態であり、前記斜対称モードＡ０とは主電極領域の振動振幅の包絡線変位が副ＩＤＴ領域の振動振幅の包絡線変位とが逆位相の状態のことである(詳細は図６の説明を参照のこと)。この場合の電極周期長比Ｐ（Ｘ）／ＰＴ０が１．０２以上から１．０４程以下程度に設定すれば十分な効果が期待できる。図１中の階段状の線１０８はＳＡＷ共振子の縦方向（すなわち、弾性表面波の位相伝搬方向）に関して、電極指の周期長Ｐ（ｘ）を図示したものである。端子１０６に接続する主ＩＤＴ１０２は常にＦＳＫ変調器の増幅回路に接続されて、Ｓ０およびＡ０モードの振動変位の片側部分を励振する。一方１０４の副ＩＤＴは、Ｓ０とＡ０モードを選択して励振できるように、ＩＤＴに加える駆動電圧の極性を設定するように制御する。Ｓ０モードを選択する場合には、主ＩＤＴと副ＩＤＴの電極指の極性を同一符号（+）とし、Ａ０モードの選択の場合には、主ＩＤＴと副ＩＤＴの電極指の極性を逆符号（+／−）の関係に設定する。前記３個のＩＤＴ(主ＩＤＴ，副ＩＤＴ，ゲイトＩＤＴ)はひとつのＩＤＴを３つに分割して形成することができる。前記の分割は給電導体を３つ区間に分離して例えば主ＩＤＴ１０２の給電導体１１１を形成するものである。さらにまた、副ＩＤＴの電極指の一部を給電導体から分離した浮き電極としても、前記のＳ０およびＡ０モードの選択が可能であり、この浮き電極の割合は副ＩＤＴの電極対数の7、8割となっても十分に周波数切り替え機能を果している。また２つの発振周波数差は浮き電極の対数の多少により大きく変化しない。この浮き電極の対数の大小により２つのモード間の切り替え時間の大小が決定される他、浮き電極により、Ｓ０とＡ０の切り替え時における電極上の発生電荷の打ち消し量が軽減できＳＡＷ共振子電流の変動が少なくなり、結果としてＦＳＫ変調器のＲＦ信号の振幅変化を押さえることができる。本発明の図１の２モード型ＳＡＷ共振子の構成条件の１例を示すと前述の水晶ＳＴカットあるいは回転ＳＴカットにおいて、アルミ電極の膜厚みｈに対する利用する弾性表面波の波長λの比ｈ／λが０．０２から０．０３であり、ＩＤＴの総対数Ｍ＝１６０対，主ＩＤＴが８０対，副ＩＤＴが３０から８０対，浮き電極が０から５０対、ゲイトＩＤＴは２０から４０対で電極周期比が１．０２から１．０４，ＩＤＴの交叉幅が４０波長，反射器は９０本である。   The SAW resonator operates with surface waves to form two stationary vibrations, and both must be designed to be elastically coupled to each other within a single SAW resonator. In order to effectively form this state, 103 gate IDTs are required. In the case of ST cut, the displacement of vibration is obtained by setting the electrode period length P (X) of the gate IDT larger than both the electrode period length PT0 of the main IDT 102 and the sub IDT 104 on both the left and right sides. The state can be controlled to effectively generate the symmetric mode S0 and the oblique symmetric mode A0. Incidentally, although not shown in FIG. 1, the above-mentioned electrode cycle length is normally defined as the electrode width (line) of electrode fingers constituting each IDT and the distance (space) between electrode guides. The symmetry mode S0 is a state in which the envelope displacement of the vibration amplitude of the main electrode region is in phase with the envelope displacement of the vibration amplitude of the sub-IDT region, and the oblique mode A0 is the vibration amplitude of the main electrode region. The envelope displacement of the sub-IDT region is in a phase opposite to the envelope displacement of the vibration amplitude in the sub-IDT region (refer to the description of FIG. 6 for details). In this case, if the electrode cycle length ratio P (X) / PT0 is set to about 1.02 or more and about 1.04 or less, a sufficient effect can be expected. A step-like line 108 in FIG. 1 illustrates the period length P (x) of the electrode fingers with respect to the longitudinal direction of the SAW resonator (that is, the phase propagation direction of the surface acoustic wave). The main IDT 102 connected to the terminal 106 is always connected to the amplifier circuit of the FSK modulator, and excites one side portion of the vibration displacement in the S0 and A0 modes. On the other hand, the sub-IDT 104 controls to set the polarity of the drive voltage applied to the IDT so that the S0 and A0 modes can be selected and excited. When the S0 mode is selected, the polarities of the electrode fingers of the main IDT and the sub IDT are set to the same sign (+). When the A0 mode is selected, the polarities of the electrode fingers of the main IDT and the sub IDT are reversed ( Set the relationship to +/-). The three IDTs (main IDT, secondary IDT, and gate IDT) can be formed by dividing one IDT into three. In the division described above, the power supply conductor is divided into three sections to form the power supply conductor 111 of the main IDT 102, for example. Furthermore, the S0 and A0 modes can also be selected as a floating electrode in which a part of the electrode finger of the sub IDT is separated from the power supply conductor, and the ratio of the floating electrode is 7 or 8 of the number of electrode pairs of the sub IDT. However, the frequency switching function is fully achieved. The difference between the two oscillation frequencies does not change greatly depending on the number of logarithms of the floating electrodes. In addition to determining the switching time between the two modes depending on the logarithm of the floating electrode, the floating electrode can reduce the amount of charge generated on the electrode when switching between S0 and A0, thereby reducing the SAW resonator current. As a result, the variation in the amplitude of the RF signal of the FSK modulator can be suppressed. An example of the configuration conditions of the two-mode SAW resonator of FIG. 1 according to the present invention is the ratio h of the wavelength λ of the surface acoustic wave used to the film thickness h of the aluminum electrode in the above-described quartz ST cut or rotational ST cut. / Λ is 0.02 to 0.03, total IDT logarithm M = 160 pairs, main IDT 80 pairs, secondary IDT 30 to 80 pairs, floating electrode 0 to 50 pairs, gate IDT 20 to 40 The pair has an electrode cycle ratio of 1.02 to 1.04, an IDT crossing width of 40 wavelengths, and 90 reflectors.

つぎに、本発明のＦＳＫ変調器に発生するＳ０とＡ０モードの振動モードにつき図４と図５，図６でさらに詳しく説明する。まず図４は一体のＩＤＴ（Ｍ＝１６０対）からなる従来の１ポート型ＳＡＷ共振子が有するアドミタンス特性を示す。同図縦軸は２０log10（Ｙ（ｆ））（ｄB）かつ単位はシーメンスにて表示し、横軸は周波数変化率df/f0，単位は10-6のｐｐｍにより表示した場合である。図中の４０３のピークが縦対称モードＳ０(基本波)であり、４０１の共振ピークが縦１次対称モードＳ１である。両者の周波数差は約３０００ｐｐｍ存在している。ただし斜対称モードＡ０は観測されないが、Ｓ０とＳ１の中間点４０２に存在する。Ｓ０とＡ１の周波数差は約１５００ｐｐｍとなり、従来の構成方法でＦＳＫ変調器のもつ２つの発振周波数ｆＨとｆＬの周波数差を１００〜２００ｐｐｍとするためには、ＩＤＴの総対数Ｍを相当大きくとることが必要であった。つぎに図５は本発明による図１の構成にて実現する２モード型ＳＡＷ共振子のアドミタンス特性Ｙ（ｆ）の場合であり、同図縦軸は２０log10（Ｙ（ｆ））（ｄB）かつ単位はシーメンスにて表示し、横軸は周波数変化率df/f0，単位は10-6のｐｐｍにより表示した場合である。図中の５０１が前記Ｓ０モード，５０２がＡ０モードである。両者の共振周波数ｆＬ，ｆＨの差（ｆＨ-ｆＬ）／ｆＬは１００〜２００ｐｐｍと近接させることが可能である。つぎに、図６は本発明の図１の構成にてＳＷ回路(図２の２０２と２０３)により副ＩＤＴに加えられる正負極性の電圧によって実現する振動変位の状態図である。図中の実線６０１が対称モードＳ０であり、破線６０２は斜対称モードである。また同図の下部に示すＳＡＷ共振子の配置図とあわせて表示した。６０３と６０７が反射器、６０４が主ＩＤＴ，６０５がゲイトＩＤＴ，６０６０が副ＩＤＴの励振電極領域，６０６１が副ＩＤＴ領域の浮き電極領域である。ゲイトＩＤＴ領域において、Ｓ０とＡ０モードの変位がゼロ近くに減少することがわかる。これによって、少ない総対数Ｍにより２個の振動モードが実現できる。 Next, the vibration modes of the S0 and A0 modes generated in the FSK modulator of the present invention will be described in more detail with reference to FIGS. First, FIG. 4 shows the admittance characteristics of a conventional 1-port SAW resonator composed of an integral IDT (M = 160 pairs). In the figure, the vertical axis represents 20 log10 (Y (f)) (dB), the unit is displayed in Siemens, the horizontal axis is the frequency change rate df / f0, and the unit is displayed in ppm of 10 −6 . A peak 403 in the figure is the longitudinal symmetry mode S0 (fundamental wave), and a resonance peak 401 is the longitudinal first order symmetry mode S1. The frequency difference between the two is about 3000 ppm. However, the oblique symmetry mode A0 is not observed, but exists at the intermediate point 402 between S0 and S1. The frequency difference between S0 and A1 is about 1500 ppm. In order to set the frequency difference between the two oscillation frequencies fH and fL of the FSK modulator to 100 to 200 ppm with the conventional configuration method, the total logarithm M of the IDT is considerably large. It was necessary. Next, FIG. 5 shows the case of the admittance characteristic Y (f) of the two-mode SAW resonator realized by the configuration of FIG. 1 according to the present invention, and the vertical axis of the figure shows 20 log10 (Y (f)) (dB) and The unit is displayed in Siemens, the horizontal axis is the frequency change rate df / f0, and the unit is displayed in ppm of 10-6 . In the figure, 501 is the S0 mode and 502 is the A0 mode. The difference between the resonance frequencies fL and fH (fH−fL) / fL can be close to 100 to 200 ppm. Next, FIG. 6 is a state diagram of vibration displacement realized by positive and negative voltages applied to the sub-IDT by the SW circuit (202 and 203 in FIG. 2) in the configuration of FIG. 1 of the present invention. A solid line 601 in the figure is the symmetry mode S0, and a broken line 602 is the oblique symmetry mode. Further, it is shown together with the layout of the SAW resonator shown at the bottom of the figure. 603 and 607 are reflectors, 604 is a main IDT, 605 is a gate IDT, 6060 is a sub-IDT excitation electrode region, and 6061 is a sub-IDT region floating electrode region. It can be seen that the displacement of the S0 and A0 modes decreases to near zero in the gate IDT region. Thereby, two vibration modes can be realized with a small total logarithm M.

以上説明したように本発明のＦＳＫ変調器はＳＡＷデバイス技術とＩＣ技術を融合して部品点数を減らすことが可能であり今後ＦＳＫ変調器を利用したセンサーシステム分野におおいに貢献できる。   As described above, the FSK modulator of the present invention can reduce the number of parts by combining the SAW device technology and the IC technology, and can greatly contribute to the sensor system field using the FSK modulator in the future.

本発明のＦＳＫ変調の構成要素である２モード型ＳＡＷ共振子の電極パターンの一実施例を示す平面図。The top view which shows one Example of the electrode pattern of the 2 mode type | mold SAW resonator which is a component of FSK modulation of this invention. 本発明のＦＳＫ変調器の回路構成の一実施例を示すブロック図。The block diagram which shows one Example of the circuit structure of the FSK modulator of this invention. 本発明のＦＳＫ変調器の動作状態を示す状態図。The state diagram which shows the operation state of the FSK modulator of this invention. 従来のＳＡＷ共振子のアドミタンス特性図。The admittance characteristic figure of the conventional SAW resonator. 本発明の２モード型ＳＡＷ共振子のアドミタンス特性図。The admittance characteristic view of the two-mode SAW resonator of the present invention. 本発明の２モード型ＳＡＷ共振子が有する変位状態図。The displacement state figure which the 2 mode type SAW resonator of the present invention has.

符号の説明Explanation of symbols

１０２ 主ＩＤＴ
１０３ ゲイトＩＤＴ
１０４ 副ＩＤＴ
１０１，１０５ 反射器
102 Main IDT
103 Gate IDT
104 Deputy IDT
101,105 reflector

Claims (4)

圧電体平板上に形成された２個の振動状態を有するＳＡＷ共振子と、増幅器とＳＷ回路とからなるＦＳＫ変調器において、
前記ＳＡＷ共振子は、1個のＩＤＴを３つあるいは４つに分割して主ＩＤＴとゲイトＩＤＴおよび副ＩＤＴを構成し、前記1個のＩＤＴ両側に1対の反射器を配置した２ポート型のＳＡＷ共振子からなり、かつ前記主ＩＤＴと前記副ＩＤＴの極性を前記ＳＷ回路にて同符号として発振器の増幅器に接続して、第１の振動状態を励振して第１の発振周波数ｆＨを発生し、
また、前記主ＩＤＴと前記副ＩＤＴの極性を前記のＳＷ回路にて逆符号として発振器の増幅器に接続して、第２の振動状態を励振して前記第１と若干異なる第２の発振周波数ｆＬを発生する構成としたことを特徴とするＦＳＫ変調器。 In an FSK modulator comprising a SAW resonator having two vibration states formed on a piezoelectric flat plate, an amplifier and a SW circuit,
The SAW resonator is a two-port type in which one IDT is divided into three or four to form a main IDT, a gate IDT, and a sub-IDT, and a pair of reflectors are arranged on both sides of the one IDT. And the polarity of the main IDT and that of the sub-IDT are connected to the amplifier of the oscillator with the same sign in the SW circuit to excite the first vibration state to obtain the first oscillation frequency fH. Occur,
Also, the polarity of the main IDT and the sub IDT is connected to the amplifier of the oscillator as the opposite sign in the SW circuit, and the second oscillation state is excited to slightly differ from the first oscillation frequency fL. The FSK modulator is characterized in that it is configured to generate. 前記ＳＡＷ共振子が有する２個の振動状態が縦の対称モードＳ０および縦の斜対称モードＡ０からなることを特徴とする請求項１記載のＦＳＫ変調器。   2. The FSK modulator according to claim 1, wherein the two vibration states of the SAW resonator are composed of a longitudinal symmetric mode S0 and a longitudinal oblique symmetric mode A0. 前記ＳＡＷ共振子が有する２個の振動状態は縦の対称モードＳ０および縦の斜対称モードＡ０からなり、副ＩＤＴに接続して配置したＩＤＴの極性を正負に切り替えるＳＷ回路により発振モードを選択して２つの周波数を位相連続して出力可能とする構成であることを特徴とする請求項１記載のＦＳＫ変調器。   The two vibration states of the SAW resonator are composed of a vertical symmetric mode S0 and a vertical oblique symmetric mode A0. The oscillation mode is selected by an SW circuit that switches the polarity of the IDT connected to the sub-IDT between positive and negative. 2. The FSK modulator according to claim 1, wherein the two frequencies can be continuously output in phase. 前記副ＩＤＴが１部に給電導体の接続端にて電極指との接続を切離した弾性表面波の励振に寄与しない浮き電極を有する構成であることを特徴とする請求項１記載のＦＳＫ変調器。   2. The FSK modulator according to claim 1, wherein the sub-IDT has a floating electrode that does not contribute to excitation of a surface acoustic wave that is disconnected from the electrode finger at a connection end of the feeder conductor in part. .
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