JP3915137B2

JP3915137B2 - Voltage controlled oscillator

Info

Publication number: JP3915137B2
Application number: JP15153596A
Authority: JP
Inventors: 好明松本; 重久黒後
Original assignee: Miyazaki Epson Corp
Current assignee: Miyazaki Epson Corp
Priority date: 1996-05-23
Filing date: 1996-05-23
Publication date: 2007-05-16
Anticipated expiration: 2016-05-23
Also published as: JPH09312521A

Description

【０００１】
【発明の属する技術分野】
本発明は、ＦＭ変調回路、位相変調回路、シンセサイザ装置の周波数切替回路などで使用される電圧制御型発振回路に関し、特に制御電圧と発振周波数との関係におけるリニア特性を向上した電圧制御型発振回路に関する。
【０００２】
【従来の技術】
ＦＭ変調回路、位相変調回路、シンセサイザ装置の周波数切替回路などで使用される電圧制御型発振回路の１つとして従来から図８に示す回路が知られている。
この図に示す電圧制御型発振回路１０１は、発振周波数の制御を行なう水晶振動子１０２と、一端が水晶振動子１０２の一端に接続され他端子が接地点に接続される抵抗１０３と、アノードが水晶振動子１０２の一端に接続されるバイアブルキャパシター（バラクタ・ダイオード）１０４と、一端が前記バイアブルキャパシター１０４のカソードに接続され他端が制御電圧入力端子１０５に接続される抵抗１０６と、カソードが抵抗１０６とバイアブルキャパシター１０４との接続点に接続され、アノードが共通入力端子１０７に接続されるバイアブルキャパシター１０８と、入力端子が水晶振動子１０２の他端に接続され出力端子が信号出力端子１０９に接続される増幅器１１０と、一端が水晶振動子１０２の前記他端に接続されるコンデンサ１１１と、一端が前記コンデンサ１１１の他端に接続され他端がバイアブルキャパシター１０８のアノードに接続されるコンデンサ１１２と、一端が各コンデンサ１１１、１１２の接続点と増幅器１１０の一端に接続され他端がバイアブルキャパシター１０８のアノードに接続される抵抗１１３とを備えている。このように構成された電圧制御発振回路は制御電圧入力端子１０５と、共通入力端子１０７との間に印加される制御電圧の値に応じて各バイアブルキャパシター１０４、１０８の容量を変化させて発振周波数を制御し、これによって得られた発振信号を信号出力端子１０９から出力する。
可変容量素子としては、一般的に傾斜接合型バイアブルキャパシターや階段接合型バイアブルキャパシターが使用されるが、これらは両端の印加電圧に反比例して容量値が変化し、上記回路においては図９に示す如く制御電圧入力端子１０５と、共通入力端子１０７との間に印加される制御電圧が高くなるほど、信号出力端子１０９から出力される発振周波数が上昇し、逆に制御電圧が低くなるほど発振周波数が低下する。
【０００３】
【発明が解決しようとする課題】
しかしながらこの時、特性曲線１１４の両端すなわち制御電圧の値が高い部分、制御電圧の値が低い部分では、変化が飽和し非直線となり、制御電圧を変化しても発振周波数がほとんど変化しない。従って電圧制御型発振回路１０１を例えばＡＦＣ回路（Automatic Frequency Control Circuit ）として機能させた場合や、制御電圧が低い部分や高い部分で発振周波数の制御が不能となる。また前記電圧制御型発振回路１０１をＦＭ変調回路として機能させた場合は変調信号振幅が小さい部分と大きい部分の被変調出力波形が歪むという問題があった。
このようなところから、このような電圧制御型発振回路１０１をＡＦＣ回路やＦＭ変調回路などに組み込んで使用する場合、従来、図９に示す特性曲線１１４の直線と見なせる部分のみを利用するようにしてこのような不都合が発生しないようにしている。
しかしながら、このような方法では図９に示す如く特性曲線１１４の直線と見なせる部分が僅かしかないことから、発振周波数の可変範囲が狭くなるという問題があった。
そこで、このような問題を解決する方法として、従来図１０に示す如く低感度のバイアブルキャパシターの特性曲線１１６に比べて、傾きの大きな高感度特性曲線１１５をもつバイアブルキャパシターを使用して制御感度を高くし、これによって印加電圧の変化に対する発振周波数の変化量を大きくすることも考えられているが、このようにすると、雑音を拾い易くなってＳ／Ｎが劣化し、外乱に対して弱くなるという問題がある。また更には、直線部分であっても詳細に見れば、非直線性を含んでおり、同様に歪みを発生していた。
本発明は上記の事情に鑑みてなされたものであり、耐雑音性を保ちつつ、しかも広い範囲にわたって、制御電圧−発振周波数特性をリニアにすることができる電圧制御型発振回路を提供することを目的としている。
【０００４】
【課題を解決するための手段】
上記の目的を達成するために本発明の電圧制御型発振回路は、入力された制御電圧に応じて電圧制御可変リアクタンス素子のリアクタンスを可変して、発振回路の発振周波数を制御する電圧制御型発振回路部と、該電圧制御型発振回路の制御電圧−発振周波数特性に於ける非直線特性と逆の非直線特性を有する電圧−周波数変換特性線形補償回路と、を備え、前記電圧−周波数変換特性線形補償回路は、制御電圧を第１制御電流に変換する第１電圧制御電流源回路と、該第１電圧制御電流源回路から出力される第１制御電流を対数関数的に第１制御電圧に変換する第１電流制御非線形素子と、前記制御電圧を入力電圧とし、該入力電圧の傾きの極性を逆にした係数を有する電圧を出力する電圧反転回路と、該電圧反転回路から出力される反転制御電圧を第２制御電流に変換する第２電圧制御電流源回路と、該第２電圧制御電流源回路から出力される第２制御電流を対数関数的に第２制御電圧に変換する第２電流制御非線形素子と、該第２電流制御非線形素子から出力される第２制御電圧と前記第１電流制御非線形素子から出力される第１制御電圧との差の電圧を生成する引き算回路と、を備えていることを特徴とする。
また本発明の電圧制御型発振回路は、前記電圧制御型発振回路部を構成する発振素子として、水晶振動子、圧電振動子、ＬＣ発振回路のいずれかを使用することを特徴とする。
【０００５】
【発明の実施の形態】
以下、本発明を図面に示した形態例に基づいて詳細に説明する。
図１は本発明による電圧制御型発振回路の一形態例を示すブロック図である。この図に示す電圧制御型発振回路１は、従来から用いられている電圧制御型発振回路部３とこれに供給する周波数制御電圧信号値に所要の修正を施すための線型補償回路２から成り、前記電圧制御型発振回路部３は上述したように制御電圧−発振周波数特性が例えば図２（ｂ）の特性曲線５で示す如く制御電圧が低い領域および高い領域で入力電圧（制御電圧Ｖ _C）の変化率に対する周波数の変化率が小さくなる。また、前記線型補償回路２は前記電圧制御型発振回路本体３の制御電圧−発振周波数特性の被線型部分を補償する電圧変換特性、例えば図２（ａ）の特性曲線４に示す如く入力電圧が低い領域および高い領域において入力電圧の変化率に対する出力電圧の変化率が高くなる電圧変換特性を持っている。入力される制御電圧Ｖ_C は図２（ａ）の破線にて示すもので、これを電圧変換して同図（ａ）実線の特性とし前記電圧制御型発振回路部３に供給する。
【０００６】
このように、この形態例では、線形補償回路２によって、図２（ａ）実線に示す電圧変換特性の制御電圧Ｖ′_C を生成し、これを図２（ｂ）に示す制御電圧−発振周波数特性を持つ電圧制御型発振回路部３に入力すれば、夫々の非直線性回路全体の制御電圧−発振周波数特性を、図２（Ｃ）の特性曲線６に示す如く制御電圧の小さい値から大きな値の広範囲にわたってリニアな制御電圧−発振周波数特性を実現することができる。この結果、制御電圧Ｖ _Cが低領域及び高領域を含み、制御電圧Ｖ _Cの変化に対する発振周波数の変化率を一定にして、リニアリティに優れたダイナミックレンジを拡大することができる。
【０００７】
図３は上述した電圧制御型発振回路１で使用される線形補償回路２の詳細な構成例を示すブロック図である。
この図に示す線形補償回路２は、入力された制御電圧Ｖ_Cに比例した第１制御電流Ｉ₁を生成する第１電圧制御電流源回路７と、前記第１電圧制御電流源回路７の出力電流Ｉ₁に基づいて非線形電圧を発生する第１電流制御非線形素子９と、前記制御電圧Ｖ_Cを入力電圧とし、該入力電圧の傾きの極性を逆にした係数を有する電圧を出力する電圧反転回路１０と、この電圧反転回路１０の出力電圧（Ｖ_K−Ｖ_C）に比例した第２の制御電流Ｉ₂を生成する第２電圧制御電流源回路１１と、該回路の出力電流Ｉ₂に基づいて非線形電圧を発生する第２電流制御非線形素子１２と、前記第１及び第２電流制御非線形素子９、１２の出力電圧の差を出力する引き算回路１３とを含んで構成したものである。
上記構成において最も特徴的な部分は、第１及び第２電流制御非直線素子９及び１２に直線性を有する電流値を供給すると、その入力端子電圧が所望の非直線特性を有するように機能することである。この非直線特性は後述するが、後段の電圧制御型発振部３の非直線特性と対応するもので、結果的に該電圧制御型発振部の非直線歪を補償し、総合的に直線特性を改善するように機能するものである。
前記第１及び第２電流制御非線形素子９と１２は、例えば夫々図４に示すように第１及び第２制御電流Ｉ、Ｉ₂の値が小さい領域においては出力電圧Ｖ_Cの変化が急峻であるが、電流値が大きくなるにつれて出力電圧Ｖ_Cの変化が小さくなるような対数関数的電流／電圧特性を有している。このような関係を得る一つの手段としては、例えばダイオ−ドやトランジスタのべ−ス・エミッタ特性等が利用可能である。
【０００８】
上記のように構成された線形補償回路２では、第１電圧制御電流源回路７において入力された制御電圧Ｖ _Cに比例した電流値の第１制御電流Ｉ₁ を生成し、第１電流制御非線形素子９に供給する。この非線形素子９は図４に示す如く第１制御電流Ｉ₁ を対数関数特性で第１制御電圧Ｖ_C1に変換する。一方、電圧反転回路１０に供給された前記制御電圧Ｖ _Cは、その大小関係を反転され、（Ｖ_K −Ｖ _C）なる電圧値となり、第２電圧制御電流源回路１１によって比例した第２制御電流Ｉ₂ を生成する。この電流Ｉ₂ は第２電流制御非線形素子１２によって図４に示すように対数関数特性的に第２制御電圧Ｖ_C2に変換される。前記２つの非線形素子９、１２の出力、即ち第１制御電圧Ｖ_C1と第２制御電圧Ｖ_C2は引き算回路１３によって減算され、この差電圧を制御電圧Ｖ’_C として出力する。
【０００９】
これにより、入力制御電圧Ｖ _Cの電圧値が小さい領域では、第１電圧制御電流源回路７、第１電流制御非線形素子９によって作出される制御電圧Ｖ_C1を非線形とし、また前記制御電圧Ｖ _Cの電圧値が高い領域では、電圧反転回路１０、第２電圧制御電流源回路１１、第２電流制御非線形素子１２によって作出される制御電圧Ｖ_C2を非線形とする。故にこれらを合成したＶ’_C は図２（ａ）に示すような電圧変換特性を持ったものとなり、この制御電圧Ｖ’_C が前記電圧制御型発振回路本体３に入力される。その結果、図２（ｂ）の特性をもつ電圧制御型発振回路の非直線歪が、それを互いに逆の非直線性となる図２（ａ）の特性に相殺されて同図（ｃ）の如く非直線性が補償されて上記線形補償回路２を構成する第１電圧制御電流源回路７、第１電流制御非線形素子９、第２電圧制御電流源回路１１、第２電流制御非線形素子１２、引き算回路１３としては、例えば図５に示す回路などが使用される。
【００１０】
この図に示す第１電圧制御電流源回路７は、増幅動作を行ない、電流発生素子として機能する第１演算増幅器１５と、一端が第１演算増幅器１５の反転入力端子に接続され他端が接地点に接続され増幅率決定用素子として機能する抵抗１６と、一端が第１演算増幅器１５の反転入力端子に接続され他端が第１演算増幅器１５の出力端子に接続され増幅率決定素子として機能する抵抗１７と、一端が制御電圧決定用の可変抵抗１８に接続され他端が第１演算増幅器１５の非反転入力端子に接続され接地電圧入力用素子として機能する抵抗１９と、一端が第１演算増幅器１５の出力端子に接続され電流値検出素子として機能する抵抗２０と、反転入力端子と出力端子とが接続され非反転入力端子が抵抗２０の他端に接続され電圧バッファとして機能する第２演算増幅器２１と、一端が第２演算増幅器２１の出力端子に接続され他端が第１演算増幅器１５の非反転入力端子に接続され検出電圧入力用素子として機能する抵抗２２とを備えている。
【００１１】
この第１電圧制御電流原回路７は抵抗１９を介して供給される制御電圧Ｖ_C に基づき、制御電圧決定用の可変抵抗１８の抵抗値に応じて電流値の第１制御電流Ｉ₁ を生成し、これを第１電流制御非線形素子９に供給する。
第１電流制御非線形素子９は、コレクタが抵抗２３を介して電源２４の正電極に接続されエミッタが接地点に接続されベースが抵抗２０の他端に接続されるトランジスタ２５によって構成されており、第１電圧制御電流源回路７から出力される第１制御電流Ｉ₁ に応じてベース・エミッタ間電圧（Ｖ_BE）が変化し、このベース・エミッタ間電圧を第１制御電圧Ｖ_C1として引き算回路１３に供給する。この場合、トランジスタ２５のベースに入力されるベース電流の値を横軸にとり、トランジスタ２５のベース・エミッタ間電圧を縦軸にとって両者の関係を図示すると、ベース電流に対して図６の特性曲線２６に示す如くなる。即ち、ベース・エミッタ間電圧が対数関数（Ｌｏｇ関数）特性となることから、第１制御電流Ｉ₁ の電流値が“Ｘ”であるとき、ベ−ス電圧はＬｏｇ（Ｘ）の値の第１制御電圧Ｖ_C1となり、これが引き算回路１３に供給される。
【００１２】
また、第２電圧制御電流源回路１１は増幅動作を行ない電流発生素子として機能する第１演算増幅器２８と、一端が第１演算増幅器２８の反転入力端子に接続され他端が接地点に接続され増幅率決定素子として機能する抵抗２９と、一端が第１演算増幅器２８の反転入力端子に接続され他端が第１演算増幅器２８の出力端子に接続され増幅率決定素子として機能する抵抗３０と、一端が制御電圧決定用の可変抵抗１８と連動して可変される反転制御電圧決定用の可変抵抗３１に接続され他端が第１演算増幅器２８の非反転入力端子に接続され接地電圧入力用素子として機能する抵抗３２と、一端が第１演算増幅器２８の出力端子に接続され電流値検出素子として機能する抵抗３３と、反転入力端子と出力端子とが接続され非反転入力端子が抵抗３３の他端に接続され電圧バッファとして機能する第２演算増幅器３４と、一端が第２演算増幅器３４の出力端子に接続され他端が第１演算増幅器２８の非反転入力端子に接続され検出電圧入力用素子として機能する抵抗３５とを備えている。この第２電圧制御電流源回路１１は抵抗３２を介して供給される反転された制御電圧に基づいて制御電圧決定用の前記可変抵抗１８と連動して調整される可変抵抗３１の抵抗値に応じて電流値の第２制御電流Ｉ₂ を生成し、これを第２電流制御非線形素子１２に供給する。
【００１３】
第２電流制御非線形素子１２は、コレクタが抵抗２３を介して前記電源２４の正電極に接続されエミッタが接地点に接続されベースが抵抗３３の他端に接続されるトランジスタ３６によって構成されており、第２電圧制御電流源回路１１から出力される第２制御電流Ｉ₂ に応じてベース・エミッタ間電圧（Ｖ _BE ）が変化し、このベース・エミッタ間電圧を第２制御電圧Ｖ_C2として、引き算回路１３に供給する。
【００１４】
この場合、第１電流制御非線形素子９と同様に、トランジスタ３６のベースに入力されるベース電流の値を横軸にとり、トランジスタ３６のベース・エミッタ間電圧を縦軸にとって図示すると、図６の特性曲線２６に示す如く、ベース電流に対して、ベース・エミッタ間電圧が対数関数（Ｌｏｇ関数）特性になる。そして、第１制御電流Ｉ₁ に対して、第２制御電流Ｉ₂ の電流値が“Ｋ−Ｘ”となっていることから、定数Ｋが“１”であると仮定すると、第２制御電流Ｉ₂ が特性曲線２７に示す如く第２制御電流Ｉ₂ がＬｏｇ（１−Ｘ）の値を持つ第２制御電圧Ｖ_C2に変換されて、引き算回路１３に供給される。なお、定数Ｋの値を“１”以外の値にしても、特性曲線２７の傾向が同じになることは云うまでもない。
【００１５】
引き算回路１３は、電圧バッファ回路３９と、反転増幅回路４３と、加算回路４９とから構成される。更に、電圧バッファ回路３９は反転入力端子と出力端子とが接続された２つの演算増幅器３７、３８によって構成され、第１、第２電流制御非線形素子９、１２から出力される第１、第２制御電圧Ｖ_C1、Ｖ_C2を各々、バッファリングする。反転増幅回路４３は、非反転入力端子が接地点に接続される１つの演算増幅器４０と、一端が前記演算増幅器４０の反転入力端子に接続され他端が演算増幅器４０の出力端子に接続される帰還用の抵抗４１と、一端が演算増幅器４０の反転入力端子に接続され他端が前記電圧バッファ回路３９を構成する演算増幅器３８の出力端子に接続される入力用の抵抗４２とによって構成され、電圧バッファ回路３９から出力される第２制御電圧Ｖ_C2を反転させる。又、加算回路４９は、増幅動作を行なう演算増幅器４４と、一端が演算増幅器４４の反転入力端子に接続され他端が接地点に接続される増幅率決定用の抵抗４５と、一端が演算増幅器４４の出力端子に接続され他端が演算増幅器４４の反転入力端子に接続される増幅率決定用の抵抗４６と、一端が演算増幅器３７の出力端子に接続され他端が演算増幅器４４の非反転入力端子に接続される入力用の抵抗４７と、一端が演算増幅器４０の出力端子に接続され他端が演算増幅器４４の非反転入力端子に接続される入力用の抵抗４８によって構成され、電圧バッファ回路３９から出力される第１制御電圧Ｖ_C1と前記反転増幅回路４３から出力される反転された第２制御電圧Ｖ_C2とを加算して制御電圧Ｖ’_C を生成する。
【００１６】
この図５に示す回路は電圧バッファ回路３９によって第１、第２電流制御非線形素子９、１２から出力される第１、第２制御電圧Ｖ_C1、Ｖ_C2を電圧バッファリングするとともに、反転増幅回路４３によって第２制御電圧Ｖ_C2を反転した後、加算回路４９によって第１制御電圧Ｖ_C1と、反転済みの第２制御電圧Ｖ_C2とを加算して制御電圧Ｖ’_C を生成し、これを電圧制御型発振回路部３に供給する。
この場合、反転増幅回路４３によって第２制御電圧Ｖ_C2が反転されて図７の特性曲線５０で示す特性にされ、加算回路４９によって図７の特性曲線５１で示される第１制御電圧Ｖ_C1と、前記特性曲線５０で示される第２制御電圧Ｖ_C2とが加算されて図７の特性曲線５２で示される特性、すなわち電圧制御型発振回路部３が有する制御電圧−発振周波数特性の非線形特性を補償して、これをリニアにする特性の制御電圧Ｖ’_C にされ、これが電圧制御型発振回路部３に供給される。
【００１７】
このように、この形態例では、電圧制御型発振回路本体３の制御電圧−発振周波数特性と逆特性となる電圧変換特性を持つ線形補償回路２によって、入力制御電圧Ｖ _Cを電圧変換し、補償した制御電圧Ｖ’_C で電圧制御型発振回路部３の発振周波数を制御するようにしたので、従来非直線のために利用不可能であった制御電圧が小さい領域と大きい領域を含む広い範囲にわたって、制御電圧−発振周波数特性をリニアにすることができる。従って従来の如く制御感度を大きくすることによって生ずる雑音の増加がない。
この際、電圧制御型発振回路部３の各バイアブルキャパシター（バラクタ・ダイオード）の印加電圧−容量特性の非直線を補償するためにトランジスタ２５、３６のベース電流−ベース・エミッタ間電圧の非直線性を利用したが、トランジスタ２５、３６以外の電流制御素子、例えば電流と電圧との関係が対数特性となるダイオードなどを使用して、第１、第２電流制御非線形素子９、１２を構成するようにしても良い。
【００１８】
また、上述した形態例においては、水晶振動子を用いた電圧制御型発振回路部３を例にして本発明による電圧制御型発振回路１を説明したが、水晶振動子以外の周波数制御素子（発振素子）、例えば他の圧電振動子やＬＣ発振回路などを用いた電圧制御型発振回路においても本発明を適用可能である。
また、上述した形態例においては、トランジスタ２５、３６などの電流制御素子が持つ対数特性を利用して、電圧制御型発振回路本体３の制御電圧−発振周波数特性曲線と、逆特性となる電圧変換特性曲線を近似するようにしているが、他の近似方法、例えば理想ダイオード回路を使用した折れ線近似で理想的な電圧変換特性曲線を近似する方法、理想的な電圧変換特性曲線のデータをＲＯＭ回路に記憶させ、制御電圧入力端子に入力された制御電圧Ｖ _CをＡ／Ｄ変換して得られたデータをアドレスデータとして、前記ＲＯＭ回路に記憶させているデータを読み出し、これをＤ／Ａ変換して、制御電圧Ｖ’_C を得る方法などを使用するようにしても良い。
このようにしても、上述した形態例と同様に、広い範囲にわたって、制御電圧−発振周波数特性をリニアにすることができる。
【００１９】
【発明の効果】
以上説明したように本発明によれば、耐雑音を保ちつつ、広い範囲にわたって、制御電圧−発振周波数特性をリニアにすることができる。
【図面の簡単な説明】
【図１】本発明による電圧制御型発振回路の一形態例を示すブロック図である。
【図２】（ａ）（ｂ）及び（ｃ）は図１に示す線形補償回路の電圧変換特性、電圧制御型発振回路本体の制御電圧−発振周波数特性、電圧制御型発振回路の制御電圧−発振周波数特性の一例を示すグラフである。
【図３】図１に示す線形補償回路の詳細な回路構成例を示すブロック図である。
【図４】図３に示す第１、第２電流制御非線形素子の電流−電圧特性例を示すグラフである。
【図５】図３に示す第１電圧制御電流源回路、第１電流制御非線形素子、第２電圧制御電流源回路、第２電流制御非線形素子、引き算回路の詳細な構成例を示す回路図である。
【図６】図５に示す各トランジスタのベース電流と、ベース・エミッタ間電圧との関係例を示すグラフである。
【図７】図５に示す各トランジスタのベース電流と、制御電圧Ｖ’_C との関係例を示すグラフである。
【図８】従来から知られている電圧制御型発振回路の一例を示す回路図である。
【図９】図８に示す電圧制御型発振回路の制御電圧−発振周波数特性例を示すグラフである。
【図１０】図８に示す電圧制御型発振回路の問題点を解決する際に使用される制御電圧−発振周波数特性例を示すグラフである。
【符号の説明】
１…電圧制御型発振回路、３…電圧制御型発振回路本体、４…特性曲線、５…特性曲線、７…第１電圧制御電流源回路、８…電源ライン、９…第１電流制御非線形素子（電流制御素子）、１０…電圧反転回路、１１…第２電圧制御電流源回路、１２…第２電流制御非線形素子（電流制御素子）、１３…引き算回路、１４…特性曲線、１５…第１演算増幅器、１６…抵抗、１７…抵抗、１８…可変抵抗、１９…抵抗、２０…抵抗、２１…第２演算増幅器、２２…抵抗、２３…抵抗、２４…電源、２５…トランジスタ、２６…特性曲線、２７…特性曲線、２８…第１演算増幅器、２９…抵抗、３０…抵抗、３１…可変抵抗、３２…抵抗、３３…抵抗、３４…第２演算増幅器、３５…抵抗、３６…トランジスタ、３７、３８…演算増幅器、３９…電圧バッファ回路、４０…演算増幅器、４１…抵抗、４２…抵抗、４３…反転増幅回路、４４…演算増幅器、４５…抵抗、４６…抵抗、４７…抵抗、４８…抵抗、４９…加算回路、５０…特性曲線、５１…特性曲線、５２…特性曲線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a voltage control type oscillation circuit used in an FM modulation circuit, a phase modulation circuit, a frequency switching circuit of a synthesizer device, and the like, and more particularly, a voltage control type oscillation circuit with improved linear characteristics in the relationship between a control voltage and an oscillation frequency. About.
[0002]
[Prior art]
Conventionally, a circuit shown in FIG. 8 is known as one of voltage controlled oscillation circuits used in an FM modulation circuit, a phase modulation circuit, a frequency switching circuit of a synthesizer device, and the like.
The voltage controlled oscillation circuit 101 shown in this figure includes a crystal resonator 102 for controlling the oscillation frequency, a resistor 103 having one end connected to one end of the crystal resonator 102 and the other terminal connected to a ground point, and an anode A viable capacitor (varactor diode) 104 connected to one end of the crystal unit 102, a resistor 106 having one end connected to the cathode of the viable capacitor 104 and the other end connected to the control voltage input terminal 105, a cathode Is connected to the connection point of the resistor 106 and the viable capacitor 104, the anode is connected to the common input terminal 107, the input terminal is connected to the other end of the crystal unit 102, and the output terminal is a signal output. An amplifier 110 connected to the terminal 109 and a capacitor having one end connected to the other end of the crystal unit 102. The capacitor 111 has one end connected to the other end of the capacitor 111 and the other end connected to the anode of the bipolar capacitor 108, and one end connected to a connection point between the capacitors 111 and 112 and one end of the amplifier 110. The other end is provided with a resistor 113 connected to the anode of the viable capacitor 108. The voltage controlled oscillation circuit configured as described above oscillates by changing the capacitance of each of the bi-directional capacitors 104 and 108 according to the value of the control voltage applied between the control voltage input terminal 105 and the common input terminal 107. The frequency is controlled, and the oscillation signal obtained thereby is output from the signal output terminal 109.
As the variable capacitance element, an inclined junction type bi-directional capacitor or a step junction type bi-directional capacitor is generally used, and the capacitance value thereof changes in inverse proportion to the applied voltage at both ends. As shown, the higher the control voltage applied between the control voltage input terminal 105 and the common input terminal 107, the higher the oscillation frequency output from the signal output terminal 109. Conversely, the lower the control voltage, the higher the oscillation frequency. Decreases.
[0003]
[Problems to be solved by the invention]
However, at this time, the change is saturated and non-linear at both ends of the characteristic curve 114, that is, the portion where the control voltage value is high and the control voltage value is low, and the oscillation frequency hardly changes even if the control voltage is changed. Therefore, when the voltage-controlled oscillation circuit 101 functions as, for example, an AFC circuit (Automatic Frequency Control Circuit), the oscillation frequency cannot be controlled at a portion where the control voltage is low or high. Further, when the voltage controlled oscillation circuit 101 is made to function as an FM modulation circuit, there is a problem that the modulated output waveform of the portion where the modulation signal amplitude is small and the portion where the modulation signal amplitude is large is distorted.
For this reason, when such a voltage-controlled oscillation circuit 101 is incorporated in an AFC circuit or FM modulation circuit, only the portion that can be regarded as a straight line of the characteristic curve 114 shown in FIG. 9 is conventionally used. Such inconvenience does not occur.
However, such a method has a problem that the variable range of the oscillation frequency becomes narrow because there are only a few portions that can be regarded as straight lines of the characteristic curve 114 as shown in FIG.
Therefore, as a method for solving such a problem, control is performed using a bi-directional capacitor having a high-sensitivity characteristic curve 115 having a larger slope than the characteristic curve 116 of the low-sensitivity bi-capacitor as shown in FIG. Although it is also considered to increase the sensitivity and thereby increase the amount of change in the oscillation frequency with respect to the change in the applied voltage, this makes it easier to pick up noise and degrades the S / N, thereby preventing disturbance. There is a problem of weakening. Furthermore, even if it is a straight line part, if it sees in detail, nonlinearity will be included and distortion will be generated similarly.
The present invention has been made in view of the above circumstances, and provides a voltage-controlled oscillation circuit capable of making the control voltage-oscillation frequency characteristics linear over a wide range while maintaining noise resistance. It is aimed.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the voltage controlled oscillation circuit of the present invention is a voltage controlled oscillation circuit that controls the oscillation frequency of the oscillation circuit by varying the reactance of the voltage controlled variable reactance element according to the input control voltage. A voltage-frequency conversion characteristic linear compensation circuit having a non-linear characteristic opposite to the non-linear characteristic in the control voltage-oscillation frequency characteristic of the voltage-controlled oscillation circuit, and the voltage-frequency conversion characteristic The linear compensation circuit includes a first voltage control current source circuit that converts a control voltage into a first control current, and a first control current output from the first voltage control current source circuit in a logarithmic function to the first control voltage. A first current control nonlinear element for conversion; a voltage inverting circuit that outputs a voltage having a coefficient obtained by reversing the polarity of the slope of the input voltage with the control voltage as an input voltage; and an inversion output from the voltage inverting circuit A second voltage controlled current source circuit for converting the control voltage into a second control current, and a second current for logarithmically converting the second control current output from the second voltage controlled current source circuit into a second control voltage A control nonlinear element, and a subtracting circuit that generates a difference voltage between the second control voltage output from the second current control nonlinear element and the first control voltage output from the first current control nonlinear element. It is characterized by.
The voltage controlled oscillation circuit according to the present invention is characterized in that any of a crystal resonator, a piezoelectric resonator, and an LC oscillation circuit is used as an oscillation element constituting the voltage controlled oscillation circuit unit.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on the embodiments shown in the drawings.
FIG. 1 is a block diagram showing an example of a voltage-controlled oscillation circuit according to the present invention. The voltage control type oscillation circuit 1 shown in this figure is composed of a voltage control type oscillation circuit unit 3 used conventionally and a linear compensation circuit 2 for making a necessary correction to the frequency control voltage signal value supplied to the circuit. As described above, the voltage-controlled oscillation circuit unit 3 has an input voltage (control voltage V _C ) in a region where the control voltage is low and high as shown by the characteristic curve 5 in FIG. 2B, for example. The rate of change of frequency with respect to the rate of change of becomes smaller. Further, the linear compensation circuit 2 has a voltage conversion characteristic that compensates for the linear part of the control voltage-oscillation frequency characteristic of the voltage controlled oscillator circuit body 3, for example, an input voltage as shown by a characteristic curve 4 in FIG. It has a voltage conversion characteristic in which the change rate of the output voltage is high with respect to the change rate of the input voltage in the low region and the high region. The input control voltage V _C is indicated by a broken line in FIG. 2A. This voltage is converted to a solid line characteristic in FIG. 2A and supplied to the voltage controlled oscillation circuit unit 3.
[0006]
As described above, in this embodiment, the linear compensation circuit 2 generates the control voltage V ′ _C having the voltage conversion characteristic shown by the solid line in FIG. 2A, which is shown in FIG. 2B as the control voltage-oscillation frequency. If the voltage-controlled oscillation circuit section 3 having the characteristics is input, the control voltage-oscillation frequency characteristics of each nonlinear circuit as a whole are increased from a small value of the control voltage as shown by the characteristic curve 6 in FIG. A linear control voltage-oscillation frequency characteristic can be realized over a wide range of values. As a result, the control voltage V _C includes a low region and a high region, and the change rate of the oscillation frequency with respect to the change of the control voltage V _C can be made constant, so that the dynamic range with excellent linearity can be expanded.
[0007]
FIG. 3 is a block diagram showing a detailed configuration example of the linear compensation circuit 2 used in the voltage-controlled oscillation circuit 1 described above.
The linear compensation circuit 2 shown in this figure includes a first voltage control current source circuit 7 that generates a first control current I ₁ that is proportional to an input control voltage V _C , and an output of the first voltage control current source circuit 7. A first current control nonlinear element 9 that generates a nonlinear voltage based on the current I ₁ , and a voltage inversion that outputs a voltage having a coefficient in which the polarity of the slope of the input voltage is reversed with the control voltage V _C as an input voltage a circuit 10, and the second control current I ₂ second voltage control current source circuit 11 for generating proportional to the output voltage (V _K -V _C) of the voltage inverter circuit 10, the output current I ₂ of the circuit This includes a second current control nonlinear element 12 that generates a nonlinear voltage based on it, and a subtraction circuit 13 that outputs the difference between the output voltages of the first and second current control nonlinear elements 9 and 12.
The most characteristic part in the above configuration is that when a linear current value is supplied to the first and second current control nonlinear elements 9 and 12, the input terminal voltage functions so as to have a desired nonlinear characteristic. That is. Although this non-linear characteristic will be described later, it corresponds to the non-linear characteristic of the voltage controlled oscillator 3 in the subsequent stage. As a result, the non-linear distortion of the voltage controlled oscillator 3 is compensated, and the linear characteristic is comprehensively obtained. It works to improve.
In the first and second current control nonlinear elements 9 and 12, for example, as shown in FIG. 4, the change of the output voltage V _C is steep in the region where the values of the first and second control currents I and I ₂ are small. However, it has a logarithmic current / voltage characteristic in which the change in the output voltage V _C decreases as the current value increases. As one means for obtaining such a relationship, for example, a diode or a base / emitter characteristic of a transistor can be used.
[0008]
In the linear compensation circuit 2 configured as described above, a first control current I ₁ having a current value proportional to the control voltage V _C input in the first voltage control current source circuit 7 is generated, and the first current control nonlinearity is generated. Supply to the element 9. As shown in FIG. 4, the non-linear element 9 converts the first control current I ₁ into a first control voltage V _C1 with logarithmic function characteristics. On the other hand, the control voltage V _C supplied to the voltage inverting circuit 10 is inverted in its magnitude relationship, becomes a voltage value of (V _K −V _C ), and is proportional to the second control by the second voltage control current source circuit 11. A current I ₂ is generated. This current I ₂ is converted by the second current control nonlinear element 12 into the second control voltage V _C2 in a logarithmic function characteristic as shown in FIG. The outputs of the two non-linear elements 9 and 12, that is, the first control voltage V _C1 and the second control voltage V _C2 are subtracted by the subtraction circuit 13, and the difference voltage is output as the control voltage V ′ _C.
[0009]
As a result, in the region where the voltage value of the input control voltage V _C is small, the control voltage V _C1 generated by the first voltage control current source circuit 7 and the first current control nonlinear element 9 is made nonlinear, and the control voltage V _C In the region where the voltage value is high, the control voltage V _C2 generated by the voltage inverting circuit 10, the second voltage control current source circuit 11, and the second current control nonlinear element 12 is nonlinear. Therefore, V ′ _C obtained by synthesizing these has voltage conversion characteristics as shown in FIG. 2A, and this control voltage V ′ _C is input to the voltage-controlled oscillation circuit body 3. As a result, the non-linear distortion of the voltage controlled oscillation circuit having the characteristics shown in FIG. 2B is offset by the characteristics shown in FIG. The first voltage control current source circuit 7, the first current control nonlinear element 9, the second voltage control current source circuit 11, the second current control nonlinear element 12, and the like, which constitute the linear compensation circuit 2 with the nonlinearity compensated as described above. As the subtraction circuit 13, for example, a circuit shown in FIG.
[0010]
The first voltage controlled current source circuit 7 shown in this figure performs an amplification operation, and has a first operational amplifier 15 that functions as a current generating element, one end connected to the inverting input terminal of the first operational amplifier 15 and the other end connected. A resistor 16 connected to the point and functioning as an amplification factor determining element, and one end connected to the inverting input terminal of the first operational amplifier 15 and the other end connected to the output terminal of the first operational amplifier 15 to function as an amplification factor determining element And a resistor 19 having one end connected to the variable resistor 18 for determining the control voltage and the other end connected to the non-inverting input terminal of the first operational amplifier 15 and functioning as a ground voltage input element. A resistor 20 connected to the output terminal of the operational amplifier 15 and functioning as a current value detecting element, an inverting input terminal and an output terminal are connected, and a non-inverting input terminal is connected to the other end of the resistor 20 to function as a voltage buffer. And a resistor 22 having one end connected to the output terminal of the second operational amplifier 21 and the other end connected to the non-inverting input terminal of the first operational amplifier 15 and functioning as a detection voltage input element. ing.
[0011]
The first voltage control current source circuit 7 generates a first control current I ₁ having a current value according to the resistance value of the variable resistor 18 for determining the control voltage based on the control voltage V _C supplied through the resistor 19. This is supplied to the first current control nonlinear element 9.
The first current control nonlinear element 9 includes a transistor 25 having a collector connected to the positive electrode of the power supply 24 via a resistor 23, an emitter connected to a ground point, and a base connected to the other end of the resistor 20. The base-emitter voltage (V _BE ) changes according to the first control current I ₁ output from the first voltage-controlled current source circuit 7, and this base-emitter voltage is used as the first control voltage V _C1 as a subtraction circuit. 13 is supplied. In this case, when the value of the base current input to the base of the transistor 25 is taken on the horizontal axis and the base-emitter voltage of the transistor 25 is taken on the vertical axis, the relationship between the two is illustrated. The characteristic curve 26 of FIG. As shown in That is, since the base-emitter voltage has a logarithmic function (Log function) characteristic, when the current value of the first control current I ₁ is “X”, the base voltage is the Log (X) value. 1 control voltage V _C1 , which is supplied to the subtraction circuit 13.
[0012]
The second voltage controlled current source circuit 11 performs an amplifying operation and functions as a current generating element, and one end is connected to the inverting input terminal of the first operational amplifier 28 and the other end is connected to the grounding point. A resistor 29 functioning as an amplification factor determining element; a resistor 30 having one end connected to the inverting input terminal of the first operational amplifier 28 and the other end connected to the output terminal of the first operational amplifier 28; One end is connected to an inversion control voltage determining variable resistor 31 that is variable in conjunction with the control voltage determining variable resistor 18, and the other end is connected to a non-inverting input terminal of the first operational amplifier 28 to be connected to a ground voltage input element. A resistor 32 that functions as a current value detecting element with one end connected to the output terminal of the first operational amplifier 28, an inverting input terminal and an output terminal, and a non-inverting input terminal serving as a resistor. A second operational amplifier 34 connected to the other end of 33 and functioning as a voltage buffer; one end connected to the output terminal of the second operational amplifier 34; the other end connected to the non-inverting input terminal of the first operational amplifier 28; And a resistor 35 functioning as an input element. This second voltage controlled current source circuit 11 is responsive to the resistance value of the variable resistor 31 adjusted in conjunction with the variable resistor 18 for determining the control voltage based on the inverted control voltage supplied through the resistor 32. The second control current I ₂ having a current value is generated and supplied to the second current control nonlinear element 12.
[0013]
The second current control nonlinear element 12 includes a transistor 36 having a collector connected to the positive electrode of the power supply 24 via a resistor 23, an emitter connected to a ground point, and a base connected to the other end of the resistor 33. The base-emitter voltage (V _BE ) changes according to the second control current I ₂ output from the second voltage control current source circuit 11, and this base-emitter voltage is set as the second control voltage V _C2 . This is supplied to the subtraction circuit 13.
[0014]
In this case, similarly to the first current control nonlinear element 9, the value of the base current input to the base of the transistor 36 is plotted on the horizontal axis, and the base-emitter voltage of the transistor 36 is plotted on the vertical axis. As shown by the curve 26, the base-emitter voltage has a logarithmic function (Log function) characteristic with respect to the base current. Since the current value of the second control current I ₂ is “K−X” with respect to the first control current I ₁ , assuming that the constant K is “1”, the second control current I 2 second control current I ₂ is converted to the second control voltage V _C2 having a value of Log (1-X) as I ₂ is shown by the characteristic curve 27, it is supplied to the subtraction circuit 13. It goes without saying that even if the value of the constant K is a value other than “1”, the tendency of the characteristic curve 27 is the same.
[0015]
The subtraction circuit 13 includes a voltage buffer circuit 39, an inverting amplification circuit 43, and an addition circuit 49. Further, the voltage buffer circuit 39 is constituted by two operational amplifiers 37 and 38 having an inverting input terminal and an output terminal connected, and the first and second current control nonlinear elements 9 and 12 output from the first and second current control nonlinear elements 9 and 12. The control voltages V _C1 and V _C2 are respectively buffered. The inverting amplifier circuit 43 has one operational amplifier 40 whose non-inverting input terminal is connected to the ground point, one end connected to the inverting input terminal of the operational amplifier 40, and the other end connected to the output terminal of the operational amplifier 40. A feedback resistor 41, and an input resistor 42 having one end connected to the inverting input terminal of the operational amplifier 40 and the other end connected to the output terminal of the operational amplifier 38 constituting the voltage buffer circuit 39; The second control voltage V _C2 output from the voltage buffer circuit 39 is inverted. The adder circuit 49 includes an operational amplifier 44 for performing an amplification operation, an amplification factor determining resistor 45 having one end connected to the inverting input terminal of the operational amplifier 44 and the other end connected to a ground point, and one end an operational amplifier. A gain determining resistor 46 connected to the output terminal 44 and the other end connected to the inverting input terminal of the operational amplifier 44, and one end connected to the output terminal of the operational amplifier 37 and the other end non-inverted of the operational amplifier 44. An input resistor 47 connected to the input terminal, an input resistor 48 having one end connected to the output terminal of the operational amplifier 40 and the other end connected to the non-inverting input terminal of the operational amplifier 44, and a voltage buffer The control voltage V ′ _C is generated by adding the first control voltage V _C1 output from the circuit 39 and the inverted second control voltage V _C2 output from the inverting amplifier circuit 43.
[0016]
The circuit shown in FIG. 5 voltage-buffers the first and second control voltages V _C1 and V _C2 output from the first and second current control nonlinear elements 9 and 12 by the voltage buffer circuit 39 and also uses an inverting amplifier circuit. 43, after the second control voltage V _C2 is inverted, the addition circuit 49 adds the first control voltage V _C1 and the inverted second control voltage V _C2 to generate the control voltage V ′ _C , The voltage control type oscillation circuit unit 3 is supplied.
In this case, the second control voltage V _C2 is inverted by the inverting amplifier circuit 43 to have the characteristic indicated by the characteristic curve 50 in FIG. 7, and the first control voltage V _C1 indicated by the characteristic curve 51 in FIG. The second control voltage V _C2 indicated by the characteristic curve 50 is added to obtain the characteristic indicated by the characteristic curve 52 in FIG. 7, that is, the nonlinear characteristic of the control voltage-oscillation frequency characteristic possessed by the voltage controlled oscillation circuit unit 3. The control voltage V ′ _C is compensated to make it linear, and is supplied to the voltage controlled oscillation circuit unit 3.
[0017]
As described above, in this embodiment, the input compensation voltage V _C is converted into a voltage by the linear compensation circuit 2 having a voltage conversion characteristic that is opposite to the control voltage-oscillation frequency characteristic of the voltage controlled oscillator circuit body 3 to compensate the voltage. Since the oscillation frequency of the voltage-controlled oscillation circuit unit 3 is controlled by the control voltage V ′ _C , the control voltage V ′ _C can be controlled over a wide range including a region where the control voltage is low and a region that is conventionally unusable due to nonlinearity. The control voltage-oscillation frequency characteristic can be made linear. Therefore, there is no increase in noise caused by increasing the control sensitivity as in the prior art.
At this time, in order to compensate for the non-linearity of the applied voltage-capacitance characteristics of each of the variable capacitors (varactor diodes) of the voltage controlled oscillation circuit unit 3, the non-linearity of the base current-base-emitter voltage of the transistors 25, 36 The first and second current control nonlinear elements 9 and 12 are configured using current control elements other than the transistors 25 and 36, such as a diode having a logarithmic relationship between the current and the voltage. You may do it.
[0018]
Further, in the above-described embodiment, the voltage control type oscillation circuit 1 according to the present invention has been described by taking the voltage control type oscillation circuit unit 3 using a crystal unit as an example. The present invention can also be applied to a voltage-controlled oscillation circuit using an element), for example, another piezoelectric vibrator or an LC oscillation circuit.
Further, in the above-described embodiment, the voltage conversion having the inverse characteristic with the control voltage-oscillation frequency characteristic curve of the voltage-controlled oscillation circuit body 3 using the logarithmic characteristic of the current control elements such as the transistors 25 and 36 is used. Although the characteristic curve is approximated, other approximation methods, for example, a method of approximating an ideal voltage conversion characteristic curve by a polygonal line approximation using an ideal diode circuit, and data of an ideal voltage conversion characteristic curve are stored in a ROM circuit The data obtained by A / D conversion of the control voltage V _C input to the control voltage input terminal is read as address data, and the data stored in the ROM circuit is read and converted to D / A conversion. Then, a method of obtaining the control voltage V ′ _C may be used.
Even in this case, the control voltage-oscillation frequency characteristic can be made linear over a wide range as in the above-described embodiment.
[0019]
【The invention's effect】
As described above, according to the present invention, the control voltage-oscillation frequency characteristic can be made linear over a wide range while maintaining noise resistance.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an example of a voltage-controlled oscillation circuit according to the present invention.
2 (a), (b) and (c) are voltage conversion characteristics of the linear compensation circuit shown in FIG. 1, control voltage-oscillation frequency characteristics of the voltage-controlled oscillation circuit body, and control voltage of the voltage-controlled oscillation circuit; It is a graph which shows an example of an oscillation frequency characteristic.
FIG. 3 is a block diagram showing a detailed circuit configuration example of the linear compensation circuit shown in FIG. 1;
4 is a graph showing an example of current-voltage characteristics of the first and second current control nonlinear elements shown in FIG. 3;
5 is a circuit diagram showing a detailed configuration example of a first voltage controlled current source circuit, a first current controlled nonlinear element, a second voltage controlled current source circuit, a second current controlled nonlinear element, and a subtracting circuit shown in FIG. 3; is there.
6 is a graph showing an example of the relationship between the base current of each transistor shown in FIG. 5 and the base-emitter voltage.
7 is a graph showing an example of the relationship between the base current of each transistor shown in FIG. 5 and the control voltage V ′ _C.
FIG. 8 is a circuit diagram showing an example of a conventionally known voltage-controlled oscillation circuit.
9 is a graph showing an example of control voltage-oscillation frequency characteristics of the voltage controlled oscillation circuit shown in FIG. 8;
10 is a graph showing an example of control voltage-oscillation frequency characteristics used when solving the problem of the voltage controlled oscillation circuit shown in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Voltage controlled oscillation circuit, 3 ... Voltage controlled oscillation circuit main body, 4 ... Characteristic curve, 5 ... Characteristic curve, 7 ... 1st voltage controlled current source circuit, 8 ... Power supply line, 9 ... 1st current controlled nonlinear element (Current control element) 10 ... Voltage inverting circuit, 11 ... Second voltage control current source circuit, 12 ... Second current control nonlinear element (current control element), 13 ... Subtraction circuit, 14 ... Characteristic curve, 15 ... First Operational amplifier 16 ... resistor 17 ... resistor 18 ... variable resistor 19 ... resistor 20 ... resistor 21 ... second operational amplifier 22 ... resistor 23 ... resistor 24 ... power source 25 ... transistor 26 ... characteristic Curve, 27 ... characteristic curve, 28 ... first operational amplifier, 29 ... resistor, 30 ... resistor, 31 ... variable resistor, 32 ... resistor, 33 ... resistor, 34 ... second operational amplifier, 35 ... resistor, 36 ... transistor, 37, 38 ... operational amplifiers, 39 ... electric Buffer circuit 40 ... Operational amplifier 41 ... Resistor 42 ... Resistor 43 ... Inverting amplifier circuit 44 ... Operational amplifier 45 ... Resistor 46 ... Resistor 47 ... Resistor 48 ... Resistor 49 ... Adder circuit 50 ... Characteristic curve 51 ... Characteristic curve 52 ... Characteristic curve

Claims

A voltage-controlled oscillation circuit unit that controls the oscillation frequency of the oscillation circuit by varying the reactance of the voltage-controlled variable reactance element according to the input control voltage, and the control voltage-oscillation frequency characteristic of the voltage-controlled oscillation circuit A voltage-frequency conversion characteristic linear compensation circuit having a non-linear characteristic opposite to the non-linear characteristic in
The voltage-frequency conversion characteristic linear compensation circuit includes a first voltage control current source circuit that converts a control voltage into a first control current, and a first control current output from the first voltage control current source circuit in a logarithmic manner. A first current control nonlinear element that converts the first control voltage into a first control voltage, a voltage inverting circuit that uses the control voltage as an input voltage, and outputs a voltage having a coefficient that reverses the polarity of the slope of the input voltage, and the voltage inversion A second voltage control current source circuit that converts the inverted control voltage output from the circuit into a second control current, and a second control voltage that is logarithmically converted to the second control current output from the second voltage control current source circuit. A second current control nonlinear element to be converted into a voltage, and a difference voltage between the second control voltage output from the second current control nonlinear element and the first control voltage output from the first current control nonlinear element A subtraction circuit, Voltage-controlled oscillator according to claim and.

2. The voltage controlled oscillation circuit according to claim 1, wherein any one of a crystal resonator, a piezoelectric resonator, and an LC oscillation circuit is used as an oscillation element constituting the voltage controlled oscillation circuit unit. Control type oscillation circuit.