JP3912896B2

JP3912896B2 - Receiving apparatus and receiving method

Info

Publication number: JP3912896B2
Application number: JP11283198A
Authority: JP
Inventors: 崇夫藤田
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1998-04-09
Filing date: 1998-04-09
Publication date: 2007-05-09
Anticipated expiration: 2018-04-09
Also published as: JPH11298376A

Description

【０００１】
【発明の属する技術分野】
本発明は、スペクトラム拡散変調信号を復調可能な受信装置に関し、特に受信信号を増幅する際のＡＧＣ（ＡｕｔｏｍａｔｉｃＧａｉｎＣｏｎｔｒｏｌ：自動利得制御）技術に関する。
【０００２】
【従来の技術】
現在、セルラー電話などで次世代の通信方式としてＣＤＭＡ（ＣｏｄｅＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅＡｃｃｅｓｓ）が注目されている。このＣＤＭＡ方式は基本技術としてスペクトラム拡散の技術を応用している。送信側に於いて擬似雑音系列符号（拡散コード）による拡散変調を行い、受信側に於いて送信側で使用したものと同一の符号を使って逆拡散復調を行うことにより通信データを再生する。この拡散コードとしては、お互いに直交する（すなわち、２つの信号を乗積して積分した結果がゼロになる）複数の符号の組み合わせを使うことができる。この複数組の直交した符号を利用して、例えば基地局からはこの複数組の直交符号をそれぞれ通信する複数の移動局に割り振り、これら各組の符号で拡散変調した信号を多重化して同時に送信する。そして、各移動局では、受信を希望する信号に対応する符号を使用して逆拡散することにより、多重化された信号の中から所望の信号のみを取り出すことが可能となる。
【０００３】
このように、スペクトラム拡散通信の受信処理においては、送信側と同一の符号により逆拡散処理を行うが、この逆拡散処理にはマッチトフィルタや、スライディング相関器などの相関演算器が使われる。この相関演算器による受信信号の相関信号は、図４に示すようなものとなり、この信号波形のピーク（相関ピーク）から伝送データを再生する。なお、この相関ピークのレベルは相関演算器に入力される受信信号のレベルの比例する。
【０００４】
従来の受信装置の例を図２、図３に示す。従来、図２の例では、直交復調器４によりＩ成分とＱ成分に分離した信号Ｉ1，Ｑ1をＡ／Ｄ変換した後、ＩとＱの二乗和を求めることにより受信電力値を得て、この結果を用いてＡＧＣ制御部にてＶＧＡ（ＶａｒｉａｂｌｅＧａｉｎＡｍｐｌｉｆｉｅｒ：利得可変増幅器）３の利得を制御することにより、Ａ／Ｄ変換器５に入力される信号レベルを無線伝搬の変動によらない一定値とする。
【０００５】
また、図３の例では、スペクトラム拡散変調処理時に使用された複数の拡散コードのうち、受信を希望する信号に対応する拡散コードで相関演算を実行する。その結果、図４に示す波形の相関ピークを得て、その相関ピークのレベルに応じてＡＧＣを行うことにより、所望の信号成分に対して精度よく利得を制御することが可能となる。
【０００６】
【発明が解決しようとする課題】
しかし、図２の例では、ＡＧＣのフィードバック制御はＡ／Ｄ変換器５のサンプルレート（このサンプルレートは、通常、ＣＤＭＡ方式では、チップレート、すなわち拡散信号の周波数の２倍以上）でサンプルされ、その各々について電力演算を実行するため、入力信号の変動に対して高速に追従できる高速なＡＧＣを実現できる。反面、基地局から各移動機へ送られてくる多重化された信号、および隣のセルの基地局からの信号など、全ての妨害波を含めた信号の全体の電力に対してＡＧＣを行うため、復調すべき信号成分に対するＡＧＣ精度は望めない。
【０００７】
一方、図３の例では、復調すべき受信信号の自己相関成分をマッチトフィルタ等による相関演算器６で取り出し、その相関ピーク信号の信号レベルに基づいてＡＧＣ制御をかけるため、図２の例に比較して所望の信号成分に対するＡＧＣ精度は良いため後段の復調特性の劣化を低減できるが、相関ピークはコード発生器１１で発生される拡散コードの１周期に１回しか発生しないため、ＡＧＣ制御部８に入力される信号が時間的に間引かれたものとなり、ＡＧＣの応答は遅くなる。
【０００８】
また、相関ピークのレベルが最大受信感度を下回るほど低下した場合を考えると、このときには相関ピークは検出されず、相関演算器６の出力は他の拡散コードにより拡散された信号からの相互相関などのノイズとなり、この時のＡＧＣは、このノイズが所定のしきい値に達するようにＶＧＡ３の利得（ゲイン）を調整する。
【０００９】
通常、自己相関のない信号による相関演算器６からの出力は小さいため、しきい値を超えるまでＶＧＡ３のゲインをあげると、その前段のＲＦ部２は総電力波形により動作しているため、信号レベルが結果的に上がり、アナログ回路であるＲＦ部２とＶＧＡ３は飽和領域に入る。この状態から受信感度範囲内のレベルの信号が入ってくると、その飽和したアナログ回路は飽和状態からの復帰動作となり、復帰に通常の応答以上の長い時間を要する。
【００１０】
本発明は、このような背景の下になされたもので、その課題は、受信したスペクトラム拡散信号を増幅する際の自動利得制御を高速、且つ高精度に行えるようにすることにある。
【００１１】
【課題を解決するための手段】
上記課題を解決するため、本発明は、スペクトラム拡散変調信号を復調可能な受信装置において、受信に係るスペクトラム拡散変調信号を利得を変更可能に増幅する可変利得増幅手段と、前記可変利得増幅手段により増幅されたスペクトラム拡散変調信号を直交復調する直交復調手段と、前記直交復調手段により直交復調された２つの直交復調信号に対して拡散コードにより相関演算を行うことにより逆拡散を行う相関演算手段と、前記直交復調手段により直交復調された２つの直交復調信号から受信電力を演算する電力演算手段と、前記相関演算手段により相関演算されて出力された相関ピーク信号に基づいて受信に係るスペクトラム拡散変調信号の信号レベルを検出する相関レベル検出手段と、前記電力演算手段と相関レベル検出手段の処理結果に基づいて前記可変利得増幅手段の利得を制御する利得制御手段とを備え、前記利得制御手段は、前記相関レベル検出手段の処理結果に基づいて前記可変利得増幅手段の利得を制御した結果、前記スペクトラム拡散変調信号の信号レベルが予め設定された誤差範囲を逸脱した場合には、前記電力演算手段の処理結果に基づく前記可変利得増幅手段の利得制御に切り換えるように構成されている。
【００１２】
また、本発明は、スペクトラム拡散変調信号を受信する受信方法において、受信に係るスペクトラム拡散変調信号を可変利得増幅手段により利得を変更可能に増幅する可変利得増幅工程と、前記可変利得増幅工程により増幅されたスペクトラム拡散変調信号を直交復調する直交復調工程と、前記直交復調工程により直交復調された２つの直交復調信号に対して拡散コードにより相関演算を行うことにより逆拡散を行う相関演算工程と、
前記直交復調工程により直交復調された２つの直交復調信号から受信電力を演算する電力演算工程と、前記相関演算工程により相関演算されて出力された相関ピーク信号に基づいて受信に係るスペクトラム拡散変調信号の信号レベルを検出する相関レベル検出工程と、
前記電力演算工程と相関レベル検出工程の処理結果に基づいて前記可変利得増幅手段の利得を制御する利得制御工程とを備え、前記利得制御工程は、前記相関レベル検出工程の処理結果に基づいて前記可変利得増幅手段の利得を制御した結果、前記スペクトラム拡散変調信号の信号レベルが予め設定された誤差範囲を逸脱した場合には、前記電力演算工程の処理結果に基づく前記可変利得増幅手段の利得制御に切り換えるように構成されている。
【００１８】
【発明の実施の形態】
以下、本発明の実施の形態を図面を参照しながら説明する。
【００１９】
図１は、本発明の実施の形態に係る受信装置の概略構成を示すブロック図であり、本装置は、受信したスペクトラム拡散変調信号を復調可能に構成され、アンテナ１、ＲＦ部２、ＶＧＡ（利得可変増幅器）３、直交復調器４、Ａ／Ｄ変換器５、相関演算器６、検波器７、ＡＧＣ制御部８、電力演算部９、相関レベル検出部１０、およびコード発生器１１を有している。
【００２０】
ＲＦ部２は、アンテナ１で受信した高周波の無線信号をダウンコンバートする等のアナログ処理を行い、次段のＶＧＡ３の入力形態に適合する信号として入力する。アンテナ１とＲＦ部２の利得は常に一定であるため、ＲＦ部２から出力される信号レベルはアンテナ１から受信された受信信号レベルに比例したレベルとなり、電波の伝搬状況の変化によりレベルは大きく変動する。ＶＧＡ３は、外部からの利得制御信号により利得を変える機能を持つ利得可変増幅器であり、ＶＧＡ３の利得は、ＡＧＣ制御部８により受信信号レベルに応じて制御される。
【００２１】
ＣＤＭＡ方式では、受信信号は互いに直交するＩ成分とＱ成分を含む形で直交変調されている。そこで、直交復調器４は、ＶＧＡ３を含む一連のＡＧＣループでレベルが一定となった受信信号の中から２つの直交成分を分離することにより復調し、信号Ｉ1とＱ1を出力する。この直交復調器４からの出力信号Ｉ1、Ｑ1は、それぞれＡ／Ｄコンバータ５によりディジタル値に変換され、ディジタル信号Ｉ2、Ｑ2として相関演算器６、および電力演算部９に出力される。ただし、このディジタル信号Ｉ2、Ｑ2は、送信時のスペクトラム拡散変調処理に使用された全ての拡散コードに対応する成分を含んでいる。
【００２２】
相関演算器６では、コード発生器１１から発生される所望の信号に対応する拡散コードに基づいて信号Ｉ2、Ｑ2について相関演算を行うことにより逆拡散を行い、２つの相関ピーク信号（相関値）Ｉ3、Ｑ3を検波器７、相関レベル検出部１０に出力する。この２つの相関ピーク信号Ｉ3、Ｑ3は、所望の信号のみに対応するものとなっている。従って、検波器７により、相関ピーク信号Ｉ3、Ｑ3に対して検波処理を行うことにより、所望の通信データＩ4、Ｑ4が復元される。
【００２３】
次に、ＡＧＣについて、詳細に説明する。
【００２４】
Ａ／Ｄコンバータ５の出力であるＩ2、Ｑ2の２つの信号から、（Ｉ²＋Ｑ²）の演算を実行すると、アンテナ１からコンバータ５までの信号の流れで受信された信号の全エネルギーに比例した信号を得ることができる。このエネルギーレベル信号を利用してＶＧＡ３の利得を制御することにより、信号Ｉ1とＱ1の信号レベルをアンテナ１にて受信された信号レベルに関係なく一定にすることが可能となる。
【００２５】
図１の例では、信号１2，Ｑ2を電力演算部９により、（Ｉ²＋Ｑ²）に相当する演算を行って総受信電力値を求める。その総電力演算値によりＡＧＣ制御部８にてＶＧＡ３を制御して、ｌ1、Ｑ1を総受信電力値に対して一定となるように制御する。以下、このＡＧＣループを電力演算によるＡＧＣと呼ぶ。
【００２６】
電力演算によるＡＧＣは、ディジタル信号I2、Ｑ2がチップレート（拡散変調信号の周波数）の２倍程度の高速なレートで出力するため、高速な応答のＡＧＣを形成することが可能になる。しかし、ＣＤＭＡ方式においては、受信信号には、本受信装置が受信したい信号、すなわち本受信装置の使用している拡散コードでスペクトラム拡散変調された信号以外に、他の受信装置に対応する別の拡散コードでスペクトラム拡散変調された信号や隣接セルの基地局からの信号など、本受信装置にとってはノイズとなる成分も含まれている。そのため、本受信装置では、それら全ての成分が加わった信号として受信する。
【００２７】
相関演算器６より前の回路では、上記ノイズ成分を含む信号から、本受信装置で受信を所望する信号成分のみを分離することはできないので、信号I2、Ｑ2は、やはり本受信装置が所望する信号成分以外のノイズ成分を含むこととなる。従って、電力演算部９により演算される受信電力値は、このノイズ成分を含む総受信電力値となる。その結果、ＡＧＣ制御部８により、この総受信電力値を使用してＶＧＡ３の利得を制御したとしても、その制御は、総受信電力を一定とするものとなり、本受信装置が所望する信号以外のノイズ成分の状態により、相関演算器６から出力される相関レベルは変化することになる。これにより、後段の検波部７へ出力する相関ピーク信号のレベルがばらつき、検波処理の精度に影響を与える。
【００２８】
そこで、本受信装置では、上記の問題を解決すべく、電力演算によるＡＧＣを行うと共に、以下に説明するように、相関レベル検出部１０の出力結果をも利用してＡＧＣを行っている。
【００２９】
すなわち、相関演算器６では、複数の拡散コードに基づいてスペクトラム拡散変調されて多重化された受信信号の中から、所望の信号を検出するために、所望の信号のスペクトラム拡散変調に使用された拡散コードをコード発生器１１から得て、その所望信号に対応する拡散コードに基づいて相関演算を行い、相関ピーク信号（相関値）Ｉ3、Ｑ3を出力する。この相関ピーク信号Ｉ3、Ｑ3の信号レベルは、所望信号のレベルにのみ比例している。そこで、相関レベル検出部１０では、相関ピークＩ3、Ｑ3のレベル値をＩ，Ｑ成分それぞれについて求める。そして、ＡＧＣ制御部８では、この相関ピークＩ3、Ｑ3のレベル値に基づいてＶＧＡ３の利得を制御することにより、受信信号のうち、所望の信号成分に対応する相関ピーク信号Ｉ3、Ｑ3の信号レベルが一定となるようにする。以下、このＡＧＣループを相関レベルによるＡＧＣと呼ぶ。
【００３０】
しかし、この相関レベルによるＡＧＣでは、相関演算器６による相関ピーク信号の検出が拡散コードの１周期に１つとなるため、時間的にはレートの低い出力しか得られない。そのために、ＡＧＣの応答としては遅いものとなるため、ＡＧＣで制御された出力値が期待するレベルに安定するまでの時間を要する。そこで、ＡＧＣ制御部８は、以下に説明するように、電力演算部９からの総受信電力の信号と、相関レベル検出部１０からの所望の受信信号の信号レベル値の両方を利用してＶＧＡ３を制御する。
【００３１】
すなわち、初期状態を本受信装置が信号をなにも受信していない状態とすると、初期状態では電力演算部９も、相関レベル検出部１０も出力する信号は非常に低いレベルとなるため、ＡＧＣ制御部８はＶＧＡ３の利得を最大として、無線信号の到来を待っている。この状態から本受信装置が送信機からの送信信号を受信すると、応答の早い電力演算部９からの総受信電力値が出力されるまでの過渡状態では、ＶＧＡ３およびＲＦ部２は増幅率が最大となっているため飽和状態となる。
【００３２】
電力演算部９からの出力が入力の飽和に応答して上昇するに従い、ＡＧＣ制御部８はＶＧＡ３の利得を落とすことにより、信号Ｉ2、Ｑ2における総受信電力レベルを一定とする。この最終安定値に対して予め設定された誤差範囲に到達した段階で、ＡＧＣ制御部８は制御ループを相関レベルによるＡＧＣに切り替える。
【００３３】
相関レベルによるＡＧＣでは、総受信電力のうち、コード発生器１１から発生された拡散コードと相関のある信号成分、すなわち本受信装置で受信を所望する信号成分の相関レベルのみに基づいてＡＧＣをかけるため、Ｉ3、Ｑ3では所望の信号成分Ｉ3、Ｑ3を一定とすることが可能となる。
【００３４】
この相関レベルによるＡＧＣを行った場合のＶＧＡ３の利得安定レベルと、先の受信電力によるＡＧＣを行った場合のＶＧＡ３の利得安定レベルとは異なる。従って、相関レベルによるＡＧＣの結果、受信電力によるＡＧＣの予め設定された誤差範囲を超えてしまうことも考えられるが、ＡＧＣ制御部８は、この状態ではそのまま相関レベルによるＡＧＣによる制御を継続する。そして、相関レベルによるＡＧＣについても別途、誤差範囲を予め設定しておき、この誤差範囲を超えた場合にのみ、受信電力によるＡＧＣに移行するようにしている。
【００３５】
このように、ペクトラム拡散変調信号を受信した初期の段階では電力演算部９にて演算された受信信号の電力に基づいてＶＧＡ３の利得を制御し、この制御により受信電力が或る程度安定した後に相関レベル検出部１０により検出された相関ピーク信号の信号レベルに基づいてＶＧＡ３の利得を制御することにより、受信信号レベルが大きく変化した場合の応答が相関レベルのみを利用した場合と比較して高速になり、また受信信号レベルが瞬時に大きな変化をした場合の飽和状態からの復帰が高速となる。さらに、安定時には相関レベルによる自動利得制御となるため、所望の信号成分にのみ注目した制御が可能となり、高精度な自動利得制御が可能となる。すなわち、自動利得制御において高速性と高精度性とを両立することができる。
【００３６】
なお、上記説明では、スペクトラム拡散変調時に使用される拡散コード系列については言及していないが、本発明は、この拡散コード系列として、Ｍ系列（ＭａｘｉｍａｍＬｅｎｇｔｈＣｏｄｅ）、Ｇｏｌｄ符号系列等の各種のＰＮ系列（ＰｓｅｕｄｏｒａｎｄａｍＮｏｉｓｅ）等を使用した場合にも適用することができる。
【００３７】
【発明の効果】
以上説明したように、本発明によれば、スペクトラム拡散変調信号を復調可能な受信装置において、受信に係るスペクトラム拡散変調信号を利得を変更可能に増幅する可変利得増幅手段と、前記可変利得増幅手段により増幅されたスペクトラム拡散変調信号を直交復調する直交復調手段と、前記直交復調手段により直交復調された２つの直交復調信号に対して拡散コードにより相関演算を行うことにより逆拡散を行う相関演算手段と、前記直交復調手段により直交復調された２つの直交復調信号から受信電力を演算する電力演算手段と、前記相関演算手段により相関演算されて出力された相関ピーク信号に基づいて受信に係るスペクトラム拡散変調信号の信号レベルを検出する相関レベル検出手段と、前記電力演算手段と相関レベル検出手段の処理結果に基づいて前記可変利得増幅手段の利得を制御する利得制御手段とを備え、前記利得制御手段は、前記相関レベル検出手段の処理結果に基づいて前記可変利得増幅手段の利得を制御した結果、前記スペクトラム拡散変調信号の信号レベルが予め設定された誤差範囲を逸脱した場合には、前記電力演算手段の処理結果に基づく前記可変利得増幅手段の利得制御に切り換えるように構成したので、受信したスペクトラム拡散変調信号を増幅する際の自動利得制御を高速、且つ高精度に行うことが可能となる。
【図面の簡単な説明】
【図１】本発明の実施の形態に係る受信装置の概略構成を示すブロック図である。
【図２】従来の第１の受信装置例の概略構成を示すブロック図である。
【図３】従来の第２の受信装置例の概略構成を示すブロック図である。
【図４】相関ピーク信号を示す図である。
【符号の説明】
３ＶＧＡ（利得可変増幅器）
４直交復調器
５Ａ／Ｄ変換器
６相関演算器
７検波器
８ＡＧＣ制御部
９電力演算部
１０相関レベル検出部
１１コード発生器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus capable of demodulating a spread spectrum modulation signal, and more particularly to an AGC (Automatic Gain Control) technique for amplifying a received signal.
[0002]
[Prior art]
At present, CDMA (Code Division Multiple Access) is attracting attention as a next-generation communication method for cellular phones and the like. This CDMA system applies spread spectrum technology as a basic technology. Communication data is reproduced by performing spread modulation with a pseudo-noise sequence code (spreading code) on the transmission side and performing despread demodulation on the reception side using the same code used on the transmission side. As this spreading code, a combination of a plurality of codes orthogonal to each other (that is, the result of multiplying and integrating two signals becomes zero) can be used. Using this plurality of sets of orthogonal codes, for example, the base station allocates this plurality of sets of orthogonal codes to a plurality of mobile stations that communicate with each other, and multiplexes signals that are spread-modulated with these sets of codes and transmits them simultaneously. To do. Each mobile station can extract only a desired signal from the multiplexed signals by despreading using a code corresponding to the signal desired to be received.
[0003]
As described above, in spread spectrum communication reception processing, despreading processing is performed using the same code as that on the transmission side. For this despreading processing, a correlation filter or a correlation calculator such as a sliding correlator is used. The correlation signal of the received signal by this correlation calculator is as shown in FIG. 4, and the transmission data is reproduced from the peak (correlation peak) of this signal waveform. The level of the correlation peak is proportional to the level of the received signal input to the correlation calculator.
[0004]
Examples of conventional receiving apparatuses are shown in FIGS. Conventionally, in the example of FIG. 2, after the signals I1 and Q1 separated into the I component and the Q component by the quadrature demodulator 4 are A / D converted, the received power value is obtained by obtaining the square sum of I and Q, Using this result, the gain of a VGA (Variable Gain Amplifier) 3 is controlled by the AGC control unit so that the signal level input to the A / D converter 5 is constant regardless of fluctuations in radio propagation. Value.
[0005]
In the example of FIG. 3, the correlation calculation is executed with a spread code corresponding to a signal desired to be received among a plurality of spread codes used in the spread spectrum modulation process. As a result, by obtaining the correlation peak of the waveform shown in FIG. 4 and performing AGC according to the level of the correlation peak, it is possible to accurately control the gain for the desired signal component.
[0006]
[Problems to be solved by the invention]
However, in the example of FIG. 2, the feedback control of AGC is sampled at the sample rate of the A / D converter 5 (this sample rate is usually more than twice the chip rate, that is, the frequency of the spread signal in the CDMA system). Since the power calculation is performed for each of them, a high-speed AGC that can follow the fluctuation of the input signal at high speed can be realized. On the other hand, in order to perform AGC on the entire power of signals including all interfering waves, such as multiplexed signals sent from the base station to each mobile device and signals from the base station of the adjacent cell. The AGC accuracy for the signal component to be demodulated cannot be expected.
[0007]
On the other hand, in the example of FIG. 3, the autocorrelation component of the received signal to be demodulated is extracted by the correlation calculator 6 such as a matched filter, and AGC control is performed based on the signal level of the correlation peak signal. Since the AGC accuracy with respect to the desired signal component is good compared to the above, the deterioration of the demodulation characteristics in the subsequent stage can be reduced. However, since the correlation peak occurs only once in one cycle of the spread code generated by the code generator 11, the AGC The signal input to the control unit 8 is thinned out in time, and the AGC response is delayed.
[0008]
Further, considering the case where the level of the correlation peak is lowered to be lower than the maximum receiving sensitivity, the correlation peak is not detected at this time, and the output of the correlation calculator 6 is a cross-correlation from a signal spread by another spreading code. The AGC at this time adjusts the gain of the VGA 3 so that the noise reaches a predetermined threshold value.
[0009]
Normally, the output from the correlation calculator 6 due to a signal having no autocorrelation is small. Therefore, when the gain of the VGA 3 is increased until the threshold value is exceeded, the RF section 2 in the previous stage operates with the total power waveform, so the signal As a result, the level rises, and the RF unit 2 and VGA 3 which are analog circuits enter a saturation region. When a signal having a level within the reception sensitivity range comes in from this state, the saturated analog circuit is restored from the saturated state, and the restoration takes a longer time than the normal response.
[0010]
The present invention has been made under such a background, and an object thereof is to enable automatic gain control at a high speed and high accuracy when a received spread spectrum signal is amplified.
[0011]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a receiving apparatus capable of demodulating a spread spectrum modulation signal by means of variable gain amplification means for amplifying the spread spectrum modulation signal related to reception so that the gain can be changed, and the variable gain amplification means. Orthogonal demodulation means for orthogonally demodulating the amplified spread spectrum modulation signal, and correlation calculation means for performing despreading by performing a correlation operation on the two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulation means using a spreading code; A power calculating means for calculating received power from two orthogonally demodulated signals orthogonally demodulated by the orthogonal demodulating means, and spread spectrum modulation related to reception based on the correlation peak signal output by correlation calculation by the correlation calculating means Correlation level detection means for detecting the signal level of the signal, the power calculation means and the correlation level detection means And a gain control means for controlling the gain of said variable gain amplifying means based on management result, said gain control means as a result of controlling the gain of said variable gain amplifying means based on the processing result of the correlation level detecting means When the signal level of the spread spectrum modulation signal deviates from a preset error range, the variable gain amplifying unit is switched to gain control based on the processing result of the power calculating unit .
[0012]
According to another aspect of the present invention, there is provided a receiving method for receiving a spread spectrum modulation signal, a variable gain amplification step for amplifying the spread spectrum modulation signal related to reception by a variable gain amplification means so that the gain can be changed, and amplification by the variable gain amplification step. An orthogonal demodulation step of orthogonally demodulating the spread spectrum modulated signal, a correlation calculation step of performing despreading by performing a correlation operation with a spreading code on the two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulation step;
A power calculation step of calculating received power from two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulation step, and a spread spectrum modulation signal related to reception based on a correlation peak signal output by correlation calculation by the correlation calculation step A correlation level detection step of detecting the signal level of
And a gain control step of controlling the gain of said variable gain amplifying means based on the processing result of the power calculation step and the correlation level detection step, said gain control step, on the basis of the processing result of the correlation level detection step As a result of controlling the gain of the variable gain amplifying means, if the signal level of the spread spectrum modulation signal deviates from a preset error range, the gain control of the variable gain amplifying means based on the processing result of the power calculation step It is comprised so that it may switch to .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0019]
FIG. 1 is a block diagram showing a schematic configuration of a receiving apparatus according to an embodiment of the present invention. This apparatus is configured to be able to demodulate a received spread spectrum modulation signal, and includes an antenna 1, an RF unit 2, a VGA ( Variable gain amplifier 3, quadrature demodulator 4, A / D converter 5, correlation calculator 6, detector 7, AGC controller 8, power calculator 9, correlation level detector 10, and code generator 11 is doing.
[0020]
The RF unit 2 performs analog processing such as down-conversion of the high-frequency radio signal received by the antenna 1 and inputs it as a signal that conforms to the input form of the VGA 3 at the next stage. Since the gains of the antenna 1 and the RF unit 2 are always constant, the signal level output from the RF unit 2 becomes a level proportional to the received signal level received from the antenna 1, and the level becomes large due to a change in radio wave propagation status. fluctuate. The VGA 3 is a variable gain amplifier having a function of changing the gain by an external gain control signal, and the gain of the VGA 3 is controlled by the AGC control unit 8 according to the received signal level.
[0021]
In the CDMA system, the received signal is orthogonally modulated in such a way as to include an I component and a Q component that are orthogonal to each other. Therefore, the quadrature demodulator 4 demodulates the signal by separating two orthogonal components from the received signal whose level is constant in a series of AGC loops including the VGA 3, and outputs signals I1 and Q1. The output signals I1 and Q1 from the quadrature demodulator 4 are converted into digital values by the A / D converter 5 and output to the correlation calculator 6 and the power calculator 9 as digital signals I2 and Q2, respectively. However, the digital signals I2 and Q2 include components corresponding to all the spread codes used for the spread spectrum modulation process at the time of transmission.
[0022]
The correlation calculator 6 performs despreading by performing correlation calculation on the signals I2 and Q2 based on the spreading code corresponding to the desired signal generated from the code generator 11, and performs two correlation peak signals (correlation values). I3 and Q3 are output to the detector 7 and the correlation level detector 10. These two correlation peak signals I3 and Q3 correspond to only desired signals. Accordingly, the detector 7 performs detection processing on the correlation peak signals I3 and Q3, thereby restoring desired communication data I4 and Q4.
[0023]
Next, AGC will be described in detail.
[0024]
When the calculation of (I ² + Q ² ) is executed from the two signals I ^{2 and} Q ² that are the outputs of the A / D converter 5, it is proportional to the total energy of the signal received in the signal flow from the antenna 1 to the converter 5. Signal can be obtained. By controlling the gain of the VGA 3 using this energy level signal, the signal levels of the signals I 1 and Q 1 can be made constant regardless of the signal level received by the antenna 1.
[0025]
In the example of FIG. 1, the signals 12 and Q2 are calculated by the power calculation unit 9 corresponding to (I ² + Q ² ) to obtain the total received power value. The AGC control unit 8 controls the VGA 3 based on the total power calculation value so that l1 and Q1 are constant with respect to the total received power value. Hereinafter, this AGC loop is referred to as AGC by power calculation.
[0026]
Since the AGC based on the power calculation outputs the digital signals I2 and Q2 at a high rate that is about twice the chip rate (frequency of the spread modulation signal), it is possible to form an AGC with a high-speed response. However, in the CDMA system, the received signal includes other signals corresponding to other receiving apparatuses, in addition to a signal that the receiving apparatus wants to receive, that is, a signal that is spread spectrum modulated by the spreading code used by the receiving apparatus. Components that become noise for the receiving apparatus, such as a signal spread spectrum modulated with a spreading code and a signal from a base station of an adjacent cell, are also included. For this reason, the receiving apparatus receives the signal as a signal in which all the components are added.
[0027]
Since the circuit before the correlation calculator 6 cannot separate only the signal components desired to be received by the receiving apparatus from the signal including the noise component, the signals I2 and Q2 are also desired by the receiving apparatus. A noise component other than the signal component is included. Therefore, the received power value calculated by the power calculator 9 is the total received power value including this noise component. As a result, even if the gain of the VGA 3 is controlled by the AGC control unit 8 using this total received power value, the control makes the total received power constant, and other than the signal desired by the receiving apparatus. Depending on the state of the noise component, the correlation level output from the correlation calculator 6 changes. As a result, the level of the correlation peak signal output to the detection unit 7 at the subsequent stage varies, which affects the accuracy of the detection process.
[0028]
Therefore, in this receiving apparatus, in order to solve the above-described problem, AGC is performed using power calculation and, as will be described below, AGC is also performed using the output result of the correlation level detection unit 10.
[0029]
That is, the correlation calculator 6 is used for spread spectrum modulation of a desired signal in order to detect a desired signal from received signals that have been spread spectrum modulated and multiplexed based on a plurality of spread codes. A spread code is obtained from the code generator 11, a correlation operation is performed based on the spread code corresponding to the desired signal, and correlation peak signals (correlation values) I3 and Q3 are output. The signal levels of the correlation peak signals I3 and Q3 are proportional only to the level of the desired signal. Therefore, the correlation level detection unit 10 obtains the level values of the correlation peaks I3 and Q3 for the I and Q components, respectively. Then, the AGC controller 8 controls the gain of the VGA 3 based on the level values of the correlation peaks I3 and Q3, so that the signal levels of the correlation peak signals I3 and Q3 corresponding to the desired signal component in the received signal. To be constant. Hereinafter, this AGC loop is referred to as AGC based on the correlation level.
[0030]
However, in the AGC based on this correlation level, since the correlation peak signal is detected by the correlation calculator 6 once in one cycle of the spread code, only an output with a low rate can be obtained in terms of time. Therefore, since the response of AGC is slow, it takes time for the output value controlled by AGC to stabilize to the expected level. Therefore, the AGC control unit 8 uses both the signal of the total reception power from the power calculation unit 9 and the signal level value of the desired reception signal from the correlation level detection unit 10 as described below, to make the VGA 3 To control.
[0031]
That is, assuming that the initial state is a state in which the receiving apparatus has not received any signal, the signals output by both the power calculation unit 9 and the correlation level detection unit 10 are very low in the initial state. The control unit 8 waits for the arrival of a radio signal with the gain of the VGA 3 being maximized. In this state, when the receiving apparatus receives a transmission signal from the transmitter, the VGA 3 and the RF unit 2 have the maximum amplification factor in a transient state until the total received power value from the power calculating unit 9 with quick response is output. Therefore, it becomes saturated.
[0032]
As the output from the power calculation unit 9 rises in response to input saturation, the AGC control unit 8 reduces the gain of the VGA 3 so that the total received power level in the signals I 2 and Q 2 is constant. When the error range set in advance for the final stable value is reached, the AGC control unit 8 switches the control loop to AGC based on the correlation level.
[0033]
In the AGC based on the correlation level, the AGC is applied based only on the signal component correlated with the spreading code generated from the code generator 11 out of the total received power, that is, the correlation level of the signal component desired to be received by the receiving apparatus. Therefore, the desired signal components I3 and Q3 can be made constant in I3 and Q3.
[0034]
The gain stability level of VGA 3 when AGC is performed based on this correlation level is different from the gain stability level of VGA 3 when AGC is performed based on the previous received power. Accordingly, it is conceivable that the error range of the AGC based on the reception power exceeds the preset error range as a result of the AGC based on the correlation level. However, in this state, the AGC control unit 8 continues the control based on the AGC based on the correlation level. In addition, an error range is set in advance separately for the AGC based on the correlation level, and only when the error range is exceeded, the AGC is shifted to the AGC based on the received power.
[0035]
In this way, at the initial stage of receiving the spectrum spread modulation signal, the gain of the VGA 3 is controlled based on the power of the received signal calculated by the power calculation unit 9, and the received power is stabilized to some extent by this control. By controlling the gain of the VGA 3 based on the signal level of the correlation peak signal detected by the correlation level detection unit 10, the response when the received signal level changes greatly is faster than when only the correlation level is used. In addition, when the received signal level changes instantaneously, the recovery from the saturated state becomes faster. Furthermore, since automatic gain control is performed based on the correlation level at the time of stabilization, it is possible to perform control with attention paid only to a desired signal component, and high-accuracy automatic gain control is possible. That is, it is possible to achieve both high speed and high accuracy in automatic gain control.
[0036]
In the above description, the spread code sequence used at the time of spread spectrum modulation is not mentioned. However, the present invention is not limited to the spread code sequence, and various PNs such as an M sequence (Maximum Length Code) and a Gold code sequence. The present invention can also be applied when a series (Pseudorand Noise) or the like is used.
[0037]
【The invention's effect】
As described above, according to the present invention, in the receiving apparatus capable of demodulating the spread spectrum modulation signal, the variable gain amplification means for amplifying the spread spectrum modulation signal related to reception so that the gain can be changed, and the variable gain amplification means Orthogonal demodulation means for orthogonally demodulating the spread spectrum modulated signal amplified by the above, and correlation calculation means for performing despreading by performing a correlation operation on the two orthogonally demodulated signals orthogonally demodulated by the orthogonal demodulation means using a spreading code Power calculation means for calculating received power from two orthogonally demodulated signals orthogonally demodulated by the orthogonal demodulation means, and spread spectrum related to reception based on the correlation peak signal output by correlation calculation by the correlation calculation means Correlation level detection means for detecting the signal level of the modulation signal, the power calculation means and the correlation level detection means Based on the processing results and a gain control means for controlling the gain of said variable gain amplifying means, said gain control means as a result of controlling the gain of said variable gain amplifying means based on the processing result of the correlation level detecting means When the signal level of the spread spectrum modulation signal deviates from a preset error range, it is configured to switch to the gain control of the variable gain amplifying unit based on the processing result of the power calculating unit . Automatic gain control when a spread spectrum modulation signal is amplified can be performed at high speed and with high accuracy.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a receiving apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a schematic configuration of a first conventional receiving apparatus example.
FIG. 3 is a block diagram showing a schematic configuration of a second conventional receiving apparatus example.
FIG. 4 is a diagram showing a correlation peak signal.
[Explanation of symbols]
3 VGA (variable gain amplifier)
4 Quadrature Demodulator 5 A / D Converter 6 Correlation Calculator 7 Detector 8 AGC Controller 9 Power Calculator 10 Correlation Level Detector 11 Code Generator

Claims

In a receiving device capable of demodulating a spread spectrum modulation signal,
Variable gain amplifying means for amplifying the spread spectrum modulation signal related to reception so that the gain can be changed;
Orthogonal demodulation means for orthogonally demodulating the spread spectrum modulation signal amplified by the variable gain amplification means;
Correlation calculating means for performing despreading by performing a correlation calculation with a spreading code on the two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulating means;
Power calculating means for calculating received power from two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulating means;
Correlation level detection means for detecting a signal level of a spread spectrum modulation signal related to reception based on a correlation peak signal output after correlation calculation by the correlation calculation means;
And a gain control means for controlling the gain of said variable gain amplifying means based on the processing result of the correlation level detecting means and the power computing means,
The gain control means controls the gain of the variable gain amplification means based on the processing result of the correlation level detection means, and as a result, the signal level of the spread spectrum modulation signal deviates from a preset error range. The receiving apparatus switches to gain control of the variable gain amplifying means based on the processing result of the power calculating means .

The receiving apparatus according to claim 1, wherein the variable gain amplifying unit and the quadrature demodulating unit process the spread spectrum modulation signal as an analog signal.

The receiving apparatus according to claim 2, wherein the correlation calculation unit performs processing on the two quadrature demodulated signals converted into digital signals.

The gain control means controls the gain of the variable gain amplifying means based on the processing result of the power calculation means at the initial stage of receiving the spread spectrum modulation signal, and the received power is stabilized to some extent by the control. 2. The receiving apparatus according to claim 1, wherein a gain of the variable gain amplifying unit is controlled later based on a processing result of the correlation level detecting unit.

In a receiving method for receiving a spread spectrum modulation signal,
A variable gain amplifying step for amplifying the spread spectrum modulation signal related to reception so that the gain can be changed by a variable gain amplifying means ;
An orthogonal demodulation step of orthogonally demodulating the spread spectrum modulation signal amplified by the variable gain amplification step;
A correlation calculation step of performing despreading by performing a correlation calculation with a spreading code on the two orthogonally demodulated signals orthogonally demodulated by the orthogonal demodulation step;
A power calculation step of calculating received power from two orthogonal demodulated signals orthogonally demodulated by the orthogonal demodulation step;
A correlation level detection step of detecting a signal level of a spread spectrum modulation signal related to reception based on the correlation peak signal output by correlation calculation in the correlation calculation step;
And a gain control step of controlling the gain of said variable gain amplifying means based on the processing result of the power calculation step and the correlation level detection step,
In the gain control step, when the gain of the variable gain amplifying means is controlled based on the processing result of the correlation level detection step, the signal level of the spread spectrum modulation signal deviates from a preset error range. The receiving method is characterized by switching to gain control of the variable gain amplifying means based on the processing result of the power calculation step .

6. The receiving method according to claim 5 , wherein the variable gain amplification step and the quadrature demodulation step perform processing on the spread spectrum modulation signal as an analog signal.

The receiving method according to claim 6 , wherein the correlation calculation step performs processing on the two quadrature demodulated signals converted into digital signals.

In the initial stage of receiving the spread spectrum modulation signal, the gain control step controls the gain of the variable gain amplification means based on the processing result of the power calculation step, and the received power is stabilized to some extent by the control. 6. The receiving method according to claim 5, wherein the gain of the variable gain amplifying means is controlled later based on the processing result of the correlation level detecting step.