JP3927521B2 - Transmitter - Google Patents

Description

【００４０】
平均電力演算部３２は、瞬時電力演算部３１により算出された瞬時電力Ｐｉｎｔ（ｔ）に基づいて、上記した加算結果信号の平均電力Ｐａｖｇを演算し、当該演算結果を閾値生成部３３へ出力する。ここで、一例として、平均電力Ｐａｖｇは、式２のように表される。なお、Ｔは、平均化を行う信号の数を表しており、種々な数が用いられてもよい。
【００４１】
【数２】

【００４２】
閾値生成部３３は、平均電力演算部３２から入力される平均電力Ｐａｖｇに基づいて、ピーク抑圧を行うための閾値電力Ｔｈｒを設定し、当該設定結果を比較部３４及び除算部３５へ出力する。ここで、一例として、（平均電力Ｐａｖｇ＋６ｄＢ）を閾値電力Ｔｈｒとして設定する場合、閾値電力Ｔｈｒは式３のように表される。
【００４３】
【数３】

【００４４】
比較部３４は、閾値生成部３３から入力される閾値電力Ｔｈｒのレベルと、瞬時電力演算部３１から入力される瞬時電力Ｐｉｎｔ（ｔ）のレベルとを比較し、当該比較結果を除算部３５及び窓関数生成部３６へ出力する。ここで、本例では、瞬時電力Ｐｉｎｔ（ｔ）が閾値電力Ｔｈｒを超える部分を上記した加算結果信号のピーク部分として検出する。
【００４５】
除算部３５は、比較部３４からの入力に基づいて、瞬時電力Ｐｉｎｔ（ｔ）が閾値電力Ｔｈｒを超えて比較部３４によりピークが検出された場合には、閾値電力Ｔｈｒと瞬時電力Ｐｉｎｔ（ｔ）との除算を行って、所定のピークファクタＧａｉｎ（ｔ）を算出し、当該算出結果をリミッタ演算部３７へ出力する。
また、除算部３５は、比較部３４からの入力に基づいて、瞬時電力Ｐｉｎｔ（ｔ）が閾値電力Ｔｈｒ以下であり比較部３４によりピークが非検出であった（つまり、検出されなかった）場合には、１の値をピークファクタＧａｉｎ（ｔ）として設定し、当該設定結果をリミッタ演算部３７へ出力する。
【００４６】
ここで、一例として、ピークファクタＧａｉｎ（ｔ）は、式４のように表される。
なお、本例では、瞬時電力Ｐｉｎｔ（ｔ）や閾値電力Ｔｈｒが電力のディメンジョンで表されているため、電圧領域でピークレベルの抑圧を行うために、平方根（ｓｑｒｔ）の演算を行っている。
【００４７】
【数４】

【００４８】
窓関数生成部３６は、比較部３４からの入力に基づいて、瞬時電力Ｐｉｎｔ（ｔ）が閾値電力Ｔｈｒを超えて比較部３４によりピークが検出された場合には、所定の窓関数Ｗｅｉｇｈｔ（ｓ）を生成して、当該生成結果をリミッタ係数演算部３７へ出力する。なお、窓関数生成部３６は、他の場合（つまり、ピークが非検出であった場合）には、例えば、１の値をリミッタ係数演算部３７へ出力する。
【００４９】
ここで、一例として、ハミング窓が用いられる場合には、窓関数Ｗｅｉｇｈｔ（ｓ）の一例は式５のように表される。
なお、Ｍは、サンプル数を表しており、例えば、２以上の整数を表す。
一般に、サンプル数Ｍが大きくなると、窓関数Ｗｅｉｇｈｔ（ｓ）の帯域は狭くなる。また、サンプル数Ｍは、例えば、送信スペクトルの規格帯域幅に応じて最適化して設定される。
【００５０】
【数５】

【００５１】
ここで、ｓは、時刻（ｔ−Ｍ／２）から時刻（ｔ＋Ｍ／２）の区間に対応して、（−Ｍ／２）から（＋Ｍ／２）の区間で値を取る（［−Ｍ／２≦ｓ≦＋Ｍ／２］）。これにより、ピークが存在する１つの時刻ｔについて、例えば、Ｍ個（或いは、（Ｍ＋１）個）のピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）が生成される。
【００５２】
リミッタ係数演算部３７は、例えばピークが存在する時刻ｔを中心とした時刻（ｔ−Ｍ／２）から時刻（ｔ＋Ｍ／２）の区間において、除算部３５から入力されるピークファクタＧａｉｎ（ｔ）に対して窓関数生成部３６から入力される窓関数Ｗｅｉｇｈｔ（ｓ）により重みを与え、当該重みを与えた結果をピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）として２個の乗算器２５、２６へ出力する。ここで、一例として、ピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）は、式６のように表される。
【００５３】
【数６】

【００５４】
このように、ピーク電力抑圧係数演算部１４では、上記した加算結果信号の瞬時電力Ｐｉｎｔ（ｔ）に対して、必要なピークレベル抑圧を実現するためのピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）を設定する。
なお、本例では、三角関数を含む窓関数Ｗｅｉｇｈｔ（ｓ）を用いたが、例えば、三角関数を含まない窓関数が用いられてもよい。
【００５５】
基本的に、窓関数の目的は、ピークレベル抑圧を行う際に発生するスペクトルの拡大を防止するために、ピークレベル抑圧信号自体を帯域制限することである。例えば、単純な矩形窓を用いる場合には、スペクトルの拡大を抑えるためには、より長時間の窓幅が必要になる。窓関数については、従来から種々な検討が為されており、一般に知られているため、本明細書では、詳しい説明は割愛する。
【００５６】
各遅延部２３、２４は、ピーク電力抑圧係数演算部１４によりピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）が算出される処理に要する時間に対応して、各加算器２１、２２から入力される加算結果信号ＡＩ（ｔ）、ＡＱ（ｔ）の遅延を調整し、当該遅延調整した信号を各乗算器２５、２６へ出力する。
【００５７】
各乗算器２５、２６は、各遅延部２３、２４から入力される加算結果信号ＡＩ（ｔ＋ｓ）、ＡＱ（ｔ＋ｓ）とリミッタ係数演算部３７から入力されるピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）とを乗算して、これによりピーク及びその周辺の信号レベルを抑圧し、当該乗算結果Ａ’Ｉ（ｔ＋ｓ）、Ａ’Ｑ（ｔ＋ｓ）を各Ｄ／Ａ変換器２７、２８へ出力する。ここで、当該乗算結果Ａ’Ｉ（ｔ＋ｓ）、Ａ’Ｑ（ｔ＋ｓ）は、式７のように表される。
【００５８】
【数７】

【００５９】
各Ｄ／Ａ変換器２７、２８は、各乗算器２５、２６から入力されるデジタル信号をアナログ信号へ変換し、当該Ｄ／Ａ変換結果をアナログ直交変調部２９へ出力する。
アナログ直交変調部２９は、２個のＤ／Ａ変換器２７、２８から入力されるＩ成分及びＱ成分から成るアナログ信号をアナログ直交変調して、これにより当該信号を無線周波数帯の信号へ変換して出力する。
【００６０】
ここで、図２には、本例におけるピーク電力抑圧の様子の一例を示してある。
具体的には、時刻（サンプリング時間ｔ）に対する瞬時電力Ｐｉｎｔ（ｔ）、平均電力Ｐａｖｇ（ｔ）、閾値電力Ｔｈｒ（ｔ）及びピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ）の一例を示してあり、また、周波数ｆに対するピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ）の一例を示してある。
【００６１】
同図に示されるように、本例では、ピークが検出されているときには、ピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ）は下に凸なグラフとなる。
また、本例では、ピークが検出されていないときには、ピークファクタＧａｉｎ（ｔ）は１となり、ピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ）は１となる。
【００６２】
上述のように、ピーク電力抑圧部１２では、上記したＩ成分及びＱ成分の加算結果信号に含まれる突出したピーク信号部分のレベルと当該ピークの周辺の信号部分のレベルが抑圧される。
このように、本例では、閾値電力Ｔｈｒを超えたピークの信号部分のみではなく、当該ピークの周辺の信号部分についてもゲイン制御が行われる。
【００６３】
以上のように、本例の送信機１では、例えば複数又は単数のキャリア周波数を用いて送信を行うに際して、送信対象となるデジタル変調結果ＡＩ（ｔ）、ＡＱ（ｔ）の瞬時電力Ｐｉｎｔ（ｔ）と平均電力Ｐａｖｇに基づく閾値電力Ｔｈｒとの比率の平方根値をピークファクタＧａｉｎ（ｔ）として算出し、当該ピークファクタＧａｉｎ（ｔ）に対して窓関数Ｗｅｉｇｈｔ（ｓ）により重みを持たせてピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）を算出し、当該ピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ＋ｓ）により前記したデジタル変調結果ＡＩ（ｔ）、ＡＱ（ｔ）のピークの電圧レベル及び当該ピークの周辺の電圧レベルをレベル制御することが行われる。
【００６４】
従って、本例の送信機１では、例えば従来と比べて、ピーク電力の低減と帯域外漏洩電力の制限との両立が可能となり、効果的にピーク電力を低減することができる。
また、本例の送信機１では、例えば従来と比べて、回路規模の低減や、窓関数のメモリ容量の低減を実現することが可能である。
【００６５】
なお、本例のようなピーク電力抑圧の処理は非線形処理であるため、線形変調方式を用いたシステムに影響を与え得る。このため、ピーク電力を低減させて増幅器の電力効率を上昇させることと、通信品質の劣化とは、トレードオフの関係にある。こうしたことから、本例のようなピーク電力抑圧の処理に用いられる具体的な数値としては、例えば、本発明を採用するシステムオペレータなどに依存して種々に決定されればよい。
【００６６】
ここで、本例の送信機１により得られる効果の具体例を示す。
図３には、１キャリア送信時において、Ｗ−ＣＤＭＡ通信方式を採用した送信機から出力される信号の周波数特性の一例を示してあり、（ａ）図９や図１１に示されるような比較例に係る送信機等１４１、１８１に関する特性例と、（ｂ）図１や図５や図６や図７に示されるような本提案に係る送信機等１、４１、８１に関する特性例と、（ｃ）ピーク電力を抑圧する機能を有さない送信機等に関する特性例を示してある。なお、図３のグラフの横軸は規格化周波数を示しており、縦軸は送信レベル［ｄＢｍ］を示している。
【００６７】
また、図３では、３２コードでの多重時における１キャリア信号の２５６０サンプル分のデータを送信する時における周波数特性の例を示してある。また、図３では、閾値電力Ｔｈｒとして（平均電力＋８ｄＢ）の値を設定した場合の例を示してある。
図３に示されるように、（ａ）比較例に係る送信機等１４１、１８１では隣接漏洩電力が増大しているが、（ｂ）本提案に係る送信機等１、４１、８１では、窓関数の重みが与えられたピーク電力抑圧係数が用いられているため、当該ピーク電力抑圧係数に帯域制限が施されて、隣接漏洩電力を比較的小さいレベルに抑えることが可能である。
【００６８】
図４には、１キャリア送信時において、Ｗ−ＣＤＭＡ通信方式を採用した送信機から出力される信号の相補累積分布関数（ＣＣＤＦ）の一例を示してあり、（ａ）図９や図１１に示されるような比較例に係る送信機等１４１、１８１に関する特性例と、（ｂ）図１や図５や図６や図７に示されるような本提案に係る送信機等１、４１、８１に関する特性例と、（ｃ）ピーク電力を抑圧する機能を有さない送信機等に関する特性例を示してある。なお、図４のグラフの横軸は平均電力を超えた分の電力［ｄＢ］を示しており、縦軸は累積的な確率［％］を示している。
【００６９】
また、図４では、３２コードでの多重時における１キャリア信号の２５６０サンプル分のデータを送信する時における相補累積分布関数（ＣＣＤＦ）の例を示してある。また、図４では、閾値電力Ｔｈｒとして（平均電力＋８ｄＢ）の値を設定した場合の例を示してある。
図４に示されるように、（ｂ）本提案に係る送信機等１、４１、８１では、（ａ）比較例に係る送信機等１４１、１８１と同様に、ピーク電力が抑圧されている。
【００７０】
また、本例の送信機１により帯域外漏洩電力が制限される理由について説明する。
すなわち、ピーク電力の抑圧は、帯域制限された変調部からの出力信号とピーク電力抑圧係数との乗算（変調）により、実行される。例えば、比較例に係る図１０に示されるように、パルス信号であるピーク電力抑圧係数Ｇａｉｎ（ｔ）は、周波数軸上で見ると全ての帯域に広がったスペクトルとなり、そして、このようなピーク電力抑圧係数Ｇａｉｎ（ｔ）の信号を変調部からの出力信号と乗算（変調）する構成では、帯域制限されたスペクトルを劣化させてしまう。これに対して、本提案に係る上記図２に示されるように、余弦関数などから構成される窓関数を用いてパルス信号の帯域制限を行って生成されるピーク電力抑圧係数Ｅｘｐ＿Ｇａｉｎ（ｔ）の信号を変調部１１からの出力信号と乗算（変調）する構成では、スペクトルの広がりを抑えることが可能となり、帯域外漏洩電力を抑えることができる。
【００７１】
なお、本例の送信機１では、瞬時電力演算部３１の機能により送信対象信号レベル検出手段が構成されており、平均電力演算部３２の機能により送信対象信号レベル平均値検出手段が構成されており、閾値生成部３３の機能により送信対象信号レベル閾値生成手段が構成されており、比較部３３の機能により送信対象信号レベル閾値大小比較手段が構成されており、除算部３５の機能によりピークファクタ設定手段が構成されており、これらの手段によりピークファクタ生成手段が構成されている。
また、本例の送信機１では、窓関数生成部３６の機能やリミッタ係数演算部３７の機能によりピーク抑圧係数生成手段が構成されており、乗算器２５、２６の機能により送信対象信号レベル抑圧手段が構成されている。
【００７２】
本発明の第２実施例に係る送信増幅器を説明する。
図５には、本例の送信増幅器４１の構成例を示してある。
本例の送信増幅器４１の構成や動作は、周波数変換部１３の後段に電力増幅部４２が備えられている点を除いては、上記第１実施例の上記図１に示した送信機１の構成や動作と同様である。また、本例では、上記図１に示したのと同様な構成部分Ｂ１〜ＢＮ、１１〜１４、Ｃ１〜ＣＮ、Ｅ１〜ＥＮ、２１〜２９、３１〜３７については、同一の符号を付して示す。
電力増幅部４２は、周波数変換部１３に備えられたアナログ直交変調部２９から出力される無線周波数信号を入力し、当該入力した信号を増幅して出力する。
【００７３】
以上のように、本例の送信増幅器４１では、例えば複数の通信チャネルから構成されるマルチキャリア信号を送信するに際して、上記第１実施例の上記図１に示した送信機と同様に窓関数を用いて送信対象となる信号のピーク及びその周辺のレベルを抑圧し、その後、電力増幅部４２により送信電力を増幅することが行われる。
従って、本例の送信増幅器４１では、上記第１実施例で述べたのと同様に、ピーク電力の低減と帯域外漏洩電力の制限との両立が可能となり、効果的にピーク電力を低減することができる。
【００７４】
本発明の第３実施例に係る増幅装置を説明する。
図６には、本例の増幅装置の構成例を示してある。
本例の増幅装置には、デジタル変調部５１と、ピーク電力抑圧部５２と、歪補償回路５３と、周波数変換部５４と、増幅器５５が備えられている。
歪補償回路５３には、遅延部６１と、電力検出部６２と、ＲＡＭ（Random Access Memory）テーブル６３と、複素乗算部６４と、歪成分検出部６５と、制御部６６が備えられている。
周波数変換部５４には、Ｄ／Ａ変換器７１と、ミキサ７２が備えられている。
【００７５】
ここで、本例の増幅装置は、デジタルプリディストーション（ＤＰＤ）方式により歪補償を行う回路（歪補償回路）５３を備えている。
そして、本例の増幅装置は、送信対象となる信号を増幅器５５により増幅するに際して、当該増幅器５５で発生する歪を歪補償回路５３により補償し、また、歪補償回路５３に入力される信号に対してピーク電力抑圧部５２によりピーク電力の抑圧を行う。
【００７６】
なお、プリディストーション方式では、素子が発生する歪の逆特性を有する歪を予め入力信号に加えておくことにより歪補償が行われ、入力信号のプリディストーション処理と素子の非線系性との整合が非常に重要となる。プリディストーション方式では、例えば、素子の飽和電力以上となった場合における歪補償劣化が著しいため、入力信号の処理において信号のピーク電力成分の抑圧処理が非常に有効となる。
【００７７】
また、本例では、ベースバンド信号から入力電力を検出するデジタル方式のプリディストーション方式を用いた場合の例を示すが、例えば、無線周波数（ＲＦ：Radio Frequency）信号の入力電力を検出するアナログ方式のプリディストーション方式に適用することも可能である。
【００７８】
本例の増幅装置により行われる動作の一例を示す。
デジタル変調部５１は、例えば上記第１実施例の上記図１に示したデジタル変調部１１と同様な構成を有しており同様な動作を行い、入力される送信対象となる信号に対して、デジタル変調結果の信号をピーク電力抑圧部５２へ出力する。
【００７９】
なお、当該デジタル変調結果の信号は、例えば、Ｉ成分とＱ成分から構成され、以降の処理においても同様である。
また、当該デジタル変調結果の信号は、デジタル信号から構成され、後述するＤ／Ａ変換器７１においてアナログ信号へ変換される。
【００８０】
ピーク電力抑圧部５２は、例えば上記第１実施例の上記図１に示したピーク電力抑圧部１２と同様な構成を有しており同様な動作を行い、デジタル変調部５１からの入力信号に対して、ピーク電力抑圧結果の信号を歪補償回路５３へ出力する。
ここで、本例のピーク電力抑圧部５２は、歪補償回路５により歪補償することができない領域の電力を抑圧し、これにより、増幅器５５の動作点を上げることや、装置の高効率化が図られている。
【００８１】
歪補償回路５３では、ピーク電力抑圧部５２からの出力信号が遅延部６１と電力検出部６２に入力される。
遅延部６１は、入力される信号を遅延させて複素乗算部６４へ出力する。
電力検出部６２は、入力される信号の瞬時電力（包絡線）を演算し、当該演算結果をＲＡＭテーブル６３へ出力する。
【００８２】
ＲＡＭテーブル６３は、振幅や位相の補正量を入力電力と対応させて記憶しており、当該対応を参照して、電力検出部６２から入力される演算結果に応じて、当該演算結果（入力電力）に対応する振幅や位相の補正量を複素乗算部６４へ出力する。これにより、入力電力のレベルに応じて振幅や位相の補正量を制御することができ、動作環境に応じた補正量を制御することができる。
なお、一例として、振幅の補正量（倍率）をＡで表し、位相の補正量をθ（ずれ）で表し、虚数部分をｊで表すと、振幅と位相の両方の補正量は（Ａ×ｅ^ｊθ）で表される。
【００８３】
複素乗算部６４は、遅延部６１から入力される信号とＲＡＭテーブル６３から入力される補正量とを複素乗算し、当該複素乗算結果を周波数変換部５４へ出力する。当該複素乗算では、補正量に応じて入力信号の振幅や位相が変化され、これにより、増幅器５５の非線形特性に対する逆特性の歪を入力信号に与えることが実現される。
【００８４】
歪成分検出部６５は、増幅器５５から出力される増幅信号に含まれる歪成分を復調により検出し、当該歪成分の電力を演算して、当該演算結果を制御部６６へ出力する。当該復調では、例えば、周波数変換して、帯域制限して、Ａ／Ｄ（Analog to Digital）変換する処理が行われる。一例として、２つの周波数ｆ０、ｆ１の信号により周波数（２ｆ０−ｆ１）及び周波数（２ｆ１−ｆ０）の３次歪が発生し、歪成分検出部６５は当該３次歪の電力を検出する。
【００８５】
制御部６６は、歪成分検出部６５から入力される歪成分の電力に関する情報に基づいて、ＲＡＭテーブル６３に記憶された入力電力と振幅や位相の補正量との対応を更新する。これにより、環境変化に応じて、ＲＡＭテーブル６３の記憶内容が更新される。
【００８６】
周波数変換部５４では、歪補償回路５３からの出力信号がＤ／Ａ変換器７１に入力される。
Ｄ／Ａ変換器７１は、入力される信号をデジタル信号からアナログ信号へ変換して、ミキサ７２へ出力する。
ミキサ７２は、Ｄ／Ａ変換器７１から入力される信号を無線周波数（ＲＦ）帯の信号へ周波数変換し、当該周波数変換結果の信号を増幅器５５へ出力する。
【００８７】
増幅器５５は、ミキサ７２から入力される信号を増幅し、当該増幅信号を送信対象として出力する。ここで、増幅器５５では、増幅信号に歪が発生するが、当該歪は上記した歪補償回路５３で与えられた歪と打ち消し合って、歪補償される。
また、増幅器５５から出力される増幅信号の一部は、例えば結合器などにより取り出されて、歪補償回路５３の歪成分検出部６５へ入力される。
【００８８】
ここで、図６（ｃ）には、増幅器５５に関する入出力電力特性の一例を示してある。なお、グラフの横軸は入力電力を示しており、縦軸は出力電力を示しており、後述する図６（ａ）、（ｂ）、（ｄ）のグラフについても同様である。
図示されるように、増幅器５５では、入力電力が比較的小さい場合には入力電力と出力電力とが比例するが、入力電力が大きくなって非線形領域となると、出力電力が飽和する。
【００８９】
図６（ｂ）には、歪補償回路５３に関する入出力電力特性の一例を示してある。
図示されるように、歪補償回路５３では、上記図６（ｃ）に示した増幅器５５に関する入出力電力特性を打ち消す入出力電力特性（逆特性）を有している。
図６（ｄ）には、本例の増幅装置（送信増幅器）の全体に関する入出力電力特性の一例を示してある。
図示されるように、増幅器５５の入出力電力特性と歪補償回路５３の入出力電力特性とが組み合わされることにより、線形な特性が得られる。
【００９０】
また、図６（ａ）には、本例の増幅装置（送信増幅器）の全体に関する入出力電力特性の一例を示してあるとともに、ピーク電力抑圧部５２によるピーク電力抑圧との関係を示してある。
図示されるように、本例では、ピーク電力抑圧前における増幅器５５の動作点と比べて、ピーク電力抑圧後における増幅器５５の動作点を（例えば、入力電力Ｐ０に対応する点に）上げることが可能である。
これは、図６（ａ）に、ピーク電力抑圧部５２によるピーク電力抑圧の一例として、時間と瞬時電力との関係の一例を示してあるように、ピーク電力の抑圧により、線形動作が可能な領域を拡大することができるためである。
【００９１】
以上のように、本例の増幅装置では、ピーク電力抑圧部５２をデジタルプリディストーション方式による歪補償回路５３と組み合わせて、送信対象となる信号を増幅するに際して、ピーク電力の抑圧処理及び歪補償処理を行う。
従って、本例の増幅装置では、上記第１実施例で述べたのと同様に、ピーク電力の低減と帯域外漏洩電力の制限との両立が可能となり、効果的にピーク電力を低減することができる。また、本例の増幅装置では、更に、増幅器５５の動作点を上げることや、装置の高効率化を図ることができる。
【００９２】
本発明の第４実施例に係る送信機を説明する。
図７には、本例の送信機８１の構成例を示してある。
本例の送信機８１には、第１変調部９１と、ピーク電力抑圧部９２と、第２変調部９３と、周波数変換部９４が備えられている。
第１変調部９１には、複数であるＮ個の波形整形フィルタＦ１〜ＦＮと、Ｎ個のデジタル直交変調部Ｇ１〜ＧＮと、２個の加算器１０１、１０２が備えられている。
周波数変換部９４には、２個のＤ／Ａ変換器１０３、１０４と、１個のアナログ直交変調部１０５が備えられている。
【００９３】
ここで、本例の送信機８１の構成や動作は、例えば、上記第１実施例の上記図１に示した送信機１と比べて、第１変調部９１と第２変調部９３を備えて、これらの間にピーク電力抑圧部９２を備えた点を除いては、上記図１に示した送信機１の構成や動作と同様であり、本例では、異なる部分について詳しく説明する。
【００９４】
すなわち、本例の送信機８１では、デジタル変調に関する第１の処理を行う第１変調部９１とデジタル変調に関する第２の処理を行う第２変調部９３との間にピーク電力抑圧部９２が備えられており、つまり、第１のデジタル変調部９１と第２のデジタル変調部９３から成るデジタル変調機能の内部にピーク電力抑圧機能が備えられており、第１のデジタル変調部９１による第１の処理と第２のデジタル変調部９３による第２の処理から成るデジタル変調処理の中にピーク電力抑圧処理が設けられている。
【００９５】
第１変調部９１の概略的な構成や動作は、例えば、上記第１実施例の上記図１に示した送信機１のデジタル変調部１１の構成や動作と同様であり、第１変調部９１は、入力される信号に対してデジタル変調を行い、当該デジタル変調結果の信号をピーク電力抑圧部９２へ出力する。なお、当該信号は、例えば、Ｉ成分及びＱ成分から構成され、以降の処理についても同様である。
【００９６】
ピーク電力抑圧部９２の概略的な構成や動作は、例えば、上記第１実施例の上記図１に示した送信機１のピーク電力抑圧部１２の構成や動作と同様であり、ピーク電力抑圧部９２は、第１変調部９１からの入力信号に対して、ピーク電力抑圧結果の信号を第２変調部９３へ出力する。
【００９７】
第２変調部９３は、ピーク電力抑圧部９２からの入力信号に対して所定の処理を行い、当該処理結果の信号を周波数変換部９４へ出力する。
周波数変換部９４の概略的な構成や動作は、例えば、上記第１実施例の上記図１に示した送信機１の周波数変換部１３の構成や動作と同様であり、周波数変換部９４は、第２変調部９３からの入力信号に対して、Ｄ／Ａ変換及び周波数変換結果の信号を出力する。
【００９８】
ここで、図８（ａ）、（ｂ）、（ｃ）には、それぞれ、第２変調部９３の構成例を示してある。
同図（ａ）に示した第２変調部９３の構成例では、第２変調部９３は、インターポレーション部１１１と、帯域制限フィルタ１１２から構成されている。
インターポレーション部１１１は、ピーク電力抑圧部９２からの入力信号のＩ成分及びＱ成分のそれぞれに対してインターポレーション処理を行い、当該処理結果を帯域制限フィルタ１１２へ出力する。なお、インターポレーション処理では、例えば、５０ＭＨｚで入力信号が“Ｘ Ｙ ”のとき、１００ＭＨｚで出力信号は“Ｘ０Ｙ０”となり、ここで、空欄は信号値が無いことを表している。
【００９９】
帯域制限フィルタ１１２は、インターポレーション部１１１からの入力信号のＩ成分及びＱ成分に対して帯域制限を行い、当該帯域制限後の信号のＩ成分及びＱ成分を周波数変換部９４へ出力する。なお、帯域制限フィルタ１１２では、例えば、レートを上げたために、折り返しスペクトルを除去する。
このような第２変調部９３の構成では、例えば、ピーク電力抑圧部９２は低いレートで動作することが可能となり、回路規模を低減することができる。
【０１００】
同図（ｂ）に示した第２変調部９３の構成例では、第２変調部９３は、デジタル直交変調部１２１から構成されている。
デジタル直交変調部１２１は、ピーク電力抑圧部９２からの入力信号のＩ成分及びＱ成分に対してデジタル直交変調を行い、当該デジタル直交変調結果の信号のＩ成分及びＱ成分を周波数変換部９４へ出力する。
このような第２変調部９３の構成では、一例として、第１変調部９１では入力信号をデジタル変調により第１の中間周波数（ＩＦ：Intermediate Frequency）の信号へ変換し、第２変調部９３では当該信号をデジタル変調により第２の中間周波数（ＩＦ）の信号へ変換する。
【０１０１】
同図（ｃ）に示した第２変調部９３の構成例では、第２変調部９３は、インターポレーション部１３１と、帯域制限フィルタ１３２と、デジタル直交変調部１３３から構成されている。
インターポレーション部１３１により行われる処理及び帯域制限フィルタ１３２により行われる処理は、それぞれ、同図（ａ）に示した構成例の場合と同様である。
更に、デジタル直交変調部１３３は、帯域制限フィルタ１３２から出力される信号のＩ成分及びＱ成分に対してデジタル直交変調を行い、当該デジタル直交変調結果の信号のＩ成分及びＱ成分を周波数変換部９４へ出力する。
【０１０２】
なお、上記図８（ａ）、（ｃ）では、インターポレーション処理を用いて低いレートの信号を高いレートの信号へ変換したが、これと共に或いは単独で、アップサンプル処理を用いることも可能である。アップサンプル処理では、例えば、５０ＭＨｚで入力信号が“Ｘ Ｙ ”のとき、１００ＭＨｚで出力信号は“ＸＸＹＹ”となり、ここで、空欄は信号値が無いことを表している。
【０１０３】
以上のように、本例の送信機８１では、デジタル変調処理を行う機能の内部にピーク電力抑圧部９２を備え、送信対象となる信号に対して、ピーク電力の抑圧処理を行う。
従って、本例の送信機８１では、上記第１実施例で述べたのと同様に、ピーク電力の低減と帯域外漏洩電力の制限との両立が可能となり、効果的にピーク電力を低減することができる。
【０１０４】
本発明の第５実施例に係る移動体通信システム及び基地局装置を説明する。
本例では、上記第１実施例の上記図１に示したような送信機１や、上記第２実施例の上記図５に示したような送信増幅器４１や、上記第３実施例の上記図６に示したような増幅装置や、上記第４実施例の上記図７に示したような送信機８１を、移動体通信システムや、移動体通信システムの基地局装置に設ける。
具体的には、一般に、移動体通信方式では、送信増幅器を線形領域で使用することが必要であることから、ピーク電力の低減と帯域外漏洩電力の制限との両立が要求される。
【０１０５】
そこで、本例では、上記第１実施例の上記図１や上記第２実施例の上記図５や上記第３実施例の上記図６や上記第４実施例の上記図７に示したような構成を備えた移動体通信システムや基地局装置を構築することにより、このような要求を満足する。
従って、本例の移動体通信システムや基地局装置では、例えば複数の通信チャネルの信号を送受信するに際して、ピーク電力の低減と帯域外漏洩電力の制限との両立が可能となり、効果的にピーク電力を低減することができる。
【０１０６】
以下で、本発明に関する技術の背景を示す。なお、ここで記載する事項は、必ずしも全てが従来の技術であるとは限定しない。
図９には、ＣＤＭＡシステムの送信機１４１の一構成例を示してある。
本例の送信機１４１の構成や動作は、ピーク電力抑圧係数演算部１５４に窓関数生成部やリミッタ係数演算部が備えられていないといった点を除いては、例えば上記第１実施例の図１に示した送信機１の構成や動作と同様である。
【０１０７】
具体的には、本例の送信機１４１には、Ｎ個の符号多重信号生成部Ｈ１〜ＨＮが接続されている。
また、本例の送信機１４１には、Ｎ個の波形整形フィルタＩ１〜ＩＮとＮ個のデジタル直交変調部Ｊ１〜ＪＮと２個の加算器１６１、１６２を有したデジタル変調部１５１と、２個の遅延部１６３、１６４と２個の乗算器１６５、１６６とピーク電力抑圧係数演算部１５４を有したピーク電力抑圧部１５２と、２個のＤ／Ａ変換器１６７、１６８とアナログ直交変調部１６９を有した周波数変換部１５３が備えられている。
また、ピーク電力抑圧係数演算部１５４には、瞬時電力演算部１７１と、平均電力演算部１７２と、閾値生成部１７３と、比較部１７４と、除算部１７５が備えられている。
【０１０８】
本例の送信機１４１では、ピーク電力抑圧係数演算部１５４において、例えば、上記式１〜上記式４に示したのと同様な演算が行われ、除算部１７５により演算されるピークファクタＧａｉｎ（ｔ）がそのままピーク電力抑圧係数として２個の乗算器１６５、１６６へ出力される。
【０１０９】
各乗算器１６５、１６６は、各遅延部１６３、１６４から入力される加算結果信号ＡＩ（ｔ）、ＡＱ（ｔ）と除算部１７５から入力されるピーク電力抑圧係数（ピークファクタ）Ｇａｉｎ（ｔ）とを乗算して、これによりピークの信号レベルを抑圧し、当該乗算結果Ａ’Ｉ（ｔ）、Ａ’Ｑ（ｔ）を各Ｄ／Ａ変換器１６７、１６８へ出力する。ここで、当該乗算結果Ａ’Ｉ（ｔ）、Ａ’Ｑ（ｔ）は、式８のように表される。
【０１１０】
【数８】

【０１１１】
図１０には、本例におけるピーク電力抑圧の様子の一例を示してある。
具体的には、時刻（サンプリング時間ｔ）に対する瞬時電力Ｐｉｎｔ（ｔ）、平均電力Ｐａｖｇ（ｔ）、閾値電力Ｔｈｒ（ｔ）及びピーク電力抑圧係数Ｇａｉｎ（ｔ）の一例を示してあり、また、周波数ｆに対するピーク電力抑圧係数Ｇａｉｎ（ｔ）の一例を示してある。
【０１１２】
上述のように、ピーク電力抑圧部１５２では、Ｉ成分及びＱ成分の加算結果信号に含まれる突出したピーク信号部分のレベルが抑圧される。
なお、ピークが検出されていないときには、ピーク電力抑圧係数Ｇａｉｎ（ｔ）は１となる。
このように、本例では、閾値電力Ｔｈｒを超えたピークの信号部分のみについてゲイン制御が行われる。
【０１１３】
また、図１１には、ＣＤＭＡシステムの送信増幅器１８１の一構成例を示してある。
本例の送信増幅器１８１の構成や動作は、周波数変換部１５３の後段に電力増幅部１８２が備えられている点を除いては、上記図９に示した送信機１４１の構成や動作と同様である。また、本例では、上記図９に示したのと同様な構成部分Ｈ１〜ＨＮ、１５１〜１５４、Ｉ１〜ＩＮ、Ｊ１〜ＪＮ、１６１〜１６９、１７１〜１７５については、同一の符号を付して示す。
【０１１４】
ここで、無線通信において通信に使用される周波数帯域は制限されるため、上記図１１に示したような電力増幅部１８２で発生する非線形歪による周波数スペクトラムの拡大を低く押さえることが要求される。このような要求から、符号多重信号を電力増幅部１８２により増幅する場合には、線形領域で動作させることが必要となる。
【０１１５】
しかしながら、上記図９に示したような送信機１４１や上記図１１に示したような送信増幅器１８１では、例えば、帯域制限された中間周波数（ＩＦ）領域において閾値を設けて信号レベルに制限を与えるような方法により、送信対象となる信号のピーク電力を抑圧するに際して、このようなピーク抑圧により、帯城外漏洩電力が増大してしまうといった不具合があった。
また、例えば、上記図９に示したような送信機１４１からの出力に対して、再度、帯域制限を行う構成では、スペクトルが元に戻ってしまい、時間波形も元に戻ってしまうため、ピーク電力の制限効果もなくなってしまう。
【０１１６】
そこで、本発明では、上記図９や上記図１１に示されるような構成においてピーク電力抑圧係数として用いられているピークファクタに窓関数の重みを与えることにより、当該ピークファクタに対して帯域制限を行い、当該帯域制限後のピークファクタを新たなピーク電力抑圧係数として設定し、送信対象となるＩ成分の信号やＱ成分の信号のピーク及びピーク周辺の振幅を制限することを行っており、これにより、効果的なピーク抑圧が実現されている。
【０１１７】
ここで、本発明に係る送信機や送信増幅器や増幅装置などの構成としては、必ずしも以上に示したものに限られず、種々な構成が用いられてもよい。なお、本発明は、例えば本発明に係る処理を実行する方法或いは方式や、このような方法や方式を実現するためのプログラムなどとして提供することも可能である。
また、本発明の適用分野としては、必ずしも以上に示したものに限られず、本発明は、種々な分野に適用することが可能なものである。
【０１１８】
また、本発明に係る送信機や送信増幅器や増幅装置などにおいて行われる各種の処理としては、例えばプロセッサやメモリ等を備えたハードウエア資源においてプロセッサがＲＯＭ（Read Only Memory）に格納された制御プログラムを実行することにより制御される構成が用いられてもよく、また、例えば当該処理を実行するための各機能手段が独立したハードウエア回路として構成されてもよい。
また、本発明は上記の制御プログラムを格納したフロッピー（登録商標）ディスクやＣＤ（Compact Disc）−ＲＯＭ等のコンピュータにより読み取り可能な記録媒体や当該プログラム（自体）として把握することもでき、当該制御プログラムを記録媒体からコンピュータに入力してプロセッサに実行させることにより、本発明に係る処理を遂行させることができる。
【０１１９】
【発明の効果】
以上説明したように、本発明に係る送信機によると、送信対象となる信号を送信するに際して、送信対象となる信号のピークを判定して、送信対象信号レベル閾値と送信対象となる信号のピークのレベルとの比に応じたピークファクタを生成し、生成したピークファクタを所定の窓関数により重み付けした結果をピーク抑圧係数として生成し、生成したピーク抑圧係数により送信対象となる信号のレベルを抑圧するようにしたため、送信対象となる信号のピーク及びその周辺のレベルが抑圧され、例えば、従来と比べて、ピークレベルの抑圧を効果的に行うことができ、具体的には、ピークレベルの抑圧と帯域外漏洩電力の低減との両方の効果を得ることができる。
【図面の簡単な説明】
【図１】 本発明の第１実施例に係る送信機の構成例を示す図である。
【図２】 ピーク電力の抑圧の様子の一例を示す図である。
【図３】 Ｗ−ＣＤＭＡ方式における送信機出力の周波数特性の一例を示す図である。
【図４】 Ｗ−ＣＤＭＡ方式における送信機出力の相補累積分布関数の一例を示す図である。
【図５】 本発明の第２実施例に係る送信増幅器の構成例を示す図である。
【図６】 本発明の第３実施例に係る増幅装置の構成例を示す図である。
【図７】 本発明の第４実施例に係る送信機の構成例を示す図である。
【図８】 第２変調部の内部構成例を示す図である。
【図９】 送信機の構成例を示す図である。
【図１０】 ピーク電力の抑圧の様子の一例を示す図である。
【図１１】 送信増幅器の構成例を示す図である。
【符号の説明】
１、８１、１４１・・送信機、 １１、５１、１５１・・デジタル変調部、
１２、５２、９２、１５２・・ピーク電力抑圧部、
１３、５４、９４、１５３・・周波数変換部、
１４、１５４・・ピーク電力抑圧係数演算部、
２１、２２、１０１、１０２、１６１、１６２・・加算器、
２３、２４、６１、１６３、１６４・・遅延部、
２５、２６、１６５、１６６・・乗算器、
２７、２８、７１、１０３、１０４、１６７、１６８・・Ｄ／Ａ変換器、
２９、１０５、１６９・・アナログ直交変調部、
３１、１７１・・瞬時電力演算部、 ３２、１７２・・平均電力演算部、
３３、１７３・・閾値生成部、 ３４、１７４・・比較部、
３５、１７５・・除算部、 ３６・・窓関数生成部、
３７・・リミッタ係数演算部、４１、１８１・・送信増幅器、
４２、１８２・・電力増幅部、
Ｂ１〜ＢＮ、Ｈ１〜ＨＮ・・符号多重信号生成部、
Ｃ１〜ＣＮ、Ｆ１〜ＦＮ、Ｉ１〜ＩＮ・・波形整形フィルタ、
Ｅ１〜ＥＮ、Ｇ１〜ＧＮ、１２１、１３３、Ｊ１〜ＪＮ・・デジタル直交変調部、
５３・・歪補償回路、 ５５・・増幅器、 ６２・・電力検出部、
６３・・ＲＡＭテーブル、 ６４・・複素乗算部、 ６５・・歪成分検出部、
６６・・制御部、 ７２・・ミキサ、 ９１・・第１変調部、
９３・・第２変調部、 １１１、１３１・・インターポレーション部、
１１２、１３２・・帯域制限フィルタ、[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transmitter that transmits a signal to be transmitted, and particularly to a transmitter that effectively suppresses the peak level of a signal to be transmitted.
[0002]
[Prior art]
The transmitter transmits a signal to be transmitted.
For example, in signal transmission employing a CDMA (Code Division Multiple Access) method, the level of a signal to be transmitted may vary, and the signal level to be transmitted is at a peak level. It is necessary to suppress the peak level.
[0003]
As an example, conventionally, in a carrier synthesis transmission circuit with a limiter circuit, the ratio between the instantaneous power and the average power of a signal obtained by multiplexing all carriers is used as an instantaneous peak factor, and the instantaneous peak factor is compared with a reference value. A limit coefficient suitable for the necessary degree of clipping is obtained, and using the limit coefficient, clipping necessary for each of the instantaneous power transmitted by each carrier before amplification by the power amplification unit is performed (for example, Patent Documents). 1).
[0004]
[Patent Document 1]
JP 2002-44054 A
[0005]
[Problems to be solved by the invention]
However, in the conventional transmitter, for example, when the peak level of a signal to be transmitted is suppressed, there is a problem that out-of-band leakage power increases. In addition, for example, when the peak level of the signal to be transmitted is suppressed and then the band of the signal to be transmitted is limited again, the peak level suppressing effect is impaired.
[0006]
The present invention has been made in view of such a conventional situation. When transmitting a signal to be transmitted, the transmission can effectively suppress the peak level of the signal to be transmitted. The purpose is to provide a machine.
More specifically, an object of the present invention is to provide a transmitter capable of obtaining both effects of peak level suppression and reduction of out-of-band leakage power.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the transmitter according to the present invention performs the following processing when transmitting a signal to be transmitted.
That is, the peak factor generation means determines the peak of the signal to be transmitted do it Then, a peak factor corresponding to the ratio between the transmission target signal level threshold (transmission target signal level threshold for determining the peak of the transmission target signal) and the peak level of the transmission target signal is generated. The peak suppression coefficient generating means generates a result obtained by weighting the peak factor generated by the peak factor generating means with a predetermined window function as a peak suppression coefficient. The transmission target signal level suppression unit suppresses the level of the signal to be transmitted by the peak suppression coefficient generated by the peak suppression coefficient generation unit.
[0008]
Therefore, when the peak factor is weighted by the window function, the peak factor is band-limited, and the peak of the signal to be transmitted using the band-limited peak factor as the peak suppression coefficient and the surrounding levels are used. Therefore, for example, peak level can be suppressed more effectively than in the past, and specifically, both peak level suppression and reduction of out-of-band leakage power can be obtained. Can do.
[0009]
Here, various signals may be used as signals to be transmitted.
As transmission, wireless transmission may be used, and wired transmission may be used.
Further, various signal parts having a relatively large level may be used as the peak of the signal to be transmitted. For example, a signal part having a level higher than the transmission target signal level threshold is regarded as a peak. Embodiments can be used.
[0010]
Various values may be used as the transmission target signal level threshold.
Various levels may be used as the level, for example, a power level, an amplitude level, or the like can be used.
Various values may be used as a peak factor corresponding to the ratio between the transmission target signal level threshold and the peak level of the transmission target signal. For example, the value of the square root of the ratio or the ratio Can be used.
[0011]
Various functions may be used as the predetermined window function.
As an example, when the suppression effect of the signal level is greater as the peak suppression coefficient is smaller, a function that takes a value that becomes the minimum at the peak time position of the signal to be transmitted and increases as the distance from the time position increases. It can be used as a window function.
As another example, when the suppression effect of the signal level is larger as the peak suppression coefficient is larger, the value is maximized at the time position of the peak of the signal to be transmitted and becomes smaller as the distance from the time position is larger. The function can be used as a window function.
[0012]
For example, a method that uses a numerical value or the like and does not use a function and performs processing substantially similar to weighting by a window function is included in the present invention.
Various values may be used as the peak suppression coefficient.
Various degrees may be used as the degree of suppression of the peak level of the signal to be transmitted. For example, it is sufficient that the peak level can be reduced to an extent that is practically effective.
[0013]
The transmitter according to the present invention has the following configuration as one configuration example.
That is, in the peak factor generation means, the transmission target signal level detection means detects the level of the signal to be transmitted, the transmission target signal level average value detection means detects the average value of the level of the signal to be transmitted, The transmission target signal level threshold generation unit generates the transmission target signal level threshold based on the detection result by the transmission target signal level average value detection unit. In the peak factor generation means, the peak factor setting means determines whether the transmission target signal level threshold generated by the transmission target signal level threshold generation means and the level of the signal to be transmitted detected by the transmission target signal level detection means. Set the peak factor according to the ratio.
[0014]
Further, the peak suppression coefficient generating means generates, as a peak suppression coefficient, a result obtained by weighting the peak factor set by the peak factor setting means of the peak factor generating means with a predetermined window function.
The transmission target signal level suppression unit multiplies the transmission target signal by the peak suppression coefficient generated by the peak suppression coefficient generation unit, thereby suppressing the level of the transmission target signal.
[0015]
Here, various average values may be used as the average value of the level of the signal to be transmitted. For example, a temporal average value can be used. For example, a plurality of signals different in time can be used. The result of summing the levels or the result of dividing the summation result by the summation number can be used.
[0016]
Further, the transmitter according to the present invention has the following configuration as one configuration example.
Note that the power level is used as an example of the signal level. T represents time.
That is, in the peak factor generation means, the transmission target signal level threshold magnitude comparison means is generated by the level Pint (t) of the transmission target signal detected by the transmission target signal level detection means and the transmission target signal level threshold generation means. Compared with the transmission target signal level threshold Thr.
The transmission target signal level threshold generation unit of the peak factor generation unit calculates a predetermined value for the average value Pavg of the level Pint (t) of the signal to be transmitted detected by the transmission target signal level average value detection unit. The result is generated as a transmission target signal level threshold value Thr.
[0017]
Further, the peak factor setting means of the peak factor generation means is configured such that the level Pint (t) of the signal to be transmitted detected by the transmission target signal level detection means is based on the comparison result by the transmission target signal level threshold magnitude comparison means. When it is larger than the transmission target signal level threshold Thr generated by the transmission target signal level threshold generation means (that is, when Pint (t)> Thr), the value of sqrt {Thr / Pint (t)} is set. The peak factor Gain (t) is set as a transmission target signal level threshold Thr that is generated by the transmission target signal level threshold generation means so that the transmission target signal level Pint (t) detected by the transmission target signal level detection means (That is, when Pint (t) ≦ Thr), 1 value is set to the peak factor. Set as ain (t). Note that sqrt represents a square root.
[0018]
Further, the peak suppression coefficient generating means uses a window function Weight (s) that takes a value in an interval from s (−M / 2) to (+ M / 2), and [1-Weight (s) · {1- Gain (t)}] is generated as a peak suppression coefficient Exp_Gain (t + s). Note that M is a predetermined value that defines the window function Weight (s).
[0019]
Here, as the transmission target signal level threshold Thr, for example, a result obtained by multiplying the average value Pavg of the level Pint (t) of the signal to be transmitted by a predetermined value, or the level Pint (t) of the signal to be transmitted The result of adding a predetermined value to the average value Pavg of can be used.
Various values may be used as the predetermined value M that defines the window function Weight (s).
[0020]
Note that the level Pint (t) of the transmission target signal detected by the transmission target signal level detection unit is equal to the transmission target signal level threshold Thr generated by the transmission target signal level threshold generation unit (that is, Pint ( For t) = Thr), for example, a configuration in which the value of sqrt {Thr / Pint (t)} is set as the peak factor Gain (t) can be used. Since Gain (t) = 1, it is substantially the same as the above configuration and is included in the present invention.
[0021]
In the above, an example in which the power level is used as the signal level is shown. However, if substantially the same processing is performed, for example, other levels such as amplitude may be used as the signal level. Those used and those using different mathematical expressions are also included in the present invention.
[0022]
In addition, there are a plurality of peaks of signals to be transmitted at close signal positions (close time positions), and peak suppression coefficients generated due to certain peaks and peak suppression generated due to other peaks. When the coefficient overlaps the same signal position (the same time position), various modes may be used. For example, an average value of a plurality of peak suppression coefficients that overlap at the same signal position. A mode in which the signal level is suppressed, a mode in which the signal level is suppressed by any one of a plurality of overlapping peak suppression coefficients, and a peak suppression coefficient generated due to the peak having the maximum level Of signal level suppression by means of, a mode of signal level suppression by the peak suppression coefficient generated due to the peak at which the level is minimum, or a plurality of overlapping peak suppression coefficients It is possible to use such aspects for performing the suppression in signal level by the sum.
[0023]
Below, the structural example which concerns on this invention is shown further.
In the transmitter according to the present invention, as one configuration example, the peak suppression coefficient generating means uses a function including a trigonometric function as a predetermined window function.
Here, as the trigonometric function, a sine function (sin), a cosine function (cos), or the like can be used.
[0024]
In the transmitter according to the present invention, as one configuration example, signals to be transmitted are an I signal and a Q signal obtained by digital quadrature modulation. Further, the transmission target signal level suppression unit suppresses the level of the signal to be transmitted for each of the I signal and the Q signal.
Here, various methods may be used as the orthogonal modulation method.
[0025]
In addition, the process which suppresses the level (peak level) of the signal used as transmission object by this invention may be performed after a modulation process, for example, or may be performed between modulation processes. As an example of suppressing the signal level during the modulation process, a first modulation processing unit that performs a first process related to modulation and a second modulation processing unit that performs a second process related to modulation are provided. It is possible to use a configuration in which signal level suppression is performed on the first processing result of the modulation processing means, and second processing is performed on the result of suppression of the signal level by the second modulation processing means. it can.
Here, various processes may be used as the first process related to the modulation and the second process related to the modulation, for example, a process for performing the modulation and other processes associated with the modulation may be used. it can.
[0026]
The transmitter according to the present invention is configured as a transmission amplifier (transmission amplification device) including an amplifier that amplifies a signal to be transmitted whose signal level is suppressed by the transmission target signal level suppression unit as one configuration example.
Here, such a transmission amplifier has, for example, a transmitter function and an amplifier function.
Various amplifiers may be used as the amplifier.
[0027]
In the transmitter according to the present invention, as a configuration example, a multicarrier signal including a plurality of carrier signals is used as a signal to be transmitted.
Here, various numbers may be used as the number of the plurality of carrier signals.
In such a multi-carrier signal, in particular, the overall level of a plurality of carrier signals is likely to fluctuate depending on the communication status and the like, and the present invention is effective.
[0028]
The transmitter according to the present invention is provided as a configuration example in a mobile communication system, a base station apparatus, a relay station apparatus, or the like of the mobile communication system.
Here, various mobile communication systems such as a mobile phone system and a simple mobile phone system (PHS: Personal Handypone System) may be used.
[0029]
The transmitter according to the present invention is provided in a radio communication system adopting the CDMA system as one configuration example.
Here, as the CDMA system, for example, various systems such as a W (Wideband) -CDMA system may be used.
The transmitter according to the present invention can also support a modulation scheme such as OFDM (Orthogonal Frequency Division Multiplex).
[0030]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments according to the present invention will be described with reference to the drawings.
In the present embodiment, a case where the present invention is applied to a transmission apparatus provided in a base station apparatus or the like of a wireless communication system employing a CDMA system is shown. In such a transmission apparatus, generally, a high power signal is amplified by an amplifier.
Note that the peak level suppression amount may be limited, but the present invention may be applied to a modulation scheme such as OFDM.
[0031]
A transmitter according to a first embodiment of the present invention will be described.
FIG. 1 shows a configuration example of the transmitter 1 of this example.
In the transmitter 1 of this example, N code multiplexed signal generation units B1 to BN are connected to a plurality of N carriers 1 to N, respectively. In addition, a plurality of (n + 1) pieces of transmission data are input to each of the code multiplexed signal generation units B1 to BN for each of the carriers 1 to N.
[0032]
The transmitter 1 of this example includes a digital modulation unit 11, a peak power suppression unit 12, and a frequency conversion unit 13.
The digital modulation unit 11 includes N waveform shaping filters C1 to CN and N digital quadrature modulation units E1 to EN corresponding to the N carriers 1 to N, and an I-phase component (I Two adders 21 and 22 are provided corresponding to the component) and the Q-phase component (Q component).
The peak power suppression unit 12 includes two delay units 23 and 24 and two multipliers 25 and 26 corresponding to the I component and the Q component, and the peak power suppression coefficient calculation unit 14 includes Is provided.
[0033]
The peak power suppression coefficient calculator 14 includes an instantaneous power calculator 31, an average power calculator 32, a threshold generator 33, a comparator 34, a divider 35, a window function generator 36, and a limiter coefficient calculator. A portion 37 is provided.
The frequency conversion unit 29 includes two D / A (Digital to Analog) converters 27 and 28 corresponding to the I component and the Q component, and also includes an analog quadrature modulation unit 29. .
[0034]
Here, each of the code multiplex signal generation units B1 to BN performs spread modulation by multiplying the input transmission data D (0) to D (n) by the code multiplex signal sequence, and performs each of the carriers 1 to N. (N + 1) spread modulation signals are combined, and the resulting I component DI and Q component DQ are output to the waveform shaping filters C1 to CN of the transmitter 1. For example, a spread code is used as the code multiplexed signal sequence.
[0035]
An example of the operation performed by the transmitter 1 of this example will be shown.
Note that t represents the sampling time.
Each of the waveform shaping filters C1 to CN inputs the carriers 1 to N, which are spread and modulated by the code multiplexed signal generators B1 to BN, for each of the I component and the Q component, and the occupied band of the input signal is Spectrum shaping is performed so as to be within a preset value, and the I component and Q component of the spectrum shaping result are output to the digital quadrature modulation units E1 to EN.
[0036]
Each of the digital quadrature modulation units E1 to EN performs digital quadrature modulation on the signals of the respective carriers 1 to N input from the respective waveform shaping filters C1 to CN, and sends the I component of the digital quadrature modulation result to one adder 21. The Q component of the digital quadrature modulation result is output to the other adder 22.
[0037]
One adder 21 adds (combines) the digital quadrature modulation results input from the N digital quadrature modulation units E1 to EN to the I component, and adds the signal AI (t) of the addition result to one delay unit. 23 and the instantaneous power calculation unit 31.
The other adder 22 adds (synthesizes) the digital quadrature modulation results input from the N digital quadrature modulation units E1 to EN with respect to the Q component, and adds the signal AQ (t) of the addition result to the other delay unit. 24 and the instantaneous power calculation unit 31.
[0038]
Based on the I component AI (t) and the Q component AQ (t) of the addition result signal input from the two adders 21 and 22, the instantaneous power calculation unit 31 determines the instantaneous power Pint (t ) And outputs the calculation result to the average power calculation unit 32, the comparison unit 34, and the division unit 35. Here, as an example, the instantaneous power Pint (t) is expressed as Equation 1.
[0039]
[Expression 1]

[0040]
The average power calculation unit 32 calculates the average power Pavg of the addition result signal described above based on the instantaneous power Pint (t) calculated by the instantaneous power calculation unit 31 and outputs the calculation result to the threshold value generation unit 33. . Here, as an example, the average power Pavg is expressed as in Equation 2. T represents the number of signals to be averaged, and various numbers may be used.
[0041]
[Expression 2]

[0042]
The threshold generation unit 33 sets the threshold power Thr for performing peak suppression based on the average power Pavg input from the average power calculation unit 32, and outputs the setting result to the comparison unit 34 and the division unit 35. Here, as an example, when (average power Pavg + 6 dB) is set as the threshold power Thr, the threshold power Thr is expressed as Equation 3.
[0043]
[Equation 3]

[0044]
The comparison unit 34 compares the level of the threshold power Thr input from the threshold value generation unit 33 with the level of the instantaneous power Pint (t) input from the instantaneous power calculation unit 31, and compares the comparison result with the division unit 35 and The result is output to the window function generator 36. Here, in this example, the portion where the instantaneous power Pint (t) exceeds the threshold power Thr is detected as the peak portion of the addition result signal described above.
[0045]
When the instantaneous power Pint (t) exceeds the threshold power Thr and a peak is detected by the comparator 34 based on the input from the comparator 34, the divider 35 detects the threshold power Thr and the instantaneous power Pint (t ), A predetermined peak factor Gain (t) is calculated, and the calculation result is output to the limiter calculation unit 37.
Further, based on the input from the comparison unit 34, the division unit 35 has a case where the instantaneous power Pint (t) is equal to or less than the threshold power Thr and the peak is not detected (that is, not detected) by the comparison unit 34. 1 is set as the peak factor Gain (t), and the setting result is output to the limiter calculation unit 37.
[0046]
Here, as an example, the peak factor Gain (t) is expressed as Equation 4.
In this example, since the instantaneous power Pint (t) and the threshold power Thr are represented by power dimensions, the square root (sqrt) is calculated to suppress the peak level in the voltage domain.
[0047]
[Expression 4]

[0048]
When the instantaneous power Pint (t) exceeds the threshold power Thr and a peak is detected by the comparison unit 34 based on the input from the comparison unit 34, the window function generation unit 36 determines a predetermined window function Weight (s ) And output the generation result to the limiter coefficient calculation unit 37. Note that the window function generator 36 outputs, for example, a value of 1 to the limiter coefficient calculator 37 in other cases (that is, when no peak is detected).
[0049]
Here, as an example, when a Hamming window is used, an example of the window function Weight (s) is expressed as Equation 5.
Note that M represents the number of samples, for example, an integer of 2 or more.
In general, as the number of samples M increases, the band of the window function Weight (s) becomes narrower. Further, the number of samples M is set by being optimized according to the standard bandwidth of the transmission spectrum, for example.
[0050]
[Equation 5]

[0051]
Here, s takes a value in a section (−M / 2) to (+ M / 2) corresponding to a section from time (t−M / 2) to time (t + M / 2) ([−M / 2 ≦ s ≦ + M / 2]). Accordingly, for example, M (or (M + 1)) peak power suppression coefficients Exp_Gain (t + s) are generated for one time t at which a peak exists.
[0052]
For example, the limiter coefficient calculation unit 37 receives a peak factor Gain (t) input from the division unit 35 in a section from time (t−M / 2) to time (t + M / 2) centered on time t at which a peak exists. Is given a weight by the window function Weight (s) input from the window function generator 36, and the weighted result is output to the two multipliers 25 and 26 as a peak power suppression coefficient Exp_Gain (t + s). . Here, as an example, the peak power suppression coefficient Exp_Gain (t + s) is expressed as Equation 6.
[0053]
[Formula 6]

[0054]
As described above, the peak power suppression coefficient calculation unit 14 sets the peak power suppression coefficient Exp_Gain (t + s) for realizing the necessary peak level suppression for the instantaneous power Pint (t) of the addition result signal described above. .
In this example, the window function Weight (s) including the trigonometric function is used. However, for example, a window function not including the trigonometric function may be used.
[0055]
Basically, the purpose of the window function is to limit the band of the peak level suppression signal itself in order to prevent the spectrum from expanding when peak level suppression is performed. For example, when a simple rectangular window is used, a longer window width is required to suppress spectrum expansion. Since various studies have been made on the window function and it is generally known, the detailed description is omitted in this specification.
[0056]
Each delay unit 23, 24 is an addition result signal input from each adder 21, 22 corresponding to the time required for the processing for calculating the peak power suppression coefficient Exp_Gain (t + s) by the peak power suppression coefficient calculation unit 14. The delays of AI (t) and AQ (t) are adjusted, and the delayed signals are output to the multipliers 25 and 26.
[0057]
The multipliers 25 and 26 use the addition result signals AI (t + s) and AQ (t + s) input from the delay units 23 and 24 and the peak power suppression coefficient Exp_Gain (t + s) input from the limiter coefficient calculation unit 37, respectively. Multiplication is performed, thereby suppressing the peak and surrounding signal levels, and outputting the multiplication results A′I (t + s) and A′Q (t + s) to the D / A converters 27 and 28. Here, the multiplication results A′I (t + s) and A′Q (t + s) are expressed as in Expression 7.
[0058]
[Expression 7]

[0059]
Each D / A converter 27, 28 converts the digital signal input from each multiplier 25, 26 into an analog signal, and outputs the D / A conversion result to the analog quadrature modulation unit 29.
The analog quadrature modulation unit 29 performs analog quadrature modulation on the analog signal composed of the I component and the Q component input from the two D / A converters 27 and 28, thereby converting the signal into a radio frequency band signal. And output.
[0060]
Here, FIG. 2 shows an example of the state of peak power suppression in this example.
Specifically, examples of instantaneous power Pint (t), average power Pavg (t), threshold power Thr (t) and peak power suppression coefficient Exp_Gain (t) with respect to time (sampling time t) are shown. An example of the peak power suppression coefficient Exp_Gain (t) with respect to the frequency f is shown.
[0061]
As shown in the figure, in this example, when a peak is detected, the peak power suppression coefficient Exp_Gain (t) is a downward convex graph.
In this example, when no peak is detected, the peak factor Gain (t) is 1, and the peak power suppression coefficient Exp_Gain (t) is 1.
[0062]
As described above, the peak power suppression unit 12 suppresses the level of the protruding peak signal part and the level of the signal part around the peak included in the addition result signal of the I component and the Q component.
As described above, in this example, gain control is performed not only on the signal portion of the peak exceeding the threshold power Thr but also on the signal portion around the peak.
[0063]
As described above, in the transmitter 1 of this example, for example, when transmission is performed using a plurality or a single carrier frequency, the instantaneous power Pint (t) of the digital modulation results AI (t) and AQ (t) to be transmitted ) And the threshold power Thr based on the average power Pavg is calculated as a peak factor Gain (t), and the peak factor Gain (t) is weighted by the window function Weight (s) to obtain a peak The power suppression coefficient Exp_Gain (t + s) is calculated, and the peak voltage level of the digital modulation results AI (t) and AQ (t) and the voltage level around the peak are calculated based on the peak power suppression coefficient Exp_Gain (t + s). Control is done.
[0064]
Therefore, in the transmitter 1 of this example, for example, it is possible to achieve both reduction in peak power and restriction of out-of-band leakage power, and effectively reduce peak power, compared to the conventional case.
Further, in the transmitter 1 of this example, it is possible to realize a reduction in circuit scale and a reduction in window function memory capacity, for example, compared to the conventional case.
[0065]
Note that the peak power suppression process as in this example is a non-linear process, which may affect a system using a linear modulation method. For this reason, there is a trade-off between reducing the peak power and increasing the power efficiency of the amplifier and the deterioration in communication quality. For this reason, specific numerical values used for the peak power suppression processing as in this example may be determined variously depending on, for example, the system operator that employs the present invention.
[0066]
Here, the specific example of the effect acquired by the transmitter 1 of this example is shown.
FIG. 3 shows an example of frequency characteristics of a signal output from a transmitter adopting the W-CDMA communication system at the time of one-carrier transmission. (A) Comparison as shown in FIG. 9 or FIG. Examples of characteristics related to the transmitters 141, 181 according to the example, and (b) characteristic examples related to the transmitters 1, 41, 81 according to the present proposal as shown in FIG. 1, FIG. 5, FIG. 6, and FIG. (C) The characteristic example regarding the transmitter etc. which do not have a function which suppresses peak electric power is shown. In addition, the horizontal axis of the graph of FIG. 3 has shown the normalized frequency, and the vertical axis | shaft has shown the transmission level [dBm].
[0067]
Further, FIG. 3 shows an example of frequency characteristics when data of 2560 samples of one carrier signal at the time of multiplexing with 32 codes is transmitted. FIG. 3 shows an example in which a value of (average power + 8 dB) is set as the threshold power Thr.
As shown in FIG. 3, (a) the adjacent leakage power is increased in the transmitters 141 and 181 according to the comparative example, but (b) the transmitters 1, 41, and 81 according to the present proposal have a window. Since the peak power suppression coefficient given the function weight is used, the peak power suppression coefficient is band-limited, and the adjacent leakage power can be suppressed to a relatively small level.
[0068]
FIG. 4 shows an example of a complementary cumulative distribution function (CCDF) of a signal output from a transmitter adopting the W-CDMA communication system at the time of one-carrier transmission. (A) FIG. 9 and FIG. (B) Transmitters etc. 1, 41, 81 according to the present proposal as shown in FIG. 1, FIG. 5, FIG. 6 or FIG. And (c) a characteristic example relating to a transmitter or the like that does not have a function of suppressing peak power. Note that the horizontal axis of the graph of FIG. 4 indicates the power [dB] exceeding the average power, and the vertical axis indicates the cumulative probability [%].
[0069]
FIG. 4 shows an example of a complementary cumulative distribution function (CCDF) when transmitting data of 2560 samples of one carrier signal when multiplexing with 32 codes. FIG. 4 shows an example in which a value of (average power + 8 dB) is set as the threshold power Thr.
As shown in FIG. 4, in (b) the transmitters 1, 41, 81 according to the present proposal, the peak power is suppressed in the same manner as (a) the transmitters 141, 181 according to the comparative example.
[0070]
The reason why the out-of-band leakage power is limited by the transmitter 1 of this example will be described.
That is, peak power suppression is performed by multiplication (modulation) of the output signal from the band-limited modulation unit and the peak power suppression coefficient. For example, as shown in FIG. 10 according to the comparative example, the peak power suppression coefficient Gain (t), which is a pulse signal, has a spectrum that extends over the entire band when viewed on the frequency axis, and such peak power In the configuration in which the signal of the suppression coefficient Gain (t) is multiplied (modulated) with the output signal from the modulation unit, the band-limited spectrum is deteriorated. On the other hand, as shown in FIG. 2 according to the present proposal, the peak power suppression coefficient Exp_Gain (t) generated by performing the band limitation of the pulse signal using a window function including a cosine function or the like. In the configuration in which the signal is multiplied (modulated) with the output signal from the modulation unit 11, it is possible to suppress the spread of the spectrum and to suppress the out-of-band leakage power.
[0071]
In the transmitter 1 of this example, the transmission target signal level detection unit is configured by the function of the instantaneous power calculation unit 31, and the transmission target signal level average value detection unit is configured by the function of the average power calculation unit 32. The transmission target signal level threshold generation unit is configured by the function of the threshold generation unit 33, the transmission target signal level threshold value comparison unit is configured by the function of the comparison unit 33, and the peak factor is configured by the function of the division unit 35. Setting means is configured, and these means constitute peak factor generation means.
Further, in the transmitter 1 of this example, the function of the window function generator 36 and the function of the limiter coefficient calculator 37 constitute a peak suppression coefficient generator, and the functions of the multipliers 25 and 26 suppress the transmission target signal level. Means are configured.
[0072]
A transmission amplifier according to a second embodiment of the present invention will be described.
FIG. 5 shows a configuration example of the transmission amplifier 41 of this example.
The configuration and operation of the transmission amplifier 41 of the present example are the same as those of the transmitter 1 shown in FIG. 1 of the first embodiment, except that the power amplification unit 42 is provided after the frequency conversion unit 13. The configuration and operation are the same. Moreover, in this example, the same components B1 to BN, 11 to 14, C1 to CN, E1 to EN, 21 to 29, and 31 to 37 as shown in FIG. Show.
The power amplifier 42 receives the radio frequency signal output from the analog quadrature modulator 29 provided in the frequency converter 13, amplifies the input signal, and outputs the amplified signal.
[0073]
As described above, in the transmission amplifier 41 of this example, when transmitting a multicarrier signal composed of, for example, a plurality of communication channels, a window function is used in the same manner as the transmitter shown in FIG. 1 of the first embodiment. The peak of the signal to be transmitted and the level around it are suppressed, and then the power amplification unit 42 amplifies the transmission power.
Therefore, in the transmission amplifier 41 of this example, as described in the first embodiment, it is possible to achieve both reduction in peak power and restriction of out-of-band leakage power, and effectively reduce peak power. Can do.
[0074]
An amplifying apparatus according to a third embodiment of the present invention will be described.
FIG. 6 shows a configuration example of the amplification device of this example.
The amplifying apparatus of this example includes a digital modulation unit 51, a peak power suppression unit 52, a distortion compensation circuit 53, a frequency conversion unit 54, and an amplifier 55.
The distortion compensation circuit 53 includes a delay unit 61, a power detection unit 62, a RAM (Random Access Memory) table 63, a complex multiplication unit 64, a distortion component detection unit 65, and a control unit 66.
The frequency conversion unit 54 includes a D / A converter 71 and a mixer 72.
[0075]
Here, the amplification device of this example includes a circuit (distortion compensation circuit) 53 that performs distortion compensation by a digital predistortion (DPD) method.
The amplifying apparatus of this example compensates for distortion generated in the amplifier 55 by the distortion compensation circuit 53 when the signal to be transmitted is amplified by the amplifier 55, and converts the signal to be input to the distortion compensation circuit 53. On the other hand, the peak power suppression unit 52 suppresses the peak power.
[0076]
Note that in the predistortion method, distortion compensation is performed by adding a distortion having an inverse characteristic of the distortion generated by the element to the input signal in advance, and matching between the predistortion processing of the input signal and the nonlinearity of the element is performed. Is very important. In the predistortion method, for example, since distortion compensation deterioration is significant when the power is equal to or higher than the saturation power of the element, suppression processing of the peak power component of the signal is very effective in processing of the input signal.
[0077]
In this example, an example of using a digital predistortion method for detecting input power from a baseband signal is shown. For example, an analog method for detecting input power of a radio frequency (RF) signal. It is also possible to apply to the predistortion method.
[0078]
An example of the operation performed by the amplification device of this example will be shown.
The digital modulation unit 51 has the same configuration as the digital modulation unit 11 shown in FIG. 1 of the first embodiment, for example, performs the same operation, and for the input signal to be transmitted, The signal of the digital modulation result is output to the peak power suppression unit 52.
[0079]
Note that the digital modulation result signal includes, for example, an I component and a Q component, and the same applies to the subsequent processing.
The signal resulting from the digital modulation is composed of a digital signal and is converted into an analog signal by a D / A converter 71 described later.
[0080]
The peak power suppression unit 52 has the same configuration as that of the peak power suppression unit 12 shown in FIG. 1 of the first embodiment, for example, performs the same operation, and receives an input signal from the digital modulation unit 51. Then, the peak power suppression result signal is output to the distortion compensation circuit 53.
Here, the peak power suppression unit 52 of this example suppresses power in a region where the distortion compensation circuit 5 cannot perform distortion compensation, thereby increasing the operating point of the amplifier 55 and increasing the efficiency of the apparatus. It is illustrated.
[0081]
In the distortion compensation circuit 53, the output signal from the peak power suppression unit 52 is input to the delay unit 61 and the power detection unit 62.
The delay unit 61 delays the input signal and outputs the delayed signal to the complex multiplication unit 64.
The power detection unit 62 calculates the instantaneous power (envelope) of the input signal and outputs the calculation result to the RAM table 63.
[0082]
The RAM table 63 stores the amplitude and phase correction amounts in association with the input power, and refers to the correspondence, and according to the calculation result input from the power detection unit 62, the calculation result (input power). ) Is output to the complex multiplier 64. Thereby, the correction amount of the amplitude or phase can be controlled according to the level of the input power, and the correction amount according to the operating environment can be controlled.
As an example, if the amplitude correction amount (magnification) is represented by A, the phase correction amount is represented by θ (deviation), and the imaginary part is represented by j, both the amplitude and phase correction amounts are (A × e). ^jθ ).
[0083]
The complex multiplier 64 performs complex multiplication on the signal input from the delay unit 61 and the correction amount input from the RAM table 63, and outputs the complex multiplication result to the frequency converter 54. In the complex multiplication, the amplitude and phase of the input signal are changed in accordance with the correction amount, and thereby, it is realized that distortion of an inverse characteristic with respect to the nonlinear characteristic of the amplifier 55 is given to the input signal.
[0084]
The distortion component detection unit 65 detects a distortion component included in the amplified signal output from the amplifier 55 by demodulation, calculates the power of the distortion component, and outputs the calculation result to the control unit 66. In the demodulation, for example, frequency conversion, band limitation, and A / D (Analog to Digital) conversion are performed. As an example, the third-order distortion of the frequency (2f0-f1) and the frequency (2f1-f0) is generated by the signals of the two frequencies f0 and f1, and the distortion component detection unit 65 detects the power of the third-order distortion.
[0085]
The control unit 66 updates the correspondence between the input power stored in the RAM table 63 and the amplitude and phase correction amount based on the information regarding the power of the distortion component input from the distortion component detection unit 65. Thereby, the stored contents of the RAM table 63 are updated in accordance with the environmental change.
[0086]
In the frequency converter 54, the output signal from the distortion compensation circuit 53 is input to the D / A converter 71.
The D / A converter 71 converts the input signal from a digital signal to an analog signal and outputs the analog signal to the mixer 72.
The mixer 72 frequency-converts the signal input from the D / A converter 71 into a radio frequency (RF) band signal, and outputs the signal resulting from the frequency conversion to the amplifier 55.
[0087]
The amplifier 55 amplifies the signal input from the mixer 72 and outputs the amplified signal as a transmission target. Here, in the amplifier 55, distortion occurs in the amplified signal, but the distortion cancels out the distortion given by the distortion compensation circuit 53 and is compensated for distortion.
A part of the amplified signal output from the amplifier 55 is extracted by, for example, a coupler and input to the distortion component detection unit 65 of the distortion compensation circuit 53.
[0088]
Here, FIG. 6C shows an example of the input / output power characteristics related to the amplifier 55. The horizontal axis of the graph indicates the input power, the vertical axis indicates the output power, and the same applies to the graphs of FIGS. 6A, 6B, and 6D described later.
As shown in the figure, in the amplifier 55, when the input power is relatively small, the input power and the output power are proportional, but when the input power becomes large and becomes a non-linear region, the output power is saturated.
[0089]
FIG. 6B shows an example of input / output power characteristics related to the distortion compensation circuit 53.
As shown in the figure, the distortion compensation circuit 53 has an input / output power characteristic (reverse characteristic) that cancels the input / output power characteristic related to the amplifier 55 shown in FIG.
FIG. 6D shows an example of input / output power characteristics related to the entire amplifying apparatus (transmission amplifier) of this example.
As shown in the figure, linear characteristics can be obtained by combining the input / output power characteristics of the amplifier 55 and the input / output power characteristics of the distortion compensation circuit 53.
[0090]
FIG. 6A shows an example of input / output power characteristics related to the entire amplifying apparatus (transmission amplifier) of this example, and also shows the relationship with peak power suppression by the peak power suppression unit 52. .
As shown in the figure, in this example, the operating point of the amplifier 55 after peak power suppression is increased (for example, to a point corresponding to the input power P0) as compared to the operating point of the amplifier 55 before peak power suppression. Is possible.
As shown in FIG. 6 (a), as an example of peak power suppression by the peak power suppression unit 52, an example of the relationship between time and instantaneous power is shown, and linear operation is possible by suppressing peak power. This is because the area can be enlarged.
[0091]
As described above, in the amplifying apparatus of this example, when the peak power suppression unit 52 is combined with the distortion compensation circuit 53 using the digital predistortion method to amplify a signal to be transmitted, peak power suppression processing and distortion compensation processing are performed. I do.
Therefore, in the amplification device of this example, as described in the first embodiment, it is possible to achieve both reduction in peak power and restriction of out-of-band leakage power, and effectively reduce peak power. it can. In the amplifying apparatus of this example, the operating point of the amplifier 55 can be further increased and the efficiency of the apparatus can be increased.
[0092]
A transmitter according to a fourth embodiment of the present invention will be described.
FIG. 7 shows a configuration example of the transmitter 81 of this example.
The transmitter 81 of this example includes a first modulation unit 91, a peak power suppression unit 92, a second modulation unit 93, and a frequency conversion unit 94.
The first modulation unit 91 includes a plurality of N waveform shaping filters F1 to FN, N digital quadrature modulation units G1 to GN, and two adders 101 and 102.
The frequency conversion unit 94 includes two D / A converters 103 and 104 and one analog quadrature modulation unit 105.
[0093]
Here, the configuration and operation of the transmitter 81 of this example includes a first modulation unit 91 and a second modulation unit 93 as compared with the transmitter 1 shown in FIG. 1 of the first embodiment. Except for the point that the peak power suppression unit 92 is provided between them, the configuration and operation of the transmitter 1 shown in FIG. 1 are the same, and in this example, different parts will be described in detail.
[0094]
That is, in the transmitter 81 of the present example, the peak power suppression unit 92 is provided between the first modulation unit 91 that performs the first process related to digital modulation and the second modulation unit 93 that performs the second process related to digital modulation. That is, a peak power suppression function is provided in the digital modulation function composed of the first digital modulation unit 91 and the second digital modulation unit 93, and the first digital modulation unit 91 performs the first The peak power suppression process is provided in the digital modulation process comprising the process and the second process by the second digital modulator 93.
[0095]
The schematic configuration and operation of the first modulation unit 91 are the same as, for example, the configuration and operation of the digital modulation unit 11 of the transmitter 1 shown in FIG. 1 of the first embodiment. Performs digital modulation on the input signal and outputs a signal of the digital modulation result to the peak power suppression unit 92. Note that the signal includes, for example, an I component and a Q component, and the same applies to the subsequent processing.
[0096]
The schematic configuration and operation of the peak power suppression unit 92 are the same as, for example, the configuration and operation of the peak power suppression unit 12 of the transmitter 1 shown in FIG. 1 of the first embodiment, and the peak power suppression unit 92 outputs a peak power suppression result signal to the second modulation unit 93 in response to the input signal from the first modulation unit 91.
[0097]
The second modulation unit 93 performs predetermined processing on the input signal from the peak power suppression unit 92 and outputs a signal of the processing result to the frequency conversion unit 94.
The schematic configuration and operation of the frequency conversion unit 94 are the same as, for example, the configuration and operation of the frequency conversion unit 13 of the transmitter 1 shown in FIG. 1 of the first embodiment. The D / A conversion and frequency conversion result signals are output for the input signal from the second modulation section 93.
[0098]
Here, FIGS. 8A, 8 </ b> B, and 8 </ b> C show configuration examples of the second modulation unit 93, respectively.
In the configuration example of the second modulation unit 93 shown in FIG. 2A, the second modulation unit 93 includes an interpolation unit 111 and a band limiting filter 112.
Interpolation section 111 performs interpolation processing on each of the I component and Q component of the input signal from peak power suppression section 92, and outputs the processing result to band limiting filter 112. In the interpolation process, for example, when the input signal is “X Y” at 50 MHz, the output signal is “X0Y0” at 100 MHz, and the blank indicates that there is no signal value.
[0099]
The band limiting filter 112 performs band limitation on the I component and Q component of the input signal from the interpolation unit 111, and outputs the I component and Q component of the band-limited signal to the frequency conversion unit 94. Note that the band limiting filter 112 removes the aliasing spectrum because, for example, the rate has been increased.
In such a configuration of the second modulation unit 93, for example, the peak power suppression unit 92 can operate at a low rate, and the circuit scale can be reduced.
[0100]
In the configuration example of the second modulation unit 93 shown in FIG. 5B, the second modulation unit 93 is configured by a digital quadrature modulation unit 121.
The digital quadrature modulation unit 121 performs digital quadrature modulation on the I component and Q component of the input signal from the peak power suppression unit 92, and sends the I component and Q component of the digital quadrature modulation result signal to the frequency conversion unit 94. Output.
In such a configuration of the second modulation unit 93, as an example, the first modulation unit 91 converts the input signal into a signal of a first intermediate frequency (IF) by digital modulation, and the second modulation unit 93 The signal is converted into a second intermediate frequency (IF) signal by digital modulation.
[0101]
In the configuration example of the second modulation unit 93 shown in FIG. 3C, the second modulation unit 93 includes an interpolation unit 131, a band limiting filter 132, and a digital orthogonal modulation unit 133.
The processing performed by the interpolation unit 131 and the processing performed by the band limiting filter 132 are the same as those in the configuration example shown in FIG.
Further, the digital quadrature modulation unit 133 performs digital quadrature modulation on the I component and Q component of the signal output from the band limiting filter 132, and the frequency conversion unit converts the I component and Q component of the signal of the digital quadrature modulation result. Output to 94.
[0102]
In FIGS. 8A and 8C, the low-rate signal is converted into the high-rate signal by using the interpolation process, but it is also possible to use the up-sampling process together or alone. is there. In the upsampling process, for example, when the input signal is “X Y” at 50 MHz, the output signal becomes “XXYY” at 100 MHz, and the blank indicates that there is no signal value.
[0103]
As described above, the transmitter 81 of this example includes the peak power suppression unit 92 inside the function of performing digital modulation processing, and performs peak power suppression processing on a signal to be transmitted.
Therefore, in the transmitter 81 of this example, as described in the first embodiment, it is possible to achieve both reduction of peak power and limitation of out-of-band leakage power, and effectively reduce peak power. Can do.
[0104]
A mobile communication system and a base station apparatus according to a fifth embodiment of the present invention are described.
In this example, the transmitter 1 as shown in FIG. 1 of the first embodiment, the transmission amplifier 41 as shown in FIG. 5 of the second embodiment, and the above diagram of the third embodiment. 6 and the transmitter 81 as shown in FIG. 7 of the fourth embodiment are provided in the mobile communication system and the base station apparatus of the mobile communication system.
Specifically, in general, in a mobile communication system, since it is necessary to use a transmission amplifier in a linear region, both reduction of peak power and limitation of out-of-band leakage power are required.
[0105]
Therefore, in this example, as shown in FIG. 1 of the first embodiment, FIG. 5 of the second embodiment, FIG. 6 of the third embodiment, and FIG. 7 of the fourth embodiment. Such a requirement is satisfied by constructing a mobile communication system and a base station apparatus having a configuration.
Therefore, in the mobile communication system and the base station apparatus of this example, for example, when transmitting / receiving signals of a plurality of communication channels, it is possible to achieve both reduction in peak power and restriction of out-of-band leakage power, and effectively increase peak power. Can be reduced.
[0106]
The background of the technology related to the present invention will be described below. Note that the matters described here are not necessarily limited to the conventional technology.
FIG. 9 shows a configuration example of the transmitter 141 of the CDMA system.
The configuration and operation of the transmitter 141 of this example is the same as that of the first embodiment shown in FIG. 1 except that the peak power suppression coefficient calculation unit 154 is not provided with a window function generation unit or a limiter coefficient calculation unit. The configuration and operation of the transmitter 1 shown in FIG.
[0107]
Specifically, N code multiplexed signal generation units H1 to HN are connected to the transmitter 141 of this example.
The transmitter 141 of this example includes a digital modulation unit 151 including N waveform shaping filters I1 to IN, N digital quadrature modulation units J1 to JN, and two adders 161 and 162, and 2 Peak power suppression unit 152 having a plurality of delay units 163 and 164, two multipliers 165 and 166, a peak power suppression coefficient calculation unit 154, two D / A converters 167 and 168, and an analog orthogonal modulation unit A frequency conversion unit 153 having 169 is provided.
The peak power suppression coefficient calculation unit 154 includes an instantaneous power calculation unit 171, an average power calculation unit 172, a threshold value generation unit 173, a comparison unit 174, and a division unit 175.
[0108]
In the transmitter 141 of this example, in the peak power suppression coefficient calculation unit 154, for example, the same calculation as that shown in Expression 1 to Expression 4 above is performed, and the peak factor Gain (t calculated by the division unit 175 is calculated. ) Is output as is to the two multipliers 165 and 166 as the peak power suppression coefficient.
[0109]
Each of the multipliers 165 and 166 includes addition result signals AI (t) and AQ (t) input from the delay units 163 and 164 and a peak power suppression coefficient (peak factor) Gain (t) input from the division unit 175. And the peak signal level is suppressed, and the multiplication results A′I (t) and A′Q (t) are output to the D / A converters 167 and 168, respectively. Here, the multiplication results A′I (t) and A′Q (t) are expressed as Equation 8.
[0110]
[Equation 8]

[0111]
FIG. 10 shows an example of the state of peak power suppression in this example.
Specifically, examples of instantaneous power Pint (t), average power Pavg (t), threshold power Thr (t) and peak power suppression coefficient Gain (t) with respect to time (sampling time t) are shown. An example of the peak power suppression coefficient Gain (t) with respect to the frequency f is shown.
[0112]
As described above, the peak power suppression unit 152 suppresses the level of the protruding peak signal portion included in the addition result signal of the I component and the Q component.
When no peak is detected, the peak power suppression coefficient Gain (t) is 1.
Thus, in this example, gain control is performed only for the peak signal portion exceeding the threshold power Thr.
[0113]
FIG. 11 shows a configuration example of the transmission amplifier 181 of the CDMA system.
The configuration and operation of the transmission amplifier 181 of the present example are the same as the configuration and operation of the transmitter 141 shown in FIG. 9 except that the power amplification unit 182 is provided after the frequency conversion unit 153. is there. In this example, the same components H1 to HN, 151 to 154, I1 to IN, J1 to JN, 161 to 169, and 171 to 175 as those shown in FIG. Show.
[0114]
Here, since the frequency band used for communication in wireless communication is limited, it is required to suppress the expansion of the frequency spectrum due to nonlinear distortion generated in the power amplification unit 182 as shown in FIG. Due to such a requirement, when the code multiplexed signal is amplified by the power amplifier 182, it is necessary to operate in the linear region.
[0115]
However, in the transmitter 141 as shown in FIG. 9 and the transmission amplifier 181 as shown in FIG. 11, for example, a threshold is provided in the band-limited intermediate frequency (IF) region to limit the signal level. When suppressing the peak power of a signal to be transmitted by such a method, there is a problem that leakage power outside the castle increases due to such peak suppression.
Further, for example, in the configuration in which band limitation is performed again on the output from the transmitter 141 as shown in FIG. 9 above, the spectrum is restored to the original, and the time waveform is also restored to the original. There will be no power limiting effect.
[0116]
Therefore, in the present invention, by applying a window function weight to the peak factor used as the peak power suppression coefficient in the configuration as shown in FIG. 9 or FIG. The peak factor after the band limitation is set as a new peak power suppression coefficient, and the peak of the I component signal and the Q component signal to be transmitted and the amplitude around the peak are limited. Thus, effective peak suppression is realized.
[0117]
Here, the configurations of the transmitter, the transmission amplifier, the amplification device, and the like according to the present invention are not necessarily limited to those described above, and various configurations may be used. The present invention can also be provided as, for example, a method or method for executing the processing according to the present invention or a program for realizing such a method or method.
The application field of the present invention is not necessarily limited to the above-described fields, and the present invention can be applied to various fields.
[0118]
In addition, as various processes performed in the transmitter, the transmission amplifier, the amplification device, and the like according to the present invention, for example, a control program in which a processor is stored in a ROM (Read Only Memory) in a hardware resource including a processor, a memory, and the like. May be used, and for example, each functional means for executing the processing may be configured as an independent hardware circuit.
Further, the present invention can be grasped as a computer-readable recording medium such as a floppy (registered trademark) disk or a CD (Compact Disc) -ROM storing the control program, or the program (itself). The processing according to the present invention can be performed by inputting a program from a recording medium to a computer and causing the processor to execute the program.
[0119]
【The invention's effect】
As described above, according to the transmitter of the present invention, when transmitting a signal to be transmitted, the peak of the signal to be transmitted is determined. do it, A peak factor corresponding to the ratio between the transmission target signal level threshold and the peak level of the signal to be transmitted is generated, and a result obtained by weighting the generated peak factor with a predetermined window function is generated as a peak suppression coefficient. Since the level of the signal to be transmitted is suppressed by the peak suppression coefficient, the peak of the signal to be transmitted and the surrounding levels are suppressed. For example, the peak level is effectively suppressed as compared with the conventional case. Specifically, the effects of both suppression of peak level and reduction of out-of-band leakage power can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a transmitter according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating an example of how peak power is suppressed;
FIG. 3 is a diagram illustrating an example of frequency characteristics of a transmitter output in the W-CDMA system.
FIG. 4 is a diagram illustrating an example of a complementary cumulative distribution function of a transmitter output in the W-CDMA system.
FIG. 5 is a diagram illustrating a configuration example of a transmission amplifier according to a second embodiment of the present invention.
FIG. 6 is a diagram illustrating a configuration example of an amplifying apparatus according to a third embodiment of the present invention.
FIG. 7 is a diagram illustrating a configuration example of a transmitter according to a fourth embodiment of the present invention.
FIG. 8 is a diagram illustrating an internal configuration example of a second modulation unit.
FIG. 9 is a diagram illustrating a configuration example of a transmitter.
FIG. 10 is a diagram illustrating an example of how peak power is suppressed;
FIG. 11 is a diagram illustrating a configuration example of a transmission amplifier.
[Explanation of symbols]
1, 81, 141 .. Transmitter 11, 51, 151 .. Digital modulation section,
12, 52, 92, 152.. Peak power suppression unit,
13, 54, 94, 153 .. frequency conversion unit,
14, 154... Peak power suppression coefficient calculator,
21, 22, 101, 102, 161, 162 .. adder,
23, 24, 61, 163, 164 .. delay unit,
25, 26, 165, 166 .. multiplier
27, 28, 71, 103, 104, 167, 168, D / A converter,
29, 105, 169 .. Analog quadrature modulation unit,
31, 171 .. Instantaneous power calculator 32, 172 .. Average power calculator,
33, 173,... Threshold generation unit, 34, 174, comparison unit,
35, 175 ·· Division unit, 36 · · Window function generation unit,
37 .. Limiter coefficient calculation unit, 41, 181... Transmission amplifier,
42, 182 .. Power amplifier,
B1 to BN, H1 to HN, a code multiplexed signal generator,
C1 to CN, F1 to FN, I1 to IN, a waveform shaping filter,
E1 to EN, G1 to GN, 121 and 133, J1 to JN, a digital quadrature modulation unit,
53 .. Distortion compensation circuit, 55 .. Amplifier, 62 .. Power detector,
63 .. RAM table, 64 .. Complex multiplier, 65 .. Distortion component detector,
66 .. Control part, 72 .. Mixer, 91 .. First modulation part,
93 .. Second modulation unit 111, 131. Interpolation unit
112, 132.. Band limiting filter,

Claims (5)

In a transmitter that transmits a multicarrier signal to be transmitted,
A peak is determined from the level based on the instantaneous power of the multicarrier signal to be transmitted, which is a signal that has been shaped for each carrier and orthogonally modulated for each carrier and then combined , Peak factor generation means for generating a peak factor according to a ratio to the peak level of the multicarrier signal to be transmitted;
A peak suppression coefficient generating means for generating, as a peak suppression coefficient, a result obtained by weighting the peak factor generated by the peak factor generating means with a predetermined window function;
Transmission target signal level suppression means for suppressing the level of the multicarrier signal to be transmitted by the peak suppression coefficient generated by the peak suppression coefficient generation means;
A transmitter characterized by comprising: In a transmitter that transmits a multicarrier signal to be transmitted,
A peak factor generating means for determining a peak of the multicarrier signal to be transmitted and generating a peak factor according to a ratio between a transmission target signal level threshold and a peak level of the multicarrier signal to be transmitted;
A peak suppression coefficient generating means for generating, as a peak suppression coefficient, a result obtained by weighting the peak factor generated by the peak factor generating means with a predetermined window function;
Transmission target signal level suppression means for suppressing the level of the multicarrier signal to be transmitted by the peak suppression coefficient generated by the peak suppression coefficient generation means,
Use the power level as the signal level,
The peak factor generation means includes an instantaneous power calculation unit that detects an instantaneous power of a multicarrier signal to be transmitted that is input at an intermediate frequency, an average power calculation unit that detects an average value of the instantaneous power, and the average power A threshold generation unit that generates a threshold power corresponding to the transmission target signal level threshold based on a detection result by the calculation unit; and a peak detected when the instantaneous power exceeds the threshold power and the threshold power It has peak factor setting means for setting the peak factor according to the ratio with the instantaneous power,
The peak suppression coefficient generating means generates, as a peak suppression coefficient, a result obtained by weighting a peak factor set by the peak factor setting means of the peak factor generating means with a predetermined window function,
The transmission target signal level suppression unit multiplies the multicarrier signal to be transmitted that is input at an intermediate frequency by the peak suppression coefficient generated by the peak suppression coefficient generation unit.
A transmitter characterized by that. The transmitter according to claim 2, wherein
If t represents time,
The peak factor generation means includes a comparison unit that compares magnitudes of the instantaneous power Pint (t) detected by the instantaneous power calculation unit and the threshold power Thr generated by the threshold generation unit,
The threshold generation unit generates, as the threshold power Thr, a result of calculating a predetermined value for the average value Pavg of the instantaneous power Pint (t) detected by the average power calculation unit,
The peak factor setting means is configured when the instantaneous power Pint (t) detected by the instantaneous power calculator is larger than the threshold power Thr generated by the threshold generator based on the comparison result by the comparator. Sets the value of sqrt {Thr / Pint (t)} as the peak factor Gain (t), and when the instantaneous power Pint (t) is less than or equal to the threshold power Thr, 1 is set to the peak factor Gain ( t)
The peak suppression coefficient generation means uses a window function Weight (s) where M is a predetermined value that defines a window function, and s takes a value in a section from (−M / 2) to (+ M / 2). , [1-Weight (s) · {1-Gain (t)}] as a peak suppression coefficient Exp_Gain (t + s),
A transmitter characterized by that. In a transmitter that transmits a multicarrier signal to be transmitted,
  A peak factor generating means for determining a peak of the multicarrier signal to be transmitted and generating a peak factor according to a ratio between a transmission target signal level threshold and a peak level of the multicarrier signal to be transmitted;
  A peak suppression coefficient generating means for generating a result obtained by weighting a peak factor generated by the peak factor generating means with a predetermined window function as a peak suppression coefficient;
  Transmission target signal level suppression means for suppressing the level of the multicarrier signal to be transmitted by the peak suppression coefficient generated by the peak suppression coefficient generation means,
  A digital modulation unit is provided before the suppression unit having the peak factor generation unit, the peak suppression coefficient generation unit, and the transmission target signal level suppression unit,
  The digital modulation unit digitally modulates a plurality of waveform shaping filters that perform spectrum shaping of each carrier signal composed of an I component and a Q component, and a spectrum shaping result signal of each carrier by each of the plurality of waveform shaping filters. A plurality of digital quadrature modulation units, and combining means for synthesizing digital quadrature modulation results by the plurality of digital quadrature modulation units to generate a multicarrier signal,
  A transmitter characterized by that. The transmitter according to any one of claims 1 to 4,
  An amplifier for amplifying a multicarrier signal to be transmitted;
  A digital predistortion type distortion compensation circuit that is provided immediately after the transmission target signal level suppressing means, compensates for distortion generated in the amplifier for the multicarrier signal to be transmitted, and outputs to the amplifier;
  A transmitter characterized by comprising:

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