JP3612255B2

JP3612255B2 - OFDM receiver

Info

Publication number: JP3612255B2
Application number: JP36195499A
Authority: JP
Inventors: 幸夫大滝
Original assignee: Alps Electric Co Ltd
Current assignee: Alps Alpine Co Ltd
Priority date: 1999-12-20
Filing date: 1999-12-20
Publication date: 2005-01-19
Anticipated expiration: 2019-12-20
Also published as: JP2001177498A

Description

【０００１】
【発明の属する技術分野】
この発明は、日本や欧州における地上波ディジタルＴＶ放送のようにＯＦＤＭ変調された信号の受信装置に関し、特に車載用として好適なダイバーシチ受信型のＯＦＤＭ受信装置に関する。
【０００２】
【従来の技術】
近年、地上波ディジタルＴＶ放送に代表されるディジタルのオーディオ信号や映像信号の伝送（変調）方式としてＯＦＤＭ（ＯｒｔｈｏｇｏｎａｌＦｒｅｑｕｅｎｃｙＤｉｖｉｓｉｏｎＭｕｌｔｉｐｌｅｘｉｎｇ、直交周波数分割多重）によるマルチキャリア（多搬送波）変調方式が実用化されつつある。この変調方式による放送は、符号化したデータを分割して千から数千以上の搬送波に振り分け、多重化して伝送する。
図１３にＯＦＤＭ送信装置の構成ブロック図を、図１４にＯＦＤＭによる変調過程を概念的に示す。
【０００３】
図１３において、ＯＦＤＭ変調手段１９１は、入力されるディジタル信号をＱＰＳＫ等の変調を行う変調手段１９２と、変調された直列信号を並列信号に変換する直／並列変換手段（Ｓ／Ｐ）１９３と、変換された並列信号を逆フーリエ変換する高速逆フーリエ変換手段（ＩＦＦＴ）１９４と、逆フーリエ変換された信号を直列系列に変換し、時間信号として出力する並／直列変換手段（Ｐ／Ｓ）１９５と、変換された信号にガードインターバルを挿入するガードインターバル挿入手段１９６とから構成されている。また、１９７は送信手段（ＴＸ）、１９８はアンテナである。
【０００４】
上記構成において、入力されたディジタル信号が変調手段１９２により所定の変調方式（例えば、ＱＰＳＫ変調）で情報変調されることにより得られた変調シンボルは、図１４に示すように、直／並列変換手段（Ｓ／Ｐ）１９３により、より低速の変調シンボル列、すなわち、一定周波数間隔（Δｆ）で並んだＮ個のそれぞれ互いに直交する搬送波の変調シンボル列に変換される。この変調シンボル列は、高速逆フーリエ変換手段（ＩＦＦＴ）１９４により高速逆フーリエ変換（ＩＦＦＴ）され、更に、並／直列変換手段（Ｐ／Ｓ）１９５により波形合成され、直交する時間軸信号の同相成分（以下Ｉと記す。）と、直交成分（以下、Ｑと記す。）が生成される。
【０００５】
さらに、ガードインターバル挿入手段１９６により所定時間（有効シンボル時間）Ｔｓで区切られた信号の末尾の所定時間分（ガードインターバル時間）Ｔｇを上記時間軸信号Ｉ，Ｑの開始部にコピーして挿入し、これをガードインターバルとする。このようにガードインターバルが挿入された時間軸信号が、ガードインターバル挿入手段６６からベースバンド時系列信号として生成される。
【０００６】
このガードインターバルは受信時に生じる遅延波妨害（干渉）の対策のために挿入されるもので、マルチパス環境下での信号の相対遅延による隣接シンボル干渉を吸収するシンボルである。
ここで、（Ｔｇ＋Ｔｓ）時間の時間軸信号が１単位のＯＦＤＭシンボルとして扱われ、受信時の処理によってこのガードインターバルが除去されてＴｓ時間の信号のみが有効シンボル信号として抽出され、復調されるものである。
そして、ガードインターバル挿入手段１９６により生成されたベースバンド時系列信号は、Ｄ／Ａ変換手段を含む送信手段（ＴＸ）１９７で所定の搬送波に乗せられ、電力増幅した後アンテナ１９８から空間に輻射される。
【０００７】
つぎに、図１５に基本的なＯＦＤＭ受信装置の構成を、図１６にＯＦＤＭによる復調過程を概念的に示す。
図１５において、ＯＦＤＭ受信装置は、アンテナ２１２と、受信手段（ＲＥＣ）２１３と、ＯＦＤＭ復調手段２１１とを有している。
また、ＯＦＤＭ復調手段２１１は、受信した信号からガードインターバルを除去して有効シンボル信号を抽出する有効シンボル抽出手段２１４、有効シンボル信号を並列信号に変換する直／並列変換手段（Ｓ／Ｐ）２１５、並列信号をフーリエ変換する高速フーリエ変換手段（ＦＦＴ）２１６、直列信号に変換する並／直列変換手段（Ｐ／Ｓ）２１７および復調手段２１８を有している。
【０００８】
図１５において、アンテナ２１２によって捕捉された信号電波は受信手段（ＲＥＣ）２１３によって増幅、周波数変換され、ベースバンド時系列信号として出力され、ＯＦＤＭ復調手段２１１によって復調される。
ＯＦＤＭ復調手段２１１では、図１６に示すように、有効シンボル抽出手段２１４において、受信したＯＦＤＭシンボルを参照し、Ｔｓ時間だけ離れた２つのシンボル信号をＴｇ時間にわたり積和を計算して自己相関信号を発生し、これを基準信号とする。続いてＯＦＤＭシンボルの基準信号（自己相関信号）のピーク（最大値）を検出し、自己相関信号のピークに基づいて挿入されたガードインターバルの開始時期を検出し、このガードインターバルを除去して有効シンボルのＩ、Ｑを抽出する。
【０００９】
次いで、直／並列変換手段（Ｓ／Ｐ）２１５により有効シンボル信号を並列信号に変換し、変換された並列信号を高速フーリエ変換手段（ＦＦＴ）２１６により高速フーリエ変換（ＦＦＴ）してΔｆずつ周波数のずれたＮ個の搬送波の変調シンボルを取り出す。このように取り出された変調シンボルを並／直列変換手段（Ｐ／Ｓ）２１７により直列状の時間系列に変換してから、復調手段２１８により所定の方式で復調して、ディジタル信号を復号する。
【００１０】
以上のように、受信したＯＦＤＭシンボルの基準信号（自己相関信号）のピーク（最大値）を検出し、自己相関信号のピークに基づいて有効シンボルを抽出するので、基準信号が正確に検出されないと、抽出した有効シンボルに隣接するＯＦＤＭシンボルのデータが含まれることとなり、ビット誤りが発生するという問題がある。
一方、ＯＦＤＭ変調による放送信号を自動車等で移動しながら受信する場合、フェージングの影響を受けてしまい、受信信号レベルが変動するので、基準信号を正確に発生できなくなる。その結果、前述のようなビット誤りが発生するので、移動受信時にはダイバーシチ受信によりレベル変動を抑制するようにしている。
【００１１】
【発明が解決しようとする課題】
ところが、上述した従来のＯＦＤＭ受信装置において、ダイバーシチ受信を行うようにしても、ＯＦＤＭシンボルのガードインターバル時間（Ｔｇ）以上に遅延した遅延波が混入していると、隣接した有効シンボルが干渉して復調後のビット誤りが多くなってしまうという問題があった。
本発明はこのような事情に鑑みてなされたものであり、ＯＦＤＭ変調信号のフーリエ変換処理手段の前段にダイバーシチ合成手段と遅延等化手段とを設けることにより、十分な信号強度を有し、かつガードインターバル時間以上の遅延時間を有する遅延波を除去した有効シンボル信号を抽出することができるダイバーシチ受信型のＯＦＤＭ受信装置を提供することを目的とする。
【００１２】
【課題を解決するための手段】
上記目的を達成するために本発明のＯＦＤＭ受信装置は、互いに離間して配置され、ＯＦＤＭ変調された信号を捕捉する複数のアンテナと、該複数のアンテナにそれぞれ接続され、供給された信号を処理してベースバンド信号にする複数の受信手段と、該複数の受信手段の各出力信号を合成するダイバーシチ合成手段と、該ダイバーシチ合成手段の合成出力からＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分を除去する遅延等化手段と、該遅延等化手段の出力信号から変調時に挿入されたガードインターバル信号を取り除き、有効シンボル信号を抽出して復調するＯＦＤＭ復調手段と、を有することを特徴とする。
【００１３】
本発明のＯＦＤＭ受信装置では、互いに離間して配置された複数のアンテナによりＯＦＤＭ変調された信号が捕捉され、該複数のアンテナにそれぞれ接続された複数の受信手段により供給された信号が処理されベースバンド信号に変換される。次いで、ダイバーシチ合成手段により前記複数の受信手段の各出力信号が合成される。さらに、遅延等化手段により該ダイバーシチ合成手段の合成出力からＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去され、ＯＦＤＭ復調手段により該遅延等化手段の出力信号から変調時に挿入されたガードインターバル信号が取り除かれ、有効シンボル信号が抽出されて復調される。
【００１４】
また、本発明のＯＦＤＭ受信装置は、前記複数の受信手段の出力側に、該複数の受信手段の各出力信号間の相互相関を検出する相互相関検出手段と、前記複数の受信手段の各出力信号の自己相関を検出する複数の第１の自己相関検出手段とが接続され、前記遅延等化手段が、前記相互相関検出手段及び前記複数の第１の自己相関検出手段の検出結果に基づいてＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分を除去することを特徴とする。
【００１５】
本発明のＯＦＤＭ受信装置では、前記複数の受信手段の出力側に接続された相互相関検出手段により、前記複数の受信手段の各出力信号間の相互相関が検出され、また、前記複数の受信手段の出力側に接続された、複数の第１の自己相関検出手段により前記複数の受信手段の各出力信号の自己相関が検出される。さらに、前記遅延等化手段により、前記相互相関検出手段及び前記複数の第１の自己相関検出手段の検出結果に基づいてＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。
【００１６】
また、本発明のＯＦＤＭ受信装置は、前記遅延等化手段は、前記複数の第１の自己相関検出手段の各々が検出した自己相関値のうち、最大自己相関値以外の極大自己相関値の前記最大自己相関値からの遅延時間と、前記極大自己相関値から算出した複素振幅係数と、前記相互相関検出手段が検出した相互相関値から算出した位相係数とに基づいて前記遅延等化手段の出力信号を負帰還させる複数の帰還手段を備えたことを特徴とする。
【００１７】
本発明のＯＦＤＭ受信装置では、前記遅延等化手段が有する複数の帰還手段により、前記複数の第１の自己相関検出手段の各々が検出した自己相関値のうち、最大自己相関値以外の極大自己相関値の前記最大自己相関値からの遅延時間と、前記極大自己相関値から算出した複素振幅係数と、前記相互相関検出手段が検出した相互相関値から算出した位相係数とに基づいて前記遅延等化手段の出力信号が負帰還される。
【００１８】
また、本発明のＯＦＤＭ受信装置は、前記相互相関検出手段は、該相互相関検出手段に供給される信号のうち、比較すべき２つの信号のうちの一の信号から複素共役信号を生成して出力する複素共役信号生成手段と、前記複素共役信号と前記比較すべき２つの信号のうちの他の信号とを乗算する乗算手段と、該乗算手段の乗算結果を所定時間だけ累算する累算手段とを有することを特徴とする。
【００１９】
本発明のＯＦＤＭ受信装置では、前記相互相関検出手段において、複素共役信号生成手段により該相互相関検出手段に供給される信号のうち、比較すべき２つの信号のうちの一の信号から複素共役信号が生成され出力される。また、乗算手段により、前記複素共役信号と前記比較すべき２つの信号のうちの他の信号とが乗算され、累算手段により前記乗算手段の乗算結果が所定時間だけ累算される。
【００２０】
また、本発明のＯＦＤＭ受信装置は、前記ダイバーシチ合成手段の出力側に、該ダイバーシチ合成手段の出力信号の自己相関を検出する第２の自己相関検出手段が接続され、前記遅延等化手段が、前記第２の自己相関検出手段の検出結果に基づいてＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分を除去することを特徴とする。
【００２１】
本発明のＯＦＤＭ受信装置では、前記ダイバーシチ合成手段の出力側に接続された第２の自己相関検出手段により、前記ダイバーシチ合成手段の出力信号の自己相関が検出され、前記遅延等化手段により、前記第２の自己相関検出手段の検出結果に基づいてＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。
【００２２】
また、本発明のＯＦＤＭ受信装置は、前記遅延等化手段は、前記第２の自己相関検出手段が検出した自己相関値のうち、最大自己相関値以外の極大自己相関値の前記最大自己相関値からの遅延時間と、前記極大自己相関値から算出した複素振幅係数とに基づいて前記遅延等化手段の出力信号を負帰還させる複数の帰還手段を備えたことを特徴とする。
【００２３】
本発明のＯＦＤＭ受信装置では、前記遅延等化手段が有する複数の帰還手段により、前記第２の自己相関検出手段が検出した自己相関値のうち、最大自己相関値以外の極大自己相関値の前記最大自己相関値からの遅延時間と、前記極大自己相関値から算出した複素振幅係数とに基づいて前記遅延等化手段の出力信号が負帰還される。
【００２４】
また、本発明のＯＦＤＭ受信装置は、前記第１、第２の自己相関検出手段は、該第１、第２の自己相関検出手段に供給される信号を有効シンボル時間だけ遅延させた遅延信号を出力する有効シンボル時間遅延手段と、前記第１、第２の自己相関検出手段に供給される信号から複素共役信号を生成して出力する複素共役信号生成手段と、前記遅延信号と前記複素共役信号とを乗算する乗算手段と、該乗算手段の乗算結果を所定時間だけ累算する累算手段とを有することを特徴とする。
【００２５】
本発明のＯＦＤＭ受信装置では、前記第１、第２の自己相関検出手段において、有効シンボル時間遅延手段により該第１、第２の自己相関検出手段に供給される信号を有効シンボル時間だけ遅延させた遅延信号が出力され、複素共役信号生成手段により前記第１、第２の自己相関検出手段に供給される信号から複素共役信号が生成され出力される。さらに、乗算手段により前記遅延信号と前記複素共役信号とが乗算され、累算手段により前記乗算手段の乗算結果が所定時間だけ累算される。
【００２６】
また、本発明のＯＦＤＭ受信装置は、前記ＯＦＤＭ復調手段は、前記複数の第１の自己相関検出手段の各々にて検出された自己相関値のうち最大値を示す最大自己相関値が検出された時点、または、第２の自己相関検出手段にて検出された自己相関値のうち最大値を示す最大自己相関値が検出された時点を基準として、前記遅延等化手段の出力信号からガードインターバル信号を取り除き、有効シンボル信号を抽出することを特徴とする。
【００２７】
本発明のＯＦＤＭ受信装置では、前記ＯＦＤＭ復調手段により、前記複数の第１の自己相関検出手段の各々にて検出された自己相関値のうち最大値を示す最大自己相関値が検出された時点、または、第２の自己相関検出手段にて検出された自己相関値のうち最大値を示す最大自己相関値が検出された時点を基準として、前記遅延等化手段の出力信号からガードインターバル信号が取り除かれ、有効シンボル信号が抽出される。
【００２８】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照して詳細に説明する。本発明の各実施の形態に係るＯＦＤＭ受信装置は、ＯＦＤＭ変調信号の有効シンボルをＦＦＴ演算するＦＦＴ演算手段の前段に、アンテナダイバーシチを行うダイバーシチ合成手段と、受信したＯＦＤＭ変調信号のうち所定時間以上遅延した信号成分（遅延波）を除去する遅延等化手段とを設け、十分な信号強度を有し、遅延の大きな信号を除去したＯＦＤＭ変調信号の有効シンボル信号を抽出することができるようにしたことを特徴としている。以下、本発明の各実施の形態に係るＯＦＤＭ受信装置ではアンテナ素子数を２とした場合について説明する。
【００２９】
図１に本発明の第１の実施の形態に係るＯＦＤＭ受信装置の構成を示す。同図において、本実施の形態に係るＯＦＤＭ受信装置は、＃１系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ａと、アンテナ１１ａと相互に離間して配置され＃２系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ｂと、受信手段１２ａ，１２ｂと、受信手段１２ａ，１２ｂの出力信号の位相を補正してから合成する信号合成手段１００と、複数の受信手段１２ａ，１２ｂの出力信号間の相互相関を検出する相互相関検出手段１３と、受信手段１２ａの出力信号の自己相関を検出する自己相関検出手段１４ａと、受信手段１２ｂの出力信号の自己相関を検出する自己相関検出手段１４ｂと、自己相関検出手段１４ａ，１４ｂの検出結果及び相互相関検出手段１３の検出結果に基づいて信号合成手段１００の合成出力から所定時間以上、遅延した信号成分を除去する遅延等化手段１６と、ＯＦＤＭ復調手段１７とを有している。
【００３０】
ここで、相互相関検出手段１３と信号合成手段１００とがダイバーシチ合成手段１５を構成し、相互相関検出手段１３の検出結果に基づいて、受信手段１２ａ，１２ｂの出力信号の位相を補正してから合成するというダイバーシチ合成を行う。また、自己相関検出手段１４ａ，１４ｂは、本発明の第１の自己相関検出手段に相当する。なお、ＯＦＤＭ復調手段１７の具体的な構成は、既知のＯＦＤＭ復調手段２１１と同じである。
【００３１】
上記構成において、アンテナ１１ａ、アンテナ１１ｂにより受信した信号は、それぞれ、受信手段１２ａ、１２ｂで増幅、周波数変換されてベースバンド信号に変換された後、それぞれ＃１系統、＃２系統の信号としてダイバーシチ合成手段１５に入力される。ダイバーシチ合成手段１５では、相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの各出力信号が同位相となるように信号合成手段１００で位相補正され、ダイバーシチ合成される。
【００３２】
次いで遅延等化手段１６では、自己相関検出手段１４ａ，１４ｂの検出結果及び相互相関検出手段１３の検出結果に基づいて信号合成手段１００の合成出力から所定時間以上、具体的にはＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。遅延等化手段１６の出力信号は、ＯＦＤＭ復調手段１８において、フーリエ変換され、変調時に挿入されたガードインターバルが取り除かれ、有効シンボルが抽出されて復調される。
【００３３】
次に図１における信号合成手段１００の具体的構成を図２に示す。同図において、信号合成手段１００は移相手段２１，２２と、加算手段２３とを有している。同図において、受信手段１２ａ，１２ｂの各出力信号は移相手段２１、２２において相互相関検出手段１３の検出結果（相互相関値）を参照して互いに同相となるように位相補正され、加算手段２３において加算されて合成され、遅延等化手段１６に出力される。このように、同位相でダイバーシチ合成すると、合成出力の電力を最大にすることができる。
【００３４】
次に、図１における遅延等化手段１６の具体的構成を図３に示す。同図に示す遅延等化手段１６は、２信号までの遅延等化が行える構成となっている。図３において、遅延等化手段１６は、加算手段３１と、加算手段３１の出力を所定時間、遅延させる遅延手段３２、３５と、遅延手段３２、３５の出力信号の複素振幅をそれぞれ、補正する複素振幅補正手段３３、３６と、複素振幅補正手段３３、３６の位相をそれぞれ、補正する移相手段３４、３７と、遅延手段３２，３５における遅延時間を算出する遅延時間算出手段３９と、複素振幅補正手段３３，３６における振幅補正量である複素振幅係数を算出する複素振幅係数算出手段４０と、移相手段３４、３７における移相量を算出する位相係数算出手段４１と、供給された自己相関値の中から最大値と極大値を探索する最大極大自己相関探索手段３８とを有している。
【００３５】
図３に示す遅延等化手段１６は２つまでの信号の遅延等化を行う構成であり、遅延手段３２と、複素振幅補正手段３３と、移相手段３４とにより構成される信号の負帰還手段により、一の信号の遅延信号が除去され、また、遅延手段３５と、複素振幅補正手段３６と、移相手段３７とにより構成される信号の負帰還手段により、もう一つの遅延信号が除去される。
【００３６】
最大極大自己相関探索手段３８は、自己相関検出手段１４ａ，１４ｂからそれぞれ自己相関値が供給されると、それらの中から自己相関の最大値と極大値を探索し、自己相関の最大値と極大値に関する制御信号を遅延時間算出手段３９と、複素振幅係数算出手段４０と、位相係数算出手段４１に送出する。例えば、信号合成手段１００の出力に３つのＯＦＤＭ変調信号が含まれていると、１つの最大自己相関値と２つの極大自己相関値が検出され、極大自己相関値を発生させる要因となった遅延信号を除去するために、これらに関する制御情報が送出される。
【００３７】
最大極大自己相関探索手段３８からの制御信号を受けて、遅延時間算出手段３９は前記の最大自己相関値を基準として、最大自己相関値以外の極大自己相関値の中で、除去すべき２つの遅延信号に対応する極大自己相関値が検出された時点までの時間を算出して、これを遅延時間としてそれぞれ遅延手段３２、３５に送出する。ここで、算出された遅延時間が所定時間、具体的にはＯＦＤＭ変調信号に含まれるガードインターバル時間より短いときには、送出する遅延時間を零とする。
【００３８】
また、複素振幅係数算出手段４０は、最大極大自己相関探索手段３８からの制御信号を受けると、最大自己相関値を基準として、最大自己相関値以外の極大自己相関値の中で除去すべき２つの遅延信号に対応する極大自己相関値との比をそれぞれ算出して、これを複素振幅係数としてそれぞれ複素振幅補正手段３３，３６に送出する。
ここで、遅延時間算出手段３９と複素振幅係数算出手段４０においては、自己相関検出手段１４ａ，１４ｂからそれぞれ供給される自己相関値を参照して、遅延時間と複素振幅補正係数を算出する。
【００３９】
更に、位相係数算出手段４１は、最大極大自己相関探索手段３８からの制御信号を受けると、最大自己相関値以外の極大自己相関値の中で除去すべき２つの遅延信号に対応する位相係数を、相互相関検出手段１３から供給される相互相関値を参照して算出し、それぞれ移相手段３４、３７に送出する。このとき、除去すべき遅延信号に対応する極大自己相関値が最大自己相関値と同じ自己相関検出手段１４ａ（または１４ｂ）にて検出されたとき位相回転が零となるような位相係数が算出され、これ以外の場合には相互相関値の位相をキャンセルするよう位相回転を与える位相係数が算出される。
【００４０】
遅延手段３２、３５は遅延時間算出手段３９により与えられる遅延時間に基づいて入力信号を遅延させる。ここで、与えられる遅延時間が零のときは、遅延信号の遅延時間がＯＦＤＭ変調信号のガードインターバル時間以下であり、除去する必要がないので、入力信号を遅延させずに、振幅が零の信号を出力する。
複素振幅補正手段３３、３６は、複素振幅係数算出手段４０により与えられる複素振幅係数に基づいて振幅補正を行う。
【００４１】
移相手段３４、３７は、位相係数算出手段４１により与えられた位相係数に基づいて入力信号の位相補正を行う。このように、遅延手段３２（３５）、複素振幅補正手段３３（３６）及び移相手段３４（３７）からなる負帰還手段を経て加算手段３１の出力が負帰還され、同じ加算手段３１の入力に供給される。
【００４２】
図１に示す構成において、信号合成手段１００のダイバーシチ合成出力信号は、加算手段３１に与えられ、加算手段３１の出力は、遅延時間算出手段３９及び複素振幅係数算出手段４０により与えられた遅延時間及び複素振幅係数に基づいて遅延手段３２、３５及び複素振幅補正手段３３、３６により、遅延時間調整及び振幅調整が行われ、移相手段３４、３７に出力される。
【００４３】
さらに、移相手段３４、３７では、位相係数算出手段４１により与えられた位相係数により位相補正がなされ、この遅延時間調整、振幅補正及び位相補正が行われた信号が逆極性で加算手段３１で加算される。この結果、信号合成手段１００のダイバーシチ合成出力からＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去され、この不要波が除去された信号がＯＦＤＭ復調手段１７に出力される。
【００４４】
次に、図１における相互相関検出手段１３の具体的構成を図４に示す。図４において、相互相関検出手段１３は、相互相関検出手段１３に供給される信号のうち、比較すべき２つの信号のうちの一の信号から複素共役信号を生成して出力する複素共役信号生成手段６０と、複素共役信号生成手段６０により生成された複素共役信号と前記比較すべき２つの信号のうちの他の信号とを乗算処理する乗算手段６１と、乗算手段６１による乗算処理結果を所定時間だけ累算する累算手段６２とを有している。
【００４５】
上記構成において、相互相関検出手段１３では、入力端子１３０、１３１を介して相互相関検出手段１３に供給される信号のうち、比較すべき２つの信号のうちの一の信号（入力端子１３１より入力される信号）が複素共役信号生成手段６０に入力され、この結果、複素共役信号生成手段６０により複素共役信号が生成され、出力される。この複素共役信号生成手段６０により得られた複素共役信号と前記比較すべき２つの信号のうちの他の信号とが乗算手段６１により乗算処理される。
【００４６】
さらに、乗算手段６１により得られた乗算処理結果が累算手段６２により所定時間だけ累算され、累算結果である相互相関値が、出力端子１３２より信号合成手段１５、または遅延等化手段に１６にそれぞれ出力される。
【００４７】
次に、図１における自己相関検出手段１４ａ（または１４ｂ）の具体的構成を図５に示す。図５において、自己相関検出手段１４ａ（または１４ｂ）は、自己相関検出手段１４ａ（または１４ｂ）に供給される信号を有効シンボル時間だけ遅延させた遅延信号を出力する有効シンボル時間遅延手段５０と、自己相関検出手段１４ａ（または１４ｂ）に供給される信号から複素共役信号を生成して出力する複素共役信号生成手段５１と、前記遅延信号と前記複素共役信号とを乗算する乗算手段５２と、乗算手段５２の乗算結果を所定時間だけ累算する累算手段５３とを有している。
【００４８】
上記構成において、自己相関検出手段１４ａ（または１４ｂ）では、有効シンボル時間遅延手段５０により入力端子１３４より自己相関検出手段に供給される信号が有効シンボル時間だけ遅延させられた遅延信号が出力され、また、複素共役信号生成手段５１により入力端子１３４より供給される信号から複素共役信号が生成され出力される。前記遅延信号と前記複素共役信号とが乗算手段５２により乗算され、乗算手段５２の乗算結果が累算手段５３により所定時間だけ累算される。さらに、累算手段５３の累算結果である相互相関値が出力端子１３５より遅延等化手段１６に出力される。
【００４９】
つぎに、図６および図７を参照して上述の構成によるＯＦＤＭ受信装置のＯＦＤＭ変調信号のデータ構成と遅延波の除去動作について説明する。図６はＯＦＤＭ変調信号のデータ構成と自己相関検出信号との関係を示している。ＯＦＤＭ変調時に有効シンボルの末尾部分の所定時間分の信号をガードインターバルとして有効シンボルのヘッド部分にコピーし、ガードインターバルと有効シンボルの和の信号をＯＦＤＭシンボルとして送信する。
【００５０】
したがって、復調時にはコピーされたガードインターバルを除去して有効シンボル信号を抽出する必要があるが、自己相関検出手段により受信信号の自己相関をとると、ガードインターバルの信号開始時に自己相関値が最大になるので、受信信号の自己相関値をモニタすることにより、ＯＦＤＭ受信装置において、ＯＦＤＭシンボルの出力タイミングを認識することができる。
【００５１】
図７は遅延波を含むＯＦＤＭ変調信号の遅延波が合成波の有効シンボルに与える影響について示している。同図において、本実施の形態に係るＯＦＤＭ受信装置において主波及び遅延波１及び遅延波２を受信したとする。受信した信号波のうち主波は自己相関の最大値の検出により時刻ｔ１１からｔ２１までの間で単位ＯＦＤＭシンボルｉを形成していることが認識され、ＯＦＤＭシンボルｉの出力期間は、有効シンボルの出力期間とこの有効シンボルの末尾からコピーされた信号によるガードインターバル期間とを含んでいる。
【００５２】
同様に、遅延波１は検出した自己相関値のうち最大自己相関値に次いで大きい極大自己相関値の検出によって時刻ｔ１２からｔ２２までの間が、遅延波２は最大自己相関値のさらにつぎの極大自己相関値の検出によって時刻ｔ１３からｔ２３の間が単位ＯＦＤＭシンボルｉを形成していることが認識される。
ここで、遅延波１のＯＦＤＭシンボル開始時期ｔ１２は、主波のガードインターバル内にあるため直接の障害にはならない。ところが、遅延波２は遅延時間が大きくＯＦＤＭシンボル開始時期ｔ１３が主波のガードインターバル期間よりも遅れているため、有効シンボル検出後の合成波のシンボルｉには、遅延波２のシンボル（ｉ−１）の末尾部分が含まれ、有効シンボルにおける干渉領域となってしまう。
【００５３】
したがって、受信信号のうち主波のガードインターバル期間よりも大きな遅延時間をもってＯＦＤＭシンボルが開始する遅延波を排除する必要があり、図３を参照して既述したように遅延等化手段１６における負帰還手段によって遅延波が排除された信号がＯＦＤＭ復調手段１７に入力され、該ＯＦＤＭ復調手段１７により良好な復調信号を得ることができる。
【００５４】
以上に説明したように、本発明の第１の実施の形態に係るＯＦＤＭ受信装置によれば、複数の受信手段１２ａ及び１２ｂの出力信号のダイバーシチ合成前に複数の受信手段１２ａ及び１２ｂの出力信号の相互相関検出および自己相関検出を行い、前記相互相関検出結果に基づいてダイバーシチ合成を行い、合成後の信号に対して前記自己相関検出結果および前記相互相関検出結果に基づいて遅延等化手段１６によって不要波を除去するようにしたので、十分な信号強度を有し、かつＯＦＤＭ変調信号のガードインターバル時間以上の遅延時間を有する遅延波（不要波）を除去した有効シンボル信号を抽出することができるＯＦＤＭ受信装置が得られる。
【００５５】
次に本発明の第２の実施の形態に係るＯＦＤＭ受信装置の構成を図８に示す。本実施の形態に係るＯＦＤＭ受信装置が第１の実施の形態に係るＯＦＤＭ受信装置と構成上、異なるのは、ダイバーシチ合成手段１５による合成後の信号に対して自己相関検出手段８１によって自己相関検出を行い、検出された自己相関値に基づいて、受信信号のうち不要の信号成分を除去するように遅延等化手段８２を制御するように構成した点であり、その他の構成は同様であるので、同一の要素には同一の符号を付し、重複する説明は省略する。
【００５６】
同図において、本発明の第２の実施の形態に係るＯＦＤＭ受信装置は、＃１系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ａと、＃２系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ｂと、受信手段１２ａ，１２ｂと、受信手段１２ａ，１２ｂの出力信号の位相を補正してから合成する信号合成手段１００と、複数の受信手段１２ａ，１２ｂの出力信号間の相互相関を検出する相互相関検出手段１３と、信号合成手段１００の出力信号の自己相関を検出する自己相関検出手段８１と、自己相関検出手段８１の検出結果に基づいて信号合成手段１００の合成出力から所定時間以上、遅延した信号成分を除去する遅延等化手段８２と、ＯＦＤＭ復調手段１７とを有している。なお、自己相関検出手段８１の構成は図５に示した自己相関検出手段１４ａ（１４ｂ）の構成と同一であり、本発明の第２の自己相関検出手段に相当する。
【００５７】
上記構成において、アンテナ１１ａ、アンテナ１１ｂにより受信した信号は、それぞれ、受信手段１２ａ、１２ｂで増幅、周波数変換されてベースバンド信号に変換された後、それぞれ＃１系統、＃２系統の信号としてダイバーシチ合成手段１５に入力される。ダイバーシチ合成手段１５では、相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの各出力信号が同位相となるように信号合成手段１００で位相補正され、ダイバーシチ合成される。
【００５８】
次いで、遅延等化手段８２では、自己相関検出手段８１の検出結果に基づいて信号合成手段１００の合成出力から所定時間以上、具体的にはＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。遅延等化手段８２の出力信号は、ＯＦＤＭ復調手段１７において、フーリエ変換され、変調時に挿入されたガードインターバルが取り除かれ、有効シンボルが抽出されて復調される。
【００５９】
次に、図８における遅延等化手段８２の具体的構成を図９に示す。同図に示す遅延等化手段８２も遅延等化手段１６と同様に、２つの信号までの遅延等化が行える構成となっている。図９において、遅延等化手段１６は、加算手段９１と、加算手段９１の出力を所定時間、遅延させる遅延手段９２、９４と、遅延手段９２、９４の出力信号の複素振幅をそれぞれ、補正する複素振幅補正手段９３、９５と、遅延手段９２、９４における遅延時間を算出する遅延時間算出手段９７と、複素振幅補正手段９３、９５における振幅補正量である複素振幅係数を算出する複素振幅係数算出手段９８と、供給された自己相関値の中から最大値と極大値を探索する最大極大自己相関探索手段９６とを有している。
【００６０】
図３に示す遅延等化手段１６の構成と比較すると、遅延等化手段８２では、相互相関値に基づいて算出された位相係数による信号の位相補正を行わないことと、供給される自己相関値が１つとなっていることが異なるが、これ以外の構成においては同じである。
ここで、遅延手段９２と、複素振幅補正手段９３とにより構成される信号の負帰還手段により、一の遅延信号が除去され、また、遅延手段９４と、複素振幅補正手段９５とにより構成される信号の負帰還手段により、もう１つの遅延信号が除去される。
【００６１】
図９において、最大極大自己相関探索手段９６は、自己相関検出手段８１から自己相関値が供給されると、それらの中から自己相関の最大値と極大値とを探索し、自己相関の最大値と極大値に関する制御信号を遅延時間算出手段９７と、複素振幅係数算出手段９８に送出する。
最大極大自己相関探索手段３８からの制御信号を受けて、遅延時間算出手段９７は前記の最大自己相関値を基準として、最大自己相関値以外の極大自己相関値の中で、除去すべき２つの遅延信号に対応する極大自己相関値が検出された時点までの時間を算出して、これを遅延時間としてそれぞれ遅延手段９２，９４に送出する。
【００６２】
ここで、算出された遅延時間が所定時間、具体的にはＯＦＤＭ変調信号に含まれるガードインターバル時間より短い時には、送出する遅延時間を零とする。
また、複素振幅係数算出手段９８は、最大極大自己相関探索手段９６からの制御信号を受けると、最大自己相関値を基準として、最大自己相関値以外の極大自己相関値の中で除去すべき２つの遅延信号に対応する極大自己相関値との比をそれぞれ算出して、これを複素振幅係数としてそれぞれ複素振幅補正手段９３、９５に送出する。
【００６３】
ここで、遅延時間算出手段３９と複素振幅係数算出手段４０においては、自己相関検出手段８１から供給される自己相関値を参照して、遅延時間と複素振幅補正係数を算出する。
遅延手段９２、９４は遅延時間算出手段９７により与えられる遅延時間に基づいて入力信号を遅延させる。ここで、与えられる遅延時間が零のときは、遅延信号の遅延時間がＯＦＤＭ変調信号のガードインターバル時間以下であり、除去する必要がないので、入力信号を遅延させずに、振幅が零の信号を出力する。
複素振幅補正手段９３、９５は、複素振幅係数算出手段９８により与えられる複素振幅係数に基づいて振幅補正を行う。
【００６４】
このように遅延手段９２（９４）及び振幅補正手段９３（９５）からなる負帰還手段を経て加算手段９１の出力が負帰還され、同じ加算手段９１の入力に供給される。
図８に示す構成において、信号合成手段１００のダイバーシチ合成出力信号は、加算手段９１に与えられ、加算手段９１の出力は、遅延時間算出手段９７及び複素振幅係数算出手段９８により与えられた遅延時間及び複素振幅係数に基づいて遅延手段９２、９４及び複素振幅補正手段９３、９５により、遅延時間調整及び振幅調整が行われ、この遅延時間調整及び振幅補正が行われた信号が逆極性で加算手段９１で加算される。この結果、信号合成手段１００のダイバーシチ合成出力からＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去され、この不要波が除去された信号がＯＦＤＭ復調手段１７に出力される。
【００６５】
以上に説明したように、本発明の第２の実施の形態に係るＯＦＤＭ受信装置によれば、複数の受信手段１２ａおよび１２ｂの出力信号のダイバーシチ合成前に相互相関検出を行い、該相互相関検出結果に基づいてダイバーシチ合成を行い、ダイバーシチ合成後の信号に対して自己相関検出手段８１により自己相関検出を行い、該自己相関検出結果に基づいて遅延等化手段８２によって不要波を除去するようにしたので、十分な信号強度を有し、かつガードシンボル時間以上の遅延時間を有する遅延波（不要波）を除去した有効シンボル信号を抽出することができるＯＦＤＭ受信装置が得られる。
【００６６】
次に、本発明の第３実施の形態に係るＯＦＤＭ受信装置の構成を図１０に示す。本実施の形態に係るＯＦＤＭ受信装置が第１の実施の形態に係るＯＦＤＭ受信装置と構成上、異なるのは、信号合成手段１０１が、相互相関検出手段１３の検出出力のみではなく、自己相関検出手段１４ａ、１４ｂの検出出力をも取り込んで、位相補正と共に振幅補正も行っている点であり、他の構成は同様である。
【００６７】
図１０において、本実施の形態に係るＯＦＤＭ受信装置は、＃１系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ａと、＃２系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ｂと、受信手段１２ａ，１２ｂと、複数の受信手段１２ａ，１２ｂの出力信号間の相互相関を検出する相互相関検出手段１３と、受信手段１２ａの出力信号の自己相関を検出する自己相関検出手段１４ａと、受信手段１２ｂの出力信号の自己相関を検出する自己相関検出手段１４ｂと、自己相関検出手段１４ａ，１４ｂの検出結果及び相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの出力信号の位相と振幅をそれぞれ補正してから合成する信号合成手段１０１と、自己相関検出手段１４ａ，１４ｂの検出結果及び相互相関検出手段１３の検出結果に基づいて信号合成手段１０１の合成出力から所定時間以上、遅延した信号成分を除去する遅延等化手段１６と、ＯＦＤＭ復調手段１７とを有している。
【００６８】
ここで、相互相関検出手段１３と、自己相関検出手段１４ａ，１４ｂと、信号合成手段１０１とが、ダイバーシチ合成手段１８を構成し、相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの出力信号の位相をそれぞれ補正し、続いて自己相関検出手段１４ａ，１４ｂの検出結果に基づいて振幅を補正してから合成するという、ダイバーシチ合成を行う。
自己相関検出手段１４ａ，１４ｂは、本発明の第１の自己相関検出手段に相当する。
【００６９】
上記構成において、アンテナ１１ａ、アンテナ１１ｂにより受信した信号は、それぞれ、受信手段１２ａ、１２ｂで増幅、周波数変換されてベースバンド信号に変換された後、それぞれ＃１系統、＃２系統の信号としてダイバーシチ合成手段１８に入力される。ダイバーシチ合成手段１８の信号合成手段１０１では、相互相関検出手段１３及び自己相関検出手段１４ａ，１４ｂの検出結果に基づいて受信手段１２ａ，１２ｂの各出力信号が、所定の振幅になるように振幅補正され、かつ同位相となるように位相補正されて、ダイバーシチ合成される。
【００７０】
次いで遅延等化手段１６では、相互相関検出手段１３の検出結果及び自己相関検出手段１４ａ，１４ｂの検出結果に基づいて信号合成手段１０１のダイバーシチ合成出力から所定時間以上、具体的にはＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。遅延等化手段１６の出力信号は、ＯＦＤＭ復調手段１７において、フーリエ変換され、変調時に挿入されたガードインターバルが取り除かれ、有効シンボルが抽出されて復調される。
【００７１】
次に図１０における信号合成手段１０１の具体的構成を図１１に示す。同図において、信号合成手段１０１は振幅補正手段１１１、１１３と、移相手段１１２，１１４と、加算手段１１５とを有している。同図において、受信手段１２ａ，１２ｂの各出力信号は、自己相関検出手段１４ａ，１４ｂの検出結果に基づいて振幅補正手段１１１、１１３により所定の振幅補正がなされ、この振幅補正された信号は、移相手段１１２、１１４において相互相関検出手段１３の検出結果（相互相関値）を参照して互いに同相となるように位相補正され、加算手段１１５において加算されて合成され、遅延等化手段１６に出力される。このとき、振幅補正手段１１１、１１３において、自己相関検出手段１４ａ，１４ｂがそれぞれ検出した自己相関値の最大値に比例して振幅補正がなされると、加算手段１１５が出力する合成出力の搬送波電力対雑音電力比（ＣＮ比）を最大とすることができる。
【００７２】
以上に説明したように、本発明の第３の実施の形態に係るＯＦＤＭ受信装置によれば、複数の受信手段１２ａ及び１２ｂの出力信号のダイバーシチ合成前に複数の受信手段１２ａ及び１２ｂの出力信号の相互相関検出および自己相関検出を行い、前記相互相関検出結果及び前記自己相関検出結果に基づいてダイバーシチ合成を行い、合成後の信号に対して前記自己相関検出結果および前記相互相関検出結果に基づいて遅延等化手段１６によって不要波を除去するようにしたので、十分な信号強度を有し、かつガードインターバル時間以上の遅延時間を有する遅延波（不要波）を除去した有効シンボル信号を抽出することができるＯＦＤＭ受信装置が得られる。
【００７３】
次に本発明の第４の実施の形態に係るＯＦＤＭ受信装置の構成を図１２に示す。本発明の実施の形態に係るＯＦＤＭ受信装置が、第３の実施の形態に係るＯＦＤＭ受信装置と構成上、異なるのは、遅延等化手段の制御入力として相互相関検出手段１３、自己相関検出手段１４ａ，１４ｂの検出出力を用いずに、信号合成手段１０１によるダイバーシチ合成後の信号に対して、自己相関検出手段８１によって自己相関検出を行い、検出された自己相関値を遅延等化手段８２が制御入力として利用し、ダイバーシチ合成後の信号のうち不要の信号成分を除去するように構成した点であり、他の構成は同様である。
【００７４】
図１２において、＃１系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ａと、＃２系統のＯＦＤＭ変調された信号を捕捉するアンテナ１１ｂと、受信手段１２ａ，１２ｂと、複数の受信手段１２ａ，１２ｂの出力信号間の相互相関を検出する相互相関検出手段１３と、受信手段１２ａの出力信号の自己相関を検出する自己相関検出手段１４ａと、受信手段１２ｂの出力信号の自己相関を検出する自己相関検出手段１４ｂと、自己相関検出手段１４ａ，１４ｂの検出結果及び相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの出力信号の位相と振幅をそれぞれ補正してから合成する信号合成手段１０１と、信号合成手段１０１の出力信号の自己相関を検出する自己相関検出手段８１と、自己相関検出手段８１の検出結果に基づいて信号合成手段１０１の合成出力から所定時間以上、遅延した信号成分を除去する遅延等化手段８２と、ＯＦＤＭ復調手段１７とを有している。
【００７５】
ここで、相互相関検出手段１３と、自己相関検出手段１４ａ，１４ｂと、信号合成手段１０１とが、ダイバーシチ合成手段１８を構成し、相互相関検出手段１３の検出結果に基づいて受信手段１２ａ，１２ｂの出力信号の位相をそれぞれ補正し、続いて自己相関検出手段１４ａ，１４ｂの検出結果に基づいて振幅を補正してから合成するという、ダイバーシチ合成を行う。自己相関検出手段１４ａ，１４ｂは、本発明の第１の自己相関検出手段に相当し、自己相関検出手段８１は本発明の第２の自己相関検出手段に相当する。
【００７６】
上記構成において、アンテナ１１ａ、アンテナ１１ｂにより受信した信号は、それぞれ、受信手段１２ａ、１２ｂで増幅、周波数変換されてベースバンド信号に変換された後、それぞれ＃１系統、＃２系統の信号としてダイバーシチ合成手段１８に入力される。ダイバーシチ合成手段１８の信号合成手段１０１では、相互相関検出手段１３及び自己相関検出手段１４ａ，１４ｂの検出結果に基づいて受信手段１２ａ，１２ｂの各出力信号が所定の振幅になるように振幅補正され、かつ同位相となるように位相補正されて、ダイバーシチ合成される。
【００７７】
次いで遅延等化手段８２では、相互相関検出手段１３の検出結果及び自己相関検出手段１４ａ，１４ｂの検出結果に基づいて合成された信号合成手段１０１の合成出力から所定時間以上、具体的にはＯＦＤＭ変調信号のガードインターバル時間以上遅延した信号成分が除去される。遅延等化手段８２の出力信号は、ＯＦＤＭ復調手段１７において、フーリエ変換され、変調時に挿入されたガードインターバルが取り除かれ、有効シンボルが抽出されて復調される。
【００７８】
以上に説明したように、本発明の第４の実施の形態に係るＯＦＤＭ受信装置によれば、複数の受信手段１２ａ及び１２ｂの出力信号のダイバーシチ合成前に複数の受信手段１２ａ及び１２ｂの出力信号の相互相関検出および自己相関検出を行い、前記相互相関検出結果及び前記自己相関検出結果に基づいてダイバーシチ合成を行い、合成後の信号に対して自己相関検出を行い、該自己相関検出結果に基づいてダイバーシチ合成後の信号から遅延等化手段８２によって不要波を除去するようにしたので、十分な信号強度を有し、かつガードインターバル時間以上の遅延時間を有する遅延波（不要波）を除去した有効シンボル信号を抽出することができるＯＦＤＭ受信装置が得られる。
【００７９】
以上、本発明の第１乃至第４の実施形態に係るＯＦＤＭ受信装置は、複数の受信信号をダイバーシチ合成を行ってから遅延等化手段により不要波を除去するように構成したものである。
【００８０】
以上、本発明の第１乃至第４の実施形態に係るＯＦＤＭ受信装置の動作を図面を参照して詳述してきたが、本発明はこれらの実施形態に限られるものではなく、本発明の要旨を逸脱しない範囲の設計変更等があっても本発明に含まれる。例えば、入力のアンテナ数は２つに限られるものではなく、３つ以上のアンテナであっても本発明に含まれる。
また、遅延等化手段においては、２つの遅延信号を除去するように負帰還手段は２系統としたが、これ以外の数の系統を含むようにしたものであってもよい。
【００８１】
【発明の効果】
以上に説明したように、本発明によれば、ダイバーシチ合成手段によって合成した信号の出力側に遅延等化手段を設け、遅延波を排除するようにしたので、充分なＣＮ比をもった出力信号を得ることができ、復調後のビット誤りをなくすことができるという効果が得られる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態に係るＯＦＤＭ受信装置の構成を示すブロック図。
【図２】図１における信号合成手段の具体的構成を示すブロック図。
【図３】図１における遅延等化手段の具体的構成を示すブロック図。
【図４】図１における相互相関検出手段の具体的構成を示すブロック図。
【図５】図１における自己相関検出手段の具体的構成を示すブロック図。
【図６】ＯＦＤＭ変調信号のデータ構成と自己相関検出信号との関係を示す説明図。
【図７】遅延波を含むＯＦＤＭ変調信号における遅延波が合成波の有効シンボルに与える影響について示す説明図。
【図８】本発明の第２の実施形態に係るＯＦＤＭ受信装置の構成を示すブロック図。
【図９】図８における遅延等化手段の具体的構成を示すブロック図。
【図１０】本発明の第３の実施形態に係るＯＦＤＭ受信装置の構成を示すブロック図。
【図１１】図１０における信号合成手段の具体的構成を示すブロック図。
【図１２】本発明の第４の実施形態に係るＯＦＤＭ受信装置の構成を示すブロック図。
【図１３】ＯＦＤＭ送信装置の構成を示すブロック図。
【図１４】ＯＦＤＭによる変調過程を概念的に示した説明図。
【図１５】従来の基本的なＯＦＤＭ受信装置の構成を示すブロック図。
【図１６】ＯＦＤＭによる復調過程を概念的に示した説明図。
【符号の説明】
１１ａ、１１ｂアンテナ
１２ａ、１２ｂ受信手段（ＲＥＣ）
１３相互相関検出手段
１４ａ、１４ｂ、８１自己相関検出手段
１５、１８ダイバーシチ合成手段
１００、１０１信号合成手段
１６、８２遅延等化手段
１７ＯＦＤＭ復調手段
２１、２２、３４、３７、１１２，１１４移相手段
２３、３１、９１，１１５加算手段
３２，３５，９２、９４遅延手段
３３，３６，９３，９５複素振幅補正手段
３８、９６最大極大自己相関探索手段
３９、９７遅延時間算出手段
４０、９８複素振幅係数算出手段
４１位相係数算出手段
１１１、１１３振幅補正手段
５２、６１乗算手段
５３、６２累算手段
５０有効シンボル時間遅延手段
５１、６０複素共役信号生成手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a receiving apparatus for OFDM-modulated signals such as terrestrial digital TV broadcasting in Japan and Europe, and more particularly to a diversity receiving type OFDM receiving apparatus suitable for in-vehicle use.
[0002]
[Prior art]
In recent years, as a transmission (modulation) system for digital audio signals and video signals represented by terrestrial digital TV broadcasting, OFDM ( O rthogonal F frequency D ivision M A multi-carrier (multi-carrier) modulation scheme based on ul- plexing (orthogonal frequency division multiplexing) is being put into practical use. In broadcasting using this modulation method, encoded data is divided and distributed to thousands to several thousand carriers, multiplexed and transmitted.
FIG. 13 is a block diagram showing the structure of an OFDM transmitter, and FIG. 14 conceptually shows a modulation process using OFDM.
[0003]
In FIG. 13, an OFDM modulation unit 191 includes a modulation unit 192 that modulates an input digital signal such as QPSK, and a serial / parallel conversion unit (S / P) 193 that converts a modulated serial signal into a parallel signal. Fast Fourier transform means (IFFT) 194 for inverse Fourier transforming the converted parallel signal, and parallel / serial conversion means (P / S) for converting the inverse Fourier transform signal to a serial series and outputting it as a time signal 195 and guard interval insertion means 196 for inserting a guard interval into the converted signal. Reference numeral 197 denotes a transmission means (TX), and 198 denotes an antenna.
[0004]
In the above configuration, the modulation symbol obtained by information modulation of the input digital signal by the modulation means 192 using a predetermined modulation method (for example, QPSK modulation) is a serial / parallel conversion means as shown in FIG. By (S / P) 193, the signal is converted into a slower modulation symbol string, that is, a modulation symbol string of N orthogonal carrier waves arranged at a certain frequency interval (Δf). This modulation symbol sequence is subjected to fast inverse Fourier transform (IFFT) by fast inverse Fourier transform means (IFFT) 194, and is further subjected to waveform synthesis by parallel / serial transform means (P / S) 195 to provide the same phase of orthogonal time axis signals. A component (hereinafter referred to as I) and an orthogonal component (hereinafter referred to as Q) are generated.
[0005]
Further, the guard interval inserting means 196 copies and inserts the predetermined time (guard interval time) Tg at the end of the signal divided by the predetermined time (effective symbol time) Ts into the start part of the time axis signals I and Q. This is the guard interval. The time axis signal with the guard interval inserted in this way is generated as a baseband time series signal from the guard interval inserting means 66.
[0006]
This guard interval is inserted as a countermeasure against delayed wave interference (interference) that occurs during reception, and is a symbol that absorbs adjacent symbol interference due to the relative delay of a signal in a multipath environment.
Here, a time axis signal of (Tg + Ts) time is treated as one unit of OFDM symbol, and this guard interval is removed by processing at the time of reception, and only a signal of Ts time is extracted and demodulated as an effective symbol signal. It is.
The baseband time-series signal generated by the guard interval insertion unit 196 is put on a predetermined carrier wave by a transmission unit (TX) 197 including a D / A conversion unit, and after power amplification, is radiated from the antenna 198 to space. The
[0007]
Next, FIG. 15 conceptually shows the configuration of a basic OFDM receiver, and FIG. 16 conceptually shows a demodulation process by OFDM.
In FIG. 15, the OFDM receiver includes an antenna 212, receiving means (REC) 213, and OFDM demodulating means 211.
The OFDM demodulator 211 also removes a guard interval from the received signal to extract an effective symbol signal 214, and a serial / parallel converter (S / P) 215 that converts the effective symbol signal into a parallel signal. Fast Fourier transform means (FFT) 216 for Fourier transforming parallel signals, parallel / serial conversion means (P / S) 217 for transforming serial signals, and demodulation means 218.
[0008]
In FIG. 15, the signal radio wave captured by the antenna 212 is amplified and frequency converted by the receiving means (REC) 213, output as a baseband time series signal, and demodulated by the OFDM demodulating means 211.
As shown in FIG. 16, the OFDM demodulating unit 211 refers to the received OFDM symbol in the effective symbol extracting unit 214, calculates a product sum of two symbol signals separated by Ts time over Tg time, and calculates an autocorrelation signal. Is used as a reference signal. Subsequently, the peak (maximum value) of the reference signal (autocorrelation signal) of the OFDM symbol is detected, the start time of the guard interval inserted based on the peak of the autocorrelation signal is detected, and this guard interval is removed and effective. I and Q of the symbol are extracted.
[0009]
Next, the effective symbol signal is converted into a parallel signal by the serial / parallel conversion means (S / P) 215, and the converted parallel signal is fast Fourier transformed (FFT) by the fast Fourier transform means (FFT) 216, and the frequency is Δf. The modulation symbols of N carrier waves that are shifted are extracted. The modulation symbol thus taken out is converted into a serial time series by a parallel / serial conversion means (P / S) 217, and then demodulated by a demodulation means 218 in a predetermined manner to decode a digital signal.
[0010]
As described above, the peak (maximum value) of the reference signal (autocorrelation signal) of the received OFDM symbol is detected, and the effective symbol is extracted based on the peak of the autocorrelation signal. The data of OFDM symbols adjacent to the extracted effective symbol is included, and there is a problem that a bit error occurs.
On the other hand, when a broadcast signal based on OFDM modulation is received while moving in an automobile or the like, it is affected by fading and the received signal level fluctuates, so that the reference signal cannot be generated accurately. As a result, the bit error as described above occurs, so that level fluctuation is suppressed by diversity reception during mobile reception.
[0011]
[Problems to be solved by the invention]
However, in the above-described conventional OFDM receiver, even if diversity reception is performed, if a delayed wave that is delayed more than the guard interval time (Tg) of the OFDM symbol is mixed, adjacent effective symbols interfere with each other. There is a problem that bit errors after demodulation increase.
The present invention has been made in view of such circumstances, and by providing the diversity combining means and the delay equalization means in the previous stage of the Fourier transform processing means of the OFDM modulation signal, it has sufficient signal strength, and An object of the present invention is to provide a diversity reception type OFDM receiver capable of extracting an effective symbol signal from which a delayed wave having a delay time equal to or longer than the guard interval time is removed.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, an OFDM receiving apparatus of the present invention is arranged apart from each other, a plurality of antennas for capturing OFDM-modulated signals, and connected to each of the plurality of antennas to process the supplied signals A plurality of receiving means to be baseband signals, diversity combining means for combining the output signals of the plurality of receiving means, and a signal component delayed from the combined output of the diversity combining means by a guard interval time of the OFDM modulation signal And an OFDM demodulator for extracting and demodulating an effective symbol signal by removing a guard interval signal inserted during modulation from the output signal of the delay equalizer. .
[0013]
In the OFDM receiver of the present invention, OFDM-modulated signals are captured by a plurality of antennas spaced apart from each other, and signals supplied by a plurality of receiving means respectively connected to the plurality of antennas are processed and processed. It is converted into a band signal. Next, the diversity combining means combines the output signals of the plurality of receiving means. Further, the delay equalization means removes the signal component delayed from the combined output of the diversity combining means by the guard interval time of the OFDM modulation signal, and the guard demodulated from the output signal of the delay equalization means by the OFDM demodulation means The interval signal is removed, and an effective symbol signal is extracted and demodulated.
[0014]
Further, the OFDM receiving apparatus of the present invention includes a cross-correlation detecting means for detecting a cross-correlation between output signals of the plurality of receiving means on the output side of the plurality of receiving means, and each output of the plurality of receiving means. A plurality of first autocorrelation detection means for detecting autocorrelation of the signal, and the delay equalization means is based on detection results of the crosscorrelation detection means and the plurality of first autocorrelation detection means; A signal component delayed by a guard interval time or more of the OFDM modulation signal is removed.
[0015]
In the OFDM receiver of the present invention, the cross-correlation between the output signals of the plurality of receiving means is detected by the cross-correlation detecting means connected to the output side of the plurality of receiving means, and the plurality of receiving means The autocorrelation of each output signal of the plurality of receiving means is detected by a plurality of first autocorrelation detecting means connected to the output side. Further, the delay equalization means removes signal components delayed by the guard interval time of the OFDM modulation signal based on the detection results of the cross correlation detection means and the plurality of first autocorrelation detection means.
[0016]
Further, in the OFDM receiver of the present invention, the delay equalization means includes the maximum autocorrelation value other than the maximum autocorrelation value among the autocorrelation values detected by each of the plurality of first autocorrelation detection means. The delay equalization means output based on the delay time from the maximum autocorrelation value, the complex amplitude coefficient calculated from the maximum autocorrelation value, and the phase coefficient calculated from the crosscorrelation value detected by the crosscorrelation detection means A plurality of feedback means for negatively feeding back the signal is provided.
[0017]
In the OFDM receiver of the present invention, the maximum self-correlation value other than the maximum autocorrelation value among the autocorrelation values detected by each of the plurality of first autocorrelation detection means by the plurality of feedback means included in the delay equalization means. Based on the delay time of the correlation value from the maximum autocorrelation value, the complex amplitude coefficient calculated from the maximum autocorrelation value, and the phase coefficient calculated from the crosscorrelation value detected by the crosscorrelation detection means The output signal of the converting means is negatively fed back.
[0018]
In the OFDM receiver of the present invention, the cross-correlation detecting unit generates a complex conjugate signal from one of the two signals to be compared among the signals supplied to the cross-correlation detecting unit. A complex conjugate signal generating means for outputting, a multiplying means for multiplying the complex conjugate signal by another signal of the two signals to be compared, and an accumulation for accumulating the multiplication result of the multiplication means for a predetermined time. Means.
[0019]
In the OFDM receiver of the present invention, in the cross-correlation detecting means, the complex conjugate signal is obtained from one of the two signals to be compared among the signals supplied to the cross-correlation detecting means by the complex conjugate signal generating means. Is generated and output. Further, the multiplication means multiplies the complex conjugate signal and the other signal of the two signals to be compared, and the accumulation means accumulates the multiplication result of the multiplication means for a predetermined time.
[0020]
In the OFDM receiver of the present invention, a second autocorrelation detecting means for detecting an autocorrelation of an output signal of the diversity combining means is connected to an output side of the diversity combining means, and the delay equalizing means comprises: A signal component delayed by the guard interval time of the OFDM modulation signal is removed based on the detection result of the second autocorrelation detection means.
[0021]
In the OFDM receiver of the present invention, the autocorrelation of the output signal of the diversity combining means is detected by the second autocorrelation detecting means connected to the output side of the diversity combining means, and the delay equalizing means Based on the detection result of the second autocorrelation detection means, the signal component delayed by the guard interval time of the OFDM modulation signal is removed.
[0022]
Further, in the OFDM receiver of the present invention, the delay equalization means includes the maximum autocorrelation value of the maximum autocorrelation value other than the maximum autocorrelation value among the autocorrelation values detected by the second autocorrelation detection means. And a plurality of feedback means for negatively feeding back the output signal of the delay equalizing means based on the delay time from the delay time and the complex amplitude coefficient calculated from the maximum autocorrelation value.
[0023]
In the OFDM receiver of the present invention, among the autocorrelation values detected by the second autocorrelation detection means by the plurality of feedback means included in the delay equalization means, the maximum autocorrelation value other than the maximum autocorrelation value is selected. The output signal of the delay equalization means is negatively fed back based on the delay time from the maximum autocorrelation value and the complex amplitude coefficient calculated from the maximum autocorrelation value.
[0024]
Further, in the OFDM receiver of the present invention, the first and second autocorrelation detecting means are configured to delay signals obtained by delaying signals supplied to the first and second autocorrelation detecting means by an effective symbol time. Effective symbol time delay means for outputting, complex conjugate signal generating means for generating and outputting a complex conjugate signal from signals supplied to the first and second autocorrelation detecting means, the delayed signal and the complex conjugate signal And multiplication means for accumulating multiplication results of the multiplication means for a predetermined time.
[0025]
In the OFDM receiver of the present invention, in the first and second autocorrelation detecting means, the signal supplied to the first and second autocorrelation detecting means is delayed by the effective symbol time by the effective symbol time delaying means. The delayed conjugate signal is output, and a complex conjugate signal is generated and output from the signal supplied to the first and second autocorrelation detecting means by the complex conjugate signal generating means. Further, the multiplication means multiplies the delayed signal and the complex conjugate signal, and the accumulation means accumulates the multiplication result of the multiplication means for a predetermined time.
[0026]
In the OFDM receiver of the present invention, the OFDM demodulator detects a maximum autocorrelation value indicating a maximum value among the autocorrelation values detected by each of the plurality of first autocorrelation detectors. A guard interval signal from the output signal of the delay equalization means based on the time point or the time point when the maximum autocorrelation value indicating the maximum value is detected among the autocorrelation values detected by the second autocorrelation detection means And an effective symbol signal is extracted.
[0027]
In the OFDM receiver of the present invention, when the OFDM demodulating means detects a maximum autocorrelation value indicating the maximum value among the autocorrelation values detected by each of the plurality of first autocorrelation detecting means, Alternatively, the guard interval signal is removed from the output signal of the delay equalization means with reference to the time point when the maximum autocorrelation value indicating the maximum value among the autocorrelation values detected by the second autocorrelation detection means is detected. Thus, an effective symbol signal is extracted.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The OFDM receiver according to each embodiment of the present invention includes a diversity combining unit that performs antenna diversity, and a predetermined time or more of the received OFDM modulated signal, before the FFT calculating unit that performs an FFT operation on the effective symbol of the OFDM modulated signal. The delay equalization means for removing the delayed signal component (delayed wave) is provided so that the effective symbol signal of the OFDM modulation signal having sufficient signal strength and removing the signal with a large delay can be extracted. It is characterized by that. Hereinafter, the case where the number of antenna elements is 2 in the OFDM receiver according to each embodiment of the present invention will be described.
[0029]
FIG. 1 shows the configuration of an OFDM receiving apparatus according to the first embodiment of the present invention. In the figure, the OFDM receiver according to the present embodiment includes an antenna 11a that captures # 1 system OFDM-modulated signals, and a # 2 system OFDM-modulated signal that is spaced apart from antenna 11a. Antenna 11b, receiving means 12a and 12b, signal synthesizing means 100 for synthesizing after correcting the phase of the output signal of receiving means 12a and 12b, and mutual output signals of the plurality of receiving means 12a and 12b. A cross-correlation detecting means 13 for detecting a correlation; an autocorrelation detecting means 14a for detecting an autocorrelation of an output signal of the receiving means 12a; an autocorrelation detecting means 14b for detecting an autocorrelation of an output signal of the receiving means 12b; Based on the detection results of the correlation detection units 14a and 14b and the detection result of the cross correlation detection unit 13, a predetermined time from the combined output of the signal combining unit 100 Moreover, a delay equalizing means 16 for removing the delayed signal component, and a OFDM demodulation means 17.
[0030]
Here, the cross-correlation detecting means 13 and the signal synthesizing means 100 constitute the diversity combining means 15, and after correcting the phases of the output signals of the receiving means 12a and 12b based on the detection result of the cross-correlation detecting means 13. Diversity synthesis is performed. The autocorrelation detection means 14a and 14b correspond to the first autocorrelation detection means of the present invention. The specific configuration of the OFDM demodulator 17 is the same as that of the known OFDM demodulator 211.
[0031]
In the above configuration, the signals received by the antenna 11a and the antenna 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals, and then diversity as signals of # 1 system and # 2 system, respectively. Input to the combining means 15. In the diversity combining means 15, the signal combining means 100 corrects the phase based on the detection result of the cross-correlation detecting means 13 so that the output signals of the receiving means 12 a and 12 b have the same phase, and the diversity combining is performed.
[0032]
Next, in the delay equalization means 16, based on the detection results of the autocorrelation detection means 14 a and 14 b and the detection result of the cross correlation detection means 13, more than a predetermined time from the combined output of the signal combining means 100, specifically, the OFDM modulated signal The signal component delayed by the guard interval time or longer is removed. The output signal of the delay equalization means 16 is subjected to Fourier transform in the OFDM demodulation means 18, the guard interval inserted at the time of modulation is removed, and effective symbols are extracted and demodulated.
[0033]
Next, a specific configuration of the signal synthesizing means 100 in FIG. 1 is shown in FIG. In the figure, the signal synthesizing unit 100 includes phase shifting units 21 and 22 and an adding unit 23. In the figure, the output signals of the receiving means 12a and 12b are phase-corrected by the phase shifting means 21 and 22 so as to be in phase with each other with reference to the detection result (cross-correlation value) of the cross-correlation detecting means 13, and adding means. The signals are added and synthesized at 23 and output to the delay equalization means 16. Thus, when diversity combining is performed in the same phase, the power of the combined output can be maximized.
[0034]
Next, a specific configuration of the delay equalization means 16 in FIG. 1 is shown in FIG. The delay equalization means 16 shown in the figure is configured to perform delay equalization up to two signals. In FIG. 3, the delay equalization means 16 corrects the addition means 31, delay means 32 and 35 for delaying the output of the addition means 31, and the complex amplitudes of the output signals of the delay means 32 and 35, respectively. Complex amplitude correcting means 33, 36, phase shifting means 34, 37 for correcting the phases of the complex amplitude correcting means 33, 36, delay time calculating means 39 for calculating the delay time in the delay means 32, 35, complex A complex amplitude coefficient calculating means 40 for calculating a complex amplitude coefficient which is an amplitude correction amount in the amplitude correcting means 33 and 36, a phase coefficient calculating means 41 for calculating a phase shift amount in the phase shifting means 34 and 37, and the supplied self Maximum maximum autocorrelation search means 38 for searching for a maximum value and a maximum value from among the correlation values is provided.
[0035]
The delay equalization means 16 shown in FIG. 3 is configured to perform delay equalization of up to two signals, and negative feedback of a signal constituted by the delay means 32, the complex amplitude correction means 33, and the phase shift means 34. The delayed signal of one signal is removed by the means, and the other delayed signal is removed by the negative feedback means of the signal constituted by the delay means 35, the complex amplitude correcting means 36, and the phase shift means 37. Is done.
[0036]
When the autocorrelation values are supplied from the autocorrelation detection means 14a and 14b, the maximum maximum autocorrelation search means 38 searches for the maximum value and the maximum value of the autocorrelation among them, and the maximum value and the maximum value of the autocorrelation. A control signal related to the value is sent to the delay time calculating means 39, the complex amplitude coefficient calculating means 40, and the phase coefficient calculating means 41. For example, if three OFDM modulated signals are included in the output of the signal synthesis unit 100, one maximum autocorrelation value and two maximum autocorrelation values are detected, and the delay that has caused the maximum autocorrelation value is generated. In order to remove the signals, control information relating to these is sent out.
[0037]
In response to the control signal from the maximum maximum autocorrelation search means 38, the delay time calculation means 39 uses the maximum autocorrelation value as a reference and uses the two maximum autocorrelation values other than the maximum autocorrelation value to be removed. The time until the point when the maximum autocorrelation value corresponding to the delay signal is detected is calculated, and this is sent as delay time to the delay means 32 and 35, respectively. Here, when the calculated delay time is shorter than a predetermined time, specifically, the guard interval time included in the OFDM modulation signal, the transmission delay time is set to zero.
[0038]
Further, when the complex amplitude coefficient calculating means 40 receives the control signal from the maximum maximum autocorrelation search means 38, the complex amplitude coefficient calculation means 40 should be removed from the maximum autocorrelation values other than the maximum autocorrelation value with reference to the maximum autocorrelation value 2. The ratios with the maximum autocorrelation values corresponding to the two delayed signals are calculated, and are sent as complex amplitude coefficients to the complex amplitude correction means 33 and 36, respectively.
Here, in the delay time calculation means 39 and the complex amplitude coefficient calculation means 40, the delay time and the complex amplitude correction coefficient are calculated with reference to the autocorrelation values supplied from the autocorrelation detection means 14a and 14b, respectively.
[0039]
Further, when the phase coefficient calculating means 41 receives the control signal from the maximum maximum autocorrelation search means 38, the phase coefficient calculating means 41 calculates phase coefficients corresponding to two delayed signals to be removed from the maximum autocorrelation values other than the maximum autocorrelation value. The cross-correlation values supplied from the cross-correlation detection means 13 are calculated with reference to the cross-correlation values and sent to the phase shift means 34 and 37, respectively. At this time, a phase coefficient is calculated such that the phase rotation becomes zero when the maximum autocorrelation value corresponding to the delayed signal to be removed is detected by the same autocorrelation detection means 14a (or 14b) as the maximum autocorrelation value. In other cases, a phase coefficient that gives phase rotation is calculated so as to cancel the phase of the cross-correlation value.
[0040]
The delay means 32 and 35 delay the input signal based on the delay time given by the delay time calculation means 39. Here, when the given delay time is zero, the delay time of the delay signal is equal to or less than the guard interval time of the OFDM modulation signal and does not need to be removed. Therefore, the signal with zero amplitude is not delayed without delaying the input signal. Is output.
The complex amplitude correction means 33 and 36 perform amplitude correction based on the complex amplitude coefficient given by the complex amplitude coefficient calculation means 40.
[0041]
The phase shift means 34 and 37 correct the phase of the input signal based on the phase coefficient given by the phase coefficient calculation means 41. As described above, the output of the adding means 31 is negatively fed back through the negative feedback means including the delay means 32 (35), the complex amplitude correcting means 33 (36), and the phase shift means 34 (37). To be supplied.
[0042]
In the configuration shown in FIG. 1, the diversity combined output signal of the signal combining unit 100 is supplied to the adding unit 31, and the output of the adding unit 31 is the delay time supplied by the delay time calculating unit 39 and the complex amplitude coefficient calculating unit 40. The delay means 32 and 35 and the complex amplitude correction means 33 and 36 perform delay time adjustment and amplitude adjustment based on the complex amplitude coefficient, and output to the phase shift means 34 and 37.
[0043]
Further, in the phase shift means 34 and 37, the phase correction is performed by the phase coefficient given by the phase coefficient calculation means 41, and the signal subjected to the delay time adjustment, the amplitude correction and the phase correction has the reverse polarity and is added by the addition means 31. Is added. As a result, the signal component delayed by the guard interval time of the OFDM modulated signal is removed from the diversity combined output of the signal combining unit 100, and the signal from which the unnecessary wave is removed is output to the OFDM demodulation unit 17.
[0044]
Next, FIG. 4 shows a specific configuration of the cross-correlation detecting means 13 in FIG. In FIG. 4, the cross-correlation detection unit 13 generates a complex conjugate signal from one of the two signals to be compared among the signals supplied to the cross-correlation detection unit 13, and outputs the complex conjugate signal. Means 60, multiplication means 61 for multiplying the complex conjugate signal generated by complex conjugate signal generation means 60 with the other signal of the two signals to be compared, and the result of the multiplication process by multiplication means 61 as a predetermined value. And accumulating means 62 for accumulating only time.
[0045]
In the above configuration, the cross-correlation detection means 13 is one of the two signals to be compared (input from the input terminal 131) among the signals supplied to the cross-correlation detection means 13 via the input terminals 130 and 131. Signal) is input to the complex conjugate signal generation means 60. As a result, the complex conjugate signal generation means 60 generates and outputs a complex conjugate signal. The complex conjugate signal obtained by the complex conjugate signal generation means 60 and the other signal of the two signals to be compared are multiplied by the multiplication means 61.
[0046]
Further, the multiplication processing result obtained by the multiplication means 61 is accumulated by the accumulation means 62 for a predetermined time, and the cross-correlation value as the accumulation result is sent from the output terminal 132 to the signal synthesis means 15 or the delay equalization means. 16 respectively.
[0047]
Next, FIG. 5 shows a specific configuration of the autocorrelation detection means 14a (or 14b) in FIG. In FIG. 5, the autocorrelation detection unit 14a (or 14b) outputs an effective symbol time delay unit 50 that outputs a delayed signal obtained by delaying the signal supplied to the autocorrelation detection unit 14a (or 14b) by an effective symbol time; A complex conjugate signal generating means 51 for generating and outputting a complex conjugate signal from a signal supplied to the autocorrelation detecting means 14a (or 14b); a multiplying means 52 for multiplying the delayed signal and the complex conjugate signal; And accumulating means 53 for accumulating the multiplication results of the means 52 for a predetermined time.
[0048]
In the above configuration, the autocorrelation detection means 14a (or 14b) outputs a delayed signal obtained by delaying the signal supplied from the input terminal 134 to the autocorrelation detection means by the effective symbol time delay means 50 by the effective symbol time, Further, a complex conjugate signal is generated from the signal supplied from the input terminal 134 by the complex conjugate signal generating means 51 and output. The delayed signal and the complex conjugate signal are multiplied by the multiplying means 52, and the multiplication result of the multiplying means 52 is accumulated by the accumulating means 53 for a predetermined time. Further, the cross-correlation value as the accumulation result of the accumulation means 53 is output from the output terminal 135 to the delay equalization means 16.
[0049]
Next, with reference to FIG. 6 and FIG. 7, the data structure of the OFDM modulation signal and the operation of removing the delayed wave of the OFDM receiving apparatus having the above-described structure will be described. FIG. 6 shows the relationship between the data structure of the OFDM modulation signal and the autocorrelation detection signal. During OFDM modulation, a signal for a predetermined time at the end portion of the effective symbol is copied as a guard interval to the head portion of the effective symbol, and a signal of the sum of the guard interval and the effective symbol is transmitted as the OFDM symbol.
[0050]
Therefore, at the time of demodulation, it is necessary to remove the copied guard interval and extract the effective symbol signal. However, if the autocorrelation of the received signal is taken by the autocorrelation detection means, the autocorrelation value is maximized at the start of the guard interval signal. Therefore, by monitoring the autocorrelation value of the received signal, the OFDM receiver can recognize the output timing of the OFDM symbol.
[0051]
FIG. 7 shows the influence of the delayed wave of the OFDM modulated signal including the delayed wave on the effective symbol of the synthesized wave. In the figure, it is assumed that the main wave, the delayed wave 1 and the delayed wave 2 are received by the OFDM receiver according to the present embodiment. Of the received signal waves, the main wave is recognized to form a unit OFDM symbol i from time t11 to t21 by detecting the maximum value of autocorrelation, and the output period of OFDM symbol i is the effective symbol. It includes an output period and a guard interval period by a signal copied from the end of the effective symbol.
[0052]
Similarly, the delay wave 1 is detected between the time t12 and t22 by detecting the maximum autocorrelation value that is next to the maximum autocorrelation value among the detected autocorrelation values, and the delay wave 2 is the next maximum of the maximum autocorrelation value. It is recognized that the unit OFDM symbol i is formed between the times t13 and t23 by detecting the autocorrelation value.
Here, since the OFDM symbol start time t12 of the delay wave 1 is within the guard interval of the main wave, there is no direct obstacle. However, the delay wave 2 has a large delay time, and the OFDM symbol start time t13 is delayed from the guard interval period of the main wave. Therefore, the symbol i of the delay wave 2 (i− The end portion of 1) is included, which becomes an interference area in the effective symbol.
[0053]
Therefore, it is necessary to eliminate a delayed wave that starts an OFDM symbol with a delay time longer than the guard interval period of the main wave in the received signal, and as described above with reference to FIG. A signal from which the delayed wave has been eliminated by the feedback means is input to the OFDM demodulation means 17, and a good demodulated signal can be obtained by the OFDM demodulation means 17.
[0054]
As described above, according to the OFDM receiving apparatus according to the first embodiment of the present invention, the output signals of the plurality of receiving units 12a and 12b before the diversity combining of the output signals of the plurality of receiving units 12a and 12b. Cross-correlation detection and auto-correlation detection, diversity combining is performed based on the cross-correlation detection result, and delay equalization means 16 is performed on the combined signal based on the auto-correlation detection result and the cross-correlation detection result. Therefore, it is possible to extract an effective symbol signal from which a delayed wave (unnecessary wave) having sufficient signal strength and having a delay time longer than the guard interval time of the OFDM modulation signal is removed. An OFDM receiver that can be obtained is obtained.
[0055]
Next, FIG. 8 shows the configuration of an OFDM receiving apparatus according to the second embodiment of the present invention. The OFDM receiving apparatus according to the present embodiment differs from the OFDM receiving apparatus according to the first embodiment in configuration in that the autocorrelation detecting unit 81 detects the autocorrelation for the signal combined by the diversity combining unit 15. The delay equalization means 82 is controlled to remove unnecessary signal components from the received signal based on the detected autocorrelation value, and the other configurations are the same. The same elements are denoted by the same reference numerals, and redundant description is omitted.
[0056]
In the figure, an OFDM receiver according to the second embodiment of the present invention includes an antenna 11a that captures # 1 system OFDM-modulated signals and an antenna 11b that captures # 2 system OFDM-modulated signals. And receiving means 12a, 12b, a signal synthesizing means 100 that synthesizes after correcting the phase of the output signals of the receiving means 12a, 12b, and a mutual correlation that detects the cross-correlation between the output signals of the plurality of receiving means 12a, 12b. Correlation detecting means 13, autocorrelation detecting means 81 for detecting the autocorrelation of the output signal of signal synthesizing means 100, and a delay of a predetermined time or more from the synthesized output of signal synthesizing means 100 based on the detection result of autocorrelation detecting means 81 The delay equalizing means 82 for removing the signal component and the OFDM demodulating means 17 are provided. The configuration of the autocorrelation detection means 81 is the same as that of the autocorrelation detection means 14a (14b) shown in FIG. 5, and corresponds to the second autocorrelation detection means of the present invention.
[0057]
In the above configuration, the signals received by the antenna 11a and the antenna 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals, and then diversity as signals of # 1 system and # 2 system, respectively. Input to the combining means 15. In the diversity combining means 15, the signal combining means 100 corrects the phase based on the detection result of the cross-correlation detecting means 13 so that the output signals of the receiving means 12 a and 12 b have the same phase, and the diversity combining is performed.
[0058]
Next, the delay equalization means 82 removes the signal component delayed from the synthesized output of the signal synthesis means 100 for a predetermined time or more, specifically, the guard interval time of the OFDM modulation signal, based on the detection result of the autocorrelation detection means 81. Is done. The output signal of the delay equalization means 82 is subjected to Fourier transform in the OFDM demodulation means 17, the guard interval inserted at the time of modulation is removed, and effective symbols are extracted and demodulated.
[0059]
Next, a specific configuration of the delay equalization means 82 in FIG. 8 is shown in FIG. Similarly to the delay equalization means 16, the delay equalization means 82 shown in the figure is configured to be able to equalize delays up to two signals. In FIG. 9, the delay equalization means 16 corrects the addition means 91, the delay means 92 and 94 for delaying the output of the addition means 91 for a predetermined time, and the complex amplitudes of the output signals of the delay means 92 and 94, respectively. Complex amplitude correction means 93 and 95, delay time calculation means 97 for calculating the delay time in the delay means 92 and 94, and complex amplitude coefficient calculation for calculating a complex amplitude coefficient that is an amplitude correction amount in the complex amplitude correction means 93 and 95 Means 98 and maximum maximal autocorrelation searching means 96 for searching for the maximum value and the maximum value from the supplied autocorrelation values.
[0060]
Compared to the configuration of the delay equalization means 16 shown in FIG. 3, the delay equalization means 82 does not perform phase correction of the signal by the phase coefficient calculated based on the cross-correlation value, and the supplied autocorrelation value. However, it is the same in other configurations.
Here, one delay signal is removed by the negative feedback means of the signal constituted by the delay means 92 and the complex amplitude correction means 93, and the delay means 94 and the complex amplitude correction means 95 are constituted. Another delayed signal is removed by the negative feedback means of the signal.
[0061]
In FIG. 9, when the autocorrelation value is supplied from the autocorrelation detection means 81, the maximum maximum autocorrelation search means 96 searches the autocorrelation maximum value and the maximum value from these, and the autocorrelation maximum value. And a control signal related to the maximum value are sent to the delay time calculating means 97 and the complex amplitude coefficient calculating means 98.
In response to the control signal from the maximum maximal autocorrelation search means 38, the delay time calculation means 97 uses the maximum autocorrelation value as a reference, and the two maximum autocorrelation values other than the maximum autocorrelation value are to be removed. The time until the time point when the maximum autocorrelation value corresponding to the delay signal is detected is calculated and sent to the delay means 92 and 94 as the delay time.
[0062]
Here, when the calculated delay time is shorter than a predetermined time, specifically, the guard interval time included in the OFDM modulation signal, the transmission delay time is set to zero.
Further, when the complex amplitude coefficient calculating unit 98 receives the control signal from the maximum autocorrelation searching unit 96, the complex amplitude coefficient calculating unit 98 should remove the maximum autocorrelation value other than the maximum autocorrelation value with reference to the maximum autocorrelation value 2. The ratios with the maximum autocorrelation values corresponding to the two delayed signals are calculated, and are sent as complex amplitude coefficients to the complex amplitude correction means 93 and 95, respectively.
[0063]
Here, the delay time calculation means 39 and the complex amplitude coefficient calculation means 40 refer to the autocorrelation value supplied from the autocorrelation detection means 81 to calculate the delay time and the complex amplitude correction coefficient.
The delay means 92 and 94 delay the input signal based on the delay time given by the delay time calculation means 97. Here, when the given delay time is zero, the delay time of the delay signal is equal to or less than the guard interval time of the OFDM modulation signal and does not need to be removed. Therefore, the signal with zero amplitude is not delayed without delaying the input signal. Is output.
The complex amplitude correction means 93 and 95 perform amplitude correction based on the complex amplitude coefficient given by the complex amplitude coefficient calculation means 98.
[0064]
In this way, the output of the adding means 91 is negatively fed back through the negative feedback means comprising the delay means 92 (94) and the amplitude correcting means 93 (95), and supplied to the input of the same adding means 91.
In the configuration shown in FIG. 8, the diversity combined output signal of the signal combining unit 100 is supplied to the adding unit 91, and the output of the adding unit 91 is the delay time supplied by the delay time calculating unit 97 and the complex amplitude coefficient calculating unit 98. The delay means 92 and 94 and the complex amplitude correction means 93 and 95 perform delay time adjustment and amplitude adjustment based on the complex amplitude coefficient, and the signal subjected to the delay time adjustment and amplitude correction is added with reverse polarity. It is added at 91. As a result, the signal component delayed by the guard interval time of the OFDM modulated signal is removed from the diversity combined output of the signal combining unit 100, and the signal from which the unnecessary wave is removed is output to the OFDM demodulation unit 17.
[0065]
As described above, according to the OFDM receiver according to the second embodiment of the present invention, cross-correlation detection is performed before diversity combining of the output signals of the plurality of receiving means 12a and 12b, and the cross-correlation detection is performed. Diversity combining is performed based on the result, autocorrelation detection is performed by the autocorrelation detection unit 81 on the signal after diversity combining, and unnecessary waves are removed by the delay equalization unit 82 based on the autocorrelation detection result. Therefore, an OFDM receiver capable of extracting an effective symbol signal from which a delayed wave (unnecessary wave) having a sufficient signal strength and a delay time equal to or longer than the guard symbol time is removed can be obtained.
[0066]
Next, FIG. 10 shows the configuration of an OFDM receiving apparatus according to the third embodiment of the present invention. The OFDM receiving apparatus according to the present embodiment differs from the OFDM receiving apparatus according to the first embodiment in configuration in that the signal combining means 101 is not only the detection output of the cross-correlation detecting means 13 but also the autocorrelation detection. The detection outputs of the means 14a and 14b are also taken in and the amplitude correction is performed together with the phase correction, and the other configurations are the same.
[0067]
In FIG. 10, the OFDM receiving apparatus according to the present embodiment includes an antenna 11a that captures # 1 system OFDM-modulated signals, an antenna 11b that captures # 2 systems OFDM-modulated signals, and receiving means 12a. , 12b, a cross-correlation detecting means 13 for detecting the cross-correlation between the output signals of the plurality of receiving means 12a, 12b, an auto-correlation detecting means 14a for detecting the auto-correlation of the output signal of the receiving means 12a, and the receiving means 12b The phase and amplitude of the output signals of the receiving means 12a and 12b based on the detection results of the autocorrelation detecting means 14b for detecting the autocorrelation of the output signal and the detection results of the autocorrelation detecting means 14a and 14b and the crosscorrelation detecting means 13 Synthesizes the signal after correcting each of them, the detection results of the autocorrelation detection means 14a and 14b, and the cross correlation detection means 1 The detection result based a predetermined time or more from the combined output of the signal combining means 101, a delay equalization means 16 for removing the delayed signal component, and a OFDM demodulation means 17.
[0068]
Here, the cross-correlation detecting means 13, the autocorrelation detecting means 14a, 14b, and the signal combining means 101 constitute a diversity combining means 18, and based on the detection result of the cross-correlation detecting means 13, the receiving means 12a, 12b. Diversity combining is performed, in which the phases of the output signals are corrected, and the amplitude is corrected based on the detection results of the autocorrelation detection means 14a and 14b, and then combined.
The autocorrelation detection means 14a and 14b correspond to the first autocorrelation detection means of the present invention.
[0069]
In the above configuration, the signals received by the antenna 11a and the antenna 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals, and then diversity as signals of # 1 system and # 2 system, respectively. It is input to the combining means 18. In the signal combining unit 101 of the diversity combining unit 18, amplitude correction is performed so that the output signals of the receiving units 12a and 12b have predetermined amplitudes based on the detection results of the cross-correlation detecting unit 13 and the autocorrelation detecting units 14a and 14b. Then, the phase is corrected so as to have the same phase, and diversity combining is performed.
[0070]
Next, in the delay equalization means 16, based on the detection result of the cross-correlation detection means 13 and the detection results of the autocorrelation detection means 14a and 14b, a predetermined time or more from the diversity combining output of the signal combining means 101, specifically, an OFDM modulation signal The signal component delayed by more than the guard interval time is removed. The output signal of the delay equalization means 16 is subjected to Fourier transform in the OFDM demodulation means 17, the guard interval inserted at the time of modulation is removed, and effective symbols are extracted and demodulated.
[0071]
Next, a specific configuration of the signal synthesis unit 101 in FIG. 10 is shown in FIG. In the figure, the signal synthesis unit 101 includes amplitude correction units 111 and 113, phase shift units 112 and 114, and an addition unit 115. In the figure, the output signals of the receiving means 12a and 12b are subjected to predetermined amplitude correction by the amplitude correcting means 111 and 113 based on the detection results of the autocorrelation detecting means 14a and 14b. The phase shift units 112 and 114 refer to the detection results (cross-correlation values) of the cross-correlation detection unit 13 so as to be in phase with each other, and the addition unit 115 adds and synthesizes them to the delay equalization unit 16. Is output. At this time, when amplitude correction is performed in the amplitude correction means 111 and 113 in proportion to the maximum value of the autocorrelation values detected by the autocorrelation detection means 14a and 14b, the carrier power of the combined output output from the addition means 115 is obtained. The noise power ratio (CN ratio) can be maximized.
[0072]
As described above, according to the OFDM receiving apparatus according to the third embodiment of the present invention, the output signals of the plurality of receiving units 12a and 12b before the diversity combining of the output signals of the plurality of receiving units 12a and 12b. Cross-correlation detection and auto-correlation detection, diversity combining is performed based on the cross-correlation detection result and the auto-correlation detection result, and based on the auto-correlation detection result and the cross-correlation detection result for the combined signal Since the unnecessary wave is removed by the delay equalization means 16, the effective symbol signal from which the delayed wave (unnecessary wave) having sufficient signal strength and having a delay time equal to or longer than the guard interval time is removed is extracted. An OFDM receiver that can be obtained is obtained.
[0073]
Next, FIG. 12 shows the configuration of an OFDM receiving apparatus according to the fourth embodiment of the present invention. The OFDM receiving apparatus according to the embodiment of the present invention differs from the OFDM receiving apparatus according to the third embodiment in configuration in that the cross-correlation detecting means 13 and the autocorrelation detecting means are used as control inputs of the delay equalizing means. The autocorrelation detection unit 81 performs autocorrelation detection on the signal after diversity combining by the signal combining unit 101 without using the detection outputs 14a and 14b, and the delay equalization unit 82 converts the detected autocorrelation value to the delayed autocorrelation unit 82. The configuration is such that unnecessary signal components are removed from the signal after diversity combining, which is used as a control input, and the other configurations are the same.
[0074]
In FIG. 12, an antenna 11a that captures an OFDM modulated signal of # 1 system, an antenna 11b that captures an OFDM modulated signal of # 2 system, receiving means 12a and 12b, and a plurality of receiving means 12a and 12b. The cross-correlation detecting means 13 for detecting the cross-correlation between the output signals of the receiver, the auto-correlation detecting means 14a for detecting the auto-correlation of the output signal of the receiving means 12a, and the auto-correlation for detecting the auto-correlation of the output signal of the receiving means 12b Detection means 14b and signal combining means for correcting the phase and amplitude of the output signals of receiving means 12a and 12b based on the detection results of autocorrelation detection means 14a and 14b and the detection result of cross-correlation detection means 13, respectively. 101, autocorrelation detection means 81 for detecting the autocorrelation of the output signal of the signal synthesis means 101, and detection results of the autocorrelation detection means 81 A predetermined time or more from the combined output of the signal combining means 101 based on a delay equalization means 82 for removing the delayed signal component, and a OFDM demodulation means 17.
[0075]
Here, the cross-correlation detecting means 13, the autocorrelation detecting means 14a, 14b, and the signal combining means 101 constitute a diversity combining means 18, and based on the detection result of the cross-correlation detecting means 13, the receiving means 12a, 12b. Diversity combining is performed, in which the phases of the output signals are corrected, and the amplitude is corrected based on the detection results of the autocorrelation detection means 14a and 14b, and then combined. The autocorrelation detection means 14a and 14b correspond to the first autocorrelation detection means of the present invention, and the autocorrelation detection means 81 corresponds to the second autocorrelation detection means of the present invention.
[0076]
In the above configuration, the signals received by the antenna 11a and the antenna 11b are amplified and frequency-converted by the receiving means 12a and 12b, respectively, and converted into baseband signals. It is input to the combining means 18. In the signal combining unit 101 of the diversity combining unit 18, the amplitude is corrected so that the output signals of the receiving units 12a and 12b have predetermined amplitudes based on the detection results of the cross correlation detecting unit 13 and the autocorrelation detecting units 14a and 14b. In addition, the phase is corrected so as to have the same phase, and diversity combining is performed.
[0077]
Next, the delay equalization means 82 performs a predetermined time or more from the synthesized output of the signal synthesis means 101 synthesized based on the detection results of the cross correlation detection means 13 and the detection results of the autocorrelation detection means 14a and 14b, specifically, OFDM. The signal component delayed by the guard interval time of the modulation signal is removed. The output signal of the delay equalization means 82 is subjected to Fourier transform in the OFDM demodulation means 17, the guard interval inserted at the time of modulation is removed, and effective symbols are extracted and demodulated.
[0078]
As described above, according to the OFDM receiver according to the fourth embodiment of the present invention, the output signals of the plurality of receiving units 12a and 12b before the diversity combining of the output signals of the plurality of receiving units 12a and 12b. Cross-correlation detection and auto-correlation detection, diversity combining is performed based on the cross-correlation detection result and auto-correlation detection result, auto-correlation detection is performed on the combined signal, and based on the auto-correlation detection result Since the unnecessary wave is removed from the signal after diversity combining by the delay equalization means 82, the delayed wave (unwanted wave) having sufficient signal strength and a delay time longer than the guard interval time is removed. An OFDM receiver capable of extracting an effective symbol signal is obtained.
[0079]
As described above, the OFDM receivers according to the first to fourth embodiments of the present invention are configured to remove unnecessary waves by the delay equalization means after performing diversity combining of a plurality of received signals.
[0080]
The operation of the OFDM receiver according to the first to fourth embodiments of the present invention has been described in detail with reference to the drawings. However, the present invention is not limited to these embodiments, and the gist of the present invention. Any design change or the like within a range that does not deviate from the above is included in the present invention. For example, the number of input antennas is not limited to two, and three or more antennas are included in the present invention.
Further, in the delay equalization means, the negative feedback means is two systems so as to remove two delay signals, but may include other numbers of systems.
[0081]
【The invention's effect】
As described above, according to the present invention, the delay equalizing means is provided on the output side of the signal synthesized by the diversity synthesizing means so as to eliminate the delayed wave, so that an output signal having a sufficient CN ratio can be obtained. The bit error after demodulation can be eliminated.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an OFDM receiving apparatus according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a specific configuration of signal synthesis means in FIG. 1;
3 is a block diagram showing a specific configuration of delay equalization means in FIG. 1. FIG.
4 is a block diagram showing a specific configuration of cross-correlation detection means in FIG. 1. FIG.
5 is a block diagram showing a specific configuration of autocorrelation detection means in FIG. 1. FIG.
FIG. 6 is an explanatory diagram showing the relationship between the data structure of an OFDM modulated signal and an autocorrelation detection signal.
FIG. 7 is an explanatory diagram showing an influence of a delayed wave on an effective symbol of a synthesized wave in an OFDM modulated signal including the delayed wave.
FIG. 8 is a block diagram showing a configuration of an OFDM receiving apparatus according to a second embodiment of the present invention.
9 is a block diagram showing a specific configuration of delay equalization means in FIG. 8. FIG.
FIG. 10 is a block diagram showing a configuration of an OFDM receiving apparatus according to a third embodiment of the present invention.
11 is a block diagram showing a specific configuration of a signal synthesis unit in FIG. 10;
FIG. 12 is a block diagram showing a configuration of an OFDM receiving apparatus according to a fourth embodiment of the present invention.
FIG. 13 is a block diagram showing a configuration of an OFDM transmitter.
FIG. 14 is an explanatory diagram conceptually showing a modulation process by OFDM.
FIG. 15 is a block diagram showing a configuration of a conventional basic OFDM receiver.
FIG. 16 is an explanatory diagram conceptually showing a demodulation process by OFDM.
[Explanation of symbols]
11a, 11b antenna
12a, 12b Receiving means (REC)
13 Cross correlation detection means
14a, 14b, 81 Autocorrelation detection means
15, 18 Diversity synthesis means
100, 101 Signal synthesis means
16, 82 Delay equalization means
17 OFDM demodulation means
21, 22, 34, 37, 112, 114 Phase shifting means
23, 31, 91, 115 addition means
32, 35, 92, 94 delay means
33, 36, 93, 95 Complex amplitude correction means
38, 96 Maximum local autocorrelation search means
39, 97 Delay time calculation means
40, 98 Complex amplitude coefficient calculating means
41 Phase coefficient calculation means
111, 113 Amplitude correction means
52, 61 multiplication means
53, 62 Accumulation means
50 Effective symbol time delay means
51, 60 Complex conjugate signal generation means

Claims

A plurality of antennas spaced apart from each other and capturing OFDM modulated signals;
A plurality of receiving means connected to the plurality of antennas, respectively, for processing the supplied signals into baseband signals;
Diversity combining means for combining the output signals of the plurality of receiving means;
Delay equalization means for removing a signal component delayed by the guard interval time of the OFDM modulation signal from the combined output of the diversity combining means;
An OFDM demodulator for removing a guard interval signal inserted at the time of modulation from the output signal of the delay equalizer and extracting and demodulating an effective symbol signal;
An OFDM receiver characterized by comprising:

A cross-correlation detecting means for detecting a cross-correlation between output signals of the plurality of receiving means on the output side of the plurality of receiving means;
A plurality of first autocorrelation detecting means for detecting autocorrelation of each output signal of the plurality of receiving means; and
The delay equalization means comprises:
2. The OFDM reception according to claim 1, wherein a signal component delayed by a guard interval time or more of the OFDM modulation signal is removed based on detection results of the cross correlation detection unit and the plurality of first autocorrelation detection units. apparatus.

The delay equalization means includes
Among autocorrelation values detected by each of the plurality of first autocorrelation detection means, a delay time from the maximum autocorrelation value of a maximum autocorrelation value other than the maximum autocorrelation value;
Complex amplitude coefficient calculated from the maximum autocorrelation value,
A phase coefficient calculated from the cross-correlation value detected by the cross-correlation detecting means;
3. The OFDM receiver according to claim 2, further comprising a plurality of feedback means for negatively feeding back the output signal of the delay equalization means based on the above.

The cross correlation detecting means includes
Complex conjugate signal generating means for generating and outputting a complex conjugate signal from one of two signals to be compared among signals supplied to the cross correlation detecting means;
Multiplying means for multiplying the complex conjugate signal by the other signal of the two signals to be compared;
Accumulating means for accumulating the multiplication results of the multiplying means for a predetermined time;
The OFDM receiving apparatus according to claim 2, wherein the OFDM receiving apparatus comprises:

A second autocorrelation detecting means for detecting an autocorrelation of the output signal of the diversity combining means is connected to the output side of the diversity combining means,
The delay equalization means comprises:
2. The OFDM receiving apparatus according to claim 1, wherein a signal component delayed by a guard interval time or more of the OFDM modulated signal is removed based on a detection result of the second autocorrelation detecting means.

The delay equalization means includes
Of the autocorrelation values detected by the second autocorrelation detection means, a delay time from the maximum autocorrelation value of the maximum autocorrelation value other than the maximum autocorrelation value;
A complex amplitude coefficient calculated from the maximum autocorrelation value;
6. The OFDM receiving apparatus according to claim 5, further comprising a plurality of feedback means for negatively feeding back the output signal of the delay equalization means based on the signal.

The first and second autocorrelation detection means are:
Effective symbol time delay means for outputting a delayed signal obtained by delaying the signal supplied to the first and second autocorrelation detection means by an effective symbol time;
Complex conjugate signal generation means for generating and outputting a complex conjugate signal from signals supplied to the first and second autocorrelation detection means;
Multiplying means for multiplying the delayed signal and the complex conjugate signal;
Accumulating means for accumulating the multiplication results of the multiplying means for a predetermined time;
The OFDM receiver according to claim 2, comprising:

The OFDM demodulating means includes:
Of the autocorrelation values detected by each of the plurality of first autocorrelation detection means, when the maximum autocorrelation value indicating the maximum value is detected, or detected by the second autocorrelation detection means The effective symbol signal is extracted by removing the guard interval signal from the output signal of the delay equalization means with reference to the time point when the maximum autocorrelation value indicating the maximum value is detected among the autocorrelation values. The OFDM receiver according to any one of 2 to 7.