JP4245268B2

JP4245268B2 - Angle demodulation apparatus, angle demodulation method, and recording medium

Info

Publication number: JP4245268B2
Application number: JP2000358845A
Authority: JP
Inventors: 紀佳桜井
Original assignee: Icom Inc
Current assignee: Icom Inc
Priority date: 2000-11-27
Filing date: 2000-11-27
Publication date: 2009-03-25
Anticipated expiration: 2020-11-27
Also published as: JP2002164741A

Description

【０００１】
【発明の属する技術分野】
この発明は、角度復調装置及び角度復調方法に関する。
【０００２】
【従来の技術】
ＦＭ（Frequency Modulation）変調信号を復調する手法として、ダイレクトコンバージョンが知られている。ダイレクトコンバージョンの手法を用いたＦＭ受信機は、例えば図３に示す構成を有する。
【０００３】
図３に示すＦＭ受信機においては、アンテナ２０１により受信されＲＦ（Radio Frequency：ラジオ周波数）増幅器２０２により増幅されたＦＭ変調信号は分波器２０３により第１のミキサ２０４Ｉ及び２０４Ｑへと供給される。ＦＭ変調信号は、第１の局部発振器２１４及び移相器２０８が作る互いに９０度位相の異なる一対の第１の局部発振信号と各々混合され、一対のベースバンド信号へと変換される。第１の局部発振信号は、受信した信号の搬送波周波数と同一の周波数に設定しておく。
【０００４】
ベースバンド信号はＬＰＦ（Low Pass Filter）２０５Ｉ及び２０５Ｑにより高調波成分をカットされ、ＡＦ（Audio Frequency：オーディオ周波数）増幅器２０６Ｉ及び２０６Ｑにより増幅された後、第２のミキサ２０７Ｉ及び２０７Ｑによって、第２の局部発振器２１５及び移相器２０９が作る互いに９０度位相の異なる一対の第２の局部発振信号と各々混合される。混合により得られた信号同士は加算器２１０により互いに加算され、これにより、単一の中間周波信号へと変換される。
【０００５】
中間周波信号は、ＢＰＦ（Band Pass Filter）２１１及びＩＦ（IntermediateFrequency：中間周波数）増幅器２１２を介してＦＭ検波器２１３に供給され、ＦＭ検波器２１３が中間周波信号を検波し、検波により得られたオーディオ信号を出力する。
【０００６】
ダイレクトコンバージョンの手法によれば、ＦＭ変調信号を復調する装置の構成を簡単にできる上、スーパーヘテロダインと異なり影像周波数近傍の信号による妨害のおそれがない、という利点が得られる。
【０００７】
【発明が解決しようとする課題】
しかし、図３に示す上述の構成のＦＭ受信機にあっては、第１のミキサにおいて妨害波の２次歪みあるいは第１の局部発振信号の２次歪みが発生した場合、これらの２次歪みに含まれる直流成分がベースバンド信号に混入する。そして、ベースバンド信号に混入した直流成分をＨＰＦ（High Pass Filter）を用いて除去した場合、ベースバンド信号に変換されたＦＭ変調信号の搬送波成分も除去されてしまうので、ＦＭ変調信号が正確に復調されない。
【０００８】
ＦＭ変調信号の復調の正確さを損なわずにこの直流成分を除去するための手法としては、例えば、特願２０００−２３２０２４に開示されている手法が考えられる。特願２０００−２３２０２４の手法は、中間周波信号を抽出して、ＰＬＬ（Phase Lock Loop）を用い、第１の局部発振信号を、抽出した中間周波信号の搬送波成分の周波数に対し一定の比率を有する値へと収束させることにより、第１の局部発振信号の周波数を、受信する対象のＦＭ変調信号の搬送波周波数から所定量オフセットさせた周波数とするものである。この手法により、第１の局部発振信号の周波数は受信する対象のＦＭ変調信号の搬送波周波数から所定量オフセットさせた周波数となり、従って、ＨＰＦを用いて、正確さを損なうことなくベースバンド信号から容易に直流成分を除去できるようになる。
【０００９】
しかし、中間周波信号はＦＭ変調された信号であって、中間周波信号の周波数は絶えず変動する。従って、特願２０００−２３２０２４の手法によった場合、第１の局部発振信号の周波数がオフセットされる量が不安定になる場合があり得た。第１の局部発振信号の周波数がオフセットされる量が不安定になると、ＦＭ受信機の復調動作が不安定になる。
【００１０】
この発明は上記実状に鑑みてなされたもので、周波数が安定した局部発振信号を生成し、ダイレクトコンバージョンの手法により安定した復調を行う角度復調装置及び角度復調方法を提供することを目的とする。
【００１１】
【課題を解決するための手段】
上記目的を達成するため、この発明の第１の観点にかかる角度復調装置は、角度変調信号を入力する角度変調信号入力部と、
前記角度変調信号の搬送波周波数と所定のオフセット周波数との和又は差に等しい周波数に収束する第１の局部発振信号を生成する第１の発振部と、
前記第１の発振部より前記第１の局部発振信号を入力し、前記第１の局部発振信号と９０度位相が異なる第１の移相信号を生成する第１の移相部と、
前記角度変調信号入力部より前記角度変調信号を入力し、前記第１の発振部より前記第１の局部発振信号を入力して、前記角度変調信号と前記第１の局部発振信号との積のうち周波数が０である成分を除いた成分から構成される第１のベースバンド信号を生成する第１の混合部と、
前記角度変調信号入力部より前記角度変調信号を入力し、前記第１の移相部より前記第１の移相信号を入力して、前記角度変調信号と前記第１の移相信号との積のうち周波数が０である成分を除いた成分から構成される第２のベースバンド信号を生成する第２の混合部と、
所定の中間周波数と前記オフセット周波数との差又は和に等しい周波数を有する第２の局部発振信号を生成する第２の発振部と、
前記第２の発振部より前記第２の局部発振信号を入力し、前記第２の局部発振信号と９０度位相が異なる第２の移相信号を生成する第２の移相部と、
前記第１の混合部より前記第１のベースバンド信号を入力し、前記第２の発振部より前記第２の局部発振信号を入力して、前記第１のベースバンド信号と前記第２の局部発振信号との積を表す第１の中間信号を生成する第３の混合部と、
前記第２の混合部より前記第２のベースバンド信号を入力し、前記第２の移相部より前記第２の移相信号を入力して、前記第２のベースバンド信号と前記第２の移相信号との積を表す第２の中間信号を生成する第４の混合部と、
前記第３の混合部より前記第１の中間信号を入力し、前記第４の混合部より前記第２の中間信号を入力し、前記第１の中間信号と前記第２の中間信号との和又は差を表す第１の中間周波信号を生成する中間周波信号生成部と、
前記中間周波信号生成部より前記第１の中間周波信号を入力して復調することにより角度復調信号を生成する復調部と、
前記第１の混合部より前記第１のベースバンド信号又は前記第２の混合部より前記第２のベースバンド信号を入力し、入力した前記第１のベースバンド信号又は前記第２のベースバンド信号に含まれる前記オフセット周波数の成分に基づいて前記中間周波数の成分を含む第２の中間周波信号を生成し、当該第２の中間周波信号に含まれる中間周波数の成分に基づいて前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させる発振制御部と、
を有することを特徴とする。
【００１２】
このような角度復調装置は、ダイレクトコンバージョンの手法により角度変調信号の復調を行う。そして、第１の局部発振信号は、第１ベースバンド信号又は第２ベースバンド信号から抽出される、オフセット周波数の成分に基づいて生成される。このため、第１の局部発振信号の周波数は安定し、従って、このような角度復調装置による復調の動作は安定する。
【００１３】
前記発振制御部は、より具体的には、例えば、前記第１の混合部より前記第１のベースバンド信号又は前記第２の混合部より前記第２のベースバンド信号を入力し、前記第２の発振部より前記第２の局部発振信号を入力して、入力した前記第１のベースバンド信号又は前記第２のベースバンド信号と入力した前記第２の局部発振信号との積を表す信号を生成する第５の混合部と、
前記第５の混合部が生成した信号のうちから、前記第２の中間周波信号を抽出する抽出部と、
前記抽出部によって抽出された前記第２の中間周波信号に含まれる中間周波数の成分に基づいて、前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させる収束制御部と、を備える。
【００１４】
前記収束制御部は、例えば、前記抽出部によって抽出された前記第２の中間周波信号を所定の第１の分周比で分周して得られる信号と前記第１の局部発振信号を所定の第２の分周比で分周して得られる信号との位相差に基づき、前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させるものとすれば、周波数が高い精度で安定した第１の局部発振信号を容易に生成することができる。
【００１５】
あるいは、前記発振制御部は、例えば、前記第１の混合部より前記第１のベースバンド信号又は前記第２の混合部より前記第２のベースバンド信号を入力し、入力した前記第１のベースバンド信号又は前記第２のベースバンド信号のうちから、前記オフセット周波数を有する成分を抽出する抽出部と、
前記第２の発振部より前記第２の局部発振信号を入力して、前記抽出部によって抽出された成分の信号と入力した前記第２の局部発振信号との積を表す信号を生成し、生成した当該信号のうち、前記第２の中間周波信号を抽出する第５の混合部と、
前記第５の混合部によって抽出された前記第２の中間周波信号に含まれる中間周波数の成分に基づいて、前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させる収束制御部と、を備えることにより第１の局部発振信号を生成してもよい。
【００１６】
この場合、前記収束制御部は、例えば、前記第５の混合部によって抽出された前記第２の中間周波信号を所定の第１の分周比で分周して得られる信号と前記第１の局部発振信号を所定の第２の分周比で分周して得られる信号との位相差に基づき、前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させるものとすれば、周波数が高い精度で安定した第１の局部発振信号を容易に生成することができる。
【００１７】
前記オフセット周波数の大きさは、３００ヘルツ以内であることが望ましい。音声信号を再生する場合、その音声信号のうち３００ヘルツ程度以下の成分は除去されても、再生される音声の正確さは損なわれない。従って、ＨＰＦやコンデンサを用いてベースバンド信号からオフセット周波数未満の成分を除去することにより、復調の正確さを損なうことなく混合部の２次歪みの直流成分が容易に除去されるようになる。
【００１８】
また、この発明の第２の観点にかかる角度復調方法は、角度変調信号を入力し、
前記角度変調信号の搬送波周波数と所定のオフセット周波数との和又は差に等しい周波数に収束する第１の局部発振信号を生成し、
前記第１の局部発振信号と９０度位相が異なる第１の移相信号を生成し、
前記角度変調信号と前記第１の局部発振信号との積のうち周波数が０である成分を除いた成分から構成される第１のベースバンド信号を生成し、
前記角度変調信号と前記第１の移相信号との積のうち周波数が０である成分を除いた成分から構成される第２のベースバンド信号を生成し、
所定の中間周波数と前記オフセット周波数との差又は和に等しい周波数を有する第２の局部発振信号を生成し、
前記第２の局部発振信号と９０度位相が異なる第２の移相信号を生成し、
前記第１のベースバンド信号と前記第２の局部発振信号との積を表す第１の中間信号を生成し、
前記第２のベースバンド信号と前記第２の移相信号との積を表す第２の中間信号を生成し、
前記第１の中間信号と前記第２の中間信号との和又は差を表す第１の中間周波信号を生成し、
前記第１の中間周波信号を復調することにより角度復調信号を生成し、
前記第１のベースバンド信号又は前記第２のベースバンド信号に含まれる前記オフセット周波数の成分に基づいて前記中間周波数の成分を含む第２の中間周波信号を生成し、当該第２の中間周波信号に含まれる中間周波数の成分に基づいて、前記第１の局部発振信号の周波数を、前記中間周波数に所定の比率を乗じた周波数に収束させることにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させる、
ことを特徴とする。
【００１９】
このような角度復調方法によれば、ダイレクトコンバージョンの手法により角度変調信号の復調が行われる。そして、第１の局部発振信号は、第１ベースバンド信号又は第２ベースバンド信号から抽出される、オフセット周波数の成分に基づいて生成される。このため、第１の局部発振信号の周波数は安定し、従って、このような角度復調方法による復調の動作は安定する。
【００２０】
また、この発明の第３の観点にかかるコンピュータ読み取り可能な記録媒体は、コンピュータを、角度変調信号を入力する角度変調信号入力部と、
前記角度変調信号の搬送波周波数と所定のオフセット周波数との和又は差に等しい周波数に収束する第１の局部発振信号を生成する第１の発振部と、
前記第１の発振部より前記第１の局部発振信号を入力し、前記第１の局部発振信号と９０度位相が異なる第１の移相信号を生成する第１の移相部と、
前記角度変調信号入力部より前記角度変調信号を入力し、前記第１の発振部より前記第１の局部発振信号を入力して、前記角度変調信号と前記第１の局部発振信号との積のうち周波数が０である成分を除いた成分から構成される第１のベースバンド信号を生成する第１の混合部と、
前記角度変調信号入力部より前記角度変調信号を入力し、前記第１の移相部より前記第１の移相信号を入力して、前記角度変調信号と前記第１の移相信号との積のうち周波数が０である成分を除いた成分から構成される第２のベースバンド信号を生成する第２の混合部と、
所定の中間周波数と前記オフセット周波数との差又は和に等しい周波数を有する第２の局部発振信号を生成する第２の発振部と、
前記第２の発振部より前記第２の局部発振信号を入力し、前記第２の局部発振信号と９０度位相が異なる第２の移相信号を生成する第２の移相部と、
前記第１の混合部より前記第１のベースバンド信号を入力し、前記第２の発振部より前記第２の局部発振信号を入力して、前記第１のベースバンド信号と前記第２の局部発振信号との積を表す第１の中間信号を生成する第３の混合部と、
前記第２の混合部より前記第２のベースバンド信号を入力し、前記第２の移相部より前記第２の移相信号を入力して、前記第２のベースバンド信号と前記第２の移相信号との積を表す第２の中間信号を生成する第４の混合部と、
前記第３の混合部より前記第１の中間信号を入力し、前記第４の混合部より前記第２の中間信号を入力し、前記第１の中間信号と前記第２の中間信号との和又は差を表す第１の中間周波信号を生成する中間周波信号生成部と、
前記中間周波信号生成部より前記第１の中間周波信号を入力して復調することにより角度復調信号を生成する復調部と、
前記第１の混合部より前記第１のベースバンド信号又は前記第２の混合部より前記第２のベースバンド信号を入力し、入力した前記第１のベースバンド信号又は前記第２のベースバンド信号に含まれる前記オフセット周波数の成分に基づいて前記中間周波数の成分を含む第２の中間周波信号を生成し、当該第２の中間周波信号に含まれる中間周波数の成分に基づいて前記第１の局部発振信号の周波数が前記中間周波数に所定の比率を乗じた周波数に収束するように前記第１の発振部を制御することにより、前記第１の局部発振信号の周波数を前記角度変調信号の搬送波周波数と前記オフセット周波数との和又は差に等しい周波数に収束させる発振制御部と、
して機能させるためのプログラムを記録したことを特徴とする。
【００２１】
このような記録媒体に記録されたプログラムを実行するコンピュータは、ダイレクトコンバージョンの手法により角度変調信号の復調を行う。そして、第１の局部発振信号は、第１ベースバンド信号又は第２ベースバンド信号から抽出される、オフセット周波数の成分に基づいて生成される。このため、第１の局部発振信号の周波数は安定し、従って、このようなコンピュータによる復調の動作は安定する。
【００２２】
【発明の実施の形態】
以下、この発明の実施の形態にかかる角度復調装置及び角度復調方法を、ＦＭ（Frequency Modulation）受信機を例として説明する。
【００２３】
図１は、この発明の実施の形態にかかるＦＭ受信機の構成の一例を示す。
図示するように、このＦＭ受信機は、アンテナ１と、ＲＦ（Radio Frequency：ラジオ周波数）増幅器２と、分波器３と、ミキサ４Ｉ、４Ｑ、８Ｉ及び８Ｑと、ＬＰＦ（Low Pass Filter）５Ｉ及び５Ｑと、ＡＦ（Audio Frequency：オーディオ周波数）増幅器６Ｉ及び６Ｑと、直流除去部７Ｉ及び７Ｑと、移相器９及び１０と、局部発振器１１と、加算器１２と、ＢＰＦ（Band Pass Filter）１３と、ＩＦ（Intermediate Frequency：中間周波数）増幅器１４と、ＦＭ検波器１５とより構成されている。
【００２４】
ＲＦ増幅器２は、電磁波によりアンテナ１に励起された信号（ＲＦ信号）をアンテナ１から供給されると、アンテナ１から供給された信号を増幅して分波器３に供給する。分波器３は、ＲＦ増幅器２から供給されたＲＦ信号を、ミキサ４Ｉ及び４Ｑに供給する。
【００２５】
ミキサ４Ｉ及び４Ｑは、互いに実質的に同一の構成を有している。ミキサ４Ｉは、分波器３から供給されるＲＦ信号と局部発振器１１から供給される後述の第１の局部発振信号との積を表す信号（Ｉチャンネルベースバンド信号）を生成して、ＬＰＦ５Ｉに供給する。ミキサ４Ｑは、分波器３から供給されるＲＦ信号と移相器９から供給される後述の第１の移相信号との積を表す信号（Ｑチャンネルベースバンド信号）を生成して、ＬＰＦ５Ｑに供給する。
【００２６】
ＬＰＦ５Ｉ及び５Ｑは、互いに実質的に同一の構成を有している。ＬＰＦ５Ｉ及び５Ｑは、ミキサ４Ｉ又は４Ｑから供給されたＩチャンネルベースバンド信号又はＱチャンネルベースバンド信号をフィルタリングする。具体的には、ＬＰＦ５Ｉは、Ｉチャンネルベースバンド信号のうち、再生されるべき後述のＡＦ信号の帯域の上限を超える周波数成分を除去し、残りの周波数成分をＡＦ増幅器６Ｉに供給する。ＬＰＦ５Ｑは、Ｑチャンネルベースバンド信号のうち、再生されるべきＡＦ信号の帯域の上限を超える周波数成分を除去し、残りの周波数成分をＡＦ増幅器６Ｑに供給する。
【００２７】
ＡＦ増幅器６Ｉ及び６Ｑは互いに実質的に同一の構成を有している。ＡＦ増幅器６Ｉは、ＬＰＦ５Ｉから供給された信号を増幅して直流除去部７Ｉに供給し、ＡＦ増幅器６Ｑは、ＬＰＦ５Ｑから供給された信号を増幅して直流除去部７Ｑに供給する。
【００２８】
直流除去部７Ｉ及び７Ｑは互いに実質的に同一の構成を有しており、例えば、いずれもコンデンサあるいはＨＰＦ（High Pass Filter）より構成されている。直流除去部７Ｉは、ＡＦ増幅器６Ｉから供給された信号のうち直流成分を除去し、その他の成分をミキサ８Ｉに供給する。直流除去部７Ｑは、ＡＦ増幅器６Ｑから供給された信号のうち直流成分を除去し、その他の成分をミキサ８Ｑ及び局部発振器１１に供給する。
【００２９】
ミキサ８Ｉ及び８Ｑは、互いに実質的に同一の構成を有している。ミキサ８Ｉは、直流除去部７Ｉから供給される信号と局部発振器１１から供給される後述の第２の局部発振信号との積を表す信号のうち、周波数がこれら２つの信号の周波数の和（又は差）に実質的に等しい成分を表す信号を生成して、加算器１２に供給する。ミキサ８Ｑは、直流除去部７Ｑから供給される信号と移相器１０から供給される後述の第２の移相信号との積を表す信号のうち、周波数がこれら２つの信号の周波数の和（又は差）に実質的に等しい成分を表す信号を生成して、加算器１２に供給する。
【００３０】
移相器９は、局部発振器１１より第１の局部発振信号を供給されると、第１の局部発振信号の位相を実質的に９０度遅らせた信号である第１の移相信号を生成し、ミキサ４Ｑに供給する。
移相器１０は、局部発振器１１より第２の局部発振信号を供給されると、第２の局部発振信号の位相を実質的に９０度遅らせた信号である第２の移相信号を生成し、ミキサ８Ｑに供給する。
【００３１】
加算器１２は、ミキサ８Ｉ及び８Ｑから供給される信号の和を表す信号を生成して、ＢＰＦ１３に供給する。
ＢＰＦ１３は、加算器１２から供給された信号をフィルタリングする。具体的には、ＢＰＦ１３は、加算器１２から供給された信号のうち、所定の中間周波数近傍の帯域の成分をＩＦ増幅器１４に供給し、その他の成分を実質的に遮断する。
ＩＦ増幅器１４は、ＢＰＦ１３から供給された成分（ＩＦ信号）を増幅して、ＦＭ検波器１５に供給する。
【００３２】
ＦＭ検波器１５は、比検波器、クワドラチャ復調回路その他任意のＦＭ検波回路や、ＡＦ増幅器及びスピーカなどから構成されており、ＩＦ増幅器１４から供給された信号の周波数変移を振幅へと変換することによりＩＦ信号のＦＭ復調を行い、復調により得られたＡＦ信号を、このＦＭ受信機の出力信号として出力し、再生する。
【００３３】
局部発振器１１は、図２に示すように、ＬＰＦ１０１及び１０９と、発振器１０２と、ミキサ１０３と、ＢＰＦ１０４と、増幅器１０５と、振幅制限器１０６と、分周器１０７及び１１１と、位相比較器１０８と、ＶＣＯ（Voltage Controlled Oscillator）１１０とより構成されている。
【００３４】
ＬＰＦ１０１は、直流除去部７Ｑより供給される信号のうち、周波数が所定のオフセット周波数以下である部分をミキサ１０３に供給し、周波数がオフセット周波数を超える成分を実質的に除去する。
発振器１０２は、交流信号を生成してミキサ１０３に供給し、また、この交流信号を、上述の第２の局部発振信号として、移相器１０及びミキサ８Ｉに供給する。第２の局部発振信号の周波数は、ＢＰＦ１３の通過帯域内の所定の中間周波数と上述のオフセット周波数との差（又は和）に実質的に等しい。
ミキサ１０３は、ＬＰＦ１０１から供給される信号と発振器１０２から供給される第２の局部発振信号との積を表す信号を生成して、ＢＰＦ１０４に供給する。
【００３５】
ＢＰＦ１０４は、ミキサ１０３より供給された信号のうち、ＬＰＦ１０１から供給される信号の周波数と第２の局部発振信号の周波数との和（又は差）にあたる周波数を有する成分を増幅器１０５に供給し、他の成分を実質的に除去する。
増幅器１０５は、ＢＰＦ１０４より供給された成分を増幅して振幅制限器１０６に供給する。
振幅制限器１０６は、増幅器１０５より供給された成分の振幅を所定値以下に制限して得られる信号を、分周器１０７に供給する。
【００３６】
ＶＣＯ１１０は交流信号を生成し、この交流信号の周波数を、自己に供給された制御信号が指定する変化分だけ変化させる。なお、ＶＣＯ１１０は、制御信号が未だ自己に供給されていない状態では、例えば、自己に固有のフリーランニング周波数の交流信号を生成するものとする。
そして、ＶＣＯ１１０は、自己が生成した交流信号を分周器１１１へと供給し、また、この交流信号を第１の局部発振信号としてミキサ４Ｉ及び移相器９へと供給する。
【００３７】
分周器１０７及び１１１は、いずれも、例えばフリップフロップ回路、カウンタ回路等より構成されている。
【００３８】
分周器１０７は、振幅制限器１０６より供給された信号を分周比Ｍ（ただし、Ｍは自然数）で分周する（すなわち、分周器１０７は、振幅制限器１０６より供給された信号に同期し、この信号の周波数のＭ分の１に実質的に等しい周波数を有する信号を生成する）。そして、分周器１０７は、自己が分周を行って得られた信号を位相比較器１０８に供給する。
【００３９】
分周器１１１は、ＶＣＯ１１０より供給された交流信号を分周比Ｎ（ただし、Ｎは自然数）で分周し、自己が分周を行って得られた信号を位相比較器１０８に供給する。
【００４０】
位相比較器１０８は、乗算回路等より構成されており、分周器１０７から供給される信号と分周器１１１から供給される信号との位相差を表す制御信号を生成し、生成した制御信号をＬＰＦ１０９へと供給する。
ＬＰＦ１０９は、位相比較器１０８より供給される制御信号に含まれる高調波成分を除去し、高調波成分が実質的に除去された制御信号をＶＣＯ１１０に供給する。
【００４１】
位相比較器１０８が出力する制御信号は、分周器１０７から供給される信号と分周器１１１から供給される信号との位相差が実質的に０であるとき、第１の局部発振信号の周波数の変化分を実質的に０と指定するものとなる（すなわち、ＶＣＯ１１０が現に生成している交流信号の周波数をそのまま保つよう指定するものとなる）。
【００４２】
一方、分周器１０７から供給される信号の位相が、分周器１１１から供給される信号の位相より進んでいるときに位相比較器１０８が出力する制御信号が示す変化分は正の値となる。すなわち、第１の局部発振信号の周波数を上昇させるよう指定するものとなる。また、分周器１０７から供給される信号の位相が、分周器１１１から供給される信号の位相より遅れているときに位相比較器１０８が出力する制御信号が示す変化分は負の値となる。すなわち、第１の局部発振信号の周波数を下降させるよう指定するものとなる。ただし、変化分の値が正負いずれである場合も、制御信号が指定する変化分の絶対値は、分周器１０７から供給される信号と分周器１１１から供給される信号との位相差が大きいほど、大きな値になるようにする。
すなわち、位相比較器１０８、ＬＰＦ１０９、ＶＣＯ１１０及び分周器１１１は、第１の局部発振信号の周波数を制御するPhase Lock Loop（ＰＬＬ）として機能する。
【００４３】
なお、上述の分周比Ｍ及びＮの値は、第１の局部発振信号の周波数が、後述する動作により、このＦＭ受信機が受信する対象のＦＭ変調信号の搬送波周波数と上述のオフセット周波数との和（又は差）に収束するような値に設定されている。
【００４４】
そして更に、上述のオフセット周波数の大きさは３００ヘルツ以内であることが望ましい。再生されるべきＡＦ信号が音声を表す場合、その音声のうち３００ヘルツ程度以下の成分は、再生されなくても再生される音声の正確さは損なわれない。従ってこの場合、Ｉチャンネルベースバンド信号やＱチャンネルベースバンド信号から直流成分を除去する直流除去部７Ｉや７Ｑは、正確に直流成分のみを除去しなくても、実質的にオフセット周波数未満の成分のみを除去するものであれば、復調の正確さを損なうことなく、またＩチャンネルベースバンド信号やＱチャンネルベースバンド信号の搬送波成分を誤って除去することもなく、ミキサ４Ｉや４Ｑが発生する２次歪みの直流成分を除去できる。
【００４５】
換言すれば、分周比Ｍ及びＮの値は、このＦＭ受信機が受信する対象のＦＭ変調信号の搬送波周波数をｆ_０、第１の局部発振信号の周波数が収束する値をｆ_１、第２の局部発振信号の値をｆ_２、中間周波数をｆ_ＩＦ、オフセット周波数をΔｆとする場合、数式１〜数式３に示す関係を実質的に満たすような値とする。そして更に、数式４に示す関係を満たすことが望ましい。
【００４６】
【数１】
ｆ_１＝ｆ_０±Δｆ
【数２】
（ｆ_１／Ｎ）＝｛（ｆ_２±Δｆ）／Ｍ｝
【数３】
（ｆ_２±Δｆ）＝ｆ_ＩＦ
【数４】
Δｆ≦３００［Ｈｚ］
【００４７】
（動作）
次に、このＦＭ受信機の動作を説明する。
このＦＭ受信機が受信する対象のＦＭ変調信号がアンテナ１にＲＦ信号を誘起すると、ＲＦ増幅器２がこのＲＦ信号を増幅して分波器３に供給し、分波器３は、ＲＦ増幅器２から供給されたＲＦ信号を、ミキサ４Ｉ及び４Ｑに供給する。
一方、ミキサ４Ｉには局部発振器１１のＶＣＯ１１０が生成する第１の局部発振信号が供給され、ミキサ４Ｑには第１の局部発振信号の位相が実質的に９０度遅れたものに相当する信号である第１の移相信号が移相器９より供給される。
【００４８】
ミキサ４Ｉは、Ｉチャンネルベースバンド信号を生成する。ミキサ４Ｉが生成したＩチャンネルベースバンド信号はＬＰＦ５Ｉによりフィルタリングされ、ＡＦ増幅器６Ｉにより増幅され、更に直流除去部７Ｉにより直流成分の除去を受けた後、ミキサ８Ｉに供給される。
ミキサ４Ｑは、Ｑチャンネルベースバンド信号を生成する。ミキサ４Ｑが生成したＱチャンネルベースバンド信号はＬＰＦ５Ｑによりフィルタリングされ、ＡＦ増幅器６Ｑにより増幅され、更に直流除去部７Ｑにより直流成分の除去を受けた後、ミキサ８Ｑに供給される。
【００４９】
第１の局部発振信号の周波数と、このＦＭ受信機が受信する対象のＦＭ変調信号の搬送波周波数との差がオフセット周波数に実質的に等しければ、局部発振器１１のＢＰＦ１０４からは、中間周波数ｆ _ＩＦに等しい周波数の信号が出力される。この信号は増幅器１０５により増幅され、振幅制限器１０６により一定の振幅を有するよう整形された上、分周器１０７によりＭ分の１に分周され、出力される。
【００５０】
そして、分周器１０７から信号が出力される場合、局部発振器１１の分周器１１１が出力する信号の周波数（つまり、第１の局部発振信号の周波数のＮ分の１）は、分周器１０７が出力する信号の周波数（つまり、第２の局部発振信号の周波数とオフセット周波数との和又は差のＭ分の１）より高いときは下降し、低いときは上昇する。
従って、第１の局部発振信号の周波数は、第２の局部発振信号の周波数とオフセット周波数との和又は差のＭ分のＮの値に収束する。また、Ｉチャンネルベースバンド信号及びＱチャンネルベースバンド信号の搬送波成分の周波数は、オフセット周波数に実質的に等しい値へと収束する。
【００５１】
一方、ミキサ８Ｉには局部発振器１１の発振器１０２が出力する第２の局部発振信号が供給され、ミキサ８Ｑには第２の局部発振信号の位相が実質的に９０度遅れたものに相当する信号である第２の移相信号が移相器１０より供給される。
【００５２】
ミキサ８Ｉは、直流除去部７Ｉが供給する信号と第２の局部発振信号との積を表す信号のうち、周波数がこれら２つの信号の周波数の和（又は差）に実質的に等しい成分を表す信号を生成し、加算器１２に供給する。
ミキサ８Ｑは、直流除去部７Ｑが供給する信号と第２の移相信号との積を表す信号のうち、周波数がこれら２つの信号の周波数の和（又は差）に実質的に等しい成分を表す信号を生成し、加算器１２に供給する。
【００５３】
加算器１２は、ミキサ８Ｉ及び８Ｑから供給される信号の和を表す信号を生成する。この信号はＢＰＦ１３によりフィルタリングされてＩＦ信号となり、ＩＦ信号はＩＦ増幅器１４により増幅される。ＩＦ信号の搬送波成分の周波数は、第２の局部発振信号の周波数とオフセット周波数との和（又は差）に実質的に等しい値となる。
【００５４】
ＩＦ増幅器１４により増幅されたＩＦ信号はＦＭ検波器１５によりＦＭ復調され、復調により得られたＡＦ信号が、このＦＭ受信機の出力信号として出力され、再生される。
【００５５】
以上説明した動作の結果、このＦＭ受信機に受信されたＦＭ変調信号が復調され、ＡＦ信号が表す音声が再生される。
このＦＭ受信機はダイレクトコンバージョンの手法によりＦＭ変調信号の復調を行う。そして、第１の局部発振信号は、Ｑチャネルベースバンド信号から抽出されるオフセット周波数の搬送波成分に基づいて生成される。このため、第１の局部発振信号の周波数は安定し、従って、このＦＭ受信機によるＦＭ復調の動作も安定する。
【００５６】
なお、このＦＭ受信機の構成は、上述のものに限られない。
例えば、分波器３は、Ａ／Ｄ（Analog-to-Digital）変換器と、ＤＳＰ（Digital Signal Processor）やＣＰＵ（Central Processing Unit）とから構成されていてもよい。また、ＦＭ検波器１５は、ＤＳＰやＣＰＵとＤ／Ａ（Digital-to-Analog）変換器とより構成されていてもよい。そして、このＦＭ受信機の他の構成要素の機能の一部又は全部が、ＤＳＰやＣＰＵにより行われていてもよい。
【００５７】
また、局部発振器１１は、直流除去部７ＱよりＱチャンネルベースバンド信号を供給される代わりに、直流除去部７ＩよりＩチャンネルベースバンド信号を供給されるようにしてもよい。
また、局部発振器１１に供給されるＱチャンネルベースバンド信号又はＩチャンネルベースバンド信号は、必ずしも直流成分を除去されたものである必要はない。従って、局部発振器１１は、直流除去部７Ｑに代えて、ＬＰＦ５Ｑ又はＡＦ増幅器６ＱからＱチャンネルベースバンド信号の供給を受けるようにしてもよいし、直流除去部７Ｉに代えて、ＬＰＦ５Ｉ又はＡＦ増幅器６ＩからＩチャンネルベースバンド信号の供給を受けるようにしてもよい。
【００５８】
また、このＦＭ受信機は、ＦＭ変調信号をアンテナ１から取得する必要はなく、例えば、ＦＭ変調信号を有線回線より取得してもよい。また、ＲＦ増幅器２は省略可能である。また、このＦＭ受信機は、ＰＭ（Phase Modulation）変調信号を復調してもよい。この場合、ＦＭ検波器１５は、例えば、ＩＦ信号をＦＭ復調して得られたＡＦ信号を積分するための積分回路等を備えるものとすればよい。
【００５９】
また、分周比Ｍ及びＮの値は、上述した関係を満たす限り任意である。従って、分周器１０７及び１１１のうち少なくとも一方が、操作者の操作に応答して自己の分周比を変えるような構成を備えていてもよい。そして、例えば、分周器１１１の分周比を可変とすれば、このＦＭ受信機は、受信する対象のＦＭ変調信号の搬送波周波数を可変とすることができる。
【００６０】
以上、この発明にかかる角度復調装置及び角度復調方法を説明したが、この発明の角度復調装置は、専用のシステムによらず、通常のコンピュータシステムを用いて実現可能である。例えば、Ａ／Ｄ変換器、Ｄ／Ａ変換器を備えるパーソナルコンピュータに、上述の動作を実行するためのプログラムを格納した媒体（フロッピー（登録商標）ディスク、ＣＤ−ＲＯＭ等）から該プログラムをインストールすることにより、上記処理を実行するＦＭ受信機を構成することができる。
【００６１】
また、例えば、通信ネットワークの掲示板（ＢＢＳ）に該プログラムを掲示し、これをネットワークを介して配信してもよい。ネットワークを介した配信は、該プログラムにより搬送波を変調して得られる変調信号を伝送することにより行ってもよい。
そして、このプログラムを起動し、ＯＳの制御下に、他のアプリケーションプログラムと同様に実行することにより、上述の処理を実行することができる。
【００６２】
なお、ＯＳが処理の一部を分担する場合、あるいは、ＯＳが本願発明の１つの構成要素の一部を構成するような場合には、記録媒体には、その部分を除いたプログラムを格納してもよい。この場合も、この発明では、その記録媒体には、コンピュータが実行する各機能又はステップを実行するためのプログラムが格納されているものとする。
【００６３】
【発明の効果】
以上説明したように、この発明によれば、周波数が安定した局部発振信号を生成し、ダイレクトコンバージョンの手法により安定した復調を行う角度復調装置及び角度復調方法が実現される。
【図面の簡単な説明】
【図１】この発明の実施の形態にかかるＦＭ受信機の基本構成を示すブロック図である。
【図２】図１のＦＭ受信機の局部発振器の基本構成を示すブロック図である。
【図３】従来のＦＭ受信機の構成を示すブロック図である。
【符号の説明】
１アンテナ
２ＲＦ増幅器
３分波器
４Ｉ、４Ｑ、８Ｉ、８Ｑ、１０３ミキサ
５Ｉ、５Ｑ、１０１、１０９ＬＰＦ
６Ｉ、６ＱＡＦ増幅器
７Ｉ、７Ｑ直流除去部
９、１０移相器
１１局部発振器
１２加算器
１３、１０４ＢＰＦ
１４ＩＦ増幅器
１５ＦＭ検波器
１０２発振器
１０５増幅器
１０６振幅制限器
１０７、１１１分周器
１０８位相比較器
１１０ＶＣＯ[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an angle demodulation device and an angle demodulation method.
[0002]
[Prior art]
  Direct conversion is known as a technique for demodulating an FM (Frequency Modulation) modulation signal. An FM receiver using the direct conversion method has a configuration shown in FIG. 3, for example.
[0003]
  In the FM receiver shown in FIG. 3, the FM modulated signal received by the antenna 201 and amplified by the RF (Radio Frequency) amplifier 202 is supplied to the first mixers 204I and 204Q by the duplexer 203. . The FM modulated signal is mixed with a pair of first local oscillation signals having a phase difference of 90 degrees generated by the first local oscillator 214 and the phase shifter 208, and converted into a pair of baseband signals. The first local oscillation signal is set to the same frequency as the carrier frequency of the received signal.
[0004]
  The baseband signal has its harmonic components cut by LPF (Low Pass Filter) 205I and 205Q, amplified by AF (Audio Frequency) amplifiers 206I and 206Q, and then secondly mixed by second mixers 207I and 207Q. The local oscillator 215 and the phase shifter 209 are mixed with a pair of second local oscillation signals that are 90 degrees out of phase with each other. Signals obtained by mixing are added to each other by an adder 210, and thereby converted into a single intermediate frequency signal.
[0005]
  The intermediate frequency signal is supplied to the FM detector 213 via a BPF (Band Pass Filter) 211 and an IF (Intermediate Frequency) amplifier 212, and the FM detector 213 detects the intermediate frequency signal and is obtained by detection. Output audio signals.
[0006]
  According to the direct conversion method, the configuration of an apparatus for demodulating an FM modulated signal can be simplified, and unlike superheterodyne, there is an advantage that there is no possibility of interference by a signal near the image frequency.
[0007]
[Problems to be solved by the invention]
  However, in the FM receiver having the above-described configuration shown in FIG. 3, when the second-order distortion of the interference wave or the second-order distortion of the first local oscillation signal occurs in the first mixer, these second-order distortions are generated. DC components included in the baseband signal. When the DC component mixed in the baseband signal is removed using an HPF (High Pass Filter), the carrier wave component of the FM modulated signal converted into the baseband signal is also removed, so that the FM modulated signal is accurately Not demodulated.
[0008]
  As a technique for removing this DC component without impairing the accuracy of demodulation of the FM modulation signal, for example, a technique disclosed in Japanese Patent Application No. 2000-23320 can be considered. The method of Japanese Patent Application No. 2000-23024 extracts an intermediate frequency signal, uses a PLL (Phase Lock Loop), and sets the first local oscillation signal at a constant ratio to the frequency of the carrier component of the extracted intermediate frequency signal. By converging it to the value it has, the frequency of the first local oscillation signal is made a frequency offset by a predetermined amount from the carrier frequency of the FM modulation signal to be received. With this technique, the frequency of the first local oscillation signal is a frequency offset by a predetermined amount from the carrier frequency of the FM modulation signal to be received. Therefore, the HPF can be easily used from the baseband signal without losing accuracy. DC component can be removed.
[0009]
  However, the intermediate frequency signal is an FM modulated signal, and the frequency of the intermediate frequency signal constantly fluctuates. Therefore, according to the method of Japanese Patent Application No. 2000-233202, the amount by which the frequency of the first local oscillation signal is offset may be unstable. When the amount by which the frequency of the first local oscillation signal is offset becomes unstable, the demodulation operation of the FM receiver becomes unstable.
[0010]
  The present invention has been made in view of the above circumstances, and an object thereof is to provide an angle demodulating apparatus and an angle demodulating method that generate a local oscillation signal having a stable frequency and perform stable demodulation by a direct conversion technique.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, an angle demodulator according to a first aspect of the present invention provides:An angle modulation signal input unit for inputting the angle modulation signal;
  Converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulated signal and a predetermined offset frequencyFirst local oscillation signalIssueGenerate firstofAn oscillation unit;
  A first phase shift unit that receives the first local oscillation signal from the first oscillation unit and generates a first phase shift signal that is 90 degrees out of phase with the first local oscillation signal;
  Input the angle modulation signal from the angle modulation signal input unit,FirstofThe first local oscillation signal from the oscillation unitIssueA first input comprising a component excluding a component having a frequency of 0 from the product of the angle modulation signal and the first local oscillation signal.ofGenerate baseband signalA first mixing section
  The angle modulation signal is input from the angle modulation signal input unit, the first phase shift signal is input from the first phase shift unit, and the product of the angle modulation signal and the first phase shift signal is input. A second mixing unit that generates a second baseband signal composed of components excluding components having a frequency of 0,
  A given intermediate frequency andAboveA second local oscillator signal having a frequency equal to the difference or sum of the offset frequencyIssueSecond to generateofAn oscillation unit;
  A second phase shift unit that inputs the second local oscillation signal from the second oscillation unit and generates a second phase shift signal that is 90 degrees out of phase with the second local oscillation signal;
  The firstofThe first from the mixing sectionBaseband signalEnter the secondofThe second local oscillation signal from the oscillation unitIssueEnter the firstofThe product of the baseband signal and the second local oscillation signalA third mixing unit for generating a first intermediate signal representing,
  The second baseband signal is input from the second mixing unit, the second phase shift signal is input from the second phase shift unit, and the second baseband signal and the second baseband signal are input. A fourth mixing unit for generating a second intermediate signal representing a product with the phase shift signal;,
  The first intermediate signal is input from the third mixing unit, the second intermediate signal is input from the fourth mixing unit, and the sum of the first intermediate signal and the second intermediate signal is input. Or an intermediate frequency signal generator for generating a first intermediate frequency signal representing the difference;
  SaidIntermediate frequency signal generatorMore thanFirstDemodulator that generates an angle demodulated signal by demodulating an intermediate frequency signalWhen,
  The first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit is input, and the input first baseband signal or second baseband signal is input. A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first intermediate frequency signal, and the first local portion is generated based on the intermediate frequency component included in the second intermediate frequency signal. By controlling the first oscillation unit so that the frequency of the oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the carrier frequency of the angle modulation signal. And an oscillation control unit that converges to a frequency equal to the sum or difference of the offset frequency,
  HavingIt is characterized by.
[0012]
  Such an angle demodulator demodulates an angle modulation signal by a direct conversion method. The first local oscillation signal is generated based on the offset frequency component extracted from the first baseband signal or the second baseband signal. For this reason, the frequency of the first local oscillation signal is stable, and thus the demodulation operation by such an angle demodulator is stable.
[0013]
  More specifically, the oscillation control unit inputs, for example, the first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit, and the second baseband signal. The second local oscillation signal is input from the oscillation unit, and a signal representing a product of the input first baseband signal or the second baseband signal and the input second local oscillation signal is provided. A fifth mixing unit to be generated;
  An extraction unit for extracting the second intermediate frequency signal from the signals generated by the fifth mixing unit;
  The second intermediate frequency signal extracted by the extraction unitTo issueBased on the component of the intermediate frequency included, the first oscillation unit is controlled so that the frequency of the first local oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio. A convergence control unit that converges the frequency of one local oscillation signal to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency.
[0014]
  SaidConvergence controllerFor example, the extraction unitByExtractionIsTheSaid second intermediate frequency signalBased on a phase difference between a signal obtained by dividing the first local oscillation signal by a predetermined second division ratio and a signal obtained by dividing the first local oscillation signal by a predetermined second division ratio,By controlling the first oscillation unit so that the frequency of the first local oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the angle. Converge to a frequency equal to the sum or difference of the carrier frequency of the modulation signal and the offset frequencyIf so, it is possible to easily generate a stable first local oscillation signal with high accuracy.be able to.
[0015]
  Or saidOscillation controllerIs an illustrationIfThe firstofThe first from the mixing sectionofBaseband signal orFrom the second mixing sectionSecondofThe baseband signal is input and the first inputofBaseband signal orAboveSecondofFrom the baseband signal,Offset frequencyAn extraction unit for extracting the components having;
  The secondofThe second local oscillation signal is input from the oscillation unit, and the extraction unitByExtractionIsTheComponentA signal representing a product of the signal and the input second local oscillation signal is generated, and among the generated signals, the signalSecond intermediate frequency signalExtract the firstOf 5A mixing section;
  Based on an intermediate frequency component included in the second intermediate frequency signal extracted by the fifth mixing unit, the frequency of the first local oscillation signal is multiplied by a predetermined ratio to the intermediate frequency. Convergence control for converging the frequency of the first local oscillation signal to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency by controlling the first oscillation unit to converge. PartAnd the first local oscillation signal may be generated.
[0016]
  In this case,Convergence controllerFor example, the firstOf 5Mixing sectionByExtractionIsTheSaid second intermediate frequency signalBased on a phase difference between a signal obtained by dividing the first local oscillation signal by a predetermined second division ratio and a signal obtained by dividing the first local oscillation signal by a predetermined second division ratio,By controlling the first oscillation unit so that the frequency of the first local oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the angle. Converge to a frequency equal to the sum or difference of the carrier frequency of the modulation signal and the offset frequencyIf so, it is possible to easily generate a stable first local oscillation signal with high accuracy.be able to.
[0017]
  The magnitude of the offset frequency is preferably within 300 hertz.When reproducing an audio signal, the accuracy of the reproduced audio is not impaired even if a component of about 300 Hz or less is removed from the audio signal. Therefore, by removing a component less than the offset frequency from the baseband signal using an HPF or a capacitor, the DC component of the secondary distortion of the mixing unit can be easily removed without degrading the accuracy of demodulation.
[0018]
  In addition, an angle demodulation method according to a second aspect of the present invention inputs an angle modulation signal,
  Generating a first local oscillation signal that converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and a predetermined offset frequency;
  Generating a first phase-shifted signal that is 90 degrees out of phase with the first local oscillation signal;
  Generating a first baseband signal composed of components obtained by removing a component having a frequency of 0 from the product of the angle modulation signal and the first local oscillation signal;
  Generating a second baseband signal composed of components obtained by removing a component having a frequency of 0 from the product of the angle modulation signal and the first phase-shifted signal;
  Generating a second local oscillation signal having a frequency equal to a difference or sum of a predetermined intermediate frequency and the offset frequency;
  Generating a second phase-shifted signal that is 90 degrees out of phase with the second local oscillation signal;
  Generating a first intermediate signal representing a product of the first baseband signal and the second local oscillation signal;
  Generating a second intermediate signal representing a product of the second baseband signal and the second phase-shifted signal;
  Generating a first intermediate frequency signal representing a sum or difference between the first intermediate signal and the second intermediate signal;
  An angle demodulated signal is generated by demodulating the first intermediate frequency signal;
  A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first baseband signal or the second baseband signal, and the second intermediate frequency signal is generated. Based on the intermediate frequency components contained in,The frequency of the first local oscillation signalTheA frequency obtained by multiplying the intermediate frequency by a predetermined ratio.ConvergeThereby, the frequency of the first local oscillation signal is converged to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency,
  It is characterized by that.
[0019]
  According to such an angle demodulation method, the angle modulation signal is demodulated by a direct conversion method. The first local oscillation signal is generated based on the offset frequency component extracted from the first baseband signal or the second baseband signal. For this reason, the frequency of the first local oscillation signal is stable. Therefore, the demodulation operation by such an angle demodulation method is stable.
[0020]
  A computer-readable recording medium according to the third aspect of the present invention provides a computer,An angle modulation signal input unit for inputting the angle modulation signal;
  Converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulated signal and a predetermined offset frequencyFirst local oscillation signalIssueGenerate firstofAn oscillation unit;
  A first phase shift unit that receives the first local oscillation signal from the first oscillation unit and generates a first phase shift signal that is 90 degrees out of phase with the first local oscillation signal;
  Input the angle modulation signal from the angle modulation signal input unit,FirstofThe first local oscillation signal from the oscillation unitIssueA first input comprising a component excluding a component having a frequency of 0 from the product of the angle modulation signal and the first local oscillation signal.ofGenerate baseband signalA first mixing section
  The angle modulation signal is input from the angle modulation signal input unit, and the first phase shift unit inputs the angle modulation signal. 1 phase shift signal is input to generate a second baseband signal composed of components obtained by removing the component having a frequency of 0 from the product of the angle modulation signal and the first phase shift signal. A second mixing section;
  A given intermediate frequency andAboveA second local oscillator signal having a frequency equal to the difference or sum of the offset frequencyIssueSecond to generateofAn oscillation unit;
  A second phase shift unit that inputs the second local oscillation signal from the second oscillation unit and generates a second phase shift signal that is 90 degrees out of phase with the second local oscillation signal;
  The firstofThe first from the mixing sectionBaseband signalEnter the secondofThe second local oscillation signal from the oscillation unitIssueEnter the firstofThe product of the baseband signal and the second local oscillation signalA third mixing unit for generating a first intermediate signal representing,
  The second baseband signal is input from the second mixing unit, the second phase shift signal is input from the second phase shift unit, and the second baseband signal and the second baseband signal are input. A fourth mixing unit for generating a second intermediate signal representing a product with the phase shift signal;,
  The first intermediate signal is input from the third mixing unit, the second intermediate signal is input from the fourth mixing unit, and the sum of the first intermediate signal and the second intermediate signal is input. Or an intermediate frequency signal generator for generating a first intermediate frequency signal representing the difference;
  SaidIntermediate frequency signal generatorMore thanFirstDemodulator that generates an angle demodulated signal by demodulating an intermediate frequency signalWhen,
  The first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit is input, and the input first baseband signal or second baseband signal is input. A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first intermediate frequency signal, and the first local portion is generated based on the intermediate frequency component included in the second intermediate frequency signal. By controlling the first oscillation unit so that the frequency of the oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the carrier frequency of the angle modulation signal. And an oscillation control unit that converges to a frequency equal to the sum or difference of the offset frequency,
  It is characterized by recording a program for making it function.
[0021]
  A computer that executes a program recorded on such a recording medium demodulates an angle modulation signal by a direct conversion method. The first local oscillation signal is generated based on the offset frequency component extracted from the first baseband signal or the second baseband signal. For this reason, the frequency of the first local oscillation signal is stable, and therefore the demodulation operation by such a computer is stable.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, an angle demodulating apparatus and an angle demodulating method according to an embodiment of the present invention will be described using an FM (Frequency Modulation) receiver as an example.
[0023]
  FIG. 1 shows an example of the configuration of an FM receiver according to an embodiment of the present invention.
  As shown in the figure, this FM receiver includes an antenna 1, an RF (Radio Frequency) amplifier 2, a duplexer 3, mixers 4I, 4Q, 8I and 8Q, and an LPF (Low Pass Filter) 5I. And 5Q, AF (Audio Frequency) amplifiers 6I and 6Q, DC removing units 7I and 7Q, phase shifters 9 and 10, a local oscillator 11, an adder 12, and a BPF (Band Pass Filter). 13, an IF (Intermediate Frequency) amplifier 14, and an FM detector 15.
[0024]
  When a signal (RF signal) excited by the electromagnetic wave from the antenna 1 is supplied from the antenna 1, the RF amplifier 2 amplifies the signal supplied from the antenna 1 and supplies the amplified signal to the duplexer 3. The duplexer 3 supplies the RF signal supplied from the RF amplifier 2 to the mixers 4I and 4Q.
[0025]
  The mixers 4I and 4Q have substantially the same configuration. The mixer 4I generates a signal (I channel baseband signal) representing the product of an RF signal supplied from the duplexer 3 and a first local oscillation signal (described later) supplied from the local oscillator 11, and supplies it to the LPF 5I. Supply. The mixer 4Q is an RF signal supplied from the branching filter 3 and a first described later supplied from the phase shifter 9.ofA signal (Q channel baseband signal) representing the product with the phase shift signal is generated and supplied to the LPF 5Q.The
[0026]
  The LPFs 5I and 5Q have substantially the same configuration. The LPFs 5I and 5Q filter the I channel baseband signal or the Q channel baseband signal supplied from the mixer 4I or 4Q. Specifically, the LPF 5I removes a frequency component that exceeds an upper limit of an AF signal band to be reproduced from the I channel baseband signal, and supplies the remaining frequency component to the AF amplifier 6I. The LPF 5Q removes the frequency component exceeding the upper limit of the band of the AF signal to be reproduced from the Q channel baseband signal, and supplies the remaining frequency component to the AF amplifier 6Q.The
[0027]
  The AF amplifiers 6I and 6Q have substantially the same configuration. The AF amplifier 6I amplifies the signal supplied from the LPF 5I and supplies it to the DC removal unit 7I. The AF amplifier 6Q amplifies the signal supplied from the LPF 5Q and supplies it to the DC removal unit 7Q.
[0028]
  The direct current removing units 7I and 7Q have substantially the same configuration, and for example, both are configured by a capacitor or HPF (High Pass Filter). The DC removing unit 7I removes a DC component from the signal supplied from the AF amplifier 6I and supplies the other components to the mixer 8I. The DC removing unit 7Q removes a DC component from the signal supplied from the AF amplifier 6Q, and supplies the other components to the mixer 8Q and the local oscillator 11.The
[0029]
  The mixers 8I and 8Q have substantially the same configuration. The mixer 8I has a frequency representing the product of a signal supplied from the direct current removing unit 7I and a second local oscillation signal (described later) supplied from the local oscillator 11, and the frequency is the sum of the frequencies of these two signals (or A signal representing a component substantially equal to the differenceIssueIt is generated and supplied to the adder 12. The mixer 8Q includes a signal supplied from the direct current removing unit 7Q and a second (described later) supplied from the phase shifter 10.ofOf the signal representing the product with the phase-shifted signal, a signal representing a component whose frequency is substantially equal to the sum (or difference) of the frequencies of these two signals is generated and supplied to the adder 12The
[0030]
  When the phase shifter 9 is supplied with the first local oscillation signal from the local oscillator 11, the phase shifter 9 is a signal that is substantially delayed by 90 degrees from the phase of the first local oscillation signal.ofA phase shift signal is generated and supplied to the mixer 4Q.
  When the phase shifter 10 is supplied with the second local oscillation signal from the local oscillator 11, the phase shifter 10 is a signal that substantially delays the phase of the second local oscillation signal by 90 degrees.ofA phase shift signal is generated and supplied to the mixer 8Q.
[0031]
  The adder 12 generates a signal representing the sum of the signals supplied from the mixers 8I and 8Q and supplies the signal to the BPF 13.
  The BPF 13 filters the signal supplied from the adder 12. Specifically, the BPF 13 supplies the band component in the vicinity of a predetermined intermediate frequency to the IF amplifier 14 in the signal supplied from the adder 12 and substantially blocks the other components.
  The IF amplifier 14 amplifies the component (IF signal) supplied from the BPF 13 and supplies the amplified component to the FM detector 15.
[0032]
  The FM detector 15 includes a ratio detector, a quadrature demodulator circuit, other arbitrary FM detector circuits, an AF amplifier, a speaker, and the like, and converts the frequency shift of the signal supplied from the IF amplifier 14 into an amplitude. The FM signal is demodulated by IF, and the AF signal obtained by the demodulation is output as an output signal of the FM receiver and reproduced.
[0033]
  As shown in FIG. 2, the local oscillator 11 includes an LPF 101 and 109, an oscillator 102, a mixer 103, a BPF 104, an amplifier 105, an amplitude limiter 106, frequency dividers 107 and 111, and a phase comparator 108. And a VCO (Voltage Controlled Oscillator) 110.
[0034]
  The LPF 101 supplies, to the mixer 103, a portion of the signal supplied from the DC removal unit 7Q whose frequency is equal to or lower than a predetermined offset frequency, and the frequency exceeds the offset frequency.MinutesVirtually eliminateThe
  The oscillator 102 generates an AC signal and supplies it to the mixer 103, and also supplies this AC signal to the phase shifter 10 and the mixer 8I as the above-mentioned second local oscillation signal. The frequency of the second local oscillation signal is substantially equal to the difference (or sum) between the predetermined intermediate frequency in the pass band of the BPF 13 and the above-described offset frequency.
  The mixer 103 generates a signal representing the product of the signal supplied from the LPF 101 and the second local oscillation signal supplied from the oscillator 102 and supplies the signal to the BPF 104.
[0035]
  The BPF 104 supplies a component having a frequency corresponding to the sum (or difference) of the frequency of the signal supplied from the LPF 101 and the frequency of the second local oscillation signal among the signals supplied from the mixer 103 to the amplifier 105. IngredientsThe fruitRemove qualitativelyThe
  The amplifier 105 amplifies the component supplied from the BPF 104 and supplies the amplified component to the amplitude limiter 106.
  The amplitude limiter 106 supplies a signal obtained by limiting the amplitude of the component supplied from the amplifier 105 to a predetermined value or less to the frequency divider 107.
[0036]
  The VCO 110 generates an AC signal, and changes the frequency of the AC signal by the change specified by the control signal supplied to itself. Note that the VCO 110 generates, for example, an AC signal having a free running frequency unique to itself when the control signal is not yet supplied to the VCO 110.
  The VCO 110 supplies the AC signal generated by itself to the frequency divider 111 and supplies this AC signal to the mixer 4I and the phase shifter 9 as the first local oscillation signal.
[0037]
  Each of the frequency dividers 107 and 111 includes, for example, a flip-flop circuit, a counter circuit, and the like.
[0038]
  The frequency divider 107 divides the signal supplied from the amplitude limiter 106 by a frequency division ratio M (where M is a natural number) (that is, the frequency divider 107 converts the signal supplied from the amplitude limiter 106 to the signal supplied from the amplitude limiter 106. Synchronize and generate a signal having a frequency substantially equal to 1 / M of the frequency of this signal). Then, the frequency divider 107 supplies a signal obtained by frequency division by itself to the phase comparator 108.
[0039]
  The frequency divider 111 divides the AC signal supplied from the VCO 110 by a frequency division ratio N (where N is a natural number), and supplies the signal obtained by frequency division to the phase comparator 108.
[0040]
  Phase comparator 108Is a squareCalculationRoadMore composedIt isThe control signal representing the phase difference between the signal supplied from the frequency divider 107 and the signal supplied from the frequency divider 111 is generated, and the generated control signal is supplied to the LPF 109.
  The LPF 109 removes the harmonic component included in the control signal supplied from the phase comparator 108 and supplies the control signal from which the harmonic component is substantially removed to the VCO 110.
[0041]
  When the phase difference between the signal supplied from the frequency divider 107 and the signal supplied from the frequency divider 111 is substantially 0, the control signal output from the phase comparator 108 is the first local oscillation signal. The change in frequency is designated as substantially 0 (that is, designation is made so as to keep the frequency of the AC signal currently generated by the VCO 110 as it is).
[0042]
  On the other hand, when the phase of the signal supplied from the frequency divider 107 is ahead of the phase of the signal supplied from the frequency divider 111, the change indicated by the control signal output from the phase comparator 108 is a positive value. Become. That is, it is designated to increase the frequency of the first local oscillation signal. Further, when the phase of the signal supplied from the frequency divider 107 is delayed from the phase of the signal supplied from the frequency divider 111, the change indicated by the control signal output from the phase comparator 108 is a negative value. Become. That is, it is designated to decrease the frequency of the first local oscillation signal. However, regardless of whether the value of the change is positive or negative, the absolute value of the change specified by the control signal is the phase difference between the signal supplied from the frequency divider 107 and the signal supplied from the frequency divider 111. The larger the value, the larger the value.
  That is, the phase comparator 108, the LPF 109, the VCO 110, and the frequency divider 111 function as a phase lock loop (PLL) that controls the frequency of the first local oscillation signal.
[0043]
  Note that the values of the frequency division ratios M and N described above are such that the frequency of the first local oscillation signal depends on the carrier frequency of the FM modulation signal to be received by the FM receiver and the offset frequency described above by the operation described later. Is set to a value that converges to the sum (or difference) of.
[0044]
  Furthermore, it is desirable that the magnitude of the offset frequency is within 300 hertz. When the AF signal to be reproduced represents a sound, the accuracy of the reproduced sound is not impaired even if a component of about 300 hertz or less is not reproduced. Therefore, in this case, the DC removing units 7I and 7Q for removing the DC component from the I channel baseband signal and the Q channel baseband signal do not remove only the DC component accurately, but only the components substantially below the offset frequency. Can eliminate the accuracy of demodulation, and can also be used for I channel baseband signals and Q channel baseband signals.CarrierThe DC component of the second order distortion generated by the mixers 4I and 4Q can be removed without removing the component by mistake.
[0045]
  In other words, the values of the frequency division ratios M and N indicate the carrier frequency of the FM modulated signal to be received by the FM receiver as f.₀, The value at which the frequency of the first local oscillation signal converges is f₁, The value of the second local oscillation signal is f₂, The intermediate frequency is f_IFWhen the offset frequency is Δf, it is set to a value that substantially satisfies the relationship shown in Equations 1 to 3. Furthermore, it is desirable to satisfy the relationship shown in Formula 4.
[0046]
[Expression 1]
f₁= F₀± Δf
[Expression 2]
(F₁/ N) = {(f₂± Δf) / M}
[Equation 3]
(F₂± Δf) = f_IF
[Expression 4]
Δf ≦ 300 [Hz]
[0047]
  (Operation)
  Next, the operation of this FM receiver will be described.
  When the FM modulation signal to be received by the FM receiver induces an RF signal in the antenna 1, the RF amplifier 2 amplifies the RF signal and supplies the RF signal to the duplexer 3. The RF signal supplied from is supplied to the mixers 4I and 4Q.
  On the other hand, the mixer 4I is supplied with a first local oscillation signal generated by the VCO 110 of the local oscillator 11, and the mixer 4Q is a signal corresponding to a phase delayed substantially by 90 degrees. A certain firstofA phase shift signal is supplied from the phase shifter 9.
[0048]
  The mixer 4I generates an I channel baseband signal. The I-channel baseband signal generated by the mixer 4I is filtered by the LPF 5I, amplified by the AF amplifier 6I, further subjected to DC component removal by the DC removal unit 7I, and then supplied to the mixer 8I.
  The mixer 4Q generates a Q channel baseband signal. The Q-channel baseband signal generated by the mixer 4Q is filtered by the LPF 5Q, amplified by the AF amplifier 6Q, further removed from the DC component by the DC removal unit 7Q, and then supplied to the mixer 8Q.
[0049]
  If the difference between the frequency of the first local oscillation signal and the carrier frequency of the FM modulation signal to be received by the FM receiver is substantially equal to the offset frequency, the BPF 104 of the local oscillator 11Intermediate frequency f _IF Of frequency equal toA signal is output. This signal is amplified by the amplifier 105, shaped to have a constant amplitude by the amplitude limiter 106, and further divided by M by the frequency divider 107 and output.
[0050]
  When the signal is output from the frequency divider 107, the frequency of the signal output from the frequency divider 111 of the local oscillator 11 (that is, 1 / N of the frequency of the first local oscillation signal) is the frequency divider. When the frequency is higher than the frequency of the signal output by 107 (that is, 1 / M of the sum or difference between the frequency of the second local oscillation signal and the offset frequency), the frequency decreases.
  Therefore, the frequency of the first local oscillation signal converges to a value of N of M of the sum or difference between the frequency of the second local oscillation signal and the offset frequency. I channel baseband signal and Q channel baseband signalOf the carrier component ofThe frequency converges to a value substantially equal to the offset frequency.
[0051]
  On the other hand, the mixer 8I is supplied with the second local oscillation signal output from the oscillator 102 of the local oscillator 11, and the mixer 8Q has a signal corresponding to the phase of the second local oscillation signal delayed substantially by 90 degrees. The secondofA phase shift signal is supplied from the phase shifter 10.
[0052]
  The mixer 8I represents a component whose frequency is substantially equal to the sum (or difference) of the frequencies of these two signals among the signals representing the product of the signal supplied from the direct current removing unit 7I and the second local oscillation signal. A signal is generated and supplied to the adder 12.
  The mixer 8Q is connected to the signal supplied from the DC removal unit 7Q and the secondofOf the signal representing the product of the phase-shifted signal, a signal representing a component whose frequency is substantially equal to the sum (or difference) of the frequencies of these two signals is generated and supplied to the adder 12.
[0053]
  The adder 12 generates a signal that represents the sum of the signals supplied from the mixers 8I and 8Q. This signal is filtered by the BPF 13 to become an IF signal, and the IF signal is amplified by the IF amplifier 14. IF signalOf the carrier component ofThe frequency is substantially equal to the sum (or difference) of the frequency of the second local oscillation signal and the offset frequency.
[0054]
  The IF signal amplified by the IF amplifier 14 is FM demodulated by the FM detector 15, and the AF signal obtained by the demodulation is output as an output signal of the FM receiver and reproduced.
[0055]
  As a result of the operation described above, the FM modulated signal received by the FM receiver is demodulated, and the sound represented by the AF signal is reproduced.
  This FM receiver demodulates an FM modulated signal by a direct conversion method. Then, the first local oscillation signal is extracted from the Q channel baseband signalOffset frequencyTransportWaveGenerated based on minutes. For this reason, the frequency of the first local oscillation signal is stabilized, and therefore the operation of the FM demodulation by this FM receiver is also stabilized.
[0056]
  Note that the configuration of the FM receiver is not limited to that described above.
  For example, the duplexer 3 may include an A / D (Analog-to-Digital) converter, a DSP (Digital Signal Processor), and a CPU (Central Processing Unit). Further, the FM detector 15 may be composed of a DSP or CPU and a D / A (Digital-to-Analog) converter. And a part or all of the function of the other component of this FM receiver may be performed by DSP or CPU.
[0057]
  The local oscillator 11 may be supplied with an I channel baseband signal from the DC removal unit 7I instead of being supplied with the Q channel baseband signal from the DC removal unit 7Q.
  Further, the Q-channel baseband signal or the I-channel baseband signal supplied to the local oscillator 11 does not necessarily need to have a DC component removed. Therefore, the local oscillator 11 may be supplied with a Q channel baseband signal from the LPF 5Q or the AF amplifier 6Q instead of the DC removing unit 7Q, or may be replaced with the LPF 5I or the AF amplifier 6I instead of the DC removing unit 7I. May be supplied with an I channel baseband signal.
[0058]
  Further, the FM receiver does not need to acquire the FM modulated signal from the antenna 1, and may acquire the FM modulated signal from a wired line, for example. Further, the RF amplifier 2 can be omitted. The FM receiver may demodulate a PM (Phase Modulation) modulation signal. In this case, the FM detector 15 may include, for example, an integration circuit for integrating the AF signal obtained by FM demodulation of the IF signal.
[0059]
  Further, the values of the frequency division ratios M and N are arbitrary as long as the above-described relationship is satisfied. Accordingly, at least one of the frequency dividers 107 and 111 may be configured to change its own frequency division ratio in response to an operation by the operator. For example, if the frequency division ratio of the frequency divider 111 is variable, the FM receiver can change the carrier frequency of the FM modulation signal to be received.
[0060]
  The angle demodulating apparatus and the angle demodulating method according to the present invention have been described above. However, the angle demodulating apparatus according to the present invention can be realized using a normal computer system, not a dedicated system. For example, a medium (floppy) storing a program for executing the above-described operation in a personal computer including an A / D converter and a D / A converter.(Registered trademark)By installing the program from a disk, CD-ROM or the like, an FM receiver that executes the above-described processing can be configured.
[0061]
  Further, for example, the program may be posted on a bulletin board (BBS) of a communication network and distributed via the network. Distribution via a network may be performed by transmitting a modulated signal obtained by modulating a carrier wave with the program.
  The above-described processing can be executed by starting this program and executing it under the control of the OS in the same manner as other application programs.
[0062]
  When the OS shares a part of the processing, or when the OS constitutes a part of one component of the present invention, a program excluding the part is stored in the recording medium. May be. Also in this case, in the present invention, it is assumed that the recording medium stores a program for executing each function or step executed by the computer.
[0063]
【The invention's effect】
  As described above, according to the present invention, an angle demodulating device and an angle demodulating method that generate a local oscillation signal with a stable frequency and perform stable demodulation by a direct conversion method are realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of an FM receiver according to an embodiment of the present invention.
2 is a block diagram showing a basic configuration of a local oscillator of the FM receiver of FIG. 1. FIG.
FIG. 3 is a block diagram showing a configuration of a conventional FM receiver.
[Explanation of symbols]
1 Antenna
2 RF amplifier
3 duplexer
4I, 4Q, 8I, 8Q, 103 mixer
5I, 5Q, 101, 109 LPF
6I, 6Q AF amplifier
7I, 7Q DC removal section
9, 10 Phase shifter
11 Local oscillator
12 Adder
13, 104 BPF
14 IF amplifier
15 FM detector
102 oscillator
105 Amplifier
106 Amplitude limiter
107, 111 frequency divider
108 Phase comparator
110 VCO

Claims

An angle modulation signal input unit for inputting the angle modulation signal;
A first oscillation unit that generates a first local oscillation signal that converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and a predetermined offset frequency;
A first phase shift unit that receives the first local oscillation signal from the first oscillation unit and generates a first phase shift signal that is 90 degrees out of phase with the first local oscillation signal;
The angle modulation signal is input from the angle modulation signal input unit, the first local oscillation signal is input from the first oscillation unit, and the product of the angle modulation signal and the first local oscillation signal is obtained. A first mixing unit that generates a first baseband signal composed of components excluding components having a frequency of 0;
The angle modulation signal is input from the angle modulation signal input unit, the first phase shift signal is input from the first phase shift unit, and the product of the angle modulation signal and the first phase shift signal is input. A second mixing unit that generates a second baseband signal composed of components excluding components having a frequency of 0,
A second oscillating unit for generating a second local oscillation signal having a frequency equal to a difference or sum of a predetermined intermediate frequency and the offset frequency;
A second phase shift unit that inputs the second local oscillation signal from the second oscillation unit and generates a second phase shift signal that is 90 degrees out of phase with the second local oscillation signal;
The first baseband signal is input from the first mixing section, the second local oscillation signal is input from the second oscillation section, and the first baseband signal and the second local section are input. A third mixing unit for generating a first intermediate signal representing a product with the oscillation signal;
The second baseband signal is input from the second mixing unit, the second phase shift signal is input from the second phase shift unit, and the second baseband signal and the second baseband signal are input. A fourth mixing unit for generating a second intermediate signal representing a product with the phase shift signal;
The first intermediate signal is input from the third mixing unit, the second intermediate signal is input from the fourth mixing unit, and the sum of the first intermediate signal and the second intermediate signal is input. Or an intermediate frequency signal generator for generating a first intermediate frequency signal representing the difference;
A demodulator for generating an angle demodulated signal by inputting and demodulating the first intermediate frequency signal from the intermediate frequency signal generator;
The first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit is input, and the input first baseband signal or second baseband signal is input. A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first intermediate frequency signal, and the first local portion is generated based on the intermediate frequency component included in the second intermediate frequency signal. By controlling the first oscillation unit so that the frequency of the oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the carrier frequency of the angle modulation signal. And an oscillation control unit that converges to a frequency equal to the sum or difference of the offset frequency,
An angle demodulating device comprising:

The oscillation control unit
The first baseband signal is input from the first mixing unit or the second baseband signal is input from the second mixing unit, and the second local oscillation signal is input from the second oscillation unit. A fifth mixing unit for generating a signal representing a product of the input first baseband signal or the second baseband signal and the input second local oscillation signal;
An extraction unit for extracting the second intermediate frequency signal from the signals generated by the fifth mixing unit;
Based on the intermediate frequency component included in the second intermediate frequency signal extracted by the extraction unit, the frequency of the first local oscillation signal converges to a frequency obtained by multiplying a predetermined ratio to said intermediate frequency By controlling the first oscillation unit as described above, a convergence control unit that converges the frequency of the first local oscillation signal to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency; ,
The angle demodulator according to claim 1, comprising:

The convergence control unit outputs a signal obtained by dividing the second intermediate frequency signal extracted by the extraction unit with a predetermined first division ratio and the first local oscillation signal to a predetermined second. The first oscillation so that the frequency of the first local oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio based on the phase difference from the signal obtained by frequency division by the frequency division ratio By controlling the unit, the frequency of the first local oscillation signal is converged to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency,
The angle demodulator according to claim 2.

The oscillation control unit
The first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit is input, and the input first baseband signal or second baseband signal is input. An extraction unit for extracting a component having the offset frequency from
The second local oscillation signal is input from the second oscillation unit, and a signal representing the product of the component signal extracted by the extraction unit and the input second local oscillation signal is generated and generated. A fifth mixing unit for extracting the second intermediate frequency signal from the signal,
Based on an intermediate frequency component included in the second intermediate frequency signal extracted by the fifth mixing unit, the frequency of the first local oscillation signal is multiplied by a predetermined ratio to the intermediate frequency. Convergence control for converging the frequency of the first local oscillation signal to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and the offset frequency by controlling the first oscillation unit to converge. And
The angle demodulator according to claim 1, comprising:

The convergence control unit predetermines a signal obtained by dividing the second intermediate frequency signal extracted by the fifth mixing unit by a predetermined first division ratio and the first local oscillation signal. The frequency of the first local oscillation signal is converged to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio based on the phase difference from the signal obtained by frequency division by the second frequency division ratio. By controlling one oscillation unit, the frequency of the first local oscillation signal is converged to a frequency equal to the sum or difference between the carrier frequency of the angle modulation signal and the offset frequency.
The angle demodulator according to claim 4.

The magnitude of the offset frequency is within 300 hertz.
The angle demodulator according to any one of claims 1 to 5, wherein

Input angle modulation signal,
Generating a first local oscillation signal that converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and a predetermined offset frequency;
Generating a first phase-shifted signal that is 90 degrees out of phase with the first local oscillation signal;
Generating a first baseband signal composed of components obtained by removing a component having a frequency of 0 from the product of the angle modulation signal and the first local oscillation signal;
Generating a second baseband signal composed of components obtained by removing a component having a frequency of 0 from the product of the angle modulation signal and the first phase-shifted signal;
Generating a second local oscillation signal having a frequency equal to a difference or sum of a predetermined intermediate frequency and the offset frequency;
Generating a second phase-shifted signal that is 90 degrees out of phase with the second local oscillation signal;
Generating a first intermediate signal representing a product of the first baseband signal and the second local oscillation signal;
Generating a second intermediate signal representing a product of the second baseband signal and the second phase-shifted signal;
Generating a first intermediate frequency signal representing a sum or difference between the first intermediate signal and the second intermediate signal;
An angle demodulated signal is generated by demodulating the first intermediate frequency signal;
A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first baseband signal or the second baseband signal, and the second intermediate frequency signal is generated. based on the intermediate frequency component included in the frequency of the first local oscillation signal, by converging to a frequency obtained by multiplying a predetermined ratio to said intermediate frequency, wherein the frequency of said first local oscillation signal Converge to a frequency equal to the sum or difference of the carrier frequency of the angle modulated signal and the offset frequency,
An angle demodulation method characterized by the above.

Computer
An angle modulation signal input unit for inputting the angle modulation signal;
A first oscillation unit that generates a first local oscillation signal that converges to a frequency equal to the sum or difference of the carrier frequency of the angle modulation signal and a predetermined offset frequency;
A first phase shift unit that receives the first local oscillation signal from the first oscillation unit and generates a first phase shift signal that is 90 degrees out of phase with the first local oscillation signal;
The angle modulation signal is input from the angle modulation signal input unit, the first local oscillation signal is input from the first oscillation unit, and the product of the angle modulation signal and the first local oscillation signal is obtained. A first mixing unit that generates a first baseband signal composed of components excluding components having a frequency of 0;
The angle modulation signal is input from the angle modulation signal input unit, the first phase shift signal is input from the first phase shift unit, and the product of the angle modulation signal and the first phase shift signal is input. A second mixing unit that generates a second baseband signal composed of components excluding components having a frequency of 0,
A second oscillating unit for generating a second local oscillation signal having a frequency equal to a difference or sum of a predetermined intermediate frequency and the offset frequency;
A second phase shift unit that inputs the second local oscillation signal from the second oscillation unit and generates a second phase shift signal that is 90 degrees out of phase with the second local oscillation signal;
The first baseband signal is input from the first mixing section, the second local oscillation signal is input from the second oscillation section, and the first baseband signal and the second local section are input. A third mixing unit for generating a first intermediate signal representing a product with the oscillation signal;
The second baseband signal is input from the second mixing unit, the second phase shift signal is input from the second phase shift unit, and the second baseband signal and the second baseband signal are input. A fourth mixing unit for generating a second intermediate signal representing a product with the phase shift signal;
The first intermediate signal is input from the third mixing unit, the second intermediate signal is input from the fourth mixing unit, and the sum of the first intermediate signal and the second intermediate signal is input. Or an intermediate frequency signal generator for generating a first intermediate frequency signal representing the difference;
A demodulator for generating an angle demodulated signal by inputting and demodulating the first intermediate frequency signal from the intermediate frequency signal generator;
The first baseband signal from the first mixing unit or the second baseband signal from the second mixing unit is input, and the input first baseband signal or second baseband signal is input. A second intermediate frequency signal including the intermediate frequency component is generated based on the offset frequency component included in the first intermediate frequency signal, and the first local portion is generated based on the intermediate frequency component included in the second intermediate frequency signal. By controlling the first oscillation unit so that the frequency of the oscillation signal converges to a frequency obtained by multiplying the intermediate frequency by a predetermined ratio, the frequency of the first local oscillation signal is changed to the carrier frequency of the angle modulation signal. And an oscillation control unit that converges to a frequency equal to the sum or difference of the offset frequency,
The computer-readable recording medium which recorded the program for making it function.