JP4432235B2

JP4432235B2 - Channel selection filter and receiver

Info

Publication number: JP4432235B2
Application number: JP2000260405A
Authority: JP
Inventors: 嘉茂吉川; 良雄堀池
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 2000-08-30
Filing date: 2000-08-30
Publication date: 2010-03-17
Anticipated expiration: 2020-08-30
Also published as: JP2002076973A

Description

【０００１】
【発明の属する技術分野】
本発明は、主としてコードレスリモコン、ページャ、コードレス電話、携帯電話等の無線通信機器に用いられるチャンネル選択フィルタおよび前記チャンネル選択フィルタを用いて構成される受信機に関する。
【０００２】
【従来の技術】
従来のチャンネル選択ミキサおよび受信機について図面を参照しながら説明する。図８は、従来の受信機の構成を示すブロック図である。
【０００３】
図８において、５は第１の局部信号源、６は第２の局部信号源、２１はアンテナ、２２はアンプ、２３は復調回路、２４は復調出力端子、３１は高周波フィルタ、４１は中間周波数フィルタ、４２はチャネル選択フィルタ、４３は第１のミキサ、４４は第２のミキサである。図８の受信機はダブルスーパーヘテロダイン方式の構成を示している。アンテナに入力した受信信号は、高周波フィルタ３１に入力され不要周波数成分を除去される。ここで、第１のミキサ４３で周波数変換するときのイメージ周波数成分が除去される。高周波フィルタ３１の出力は、アンプ２２で増幅される。アンプ２２の出力と第１の局部信号源５の出力が第１のミキサ４３でミキシングされ、第１の中間周波数信号に変換される。第１の中間周波数信号は、中間周波数フィルタ４１で第２のミキサ４４でのミキシング時のイメージ周波数成分が除去される。中間周波数フィルタ４１の出力と第２の局部信号源６の出力が第２のミキサ４４でミキシングされ、第２の中間周波数信号に変換される。第２の中間周波数信号は、チャネル選択フィルタ４２に入力され、受信チャネル成分以外の不要な成分が除去される。ここでチャネル選択フィルタ４２には、セラミックフィルタや水晶フィルタなどの受動素子や、トランジスタなどの能動素子を用いて構成したｇ−ｍｃフィルタなどが用いられる。チャネル選択フィルタ４２の出力が復調回路２３に入力され、復調出力が復調出力端子２４より出力される。
【０００４】
【発明が解決しようとする課題】
しかしながら、前記従来のチャネル選択フィルタでは、小型化や省電力化に問題があった。すなわち、セラミックフィルタなど受動素子のフィルタでは、集積化が困難であるため小型化が難しかった。また、能動素子を用いてｇ―ｍｃフィルタなどを構成した場合、急峻で減衰量の大きなフィルタ特性を実現するためには消費電流が大きくなるという問題があった。また、素子数が多くなり、半導体ＩＣに集積化しても、チップサイズが大きくなり、コストが高くなる要因となっていた。
【０００５】
そして、上記のようなチャネル選択フィルタを用いた受信機は、小型化が困難であるという問題があった。また、消費電流が大きく、コストが高いという問題があった。
【０００６】
【課題を解決するための手段】
前記従来の課題を解決するために、本発明のチャネル選択フィルタは、受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ低い周波数の信号を出力する第１の局部信号源と、前記受信信号と前記第１の局部信号源の出力を入力し前記受信信号成分のうち前記第１の局部信号源周波数より低い周波数成分を抑圧し前記受信信号のうち前記第１の局部信号源周波数より高い周波数成分を第１の中間周波数信号に変換して出力する第１のイメージリジェクションミキサと、前記チャネル周波数間隔と同じ周波数の信号を出力する第２の局部信号源と、前記第１の中間周波数信号と前記第２の局部信号源の出力を入力し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第２の中間周波数信号に変換して出力する第２のイメージリジェクションミキサを備えたものである。
【０００７】
これによって、大幅に回路規模を低減することができ、消費電流が低減できる。また、半導体ＩＣで構成した場合にチップサイズを小さくすることができるため低コスト化を実現できる。
【０００８】
【発明の実施の形態】
請求項１記載の発明は、受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ低い周波数の信号を出力する第１の局部信号源と、前記受信信号と前記第１の局部信号源の出力を入力し前記受信信号成分のうち前記第１の局部信号源周波数より低い周波数成分を抑圧し前記受信信号のうち前記第１の局部信号源周波数より高い周波数成分を第１の中間周波数信号に変換して出力する第１のイメージリジェクションミキサと、前記チャネル周波数間隔と同じ周波数の信号を出力する第２の局部信号源と、前記第１の中間周波数信号と前記第２の局部信号源の出力を入力し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第２の中間周波数信号に変換して出力する第２のイメージリジェクションミキサと、前記第２の中間周波数信号と前記第２の局部信号源の出力を入力し前記第２の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第２の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第３の中間周波数信号に変換して出力する第３のイメージリジェクションミキサと、前記第３の中間周波数信号と前記第２の局部信号源の出力を入力し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第４の中間周波数信号に変換して出力する第４のイメージリジェクションミキサとを備え、前記第２のイメージリジェクションミキサ、第３のイメージリジェクションミキサ及び第４のイメージリジェクションミキサは、前記第２の局部信号源の出力を入力することを特徴とするものである。これによれば、イメージリジェクションミキサの段数を増やすことにより、チャネル選択フィルタの帯域外減衰量を大きくすることができる。
【０００９】
また請求項２記載の発明は、受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ高い周波数の信号を出力する第１の局部信号源と、前記受信信号と前記第１の局部信号源の出力を入力し前記受信信号成分のうち前記第１の局部信号源周波数より高い周波数成分を抑圧し前記受信信号のうち前記第１の局部信号源周波数より低い周波数成分を第１の中間周波数信号に変換して出力する第１のイメージリジェクションミキサと、前記チャネル周波数間隔と同じ周波数の信号を出力する第２の局部信号源と、前記第１の中間周波数信号と前記第２の局部信号源の出力を入力し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第２の中間周波数信号に変換して出力する第２のイメージリジェクションミキサと、前記第２の中間周波数信号と前記第２の局部信号源の出力を入力し前記第２の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第２の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第３の中間周波数信号に変換して出力する第３のイメージリジェクションミキサと、前記第３の中間周波数信号と前記第２の局部信号源の出力を入力し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第４の中間周波数信号に変換して出力する第４のイメージリジェクションミキサとを備え、前記第２のイメージリジェクションミキサ、第３のイメージリジェクションミキサ及び第４のイメージリジェクションミキサは、前記第２の局部信号源の出力を入力することを特徴とするものである。これによれば、イメージリジェクションミキサの段数を増やすことにより、チャネル選択フィルタの帯域外減衰量を大きくすることができる。
【００１１】
また請求項３記載の発明は、請求項１または２記載のチャネル選択フィルタと、前記チャネル選択フィルタの出力を入力し復調を行う復調回路を備えた受信機である。そして、イメージリジェクションミキサでチャネル選択フィルタを構成していることにより、チャンネル選択フィルタを低消費電流で小型に構成でき、高周波フィルタや中間周波数フィルタも不要となるため、機器の大幅な小型化と低コスト化を実現できる。
【００１２】
また請求項４、５記載の発明は、第１のイメージリジェクションミキサの前段に受信信号を前記受信信号周波数より低い周波数である前置周波数信号に変換する前置ミキサを備え、前記受信信号の代りに前期前置周波数信号を前記第１のイメージリジェクションミキサに入力するチャンネル選択フィルタまたは受信機である。そして、予め受信信号の周波数を低い周波数に変換することにより、イメージリジェクションミキサの精度を出しやすく、チャネル選択フィルタとしての減衰量を大きくしやすい。また、消費電流を抑えることができる。
【００１３】
【実施例】
以下、図面を参照して本発明の実施例について説明する。
【００１４】
（実施例１）
図１は、本発明による実施例１のチャネル選択フィルタの構成を示すブロック図である。また、図２は本発明の構成要素であるイメージリジェクションミキサの構成をしめすブロック図である。また、図３は、本発明のチャネル選択フィルタの出力信号の周波数特性を示すグラフである。図１から３を用いて本実施例のチャネル選択フィルタについて説明する。
【００１５】
図１において、１は入力端子、２は出力端子、３は第１のイメージリジェクションフィルタ、４は第２のイメージリジェクションフィルタ、５は第１の局部信号源、６は第２の局部信号源である。
【００１６】
図２において、１１は受信信号入力端子、１２は中間周波数信号出力端子、１３は局部信号入力端子、１４はミキサ、１５は＋９０度移相器、１６は＋４５度移相器、１７は−４５度移相器、１８は加算器である。
【００１７】
まず、図２のイメージリジェクションミキサの動作について説明する。受信信号入力端子１１に入力された受信信号は分岐されて２つのミキサ１４に入力される。また、局部信号入力端子１３に入力された局部信号は、分岐されて前記２つのミキサ１４に入力される。ここで、局部信号入力端子１３に入力される局部信号源の周波数は、前記受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ低く設定されている。チャネル周波数間隔は、使用する周波数帯により予め決められており、チャネルが配置される周波数間隔である。例えば、日本の４００MHz帯の小電力無線では、チャネル周波数間隔は１２．５kHzに決められている。この場合、局部信号源の周波数は、希望チャネル周波数より６．２５kHz低く設定される。以下は、この小電力無線の場合を例にして説明する。
【００１８】
２つのミキサ１４に入力される局部信号は片方の経路に＋９０度移相器１５が挿入されているため互いに９０度位相差をもっている。
【００１９】
２つのミキサ１４でそれぞれ受信信号と局部信号がミキシングされ、変換された信号が出力される。前記変換された信号の一方は＋４５度位相器１６を経由して加算器１８に入力される。他方は−４５度位相器１７を経由して前記加算器１８に入力される。上記２信号を加算した信号が中間周波数信号出力端子１２より出力される。
【００２０】
上記の構成のイメージリジェクションミキサでは、互いに直交した局部信号が２つのミキサ１４に入力されるため、前記２つのミキサ１４の出力信号も互いに直交している。そして、＋４５度移相器１６と−４５度移相器１７により相対位相をさらに９０度回している。ここで、受信信号のうち局部信号源周波数より高い周波数の成分は、２つのミキサ１４の出力で互いに同位相となるため加算器１８で加算される。また、受信信号のうち局部信号源周波数より低い周波数の成分は、２つのミキサ１４の出力で互いに逆位相となるため加算器１８で打ち消し合い抑圧される。
【００２１】
また、上記の説明では加算器を用いたが、減算器を用いることにより抑圧する周波数を変えることができる。すなわち、減算器を用いれば、受信信号のうち局部信号源周波数より高い周波数の成分は、２つのミキサの出力で互いに同位相となるため打ち消し合い抑圧される。また、受信信号のうち局部信号源周波数より低い周波数の成分は、２つのミキサの出力で互いに逆位相となるため加算される。このように加算器または減算器を用いることで、受信信号のうち局部信号源周波数より高い周波数の成分を抑圧するか、低い周波数の成分を抑圧するかを選ぶことができる。
【００２２】
次に、図１を用いてチャネル選択フィルタについて説明する。
【００２３】
受信信号入力端子１に入力された受信信号と第１の局部信号源６の出力が、第１のイメージリジェクションミキサ３に入力される。ここで、第１のイメージリジェクションフィルタ３の構成は、図２に示したものである。そして、第１の局部信号源５の周波数は、希望チャネル周波数よりチャネル周波数間隔の２分の１だけ低く設定されている。そのため、第１のイメージリジェクションミキサ３の出力には、受信信号のうち第１の局部信号源周波数より高い周波数成分が第１の中間周波数信号として出力され、第１の局部信号源周波数より低い周波数成分は抑圧される。
【００２４】
この時、第１の中間周波数信号の６．２５kHzを中心周波数として、希望チャンネルの信号成分がある。
【００２５】
次に、第１の中間周波数信号と第２の局部信号源の出力が第２のイメージリジェクションミキサ４に入力される。ここで、第２のイメージリジェクションミキサ４は、図２に示す構成のものである。第２の局部信号源６の周波数は、チャネル周波数間隔と同じ１２．５kHzに設定されている。そのため、希望チャンネルの信号成分は、再び６．２５kHzを中心とした信号である第２の中間周波数信号に変換される。そして、第１の中間周波数信号のうち第２の局部信号源周波数６より低い周波数成分が加算器で加算されて出力され、第２の局部信号源周波数６より高い周波数成分が抑圧される。
【００２６】
図３に、出力端子２に出力される信号振幅の周波数特性を示す。図３の横軸は周波数、縦軸は希望チャネルの出力信号振幅を基準にした各周波数の出力振幅である。図３でＡで示した帯域は、希望チャネルの帯域である。また、Ｂの帯域は、第１のイメージリジェクションミキサで抑圧された成分である。また、Ｃの帯域は第２のイメージリジェクションミキサで抑圧された成分である。このように、希望チャネル成分の両側の周波数成分が抑圧され、チャネル選択フィルタの特性となっている。
【００２７】
図３では、抑圧量は３０ｄＢとなっているが、抑圧量は、第１および第２のイメージリジェクションミキサの精度で決まる。
【００２８】
上記の実施例では、第１の局部信号の周波数が希望チャネル周波数より低い場合を示したが、受信周波数より高い周波数に設定する構成をとることができる。すなわち、第１の局部信号源の周波数が、希望チャンネル周波数より、チャネル周波数間隔の２分の１だけ高く設定される。この構成では、第１のイメージリジェクションミキサの加算器の代わりに減算器を用いる。これにより、受信信号のうち第１の局部信号源周波数より低い周波数成分が第１の中間周波数信号として出力され、第１の局部信号源周波数より高い周波数成分は抑圧される。
【００２９】
従来のｇ−ｍｃフィルタを用いて急峻な減衰特を得るためには、高次のフィルタを構成する必要があり、回路規模が非常に大きくなる。本実施例のように、イメージリジェクションミキサを２段に構成してバンドパスフィルタの特性を得ることにより、少ない素子数で構成でき、大幅に回路規模を低減することができる。そして消費電流を低減する事が出来る。そのため、半導体ＩＣで構成した場合にチップサイズを小さくすることができるため低コスト化を実現できるというメリットがある。
【００３０】
（実施例２）
図４は、本発明の実施例２のチャネル選択フィルタの構成を示すブロック図である。図４において、７は第３のイメージリジェクションミキサ、８は第４のイメージリジェクションミキサである。また、図１と同じ構成要素に同一の番号を付けて示した。また、図５は、本発明のチャネル選択フィルタの出力信号の周波数特性を示すグラフである。図４および図５を用いて本実施例のチャネル選択フィルタについて説明する。
【００３１】
本実施例と上記の実施例１の違いは、第３および第４のイメージリジェクションフィルタを用いることにより、希望チャネル周波数以外の周波数の減衰量を大きくしたことである。すなわち、第１および第２のイメージリジェクションミキサまでの構成は、実施例２と同様な動作である。本実施例では、第２のイメージリジェクションミキサ４の後段に第３のイメージリジェクションミキサ７を配置している。第３のイメージリジェクションミキサ７に第２のイメージリジェクションミキサ４の出力と第２の局部信号源６の出力が入力される。第３のイメージリジェクションミキサ７の動きは前記実施例１で述べた第２イメージリジェクションミキサ４と同様である。さらに第３のイメージリジェクションミキサ７の出力である第３の中間周波数信号と第２の局部信号源の出力が第４のイメージリジェクションミキサ８に入力される。第４のイメージリジェクションミキサ８の動きも第２および第３のイメージリジェクションミキサと同様である。第４のイメージリジェクションミキサ８の出力として第４の中間周波数信号が得られる。
【００３２】
図５に、出力端子２に出力される信号振幅の周波数特性を示す。
【００３３】
図５でＡで示した帯域は、希望チャネルの帯域である。また、Ｂは、第１のイメージリジェクションミキサで抑圧された成分である。また、Ｃは第２のイメージリジェクションミキサで抑圧された成分である。また、Ｄは第３のイメージリジェクションミキサで抑圧された成分である。また、Ｅは第４のイメージリジェクションミキサで抑圧された成分である。このように、第３および第４のイメージリジェクションミキサを設けることにより、隣々接チャンネル以上離れたチャネル周波数の成分の減衰量を大きくできる。図５では、隣接チャネルの減衰量が３０ｄＢ、隣々接チャネル以上の減衰が６０ｄＢとなっている。ここで、減衰量は各イメージリジェクションミキサの位相および振幅の精度で決まる。
【００３４】
本実施例でも前記実施例１と同様に、第１の局部信号源周波数を希望チャネル周波数より低くあるいは高く設定して構成することができる。低く設定したときの第１のイメージリジェクションミキサには加算器、高く設定したときの第１のイメージリジェクションミキサには減算器を用いる。
【００３５】
このように、イメージリジェクションミキサを４段にして構成したことにより、チャネル選択フィルタの帯域外減衰量を大きくすることができる。
【００３６】
尚、本実施例ではイメージリジェクションミキサの段数は４段としたが、５段以上とすることにより、さらに減衰量を大きくすることができる。
【００３７】
（実施例３）
図６は、本発明による実施例３の受信機の構成を示すブロック図である。図６において、２１はアンテナ、２２はアンプ、２３は復調回路、２４は復調出力端子である。また、図１〜図４と同じ構成要素に同一の番号を付けて示した。
【００３８】
アンテナ２１に入力した受信信号は、アンプ２２で増幅される。アンプ２２の出力と第１の局部信号源５の出力が第１のイメージリジェクションミキサ３に入力される。そして、第１のイメージリジェクションミキサ３の出力である第１の中間周波数信号と第２の局部信号源の出力が第２のイメージリジェクションミキサ４に入力される。ここで、第１および第２の局部信号源５，６の周波数は、前記実施例１および実施例２と同様に設定される。そして、第２のイメージリジェクションミキサ４の出力である第２の中間周波数信号が復調回路２３に入力され、復調出力が復調出力端子２４より出力される。
【００３９】
このように、本実施例の受信機では、チャンネル選択フィルタを低消費電流で小型に構成できるのに加え、従来の受信機でイメージ除去のために用いられていた高周波フィルタや中間周波数フィルタが不要となるため、機器の大幅な小型化と低コスト化を実現することができる。
【００４０】
（実施例４）
図７は、本発明による実施例４の受信機の構成を示すブロック図である。図７において、３１は高周波フィルタ、３２は前置ミキサ、３３は前置局部信号源である。また、図６と同じ構成要素に同一の番号を付けて示した。
【００４１】
本実施例と実施例３との違いは、前置ミキサ３２を設けたことにある。高周波アンプ２２と第１のイメージリジェクションミキサ３の間に前置ミキサ３２を設けて、受信信号を、例えば受信信号の周波数が４００MHz帯の場合には、２０MHzといった比較的周波数の低い前置周波数に変換している。ここで、前置ミキサ３２でのイメージ周波数成分を除去するために高周波フィルタ３１が高周波アンプ２２の前段に設けられている。
【００４２】
このように予め比較的低い周波数に変換してから第１のイメージリジェクションミキサ３へ入力しているのは、周波数が低い方が信号の位相および振幅の精度を上げやすいからである。そのためチャネル選択フィルタとしての減衰量を大きくしやすいという利点がある。また、高周波で動作するイメージリジェクションミキサを構成した場合、消費電流が大きくなる傾向にあるが、単純な構成の前置ミキサを用いることにより、消費電流を抑えることができる。
【００４３】
【発明の効果】
以上の説明から明らかなように本発明のチャネル選択フィルタによれば、次の効果が得られる。
【００４４】
受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ低い周波数の信号を出力する第１の局部信号源と、前記受信信号と前記第１の局部信号源の出力を入力し前記受信信号成分のうち前記第１の局部信号源周波数より低い周波数成分を抑圧し前記受信信号のうち前記第１の局部信号源周波数より高い周波数成分を第１の中間周波数信号に変換して出力する第１のイメージリジェクションミキサと、前記チャネル周波数間隔と同じ周波数の信号を出力する第２の局部信号源と、前記第１の中間周波数信号と前記第２の局部信号源の出力を入力し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第２の中間周波数信号に変換して出力する第２のイメージリジェクションミキサを備えているため、従来のｇ−ｍｃフィルタなどを用いる場合より大幅に回路規模を低減することができ、消費電流が低減できる。また、半導体ＩＣで構成した場合にチップサイズを小さくすることができるため低コスト化を実現できるという効果がある。
【００４５】
また、第２の中間周波数信号と第２の局部信号源の出力を入力し第２の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第２の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第３の中間周波数信号に変換して出力する第３のイメージリジェクションミキサと、前記第３の中間周波数信号と前記第２の局部信号源の出力を入力し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第３の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第４の中間周波数信号に変換して出力する第４のイメージリジェクションミキサを備えているため、チャネル選択フィルタの帯域外減衰量を大きくすることができるという効果がある。また、イメージリジェクションミキサの段数を５段以上とすることにより、さらに減衰量を大きくすることができるという効果がある。
【００４６】
また、本発明の受信機によれば、次の効果が得られる。
【００４７】
受信信号の希望チャンネル周波数よりチャネル周波数間隔の２分の１だけ低い周波数を出力する第１の局部信号源と、前記受信信号と前記第１の局部信号源の出力を入力し前記受信信号成分のうち前記第１の局部信号源周波数より低い周波数成分を抑圧し前記受信信号のうち前記第１の局部信号源周波数より高い周波数成分を第１の中間周波数信号に変換して出力する第１のイメージリジェクションミキサと、前記チャネル周波数間隔と同じ周波数を出力する第２の局部信号源と、前記第１の中間周波数信号と前記第２の局部信号源の出力を入力し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より高い周波数成分を抑圧し前記第１の中間周波数信号のうち前記第２の局部信号源周波数より低い周波数成分を第２の中間周波数信号に変換して出力する第２のイメージリジェクションミキサと、前記第２のイメージリジェクションミキサの出力を入力し復調を行う復調回路を備えているため、チャンネル選択フィルタ部を低消費電流で小型に構成できるのに加え、イメージ除去のための高周波フィルタや中間周波数フィルタが不要となるため、機器の大幅な小型化と低コスト化を実現できるという効果がある。
【００４８】
また、第１のイメージリジェクションミキサの前段に受信信号を前記受信信号周波数より低い周波数である前置周波数信号に変換する前置ミキサを備え、前記受信信号の代りに前期前置周波数信号を前記第１のイメージリジェクションミキサに入力するため、チャネル選択フィルタとしての減衰量を大きくできるという効果がある。また、高周波部に単純な構成の前置ミキサを用いるので、消費電流を抑えることができるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施例１におけるチャンネル選択フィルタのブロック図
【図２】本発明の実施例１におけるイメージリジェクションミキサのブロック図
【図３】本発明の実施例１におけるイメージリジェクションミキサの出力振幅の周波数特性を示すグラフ
【図４】本発明の実施例２におけるチャンネル選択フィルタのブロック図
【図５】本発明の実施例２におけるイメージリジェクションミキサの出力振幅の周波数特性を示すグラフ
【図６】本発明の実施例３における受信機のブロック図
【図７】本発明の実施例４における受信機のブロック図
【図８】従来の受信機のブロック図
【符号の説明】
３第１のイメージリジェクションミキサ
４第２のイメージリジェクションミキサ
５第１の局部信号源
６第２の局部信号源
７第３のイメージリジェクションミキサ
８第４のイメージリジェクションミキサ
１４ミキサ
１５＋９０度移相器
１６＋４５度移相器
１７ −４５度移相器
１８加算器
２２高周波アンプ
２３復調回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a channel selection filter mainly used for wireless communication devices such as a cordless remote controller, a pager, a cordless telephone, and a mobile phone, and a receiver configured using the channel selection filter.
[0002]
[Prior art]
A conventional channel selection mixer and receiver will be described with reference to the drawings. FIG. 8 is a block diagram showing a configuration of a conventional receiver.
[0003]
In FIG. 8, 5 is a first local signal source, 6 is a second local signal source, 21 is an antenna, 22 is an amplifier, 23 is a demodulation circuit, 24 is a demodulation output terminal, 31 is a high frequency filter, and 41 is an intermediate frequency. A filter, 42 is a channel selection filter, 43 is a first mixer, and 44 is a second mixer. The receiver in FIG. 8 shows a double superheterodyne configuration. The received signal input to the antenna is input to the high frequency filter 31 to remove unnecessary frequency components. Here, the image frequency component when the frequency is converted by the first mixer 43 is removed. The output of the high frequency filter 31 is amplified by the amplifier 22. The output of the amplifier 22 and the output of the first local signal source 5 are mixed by the first mixer 43 and converted into a first intermediate frequency signal. From the first intermediate frequency signal, an image frequency component at the time of mixing in the second mixer 44 is removed by the intermediate frequency filter 41. The output of the intermediate frequency filter 41 and the output of the second local signal source 6 are mixed by the second mixer 44 and converted into a second intermediate frequency signal. The second intermediate frequency signal is input to the channel selection filter 42, and unnecessary components other than the reception channel component are removed. Here, as the channel selection filter 42, a passive element such as a ceramic filter or a crystal filter, or a g-mc filter configured using an active element such as a transistor is used. The output of the channel selection filter 42 is input to the demodulation circuit 23, and the demodulation output is output from the demodulation output terminal 24.
[0004]
[Problems to be solved by the invention]
However, the conventional channel selection filter has problems in miniaturization and power saving. That is, a passive element filter such as a ceramic filter is difficult to be integrated, and thus it is difficult to reduce the size. Further, when a g-mc filter or the like is configured using active elements, there is a problem that current consumption increases in order to realize a steep and high attenuation filter characteristic. Further, even if the number of elements is increased and the semiconductor IC is integrated, the chip size is increased and the cost is increased.
[0005]
The receiver using the channel selection filter as described above has a problem that it is difficult to reduce the size. In addition, there are problems that current consumption is large and cost is high.
[0006]
[Means for Solving the Problems]
In order to solve the conventional problem, a channel selection filter according to the present invention includes a first local signal source that outputs a signal having a frequency that is lower than a desired channel frequency of a received signal by a half of a channel frequency interval, The received signal and the output of the first local signal source are input, and the frequency component lower than the first local signal source frequency is suppressed among the received signal components, and the first local signal source frequency of the received signal is suppressed. A first image rejection mixer that converts a high frequency component into a first intermediate frequency signal and outputs the first intermediate signal; a second local signal source that outputs a signal having the same frequency as the channel frequency interval; and the first intermediate signal source A frequency signal and an output of the second local signal source are input, and a frequency component higher than the second local signal source frequency in the first intermediate frequency signal is suppressed to suppress the first intermediate frequency. Those having a second image rejection mixer for converting the frequency components lower than said second local signal source frequency to a second intermediate frequency signal of several signals.
[0007]
As a result, the circuit scale can be greatly reduced, and current consumption can be reduced. Further, when the semiconductor IC is used, the chip size can be reduced, so that the cost can be reduced.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
  The invention according to claim 1 is a first local signal source that outputs a signal having a frequency lower by a half of a channel frequency interval than a desired channel frequency of the received signal, the received signal, and the first local signal source. Of the received signal component, the frequency component lower than the first local signal source frequency is suppressed, and the frequency component higher than the first local signal source frequency is included in the received signal as the first intermediate frequency signal. A first image rejection mixer that converts and outputs the signal, a second local signal source that outputs a signal having the same frequency as the channel frequency interval, the first intermediate frequency signal, and the second local signal source Of the first intermediate frequency signal, the frequency component higher than the second local signal source frequency is suppressed, and the second local signal source frequency of the first intermediate frequency signal is suppressed. Second image rejection mixer for converting the low frequency component to the second intermediate frequency signalAnd the second intermediate frequency signal and the output of the second local signal source are input to suppress a frequency component higher than the second local signal source frequency in the second intermediate frequency signal to suppress the second intermediate frequency signal. A third image rejection mixer that converts a frequency component lower than the second local signal source frequency of the intermediate frequency signal into a third intermediate frequency signal and outputs the third intermediate frequency signal, the third intermediate frequency signal, and the second intermediate frequency signal Of the third intermediate frequency signal, the frequency component higher than the second local signal source frequency is suppressed, and the second local signal source frequency of the third intermediate frequency signal is suppressed. A fourth image rejection mixer that converts a lower frequency component into a fourth intermediate frequency signal and outputs the fourth intermediate frequency signal, and the second image rejection mixer and the third image rejection Kisa and fourth image rejection mixer is characterized in that an output of the second local signal sources. According to this, the out-of-band attenuation amount of the channel selection filter can be increased by increasing the number of stages of the image rejection mixer.
[0009]
  According to a second aspect of the present invention, there is provided a first local signal source that outputs a signal having a frequency that is higher by a half of a channel frequency interval than a desired channel frequency of the received signal, the received signal, and the first local signal. The output of the source is inputted, the frequency component higher than the first local signal source frequency among the received signal components is suppressed, and the frequency component lower than the first local signal source frequency among the received signals is set to the first intermediate frequency. A first image rejection mixer that converts and outputs a signal; a second local signal source that outputs a signal having the same frequency as the channel frequency interval; the first intermediate frequency signal; and the second local signal. The output of the source is inputted, the frequency component higher than the second local signal source frequency in the first intermediate frequency signal is suppressed, and the second local signal source frequency in the first intermediate frequency signal is suppressed. Second image rejection mixer for converting the lower frequency component to a second intermediate frequency signalAnd the second intermediate frequency signal and the output of the second local signal source are input to suppress a frequency component higher than the second local signal source frequency in the second intermediate frequency signal to suppress the second intermediate frequency signal. A third image rejection mixer that converts a frequency component lower than the second local signal source frequency of the intermediate frequency signal into a third intermediate frequency signal and outputs the third intermediate frequency signal, the third intermediate frequency signal, and the second intermediate frequency signal Of the third intermediate frequency signal, the frequency component higher than the second local signal source frequency is suppressed, and the second local signal source frequency of the third intermediate frequency signal is suppressed. A fourth image rejection mixer that converts a lower frequency component into a fourth intermediate frequency signal and outputs the fourth intermediate frequency signal, and the second image rejection mixer and the third image rejection Kisa and fourth image rejection mixer is characterized in that an output of the second local signal sources. According to this, the out-of-band attenuation amount of the channel selection filter can be increased by increasing the number of stages of the image rejection mixer.
[0011]
  AlsoClaim 3The inventionClaim 1 or 2The receiver includes a channel selection filter and a demodulation circuit that receives the output of the channel selection filter and performs demodulation. In addition, since the channel selection filter is configured with the image rejection mixer, the channel selection filter can be configured in a small size with low current consumption, and a high frequency filter and an intermediate frequency filter are not required. Cost reduction can be realized.
[0012]
  AlsoClaims 4 and 5The invention includes a premixer that converts a received signal into a pre-frequency signal that is lower than the received signal frequency before the first image rejection mixer, and the pre-frequency signal is replaced with the pre-frequency signal instead of the received signal. It is a channel selection filter or receiver that inputs to the first image rejection mixer. Then, by converting the frequency of the received signal to a low frequency in advance, it is easy to increase the accuracy of the image rejection mixer, and it is easy to increase the amount of attenuation as a channel selection filter. Further, current consumption can be suppressed.
[0013]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0014]
Example 1
FIG. 1 is a block diagram showing the configuration of the channel selection filter according to the first embodiment of the present invention. FIG. 2 is a block diagram showing the configuration of an image rejection mixer which is a component of the present invention. FIG. 3 is a graph showing the frequency characteristics of the output signal of the channel selection filter of the present invention. The channel selection filter of this embodiment will be described with reference to FIGS.
[0015]
In FIG. 1, 1 is an input terminal, 2 is an output terminal, 3 is a first image rejection filter, 4 is a second image rejection filter, 5 is a first local signal source, and 6 is a second local signal. Is the source.
[0016]
In FIG. 2, 11 is a received signal input terminal, 12 is an intermediate frequency signal output terminal, 13 is a local signal input terminal, 14 is a mixer, 15 is a +90 degree phase shifter, 16 is a +45 degree phase shifter, and 17 is -45. A phase shifter 18 is an adder.
[0017]
First, the operation of the image rejection mixer of FIG. 2 will be described. The reception signal input to the reception signal input terminal 11 is branched and input to the two mixers 14. The local signal input to the local signal input terminal 13 is branched and input to the two mixers 14. Here, the frequency of the local signal source input to the local signal input terminal 13 is set to be lower by a half of the channel frequency interval than the desired channel frequency of the received signal. The channel frequency interval is determined in advance depending on the frequency band to be used, and is a frequency interval at which channels are arranged. For example, in the 400 MHz band low power radio in Japan, the channel frequency interval is determined to be 12.5 kHz. In this case, the frequency of the local signal source is set 6.25 kHz lower than the desired channel frequency. Hereinafter, the case of this low power radio will be described as an example.
[0018]
The local signals input to the two mixers 14 have a 90-degree phase difference from each other because the + 90-degree phase shifter 15 is inserted in one of the paths.
[0019]
The two mixers 14 mix the received signal and the local signal, respectively, and output a converted signal. One of the converted signals is input to the adder 18 via the +45 degree phase shifter 16. The other is input to the adder 18 via the -45 degree phase shifter 17. A signal obtained by adding the two signals is output from the intermediate frequency signal output terminal 12.
[0020]
In the image rejection mixer having the above configuration, since the local signals orthogonal to each other are input to the two mixers 14, the output signals of the two mixers 14 are also orthogonal to each other. The relative phase is further rotated 90 degrees by the +45 degree phase shifter 16 and the −45 degree phase shifter 17. Here, the components of the received signal whose frequency is higher than the local signal source frequency are in phase with each other at the outputs of the two mixers 14 and are added by the adder 18. Further, components of the received signal having a frequency lower than the local signal source frequency are opposite in phase to each other at the outputs of the two mixers 14 and are canceled and suppressed by the adder 18.
[0021]
In the above description, an adder is used, but the frequency to be suppressed can be changed by using a subtractor. In other words, if a subtracter is used, components of the received signal having a frequency higher than the local signal source frequency are canceled out and suppressed because they have the same phase at the outputs of the two mixers. Further, components of the received signal having a frequency lower than the local signal source frequency are added because the outputs of the two mixers have opposite phases. By using an adder or a subtracter in this way, it is possible to select whether to suppress a component having a frequency higher than the local signal source frequency or to suppress a component having a lower frequency in the received signal.
[0022]
Next, the channel selection filter will be described with reference to FIG.
[0023]
The reception signal input to the reception signal input terminal 1 and the output of the first local signal source 6 are input to the first image rejection mixer 3. Here, the configuration of the first image rejection filter 3 is as shown in FIG. The frequency of the first local signal source 5 is set to be lower than the desired channel frequency by a half of the channel frequency interval. Therefore, a frequency component higher than the first local signal source frequency in the received signal is output as the first intermediate frequency signal in the output of the first image rejection mixer 3 and is lower than the first local signal source frequency. The frequency component is suppressed.
[0024]
At this time, there is a signal component of the desired channel with the center frequency of 6.25 kHz of the first intermediate frequency signal.
[0025]
Next, the output of the first intermediate frequency signal and the second local signal source are input to the second image rejection mixer 4. Here, the second image rejection mixer 4 has the configuration shown in FIG. The frequency of the second local signal source 6 is set to 12.5 kHz which is the same as the channel frequency interval. Therefore, the signal component of the desired channel is converted again into the second intermediate frequency signal which is a signal centered on 6.25 kHz. Then, a frequency component lower than the second local signal source frequency 6 in the first intermediate frequency signal is added and output by the adder, and a frequency component higher than the second local signal source frequency 6 is suppressed.
[0026]
FIG. 3 shows the frequency characteristics of the signal amplitude output to the output terminal 2. In FIG. 3, the horizontal axis represents the frequency, and the vertical axis represents the output amplitude of each frequency based on the output signal amplitude of the desired channel. The band indicated by A in FIG. 3 is the band of the desired channel. The band B is a component suppressed by the first image rejection mixer. The band C is a component suppressed by the second image rejection mixer. In this way, the frequency components on both sides of the desired channel component are suppressed, and the characteristics of the channel selection filter are obtained.
[0027]
In FIG. 3, the suppression amount is 30 dB, but the suppression amount is determined by the accuracy of the first and second image rejection mixers.
[0028]
In the above embodiment, the case where the frequency of the first local signal is lower than the desired channel frequency has been described. However, a configuration in which the frequency is higher than the reception frequency can be adopted. That is, the frequency of the first local signal source is set higher than the desired channel frequency by one half of the channel frequency interval. In this configuration, a subtracter is used instead of the adder of the first image rejection mixer. Thereby, a frequency component lower than the first local signal source frequency in the received signal is output as the first intermediate frequency signal, and a frequency component higher than the first local signal source frequency is suppressed.
[0029]
In order to obtain a steep attenuation characteristic using the conventional g-mc filter, it is necessary to configure a high-order filter, and the circuit scale becomes very large. As in this embodiment, by configuring the image rejection mixer in two stages and obtaining the characteristics of the bandpass filter, it can be configured with a small number of elements, and the circuit scale can be greatly reduced. And current consumption can be reduced. Therefore, there is an advantage that the cost can be reduced since the chip size can be reduced when the semiconductor IC is used.
[0030]
(Example 2)
FIG. 4 is a block diagram illustrating the configuration of the channel selection filter according to the second embodiment of the present invention. In FIG. 4, 7 is a third image rejection mixer, and 8 is a fourth image rejection mixer. Also, the same components as those in FIG. FIG. 5 is a graph showing the frequency characteristics of the output signal of the channel selection filter of the present invention. The channel selection filter of the present embodiment will be described with reference to FIGS.
[0031]
The difference between the present embodiment and the first embodiment is that the attenuation amount of the frequency other than the desired channel frequency is increased by using the third and fourth image rejection filters. That is, the configuration up to the first and second image rejection mixers is the same as that of the second embodiment. In the present embodiment, the third image rejection mixer 7 is disposed after the second image rejection mixer 4. The output of the second image rejection mixer 4 and the output of the second local signal source 6 are input to the third image rejection mixer 7. The movement of the third image rejection mixer 7 is the same as that of the second image rejection mixer 4 described in the first embodiment. Further, the third intermediate frequency signal that is the output of the third image rejection mixer 7 and the output of the second local signal source are input to the fourth image rejection mixer 8. The movement of the fourth image rejection mixer 8 is the same as that of the second and third image rejection mixers. A fourth intermediate frequency signal is obtained as an output of the fourth image rejection mixer 8.
[0032]
FIG. 5 shows the frequency characteristics of the signal amplitude output to the output terminal 2.
[0033]
The band indicated by A in FIG. 5 is the band of the desired channel. B is a component suppressed by the first image rejection mixer. C is a component suppressed by the second image rejection mixer. D is a component suppressed by the third image rejection mixer. E is a component suppressed by the fourth image rejection mixer. As described above, by providing the third and fourth image rejection mixers, it is possible to increase the attenuation amount of the component of the channel frequency that is distant from the adjacent channel. In FIG. 5, the attenuation amount of the adjacent channel is 30 dB, and the attenuation of the adjacent channel or more is 60 dB. Here, the amount of attenuation is determined by the accuracy of the phase and amplitude of each image rejection mixer.
[0034]
In the present embodiment, similarly to the first embodiment, the first local signal source frequency can be set lower or higher than the desired channel frequency. An adder is used for the first image rejection mixer when set low, and a subtractor is used for the first image rejection mixer when set high.
[0035]
Thus, by configuring the image rejection mixer in four stages, the out-of-band attenuation of the channel selection filter can be increased.
[0036]
In this embodiment, the number of stages of the image rejection mixer is four, but the attenuation can be further increased by using five or more stages.
[0037]
(Example 3)
FIG. 6 is a block diagram showing the configuration of the receiver according to the third embodiment of the present invention. In FIG. 6, 21 is an antenna, 22 is an amplifier, 23 is a demodulation circuit, and 24 is a demodulation output terminal. Also, the same components as those shown in FIGS.
[0038]
The received signal input to the antenna 21 is amplified by the amplifier 22. The output of the amplifier 22 and the output of the first local signal source 5 are input to the first image rejection mixer 3. Then, the first intermediate frequency signal that is the output of the first image rejection mixer 3 and the output of the second local signal source are input to the second image rejection mixer 4. Here, the frequencies of the first and second local signal sources 5 and 6 are set in the same manner as in the first and second embodiments. Then, the second intermediate frequency signal that is the output of the second image rejection mixer 4 is input to the demodulation circuit 23, and the demodulation output is output from the demodulation output terminal 24.
[0039]
As described above, in the receiver of this embodiment, the channel selection filter can be configured in a small size with low current consumption, and the high frequency filter and the intermediate frequency filter used for image removal in the conventional receiver are unnecessary. As a result, the device can be significantly reduced in size and cost.
[0040]
Example 4
FIG. 7 is a block diagram illustrating a configuration of a receiver according to the fourth embodiment of the present invention. In FIG. 7, 31 is a high frequency filter, 32 is a premixer, and 33 is a prelocal signal source. Also, the same components as those in FIG.
[0041]
The difference between the present embodiment and the third embodiment is that a premixer 32 is provided. A pre-mixer 32 is provided between the high-frequency amplifier 22 and the first image rejection mixer 3, and the received signal is, for example, a pre-frequency having a relatively low frequency such as 20 MHz when the frequency of the received signal is 400 MHz. Has been converted. Here, a high frequency filter 31 is provided in front of the high frequency amplifier 22 in order to remove the image frequency component in the premixer 32.
[0042]
The reason why the signal is converted to a relatively low frequency in advance and then input to the first image rejection mixer 3 is that the lower the frequency, the higher the accuracy of the phase and amplitude of the signal. Therefore, there is an advantage that the attenuation as the channel selection filter can be easily increased. Further, when an image rejection mixer that operates at a high frequency is configured, the current consumption tends to increase. However, the current consumption can be suppressed by using a pre-mixer having a simple configuration.
[0043]
【The invention's effect】
As apparent from the above description, the channel selection filter of the present invention provides the following effects.
[0044]
A first local signal source for outputting a signal having a frequency lower than a desired channel frequency of the received signal by a half of a channel frequency interval; and an input of the received signal and the output of the first local signal source. A frequency component lower than the first local signal source frequency is suppressed from among the components, and a frequency component higher than the first local signal source frequency is converted into a first intermediate frequency signal and output from the received signal. An image rejection mixer, a second local signal source that outputs a signal having the same frequency as the channel frequency interval, an output of the first intermediate frequency signal and the second local signal source, and the first The frequency component higher than the second local signal source frequency in the intermediate frequency signal is suppressed, and the frequency component lower than the second local signal source frequency in the first intermediate frequency signal is second. Due to the provision of a second image rejection mixer for converting an intermediate frequency signal, it is possible to significantly reduce the circuit scale than with such conventional g-mc filter, the current consumption can be reduced. Further, when the semiconductor IC is used, the chip size can be reduced, so that the cost can be reduced.
[0045]
Further, the second intermediate frequency signal and the output of the second local signal source are input, and the second intermediate frequency signal is suppressed by suppressing a frequency component higher than the second local signal source frequency in the second intermediate frequency signal. A third image rejection mixer that converts a frequency component lower than the second local signal source frequency into a third intermediate frequency signal and outputs the third intermediate frequency signal, and the third intermediate frequency signal and the second local signal. A frequency output higher than the second local signal source frequency in the third intermediate frequency signal is suppressed, and a frequency lower than the second local signal source frequency in the third intermediate frequency signal is input. Since the fourth image rejection mixer that converts the component into the fourth intermediate frequency signal and outputs the fourth intermediate frequency signal is provided, the effect of increasing the out-of-band attenuation of the channel selection filter can be obtained. That. In addition, by setting the number of stages of the image rejection mixer to five or more, there is an effect that the amount of attenuation can be further increased.
[0046]
Further, according to the receiver of the present invention, the following effects can be obtained.
[0047]
A first local signal source that outputs a frequency that is one-half of the channel frequency interval lower than the desired channel frequency of the received signal, and an input of the received signal and the output of the first local signal source. A first image in which a frequency component lower than the first local signal source frequency is suppressed and a frequency component higher than the first local signal source frequency in the received signal is converted into a first intermediate frequency signal and output. A rejection mixer; a second local signal source that outputs the same frequency as the channel frequency interval; and an input of the first intermediate frequency signal and the output of the second local signal source to input the first intermediate frequency signal The frequency component higher than the second local signal source frequency is suppressed, and the frequency component lower than the second local signal source frequency of the first intermediate frequency signal is suppressed to the second intermediate frequency. Since the second image rejection mixer that converts the signal into a signal and outputs the signal and the demodulation circuit that inputs and demodulates the output of the second image rejection mixer, the channel selection filter unit can be reduced in size with low current consumption. In addition, the high frequency filter and the intermediate frequency filter for removing the image are not necessary, so that the device can be significantly reduced in size and cost.
[0048]
In addition, a premixer that converts a received signal into a prefrequency signal that is a frequency lower than the received signal frequency is provided in a previous stage of the first image rejection mixer. Since it is input to the first image rejection mixer, there is an effect that the attenuation amount as the channel selection filter can be increased. In addition, since a pre-mixer having a simple configuration is used for the high-frequency part, there is an effect that current consumption can be suppressed.
[Brief description of the drawings]
FIG. 1 is a block diagram of a channel selection filter in Embodiment 1 of the present invention.
FIG. 2 is a block diagram of an image rejection mixer according to the first embodiment of the present invention.
FIG. 3 is a graph showing frequency characteristics of output amplitude of the image rejection mixer according to the first embodiment of the present invention.
FIG. 4 is a block diagram of a channel selection filter in Embodiment 2 of the present invention.
FIG. 5 is a graph showing frequency characteristics of output amplitude of the image rejection mixer according to the second embodiment of the present invention.
FIG. 6 is a block diagram of a receiver according to a third embodiment of the present invention.
FIG. 7 is a block diagram of a receiver according to a fourth embodiment of the present invention.
FIG. 8 is a block diagram of a conventional receiver.
[Explanation of symbols]
3 First image rejection mixer
4 Second image rejection mixer
5 First local signal source
6 Second local signal source
7 Third image rejection mixer
8 Fourth image rejection mixer
14 Mixer
15 +90 degree phase shifter
16 +45 degree phase shifter
17-45 degree phase shifter
18 Adder
22 High frequency amplifier
23 Demodulator

Claims

A first local signal source that outputs a signal having a frequency that is one-half the channel frequency interval lower than the desired channel frequency of the received signal;
The received signal and the output of the first local signal source are input, and a frequency component lower than the first local signal source frequency is suppressed among the received signal components, and the first local signal source frequency of the received signal is suppressed. A first image rejection mixer that converts a higher frequency component into a first intermediate frequency signal and outputs the first intermediate frequency signal;
A second local signal source that outputs a signal having the same frequency as the channel frequency interval;
The first intermediate frequency signal and the output of the second local signal source are input, and a frequency component higher than the second local signal source frequency is suppressed in the first intermediate frequency signal, and the first intermediate frequency is suppressed. A second image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a second intermediate frequency signal and outputs the second intermediate frequency signal ;
The second intermediate frequency signal and the output of the second local signal source are input, and a frequency component higher than the second local signal source frequency is suppressed in the second intermediate frequency signal, and the second intermediate frequency is suppressed. A third image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a third intermediate frequency signal and outputs the third intermediate frequency signal;
The third intermediate frequency signal and the output of the second local signal source are input to suppress a frequency component higher than the second local signal source frequency in the third intermediate frequency signal to suppress the third intermediate frequency. A fourth image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a fourth intermediate frequency signal and outputs the fourth intermediate frequency signal;
The channel selection filter, wherein the second image rejection mixer, the third image rejection mixer, and the fourth image rejection mixer input an output of the second local signal source .

A first local signal source that outputs a signal having a frequency that is one-half the channel frequency interval higher than the desired channel frequency of the received signal;
The received signal and the output of the first local signal source are input, and a frequency component higher than the first local signal source frequency is suppressed among the received signal components, and the first local signal source frequency of the received signal is suppressed. A first image rejection mixer that converts a lower frequency component into a first intermediate frequency signal and outputs the first intermediate frequency signal;
A second local signal source that outputs a signal having the same frequency as the channel frequency interval;
The first intermediate frequency signal and the output of the second local signal source are input, and a frequency component higher than the second local signal source frequency is suppressed in the first intermediate frequency signal, and the first intermediate frequency is suppressed. A second image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a second intermediate frequency signal and outputs the second intermediate frequency signal ;
The second intermediate frequency signal and the output of the second local signal source are input, and a frequency component higher than the second local signal source frequency is suppressed in the second intermediate frequency signal, and the second intermediate frequency is suppressed. A third image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a third intermediate frequency signal and outputs the third intermediate frequency signal;
The third intermediate frequency signal and the output of the second local signal source are input to suppress a frequency component higher than the second local signal source frequency in the third intermediate frequency signal to suppress the third intermediate frequency. A fourth image rejection mixer that converts a frequency component lower than the second local signal source frequency of the signal into a fourth intermediate frequency signal and outputs the fourth intermediate frequency signal;
The channel selection filter, wherein the second image rejection mixer, the third image rejection mixer, and the fourth image rejection mixer input an output of the second local signal source .

3. A receiver comprising: the channel selection filter according to claim 1; and a demodulation circuit that receives the output of the channel selection filter and performs demodulation.

A pre-mixer that converts a received signal into a pre-frequency signal that is lower in frequency than the received signal frequency before the first image rejection mixer, and the holistic frequency signal is replaced with the first frequency signal instead of the received signal; The receiver according to claim 3, wherein the receiver is input to an image rejection mixer.

A premixer that converts a received signal into a pre-frequency signal that is a frequency lower than the received signal frequency is provided in a stage preceding the first image rejection mixer, and the first pre-frequency signal is used instead of the received signal. The channel selection filter according to claim 1, wherein the channel selection filter is input to the image rejection mixer.