JP2005033247A - Digital signal receiver - Google Patents

Digital signal receiver Download PDF

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Publication number
JP2005033247A
JP2005033247A JP2003192654A JP2003192654A JP2005033247A JP 2005033247 A JP2005033247 A JP 2005033247A JP 2003192654 A JP2003192654 A JP 2003192654A JP 2003192654 A JP2003192654 A JP 2003192654A JP 2005033247 A JP2005033247 A JP 2005033247A
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JP
Japan
Prior art keywords
signal
amplifier
gain
mixer
rfagc
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2003192654A
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Japanese (ja)
Inventor
Masami Takigawa
雅巳 瀧川
Hiroaki Ozeki
浩明 尾関
Hideki Ouchi
英樹 大内
Akira Ito
明 伊藤
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Panasonic Holdings Corp
Original Assignee
Matsushita Electric Industrial Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Matsushita Electric Industrial Co Ltd filed Critical Matsushita Electric Industrial Co Ltd
Priority to JP2003192654A priority Critical patent/JP2005033247A/en
Priority to CNB200480000701XA priority patent/CN100411311C/en
Priority to PCT/JP2004/009294 priority patent/WO2005004341A1/en
Publication of JP2005033247A publication Critical patent/JP2005033247A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03G—CONTROL OF AMPLIFICATION
    • H03G3/00—Gain control in amplifiers or frequency changers without distortion of the input signal
    • H03G3/20—Automatic control
    • H03G3/30—Automatic control in amplifiers having semiconductor devices
    • H03G3/3052—Automatic control in amplifiers having semiconductor devices in bandpass amplifiers (H.F. or I.F.) or in frequency-changers used in a (super)heterodyne receiver
    • H03G3/3068—Circuits generating control signals for both R.F. and I.F. stages

Abstract

<P>PROBLEM TO BE SOLVED: To enable stably receiving of digital broadcast signals. <P>SOLUTION: To achieve the above purpose, this receiver is provided with a tuner 1 having a terminal 1a and an RFAGC amplifier, a filter 2, an IFAGC amplifier 3 for amplifying the signal having passed through this filter 2, a mixer 4 for converting the signal amplified by this IFAGC amplifier 3 into a signal having lower frequency, a local oscillator 5, a demodulator 6, a level detector 7 for detecting the level of an output signal of the mixer 4, a gain controller 9 for receiving the signal from the level detector 7 and independently controlling a gain of the RFAGC amplifier and a gain of the IFAGC amplifier 3, and a microcomputer 10 for receiving a signal from the level detector 7 and outputting channel selecting data of a target channel to the tuner 1 by a channel selecting command outputted from a host system 11 and a signal of reproduction transmission hierarchy. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、デジタル変調された放送信号を受信するデジタル信号受信機に関するものである。
【０００２】
【従来の技術】
近年、テレビジョン放送のデジタル化が進みつつある。このデジタル化された放送信号は、様々な変調方式により変調された放送信号が多重化されている。これにより、１チャネルで複数の番組を送信することができる。
【０００３】
このデジタル化された放送信号を受信する受信機としては、シングルチューナと呼ばれるものがある。このシングルチューナは一つの局部発振器を有しており、これを用いて前記放送信号である高周波信号（以下ＲＦ信号と記す）を中間周波数信号（以下ＩＦ信号と記す）に変換している。シングルチューナの利点は、二つの局部発振器を有するダブルチューナと異なり二つの局部発振器から漏洩する位相雑音は発生せず、それ故受信信号のビット誤り率を劣化させることがない。つまり、前記位相雑音による受信妨害が起きないという点である。
【０００４】
なお、この出願の発明に関連する先行技術文献情報としては、例えば、特許文献１が知られている。
【０００５】
【特許文献１】
特開平９−１０７３０４号公報
【０００６】
【発明が解決しようとする課題】
一方、放送信号においては周波数の比較的近いところに、受信信号レベルと同等もしくはそれ以上の強度の放送信号（隣接チャネル信号）が現れることが多くなってきた。そのためこの隣接チャネル信号からの妨害特性（混変調特性）が安定とならず、その結果、デジタル放送信号を安定して受信しにくいという問題があった。
【０００７】
そこで本発明は、デジタル放送信号を安定して受信することを目的とする。
【０００８】
【課題を解決するための手段】
この目的を達成するために本発明の請求項１に記載の発明は、特に、レベル検出器からの信号が入力されるとともにＲＦＡＧＣ増幅器およびＩＦＡＧＣ増幅器の利得をそれぞれ独立して制御する利得制御器と、前記レベル検出器からの信号が入力されるとともにホストシステムから出力されたチャネル選局指令および再生伝送階層の信号によりチューナに目的チャネルの選局データを出力するマイコンとを備えたものであり、以上の構成により受信信号の隣接妨害特性カーブを受信電界強度値からみて最適領域に移動させることができ、その結果、デジタル放送信号を安定して受信することができるという作用を有する。
【０００９】
請求項２に記載の発明は、特に、マイコンは、利得制御器を介した利得制御においてＲＦＡＧＣ増幅器の利得制御を開始する動作開始点にてＩＦＡＧＣ増幅器の利得が一定になるようにしかつ前記ＲＦＡＧＣ増幅器の利得制御を開始する動作開始点を任意に設定するとしたものであり、請求項１と同様の効果を有する。
【００１０】
請求項３に記載の発明は、特に、マイコンは、利得制御器を介した利得制御において目的チャンネル選択時ＲＦＡＧＣ増幅器の利得制御を開始する動作開始点を一定値としたものであり、請求項１と同様の効果を有する。
【００１１】
請求項４に記載の発明は、特に、マイコンは、利得制御器を介した利得制御においてレベル検出器で検出されるレベル信号に応じた制御を行うとしたものであり、請求項１と同様の効果を有する。
【００１２】
請求項５に記載の発明は、特に、変調状態検出器を設けたものであり、これにより安定して受信することができる。すなわち、前記変調状態検出器により受信信号の変調方式に応じた利得制御を行うことができるので、変調方式に関係なく安定して受信することができるという効果を有する。
【００１３】
請求項６に記載の発明は、特に、マイコンは、ＲＦＡＧＣ増幅器の利得制御の動作開始点を変調状態検出器からの出力信号に応じて設定するとしたものであり、請求項５と同様の効果を有する。
【００１４】
請求項７に記載の発明は、特に、マイコンは、ＲＦＡＧＣ増幅器の利得制御の動作開始点を目的チャネルの周波数に応じて設定するとしたものであり、請求項５と同様の効果を有する。
【００１５】
【発明の実施の形態】
以下、本発明のデジタル信号受信機について実施の形態および図面を用いて説明する。
【００１６】
（実施の形態１）
本実施の形態１および図１〜図３を用いて特に、請求項１〜４に記載の発明を説明する。
【００１７】
図１は本実施の形態１におけるデジタル信号受信機のブロック図である。
【００１８】
ホストシステム１１からの選局指令によりマイコン１０はチューナ１にチャネル選局データを設定する。チューナ１には受信信号を入力するための端子１ａが設けられており、アンテナ（図示せず）等から入力された受信信号はこの端子を介してチューナ１に内蔵されたＲＦＡＧＣ増幅器（図示せず）に入力される。この受信信号はチューナ１により目的とするチャネルが選択され、フィルタ２、ＩＦＡＧＣ増幅器３，ミキサ４を経て復調器６に入力され、この復調器６でデジタル復調され、復調された信号が再生データとしてホストシステム１１に出力される。なお、前記ミキサ４には局部発振器５が接続されており、前記ＩＦＡＧＣ増幅器３にて増幅されたＩＦ信号と、前記局部発振器５から出力される一定の周波数信号とを前記ミキサ４にて混合している。復調器６に入力する信号のレベルをレベル検出器７が検出しこの検出データを利得制御器９とマイコン１０に入力する。このマイコン１０により利得制御器９はＩＦＡＧＣ増幅器３の利得を一定に保持し、ＲＦＡＧＣ増幅器の利得制御の動作開始点（以下ディレイポイントと記す）が設定される。これによりＲＦＡＧＣ増幅器とＩＦＡＧＣ増幅器３の利得配分が決定される。すなわち復調器６への入力レベルを一定に保つようにレベル検出器７、利得制御器９を介したＡＧＣループでＲＦＡＧＣ増幅器の利得量が制御される。これについて図２を用いてさらに説明する。図２はディレイポイントが−７０ｄＢｍ、受信信号の電界強度が−５０ｄＢｍの場合の入力電界強度対ＡＧＣ利得減衰量の関係図である。ＩＦＡＧＣ利得減衰量はディレイポイント（−７０ｄＢｍ）で一定値となり、このディレイポイントにより高電界強度側に対してはＲＦＡＧＣ利得減衰がかかることで前記ＡＧＣループが作用する。
【００１９】
ここで例えば図３（ａ）に示すように、前記ディレイポイントをより弱電界方向に設定するとＩＦＡＧＣ利得がより多くなり（ＩＦＡＧＣ利得減衰量が低下）、ＲＦＡＧＣ利得がより少なく（ＲＦＡＧＣ利得減衰量が増加）なるゲイン配分となる。逆に図３（ｂ）に示すようにディレイポイントをより強電界方向に設定するとＩＦＡＧＣ利得がより少なくなり、ＲＦＡＧＣ利得がより多くなるゲイン配分となる。このディレイポイントを設定出来る範囲は受信機のシステムを組む上で決まる。強電界方向の上限値はＩＦＡＧＣ利得減衰量により決まる。目的チャネル選択時には、ディレイポイントを強電界方向の上限値に設定し選局を行う。このディレイポイントの設定は、前段のＲＦＡＧＣ増幅器の利得を後段のＩＦＡＧＣ増幅器の利得に比べ大きく設定しており、雑音（Ｃ／Ｎ）妨害に有利な受信機特性でありこの特性として選局を行う。
【００２０】
マイコン１０はレベル検出器７で検出されるレベル信号を読み取ることにより受信電界強度（ＲＦＡＧＣ、ＩＦＡＧＣ利得減衰量）を検知することができる。図４は、入力電界強度対ＡＧＣ利得減衰量の関係図にチューナの隣接妨害特性を示した図である。図４に示すように、受信電界強度が隣接妨害特性カーブの良化ピーク点（図４のＡ）からずれている場合（図４のＢ）、ディレイポイントを弱電界方向に移動することにより、チューナ１の隣接妨害特性カーブをずらせて隣接妨害特性が良化する領域に合わせることができる。すなわち隣接妨害特性カーブをずらすことにより、受信電界強度を図４のＢから同図のＣへ移動したことになり、移動後の隣接妨害特性カーブの良化ピーク点（同図のＤ）に近づけることができる。このように本発明は、適応的に受信電界強度を隣接妨害特性の良化領域に合わせることができ、その結果、安定してデジタル地上波放送を受信することができる。
【００２１】
（実施の形態２）
次に本実施の形態２および図５を用いて特に、請求項５，６について説明する。図５は図１のブロック図に伝送階層毎の変調方式を検出する変調状態検出器８を設けこの変調状態検出器８の出力をマイコン１０に入力する構成としたデジタル信号受信機のブロック図である。デジタル地上波放送のチャネル中には複数の伝送階層が異なった変調方式で変調されており、ホストシステム１１にて階層分離されその中のある階層が選択されて再生される。変調方式が異なると所要Ｃ／Ｎが異なるのでＱＰＳＫ方式、１６ＱＡＭ方式、６４ＱＡＭ方式の順により多値化された変調方式となるにつれて所要Ｃ／Ｎレベルが高くなる。ディレイポイントをより強電界方向に設定するとＣ／Ｎ雑音特性に有利な受信機状態となる。受信機は変調方式に応じて所要Ｃ／Ｎを満たす受信特性を得ることが必要である。したがって変調方式に応じて所要Ｃ／Ｎを得るためのディレイポイント設定値が変わってくる。具体例を図６に示す。図６は、入力電界強度対ＡＧＣ利得減衰量の関係図に変調方式に応じたディレイポイント設定値の一例を示したものである。図６に示すように前述のＱＰＳＫ方式、１６ＱＡＭ方式、６４ＱＡＭ方式の順に、所要Ｃ／Ｎを得るためのディレイポイント設定値は強電界方向に向かう設定値となる。このように変調方式に応じて所要Ｃ／Ｎを得られるように、ディレイポイント設定を切り換える構成とすることにより隣接妨害特性に対する特性を高めることができる。
【００２２】
（実施の形態３）
次に本実施の形態３および図７、図８を用いて特に、請求項７について説明する。移動しながらデジタル地上波放送を受信するという用途が今後更に広がることが考えられる。移動しながら受信する場合特有のフェージング妨害が発生する。このフェージング妨害の量は一般的にドップラ周波数で表され、ドップラ周波数が高いほど妨害程度が多い。
【００２３】
ここで移動速度をＶｓ（ｋｍ／ｈ）、受信チャネル周波数をＦｃｈ（ＭＨｚ）、ドップラ周波数をＦｄｏｐｐ（Ｈｚ）とすると以下式が成り立つ。
【００２４】
【数１】

Figure 2005033247
ここで（数１）の分母は１時間当たりの光速（ｍ／ｈ）である。
【００２５】
（数１）より受信チャネル周波数Ｆｃｈが高いほど、また移動速度Ｖｓが速いほどドップラ周波数Ｆｄｏｐｐが大きくなる。すなわちフェージング妨害の影響が大きくなることが判る。この関係を図７に示す。なお同等資料は社団法人電波産業会資料「規格番号ＡＲＩＢ ＳＴＤ−Ｂ２９（標準規格名 地上デジタル音声放送の伝送方式）」にも掲載されている。フェージングによる妨害波は希望波に対して、位相・振幅成分の妨害を与えており雑音としての妨害を与える事と等価である。従って受信機特性としてディレイポイントを強電界方向に設定することでフェージング妨害に対して有利な状態となる。移動受信を想定する上で、移動速度Ｖｓを例えば１００ｋｍ／ｈと想定した場合発生するドップラ周波数Ｆｄｏｐｐは受信チャネルにより異なる。これは受信チャネル周波数Ｆｃｈに応じて所要ドップラ周波数Ｆｄｏｐｐを満たすためのディレイポイントの設定値が変わってくることを示している。
【００２６】
ここで図８に受信チャネル周波数に応じたディレイポイント設定値の一例を示す。図８に示すように低周波数から高周波数になるに従い所要ドップラ周波数Ｆｄｏｐｐを得るためのディレイポイントの設定値は強電界方向の設定値となる。このように受信周波数に従ったディレイポイントを設定することで、各周波数のチャネル受信時の隣接妨害特性に対する特性を高める構成とすることができる。
【００２７】
なお本実施の形態ではチューナや復調部など受信機フロントエンドを例示して説明したが、本発明はこれに限定されることなくデータ再生部や表示部まで含んだセットトップボックス、テレビジョンシステム、移動受信システム、車載システムにも適用できるものである。
【００２８】
【発明の効果】
以上のように本発明は、受信信号を入力するための端子と、この端子から入力された前記受信信号を増幅するＲＦＡＧＣ増幅器を有しこのＲＦＡＧＣ増幅器によって増幅された受信信号から目的チャネルの受信信号を選択し中間周波数信号に変換するチューナと、前記中間周波数信号を選択的に通過させるフィルタと、このフィルタを通過した信号を増幅するＩＦＡＧＣ増幅器と、このＩＦＡＧＣ増幅器によって増幅された信号をその信号の周波数より低い周波数の信号に変換するミキサと、このミキサへ入力する局部発振周波数信号を発生する局部発振器と、前記ミキサより出力された出力信号をデジタル復調しホストシステムへ出力する復調器と、前記出力信号のレベルを検出するレベル検出器と、このレベル検出器からの信号が入力されるとともに前記ＲＦＡＧＣ増幅器および前記ＩＦＡＧＣ増幅器の利得をそれぞれ独立して制御する利得制御器と、前記レベル検出器からの信号が入力されるとともに前記ホストシステムから出力されたチャネル選局指令および再生伝送階層の信号により前記チューナに目的チャネルの選局データを出力するマイコンとを備えたものであり、以上の構成により受信信号の隣接妨害特性カーブを受信電界強度値からみて最適領域に移動させることができ、その結果、デジタル放送信号を安定して受信することができるという作用を有する。
【図面の簡単な説明】
【図１】本発明の実施の形態１のデジタル信号受信機の構成を示すブロック図
【図２】入力電界強度対ＡＧＣ利得減衰量の関係図
【図３】（ａ）（ｂ）ともに入力電界強度対ＡＧＣ利得減衰量の関係図
【図４】チューナの隣接妨害特性を示した入力電界強度対ＡＧＣ利得減衰量の関係図
【図５】本発明の実施の形態２のデジタル信号受信機の構成を示すブロック図
【図６】変調方式に応じたディレイポイント設定値の一例を示した入力電界強度対ＡＧＣ利得減衰量の関係図
【図７】移動速度とドップラ周波数の相関図
【図８】受信チャネル周波数に応じたディレイポイント設定値の一例を示した入力電界強度対ＡＧＣ利得減衰量の関係図
【符号の説明】
１ チューナ
１ａ 端子
２ フィルタ
３ ＩＦＡＧＣ増幅器
４ ミキサ
５ 局部発振器
６ 復調器
７ レベル検出器
８ 変調状態検出器
９ 利得制御器
１０ マイコン
１１ ホストシステム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital signal receiver for receiving a digitally modulated broadcast signal.
[0002]
[Prior art]
In recent years, digitalization of television broadcasting has been progressing. The digitized broadcast signal is multiplexed with a broadcast signal modulated by various modulation methods. Thereby, a plurality of programs can be transmitted by one channel.
[0003]
As a receiver that receives this digitized broadcast signal, there is a so-called single tuner. This single tuner has one local oscillator, and uses this to convert a high-frequency signal (hereinafter referred to as an RF signal), which is the broadcast signal, into an intermediate frequency signal (hereinafter referred to as an IF signal). The advantage of the single tuner is that, unlike a double tuner having two local oscillators, phase noise leaking from the two local oscillators is not generated, and therefore the bit error rate of the received signal is not deteriorated. That is, reception interference due to the phase noise does not occur.
[0004]
As prior art document information related to the invention of this application, for example, Patent Document 1 is known.
[0005]
[Patent Document 1]
JP-A-9-107304 [0006]
[Problems to be solved by the invention]
On the other hand, in broadcast signals, broadcast signals (adjacent channel signals) having an intensity equal to or higher than the received signal level often appear at relatively close frequencies. Therefore, the disturbance characteristic (cross modulation characteristic) from the adjacent channel signal is not stable, and as a result, there is a problem that it is difficult to stably receive the digital broadcast signal.
[0007]
Therefore, an object of the present invention is to stably receive a digital broadcast signal.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 of the present invention, in particular, includes a gain controller for receiving a signal from a level detector and independently controlling the gains of the RFAGC amplifier and the IFAGC amplifier. And a microcomputer that outputs the channel selection data of the target channel to the tuner in response to the channel selection command and the reproduction transmission layer signal output from the host system as the signal from the level detector is input, With the above configuration, the adjacent disturbance characteristic curve of the received signal can be moved to the optimum region as seen from the received electric field strength value, and as a result, the digital broadcast signal can be stably received.
[0009]
According to a second aspect of the present invention, in particular, the microcomputer makes the gain of the IFAGC amplifier constant at an operation start point at which gain control of the RFAGC amplifier is started in gain control via the gain controller, and the RFAGC amplifier. The operation starting point for starting the gain control is arbitrarily set, and the same effect as in the first aspect is obtained.
[0010]
In the invention described in claim 3, in particular, the microcomputer sets the operation start point for starting the gain control of the RFAGC amplifier when the target channel is selected in the gain control via the gain controller as a constant value. Has the same effect.
[0011]
In the invention described in claim 4, in particular, the microcomputer performs control according to the level signal detected by the level detector in the gain control via the gain controller. Has an effect.
[0012]
The invention described in claim 5 is particularly provided with a modulation state detector, whereby stable reception is possible. That is, since the gain control according to the modulation method of the received signal can be performed by the modulation state detector, there is an effect that the signal can be stably received regardless of the modulation method.
[0013]
In the invention described in claim 6, in particular, the microcomputer sets the operation start point of the gain control of the RFAGC amplifier in accordance with the output signal from the modulation state detector. Have.
[0014]
According to the seventh aspect of the present invention, in particular, the microcomputer sets the operation start point of the gain control of the RFAGC amplifier according to the frequency of the target channel, and has the same effect as the fifth aspect.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a digital signal receiver according to the present invention will be described with reference to embodiments and drawings.
[0016]
(Embodiment 1)
In particular, the invention described in claims 1 to 4 will be described with reference to the first embodiment and FIGS.
[0017]
FIG. 1 is a block diagram of a digital signal receiver according to the first embodiment.
[0018]
In response to a channel selection command from the host system 11, the microcomputer 10 sets channel selection data in the tuner 1. The tuner 1 is provided with a terminal 1a for inputting a received signal, and a received signal input from an antenna (not shown) or the like is an RFAGC amplifier (not shown) built in the tuner 1 through this terminal. ). A target channel of the received signal is selected by the tuner 1 and is input to the demodulator 6 through the filter 2, the IFAGC amplifier 3 and the mixer 4, and is digitally demodulated by the demodulator 6. It is output to the host system 11. A local oscillator 5 is connected to the mixer 4, and the IF signal amplified by the IFAGC amplifier 3 and a constant frequency signal output from the local oscillator 5 are mixed by the mixer 4. ing. The level detector 7 detects the level of the signal input to the demodulator 6 and inputs the detected data to the gain controller 9 and the microcomputer 10. By this microcomputer 10, the gain controller 9 keeps the gain of the IFAGC amplifier 3 constant, and an operation start point (hereinafter referred to as a delay point) of gain control of the RFAGC amplifier is set. Thereby, the gain distribution between the RFAGC amplifier and the IFAGC amplifier 3 is determined. That is, the gain of the RFAGC amplifier is controlled by an AGC loop through the level detector 7 and the gain controller 9 so as to keep the input level to the demodulator 6 constant. This will be further described with reference to FIG. FIG. 2 is a graph showing the relationship between input electric field strength and AGC gain attenuation when the delay point is -70 dBm and the electric field strength of the received signal is -50 dBm. The IFAGC gain attenuation amount becomes a constant value at the delay point (−70 dBm), and the AGC loop acts by applying the RFAGC gain attenuation to the high electric field strength side by this delay point.
[0019]
Here, for example, as shown in FIG. 3A, if the delay point is set to a weaker electric field direction, the IFAGC gain increases (IFAGC gain attenuation decreases) and the RFAGC gain decreases (RFAGC gain attenuation decreases). Increase) gain distribution. On the contrary, as shown in FIG. 3B, when the delay point is set in the direction of a stronger electric field, the IFAGC gain becomes smaller and the RFAGC gain becomes larger. The range in which this delay point can be set is determined when the receiver system is built. The upper limit value in the direction of the strong electric field is determined by the IFAGC gain attenuation amount. When selecting the target channel, the delay point is set to the upper limit value in the direction of the strong electric field and the channel is selected. In this delay point setting, the gain of the RFAGC amplifier at the front stage is set larger than the gain of the IFAGC amplifier at the rear stage, and this is a receiver characteristic advantageous for noise (C / N) interference, and tuning is performed as this characteristic. .
[0020]
The microcomputer 10 can detect the received electric field strength (RFAGC, IFAGC gain attenuation) by reading the level signal detected by the level detector 7. FIG. 4 is a diagram showing the adjacent disturbance characteristic of the tuner in the relational diagram of the input electric field strength versus the AGC gain attenuation. As shown in FIG. 4, when the received electric field strength is deviated from the improved peak point (A in FIG. 4) of the adjacent disturbance characteristic curve (B in FIG. 4), by moving the delay point in the weak electric field direction, The adjacent disturbance characteristic curve of the tuner 1 can be shifted to match the region where the adjacent disturbance characteristic is improved. That is, by shifting the adjacent disturbance characteristic curve, the received electric field intensity is moved from B in FIG. 4 to C in the same figure, and approaches the improved peak point (D in the same figure) of the adjacent disturbance characteristic curve after the movement. be able to. As described above, the present invention can adaptively adjust the received electric field intensity to the improved region of the adjacent disturbance characteristic, and as a result, can stably receive the digital terrestrial broadcast.
[0021]
(Embodiment 2)
Next, claims 5 and 6 will be described in particular with reference to the second embodiment and FIG. FIG. 5 is a block diagram of a digital signal receiver in which the modulation state detector 8 for detecting the modulation method for each transmission layer is provided in the block diagram of FIG. 1 and the output of the modulation state detector 8 is input to the microcomputer 10. is there. In a digital terrestrial broadcast channel, a plurality of transmission layers are modulated by different modulation schemes, and the host system 11 separates the layers, and a certain layer is selected and reproduced. Since the required C / N is different for different modulation schemes, the required C / N level increases as the modulation scheme becomes multi-valued in the order of QPSK, 16QAM, and 64QAM. If the delay point is set to a stronger electric field direction, a receiver state that is advantageous for C / N noise characteristics is obtained. The receiver needs to obtain reception characteristics that satisfy the required C / N according to the modulation method. Therefore, the delay point setting value for obtaining the required C / N varies depending on the modulation method. A specific example is shown in FIG. FIG. 6 shows an example of the delay point setting value corresponding to the modulation method in the relationship diagram of input electric field strength versus AGC gain attenuation. As shown in FIG. 6, the delay point setting value for obtaining the required C / N in the order of the above-described QPSK method, 16QAM method, and 64QAM method is a setting value toward the strong electric field direction. In this way, by setting the delay point setting so as to obtain the required C / N according to the modulation method, it is possible to improve the characteristic for the adjacent disturbance characteristic.
[0022]
(Embodiment 3)
Next, claim 7 will be described in particular with reference to the third embodiment and FIGS. The use of receiving digital terrestrial broadcasts while moving can be expected to expand further in the future. A fading disturbance peculiar to the case of receiving while moving occurs. The amount of fading interference is generally expressed in terms of Doppler frequency, and the higher the Doppler frequency, the greater the degree of interference.
[0023]
Here, when the moving speed is Vs (km / h), the reception channel frequency is Fch (MHz), and the Doppler frequency is Fdopp (Hz), the following equation is established.
[0024]
[Expression 1]
Figure 2005033247
Here, the denominator of (Equation 1) is the speed of light per hour (m / h).
[0025]
From (Equation 1), the higher the receiving channel frequency Fch and the faster the moving speed Vs, the higher the Doppler frequency Fdopp. That is, it can be seen that the influence of fading interference is increased. This relationship is shown in FIG. Equivalent materials are also published in the Japan Radio Industry Association document “Standard Number ARIB STD-B29 (Standard Standard Terrestrial Digital Audio Broadcasting Transmission System)”. The interference wave due to fading has a phase / amplitude component interference to the desired wave, which is equivalent to interference as noise. Therefore, by setting the delay point in the direction of a strong electric field as a receiver characteristic, it becomes an advantageous state against fading interference. In assuming mobile reception, the Doppler frequency Fdopp generated when the moving speed Vs is assumed to be 100 km / h, for example, differs depending on the reception channel. This indicates that the set value of the delay point for satisfying the required Doppler frequency Fdopp changes according to the reception channel frequency Fch.
[0026]
Here, FIG. 8 shows an example of the delay point setting value corresponding to the reception channel frequency. As shown in FIG. 8, the setting value of the delay point for obtaining the required Doppler frequency Fdopp becomes the setting value in the strong electric field direction as the frequency increases from a low frequency. By setting the delay point according to the reception frequency in this way, it is possible to improve the characteristic with respect to the adjacent disturbance characteristic at the time of channel reception of each frequency.
[0027]
In this embodiment, the receiver front end such as a tuner and a demodulator is illustrated and described. However, the present invention is not limited to this, and a set top box including a data reproducing unit and a display unit, a television system, The present invention can also be applied to mobile reception systems and in-vehicle systems.
[0028]
【The invention's effect】
As described above, the present invention has a terminal for inputting a received signal and an RFAGC amplifier for amplifying the received signal input from the terminal, and receives the received signal of the target channel from the received signal amplified by the RFAGC amplifier. And a filter that selectively passes the intermediate frequency signal, an IFAGC amplifier that amplifies the signal that has passed through the filter, and a signal amplified by the IFAGC amplifier. A mixer that converts the signal to a frequency lower than the frequency, a local oscillator that generates a local oscillation frequency signal that is input to the mixer, a demodulator that digitally demodulates the output signal output from the mixer and outputs the demodulated signal to the host system, and A level detector that detects the level of the output signal and the signal from this level detector are input. And a gain controller for independently controlling the gains of the RFAGC amplifier and the IFAGC amplifier, and a channel selection command and a reproduction transmission layer that are input from the level detector and output from the host system And a microcomputer that outputs the channel selection data of the target channel to the tuner according to the above signal, and the adjacent disturbance characteristic curve of the received signal can be moved to the optimum region in view of the received electric field strength value by the above configuration. As a result, the digital broadcast signal can be stably received.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a digital signal receiver according to a first embodiment of the present invention. FIG. 2 is a relationship diagram of input electric field strength versus AGC gain attenuation. FIG. 4 is a diagram showing the relationship between the strength and the AGC gain attenuation. FIG. 4 is a diagram showing the relationship between the input electric field strength and the AGC gain attenuation showing the adjacent interference characteristics of the tuner. FIG. 6 is a relationship diagram of input electric field strength vs. AGC gain attenuation, showing an example of delay point setting values according to modulation schemes. FIG. 7 is a correlation diagram of moving speed and Doppler frequency. Relationship between input electric field strength and AGC gain attenuation, showing an example of delay point setting value according to channel frequency
1 tuner 1a terminal 2 filter 3 IFAGC amplifier 4 mixer 5 local oscillator 6 demodulator 7 level detector 8 modulation state detector 9 gain controller 10 microcomputer 11 host system

Claims (7)

受信信号を入力するための端子と、この端子から入力された前記受信信号を増幅するＲＦＡＧＣ増幅器を有しこのＲＦＡＧＣ増幅器によって増幅された受信信号から目的チャネルの受信信号を選択し中間周波数信号に変換するチューナと、前記中間周波数信号を選択的に通過させるフィルタと、このフィルタを通過した信号を増幅するＩＦＡＧＣ増幅器と、このＩＦＡＧＣ増幅器によって増幅された信号をその信号の周波数より低い周波数の信号に変換するミキサと、このミキサへ入力する局部発振周波数信号を発生する局部発振器と、前記ミキサより出力された出力信号をデジタル復調しホストシステムへ出力する復調器と、前記出力信号のレベルを検出するレベル検出器と、このレベル検出器からの信号が入力されるとともに前記ＲＦＡＧＣ増幅器および前記ＩＦＡＧＣ増幅器の利得をそれぞれ独立して制御する利得制御器と、前記レベル検出器からの信号が入力されるとともに前記ホストシステムから出力されたチャネル選局指令および再生伝送階層の信号により前記チューナに目的チャネルの選局データを出力するマイコンとを備えたデジタル信号受信機。A terminal for inputting a received signal and an RFAGC amplifier for amplifying the received signal input from this terminal are selected and the received signal of the target channel is selected from the received signal amplified by the RFAGC amplifier and converted to an intermediate frequency signal A tuner that selectively passes the intermediate frequency signal, an IFAGC amplifier that amplifies the signal that has passed through the filter, and a signal amplified by the IFAGC amplifier is converted to a signal having a frequency lower than that of the signal. A mixer for generating a local oscillation frequency signal to be input to the mixer, a demodulator for digitally demodulating the output signal output from the mixer and outputting it to a host system, and a level for detecting the level of the output signal A detector and a signal from the level detector are input and the RFA A gain controller for independently controlling the gains of the C amplifier and the IFAGC amplifier, and a channel selection command and a reproduction transmission layer signal output from the host system while receiving a signal from the level detector A digital signal receiver comprising: a microcomputer that outputs channel selection data of a target channel to the tuner. マイコンは、利得制御器を介した利得制御においてＲＦＡＧＣ増幅器の利得制御を開始する動作開始点にてＩＦＡＧＣ増幅器の利得が一定になるようにしかつ前記ＲＦＡＧＣ増幅器の利得制御を開始する動作開始点を任意に設定する請求項１に記載のデジタル信号受信機。The microcomputer makes the gain of the IFAGC amplifier constant at the operation start point for starting the gain control of the RFAGC amplifier in the gain control via the gain controller, and arbitrarily sets the operation start point for starting the gain control of the RFAGC amplifier. The digital signal receiver according to claim 1, wherein マイコンは、利得制御器を介した利得制御において目的チャネル選択時ＲＦＡＧＣ増幅器の利得制御を開始する動作開始点を一定値とする請求項１に記載のデジタル信号受信機。The digital signal receiver according to claim 1, wherein the microcomputer sets a constant value as an operation start point for starting gain control of the RFAGC amplifier when a target channel is selected in gain control via the gain controller. マイコンは、利得制御器を介した利得制御においてレベル検出器で検出されるレベル信号に応じた制御を行う請求項１に記載のデジタル信号受信機。The digital signal receiver according to claim 1, wherein the microcomputer performs control according to the level signal detected by the level detector in gain control via the gain controller. 受信信号を入力するための端子と、この端子から入力された前記受信信号を増幅するＲＦＡＧＣ増幅器を有しこのＲＦＡＧＣ増幅器によって増幅された受信信号から目的チャネルの受信信号を選択し中間周波数信号に変換するチューナと、前記中間周波数信号を選択的に通過させるフィルタと、このフィルタを通過した信号を増幅するＩＦＡＧＣ増幅器と、このＩＦＡＧＣ増幅器によって増幅された信号をその信号の周波数より低い周波数に変換するミキサと、このミキサに入力する局部発振周波数信号を発生する局部発振器と、前記ミキサより出力された出力信号をデジタル復調しホストシステムに出力する復調器と、前記ミキサより出力された出力信号のレベルを検出するレベル検出器と、前記ミキサより出力された出力信号の伝送階層毎の変調方式を検出する変調状態検出器と、前記レベル検出器からの信号が入力されるとともに前記ＲＦＡＧＣ増幅器および前記ＩＦＡＧＣ増幅器の利得をそれぞれ独立して制御する利得制御器と、前記ホストシステムから出力されたチャネル選局指令および再生伝送階層の信号により前記チューナに目的チャネルの選局データを出力するとともに前記レベル検出器および前記変調状態検出器からの信号が入力されるマイコンとを備えたデジタル信号受信機。A terminal for inputting a received signal and an RFAGC amplifier for amplifying the received signal input from this terminal are selected and the received signal of the target channel is selected from the received signal amplified by the RFAGC amplifier and converted to an intermediate frequency signal A tuner that selectively passes the intermediate frequency signal, an IFAGC amplifier that amplifies the signal that has passed through the filter, and a mixer that converts the signal amplified by the IFAGC amplifier to a frequency lower than the frequency of the signal A local oscillator that generates a local oscillation frequency signal input to the mixer, a demodulator that digitally demodulates the output signal output from the mixer and outputs the demodulated signal to a host system, and a level of the output signal output from the mixer. Level detector to detect and transmission hierarchy of output signal output from the mixer A modulation state detector that detects the modulation method of the signal, a gain controller that receives the signal from the level detector and controls the gains of the RFAGC amplifier and the IFAGC amplifier independently of each other, and outputs from the host system A digital signal comprising: a microcomputer for outputting channel selection data of a target channel to the tuner according to a channel selection command and a reproduction transmission layer signal, and to which signals from the level detector and the modulation state detector are input Receiving machine. マイコンは、ＲＦＡＧＣ増幅器の利得制御の動作開始点を変調状態検出器からの出力信号に応じて設定する請求項得５に記載のデジタル信号受信機。6. The digital signal receiver according to claim 5, wherein the microcomputer sets an operation start point of gain control of the RFAGC amplifier in accordance with an output signal from the modulation state detector. マイコンは、ＲＦＡＧＣ増幅器の利得制御の動作開始点を目的チャネルの周波数に応じて設定する請求項５に記載のデジタル信号受信機。The digital signal receiver according to claim 5, wherein the microcomputer sets an operation start point of gain control of the RFAGC amplifier in accordance with a frequency of a target channel.
JP2003192654A 2003-07-07 2003-07-07 Digital signal receiver Pending JP2005033247A (en)

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