JP3707463B2 - Signal transmission method, signal transmission device, and signal reception device - Google Patents

Description

【００２５】
【数２】

【００２６】
数式１及び数式２から分かる様に、電磁界の強さはアンテナからの距離Ｒ、距離Ｒの２乗、距離Ｒの３乗に反比例する成分のベクトル和で表され、それぞれ、輻射電磁界、誘導電磁界、静電磁界と呼ばれる。このうち、磁界Ｈの成分には１／Ｒ³の項はない。
【００２７】
図６は、上述した各項の電界強度とアンテナからの距離との関係を示す特性図である。なお、電圧レベルに特別の意味はない。また、図７は、周波数ｆ＝２００ＭＨｚ、送信端子電圧＝１００ｄＢμＶ（７５Ω）の場合において、λ／２．２のダイポールアンテナと３．４ｃｍφのループアンテナ、及び８ｃｍφ，３．４ｃｍφのループアンテナの電界強度と距離とを示す図である。
【００２８】
図６及び図７に示すように、上記輻射電磁界（１／Ｒ項）、誘導電磁界（１／Ｒ²項）、静電磁界（１／Ｒ³項）の強度は、λ／２πの距離において等しくなり、距離がこれ以下の場合には急激に増加する。ｆ＝１１ＭＨｚならば、この距離は約４．３ｍとなる。したがって、本方式は静電磁界を主として使用した伝送方式であり、人体と、以下に述べる静電磁界とを伝送路とすることを特徴としている。なお、一般的な無線伝送では、アンテナから十分離れた距離を考えるので、輻射電磁界（１／Ｒの項）を使用することになる。
【００２９】
２−２．最適キャリア周波数
本実施形態では、ＬＥＤによる空間伝送のフォーマットそのままを用いたが、キャリアの最適周波数は、静電磁界の支配的となる空間距離、ＥＭＩ規制、電波使用状況等を考えて決定することが望ましい。
【００３０】
静電磁界：
情報伝送のために、どの種の電磁界を用いるは任意であるが、静電磁界を主として用いるとすると、この部分は周波数が高くなるほど、カバーレンジが短くなる。一人の人間が手で持って使う範囲を考えると、直径２ｍ程度と考えられる。したがって、２０ＭＨｚ程度以下が望ましい。
【００３１】
電波使用状況：
０．５ＭＨｚ〜１．６ＭＨｚ帯はＡＭ放送、８０ＭＨｚ付近にはＦＭ放送がある。また、９０ＭＨｚ〜２１７ＭＨｚはテレビのＶＨＦ帯が、４７０ＭＨｚ〜８８６ＭＨｚはＵＨＦ帯がある。したがって、この範囲は避けることが望ましい。
【００３２】
ＥＭＩ規制：
電界強度が次の値以下ならば電波法の規制を受けない。
３３２ＭＨｚ以下 ５００μＶ／ｍ３３２ＭＨｚ〜１０ＧＨｚ ３５μＶ／ｍ
【００３３】
したがって、周波数は３３２ＭＨｚ以下とするのが望ましい。このような点を考慮すると、赤外線伝送の周波数は、手による接触伝送にも適していることが分かる。
【００３４】
２−３．キャリアレベル
本実施形態では、静電磁界を用いるため、信号レベルが送受信機間の距離の３乗に反比例して弱くなり、両手を一杯に広げた時など伝送品質が落ちる傾向がある。したがって、送信レベルは電波法内で、できるだけ大きく取ることが望ましい。また、最大レベルを理論的に計算するのは人体の等価回路が不明なため困難である。そこで、本実施例では、不要な輻射レベルを測定して電波法内に入っていることを確認することにより、実験的に決定した。
【００３５】
２−４．人体への影響
小さな電力とはいえ、人体を通して信号を伝送するのであるから、健康面への影響についても考えておかねばならない。この指針としては郵政省から電波防護指針が出されている。電波防護指針では管理された電磁環境に適用される条件Ｐと、管理されてない電磁環境に適用される条件Ｇがあり、条件Ｇは条件Ｐに比べて約５倍の安全率を見込んでいる。
【００３６】
一般向け機器では、当然、条件Ｇを適用する。また、低電力の電磁放射源に関する指針では定格出力７Ｗ以下のものは評価不要となっている。但し、放射源が身体に極めて近い場合は注意を要するとしている。本実施形態に係るシステムの場合、７Ｗ以下であるが、放射源に触れて使用することになるので、指針の中の接触電流について検討する。指針では、１００ｋＨｚ〜１００ＭＨｚにおいて４５ｍＡ以下（６分）となっている。
【００３７】
その根拠は以下の通りである。周波数が１００ｋＨｚ〜１００ＭＨｚでは、流入電流は刺激作用ではなく、熱作用が支配的であり、この周波数帯では、接触電流による熱傷の限界は２００ｍＡと言われている。また、２００ｍＡが１００ｋＨｚ以上では感知限と言われている。そこで、これに対してマージンを見て決定されている。なお、商用周波数では、流入電流は刺激作用となり、ＩＥＣやＪＩＳでは１ｍＡ以下となっている。
【００３８】
そこで、以下に人体への流入電流がどの程度となるかを試算する。図８は、送信側の出力段と、人体と、受信側との接続関係を示す略構成図である。図において、送信側と受信側のＧＮＤは静電結合となっている。したがって、人体を流れる電流は静電容量Ｃも考慮すべきであるが、値が確定できないため、静電容量Ｃは無限大（即ち電気的に接続されている）として流入電流を求めた。
【００３９】
図８に示すように、周波数は約１３ＭＨｚ、出力部のレベルは２Ｖｐｐ（０．７１Ｖｒｍｓ）とする。前述した３−１項において測定した値に基づいて人体のインピーダンスを求めると、約７．５ｋΩとなる。一方、ドライバと人体間は１００ｐＦのコンデンサカップルとしているので、１３ＭＨｚでのインピーダンスは、ドライバの出力インピーダンスが０Ωであっても１２０Ωである。すなわち、電流は０．７１Ｖ／７．６２ｋΩ＝０．０９３ｍＡとなる。これは、上述した指針と比べても十分に小さく問題ない。
【００４０】
３．各部の詳細
次に、上述した送信装置及び受信装置の詳細な構成について、図９及び図１０を参照しながら説明する。
【００４１】
３−１．送信装置
図９は、上述した送信装置の詳細な構成を示すブロック図である。図において、バッファ回路２０は、ビデオ信号Ｖ１のレベルを調整して変調回路２１へ供給する。変調回路２１は、レベル調整されたビデオ信号をＦＭ変調し、バンドパスフィルタ２２へ供給する。バンドパスフィルタは、必要なキャリア成分のみを通すための１１ＭＨｚの帯域フィルタであり、上記ＦＭ変調信号をフィルタリングした後、混合回路２７へ供給する。一方、オーディオ用の変調回路２３，２４は、各々、オーディオ信号（Ｌ）Ａ１，（Ｒ）Ａ２をＦＭ変調し、バンドパスフィルタ２５，２６へ供給する。
【００４２】
バンドパスフィルタ２５，２６は、各々、必要なキャリア成分のみを通すための２．３ＭＨｚ、及び２．８ＭＨｚの帯域フィルタであり、上記ＦＭ変調されたオーディオ信号Ａ１，Ａ２をフィルタリングし、上記混合回路２７へ供給する。混合回路２７は、その抵抗比によりビデオ信号Ｖ１、オーディオ信号Ａ１，Ａ２の混合比を決めて、ＦＭ変調されたビデオ信号Ｖ１及びオーディオ信号Ａ１，Ａ２を混合し、混合信号ＭＳとしてバッファアンプ２８へ供給する。
【００４３】
バッファアンプ２８は、図１に示す増幅回路３に相当し、混合信号ＭＳを適当なレベルに増幅し、電極４へ送出する。なお、ＥＩＡＪによる赤外線伝送フォーマットに準ずる場合にはビデオ／オーディオ信号のキャリアレベル、混合比等は決まっているが、本発明ではこれに準ずる必要はない。
【００４４】
３−２．受信装置
図１０は、上述した受信装置の詳細な構成を示すブロック図である。同図において、信号選択回路３０は、図１に示す選択回路７に相当し、電極６から供給される信号から必要な周波数帯の信号を取り出し、バンドパスフィルタ３１及び増幅器３５へ供給する。バンドパスフィルタ３１は、上記信号選択回路３０によって取り出された信号をフィルタリングすることにより、ビデオ信号のキャリア成分のみを通過させ、これをリミッタ回路３２へ供給する。リミッタ回路３２は、信号のレベル（振幅）を一定値に抑え、復調回路３３へ供給する。復調回路３３はリミッタ回路の出力信号からビデオ信号を取り出し、バッファアンプ３４へ供給する。バッファアンプ３４は、ビデオ信号を所定のレベルに増幅し、後段の回路へ出力する。
【００４５】
一方、増幅器３５は、上記信号選択回路３０によって取り出された信号を増幅し、オーディオ信号（Ｌ），（Ｒ）に対応するバンドパスフィルタ３６，３７の各々へ供給する。バンドパスフィルタ３６，３７は、各々、増幅器３５からの信号をフィルタリングすることにより、オーディオ信号のキャリア成分のみを通過させ、これを復調回路３８，３９へ供給する。復調回路３８，３９は、各々、信号のレベル（振幅）を一定値に抑えるとともに、オーディオ信号Ａ１，Ａ２を取り出し、バッファアンプ４０，４１へ供給する。バッファアンプ４０，４１は、各々、オーディオ信号Ａ１，Ａ２を所定のレベルに増幅し、後段の回路へ出力する。
【００４６】
４．具体的な構成例
４−１．送信装置の増幅回路
図１１は、送信装置１の最終段である増幅回路３（２８）の構成を示す回路図である。同図において、増幅回路３（２８）は、従来の赤外線伝送用の最終段のＬＥＤドライバを取り除き、この代わりに手で触れられるよう電極４が接続されている点以外、赤外線伝送用変調回路と同様の構成である。オペアンプＯＰ１は、通常の反転増幅器として用いられており、非反転入力端には、グランド間にコンデンサＣ１（２２μＦ），Ｃ２（０．１μＦ）、抵抗Ｒ１（２．７ｋΩ）が並列接続されている。また、反転入力端（−）には、出力端に一端が接続された帰還用の抵抗Ｒ２（１０ｋΩ）の他端が接続され、上記出力端には、グランド間に抵抗Ｒ３（４７０Ω）が接続されている。また、オペアンプＯＰ１の出力は、前述したように、コンデンサＣ３（１０ｐＦ）を介して電極４に接続され、直流的に切り離されている。また、電極４は、本実施形態では２×３ｃｍの銅箔を用いている。
【００４７】
送信装置１はシールドしたプラスチックケース内に納められ、図１２に示すように、ビデオカメラ（ＣＣＤ−Ｇ１）３０の下部に取り付け、全体をバッテリー（電源）３１により駆動できるようにする。このように、全体を独立した構成とすることで、送信側と受信側のグラウンド部分の結合を空間の静電磁界によるものだけとすることができる。上記電極４は、ビデオカメラ３０を手で持ったときに、丁度、手が触れるビデオカメラの本体に露出して設けられている。また、ビデオカメラ３０の出力であるビデオ信号は、カメラコネクタ３２に接続されたケーブルを介して送信装置１へ供給されるようになっている。
【００４８】
なお、送受信側ともＡＣアダプタ等で動作させるとグランド側に確実な結合ができ、高品質な映像が得られるが、ビデオカメラを手で持ってデッキに記録する場合などの検討にはならない。
【００４９】
４−２．受信装置の選択回路
図１３は、受信装置５の選択回路７（３０）の構成を示す回路図である。同図において、選択回路７（３０）は、ハイ・インピーダンスバッファ５０とＬＣ共振回路５１を組み合わせたものである。また、電極６は、本実施例では１×１ｃｍの銅箔を用いている。これら以外は、送信装置１の増幅回路３と同様に、ＬＥＤによる赤外線伝送の回路と同様の構成であるので説明を省略する。この受信装置５は、ＧＶ−ＳＸ５０用チューナケースに組み込み、ＳＸ−５０で映像を出している。
【００５０】
図１４は、上記構成による選択回路７の周波数特性を示す特性図であり、図１５は同構成においてカラーバーを受信した時のスペクトラム（ＳＸ−５０出力端子で測定；この時、送信側はブレッドボードを用いた）を示す特性図である。図１４に示すように、選択回路７の周波数特性は、１ＭＨｚ〜約１５ＭＨｚまでは緩やかに上昇し、それ以降では急激に減衰するという特性をとる。また、図１５に示すように、カラーバーを受信したときのスペクトラムは、１５ＭＨｚ附近に最大ピークを有する特性をとることが分る。
【００５１】
４−３．特性測定
前述した図１２に示す構成では、送信側のビデオカメラ、受信側のＶＷともバッテリー駆動にしたため、特性測定が困難であった。そこで、送信側は赤外線伝送検討用のブレッドボード（商用電源駆動）を用いて、受信側のみバッテリー駆動のＶＷとした。
【００５２】
図１６は、この場合の伝送経路の特性測定系の構成を示すブロック図である。同図において、送信側には、ブレッドボード５０を用いており、該ブレッドボード５０には、やはり商用電源で駆動されるビデオ信号発生器（ＴＧ−７／１）５１からのビデオ信号が供給されるようになっている。また、受信側には、バッテリ５３によって駆動されるＶＷ（ＧＶ−ＳＸ５０）５２を用いており、その出力は、商用電源で駆動されるノイズメータ（９２５Ｄ／１）５４へ供給される。上記ブレッドボード５０には、出力用の電極５１（電極４に相当）が設けられており、同様に、受信側のＶＷ５２にも、入力用の電極５２（電極６）が設けられている。上記電極５１と電極５２との間が人体１０によって電気的に接続される。
【００５３】
この構成によれば、受信側もビデオアウトを測定器に接続するため、送信側と受信側のＧＮＤループは接続されたことと等価になる。したがって、伝送条件は、ビデオカメラとＶＷとをそれぞれ単体で使用した場合より良くなるので一応の目安と考える。以下に、上記構成によって計測した測定値を示す。これらは、ビデオデッキのビデオ特性測定方法により測定した。
Ｙ Ｓ／Ｎ ４７．５ｄＢクロマ ＡＭ ４３ ｄＢクロマ ＰＭ ４４ ｄＢ
【００５４】
５．本実施形態の動作
次に、上述した図９及び図１０に示す送受信装置を用いた場合の動作について説明する。入力されたビデオ信号Ｖ１は、バッファ回路において、レベルが調整された後、変調回路２１によりＦＭ変調される。オーディオ信号Ａ１，Ａ２も、簡単なバッファ回路（図では省略）を通った後、変調回路２３，２４によってＦＭ変調される。各々の変調出力は必要なキャリア成分のみを通すバンドパスフィルタ２２，２５，２６を通過した後、混合回路２７において、その抵抗比に応じて混合された後、増幅器により適当なレベルに増幅され、電極４から出力される。
【００５５】
電極４から送出される信号は、人体１０を介して受信装置の電極６へ伝送される。電極６に供給された信号は信号選択回路３０で必要な周波数帯の信号が取り出され、ビデオ信号Ｖ１のキャリアはバンドパスフィルタ３１を通過した後、リミッタ３２を介して復調回路３３により、原信号であるビデオ信号Ｖ１に復調される。一方、オーディオ信号Ａ１，Ａ２のキャリアは、増幅器３５によって増幅された後、各々、バンドパスフィルタ３６，３７を通過した後、復調回路３８，３９で原信号であるオーディオ信号Ａ１，Ａ２に復調される。
【００５６】
６．変形例
６−１．キャリア周波数を増加させ多チャネルとする例
本発明のように、静電磁界を使用した場合、伝送距離は周波数に反比例する。実用的な距離を２ｍとすれば、キャリア周波数は２０ＭＨｚ位となる。この帯域まで使用することを考えると、ビデオ信号がさらに２チャネル程度は取れる。オーディオとしてはチャネルの空きは十分に余裕がある。したがって、上述した構成を多チャネルのＡ／Ｖ伝送に用いてもよい。
【００５７】
６−２．多チャネル、汎用信号伝送
上述した本発明の実施形態では、Ａ／Ｖ伝送についてのみ説明したが、数ＭＨｚ程度の周波数帯域を持つ信号ならば、その内容に拘らず伝送可能であり、上述した構成を他の信号伝送に用いてもよい。このとき、チャネル数は伝送する信号の占める帯域で決めればよい。
【００５８】
［追補］
以上、特定の実施形態を参照しながら、本発明について詳解してきた。しかしながら、本発明の要旨を逸脱しない範囲で当業者が該実施形態の修正や代用を成し得ることは自明である。すなわち、例示という形態で本発明を開示してきたのであり、本明細書の記載内容を限定的に解釈するべきではない。本発明の要旨を判断するためには、冒頭に記載した特許請求の範囲の欄を参酌すべきである。
【００５９】
【発明の効果】
以上詳記したように、本発明によれば、原信号を変調する変調手段を有し、最終出力信号を外部に露出して設けられた第１の導電性部材から出力する送信装置の前記第１の導電性部材と、受信信号を復調する復調手段を有し、前記受信信号を外部に露出して設けられた第２の導電性部材から受信する受信装置の前記第２の導電性部材とに、人体が接触することによって、前記送信装置及び前記受信装置間の信号伝送を行なうようにしたため、実使用上、ワイアレスで信号伝送ができ、且つ送信装置及び受信装置間の相対位置が自由であるため使用感が極めて向上する。また、本発明によれば送信装置及び受信装置に要する電力が小さく、ポータブル機器に応用できる。さらに、バイザートロンのように、身体に装着して使用する機器の使用感向上が図れるという利点が得られる。
【００６０】
なお、人体誘導電界を用いる通信方式では、送受信機間に、人体以外にも少なくとも１つの信号経路を形成する必要がある。本発明に係る信号伝送方式によれば、この人体以外の信号経路として、送信装置−受信装置間に形成される空間の電磁界を用いている。
【００６１】
これに対し、例えば特開昭６１−４６６３７号公報並びに特開昭６１−４６６３９号公報には、生体が接触可能な接触電極並びに該接触電極を介して情報の伝送信号を送受信する伝送回路を具備したホスト・ユニットと、生体表面に接し得る生体電極及び該生体電極を介して情報の伝送信号を送受信する伝送回路を具備した携帯可能なサブユニットよりなる情報伝送装置について開示されている。また、特開平４−２１７０８６号公報には、ＩＣカードリーダとＩＣカード外部機器間の情報転送を人体を介して行なう点について開示されている。しかしながら、これらの従来技術では、人体以外の信号経路としてグラウンドを利用している。これは、各公報では空間電磁界についてまったく言及されていないこと、あるいは送信機／受信機を接地させることが前提となっていることから、当業者には容易に想到される。
【００６２】
換言すれば、本発明に係る信号伝送方式によれば、人体以外の信号経路として空間の電磁界を私用するため、必ずしも送受信機のグラウンドをとる必要がない。すなわち、送受信機ともに携帯型の装置として構成することができる。これに対し、上記の従来技術では、人体以外の信号経路にグラウンドを利用するため、少なくとも送受信機のいずれか一方は接地型の装置して構成しなければならない。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る送受信装置全体の基本構成を示したブロック図である。
【図２】本発明の一実施形態に係る信号伝送の原理を説明するために、その基本構成を示した略概念図である。
【図３】微小ダイポールアンテナが発生する電磁界の様子を示す概念図である。
【図４】１ＭＨｚ〜２０ＭＨｚの範囲で、スペクトラムアナライザを用いて測定した人体の伝送特性（両手間）を示す特性図である。
【図５】１ＭＨｚ〜３０ＭＨｚの範囲で、スペクトラムアナライザを用いて測定した人体の伝送特性（両手間）を示す特性図である。
【図６】電界強度とアンテナからの距離との関係を示す特性図である。
【図７】λ／２．２のダイポールアンテナと３．４ｃｍφのループアンテナ、および８ｃｍφ，３．４ｃｍφのループアンテナの電界強度とアンテナからの距離との関係を示す特性図である。
【図８】人体への流入電流がどの程度となるかを説明するための送信側の出力段、人体、及び受信側との接続関係を示す略構成図である。
【図９】本発明の実施形態に係る送信装置の詳細な構成を示すブロック図である。
【図１０】本発明の実施形態に係る受信装置の詳細な構成を示すブロック図である。
【図１１】本発明の実施形態に係る送信装置１の最終段である増幅回路３（２８）の構成を示す回路図である。
【図１２】本発明の実施形態に係る送信装置のビデオカメラへの取り付け状態を示す外観図である。
【図１３】本発明の実施形態に係る受信装置５の選択回路７（３０）の構成を示す回路図である。
【図１４】本発明の実施形態に係る受信装置の周波数特性を示す特性図である。
【図１５】本発明の実施形態に係る受信装置がカラーバーを受信したときのスペクトラムを示す特性図である。
【図１６】本発明の実施形態に係る伝送経路の特性測定系の構成を示すブロック図である。
【符号の説明】
１…送信装置
２…ＦＭ変調回路（変調手段）
３…増幅回路
４…電極（第１の導電性部材）
５…受信装置
６…電極（第２の導電性部材）
７…選択回路
８…ＦＭ復調回路
３３，３８，３９…復調回路
１０…人体
２０…バッファ回路
２１，２３，２４…変調回路
２２，３１，３６，３７…バンドパスフィルタ
２７…混合回路
２８，３４，４０，４１…バッファアンプ
３０…信号選択回路
３２…リミッタ
３５…増幅器（増幅回路）
Ｖ１…ビデオ信号（原信号）
Ａ１，Ａ２…オーディオ信号（原信号）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to signal transmission over a short distance, and more particularly to a signal transmission system suitable for use in audio / video signal transmission.
[0002]
[Prior art]
Conventionally, as a technical means for wirelessly transmitting an audio / video (hereinafter referred to as AV) signal over a relatively short distance, a method using radio waves and a method using infrared rays are known. In AV equipment, if audio signals and video signals can be connected wirelessly, the usability is improved and it is very convenient. Actually, various devices are manufactured and sold for this purpose.
[0003]
For example, an infrared signal is used for AV signals, an infrared signal is used for audio signals only, and a weak radio wave is used. Technically it is best to use radio waves. However, although there is bandwidth allocation in the United States, in Japan, practical level output is not possible due to regulations of the Radio Law, and transmission of video signals is almost impossible.
[0004]
Therefore, only the latter infrared system is put into practical use in Japan. Equipment using infrared rays has been technically completed, and standardization by the EIAJ (Japan Electronic Machinery Manufacturers Association) is also progressing.
[0005]
[Problems to be solved by the invention]
By the way, in the infrared system mentioned above, since light (infrared rays) is used, directivity is sharp and the installation position of the transmission / reception device between the transceivers is limited. In addition, the biggest drawback of the infrared method is that if there is an obstacle between the transmitter and the receiver, the optical path is blocked and transmission becomes impossible. Furthermore, the power consumption is large (especially the LED on the transmission side), and the transmission using the infrared method has not been put into practical use for portable devices.
[0006]
On the other hand, as AV devices are widely used in the world, the number of variations has increased, and there is an increasing demand for wireless signal transmission even if the distance is very short. For example, when video shooting is performed with a small camera and a small deck, if the signal transmission between them can be performed wirelessly, the usability is greatly improved. However, in the conventional infrared method, even if the problem of power consumption is solved in this case, it is impossible to eliminate the possibility that the light is blocked by an obstacle such as the body, so that a signal cannot be transmitted between them. The problem arises.
[0007]
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a signal transmission method that can transmit a signal wirelessly, reduce power consumption of the transmission / reception device, and improve the feeling of use of the transmission / reception device. Yes.
[0008]
[Means and Actions for Solving the Problems]
The present invention has been made in consideration of the above problems, and a first aspect of the present invention is that a modulation unit that modulates an original signal, a first conductive member, and an output signal from the first conductive member. A signal transmission device having an output unit for outputting
A signal receiving device having a second conductive member, a receiving unit that receives a signal from the second conductive member, and a demodulating unit that demodulates the received signal;
With
In signal transmission between the signal transmitting device and the signal receiving device, a human body that is in contact with the first conductive member and the second conductive member and a space formed between the transmitting device and the receiving device. An electromagnetic field is used as a transmission line,
This is a signal transmission system.
[0009]
However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.
[0010]
The second aspect of the present invention includes a modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member,
In the case where signal transmission is performed between a second conductive member, a receiving device that receives a signal from the second conductive member, and a demodulating unit that demodulates the received signal, the first conductive member A human body in contact with the conductive member and the second conductive member, and an electromagnetic field in a space formed between the transmitter and the receiver as a transmission path,
This is a signal transmission device characterized by the above.
[0011]
In addition, a third aspect of the present invention includes a second conductive member, a receiving unit that receives a signal from the second conductive member, and a demodulating unit that demodulates the received signal,
When signal transmission is performed between a signal transmission device including a modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member, A human body in contact with the conductive member and the second conductive member, and an electromagnetic field in a space formed between the transmitting device and the receiving device is used as a transmission path.
This is a signal receiving device characterized by the above.
[0012]
Here, an electrostatic magnetic field can be used as an electromagnetic field in a space formed between the transmission device and the reception device used as a transmission path.
[0013]
In signal transmission between the transmission device and the reception device, a ground to which the transmission device and the reception device are electrostatically coupled can be further used as a transmission path.
[0014]
In the present invention, the modulation signal from the modulation means of the transmission device is output from the first conductive member exposed to the outside, transmitted to the second conductive member provided in the reception device via the human body, Demodulated by the demodulating means. Therefore, in actual use, signal transmission can be performed wirelessly, and the relative position between the transmission device and the reception and transmission is free, so that the feeling of use is greatly improved. Further, the power required for the transmission device and the reception device is small, and it can be applied to portable devices. Further, the receiving device may include an amplifier circuit that amplifies the modulated transmission signal. The original signal may be either a video signal or an audio signal, or both. Further, the modulation method may be frequency modulation.
[0015]
Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0017]
1. Schematic configuration
FIG. 1 shows a basic configuration of the entire transmitting / receiving apparatus according to an embodiment of the present invention. In the figure, the transmission apparatus 1 basically includes an FM modulation circuit 2 for left and right audio signals and a video signal, and an amplification circuit 3 that amplifies the mixed signal. The carrier frequency is the same as that of the infrared transmission format, which is about 11.5 MHz to 13.5 MHz for the video signal, 2.8 MHz for the audio (R) signal, and 2.3 MHz for the audio (L) signal.
[0018]
As shown in the figure, in the transmission device 1, the output of the amplifier circuit 3 is supplied to the electrode 4 instead of driving the LED in the final stage. Note that the output of the amplifier circuit 3 is connected to the electrode 4 via a capacitor (not shown) and is separated in a direct current manner. This is to ensure a sufficient margin for the radio wave protection guidelines issued by the Ministry of Posts and Telecommunications and to protect the device against when the electrode 4 is shorted outside. Further, the output level of the electrode 4 is set to be less than or equal to the weak electric power (500 μV / M) regulated by the Radio Law when touched by the body.
[0019]
Next, the receiving device 5 includes a selection circuit 7 for extracting only a necessary frequency band from the signal input to the input electrode 6, and an FM demodulation circuit 8 for left and right audio signals and video signals. On the reception side, a high-impedance input circuit is provided in the selection circuit 7 instead of the pin diode, and the electrode 6 is connected in the same manner as the transmission device 1. These circuits are known, and in this embodiment, a receiving circuit for infrared transmission is used. In this embodiment, signal transmission is performed by touching the electrode 4 on the transmission device 1 side and the electrode 6 on the reception device 5 side with a body (both hands) 10.
[0020]
2. principle
Next, the transmission principle of the transmission device 1 and the reception device 5 according to the present embodiment will be described with reference to FIGS.
[0021]
2-1. Transmission principle
FIG. 2 is a schematic conceptual diagram showing the basic configuration in order to explain the principle of signal transmission according to the present embodiment. As shown in FIG. 2, in this system, one side of the signal source on the transmission device 1 side and one side on the reception device 5 side are connected by a human body 10. Since most of the human body 10 is considered to be a conductive container made of water containing salt, it is generally a conductor in the several MHz band. When the DC resistance between both hands is measured with a tester or the like, a value of 500 kΩ to 2,3 MΩ is shown depending on the state of the hand.
[0022]
In the measurements shown in FIGS. 4 and 5, both the output impedance of the tracking generator and the input impedance of the spectrum analyzer are 75Ω. Therefore, if the impedance between both hands is 1 mega ohm, for example, in terms of alternating current, the attenuation should reach -80 dB. However, in practice, the amount of attenuation is far less, which proves the possibility of signal transmission through the human body.
[0023]
As described above, the transmitter 1 side is considered to be a minute dipole antenna as shown in FIG. 2, and the state of the electromagnetic field generated by this is sufficiently analyzed. According to this, the state of the electromagnetic field generated by the human body becomes the electromagnetic field generated by the minute dipole antenna as shown in FIG. 3, and the electric field E and magnetic field H at a point of distance R from the dipole antenna of length L are Respectively, it is expressed as Equation 1 and Equation 2 below.
[0024]
[Expression 1]

[0025]
[Expression 2]

[0026]
As can be seen from Equations 1 and 2, the strength of the electromagnetic field is represented by a vector sum of components that are inversely proportional to the distance R from the antenna, the square of the distance R, and the cube of the distance R, respectively. It is called an induction electromagnetic field or an electrostatic magnetic field. Of these, the component of the magnetic field H is 1 / R^ThreeThere is no term.
[0027]
FIG. 6 is a characteristic diagram showing the relationship between the electric field strength of each term and the distance from the antenna. The voltage level has no special meaning. FIG. 7 shows the electric field of the λ / 2.2 dipole antenna, the 3.4 cmφ loop antenna, and the 8 cmφ and 3.4 cmφ loop antennas when the frequency f is 200 MHz and the transmission terminal voltage is 100 dBμV (75Ω). It is a figure which shows intensity | strength and distance.
[0028]
As shown in FIGS. 6 and 7, the radiated electromagnetic field (1 / R term), the induction electromagnetic field (1 / R²Term), electrostatic magnetic field (1 / R^ThreeThe intensity of the term) becomes equal at a distance of λ / 2π, and increases rapidly when the distance is less than this. If f = 11 MHz, this distance is about 4.3 m. Therefore, this system is a transmission system mainly using an electrostatic magnetic field, and is characterized by using a human body and an electrostatic magnetic field described below as a transmission path. In general wireless transmission, since a distance sufficiently away from the antenna is considered, a radiated electromagnetic field (1 / R term) is used.
[0029]
2-2. Optimal carrier frequency
In this embodiment, the spatial transmission format by the LED is used as it is, but it is desirable that the optimum frequency of the carrier be determined in consideration of the spatial distance, EMI regulations, radio wave usage conditions, etc. that are dominant in the electrostatic magnetic field.
[0030]
Electrostatic field:
It is optional to use any type of electromagnetic field for information transmission. However, assuming that an electrostatic magnetic field is mainly used, the higher the frequency of this part, the shorter the cover range. Considering the range that one person can use with his / her hand, it is considered to be about 2 m in diameter. Therefore, about 20 MHz or less is desirable.
[0031]
Radio wave usage:
There are AM broadcasts in the 0.5 MHz to 1.6 MHz band, and FM broadcasts in the vicinity of 80 MHz. Also, 90 MHz to 217 MHz has a television VHF band, and 470 MHz to 886 MHz has a UHF band. It is therefore desirable to avoid this range.
[0032]
EMI regulations:
If the electric field strength is less than or equal to
332 MHz or less 500 μV / m 332 MHz to 10 GHz 35 μV / m
[0033]
Therefore, the frequency is desirably 332 MHz or less. Considering this point, it can be seen that the frequency of infrared transmission is also suitable for manual contact transmission.
[0034]
2-3. Career level
In this embodiment, since an electrostatic magnetic field is used, the signal level becomes weak in inverse proportion to the cube of the distance between the transmitter and the receiver, and the transmission quality tends to decrease when both hands are fully extended. Therefore, it is desirable that the transmission level be as large as possible within the Radio Law. Also, it is difficult to theoretically calculate the maximum level because the equivalent circuit of the human body is unknown. Therefore, in this embodiment, the unnecessary radiation level was measured and confirmed experimentally by confirming that it was within the Radio Law.
[0035]
2-4. Impact on the human body
Even though it's a small amount of electricity, it transmits signals through the human body, so you must consider the health implications. As this guideline, the Ministry of Posts and Telecommunications has issued a radio wave protection guideline. In the radio wave protection guidelines, there are a condition P that is applied to a controlled electromagnetic environment and a condition G that is applied to an uncontrolled electromagnetic environment. Condition G expects a safety factor approximately five times that of condition P. .
[0036]
Naturally, the condition G is applied to general-purpose equipment. In addition, according to the guideline regarding the low-power electromagnetic radiation source, those with a rated output of 7 W or less are not required for evaluation. However, caution is required when the radiation source is very close to the body. In the case of the system according to the present embodiment, the power consumption is 7 W or less, but since it is used by touching the radiation source, the contact current in the pointer is examined. According to the guideline, the current is 45 mA or less (6 minutes) at 100 kHz to 100 MHz.
[0037]
The grounds are as follows. When the frequency is 100 kHz to 100 MHz, the inflow current is not a stimulating action but a thermal action is dominant, and in this frequency band, the limit of the burn due to the contact current is said to be 200 mA. Further, it is said that the detection limit is 200 mA at 100 kHz or more. Therefore, this is determined by looking at the margin. In addition, in the commercial frequency, the inflow current has a stimulating action, and is less than 1 mA in IEC and JIS.
[0038]
Therefore, the following will estimate how much the current flowing into the human body will be. FIG. 8 is a schematic configuration diagram showing a connection relationship between the output stage on the transmission side, the human body, and the reception side. In the figure, GND on the transmission side and reception side are electrostatically coupled. Therefore, although the electrostatic capacity C should be taken into consideration for the current flowing through the human body, since the value cannot be determined, the inflow current was obtained with the electrostatic capacity C being infinite (that is, electrically connected).
[0039]
As shown in FIG. 8, the frequency is about 13 MHz, and the level of the output unit is 2 Vpp (0.71 Vrms). When the impedance of the human body is obtained based on the value measured in the above item 3-1, it is about 7.5 kΩ. On the other hand, since the capacitor between the driver and the human body is a 100 pF capacitor couple, the impedance at 13 MHz is 120Ω even if the output impedance of the driver is 0Ω. That is, the current is 0.71 V / 7.62 kΩ = 0.093 mA. This is sufficiently small as compared with the above-mentioned guideline, and there is no problem.
[0040]
3. Details of each part
Next, detailed configurations of the above-described transmission device and reception device will be described with reference to FIGS. 9 and 10.
[0041]
3-1. Transmitter
FIG. 9 is a block diagram illustrating a detailed configuration of the transmission apparatus described above. In the figure, the buffer circuit 20 adjusts the level of the video signal V1 and supplies it to the modulation circuit 21. The modulation circuit 21 FM modulates the level-adjusted video signal and supplies it to the bandpass filter 22. The bandpass filter is an 11 MHz bandpass filter for passing only the necessary carrier component, and after filtering the FM modulated signal, supplies it to the mixing circuit 27. On the other hand, the audio modulation circuits 23 and 24 FM-modulate the audio signals (L) A1 and (R) A2 and supply them to the bandpass filters 25 and 26, respectively.
[0042]
The bandpass filters 25 and 26 are band filters of 2.3 MHz and 2.8 MHz for passing only necessary carrier components, respectively, and filter the FM-modulated audio signals A1 and A2, and the mixing circuit. 27 is supplied. The mixing circuit 27 determines the mixing ratio of the video signal V1 and the audio signals A1 and A2 based on the resistance ratio, mixes the FM-modulated video signal V1 and the audio signals A1 and A2, and supplies the mixed signal MS to the buffer amplifier 28. Supply.
[0043]
The buffer amplifier 28 corresponds to the amplifier circuit 3 shown in FIG. 1, amplifies the mixed signal MS to an appropriate level, and sends it to the electrode 4. In the case of conforming to the infrared transmission format by EIAJ, the carrier level and mixing ratio of the video / audio signal are determined, but in the present invention, it is not necessary to conform to this.
[0044]
3-2. Receiver
FIG. 10 is a block diagram illustrating a detailed configuration of the above-described receiving apparatus. In the figure, a signal selection circuit 30 corresponds to the selection circuit 7 shown in FIG. 1, extracts a signal in a necessary frequency band from the signal supplied from the electrode 6, and supplies the signal to the bandpass filter 31 and the amplifier 35. The band pass filter 31 filters the signal extracted by the signal selection circuit 30 to pass only the carrier component of the video signal and supplies it to the limiter circuit 32. The limiter circuit 32 suppresses the signal level (amplitude) to a constant value and supplies the signal to the demodulation circuit 33. The demodulating circuit 33 extracts a video signal from the output signal of the limiter circuit and supplies it to the buffer amplifier 34. The buffer amplifier 34 amplifies the video signal to a predetermined level and outputs it to the subsequent circuit.
[0045]
On the other hand, the amplifier 35 amplifies the signal extracted by the signal selection circuit 30 and supplies the amplified signal to the band-pass filters 36 and 37 corresponding to the audio signals (L) and (R). The band pass filters 36 and 37 respectively filter only the signal from the amplifier 35 to pass only the carrier component of the audio signal and supply it to the demodulation circuits 38 and 39. Each of the demodulation circuits 38 and 39 suppresses the level (amplitude) of the signal to a constant value, takes out the audio signals A1 and A2, and supplies them to the buffer amplifiers 40 and 41. The buffer amplifiers 40 and 41 amplify the audio signals A1 and A2 to a predetermined level, respectively, and output them to the subsequent circuit.
[0046]
4). Specific configuration example
4-1. Amplifier circuit of transmitter
FIG. 11 is a circuit diagram showing a configuration of the amplifier circuit 3 (28) which is the final stage of the transmission apparatus 1. In the figure, the amplifier circuit 3 (28) is the same as the modulation circuit for infrared transmission except that the conventional LED driver for the final stage for infrared transmission is removed and the electrode 4 is connected to be touched instead. It is the same composition. The operational amplifier OP1 is used as a normal inverting amplifier, and capacitors C1 (22 μF) and C2 (0.1 μF) and a resistor R1 (2.7 kΩ) are connected in parallel between the non-inverting input terminals between the grounds. . Further, the other end of the feedback resistor R2 (10 kΩ) whose one end is connected to the output end is connected to the inverting input end (−), and the resistor R3 (470Ω) is connected between the output end and the ground. Has been. Further, as described above, the output of the operational amplifier OP1 is connected to the electrode 4 via the capacitor C3 (10 pF) and is disconnected in a direct current manner. Further, the electrode 4 uses a 2 × 3 cm copper foil in this embodiment.
[0047]
The transmitter 1 is housed in a shielded plastic case, and is attached to the lower part of a video camera (CCD-G1) 30 as shown in FIG. 12, so that the whole can be driven by a battery (power source) 31. In this way, by adopting an independent configuration as a whole, the ground part on the transmission side and the reception side can be coupled only by a spatial electrostatic magnetic field. The electrode 4 is provided so as to be exposed to the main body of the video camera that is touched by the hand when the video camera 30 is held by hand. A video signal that is an output of the video camera 30 is supplied to the transmission device 1 via a cable connected to the camera connector 32.
[0048]
Note that when the transmitter and receiver are operated with an AC adapter or the like, the ground side can be securely coupled and a high-quality image can be obtained, but this is not considered when the video camera is held by hand and recorded on the deck.
[0049]
4-2. Receiver selection circuit
FIG. 13 is a circuit diagram illustrating a configuration of the selection circuit 7 (30) of the reception device 5. In the figure, a selection circuit 7 (30) is a combination of a high impedance buffer 50 and an LC resonance circuit 51. Moreover, the electrode 6 uses a 1 × 1 cm copper foil in this embodiment. Other than these, like the amplifier circuit 3 of the transmission apparatus 1, the configuration is the same as that of the infrared transmission circuit using the LED, and thus the description thereof is omitted. This receiving device 5 is incorporated in a tuner case for GV-SX50, and images are output by SX-50.
[0050]
FIG. 14 is a characteristic diagram showing the frequency characteristics of the selection circuit 7 having the above-described configuration. FIG. 15 is a spectrum when the color bar is received in the same configuration (measured at the SX-50 output terminal; It is a characteristic view showing a board). As shown in FIG. 14, the frequency characteristic of the selection circuit 7 has a characteristic that it gradually rises from 1 MHz to about 15 MHz, and abruptly attenuates thereafter. Further, as shown in FIG. 15, it is understood that the spectrum when the color bar is received has a characteristic having a maximum peak near 15 MHz.
[0051]
4-3. Characteristic measurement
In the configuration shown in FIG. 12, the characteristic measurement is difficult because both the video camera on the transmission side and the VW on the reception side are driven by the battery. Therefore, a breadboard (commercial power supply drive) for infrared transmission examination was used on the transmission side, and the battery side VW was used only on the reception side.
[0052]
FIG. 16 is a block diagram showing the configuration of the transmission path characteristic measurement system in this case. In the figure, a breadboard 50 is used on the transmission side, and a video signal from a video signal generator (TG-7 / 1) 51 which is also driven by a commercial power source is supplied to the breadboard 50. It has become so. On the receiving side, a VW (GV-SX50) 52 driven by a battery 53 is used, and its output is supplied to a noise meter (925D / 1) 54 driven by a commercial power source. The breadboard 50 is provided with an output electrode 51 (corresponding to the electrode 4). Similarly, the receiving side VW 52 is also provided with an input electrode 52 (electrode 6). The electrode 51 and the electrode 52 are electrically connected by the human body 10.
[0053]
According to this configuration, since the receiving side also connects the video out to the measuring instrument, it is equivalent to the GND loops on the transmitting side and the receiving side being connected. Therefore, the transmission conditions are better than the case where the video camera and the VW are each used alone, so it is considered as a rough standard. Below, the measured value measured by the said structure is shown. These were measured by the video characteristic measurement method of the video deck.
Y S / N 47.5 dB chroma AM 43 dB chroma PM 44 dB
[0054]
5. Operation of this embodiment
Next, the operation when the above-described transmission / reception apparatus shown in FIGS. 9 and 10 is used will be described. The input video signal V1 is FM-modulated by the modulation circuit 21 after the level is adjusted in the buffer circuit. The audio signals A1 and A2 are also FM-modulated by the modulation circuits 23 and 24 after passing through a simple buffer circuit (not shown). Each modulation output passes through bandpass filters 22, 25, and 26 that pass only necessary carrier components, and is mixed in the mixing circuit 27 according to its resistance ratio, and then amplified to an appropriate level by an amplifier. Output from the electrode 4.
[0055]
A signal transmitted from the electrode 4 is transmitted to the electrode 6 of the receiving device via the human body 10. From the signal supplied to the electrode 6, a signal in a necessary frequency band is extracted by the signal selection circuit 30, and the carrier of the video signal V1 passes through the band-pass filter 31, and then is demodulated by the demodulation circuit 33 via the limiter 32. Is demodulated into a video signal V1. On the other hand, the carriers of the audio signals A1 and A2 are amplified by the amplifier 35, pass through the bandpass filters 36 and 37, respectively, and then demodulated into the audio signals A1 and A2 which are the original signals by the demodulation circuits 38 and 39. The
[0056]
6). Modified example
6-1. Example of increasing the carrier frequency and increasing the number of channels
As in the present invention, when an electrostatic magnetic field is used, the transmission distance is inversely proportional to the frequency. If the practical distance is 2 m, the carrier frequency is about 20 MHz. Considering the use up to this band, the video signal can take about 2 channels. As audio, there is plenty of room in the channel. Therefore, the above-described configuration may be used for multi-channel A / V transmission.
[0057]
6-2. Multi-channel, general-purpose signal transmission
In the above-described embodiment of the present invention, only A / V transmission has been described. However, a signal having a frequency band of about several MHz can be transmitted regardless of its contents, and the above-described configuration can be used for other signal transmissions. It may be used. At this time, the number of channels may be determined by the band occupied by the signal to be transmitted.
[0058]
[Supplement]
The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention. That is, the present invention has been disclosed in the form of exemplification, and the contents described in the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims section described at the beginning should be considered.
[0059]
【The invention's effect】
As described in detail above, according to the present invention, the transmitter of the transmitting device that has the modulation means for modulating the original signal and outputs the final output signal from the first conductive member that is exposed to the outside is provided. A first conductive member and a second conductive member of a receiving device that has a demodulating unit that demodulates a received signal and receives the received signal from a second conductive member that is exposed to the outside. In addition, since a signal is transmitted between the transmitting device and the receiving device by contact with a human body, the signal can be transmitted wirelessly in practical use, and the relative position between the transmitting device and the receiving device is free. Therefore, the feeling of use is greatly improved. Further, according to the present invention, the power required for the transmission device and the reception device is small, and can be applied to portable devices. Further, there is an advantage that the feeling of use of the device worn on the body and used like the visortron can be improved.
[0060]
In the communication system using the human body induction electric field, it is necessary to form at least one signal path other than the human body between the transmitter and the receiver. According to the signal transmission method of the present invention, the electromagnetic field in the space formed between the transmission device and the reception device is used as the signal path other than the human body.
[0061]
On the other hand, for example, Japanese Patent Laid-Open Nos. 61-46637 and 61-46639 include a contact electrode that can be contacted by a living body and a transmission circuit that transmits and receives an information transmission signal through the contact electrode. An information transmission device comprising a host unit, a portable electrode that can be in contact with the surface of a living body, and a portable subunit that includes a transmission circuit that transmits and receives information transmission signals via the living body electrode is disclosed. Japanese Patent Laid-Open No. 4-217086 discloses that information is transferred between an IC card reader and an IC card external device via a human body. However, these conventional techniques use the ground as a signal path other than the human body. This is easily conceived by those skilled in the art because each publication does not mention any spatial electromagnetic field, or assumes that the transmitter / receiver is grounded.
[0062]
In other words, according to the signal transmission system according to the present invention, since the electromagnetic field in space is used as a signal path other than the human body, it is not always necessary to ground the transceiver. That is, the transceiver can be configured as a portable device. On the other hand, in the above prior art, since the ground is used for a signal path other than the human body, at least one of the transceivers must be configured as a grounded device.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration of a whole transmitting / receiving apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic conceptual diagram showing the basic configuration for explaining the principle of signal transmission according to an embodiment of the present invention.
FIG. 3 is a conceptual diagram showing an electromagnetic field generated by a minute dipole antenna.
FIG. 4 is a characteristic diagram showing transmission characteristics (between hands) of a human body measured using a spectrum analyzer in the range of 1 MHz to 20 MHz.
FIG. 5 is a characteristic diagram showing transmission characteristics (between hands) of a human body measured using a spectrum analyzer in a range of 1 MHz to 30 MHz.
FIG. 6 is a characteristic diagram showing the relationship between the electric field strength and the distance from the antenna.
FIG. 7 is a characteristic diagram showing the relationship between the electric field strength and the distance from the antenna of a λ / 2.2 dipole antenna, a 3.4 cmφ loop antenna, and 8 cmφ and 3.4 cmφ loop antennas.
FIG. 8 is a schematic configuration diagram showing a connection relationship between an output stage on a transmitting side, a human body, and a receiving side for explaining how much an inflow current flows into the human body.
FIG. 9 is a block diagram showing a detailed configuration of a transmission apparatus according to an embodiment of the present invention.
FIG. 10 is a block diagram showing a detailed configuration of a receiving apparatus according to an embodiment of the present invention.
FIG. 11 is a circuit diagram showing a configuration of an amplifier circuit 3 (28) which is the final stage of the transmission apparatus 1 according to the embodiment of the present invention.
FIG. 12 is an external view showing a state where the transmission apparatus according to the embodiment of the present invention is attached to a video camera.
FIG. 13 is a circuit diagram showing a configuration of a selection circuit 7 (30) of the reception device 5 according to the embodiment of the present invention.
FIG. 14 is a characteristic diagram showing frequency characteristics of the receiving apparatus according to the embodiment of the present invention.
FIG. 15 is a characteristic diagram showing a spectrum when a receiving apparatus according to an embodiment of the present invention receives a color bar.
FIG. 16 is a block diagram showing a configuration of a transmission path characteristic measurement system according to the embodiment of the present invention;
[Explanation of symbols]
1 ... Transmitter
2 ... FM modulation circuit (modulation means)
3 ... Amplifier circuit
4 ... Electrode (first conductive member)
5 ... Receiver
6 ... Electrode (second conductive member)
7 ... Selection circuit
8 ... FM demodulation circuit
33, 38, 39 ... demodulation circuit
10 ... human body
20 ... Buffer circuit
21, 23, 24 ... modulation circuit
22, 31, 36, 37 ... band pass filter
27 ... Mixed circuit
28, 34, 40, 41 ... buffer amplifier
30. Signal selection circuit
32 ... Limiter
35 ... Amplifier
V1 ... Video signal (original signal)
A1, A2 ... Audio signal (original signal)

Claims (7)

A signal transmission device including a modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member;
A signal receiving device having a second conductive member, a receiving unit that receives a signal from the second conductive member, and a demodulating unit that demodulates the received signal;
With
In signal transmission between the signal transmitting device and the signal receiving device, a human body to which the first conductive member and the second conductive member are electrically connected as a transmission path, and the transmitting device and the receiving device. The electromagnetic field of the space formed between the devices is used,
A signal transmission system characterized by that. A modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member;
When performing signal transmission between a second conductive member, a receiving device that receives a signal from the second conductive member, and a demodulating unit that demodulates a received signal, as a transmission path, Using a human body to which the first conductive member and the second conductive member are electrically connected, and an electromagnetic field in a space formed between the transmitting device and the receiving device,
A signal transmission apparatus characterized by that. An electrostatic magnetic field is used as the electromagnetic field.
The signal transmission apparatus according to claim 2. In signal transmission between the transmission device and the reception device, a ground to which the transmission device and the reception device are electrostatically coupled is further used as a transmission path.
The signal transmission apparatus according to claim 2. A second conductive member, a receiving unit that receives a signal from the second conductive member, and a demodulating unit that demodulates the received signal;
When signal transmission is performed between a signal transmission device including a modulation unit that modulates an original signal, a first conductive member, and an output unit that outputs an output signal from the first conductive member , , Using a human body to which the first conductive member and the second conductive member are electrically connected, and an electromagnetic field in a space formed between the transmitting device and the receiving device,
A signal receiving device. An electrostatic magnetic field is used as the electromagnetic field.
The signal receiving apparatus according to claim 5. In signal transmission between the transmission device and the reception device, a ground to which the transmission device and the reception device are electrostatically coupled is further used as a transmission path.
The signal receiving apparatus according to claim 5.

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