JP4513154B2

JP4513154B2 - Reception circuit and security system using the same

Info

Publication number: JP4513154B2
Application number: JP2000039806A
Authority: JP
Inventors: 和之迫田; 裕昭高野
Original assignee: Sony Corp
Current assignee: Sony Corp
Priority date: 2000-02-14
Filing date: 2000-02-14
Publication date: 2010-07-28
Anticipated expiration: 2020-02-14
Also published as: JP2001229474A

Description

【０００１】
【発明の属する技術分野】
本発明は、電波を送受信装置の間にマルチパスを形成し、受信装置によって受信された信号に基づき、マルチパスに侵入者の有無を検出可能な電波受信装置及びそれを含むセキュリティシステムに関するものである。
【０００２】
【従来の技術】
これまでに、屋内などの所定の区域内において侵入者の有無を自動的に検知するセキュリティシステムとしては、赤外線レーザを用いた検知システムが実用化されている。
図８は、このシステムの一構成例を示している。図示のように、このようなシステムにおいては、監視区域内に複数の赤外線レーザの送信器（Ｔｘ）と受信器（Ｒｘ）がそれぞれ対をなして設置されている。侵入者が対をなす送信機と受信機との間を通ると、レーザ光線が遮断され、その間受信器にはレーザ光線の入射がなくなる。受信機は、このレーザ光線の遮断が検出されると、この情報はセキュリティシステムのコントロールセンターに通報され、コントロールセンターによって然るべき処置が行われる。
【０００３】
【発明が解決しようとする課題】
ところで、上述した従来のセキュリティシステムにおいては、送信機から送信されるレーザ光線が見通して受信できるように送信機と受信機の配置を行わなければならず、設置場所が一定の制限を受けるという不利益が生じる。また、基本的に、受信機と送信機との対によって監視できる区域が送信機と受信機の間の空間のみであり、広範囲の空間を監視する場合に多数の送受信機を設置しないと侵入者の検知を確実に行うことができない。
さらに、送信機と受信機は対にをなして設置しなければならないため、多くの装置を設置する必要があって、システムの構築が煩雑であり、コストがかかるという不利益がある。
【０００４】
本発明は、かかる事情に鑑みてなされたものであり、その目的は、数少ない送受信機によって所定の区域を監視可能であり、装置の設置数を大幅に削減しつつ、従来よりも広い範囲の監視を容易に実現でき、最低１対の送受信機のみを用いて構築できるセキュリティシステムを提供することにある。
【０００５】
【課題を解決するための手段】
上記目的を達成するため、本発明の受信回路は、送信回路において所定の周波数帯域に変調され、散乱して空間に放射された電波信号をマルチパスを介して受信し、当該受信信号に応じて上記電波信号のマルチパス上に生じたフェーディングの変化を検出する受信回路であって、上記マルチパスを介して伝搬された電波信号を受信し、受信信号に対して周波数変換を行う受信手段と、上記受信手段によって得られた受信信号を所定の変調方式に対応する復調方式によって復調する復調手段と、上記受信手段が連続して複数回受信して上記復調手段で復調した信号を平滑化手段で平滑化し、当該平滑化した信号を測定する測定手段と、所定期間連続して複数回受信した受信信号に対して上記平滑化手段で平滑化して雑音の影響を除去した信号を上記測定手段で測定し、測定して求められた信号が上記測定手段から出力される出力信号と、上記受信回路が検出動作の前に行う初期化のとき、上記平滑化手段で一定期間連続して受信した複数の受信信号について平均化処理して雑音を除去して得られた所定の基準信号を比較し、当該比較結果に応じて上記電波信号の上記マルチパス上に変化が生じたか否かを判断する検出手段と、を有する。
【０００６】
また、本発明のセキュリティシステムは、所定の周波数帯域に変調した信号を散乱させて空間に放射する送信回路と、上記送信回路によって送信された信号をマルチパスを介して受信し、受信信号に応じて上記送信回路からの電波信号のマルチパス上に侵入者が存在するか否かを検出する受信回路とを有し、上記受信回路は、受信信号を上記送信回路に行われた変調方式に対応する復調方式で復調する復調手段と、上記受信回路が連続して複数回受信して上記復調手段で復調した信号を平滑化手段で平滑化し、当該平滑化した信号を測定する測定手段と、所定期間連続して複数回受信した受信信号に対して上記平滑化手段で平滑化して雑音の影響を除去した信号を上記測定手段で測定し、測定して求められた信号が上記測定手段から出力される出力信号と、上記受信回路が検出動作の前に行う初期化のとき、上記平滑化手段で一定期間連続して受信した複数の受信信号について平均化処理して雑音を除去して得られた所定の基準信号を比較し、当該比較結果に応じて上記送信回路と受信回路との間の上記マルチパス上に侵入者が存在するか否かを判断する検出手段とを有する。
【０００８】
また、本発明では、好適には、上記基準電力は、第１の基準及び当該第１の基準電力より値が大きい第２の基準電力とを有し、上記比較手段は、上記受信電力と第１及び第２の基準電力とをそれぞれ比較し、上記判断手段は、上記受信電力が上記第１と第２の基準電力の間にあるとき、上記送信回路と受信回路との間の信号伝搬経路上に侵入者が存在しないと判断し、上記受信電力が上記第１の基準電力より小さく、または上記第２の基準電力より大きいとき、上記送信回路と受信回路との間の信号伝搬経路上に侵入者が存在すると判断する。
【００１１】
また、本発明では、好適には、上記比較手段は、上記測定したベクトルと上記基準ベクトルとの差の絶対値を計算するベクトル演算手段と、上記ベクトル演算手段によって算出した上記ベクトル差の絶対値と所定の許容誤差とを比較する比較回路とを有する。
【００１２】
また、本発明では、好適には、上記送信回路は、上記送信信号を所定の疑似雑音符号（ＰＮ符号）を用いてスペクトル拡散を行うスペクトル拡散回路を有する。
【００１３】
さらに、本発明では、好適には、上記受信回路は、上記送信回路と同じ疑似雑音符号を用いてスペクトル逆拡散を行う逆拡散回路を有する。
【００１４】
【発明の実施の形態】
第１実施形態
図１は本発明に係るセキュリティシステムの一実施形態を示す回路図である。図示のように、本実施形態のセキュリティシステムは、送信機（Ｔｘ）１０、受信機（Ｒｘ）２０−１，２０−２，…，２０−ｎ、モニター３０及びセキュリティコントロールセンターによって構成されている。
以下、本実施形態のセキュリティシステムの各部分の構成及び動作について説明する。
【００１５】
送信機１０は、所定の高周波帯域に変調された信号を複数の方向に散乱させて送信する。送信された高周波信号が監視区域内において不特定の方向に伝送されるため、送信機１０と受信機２０−１，２０−２，…，２０−ｎ（ｎは自然数、かつｎ≧２）の間にマルチパスが形成され、マルチパスを介して伝送された信号がそれぞれの受信機によって受信される。
【００１６】
受信機２０−１，２０−２，…，２０−ｎは、マルチパスを介して伝送されてきた信号を受信し、受信信号と予め設定されたリファレンス信号とを比較し、当該比較結果に応じて、監視区域内に侵入者がいるか否かを判断し、侵入者の存在を検出した場合、モニター３０に検知信号を送信する。
モニター３０は、受信機２０−１，２０−２，…，２０−ｎのうち、何れかの受信機から送信された検知信号を受信したとき、監視区域内に侵入者がいると判断し、セキュリティコントロールセンター４０に通報する。セキュリティコントロールセンター４０がモニター３０からの通報を受けたとき、他の情報に基づき、監視区域に侵入者の有無を確認し、然るべき処置をとる。
【００１７】
なお、図１に示すセキュリティシステムにおいて、送信機１０に対して、複数の受信機が設けられているが、本発明は、この構成に限定されることなく、例えば、１台の送信機に対して、１台の受信機のみを用いてセキュリティシステムを構成することもできる。
【００１８】
以下、本実施形態のセキュリティシステムの原理について説明する。
上述したセキュリティシステムにおいて、送信機１０によって高周波に変調された送信信号が、例えば、無指向性アンテナによって送信される結果、送信電波があらゆる方向に散乱される。このため、各受信機において、様々な方向から電波が到来し、これにより各受信機においてはマルチパスフェーディング（Fading）状態となる。この場合、送受信機の場所が変化したり、送受信機間の電波の伝搬経路に変動が生じたとき、受信機において受信された信号電力ＲＳＳＩが変動する。
送受信機の設置場所が一定である場合、マルチパスが形成されている監視区域内に侵入者がいなく、かつ外部からの電波干渉もない安定した条件において、各受信機における受信電力ＲＳＳＩはほぼ一定になる。
【００１９】
監視区域内に侵入者が入った場合、送信機１０と何れか１つまたは複数の受信機間の電波伝搬経路に変化が生じる。この変化によって、１つまたは複数の受信機の受信電力ＲＳＳＩが変動する。受信機は、予め安定した条件において得られた受信電力を基準値として設定し、それ以降各時刻に受信した信号の電力と設定した基準値とを比較し、受信電力と当該基準値との差分が所定のしきい値を越えたとき、監視区域内に侵入者が存在すると判断し、モニター３０に検知信号を送信する。
【００２０】
以下、受信機の２つの実施例を示し、本実施形態のセキュリティシステムを形成する受信機の構成及び動作について説明する。
受信機の第１の実施例
図２は、受信機の一構成例を示す回路図である。図示のように、受信機２０ａは、アンテナ２１、高周波受信部（ＲＦ受信部）２２、受信電力測定部２３、検出部２４、電源供給部２５及びタイマー２６によって構成されている。
【００２１】
高周波受信部２１は、アンテナ２１によって受信した高周波信号を増幅し、さらに必要に応じて、周波数変換によって受信信号を所定の中間周波数またはベースバンド帯域に変換し、変換した中間周波信号またはベースバンド信号を受信電力測定部２３に供給する。
【００２２】
受信電力測定部２３は、高周波受信部２２から入力された信号の電力を測定する。ここで、信号電力の測定は、振幅を測定し、測定した振幅に応じて信号電力をはかるなどの方法によって行われる。
なお、受信電力を測定する前に、必要に応じて、信号を復調する復調処理を行うこともある。例えば、送信機１０において、所定の信号に変調が行われた場合、受信機において、送信機によって行われた変調方式に応じて受信信号を復調し、復調した信号に対して受信電力を測定する。この復調処理は、高周波受信部２１の出力信号に対して行われるので、受信電力測定部２３に復調回路を設けるか、あるいは、受信電力測定部２３の前に復調回路を別に設けることができる。
【００２３】
検出部２４は、受信電力測定部２３によって測定した受信電力と予め設定した基準値とを比較し、当該比較結果に基づいて侵入者の有無を検知し、侵入者を検知した場合、検知信号Ｓ_Dを発生し、モニター３０に送信する。
検出部２４は、外部から入力された基準値、または予め内部のメモリに記憶されている基準値を用いて、受信電力測定部２３によって測定した受信電力とを比較し、侵入者の検知を行う。送受信機の設置場所、監視区域の環境などの条件によって、受信機において受信された信号の電力が変化する。このため、検出部２４において用いられる基準値を測定条件に応じて適宜設定することが好適である。例えば、受信機において電源が投入される初期状態、あるいはタイマー２６によって予め設定された時間において、受信電力を採集し、当該受信電力を基準値をしてメモリに格納する。また、好ましくは一定の時間帯において連続して採集した複数の受信電力に対して平均化処理などの方法によって雑音を除去し、得られた受信電力を基準値としてメモリに格納する。
【００２４】
電源部２５は、高周波受信部２２、受信電力測定部２３、検出部２４及びタイマー２６に電源電圧を供給する。
【００２５】
タイマー２６は、受信機２０ａの全体の動作タイミングを制御する基準タイミング信号を発生し、受信機を構成する各部分回路に供給する。また、タイマー２６によって、電源部２５に電源供給をオン／オフさせる電源制御信号Ｓ_Eを送信する。電源部２５は、この電源供給制御信号Ｓ_Eに応じて、各部分回路への電源の供給をオン／オフする。例えば、タイマー２６に予め監視動作が不要な時間帯を入力しておくと、この休止時間帯が開始したとき、タイマー２６は、電源部２５に電源供給を停止させる信号を送信し、受信機２０ａの各部分回路への電源の供給を停止させ、待機状態における消費電力の低減をはかる。休止時間帯が終わったとき、タイマー２６は電源供給部２５に電源供給をイネーブルさせる信号を送信し、受信機２０ａの各部分回路への電源の供給を開始させる。
【００２６】
図３は、本実施形態の受信回路２０ａの動作を示すフローチャートである。以下、図２及び図３を参照しつつ、受信回路２０ａの動作を説明する。
セキュリティシステムがイネーブルされたあと、まず、受信機２０ａは、予め定められた時間Ｔ_Sの間を待ち時間とする。タイマー２６は、この待ち時間Ｔ_Sを計測し、待ち時間Ｔ_Sが経過したとき、電源供給部２５に電源供給をイネーブルさせる信号を送信し、受信機２０ａの各部分回路への電源の供給を開始させ、受信機２０ａを起動させる（ステップＳ１）。
【００２７】
受信機２０ａが起動したあと、タイマー２６によって設定された時刻に、受信動作を行い、受信電力を採集し、それに基づき検出部２４に基準値を設定する（ステップＳ２）。なお、基準値の設定は上述したように、例えば、ある時間帯において連続して採集した複数の受信電力値に基づき、平均化処理などによって雑音成分を除去した値を基準値として、また、採集した受信電力値に応じて、検出部２４において検出を行う場合の最大値ＴＨ_Hと最小値ＴＨ_Lを設定し、メモリに格納する（ステップＳ３）。
【００２８】
上述した処理が終了したあと、受信機２０ａはタイマー２６によって設定した時間において受信電力を連続して測定し、測定結果に応じて侵入者の有無を検知する。
まず、ステップＳ４において、高周波受信部２２によって受信した信号に応じて、受信電力測定部２３によって信号受信電力を測定する。
【００２９】
次に、検出部２４において、受信電力測定部２３によって測定した受信電力とメモリに格納されている最大値ＴＨ_H、最小値ＴＨ_Lとをそれぞれ比較し、比較の結果に応じて、侵入者の有無を判定する。
ステップＳ５において、測定された受信電力Ｒ_Eと基準値の最大値ＴＨ_Hとが比較され、測定値が最大値ＴＨ_Hより大きい場合（Ｒ_E＞ＴＨ_H）、侵入者が存在すると判断し、ステップＳ８において検知信号をモニターに送信する。
ステップＳ６において、測定された受信電力Ｒ_Eと基準値の最小値ＴＨ_Lとが比較され、測定値が最小値ＴＨ_Lより小さい場合（Ｒ_E＜ＴＨ_L）、侵入者が存在すると判断し、ステップＳ８において検知信号をモニターに送信する。
【００３０】
即ち、侵入者がいない場合、マルチパスを介して受信機２０ａに入力される電波の受信電力がほとんど変化しないので、信号の受信電力Ｒ_Eは、最大値ＴＨ_Hと最小値ＴＨ_Lとの間にある（ＴＨ_L＜Ｒ_E＜ＴＨ_H）。一方、侵入者が存在する場合に、マルチパスを介して受信機２０ａに入力された電波の受信電力が変化し、測定された受信電力Ｒ_Eは、最大値ＴＨ_Hと最小値ＴＨ_Lによって規定された範囲を越える（Ｒ_E＞ＴＨ_HあるいはＲ_E＜ＴＨ_L）。
【００３１】
このように、検出部２４によって測定された受信電力Ｒ_Eと予め設定された最大値ＴＨ_H、最小値ＴＨ_Lとを比較することによって、監視区域内に侵入者が存在するか否かを検出できる。
【００３２】
一回の検出処理が終了したとき、処理を続行するか否かが判断される。即ち、受信電力の測定が終了するか否かを判断し、終了しない場合にステップＳ４に戻り、上述したステップＳ４〜Ｓ６の処理が繰り返して行われる。
検出処理が終了した場合、例えば、電源供給部２５に電源供給を停止させる信号が送信される。この信号を受けて、電源供給部２５が電源を供給を停止、受信機２０ａが待機状態に保持される。
【００３３】
なお、上述した検出処理は、受信電力測定部２３によって測定した受信電力を用いて、検出部２４において当該受信電力と基準値の最大値ＴＨ_H及び最小値ＴＨ_Lとの比較結果に応じて侵入者の有無を判断するが、電波干渉などの雑音の影響によって瞬間的に受信電力に大きなが変化が生じることがある。この場合、受信電力の測定値が最大値ＴＨ_H及び最小値ＴＨ_Lで設定した範囲を越えて、検出部２４によって侵入者が存在したと誤って判断し、誤警報を発することがある。これを防止するために、所定の期間において連続して複数回受信した信号に対して平滑化フィルタなどによって雑音の影響を除去した値を用いて、侵入者の有無を判断する方法が有効である。なお、この受信信号の平滑化処理は、受信機の初期化のときに基準値を設定するために行われている受信電力の平均化処理と共通の処理回路を用いて実行できるので、回路規模の増加を必要最小限に抑制できる。
【００３４】
以上説明したように、本実施例の受信機２０ａによれば、高周波受信部２２によって受信され、さらに周波数変換された受信信号が受信電力測定部２４に供給され、受信電力Ｒ_Eが測定される。検出部２４において、受信電力Ｒ_Eと予め設定された基準値の最大値ＴＨ_H及び最小値ＴＨ_Lとが比較され、受信電力Ｒ_Eが最大値ＴＨ_Hと最小値ＴＨ_Lによって設定した範囲内にあるとき、監視区域内に侵入者が存在しないと判断し、一方、受信電力Ｒ_Eが最大値ＴＨ_Hと最小値ＴＨ_Lによって設定した範囲外にあるとき、監視区域内に侵入者が存在すると判断され、モニター３０に検知信号が送信される。送受信機の間に形成されたマルチパスによるフェーディングによる信号の受信レベルの変化に基づき、マルチパスの形成区域における侵入者の存在を検出することが可能であり、簡単なシステムの構成で広範囲の区域を監視でき、システムの簡素化、低コスト化が図れる。
【００３５】
受信機の第２の実施例
図４は、受信機の他の構成例を示す回路図である。図示のように、受信機２０ｂは、アンテナ２１、高周波受信部（ＲＦ受信部）２２、受信ベクトル測定部２３ａ、検出部２４ｂ、電源供給部２５及びタイマー２６によって構成されている。
【００３６】
本実施例の受信機２０ｂは、前述した第１の実施例の受信機２０ａに比べて、受信電力を測定し、それに応じて侵入者を検知する代わりに、受信信号のベクトルを測定し、当該受信ベクトルの変化に応じて侵入者を検知する。
以下、本実施例における受信ベクトル測定部２３ａと検出部２４ａの構成及び動作を中心し、本実施例の受信機２０ｂの構成及び動作について説明する。
【００３７】
高周波受信部２２によって受信され、さらに周波数変換された信号が受信ベクトル測定部２３ａに入力される。即ち、受信ベクトル測定部２３ａに入力された信号は、中間周波信号あるいはベースバンドの信号である。
受信ベクトル測定部２３ａは、入力信号のベクトルを測定する。ここで、送信機１０によって、ある変調方式に従って変調された信号が送信されると仮定する。受信ベクトル測定部２３ａにおいて、入力した信号を復調し、復調した信号の実数部と虚数部を求めて、受信ベクトルを求める。
なお、送信機１０に用いられる変調方式は、例えば、ＰＳＫ変調、ＱＰＳＫ変調などである。
【００３８】
検出部２４ａは、受信ベクトル測定部２３ａによって得られた受信ベクトルと予め設定された基準ベクトルとを比較し、当該比較の結果に応じて、監視区域内に侵入者が存在するか否かを判断する。
【００３９】
以下、本実施例の受信機２０ｂの原理について説明する。
上述したように、送信機１０において無指向性アンテナによって、あらゆる方向に散乱した電波が送信される。これによって、送信機１０と受信機２０ｂとの間に、マルチパスが形成され、送信機１０によって送信された電波がマルチパスを介して、受信機２０ｂに到達する。受信機２０においては、マルチパスフェーディングによって受信信号の振幅及び位相が変化する。
【００４０】
送受信機の設置場所が一定である場合、マルチパスが形成されている監視区域内に侵入者がいなく、かつ外部からの電波干渉もない安定した条件において、受信機２０ｂにおける受信ベクトルがほぼ一定になる。しかし、マルチパスの形成されている区域内に侵入者が入った場合、送受信機間の信号伝送経路に変化が生じる。この変化によって、受信機２０ｂの受信信号の振幅または位相が変化する。このため、受信機２０ｂにおいて、受信ベクトルと予め設定した基準ベクトルとを比較し、これらベクトルの誤差がある一定の誤差範囲内にあれば、送受信機間のマルチパスに大きな変化がなく、即ち、侵入者が存在しないと判断できる。一方、受信ベクトルと基準ベクトルとのベクトル誤差がある一定の誤差範囲を越えたとき、送受信機間のマルチパスに大きな変化があり、侵入者が存在すると判断できる。
【００４１】
図５は、本実施例の受信機２０ｂの検出原理を示す図である。ここで、Ｒ_V0は基準ベクトル、ｒは許容誤差を示す。基準ベクトルＲ_V0と許容誤差ｒによって決められた範囲は誤差範囲として、受信ベクトルＲ_Vがこの誤差範囲内にあるとき、送受信機間のマルチパスに大きな変化がなく、侵入者がいないと判断される。逆に、受信ベクトルＲ_Vがこの誤差範囲の外にあるとき、送受信機間のマルチパスに大きな変化が生じ、侵入者が存在すると判断される。
【００４２】
図６は、本実施例の受信機２０ｂの動作を示すフローチャートである。以下、図４〜図６を参照しつつ、本実施例の受信機２０ｂの動作を説明する。
まず、受信機２０ｂは、予め定められた時間Ｔ_Sの間を待ち時間とする。タイマー２６は、この待ち時間Ｔ_Sを計測し、待ち時間Ｔ_Sが経過したとき、電源供給部２５に電源供給をイネーブルさせる信号を送信し、受信機２０ｂの各部分回路への電源の供給を開始させ、受信機２０ｂを起動させる（ステップＳＳ１）。
【００４３】
受信機２０ｂが起動したあと、タイマー２６によって設定された時刻に、受信動作を行い、受信ベクトルを測定し（ステップＳＳ２）、それに基づき検出部２４ａに基準ベクトル及び許容誤差ｒを設定する（ステップＳＳ３）。なお、基準ベクトル及び許容誤差ｒの設定は上述したように、例えば、ある時間帯において連続して測定した複数の受信ベクトルに基づき、平均化処理などによって雑音成分を除去したベクトルを基準ベクトルＲ_V0として、また、基準ベクトルＲ_V0に対して、測定した各受信電力ベクトルの偏差などに応じて、検出部２４ａにおいて検出を行う場合の許容誤差ｒを設定し、メモリに格納する（ステップＳＳ３）。
【００４４】
上述した処理が終了したあと、受信機２０ｂはタイマー２６によって設定した時間において連続して受信ベクトルＲ_Vを測定し、測定結果に基づき侵入者の有無を検知する。
まず、ステップＳＳ４において、高周波受信部２２によって受信した信号に応じて、受信ベクトル測定部２３ａによって信号受信ベクトルを測定する。
【００４５】
次に、検出部２４ａにおいて、受信ベクトル測定部２３ａによって測定した受信ベクトルとメモリに格納されている基準ベクトルとの誤差ΔＲ（ΔＲ＝｜Ｒ_V−Ｒ_V0｜）を求め、算出したΔＲと許容誤差ｒとを比較し、比較の結果に応じて侵入者の有無を判定する（ステップＳＳ５）。
【００４６】
ΔＲが許容誤差ｒより大きい場合（ΔＲ＞ｒ）、侵入者が存在すると判断し、ステップＳＳ７において検知信号をモニターに送信する。
一方、ΔＲが許容誤差ｒより小さい場合（ΔＲ＜ｒ）、侵入者が存在しないと判断し、次のステップＳＳ６に進む。
【００４７】
このように、検出部２４ａによって測定された受信ベクトルＲ_Vと予め設定された基準ベクトルＲ_V0とを比較することによって、監視区域内に侵入者が存在するか否かを検出できる。
【００４８】
一回の検出処理が終了したとき、処理を続行するか否かが判断される。即ち、侵入者を検知する処理が終了するか否かを判断し、終了しない場合にステップＳＳ４に戻り、上述したステップＳＳ４〜ＳＳ５の処理が繰り返して行われる。
検知処理が終了した場合、例えば、電源供給部２５に電源供給を停止させる信号が送信される。この信号を受けて、電源供給部２５が電源を供給を停止、受信機２０ｂが待機状態に保持される。
【００４９】
なお、上述した検出処理は、受信ベクトル測定部２３ａによって測定した受信ベクトルを用いて、検出部２４ａにおいては当該受信ベクトルが基準ベクトル及び許容誤差ｒによって設定した範囲内にあるか否かによって侵入者の有無を判断するが、電波干渉などの雑音の影響で瞬間的に受信ベクトルの振幅または位相が大きく変化することがある。この場合、受信ベクトルの測定値が基準ベクトルＲ_V0及び許容誤差ｒで設定した範囲を外れ、検出部２４によって侵入者が存在したと誤って判断し、誤警報を発することがある。これを防止するために、所定の期間において連続して複数回受信した信号に対して、平滑化フィルタなどによって雑音の影響を除去してから、侵入者の有無を判断する方法が有効である。なお、この受信信号の平滑化処理は、受信機の初期化のときに基準ベクトルＲ_V0及び許容誤差ｒを設定するために行われている受信ベクトルの平均化処理と共通の処理回路を用いて実行できるので、回路規模の増加が必要最小限に止まる。
【００５０】
以上説明したように、本実施例の受信機２０ｂによれば、高周波受信部２２によって受信され、さらに周波数変換された受信信号が受信ベクトル測定部２４ａに供給され、受信ベクトルＲ_Vが測定される。検出部２４ａにおいて、受信ベクトルＲ_Vと予め設定された基準ベクトルＲ_V0との誤差ΔＲが求められ、当該誤差ΔＲが予め設定された許容誤差ｒより小さいとき、監視区域内に侵入者が存在しないと判断し、一方、算出した誤差ΔＲが予め設定された誤差ｒより大きいとき、監視区域内に侵入者が存在すると判断され、モニター３０に検知信号が送信される。
このように、送受信機の間に形成されたマルチパスによるフェーディングによる受信ベクトルの振幅及び位相変化に基づき、マルチパスの形成区域における侵入者の有無を検出することが可能であり、簡単なシステムの構成で広範囲の区域を監視でき、システムの簡素化、低コスト化が図れる。
【００５１】
なお、上述したセキュリティシステムにおいて、電波干渉などの雑音の影響を低減するために、送信機１０において、送信信号を疑似雑音符号（ＰＮ符号、例えば、Ｍ系列）によってスペクトル拡散を行う、いわゆる２次変調を行った信号を送信する。受信機では受信信号を送信側と同じＰＮ符号を用いて逆拡散を行い、通常の復調処理などを行う。これによって、雑音の成分が分散され、瞬時的な電波干渉による誤検出を防止可能である。
【００５２】
図７は、本発明の送信回路における送信アンテナ及びその反射器の構成を示す構成図である。上述したように、本発明のセキュリティシステムにおいて、送信機１０は送信電波を散乱させ、あらゆる方向に放射させることによって、送受信機の間にマルチパスを形成させる。送信電波を散乱させるために用いられる送信アンテナの一構成例を図７に示す。
【００５３】
図７（ａ）に示すように、送信アンテナはアンテナ素子１２及び反射器１４によって構成されている。アンテナ素子１２は、図示しない送信部によって発生した高周波の送信信号を空間に放射する。通常、電波送信機に用いられている反射器は、送信電波を一定の方向に反射する、いわゆる電波を収束させるために用いられているが、本発明では、マルチパスを形成するために、反射器１４は、アンテナ素子１２によって放射した電波をあらゆる方向に反射させる、いわゆる無指向性の放射特性を持つことが望まれる。
【００５４】
図７（ｂ）は、反射器１４の一例を示している。図示のように、反射器１４の内壁に無数の凹凸が形成される。これらの凹凸によって、アンテナ素子１２によって放射した電波が散乱され、反射波が異なる方向に放射される。これによって、送受信機によって放射された電波がそれぞれ複数の異なる経路を経て受信機に到達するので、マルチパスが形成される。
【００５５】
【発明の効果】
以上説明したように、本発明のセキュリティシステムによれば、数少ない送受信機によって所定の区域を監視可能であり、装置の設置数を大幅に削減しつつ、従来よりも広い範囲の監視を容易に実現でき、最低１対の送受信機のみを用いて構築できるセキュリティシステムを実現できる利点がある。
また、本発明では、セキュリティシステムを構成する送信回路によって、ＰＮ符号を用いて送信信号に対して、スペクトル拡散処理を行い、受信回路では、送信回路と同じＰＮ符号を用いて受信信号に対してスペクトル逆拡散を行うことによって、バーストなどの電波干渉による誤警報を防止できる。
【図面の簡単な説明】
【図１】本発明に係るのセキュリティシステムの一実施形態を示す回路図である。
【図２】本発明のセキュリティシステムに用いられる受信機の第１の実施例を示す回路図である。
【図３】受信機の第１の実施例の動作を示すフローチャートである。
【図４】本発明のセキュリティシステムに用いられる受信機の第２の実施例を示す回路図である。
【図５】受信機の第２の実施例の動作原理を示す図である。
【図６】受信機の第２の実施例の動作を示すフローチャートである。
【図７】送信機における送信アンテナの構成を示す図である。
【図８】従来のセキュリティシステムの一構成例を示す図である。
【符号の説明】
１０…送信機、
２０，２０ａ，２０ｂ，２０−１，２０−２，…，２０−ｎ…受信機、
２１…アンテナ、
２２…高周波受信部、
２３…受信ベクトル測定部、
２４…検出部、
２５…電源供給部、
２６…タイマー、
３０…モニター、
４０…セキュリティコントロールセンター。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a radio wave receiving apparatus capable of forming a multipath between radio wave transmitting / receiving apparatuses and detecting the presence or absence of an intruder on the multipath based on a signal received by the receiving apparatus, and a security system including the radio wave receiving apparatus. is there.
[0002]
[Prior art]
So far, a detection system using an infrared laser has been put into practical use as a security system that automatically detects the presence or absence of an intruder in a predetermined area such as indoors.
FIG. 8 shows an example of the configuration of this system. As shown in the figure, in such a system, a plurality of infrared laser transmitters (Tx) and receivers (Rx) are installed in pairs in the monitoring area. When an intruder passes between a transmitter and a receiver that are paired, the laser beam is cut off, while the laser beam is not incident on the receiver. When the receiver detects that the laser beam has been blocked, this information is reported to the control center of the security system and appropriate action is taken by the control center.
[0003]
[Problems to be solved by the invention]
By the way, in the above-described conventional security system, the transmitter and the receiver must be arranged so that the laser beam transmitted from the transmitter can be seen and received, and the installation location is subject to certain restrictions. Profits are generated. Basically, the only area that can be monitored by the receiver-transmitter pair is the space between the transmitter and the receiver. If a large number of transceivers are not installed when monitoring a wide area, an intruder must be installed. Cannot be reliably detected.
Furthermore, since the transmitter and the receiver must be installed in pairs, it is necessary to install many devices, and there is a disadvantage that the construction of the system is complicated and the cost is high.
[0004]
The present invention has been made in view of such circumstances, and an object of the present invention is to monitor a predetermined area with a small number of transmitters / receivers, and to monitor a wider range than before while greatly reducing the number of installed devices. It is an object of the present invention to provide a security system that can be easily realized and can be constructed using at least one pair of transceivers.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, a receiving circuit of the present invention receives a radio signal modulated in a predetermined frequency band in a transmitting circuit, scattered and radiated into space via a multipath, and according to the received signal. A receiving circuit for detecting a change in fading generated on the multipath of the radio signal, the receiving circuit receiving the radio signal propagated through the multipath and performing frequency conversion on the received signal; A demodulating means for demodulating the received signal obtained by the receiving means by a demodulation method corresponding to a predetermined modulation method; and a smoothing means for a signal received by the receiving means a plurality of times and demodulated by the demodulating means And measuring means for measuring the smoothed signal,A signal obtained by smoothing the received signal received a plurality of times continuously for a predetermined period by the smoothing means and removing the influence of noise is measured by the measuring means, and a signal obtained by measurement is obtained.Output from the above measuring meansOutputSignal andWhen initialization is performed before the detection operation by the reception circuit, the smoothing means is obtained by averaging a plurality of reception signals continuously received for a certain period and removing noise.Detecting means for comparing a predetermined reference signal and determining whether or not a change has occurred on the multipath of the radio wave signal according to the comparison result.
[0006]
  In addition, the security system of the present invention receives a signal transmitted by the transmitter circuit via a multipath by scattering a signal modulated in a predetermined frequency band and radiating it into the space, and responds to the received signal. And a receiving circuit for detecting whether or not an intruder exists on the multipath of the radio signal from the transmitting circuit, and the receiving circuit corresponds to a modulation method performed on the received signal to the transmitting circuit. Demodulating means for demodulating in accordance with a demodulation method, measuring means for smoothing a signal demodulated by the demodulating means received by the receiving circuit a plurality of times and smoothing the smoothed signal, and measuring the smoothed signal,A signal obtained by smoothing the received signal received a plurality of times continuously for a predetermined period by the smoothing means and removing the influence of noise is measured by the measuring means, and a signal obtained by measurement is obtained.Output from the above measuring meansOutputSignal andWhen initialization is performed before the detection operation by the reception circuit, the smoothing means is obtained by averaging a plurality of reception signals continuously received for a certain period and removing noise.And detecting means for comparing predetermined reference signals and determining whether or not an intruder exists on the multipath between the transmitting circuit and the receiving circuit according to the comparison result.
[0008]
In the present invention, it is preferable that the reference power includes a first reference and a second reference power having a value larger than the first reference power, and the comparing means includes the received power and the first reference power. The first and second reference powers are respectively compared, and when the received power is between the first and second reference powers, the determining means is a signal propagation path between the transmitting circuit and the receiving circuit. When it is determined that there is no intruder above and the received power is smaller than the first reference power or larger than the second reference power, the signal is on the signal propagation path between the transmitting circuit and the receiving circuit. Determine that there is an intruder.
[0011]
In the present invention, it is preferable that the comparison unit includes a vector calculation unit that calculates an absolute value of a difference between the measured vector and the reference vector, and an absolute value of the vector difference calculated by the vector calculation unit. And a comparison circuit for comparing the predetermined allowable error.
[0012]
In the present invention, it is preferable that the transmission circuit includes a spread spectrum circuit that spreads the transmission signal using a predetermined pseudo-noise code (PN code).
[0013]
In the present invention, it is preferable that the receiving circuit includes a despreading circuit that performs spectrum despreading using the same pseudo-noise code as the transmitting circuit.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
First embodiment
FIG. 1 is a circuit diagram showing an embodiment of a security system according to the present invention. As shown in the figure, the security system of the present embodiment includes a transmitter (Tx) 10, receivers (Rx) 20-1, 20-2, ..., 20-n, a monitor 30, and a security control center. .
Hereinafter, the configuration and operation of each part of the security system of the present embodiment will be described.
[0015]
The transmitter 10 scatters and transmits a signal modulated in a predetermined high frequency band in a plurality of directions. Since the transmitted high-frequency signal is transmitted in an unspecified direction within the monitoring area, the transmitter 10 and the receivers 20-1, 20-2,..., 20-n (n is a natural number and n ≧ 2) A multipath is formed between them, and a signal transmitted via the multipath is received by each receiver.
[0016]
The receivers 20-1, 20-2,..., 20-n receive a signal transmitted via multipath, compare the received signal with a preset reference signal, and according to the comparison result. Then, it is determined whether or not there is an intruder in the monitoring area, and when the presence of the intruder is detected, a detection signal is transmitted to the monitor 30.
When the monitor 30 receives a detection signal transmitted from any one of the receivers 20-1, 20-2,..., 20-n, the monitor 30 determines that there is an intruder in the monitoring area, Report to the security control center 40. When the security control center 40 receives a report from the monitor 30, it checks the presence or absence of an intruder in the monitoring area based on other information and takes appropriate measures.
[0017]
In the security system shown in FIG. 1, a plurality of receivers are provided for the transmitter 10, but the present invention is not limited to this configuration, and for example, for one transmitter. Thus, a security system can be configured using only one receiver.
[0018]
Hereinafter, the principle of the security system of the present embodiment will be described.
In the security system described above, a transmission signal modulated to a high frequency by the transmitter 10 is transmitted by, for example, an omnidirectional antenna, and as a result, transmission radio waves are scattered in all directions. For this reason, radio waves arrive from various directions at each receiver, and each receiver enters a multipath fading state. In this case, the signal power RSSI received at the receiver fluctuates when the location of the transceiver changes or when the propagation path of the radio wave between the transceivers fluctuates.
When the installation location of the transceiver is constant, the received power RSSI at each receiver is almost constant under stable conditions where there is no intruder in the monitoring area where the multipath is formed and there is no external radio interference. become.
[0019]
When an intruder enters the monitoring area, a change occurs in the radio wave propagation path between the transmitter 10 and any one or more receivers. This change causes the received power RSSI of one or more receivers to vary. The receiver sets the received power obtained under stable conditions in advance as a reference value, compares the signal power received at each time thereafter with the set reference value, and the difference between the received power and the reference value When the value exceeds a predetermined threshold value, it is determined that an intruder exists in the monitoring area, and a detection signal is transmitted to the monitor 30.
[0020]
Hereinafter, two examples of the receiver will be shown, and the configuration and operation of the receiver forming the security system of this embodiment will be described.
First embodiment of receiver
FIG. 2 is a circuit diagram illustrating a configuration example of the receiver. As illustrated, the receiver 20 a includes an antenna 21, a high frequency receiving unit (RF receiving unit) 22, a received power measuring unit 23, a detecting unit 24, a power supply unit 25, and a timer 26.
[0021]
The high-frequency receiving unit 21 amplifies the high-frequency signal received by the antenna 21, further converts the received signal to a predetermined intermediate frequency or baseband by frequency conversion, if necessary, and converts the converted intermediate-frequency signal or baseband signal. Is supplied to the received power measuring unit 23.
[0022]
The received power measuring unit 23 measures the power of the signal input from the high frequency receiving unit 22. Here, the measurement of the signal power is performed by a method such as measuring the amplitude and measuring the signal power according to the measured amplitude.
In addition, before measuring the received power, a demodulation process for demodulating the signal may be performed as necessary. For example, when the transmitter 10 modulates a predetermined signal, the receiver demodulates the received signal in accordance with the modulation scheme performed by the transmitter, and measures the received power for the demodulated signal. . Since this demodulation processing is performed on the output signal of the high-frequency receiving unit 21, a demodulation circuit can be provided in the reception power measurement unit 23, or a demodulation circuit can be separately provided before the reception power measurement unit 23.
[0023]
The detection unit 24 compares the reception power measured by the reception power measurement unit 23 with a preset reference value, detects the presence or absence of an intruder based on the comparison result, and detects the intruder when the detection signal S is detected._DIs transmitted to the monitor 30.
The detection unit 24 compares the received power measured by the received power measurement unit 23 using a reference value input from the outside or a reference value stored in advance in an internal memory, and detects an intruder. . The power of the signal received at the receiver varies depending on conditions such as the location of the transceiver and the environment of the monitoring area. Therefore, it is preferable to appropriately set the reference value used in the detection unit 24 according to the measurement conditions. For example, in the initial state where the power is turned on in the receiver, or in the time preset by the timer 26, the received power is collected, and the received power is stored as a reference value in the memory. Preferably, noise is removed by a method such as an averaging process for a plurality of received power continuously collected in a certain time period, and the obtained received power is stored in a memory as a reference value.
[0024]
The power supply unit 25 supplies a power supply voltage to the high frequency reception unit 22, the reception power measurement unit 23, the detection unit 24, and the timer 26.
[0025]
The timer 26 generates a reference timing signal for controlling the overall operation timing of the receiver 20a, and supplies the reference timing signal to each partial circuit constituting the receiver. Further, a power control signal S for turning on / off the power supply to the power supply unit 25 by the timer 26._ESend. The power supply unit 25 supplies the power supply control signal S_EIn response to this, the power supply to each partial circuit is turned on / off. For example, if a time zone that does not require a monitoring operation is input to the timer 26 in advance, when this pause time zone starts, the timer 26 transmits a signal for stopping power supply to the power supply unit 25, and the receiver 20a. The power supply to each of the partial circuits is stopped to reduce power consumption in the standby state. When the pause period ends, the timer 26 transmits a signal for enabling the power supply to the power supply unit 25 to start supplying the power to each partial circuit of the receiver 20a.
[0026]
FIG. 3 is a flowchart showing the operation of the receiving circuit 20a of this embodiment. Hereinafter, the operation of the receiving circuit 20a will be described with reference to FIGS.
After the security system is enabled, the receiver 20a first determines that the predetermined time T_SIs the waiting time. The timer 26 waits for this waiting time T._SAnd wait time T_SWhen elapses, a signal for enabling the power supply is transmitted to the power supply unit 25, the supply of power to each partial circuit of the receiver 20a is started, and the receiver 20a is activated (step S1).
[0027]
After the receiver 20a is activated, a reception operation is performed at the time set by the timer 26, the received power is collected, and a reference value is set in the detection unit 24 based on the received power (step S2). As described above, the reference value is set based on, for example, a value obtained by removing noise components by averaging processing based on a plurality of reception power values continuously collected in a certain time zone, and collecting the reference value. The maximum value TH when the detection unit 24 performs detection according to the received power value_HAnd the minimum value TH_LIs set and stored in the memory (step S3).
[0028]
After the above processing is completed, the receiver 20a continuously measures the received power at the time set by the timer 26, and detects the presence or absence of an intruder according to the measurement result.
First, in step S <b> 4, the received signal power is measured by the received power measuring unit 23 according to the signal received by the high frequency receiving unit 22.
[0029]
Next, in the detecting unit 24, the received power measured by the received power measuring unit 23 and the maximum value TH stored in the memory._H, Minimum value TH_LAnd the presence / absence of an intruder is determined according to the comparison result.
In step S5, the measured received power R_EAnd standard value TH_HAnd the measured value is the maximum value TH_HGreater than (R_E> TH_H), It is determined that there is an intruder, and a detection signal is transmitted to the monitor in step S8.
In step S6, the measured received power R_EAnd the minimum value TH of the reference value_LAnd the measured value is the minimum value TH_LLess than (R_E<TH_L), It is determined that there is an intruder, and a detection signal is transmitted to the monitor in step S8.
[0030]
That is, when there is no intruder, the received power of the radio wave input to the receiver 20a through the multipath hardly changes._EIs the maximum value TH_HAnd the minimum value TH_L(TH_L<R_E<TH_H). On the other hand, when there is an intruder, the received power of the radio wave input to the receiver 20a through the multipath changes, and the measured received power R_EIs the maximum value TH_HAnd the minimum value TH_LExceeding the range defined by (R_E> TH_HOr R_E<TH_L).
[0031]
Thus, the received power R measured by the detection unit 24._EAnd preset maximum value TH_H, Minimum value TH_LCan be detected whether or not there is an intruder in the monitored area.
[0032]
When one detection process is completed, it is determined whether or not to continue the process. That is, it is determined whether or not the measurement of the received power is finished. If not finished, the process returns to step S4, and the processes of steps S4 to S6 described above are repeated.
When the detection process ends, for example, a signal for stopping the power supply is transmitted to the power supply unit 25. In response to this signal, the power supply unit 25 stops supplying power, and the receiver 20a is held in a standby state.
[0033]
Note that the detection processing described above uses the received power measured by the received power measurement unit 23, and the detection unit 24 uses the received power and the maximum value TH of the reference value._HAnd the minimum value TH_LThe presence or absence of an intruder is determined according to the comparison result, but the received power may change momentarily due to the influence of noise such as radio wave interference. In this case, the measured value of received power is the maximum value TH._HAnd the minimum value TH_LIn some cases, the detection unit 24 erroneously determines that an intruder has existed and exceeds the range set in step 1, and issues a false alarm. In order to prevent this, it is effective to determine the presence or absence of an intruder using a value obtained by removing the influence of noise by a smoothing filter or the like on a signal received a plurality of times continuously in a predetermined period. . Note that this received signal smoothing process can be performed using a processing circuit common to the received power averaging process performed to set the reference value at the time of initialization of the receiver. Can be minimized.
[0034]
As described above, according to the receiver 20a of the present embodiment, the received signal that is received by the high-frequency receiving unit 22 and further frequency-converted is supplied to the received power measuring unit 24, and the received power R_EIs measured. In the detection unit 24, the received power R_EAnd the preset reference value TH_HAnd the minimum value TH_LAnd the received power R_EIs the maximum value TH_HAnd the minimum value TH_LWhen it is within the range set by, it is determined that there is no intruder in the monitored area, while the received power R_EIs the maximum value TH_HAnd the minimum value TH_LWhen it is out of the range set by, it is determined that an intruder exists in the monitoring area, and a detection signal is transmitted to the monitor 30. It is possible to detect the presence of an intruder in the multipath formation area based on the change in the signal reception level due to the fading due to multipath formed between the transmitter and the receiver. The area can be monitored, and the system can be simplified and the cost can be reduced.
[0035]
Second embodiment of receiver
FIG. 4 is a circuit diagram illustrating another configuration example of the receiver. As illustrated, the receiver 20b includes an antenna 21, a high frequency receiving unit (RF receiving unit) 22, a received vector measuring unit 23a, a detecting unit 24b, a power supply unit 25, and a timer 26.
[0036]
The receiver 20b of this embodiment measures the received power as compared to the receiver 20a of the first embodiment described above, and instead measures the received signal vector instead of detecting the intruder, An intruder is detected according to a change in the received vector.
Hereinafter, the configuration and operation of the receiver 20b of this embodiment will be described focusing on the configuration and operation of the reception vector measurement unit 23a and the detection unit 24a in this embodiment.
[0037]
A signal received by the high-frequency receiving unit 22 and further frequency-converted is input to the reception vector measuring unit 23a. That is, the signal input to the reception vector measuring unit 23a is an intermediate frequency signal or a baseband signal.
The reception vector measuring unit 23a measures the vector of the input signal. Here, it is assumed that the transmitter 10 transmits a signal modulated according to a certain modulation scheme. In the reception vector measuring unit 23a, the input signal is demodulated, the real part and the imaginary part of the demodulated signal are obtained, and the reception vector is obtained.
Note that the modulation scheme used in the transmitter 10 is, for example, PSK modulation, QPSK modulation, or the like.
[0038]
The detecting unit 24a compares the received vector obtained by the received vector measuring unit 23a with a preset reference vector, and determines whether there is an intruder in the monitoring area according to the result of the comparison. To do.
[0039]
Hereinafter, the principle of the receiver 20b of the present embodiment will be described.
As described above, the transmitter 10 transmits radio waves scattered in all directions by the omnidirectional antenna. As a result, a multipath is formed between the transmitter 10 and the receiver 20b, and the radio wave transmitted by the transmitter 10 reaches the receiver 20b via the multipath. In the receiver 20, the amplitude and phase of the received signal change due to multipath fading.
[0040]
When the installation location of the transmitter / receiver is constant, the reception vector at the receiver 20b is almost constant under stable conditions where there is no intruder in the monitoring area where the multipath is formed and there is no external radio wave interference. Become. However, when an intruder enters an area where a multipath is formed, the signal transmission path between the transceivers changes. Due to this change, the amplitude or phase of the received signal of the receiver 20b changes. For this reason, the receiver 20b compares the received vector with a preset reference vector, and if the error of these vectors is within a certain error range, there is no significant change in the multipath between the transceivers, that is, It can be determined that no intruder exists. On the other hand, when the vector error between the received vector and the reference vector exceeds a certain error range, it can be determined that there is a large change in the multipath between the transceivers and that an intruder exists.
[0041]
FIG. 5 is a diagram illustrating the detection principle of the receiver 20b of the present embodiment. Where R_V0Is a reference vector, and r is an allowable error. Reference vector R_V0And the range determined by the allowable error r is an error range, and the received vector R_VIs within this error range, it is determined that there is no significant change in the multipath between the transceivers and that there is no intruder. Conversely, the received vector R_VIs outside this error range, a large change occurs in the multipath between the transceivers, and it is determined that an intruder exists.
[0042]
FIG. 6 is a flowchart showing the operation of the receiver 20b of this embodiment. Hereinafter, the operation of the receiver 20b of the present embodiment will be described with reference to FIGS.
First, the receiver 20b receives a predetermined time T._SIs the waiting time. The timer 26 waits for this waiting time T._SAnd wait time T_SWhen elapses, a signal for enabling the power supply is transmitted to the power supply unit 25, the supply of power to each partial circuit of the receiver 20b is started, and the receiver 20b is activated (step SS1).
[0043]
After the receiver 20b is started, a reception operation is performed at a time set by the timer 26, a reception vector is measured (step SS2), and a reference vector and an allowable error r are set in the detection unit 24a based on the reception vector (step SS3). ). Note that the reference vector and the allowable error r are set as described above, for example, based on a plurality of received vectors measured continuously in a certain time zone, a vector from which noise components have been removed by averaging or the like is used as the reference vector R._V0And also the reference vector R_V0On the other hand, an allowable error r for detection in the detection unit 24a is set according to the measured deviation of each received power vector and stored in the memory (step SS3).
[0044]
After the above-described processing is completed, the receiver 20b continuously receives the reception vector R at the time set by the timer 26._VAnd detects the presence or absence of an intruder based on the measurement result.
First, in step SS4, the signal reception vector is measured by the reception vector measurement unit 23a in accordance with the signal received by the high frequency reception unit 22.
[0045]
Next, in the detection unit 24a, an error ΔR (ΔR = | R) between the reception vector measured by the reception vector measurement unit 23a and the reference vector stored in the memory._V-R_V0|) Is calculated, the calculated ΔR is compared with the allowable error r, and the presence or absence of an intruder is determined according to the comparison result (step SS5).
[0046]
If ΔR is larger than the allowable error r (ΔR> r), it is determined that there is an intruder, and a detection signal is transmitted to the monitor in step SS7.
On the other hand, if ΔR is smaller than the allowable error r (ΔR <r), it is determined that there is no intruder and the process proceeds to the next step SS6.
[0047]
Thus, the reception vector R measured by the detection unit 24a._VAnd a preset reference vector R_V0Can be detected whether or not there is an intruder in the monitored area.
[0048]
When one detection process is completed, it is determined whether or not to continue the process. That is, it is determined whether or not the process for detecting an intruder is to be ended. If not, the process returns to step SS4, and the processes in steps SS4 to SS5 described above are repeated.
When the detection process ends, for example, a signal for stopping the power supply is transmitted to the power supply unit 25. In response to this signal, the power supply unit 25 stops supplying power, and the receiver 20b is held in a standby state.
[0049]
The detection process described above uses the reception vector measured by the reception vector measurement unit 23a, and the detection unit 24a determines whether the reception vector is within the range set by the reference vector and the allowable error r. However, the amplitude or phase of the received vector may change greatly instantaneously due to the influence of noise such as radio wave interference. In this case, the measured value of the received vector is the reference vector R_V0The detection unit 24 may mistakenly determine that an intruder has existed and cause a false alarm. In order to prevent this, it is effective to determine the presence or absence of an intruder after removing the influence of noise on a signal received a plurality of times continuously in a predetermined period using a smoothing filter or the like. Note that this received signal smoothing process is performed by the reference vector R at the time of initialization of the receiver._V0In addition, since the processing can be performed using a processing circuit common to the reception vector averaging processing performed for setting the allowable error r, an increase in the circuit scale is minimized.
[0050]
As described above, according to the receiver 20b of the present embodiment, the received signal that is received by the high-frequency receiving unit 22 and frequency-converted is supplied to the received vector measuring unit 24a, and the received vector R_VIs measured. In the detector 24a, the received vector R_VAnd a preset reference vector R_V0And when the error ΔR is smaller than the preset allowable error r, it is determined that there is no intruder in the monitoring area, while the calculated error ΔR is greater than the preset error r. When it is larger, it is determined that there is an intruder in the monitoring area, and a detection signal is transmitted to the monitor 30.
In this way, it is possible to detect the presence or absence of an intruder in the multipath formation area based on the amplitude and phase change of the received vector due to multipath fading formed between the transceivers, and a simple system With this configuration, a wide area can be monitored, and the system can be simplified and the cost can be reduced.
[0051]
In the security system described above, in order to reduce the influence of noise such as radio wave interference, the transmitter 10 performs so-called secondary spreading in which the transmission signal is subjected to spread spectrum using a pseudo-noise code (PN code, for example, M sequence). Transmit the modulated signal. The receiver despreads the received signal using the same PN code as that on the transmission side, and performs normal demodulation processing and the like. As a result, noise components are dispersed, and erroneous detection due to instantaneous radio wave interference can be prevented.
[0052]
FIG. 7 is a configuration diagram showing the configuration of the transmission antenna and its reflector in the transmission circuit of the present invention. As described above, in the security system of the present invention, the transmitter 10 scatters the transmission radio wave and radiates it in all directions, thereby forming a multipath between the transceivers. FIG. 7 shows a configuration example of a transmission antenna used for scattering transmission radio waves.
[0053]
As shown in FIG. 7A, the transmission antenna is composed of an antenna element 12 and a reflector 14. The antenna element 12 radiates a high-frequency transmission signal generated by a transmission unit (not shown) into space. Usually, the reflector used in the radio wave transmitter is used to converge the so-called radio wave that reflects the transmission radio wave in a certain direction, but in the present invention, the reflector is used to form a multipath. It is desirable that the device 14 has a so-called non-directional radiation characteristic that reflects the radio wave radiated by the antenna element 12 in all directions.
[0054]
  FIG. 7B shows an example of the reflector 14. As shownInInnumerable irregularities are formed on the inner wall of the reflector 14. Due to these irregularities, radio waves radiated by the antenna element 12 are scattered, and reflected waves are radiated in different directions. As a result, radio waves radiated by the transceiver reach the receiver via a plurality of different paths, thereby forming a multipath.
[0055]
【The invention's effect】
As described above, according to the security system of the present invention, it is possible to monitor a predetermined area with a small number of transceivers, and it is possible to easily monitor a wider range than before while greatly reducing the number of installed devices. There is an advantage that a security system that can be constructed using only a pair of transceivers can be realized.
In the present invention, the transmission circuit constituting the security system performs spread spectrum processing on the transmission signal using the PN code, and the reception circuit applies the same PN code to the reception signal as the transmission circuit. By performing spectrum despreading, false alarms due to radio wave interference such as bursts can be prevented.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a security system according to the present invention.
FIG. 2 is a circuit diagram showing a first embodiment of a receiver used in the security system of the present invention.
FIG. 3 is a flowchart showing the operation of the first embodiment of the receiver;
FIG. 4 is a circuit diagram showing a second embodiment of a receiver used in the security system of the present invention.
FIG. 5 is a diagram showing the operating principle of a second embodiment of the receiver.
FIG. 6 is a flowchart showing the operation of the second embodiment of the receiver.
FIG. 7 is a diagram illustrating a configuration of a transmission antenna in a transmitter.
FIG. 8 is a diagram illustrating a configuration example of a conventional security system.
[Explanation of symbols]
10 ... Transmitter,
20, 20a, 20b, 20-1, 20-2,..., 20-n.
21 ... antenna,
22 ... high frequency receiver,
23: Received vector measuring unit,
24. Detection unit,
25 ... Power supply unit,
26 ... Timer,
30 ... monitor,
40 ... Security control center.

Claims

A radio signal modulated to a predetermined frequency band in a transmission circuit, scattered and radiated into space is received via a multipath, and a change in fading generated on the multipath of the radio signal according to the received signal A receiving circuit for detecting
Receiving means for receiving a radio signal propagated through the multipath and performing frequency conversion on the received signal;
Demodulation means for demodulating the received signal obtained by the receiving means by a demodulation method corresponding to a predetermined modulation method;
Measuring means for smoothing the signal received by the receiving means a plurality of times and demodulated by the demodulating means with a smoothing means, and measuring the smoothed signal;
A signal obtained by smoothing the received signal received a plurality of times continuously for a predetermined period by the smoothing means and removing the influence of noise is measured by the measuring means, and a signal obtained by measurement is output from the measuring means. and an output signal that will be, upon initialization of the receiving circuit performs the previous detection operation, obtained by removing noise by averaging a plurality of received signals received predetermined period continuously by the smoothing means Detecting means for comparing the predetermined reference signal and determining whether a change has occurred on the multipath of the radio signal according to the comparison result;
A receiving circuit.

The measurement means includes reception power measurement means for measuring reception power of the smoothed signal,
The detection means includes a power comparator for comparing the received power with a predetermined reference power, and judgment means for judging whether or not a change on the multipath in accordance with the comparison result of the upper Symbol power comparison means has occurred The receiving circuit according to claim 1.

The reference power includes a first reference power and a second reference power having a value larger than the first reference power,
The comparing means compares the received power with the first and second reference powers, respectively, and the judging means determines the multipath when the received power is between the first and second reference powers. 3. The reception according to claim 2, wherein it is determined that there is no change, and when the received power is smaller than the first reference power or greater than the second reference power, it is determined that a change has occurred on the multipath. circuit.

The measuring means includes vector measuring means for measuring a vector of the smoothed signal,
The detection means includes vector comparison means for comparing the measured vector with a predetermined reference vector;
The receiving circuit according to claim 1, further comprising: a determination unit that determines whether a change has occurred on the multipath according to a comparison result of the vector comparison unit.

The comparison means includes vector calculation means for calculating an absolute value of a difference between the measured vector and the reference vector;
The receiving circuit according to claim 4 , further comprising: a comparison circuit that compares the absolute value of the vector difference calculated by the vector calculation means with a predetermined allowable error.

A transmission circuit that scatters a signal modulated into a predetermined frequency band and radiates the signal into space;
A reception circuit that receives a signal transmitted by the transmission circuit via a multipath and detects whether an intruder is present on the multipath of the radio signal from the transmission circuit according to the received signal. And
The receiving circuit is configured to demodulate a received signal by a demodulation method corresponding to a modulation method performed by the transmitting circuit;
Measuring means for smoothing the signal received by the receiving circuit a plurality of times continuously and demodulated by the demodulating means by the smoothing means, and measuring the smoothed signal;
A signal obtained by smoothing the received signal received a plurality of times continuously for a predetermined period by the smoothing means and removing the influence of noise is measured by the measuring means, and a signal obtained by measurement is output from the measuring means. an output signal that will be, upon initialization of the receiving circuit performs the previous detection operation, obtained by removing noise by averaging a plurality of received signals received predetermined period continuously by the smoothing means A detection unit that compares predetermined reference signals and determines whether or not an intruder exists on the multipath between the transmission circuit and the reception circuit according to the comparison result.

The measuring means of the receiving circuit has a received power measuring means for measuring the received power of the signal demodulated by the demodulating means,
The detection means includes power comparison means for comparing the received power with a predetermined reference power;
The security system according to claim 6, further comprising: a determination unit that determines whether an intruder exists on the multipath between the transmission circuit and the reception circuit according to a comparison result of the power comparison unit.

The reference power includes a first reference power and a second reference power having a value larger than the first reference power,
The comparing means compares the received power with the first and second reference powers, respectively, and the judging means is configured to transmit the transmission circuit when the received power is between the first and second reference powers. When the reception power is smaller than the first reference power or larger than the second reference power, it is determined that there is no intruder on the multipath between the transmission circuit and the reception circuit. The security system according to claim 7, wherein it is determined that an intruder exists on the multipath to the circuit.

The measuring means of the receiving circuit has a vector measuring means for measuring a vector of the signal demodulated by the demodulating means,
The detection means includes vector comparison means for comparing the measured vector with a predetermined reference vector;
The security system according to claim 7 , further comprising: a determination unit that determines whether an intruder exists on the multipath between the transmission circuit and the reception circuit according to a comparison result of the vector comparison unit.

The comparison means includes vector calculation means for calculating an absolute value of a difference between the measured vector and the reference vector;
The security system according to claim 9 , further comprising: a comparison circuit that compares the absolute value of the vector difference calculated by the vector calculation means with a predetermined allowable error.

The security system according to claim 8, wherein the transmission circuit includes a spread spectrum circuit that performs spread spectrum on the transmission signal using a predetermined pseudo noise code (PN code).

The security system according to claim 11 , wherein the reception circuit includes a despreading circuit that performs spectrum despreading using the same pseudo-noise code as the transmission circuit.