JP2004340855A - Method and system of satellite positioning - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a satellite positioning system capable of finding signal receiving position at ultra-high sensitivity and good responseness even for an attenuated satellite reception signal. <P>SOLUTION: A receiver terminal comprises a pseudo pattern 22 for storing a pseudo pattern A, a storage 7 where a replica PN sign is stored, a first calculation part 8 which makes the pseudo pattern A act to change polarity of the PN sign, a second calculation part 9 for synchronous adding of the PN signal whose polarity is changed, a third calculation part 10 for correlation calculation with the synchronous addition PN signal having been added synchronously and the replica PN sign, and a pseudo distance detecting device 19 which detects a correlation peak value and a delay value corresponding to the correlation peak value resulting from the correlation calculation, and acquires a pseudo distance from the delay value. Since the polarity of reception PN signal is equalized with the pseudo pattern A, sensitivity is improved by synchronous addition and correlation calculation. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４７】
信号に重畳している雑音が統計的性質に合うガウス性のものとすると、ｍ回の加算により雑音の成分は１／√ｍに減少することが知られている。本発明の実施例ではｍ＝２０である。そのため本発明の同期加算による雑音軽減は１／√２０である。
【００４８】
それぞれ同期加算した結果は、図１０のメモリ部Ｒ_１ ，Ｒ_２ …Ｒ_２０にて記憶する。また、メモリ部Ｒ_１ の同期加算結果はＵ_１ （１，１：Ｎ） として、メモリ部Ｒ_２ の同期加算結果はＵ_２ （２，１：Ｎ） として、…メモリ部Ｒ_２０の同期加算結果はＵ_２０（２０，１：Ｎ）として全体として図４のメモリ部５３，６３に記憶される（工程Ｆ_６ ）。
そして、これら各１行Ｎ列の２０組データのそれぞれと図８の受信機端末１１が予め有しているレプリカＰＮ符号（Ｃ／Ａコード信号）とで相関計算を行う。レプリカＰＮ符号（Ｃ／Ａコード信号）や相関計算は広く知られた内容であるが、以下簡単に説明する。
【００４９】
一般にＧＰＳ衛星Ｓは地球上を複数個回っており、各衛星Ｓからは、１５７５．４２ ＭＨｚ の搬送波を、それぞれ個別の衛星Ｓに対応したＣ／Ａコード信号でスペクトラム拡散変調がなされ地球上に送信している。たとえば１５７５．４２ ＭＨｚ を、衛星Ｓ_１ はＣ／Ａコードａで、衛星Ｓ_２ はＣ／Ａコードｂで、スペクトラム拡散変調して送信しているとする。衛星Ｓ_１ の信号を受信機端末１１にて取り出す（復調させる）ためには受信機端末１１側であらかじめＣ／Ａコードａと同一のＣ／Ａコードａ′を記憶させておき、このＣ／Ａコードａ′により衛星Ｓ_１ はＣ／Ａコードａを受信機端末１１にて復調させる。そして、衛星Ｓ_２ を受信するためには、あらかじめ受信機端末１１側にＣ／Ａコードｂと同じＣ／Ａコードｂ′を記憶しておかなければならない。したがって受信機端末１１側には、あらかじめ各衛星Ｓから発射される各衛星Ｓに対応するすべてのＣ／Ａコードをもっていなければ、各衛星Ｓの信号を受信できない。そして本発明において、このあらかじめ用意されているＣ／ＡコードをレプリカＰＮ符号としている。
そして、各ＧＰＳ衛星Ｓに対応する（衛星受信信号を復調させる）各レプリカＰＮ符号は、あらかじめＧＰＳ受信機端末１１が備える信号処理部２１のＲＯＭ４６───記憶部７───に記憶させている。
【００５０】
また、一般にデータＸをｘ（ｎ）（ただし ｎ＝０：Ｎ ）、データＹをｈ（ｎ）（ただし ｎ＝０：Ｎ ）、ｋを整数として０≦ｋ≦Ｎとしたとき、数２の式のように表現する。
【００５１】
【数２】

【００５２】
そして、ｙ（１），ｙ（２），ｙ（３） …ｙ（Ｎ） を計算する。ここでｙ （ｋ） の計算においてデータの加算回数はＮ個である。従って、このとき信号に重畳している雑音が統計的性質に合うガウス性のものとすると、Ｎ回の加算により雑音の成分は１／√Ｎに減少することが知られている。このためこの計算による雑音低減は１／√Ｎである。そして、この計算を相関計算という。（等価な相関計算は高速演算としてＦＦＴを用いて一般によく知られて用いられる方法があるが、ここでは原理説明のために一般的な計算法を示した。）
【００５３】
また、ｙ（１），ｙ（２），ｙ（３） …ｙ（Ｎ） のそれぞれの絶対値で、ｙ（ｎｎ）の絶対値が最大の値であれば、ｙ（ｎｎ）の絶対値を相関のピーク値とする（ただし０≦ｎｎ≦Ｎ）。このときのｎｎを遅延量τと呼ぶ。また、遅延量τとピーク値ｙ（ｎｎ）を求めることを、相関のピークを求めるという。
また、ここでデータＸが信号をｍ回同期加算して得られたｘ（ｎ）とすれば、この相関計算により雑音軽減量は数３の式となる。
【００５４】
【数３】

【００５５】
そして、本発明ではＣ／Ａコードをｘ（ｎ）、レプリカＰＮ符号をｈ（ｎ）、ｍを同期加算回数、ＮをＣ／Ａコード信号１周期分のサンプル数とし、実施例としてｍ＝２０、Ｎ＝２０４６００を想定している。
従って、２０ｍｓｅｃのＧＰＳデータ取得のみで、雑音軽減量は上記数３の式の結果の効果を出すことが可能である。すなわち雑音にうもれた超微弱信号であっても遅延量τを求めることができる。
【００５６】
同期加算の結果、Ｕ_１（１，１：Ｎ）， Ｕ_２（２，１：Ｎ）， Ｕ_３ （３，１：Ｎ） …Ｕ_２０（２０，１：Ｎ）の２０組のデータは、メモリ部５３，６３に記憶されているが、これら各１行Ｎ列の２０組データのそれぞれと図８のレプリカＰＮ符号とで、相関計算部Ｃにて、相関計算を行う。
つまり、相関計算部Ｃ_１ にて、同期加算部Ｕの同期加算結果Ｕ_１（１，１：Ｎ）と、レプリカＰＮ符号との相関計算を行う。そして、相関計算部Ｃ_１ での相関計算の結果である１行Ｎ列のデータＣ_１（１，１：Ｎ）を記憶させる。同様にして相関計算部Ｃ_２ の相関計算の結果Ｃ_２（２，１：Ｎ）を記憶させ、これを順次繰り返し、相関計算部Ｃ_２０の相関計算の結果Ｃ_２０（２０，１：Ｎ）を記憶させる。
なお、Ｉ信号の相関計算について行なったが、Ｑ信号についても同様の計算を行う。
【００５７】
そして、Ｉ信号の相関計算結果はメモリ部５４（図４）に記憶させ、記憶データをＣ−Ｉ（１：２０，１：Ｎ）と表現する。
また、Ｑ信号の相関計算結果はメモリ部６４（図４）に記憶させ、記憶データはＣ−Ｑ（１：２０，１：Ｎ）と表現する。
次にＩ信号、Ｑ信号の合成を行う。Ｃ−Ｉ（１：２０，１：Ｎ）、Ｃ−Ｑ（１：２０，１：Ｎ）から合成したＣ−ＩＱ（１：２０，１：Ｎ）の行列を作る。
すなわち、Ｃ−Ｉ（１：２０，１：Ｎ）、Ｃ−Ｑ（１：２０，１：Ｎ）のそれぞれのｘ行目、ｚ列目の項のデータで〔｛Ｃ−Ｉ（ｘ，ｚ） ｝^２ ＋｛Ｃ−Ｑ（ｘ，ｚ） ｝^２ 〕^０．５ を計算し、その結果をＣ−ＩＱ（１：２０，１：Ｎ）のｘ 行目、ｚ 列目の項のデータとする。
ｘ＝１：２０、 ｚ＝１：Ｎ について同様にそれぞれ計算を行った結果をＣ−ＩＱ（１：２０，１：Ｎ）として、これをメモリ部７０に記憶させる（図４）。
【００５８】
図８における擬似距離検出装置１９の動作について説明する。擬似距離検出装置１９は相関計算部Ｃ_１ ，Ｃ_２ …Ｃ_２０にて得られた結果でありメモリ部７０に記憶されているＣ−ＩＱ（１：２０，１：Ｎ）を、２０行Ｎ列のデータにおいて絶対値が最大となるデータを検索する。すなわちＣ−ＩＱ（ｚ，τ） の絶対値が最大ならば、Ｃ−ＩＱ（ｚ，１：Ｎ） の中で得られた相関ピーク値Ｃ−ＩＱ（ｚ， τ） の絶対値と、遅延量τが検出結果である。
この遅延量τが求まれば、この遅延量τから擬似距離（衛星ＳとＧＰＳ受信機端末１１との間の距離）を求めることができる。なお、遅延量τから擬似距離を求める手段は、一般に広く知られており容易に実現できる。
その後、図２の位置計算装置２０のブロックにて、基地局１からの基地局位置、各衛星位置、各衛星と基地局間の擬似距離の情報を受信機端末１１の受信部１２で取得して自己位置が決定される。なお、位置計算装置２０もここで求めた擬似距離と、基地局位置、各衛星位置、各衛星と基地局間の擬似距離から自己位置を決定する方法は一般に広く知られており容易に実現できる。
【００５９】
以上の動作は遅延量τを求めるのに、２０行Ｎ列の離散化されたＧＰＳ受信信号（ＰＮコード）に対して、ＰＮ極性を最大限同一化させた状態で同期加算および相関計算を行って遅延量τを得たことと等価である。そして、実施例としてｍ＝２０、Ｎ＝２０４６００としており、２０ｍｓｅｃ（航法データ１ビットの時間相当）のＧＰＳ信号の取得のみで、ＰＮ極性を同一化した状態で遅延量τを求めたのと等価であるので、雑音軽減量は数４の式の結果に近い効果を出すことが可能である。すなわち雑音にうもれた超微弱信号であっても遅延量τを求めることができる。したがって超微弱信号であっても、位置計測が可能となる。
【００６０】
【数４】

【００６１】
ＧＰＳ測位システムにおいて、ビルの中等においては、従来では自己位置を決定することはほとんど不可能であったが、本発明により、ＧＰＳ受信機端末１１で受信できる感度を、従来不可能と呼ばれていたビルの中など超微弱信号であっても、劇的に感度を向上でき、位置計測を可能とする。また、基本的に２０ｍｓｅｃ（航法データ１ビットの時間相当）のＧＰＳデータ取得のみで、超高感度を実現している。取得した２０ｍｓｅｃ（航法データ１ビットの時間相当）のＧＰＳデータにおいて、２０個の擬似パターンＡをあらかじめ用意し、これをＧＰＳ受信信号に作用させることにより、ＰＮ極性を同一化した状態で遅延量τを求めたのと等価にした。つまり、本発明はビルの中など、超微弱信号であっても、ＧＰＳによる位置計測を可能にできる。
【００６２】
さらに、従来のようにＣ／Ａコードの極性が航法データにより変化しているため、Ｃ／Ａコードの極性により同期加算する時に信号成分が互いに相殺されて感度（Ｓ／Ｎ）向上が十分でないという欠点を排除できるという効果を奏する。
また本動作は実施例ではＰＮ信号 Ｄ（１：２０，１：Ｎ）のデータで説明したが、Ｄ／Ａコンバータのサンプリング周波数を変えて、Ｄ（１：２０，１： ｍ） のｍを変更しても良い。相関計算部ではｍを増大することによりより良い感度（Ｓ／Ｎ）向上ができる。
【００６３】
次に、本発明の他の実施の形態を説明する。図２におけるドップラ補正部１６，極性変更装置１７， 同期加算・相関計算装置１８， 疑似距離検出装置１９の部分の機能ブロックは、ソフトウェアによるアルゴリズムで説明したが、ドップラ補正部１６について、及び、図６の機能ブロック、乗算器２６，２７，２８，２９、加算器３０、減算器３１について、図８の乗算器Ｐ_１ 〜Ｐ_２０、相関計算部Ｃ_１ 〜Ｃ_２０の機能ブロックをハードウェアで構成しても良い。
また、ソフトウェア、ハードウェアの混合で構成しても良い。
【００６４】
また図８で、擬似パターンＡ_１ ，Ａ_２ …Ａ_２０をあらかじめＲＯＭ４６に用意したが、プログラムにより、等価な方法でパタ−ンを発生させてもよい。たとえば１行２０列のすべて１または０などの２０個のデータを左シフト、右シフトさせるなどで発生させて上記説明したものと等価なパターンを発生させても良い。
また擬似パターンＡ_１ ，Ａ_２ …Ａ_２０の２０個のパターンを用意したが、図８のＡ_２０はすべて０のパターンであり、これは乗算器Ｐ_２０の計算で極性をすべて変更して同期加算、相関計算を行い、相関ピーク値の絶対値をとることになるので、図示省略するが、疑似パターンＡ_２０、乗算器Ｐ_２０を省略して１９個の擬似パターンＡ_１ ，Ａ_２ …Ａ_１９としても良い。
さらに、図８で、擬似パターンＡの０のかわりに１、１のかわりに０と変えても良い。この場合も、疑似パターンＡ_２０はすべて１のパターンであり、疑似パターンＡ_２０、乗算器Ｐ_２０を省略して１９個の擬似パターンＡ_１ ，Ａ_２ …Ａ_１９としても良い。
【００６５】
さらに、別の実施の形態としては、図８において、２０ｍｓｅｃの受信ＰＮ信号を対象としたが、これ以外の場合にも適用できる。すなわち、図８において、入力ＰＮ信号がＤｍｓｅｃであれば 各擬似パターンの長さは１行Ｄ列で、擬似パターンＡの個数は、その数だけ用意すれば適用できる。
【００６６】
つまり、本発明の衛星測位システムによる測位方法は、受信機端末１１が、衛星受信信号に受信機端末１１が予め用意する疑似パターンＡを作用させて該衛星受信信号におけるＰＮ信号の極性を変化させ、極性を変化させたＰＮ信号を同期加算し、同期加算した同期加算ＰＮ信号と受信機端末１１が予め用意するレプリカＰＮ符号とで相関計算を行ない、相関計算による結果から相関ピーク値と相関ピーク値に対応する遅延値とを検出し、遅延値から疑似距離を求めている。
そして、受信機端末１１は、衛星Ｓからの信号の航法データのうち、航法データの１ビット区間の衛星受信信号に対して、処理を行ない、また、１ビット区間の衛星受信信号の１フレームを単位として、１ビット区間のＰＮ信号の極性を変化させている。
【００６７】
これにより、本発明は、従来ある問題点を解消するものであり、受信機端末１１内部にあらかじめ用意した符号で受信信号（ Ｃ／Ａコード） の極性をすべて同一にして、同期加算及び相関計算を、または同期加算を行うことにより、同期加算などにおいて信号成分が互いに相殺されて感度（Ｓ／Ｎ）向上が劣化することを完全に排除している。
すなわち、受信機端末１１内部にあらかじめ用意した擬似パターンで、受信信号（Ｃ／Ａコード）の極性を同一にして、同期加算、相関計算を行うことにより、劇的な感度（Ｓ／Ｎ）の向上を図り、家屋内、建物の陰、ビルの中などでも、安定した測位のできる高感度衛星測位手段（方法）を得るものである。
【００６８】
また、本発明は、衛星受信信号（Ｃ／Ａコード）の極性を同一化するために、従来技術のように外部基地局から航法データを取り入れる方法とは異なるため、外部基地局から開放できるものである。すなわち衛星受信信号（Ｃ／Ａコード）の極性を同一化するために外部基地局の情報を不必要とし、また、受信信号（Ｃ／Ａコード）の極性を同一化してその後、同期加算を行うことで、理想的なノイズの低減効果を持ったものとできる。
つまり、外部基地局から通信手段Ｌにより航法データを受信しなくても、例えばビル中に存在する受信機端末１１で受信した受信信号のみから、（外部基地局からの衛星Ｓの航法データを使わないで）受信機端末１１自身で、Ｃ／Ａコードのすべての極性を同一化して、同期加算する。従って、通信手段Ｌによる外部からの航法データに依存することなく、Ｃ／Ａコード信号のすべての極性を同一化し、同期加算、相関計算により、ノイズに埋もれたＣ／Ａコード信号を、ノイズの中から浮かび上がらせることにより超高感度を得る。
そして、本発明は２０ｍｓｅｃの短時間の連続信号を受信するのみで、Ａ／Ｄコンバータ３８，３９におけるサンプリング数を増大することで相関計算において感度（Ｓ／Ｎ比）を著しく向上させ、また、建物の中などでも衛星Ｓとの擬似距離を正確かつ迅速に検出させる。
【００６９】
なお、上記ＰＮ（Ｃ／Ａコード）信号はＧＰＳ信号ＰＮ（Ｃ／Ａコード，Ｌ２Ｃコード），Ｇａｌｌｉｌｅｏ受信ＰＮ（Ｌ２コード）信号等にも適用できる。
【００７０】
【発明の効果】
本発明は上述の構成により次のような効果を奏する。
【００７１】
（請求項１又は請求項５によれば）受信機端末１１内部の擬似パターンＡにより、受信ＰＮ信号（Ｃ／Ａコード）の極性を同一化させるため、同期加算および相関計算により感度（信号対雑音比）を著しく向上できる。
従来のように、航法データによるＣ／Ａコード信号の位相反転の境目を検出するために外部基地局からのＧＰＳ航法データを必要としないため、また受信機端末１１内部で受信する信号の航法データを必要としないため、ノイズに埋もれたＰＮ信号（Ｃ／Ａコード）を、著しくＳ／Ｎの向上させて検出できる。つまり、ノイズの中からＰＮ信号を効率よく浮かび上がらせることができ、建物の中やビルの中など、ＧＰＳ信号（ＧＰＳ電波）が著しく減衰した場所においても、衛星Ｓとの擬似距離を精度良くかつ応答性良く測定できる。
【００７２】
（請求項２又は請求項６によれば）必要な衛星受信信号が短くて済み、受信時間による待ち時間がなくなり、応答性が極めて良くなる。
（請求項３又は請求項７によれば）ノイズを低減でき、感度の向上が図れる。
（請求項４又は請求項８によれば）ノイズがさらに低減でき、また、精度を高め、感度を良くすることができる。
【図面の簡単な説明】
【図１】ＧＰＳ受信信号におけるＣ／Ａコード構造を説明する説明図である。
【図２】本発明の実施の一形態の概要を示すブロック図である。
【図３】ＧＰＳ受信機端末の構成を示すブロック図である。
【図４】メモリ部のメモリ内容を示す説明図である。
【図５】Ｉ・Ｑ信号変換搬送波除去部、Ａ／Ｄコンバータ及びその出力を記憶するメモリ部の動作説明図である。
【図６】搬送波除去後のＩ，Ｑ信号からドップラ補正を行いＰＮ信号を得る動作説明図である。
【図７】ＧＰＳ信号を受信してから擬似距離を得るまでのフローチャートである。
【図８】擬似パターンをＰＮ信号に作用させて相関計算結果を得る動作を説明する説明図である。
【図９】信号をサンプリングして得られた結果を記憶したメモリ部の記憶状態図である。
【図１０】入力ＰＮ信号に対して擬似パターンを乗算したときのＲＡＭのメモリパターンを示す説明図である。
【図１１】従来のＧＰＳ測位システムを示すブロック図である。
【図１２】従来のＧＰＳ測位システムを説明する説明図である。
【符号の説明】
７ 記憶部
８ 第一演算部
９ 第二演算部
１０ 第三演算部
１１ 受信機端末
１９ 疑似距離検出装置
２２ 疑似パターン部
Ａ 疑似パターン
Ｓ 衛星[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a satellite positioning system and a satellite positioning method for obtaining a pseudo distance between a satellite and a receiver terminal based on a signal from the satellite.
[0002]
[Prior art]
Many positioning satellites orbit the earth, and signals are continuously transmitted at the same carrier frequency. A PN code (called a C / A code in the case of GPS) is assigned to each satellite, which differs for each satellite, and is continuously transmitted as a pseudo noise signal from each satellite. Navigation data including information such as the orbit of the satellite is transmitted from the satellite. The polarity of the PN code is inverted by the navigation data, and PSK modulation is performed on the same carrier and the data is continuously transmitted. In the case of a GPS signal, as shown in FIG. 1, 1 msec (1 millisecond) of a PN code (C / A code) is one PN frame, and this one PN frame is transmitted as a periodic continuous signal.
That is, the navigation data is 1 bit {20 msec (50 bps)}, and the polarity of the C / A code is inverted according to the polarity of the navigation data. That is, if the navigation data is 1, the polarity of the C / A code remains unchanged, and if the navigation data is -1, the polarity of the C / A code is also inverted.
[0003]
As a conventional satellite positioning system that improves reception sensitivity, there is an assisted GPS (for example, see Patent Document 1). In this system, as shown in FIG. 11, a receiving unit 104 includes an RF to IF converter 106 having a GPS receiving antenna 105, an A / D converter 107 for converting an analog signal from the converter 106 into a digital signal, It has a memory (digital snapshot memory) 108 for recording the output from the A / D converter 107, and a general-purpose programmable digital signal processing circuit (hereinafter abbreviated as DSP circuit) 109 for processing signals from the memory 108.
In addition, a program EPROM (ROM, memory) 110, a frequency synthesizer 111, a power regulator circuit 112, an address writing circuit 113, a microprocessor 114, a RAM (memory) 115, and an EEPROM (ROM, memory) connected to the DSP circuit 109. ) 116, and a modem 118 having a transmitting / receiving antenna 117 and connected to the microprocessor 114.
[0004]
Next, the operation will be described. The base station 101 issues commands to the receiving unit 104 to perform measurements via messages transmitted by the data communication link 119. The base station 101 transmits Doppler data of satellite information for the target satellite in this message. The Doppler data has a format of frequency information, and the message specifies a target satellite. This message is received by a modem 118 which is part of the receiving unit 104 and stored in a memory 108 coupled to a microprocessor 114. The microprocessor 114 handles transmission of data information between the DSP circuit 109, the address writing circuit 113 and the modem 118, and controls the power management function in the receiving unit 104.
When the receiving unit 104 receives an instruction for GPS processing and Doppler information (for example, from the base station 101), the microprocessor 114 activates the power regulator circuit 112 according to the instruction. The power regulator circuit 112 provides functions to the RF-to-IF converter 106, the A / D converter 107, the memory 108, the DSP circuit 109, and the frequency synthesizer 111 via power lines 120a to 120e. As a result, the signal from the GPS satellite received via the GPS receiving antenna 105 is down-converted to the IF frequency and then digitized.
[0005]
The signal to be processed usually corresponds to a time of 100 msec to 1 sec (or longer). Such a continuous data set is stored in the memory 108.
The DSP circuit 109 performs a sword range calculation. In addition, the DSP circuit 109 performs a number of correlation operations between the locally generated reference and the received signal quickly, thereby enabling a very fast computation of the sword range (FFT). ) Enable the use of the algorithm. The Fast Fourier Transform algorithm searches all such positions simultaneously in parallel, accelerating the computation process.
[0006]
When the DSP circuit 109 completes the calculation of the sword range for each of the target satellites, it transmits this information to the microprocessor 114 via the interconnect bus 122. Next, the microprocessor 114 utilizes the modem 118 to transmit the sword range data to the base station 101 via the data communication link 119 for final position estimation. In addition to the sword data, a time lag indicating the elapsed time from the initial data collection in the memory 108 to the time of transmission of the data over the data communication link 119 can be transmitted to the base station 101 at the same time. This time lag enhances the ability of the base station 101 to perform position calculations. This is because this allows the GPS satellite position to be determined at the time of data collection. Modem 118 utilizes a separate transmit / receive antenna 117 for transmitting and receiving messages over data communication link 119. It is understood that modem 118 includes a communication receiver and a communication transmitter, both of which are alternately coupled to transmit / receive antenna 117. Similarly, the base station 101 can use separate transmit and receive antennas 103 to transmit and receive data link messages, and thus continuously transmit GPS signals via the GPS receive antenna 102 at the base station 101. Can be received.
[0007]
It is expected that the time required for the position calculation in the DSP circuit 109 will be several seconds or less depending on the amount of data stored in the memory 108 and the speed of the DSP circuit 109 or some DSP circuits. As described above, the memory 108 captures records corresponding to a relatively long time. Efficient processing of large blocks of data using the fast convolution method contributes to the performance of processing signals at low reception levels (for example, when reception levels decrease due to significant blockage by buildings, trees, etc.). ). All sword ranges for visible GPS satellites are calculated using this same buffered data. This results in improved performance for continuous tracking GPS receivers in situations where the amplitude of the signal changes rapidly (such as urban fault conditions).
[0008]
Regarding the signal processing performed by the DSP circuit 109, the purpose of the processing is to determine the timing of the received waveform with respect to the locally generated waveform, and to obtain a higher sensitivity, an extremely long portion of the waveform, Normally, a portion ranging from 100 msec to 1 sec is processed. The received GPS signal (C / A code) is made up of a repetitive source random (PN frame) of 1023 bits = 1 msec. Therefore, the preceding and succeeding PN frames are added to each other. For example, since there are 1000 PN frames per second, the first frame is coherently added to the next second frame, and the resulting one is added to the third frame. Hereinafter, as shown in FIG. 12A to FIG. As a result, a signal having a duration of 1PN frame = 1023 bits is obtained. By comparing the phase of this sequence with the local reference sequence, the relative timing between the two, ie, the sword range (pseudorange), can be determined. The signal processing performed by the DSP circuit 109 will be described with reference to FIG.
[0009]
FIG. 12 is different from an actual GPS signal, and is drawn as a pseudo explanatory diagram for description. In the section (20 msec) where the navigation data is 0 (−1) or 1, there are actually 20 frames (for 20 cycles of the C / A code), but these are written as 4 frames for explanation. In FIG. 12A, the phase of each frame (FRAME: 1 msec each) is reversed between the section of DATA = 0 and the section of DATA = 1. In this state, the GPS signal (C / A code signal) is input to the receiving antenna.
[0010]
FIG. 12B is a diagram illustrating a case where a GPS signal (C / A code signal) is extracted from a rising point (the beginning of data) at which DATA becomes 0. It should be noted that this diagram is a diagram captured at a timing of a special condition which is provided for clarity of description. That is, this is a diagram when a very special condition is satisfied when the data is captured from the rising point (the beginning of data) where DATA becomes 0. The operation shown in FIG. 12B starts taking a received signal (C / A code) from a certain point in time and adds and averages the received signals (C / A code) for every four frames.
However, it should be noted that if the received signal (C / A code) starts to be taken from the beginning of frame 2 (FRAME 2) of the first DATA = 0, the result of addition and averaging will be 0.
In practice, when a receiver starts to take a signal, it is almost impossible to take it out from the beginning of DATA. That is, it is practical to start taking data from the middle of the navigation data and the middle of the frame.
[0011]
In FIG. 12B, a continuous reception signal captured from a certain point in time is synchronously added and averaged every four cycles (for four C / A codes). Next, FIG. 12 (C) shows a correlation calculation result between the replica PN code (replica C / A code) inside the receiver and the result of FIG. 12 (B). The polarity of the peak value in the correlation calculation is positive when the polarity of the result of the synchronous addition and averaging in FIG. 12B and the polarity of the replica PN code in the receiver match, and negative when they differ.
FIG. 12 (D) shows a diagram obtained by taking the absolute value of the correlation result of FIG. 12 (C). That is, the absolute value of each correlation calculation is taken in FIG. FIG. 12E synchronously adds the respective correlation calculations obtained by the absolute values. The sensitivity (S / N) is improved by adding the PN (C / A code) signal which is a periodic signal many times by the above-described synchronous addition and correlation calculation.
[0012]
Other conventional satellite positioning systems include the following.
The C / A code of the GPS reception signal is temporarily stored in the memory by the A / D converter for a certain period of time. The C / A code signal has a portion where the polarity is inverted due to GPS navigation data. In this patent, a C / A code signal buried in noise is obtained from external navigation data in order to emerge from the noise, and the polarity of the C / A code signal is made completely the same, and synchronous addition and correlation calculation are performed. To perform high-sensitivity reception. This system incorporates navigation data from a server of an external base station into a receiver terminal via a communication line, and converts the phase of the navigation data and the C / A code signal in the received signal of the receiver terminal into a signal received by the receiver terminal. The C / A code signal buried in the noise by changing the polarity of the received PN code with this navigation data to equalize all the polarities of the C / A code signal and performing synchronous addition Is made to emerge from the noise to obtain ultra-high sensitivity.
[0013]
In this system, the phase of the C / A code signal in the received signal received by the server of the external base station and the receiver terminal and the phase of the navigation data from the server of the external base station into the receiver through the communication line. Does not match. The reason is that there are variations and delays in the communication time in the communication line.
For this purpose, the GPS terminal of the GPS positioning system sends its own time signal to a time server that outputs an accurate time signal, and receives the time signal from this time server so as to know the communication time to the time server. .
By knowing this communication time, the navigation data taken from the server of the external base station to the receiver via the communication line is minimized in phase difference, and the navigation data from outside is scanned and the phase difference is reduced. Complete adjustment is performed (for example, see Patent Document 2).
[0014]
[Patent Document 1]
U.S. Pat.
[Patent Document 2]
US Patent 6,329,946
[0015]
[Problems to be solved by the invention]
Although the conventional GPS positioning system is configured as described above, the phase of the C / A code included in the GPS reception signal is inverted in the section and polarity of the navigation data according to the content of the navigation data. Therefore, in such processing, since the polarity of the C / A code is changed by the navigation data, the signal components cancel each other in the process of FIG. There is a drawback that the sensitivity (S / N) is not sufficiently improved. That is, the boundary of the polarity reversal of the navigation data was not detected. Therefore, there is a problem that the improvement of the sensitivity (S / N) is insufficient.
In addition, taking the absolute value of the correlation calculation value and performing synchronous addition in the processing steps of FIGS. 12D and 12E does not reduce white noise itself, and thus does not improve sensitivity (S / N). There is a problem that it is enough.
[0016]
Further, in the conventional GPS positioning system (Patent Document 2), at the time of synchronous addition, the signal components cancel each other out in the process of FIG. 12B due to the polarity of the C / A code to improve the sensitivity (S / N). The problem that it is not enough is solved. Specifically, in order to equalize the polarity of the received signal (C / A code), information on navigation data is received from the base station, and the received signal (C / A code) is multiplied to equalize the polarity. I have. Then, by performing synchronous addition, an ideal noise reduction effect is obtained.
However, it has the following problems. In this case, the communication time from the base station to the receiver terminal is not zero. When the communication line is the Internet or packet communication, there is considerable variation in the communication time, and the phase error becomes extremely large, so the scan time also increases.Therefore, the variation in the delay in the communication line affects the response time of position measurement. It will be greatly involved. In other words, in order to realize high-sensitivity positioning, there is a serious drawback that a receiver cannot be measured with a practical response time unless strict requirements are set for a communication time standard in a communication line.
[0017]
Therefore, the present invention provides a satellite positioning system and a satellite positioning system which can receive a signal from a satellite in a building or the like, that is, can detect a reception position with high sensitivity and good responsiveness even with an attenuated satellite reception signal. It provides a method.
[0018]
[Means for Solving the Problems]
In order to achieve the above object, a satellite positioning system according to the present invention is configured such that a receiver terminal receives a signal from a satellite, and the receiver terminal determines a pseudo distance between the satellite terminal and the satellite by a received satellite reception signal. In the required satellite positioning system, the receiver terminal includes a pseudo pattern unit for storing or generating a pseudo pattern for changing the polarity of the satellite reception signal, and a storage unit for storing a replica PN code for demodulating the satellite reception signal. A first operation unit for applying the pseudo pattern to the satellite reception signal to change the polarity of the PN signal in the satellite reception signal; a second operation unit for synchronously adding the PN signal having the changed polarity; A third calculating unit for calculating a correlation between the added synchronously added PN signal and the replica PN code; and detecting a correlation peak value and a delay value corresponding to the correlation peak value from a result of the correlation calculation. It is obtained and a pseudo distance detecting device for determining the pseudorange from the delay value.
[0019]
Also, the receiver terminal performs processing on the satellite reception signal in one bit section of the navigation data among the navigation data of the signal from the satellite. Further, the receiver terminal is configured to change the polarity of the PN signal in the one-bit section in units of one frame of the satellite reception signal in the one-bit section. Further, the receiver terminal is configured to process the PN signal of one frame as a value discretized at a predetermined sample interval.
[0020]
A satellite positioning method according to the present invention is a satellite positioning method in which a signal from a satellite is received by a receiver terminal, and the receiver terminal obtains a pseudo distance from the satellite based on the received satellite reception signal. The receiver terminal changes the polarity of the PN signal in the satellite reception signal by applying a pseudo pattern prepared in advance by the receiver terminal to the satellite reception signal, and synchronously adds the PN signal having the changed polarity. Then, a correlation calculation is performed between the synchronously added PN signal obtained by the synchronous addition and the replica PN code prepared in advance by the receiver terminal, and a correlation peak value and a delay value corresponding to the correlation peak value are detected from the result of the correlation calculation. Then, the pseudo distance is obtained from the delay value.
[0021]
Also, the receiver terminal performs processing on the satellite reception signal in one bit section of the navigation data among the navigation data of the signal from the satellite. Further, the receiver terminal changes the polarity of the PN signal in the one-bit section in units of one frame of the satellite reception signal in the one-bit section. The receiver terminal processes the PN signal of one frame as a value discretized at a predetermined sample interval.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on the illustrated embodiments.
[0023]
FIG. 1 is an explanatory diagram illustrating a C / A code structure in a GPS satellite reception signal, and FIG. 2 is a block diagram illustrating an outline of a satellite positioning system.
The present invention is a satellite positioning system and method in which a signal from a satellite S is received by a receiver terminal 11, and the receiver terminal 11 obtains a pseudo distance from the satellite S based on the received satellite reception signal.
In FIG. 2, S ₁ , S ₂ , S ₃ , S ₄ Is a target positioning satellite orbiting the earth, and 1 is a base station. The base station 1 includes a receiving antenna 2 installed in an environment with a good view, and a GPS reference signal server receiver 3 receives a GPS signal. The GPS reference signal server receiver 3 extracts Doppler information 4 from the received satellite reception signal (GPS signal). Further, a base station position, each satellite position, and a pseudo distance between each satellite and the position of the receiving antenna 2 are extracted. These pieces of information are transmitted to the receiver terminal 11 via the communication unit L by the transmission unit 5. This transmission is generally performed by broadcasting. The communication means L may be a mobile phone line, a terrestrial broadcast, or a satellite broadcast. Alternatively, an Internet line may be used, and all possible means (by electromagnetic methods) are covered.
[0024]
Reference numeral 11 denotes a GPS receiver terminal. The Doppler information 4 and information on the base station position, each satellite position, and the pseudo distance 6 between each satellite and the base station from the base station 1 are received by the receiving unit 12 of the GPS receiver terminal 11. If the frequency of the broadcast radio wave is in a frequency band near the GPS radio wave (signal), the receiving unit 12 may be shared with the GPS receiving unit 13. The present invention is based on the assumption that many terminals 11 can simultaneously receive data via communication means L (line, broadcast, mobile phone, Internet, etc.). FIG. 2 shows one GPS receiver terminal 11.
[0025]
Reference numeral 14 denotes an antenna unit of the GPS receiver terminal 11. The location of the GPS receiver terminal 11 (antenna unit 14) is not only a place where the satellite S can be directly seen, but also the strength of the GPS radio wave such as a shade of a tree (other than the reception in a normal field) or a building. We assume weak places. The receiving unit 13 is an A / D conversion unit that converts an analog signal of the GPS reception signal {PN signal (C / A code)} into a digital signal. The digitized PN signal (C / A code) is stored in a memory (RAM) 15 {GPS signal storage unit}. Note that the above configuration is widely used widely in the conventional GPS technology, and a detailed description thereof will be omitted.
[0026]
The receiver terminal 11 included in the satellite positioning system of the present invention includes a first operation unit 8 that applies the pseudo pattern A to the satellite reception signal to change the polarity of the PN signal in the satellite reception signal, and a PN having the changed polarity. A second operation unit 9 for synchronously adding signals, a third operation unit 10 for performing correlation calculation using the synchronously added PN signal and the replica PN code, and corresponding to a correlation peak value and a correlation peak value based on a result of the correlation calculation. And a pseudo-range detecting device 19 for detecting a pseudo-distance from the delay value. Hereinafter, the first calculation unit 8 is referred to as a polarity changing device 17, and the second calculation unit 9 and the third calculation unit 10 are referred to as a synchronous addition / correlation calculation device 18.
[0027]
Then, an embodiment in the case of storing the GPS signal in the 20 msec section will be described. As will be described later, the present invention can be applied to any storage time.
In the signal from the continuous satellite S, the 20 msec section has the same time as the 1-bit section of the navigation data.
In FIG. 2, reference numeral 21 denotes a signal processing unit included in the receiver terminal 11. The Doppler correction unit 16, the polarity change unit 17, the synchronous addition / correlation calculation unit 18, and the pseudo distance detection unit 19 indicate functional blocks, and the signal processing unit 21 stores the accumulated PN signal (C / A code) for 20 msec. ) Are made to have the same polarity (+-), and a pseudo distance is obtained by performing synchronous addition and correlation calculation.
[0028]
The PN code polarity changing device 17 stores 20 kinds of pseudo patterns A for changing the polarity of the satellite reception signal prepared (stored) in the pseudo pattern unit 22 in the 20 msec satellite reception signal ───PN stored in the memory 15. A signal (C / A code) which acts on the signal (C / A code) to change the polarity of the signal and change the polarity of the stored signal. That is, as will be described later, the polarity of the PN signal (C / A code) stored in the memory 15 by the PN code polarity changing device 17 is changed by each of the 20 types of pseudo patterns A. Then, synchronous addition and correlation calculation are performed on the respective PN signals (C / A codes) by the synchronous addition / correlation calculator 18. After that, the pseudo-range detecting device 19 detects a pseudo-range between the receiver terminal 11 and the satellite S by detecting a value (delay value τ) at which the correlation calculation peak value becomes the maximum value from among them. The detected delay value τ is equal to the result of performing synchronous addition and correlation calculation with 20 msec data in which the polarity of the PN signal (C / A code) is all the same.
[0029]
With the PN signal (C / A code) having the same polarity within 20 msec, the noise reduction by the synchronous addition and the correlation calculation is improved to the maximum. Then, the pseudo-range detecting device 19 detects the pseudo-range in a state in which the noise reduction is maximized by equalizing the polarity of the PN signal (C / A code) within 20 msec.
Based on the pseudo distance obtained here and the information on the base station position, each satellite position, and the pseudo distance between the base station and each satellite from the receiving unit 12, the position calculation device 20 can know the self-position of the receiver terminal 11. it can.
[0030]
FIG. 3 shows a detailed hardware block diagram of the GPS receiver terminal 11. The code of each block in FIG. 2 corresponds to the code of the block in FIG. The Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, the pseudo distance detection device 19, and the position calculation device 20 in FIG. 2 are functional blocks. Means for configuring the functional block may be a hardware configuration, a software configuration, or a combination thereof. The signal processing unit 21 shows a hardware configuration for executing software processing, which is a means constituting the functional block.
[0031]
In FIG. 3, reference numeral 14 denotes a receiving antenna unit, and 13 denotes a GPS receiving unit, which includes a high-frequency amplifier 32, a frequency converter 33 for down-converting the frequency, a frequency synthesizer 34, an I-signal converted carrier remover 35, and a Q-signal converted carrier. It has a removing unit 36, a 90-degree phase shifter 37, and A / D converters 38 and 39, 15 is a memory (RAM) for temporarily storing information, 21 is a signal processing unit, and a DSP unit. 41, a CPU section 42, a pseudo pattern section (ROM) 22 for storing or generating the pseudo pattern A, a DSP ROM 44 of the DSP section 41, a RAM 45, and a ROM 46, and the storage section 7 connected to the CPU section 42. Reference numeral 12 denotes a receiving unit for obtaining information from the base station 1 in FIG. FIG. 4 shows a memory arrangement in the RAM 45 of the signal processing unit 21.
[0032]
Next, an outline of the operation in FIG. 3 will be described.
1.5 GH, spread spectrum modulated with a PN signal from the receiving antenna unit 14 _Z The GPS signal in the band is received by the high-frequency amplifier 32. The signal is down-converted by the frequency synthesizer unit 34 and the frequency conversion unit 33 and converted into, for example, a 70-MHz band frequency region. The frequency synthesizer 34 and the 90-degree phase shifter 37 multiply the signals by 70-MHz carrier waves having phases different from each other by 70 MHz, that is, the I-signal-converted carrier-wave remover 35 and the Q-signal-converted carrier-wave remover 36 convert the carrier 70 MHz into each other. The removed PN codes (C / A code codes) of I and Q orthogonal to each other are extracted. This operation is shown in FIG. FIG. 5 is a diagram showing the outline of the operation of the I signal conversion carrier removal unit 35 and the Q signal conversion carrier removal unit 36. In FIG. 5, the I signal conversion carrier removal unit 35, the Q signal conversion carrier removal unit 36, and the phase shifter 37 are used. , A / D converter 38, A / D converter 39, and memory 15 correspond to the reference numerals in FIG.
47 and 48 are multipliers. 49 and 50 are low-pass filters.
[0033]
The GPS reception signal down-converted to the 70 MHz band by the frequency conversion unit 33 is a PN. cos ((w + Δw) t + Φ). Δw is the Doppler frequency. Δw is a combination of the Doppler frequency variation of the satellite signal captured by the antenna unit 14 and the frequency variation of the frequency synthesizer unit 34. Here, the description will be made on the assumption that there is no frequency variation of the frequency synthesizer unit 34. In this case, Δw is only the Doppler frequency variation of the satellite signal captured by the antenna unit 14.
The signal from the frequency synthesizer section 34 in FIG. 3 and the signal having a phase difference of 90 degrees by the 90-degree phase shifter 37 are represented by carrier waves cos (wt) and sin (wt) orthogonal to each other. These orthogonal signals and the signal PN. cos ((w + Δw) t + Φ) is multiplied by multipliers 47 and 48 and passed through low-pass filters 49 and 50 to obtain PN. cos (Δwt + Φ), -PN. sin (Δwt + Φ) is obtained. These conversions are generally used as I and Q converters. In this embodiment, the signal PN. Since the carrier waves cos (wt) and sin (wt) which are orthogonal to each other with respect to cos ((w + Δw) t + Φ) are the same, the carrier wave is removed.
[0034]
The mutually orthogonal signals (analog signals) from which the carrier waves have been removed are converted from analog signals into digitized discrete signals by A / D converters 38 and 39, respectively. These two signals are stored in the memory (RAM) 15 for 20 msec (the length of one bit of the navigation data). The high-frequency amplifier 32, the frequency converter 33, the synthesizer 34, the I-signal-converted carrier-wave remover 35, the Q-signal-converted carrier-wave remover 36, the phase shifter 37, the A / D converter 38, and the A / D converter described above. Each of the 39 is a general-purpose one and is generally widely used.
[0035]
The (digital) signal processing unit 21 in FIG. 3 includes a CPU unit 42 connected to the receiving unit 12, a memory (RAM) 45 connected thereto, and a memory (ROM) in order to take in data obtained through the receiving unit 12. 46, a DSP unit 41 connected to a memory (RAM) 45, a memory (ROM) 44 connected to the DSP unit 41, and a pseudo pattern unit 22. The pseudo pattern unit 22 is a storage part (ROM) of a pseudo pattern stored in advance. Further, the CPU section 42 and the DSP section 41 are connected to each other. The CPU 42, the RAM 45, and the ROM 46 operate as a microprocessor.
The ROM 46 is a part that also stores an execution program for digital signal processing. The hardware units of the digital signal processing unit 21, that is, the DSP unit 41, the CPU unit 42, the RAM 45, the ROM 46, and the ROM 44 are configured by a conventional CPU, It is widely and generally used and known as a general-purpose digital signal processing configuration using a DSP and a memory (RAM, ROM).
[0036]
Then, the digital signal processing unit 21 causes the Doppler correction unit 16, the polarity changing device 17, the synchronous addition / correlation calculation device 18, the pseudo distance detection device 19, and the position calculation device 20 of FIG. Then, a case where this functional block is executed by digital signal processing by software will be described.
[0037]
FIG. 8 is a diagram illustrating functional block operations of the polarity changing device 17, the synchronous addition / correlation calculating device 18, and the pseudo distance detecting device 19 in FIG.
The pseudo pattern A of the pseudo pattern unit 22 is shown in FIG. ₁ From A ₂₀ A set of 20 types up to the pattern. This pseudo pattern A is a 20-bit pattern composed of a combination of a continuous 0 data string such as [0000 ...] and a continuous 1 data string such as [1111 ...]. And the number of 1s consists of 20 bits. That is, A ₁ From A ₂₀ Is a pseudo pattern A composed of 20 bits.
FIG. 8A illustrates an example of the pseudo pattern A. ₁ From A ₂₀ Will be described below. A ₁ Is one data string and the other 19 bits are continuous ones [0111 ... 1]. A ₂ Is a two-bit continuous 0 data string, and the other 18 bits are a continuous 1 data string [0011 ... 1]. That is, if k is any integer from 1 to 20, Ak is a data string of 0s with k bits continuous and a data string of 1s with (20-k) bits continuous. As another embodiment, these pseudo patterns A may be set to 1 instead of 0 and to -1 instead of 1.
[0038]
Next, the operation of the digital signal processing unit 21 will be described.
FIG. 7 shows a flowchart for executing the functional blocks of the digital signal processing unit 21 in FIG. 2 by software. The Doppler corrector 16, polarity changing device 17, synchronous addition / correlation calculator 18, pseudo-range detector 19, and position calculator 20, which are functional blocks in FIG. 7, correspond to the functional blocks in the digital signal processor 21 in FIG. are doing. F in FIG. ₁ To F ₁₀ Up to this point are software blocks (processes) processed by each functional block.
First, a received signal of 20 msec is taken from the memory 15 (step F). ₁ ). The digital data of the I and Q signals stored in the memory 15 from the A / D converters 38 and 39 in FIG. cos (Δwt + Φ), -0.5PN. sin (Δwt + Φ) includes a Doppler component. Next, the Doppler frequency Δw is taken in from outside (base station 1) (step F ₂ ).
This Doppler frequency Δw can be obtained from the base station 1 (server) in FIG. 2 by the receiving unit 12 of the GPS receiver terminal 11. This Δw is received by the CPU 42 and stored in the RAM 45.
[0039]
Next, Doppler correction is performed by the following algorithm (step F). ₃ ). Digital data of the discrete I and Q signals stored in the memory 15 based on the Doppler correction information Δw 0.5PN. cos (Δwt + Φ), -0.5PN. FIG. 6 shows an operation of performing Doppler correction on sin (Δwt + Φ).
FIG. 6 is a functional block diagram performed by a program. 26, 27, 28 and 29 are multipliers, 30 is an adder, and 31 is a subtractor. t is a discretized value and is t = 0: Δt: W × T, which means that t is a value discretized from 0 to W × T at a sample interval Δt. The sampling frequency is fKHz. Here, the description will be made assuming that f = N. T = 1 msec; W = 20. The sampling interval Δt is Δt = 1 / f.
[0040]
As shown in FIG. 6, the signals (data) of the discretized I signal and Q signal stored in the memory 15 of FIG. cos (Δwt + Φ), -0.5PN. sin (Δwt + Φ).
These signals are multiplied by cos (Δwt) and sin (Δwt) from the Doppler frequency Δw obtained from the receiving unit 12 by multipliers 26, 27, 28 and 29, and passed through an adder 30 and a subtractor 31. And -0.25PN. sin (Φ), 0.25 PN. cos (Φ) is obtained.
The multipliers 26, 27, 28, 29, the adder 30, and the subtractor 31 can be easily realized by a program (arithmetic means). That is, the following calculation is performed.
The digital data PN. cos (Δwt + Φ), -PN. The input signal of sin (Δwt + Φ) is SIin = −0.5PN. sin (Δwt + Φ), SQin = 0.5PN. Assuming that cos (Δwt + Φ), −SIin × cos (Δwt) + SQin × sin (Δwt) and SQin × cos (Δwt) −SIin × sin (Δwt) are calculated. And, as a calculation result, -0.25PN. sin (Φ), 0.25PN. cos (Φ) is obtained.
The thus obtained I and Q PN signals orthogonal to each other are stored in the memory units 51 and 61 in FIG. 4 (step F). ₄ ). The stored data does not include the Doppler component Δw.
[0041]
FIG. 9 shows an example of data in which one of the I and Q signals is stored. FIG. 9 is composed of a matrix of 20 rows and N columns. In this figure, one row and N columns on the horizontal axis correspond to one cycle of the C / A code because one cycle of the C / A code (1 msec) is sampled at NKHz. That is, one line is equivalent to one cycle of the C / A code (corresponding to one frame). Since the data for 20 msec was collected, it is shown that the data consists of 20 lines.
These matrices will be described below by defining the matrices in the following expressions. D (M1: M2, N1: N2) is defined as a matrix from the M1 row to the M2 row and from the N1 column to the N2 column. NI: N2 is described as indicating a natural number from N1 to N2. D (A, B: C) indicates the Ath row from the Bth column to the Cth column
Therefore, the matrix in FIG. 9 can be represented by D (1:20, 1: N) (FIG. 9 shows N = 2046).
The operation of synchronizing the PN polarities with respect to the discretized I and Q PN signals (data) of 20 rows and N columns and obtaining the correlation calculation result will be described below.
That is, the operation of the polarity changing device 17, the synchronous addition / correlation calculating device 18, and the pseudo distance detecting means 19 in the flowchart of FIG.
[0042]
This operation will be described with reference to FIG. Actually, the blocks shown in FIG. 8 are provided for the I signal and the Q signal respectively, but are similar blocks, and the operations are the same for both. Therefore, only one of the signals will be described here.
In FIG. 8, reference numeral 22 denotes a pseudo pattern portion. A ₁ , A ₂ , ... A ₂₀ Is a set of 20 pseudo patterns, A ₁ From A ₂₀ Is a pseudo pattern composed of data obtained by shifting 0s from the left one by one as shown in the figure. The output of FIG. sin (Φ), 0.25PN. Each signal of cos (Φ) is stored in the memory units 51 and 61 (FIG. 4). The following 0.25PN. The signal of cos (Φ) will be described (the operation is the same for -0.25PN.sin (Φ)).
[0043]
P ₁ To P ₂₀ Up to A in each row of the PN signal (here, 0.25PN.cos (Φ)) which is an input signal. ₁ From A ₂₀ Are multipliers that respectively multiply a set of pseudo patterns. However, each pseudo pattern A ₁ ... A ₂₀ Is multiplied by replacing it with -1 in the multiplication. That is, A ₁ From A ₂₀ Is multiplied by each row (20 rows in total) of D (1:20, 1: N) in FIG. Hereinafter, the multiplication will be described. Note that the value 0 is replaced with -1. Multiplying by -1 means that the polarity of the PN signal (code) is inverted because the sign is inverted. Multiplying by one means that the polarity does not change.
[0044]
Pseudo pattern A ₁ From A ₂₀ Is A ₁ (1: N), A ₂ (1: N), A ₃ (1: N),... AD ₂₀ (1: N). Multiplier P ₁ Then the first pseudo pattern A ₁ Is multiplied to each row of D (1:20, 1: N) in FIG. That is, D (1,1: N) is A ₁ (1) = 0, A in D (2,1: N) ₁ (2) = 1, A in D (3,1: N) ₁ (3) = 1 ... A in D (20,1: N) ₁ (20) = 1 is multiplied. The result D1 (1:20, 1: N) is stored in the memory unit R ₁ (FIG. 10).
Multiplier P ₂ Then the following pseudo pattern A ₂ To each row of D (1:20, 1: N). That is, D (1,1: N) is A ₂ (1) = 0, A in D (2,1: N) ₂ (2) = 0, A in D (3,1: N) ₂ (3) = 1 ... A in D (20,1: N) ₂ (20) = 1 is multiplied. The result D2 (1:20, 1: N) is stored in the memory unit R ₂ (FIG. 10).
Similarly, the same calculation is repeated below, and the multiplier P ₁₉ Then pseudo pattern A ₁₉ To each row of D (1:20, 1: N). That is, D (1,1: N) is A ₁₉ (1) = 0, D (2, 1: N) ₁₉ (2) = 0, D (3, 1: N) and A ₁₉ (3) = 0,..., D (20, 1: N) and A ₁₉ (20) = 1 is multiplied. The result D19 (1:20, 1: N) is stored in the memory unit R ₁₉ To memorize.
And the multiplier P ₂₀ Then pseudo pattern A ₂₀ To each row of D (1:20, 1: N). That is, D (1,1: N) is A ₂₀ (1) = 0, D (2, 1: N) ₂₀ (2) = 0, D (3, 1: N) and A ₂₀ (3) = 0,..., D (20, 1: N) and A ₂₀ (20) = 0 is multiplied. The result D20 (1:20, 1: N) is stored in the memory unit R ₂₀ To memorize.
As shown in FIG. 10, the results of the multiplications are data D1 (1:20, 1: N), D2 (1:20, 1: N), D3 (1:20, 1) of 20 rows and N columns, respectively. : N),... D20 (1:20, 1: N) ₁ , R ₂ ... R ₁₉ , R ₂₀ Is stored in the memory units 52 and 62 in FIG. ₅ ).
[0045]
Next, synchronous addition is performed for each of the data in each of the 20 rows and N columns. In general, synchronous addition is widely known as a method for reducing noise in a periodic signal in a digital signal processing circuit. The calculation will be described. In general, when a signal of one cycle is sampled with s sampling pulses for a periodic signal and data of m cycles is obtained, data of D (1: m, 1: s) can be obtained ( s is the number of samples, m is the number of additions). At this time, the synchronous averaging result of the M-th row is represented by the equation (1).
[0046]
(Equation 1)

[0047]
It is known that if the noise superimposed on a signal is Gaussian in conformity with statistical properties, the noise component is reduced to 1 / √m by m additions. In the embodiment of the present invention, m = 20. Therefore, the noise reduction by the synchronous addition of the present invention is 1 / √20.
[0048]
The result of the synchronous addition is shown in the memory section R in FIG. ₁ , R ₂ ... R ₂₀ Remember. Also, the memory unit R ₁ Is the synchronous addition result of U ₁ (1, 1: N) as the memory unit R ₂ Is the synchronous addition result of U ₂ (2, 1: N) as follows: memory unit R ₂₀ Is the synchronous addition result of U ₂₀ (20, 1: N) as a whole is stored in the memory units 53 and 63 in FIG. ₆ ).
Then, a correlation calculation is performed using each of the 20 sets of data in each row and N column and the replica PN code (C / A code signal) which the receiver terminal 11 of FIG. 8 has in advance. Although the replica PN code (C / A code signal) and the correlation calculation are widely known, they will be briefly described below.
[0049]
In general, a plurality of GPS satellites S orbit around the earth, and each satellite S performs a spread spectrum modulation on a carrier of 1575.42 MHz with a C / A code signal corresponding to each individual satellite S, thereby causing a spread on the earth. Sending. For example, if 1575.42 MHz is ₁ Is the C / A code a and the satellite S ₂ Is a C / A code b, which is assumed to be spread spectrum modulated and transmitted. Satellite S ₁ In order to take out (demodulate) the signal at the receiver terminal 11, the same C / A code a 'as the C / A code a is stored in the receiver terminal 11 in advance, and this C / A code a 'To the satellite S ₁ Causes the receiver terminal 11 to demodulate the C / A code a. And the satellite S ₂ In order to receive the C / A code b ', the same C / A code b' as the C / A code b must be stored in the receiver terminal 11 in advance. Therefore, unless the receiver terminal 11 has all the C / A codes corresponding to each satellite S emitted from each satellite S in advance, the signal of each satellite S cannot be received. In the present invention, the C / A code prepared in advance is used as a replica PN code.
Each replica PN code corresponding to each GPS satellite S (for demodulating a satellite reception signal) is stored in advance in the ROM 46 {storage unit 7} of the signal processing unit 21 provided in the GPS receiver terminal 11. I have.
[0050]
In general, when data X is x (n) (where n = 0: N), data Y is h (n) (where n = 0: N), and k is an integer, 0 ≦ k ≦ N, It expresses like the expression of.
[0051]
(Equation 2)

[0052]
Then, y (1), y (2), y (3)... Y (N) are calculated. Here, the number of data additions in the calculation of y (k) is N. Therefore, it is known that if the noise superimposed on the signal at this time is Gaussian in conformity with the statistical property, the noise component is reduced to 1 / √N by N additions. Therefore, the noise reduction by this calculation is 1 / √N. This calculation is called a correlation calculation. (Equivalent correlation calculation is generally well-known using FFT as a high-speed operation, but a general calculation method is shown here for explanation of the principle.)
[0053]
Further, if the absolute value of y (nn) is the maximum value among the absolute values of y (1), y (2), y (3),..., Y (N), the absolute value of y (nn) Is the peak value of the correlation (where 0 ≦ nn ≦ N). The nn at this time is called a delay amount τ. Obtaining the delay amount τ and the peak value y (nn) is referred to as obtaining a correlation peak.
If the data X is x (n) obtained by synchronously adding the signal m times, the amount of noise reduction is given by Equation 3 by this correlation calculation.
[0054]
[Equation 3]

[0055]
In the present invention, the C / A code is x (n), the replica PN code is h (n), m is the number of synchronous additions, N is the number of samples for one period of the C / A code signal, and m = 20, N = 204600.
Therefore, the noise reduction amount can achieve the effect of the result of the above equation (3) only by acquiring the GPS data for 20 msec. That is, the delay amount τ can be obtained even for a very weak signal buried in noise.
[0056]
As a result of synchronous addition, U ₁ (1,1: N), U ₂ (2,1: N), U ₃ (3,1: N) ... U ₂₀ The 20 sets of data (20, 1: N) are stored in the memory units 53 and 63, and the correlation calculation is performed using each of the 20 sets of data in each row and N columns and the replica PN code in FIG. In part C, a correlation calculation is performed.
That is, the correlation calculator C ₁ , The synchronous addition result U of the synchronous addition unit U ₁ (1, 1: N) and a replica PN code are calculated. And the correlation calculator C ₁ C in one row and N columns, which is the result of the correlation calculation in ₁ (1, 1: N) is stored. Similarly, the correlation calculator C ₂ Calculation result C ₂ (2, 1: N) is stored, and this is sequentially repeated, and the correlation calculation unit C ₂₀ Calculation result C ₂₀ (20, 1: N) is stored.
Although the correlation calculation for the I signal was performed, the same calculation is performed for the Q signal.
[0057]
Then, the correlation calculation result of the I signal is stored in the memory unit 54 (FIG. 4), and the stored data is expressed as CI (1:20, 1: N).
The correlation calculation result of the Q signal is stored in the memory unit 64 (FIG. 4), and the stored data is expressed as CQ (1:20, 1: N).
Next, the I signal and the Q signal are combined. A matrix of C-IQ (1:20, 1: N) synthesized from C-I (1:20, 1: N) and CQ (1:20, 1: N) is created.
That is, the data of the item of the x-th row and the z-th column of CI (1:20, 1: N) and CQ (1:20, 1: N) are represented by [｛CI (x, z)｝ ² + {C-Q (x, z)} ² ] ^0.5 Is calculated, and the result is used as data of the item of the x-th row and the z-th column of C-IQ (1:20, 1: N).
The result of the same calculation for x = 1: 20 and z = 1: N is stored as C-IQ (1:20, 1: N) in the memory unit 70 (FIG. 4).
[0058]
The operation of the pseudo distance detection device 19 in FIG. 8 will be described. The pseudo distance detecting device 19 includes a correlation calculating unit C ₁ , C ₂ ... C ₂₀ The C-IQ (1:20, 1: N), which is the result obtained in step (1) and stored in the memory unit 70, is searched for the data having the maximum absolute value in the data of 20 rows and N columns. That is, if the absolute value of C-IQ (z, τ) is the maximum, the absolute value of the correlation peak value C-IQ (z, τ) obtained in C-IQ (z, 1: N) and the delay The quantity τ is the detection result.
Once the delay amount τ is obtained, the pseudo distance (the distance between the satellite S and the GPS receiver terminal 11) can be obtained from the delay amount τ. The means for obtaining the pseudorange from the delay amount τ is generally widely known and can be easily realized.
Thereafter, in the block of the position calculation device 20 in FIG. 2, information on the base station position from the base station 1, each satellite position, and the pseudo distance between each satellite and the base station is acquired by the receiving unit 12 of the receiver terminal 11. The self-position is determined. The method of determining the position of the position calculation device 20 from the pseudo distance obtained here, the base station position, each satellite position, and the pseudo distance between each satellite and the base station is widely known in general and can be easily realized. .
[0059]
In the above operation, in order to obtain the delay amount τ, synchronous addition and correlation calculation are performed on the discretized GPS reception signal (PN code) of 20 rows and N columns while the PN polarity is maximized to the maximum. This is equivalent to obtaining the delay amount τ. In the embodiment, m = 20 and N = 204600, which is equivalent to obtaining the delay amount τ in a state where the PN polarity is the same, only by acquiring the GPS signal of 20 msec (corresponding to one bit of the navigation data). Therefore, the amount of noise reduction can produce an effect close to the result of the equation (4). That is, the delay amount τ can be obtained even for a very weak signal buried in noise. Therefore, even if it is a very weak signal, the position can be measured.
[0060]
(Equation 4)

[0061]
In a GPS positioning system, in a building or the like, it has been almost impossible to determine its own position in the past, but according to the present invention, the sensitivity that can be received by the GPS receiver terminal 11 is conventionally called impossible. Even if the signal is very weak, such as inside a building, the sensitivity can be dramatically improved and position measurement is possible. Ultra-high sensitivity is achieved only by acquiring GPS data of basically 20 msec (corresponding to one bit of navigation data). In the acquired GPS data of 20 msec (corresponding to one bit of navigation data time), 20 pseudo patterns A are prepared in advance, and these are applied to the GPS reception signal, so that the delay amount .tau. Was obtained. That is, the present invention enables the position measurement by GPS even in the case of a very weak signal such as in a building.
[0062]
Further, since the polarity of the C / A code is changed by the navigation data as in the related art, the signal components cancel each other out when the synchronous addition is performed by the polarity of the C / A code, and the sensitivity (S / N) is not sufficiently improved. This has the effect of eliminating the disadvantage of the above.
In this embodiment, the operation has been described using the data of the PN signal D (1:20, 1: N). However, the sampling frequency of the D / A converter is changed to change the m of D (1:20, 1: m). You may change it. In the correlation calculation unit, the sensitivity (S / N) can be improved more by increasing m.
[0063]
Next, another embodiment of the present invention will be described. Although the functional blocks of the Doppler correction unit 16, the polarity change unit 17, the synchronous addition / correlation calculation unit 18, and the pseudo distance detection unit 19 in FIG. 2 have been described using the algorithm by software, the Doppler correction unit 16 and the diagram The functional block No. 6, the multipliers 26, 27, 28, 29, the adder 30, and the subtractor 31 are shown in FIG. ₁ ~ P ₂₀ , Correlation calculator C ₁ ~ C ₂₀ May be configured by hardware.
Further, it may be composed of a mixture of software and hardware.
[0064]
Also, in FIG. ₁ , A ₂ ... A ₂₀ Are prepared in the ROM 46 in advance, but the pattern may be generated by an equivalent method using a program. For example, a pattern equivalent to that described above may be generated by shifting all 20 data such as 1 or 0 in one row and 20 columns by shifting left or right.
In addition, pseudo pattern A ₁ , A ₂ ... A ₂₀ 8 patterns are prepared. ₂₀ Is a pattern of all zeros, which is a multiplier P ₂₀ , The synchronous addition and the correlation calculation are performed by changing all the polarities, and the absolute value of the correlation peak value is obtained. ₂₀ , Multiplier P ₂₀ Is omitted and 19 pseudo patterns A ₁ , A ₂ ... A ₁₉ It is good.
Further, in FIG. 8, the pseudo pattern A may be changed to 0 instead of 0 instead of 1. Also in this case, the pseudo pattern A ₂₀ Are all 1 patterns and the pseudo pattern A ₂₀ , Multiplier P ₂₀ Is omitted and 19 pseudo patterns A ₁ , A ₂ ... A ₁₉ It is good.
[0065]
Further, as another embodiment, the receiving PN signal of 20 msec is targeted in FIG. 8, but the present invention can be applied to other cases. That is, in FIG. 8, if the input PN signal is Dmsec, the length of each pseudo pattern is one row and D column, and the number of pseudo patterns A can be applied if the number is prepared.
[0066]
That is, in the positioning method using the satellite positioning system of the present invention, the receiver terminal 11 changes the polarity of the PN signal in the satellite reception signal by applying the pseudo pattern A prepared in advance by the receiver terminal 11 to the satellite reception signal. , The PN signal of which polarity is changed is synchronously added, a correlation calculation is performed with the synchronously added PN signal obtained by the synchronous addition and the replica PN code prepared in advance by the receiver terminal 11, and a correlation peak value and a correlation peak are obtained from the result of the correlation calculation. A delay value corresponding to the value is detected, and a pseudo distance is obtained from the delay value.
Then, the receiver terminal 11 processes the satellite reception signal in the 1-bit section of the navigation data among the navigation data of the signal from the satellite S, and converts one frame of the satellite reception signal in the 1-bit section. As a unit, the polarity of the PN signal in one bit section is changed.
[0067]
Thus, the present invention solves the conventional problem, and makes all the polarities of the received signal (C / A code) identical with the codes prepared in advance in the receiver terminal 11 to thereby perform synchronous addition and correlation calculation. Or by performing synchronous addition, it is completely eliminated that signal components are canceled each other in synchronous addition and the like, and the sensitivity (S / N) improvement is degraded.
That is, by performing the synchronous addition and the correlation calculation with the same polarity of the received signal (C / A code) using a pseudo pattern prepared in advance in the receiver terminal 11, a dramatic sensitivity (S / N) is obtained. An object of the present invention is to provide high-sensitivity satellite positioning means (method) capable of performing stable positioning even inside a house, behind a building, inside a building, and the like.
[0068]
Also, the present invention is different from the method of taking navigation data from an external base station as in the prior art in order to make the polarity of the satellite reception signal (C / A code) the same, so that it can be released from the external base station. It is. That is, the information of the external base station is not required to make the polarity of the satellite reception signal (C / A code) the same, and the polarity of the reception signal (C / A code) is made the same, and then the synchronous addition is performed. Thus, an ideal noise reduction effect can be obtained.
That is, even if navigation data is not received from the external base station by the communication means L, for example, the navigation data of the satellite S from the external base station is used only from the reception signal received by the receiver terminal 11 existing in the building. The receiver terminal 11 itself makes all the polarities of the C / A code identical and performs synchronous addition. Accordingly, all the polarities of the C / A code signal are made the same without depending on the navigation data from the outside by the communication means L, and the C / A code signal buried in the noise is converted into the noise by the synchronous addition and the correlation calculation. Super-high sensitivity is obtained by emerging from the inside.
In the present invention, the sensitivity (S / N ratio) is significantly improved in the correlation calculation by increasing the number of samplings in the A / D converters 38 and 39 only by receiving a short-time continuous signal of 20 msec. The pseudo distance to the satellite S is accurately and quickly detected even in a building or the like.
[0069]
The PN (C / A code) signal can be applied to a GPS signal PN (C / A code, L2C code), a Galileo reception PN (L2 code) signal, and the like.
[0070]
【The invention's effect】
The present invention has the following effects by the above configuration.
[0071]
According to claim 1 or claim 5, in order to equalize the polarity of the received PN signal (C / A code) by the pseudo pattern A inside the receiver terminal 11, the sensitivity (signal pair) is calculated by synchronous addition and correlation calculation. Noise ratio) can be significantly improved.
Unlike the prior art, the GPS navigation data from the external base station is not required to detect the boundary of the phase inversion of the C / A code signal by the navigation data, and the navigation data of the signal received inside the receiver terminal 11 is not required. Is not required, a PN signal (C / A code) buried in noise can be detected with significantly improved S / N. That is, the PN signal can be efficiently emerged from the noise, and even in a place where the GPS signal (GPS radio wave) is significantly attenuated, such as in a building or a building, the pseudo distance to the satellite S can be accurately and accurately determined. Measurement can be performed with good responsiveness.
[0072]
(According to claim 2 or claim 6) The required satellite reception signal is short, the waiting time due to the reception time is eliminated, and the responsiveness is extremely improved.
(According to claim 3 or claim 7) noise can be reduced and sensitivity can be improved.
According to claim 4 or claim 8, noise can be further reduced, accuracy can be increased, and sensitivity can be improved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a C / A code structure in a GPS reception signal.
FIG. 2 is a block diagram showing an outline of an embodiment of the present invention.
FIG. 3 is a block diagram illustrating a configuration of a GPS receiver terminal.
FIG. 4 is an explanatory diagram showing memory contents of a memory unit.
FIG. 5 is an operation explanatory diagram of an IQ signal conversion carrier removal unit, an A / D converter, and a memory unit for storing an output thereof;
FIG. 6 is an explanatory diagram of an operation for obtaining a PN signal by performing Doppler correction from the I and Q signals after removing the carrier.
FIG. 7 is a flowchart from when a GPS signal is received to when a pseudorange is obtained.
FIG. 8 is an explanatory diagram illustrating an operation of obtaining a correlation calculation result by applying a pseudo pattern to a PN signal.
FIG. 9 is a storage state diagram of a memory unit that stores a result obtained by sampling a signal.
FIG. 10 is an explanatory diagram showing a memory pattern of a RAM when an input PN signal is multiplied by a pseudo pattern.
FIG. 11 is a block diagram showing a conventional GPS positioning system.
FIG. 12 is an explanatory diagram illustrating a conventional GPS positioning system.
[Explanation of symbols]
7 Storage unit
8 First operation unit
9 Second operation unit
10 Third operation unit
11 Receiver terminal
19 Pseudo distance detection device
22 pseudo pattern part
A pseudo pattern
S satellite

Claims (8)

In a satellite positioning system, a signal from a satellite (S) is received by a receiver terminal (11), and the receiver terminal (11) obtains a pseudo distance from the satellite (S) based on the received satellite reception signal. The receiver terminal (11) stores a pseudo pattern unit (22) for storing or generating a pseudo pattern (A) for changing the polarity of the satellite reception signal and a replica PN code for demodulating the satellite reception signal. A first calculating unit (8) for applying the pseudo pattern (A) to the satellite reception signal to change the polarity of the PN signal in the satellite reception signal; and a storage unit (8) for changing the polarity of the PN signal in the satellite reception signal. A second arithmetic unit (9) for synchronously adding signals; a third arithmetic unit (10) for calculating a correlation between the synchronously added PN signal and the replica PN code; and a correlation peak value based on the result of the correlation calculation. And the correlation peak value Satellite positioning system, characterized by comprising detecting a delay value to respond pseudorange detecting device for determining the pseudorange from the delay value (19), the. The satellite positioning system according to claim 1, wherein the receiver terminal (11) processes the satellite reception signal in one bit section of the navigation data among the navigation data of the signal from the satellite (S). . The satellite positioning system according to claim 2, wherein the receiver terminal (11) is configured to change the polarity of the PN signal in the one bit section in units of one frame of the satellite reception signal in the one bit section. The satellite positioning system according to claim 3, wherein the receiver terminal (11) is configured to process the PN signal of one frame as a value discretized at a predetermined sample interval. In a satellite positioning method, a signal from a satellite (S) is received by a receiver terminal (11), and the receiver terminal (11) obtains a pseudo distance from the satellite (S) based on the received satellite reception signal. The receiver terminal (11) changes the polarity of the PN signal in the satellite reception signal by applying a pseudo pattern (A) prepared in advance by the receiver terminal (11) to the satellite reception signal. The PN signal obtained by changing the PN signal is synchronously added, a correlation calculation is performed using the synchronously added PN signal obtained by the synchronous addition and the replica PN code prepared in advance by the receiver terminal (11), and a correlation peak value is obtained from the result of the correlation calculation. And a delay value corresponding to the correlation peak value, and calculating the pseudo distance from the delay value. The satellite positioning method according to claim 5, wherein the receiver terminal (11) processes the satellite reception signal in one bit section of the navigation data among the navigation data of the signal from the satellite (S). . The satellite positioning method according to claim 6, wherein the receiver terminal (11) changes the polarity of the PN signal in the one-bit section in units of one frame of the satellite reception signal in the one-bit section. The satellite positioning method according to claim 7, wherein the receiver terminal (11) processes the PN signal of one frame as a value discretized at a predetermined sample interval.

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