JP3755349B2 - Radar equipment - Google Patents

Description

【００２０】
Ｕｐビーム用アンテナ１により形成されるビーム照射範囲２１およびＤｏｗｎビーム用アンテナ２により形成されるビーム照射範囲２２の、距離測定方向１８における信号レベルを同一とするためには、各ビームのエレベーション方向のアンテナビーム幅θ_EBWを同一とし、さらに、距離測定方向１８に対するビーム中心角度２４も同一とする必要がある。ビーム中心角度２４をΔθ／２とすると、Δθ／２は”数２”の式で計算される。
【００２１】
【数２】

【００２２】
ビーム間隔算出器５は、上記”数１”および”数２”の計算を行い、ビーム中心角度Δθ／２を出力する。ビーム制御器６は、ビーム中心角度Δθ／２および距離測定方位角θ_ELより、Ｕｐビーム用アンテナ１のビーム中心方向をθ_EL−Δθ／２、Ｄｏｗｎビーム用アンテナ２のビーム中心方向をθ_EL＋Δθ／２となるように制御する。これにより、距離測定方位角θ_ELが変化しても、ビームが重なり合うレンジビン数は、常にＮレンジビンに保たれることになる。以後の動作は、従来装置と全く同一であり、直線近似器１５において処理するレンジビン数をＮとすれば、Δ／Σデータは処理レンジビン内で常に一定の傾きを持つことになる。図１３に示す距離測定方位角１９が小さい場合２９は、ビーム中心角度２４が大きくなり、図１３（ｂ）に示すΔ／Σデータの形状を得ることが出来る。また、距離測定方位角１９が大きい場合３０は、ビーム中心角度２４が小さくなるため、Δ／Σデータの飽和特性は発生せず、図１３（ｂ）に示すΔ／Σデータの形状を得ることが出来る。これにより、誤差の増大を防ぎ、精度の良い距離測定を行うことが可能である。
【００２３】
距離測定方位角１９が、レンジ分解能４８に対して大きい場合、図２（ｂ）に示すように、Ｕｐビーム用アンテナ１により形成されるビーム照射範囲２１およびＤｏｗｎビーム用アンテナ２により形成されるビーム照射範囲２２の、地表面２３からの受信信号が、全て１レンジビン内に収まってしまう場合がある。この場合、Ｕｐビーム振幅データ３７およびＤｏｗｎビーム振幅データ３８のメインビームクラッタは、同一レンジビンのみに振幅を持ち、ΣΔ生成器１２より出力されるΔデータ４０は、正側または負側のみに振幅を持つため、以後の処理で距離測定を行うことが不可能となる。この条件を式で表わすと、”数３”となる。
【００２４】
【数３】

【００２５】
この条件が成り立つ時、ビーム間隔算出器５において、”数４”に従ってビーム中心角度Δθ／２を算出する。
【００２６】
【数４】

【００２７】
このビーム中心角度２４を使用して、ビーム制御器６により各アンテナのビーム中心方向を制御すれば、Ｕｐビーム振幅データ３７およびＤｏｗｎビーム振幅データ３８のメインビームクラッタを１レンジビン以上離すことが可能となる。これにより、ΣΔ生成器１２より出力されるΔデータ４０は、正側および負側の両方に振幅を持つことになり、以後の処理での距離測定が可能となる。
【００２８】
以上のようにこの発明は、距離測定方位角および自機高度に応じて、処理範囲内でΔ／Σデータの傾きを一定にするために必要な、 Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の距離測定方向に対するビーム中心角度を計算し、ビーム中心方向を変更することにより、距離測定方位角に関わらずΔ／Σデータの傾きを一定に保つことが出来る。これにより、距離測定方位角が小さい場合は、距離測定誤差の増大を防ぐことが出来、距離測定方位角が大きい場合には、飽和特性による距離測定誤差増大を防ぐことが出来るため、精度の良い距離測定を行うことが出来る。また、距離測定方位角がレンジ分解能に対して大きく、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の地表面からの受信信号が、全て１レンジビン内に収まってしまい、距離測定が不可能となる場合でも、ビーム中心方向を変更することにより、Ｕｐビーム用アンテナおよびＤｏｗｎビーム用アンテナの地表面からの受信信号を１レンジビン以上離すことが出来、距離測定を可能とすることができる。
【００２９】
実施の形態２．
図３はこの発明の実施の形態２を示す図であり、図において４、７〜１６は従来装置と全く同一のものである。１〜３、６は実施の形態１と全く同一のものである。２５は、高度計３より出力される自機高度およびレーダ制御器４より出力される距離測定方位角より、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の距離測定方向に対するビーム中心角度を、予め計算されたテーブルより参照して出力するビーム間隔テーブルである。
【００３０】
前記のように構成されたレーダ装置においては、実施の形態１と同様に、レーダ制御器４より距離測定方位角１９が出力され、高度計３より自機高度２０が出力される。ビーム間隔テーブル２５には、”数１”および”数２”の計算を、距離測定方位角１９および自機高度２０の各値に関して実施した結果が格納されており、距離測定方位角θ_ELおよび自機高度Ｈを入力すると、テーブルから入力に応じたビーム中心角度Δθ／２を読み出し出力する。これにより、実施の形態１と同様の効果を得ることが出来る。”数１”の演算を高速に実施するためには、複雑な回路が必要となるが、テーブルとすることにより、簡易な構成で実現が可能である。
【００３１】
距離測定方位角１９が、レンジ分解能４８に対して大きい場合、”数３”の条件が成り立つ時のテーブルのデータを”数４”の計算結果としておくことにより、実施の形態１と同様の効果を得ることが出来る。
【００３２】
以上のように、この発明は、距離測定方位角および自機高度に応じて、処理範囲内でΔ／Σデータの傾きを一定にするために必要な、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム中心角度を、予め計算されたテーブルを参照することにより求め、ビーム中心方向を変更することにより、距離測定方位角に関わらずΔ／Σデータの傾きを一定に保つことが出来る。これにより、距離測定方位角が小さい場合は、距離測定誤差の増大を防ぐことが出来、距離測定方位角が大きい場合には、飽和特性による距離測定誤差増大を防ぐことが出来るため、精度の良い距離測定を行うことが出来る。また、距離測定方位角がレンジ分解能に対して大きく、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の地表面からの受信信号が、全て１レンジビン内に収まってしまい、距離測定が不可能となる場合でも、ビーム中心方向を変更することにより、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の地表面からの受信信号を１レンジビン以上離すことが出来、距離測定を可能とすることができる。さらに、この発明の実施の形態１よりも簡易な構成で実現可能である。
【００３３】
実施の形態３．
図４はこの発明の実施の形態３を示す図であり、図において４、７〜１６は従来装置と全く同一のものである。３は実施の形態１と全く同一のものである。
１は、距離測定方向に対してエレベーション方向の上側に、一定角度離れたビーム中心方向を持ち、ビーム幅が変更可能で、パルス状の送信波を放射し、地表面からの反射波を受信するＵｐビーム用アンテナ、２は、距離測定方向に対してエレベーション方向の下側に、一定角度離れたビーム中心方向を持ち、ビーム幅が変更可能で、パルス状の送信波を放射し、地表面からの反射波を受信するＤｏｗｎビーム用アンテナ、２６は、高度計３より出力される自機高度およびレーダ制御器４より出力される距離測定方向より、上記Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム幅を計算するビーム幅算出器、６は、ビーム幅算出器２６より出力されるビーム幅およびレーダ制御器４より出力される距離測定方位角より、上記Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム中心方向およびビーム幅を制御するビーム制御器である。
【００３４】
前記のように構成されたレーダ装置においては、実施の形態１と同様に、レーダ制御器４より距離測定方位角１９が出力され、高度計３より自機高度２０が出力される。ビーム幅算出器２２は、距離測定方位角１９および自機高度２０より、処理範囲内でΔ／Σデータの傾きを一定にするために必要な、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム幅を計算する。実施の形態１と同様にビームが重なり合う角度θ_OVERを、”数１”により算出する。Ｕｐビーム用アンテナ１により形成されるビーム２１およびＤｏｗｎビーム用アンテナ２により形成されるビーム２２の、距離測定方向１８における信号レベルを同一とするためには、各ビームのエレベーション方向のアンテナビーム幅θ_EBWを同一とし、さらに、距離測定方向１８に対するビーム中心角度２４も同一とする必要がある。ビーム中心角度２４をΔθ／２とすると、θ_EBWは”数５”の式で計算される。
【００３５】
【数５】

【００３６】
ビーム幅算出器２２は、”数１”および”数５”の計算を行い、ビーム幅θ_EBWを出力する。ビーム制御器６は、ビーム幅θ_EBWおよび距離測定方位角θ_ELを、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２に対して設定する。これにより、距離測定方位角１８が変化しても、ビームが重なり合うレンジビン数は、常にＮレンジビンに保たれることになる。以後の動作は、従来装置と全く同一であり、直線近似器１５において処理するレンジビン数をＮとすれば、Δ／Σデータは処理レンジビン内で常に一定の傾きを持つことになる。図１３に示す距離測定方位角１９が小さい場合２９は、ビーム中心角度２４が大きくなり、図１３（ｂ）に示すΔ／Σデータの形状を得ることが出来る。また、距離測定方位角１９が大きい場合３０は、ビーム中心角度２４が小さくなるため、Δ／Σデータの飽和特性は発生せず、図１３（ｂ）に示すΔ／Σデータの形状を得ることが出来る。これにより、誤差の増大を防ぎ、精度の良い距離測定を行うことが可能である。距離測定方位角１９が、レンジ分解能４８に対して大きい場合、”数３”の条件が成り立つ時のビーム幅θ_EBWを、”数６”に従って算出する。
【００３７】
【数６】

【００３８】
このビーム幅θ_EBWを使用して、ビーム制御器６により各アンテナのビーム幅を設定すれば、実施の形態１と同様の効果を得ることが出来る。
【００３９】
以上のように、この発明は、距離測定方位角および自機高度に応じて、処理範囲内でΔ／Σデータの傾きを一定にするために必要な、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム幅を計算し、ビーム幅を変更することにより、距離測定方位角に関わらずΔ／Σデータの傾きを一定に保つことが出来る。これにより、距離測定方位角が小さい場合は、距離測定誤差の増大を防ぐことが出来、距離測定方位角が大きい場合には、飽和特性による距離測定誤差増大を防ぐことが出来るため、精度の良い距離測定を行うことが出来る。また、距離測定方位角がレンジ分解能に対して大きく、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の地表面からの受信信号が、全て１レンジビン内に収まってしまい、距離測定が不可能となる場合でも、ビーム幅を変更することにより、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２の地表面からの受信信号を１レンジビン以上離すことが出来、距離測定を可能とすることができる。
【００４０】
実施の形態４．
図５はこの発明の実施の形態４を示す図であり、図において４、７〜１６は従来装置と全く同一のものである。１〜３、６は実施の形態３と全く同一のものである。２７は、高度計３より出力される自機高度およびレーダ制御器４より出力される距離測定方位角より、上記Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム幅を、予め計算されたテーブルより参照して出力するビーム幅テーブルである。
【００４１】
前記のように構成されたレーダ装置においては、実施の形態３と同様に、レーダ制御器４より距離測定方位角１９が出力され、高度計３より自機高度２０が出力される。ビーム幅テーブル２７には、”数１”および”数５”の計算を、距離測定方位角１９および自機高度２０の各値に関して実施した結果が格納されており、距離測定方位角θ_ELおよび自機高度Ｈを入力すると、テーブルに格納されたデータから入力に応じたビーム幅θ_EBWを読み出し出力する。これにより、実施の形態３と同様の効果を得ることが出来る。”数１”の演算を高速に実施するためには、複雑な回路が必要となるが、テーブルとすることにより、簡易な構成で実現が可能である。
【００４２】
距離測定方位角１９が、レンジ分解能４８に対して大きい場合、”数３”の条件が成り立つ時のテーブルのデータを”数６”の計算結果としておくことにより、実施の形態３と同様の効果を得ることが出来る。
【００４３】
以上のように、この発明は、距離測定方位角および自機高度より、処理範囲内でΔ／Σデータの傾きを一定にするために必要な、Ｕｐビーム用アンテナ１およびＤｏｗｎビーム用アンテナ２のビーム幅を、予め計算されたテーブルを参照することにより求め、ビーム制御器６により各アンテナのビーム幅を変更することにより、距離測定方位角に関わらずΔ／Σデータの傾きを一定に保つことが出来る。
【００４４】
実施の形態５．
図６はこの発明の実施の形態５を示す図であり、図において１、２、４〜１４、１６は従来装置と全く同一のものである。３は、実施の形態１と全く同一のものである。２８は、上記高度計３より出力される自機高度および上記レーダ制御器４より出力される距離測定方位角より、上記直線近似器１５に対して近似を行う範囲を示すためのレンジゲート幅を算出し、レンジゲート幅を出力するゲート幅算出器、１５は、上記レーダ制御器４より出力される処理開始レンジおよび上記ゲート幅算出器２８より出力されるレンジゲート幅で示されるレンジビンに対して、上記Δ／Σ演算器から出力されるレンジビン毎のΔ／Σデータを直線で近似し、傾きおよびオフセット値を出力する直線近似器である。
【００４５】
前記のように構成されたレーダ装置においては、Δ／Σ演算器１４において、Δ／Σデータ４２を得るまでは、従来装置と全く同一である。レーダ制御器４より距離測定方位角１９が出力され、高度計３より自機高度２０が出力されると、ゲート幅算出器２８は、距離測定方位角１９および自機高度２０より、処理範囲内でΔ／Σデータが飽和特性を持たないために必要な、直線近似器１５において近似を行う範囲を示すためのレンジゲート幅を算出する。例えば、距離測定方位角１９をθ_EL、自機高度２０をＨ、ビームが重なり合う角度をθ_OVER、ビームが重なり合うレンジビン数をＮ、レンジビン間隔をΔＲとすると、ビームが重なり合うレンジビン数Ｎは、”数７”に従って計算すればよい。
【００４６】
【数７】

【００４７】
なお、ビームが重なり合う角度θ_OVERは、ビーム幅θ_EBW、ビーム中心角度Δθ／２を用いて、”数８”のように表わすことが出来る。
【００４８】
【数８】

【００４９】
ゲート幅算出器２４は、”数７”および”数８”の計算を行い、レンジゲート幅Ｎを出力する。図７に示すように、距離測定方位角が小さい場合２９は、レンジゲート幅Ｎが大きくなり、距離測定方位角が大きい場合３０は、レンジゲート幅Ｎが小さくなるため、各場合のレンジゲート幅に内のΔ／Σデータは、それぞれ図７（ａ）、図７（ｂ）に示す形状となる。直線近似器１５は、Δ／Σ演算器１４より出力されるΔ／Σデータ４２に対し、レーダ制御器４より出力される処理開始レンジビン４３より、ゲート幅算出器２８に示されるレンジゲート幅内で、レンジビン毎のΔ／Σデータ４２に対して、最小二乗法等によりａｘ＋ｂの直線４５に近似を行い、傾きａとオフセットｂを出力する。距離算出器１６では、ａｘ＋ｂ＝０となるｘを算出し、ｘをビーム指向方向測定距離４６とする。これにより、レンジゲート幅内では、Δ／Σデータ４２が飽和特性を持たないようにすることが出来るため、誤差の増大を防ぎ、精度の良い距離測定を行うことが可能である。
【００５０】
以上のようにこの発明は、距離測定方位角および自機高度より、処理範囲内でΔ／Σデータが飽和特性を持たないようにするために必要なレンジゲート幅を算出し、直線近似器１５において、レンジゲート幅内で直線近似を行うことにより、距離測定方位角に関わらずΔ／Σデータが飽和特性を持たないようにすることが出来る。
【００５１】
実施の形態６．
図８はこの発明の実施の形態６を示す図であり、図において１、２、４〜１４、１６は従来装置と全く同一のものである。３は実施の形態１と全く同一のものである。１５は、実施の形態５と全く同一のものである。３１は、高度計３より出力される自機高度およびレーダ制御器４より出力される距離測定方位角より、近似を行う範囲を示すためのレンジゲート幅を、予め計算されたテーブルより参照して出力するゲート幅テーブルである。
【００５２】
前記のように構成されたレーダ装置においては、Δ／Σ演算器１４において、Δ／Σデータ４２を得るまでは、従来装置と全く同一である。実施の形態５と同様に、レーダ制御器４より距離測定方位角１９が出力され、高度計３より自機高度２０が出力されると、ゲート幅テーブル３１には、”数７”および”数８”の計算を、距離測定方位角１９および自機高度２０の各値に関して実施した結果が格納されており、距離測定方位角θ_ELおよび自機高度Ｈを入力すると、テーブルに格納されたデータから上記入力に応じたレンジゲート幅Ｎを読み出し出力する。これにより、実施の形態５と同様の効果を得ることが出来る。”数７”の演算を高速に実施するためには、複雑な回路が必要となるが、テーブルとすることにより、簡易な構成で実現が可能である。
【００５３】
以上のようにこの発明は、距離測定方位角および自機高度より、処理範囲内でΔ／Σデータの傾きを確保するために必要なレンジゲート幅を、予め計算されたテーブルを参照することにより求め、直線近似器１５において、レンジゲート幅内で直線近似を行うことにより、距離測定方位角に関わらずΔ／Σデータが飽和特性を持たないようにすることが出来る。
【００５４】
【発明の効果】
この発明によれば、距離測定方位角に関わらずΔ／Σデータの傾きを一定に保つことが出来る。
【００５５】
またこの発明によれば、距離測定方位角および自機高度に応じて、処理範囲内でΔ／Σデータが飽和特性を持たないために必要なレンジゲート幅を算出し、レンジゲート幅内で直線近似を行うことにより、距離測定方位角が大きい場合には、飽和特性による距離測定誤差増大を防ぐことが出来るため、精度の良い距離測定を行うことが出来る
【図面の簡単な説明】
【図１】 この発明によるレーダ装置の実施の形態１を示す図である。
【図２】 実施の形態１におけるプラットフォーム、ビーム指向方向および地表面の位置関係を示す図である。
【図３】 この発明によるレーダ装置の実施の形態２を示す図である。
【図４】 この発明によるレーダ装置の実施の形態３を示す図である。
【図５】 この発明によるレーダ装置の実施の形態４を示す図である。
【図６】 この発明によるレーダ装置の実施の形態５を示す図である。
【図７】 実施の形態５における距離測定方位角とレンジゲート幅の関係を示す図である。
【図８】 この発明によるレーダ装置の実施の形態６を示す図である。
【図９】 従来のレーダ装置を示す図である。
【図１０】 従来のレーダ装置におけるプラットフォーム、ビーム指向方向および地表面の位置関係を示す図である。
【図１１】 従来のレーダ装置における、送信信号から振幅データを得るまでの経過を示す図である。
【図１２】 従来のレーダ装置における、ビーム指向方向距離の測定方法を示す図である。
【図１３】 従来のレーダ装置における、ビーム指向方向測定距離の誤差を示す図である。
【符号の説明】
１ Ｕｐビーム用アンテナ、２ Ｄｏｗｎビーム用アンテナ、３ 高度計、４レーダ制御器、５ ビーム間隔算出器、６ ビーム制御器、７ 送信機、８ サーキュレータ、９ 受信機、１０ Ａ／Ｄ変換器、１１ 積分器、１２ ΣΔ生成器、
１３ クラッタ検出器、１４ Δ／Σ演算器、１５ 直線近似器、１６ 距離算出器、１７ プラットフォーム、２５ ビーム間隔テーブル、２６ ビーム幅算出器２７ ビーム幅テーブル、２８ ゲート幅算出器、３１ ゲート幅テーブル。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pulse-type radar device mounted on a flying platform such as an aircraft and measuring a distance to a ground surface in a specific direction.
[0002]
[Prior art]
FIG. 9 is a diagram showing a conventional radar apparatus mounted on an aircraft. 1 is a pulse-shaped transmission wave having a beam center direction that is a predetermined angle away from the distance measurement direction and above the elevation direction. Up (up) beam antenna 2 that receives the reflected wave from the ground surface, 2 has a beam center direction at a certain angle below the elevation direction with respect to the distance measurement direction, and has a pulse shape A down (down) beam antenna that radiates a transmitted wave and receives a reflected wave from the ground surface, 4 is a radar controller that outputs a distance measurement azimuth and a processing start range bin, and 6 is the radar controller 4 described above. A beam controller 7 for controlling the beam center direction of the Up beam antenna 1 and the Down beam antenna 2 based on the distance measurement azimuth angle output from the distance measurement azimuth, A circulator for supplying a transmission signal from the transmitter 7 to the Up beam antenna 1 and the Down beam antenna 2 and supplying a received reception signal to the receiver; A receiver that amplifies and detects a reception signal output from the circulator 8 and outputs it as a video signal, 10 is an A / D converter that converts the video signal output from the receiver 9 into a digital video signal, and 11 , An integrator that integrates the digital video signal output from the A / D converter 10 by the number of pulses necessary for main beam clutter detection and outputs it as amplitude data, and 12 includes the Up beam antenna 1 and the Down beam. Σ (sum) data is added to and subtracted from the amplitude data output from the integrator 11 corresponding to the antenna 2 for each range. A ΣΔ generator 13 for outputting data and Δ (difference) data, a clutter detection gate for detecting a main beam clutter from the Σ data output from the ΣΔ generator 12 and identifying a range bin of the main beam clutter. The clutter detector 14 for generating a Δ / Σ operation from the Σ data and Δ data output from the ΣΔ generator 12 within the range of the clutter detection gate output from the clutter detector 13, A Δ / Σ calculator 15 for outputting / Σ data, for each range bin output from the Δ / Σ calculator 14 for a certain number of range bins from the processing start range bin output from the radar controller 4. A linear approximator for approximating Δ / Σ data of a straight line and outputting an inclination and an offset value, 16 is an inclination and an offset value output from the linear approximation unit 15 Thus, the distance calculator calculates a range where the straight line intersects with 0 as a measurement distance.
[0003]
The conventional radar apparatus is configured as described above. As shown in FIG. 10, the radar apparatus is mounted on the platform 17, and a distance measurement azimuth angle 19 indicating the distance measurement direction 18 is output from the radar controller 4. The beam controller 6 controls the beam pointing directions of the Up beam antenna 1 and the Down beam antenna 2 so that the distance measuring direction 18 becomes the distance measuring azimuth angle 19. The Up beam antenna 1 and the Down beam antenna 2 radiate pulsed transmission signals to the ground surface 23 in the respective beam irradiation ranges 21 and 22. The transmitter 7 generates a pulse-like transmission signal 32 as shown in FIG. 11, and the radio wave reflected by the ground surface 23 is received by the Up beam antenna 1 and the Down beam antenna 2 and passes through the circulator 8. Thus, the received signal is supplied to the receiver 9 corresponding to each antenna. The received signal is amplified and detected by the receiver 9, and becomes an Up beam video signal 33 corresponding to the Up beam antenna 1 and a Down beam video signal 34 corresponding to the Down beam antenna 2 as shown in FIG.
[0004]
These video signals are respectively converted by the A / D converter 10 into an Up beam digital video signal 35 and a Down beam digital video signal 36 as shown in FIG. 11, and the Up beam amplitude integrated for the number of pulses necessary for target detection. The data 37 and Down beam amplitude data 38 are output from the integrator 11. For each amplitude data, the ΣΔ generator 12 performs calculation for each range as Σ data 39 = Up beam amplitude data 37 + Down beam amplitude data 38, Δ data 40 = Up beam amplitude data 37−Down beam amplitude data 38. And the amplitude shown in FIG. 12 is obtained.
[0005]
The clutter detector 13 performs main beam clutter detection on the Σ data 39 and outputs a clutter detection gate 41 for identifying the main beam clutter. The Δ / Σ calculator 14 calculates Δ / Σ in the range of the clutter detection gate 41 using the Σ data 39 and the Δ data 40 and outputs the result as Δ / Σ data 42. In the linear approximation unit 15, the processing start range bin 43 output from the radar controller 4 is set to a fixed number of processing range bins 44, and Δ / Σ data 42 for each range is ax + b by the least square method or the like. An approximation is made to the straight line 45, and the inclination a and the offset b are output. The distance calculator 16 calculates x that satisfies ax + b = 0, and sets x as the beam pointing direction measurement distance 46.
[0006]
[Problems to be solved by the invention]
In the conventional radar apparatus as described above, as shown in FIG. 13, when the distance measurement azimuth angle 19 is small 29 and the normal case 47 are compared, when the range resolution 48 is ΔR, the beam directivity for each range bin. The angle 49 from the direction is smaller when the distance measurement azimuth angle 19 is smaller. Therefore, the Δ / Σ data 42 also has a smaller amount of change for each range bin, so that the inclination becomes smaller. When processing the fixed number of processing range bins 44, when the distance measurement azimuth angle 19 is normal 47, Δ / Σ The data 42 has the shape shown in FIG. 13B, and when the distance measurement azimuth angle 19 is small 29, it has the shape shown in FIG. In actual observation, an error occurs in the Δ / Σ data 42 due to noise. Therefore, the Δ / Σ data 42 exists in the Δ / Σ data error range 50 shown in FIG. When the distance measurement azimuth angle 19 is normal 47, the distance error range 51 is as shown in FIG. 13B with respect to the Δ / Σ data error range 50, but when the distance measurement azimuth angle 19 is small 29 Is larger than the Δ / Σ data error range 50, the distance error range 51 becomes larger as shown in FIG. For this reason, there is a problem that an error also increases in the approximate straight line of the Δ / Σ data 42, resulting in an increase in distance measurement error. Further, when the distance measurement azimuth angle 19 is large, the Δ / Σ data 42 has an asymmetric saturation characteristic within the processing range as shown in FIG. There was a problem that the distance measurement error increased.
[0007]
The present invention has been made to solve such a problem. When the distance measurement azimuth angle 19 is small 29, the slope of the Δ / Σ data 42 is kept constant within the processing range, and the distance measurement azimuth angle is maintained. When 19 is large, the object is to obtain a radar apparatus capable of performing distance measurement with high accuracy by preventing saturation of Δ / Σ data 42 to prevent increase in distance measurement error.
[0008]
[Means for Solving the Problems]
The radar apparatus according to the first aspect of the invention has a beam center direction whose angle can be changed above the elevation direction with respect to the distance measurement direction, emits a pulsed transmission wave, and receives a reflected wave from the ground surface. A first antenna has a beam center direction whose angle can be changed below the elevation direction with respect to the distance measurement direction, emits a pulsed transmission wave, and receives a reflected wave from the ground surface. Antenna, an altimeter that outputs the altitude of the flying object, a radar controller that outputs a distance measurement azimuth and a processing start range bin, an altitude output from the altimeter and a distance measurement output from the radar controller Beam center angle output means for outputting a beam center angle with respect to the distance measuring direction of the first antenna and the second antenna from the azimuth angle, and the beam center angle output means Than a distance measured azimuth angle output from the beam center angle and the radar controller is et output, in which a beam controller for controlling the beam center direction of the first and second antennas.
[0009]
According to a second aspect of the present invention, there is provided the radar apparatus according to the first aspect, wherein the beam center angle output means includes the altitude output from the altimeter and the distance measurement azimuth output from the radar controller. And a beam interval calculator for calculating a beam center angle with respect to the distance measuring direction of the second antenna.
[0010]
According to a third aspect of the present invention, there is provided the radar apparatus according to the first aspect, wherein the distance between the first antenna and the second antenna according to the altitude of the flying object and the distance measurement azimuth is used as the beam center angle output means. The beam center angle with respect to the measurement direction has a table that is pre-calculated and stored, and inputs the own altitude output from the altimeter and the distance measurement azimuth output from the radar controller, and measures the altitude and distance. Means for reading out and outputting the beam center angle corresponding to the azimuth angle from the table is provided.
[0011]
A radar apparatus according to a fourth aspect of the invention has a beam center direction that is apart from the distance measurement direction by a certain angle above the elevation direction, the beam width can be changed, and a pulsed transmission wave is emitted. A first antenna that receives a reflected wave from the ground surface, a beam center direction at a certain angle below the elevation direction with respect to the distance measurement direction, a beam width that can be changed, and a pulse-like shape A second antenna that radiates a transmission wave and receives a reflected wave from the ground surface; an altimeter that outputs the altitude of the flying object; a radar controller that outputs a distance measurement azimuth and a processing start range bin; and Beam width output means for outputting the beam widths of the first antenna and the second antenna from the altitude output from the altimeter and the distance measurement azimuth angle output from the radar controller; A beam controller for controlling the beam center direction and the beam width of the first antenna and the second antenna from the beam width output from the beam width output means and the distance measurement azimuth angle output from the radar controller. It is a thing.
[0012]
According to a fifth aspect of the present invention, there is provided a radar apparatus according to the fourth aspect, wherein the first antenna and the second antenna are used as the beam width output means from the altitude output from the altimeter and the distance measurement azimuth output from the radar controller. This comprises a beam width calculator for calculating the beam width of the antenna.
[0013]
According to a sixth aspect of the present invention, there is provided a radar apparatus according to the fourth aspect, wherein the beam of the first antenna and the second antenna according to the altitude of the flying object and the distance measurement azimuth as the beam width output means. The table has a table in which the width is calculated and stored in advance, and inputs the altitude of the flying object output from the altimeter and the distance measurement azimuth output from the radar controller, and the height and distance measurement azimuth Means for reading out and outputting the corresponding beam width from the table is provided.
[0014]
A radar apparatus according to a seventh aspect of the invention has a beam center direction at a certain angle above the elevation direction with respect to the distance measurement direction, emits a pulsed transmission wave, and receives a reflected wave from the ground surface. A second antenna having a beam center direction at a certain angle below the elevation direction with respect to the distance measurement direction, emitting a pulsed transmission wave and receiving a reflected wave from the ground surface; Antenna, an altimeter that outputs the altitude of the flying object, a radar controller that outputs a distance measurement azimuth and processing start range bin, an altitude output from the altimeter and a distance measurement output from the radar controller Gate width output means for outputting the range gate width from the azimuth angle, and the beam of the first antenna and the second antenna from the distance measurement azimuth angle output from the radar controller A beam controller for controlling the direction of the heart; first and second receivers for amplifying and detecting the received signals received by the first antenna and the second antenna and outputting them as video signals; 1. First and second integrators that integrate the video signals output from the second receiver by the number of pulses necessary for main beam clutter detection and output as amplitude data, and the first and second integrators. The main beam clutter is detected from the ΣΔ generator that outputs Σ data and Δ data by addition and subtraction for each range bin, and the Σ data output from the ΣΔ generator. A clutter detector for generating a clutter detection gate for identifying a range bin of the main beam clutter, and a range of the clutter detection gate output from the clutter detector A Δ / Σ arithmetic unit that performs Δ / Σ operation from the Σ data and Δ data output from the ΣΔ generator, and outputs a Δ / Σ data, a processing start range bin output from the radar controller, and A straight line that approximates the Δ / Σ data for each range bin output from the Δ / Σ calculator with a straight line and outputs a slope and an offset value with respect to the range bin indicated by the range gate width output from the gate width output means. And an approximation device.
[0015]
The radar apparatus according to the eighth invention approximates the linear approximation device from the altitude output from the altimeter and the distance measurement azimuth angle output from the radar controller as the gate width output means in the seventh invention. And a gate width calculator for calculating a range gate width for indicating a range in which to perform and outputting the range gate width.
[0016]
According to a ninth aspect of the invention, there is provided a radar apparatus according to the seventh aspect, wherein the gate width output means has a table in which a range gate width corresponding to the altitude of the flying object and the distance measurement azimuth is calculated and stored in advance. And means for inputting the altitude output from the altimeter and the distance measurement azimuth angle output from the radar controller, and reading out and outputting the range gate width corresponding to the altitude and the distance measurement azimuth angle from the table. Is.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a diagram showing Embodiment 1 of the present invention. In the figure, reference numerals 4 and 7 to 16 are the same as those of the conventional apparatus. Reference numeral 1 denotes an Up beam antenna that has a beam center direction in which the angle can be changed above the elevation direction with respect to the distance measurement direction, emits a pulsed transmission wave, and receives a reflected wave from the ground surface. Has a beam center direction whose angle can be changed below the elevation direction with respect to the distance measurement direction, emits a pulsed transmission wave, and receives a reflected wave from the ground surface, 3 Is an altimeter that outputs its own altitude, and 5 is an altitude meter output from the altimeter 3 and a distance measurement azimuth angle output from the radar controller 4, and the Up beam antenna 1 and Down beam antenna 2 are A beam interval calculator 6 for calculating a beam center angle with respect to the distance measurement direction, and a beam center angle output from the beam interval calculator 5 and an output from the radar controller 4. From that distance measurement azimuth, a beam controller that controls the beam center direction of the Up-beam antenna 1 and Down-beam antenna 2.
[0018]
In the radar apparatus configured as described above, the distance measurement azimuth angle 19 indicating the distance measurement direction 18 is output from the radar controller 4 by being mounted on the platform 17 as shown in FIG. The beam interval calculator 5 uses the Up beam antenna 1 and the beam distance calculating azimuth 19 and the own altitude 20 output from the altimeter 3, which are necessary for making the slope of Δ / Σ data constant within the processing range. The beam center angle 24 with respect to the distance measurement direction 18 of the down beam antenna 2 is calculated. For example, the distance measurement azimuth 18 is θ _EL The altitude 20 is H, the angle at which the beams overlap is θ _OVER When the number of range bins where the beams overlap is N and the range resolution 48 is ΔR, the beam irradiation range 21 formed by the Up beam antenna 1 and the beam irradiation range 22 formed by the Down beam antenna 2 from the ground surface 23. In order to make the received signals overlap only by the N-range bin, the calculation may be performed according to “Equation 1”.
[0019]
[Expression 1]

[0020]
In order to make the signal level in the distance measuring direction 18 the same in the beam irradiation range 21 formed by the Up beam antenna 1 and the beam irradiation range 22 formed by the Down beam antenna 2, the elevation direction of each beam Antenna beam width θ _EBW And the beam center angle 24 with respect to the distance measuring direction 18 must be the same. Assuming that the beam center angle 24 is Δθ / 2, Δθ / 2 is calculated by the formula “Equation 2”.
[0021]
[Expression 2]

[0022]
The beam interval calculator 5 performs the calculations of “Equation 1” and “Equation 2” and outputs the beam center angle Δθ / 2. The beam controller 6 includes a beam center angle Δθ / 2 and a distance measurement azimuth angle θ. _EL Thus, the beam center direction of the Up beam antenna 1 is θ _EL −Δθ / 2, the beam center direction of the Down beam antenna 2 is θ _EL Control so that + Δθ / 2. Thereby, the distance measurement azimuth angle θ _EL Even if changes, the number of range bins where the beams overlap is always kept in the N range bin. The subsequent operation is exactly the same as that of the conventional apparatus, and if the number of range bins processed in the linear approximation unit 15 is N, Δ / Σ data always has a constant slope in the processing range bin. When the distance measurement azimuth angle 19 shown in FIG. 13 is small 29, the beam center angle 24 becomes large, and the shape of Δ / Σ data shown in FIG. 13B can be obtained. Further, when the distance measurement azimuth angle 19 is large 30, the beam center angle 24 is small, so that the saturation characteristic of Δ / Σ data does not occur, and the shape of Δ / Σ data shown in FIG. 13B is obtained. I can do it. As a result, it is possible to prevent an increase in error and perform accurate distance measurement.
[0023]
When the distance measurement azimuth angle 19 is larger than the range resolution 48, as shown in FIG. 2B, the beam irradiation range 21 formed by the Up beam antenna 1 and the beam formed by the Down beam antenna 2 are used. In some cases, the reception signals from the ground surface 23 in the irradiation range 22 are all contained in one range bin. In this case, the main beam clutter of the Up beam amplitude data 37 and the Down beam amplitude data 38 has an amplitude only in the same range bin, and the Δ data 40 output from the ΣΔ generator 12 has an amplitude only on the positive side or the negative side. Therefore, it becomes impossible to measure the distance in the subsequent processing. When this condition is expressed by an equation, "Equation 3" is obtained.
[0024]
[Equation 3]

[0025]
When this condition is satisfied, the beam center calculator 5 calculates the beam center angle Δθ / 2 according to “Equation 4”.
[0026]
[Expression 4]

[0027]
If the beam controller 6 controls the beam center direction of each antenna using the beam center angle 24, the main beam clutter of the Up beam amplitude data 37 and the Down beam amplitude data 38 can be separated by one range bin or more. Become. As a result, the Δ data 40 output from the ΣΔ generator 12 has amplitudes on both the positive side and the negative side, and distance measurement is possible in the subsequent processing.
[0028]
As described above, according to the present invention, the Up beam antenna 1 and the Down beam antenna 2 necessary for making the slope of Δ / Σ data constant within the processing range according to the distance measurement azimuth and the altitude of the aircraft. By calculating the beam center angle with respect to the distance measurement direction and changing the beam center direction, the slope of Δ / Σ data can be kept constant regardless of the distance measurement azimuth angle. Accordingly, when the distance measurement azimuth is small, an increase in distance measurement error can be prevented, and when the distance measurement azimuth is large, an increase in distance measurement error due to saturation characteristics can be prevented, so that the accuracy is high. Distance measurement can be performed. In addition, the distance measurement azimuth is larger than the range resolution, and all the received signals from the ground surfaces of the Up beam antenna 1 and the Down beam antenna 2 are contained in one range bin, making distance measurement impossible. Even in this case, by changing the beam center direction, the received signals from the ground surface of the Up beam antenna and the Down beam antenna can be separated by one range bin or more, and distance measurement can be made possible.
[0029]
Embodiment 2. FIG.
FIG. 3 is a diagram showing a second embodiment of the present invention, in which 4 and 7 to 16 are the same as those of the conventional apparatus. 1 to 3 and 6 are exactly the same as those in the first embodiment. 25, the beam center angle with respect to the distance measurement direction of the Up beam antenna 1 and the Down beam antenna 2 is calculated in advance based on the altitude output from the altimeter 3 and the distance measurement azimuth angle output from the radar controller 4. This is a beam interval table which is output by referring to the table.
[0030]
In the radar apparatus configured as described above, the distance measurement azimuth angle 19 is output from the radar controller 4 and the own altitude 20 is output from the altimeter 3 as in the first embodiment. The beam interval table 25 stores the results of calculation of “Equation 1” and “Equation 2” for each value of the distance measurement azimuth angle 19 and the aircraft altitude 20 and the distance measurement azimuth angle θ. _EL When the altitude H is input, the beam center angle Δθ / 2 corresponding to the input is read from the table and output. As a result, the same effect as in the first embodiment can be obtained. In order to perform the calculation of “Equation 1” at high speed, a complicated circuit is required. However, by using a table, it is possible to realize it with a simple configuration.
[0031]
When the distance measurement azimuth angle 19 is larger than the range resolution 48, the table data when the condition of “Equation 3” is satisfied is set as the calculation result of “Equation 4”. Can be obtained.
[0032]
As described above, according to the present invention, the Up beam antenna 1 and the Down beam antenna necessary for making the slope of Δ / Σ data constant within the processing range according to the distance measurement azimuth and the altitude of the aircraft. 2 is obtained by referring to a pre-calculated table, and by changing the beam center direction, the slope of Δ / Σ data can be kept constant regardless of the distance measurement azimuth. Accordingly, when the distance measurement azimuth is small, an increase in distance measurement error can be prevented, and when the distance measurement azimuth is large, an increase in distance measurement error due to saturation characteristics can be prevented, so that the accuracy is high. Distance measurement can be performed. In addition, the distance measurement azimuth is larger than the range resolution, and all the received signals from the ground surfaces of the Up beam antenna 1 and the Down beam antenna 2 are contained in one range bin, making distance measurement impossible. Even in this case, by changing the beam center direction, the reception signals from the ground surfaces of the Up beam antenna 1 and the Down beam antenna 2 can be separated by one range bin or more, and distance measurement can be performed. Furthermore, it is realizable with a simpler structure than Embodiment 1 of this invention.
[0033]
Embodiment 3 FIG.
FIG. 4 is a diagram showing a third embodiment of the present invention. In the figure, reference numerals 4 and 7 to 16 are the same as those of the conventional apparatus. 3 is exactly the same as in the first embodiment.
1 has a beam center direction at a certain angle above the elevation direction with respect to the distance measurement direction, the beam width can be changed, a pulsed transmission wave is radiated, and a reflected wave from the ground surface is received. The up beam antenna 2 has a beam center direction at a certain angle below the elevation direction with respect to the distance measurement direction, the beam width can be changed, and a pulsed transmission wave is radiated. A down beam antenna 26 that receives a reflected wave from the surface, and the up beam antenna 1 and the down beam antenna from the altitude output from the altimeter 3 and the distance measurement direction output from the radar controller 4. The beam width calculator 6 for calculating the beam width of 2 is higher than the beam width output from the beam width calculator 26 and the distance measurement azimuth angle output from the radar controller 4. Up is a beam controller for controlling the beam center direction and beam width of the beam antenna 1 and Down-beam antenna 2.
[0034]
In the radar apparatus configured as described above, the distance measurement azimuth angle 19 is output from the radar controller 4 and the own altitude 20 is output from the altimeter 3 as in the first embodiment. The beam width calculator 22 determines the up beam antenna 1 and the down beam antenna 2 necessary for making the slope of Δ / Σ data constant within the processing range from the distance measurement azimuth angle 19 and the own altitude 20. Calculate the beam width. The angle θ at which the beams overlap as in the first embodiment _OVER Is calculated by “Equation 1”. In order to make the signal level in the distance measuring direction 18 the same for the beam 21 formed by the Up beam antenna 1 and the beam 22 formed by the Down beam antenna 2, the antenna beam width in the elevation direction of each beam. θ _EBW And the beam center angle 24 with respect to the distance measuring direction 18 must be the same. When the beam center angle 24 is Δθ / 2, θ _EBW Is calculated by the formula of “Equation 5”.
[0035]
[Equation 5]

[0036]
The beam width calculator 22 calculates “Equation 1” and “Equation 5” and calculates the beam width θ. _EBW Is output. The beam controller 6 has a beam width θ _EBW And distance measurement azimuth θ _EL Are set for the Up beam antenna 1 and the Down beam antenna 2. Thereby, even if the distance measurement azimuth angle 18 changes, the number of range bins where the beams overlap is always kept in the N range bin. The subsequent operation is exactly the same as that of the conventional apparatus, and if the number of range bins processed in the linear approximation unit 15 is N, Δ / Σ data always has a constant slope in the processing range bin. When the distance measurement azimuth angle 19 shown in FIG. 13 is small 29, the beam center angle 24 becomes large, and the shape of Δ / Σ data shown in FIG. 13B can be obtained. Further, when the distance measurement azimuth angle 19 is large 30, the beam center angle 24 is small, so that the saturation characteristic of Δ / Σ data does not occur, and the shape of Δ / Σ data shown in FIG. 13B is obtained. I can do it. As a result, it is possible to prevent an increase in error and perform accurate distance measurement. When the distance measurement azimuth angle 19 is larger than the range resolution 48, the beam width θ when the condition of “Equation 3” is satisfied. _EBW Is calculated according to “Equation 6”.
[0037]
[Expression 6]

[0038]
This beam width θ _EBW If the beam controller 6 is used to set the beam width of each antenna, the same effect as in the first embodiment can be obtained.
[0039]
As described above, according to the present invention, the Up beam antenna 1 and the Down beam antenna necessary for making the slope of Δ / Σ data constant within the processing range according to the distance measurement azimuth and the altitude of the aircraft. By calculating the beam width of 2 and changing the beam width, the slope of Δ / Σ data can be kept constant regardless of the distance measurement azimuth angle. Accordingly, when the distance measurement azimuth is small, an increase in distance measurement error can be prevented, and when the distance measurement azimuth is large, an increase in distance measurement error due to saturation characteristics can be prevented, so that the accuracy is high. Distance measurement can be performed. In addition, the distance measurement azimuth is larger than the range resolution, and all the received signals from the ground surfaces of the Up beam antenna 1 and the Down beam antenna 2 are contained in one range bin, making distance measurement impossible. Even in this case, by changing the beam width, the reception signals from the ground surfaces of the Up beam antenna 1 and the Down beam antenna 2 can be separated by one range bin or more, and distance measurement can be performed.
[0040]
Embodiment 4 FIG.
FIG. 5 is a diagram showing a fourth embodiment of the present invention, in which 4 and 7 to 16 are the same as those of the conventional apparatus. 1 to 3 and 6 are exactly the same as those in the third embodiment. 27 shows the beam widths of the Up beam antenna 1 and the Down beam antenna 2 from the table calculated in advance based on the altitude output from the altimeter 3 and the distance measurement azimuth angle output from the radar controller 4. It is a beam width table that is output with reference.
[0041]
In the radar apparatus configured as described above, the distance measurement azimuth angle 19 is output from the radar controller 4 and the own altitude 20 is output from the altimeter 3 as in the third embodiment. The beam width table 27 stores the results of calculation of “Equation 1” and “Equation 5” for each value of the distance measurement azimuth angle 19 and the aircraft altitude 20 and the distance measurement azimuth angle θ. _EL When the altitude H is input, the beam width θ corresponding to the input from the data stored in the table _EBW Is read out and output. As a result, the same effect as in the third embodiment can be obtained. In order to perform the calculation of “Equation 1” at high speed, a complicated circuit is required. However, by using a table, it is possible to realize it with a simple configuration.
[0042]
When the distance measurement azimuth angle 19 is larger than the range resolution 48, the data of the table when the condition of “Equation 3” is satisfied is set as the calculation result of “Equation 6”. Can be obtained.
[0043]
As described above, according to the present invention, the Up beam antenna 1 and the Down beam antenna 2 required to make the slope of Δ / Σ data constant within the processing range from the distance measurement azimuth and the own altitude. The beam width is obtained by referring to a pre-calculated table, and the beam controller 6 changes the beam width of each antenna to keep the slope of Δ / Σ data constant regardless of the distance measurement azimuth. I can do it.
[0044]
Embodiment 5. FIG.
FIG. 6 is a diagram showing a fifth embodiment of the present invention. In the figure, 1, 2, 4 to 14 and 16 are exactly the same as those of the conventional apparatus. 3 is exactly the same as in the first embodiment. 28 calculates a range gate width for indicating a range to be approximated with respect to the linear approximation device 15 from the altitude of the aircraft output from the altimeter 3 and the distance measurement azimuth angle output from the radar controller 4. The gate width calculator 15 for outputting the range gate width, for the range bin indicated by the processing start range output from the radar controller 4 and the range gate width output from the gate width calculator 28, This is a linear approximator that approximates Δ / Σ data for each range bin output from the Δ / Σ calculator with a straight line, and outputs a slope and an offset value.
[0045]
The radar apparatus configured as described above is exactly the same as the conventional apparatus until the Δ / Σ calculator 42 obtains the Δ / Σ data 42. When the distance measurement azimuth angle 19 is output from the radar controller 4 and the own altitude 20 is output from the altimeter 3, the gate width calculator 28 determines that the distance measurement azimuth 19 and the own altitude 20 are within the processing range. A range gate width is calculated to indicate a range to be approximated in the linear approximation unit 15 necessary for the Δ / Σ data not to have saturation characteristics. For example, the distance measurement azimuth angle 19 is θ _EL The altitude 20 is H, the angle at which the beams overlap is θ _OVER If the number of range bins where beams overlap is N and the range bin interval is ΔR, the number N of range bins where beams overlap may be calculated according to “Equation 7”.
[0046]
[Expression 7]

[0047]
Note that the angle θ at which the beams overlap _OVER Is the beam width θ _EBW The beam center angle Δθ / 2 can be expressed as “Equation 8”.
[0048]
[Equation 8]

[0049]
The gate width calculator 24 calculates “Equation 7” and “Equation 8” and outputs the range gate width N. As shown in FIG. 7, when the distance measurement azimuth is small 29, the range gate width N is large, and when the distance measurement azimuth is large 30, the range gate width N is small. The Δ / Σ data in FIG. 7 have the shapes shown in FIGS. 7A and 7B, respectively. The straight line approximator 15 receives the Δ / Σ data 42 output from the Δ / Σ calculator 14 within the range gate width indicated by the gate width calculator 28 from the processing start range bin 43 output from the radar controller 4. Then, the Δ / Σ data 42 for each range bin is approximated to the straight line 45 of ax + b by the least square method or the like, and the inclination a and the offset b are output. The distance calculator 16 calculates x such that ax + b = 0, and sets x to the beam directing direction measurement distance 46. As a result, the Δ / Σ data 42 can be prevented from having saturation characteristics within the range gate width, so that an increase in error can be prevented and accurate distance measurement can be performed.
[0050]
As described above, according to the present invention, the range gate width necessary for preventing the Δ / Σ data from having saturation characteristics within the processing range is calculated from the distance measurement azimuth and the own altitude, and the linear approximation unit 15 Thus, by performing linear approximation within the range gate width, it is possible to prevent the Δ / Σ data from having saturation characteristics regardless of the distance measurement azimuth angle.
[0051]
Embodiment 6 FIG.
FIG. 8 is a diagram showing a sixth embodiment of the present invention. In the figure, 1, 2, 4 to 14 and 16 are the same as those of the conventional apparatus. 3 is exactly the same as in the first embodiment. 15 is the same as that of the fifth embodiment. 31 indicates a range gate width for indicating a range to be approximated based on the altitude output from the altimeter 3 and the distance measurement azimuth angle output from the radar controller 4 by referring to a previously calculated table. It is a gate width table.
[0052]
The radar apparatus configured as described above is exactly the same as the conventional apparatus until the Δ / Σ calculator 42 obtains the Δ / Σ data 42. Similarly to the fifth embodiment, when the distance measurement azimuth angle 19 is output from the radar controller 4 and the own altitude 20 is output from the altimeter 3, the gate width table 31 displays “Equation 7” and “Equation 8”. Is stored for each value of the distance measurement azimuth 19 and the aircraft altitude 20, and the distance measurement azimuth θ _EL When the altitude H is input, the range gate width N corresponding to the input is read out from the data stored in the table and output. As a result, the same effect as in the fifth embodiment can be obtained. In order to perform the operation of “Equation 7” at high speed, a complicated circuit is required. However, by using a table, it is possible to realize the calculation with a simple configuration.
[0053]
As described above, according to the present invention, the range gate width necessary for securing the slope of Δ / Σ data within the processing range is referred to the table calculated in advance from the distance measurement azimuth and the altitude. Thus, the linear approximation unit 15 performs linear approximation within the range gate width, so that Δ / Σ data does not have saturation characteristics regardless of the distance measurement azimuth angle.
[0054]
【The invention's effect】
According to the present invention, the slope of Δ / Σ data can be kept constant regardless of the distance measurement azimuth.
[0055]
Further, according to the present invention, the range gate width required for the Δ / Σ data not to have saturation characteristics within the processing range is calculated according to the distance measurement azimuth and the altitude of the aircraft, and the straight line within the range gate width is calculated. By performing approximation, when the distance measurement azimuth is large, an increase in distance measurement error due to saturation characteristics can be prevented, so accurate distance measurement can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a first embodiment of a radar apparatus according to the present invention.
FIG. 2 is a diagram showing a positional relationship between a platform, a beam pointing direction, and a ground surface in the first embodiment.
FIG. 3 is a diagram showing a second embodiment of a radar apparatus according to the present invention.
FIG. 4 is a diagram showing a third embodiment of a radar apparatus according to the present invention.
FIG. 5 is a diagram showing a fourth embodiment of a radar apparatus according to the present invention.
FIG. 6 is a diagram showing a fifth embodiment of a radar apparatus according to the present invention.
FIG. 7 is a diagram showing a relationship between a distance measurement azimuth angle and a range gate width in the fifth embodiment.
FIG. 8 is a diagram showing a sixth embodiment of a radar apparatus according to the present invention.
FIG. 9 is a diagram showing a conventional radar apparatus.
FIG. 10 is a diagram showing a positional relationship between a platform, a beam pointing direction, and a ground surface in a conventional radar apparatus.
FIG. 11 is a diagram showing a process until amplitude data is obtained from a transmission signal in a conventional radar apparatus.
FIG. 12 is a diagram showing a method of measuring a beam pointing direction distance in a conventional radar apparatus.
FIG. 13 is a diagram illustrating an error in a beam pointing direction measurement distance in a conventional radar apparatus.
[Explanation of symbols]
1 Up beam antenna, 2 Down beam antenna, 3 altimeter, 4 radar controller, 5 beam interval calculator, 6 beam controller, 7 transmitter, 8 circulator, 9 receiver, 10 A / D converter, 11 Integrator, 12 ΣΔ generator,
13 Clutter Detector, 14 Δ / Σ Calculator, 15 Linear Approximator, 16 Distance Calculator, 17 Platform, 25 Beam Spacing Table, 26 Beam Width Calculator 27 Beam Width Table, 28 Gate Width Calculator, 31 Gate Width Table .

Claims (3)

In a pulse-type radar device that is mounted on a flying object such as an aircraft and measures the distance to the ground surface in a specific direction, a beam center direction that can change the angle is set above the elevation direction with respect to the distance measurement direction. A first antenna that radiates a pulsed transmission wave and receives a reflected wave from the ground surface, and has a beam center direction that can change the angle below the elevation direction with respect to the distance measurement direction, A second antenna that emits a pulsed transmission wave and receives a reflected wave from the ground surface, an altimeter that outputs the altitude of the flying object, and a radar controller that outputs a distance measurement azimuth and a processing start range bin And the distance measurement azimuth angle output from the radar controller and the distance measurement azimuth angle output from the radar controller. Beam center angle output means for outputting a center angle, beam center angle output from the beam center angle output means, and distance measurement azimuth angle output from the radar controller, the first antenna and the second antenna A beam controller for controlling the beam center direction of the first and second receivers for amplifying and detecting the received signals received by the first antenna and the second antenna, respectively, and outputting them as video signals; The video signals output from the first and second receivers are respectively integrated by the number of pulses necessary for main beam clutter detection, and output as amplitude data, and the first and second integrators, From the amplitude data output from the second integrator, a ΣΔ generator that outputs Σ data and Δ data by addition and subtraction for each range bin, and the ΣΔ generator Within the range of the clutter detector that detects the main beam clutter from the input Σ data and generates a clutter detection gate for identifying the range bin of the main beam clutter, and the clutter detection gate output from the clutter detector A radar apparatus comprising: a Σ data output from the ΣΔ generator and a Δ / Σ calculator for performing Δ / Σ calculation from the Δ data and outputting Δ / Σ data. The beam center angle output means calculates a beam center angle with respect to a distance measurement direction of the first antenna and the second antenna from an altitude output from the altimeter and a distance measurement azimuth angle output from the radar controller. The radar apparatus according to claim 1, further comprising a beam interval calculator. The beam center angle output means calculates and stores in advance the beam center angle with respect to the distance measurement direction of the first antenna and the second antenna according to the altitude of the flying object and the distance measurement azimuth angle. It has a table, inputs its own altitude output from the altimeter and the distance measurement azimuth angle output from the radar controller, and reads the beam center angle corresponding to the altitude and the distance measurement azimuth angle from the table 2. The radar apparatus according to claim 1, further comprising means for outputting.

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