JP3717038B2 - Diversity receiver for OFDM signal - Google Patents

Description

【００２５】
【数２】

【００２６】
【数３】

【００２７】
説明の簡単化のため、直交復調後の複素ＦＦＴ処理において、正の周波数のキャリア数と負の周波数のキャリア数が等しくなるように直交復調時のローカル信号周波数ｆ_QDEMを設定すると、次の（数４）式が成立する。
【００２８】
【数４】

【００２９】
（数３）式は各受信系統のＩＦ信号のスペクトルがお互いに重ならないようにするための条件である。ＣＨ１〜ＣＨ５の隣り合うローカル信号間の周波数差をｆ_di（ｉ＝１〜ｍ−１）と記すると、ｇ_i（ｉ＝１〜ｍ−１）を０より大きい整数として次の（数５）式が成立する。
【００３０】
【数５】

【００３１】
さらに、周波数変換に伴って発生するイメージ成分と本来のスペクトルが直交復調時に互いに重なり合わないようにするための条件を次の（数６）式に示す。
【００３２】
【数６】

【００３３】
ここで、ｇ_i×Δｆ（ｉ＝１〜ｍ−１）は、図４に示すＩＦ信号スペクトルにおいて、隣合う受信系統のスペクトル間（例えば、それぞれ斜線部が示すｉｆ₁を中心周波数とするスペクトルとｉｆ₂を中心周波数とするスペクトル間）のガードバンドＧｂ１〜Ｇｂ４に相当する周波数幅である。ｇ_i（ｉ＝１〜ｍ−１）は必ずしも同一値である（各ガードバンドが同一帯域幅である）必要はない。
【００３４】
このとき、後段のＦＦＴ（fast Fourier transform）処理回路３８では次の（数７）式で表されるポイント数の複素ＦＦＴ処理を実行することになる。（数７）式において、ＬはＦＦＴの次数を表す正の整数である。
【００３５】
【数７】

【００３６】
アナログ乗算器１６〜２０に入力するＣＨ１〜ＣＨ５の各ローカル信号の発生方法については後述する。
【００３７】
アナログ乗算器１６〜２０から出力され、ＩＦ帯の所定通過帯域のＢＰＦ２１〜２５によってイメージ成分を除去された各受信系統の信号は、加算器によって加算合成されて一系統の合成信号とされる。すなわち、第１系統（ＣＨ１）と第２系統（ＣＨ２）の信号がアナログ加算器２６で加算され、その加算結果がアナログ加算器２８に入力される。第３系統（ＣＨ３）の信号は、そのままアナログ加算器２８に入力される。また、第４系統（ＣＨ４）と第５系統（ＣＨ５）の信号はアナログ加算器２７で加算され、その加算結果がアナログ加算器２８に入力される。
【００３８】
アナログ加算器２８により上記３入力を加算した出力は、合せて５系統のＩＦ信号が合成された結果である。合成ＩＦ信号のスペクトルは図４に示すように各チャンネルの中心周波数ｉｆ₁〜ｉｆ₅が所定周波数間隔で配置され、それぞれの間に所定幅のガードバンドＧｂ１〜Ｇｂ４が配置されている。当該スペクトルの合成信号に対して、ＩＦ増幅器２９以降の一系統の処理回路によって、一括ＦＦＴ、復調を含む処理が行われる。
【００３９】
アナログ加算器２８の出力信号はＩＦ増幅器２９で増幅された後、図２のＡ／Ｄ変換器３０でデジタル信号に変換される。本実施形態では、Ａ／Ｄ変換のサンプリング周波数ｆ_sをＦＦＴクロック周波数ｆ_FFTの４倍とし、ＩＦ信号の中心周波数、すなわちｆ_QDEMを、ＦＦＴクロック周波数ｆ_FFTに設定している。ＦＦＴクロック周波数ｆ_FFTは、ＦＦＴのポイント数をＮ_FFT、ＯＦＤＭ信号のキャリア間隔をΔｆとして次の（数８）式で表される。
【００４０】
【数８】

【００４１】
Ａ／Ｄ変換後の信号スペクトルを図５に示す。
【００４２】
Ａ／Ｄ変換器３０から出力された上記スペクトルを有するデジタル信号はＩ軸側信号とＱ軸側信号に２分配され、Ｉ軸側信号はデジタル乗算器３１に、Ｑ軸側信号はデジタル乗算器３２にそれぞれ入力される。デジタル乗算器３１および３２にはさらに、キャリア再生回路４１にて再生された各キャリア信号がそれぞれ入力される。このとき、Ｉ軸側のデジタル乗算器３１に供給される再生キャリア信号に対して、Ｑ軸側のデジタル乗算器３２に供給される再生キャリア信号は９０度の位相遅れがあり、かつ、両キャリアは互いに直交している。
【００４３】
上記キャリアを用いてデジタル乗算器３１，３２により周波数変換することでデジタル直交復調が行われる。復調して得られたＩ軸信号、Ｑ軸信号のスペクトルをスカラー表現するとそれぞれ図６に示す通りになる。すなわち、サンプリング周波数ｆ_sの周りと周波数０の周りの成分、および両成分の間のイメージ成分で表される。
【００４４】
デジタル乗算器３１の出力はデジタルＬＰＦ３３に、デジタル乗算器３２の出力はデジタルＬＰＦ３４に入力され、それぞれ不要な上記イメージ成分を除去されて出力される。すなわち、デジタルＬＰＦ３３，３４はそれぞれ上記イメージ成分を含まない所定帯域を通過し、それぞれ図７に示すスペクトルの信号を出力する。
【００４５】
デジタルＬＰＦ３３から出力されたＩ軸信号は２分配され、一方はサブサンプル回路３５に入力される。もう一方はさらに２分配され、クロック再生回路４２とキャリア再生回路４１にそれぞれ供給される。同様に、デジタルＬＰＦ３４から出力されたＱ軸信号も２分配され、一方はサブサンプル回路３６に入力される。もう一方はさらに２分配され、クロック再生回路４２とキャリア再生回路４１にそれぞれ供給される。
【００４６】
分配されてサブサンプル回路３５，３６に入力されたＩ軸信号とＱ軸信号はそれぞれ４：１に間引かれ、図８に示す通りサンプリング周波数をｆ_sの１／４とされる。
【００４７】
サブサンプル回路３５，３６から出力されたＩ軸信号、Ｑ軸信号はガード・インターバル除去回路３７にそれぞれ入力され、ここで有効シンボル期間を抽出されてＦＦＴ処理回路３８に入力される。ＦＦＴ処理回路３８は、シンボル単位の時間軸信号を周波数軸上の複素信号に変換する。受信したＯＦＤＭ信号のキャリア数をＮ_c、ダイバーシティによる受信系統数をｍとすると、１シンボルにつきＮ_c×ｍ個の複素数データが得られ、当該データは差動復調回路３９に入力される。
【００４８】
ＦＦＴ処理回路３８から出力される複素キャリアデータをＣ_i，_j，_k（ｉ：受信系統番号、ｊ：キャリア番号、ｋ：シンボル番号）とすると、差動復調回路３９では、これらＣ_i，_j，_kについて次の（数９）式で表される演算を行う。（数９）式のＤ_i，_j，_kは差動復調回路３９から出力されるＮ_c×ｍ個の複素データを表し、Ｃ_i，_j，_k-1に付された＊は複素共役を表す。
【００４９】
【数９】

【００５０】
差動復調回路３９から出力された１シンボル当たりＮ_c×ｍ個の複素データはキャリア選択／合成処理回路４０に入力され、ここでは、各受信系統に対してキャリア単位で、次の（数１０）式に示すような合成処理が行われる。
【００５１】
【数１０】

【００５２】
（数１０）式のＯ_j，_kはキャリア選択／合成処理回路４０からの出力複素データを表し、ｊ＝１〜Ｎ_c、ｋはシンボル番号である。すなわち、キャリア選択／合成処理回路４０はＮ_c個の複素データを、以降の判定復号処理部（図示せず）へと送出する。
【００５３】
本実施形態では、ダイバーシティ効果を得るために、各受信系統のそれぞれのキャリアに対してベクトル合成を行ったが、この他に、キャリア振幅が最も大きい受信系統のキャリアデータを選択して出力する方式なども考えられる。
【００５４】
次に、各受信系統のＲＦ信号のＩＦ信号への周波数変換に使用したｆ_L1〜ｆ_L5の各ローカル信号の発生方法について説明する。
【００５５】
ローカル信号発生の概略動作を説明すると、デジタル直交復調後のＩ軸信号、Ｑ軸信号を入力したクロック再生回路４２は、当該入力に基づきシンボル・クロック、ＦＦＴクロック、Ａ／Ｄ変換に用いるサンプリング・クロック等、種々処理の基準として必要な各種クロック信号を再生し、これらクロックを装置各部に供給する。クロック再生回路４２におけるクロック再生は、各種公知技術、すなわちガード・インターバル相関法やチャープ信号などの基準シンボルを用いる方法により行うことができる。ここでは、これら公知の技術の詳しい説明は省略する。
【００５６】
クロック再生回路４２から出力されたシンボル・クロック周波数の基準信号は分配器４３で５分配され、それぞれが基準信号としてＰＬＬ（Phase Locked Loop）回路４４〜４８に入力される。位相同期ループを持つＰＬＬ回路４４〜４８はそれぞれ、入力基準信号の周波数とそれぞれ異なる整数比の関係を有する周波数の正弦波信号を生成、出力する。本明細書において整分数比とは、入力基準信号の周波数のｂ／ａ倍で表される値を意味し、ここでａとｂはそれぞれ整数である。単一の周波数成分を持った各正弦波信号はそれぞれ、アナログ乗算器５１〜５５に入力される。
【００５７】
一方、基準局部発振器（Signal Generator；ＳＧ）４９から出力された正弦波信号は分配器５０により５分配され、それぞれがアナログ乗算器５１〜５５に印加される。各アナログ乗算器５１〜５５では、印加された正弦波信号とＰＬＬ回路４４〜４８からのそれぞれの正弦波信号をそれぞれ乗算して、異なる周波数への周波数変換を行う。各周波数変換信号は、それぞれ異なる通過帯域のＬＯ−ＢＰＦ５６〜６０によって周波数変換に伴い発生したイメージ成分を除去された後、それぞれ異なる周波数のローカル信号ｆ_L1〜ｆ_L5としてアナログ乗算回路１６〜２０に入力される。
【００５８】
続いて、上述したローカル信号発生に関連する各部の周波数関係の一例を説明する。
【００５９】
説明の簡単化のため、ここではＯＦＤＭ信号のキャリア数Ｎ_cを奇数とし、ＩＦ信号スペクトルにおいて隣合う受信系統のスペクトル間のガードバンド幅を規定するｇ_i（ｉ＝１〜ｍ−１）を同一値ｇとする。本実施形態では、一例としてＣ番目（５系統のうち３番目）の受信系統の中心周波数をＩＦ信号の中心周波数と一致させる場合を想定している。また前述した通り、デジタル直交復調処理を想定しているために、ＩＦ信号の中心周波数（すなわち、直交復調後に直流に変換される信号の周波数）はＦＦＴクロック周波数と同一とし、Ａ／Ｄ変換のサンプリング周波数ｆ_sをＦＦＴクロック周波数ｆ_FFTの４倍の周波数４ｆ_FFTとしている。
【００６０】
受信ＯＦＤＭ信号の中心周波数ｆ_rと各受信系統に対応するローカル信号の周波数ｆ_L1〜ｆ_L5との差の周波数ｉｆ₁〜ｉｆ₅は、周波数変換後のＩＦ信号（図４参照）におけるそれぞれの受信系統に対応するスペクトルの中心周波数に等しい。したがって、各受信系統に対応するローカル信号の周波数ｆ_L1〜ｆ_L5は、次の（数１１）式で表される。
【００６１】
【数１１】

【００６２】
ここで、ｉｆ₁〜ｉｆ₅は次の（数１２）式で表される。
【００６３】
【数１２】

【００６４】
（数１２）式を（数１１）式に代入して、次の（数１３）式が得られる。
【００６５】
【数１３】

【００６６】
一方、各受信系統に対応するローカル信号は、ＳＧ４９の出力信号を分配器５０で分配し、それぞれアナログ乗算器５１〜５５で周波数変換を行った結果として得られ、その周波数はそれぞれ（数１３）式で表される。また、アナログ乗算器５１〜５５にそれぞれ入力されるＰＬＬ回路４４〜４８からの各正弦波信号の周波数は、クロック再生回路４２からの基準信号周波数との比率を前述した通りの整分数比とされている。
【００６７】
クロック再生回路４２からの基準信号の周波数をＦＦＴクロック周波数ｆ_FFTとし、Ｐ_i、Ｑ_i（ｉ＝１〜ｍ）をそれぞれ整数とすると、ＰＬＬ回路４４〜４８からの各出力信号の周波数は次の（数１４）式で表される。
【００６８】
【数１４】

【００６９】
また、ＳＧ４９からの出力信号である局部発振の周波数をｆ_SGとすると、次の（数１５）式が成立する。
【００７０】
【数１５】

【００７１】
（数１５）式に（数１３）式、（数１４）式を代入すると次の（数１６）式が得られる。
【００７２】
【数１６】

【００７３】
ここで、ＳＧ４９による局部発振周波数ｆ_SGと受信ＯＦＤＭ信号の中心周波数ｆ_rとＦＦＴクロック周波数ｆ_FFTが次の（数１７）式に示す関係となるようにｆ_SGの値を設定すると、（数１６）式を書き換えて続く（数１８）式が得られる。
【００７４】
【数１７】

【００７５】
【数１８】

【００７６】
次に、Ｑ_i＝Ｎ_FFT，ｉ＝１〜ｍとすると、次の（数１９）式の関係を用いて（数１８）式を書き換えることで、続く（数２０）式が得られる。
【００７７】
【数１９】

【００７８】
【数２０】

【００７９】
（数２０）式より、ＰＬＬ回路４４〜４８における基準入力信号周波数ｆ_FFTと出力信号周波数の前述した整分数比を求めることができる。また、アナログ乗算器５１〜５５が出力する周波数変換信号には、ＳＧ４９からの出力信号周波数であるｆ_SGとＰＬＬ回路４４〜４８の出力信号周波数であるｆ_Pi（ｉ＝１〜ｍ）の和の周波数を持つ信号と、ｆ_SGとｆ_Piの差の周波数を持つ信号の両方が含まれる。
【００８０】
（数２０）式より求められるＰ_i（ｉ＝１〜ｍ）が正の整数の場合は上記和の周波数に相当する信号成分を、負の整数の場合は上記差の周波数に相当する信号成分を、それぞれ所定通過帯域とされたＬＯ−ＢＰＦ５６〜６０により抽出して不要信号成分を除去することで、前述の、それぞれ異なる所望周波数のｍ個のローカル信号を得ることができる。ただし、ｉ＝Ｃの場合は（数２０）式よりＰ_i＝Ｏとなるため、ＳＧ４９の出力信号を直接ＬＯ−ＢＰＦに供給して周波数変換は行わず、ＲＦ信号からＩＦ信号への周波数変換を行うための乗算器に当該ＬＯ−ＢＰＦの出力をローカル信号として供給する。
【００８１】
なお、ここで説明した周波数関係は一例にすぎず、本発明を実現可能な周波数パラメータは、例示した他にも多く存在する。
【００８２】
これらの周波数パラメータの条件として、各受信系統に相当するスペクトルがＩＦ信号において互いに重ならないこと、すなわち同一周波数成分を持たないことが必要である。さらに、図９に示すような周波数関係のＩＦ信号スペクトルを得ることで、直交復調後の各受信系統に相当するＯＦＤＭ信号の各キャリア周波数をＦＦＴ処理における周波数軸上のサンプリング点の周波数と一致させることも必要である。図９は一例として受信系統数ｍ＝５の場合の、ＩＦ信号の各受信系統におけるＯＦＤＭ信号の各キャリアの周波数関係を示している。
【００８３】
(第２実施形態)
また、図１０乃至図１１は、本発明に係る一括ＦＦＴ方式を用いたＯＦＤＭ信号のダイバーシティ受信装置の第２実施形態を示すブロック構成図である。
【００８４】
図１０乃至図１１の構成例では、Ａ／Ｄ変換器３０の出力に対するデジタル直交復調において、第１実施形態のようにキャリア再生回路４１（図２）からの再生キャリア信号を用いるのではなく、２つのパターン・データ発生回路６１，６２が発生する一定パターンのデータを用いた復調方式を採用している。
【００８５】
この方式はＩＦ信号の中心周波数がＡ／Ｄ変換回路のクロック周波数の１／４であることを利用したもので、次のようにローカル信号を生成する。パターン・データ発生回路６１は、Ａ／Ｄ変換器３０のＡ／Ｄ変換クロック信号と同期して一定パターン｛１，０，−１，０．．．．｝のデータを発生してＩ軸側のデジタル乗算器３１にローカル信号として供給する。パターン・データ発生回路６２は、当該Ａ／Ｄ変換クロック信号と同期して一定パターン｛０，１，０，−１．．．．｝で、Ｉ軸側より遅れたタイミングのデータを発生してＱ軸側のデジタル乗算器３２にローカル信号として供給する。
【００８６】
また、実際の伝送系では、送信側の周波数ずれや受信装置のローカル信号の周波数ドリフトなどが存在する。このため本実施形態では、第１実施形態で使用していたキャリア再生回路４１の代わりに周波数／位相誤差検出回路６３を用い、デジタルＬＰＦ３３，３４を通過した直交復調後のＩ軸、Ｑ軸信号から周波数誤差、位相誤差を検出し、ここで得られた周波数誤差情報に基づきＶＣＯ（Voltage Controlled Oscillator）６４を制御することで、受信信号の周波数ずれを補正する方式を採用している。
【００８７】
上記実施形態を開示された本発明に係るＯＦＤＭ信号のダイバーシティ受信装置は、地上デジタル放送の規格であるＢＳＴ−ＯＦＤＭ信号にも適用可能であり、これにより、著しい装置の大型化や消費電力の増大なしに、移動受信特性の性能向上を実現することができる。
【００８８】
また、上述した２つの実施形態では直交復調処理をデジタル回路で実現しているが、アナログ直交復調回路を用いて直交復調処理を行うことも当然可能である。
【００８９】
【発明の効果】
以上説明した通り本発明によれば、たとえばダイバーシティ受信を行うＯＦＤＭ方式デジタルＦＰＵ装置に適用して、所定周波数間隔の複数のローカル信号を用い、ＯＦＤＭ信号を複数の受信アンテナで受信して得られる同一周波数で複数の受信信号を異なる帯域の、同一周波数成分を持たない複数のＩＦ信号に周波数変換し、さらにこれら複数のＩＦ信号を合成し、ＩＦ周波数の一つの合成信号に対し一括的に所定の処理を行うようにしたので、Ａ／Ｄ変換器、直交復調器、ガード・インターバル除去回路、ＦＦＴ回路などの処理回路を一系統に簡略化することが可能で、受信装置のサイズ、重量、消費電力を大幅に削減するとともに、敷設するケーブル数を受信系統数にかかわらず一本にすることで運用性を改善できる効果がある。
【００９０】
さらに、合成ＩＦ信号を変換して生成したデジタル信号を直交復調し、Ｉ軸信号およびＱ軸信号を得て、当該信号から生成したクロック信号を基準信号として各周波数が所定の関係にある単一周波数信号を複数生成するＰＬＬ手段を備え、ＯＦＤＭ信号の周波数およびＦＦＴ手段のクロック周波数と所定の関係にある別の単一周波数信号をＰＬＬ手段からの複数の単一周波数信号と乗算することで所定周波数間隔の複数のローカル信号を生成するようにしたので、上記効果と併せて、ＩＦ信号において周波数多重された受信系統数分の各ＯＦＤＭ信号間の周波数同期を高い精度で実現でき、良好な帯域分割ダイバーシティ効果が得られる効果がある。
【図面の簡単な説明】
【図１】本発明に係る一括ＦＦＴ方式を用いたＯＦＤＭ信号のダイバーシティ受信装置の第１実施形態を示すブロック図である。
【図２】本発明に係る一括ＦＦＴ方式を用いたＯＦＤＭ信号のダイバーシティ受信装置の第１実施形態を示すブロック図である。
【図３】第１実施形態のダイバーシティ受信装置における、受信信号のスペクトルと周波数変換用局部発振器周波数の関係を示す説明図である。
【図４】第１実施形態のダイバーシティ受信装置における周波数変換および各チャンネル合成後のＩＦ信号スペクトルの特性図である。
【図５】第１実施形態のダイバーシティ受信装置におけるＡ／Ｄ変換後のＩＦ信号スペクトルの特性図である。
【図６】第１実施形態のダイバーシティ受信装置におけるデジタル直交復調後の信号スペクトルの特性図である。
【図７】第１実施形態のダイバーシティ受信装置におけるＬＰＦ処理後の信号スペクトルの特性図である。
【図８】第１実施形態のダイバーシティ受信装置における間引き後の信号スペクトルの特性図である。
【図９】第１実施形態のダイバーシティ受信装置における、ＩＦ信号における各受信系統のＯＦＤＭ信号の各キャリアの周波数関係を示す説明図である。
【図１０】本発明に係る一括ＦＦＴ方式を用いたＯＦＤＭ信号のダイバーシティ受信装置の、第２実施形態を示すブロック図である。
【図１１】本発明に係る一括ＦＦＴ方式を用いたＯＦＤＭ信号のダイバーシティ受信装置の、第２実施形態を示すブロック図である。
【図１２】従来のＯＦＤＭ信号のダイバーシティ受信装置の一例を示すブロック図である。
【図１３】従来のＯＦＤＭ信号のダイバーシティ受信装置の一例を示すブロック図である。
【符号の説明】
１〜５ 受信アンテナ
６〜１０ ＲＦ−ＢＰＦ
１１〜１５ ＲＦ増幅器
１６〜２０ アナログ乗算器
２１〜２５ ＩＦ−ＢＰＦ
２６〜２７ ２入力合成器
２８ ３入力合成器
２９ ＩＦ増幅器
３０ Ａ／Ｄ変換器
３１，３２ デジタル乗算器
３３，３４ デジタルＬＰＦ
３５，３６ ４：１サブサンプル回路
３７ ガード・インターバル除去回路
３８ ＦＦＴ（fast Fourier transform）処理回路
３９ 差動復調回路
４０ キャリア選択・合成回路
４１ キャリア再生回路
４２ クロック再生回路
４３，５０ ５分配器
４４〜４８ ＰＬＬ（Phase Locked Loop）回路
４９ 基準局部発振器（ＳＧ）
５１〜５５ アナログ乗算器
５６〜６０ ＬＯ−ＢＰＦ
６１ Ｉ軸用パターン・データ発生回路
６２ Ｑ軸用パターン・データ発生回路
６３ 周波数／位相誤差検出回路
６４ ＶＣＯ（Voltage Controlled Oscillator）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an OFDM signal diversity receiver, and in particular, in an OFDM digital FPU device, receives OFDM signals using a plurality of different receiving antennas, and performs band division diversity reception using a plurality of received signals of the same frequency. The present invention relates to a diversity receiver for a mobile transmission apparatus that improves reception performance and uses the collective FFT method to reduce the size of the apparatus and improve mobility.
[0002]
[Prior art]
Since the digital FPU device (Field Pick-up Unit) using the OFDM system has excellent multipath resistance, it shows high performance in large-scale mobile relay such as marathon relay. On the other hand, as shown in Japanese Patent Publication No. 9-284191 (name of invention “diversity receiver”), the OFDM signal can be received by a band division diversity reception method. It is possible to further improve the reception performance of the OFDM digital FPU device that exhibits performance.
[0003]
An example of a conventional diversity receiver that receives an OFDM signal is shown in FIGS.
[0004]
As shown in both figures, the receiving apparatus includes five receiving antennas 1 to 5 and is configured to be able to receive five systems in combination. From the RF stage following the receiving antennas 1 to 5 up to the carrier synthesis / selection circuit 170, each element is provided for the number of reception systems. That is, RF band-pass filters (BPF) 6 to 10, RF amplifiers 11 to 15, multipliers 16 to 20, IF band-pass filters (BPF) 21 to 25, IF amplifiers 101 to 105, A / D converters 106-110, distributors 111-115, I-axis multipliers 131, 133, 135, 137, 139, Q-axis multipliers 132, 134, 136, 138, 140, I-axis LPFs 141, 143, 145, 147 149, Q-axis LPFs 142, 144, 146, 148, 150, guard interval removal circuits 151-155, and FFT processing circuits 156-160.
[0005]
[Problems to be solved by the invention]
Since the conventional diversity receiving apparatus includes the same elements for a plurality of systems, the circuit scale, the apparatus dimensions, and the apparatus weight increase, and at the same time the power consumption increases, and the signal delay amount of each system needs to be matched. There was a problem that there was.
[0006]
Moreover, in the relay program production by the FPU device using the above conventional diversity receiver, a cable of several hundred meters in length is often laid in the connection between the reception head installed at the reception point and the reception control unit. There is another problem that only as many as the number of receiving systems (the number of receiving systems) is required, and there is a lot of work for setting up the equipment.
[0007]
Therefore, the present invention has been made in view of the above-described points, and solves the above-described problems caused by the increase in the number of reception systems when realizing diversity reception, that is, a device or the like regardless of the number of reception systems. It is an object of the present invention to provide a diversity receiver that can prevent an increase in scale and reduce the number of installed cables to one.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention of claim 1 generates a plurality of local signals at predetermined frequency intervals, and receiving means for receiving a plurality of reception signals at the same frequency, which are received by a plurality of reception antennas. Local signal generating means, and means for frequency-converting each received signal into a plurality of IF signals in different bands using each local signal, each band having the same frequency component, and each IF signal Conversion means for converting the frequency so that the interval of the center frequency is an integral multiple of the carrier interval of the OFDM signal, IF combining means for combining the plurality of IF signals from the conversion means, and based on the combined IF signal Provided is a diversity receiver for OFDM signals, comprising batch processing means for collectively performing predetermined processing on the OFDM signals of IF frequency.
[0009]
According to a second aspect of the present invention, in the first aspect, the collective processing unit extracts a demodulating unit that quadrature-demodulates the combined IF signal, an effective symbol period excluding a guard interval of the demodulated output, and the receiving antenna. FFT means for obtaining frequency axis data by performing fast Fourier transform in accordance with the number of signals and the number of carriers of the OFDM signal, and carrier data after differential demodulation of the OFDM signal obtained by calculating a difference between symbols of the frequency axis data A diversity reception apparatus for OFDM signals, comprising: selection combining output means for selecting or combining and outputting the signals.
[0010]
According to a third aspect of the present invention, in the second aspect of the present invention, the demodulating means comprises an A / D converting means for converting the combined IF signal into a digital signal, quadrature demodulating the digital signal, and an I-axis signal and a Q-axis signal. Digital quadrature demodulating means for obtaining a demodulated output of the signal, and the local signal generating means inputs a clock signal generated from the demodulated output of the I-axis signal and Q-axis signal as a reference signal, and each frequency is predetermined. PLL means for generating a plurality of single frequency signals having the relationship of the above, and a plurality of single frequency signals from the PLL means for generating another single frequency signal having a predetermined relation with the frequency of the OFDM signal and the clock frequency of the FFT means. Diversity of an OFDM signal comprising signal generation means for generating the plurality of local signals having the predetermined frequency interval by multiplying with a frequency signal To provide a communication apparatus.
[0011]
According to a fourth aspect of the present invention, in the third aspect, the digital quadrature demodulating means demodulates the digital signal using two carrier signals having a phase difference of 90 ° to demodulate the I-axis signal and the Q-axis signal. An OFDM signal diversity receiving apparatus is obtained.
[0012]
According to a fifth aspect of the present invention, in the third aspect, the digital quadrature demodulating means predetermines the first pattern data that repeats a predetermined pattern at a predetermined cycle and the same pattern as the predetermined pattern at the same cycle as the predetermined cycle. An OFDM signal diversity receiving apparatus is provided that demodulates the digital signal using second pattern data repeated with timing delay as carrier data to obtain demodulated outputs of the I-axis signal and the Q-axis signal.
[0013]
[Action]
According to the present invention configured as described above, a plurality of local signals having a predetermined frequency interval are used, and a plurality of received signals at the same frequency obtained by receiving an OFDM signal by a plurality of receiving antennas are provided with the same frequency component in different bands. By performing frequency conversion to a plurality of IF signals that do not have, and further synthesizing the plurality of IF signals, it is possible to collectively perform a predetermined process on one synthesized signal of the IF frequency. The number of cables to be laid can be made one regardless of the number of receiving systems, and the device size, power consumption, and weight can be reduced.
[0014]
In addition, the digital signal generated by converting the synthesized IF signal is orthogonally demodulated to obtain the I-axis signal and the Q-axis signal, and each frequency has a predetermined relationship with the clock signal generated from the signal as a reference signal. A PLL unit that generates a plurality of frequency signals is provided, and another single frequency signal having a predetermined relationship with the frequency of the OFDM signal and the clock frequency of the FFT unit is multiplied by a plurality of single frequency signals from the PLL unit. Since a plurality of local signals having frequency intervals are generated, frequency synchronization between OFDM signals corresponding to the number of reception systems frequency-multiplexed in IF signals can be realized with high accuracy, and a good band division diversity effect can be obtained.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0016]
(First embodiment)
FIG. 1 and FIG. 2 are block configuration diagrams of an OFDM signal diversity receiver according to the first embodiment of the present invention. The configuration of the figure is a configuration example in which a collective FFT (fast Fourier transform) system according to the present invention is applied to a diversity receiver that receives signals from five receiving antennas in the conventional configuration shown in FIGS. is there.
[0017]
The signals entering the receiving antennas 1 to 5 are OFDM signals synchronized with each other from the same or a plurality of transmitters, and the modulation scheme of each carrier is, for example, DQPSK (differential four-phase phase shift keying).
[0018]
The five receiving antennas 1 to 5 may be arranged with a spatial distance, and may further be arranged with different polarization planes. ) Are input to the BPFs 6 to 10 in the predetermined pass band of the RF band, and are output after removing unnecessary out-of-band components. The signals in the predetermined band are amplified by the RF amplifiers 11 to 15 and then input to the analog multipliers 16 to 20. At this time, each signal corresponding to the five receiving systems having each antenna as an input has the same frequency f. _r However, the distortion experienced by the transmission line differs depending on the spatial arrangement of each antenna.
[0019]
In the conventional OFDM signal diversity receiver (see FIG. 12), the signals input to the analog multipliers 16 to 20 are the same frequency local signals (local parts) output from one local oscillator 119 and distributed by the distributor 120. Using the oscillation signal, the multipliers 16 to 20 perform frequency conversion to the same IF frequency.
[0020]
Here, in the diversity receiver that realizes the collective FFT method according to the present embodiment shown in FIGS. 1 to 2, the receiving system having the antenna n (n is an integer of 1 to 5) as an input is the n-th system (CHn). ), In the apparatus, for example, different frequencies f indicated by CH1 to CH5 in FIG. _L1 ~ F _L5 Each of the local signals is used to convert the multipliers 16 to 20 into IF signals having different frequencies.
[0021]
The frequency of each of the local signals CH1 to CH5 is such that the IF signal spectra after frequency conversion do not overlap, and the interval of the center frequency of the IF signal corresponding to the receiving system is an integer of the carrier interval of the OFDM signal. Must be set to double.
[0022]
Hereinafter, the required frequency condition will be specifically described.
[0023]
The number of carriers of the received OFDM signal is N _c The carrier interval is Δf, and the center frequency f of the received OFDM signal as shown in FIG. _r And local signal f of each receiving system _L1 ~ F _L5 The frequency difference between ₁ ~ If _Five And Here, m is the number of receiving systems, and is 5 in this embodiment. In the following description, m is an odd number for simplification of description, but the collective FFT method according to the present invention can be realized even in the case of an even number. C is an integer that satisfies the following equation (1).
[0024]
[Expression 1]

[0025]
[Expression 2]

[0026]
[Equation 3]

[0027]
For simplicity of explanation, in the complex FFT processing after quadrature demodulation, the local signal frequency f during quadrature demodulation is set so that the number of positive frequency carriers and the number of negative frequency carriers are equal. _QDEM Is set, the following equation (4) is established.
[0028]
[Expression 4]

[0029]
Equation (3) is a condition for preventing the spectrum of IF signals of each receiving system from overlapping each other. The frequency difference between adjacent local signals of CH1 to CH5 is f _di (I = 1 to m-1) g _i When (i = 1 to m−1) is an integer larger than 0, the following equation (5) is established.
[0030]
[Equation 5]

[0031]
Furthermore, the following equation (6) shows the condition for preventing the image component generated along with the frequency conversion and the original spectrum from overlapping each other during orthogonal demodulation.
[0032]
[Formula 6]

[0033]
Where g _i XΔf (i = 1 to m−1) is the IF signal spectrum shown in FIG. 4, between the spectra of adjacent receiving systems (for example, the ₁ Spectrum with if as the center frequency and if ₂ Is a frequency width corresponding to the guard bands Gb1 to Gb4 (between spectra having a center frequency). g _i (I = 1 to m−1) are not necessarily the same value (each guard band has the same bandwidth).
[0034]
At this time, the subsequent FFT (fast Fourier transform) processing circuit 38 executes the complex FFT processing of the number of points expressed by the following equation (7). In the equation (7), L is a positive integer representing the order of FFT.
[0035]
[Expression 7]

[0036]
A method for generating the local signals CH1 to CH5 input to the analog multipliers 16 to 20 will be described later.
[0037]
The signals of each reception system that are output from the analog multipliers 16 to 20 and from which the image components have been removed by the BPFs 21 to 25 in the IF band in a predetermined pass band are added and synthesized by an adder to form a synthesized signal of one system. That is, the signals of the first system (CH 1) and the second system (CH 2) are added by the analog adder 26, and the addition result is input to the analog adder 28. The third system (CH3) signal is input to the analog adder 28 as it is. Further, the signals of the fourth system (CH 4) and the fifth system (CH 5) are added by the analog adder 27, and the addition result is input to the analog adder 28.
[0038]
The output obtained by adding the three inputs by the analog adder 28 is the result of synthesizing five IF signals. The spectrum of the synthesized IF signal is the center frequency if of each channel as shown in FIG. ₁ ~ If _Five Are arranged at predetermined frequency intervals, and guard bands Gb1 to Gb4 having a predetermined width are arranged therebetween. The combined signal of the spectrum is subjected to processing including batch FFT and demodulation by a single processing circuit after the IF amplifier 29.
[0039]
The output signal of the analog adder 28 is amplified by the IF amplifier 29 and then converted into a digital signal by the A / D converter 30 of FIG. In this embodiment, the sampling frequency f of A / D conversion _s FFT clock frequency f _FFT 4 times the center frequency of the IF signal, that is, f _QDEM FFT clock frequency f _FFT Is set. FFT clock frequency f _FFT Is the number of FFT points N _FFT The carrier interval of the OFDM signal is expressed by the following equation (8) with Δf.
[0040]
[Equation 8]

[0041]
The signal spectrum after A / D conversion is shown in FIG.
[0042]
The digital signal having the spectrum output from the A / D converter 30 is divided into two signals, the I-axis side signal and the Q-axis side signal, the I-axis side signal is sent to the digital multiplier 31, and the Q-axis side signal is sent to the digital multiplier. 32 respectively. Each of the carrier signals reproduced by the carrier reproduction circuit 41 is further input to the digital multipliers 31 and 32, respectively. At this time, the reproduced carrier signal supplied to the digital multiplier 32 on the Q-axis side has a phase delay of 90 degrees with respect to the reproduced carrier signal supplied to the digital multiplier 31 on the I-axis side, and both carriers Are orthogonal to each other.
[0043]
Digital quadrature demodulation is performed by performing frequency conversion by the digital multipliers 31 and 32 using the carrier. When the spectrum of the I-axis signal and the Q-axis signal obtained by demodulation is expressed as a scalar, each is as shown in FIG. That is, the sampling frequency f _s And the component around the frequency 0 and the image component between the two components.
[0044]
The output of the digital multiplier 31 is input to the digital LPF 33, and the output of the digital multiplier 32 is input to the digital LPF 34, and unnecessary image components are removed and output. That is, each of the digital LPFs 33 and 34 passes a predetermined band not including the image component, and outputs a signal having a spectrum shown in FIG.
[0045]
The I-axis signal output from the digital LPF 33 is divided into two, and one is input to the sub-sample circuit 35. The other is further divided into two and supplied to the clock recovery circuit 42 and the carrier recovery circuit 41, respectively. Similarly, the Q-axis signal output from the digital LPF 34 is also divided into two, and one is input to the sub-sample circuit 36. The other is further divided into two and supplied to the clock recovery circuit 42 and the carrier recovery circuit 41, respectively.
[0046]
The I-axis signal and the Q-axis signal that are distributed and input to the sub-sample circuits 35 and 36 are each thinned out to 4: 1, and the sampling frequency is set to f as shown in FIG. _s 1/4.
[0047]
The I-axis signal and the Q-axis signal output from the sub-sample circuits 35 and 36 are respectively input to the guard interval removal circuit 37, where the effective symbol period is extracted and input to the FFT processing circuit 38. The FFT processing circuit 38 converts the time-axis signal in symbol units into a complex signal on the frequency axis. The number of carriers of the received OFDM signal is N _c If the number of receiving systems due to diversity is m, N per symbol _c Xm complex data is obtained, and the data is input to the differential demodulation circuit 39.
[0048]
The complex carrier data output from the FFT processing circuit 38 is converted into C _i , _j , _k Assuming that (i: reception system number, j: carrier number, k: symbol number), the differential demodulator circuit 39 uses these Cs. _i , _j , _k The calculation represented by the following equation (9) is performed. D in equation (9) _i , _j , _k N output from the differential demodulation circuit 39 _c X represents complex data, C _i , _j , _k-1 * Attached to indicates a complex conjugate.
[0049]
[Equation 9]

[0050]
N per symbol output from the differential demodulation circuit 39 _c The xm pieces of complex data are input to the carrier selection / combination processing circuit 40. Here, the combination processing shown in the following equation (10) is performed for each reception system in units of carriers.
[0051]
[Expression 10]

[0052]
O in the formula (10) _j , _k Represents complex output data from the carrier selection / synthesis processing circuit 40, and j = 1 to N. _c , K are symbol numbers. That is, the carrier selection / combination processing circuit 40 has N _c The pieces of complex data are sent to the subsequent determination decoding processing unit (not shown).
[0053]
In this embodiment, in order to obtain the diversity effect, vector synthesis is performed for each carrier of each reception system. In addition to this, a method for selecting and outputting carrier data of the reception system having the largest carrier amplitude is also provided. Etc. are also conceivable.
[0054]
Next, f used for frequency conversion of the RF signal of each receiving system to an IF signal _L1 ~ F _L5 A method of generating each local signal will be described.
[0055]
The general operation of local signal generation will be described. A clock recovery circuit 42 to which an I-axis signal and a Q-axis signal after digital quadrature demodulation have been input receives a sampling clock used for symbol clock, FFT clock, A / D conversion based on the input. Various clock signals necessary as a reference for various processing such as a clock are reproduced, and these clocks are supplied to each part of the apparatus. The clock recovery in the clock recovery circuit 42 can be performed by various known techniques, that is, a method using a reference symbol such as a guard interval correlation method or a chirp signal. Here, detailed description of these known techniques is omitted.
[0056]
The reference signal of the symbol clock frequency output from the clock recovery circuit 42 is divided into five by the distributor 43, and each is input to PLL (Phase Locked Loop) circuits 44 to 48 as reference signals. Each of the PLL circuits 44 to 48 having a phase locked loop generates and outputs a sine wave signal having a frequency having a different integer ratio from the frequency of the input reference signal. In this specification, the fractional ratio means a value represented by b / a times the frequency of the input reference signal, where a and b are integers. Each sine wave signal having a single frequency component is input to analog multipliers 51 to 55, respectively.
[0057]
On the other hand, the sine wave signal output from the reference local oscillator (Signal Generator; SG) 49 is divided into five by the distributor 50 and applied to the analog multipliers 51 to 55. Each of the analog multipliers 51 to 55 multiplies the applied sine wave signal by each sine wave signal from the PLL circuits 44 to 48 to perform frequency conversion to a different frequency. Each frequency conversion signal is subjected to removal of image components generated by frequency conversion by LO-BPFs 56 to 60 having different passbands, and then local signals f having different frequencies. _L1 ~ F _L5 Are input to the analog multiplication circuits 16 to 20.
[0058]
Then, an example of the frequency relationship of each part relevant to the local signal generation mentioned above is demonstrated.
[0059]
For simplicity of explanation, here, the number of OFDM signal carriers N _c Is an odd number and defines a guard bandwidth between the spectrums of adjacent receiving systems in the IF signal spectrum. _i Let (i = 1 to m−1) be the same value g. In the present embodiment, as an example, a case is assumed in which the center frequency of the C-th (third of five systems) reception system is matched with the center frequency of the IF signal. Also, as described above, since digital quadrature demodulation processing is assumed, the center frequency of the IF signal (that is, the frequency of the signal converted to DC after quadrature demodulation) is the same as the FFT clock frequency, and A / D conversion is performed. Sampling frequency f _s FFT clock frequency f _FFT 4 times the frequency 4f _FFT It is said.
[0060]
Center frequency f of received OFDM signal _r And the frequency f of the local signal corresponding to each receiving system _L1 ~ F _L5 Frequency if of difference with ₁ ~ If _Five Is equal to the center frequency of the spectrum corresponding to each reception system in the IF signal after frequency conversion (see FIG. 4). Therefore, the frequency f of the local signal corresponding to each receiving system _L1 ~ F _L5 Is expressed by the following equation (11).
[0061]
[Expression 11]

[0062]
Where if ₁ ~ If _Five Is expressed by the following equation (12).
[0063]
[Expression 12]

[0064]
By substituting the equation (12) into the equation (11), the following equation (13) is obtained.
[0065]
[Formula 13]

[0066]
On the other hand, the local signal corresponding to each receiving system is obtained as a result of distributing the output signal of SG49 by the distributor 50 and performing frequency conversion by the analog multipliers 51 to 55, respectively, and the frequency thereof is (Equation 13) It is expressed by a formula. The frequency of each sine wave signal from the PLL circuits 44 to 48 input to the analog multipliers 51 to 55 is the ratio of the reference signal frequency from the clock recovery circuit 42 to the fractional ratio as described above. ing.
[0067]
The frequency of the reference signal from the clock recovery circuit 42 is the FFT clock frequency f. _FFT And P _i , Q _i When (i = 1 to m) is an integer, the frequency of each output signal from the PLL circuits 44 to 48 is expressed by the following equation (14).
[0068]
[Expression 14]

[0069]
Also, the frequency of local oscillation, which is the output signal from SG49, is f _SG Then, the following equation (15) is established.
[0070]
[Expression 15]

[0071]
Substituting (Equation 13) and (Equation 14) into (Equation 15) yields the following (Equation 16).
[0072]
[Expression 16]

[0073]
Here, the local oscillation frequency f by SG49 _SG And the center frequency f of the received OFDM signal _r And FFT clock frequency f _FFT So that the relationship shown in the following equation (17) is satisfied. _SG Is set, the following equation (18) is obtained by rewriting equation (16).
[0074]
[Expression 17]

[0075]
[Expression 18]

[0076]
Next, Q _i = N _FFT , I = 1 to m, the following equation (20) is obtained by rewriting the equation (18) using the relationship of the following equation (19).
[0077]
[Equation 19]

[0078]
[Expression 20]

[0079]
From the equation (20), the reference input signal frequency f in the PLL circuits 44 to 48 is calculated. _FFT And the above-described fractional ratio of the output signal frequency can be obtained. Further, the frequency conversion signal output from the analog multipliers 51 to 55 includes f which is the output signal frequency from SG49. _SG And f which is the output signal frequency of the PLL circuits 44 to 48 _Pi A signal having a sum frequency (i = 1 to m) and f _SG And f _Pi Both signals with different frequencies are included.
[0080]
P obtained from equation (20) _i When (i = 1 to m) is a positive integer, the signal component corresponding to the sum frequency is negative, and when it is a negative integer, the signal component corresponding to the difference frequency is a predetermined pass band. -Extracting by the BPFs 56 to 60 to remove unnecessary signal components, it is possible to obtain m local signals having different desired frequencies as described above. However, in the case of i = C, P is calculated from the equation (20). _i Since the output signal of SG49 is directly supplied to the LO-BPF and frequency conversion is not performed, the output of the LO-BPF is used as a local signal to a multiplier for performing frequency conversion from the RF signal to the IF signal. Supply as.
[0081]
Note that the frequency relationship described here is merely an example, and there are many frequency parameters that can implement the present invention in addition to those illustrated.
[0082]
As a condition of these frequency parameters, it is necessary that the spectrum corresponding to each receiving system does not overlap each other in the IF signal, that is, does not have the same frequency component. Further, by obtaining a frequency-related IF signal spectrum as shown in FIG. 9, each carrier frequency of the OFDM signal corresponding to each receiving system after orthogonal demodulation is matched with the frequency of the sampling point on the frequency axis in the FFT processing. It is also necessary. FIG. 9 shows, as an example, the frequency relationship of each carrier of the OFDM signal in each reception system of IF signals when the number of reception systems m = 5.
[0083]
(Second embodiment)
FIGS. 10 to 11 are block configuration diagrams showing a second embodiment of the OFDM signal diversity receiving apparatus using the collective FFT method according to the present invention.
[0084]
In the configuration examples of FIGS. 10 to 11, in the digital quadrature demodulation for the output of the A / D converter 30, the reproduced carrier signal from the carrier reproducing circuit 41 (FIG. 2) is not used as in the first embodiment. A demodulation system using a fixed pattern of data generated by the two pattern data generation circuits 61 and 62 is employed.
[0085]
This method utilizes the fact that the center frequency of the IF signal is 1/4 of the clock frequency of the A / D conversion circuit, and generates a local signal as follows. The pattern data generation circuit 61 synchronizes with the A / D conversion clock signal of the A / D converter 30 to generate a fixed pattern {1, 0, -1, 0. . . . } Data is generated and supplied as a local signal to the digital multiplier 31 on the I-axis side. The pattern data generation circuit 62 synchronizes with the A / D conversion clock signal to generate a fixed pattern {0, 1, 0, −1. . . . }, Timing data delayed from the I-axis side is generated and supplied to the digital multiplier 32 on the Q-axis side as a local signal.
[0086]
In an actual transmission system, there are a frequency shift on the transmission side, a frequency drift of a local signal of the receiving device, and the like. Therefore, in this embodiment, the frequency / phase error detection circuit 63 is used in place of the carrier recovery circuit 41 used in the first embodiment, and the I-axis and Q-axis signals after orthogonal demodulation that have passed through the digital LPFs 33 and 34 are used. A frequency error and phase error are detected from the signal, and a VCO (Voltage Controlled Oscillator) 64 is controlled based on the frequency error information obtained here, thereby correcting the frequency shift of the received signal.
[0087]
The OFDM signal diversity receiving apparatus according to the present invention disclosing the above-described embodiment can also be applied to a BST-OFDM signal which is a standard of terrestrial digital broadcasting, thereby significantly increasing the apparatus size and power consumption. No improvement in performance of mobile reception characteristics can be realized.
[0088]
In the two embodiments described above, the quadrature demodulation process is realized by a digital circuit, but it is naturally possible to perform the quadrature demodulation process using an analog quadrature demodulation circuit.
[0089]
【The invention's effect】
As described above, according to the present invention, it is applied to, for example, an OFDM digital FPU apparatus that performs diversity reception, and a plurality of local signals with a predetermined frequency interval are used and OFDM signals are received by a plurality of receiving antennas. A plurality of received signals at different frequencies are frequency-converted into a plurality of IF signals of different bands and not having the same frequency component, and further, the plurality of IF signals are synthesized, and a predetermined signal is collectively obtained for one synthesized signal of the IF frequency. Since the processing is performed, it is possible to simplify the processing circuits such as A / D converter, quadrature demodulator, guard interval removal circuit, FFT circuit, etc., and the size, weight and consumption of the receiving device In addition to greatly reducing power, the number of cables to be laid is one regardless of the number of receiving systems, and operability can be improved.
[0090]
Further, the digital signal generated by converting the combined IF signal is orthogonally demodulated to obtain an I-axis signal and a Q-axis signal, and each frequency has a predetermined relationship with the clock signal generated from the signal as a reference signal. A PLL unit that generates a plurality of frequency signals is provided, and another single frequency signal having a predetermined relationship with the frequency of the OFDM signal and the clock frequency of the FFT unit is multiplied by a plurality of single frequency signals from the PLL unit. Since a plurality of local signals with frequency intervals are generated, in addition to the above effects, frequency synchronization between OFDM signals corresponding to the number of reception systems frequency-multiplexed in IF signals can be realized with high accuracy, and a good bandwidth There is an effect that a division diversity effect can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a first embodiment of an OFDM signal diversity receiving apparatus using a collective FFT method according to the present invention;
FIG. 2 is a block diagram showing a first embodiment of an OFDM signal diversity receiving apparatus using a collective FFT method according to the present invention;
FIG. 3 is an explanatory diagram showing a relationship between a spectrum of a received signal and a local oscillator frequency for frequency conversion in the diversity receiver of the first embodiment.
FIG. 4 is a characteristic diagram of an IF signal spectrum after frequency conversion and channel synthesis in the diversity receiver of the first embodiment.
FIG. 5 is a characteristic diagram of an IF signal spectrum after A / D conversion in the diversity receiver of the first embodiment.
FIG. 6 is a characteristic diagram of a signal spectrum after digital quadrature demodulation in the diversity receiver according to the first embodiment.
FIG. 7 is a characteristic diagram of a signal spectrum after LPF processing in the diversity receiver of the first embodiment.
FIG. 8 is a characteristic diagram of a signal spectrum after decimation in the diversity receiver of the first embodiment.
FIG. 9 is an explanatory diagram showing a frequency relationship of each carrier of an OFDM signal of each reception system in an IF signal in the diversity receiver of the first embodiment.
FIG. 10 is a block diagram showing a second embodiment of an OFDM signal diversity receiving apparatus using the collective FFT method according to the present invention.
FIG. 11 is a block diagram showing a second embodiment of an OFDM signal diversity receiving apparatus using the collective FFT method according to the present invention.
FIG. 12 is a block diagram illustrating an example of a conventional OFDM signal diversity receiver.
FIG. 13 is a block diagram illustrating an example of a conventional OFDM signal diversity receiver.
[Explanation of symbols]
1 to 5 receiving antenna
6-10 RF-BPF
11-15 RF amplifier
16-20 analog multiplier
21-25 IF-BPF
26-27 2-input synthesizer
28 3-input synthesizer
29 IF amplifier
30 A / D converter
31, 32 Digital multiplier
33,34 Digital LPF
35, 36 4: 1 subsample circuit
37 Guard interval removal circuit
38 FFT (fast Fourier transform) processing circuit
39 Differential demodulation circuit
40 Carrier selection / synthesis circuit
41 Carrier regeneration circuit
42 Clock recovery circuit
43,50 5 distributor
44-48 PLL (Phase Locked Loop) circuit
49 Reference local oscillator (SG)
51-55 Analog multiplier
56-60 LO-BPF
61 I-axis pattern data generation circuit
62 Q-axis pattern data generation circuit
63 Frequency / phase error detection circuit
64 VCO (Voltage Controlled Oscillator)

Claims (5)

Receiving means for inputting a plurality of received signals at the same frequency received by a plurality of receiving antennas of the OFDM signal;
Local signal generating means for generating a plurality of local signals at predetermined frequency intervals;
A means for frequency-converting each received signal into a plurality of IF signals in different bands using each local signal, wherein each band does not have the same frequency component, and the interval between the center frequencies of the IF signals is Conversion means for frequency conversion so as to follow an integer multiple of the carrier interval of the OFDM signal;
IF synthesis means for synthesizing the plurality of IF signals from the conversion means;
An OFDM signal diversity receiving apparatus, comprising: batch processing means for collectively performing predetermined processing on the OFDM signal having an IF frequency based on the combined IF signal. In claim 1,
The batch processing means includes
Demodulation means for orthogonally demodulating the combined IF signal;
FFT means for extracting effective symbol periods excluding the guard interval of the demodulated output and performing fast Fourier transform according to the number of the receiving antennas and the number of carriers of the OFDM signal to obtain frequency axis data;
Diversity of an OFDM signal, comprising: a selection / synthesis output means for selecting or synthesizing and outputting carrier data after differential demodulation of the OFDM signal obtained by calculating a difference between symbols of the frequency axis data Receiver device. In claim 2,
The demodulating means includes
A / D conversion means for converting the combined IF signal into a digital signal;
Digital quadrature demodulation means for performing quadrature demodulation of the digital signal to obtain demodulated outputs of the I-axis signal and the Q-axis signal, and
The local signal generation means includes
PLL means for inputting a clock signal generated from the demodulated output of the I-axis signal and the Q-axis signal as a reference signal, and generating a plurality of single frequency signals in which each frequency has a predetermined relationship;
By multiplying the single frequency signal from the PLL means by another single frequency signal having a predetermined relationship with the frequency of the OFDM signal and the clock frequency of the FFT means, the predetermined frequency interval is set. An OFDM signal diversity receiving apparatus, comprising: signal generating means for generating a plurality of local signals. In claim 3,
The OFDM signal diversity receiving apparatus, wherein the digital quadrature demodulating means demodulates the digital signal using two carrier signals having a phase difference of 90 ° to obtain a demodulated output of the I-axis signal and the Q-axis signal. . In claim 3,
The digital quadrature demodulating means carries first pattern data that repeats a predetermined pattern at a predetermined cycle and second pattern data that repeats the same pattern as the predetermined pattern at the same cycle as the predetermined cycle with a predetermined timing delay. An OFDM signal diversity receiving apparatus, wherein the digital signal is demodulated using the data to obtain demodulated outputs of the I-axis signal and the Q-axis signal.

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