JP3550307B2 - Receiver and receiving method - Google Patents

Description

【００４３】
とする。
【００４４】
このときｍ番目の受信アンテナ（ブランチ）での受信信号を
【００４５】
【数２】

【００４６】
とすると、受信信号は
【００４７】
【数３】

【００４８】
と書き表す事ができる。
【００４９】
ここで
【００５０】
【数４】

【００５１】
はｍ番目の受信アンテナでの白色雑音である。
【００５２】
それぞれのアンテナで受信された信号は重み係数を乗算されて加算される。
【００５３】
加算後の受信信号を
【００５４】
【数５】

【００５５】
とすると次式で表される。
【００５６】
【数６】

【００５７】
ここでｍ番目のブランチの重み係数は
【００５８】
【数７】

【００５９】
である。
【００６０】
受信機では上記受信信号をＤＦＴ処理する事で復調を行う。
【００６１】
したがって、ＤＦＴ出力信号を
【００６２】
【数８】

【００６３】
とすると、受信信号は次式で表現できる。
【００６４】
【数９】

【００６５】
本発明の空間ダイバーシチでは受信した各ブランチ信号をＤＦＴ前に合成し、ＤＦＴ後のＳＮＲを最大にするように重み係数を求める事になる。
【００６６】
合成前の各サブチャンネルのそれぞれのアンテナで受信された各ブランチのＳＮＲは次式で表される。
【００６７】
【数１０】

【００６８】
式を変形して複素振幅のみを用いて書き表すと次式の通りとなる。
【００６９】
【数１１】

【００７０】
ここで、各受信アンテナの重み係数の重みベクトルｗを
【００７１】
【数１２】

【００７２】
とする。
【００７３】
伝送路の特性を表す行列を伝送路行列Ｇとすると
【００７４】
【数１３】

【００７５】
ここで、ｌは１番目のパスを、ｉ、ｋはｉ番目のブランチ、ｋ番目のブランチを表す。
【００７６】
合成後の復調されたＳＮＲは次式で書き表せる。
【００７７】
【数１４】

【００７８】
ここで、ΛはＧの固有値λｍを対角要素とする対角行列であり、Ｕは固有値λｍに対応する固有ベクトルをｍ列とするユニタリ行列である。
【００７９】
上式を最大にする重みベクトルｗは最大の固有値に対応する固有ベクトルである。
【００８０】
Ｍ個の受信アンテナで受信された信号より共分散行列Ｒを求めると
【００８１】
【数１５】

【００８２】
ｉ、ｋはｉ番目のブランチ、ｋ番目のブランチを表し、ｐは時間を表す添え字である。
【００８３】
式を変形して行列の形で書き表すと共分散行列Ｒは
【００８４】
【数１６】

【００８５】
と書ける。ここでＩは単位行列である。
【００８６】
以上より、最適な重み係数は最大固有値に対する固有ベクトルと一致する事になり、受信信号の共分散行列を求め、その行列の最大の固有値に対する固有ベクトルを重み係数Ｗにすれば良い。
【００８７】
図２本発明の重み係数計算部のブロック図を示す。
【００８８】
Ｍ個の受信アンテナで受信された信号は入力端子（２２ａ、２２ｂ、２２ｃ）より重み係数計算部（２１）へ入力され、まず共分散行列計算部（２３）により共分散行列が計算される。その結果は固有ベクトル計算部（２４）により前記行列の最大の固有値に対する固有ベクトルを求める。計算結果は出力端子（２５ａ、２５ｂ、２５ｃ）より出力される。出力された信号は図１における乗算器（１２ａ、１２ｂ、１２ｃ）へわたされ、受信信号と掛け合わされる。
【００８９】
図３は共分散行列推定器の構成を示すブロック図である。
【００９０】
入力端子（３１ａ、３１ｂ、３１ｃ）より入力された信号は一つは相関器（３３ａ〜３３ｅ）の一方の入力端子へ接続されている。もう一つは複素共役回路（３２ａ、３２ｂ、３２ｃ）により入力信号の複素共役をとり、相関器（３３ａ〜３ｅ）のもう一方の入力端子に接続されている。それぞれの相関結果は出力端子より出力される。
【００９１】
図４は相関器のブロック図を示す。
【００９２】
相関器（４１）は２つの入力端子（４２、４３）より入力された信号は乗算器４４により乗算され、後段の積分器（４５）へ渡される。積分器（４５）では入力信号の積分をし、出力端子（４６）から積分結果を出力する。
【００９３】
図５に最大固有値演算部のブロック図を示す。
【００９４】
前記共分散行列計算部（２３）により計算された共分散行列は最大固有値演算部のそれぞれの入力端子に渡され、フィードバック系の重み係数出力信号と乗算器（５３ａ〜５３ｃ、５４ａ〜５４ｃ、５５ａ〜５５ｃ）により乗算される。乗算結果は加算器（５６ａ〜ｃ、５７ａ〜ｃ）により加算れる。加算された結果は正規化の為の乗算器（５８ａ〜５８ｃ）により正規化が行われる。正規化はそれぞれの加算結果よりノルム演算回路（５９）に入力されてノルムが計算される。計算された値は逆数計算部（６０）により逆数が計算される。逆数計算部（６０）の結果はそれぞれの信号と乗算される。
【００９５】
正規化されたそれぞれの信号は一つは重み係数として出力端子（６１ａ〜６１ｃ）より出力される。もう一つは前記フィードバック信号として、前記乗算器（５３ａ〜５３ｃ、５４ａ〜５４ｃ、５５ａ〜５５ｃ）により前記最大固有値演算部（２４）の入力信号と乗算される。
【００９６】
図６はノルム演算部（５９）のブロック図を示す。
【００９７】
入力端子（６４ａ〜６４ｃ）より入力された信号は２乗回路（６５ａ〜６５ｃ）により入力信号の２乗値が計算され、後段の加算回路（６６）により加算される。加算された結果は平方根回路（６７）によりその平方根が計算され、出力端子（６８）より出力される。
【００９８】
図１１は波形等価回路のブロック図を示す。
【００９９】
ＤＦＴ出力信号は入力端子（１１１）より入力され乗算器（１１２）とパイロット信号抜き取り回路（１１３）に接続されている。パイロット信号抜き取り回路（１１３）により抽出されたパイロット信号をもとに伝送路推定回路（１１５）により伝送路を推定する。推定結果をもとにして補正値を計算し乗算器（１１２）に渡す。乗算器（１１２）により乗算された信号が補正されたデータとなり、出力端子（１１４）により出力される。
【０１００】
伝送路推定部では推定に際して、基準信号発生回路（１１６）からの基準信号により推定を行う。伝送路推定回路（１１５）の推定結果をもとに振幅の変動及び位相変動の激しい状態におかれた信号は状態判定回路（１１７）により等化が正確に行われなかったとしてその等化状態を出力端子（１１８）により出力する。
【０１０１】
図１２は復号部のブロック図を示す。
【０１０２】
前記波形等化部の出力端子（１１４）より出力された信号は復号部の入力端子（１２１）に入力される。入力信号はデインターリーブ回路（１２３）により送信側で符号化されたインターリブ回路の逆の処理を行う。処理されたデータはデマッピング回路（１２４）に渡され、キャリア変調方式に応じてデマッピング処理を行う。処理されたデータは後段のビタビデコーダ回路（１２５）に渡され、ビタビデコードされる。ビタビデコード回路（１２５）の出力は誤り訂正回路（１２６）に接続され送信側の符号器の逆の処理を行う。処理されたデータは出力端子（１２７）よりＴＳ信号として出力される。
【０１０３】
入力端子（１２２）より入力された等化状態信号はビタビデコーダに入力される。
【０１０４】
図１３はビタビデコーダ回路の構成図を示す。
【０１０５】
入力端子（１３１）より入力された信号はブランチメトリック回路（１３３）より０か１に対して誤差をどれだけ持っているか判定する。すなわち入力された信号は判定の結果どちらの信号として受信されているか、誤差を計算して判定する。その誤差信号はＡＳＣ回路（１３４）により、入力され誤差を積算し、どのパスが最も確からしいか比較する。
【０１０６】
比較した結果基づき最も誤差の少ない方を選択する。選択した結果をメモリ（１３５）に蓄積し、生き残りパスを決定する。以上の処理により受信信号より最も確からしい、データを決定し、出力端子（１３６）より出力する。
【０１０７】
入力端子（１３２）より入力された等化状態信号はブランチメトリック計算回路（１３３）へ入力され、等化状態信号により等化がうまく行われなかったと判定されたとき、入力端子１３１）より入力されたデータはブランチメトリック計算回路（１３３）に使用しない、もしくはその判定確率が中立（例えば０．５の確率）であるように回路の処理を行う。つまり入力された不確かなデータにより判定に誤動作を引き起こさないように処理する事である。
【０１０８】
【発明の効果】
以上のように、発明によれば、移動受信時のマルチパスフェージングや受信電界強度が弱いときでも良好に受信する事が可能となる。
【０１０９】
また、伝送路の状態が悪くても復号する過程でそのデータの処理を無効もしくは中立にする事でデータの信頼性を向上させる事ができる。
【０１１０】
更に、ＯＦＤＭ復調部は従来のダイバーシチのように、受信アンテナの数だけ用いる必要はなく、回路規模の縮小により小型化が可能となり又、消費電力の低減がはかれる。
【図面の簡単な説明】
【図１】本発明の実施形態における受信機の構成を示すブロック図である。
【図２】本発明の重み係数計算部の構成を示すブロック図である。
【図３】本発明の共分散行列推定器の構成を示すブロック図である。
【図４】本発明の相関器の構成を示すブロック図である。
【図５】本発明の最大固有値演算部の構成を示すブロック図である。
【図６】本発明のノルム演算部の構成を示すブロック図である。
【図７】従来のＯＦＤＭ変調機の構成を示すブロック図である。
【図８】従来のＯＦＤＭ受信機の構成を示すブロック図である。
【図９】従来の空間ダイバーシチ受信機の構成を示すブロック図である。
【図１０】ＯＦＤＭのスペクトラム波形である。
【図１１】発明の波形等価回路のブロック図である。
【図１２】本発明の復号部のブロック図である。
【図１３】発明のビタビデコーダのブロック図である。
【符号の説明】
１１ 受信アンテナ
１２ 乗算器
１３ ＯＦＤＭ復調部
１４ フーリエ変換部
１５ａ 波形等化部
１５ｂ 等化データ出力端子
１５ｃ 等化状態出力端子
１６ 復号部
１７ 重み係数計算部
１８ 復調データ出力端子
２１ 重み係数計算部
２２ 受信信号入力端子
２３ 共分散行列計算部
２４ 固有ベクトル計算部
２５ 係数出力端子
３１ 入力端子
３２ 複素共役回路
３３ 相関器
４１ 相関器
４２ 入力端子１
４３ 入力端子２
４４ 乗算器
４５ 積分器
４６ 相関出力端子
５２ マトリックス計算回路
５３ 第１乗算器
５４ 第２乗算器
５５ 第３乗算器
５６ 第１加算器
５７ 第２加算器
５８ 正規化乗算器
５９ ノルム演算器
６０ 逆数回路
６１ 係数出力端子
６３ ノルム演算器
６４ ノルム入力端子
６５ ２乗回路
６６ 加算器
６７ 平方根回路
６８ 出力端子
７１ データ入力端子
７２ 符号部
７３ 逆フーリエ変換部
７４ ガードインターバル挿入回路
７５ 直交変調回路
７６ 周波数変換回路
７７ 送信アンテナ
８１ 受信アンテナ
８２ チューナ
８３ 直交復調部
８４ ガードインターバル除部
８５ フーリエ変換部
８６ 波形等化部
８７ 復号部
８８ 制御回路
８９ データ出力端子
９１ 受信アンテナ
９２ フーリエ変換部
９３ 波形等化部
９４ 復号部
９５ 最適合成部
９６ 出力端子
１０１ サブキャリア
１１１ 入力端子
１１２ 乗算器
１１３ パイロット信号抜き取り回路
１１４ 出力端子
１１５ 伝送推定回路
１１６ 基準信号発生回路
１１７ 状態判定回路
１１８ 等化状態出力端子
１２１ データ入力端子
１２２ 等化状態入力端子
１２３ デインターリーブ回路
１２４ デマッピング回路
１２５ ビタビデコーダ回路
１２６ 誤り訂正回路
１２７ データ出力端子
１３１ データ入力端子
１３２ 等化状態入力端子
１３３ ブランチメトリック計算回路
１３４ ＡＣＳ回路
１３５ メモリ
１３６ データ出力端子[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a receiver and a receiving method, and in particular, is preferably applied to a receiver and a receiving method in which digital information is coded for error correction and the data is received by a signal modulated by an orthogonal frequency division multiplexing method. Available.
[0002]
[Prior art]
Conventional television broadcasting and audio broadcasting are analog systems for broadcasting video and audio using AM modulation and FM modulation. If these are interfered or disturbed by noise, ghost, or multipath, the video and audio are disturbed. In mobile reception, multipath fading causes severe image disturbance and deteriorates reception quality.
[0003]
Digitalization of terrestrial television broadcasting is being studied to overcome the above-mentioned problems and to realize effective use of SFN and bandwidth.
[0004]
2. Description of the Related Art Orthogonal frequency division multiplexing (OFDM) is used as a transmission system for digital terrestrial broadcasting.
[0005]
This OFDM system is one of multi-carrier transmission systems for transmitting signals by using a plurality of carriers (subcarriers) at the same time. Adjacent carriers are orthogonal to each other, and each carrier is modulated using DQPSK, 16QPSK, and 64QAM.
[0006]
In broadcasting, data to be sent, such as video, audio, and data, is subjected to data compression by a compression method such as MPEG and multiplexed to generate one transport stream (TS) signal. The generated TS signal is passed to a digital modulator as a digital signal and modulated.
[0007]
FIG. 7 is a schematic configuration diagram for explaining a modulation method on the transmission side.
[0008]
In FIG. 7, the TS signal is input from an input terminal (71). The input TS signal is encoded by the encoding unit (72). The encoding unit (72) performs encoding such as spreading processing, Reed-Solomon encoding for error correction, interleaving processing, and convolution processing.
[0009]
The encoded data is passed to the inverse Fourier transform unit (73). The inverse Fourier transform unit (73) performs an inverse discrete Fourier transform (hereinafter, referred to as IDFT (Inverted Discrete Fourier Transformer)) of the input signal from about 2048 points to about 8192 points. A guard interval signal is added to the IDFT data by a guard interval insertion circuit (74). The added signal is quadrature-modulated by the quadrature modulator (75).
[0010]
The orthogonally-modulated signal is frequency-converted by a frequency converter (76) to a transmission frequency band (UHF, VHF, etc.) and transmitted.
[0011]
With the above processing, video and audio are transmitted on the transmission side. Modulates data information.
[0012]
On the other hand, the receiver performs the reverse process of the above process to reproduce video, audio, and data.
[0013]
FIG. 8 is a configuration diagram of a conventional receiver.
[0014]
The received signal received by the antenna (81) is tuned by the tuner (82), orthogonally demodulated by the orthogonal demodulator (83), and converted from a band signal to a baseband signal. From the orthogonally demodulated signal, a signal in an effective symbol period is extracted by a guard interval removing circuit (84).
[0015]
The extracted effective symbol signal is subjected to a discrete Fourier transform (hereinafter, referred to as DFT (Discrete Fourier Transformer)) by a Fourier transform circuit (85). The discrete Fourier transform (DFT) generally uses about 2048 to 8192 points. The signal subjected to the discrete Fourier transform is used for estimating and compensating for the distortion received on the transmission path by a waveform equalizer (86) at the subsequent stage. At this time, it is general to insert a pilot signal serving as a signal reference on the transmission side. The waveform equalizer (86) estimates a transmission path using the pilot signal.
[0016]
The equalized signal is passed to a decoding unit (87), and the decoding unit (87) performs demapping processing, deinterleaving processing, Viterbi decoding processing, Reed-Solomon decoding, despreading processing, and the like. The processed signal outputs a TS signal from an output terminal (89) as demodulated data.
[0017]
The TS signal thus demodulated is decoded by MPEG or the like to reproduce video, audio and data. The above is the processing procedure of the conventional receiver.
[0018]
Since the OFDM system divides data into a number of subcarriers, the transmission speed of each subchannel is sufficiently small, and the length of one symbol is sufficiently long. Since one symbol length is long, it has a feature that it is hardly affected by a multipath delay wave. The guard interval is provided to completely remove the code interference caused by the delayed wave and to enable transmission of high-quality information. Is added.
[0019]
At this time, a part of the effective symbol is cut out and added to the guard interval. Also, the length to be added corresponds to a period from a fraction to a tenth of the whole.
[0020]
By providing such a guard interval, if the delay time of the multipath delay wave is within the guard interval, reception can be performed without intersymbol interference, and deterioration of transmission characteristics can be suppressed.
[0021]
[Problems to be solved by the invention]
However, during reception while moving, multipath fading occurs in addition to the multipath delay wave, and the frequency characteristics of the transmission path fluctuate with time and the characteristics deteriorate significantly.
[0022]
In the OFDM system, data is divided into subcarriers, and error correction and interleaving are performed by encoding, so that errors in received data can be corrected even if transmission characteristics deteriorate due to multipath delay waves.
[0023]
However, there is an environment in which direct waves cannot be received or an environment in which the received electric field decreases in mobile reception, and there has been a problem that reception quality is deteriorated and reception is not possible.
[0024]
In order to solve such a problem, there has been proposed space diversity for receiving signals using a plurality of antennas.
[0025]
FIG. 9 shows a configuration diagram of a conventional space diversity system that receives an OFDM reception signal.
[0026]
The signal received by the receiving antenna (91a) is subjected to DFT processing by a Fourier transform circuit (92a), and the signal subjected to DFT processing is equalized by a waveform equalizing unit (93a) and passed to a subsequent decoding unit (94a). It is. The decoding unit (94a) performs an inverse process of the encoding performed on the transmission side and outputs a signal. This output signal is passed to the optimum combining circuit (96). Similarly, the signal received by the receiving antenna (91b) is processed independently of the above processing. The same applies to the signal received by the receiving antenna (91c). For the signal received and demodulated in each branch, data having the least error between subcarriers is selected by the optimum combining circuit (96).
[0027]
However, as described above, in the conventional space diversity, it is necessary to perform OFDM demodulation on signals received by a plurality of antennas, and to combine optimal data for each subchannel. That is, as many OFDM demodulators as the number of antennas (branches) are required, and there is a problem that the circuit becomes large-scale.
[0028]
SUMMARY OF THE INVENTION The present invention provides an OFDM receiver that improves the characteristics of a received signal by processing and combining signals received by a plurality of antennas before OFDM demodulation.
[0029]
[Means for Solving the Problems]
In order to solve such a problem, the present invention has the following configuration and method.
[0030]
A first invention of the present application provides an orthogonal frequency division multiplexing receiver for receiving and demodulating a signal multiplexed and transmitted by an orthogonal frequency division multiplexing method, wherein the transmitted data is received by a plurality of receiving antennas. Receiving means, determine an eigenvector from a correlation value between a plurality of received signals received by the receiving means, weighting coefficient calculation means to use the eigenvector as a weighting coefficient, a plurality of received signals received by the receiving means, Multiplying means for multiplying the weight coefficient; first adding means for obtaining a sum of products obtained by the multiplying means; and orthogonal frequency division multiplex demodulation of the sum signal obtained by the first adding means. And demodulating means.
[0031]
In a second aspect of the present invention, the weighting factor calculating means includes a covariance matrix estimating means for obtaining a covariance matrix of the received signals received by the plurality of receiving antennas, and a covariance matrix estimating means obtained by the covariance matrix estimating means. Eigenvector calculating means for calculating a maximum eigenvalue from a variance matrix.
In a third aspect of the present invention, the covariance matrix estimating means is obtained by a complex conjugate calculating means for obtaining a complex conjugate of a received signal received by the plurality of antennas, and a complex conjugate calculating means for obtaining the complex conjugate of the received signal. Correlation value calculation means for calculating a correlation value between the values.
According to a fourth aspect of the present invention, the eigenvector computing means is a multiplier that multiplies a covariance matrix of the covariance matrix estimating means by a weight coefficient output obtained from the covariance matrix, And a normalizing means for normalizing the result obtained by the second adding means.
In a fifth aspect of the present invention, the demodulation means is a fast Fourier transform means for performing a Fourier transform on the sum signal obtained by the first adder means, and equalizes the signal Fourier transformed by the fast Fourier transform means. Waveform equalizing means, decoding means for decoding the signal equalized by the waveform equalizing means, and output means for notifying the decoding means of the waveform equalizing means to the decoding means,
It is characterized by having.
[0032]
The sixth invention of the present application is a receiving method of an orthogonal frequency division multiplexing method for receiving and demodulating a signal multiplexed and transmitted by an orthogonal frequency division multiplexing method, wherein the transmitted data is received by a plurality of receiving antennas. Receiving, obtaining an eigenvector from a correlation value between the received signals , using the eigenvector as a weighting factor, multiplying the plurality of reception signals by the weighting factor, and multiplying the plurality of reception signals by the weighting factor. , And orthogonal frequency division multiplex demodulation is performed after obtaining the sum of
[0033]
It should be noted that the above components can be combined with each other as much as possible.
[0034]
By the above means, mobile reception and stable reception can be performed even in a weak reception electric field, and transmission characteristics can be improved without increasing the scale of hardware.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0036]
FIG. 1 is a configuration diagram showing a configuration of a system of a proposed spatial diversity COFDM receiver according to a first embodiment of the present invention.
[0037]
In FIG. 1, radio waves transmitted from the transmitter shown in FIG. 7 are received by receiving antennas (11a to 11c). The received signals are multiplied by weighting factors by multipliers (12a to 12c) and added by an adder. The weight coefficient is obtained from the received signal by the weight coefficient calculation unit (17).
[0038]
The signal added by the adder is demodulated by an OFDM demodulator (13). The demodulated signal is output from an output terminal (18).
[0039]
In the OFDM demodulation unit (13), the input data is subjected to fast Fourier transform by the Fourier transform unit (14), the waveform is equalized by the waveform equalizer (15a), and the equalized data is output as data ( 15b). At the same time, a signal indicating the state of the waveform equalization is output from the state output terminal (15c). The decoding section (16) at the subsequent stage performs inverse processing on the transmission side based on these input signals.
[0040]
In the OFDM receiver of the present invention, the broadcast waves transmitted from the transmitter are independently received by the N receiving antennas (11a, 11b, 11c).
[0041]
It is assumed that a multipath having L paths has arrived at each receiving antenna, and the complex amplitude of the l-th path arriving at the m-th receiving antenna is represented by
(Equation 1)

[0043]
And
[0044]
At this time, the received signal at the m-th receiving antenna (branch) is
(Equation 2)

[0046]
Then, the received signal becomes
(Equation 3)

[0048]
Can be written.
[0049]
Here [0050]
(Equation 4)

[0051]
Is the white noise at the m-th receiving antenna.
[0052]
The signals received by each antenna are multiplied by a weighting factor and added.
[0053]
The received signal after the addition is
(Equation 5)

[0055]
Is represented by the following equation.
[0056]
(Equation 6)

[0057]
Here, the weight coefficient of the m-th branch is
(Equation 7)

[0059]
It is.
[0060]
The receiver performs DFT processing on the received signal to perform demodulation.
[0061]
Therefore, the DFT output signal is
(Equation 8)

[0063]
Then, the received signal can be expressed by the following equation.
[0064]
(Equation 9)

[0065]
In the spatial diversity of the present invention, each received branch signal is combined before DFT, and a weight coefficient is determined so as to maximize the SNR after DFT.
[0066]
The SNR of each branch received by each antenna of each sub-channel before combining is represented by the following equation.
[0067]
(Equation 10)

[0068]
The following equation is obtained by transforming the equation and writing it using only the complex amplitude.
[0069]
(Equation 11)

[0070]
Here, the weight vector w of the weight coefficient of each receiving antenna is
(Equation 12)

[0072]
And
[0073]
If the matrix representing the characteristics of the transmission path is a transmission path matrix G,
(Equation 13)

[0075]
Here, 1 represents the first path, i and k represent the i-th branch and the k-th branch.
[0076]
The demodulated SNR after combining can be expressed by the following equation.
[0077]
[Equation 14]

[0078]
Here, Λ is a diagonal matrix having the eigenvalue λm of G as a diagonal element, and U is a unitary matrix having m columns of eigenvectors corresponding to the eigenvalue λm.
[0079]
The weight vector w that maximizes the above equation is an eigenvector corresponding to the largest eigenvalue.
[0080]
When the covariance matrix R is obtained from the signals received by the M receiving antennas,
(Equation 15)

[0082]
i and k represent the i-th branch and the k-th branch, and p is a subscript representing time.
[0083]
When the equation is transformed and written in the form of a matrix, the covariance matrix R becomes
(Equation 16)

[0085]
Can be written. Here, I is a unit matrix.
[0086]
From the above, the optimum weighting factor coincides with the eigenvector for the maximum eigenvalue, the covariance matrix of the received signal is obtained, and the eigenvector for the maximum eigenvalue of the matrix may be set as the weighting factor W.
[0087]
FIG. 2 shows a block diagram of a weighting factor calculator of the present invention.
[0088]
Signals received by the M receiving antennas are input from input terminals (22a, 22b, 22c) to a weighting coefficient calculator (21), and a covariance matrix is calculated by a covariance matrix calculator (23). From the result, an eigenvector for the largest eigenvalue of the matrix is obtained by an eigenvector calculation unit (24). The calculation result is output from output terminals (25a, 25b, 25c). The output signal is passed to the multipliers (12a, 12b, 12c) in FIG. 1 and is multiplied by the received signal.
[0089]
FIG. 3 is a block diagram showing a configuration of the covariance matrix estimator.
[0090]
One of the signals input from the input terminals (31a, 31b, 31c) is connected to one of the input terminals of the correlators (33a to 33e). The other one takes the complex conjugate of the input signal by a complex conjugate circuit (32a, 32b, 32c) and is connected to the other input terminal of the correlator (33a-3e). Each correlation result is output from an output terminal.
[0091]
FIG. 4 shows a block diagram of the correlator.
[0092]
The signal input from the two input terminals (42, 43) of the correlator (41) is multiplied by the multiplier 44 and passed to the integrator (45) at the subsequent stage. An integrator (45) integrates the input signal and outputs an integration result from an output terminal (46).
[0093]
FIG. 5 shows a block diagram of the maximum eigenvalue calculation unit.
[0094]
The covariance matrix calculated by the covariance matrix calculation unit (23) is passed to each input terminal of the maximum eigenvalue calculation unit, and the weight coefficient output signal of the feedback system and the multipliers (53a to 53c, 54a to 54c, 55a). ~ 55c). The multiplication results are added by adders (56a-c, 57a-c). The result of the addition is normalized by multipliers (58a to 58c) for normalization. In the normalization, a norm is calculated by inputting the result of each addition to a norm operation circuit (59). A reciprocal of the calculated value is calculated by a reciprocal calculator (60). The result of the reciprocal calculator (60) is multiplied by each signal.
[0095]
One of the normalized signals is output from the output terminals (61a to 61c) as a weight coefficient. The other is multiplied by the multiplier (53a-53c, 54a-54c, 55a-55c) with the input signal of the maximum eigenvalue calculator (24) as the feedback signal.
[0096]
FIG. 6 shows a block diagram of the norm operation unit (59).
[0097]
For the signals input from the input terminals (64a to 64c), the square values of the input signals are calculated by the squaring circuits (65a to 65c), and are added by the subsequent adding circuit (66). The square root of the added result is calculated by a square root circuit (67) and output from an output terminal (68).
[0098]
FIG. 11 shows a block diagram of a waveform equivalent circuit.
[0099]
The DFT output signal is input from an input terminal (111) and is connected to a multiplier (112) and a pilot signal extracting circuit (113). A transmission path is estimated by a transmission path estimation circuit (115) based on the pilot signal extracted by the pilot signal extraction circuit (113). A correction value is calculated based on the estimation result and passed to the multiplier (112). The signal multiplied by the multiplier (112) becomes corrected data, which is output from the output terminal (114).
[0100]
At the time of estimation, the transmission path estimating unit performs estimation based on the reference signal from the reference signal generation circuit (116). A signal in a state where the amplitude fluctuation and the phase fluctuation are intense based on the estimation result of the transmission path estimation circuit (115) is determined to have been equalized by the state determination circuit (117) because the equalization was not performed accurately. Is output from the output terminal (118).
[0101]
FIG. 12 shows a block diagram of the decoding unit.
[0102]
The signal output from the output terminal (114) of the waveform equalizer is input to the input terminal (121) of the decoder. The input signal is processed by the deinterleave circuit (123) in the reverse order of the interleave circuit encoded on the transmission side. The processed data is passed to a demapping circuit (124) and performs a demapping process according to the carrier modulation scheme. The processed data is passed to a subsequent Viterbi decoder circuit (125) and Viterbi decoded. The output of the Viterbi decode circuit (125) is connected to an error correction circuit (126) and performs the reverse processing of the encoder on the transmission side. The processed data is output from the output terminal (127) as a TS signal.
[0103]
The equalization state signal input from the input terminal (122) is input to the Viterbi decoder.
[0104]
FIG. 13 shows a configuration diagram of the Viterbi decoder circuit.
[0105]
The branch metric circuit (133) determines how much the signal input from the input terminal (131) has an error with respect to 0 or 1. That is, the input signal is determined as a result of the determination as to which signal is received by calculating an error. The error signal is input by an ASC circuit (134), the errors are integrated, and a comparison is made as to which path is most likely.
[0106]
The one with the smallest error is selected based on the comparison result. The selected result is stored in the memory (135), and the surviving path is determined. Through the above processing, data which is most likely than the received signal is determined, and is output from the output terminal (136).
[0107]
The equalization state signal input from the input terminal (132) is input to the branch metric calculation circuit (133), and is input from the input terminal 131) when it is determined by the equalization state signal that equalization was not successfully performed. The data is not used in the branch metric calculation circuit (133), or the circuit is processed so that the determination probability is neutral (for example, a probability of 0.5). That is, the processing is performed so that the input uncertain data does not cause a malfunction in the determination.
[0108]
【The invention's effect】
As described above, according to the present invention, it is possible to perform good reception even when multipath fading at the time of mobile reception or reception electric field strength is weak.
[0109]
Further, even if the state of the transmission path is poor, the reliability of data can be improved by invalidating or neutralizing the processing of the data during the decoding process.
[0110]
Further, the OFDM demodulation unit does not need to be used by the number of receiving antennas as in the case of the conventional diversity. The size of the circuit can be reduced by reducing the circuit size, and the power consumption can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a receiver according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of a weight coefficient calculator according to the present invention.
FIG. 3 is a block diagram illustrating a configuration of a covariance matrix estimator of the present invention.
FIG. 4 is a block diagram illustrating a configuration of a correlator according to the present invention.
FIG. 5 is a block diagram illustrating a configuration of a maximum eigenvalue calculator according to the present invention.
FIG. 6 is a block diagram illustrating a configuration of a norm calculation unit according to the present invention.
FIG. 7 is a block diagram illustrating a configuration of a conventional OFDM modulator.
FIG. 8 is a block diagram illustrating a configuration of a conventional OFDM receiver.
FIG. 9 is a block diagram showing a configuration of a conventional spatial diversity receiver.
FIG. 10 is a spectrum waveform of OFDM.
FIG. 11 is a block diagram of a waveform equivalent circuit of the present invention.
FIG. 12 is a block diagram of a decoding unit according to the present invention.
FIG. 13 is a block diagram of a Viterbi decoder according to the present invention.
[Explanation of symbols]
Reference Signs List 11 receiving antenna 12 multiplier 13 OFDM demodulation unit 14 Fourier transform unit 15a waveform equalization unit 15b equalization data output terminal 15c equalization state output terminal 16 decoding unit 17 weight coefficient calculation unit 18 demodulation data output terminal 21 weight coefficient calculation unit 22 Received signal input terminal 23 Covariance matrix calculation unit 24 Eigenvector calculation unit 25 Coefficient output terminal 31 Input terminal 32 Complex conjugate circuit 33 Correlator 41 Correlator 42 Input terminal 1
43 input terminal 2
44 Multiplier 45 Integrator 46 Correlation output terminal 52 Matrix calculation circuit 53 First multiplier 54 Second multiplier 55 Third multiplier 56 First adder 57 Second adder 58 Normalization multiplier 59 Norm operator 60 Reciprocal Circuit 61 Coefficient output terminal 63 Norm operation unit 64 Norm input terminal 65 Square circuit 66 Adder 67 Square root circuit 68 Output terminal 71 Data input terminal 72 Sign unit 73 Inverse Fourier transform unit 74 Guard interval insertion circuit 75 Quadrature modulation circuit 76 Frequency conversion Circuit 77 Transmit antenna 81 Receive antenna 82 Tuner 83 Quadrature demodulator 84 Guard interval remover 85 Fourier transformer 86 Waveform equalizer 87 Decoder 88 Control circuit 89 Data output terminal 91 Receive antenna 92 Fourier transformer 93 Waveform equalizer 94 Decoding unit 95 optimal combining unit 96 output terminal 101 A 111 Input terminal 112 Multiplier 113 Pilot signal extraction circuit 114 Output terminal 115 Transmission estimation circuit 116 Reference signal generation circuit 117 State determination circuit 118 Equalization state output terminal 121 Data input terminal 122 Equalization state input terminal 123 Deinterleave circuit 124 Mapping circuit 125 Viterbi decoder circuit 126 Error correction circuit 127 Data output terminal 131 Data input terminal 132 Equalization state input terminal 133 Branch metric calculation circuit 134 ACS circuit 135 Memory 136 Data output terminal

Claims (6)

Multiplexed by the orthogonal frequency division multiplexing method, receiving the transmitted signal, in the orthogonal frequency division multiplexing receiver to demodulate,
Receiving means for receiving the transmitted data by a plurality of receiving antennas,
A weighting factor calculation unit that obtains an eigenvector from a correlation value between a plurality of reception signals received by the reception unit and uses the eigenvector as a weighting factor ,
Multiplying means for multiplying the plurality of received signals received by the receiving means by the weighting coefficient,
First adding means for obtaining the sum of the products obtained by the multiplying means;
Demodulating means for performing orthogonal frequency division multiplex demodulation on the sum signal obtained by the first adding means;
A receiver comprising: The weighting factor calculation means,
Covariance matrix estimating means for determining the covariance matrix of the received signals received by the plurality of receiving antennas,
Eigenvector operation means for calculating the maximum eigenvalue from the covariance matrix determined by the covariance matrix estimation means,
The receiver according to claim 1, further comprising: The covariance matrix estimating means,
Complex conjugate calculation means for obtaining a complex conjugate of the received signals received by the plurality of antennas,
Correlation value calculation means for calculating a correlation value between the received signal and the value determined by the complex conjugate calculation means,
The receiver according to claim 1, further comprising: The eigenvector calculation means includes:
A multiplier for multiplying the covariance matrix of the covariance matrix estimating means and the weight coefficient output obtained from the covariance matrix,
Second adding means for adding the result obtained by the multiplier;
Normalizing means for normalizing the result obtained by the second adding means;
The receiver according to claim 1, further comprising: The demodulation means,
Fast Fourier transform means for performing a Fourier transform on the signal of the sum obtained by the first adding means;
Waveform equalizing means for equalizing the signal Fourier transformed by the fast Fourier transform means,
Decoding means for decoding the signal equalized by the waveform equalization means,
Output means for notifying the decoding means of the state of equalization, the waveform equalizing means,
The receiver according to claim 1, further comprising: A reception method of an orthogonal frequency division multiplexing method, which is multiplexed by an orthogonal frequency division multiplexing method, receives a transmitted signal, and demodulates the signal.
The transmitted data is received by a plurality of receiving antennas, an eigenvector is obtained from a correlation value between the received signals , the eigenvector is used as a weighting factor, and the weighting factor is multiplied by the plurality of receiving signals. Receiving a sum of a plurality of received signals multiplied by the weighting coefficient, and then performing orthogonal frequency division multiplex demodulation.

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