JP7102072B2 - Adaptive equalizer and carrier regenerative circuit - Google Patents

Adaptive equalizer and carrier regenerative circuit Download PDF

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JP7102072B2
JP7102072B2 JP2018175345A JP2018175345A JP7102072B2 JP 7102072 B2 JP7102072 B2 JP 7102072B2 JP 2018175345 A JP2018175345 A JP 2018175345A JP 2018175345 A JP2018175345 A JP 2018175345A JP 7102072 B2 JP7102072 B2 JP 7102072B2
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康英 田中
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Description

本発明は、デジタル無線伝送において搬送波・受信波を再生するのに使用される適応等化器および、この適応等化器を備えた搬送波再生回路に関する。 The present invention relates to an adaptive equalizer used for reproducing a carrier wave / received wave in digital wireless transmission, and a carrier wave regenerative circuit provided with the adaptive equalizer.

近年、無線トラフィックが増々増加しており、周波数利用の高効率化の観点からデジタル無線伝送においては、高多値QAM(Quadrature Amplitude Modulation、直角位相振幅変調)方式による高速伝送の要求が高まっている。この高多値QAM方式では、送信装置や受信装置において生じる搬送波の位相ノイズ(位相誤差)などによって、復調性能が劣化する場合がある。このため、位相ノイズと熱雑音の影響度に基づいて復調性能(ビット誤り率)を向上させる、という搬送波再生回路が知られている(例えば、特許文献1参照。)。 In recent years, wireless traffic has been increasing more and more, and from the viewpoint of improving the efficiency of frequency utilization, there is an increasing demand for high-speed transmission by the high multi-value QAM (Quadrature Amplitude Modulation) method in digital wireless transmission. .. In this high multi-level QAM method, the demodulation performance may deteriorate due to the phase noise (phase error) of the carrier wave generated in the transmitting device or the receiving device. Therefore, there is known a carrier regenerative circuit that improves demodulation performance (bit error rate) based on the degree of influence of phase noise and thermal noise (see, for example, Patent Document 1).

この搬送波再生回路は、位相誤差検出器が検出する位相誤差と振幅誤差検出器が検出する振幅誤差とに基づいて、ループフィルタ制御部がループフィルタの帯域幅を制御することで、位相ノイズや熱雑音に応じた適切な帯域幅に設定し、復調性能を向上させる、というものである。 In this carrier wave reproduction circuit, the loop filter control unit controls the bandwidth of the loop filter based on the phase error detected by the phase error detector and the amplitude error detected by the amplitude error detector, thereby causing phase noise and heat. The bandwidth is set appropriately according to the noise to improve the demodulation performance.

特開2011-101177号公報Japanese Unexamined Patent Publication No. 2011-101177

ところで、熱雑音のみが存在する場合、C/N(搬送波対雑音比)が高いと図7(a)に示すように、理想点Rを中心とする小円状の信号分布領域が存在し、C/Nが低いと図7(b)に示すように、理想点Rを中心とする大円状の信号分布領域が存在する。さらに、熱雑音と位相雑音とが存在する場合、図8に示すように、理想点Rを中心とする円状の熱雑音分布領域が存在するとともに、複素平面上の原点Cを中心とする円弧状で理想点Rを通る位相雑音分布領域が存在する。 By the way, when only thermal noise is present, a small circular signal distribution region centered on the ideal point R exists as shown in FIG. 7A when the C / N (carrier-to-noise ratio) is high. When the C / N is low, as shown in FIG. 7B, there is a large circular signal distribution region centered on the ideal point R. Further, when thermal noise and phase noise are present, as shown in FIG. 8, there is a circular thermal noise distribution region centered on the ideal point R, and a circle centered on the origin C on the complex plane. There is a phase noise distribution region that is arcuate and passes through the ideal point R.

また、高多値化変調においては、搬送波・キャリア再生の位相誤差検出範囲が著しく狭くなる。すなわち、低多値の場合には、隣接する理想点間の距離が大きいため位相誤差検出範囲が広いが、高多値の場合には、隣接する理想点間の距離が小さいため位相誤差検出範囲が狭くなる。そして、位相誤差検出範囲が著しく狭くなるため、位相ノイズ環境下で図9に示すような位相ジッタ(位相の揺らぎ)が増加し、搬送波再生の同期外れに至る可能性がある。 Further, in the high multi-value modulation, the phase error detection range of the carrier wave / carrier reproduction is remarkably narrowed. That is, in the case of a low multi-value, the phase error detection range is wide because the distance between adjacent ideal points is large, but in the case of a high multi-value, the phase error detection range is small because the distance between adjacent ideal points is small. Becomes narrower. Since the phase error detection range is remarkably narrowed, phase jitter (phase fluctuation) as shown in FIG. 9 increases in a phase noise environment, which may lead to out-of-synchronization of carrier wave reproduction.

すなわち、単に適応等化器の出力信号Sに最も近い理想点Rを基準にすると、例えば、図9に示す複素平面上の原点Cから遠く位相回転の影響が大きい領域において、信号点S(図中四角い破線で囲まれた黒丸、出力信号)に対して誤った理想点Rを基準にしてタップ係数を更新してしまい、意図しない信号点配置に収束する事象が生じてしまう。一方、特許文献1に記載の搬送波再生回路では、熱雑音の軽減を優先するか、位相ノイズの軽減を優先するかによって、高多値時の搬送波再生ループの諸元を切り替えるものであり、高多値化に伴う位相誤差検出範囲の低下による不安定動作については考慮されていない。 That is, based on the ideal point R closest to the output signal S of the adaptive equalizer, for example, the signal point S (FIG. 9) is located in a region far from the origin C on the complex plane shown in FIG. 9 and greatly affected by the phase rotation. The tap coefficient is updated with reference to the erroneous ideal point R for the black circle surrounded by the middle square broken line, the output signal), and an event occurs in which the tap coefficient converges to an unintended signal point arrangement. On the other hand, in the carrier wave reproduction circuit described in Patent Document 1, the specifications of the carrier wave reproduction loop at the time of high multi-value are switched depending on whether the reduction of thermal noise is prioritized or the reduction of phase noise is prioritized. Unstable operation due to a decrease in the phase error detection range due to the increase in value is not considered.

そこで本発明は、高多値においても安定した高い復調性能を実現可能にする、適応等化器およびこれを備えた搬送波再生回路を提供することを目的とする。 Therefore, an object of the present invention is to provide an adaptive equalizer and a carrier regenerative circuit provided with the adaptive equalizer, which can realize stable and high demodulation performance even at high multi-values.

上記課題を解決するために、請求項1に記載の発明は、入力信号の周波数特性を補償する適応等化部と、複素平面上に配置された理想点と前記適応等化部の出力信号との誤差に基づくアルゴリズムで、前記適応等化部に対するタップ係数を更新するタップ更新部と、を備え、前記タップ更新部は、前記適応等化部の出力信号の位相雑音が所定状態よりも大きい場合、前記複素平面上の原点を中心にして前記適応等化部の出力信号を回転させて、前記適応等化部の出力信号に最も近い前記理想点を選定し、該選定した理想点と前記適応等化部の出力信号との誤差に基づいて前記タップ係数を更新する、ことを特徴とする適応等化器である。 In order to solve the above problems, the invention according to claim 1 includes an adaptive equalization unit that compensates for the frequency characteristics of the input signal, an ideal point arranged on a complex plane, and an output signal of the adaptive equalization unit. When the phase noise of the output signal of the adaptive equalization unit is larger than a predetermined state, the tap update unit includes a tap update unit that updates the tap coefficient with respect to the adaptive equalization unit by an algorithm based on the error of the above. , The output signal of the adaptive equalization unit is rotated around the origin on the complex plane, the ideal point closest to the output signal of the adaptive equalization unit is selected, and the selected ideal point and the adaptation are selected. The adaptive equalizer is characterized in that the tap coefficient is updated based on an error with the output signal of the equalization unit.

請求項2に記載の発明は、入力信号の位相を回転する第1の位相回転器と、前記第1の位相回転器によって位相が回転された入力信号である位相回転信号の周波数特性を補償する、請求項1に記載の適応等化器と、前記適応等化器によって補償された位相回転信号に含まれる位相誤差を検出する位相誤差検出器と、前記位相誤差に基づいて位相回転制御信号を生成する回転信号生成部と、前記位相回転制御信号に基づいて前記入力信号の位相を回転する第2の位相回転器と、を備え、前記第1の位相回転器は、前記位相回転制御信号に基づいて前記入力信号の位相を回転する、ことを特徴とする搬送波再生回路である。 The invention according to claim 2 compensates for the frequency characteristics of a first phase rotator that rotates the phase of the input signal and a phase rotation signal that is an input signal whose phase is rotated by the first phase rotator. The adaptive equalizer according to claim 1, a phase error detector that detects a phase error included in the phase rotation signal compensated by the adaptive equalizer, and a phase rotation control signal based on the phase error. A rotation signal generation unit to be generated and a second phase rotator that rotates the phase of the input signal based on the phase rotation control signal are provided, and the first phase rotator is used as the phase rotation control signal. The carrier reproduction circuit is characterized in that the phase of the input signal is rotated based on the above.

請求項1に記載の発明によれば、適応等化部の出力信号の位相雑音が所定状態よりも大きい場合、複素平面上の原点を中心にして適応等化部の出力信号を回転させて、適応等化部の出力信号に最も近い理想点を選定する。つまり、位相雑音(位相ジッタ)が大きいときには、単に適応等化部の出力信号に最も近い理想点を選定するのではなく、出力信号を回転させて対応する理想点を選定するため、正しい理想点を選定することが可能となる。そして、この正しい理想点と適応等化部の出力信号との誤差に基づいてタップ係数を更新することで、適応等化器から安定した出力を得ることが可能となる。この結果、高多値においても高精度かつ安定した復調性能・搬送波再生を実現することが可能となる。 According to the invention of claim 1, when the phase noise of the output signal of the adaptive equalization unit is larger than a predetermined state, the output signal of the adaptive equalization unit is rotated around the origin on the complex plane. Select the ideal point closest to the output signal of the adaptive equalization unit. In other words, when the phase noise (phase jitter) is large, the ideal point that is closest to the output signal of the adaptive equalization unit is not simply selected, but the corresponding ideal point is selected by rotating the output signal, so the correct ideal point is selected. Can be selected. Then, by updating the tap coefficient based on the error between the correct ideal point and the output signal of the adaptive equalizer unit, it is possible to obtain a stable output from the adaptive equalizer. As a result, it is possible to realize highly accurate and stable demodulation performance and carrier wave reproduction even at high multi-values.

請求項2に記載の発明によれば、適応等化器で周波数特性が補償された位相回転信号の位相誤差に基づいて、位相回転制御信号が生成され入力信号の位相が回転されるため、フェージングによる波形歪がある場合でも、搬送波の位相ノイズを高精度に推定して高い復調性能・搬送波再生を実現することが可能となる。しかも、上記のように、安定した適応等化器出力が得られるため、より高精度かつ安定した復調性能・搬送波再生を実現することが可能となる。さらに、適応等化器で位相回転信号の周波数特性が補償されるため、熱雑音の影響も軽減することが可能となる。 According to the invention of claim 2, the phase rotation control signal is generated and the phase of the input signal is rotated based on the phase error of the phase rotation signal whose frequency characteristic is compensated by the adaptive equalizer, so that the phase is faded. Even if there is waveform distortion due to the above, it is possible to estimate the phase noise of the carrier wave with high accuracy and realize high demodulation performance and carrier wave reproduction. Moreover, as described above, since a stable adaptive equalizer output can be obtained, it is possible to realize more accurate and stable demodulation performance and carrier wave reproduction. Further, since the frequency characteristic of the phase rotation signal is compensated by the adaptive equalizer, the influence of thermal noise can be reduced.

この発明の実施の形態に係る搬送波再生回路を示す概略構成ブロック図である。It is a schematic block diagram which shows the carrier wave regenerative circuit which concerns on embodiment of this invention. 図1の搬送波再生回路を備えるマイクロ波無線システムを示す概略構成図である。It is a schematic block diagram which shows the microwave radio system which includes the carrier wave regenerative circuit of FIG. 図1の搬送波再生回路の適応等化器を示す概略構成ブロック図である。It is a schematic block diagram which shows the adaptation equalizer of the carrier wave regenerative circuit of FIG. 図3の適応等化器のC/N推定部によって、位相雑音の大きさを推定する方法を説明するための図である。It is a figure for demonstrating the method of estimating the magnitude of phase noise by the C / N estimation part of the adaptive equalizer of FIG. 図3の適応等化器の回転部によって、理想点を選定する方法を説明するための図である。It is a figure for demonstrating the method of selecting an ideal point by the rotating part of the adaptive equalizer of FIG. 図3の適応等化器の回転部によって、位相回転の影響が大きい領域で選定された理想点を示す図である。It is a figure which shows the ideal point selected by the rotating part of the adaptive equalizer of FIG. 3 in the region where the influence of a phase rotation is large. 熱雑音のみが存在する場合における、C/Nが高い際の信号分布領域(a)とC/Nが低い際の信号分布領域(b)を示す図である。It is a figure which shows the signal distribution area (a) when C / N is high, and the signal distribution area (b) when C / N is low, when only thermal noise is present. 熱雑音と位相雑音とが存在する場合における、熱雑音分布領域と位相雑音分布領域を示す図である。It is a figure which shows the thermal noise distribution region and the phase noise distribution region in the case where thermal noise and phase noise are present. 位相回転の影響が大きい領域において、信号点に対して誤った理想点を基準にしてしまう場合を示す図である。It is a figure which shows the case where an erroneous ideal point is used as a reference with respect to a signal point in a region where the influence of a phase rotation is large.

以下、この発明を図示の実施の形態に基づいて説明する。 Hereinafter, the present invention will be described based on the illustrated embodiment.

図1~図6は、この発明の実施の形態を示し、図3は、この実施の形態に係る適応等化器3を示す概略構成ブロック図であり、図1は、この適応等化器3を備える搬送波再生回路1を示す概略構成ブロック図である。この搬送波再生回路1は、デジタル無線伝送において搬送波を再生する回路であり、図2に示すマイクロ波無線システムの受信装置102に設けられている。ここで、マイクロ波無線システムについてまず簡単に説明すると、送信装置101においてマッピングおよび変調された送信信号がアナログ変換され、搬送波W1で乗算されてアンテナから送信される。そして、マルチパスフェージング環境を経て受信装置102のアンテナで受信されると、搬送波W2で乗算され、周波数変換されたのち、ADCでデジタル変換され、搬送波再生回路1で復調されてデマッピングされるものである。 1 to 6 show an embodiment of the present invention, FIG. 3 is a schematic block diagram showing an adaptive equalizer 3 according to this embodiment, and FIG. 1 is a schematic block diagram showing the adaptive equalizer 3. It is a schematic block diagram which shows the carrier wave regenerative circuit 1. The carrier wave regeneration circuit 1 is a circuit that reproduces a carrier wave in digital wireless transmission, and is provided in the receiving device 102 of the microwave wireless system shown in FIG. Here, the microwave wireless system will be briefly described. The transmitted signal mapped and modulated in the transmitting device 101 is analog-converted, multiplied by the carrier wave W1, and transmitted from the antenna. Then, when it is received by the antenna of the receiving device 102 via the multipath fading environment, it is multiplied by the carrier wave W2, frequency-converted, digitally converted by the ADC, demodulated by the carrier wave reproduction circuit 1, and demapped. Is.

搬送波再生回路1は、主として、第1の位相回転器2と、適応等化器3と、位相誤差検出器4と、LPF5と、NCO(回転信号生成部)6と、第2の位相回転器7と、等化器8と、を備える。 The carrier wave reproduction circuit 1 mainly includes a first phase rotator 2, an adaptive equalizer 3, a phase error detector 4, an LPF 5, an NCO (rotation signal generator) 6, and a second phase rotator. 7 and an equalizer 8 are provided.

第1の位相回転器2は、入力信号の位相を回転する回転器・乗算器であり、後述するNCO6の位相回転制御信号に基づいて入力信号の位相を回転する。具体的には、デジタル信号に変換されたIチャネルのベースバンド信号およびQチャネルのベースバンド信号の各々に対して、NCO6の位相回転制御信号の正弦波および余弦波に基づいて位相回転を行うものである。 The first phase rotator 2 is a rotator / multiplier that rotates the phase of the input signal, and rotates the phase of the input signal based on the phase rotation control signal of NCO6 described later. Specifically, for each of the I-channel baseband signal and the Q-channel baseband signal converted into digital signals, phase rotation is performed based on the sine wave and cosine wave of the phase rotation control signal of NCO6. Is.

適応等化器3は、第1の位相回転器2によって位相が回転された入力信号である位相回転信号の周波数特性を補償する、つまり、位相回転信号の波形歪やデータ誤りを解消する等化器である。ここで、適応等化器3は、判定帰還型等化器(DFE:Decision Feedback Equalizer)や線形等化器で構成され、後述するようにして、タップ係数を更新するようになっている。 The adaptive equalizer 3 compensates for the frequency characteristics of the phase rotation signal, which is an input signal whose phase has been rotated by the first phase rotation unit 2, that is, equalizes to eliminate waveform distortion and data error of the phase rotation signal. It is a vessel. Here, the adaptive equalizer 3 is composed of a determination feedback equalizer (DFE: Decision Feedback Equalizer) and a linear equalizer, and the tap coefficient is updated as described later.

位相誤差検出器4は、適応等化器3によって補償された位相回転信号に含まれる位相誤差を検出する検出器である。具体的な検出方法は周知の技術であり、例えば、送受信装置101、102間で用いられる変調方式の信号点配列のなかから、出力信号に応じた信号点を選択し、選択した信号点の座標と入力信号点の座標とを比較して、位相誤差値を算出する。 The phase error detector 4 is a detector that detects the phase error included in the phase rotation signal compensated by the adaptive equalizer 3. A specific detection method is a well-known technique. For example, a signal point corresponding to an output signal is selected from the signal point arrangement of the modulation method used between the transmission / reception devices 101 and 102, and the coordinates of the selected signal point are selected. And the coordinates of the input signal point are compared to calculate the phase error value.

LPF5は、位相誤差検出器4で検出された位相誤差の高周波成分を、所定の帯域幅に応じて除去するフィルタであり、ローパスフィルタ(Low Pass Filter)で構成されている。 The LPF 5 is a filter that removes high-frequency components of the phase error detected by the phase error detector 4 according to a predetermined bandwidth, and is composed of a low-pass filter (Low Pass Filter).

NCO6は、LPF5で高周波成分が除去された位相誤差に基づいて、位相回転制御信号を生成する生成部であり、NCO(Numerically Controlled Oscillator、数値制御発振器)で構成されている。具体的には、LPF5からの位相誤差に基づいて逆位相の正弦波および余弦波を生成し、第1の位相回転器2に出力することで、第1の位相回転器2による位相回転を制御するものである。さらに、生成した位相回転制御信号を第2の位相回転器7に出力する。 The NCO 6 is a generator that generates a phase rotation control signal based on the phase error from which the high frequency component is removed by the LPF 5, and is composed of an NCO (Numerically Controlled Oscillator). Specifically, the phase rotation by the first phase rotator 2 is controlled by generating an antiphase sine wave and a cosine wave based on the phase error from the LPF 5 and outputting them to the first phase rotator 2. To do. Further, the generated phase rotation control signal is output to the second phase rotation device 7.

第2の位相回転器7は、入力信号の位相を回転する回転器・乗算器であり、NCO6からの位相回転制御信号に基づいて入力信号の位相を回転して、周波数特性を補償する等化器8に出力する。すなわち、適応等化器3によって周波数特性補償(波形歪等が解消)されて検出された位相誤差に基づくNCO6からの正弦波および余弦波に基づいて、入力信号の位相を回転する。このように、搬送波再生ループ(第1の位相回転器2、位相誤差検出器4、LPF5およびNCO6のループ)のなかに適応等化器3が実装されており、これにより、周波数特性を補償した後に推定した位相誤差値に基づいて、入力信号の位相ノイズをキャンセルする。 The second phase rotator 7 is a rotator / multiplier that rotates the phase of the input signal, and rotates the phase of the input signal based on the phase rotation control signal from the NCO 6 to compensate for the frequency characteristics. Output to vessel 8. That is, the phase of the input signal is rotated based on the sine wave and the cosine wave from the NCO 6 based on the phase error detected by the frequency characteristic compensation (waveform distortion and the like are eliminated) by the adaptive equalizer 3. In this way, the adaptive equalizer 3 is mounted in the carrier wave reproduction loop (first phase rotor 2, phase error detector 4, LPF5 and NCO6 loop), thereby compensating for the frequency characteristics. The phase noise of the input signal is canceled based on the phase error value estimated later.

次に、適応等化器3におけるタップ係数の更新方法について説明する。適応等化器3は、図3に示すように、入力信号の周波数特性を補償する適応等化部(等化器本体、フィルタ)31と、適応等化部31に対するタップ係数を更新するタップ更新部32と、を備える。 Next, a method of updating the tap coefficient in the adaptive equalizer 3 will be described. As shown in FIG. 3, the adaptive equalizer 3 includes an adaptive equalizer unit (equalizer body, filter) 31 that compensates for the frequency characteristics of the input signal, and a tap update that updates the tap coefficient for the adaptive equalizer unit 31. A unit 32 is provided.

タップ更新部32は、複素平面上に配置された理想点(基準信号)Rと適応等化部31の出力信号Sとの誤差に基づくアルゴリズム(判定指向アルゴリズム)で、適応等化部31に対するタップ係数を更新する(先のタップ係数を更新する)更新部である。すなわち、最小平均二乗誤差(MMSE:Minimum Mean Square Error)を規範とする判定指向アルゴリズムを利用して、出力信号Sと理想点Rとの誤差電力が最小になるようにタップ係数を算出、更新するものであり、判定指向アルゴリズムとして、LMS(Least Mean Square)アルゴリズムやRLS(Recursive Least Square)アルゴリズムが採用される。 The tap update unit 32 is an algorithm (determination-oriented algorithm) based on the error between the ideal point (reference signal) R arranged on the complex plane and the output signal S of the adaptive equalization unit 31, and is a tap for the adaptive equalization unit 31. It is an update unit that updates the coefficient (updates the previous tap coefficient). That is, the tap coefficient is calculated and updated so that the error power between the output signal S and the ideal point R is minimized by using a judgment-oriented algorithm based on the least mean squares error (MMSE: Minimum Mean Square Error). As a determination-oriented algorithm, an LMS (Least Mean Square) algorithm or an RLS (Recursive First Square) algorithm is adopted.

この際、平常時は、所定の等間隔で格子状に配置された理想点Rのなかから、単に適応等化部31の出力信号Sに最も近い理想点Rを選定し、この理想点Rと出力信号Sとの誤差に基づいてタップ係数を更新する。一方、適応等化部31の出力信号Sの位相雑音が所定状態よりも大きい場合、複素平面上の原点Cを中心にして適応等化部31の出力信号Sを回転させて、適応等化部31の出力信号Sに最も近い理想点Rを選定し、該選定した理想点Rと適応等化部31の出力信号Sとの誤差に基づいてタップ係数を更新する。 At this time, in normal times, the ideal point R closest to the output signal S of the adaptive equalization unit 31 is simply selected from the ideal points R arranged in a grid pattern at predetermined equal intervals, and this ideal point R is used. The tap coefficient is updated based on the error with the output signal S. On the other hand, when the phase noise of the output signal S of the adaptive equalization unit 31 is larger than the predetermined state, the output signal S of the adaptive equalization unit 31 is rotated around the origin C on the complex plane to rotate the adaptive equalization unit 31. The ideal point R closest to the output signal S of 31 is selected, and the tap coefficient is updated based on the error between the selected ideal point R and the output signal S of the adaptive equalization unit 31.

具体的には、まず、適応等化部31の出力信号Sの位相雑音が所定状態よりも大きいか否かを判定する。この実施の形態では、位相雑音が所定状態よりも大きいとは、位相雑音レベルが熱雑音レベルよりも大きい場合であり、C/N推定部321で推定するC/Nによって判断する。すなわち、図4に示すように、複素平面上の原点Cの周辺(領域C1内)においては位相雑音による位相回転の影響(回転移動量)が小さく、この領域C1内の出力信号Sを利用してC/Nを推定する。そして、C/Nが所定値以上の場合(熱雑音が小さい場合)には位相雑音が所定状態よりも大きいと判断し、C/Nが所定値よりも小さい場合(熱雑音が大きい場合)には位相雑音が所定状態よりも大きくないと判断する。 Specifically, first, it is determined whether or not the phase noise of the output signal S of the adaptive equalization unit 31 is larger than the predetermined state. In this embodiment, the phase noise is larger than the predetermined state when the phase noise level is larger than the thermal noise level, and it is determined by the C / N estimated by the C / N estimation unit 321. That is, as shown in FIG. 4, the influence of phase rotation (rotational movement amount) due to phase noise is small around the origin C on the complex plane (inside the region C1), and the output signal S in this region C1 is used. Estimate the C / N. Then, when the C / N is equal to or more than a predetermined value (when the thermal noise is small), it is determined that the phase noise is larger than the predetermined state, and when the C / N is smaller than the predetermined value (when the thermal noise is large). Determines that the phase noise is not greater than the predetermined state.

ここで、所定値は、C/Nによって位相雑音レベルが熱雑音レベルよりも大きいと判断できる値に設定されており、レベル差が1.5倍、2倍などになるように所定値を設定してもよい。そして、このようにして判断した判断結果、つまり、出力信号Sの位相雑音が所定状態よりも大きいか否かを切替スイッチ323に入力する。 Here, the predetermined value is set to a value at which the phase noise level can be determined to be larger than the thermal noise level by C / N, and the predetermined value is set so that the level difference becomes 1.5 times, 2 times, or the like. You may. Then, the determination result determined in this way, that is, whether or not the phase noise of the output signal S is larger than the predetermined state is input to the changeover switch 323.

次に、回転部322において、複素平面上の原点Cを中心にして適応等化部31の出力信号Sを回転させて、適応等化部31の出力信号Sに最も近い理想点Rを選定する。すなわち、図5に示すように、複素平面上の原点Cを中心に、時計回りおよび反時計回りに出力信号Sを回転させて、最も小さい回転角で出力信号Sが最接近する理想点Rを選定する。例えば、図5に示す第1の出力信号S1の場合、時計回りに回転させた際に最も小さい回転角で最接近する第1の理想点R1を選定する。 Next, in the rotating unit 322, the output signal S of the adaptive equalization unit 31 is rotated around the origin C on the complex plane, and the ideal point R closest to the output signal S of the adaptive equalization unit 31 is selected. .. That is, as shown in FIG. 5, the output signal S is rotated clockwise and counterclockwise around the origin C on the complex plane, and the ideal point R where the output signal S comes closest to is set at the smallest rotation angle. Select. For example, in the case of the first output signal S1 shown in FIG. 5, the first ideal point R1 that comes closest to the smallest rotation angle when rotated clockwise is selected.

このように、この実施の形態では、回転部322において出力信号Sを回転させて出力信号Sに最も近い理想点Rを選定しているが、次のようにしてもよい。すなわち、回転部322においては、各出力信号Sがそれぞれ理想点Rに最接近するのに要する回転方向と回転角を算出し、後述する判定部324においてこの回転角だけ出力信号Sを回転させて理想点を選定するようにしてもよい。 As described above, in this embodiment, the output signal S is rotated by the rotating unit 322 to select the ideal point R closest to the output signal S, but the following may be used. That is, the rotating unit 322 calculates the rotation direction and the rotation angle required for each output signal S to come closest to the ideal point R, and the determination unit 324, which will be described later, rotates the output signal S by this rotation angle. The ideal point may be selected.

一方、切替スイッチ323は、適応等化部31の出力信号Sと理想点Rをそのまま判定部324に入力するか、回転部322で選定した理想点Rと出力信号Sを判定部324に入力するかを切替自在になっている。すなわち、C/N推定部321による判断結果に基づいて、平常時は出力信号Sと理想点Rをそのまま判定部324に入力し、出力信号Sの位相雑音が所定状態よりも大きい場合には、回転部322で選定した理想点Rと出力信号Sを判定部324に入力する。 On the other hand, the changeover switch 323 inputs the output signal S and the ideal point R of the adaptive equalization unit 31 to the determination unit 324 as they are, or inputs the ideal point R and the output signal S selected by the rotation unit 322 to the determination unit 324. Can be switched freely. That is, based on the determination result by the C / N estimation unit 321, the output signal S and the ideal point R are directly input to the determination unit 324 in normal times, and when the phase noise of the output signal S is larger than the predetermined state, The ideal point R and the output signal S selected by the rotating unit 322 are input to the determination unit 324.

次に、判定部324は、入力された出力信号Sと理想点Rとのタップ更新用誤差に基づいてタップ係数を更新する。この結果、平常時つまり出力信号Sの位相雑音が小さい場合には、格子状に配置された理想点Rのなかで単に出力信号Sに最も近い理想点Rと、出力信号Sとの誤差に基づいてタップ係数を更新する。一方、出力信号Sの位相雑音が大きい場合には、回転部322によって出力信号Sを回転させて選定された理想点Rと、出力信号Sとの誤差に基づいてタップ係数を更新する。そして、このようにして更新したタップ係数を適応等化部31に入力する。 Next, the determination unit 324 updates the tap coefficient based on the tap update error between the input output signal S and the ideal point R. As a result, in normal times, that is, when the phase noise of the output signal S is small, it is based on the error between the ideal point R closest to the output signal S among the ideal points R arranged in a grid pattern and the output signal S. And update the tap coefficient. On the other hand, when the phase noise of the output signal S is large, the tap coefficient is updated based on the error between the ideal point R selected by rotating the output signal S by the rotating unit 322 and the output signal S. Then, the tap coefficient updated in this way is input to the adaptive equalization unit 31.

以上のように、この適応等化器3によれば、適応等化部31の出力信号Sの位相雑音が所定状態よりも大きい場合、複素平面上の原点Cを中心にして適応等化部31の出力信号Sを回転させて、適応等化部31の出力信号Sに最も近い理想点Rを選定する。つまり、位相雑音(位相ジッタ)が大きいときには、単に適応等化部31の出力信号Sに最も近い理想点Rを選定するのではなく、出力信号Sを回転させて対応する理想点Rを選定するため、正しい理想点Rを選定することが可能となる。例えば、図6に示すように、複素平面上の原点Cから遠く位相回転の影響が大きい領域においても、図9の場合とは異なり、正しい理想点Rを選定することができる。そして、この正しい理想点Rと適応等化部31の出力信号Sとのタップ更新用誤差に基づいてタップ係数を更新することで、適応等化器3から安定した出力を得ることが可能となる。この結果、高多値においても高精度かつ安定した復調性能・搬送波再生を実現することが可能となる。 As described above, according to the adaptive equalizer 3, when the phase noise of the output signal S of the adaptive equalizer 31 is larger than the predetermined state, the adaptive equalizer 31 is centered on the origin C on the complex plane. The output signal S of the above is rotated to select the ideal point R closest to the output signal S of the adaptive equalization unit 31. That is, when the phase noise (phase jitter) is large, the ideal point R closest to the output signal S of the adaptive equalization unit 31 is not simply selected, but the corresponding ideal point R is selected by rotating the output signal S. Therefore, it is possible to select the correct ideal point R. For example, as shown in FIG. 6, the correct ideal point R can be selected even in a region far from the origin C on the complex plane and greatly affected by the phase rotation, unlike the case of FIG. Then, by updating the tap coefficient based on the tap update error between the correct ideal point R and the output signal S of the adaptive equalizer unit 31, it is possible to obtain a stable output from the adaptive equalizer 3. .. As a result, it is possible to realize highly accurate and stable demodulation performance and carrier wave reproduction even at high multi-values.

また、この搬送波再生回路1によれば、適応等化器3で周波数特性が補償(波形歪等が解消)された位相回転信号の位相誤差に基づいて、位相回転制御信号が生成され入力信号の位相が回転されるため、フェージングによる波形歪がある場合でも、搬送波の位相ノイズを高精度に推定(位相誤差検出器4で検出)して高い復調性能・搬送波再生を実現することが可能となる。しかも、上記のように、安定した適応等化器出力が得られるため、より高精度かつ安定した復調性能・搬送波再生を実現することが可能となる。さらに、適応等化器3で位相回転信号の周波数特性が補償されるため、熱雑音の影響も軽減することが可能となる。 Further, according to the carrier wave reproduction circuit 1, a phase rotation control signal is generated based on the phase error of the phase rotation signal whose frequency characteristics are compensated (the waveform distortion and the like are eliminated) by the adaptive equalizer 3, and the input signal is used. Since the phase is rotated, even if there is waveform distortion due to fading, it is possible to estimate the phase noise of the carrier wave with high accuracy (detected by the phase error detector 4) and realize high demodulation performance and carrier wave reproduction. .. Moreover, as described above, since a stable adaptive equalizer output can be obtained, it is possible to realize more accurate and stable demodulation performance and carrier wave reproduction. Further, since the frequency characteristic of the phase rotation signal is compensated by the adaptive equalizer 3, the influence of thermal noise can be reduced.

以上、この発明の実施の形態について説明したが、具体的な構成は、上記の実施の形態に限られるものではなく、この発明の要旨を逸脱しない範囲の設計の変更等があっても、この発明に含まれる。例えば、上記の実施の形態では、予め常に回転部322において出力信号Sを回転させて理想点Rを選定しているが、C/N推定部321によって位相雑音が所定状態よりも大きいと判断された場合にのみ、回転部322で理想点Rを選定して判断部324に入力してもよい。 Although the embodiment of the present invention has been described above, the specific configuration is not limited to the above-described embodiment, and even if there is a design change or the like within a range that does not deviate from the gist of the present invention, this embodiment is described. Included in the invention. For example, in the above embodiment, the output signal S is always rotated in advance by the rotating unit 322 to select the ideal point R, but the C / N estimation unit 321 determines that the phase noise is larger than the predetermined state. Only in this case, the ideal point R may be selected by the rotating unit 322 and input to the determination unit 324.

1 搬送波再生回路
2 第1の位相回転器
3 適応等化器
31 適応等化部
32 タップ更新部
321 C/N推定部
322 回転部
323 切替スイッチ
324 判定部
4 位相誤差検出器
5 LPF
6 NCO(回転信号生成部)
7 第2の位相回転器
8 等化器
S 出力信号(信号点)
R 理想点
1 Carrier regenerative circuit 2 First phase rotator 3 Adaptation equalizer 31 Adaptation equalization unit 32 Tap update unit 321 C / N estimation unit 322 Rotation unit 323 Changeover switch 324 Judgment unit 4 Phase error detector 5 LPF
6 NCO (Rotation signal generator)
7 Second phase rotator 8 Equalizer S Output signal (signal point)
R ideal point

Claims (2)

入力信号の周波数特性を補償する適応等化部と、
複素平面上に配置された理想点と前記適応等化部の出力信号との誤差に基づくアルゴリズムで、前記適応等化部に対するタップ係数を更新するタップ更新部と、
を備え、前記タップ更新部は、前記適応等化部の出力信号の位相雑音が所定状態よりも大きい場合、前記複素平面上の原点を中心にして前記適応等化部の出力信号を回転させて、前記適応等化部の出力信号に最も近い前記理想点を選定し、該選定した理想点と前記適応等化部の出力信号との誤差に基づいて前記タップ係数を更新する、
ことを特徴とする適応等化器。
An adaptive equalization unit that compensates for the frequency characteristics of the input signal,
An algorithm based on the error between the ideal point arranged on the complex plane and the output signal of the adaptive equalization unit, the tap update unit that updates the tap coefficient for the adaptive equalization unit, and the tap update unit.
When the phase noise of the output signal of the adaptive equalization unit is larger than a predetermined state, the tap update unit rotates the output signal of the adaptive equalization unit around the origin on the complex plane. , The ideal point closest to the output signal of the adaptive equalization unit is selected, and the tap coefficient is updated based on the error between the selected ideal point and the output signal of the adaptive equalization unit.
An adaptive equalizer characterized by that.
入力信号の位相を回転する第1の位相回転器と、
前記第1の位相回転器によって位相が回転された入力信号である位相回転信号の周波数特性を補償する、請求項1に記載の適応等化器と、
前記適応等化器によって補償された位相回転信号に含まれる位相誤差を検出する位相誤差検出器と、
前記位相誤差に基づいて位相回転制御信号を生成する回転信号生成部と、
前記位相回転制御信号に基づいて前記入力信号の位相を回転する第2の位相回転器と、
を備え、前記第1の位相回転器は、前記位相回転制御信号に基づいて前記入力信号の位相を回転する、
ことを特徴とする搬送波再生回路。
A first phase rotator that rotates the phase of the input signal,
The adaptive equalizer according to claim 1, which compensates for the frequency characteristics of the phase rotation signal, which is an input signal whose phase is rotated by the first phase rotation device.
A phase error detector that detects the phase error included in the phase rotation signal compensated by the adaptive equalizer, and a phase error detector.
A rotation signal generator that generates a phase rotation control signal based on the phase error,
A second phase rotator that rotates the phase of the input signal based on the phase rotation control signal, and
The first phase rotator rotates the phase of the input signal based on the phase rotation control signal.
A carrier wave regenerative circuit characterized by that.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000138722A (en) 1998-08-27 2000-05-16 Matsushita Electric Ind Co Ltd Psk demodulator
JP2006074314A (en) 2004-09-01 2006-03-16 Japan Radio Co Ltd Pull-in method for blind adaptive equalizer and blind adaptive equalizer
JP2015115771A (en) 2013-12-11 2015-06-22 インターナショナル・ビジネス・マシーンズ・コーポレーションInternational Business Machines Corporation Receiver, communication system, circuit device, communication method and program (signal compensation in high-speed communication)

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CA2073944C (en) * 1991-07-26 2000-09-19 Woo H. Paik Carrier phase recovery for an adaptive equalizer

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000138722A (en) 1998-08-27 2000-05-16 Matsushita Electric Ind Co Ltd Psk demodulator
JP2006074314A (en) 2004-09-01 2006-03-16 Japan Radio Co Ltd Pull-in method for blind adaptive equalizer and blind adaptive equalizer
JP2015115771A (en) 2013-12-11 2015-06-22 インターナショナル・ビジネス・マシーンズ・コーポレーションInternational Business Machines Corporation Receiver, communication system, circuit device, communication method and program (signal compensation in high-speed communication)

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