JP2014179823A - Sync signal detector and method for detecting sync signal - Google Patents
Sync signal detector and method for detecting sync signal Download PDFInfo
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Abstract
Description
本発明は、同期信号検出装置、及び同期信号検出方法に関する。 The present invention relates to a synchronization signal detection device and a synchronization signal detection method.
一般的に、送信機と受信機との間で伝送されるデジタル無線通信においては、データをフレーム単位で送受信している。このとき、各フレームの所定位置には、特定の信号配列パターンを有する同期信号(同期ワード)が挿入されている。従って、受信機は、受信したデータから同期ワードを検出することによって同期を確立してフレーム内のデータを取得し、例えば音声信号などに復調して出力している。このとき、送信機と受信機との間で周波数オフセット（周波数偏差：Δｆ）が存在すると正しい同期ワードの位置を検出することができないので、様々な技術によって周波数オフセット（周波数偏差）の補正（Δｆ補正）が行われている。 In general, in digital wireless communication transmitted between a transmitter and a receiver, data is transmitted and received in frame units. At this time, a synchronization signal (synchronization word) having a specific signal arrangement pattern is inserted at a predetermined position of each frame. Therefore, the receiver establishes synchronization by detecting a synchronization word from the received data, acquires data in the frame, and demodulates and outputs, for example, an audio signal. At this time, if there is a frequency offset (frequency deviation: Δf) between the transmitter and the receiver, the correct sync word position cannot be detected. Therefore, correction of the frequency offset (frequency deviation) by various techniques (Δf) Correction) has been performed.
例えば、送受信機間で常に信号が流れている常送通信システムにおいては、受信器が同期ワードを取得する前に周波数推定に時間をかけることによって（すなわち、周波数を追尾することによって）Δｆ補正を行い、正しい同期ワードの取得を行っている。言い換えると、受信機は、受信したデータのフレームごとに、逐次、同期位置を推定しながらΔｆ補正を行い、正確な同期ワードの取得を行っている。また、送受信機間において通信時のみ信号が流れている非常送通信システムにおいては、送信機が同期ワードを送出する前にプリアンブル信号が送出される。従って、受信機側では、このプリアンブル信号を受信してΔｆ補正を行い、正しい同期ワードの取得を行っている。 For example, in a regular communication system in which a signal always flows between the transceivers, Δf correction is performed by taking time for frequency estimation (that is, by tracking the frequency) before the receiver acquires the synchronization word. To get the correct sync word. In other words, the receiver performs Δf correction while estimating the synchronization position for each frame of the received data, and acquires an accurate synchronization word. Further, in an emergency transmission communication system in which a signal flows only between the transmitter and the receiver, a preamble signal is transmitted before the transmitter transmits a synchronization word. Therefore, the receiver side receives this preamble signal, performs Δf correction, and acquires a correct synchronization word.
また、広域フィルタを使用することなく、周波数オフセットに起因するＤＣオフセット量を適正に補正して、受信すべき最初の同期信号を正確に検出する技術が開示されている（例えば、特許文献１参照）。この技術では、受信機側において、受信検波信号と既知のフレーム同期ワードとを相関処理して得られた相関値のピーク値を、予め定められた第１の閾値と比較している。そして、このピーク値が第１の閾値より大きい場合には、該当する受信検波信号の検波出力を同期ワードの候補とみなして、受信検波信号に含まれるＤＣオフセット量を算出している。そして、前記検波出力から、算出したＤＣオフセット量を減算して、同期ワードの補正信号を生成している。さらに、この同期ワードの補正信号と既知のフレーム同期ワードとのベクトル誤差を算出している。そして、このベクトル誤差を第２の閾値と比較し、ベクトル誤差が第２の閾値より小さいときに同期が確立したと判定している。 Further, a technique is disclosed in which the first synchronization signal to be received is accurately detected by appropriately correcting the DC offset amount due to the frequency offset without using a wide-area filter (see, for example, Patent Document 1). ). In this technique, the peak value of the correlation value obtained by correlating the received detection signal and the known frame synchronization word is compared with a predetermined first threshold value on the receiver side. When this peak value is larger than the first threshold value, the detection output of the corresponding reception detection signal is regarded as a synchronization word candidate, and the DC offset amount included in the reception detection signal is calculated. Then, the calculated DC offset amount is subtracted from the detection output to generate a synchronization word correction signal. Further, a vector error between the synchronization word correction signal and a known frame synchronization word is calculated. Then, this vector error is compared with the second threshold value, and it is determined that synchronization is established when the vector error is smaller than the second threshold value.
しかしながら、受信信号の同期ワード（シンボルデータ）と既知のフレーム同期ワードとの相関計算によって正確な同期ワードの位置をサーチする際、送信機側と受信機側との間で周波数オフセット（周波数偏差）が存在すると、受信機側で求められた同期ワードの相関値に誤差が発生する。その結果、受信機側では必要とする同期ワードの位置を正確に検出することができない。このため、従来技術では、周波数オフセット量を追尾しながら真の同期ワードの位置を検出してフレーム同期を確立したり、プリアンブル信号を用いてフレーム同期を確立したりしていたので、フレーム同期の確立を短時間かつ高精度に行うことができないなどの問題が生じていた。 However, when searching for the exact sync word position by calculating the correlation between the sync word (symbol data) of the received signal and the known frame sync word, the frequency offset (frequency deviation) between the transmitter side and the receiver side. Exists, an error occurs in the correlation value of the synchronization word obtained on the receiver side. As a result, the position of the required synchronization word cannot be accurately detected on the receiver side. For this reason, in the prior art, frame synchronization is established by detecting the position of the true synchronization word while tracking the frequency offset amount, or frame synchronization is established using a preamble signal. There has been a problem that establishment cannot be performed in a short time with high accuracy.
本発明は、このような事情に鑑みてなされたものであり、フレーム同期の確立を迅速かつ高精度に行うことができる同期信号検出装置、及び同期信号検出方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and an object of the present invention is to provide a synchronization signal detection apparatus and a synchronization signal detection method capable of quickly and accurately establishing frame synchronization.
上述の課題を解決するために、本発明の一態様に係る同期信号検出装置は、受信信号から抽出した受信検波信号と既知のフレーム同期ワードとの第１の相関値を算出する第１相関値算出部と、前記第１相関値算出部が算出した第１の相関値の極小値を検出するピーク検出部と、前記ピーク検出部が検出した極小値の時間軸上の位置において、前記受信検波信号と前記フレーム同期ワードとの周波数の誤差を周波数偏差として算出する周波数偏差算出部と、前記周波数偏差算出部が算出した周波数偏差に基づいて前記受信検波信号の周波数を補正する補正部と、補正後の受信検波信号と前記フレーム同期ワードとの第２の相関値を算出する第２相関値算出部と、前記第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に基づいて同期確立の判定を行う同期確立判定部と、を備えることを特徴としている。 In order to solve the above-described problem, a synchronization signal detection apparatus according to an aspect of the present invention calculates a first correlation value between a received detection signal extracted from a received signal and a known frame synchronization word. The reception detection at the position on the time axis of the minimum value detected by the calculation unit, the minimum value of the first correlation value calculated by the first correlation value calculation unit, and the minimum value detected by the peak detection unit A frequency deviation calculation unit that calculates a frequency error between a signal and the frame synchronization word as a frequency deviation, a correction unit that corrects the frequency of the received detection signal based on the frequency deviation calculated by the frequency deviation calculation unit, and a correction A second correlation value calculation unit that calculates a second correlation value between a later received detection signal and the frame synchronization word, and a comparison between the second correlation value calculated by the second correlation value calculation unit and a predetermined threshold value Based on results It is characterized by and a synchronization establishment determination section for determining synchronization establishment.
また、本発明の一態様に係る同期信号検出装置において、前記受信検波信号は４値ＦＳＫ信号であり、前記第１相関値算出部は、前記４値ＦＳＫ信号のシンボルデータの時間軸上の位置と前記既知のフレーム同期ワードの時間軸上の位置との相関値を前記第１の相関値として算出するようにしてもよい。 Further, in the synchronization signal detection device according to one aspect of the present invention, the received detection signal is a quaternary FSK signal, and the first correlation value calculation unit is a position on the time axis of the symbol data of the quaternary FSK signal. And the correlation value between the position of the known frame synchronization word on the time axis and the first correlation value may be calculated.
また、本発明の一態様に係る同期信号検出装置において、前記第１の相関値は、前記４値ＦＳＫ信号のシンボルデータの時間軸上の位置と前記既知のフレーム同期ワードの時間軸上の位置とのズレを示す誤差レベルであって、前記ピーク検出部は、前記誤差レベルの極小値を検出するようにしてもよい。 In the synchronization signal detection apparatus according to an aspect of the present invention, the first correlation value is a position on the time axis of the symbol data of the quaternary FSK signal and a position on the time axis of the known frame synchronization word. The peak detection unit may detect a minimum value of the error level.
また、本発明の一態様に係る同期信号検出装置において、前記周波数偏差に基づいて補正された４値ＦＳＫ信号のシンボルデータの硬判定処理を行う硬判定復調部をさらに備え、前記同期確立判定部は、前記第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に加えて、前記硬判定復調部で硬判定処理された前記４値ＦＳＫ信号のシンボルデータと前記既知のフレーム同期ワードとの比較結果を参照して、同期確立の判定を行うようにしてもよい。 The synchronization signal detection apparatus according to an aspect of the present invention may further include a hard decision demodulation unit that performs a hard decision process on the symbol data of the four-value FSK signal corrected based on the frequency deviation, and the synchronization establishment determination unit In addition to the comparison result between the second correlation value calculated by the second correlation value calculation unit and a predetermined threshold, the symbol data of the four-value FSK signal subjected to the hard decision processing by the hard decision demodulation unit, and the The synchronization establishment may be determined with reference to a comparison result with a known frame synchronization word.
上述の課題を解決するために、本発明の一態様に係る同期信号検出方法は、受信信号から抽出した受信検波信号と既知のフレーム同期ワードとの第１の相関値を算出する第１のステップと、前記第１のステップで算出された第１の相関値の極小値を検出する第２のステップと、前記第２のステップで検出された極小値の時間軸上の位置において、前記受信検波信号と前記フレーム同期ワードとの周波数偏差を算出する第３のステップと、前記第３のステップで算出された周波数偏差に基づいて前記受信検波信号の周波数を補正する第４のステップと、前記第４のステップで周波数が補正された補正後の受信検波信号と前記フレーム同期ワードとの第２の相関値を算出する第５のステップと、前記第５のステップで算出された第２の相関値と所定の閾値との比較結果に基づいて同期確立の判定を行う第６のステップと、を含むことを特徴としている。 In order to solve the above-described problem, a synchronization signal detection method according to an aspect of the present invention includes a first step of calculating a first correlation value between a received detection signal extracted from a received signal and a known frame synchronization word. A second step of detecting a minimum value of the first correlation value calculated in the first step, and the reception detection at a position on the time axis of the minimum value detected in the second step. A third step of calculating a frequency deviation between the signal and the frame synchronization word; a fourth step of correcting the frequency of the received detection signal based on the frequency deviation calculated in the third step; A fifth step of calculating a second correlation value between the received detection signal after correction whose frequency is corrected in step 4 and the frame synchronization word, and a second correlation value calculated in the fifth step And place It is characterized in that it comprises a sixth step of performing a comparison result to the judgment of the establishment of synchronization based with the threshold value, the.
本発明によれば、同期信号検出装置は、フレーム同期の確立を迅速かつ高精度に行うことができる。 According to the present invention, the synchronization signal detection apparatus can quickly and accurately establish frame synchronization.
［実施形態の概要］
本実施形態の同期信号検出装置は、まず、未加工の受信信号の同期ワード（シンボルデータ）と既知のフレーム同期ワードとの相関値（第１の相関値）を求め、この第１の相関値の極小値を検出（ピーク点検出）する。次に、同期信号検出装置は、この極小値（ピーク点）を仮のポイントとして、受信信号と既知のフレーム同期ワードとの周波数偏差（Δｆ）を推定する。そして、同期信号検出装置は、推定された周波数偏差（Δｆ）に基づいて求められた周波数偏差補正値（Δｆ補正値）によって受信信号の周波数を補正する。さらに、同期信号検出装置は、補正後の受信信号の同期ワードと既知のフレーム同期ワードとの相関値（第２の相関値）を求め、この第２の相関値が所定の閾値より小さくなったときに真の同期ワードを検出して同期が確立したと判定する。このようにして、同期信号検出装置は、周波数の追尾を行うことなく、受信信号の同期ワード（シンボルデータ）と既知のフレーム同期ワードとの２度の相関計算によって真の同期ワードを求めている。従って、同期信号検出装置は、フレーム同期の確立を短時間かつ高精度に行うことができる。
[Outline of Embodiment]
The synchronization signal detection apparatus according to the present embodiment first obtains a correlation value (first correlation value) between a synchronization word (symbol data) of a raw received signal and a known frame synchronization word, and this first correlation value. Is detected (peak point detection). Next, the synchronization signal detection apparatus estimates the frequency deviation (Δf) between the received signal and a known frame synchronization word using the minimum value (peak point) as a temporary point. Then, the synchronization signal detecting device corrects the frequency of the received signal with the frequency deviation correction value (Δf correction value) obtained based on the estimated frequency deviation (Δf). Further, the synchronization signal detecting device obtains a correlation value (second correlation value) between the corrected synchronization word of the received signal and the known frame synchronization word, and the second correlation value is smaller than a predetermined threshold value. Sometimes a true synchronization word is detected and it is determined that synchronization has been established. In this way, the synchronization signal detection device obtains the true synchronization word by performing the correlation calculation twice between the synchronization word (symbol data) of the received signal and the known frame synchronization word without tracking the frequency. . Therefore, the synchronization signal detection apparatus can establish frame synchronization in a short time and with high accuracy.
以下、本発明の具体的な実施形態について図面を参照しつつ詳細に説明する。なお、以下に述べる実施形態は本発明の理解を容易にするための一例であるので、本発明は、以下の実施形態の内容に限定されるものではない。 Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. In addition, since embodiment described below is an example for making an understanding of this invention easy, this invention is not limited to the content of the following embodiment.
図１は、本実施形態にかかるデジタル無線通信機の受信機１の概略構成を示すブロック図である。この受信機１は、一例として、受信信号を音声信号に変換して出力する構成で示されている。図１に示すように、受信機１は、アンテナ２、受信部３、復調部４、出力部５、及びスピーカ６を備えている。 FIG. 1 is a block diagram showing a schematic configuration of a receiver 1 of a digital wireless communication apparatus according to the present embodiment. As an example, the receiver 1 is configured to convert a received signal into an audio signal and output it. As shown in FIG. 1, the receiver 1 includes an antenna 2, a receiver 3, a demodulator 4, an output unit 5, and a speaker 6.
アンテナ２は、図示しない送信機から無線電波を受信する。
受信部３は、アンテナ２で受信された無線信号（受信信号）を、周知の濾波・増幅・混合等の処理を行い、処理後の信号を復調部４へ出力する。
復調部４は、受信部３から入力された受信信号を復調信号（音声信号）に復調する。このとき、復調部４では、周波数−電圧変換が行われるため、送信機と受信機との周波数誤差の関係で周波数オフセット（周波数偏差：Δｆ）に起因するＤＣオフセットが重畳する。
このような周波数偏差（Δｆ）に起因するＤＣオフセットが存在すると、受信信号の各フレームの所定位置に挿入されている同期ワードを検出するときに検出誤差が生じる。言い換えると、復調部４は、ＤＣオフセットが存在すると同期の確立を正確に行うことができない。そこで、復調部４では、受信信号の同期ワードと既知のフレーム同期ワードとの２度の相関計算によって真の同期ワードを求めて同期の確立を行っているが、この手法の詳細については後述する。
The antenna 2 receives radio waves from a transmitter (not shown).
The receiving unit 3 performs processes such as well-known filtering, amplification, and mixing on the radio signal (received signal) received by the antenna 2, and outputs the processed signal to the demodulating unit 4.
The demodulator 4 demodulates the received signal input from the receiver 3 into a demodulated signal (audio signal). At this time, since the demodulator 4 performs frequency-voltage conversion, a DC offset caused by the frequency offset (frequency deviation: Δf) is superimposed due to the frequency error between the transmitter and the receiver.
If a DC offset due to such a frequency deviation (Δf) exists, a detection error occurs when a synchronization word inserted at a predetermined position in each frame of the received signal is detected. In other words, the demodulation unit 4 cannot accurately establish synchronization when a DC offset exists. Therefore, the demodulator 4 establishes synchronization by obtaining a true synchronization word by calculating the correlation between the synchronization word of the received signal and the known frame synchronization word twice. Details of this method will be described later. .
出力部５は、復調部４で同期が確立されて出力された復調信号（音声信号）を入力し、この復調信号（音声信号）をデジタル／アナログ変換して増幅した後にスピーカ６へ出力する。
スピーカ６はアナログ変換された復調信号（音声信号）を音響化して音声として出力する。
The output unit 5 inputs the demodulated signal (sound signal) output after synchronization is established by the demodulating unit 4, amplifies the demodulated signal (sound signal) by digital / analog conversion, and outputs the amplified signal to the speaker 6.
The speaker 6 sonicates the analog-converted demodulated signal (sound signal) and outputs it as sound.
図２は、本実施形態に係る復調部４の詳細な構成を示すブロック図である。図２に示すように、復調部４は、Ｖ／Ｆ変換器１１、第１相間計算器１２、ピーク検出器１３、Δｆ検出器１４、減算器１５、第２相関計算器１６、閾値判定器１７、硬判定復調器１８、同期ワード検出器１９、同期確立判定器２０を備えている。 FIG. 2 is a block diagram showing a detailed configuration of the demodulator 4 according to the present embodiment. As shown in FIG. 2, the demodulator 4 includes a V / F converter 11, a first interphase calculator 12, a peak detector 13, a Δf detector 14, a subtractor 15, a second correlation calculator 16, and a threshold value determiner. 17, a hard decision demodulator 18, a synchronization word detector 19, and a synchronization establishment decision unit 20.
図１の受信部３から復調部４へ入力された受信信号は、図２に示すように、２４ｋサンプル／ｓｅｃでサンプリングされたＩＱ信号（変調信号）としてＶ／Ｆ変換器１１へ入力される。
Ｖ／Ｆ変換器１１は、２４ｋサンプル／ｓｅｃでサンプリングされたＩＱ信号を、シンボル周波数偏差間隔が狭い２４ｋサンプル／ｓｅｃの４値ＦＳＫ信号に変換して第１相間計算器１２へ入力する。
第１相間計算器１２は、２４ｋサンプル／ｓｅｃの４値ＦＳＫ信号（すなわち、受信信号のシンボルデータ）と既知のフレーム同期ワードとの周波数偏差（Δｆ）の相関計算を行って第１の相関値を求める。
As shown in FIG. 2, the received signal input from the receiving unit 3 to the demodulating unit 4 in FIG. 1 is input to the V / F converter 11 as an IQ signal (modulated signal) sampled at 24 ksample / sec. .
The V / F converter 11 converts the IQ signal sampled at 24 ksample / sec into a 4-value FSK signal of 24 ksample / sec with a narrow symbol frequency deviation interval, and inputs it to the first interphase calculator 12.
The first inter-phase calculator 12 performs a correlation calculation of the frequency deviation (Δf) between the quaternary FSK signal of 24 ksamples / sec (that is, the symbol data of the received signal) and the known frame synchronization word to obtain the first correlation value. Ask for.
ピーク検出器１３は、第１相間計算器１２により相関計算によって求められた第１の相関値に基づいて、受信信号のシンボル位置と既知のフレーム同期ワードの位置との誤差レベルの極小値（すなわち、ピーク点）を検出する。
Δｆ検出器１４は、ピーク検出器１３からのピーク点情報とＶ／Ｆ変換器１１からの２４ｋサンプル／ｓｅｃの４値ＦＳＫ信号とに基づいて、誤差レベルが極小値となる位置の周波数偏差Δｆの情報を減算器１５へ出力する。
減算器１５は、Ｖ／Ｆ変換器１１が送信した２４ｋサンプル／ｓｅｃの４値ＦＳＫ信号（すなわち、受信信号のシンボルデータ）から、誤差レベルが極小値となる位置の周波数偏差Δｆを減算して、補正後の受信信号（すなわち、周波数偏差補正値（Δｆ補正値）のデータ）を求める。
Based on the first correlation value obtained by the correlation calculation by the first interphase calculator 12, the peak detector 13 has a minimum value of the error level between the symbol position of the received signal and the position of the known frame synchronization word (that is, the peak detector 13). , Peak point).
The Δf detector 14 is based on the peak point information from the peak detector 13 and the 4-value FSK signal of 24 ksamples / sec from the V / F converter 11, and the frequency deviation Δf at the position where the error level becomes the minimum value. Is output to the subtractor 15.
The subtracter 15 subtracts the frequency deviation Δf at the position where the error level becomes the minimum value from the 24 ksample / sec 4-value FSK signal transmitted by the V / F converter 11 (that is, the symbol data of the received signal). Then, a corrected received signal (that is, data of a frequency deviation correction value (Δf correction value)) is obtained.
第２相関計算器１６は、演算対象サンプルとして決定されたピーク検出器１３からのピーク点情報と、減算器１５からの周波数偏差補正値（Δｆ補正値）のデータとに基づいて、補正後の受信信号のシンボルデータと既知のフレーム同期ワードとの相関計算を行い、補正後の受信信号シンボルデータの周波数と既知のフレーム同期ワードの周波数との相関値（第２の相関値）を求める。
閾値判定器１７は、第２相関計算器１６で求められた第２の相関値が所定の閾値を下回ったか否かを判定して、その判定結果を同期確立判定器２０へ送信する。
Based on the peak point information from the peak detector 13 determined as the calculation target sample and the data of the frequency deviation correction value (Δf correction value) from the subtractor 15, the second correlation calculator 16 A correlation calculation between the symbol data of the received signal and the known frame synchronization word is performed, and a correlation value (second correlation value) between the corrected frequency of the received signal symbol data and the frequency of the known frame synchronization word is obtained.
The threshold determination unit 17 determines whether or not the second correlation value obtained by the second correlation calculator 16 is below a predetermined threshold, and transmits the determination result to the synchronization establishment determination unit 20.
硬判定復調器１８は、演算対象サンプルとして決定されたピーク検出器１３からのピーク点情報と、減算器１５からの周波数偏差補正値（Δｆ補正値）のデータとに基づいて、Ｖ／Ｆ変換器１１から送信された４値ＦＳＫ信号（受信信号のシンボルデータ）の硬判定復調を行う。硬判定復調では、Ｖ／Ｆ変換器１１から送信された４値ＦＳＫ信号（受信信号のシンボルデータ）に対して、１つのビットごとに対応して所定の閾値で０，１判定を行う。
同期ワード検出器１９は、硬判定復調された４値ＦＳＫ信号（受信信号のシンボルデータ）と既知のフレーム同期ワードパターンのシンボルを比較判定し、その判定結果を同期確立判定器２０へ送信する。
The hard decision demodulator 18 performs V / F conversion based on the peak point information from the peak detector 13 determined as the calculation target sample and the data of the frequency deviation correction value (Δf correction value) from the subtractor 15. The hard decision demodulation of the quaternary FSK signal (symbol data of the received signal) transmitted from the device 11 is performed. In the hard decision demodulation, the quaternary FSK signal (symbol data of the received signal) transmitted from the V / F converter 11 is subjected to 0 or 1 decision with a predetermined threshold corresponding to each bit.
The synchronization word detector 19 compares and determines the quaternary FSK signal (symbol data of the received signal) subjected to hard decision demodulation and a symbol of a known frame synchronization word pattern, and transmits the determination result to the synchronization establishment determination unit 20.
同期確立判定器２０は、閾値判定器１７から送信された第２の相関値が閾値を下回ったか否かの判定結果と、同期ワード検出器１９から送信された硬判定復調後の４値ＦＳＫ信号（受信信号のシンボルデータ）と既知のフレーム同期ワードパターンのシンボル比較の判定結果とに基づいて、真の同期ワードを検出して同期の確立を行う。 The synchronization establishment determiner 20 determines whether or not the second correlation value transmitted from the threshold determiner 17 is below the threshold, and the quaternary FSK signal after hard decision demodulation transmitted from the synchronization word detector 19. Based on (symbol data of the received signal) and a determination result of symbol comparison of a known frame synchronization word pattern, a true synchronization word is detected and synchronization is established.
図３は、本実施形態に係る復調部４の内部回路を機能的に示すブロック図である。従って、図２を参照しながら、図３に示す復調部の内部回路の動作を説明する。なお、図３では、図２と同一構成要素については同一番号で示してある。図３において、受信信号である４値ＦＳＫ復調信号は、Ｖ／Ｆ変換器１１（図２参照）に記憶されている受信ワードパターン２１に基づいて受信ワード（受信信号の同期ワード）に変換され、第１相間計算器１２へ入力される。一方、同期ワードパターン２２に基づいて生成された既知のフレーム同期ワードも第１相間計算器１２へ入力される。 FIG. 3 is a block diagram functionally showing the internal circuit of the demodulator 4 according to the present embodiment. Therefore, the operation of the internal circuit of the demodulator shown in FIG. 3 will be described with reference to FIG. In FIG. 3, the same components as those in FIG. 2 are denoted by the same numbers. In FIG. 3, a 4-level FSK demodulated signal that is a received signal is converted into a received word (synchronized word of the received signal) based on the received word pattern 21 stored in the V / F converter 11 (see FIG. 2). , And input to the first interphase calculator 12. On the other hand, a known frame synchronization word generated based on the synchronization word pattern 22 is also input to the first interphase calculator 12.
これによって、第１相間計算器１２は、受信信号の同期ワードと既知のフレーム同期ワードとの相関計算を行って相関値（第１の相関値）を求め、この相関値（第１の相関値）をピーク検出器１３へ送信する。次に、ピーク検出器１３は、第１の相関値に基づいて、受信信号の同期ワードの位置と既知のフレーム同期ワードの位置との誤差が極小値となるピーク点を検出すると共に、ピーク点を検出した場合は実行フラグを立てる。 As a result, the first interphase calculator 12 calculates the correlation value (first correlation value) by calculating the correlation between the synchronization word of the received signal and the known frame synchronization word, and this correlation value (first correlation value). ) Is transmitted to the peak detector 13. Next, the peak detector 13 detects a peak point where the error between the position of the synchronization word of the received signal and the position of the known frame synchronization word is a minimum value based on the first correlation value, and the peak point If it is detected, an execution flag is set.
次に、Δｆ検出器１４（図２参照）に内蔵された減算器２３が、ピーク点における受信信号の同期ワードの周波数から既知のフレーム同期ワードの周波数を減算して、ピーク点における受信信号の同期ワードと既知のフレーム同期ワードとの周波数偏差Δｆに対応するＤＣオフセット量を求める。そして、減算器１５が、受信信号の同期ワードから周波数偏差Δｆ（ＤＣオフセット量）を減算して、補正ワードパターン（すなわち、Δｆ補正値で補正した補正後の受信信号の同期ワード）を求める。 Next, a subtracter 23 incorporated in the Δf detector 14 (see FIG. 2) subtracts the frequency of the known frame synchronization word from the frequency of the synchronization word of the reception signal at the peak point, and A DC offset amount corresponding to the frequency deviation Δf between the synchronization word and the known frame synchronization word is obtained. Then, the subtracter 15 subtracts the frequency deviation Δf (DC offset amount) from the synchronization word of the reception signal to obtain a correction word pattern (that is, the synchronization word of the reception signal after correction corrected with the Δf correction value).
さらに、第２相関計算器１６が、補正ワードパターン（補正後の受信信号の同期ワード）と既知のフレーム同期ワードとの相関計算を行い、補正後の受信信号の同期ワードと既知のフレーム同期ワードとの相関誤差（第２の相関値）を求める。そして、閾値判定器１７が、第２相関計算器１６で求められた第２の相関値が所定の閾値２４を下回ったか否かを判定し、判定結果を同期確立判定器２０へ送信する。 Further, the second correlation calculator 16 calculates the correlation between the corrected word pattern (corrected received signal synchronization word) and the known frame synchronization word, and the corrected received signal synchronization word and the known frame synchronization word. A correlation error (second correlation value) is obtained. Then, the threshold determination unit 17 determines whether or not the second correlation value obtained by the second correlation calculator 16 is below a predetermined threshold 24, and transmits the determination result to the synchronization establishment determination unit 20.
一方、硬判定復調器１８（図２参照）に内蔵されたシンボル硬判定器２５は、補正ワードパターン（補正後の受信信号の同期ワード）と既知のフレーム同期ワードとに基づいて、補正後の受信信号の同期ワードにおけるシンボルデータの硬判定を行い、硬判定されたシンボルデータと既知のフレーム同期ワードパターンとのシンボルを比較判定し、その判定結果を同期確立判定器２０へ送信する。 On the other hand, the symbol hard decision unit 25 incorporated in the hard decision demodulator 18 (see FIG. 2) is based on the corrected word pattern (the synchronization word of the received signal after correction) and the known frame synchronization word. The hard decision of the symbol data in the synchronization word of the received signal is performed, the symbol data of the hard decision is compared with the symbol of the known frame synchronization word pattern, and the determination result is transmitted to the synchronization establishment determiner 20.
同期確立判定器２０は、閾値判定器１７から送信された第２の相関値が閾値２４を下回ったか否かの判定結果と、シンボル硬判定器２５から送信された硬判定後の受信信号のシンボルデータと既知のフレーム同期ワードパターンとのシンボル比較の判定結果とに基づいて、真の同期ワードを検出して同期の確立を行う。すなわち、同期確立判定器２０は、第２の相関値が閾値２４を下回っていて、かつ、受信信号のシンボルデータと既知のフレーム同期ワードパターンのシンボルが一致したとき、真の同期ワードを検出して同期を確立する。 The synchronization establishment determiner 20 determines whether or not the second correlation value transmitted from the threshold determiner 17 is below the threshold 24 and the symbol of the received signal after the hard determination transmitted from the symbol hard determiner 25. Based on the determination result of the symbol comparison between the data and the known frame synchronization word pattern, a true synchronization word is detected and synchronization is established. That is, the synchronization establishment determination unit 20 detects a true synchronization word when the second correlation value is lower than the threshold 24 and the symbol data of the received signal matches the symbol of the known frame synchronization word pattern. Establish synchronization.
図４は、本実施形態に係る復調部４が同期検出を行うときの処理の流れを示すフローチャートである。なお、図４の各処理を示すステップ番号は図３にも対応して示されている。さらに理解を容易にするために、図４の各処理を示すステップ番号は図２にも対応して示されている。以下、図３に示すステップ番号を参照しながら（必要に応じて図２に示すステップ番号も参照しながら）、図４のフローチャートの流れに従って復調部が同期検出を行うときの処理の流れを説明する。 FIG. 4 is a flowchart showing a flow of processing when the demodulator 4 according to the present embodiment performs synchronization detection. Note that step numbers indicating the respective processes in FIG. 4 are also shown in FIG. For easier understanding, the step numbers indicating the processes in FIG. 4 are also shown in FIG. Hereinafter, referring to the step numbers shown in FIG. 3 (also referring to the step numbers shown in FIG. 2 if necessary), the flow of processing when the demodulator performs synchronization detection according to the flow of the flowchart of FIG. 4 will be described. To do.
（ステップＳ１）第１相間計算器１２が、受信信号の同期ワードと既知のフレーム同期ワードとの相関計算を行う。
（ステップＳ２）ピーク検出器１３は、相関計算された第１の相関値に基づいて、受信信号の同期ワードの位置と既知のフレーム同期ワードの位置との誤差が極小値となるピーク点を検出したか否かを判定する。この処理（ステップＳ１、Ｓ２の処理）は、受信信号の１つのシンボルが実行されるごとに行われる。ピーク検出器１３は、受信信号の同期ワードの位置と既知のフレーム同期ワードの位置との誤差が極小値となるピーク点を検出したと判定した場合（ステップＳ２；Ｙｅｓ）、ステップＳ３に進み、受信信号の同期ワードの位置と既知のフレーム同期ワードの位置との誤差が極小値となるピーク点を検出していない判定した場合（ステップＳ２；Ｎｏ）、ステップＳ１に戻る。
(Step S1) The first interphase calculator 12 performs a correlation calculation between the synchronization word of the received signal and the known frame synchronization word.
(Step S2) The peak detector 13 detects a peak point at which the error between the position of the synchronization word of the received signal and the position of the known frame synchronization word is a minimum value based on the first correlation value calculated for correlation. Determine whether or not. This process (the processes of steps S1 and S2) is performed every time one symbol of the received signal is executed. When the peak detector 13 determines that the peak point at which the error between the position of the synchronization word of the received signal and the position of the known frame synchronization word is a minimum value (step S2; Yes), the process proceeds to step S3. When it is determined that the peak point where the error between the position of the synchronization word of the received signal and the position of the known frame synchronization word is a minimum value is not detected (step S2; No), the process returns to step S1.
（ステップＳ３）ステップＳ２の判定でピーク点が検出された場合、減算器２３は、ピーク点における受信信号の同期ワードの周波数から既知のフレーム同期ワードの周波数を減算して、ピーク点における受信信号の同期ワードと既知のフレーム同期ワードとの周波数偏差Δｆ（すなわち、ＤＣオフセット）を求める。
（ステップＳ４）減算器１５が、受信信号の同期ワードから周波数偏差Δｆを減算して、Δｆ補正後の受信信号の同期ワード（補正ワードパターン）を求める。
(Step S3) When the peak point is detected in the determination of step S2, the subtracter 23 subtracts the frequency of the known frame synchronization word from the frequency of the synchronization word of the reception signal at the peak point, and receives the received signal at the peak point. The frequency deviation Δf (that is, DC offset) between the synchronization word and the known frame synchronization word is obtained.
(Step S4) The subtractor 15 subtracts the frequency deviation Δf from the synchronization word of the reception signal to obtain the synchronization word (correction word pattern) of the reception signal after Δf correction.
（ステップＳ５）第２相関計算器１６が、補正後の受信信号の同期ワード（補正ワードパターン）と既知のフレーム同期ワードとの相関計算を行い、補正後の受信信号の同期ワードと既知のフレーム同期ワードとの相関誤差（第２の相関値）を求める。そして、閾値判定器１７は、第２の相関値が所定の閾値２４を下回ったか否かを判定する（ステップＳ６）。閾値判定器１７は、第２の相関値が所定の閾値２４を下回ったと判定した場合（ステップＳ６；Ｙｅｓ）、ステップＳ７に進み、第２の相関値が所定の閾値２４を下回っていないと判定した場合（ステップＳ６；Ｎｏ）、ステップＳ１に戻る。 (Step S5) The second correlation calculator 16 calculates the correlation between the corrected received signal synchronization word (corrected word pattern) and the known frame synchronization word, and the corrected received signal synchronization word and the known frame. A correlation error (second correlation value) with the synchronization word is obtained. Then, the threshold determination unit 17 determines whether or not the second correlation value is below a predetermined threshold 24 (step S6). If the threshold determination unit 17 determines that the second correlation value has fallen below the predetermined threshold 24 (step S6; Yes), the threshold determination unit 17 proceeds to step S7 and determines that the second correlation value has not fallen below the predetermined threshold 24. If so (step S6; No), the process returns to step S1.
（ステップＳ７）硬判定復調器１８（図２参照）に内蔵されたシンボル硬判定器２５は、補正後の受信信号の同期ワード（補正ワードパターン）のシンボルと既知のフレーム同期ワードのシンボルとを比較（シンボル比較）して、補正後の受信信号の同期ワードにおけるシンボルデータの硬判定を行う。 (Step S7) The hard symbol demodulator 25 incorporated in the hard decision demodulator 18 (see FIG. 2) obtains the symbol of the synchronization word (correction word pattern) of the received signal after correction and the symbol of the known frame synchronization word. Comparison (symbol comparison) is performed to make a hard decision on the symbol data in the synchronization word of the received signal after correction.
（ステップＳ８）同期確立判定器２０は、第２の相関値が所定の閾値２４を下回ったとき、硬判定された受信信号のシンボルデータと既知のフレーム同期ワードパターンとのシンボル比較の判定結果とに基づいて、真の同期ワードを検出したか否かを判定する（ステップＳ８）。同期確立判定器２０は、真の同期ワードを検出したと判定した場合（ステップＳ８；Ｙｅｓ）、ステップＳ９に進み、真の同期ワードを検出していないと判定した場合（ステップＳ８；Ｎｏ）、ステップＳ１に戻る。
（ステップＳ９）同期確立判定器２０は、受信信号の同期を確立する。
以上で、同期検出の処理を終了する。
(Step S8) When the second correlation value falls below a predetermined threshold value 24, the synchronization establishment determination unit 20 determines the symbol comparison determination result between the symbol data of the received signal subjected to the hard determination and the known frame synchronization word pattern. Based on the above, it is determined whether or not a true synchronization word has been detected (step S8). When the synchronization establishment determination unit 20 determines that a true synchronization word is detected (step S8; Yes), the process proceeds to step S9, and when it is determined that a true synchronization word is not detected (step S8; No). Return to step S1.
(Step S9) The synchronization establishment determination unit 20 establishes synchronization of the received signal.
This completes the synchronization detection process.
図５は、受信信号のシンボルと既知のフレーム同期ワードとの１スロット分の相関値を示す実測波形である。図５（ａ）は周波数偏差が０Ｈｚのときの実測波形であり、図５（ｂ）は周波数偏差が６００Ｈｚのときの実測波形である。図５（ａ）および図５（ｂ）において、横軸は時間、縦軸は受信信号のシンボルと既知のフレーム同期ワードとの周波数偏差との誤差レベルを表す。 FIG. 5 is an actual measurement waveform showing a correlation value for one slot between a symbol of a received signal and a known frame synchronization word. FIG. 5A shows an actual measurement waveform when the frequency deviation is 0 Hz, and FIG. 5B shows an actual measurement waveform when the frequency deviation is 600 Hz. 5A and 5B, the horizontal axis represents time, and the vertical axis represents the error level between the symbol of the received signal and the frequency deviation between the known frame synchronization words.
図５（ａ）に示すように、受信信号のシンボルと既知のフレーム同期ワードとの周波数偏差がゼロのときは、同期ワード検出位置（ＳＷ位置）における受信信号のシンボルと既知のフレーム同期ワードとの誤差レベルはゼロになっている。すなわち、周波数オフセット（周波数偏差）が存在していないために、正しい同期ワードの位置を検出することができる。 As shown in FIG. 5A, when the frequency deviation between the received signal symbol and the known frame synchronization word is zero, the received signal symbol and the known frame synchronization word at the synchronization word detection position (SW position) The error level is zero. That is, since there is no frequency offset (frequency deviation), the correct sync word position can be detected.
一方、図５（ｂ）に示すように、受信信号のシンボルと既知のフレーム同期ワードとの周波数偏差が６００Ｈｚのときは、同期ワード検出位置（ＳＷ位置）における受信信号のシンボルと既知のフレーム同期ワードとの誤差レベルはゼロではない。すなわち、周波数オフセット（周波数偏差）が存在しているために、正しい同期ワードの位置を検出することができない。 On the other hand, as shown in FIG. 5B, when the frequency deviation between the received signal symbol and the known frame synchronization word is 600 Hz, the received signal symbol and the known frame synchronization at the synchronization word detection position (SW position). The error level with the word is not zero. That is, since there is a frequency offset (frequency deviation), it is not possible to detect the correct sync word position.
従って、本実施形態では、前述したように、受信信号のシンボルと既知のフレーム同期ワードとの誤差レベルが極小値となったピーク点を同期ワード検出位置（ＳＷ位置）として周波数偏差（Δｆ）を推定している。そして、推定された周波数偏差（Δｆ）に基づいて受信信号のシンボル補正を行い、シンボル補正した受信信号と既知のフレーム同期ワードとの相関値が所定の閾値以下になったときに受信信号の真の同期ワードを検出して同期の確立を行っている。これによって、周波数偏差の有無に関わらず、受信信号の同期確立を短時間かつ高精度に行うことができる。 Therefore, in the present embodiment, as described above, the frequency deviation (Δf) is determined by setting the peak point where the error level between the symbol of the received signal and the known frame synchronization word is a minimum value as the synchronization word detection position (SW position). Estimated. Then, symbol correction of the received signal is performed based on the estimated frequency deviation (Δf), and when the correlation value between the symbol-corrected received signal and a known frame synchronization word becomes a predetermined threshold value or less, The synchronization word is detected and synchronization is established. This makes it possible to establish synchronization of the received signal in a short time and with high accuracy regardless of the presence or absence of a frequency deviation.
なお、周波数偏差がゼロのときは同期ワード検出位置（ＳＷ位置）における受信信号のシンボルと既知のフレーム同期ワードとの誤差レベルがゼロであり、周波数偏差が６００Ｈｚのときは誤差レベルがゼロとならない理由は次の通りである。 When the frequency deviation is zero, the error level between the received signal symbol and the known frame synchronization word at the synchronization word detection position (SW position) is zero, and when the frequency deviation is 600 Hz, the error level does not become zero. The reason is as follows.
周波数偏差がゼロのとき、受信信号の周波数をＡ、既知のフレーム同期ワードの周波数をＢ、受信信号のシンボル数を１０とすると、誤差レベルδは、δ＝Σ（Ａ−Ｂ）２／１０で表わされる。ここで、周波数偏差がゼロのときはＡ＝Ｂであるので、誤差レベルδ＝０となる。 When the frequency deviation is zero, the frequency of the received signal A, B frequencies known frame sync word, and the number of symbols of the received signal and 10, the error level δ, δ = Σ (A- B) 2/10 It is represented by Here, when the frequency deviation is zero, since A = B, the error level δ = 0.
一方、周波数偏差が６００Ｈｚのときは、受信信号の周波数をＡ１（＝Ａ＋６００）、既知のフレーム同期ワードの周波数をＢ、受信信号のシンボル数を１０とすると、誤差レベルδ１は、δ１＝Σ（Ａ１−Ｂ）２／１０＝Σ（Ａ−Ｂ＋６００）２／１０で表わされる。従って、周波数偏差が６００ＨｚのときはＡ＝Ｂであっても、誤差レベルδ１はゼロより大きくなる。 On the other hand, when the frequency deviation is 600 Hz, assuming that the frequency of the received signal is A1 (= A + 600), the frequency of the known frame synchronization word is B, and the number of symbols of the received signal is 10, the error level δ1 is δ1 = Σ ( A1-B) is represented by 2/10 = Σ (A- B + 600) 2/10. Therefore, when the frequency deviation is 600 Hz, even if A = B, the error level δ1 is greater than zero.
［比較例］
ここで、本実施形態の優位性を示すために、同期ワードを検出して同期の確立を行う比較例における技術の一例について説明する。比較例では、最初に受信信号の周波数と既知のフレーム同期ワードの周波数との周波数偏差（Δｆ）を算出し、受信信号の周波数から周波数偏差（Δｆ）を減算して補正後の受信信号を求める。次に、比較例では、補正後の受信信号と既知のフレーム同期ワードとの相関計算を行い、相関計算で求めた相関値が所定の閾値より小さいか否かを判定する。比較例では、相関計算で求めた相関値が所定の閾値より小さい場合、補正後の受信信号と既知のフレーム同期ワードとに基づいて、補正後の受信信号のシンボルデータの硬判定を行っている。そして、比較例では、硬判定された受信信号のシンボルデータと既知のフレーム同期ワードパターンとのシンボル比較の判定結果に基づいて、真の同期ワードを検出する。
[Comparative example]
Here, in order to show the superiority of this embodiment, an example of a technique in a comparative example in which synchronization word is detected and synchronization is established will be described. In the comparative example, first, the frequency deviation (Δf) between the frequency of the received signal and the frequency of the known frame synchronization word is calculated, and the corrected received signal is obtained by subtracting the frequency deviation (Δf) from the frequency of the received signal. . Next, in the comparative example, the correlation calculation between the corrected received signal and the known frame synchronization word is performed, and it is determined whether or not the correlation value obtained by the correlation calculation is smaller than a predetermined threshold value. In the comparative example, when the correlation value obtained by the correlation calculation is smaller than a predetermined threshold, the hard decision is performed on the symbol data of the corrected received signal based on the corrected received signal and the known frame synchronization word. . In the comparative example, the true synchronization word is detected based on the determination result of the symbol comparison between the symbol data of the received signal subjected to the hard decision and the known frame synchronization word pattern.
すなわち、この比較例の場合は、周波数偏差（Δｆ）の推定を受信信号のフレームごとに逐次行っているため、受信信号の同期ワードが推定できた場合でも、次のフレームで、再度、周波数偏差（Δｆ）を算出して推定し直さなければならない。一方、本実施形態の場合は、受信信号のシンボル位置と既知のフレーム同期ワードの位置との誤差レベルの極小値（ピーク点）で推定された周波数偏差（Δｆ）は精度が高いため、図４の処理フローのループ内で算出された最新の周波数偏差（Δｆ）を、再計算することなくそのまま使用して、真の同期ワードを検出することができる。そのため、受信信号の同期確立を迅速かつ高精度に行うことができると共に、受信信号の同期引き込みが速くなる。 That is, in the case of this comparative example, the frequency deviation (Δf) is estimated for each frame of the received signal, so even if the synchronization word of the received signal can be estimated, the frequency deviation is again detected in the next frame. (Δf) must be calculated and re-estimated. On the other hand, in the case of the present embodiment, the frequency deviation (Δf) estimated by the minimum value (peak point) of the error level between the symbol position of the received signal and the position of the known frame synchronization word is highly accurate. The latest frequency deviation (Δf) calculated in the loop of the process flow can be used as it is without recalculation to detect a true synchronization word. As a result, the synchronization of the received signal can be established quickly and with high accuracy, and the synchronization of the received signal is accelerated.
以上のように、本実施形態に係る同期信号検出装置（復調部４）は、受信信号から抽出した受信検波信号と既知のフレーム同期ワードとの第１の相関値を算出する第１相関値算出部と、第１相関値算出部（第１相間計算器１２）が算出した第１の相関値の極小値を検出するピーク検出部（ピーク検出器１３）と、ピーク検出部が検出した極小値の時間軸上の位置において、受信検波信号とフレーム同期ワードとの周波数の誤差を周波数偏差として算出する周波数偏差算出部（Δｆ検出器１４）と、周波数偏差算出部が算出した周波数偏差に基づいて受信検波信号の周波数を補正する補正部（減算器１５）と、補正後の受信検波信号とフレーム同期ワードとの第２の相関値を算出する第２相関値算出部（第２相関計算器１６）と、第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に基づいて同期確立の判定を行う同期確立判定部（同期確立判定器２０）と、を備える。 As described above, the synchronization signal detection apparatus (demodulation unit 4) according to the present embodiment calculates the first correlation value for calculating the first correlation value between the received detection signal extracted from the received signal and the known frame synchronization word. , A peak detection unit (peak detector 13) for detecting a minimum value of the first correlation value calculated by the first correlation value calculation unit (first interphase calculator 12), and a minimum value detected by the peak detection unit Based on the frequency deviation calculated by the frequency deviation calculator and the frequency deviation calculator (Δf detector 14) that calculates the frequency error of the received detection signal and the frame synchronization word as a frequency deviation at the position on the time axis. A correction unit (subtractor 15) that corrects the frequency of the received detection signal, and a second correlation value calculation unit (second correlation calculator 16) that calculates a second correlation value between the corrected reception detection signal and the frame synchronization word. ) And second correlation value calculation Comprising synchronization establishment determination section which part is based on a comparison result between the second correlation value with a predetermined threshold calculated and determines synchronization establishment (the synchronization establishment determination unit 20), the.
また、本実施形態に係る同期信号検出装置（復調部４）は、周波数偏差に基づいて補正された４値ＦＳＫ信号のシンボルデータの硬判定処理を行う硬判定復調部（硬判定復調器１８）をさらに備え、同期確立判定部は、第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に加えて、硬判定復調部で硬判定処理された４値ＦＳＫ信号のシンボルデータと既知のフレーム同期ワードとの比較結果を参照して、同期確立の判定を行う。 Further, the synchronization signal detection apparatus (demodulation unit 4) according to the present embodiment performs a hard decision demodulation unit (hard decision demodulator 18) that performs a hard decision process on the symbol data of the quaternary FSK signal corrected based on the frequency deviation. The synchronization establishment determination unit includes a 4-value FSK signal subjected to hard decision processing by the hard decision demodulation unit in addition to a comparison result between the second correlation value calculated by the second correlation value calculation unit and a predetermined threshold value. The synchronization establishment is determined with reference to a comparison result between the symbol data of the first frame and the known frame synchronization word.
このような構成により、本実施形態では、受信機側が、既知のフレーム同期ワードの位置と未加工の受信信号の同期ワード（シンボルデータ）の位置との誤差の極小値を用いて、周波数オフセット（周波数偏差：Δｆ）を推定している。そして、推定した周波数偏差（Δｆ）に基づいて求められた周波数偏差の補正値（Δｆ補正値）で補正された受信信号の同期ワード（シンボルデータ）と既知のフレーム同期ワードとの相関値が所定の閾値を下回ったとき、真の同期ワードを検出して同期の確立を行っている。従って、受信機は、真の同期ワードを取得するときの周波数追尾に時間がかからない。すなわち、受信機は、周波数追尾の追い込みを行う必要がないので、送受信機間において通信時のみ信号が流れる非常送信号の１フレーム目から同期の確立を行うことができる。また、受信機は、受信信号の同期ワードと既知のフレーム同期ワードとの相関計算を２回行っているので、フレーム同期を高精度に確立させることができる。言い換えると、受信機はフレーム同期の確立を短時間かつ高精度に行うことができる。 With this configuration, in the present embodiment, the receiver side uses the minimum value of the error between the position of the known frame synchronization word and the position of the synchronization word (symbol data) of the raw received signal to generate a frequency offset ( Frequency deviation: Δf) is estimated. A correlation value between a synchronization word (symbol data) of a received signal corrected with a correction value (Δf correction value) of a frequency deviation obtained based on the estimated frequency deviation (Δf) and a known frame synchronization word is predetermined. When the value falls below the threshold value, a true synchronization word is detected to establish synchronization. Therefore, the receiver does not take time to track the frequency when acquiring the true synchronization word. That is, since the receiver does not need to perform frequency tracking, synchronization can be established from the first frame of the emergency transmission signal in which a signal flows only between the transmitter and the receiver. In addition, since the receiver performs the correlation calculation between the synchronization word of the received signal and the known frame synchronization word twice, frame synchronization can be established with high accuracy. In other words, the receiver can establish frame synchronization in a short time and with high accuracy.
さらに、受信機は、同期ワードを検出の対象としているので、データの冒頭にプリアンブルがない場合でも、周波数オフセット（周波数偏差：Δｆ）を推定して同期の確立を行うことができる。例えば、通信中の無線通信システムに途中から電源を入れて後から参入した受信機であっても、受信したデータの１フレーム目から、既知のフレーム同期ワードの位置と未加工の受信信号の同期ワード（シンボルデータ）の位置との誤差の極小値に基づいて周波数偏差（Δｆ）を推定し、周波数偏差補正値（Δｆ補正値）で補正された受信信号と既知のフレーム同期ワードとの相関値から、高精度に同期の確立を行うことができる。 Furthermore, since the receiver uses the synchronization word as a detection target, even if there is no preamble at the beginning of the data, the receiver can estimate the frequency offset (frequency deviation: Δf) and establish synchronization. For example, even in a receiver that has entered the wireless communication system during communication and entered later, synchronization of the position of the known frame synchronization word and the raw received signal from the first frame of the received data The frequency deviation (Δf) is estimated based on the minimum value of the error from the position of the word (symbol data), and the correlation value between the received signal corrected with the frequency deviation correction value (Δf correction value) and the known frame synchronization word Therefore, synchronization can be established with high accuracy.
なお、同期信号検出装置（復調部４）の全部または一部の機能を実現するためのプログラムをコンピュータ読み取り可能な記録媒体に記録して、この記録媒体に記録されたプログラムをコンピュータシステムに読み込ませ、実行することにより各部の処理を行ってもよい。なお、ここでいう「コンピュータシステム」とは、ＯＳや周辺機器等のハードウェアを含むものとする。
また、「コンピュータシステム」は、ＷＷＷシステムを利用している場合であれば、ホームページ提供環境（あるいは表示環境）も含むものとする。
また、「コンピュータ読み取り可能な記録媒体」とは、フレキシブルディスク、光磁気ディスク、ＲＯＭ、ＣＤ−ＲＯＭ等の可搬媒体、コンピュータシステムに内蔵されるハードディスク等の記憶装置のことをいう。さらに「コンピュータ読み取り可能な記録媒体」とは、インターネット等のネットワークや電話回線等の通信回線を介してプログラムを送信する場合の通信線のように、短時間の間、動的にプログラムを保持するもの、その場合のサーバやクライアントとなるコンピュータシステム内部の揮発性メモリのように、一定時間プログラムを保持しているものも含むものとする。また上記プログラムは、前述した機能の一部を実現するためのものであっても良く、さらに前述した機能をコンピュータシステムにすでに記録されているプログラムとの組み合わせで実現できるものであっても良い。
A program for realizing all or part of the functions of the synchronization signal detection device (demodulation unit 4) is recorded on a computer-readable recording medium, and the program recorded on the recording medium is read into a computer system. The processing of each unit may be performed by executing. Here, the “computer system” includes an OS and hardware such as peripheral devices.
Further, the “computer system” includes a homepage providing environment (or display environment) if a WWW system is used.
The “computer-readable recording medium” refers to a storage device such as a flexible medium, a magneto-optical disk, a portable medium such as a ROM and a CD-ROM, and a hard disk incorporated in a computer system. Furthermore, the “computer-readable recording medium” dynamically holds a program for a short time like a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line. In this case, a volatile memory in a computer system serving as a server or a client in that case, and a program that holds a program for a certain period of time are also included. The program may be a program for realizing a part of the functions described above, and may be a program capable of realizing the functions described above in combination with a program already recorded in a computer system.
１…受信機、２…アンテナ、３…受信部、４…復調部、５…出力部、６…スピーカ、１１…Ｖ／Ｆ変換器、１２…第１相間計算器、１３…ピーク検出器、１４…Δｆ検出器、１５…減算器、１６…第２相関計算器、１７…閾値判定器、１８…硬判定復調器、１９…同期ワード検出器、２０…同期確立判定器、２１…受信ワードパターン、２２…同期ワードパターン、２３…減算器、２４…閾値、２５…シンボル硬判定器 DESCRIPTION OF SYMBOLS 1 ... Receiver, 2 ... Antenna, 3 ... Reception part, 4 ... Demodulation part, 5 ... Output part, 6 ... Speaker, 11 ... V / F converter, 12 ... First interphase calculator, 13 ... Peak detector, DESCRIPTION OF SYMBOLS 14 ... (DELTA) f detector, 15 ... Subtractor, 16 ... 2nd correlation calculator, 17 ... Threshold determination device, 18 ... Hard decision demodulator, 19 ... Synchronization word detector, 20 ... Synchronization establishment determination device, 21 ... Reception word Pattern, 22 ... Synchronized word pattern, 23 ... Subtractor, 24 ... Threshold, 25 ... Symbol hard decision unit
Claims (5)
前記第１相関値算出部が算出した第１の相関値の極小値を検出するピーク検出部と、
前記ピーク検出部が検出した極小値の時間軸上の位置において、前記受信検波信号と前記フレーム同期ワードとの周波数の誤差を周波数偏差として算出する周波数偏差算出部と、
前記周波数偏差算出部が算出した周波数偏差に基づいて前記受信検波信号の周波数を補正する補正部と、
補正後の受信検波信号と前記フレーム同期ワードとの第２の相関値を算出する第２相関値算出部と、
前記第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に基づいて同期確立の判定を行う同期確立判定部と、
を備えることを特徴とする同期信号検出装置。 A first correlation value calculation unit for calculating a first correlation value between a received detection signal extracted from the received signal and a known frame synchronization word;
A peak detector that detects a minimum value of the first correlation value calculated by the first correlation value calculator;
A frequency deviation calculation unit that calculates an error in frequency between the received detection signal and the frame synchronization word as a frequency deviation at a position on the time axis of the minimum value detected by the peak detection unit;
A correction unit that corrects the frequency of the received detection signal based on the frequency deviation calculated by the frequency deviation calculation unit;
A second correlation value calculation unit for calculating a second correlation value between the received detection signal after correction and the frame synchronization word;
A synchronization establishment determination unit configured to determine synchronization establishment based on a comparison result between the second correlation value calculated by the second correlation value calculation unit and a predetermined threshold;
A synchronization signal detection apparatus comprising:
前記第１相関値算出部は、前記４値ＦＳＫ信号のシンボルデータの時間軸上の位置と前記既知のフレーム同期ワードの時間軸上の位置との相関値を前記第１の相関値として算出する
ことを特徴とする請求項１に記載の同期信号検出装置。 The received detection signal is a quaternary FSK signal,
The first correlation value calculation unit calculates a correlation value between the position on the time axis of the symbol data of the quaternary FSK signal and the position on the time axis of the known frame synchronization word as the first correlation value. The synchronization signal detecting apparatus according to claim 1, wherein:
前記ピーク検出部は、前記誤差レベルの極小値を検出する
ことを特徴とする請求項２に記載の同期信号検出装置。 The first correlation value is an error level indicating a deviation between a position on the time axis of the symbol data of the quaternary FSK signal and a position on the time axis of the known frame synchronization word,
The synchronization signal detection apparatus according to claim 2, wherein the peak detection unit detects a minimum value of the error level.
前記同期確立判定部は、前記第２相関値算出部が算出した第２の相関値と所定の閾値との比較結果に加えて、前記硬判定復調部で硬判定処理された前記４値ＦＳＫ信号のシンボルデータと前記既知のフレーム同期ワードとの比較結果を参照して、同期確立の判定を行う
ことを特徴とする請求項３に記載の同期信号検出装置。 A hard decision demodulator that performs a hard decision process on the symbol data of the quaternary FSK signal corrected based on the frequency deviation;
In addition to the comparison result between the second correlation value calculated by the second correlation value calculation unit and a predetermined threshold, the synchronization establishment determination unit includes the 4-value FSK signal subjected to hard decision processing by the hard decision demodulation unit. The synchronization signal detection apparatus according to claim 3, wherein synchronization is determined by referring to a comparison result between the symbol data and the known frame synchronization word.
前記第１のステップで算出された第１の相関値の極小値を検出する第２のステップと、
前記第２のステップで検出された極小値の時間軸上の位置において、前記受信検波信号と前記フレーム同期ワードとの周波数偏差を算出する第３のステップと、
前記第３のステップで算出された周波数偏差に基づいて前記受信検波信号の周波数を補正する第４のステップと、
前記第４のステップで周波数が補正された補正後の受信検波信号と前記フレーム同期ワードとの第２の相関値を算出する第５のステップと、
前記第５のステップで算出された第２の相関値と所定の閾値との比較結果に基づいて同期確立の判定を行う第６のステップと、
を含むことを特徴とする同期信号検出方法。 A first step of calculating a first correlation value between a received detection signal extracted from the received signal and a known frame synchronization word;
A second step of detecting a minimum value of the first correlation value calculated in the first step;
A third step of calculating a frequency deviation between the received detection signal and the frame synchronization word at a position on the time axis of the minimum value detected in the second step;
A fourth step of correcting the frequency of the received detection signal based on the frequency deviation calculated in the third step;
A fifth step of calculating a second correlation value between the received detection signal after the correction in which the frequency is corrected in the fourth step and the frame synchronization word;
A sixth step of determining synchronization establishment based on a comparison result between the second correlation value calculated in the fifth step and a predetermined threshold;
A synchronization signal detection method comprising:
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| JP2010154107A (en) * | 2008-12-24 | 2010-07-08 | Mitsubishi Electric Corp | Synchronization detecting circuit, synchronization detection method and receiving device |
| JP2011023969A (en) * | 2009-07-15 | 2011-02-03 | Japan Radio Co Ltd | Frequency correction apparatus, and method of controlling the same |
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