JP2000209117A - Receiver for single side band - Google Patents
Receiver for single side bandInfo
- Publication number
- JP2000209117A JP2000209117A JP11004794A JP479499A JP2000209117A JP 2000209117 A JP2000209117 A JP 2000209117A JP 11004794 A JP11004794 A JP 11004794A JP 479499 A JP479499 A JP 479499A JP 2000209117 A JP2000209117 A JP 2000209117A
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- JP
- Japan
- Prior art keywords
- signal
- frequency
- ssb
- receiver
- spectrum
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【0001】[0001]
【発明の属する技術分野】本発明は単側波帯通信用受信
機に関し、特に信号検波のために発生させる局部発振器
出力信号の周波数を自動的に受信単側波帯波の周波数に
一致させて同調させることができる手段に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single sideband communication receiver, and more particularly to a receiver for automatically detecting the frequency of a local oscillator output signal generated for signal detection to match the frequency of a received single sideband wave. It relates to means that can be tuned.
【0002】[0002]
【従来の技術】アマチュア無線や漁業無線などの専用
(業務)通信では、送信電力の節減や周波数帯域幅(周波
数資源)を有効に利用するため、AM変調などの両側帯波
通信方式に比べて信号の伝送エネルギが半分で済む搬送
波抑圧単側波帯通信方式(Single Side Band-Suppressed
Carrier、以下、SSB-SCと記述する)が広く用いられて
いる。また、国際電気通信連合(ITU)でも、上記理
由から完全な抑圧搬送波ではないが短波放送のSSB化を
進めている。しかし、SSB-SCではFM変調などとは異な
り搬送波が送信されないため、受信側において搬送波に
基づく一般的な自動周波数制御(Automatic Frequency C
ontorol、以下、AFCと記述する)を利用して安定に信
号を復調することができない。また、周知のように受信
機において乗積検波などによる信号復調のために局部発
振器により生成する基準周波数と受信SSB-SC信号周波数
との差(これを離調という)がそのまま受信音声のひずみ
となって現れる。SSB-SCでは上述した理由からAMやFMに
比べ離調が生じ易いため復調した音声の品質劣化が著し
い。従って、SSB-SCの受信では常時完全に同調をとるこ
と(上記局部発振器の出力信号周波数(基準周波数)を受
信SSB-SC信号周波数に一致させること)が極めて重要で
ある。[Prior Art] Exclusive use for amateur radio and fishery radio
(Business) In communication, carrier-suppressed single-side waves that require only half the signal transmission energy compared to double-sided band communication systems such as AM modulation in order to save transmission power and effectively use frequency bandwidth (frequency resources) Band communication method (Single Side Band-Suppressed
Carrier (hereinafter referred to as SSB-SC) is widely used. In addition, the International Telecommunication Union (ITU) is also promoting the SSB conversion of shortwave broadcasting, although it is not a completely suppressed carrier for the above reasons. However, in SSB-SC, a carrier is not transmitted unlike FM modulation and the like, so that a general automatic frequency control (Automatic Frequency C
Signals cannot be stably demodulated using ontorol (hereinafter referred to as AFC). Also, as is well known, the difference between the received SSB-SC signal frequency and the reference frequency generated by the local oscillator for signal demodulation such as product detection in the receiver (this is called detuning) is the distortion of the received voice as it is. Appears. In SSB-SC, detuning is more likely to occur than in AM or FM for the reasons described above, so that the quality of demodulated voice is significantly deteriorated. Therefore, it is extremely important to always tune completely (match the output signal frequency (reference frequency) of the local oscillator to the received SSB-SC signal frequency) in SSB-SC reception.
【0003】従来、SSB-SC受信機における同調は、受信
音声を聴きながらオペレータが手動で基準周波数を調整
していた。このとき、オペレータがかなり熟練していて
も完全な同調は困難であり、同調の確度(精度)は 30 Hz
程度であることが知られている。また、一度同調をと
っても、送信機の送信周波数、或いは、受信機における
IF周波数や上記基準周波数が、それぞれ使用する局部発
振器の発振周波数安定度に起因して徐々に変動するた
め、時間の経過とともに再度同調を取り直す必要があっ
た。Conventionally, tuning in an SSB-SC receiver has been manually adjusted by an operator while listening to received voice. At this time, perfect tuning is difficult even if the operator is quite skilled, and the tuning accuracy (accuracy) is 30 Hz.
Is known to be of the order. Also, once tuning is performed, the transmission frequency of the transmitter or the
Since the IF frequency and the above-mentioned reference frequency gradually change due to the stability of the oscillation frequency of the local oscillator used, it is necessary to re-tune with the passage of time.
【0004】そこで、SSB-SC受信機においてAFCを利用
する方式が種々研究されている。例えば、搬送波を残し
て(付加して)SSB信号を送信し、受信側では狭帯域フィ
ルタで信号を検出し、そのフィルタ出力信号に基づき受
信機の基準周波数を生成する局部発振器を制御してAF
Cをかける方法が考案されている。しかし、送信電力節
減のため搬送波レベルを抑圧すると(搬送波レベルを小
さくすると)本方式は有効に動作しないなど問題があ
る。[0004] Therefore, various studies have been made on a method of using AFC in an SSB-SC receiver. For example, an SSB signal is transmitted while leaving a carrier wave (added), a signal is detected by a narrow band filter on a receiving side, and a local oscillator that generates a reference frequency of a receiver based on the filter output signal is controlled to control an AF.
A method of applying C has been devised. However, when the carrier level is suppressed to reduce the transmission power (when the carrier level is reduced), there is a problem that this method does not operate effectively.
【0005】また、SSB-SCの信号をそのまま包絡線検波
した波形と正常に検波した波形とを比較し、一種の位相
同期により受信周波数を制御する方式(米国特許、第29
38114号、1960年5月24日)が提案されている。さら
に、類似する方式がIEEE(米国電気電子学会)学会誌にも
発表されている(C. G. Villard, IEEE Trans. COM19,
No. 6, pp.729-733, 1971)。[0005] Further, a method of comparing the waveform of the envelope detection of the SSB-SC signal as it is with the waveform of the normally detected signal, and controlling the reception frequency by a kind of phase synchronization (US Pat.
38114, May 24, 1960). In addition, a similar method has been published in the IEEE (Institute of Electrical and Electronics Engineers) journal (CG Villard, IEEE Trans. COM19,
No. 6, pp. 729-733, 1971).
【0006】一方、離調した受信音声からケプストラム
分析によって基本周波数を抽出し、これから生成した周
波数スペクトルと受信周波数スペクトルとを比較するこ
とによるAFC方式が提案されている(日本国特許、特
許番号1577637号、平成2年9月13日)。さらに、これを
発展させた方式を、本願発明者らは下記文献に発表する
と共に特許出願した。「(1)鈴木他:電子情報通信学会研
究会資料、CS93-60、平成5年6月。(2)金子他:電子
情報通信学会論文誌、J81-D-・、No.7、pp.1501-150
9。(3)特願平08-068647、平成8年3月25日」。On the other hand, there has been proposed an AFC system in which a fundamental frequency is extracted from a detuned received voice by cepstrum analysis, and a frequency spectrum generated from the fundamental frequency is compared with a received frequency spectrum (Japanese Patent No. 1577637). No., September 13, 1990). Further, the inventors of the present application have published a patent application and published the following literature. "(1) Suzuki et al .: IEICE Workshop, CS93-60, June 1993. (2) Kaneko et al .: IEICE Transactions, J81-D-, No. 7, pp. 1501-150
9. (3) Japanese Patent Application No. 08-068647, March 25, 1996. "
【0007】しかし、詳細な説明は記述が煩雑になるの
で省略するが、上述した各方式には耐雑音性や安定性な
どに問題があり、また、多点のフーリエ変換を必要とす
るため処理時間が長くなりリアルタイム処理ができない
など実用化することが困難である。なお、現行の短波放
送では、周波数帯域幅がやや広くなるが残留搬送波の単
側帯波通信方式を採用することでAFC技術を適用し、上
述した受信時の同調問題を回避している。However, a detailed description is omitted because the description is complicated, but the above-described methods have problems in noise resistance, stability, and the like, and require a multi-point Fourier transform. It is difficult to put it to practical use because the time is long and real-time processing cannot be performed. In the current short-wave broadcasting, the frequency bandwidth is slightly widened, but the AFC technology is applied by adopting the single-sideband communication system of the residual carrier to avoid the above-mentioned tuning problem at the time of reception.
【0008】[0008]
【発明が解決しようとする課題】上述したように従来の
SSB-SC受信機においては以下に示すような問題点があっ
た。つまり、理論的には可能であっても耐雑音性や安定
性の観点で、さらには多点フーリエ変換のリアルタイム
処理の困難性により、実際的にはAFC手法を利用して自
動同調を実現することが不可能であり、そのために依然
として信号復調の際にはオペレータが手動で同調操作を
する必要があった。また、送受信機内部で使用する発振
器の周波数安定度に起因する周波数変動により同調がず
れるので、その都度オペレータが同調をとり直す必要が
ありオペレータへの負担が過大になるなど問題であっ
た。本発明は、上述した従来のSSB-SC受信機に関する問
題を解決するためになされたもので、オペレータの操作
を介することなく自動的に信号復調のための同調をとる
ことが可能なSSB受信機を提供することを目的とする。SUMMARY OF THE INVENTION As described above, the conventional
The SSB-SC receiver has the following problems. In other words, even if it is theoretically possible, in terms of noise resistance and stability, and because of the difficulty of real-time processing of multipoint Fourier transform, in practice, automatic tuning is realized using the AFC method However, it was still impossible to manually tune the signal when demodulating the signal. Further, since the tuning is deviated due to the frequency fluctuation caused by the frequency stability of the oscillator used in the transceiver, the operator has to re-tune each time and the burden on the operator becomes excessive. SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems relating to the conventional SSB-SC receiver, and is an SSB receiver capable of automatically performing tuning for signal demodulation without an operator's operation. The purpose is to provide.
【0009】[0009]
【課題を解決するための手段】上記目的を達成するため
に、本発明に係わるSSB受信機の請求項1記載の発明は、
受信した単側波帯波に所要周波数の局部発振器出力信号
を混合、若しくは加算することにより復調する単側波帯
通信用受信機において、前記復調した音声信号をディジ
タル化した後に第1および第2のフーリエ変換を行うこと
によって、復調した音声信号の所定タイムスロットにお
ける当該音声の基本周波数に係わる周期と位相の情報を
得ると共に、前記各情報に基づき信号復調のための同調
を自動的に行うようにする。本発明に係わるSSB受信機
の請求項2記載の発明は、請求項1記載のSSB受信機にお
いて、前記第1のフーリエ変換によって得られる周波数
スペクトルの振幅を圧縮する。本発明に係わるSSB受信
機の請求項3記載の発明は、請求項2記載のSSB受信機に
おいて、前記振幅を圧縮したスペクトルを対数スペクト
ルとする。本発明に係わるSSB受信機の請求項4記載の発
明は、請求項1、請求項2または請求項3記載のSSB受信機
において、前記局部発振器を検波用局部発振器とする。
本発明に係わるSSB受信機の請求項5記載の発明は、請求
項1、請求項2、請求項3または請求項4記載のSSB受信機
において、前記第2のフーリエ変換の代わりにフーリエ
逆変換を行って得られるケプストラム波形を用いるよう
にする。本発明に係わるSSB受信機の請求項6記載の発明
は、請求項1、請求項2、請求項3、請求項4または請求項
5記載のSSB受信機において、変調信号を音声以外の調波
構造を有する信号とする。Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the SSB receiver according to the present invention,
In a single-sideband communication receiver for demodulating by mixing or adding a local oscillator output signal of a required frequency to the received single-sideband, the first and second after demodulating the demodulated audio signal are digitized. By performing Fourier transform of the above, information of the period and phase related to the fundamental frequency of the sound in a predetermined time slot of the demodulated sound signal is obtained, and tuning for signal demodulation is automatically performed based on each of the information. To The invention according to claim 2 of the SSB receiver according to the present invention compresses the amplitude of the frequency spectrum obtained by the first Fourier transform in the SSB receiver according to claim 1. The invention according to claim 3 of the SSB receiver according to the present invention is the SSB receiver according to claim 2, wherein the spectrum whose amplitude is compressed is a logarithmic spectrum. The invention according to claim 4 of the SSB receiver according to the present invention is the SSB receiver according to claim 1, 2, or 3, wherein the local oscillator is a local oscillator for detection.
The invention according to claim 5 of the SSB receiver according to the present invention is the SSB receiver according to claim 1, claim 2, claim 3 or claim 4, wherein, instead of the second Fourier transform, an inverse Fourier transform is used. Is used to use the cepstrum waveform obtained. The invention according to claim 6 of the SSB receiver according to the present invention is characterized by claim 1, claim 2, claim 3, claim 4, or claim
5. In the SSB receiver according to 5, the modulated signal is a signal having a harmonic structure other than voice.
【0010】[0010]
【発明の実施の形態】本発明に係わるSSB受信機の説明
に先立ち、まず、SSB-SCを用いて音声信号を伝送する際
の周波数スペクトルについて説明する。図4はSSB-SCに
より送受信された音声の周波数スペクトルの例を示す図
である。図4(a)は原音声の送信周波数スペクトル、同図
(b)及び(c)は同図(a)の送信信号(音声)を周波数±Fだ
け離調(受信機の検波用基準信号周波数と送信信号周波
数との差が±F)して復調した場合の周波数スペクトルを
示す。ここで、(b)図はF<0、(c)図はF>0の場合で
あり、同調が完全な場合は(a)図と同じ周波数スペクト
ルを持つ信号が復調される。なお、SSB-SCにおいて側帯
波の上下どちらを用いるかにより、Fの正負と送信周波
数、検波用基準周波数の周波数位置関係は異なるが、こ
こでは原音声の送信周波数スペクトルと受信した周波数
スペクトルとの相対関係でFの正負を考える。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to description of an SSB receiver according to the present invention, first, a frequency spectrum when transmitting a speech signal using SSB-SC will be described. FIG. 4 is a diagram illustrating an example of a frequency spectrum of a voice transmitted and received by the SSB-SC. Fig. 4 (a) shows the transmission frequency spectrum of the original sound,
(b) and (c) are demodulated by detuning the transmission signal (voice) of FIG. (a) by a frequency ± F (the difference between the detection signal frequency of the receiver and the transmission signal frequency is ± F). The frequency spectrum in the case is shown. Here, FIG. (B) shows the case where F <0, and FIG. (C) shows the case where F> 0, and when the tuning is complete, a signal having the same frequency spectrum as in FIG. (A) is demodulated. Depending on whether the upper or lower sideband is used in SSB-SC, the positive / negative of F, the transmission frequency, and the frequency positional relationship of the detection reference frequency are different, but here, the transmission frequency spectrum of the original voice and the received frequency spectrum are different. Consider the sign of F in a relative relationship.
【0011】原理上、音声は生成の過程により有声音と
無声音とに大別され、図4には有声音を送信する場合の
周波数スペクトルの例を示した。有声音は声帯の振動に
よる気流の変化を音源とし、これに声道が共振して生成
された音波が空中に放射されたものである。このとき、
声帯の振動が準周期的であるため、音声は声帯の基本的
振動周波数 fo を基本周波数とした準周期的な波形とな
る。図4(a)に示したように、有声音の周波数スペクトル
は fo とその高調波2f0,3f0,・・・・nf0とからなり、ま
た、それぞれのピークレベル値は等間隔に発生する調波
構造をもつ。In principle, speech is roughly classified into voiced sound and unvoiced sound according to the generation process, and FIG. 4 shows an example of a frequency spectrum when a voiced sound is transmitted. A voiced sound is a sound source that uses a change in airflow due to vibration of a vocal cord as a sound source, and generates a sound wave generated by resonance of a vocal tract. At this time,
Since the vibration of the vocal cords is quasi-periodic, the voice has a quasi-periodic waveform with the fundamental vibration frequency fo of the vocal cords as the fundamental frequency. As shown in FIG. 4 (a), the frequency spectrum of the voiced sound is composed of fo and its harmonics 2f0, 3f0,..., Nf0, and each peak level value is a harmonic generated at equal intervals. Has a structure.
【0012】SSB-SCでは、図4(b)及び(c)に示したよう
に送信信号が離調して受信された場合には、図4(a)に示
されたスペクトルが周波数軸を平行移動した周波数スペ
クトルをもつが、このスペクトルは局所的にピークレベ
ルを発生するものの図4(a)に示したような基本振動周波
数f0に対しての調波関係がくずれるため、これが歪みと
なって現れることになる。このような調波構造にひずみ
の生じた音声は自然性、個人性が低下するだけでなく、
離調周波数Fが大きくなると上記理由により歪みが大き
くなるので音声の了解性も低下する。従って、上述した
ようにSSB受信機では離調のない(F=0)同調を取ることが
重要である。In the SSB-SC, when the transmission signal is detuned and received as shown in FIGS. 4B and 4C, the spectrum shown in FIG. Although the frequency spectrum has been translated, this spectrum locally generates a peak level, but the harmonic relationship with the fundamental vibration frequency f0 as shown in FIG. Will appear. Such a harmonically distorted sound not only reduces naturalness and personality,
When the detuning frequency F increases, the distortion increases for the above-described reason, so that the intelligibility of the voice also decreases. Therefore, it is important for the SSB receiver to tune without detuning (F = 0) as described above.
【0013】以下、図示した実施の形態例に基づいて本
発明を詳細に説明する。なお、本発明は搬送波を抑圧し
た(搬送波を用いない)通信方式に用いることができる
が、一例として搬送波抑圧単側波帯通信(SSB-SC)に適用
した場合について説明する。Hereinafter, the present invention will be described in detail based on illustrated embodiments. Although the present invention can be used for a communication system in which a carrier is suppressed (a carrier is not used), an example in which the present invention is applied to carrier suppressed single sideband communication (SSB-SC) will be described.
【0014】図1は本発明に係わるSSB受信機の実施の形
態例を示す機能ブロック図である。また、図2は図1に示
した離調周波数制御部13の処理手順を説明するための機
能ブロック図を兼ねたフローチャート図である。図1に
示すSSB受信機は、到来するSSB-SC信号を受信するアン
テナ11に接続されたRF増幅器12の出力信号と第1の局部
発振器13の出力信号とに基づき周波数変換してIF増幅器
14に供給する第1のミキサ15と、前記IF増幅器14の出力
信号と第2の局部発振器16の出力信号とに基づきSSB-SC
信号を乗積検波して復調信号を出力する第2のミキサ17
と、前記第2のミキサ17の出力信号に基づき動作し前記
第2の局部発振器16に制御信号を供給する離調周波数制
御部18とから構成される。以下、図2を参照しつつ図1に
示した本発明に係わるSSB受信機の動作について説明す
る。FIG. 1 is a functional block diagram showing an embodiment of an SSB receiver according to the present invention. FIG. 2 is a flow chart that also serves as a functional block diagram for explaining the processing procedure of the detuning frequency control unit 13 shown in FIG. The SSB receiver shown in FIG. 1 performs IF conversion based on an output signal of an RF amplifier 12 connected to an antenna 11 for receiving an incoming SSB-SC signal and an output signal of a first local oscillator 13, and an IF amplifier.
A first mixer 15 that supplies the output signal of the IF amplifier 14 and an output signal of the second local oscillator 16 to the SSB-SC
Second mixer 17 for multiplying and detecting the signal and outputting a demodulated signal
And a detuning frequency control unit 18 that operates based on the output signal of the second mixer 17 and supplies a control signal to the second local oscillator 16. Hereinafter, the operation of the SSB receiver according to the present invention shown in FIG. 1 will be described with reference to FIG.
【0015】まず、アンテナ11を介して受信されたSSB-
SC信号は、RF増幅器12により増幅された後、第1の局部
発振器13と第1のミキサ15とによりIF周波数に周波数変
換されると共にIF増幅器14により増幅され第2のミキサ1
7に出力される。第2の局部発振器16がIF周波数のSSB-SC
信号をベースバンドに周波数変換するための所定周波数
の検波用基準信号を第2のミキサ17に供給するとこのSSB
-SC信号は乗積検波され、復調された信号が第2のミキサ
17から出力される。この際に、上述した理由により前記
検波用基準信号周波数とSSB-SC信号の周波数とが完全に
一致しないため、離調状態のまま同調がとられ、信号が
復調され音声が生成されることになる。上述したように
この再生された音声には離調周波数に起因して所定の歪
みが含まれる。First, the SSB-received via the antenna 11
The SC signal is amplified by the RF amplifier 12, then frequency-converted to an IF frequency by the first local oscillator 13 and the first mixer 15, and amplified by the IF amplifier 14 to the second mixer 1.
Output to 7. The second local oscillator 16 is an IF frequency SSB-SC
When a reference signal for detection of a predetermined frequency for converting the frequency of the signal to baseband is supplied to the second mixer 17, this SSB
-SC signal is multiplied detection and the demodulated signal is
Output from 17. At this time, since the detection reference signal frequency and the frequency of the SSB-SC signal do not completely match for the above-described reason, tuning is performed in a detuned state, and the signal is demodulated to generate sound. Become. As described above, the reproduced sound includes a predetermined distortion due to the detuning frequency.
【0016】この再生された受信音声(復調信号)が離調
周波数制御部18に入力すると図2に示す如く、まず、標
本化(サンプリング)されてディジタル信号に変換される
(ST1)。次に、このディジタル信号は一定の窓長(信号区
間)で切りだされた後(ST2)、第1のフーリェ変換(ST3)に
より周波数スペクトル G (f) に変換される。このスペ
クトルG(f)は複素数であるので、これより絶対値| G
(f) |を求め、さらに信号処理の利便性を考慮してこの
スペクトル波形の振幅を圧縮するため、これを対数スペ
クトル log| G (f) |に変換する(ST4)。このときの周
波数スペクトルは、上述したように図4(b)や(c)の如く
基本周波数f0に対して調波構造とはならず、離調周波数
をFとすると原音声の対数スペクトルがFだけ周波数軸
(横軸)方向に平行移動したものになる。When the reproduced received voice (demodulated signal) is input to the detuning frequency control unit 18, it is first sampled (sampled) and converted into a digital signal as shown in FIG.
(ST1). Next, this digital signal is cut out at a fixed window length (signal section) (ST2), and then converted into a frequency spectrum G (f) by a first Fourier transform (ST3). Since this spectrum G (f) is a complex number, its absolute value |
(f) | is obtained and further converted into a logarithmic spectrum log | G (f) | in order to compress the amplitude of this spectrum waveform in consideration of the convenience of signal processing (ST4). As described above, the frequency spectrum at this time does not have a harmonic structure with respect to the fundamental frequency f0 as shown in FIGS. 4B and 4C. When the detuning frequency is F, the logarithmic spectrum of the original voice is F Only frequency axis
(Transverse axis).
【0017】次に、前記対数スペクトルlog|G(f)|に
ついて、このスペクトルの周期と位相の情報を検出する
ため第2のフーリェ変換(ST5)を施して振幅スペクトルC
(t)と位相成分Pとを導出する。図3(a)は振幅スペクトル
C(t)の時間波形を、また、同図(b)は位相成分をそれぞ
れ示す図である。図3(a)に示すようにC(t)として時間軸
上に前記対数スペクトルの周期に係わる所定のピークレ
ベルを持つ波形が得られる。ここで、このピーク値に達
する時間は対数スペクトル log| G (f) | の周期、すな
わち音声の周期に対応する。この周期をTとすると、T
の逆数はlog| G(f) |上で観測される最大の単一周波数
成分、すなわち基本周波数fo に対応する。Next, the logarithmic spectrum log | G (f) | is subjected to a second Fourier transform (ST5) in order to detect information on the period and phase of the spectrum, and the amplitude spectrum C |
(t) and the phase component P are derived. Figure 3 (a) shows the amplitude spectrum
FIG. 7B is a diagram showing a time waveform of C (t), and FIG. 7B is a diagram showing a phase component. As shown in FIG. 3 (a), a waveform having a predetermined peak level related to the period of the logarithmic spectrum is obtained on the time axis as C (t). Here, the time to reach this peak value corresponds to the period of the logarithmic spectrum log | G (f) | If this cycle is T, T
The reciprocal of corresponds to the largest single frequency component observed on log | G (f) |, ie, the fundamental frequency fo.
【0018】このとき、対数スペクトルlog|G(f)|が
図4(a)に示されたような基本周波数f0に対して調波構造
(F=0)の波形であれば図3(b)に示すように位相成分Pは零
になるが、図4(b)、(c)に示されたような基本周波数f0
に対して調波構造を有しない(離調周波数Fを有する)波
形であればt=Tの位相成分PはFに対応した値(図3(b)のP=
P') を呈することが知られている。そこで、図3に図示
したT(対数スペクトルlog|G(f)|の基本周波数f0の周
期)に係わる位相Pを周期Tの余弦波の位相として、こ
れをP'とすれば(ST6)、P'は図4(b)、(c)における余弦
波(cos (2πT)f)の位相項にあたり、離調周波数(F)
に対応する。つまり、 F'=(f0P')/2π=P'/(2πT) (1) が離調周波数の近似値を与える(ST7)。At this time, the logarithmic spectrum log | G (f) | has a harmonic structure with respect to the fundamental frequency f0 as shown in FIG.
If the waveform is (F = 0), the phase component P becomes zero as shown in FIG. 3 (b), but the fundamental frequency f0 as shown in FIGS. 4 (b) and (c).
For a waveform having no harmonic structure (having a detuning frequency F), the phase component P of t = T is a value corresponding to F (P = P in FIG. 3 (b)).
P ') is known. Therefore, if the phase P related to T (the period of the fundamental frequency f0 of the logarithmic spectrum log | G (f) |) shown in FIG. 3 is set as the phase of the cosine wave of the period T, and this is P ′ (ST6), P ′ corresponds to the phase term of the cosine wave (cos (2πT) f) in FIGS. 4B and 4C, and the detuning frequency (F)
Corresponding to That is, F ′ = (f0P ′) / 2π = P ′ / (2πT) (1) gives an approximate value of the detuning frequency (ST7).
【0019】従って、この検出されたF’情報に基づい
て検波用基準信号を出力する第2の局部発振器16をフィ
ードバック制御し、検波用基準信号の周波数が受信SSB-
SC信号の周波数と一致するように、即ちF´が零に近づ
くように第2の局部発振器16を制御すれば自動的に同調
がとれる。Therefore, the second local oscillator 16 that outputs the detection reference signal is feedback-controlled based on the detected F ′ information, and the frequency of the detection reference signal is changed to the reception SSB−.
If the second local oscillator 16 is controlled so that it matches the frequency of the SC signal, that is, F 'approaches zero, tuning can be automatically performed.
【0020】要するに本発明に係わるSSB受信機は、有
声音がその基本周波数に関して調波構造を有することに
着目すると共に、離調して受信した音声でも、その周波
数スペクトルのパタンには元来有音声が持っていた調波
構造に起因した周期性が観測されることを利用して離調
状態を解消し同調を得るものであって、具体的には前記
周波数スペクトルの周期性(位相情報を含む)を第2のフ
ーリエ変換によって求めることにより受信SSB-SC信号の
周波数と検波用基準信号の周波数との差、即ち離調周波
数を検出し、これに基づき自動的に検波用局部発振器の
基準信号周波数を制御して同調をとるように構成したも
のである。従って、本発明に係わるSSB受信機は、従来
のAFC技術を用いることなく搬送波が抑圧されたSSB-SC
信号であっても、これを受信して自動的に同調をとり信
号を復調することが可能になる。In short, the SSB receiver according to the present invention focuses on the fact that a voiced sound has a harmonic structure with respect to its fundamental frequency. The detuning state is canceled by using the fact that the periodicity caused by the harmonic structure of the voice is observed, and tuning is obtained.Specifically, the periodicity of the frequency spectrum (phase information is ) By the second Fourier transform to detect the difference between the frequency of the received SSB-SC signal and the frequency of the detection reference signal, i.e., the detuning frequency, and automatically detect the reference of the local oscillator for detection based on this. In this configuration, tuning is performed by controlling the signal frequency. Therefore, the SSB receiver according to the present invention is a carrier-suppressed SSB-SC without using the conventional AFC technology.
Even if a signal is received, it is possible to automatically tune the signal and demodulate the signal.
【0021】ここで、図2に示した本発明に係わるSSB受
信機に用いる離調周波数制御部18の実施の形態例をさら
に具体的に説明する。まず、受信音声に対する標本化の
周波数を標本化定理(サンプリング定理)に基づき音声信
号帯域(3kHz)の2倍以上である10 kHz に設定する。この
標本化信号を 512 点の窓(区間長)で切り出し、高速フ
ーリェ変換(FFT)によって、周波数スペクトルに変換
(第1のフーリエ変換)する。この周波数スペクトル振幅
値をソフトウェアによる計算、或いは数表を利用して対
数に変換した後に再度FFTを施して第2のフーリェ変換を
すると、精度が標本化の周期0.1ms(1/10kHz)となる信号
C(t)が得られる。このとき、基本周期Tも同じ精度で得
ることができるが、その逆数である基本周波数foは、fo
が125 Hzの場合は約1.5 Hz、foが300 Hzでは9 Hz程度の
誤差で求めることができる。Here, an embodiment of the detuning frequency control unit 18 used in the SSB receiver according to the present invention shown in FIG. 2 will be described more specifically. First, the sampling frequency for the received voice is set to 10 kHz, which is at least twice the audio signal band (3 kHz), based on the sampling theorem (sampling theorem). This sampled signal is cut out in a 512-point window (section length) and converted to a frequency spectrum by Fast Fourier Transform (FFT).
(First Fourier transform). When this frequency spectrum amplitude value is calculated by software or converted to logarithm using a numerical table, it is subjected to FFT again and the second Fourier transform is performed, the accuracy becomes 0.1 ms (1/10 kHz) of the sampling period signal
C (t) is obtained. At this time, the fundamental period T can be obtained with the same accuracy, but the fundamental frequency fo, which is the reciprocal thereof, is fo
Can be obtained with an error of about 1.5 Hz when is 125 Hz, and about 9 Hz when fo is 300 Hz.
【0022】なお、最初のフーリェ変換の点数は、上記
例の半分の256点でも差し支えない。有音声の場合、周
期20ms〜30ms以上は定常的と考えられるので、この点数
のフーリエ変換で安定した分析ができる。また、本発明
は有声音の調波構造を利用するものであるが、有声音と
無音声の区別は振幅スペクトルC(t)のピークレベル値の
高低により容易に判定できる。さらに、一旦同調が確立
すると離調周波数Fは時間的にゆっくりと変化するの
で、自動同調を行うための上述した計算(処理)を時々刻
々行う必要はなく、上記標本化のためのサンプリングな
どを行う時間間隔を適宜間引きしてもよい。Incidentally, the number of points of the first Fourier transform may be 256 points, which is half of the above example. In the case of voiced speech, since the period of 20 ms to 30 ms or more is considered to be stationary, stable analysis can be performed by Fourier transform of this score. Further, the present invention utilizes the harmonic structure of voiced sounds, but the distinction between voiced sounds and unvoiced sounds can be easily determined based on the level of the peak level value of the amplitude spectrum C (t). Further, once the tuning is established, the detuning frequency F changes slowly with time, so that the above-described calculation (processing) for performing the automatic tuning does not need to be performed every moment. The time interval for performing may be appropriately thinned out.
【0023】また、本発明においては上述したように検
波用局部発振器の出力周波数を離調周波数に応じて制御
する必要があるが、これを実現するためには検波用局部
発振器としてVCOを用いて電圧により発振周波数を制御
してもよいし、或いは、ディジタル的にシンセサイザを
制御するように構成してもよい。In the present invention, as described above, it is necessary to control the output frequency of the local oscillator for detection in accordance with the detuning frequency. To achieve this, a VCO is used as the local oscillator for detection. The oscillation frequency may be controlled by a voltage, or the synthesizer may be digitally controlled.
【0024】ところで、SSBは側帯波の上下いずれを用
いるかで、基準周波数の制御の方向が異なる。つまり、
上側帯波を用いる方式のときは-F’、下側帯波を用い
る方式のときはF’だけ基準周波数をシフトすればよ
い。通常は、利用するシステムやサービス毎にどちらの
側帯波を使用しているのか既知であるはずであるが、仮
に、未知の場合はとりあえず任意に制御を行い、つぎに
測定したF’が前の値より大きくなったときは、制御の
方向を反転すればよい。The direction of control of the reference frequency differs depending on whether the SSB uses the upper or lower sideband. That is,
The reference frequency may be shifted by -F 'in the case of using the upper band, and F' in the case of using the lower band. Normally, it should be known which sideband is being used for each system or service to be used. However, if unknown, if it is unknown, control is arbitrarily performed, and the next measured F 'is When it becomes larger than the value, the control direction may be reversed.
【0025】以上、SSB-SCにより送信された音声信号を
復調する場合について説明したが、本発明に係わるSSB
受信機を用いれば、音楽など調波構造のある音声以外の
信号でも上述したような自動同調により容易に復調する
ことができる。つまり、無線通信一般では、上記音楽な
ども含めて電話と同様に利用可能なチャネル数を増やす
ため信号を 300 Hz 〜3 kHz 程度に帯域制限して伝送す
ることが多い。このときは、例えば、信号の周波数スペ
クトルにはfoや 2fo といった低周波成分が存在しない
ので図4に示した|G(f)| の低周波成分はなくなるが、そ
の周波数スペクトルの形は調波構造を呈するので、上述
した音声信号と同様な処理を用いて自動同調を行うこと
ができる。The case where the audio signal transmitted by the SSB-SC is demodulated has been described above, but the SSB according to the present invention is demodulated.
If a receiver is used, signals other than sound having a harmonic structure, such as music, can be easily demodulated by the automatic tuning as described above. In other words, in general wireless communication, in order to increase the number of usable channels including the above-mentioned music and the like as in the case of a telephone, a signal is often transmitted with its band limited to about 300 Hz to 3 kHz. At this time, for example, since the low frequency components such as fo and 2fo do not exist in the frequency spectrum of the signal, the low frequency components of | G (f) | shown in FIG. 4 disappear, but the shape of the frequency spectrum is harmonic. Since it has a structure, automatic tuning can be performed using the same processing as the above-described audio signal.
【0026】なお、上述した実施の形態例においては振
幅スペクトルC(t)を第2のフーリェ変換により導出した
が、本発明に係わるSSB受信機ではこの第2のフーリエ変
換の代わりに逆フーリェ変換を用いてもさしつかえな
い。このときは、逆フーリエ変換の出力においてケプス
トラム波形が得られるが、これは上記C(t)と同様な波形
である。Although the amplitude spectrum C (t) is derived by the second Fourier transform in the above-described embodiment, the SSB receiver according to the present invention uses the inverse Fourier transform instead of the second Fourier transform. Can be used. At this time, a cepstrum waveform is obtained at the output of the inverse Fourier transform, which is similar to the above C (t).
【0027】また、以上の説明ではSSB-SC信号を乗積検
波する例について説明したが、本発明は図1に示した第2
のミキサ(混合器)17の代わりに加算器と包絡線検波器と
を用いる構成に適用しても上記と同様な動作により自動
同調が可能であること、特に説明を要さないであろう。In the above description, an example in which the multiplication detection of the SSB-SC signal is performed has been described.
Even if the present invention is applied to a configuration in which an adder and an envelope detector are used instead of the mixer (mixer) 17, it is unnecessary to particularly explain that automatic tuning can be performed by the same operation as described above.
【0028】[0028]
【発明の効果】本発明は以上説明したように有声音がそ
の基本周波数に関して調波構造を有することに着目して
複数のフーリエ変換手段により離調周波数を検出し、信
号を検波するための局部発振器出力信号の周波数を受信
SSB-SC信号の周波数に自動的に同調させて復調するよう
にしたので、搬送波が抑圧された通信方式の通話品質を
向上させることができるとともに、オペレータの同調操
作を不要にすることが可能なSSB受信機を実現する上で
著効を奏す。さらに、本発明に係わる自動同調の技術を
用いれば、通常は送信周波数を測定することが困難なSS
B-SCなどの搬送波が抑圧された通信における送信周波数
を正確に知ることができるので、秩序ある通信の確立
や、電波監視にも役立てることができる。As described above, the present invention focuses on the fact that a voiced sound has a harmonic structure with respect to its fundamental frequency, and detects a detuning frequency by a plurality of Fourier transform means to detect a signal. Receives the frequency of the oscillator output signal
Automatically tuned to the frequency of the SSB-SC signal and demodulated, so that it is possible to improve the communication quality of the communication system in which the carrier wave is suppressed and eliminate the need for the operator to perform tuning operation. It is very effective in realizing an SSB receiver. Further, if the automatic tuning technique according to the present invention is used, it is usually difficult to measure the transmission frequency of the SS.
Since it is possible to accurately know the transmission frequency in communication in which carrier waves such as B-SC are suppressed, it can be useful for establishing orderly communication and monitoring radio waves.
【図1】本発明に係わるSSB受信機の実施の形態例を示
す機能ブロック図FIG. 1 is a functional block diagram showing an embodiment of an SSB receiver according to the present invention.
【図2】本発明に係わるSSB受信機で用いる離調周波数
制御部の処理手順を説明するためのブロック図FIG. 2 is a block diagram for explaining a processing procedure of a detuning frequency control unit used in the SSB receiver according to the present invention.
【図3】本発明に係わる第2のフーリエ変換出力の時間
波形を示す図FIG. 3 is a diagram showing a time waveform of a second Fourier transform output according to the present invention;
【図4】音声信号をSSB-SC方式で送受信する場合の周波
数スペクトルを示す図FIG. 4 is a diagram showing a frequency spectrum when a voice signal is transmitted and received by the SSB-SC method;
11・・アンテナ 12・・RF増幅器 13・・第1の局部発振器 14・・IF増幅器 15・・第1のミキサ 16・・第2の局部発振器(検波用局部発振器) 17・・第2のミキサ(検波用ミキサ) 18・・離調周波数制御部 11 Antenna 12 RF amplifier 13 First local oscillator 14 IF amplifier 15 First mixer 16 Second local oscillator (detection local oscillator) 17 Second mixer (Detection mixer) 18 ・ ・ Detuning frequency control unit
Claims (6)
発振器出力信号を混合、若しくは加算することにより復
調する単側波帯通信用受信機において、 前記復調した音声信号をディジタル化した後に第1およ
び第2のフーリエ変換を行うことによって、復調した音
声信号の所定タイムスロットにおける当該音声の基本周
波数に係わる周期と位相の情報を得ると共に、前記各情
報に基づき信号復調のための同調を自動的に行うように
したことを特徴とする単側波帯通信用受信機。1. A single-sideband communication receiver for demodulating by mixing or adding a local oscillator output signal of a required frequency to a received single-sideband, wherein the demodulated audio signal is digitized. By performing the first and second Fourier transforms, information on the period and phase related to the fundamental frequency of the sound in a predetermined time slot of the demodulated sound signal is obtained, and tuning for signal demodulation is performed based on the information. A single-sideband communication receiver characterized in that the reception is performed automatically.
る周波数スペクトルの振幅を圧縮したことを特徴とする
請求項1記載の単側波帯通信用受信機。2. The single sideband communication receiver according to claim 1, wherein an amplitude of a frequency spectrum obtained by said first Fourier transform is compressed.
ペクトルであることを特徴とする請求項2記載の単側波
帯通信用受信機。3. The single sideband communication receiver according to claim 2, wherein the spectrum whose amplitude is compressed is a logarithmic spectrum.
ることを特徴とする請求項1、請求項2または請求項3記
載の単側波帯通信用受信機。4. The single sideband communication receiver according to claim 1, wherein the local oscillator is a local oscillator for detection.
リエ逆変換を行って得られるケプストラム波形を用いる
ようにしたことを特徴とする請求項1、請求項2、請求項
3または請求項4記載の単側波帯通信用受信機。5. The method according to claim 1, wherein a cepstrum waveform obtained by performing an inverse Fourier transform is used instead of the second Fourier transform.
5. The receiver for single sideband communication according to claim 3 or claim 4.
信号であることを特徴とする請求項1、請求項2、請求項
3、請求項4または請求項5記載の単側波帯通信用受信
機。6. The signal according to claim 1, wherein the modulated signal is a signal having a harmonic structure other than voice.
3. The receiver for single sideband communication according to claim 4, wherein the receiver is a single sideband communication receiver.
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JP11004794A JP2000209117A (en) | 1999-01-12 | 1999-01-12 | Receiver for single side band |
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Application Number | Priority Date | Filing Date | Title |
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JP11004794A JP2000209117A (en) | 1999-01-12 | 1999-01-12 | Receiver for single side band |
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Publication Number | Publication Date |
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JP2000209117A true JP2000209117A (en) | 2000-07-28 |
Family
ID=11593695
Family Applications (1)
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JP11004794A Pending JP2000209117A (en) | 1999-01-12 | 1999-01-12 | Receiver for single side band |
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7826561B2 (en) | 2006-12-20 | 2010-11-02 | Icom America, Incorporated | Single sideband voice signal tuning method |
-
1999
- 1999-01-12 JP JP11004794A patent/JP2000209117A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7826561B2 (en) | 2006-12-20 | 2010-11-02 | Icom America, Incorporated | Single sideband voice signal tuning method |
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