JPH07115447A - Automatic frequency controller for m-phase psk receiver - Google Patents
Automatic frequency controller for m-phase psk receiverInfo
- Publication number
- JPH07115447A JPH07115447A JP5262161A JP26216193A JPH07115447A JP H07115447 A JPH07115447 A JP H07115447A JP 5262161 A JP5262161 A JP 5262161A JP 26216193 A JP26216193 A JP 26216193A JP H07115447 A JPH07115447 A JP H07115447A
- Authority
- JP
- Japan
- Prior art keywords
- output
- frequency
- signal
- multiplier
- multiplication
- 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.)
- Pending
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- Digital Transmission Methods That Use Modulated Carrier Waves (AREA)
Abstract
Description
【0001】[0001]
【産業上の利用分野】この発明は、例えばデジタル衛星
通信やデジタル移動通信等の受信機に適応され、入力M
相(M=2n :nは1以上の整数)PSK信号のような
デジタル位相変調信号を局部信号と乗算し、その乗算出
力から周波数誤差を検出し、その検出誤差に応じて局部
信号の周波数を制御するようにした自動周波数制御装置
に関する。BACKGROUND OF THE INVENTION The present invention is applied to a receiver such as digital satellite communication or digital mobile communication, and has an input M.
Phase (M = 2 n : n is an integer of 1 or more) A digital phase modulation signal such as a PSK signal is multiplied with a local signal, a frequency error is detected from the multiplication output, and the frequency of the local signal is detected according to the detected error. The present invention relates to an automatic frequency control device adapted to control.
【0002】[0002]
【従来の技術】図3Aに従来のこの種の自動周波数制御
装置を示す。入力端子11から4相PSK信号が入力さ
れ直交検波器12に於いて局部発振器13からの局部信
号により直交検波されてI信号及びQ信号が出力され
る。即ち直交検波器12においては局部発振器13より
の局部信号が乗算器14により入力信号と乗算されると
共に、局部信号が移相器15によりπ/2シフトされて
入力信号と乗算器16で乗算され、乗算器14、16か
ら入力信号の互いに直交した成分の検波出力I信号及び
Q信号が出力される。これらI信号及びQ信号は複素周
波数逓倍器17において周波数が4逓倍され、その逓倍
された信号はクロスプロダクト器19においてクロスプ
ロダクト演算される。即ち、この演算はデジタル信号に
変換されて行われ、その変換サンプリング周期だけ、逓
倍器17からの二つの出力I' 、Q'がそれぞれ遅延器
21、22において遅延され、遅延器21の出力と逓倍
器17の出力Q' とが乗算器23で乗算され、又遅延器
22の出力と逓倍器17の出力Iとが乗算器24で乗算
され、乗算器23の出力と乗算器24の出力を反転した
ものが加算器25で加算されてクロスプロダクト演算の
結果として出力される。このクロスプロダクト器19の
出力が、低域通過フィルタ20を通じて局部発振器13
へ供給される。低域通過フィルタ20の出力が入力端子
11よりのPSK信号の搬送波周波数と局部発振器13
の局部信号周波数との差に対応した誤差信号であって、
この誤差信号によって局部発振器13の発振周波数が制
御されて誤差信号が小さくなるようにされる。尚、入力
端子11には地上局よりの受信電波がI信号、Q信号の
ベースバンド信号に変換されて入力され、局部信号と複
素乗算(直交検波器12と対応する部分で)され、入力
信号のベースバンド搬送波周波数の基準周波数からのず
れ、つまり周波数誤差がクロスプロダクト器19から検
出され、このずれと対応した周波数で局部発振器13を
発振させる方式もある。この場合、入力信号搬送波周波
数の基準周波数からのずれがゼロの場合は局部発振器1
3の発振周波数はゼロとなる。そしてこの誤差信号がゼ
ロになった場合、ベースバンド信号に変換するための局
部信号周波数は入力搬送波周波数と一致するようにな
る。逓倍器としては例えば図3Bに示すように、入力I
信号及びQ信号が自乗器31、32でそれぞれ自乗され
るとともに乗算器33で互いに乗算される。自乗器3
1、32の出力は加算器34で加算されてI’信号とし
て出力される。又、乗算器33の出力は掛け算器35で
2倍にされてQ’信号として出力され、つまり複素逓倍
される。この複素逓倍は2逓倍であってこれがもう1度
縦続的に行われて4逓倍が行われる。2. Description of the Related Art FIG. 3A shows a conventional automatic frequency control device of this type. The 4-phase PSK signal is input from the input terminal 11, and is quadrature-detected by the quadrature detector 12 by the local signal from the local oscillator 13 to output the I signal and the Q signal. That is, in the quadrature detector 12, the local signal from the local oscillator 13 is multiplied by the input signal by the multiplier 14, and the local signal is shifted by π / 2 by the phase shifter 15 and is multiplied by the input signal by the multiplier 16. The multipliers 14 and 16 output the detection output I signal and Q signal of mutually orthogonal components of the input signal. The frequencies of the I signal and the Q signal are multiplied by 4 in the complex frequency multiplier 17, and the multiplied signals are subjected to cross product calculation in the cross product unit 19. That is, this operation is performed after being converted into a digital signal, and the two outputs I ′ and Q ′ from the multiplier 17 are delayed by the delay devices 21 and 22 for the conversion sampling period, and the output of the delay device 21 is obtained. The output Q ′ of the multiplier 17 is multiplied by the multiplier 23, and the output of the delay device 22 and the output I of the multiplier 17 are multiplied by the multiplier 24, and the output of the multiplier 23 and the output of the multiplier 24 are The inverted ones are added by the adder 25 and output as the result of the cross product calculation. The output of the cross product unit 19 is passed through the low pass filter 20 and the local oscillator 13
Is supplied to. The output of the low-pass filter 20 is the carrier frequency of the PSK signal from the input terminal 11 and the local oscillator 13.
Error signal corresponding to the difference from the local signal frequency of
The error signal controls the oscillation frequency of the local oscillator 13 so that the error signal becomes smaller. It should be noted that the input terminal 11 converts the received radio wave from the ground station into the baseband signal of the I signal and the Q signal and inputs it, and the complex multiplication with the local signal (at the portion corresponding to the quadrature detector 12) is performed. There is also a system in which a deviation from the reference frequency of the baseband carrier frequency of, that is, a frequency error is detected from the cross product unit 19, and the local oscillator 13 is oscillated at a frequency corresponding to this deviation. In this case, if the deviation of the input signal carrier frequency from the reference frequency is zero, the local oscillator 1
The oscillation frequency of 3 becomes zero. When this error signal becomes zero, the local signal frequency for converting into the baseband signal becomes equal to the input carrier frequency. As a multiplier, for example, as shown in FIG.
The signal and the Q signal are squared by the squarers 31 and 32, respectively, and are multiplied by each other by the multiplier 33. Squarer 3
The outputs of 1 and 32 are added by the adder 34 and output as an I ′ signal. The output of the multiplier 33 is doubled by the multiplier 35 and output as a Q'signal, that is, complex-multiplied. This complex multiplication is 2 multiplication, and this is repeated once again in cascade to perform 4 multiplication.
【0003】[0003]
【発明が解決しようとする課題】この図3Aに示した従
来の自動周波数制御装置における周波数誤差の検出出
力、つまりクロスプロダクト器19の出力は、入力搬送
周波数と局部信号周波数との差で引き込み可能な最大周
波数、つまり引き込み可能な最大周波数オフセットをf
mとすると、図2Aに示すように、周波数オフセットが
0の点より周波数オフセットが大きくなるにしたがって
検出誤差信号が正弦波的に変化し、その周期は2倍のf
mとなる。このように従来の自動周波数制御装置におい
ては、その検出誤差は引き込み可能な最大値に近づくと
検出誤差のレベルが小さくなり、従ってドプラーシフ
ト、機器の不安定性等で入力搬送周波数が急に変動する
とこの周波数制御が追いつかず制御範囲から外れてしま
い、所謂ハングアップ現象が生じ、周波数引き込みに長
い時間がかかる問題があった。The detection output of the frequency error in the conventional automatic frequency control device shown in FIG. 3A, that is, the output of the cross product unit 19 can be pulled in by the difference between the input carrier frequency and the local signal frequency. Maximum frequency, that is, the maximum frequency offset that can be drawn is f
2A, as shown in FIG. 2A, the detection error signal changes sinusoidally as the frequency offset becomes larger than the point where the frequency offset is 0, and the period thereof is twice f.
m. As described above, in the conventional automatic frequency control device, the detection error becomes smaller as the detection error approaches the maximum value that can be pulled in, and therefore the input carrier frequency suddenly fluctuates due to Doppler shift, instability of equipment, etc. There is a problem that this frequency control does not catch up and goes out of the control range, a so-called hang-up phenomenon occurs, and it takes a long time to pull in the frequency.
【0004】この発明の目的は、周波数オフセットが比
較的大きくても急速に入力信号周波数に追従することが
できるM相PSK信号受信機の自動周波数制御装置を提
供することにある。An object of the present invention is to provide an automatic frequency control device for an M-phase PSK signal receiver which can rapidly follow the input signal frequency even if the frequency offset is relatively large.
【0005】[0005]
【課題を解決するための手段】この発明によれば入力M
相PSK信号は第1逓倍手段で周波数がM/2逓倍さ
れ、そのM/2逓倍出力に対しクロスプロダクト演算が
第1クロスプロダクト手段により行われ、又入力M相P
SK信号が第2逓倍手段によって周波数がM逓倍され、
このM逓倍出力の符号とM/2逓倍出力の絶対値とが乗
算手段で乗算されて周波数誤差検出出力とされる。つま
りこの検出出力により局部信号周波数が制御される。According to the present invention, the input M
The frequency of the phase PSK signal is multiplied by M / 2 by the first multiplying means, the cross product calculation is performed by the first cross product means on the M / 2 multiplied output, and the input M phase P
The frequency of the SK signal is multiplied by M by the second multiplying means,
The sign of the M-multiplied output and the absolute value of the M / 2-multiplied output are multiplied by the multiplying means to obtain a frequency error detection output. That is, the local signal frequency is controlled by this detection output.
【0006】[0006]
【実施例】図1にこの発明を4相PSK(M=4)信号
に対する受信機に適応した場合を示し、図3Aと対応す
る部分には同一符号を付けて示す。この発明においても
直交検波器12よりのI信号及びQ信号は4逓倍器17
において複素4逓倍され、その逓倍出力がクロスプロダ
クト演算がなされる。この発明においては更に直交検波
器12よりの出力がM/2逓倍、つまりこの例では4/
2=2逓倍され、その出力はクロスプロダクト器31に
てクロスプロダクト演算がなされる。この例では4逓倍
器17における初段の2逓倍部17aの出力がクロスプ
ロダクト器31に分岐供給される。クロスプロダクト器
31はクロスプロダクト器19と同様に構成されてい
る。このクロスプロダクト器31の出力は絶対値演算器
32において絶対値が演算される。一方クロスプロダク
ト器19の出力、つまり従来における周波数誤差検出出
力の符号が符号判定器33で判定され、つまり正である
か負であるかの判定がされ、+1又は−1が出力され
る。この符号判定器33の判定出力と絶対値演算器32
の演算出力とが乗算器34で互いに乗算される。この乗
算器34の出力が局部発振器13に検出誤差信号として
供給され、この誤差信号が小さくなるように局部発振周
波数が制御される。1 shows a case where the present invention is applied to a receiver for 4-phase PSK (M = 4) signals, and parts corresponding to those in FIG. 3A are designated by the same reference numerals. Also in the present invention, the I signal and Q signal from the quadrature detector 12 are quadrupler 17
In (4), the complex product is multiplied by 4 and the multiplied output is subjected to cross product calculation. In the present invention, the output from the quadrature detector 12 is multiplied by M / 2, that is, 4 / in this example.
It is multiplied by 2 = 2, and the output is subjected to a cross product operation in the cross product unit 31. In this example, the output of the first-stage doubler unit 17a in the fourth multiplier 17 is branched and supplied to the cross product unit 31. The cross product device 31 is configured similarly to the cross product device 19. An absolute value calculator 32 calculates the absolute value of the output of the cross product device 31. On the other hand, the sign of the output of the cross product device 19, that is, the sign of the conventional frequency error detection output is judged by the sign judging device 33, that is, it is judged whether it is positive or negative, and +1 or -1 is output. The judgment output of the sign judgment unit 33 and the absolute value calculator 32
And the operation output of are multiplied by each other in the multiplier 34. The output of the multiplier 34 is supplied to the local oscillator 13 as a detection error signal, and the local oscillation frequency is controlled so that the error signal becomes small.
【0007】先に述べたようにクロスプロダクト器19
の出力は第2図Aに示すように周波数オフセットが大き
くなるにしたがって正弦波状に変化し、従って符号判定
器33においては図2Bに示すようにその正にずれた側
は+1の出力が出力され、負側にずれた場合は−1が出
力される。一方クロスプロダクト器31の出力を絶対値
演算器32により絶対値を取った出力は、図2Cに示す
ように周波数オフセットが正側にずれても負側にずれて
も大きくなり、引き込み周波数の最大値fmで最大とな
り、2倍のfmで最小となるように変化する。つまり図
2Aにおける正弦波の負側が正に反転され、しかも周波
数軸が2倍に広げられた状態となる。このような誤差の
絶対値出力(図2C)と、符号判定出力(図2B)とが
乗算器34により乗算され、乗算器34の出力は図2D
に示すような特性となり、周波数のずれがないところ
(周波数オフセット0)で出力が0となり、正側に周波
数オフセットが生じるとこれに応じて検出誤差出力が大
きくなって、引き込み最大周波数のfmにおいて検出誤
差のレベルが最大となる。逆に負方向に周波数オフセッ
トが生じると負の検出誤差が生じ、又、そのオフセット
周波数がfmとなると検出誤差レベルが負方向で最大と
なる。従って入力信号に周波数変動が生じて、周波数オ
フセットが引き込み周波数fmに近くなるほど制御が強
く行われる。このため高速に周波数引き込みが行われ
る。このためドプラーシフトによる周波数変動や或いは
局部発振器の発振周波数の不安定性などによる周波数変
動などに対して周波数オフセットが大きく、かつ比較的
急速に生じる場合でも十分その変動に対して追従し、正
しい復調をすることが可能となる。As described above, the cross product device 19
2A changes sinusoidally as the frequency offset increases as shown in FIG. 2A. Therefore, as shown in FIG. 2B, the sign discriminator 33 outputs a +1 output on the positively displaced side. , -1 is output when it is shifted to the negative side. On the other hand, the output obtained by taking the absolute value of the output of the cross product unit 31 by the absolute value calculator 32 becomes large regardless of whether the frequency offset shifts to the positive side or the negative side as shown in FIG. The value changes to have a maximum value fm and a minimum value twice fm. That is, the negative side of the sine wave in FIG. 2A is inverted to the positive side, and the frequency axis is doubled. The output of the absolute value of such an error (FIG. 2C) and the sign determination output (FIG. 2B) are multiplied by the multiplier 34, and the output of the multiplier 34 is shown in FIG. 2D.
The output becomes 0 when there is no frequency shift (frequency offset 0), and if a frequency offset occurs on the positive side, the detection error output increases accordingly, and at the maximum pull-in frequency fm. The level of detection error is maximum. Conversely, when a frequency offset occurs in the negative direction, a negative detection error occurs, and when the offset frequency becomes fm, the detection error level becomes maximum in the negative direction. Therefore, the frequency is changed in the input signal, and the closer the frequency offset is to the pull-in frequency fm, the stronger the control. Therefore, the frequency pull-in is performed at high speed. Therefore, the frequency offset is large with respect to the frequency fluctuation due to the Doppler shift or the frequency fluctuation due to the instability of the oscillation frequency of the local oscillator, and even if it occurs relatively quickly, it sufficiently follows the fluctuation and correct demodulation is performed. It becomes possible to do.
【0008】上述においてはこの発明を4相PSK信号
の受信に適応したが、一般にM相PQS信号の受信に適
応できその場合は4逓倍器17としたM逓倍器を使用
し、2逓倍部17aとしてはM/2逓倍部を用いればよ
い。また、この発明は前述したように複素ベースバンド
信号入力のゼロ周波数からのずれを補正する場合にも適
用できる。Although the present invention has been applied to the reception of a 4-phase PSK signal in the above description, it can be generally applied to the reception of an M-phase PQS signal. In that case, the M multiplier used as the quadrupler 17 is used, and the doubling unit 17a is used. For this, an M / 2 multiplication unit may be used. The present invention can also be applied to the case where the deviation of the complex baseband signal input from the zero frequency is corrected as described above.
【0009】[0009]
【発明の効果】以上述べたようにこの発明によれば、こ
の位相検出誤差はオフセット周波数が−fmから+fm
の間においてほぼ一定の傾斜を持った特性となってお
り、その引き込み周波数の最大値付近で検出レベルが最
大となり、周波数オフセットが大きいほど局部発振器に
対する制御が大きくなって急速な引き込みが行われ、速
い周波数変動に対して追従することができる。As described above, according to the present invention, this phase detection error has an offset frequency of -fm to + fm.
The characteristic is that it has a substantially constant slope between, the detection level becomes maximum near the maximum value of the pull-in frequency, the larger the frequency offset, the greater the control over the local oscillator, and the quick pull-in is performed. It can follow fast frequency fluctuations.
【図1】この発明の実施例を示すブロック図。FIG. 1 is a block diagram showing an embodiment of the present invention.
【図2】図1の動作を説明するための各部の出力波形特
性を示す図。FIG. 2 is a diagram showing output waveform characteristics of each part for explaining the operation of FIG.
【図3】Aは従来の自動周波数制御装置を示すブロック
図、Bは複素2逓倍を示すブロック図である。FIG. 3A is a block diagram showing a conventional automatic frequency control device, and B is a block diagram showing complex doubling.
Claims (1)
数)PSK信号を局部発振器の局部信号と乗算し、その
乗算出力から周波数誤差を検出し、その誤差に応じて上
記局部発振器を制御して上記誤差が無くなるようにした
M相PSK信号受信機の自動周波数制御装置において、 上記入力M相PSK信号を周波数M/2逓倍する第1逓
倍手段と、 そのM/2逓倍出力に対しクロスプロダクト演算を行う
第1クロスプロダクト手段と、 上記M相PSK信号を周波数M逓倍する第2逓倍手段
と、 上記M逓倍出力の符号と上記M/2逓倍出力の絶対値と
を乗算して上記誤差として出力する乗算手段と、 を設けたことを特徴とするM相PSK受信機の自動周波
数制御装置。1. An input M-phase (M = 2 n : n is an integer of 1 or more) PSK signal is multiplied by a local signal of a local oscillator, a frequency error is detected from the multiplication output, and the local signal is detected according to the error. An automatic frequency control device for an M-phase PSK signal receiver which controls an oscillator to eliminate the above error, and a first multiplication means for multiplying the input M-phase PSK signal by a frequency M / 2, and its M / 2 multiplication output. A first cross product means for performing a cross product operation, a second multiplication means for multiplying the M-phase PSK signal by frequency M, a sign of the M multiplication output and an absolute value of the M / 2 multiplication output. An automatic frequency control device for an M-phase PSK receiver, comprising:
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5262161A JPH07115447A (en) | 1993-10-20 | 1993-10-20 | Automatic frequency controller for m-phase psk receiver |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5262161A JPH07115447A (en) | 1993-10-20 | 1993-10-20 | Automatic frequency controller for m-phase psk receiver |
Publications (1)
Publication Number | Publication Date |
---|---|
JPH07115447A true JPH07115447A (en) | 1995-05-02 |
Family
ID=17371915
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP5262161A Pending JPH07115447A (en) | 1993-10-20 | 1993-10-20 | Automatic frequency controller for m-phase psk receiver |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH07115447A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2000014553A1 (en) * | 1998-09-09 | 2000-03-16 | Qualcomm Incorporated | Accumulated phase measurement using open-loop phase estimation |
-
1993
- 1993-10-20 JP JP5262161A patent/JPH07115447A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2000014553A1 (en) * | 1998-09-09 | 2000-03-16 | Qualcomm Incorporated | Accumulated phase measurement using open-loop phase estimation |
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