JP3943215B2 - Quadrature modem - Google Patents

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JP3943215B2
JP3943215B2 JP33416297A JP33416297A JP3943215B2 JP 3943215 B2 JP3943215 B2 JP 3943215B2 JP 33416297 A JP33416297 A JP 33416297A JP 33416297 A JP33416297 A JP 33416297A JP 3943215 B2 JP3943215 B2 JP 3943215B2
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Prior art keywords
frequency
local
signal
quadrature
intermediate frequency
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JPH11168517A (en
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直樹 新子
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Hitachi Kokusai Electric Inc
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Hitachi Kokusai Electric Inc
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Description

【０００１】
【発明の属する技術分野】
この発明は、送受信機に用いられ、送信系と受信系のベースバンド信号をコヒーレントに形成するための直交変復調器の改良に関するものである。
【０００２】
【従来の技術】
従来より、送信出力から受信出力への回り込み干渉が生ずる恐れのある中継増幅器などにおいては、干渉をベースバンド領域でキャンセルする技術が知られている。この場合、送信系と受信系の各々のベースバンド信号は、コヒーレントに構成し、周波数オフセットなどによる相対的なベースバンド信号の回転の発生を防ぐ必要がある。
【０００３】
図２は、このような従来の直交変復調器の構成を示すブロック図である。
図２において、１は水晶等を備えてなる基準発振器、２は基準発振器１の出力側に接続され、直交検波用の局発信号を発生する直交検波用局部発振器、３は基準発振器１に接続され、直交変調用の局発信号を発生する直交変調用局部発振器、４は基準発振器１に接続され、送信系の中間周波数を生成する送信系中間周波数生成ＭＩＸ（ミキサ）用局部発振器、５は直交検波用局部発振器２の出力側に接続された直交検波回路、６は直交変調用局部発振器３の出力側に接続された直交変調回路、７は送信系中間周波数生成ＭＩＸ用局部発振器４の出力側と直交変調回路６の出力側に接続された送信系中間周波数生成ＭＩＸ（ミキサ）である。
【０００４】
直交検波用局部発振器２と、直交変調用局部発振器３と、送信系中間周波数生成ＭＩＸ用局部発振器４とは、共通の基準発振器１の発振周波数を基準としているので、送信系、受信系の中間周波数ｆIFTとｆIFRが等しい限り、送信系と受信系のベースバンド信号はコヒーレントに保つことができる。
【０００５】
【発明が解決しようとする課題】
しかしながら、従来の直交変復調器では、直交検波用局部発振器２、直交変調用局部発振器３、送信系中間周波数生成ＭＩＸ用局部発振器４で示されるように、ＰＬＬ構成で実現される局部発振器を３系統必要とする。
ＰＬＬを有する局部発振器２、３、４を３系等も備えると、回路規模が大きくなり、コスト高となり、またＰＬＬは、雑音等に敏感であるため、結果的に直交変復調器が雑音等に敏感となり、雑音等の影響を受け易くなるという問題点がある。
【０００６】
この発明は、ＰＬＬ構成で実現される局部発振器を減らすことで、低コストで回路規模を小さくすることができると共に、雑音等の影響も受けにくい直交変復調器を得ることを目的としている。
【０００７】
【課題を解決するための手段】
従来の課題を解決するため、この発明は、直交検波用局発信号（直交検波用局部発振周波数）ｆIFが入力される直交検波回路１４と、直交変調用局発信号（直交変調用局部発振周波数）Δｆが入力される直交変調回路１６と、ミキサ用局発信号（送信系中間周波数生成ＭＩＸ用局部発振周波数（ｆIF＋Δｆ））が入力され、前記直交変調回路１６より出力される信号（Δｆ）を変換するためのミキサ１７とを備えてなる直交変復調器において、
前記直交検波用局発信号ｆIFを出力する直交検波用局部発振器１２と、前記ミキサ用局発信号（ｆIF＋Δｆ）を出力するミキサ用局部発振器（送信系中間周波数生成ＭＩＸ用局部発振器）１３とを備え、前記直交変調用局発信号Δｆを前記直交検波用局発信号ｆIFと前記ミキサ用局発信号（ｆIF＋Δｆ）を混合して得るようにしたものである。
【０００８】
このような構成によれば、従来のように直交変調用周波数を得るための局部発振器をミキサにより構成することができ、従って、ＰＬＬ構成で実現される局部発振器を減らすことができる。
【０００９】
なお、実施の形態における直交変復調器は、受信系中間周波からベースバンド信号を生成する直交検波回路１４と、前記ベースバンド信号を生成するのに必要な局部発振周波数を出力する直交検波用局部発振器１２と、直交変調周波数から送信系中間周波数を生成するミキサ１７と、前記送信系中間周波数を生成するのに必要な局部発振周波数を出力する送信系中間周波数生成用局部発振器１３と、ベースバンド信号から直交変調信号を生成する直交変調回路１６と、前記直交検波用局部発振器１２と前記送信系中間周波数生成用局部発振器１３から前記直交変調信号生成に必要な局部発振周波数を出力するミキサ１５と、前記各局部発振器の基準周波数を出力する基準発振器１１から構成される。ここで、受信系中間周波、送信系中間周波はそれぞれ受信波、送信波でもよい。
【００１０】
【発明の実施の形態】
図１はこの発明の実施の形態に係る直交変復調器を示すブロック図である。
図１において、１１は水晶等を備えてなる基準発振器、１２は入力側が基準発振器１１の出力側に接続された直交検波用局部発振器、１３は入力側が基準発振器１１の出力側に接続された送信系中間周波数生成ＭＩＸ用局部発振器である。
【００１１】
また、図１において、１４は第１の入力端子１４ａが直交検波用局部発振器１２の出力端子に接続され、また、その第２の入力端子１４ｂに受信系の中間周波数信号ｆIFRが入力される直交検波回路、１５は第１の入力端子１５ａが直交検波用局部発振器１２の出力端子に接続され、第２の入力端子１５ｂが送信系中間周波数生成ＭＩＸ用局部発振器１３の出力端子に接続されたミキサである。
【００１２】
また、１６は第１の入力端子１６ａにミキサ１５の出力端子が接続され、第２、第３の入力端子１６ｂ，１６ｃそれぞれにＩ（ｔ）信号とＱ（ｔ）信号（ベースバンド信号）が入力される直交変調回路、１７は第１の入力端子１７ａに直交変調回路１６の出力端子が接続され、第２の入力端子１７ｂに送信系中間周波数生成ＭＩＸ用局部発振器１３の出力端子が接続されたミキサである。
【００１３】
以下に実施の形態の動作について説明する。
直交検波回路１４は、直交検波用局部発振器１２より出力された直交検波用局部発振周波数ｆIFにより受信系の中間周波数信号ｆIFRを直交検波し、Ｉ（ｔ）信号とＱ（ｔ）信号（ベースバンド信号）を得る。
【００１４】
ミキサ１５は直交検波用局部発振器１２より出力された直交検波用局部発振周波数ｆIFと送信系中間周波数生成ＭＩＸ用局部発振器１３より出力された送信系中間周波数生成ＭＩＸ用局部発振周波数（ｆIF＋Δｆ）を混合し、直交変調用周波数Δｆを生成し、直交変調回路１６の入力端子１６ａに出力する。
【００１５】
直交変調回路１６は直交変調用周波数Δｆにより、入力されるＩ（ｔ）信号とＱ（ｔ）信号（ベースバンド信号）を変調し、周波数Δｆの変調信号を得る。
【００１６】
ミキサ１７は送信系中間周波数生成ＭＩＸ用局部発振器１３より出力された送信系中間周波数生成ＭＩＸ用局部発振周波数（ｆIF＋Δｆ）と直交変調回路１６より出力された周波数Δｆの変調信号周波数を混合し、送信系の中間周波数信号ｆIFTを得る。
【００１７】
以上の構成によれば、直交検波用局部発振器１２と送信系中間周波数生成ＭＩＸ用局部発振器１３とは共通の基準発振器１１の発振周波数を基準としており、またミキサ１５から出力される直交変調用周波数Δｆも基準発振器１１の発振周波数を基準としていることになり、送信系、受信系の中間周波数ｆIFT、ｆIFRが等しければ、送信系と受信系のベースバンド信号はコヒーレントに保つことができる。
【００１８】
【発明の効果】
以上の説明より明らかなように、この発明によれば、従来３系統必要であった局部発振器の一つを、他の二つの局部発振器からの局部発振周波数を混合するミキサで機能的に実現することにより、局部発振器の数を減らすことが可能となり、よって、ＰＬＬ構成で実現される局部発振器を減らすことで、低コストで回路規模を小さくすることができると共に、雑音等の影響も受けにくい直交変復調器を得ることができるという効果を奏する。
【図面の簡単な説明】
【図１】この発明の実施の形態に係る直交変復調器を示すブロック図である。
【図２】従来の直交変復調器を示すブロック図である。
【符号の説明】
１１ 基準発振器
１２ 直交検波用局部発振器
１３ 送信系中間周波数生成ＭＩＸ用局部発振器
１４ 直交検波回路
１５、１７ ミキサ
１６ 直交変調回路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a quadrature modulator / demodulator for use in a transmitter / receiver for coherently forming baseband signals of a transmission system and a reception system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a technique for canceling interference in a baseband region is known in a relay amplifier or the like that may cause sneak interference from a transmission output to a reception output. In this case, it is necessary to configure the baseband signals of the transmission system and the reception system to be coherent and prevent relative baseband signal rotation due to frequency offset or the like.
[0003]
FIG. 2 is a block diagram showing the configuration of such a conventional quadrature modulator / demodulator.
In FIG. 2, reference numeral 1 is a reference oscillator provided with a crystal or the like, 2 is connected to the output side of the reference oscillator 1, and is a local oscillator for quadrature detection that generates a local oscillation signal for quadrature detection, and 3 is connected to the reference oscillator 1. A local oscillator for quadrature modulation that generates a local oscillation signal for quadrature modulation, 4 is connected to the reference oscillator 1, and a local oscillator for transmission intermediate frequency generation MIX (mixer) 5 for generating an intermediate frequency of the transmission system The quadrature detection circuit connected to the output side of the quadrature detection local oscillator 2, 6 is the quadrature modulation circuit connected to the output side of the quadrature modulation local oscillator 3, and 7 is the output of the local oscillator 4 for transmission system intermediate frequency generation MIX And a transmission system intermediate frequency generation MIX (mixer) connected to the output side of the quadrature modulation circuit 6.
[0004]
Since the quadrature detection local oscillator 2, the quadrature modulation local oscillator 3, and the transmission system intermediate frequency generation MIX local oscillator 4 are based on the oscillation frequency of the common reference oscillator 1, they are intermediate between the transmission system and the reception system. As long as the frequencies f IFT and f IFR are equal, the baseband signals of the transmission system and the reception system can be kept coherent.
[0005]
[Problems to be solved by the invention]
However, in the conventional quadrature modulator / demodulator, as shown by the quadrature detection local oscillator 2, the quadrature modulation local oscillator 3, and the transmission system intermediate frequency generation MIX local oscillator 4, three systems of local oscillators realized by a PLL configuration are provided. I need.
If the local oscillators 2, 3, 4 having a PLL are also provided with a system 3 or the like, the circuit scale becomes large and the cost is high, and the PLL is sensitive to noise and the like. There is a problem that it becomes sensitive and easily affected by noise and the like.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to obtain a quadrature modulator / demodulator that can reduce the circuit scale at a low cost by reducing the number of local oscillators realized by a PLL configuration, and is less susceptible to noise and the like.
[0007]
[Means for Solving the Problems]
In order to solve the conventional problems, the present invention includes a quadrature detection circuit 14 to which a quadrature detection local oscillation signal (orthogonal detection local oscillation frequency) f IF is input, and a quadrature modulation local oscillation signal (orthogonal modulation local oscillation). The frequency modulation circuit 16 to which the frequency (Δf) is input and the mixer local oscillation signal (transmission system intermediate frequency generation MIX local oscillation frequency (f IF + Δf)) are input and the signal output from the orthogonal modulation circuit 16 ( In a quadrature modulator / demodulator comprising a mixer 17 for converting Δf),
A quadrature detection for the local oscillator 12 which outputs the quadrature detection for local oscillation signal f IF, the mixer for local oscillation signal (f IF + Δf) mixer local oscillator for outputting a (local oscillator for transmission based intermediate frequency generation MIX) 13 The quadrature modulation local oscillation signal Δf is obtained by mixing the quadrature detection local oscillation signal f IF and the mixer local oscillation signal (f IF + Δf).
[0008]
According to such a configuration, a local oscillator for obtaining a quadrature modulation frequency can be configured by a mixer as in the prior art, and therefore the number of local oscillators realized by a PLL configuration can be reduced.
[0009]
The quadrature modulator / demodulator according to the embodiment includes a quadrature detection circuit 14 that generates a baseband signal from a reception intermediate frequency, and a quadrature detection local oscillator that outputs a local oscillation frequency necessary for generating the baseband signal. 12, a mixer 17 that generates a transmission system intermediate frequency from the orthogonal modulation frequency, a transmission system intermediate frequency generation local oscillator 13 that outputs a local oscillation frequency necessary to generate the transmission system intermediate frequency, and a baseband signal A quadrature modulation circuit 16 for generating a quadrature modulation signal from the above, a mixer 15 for outputting a local oscillation frequency necessary for generating the quadrature modulation signal from the quadrature detection local oscillator 12 and the transmission system intermediate frequency generation local oscillator 13; The reference oscillator 11 is configured to output a reference frequency of each local oscillator. Here, the reception system intermediate frequency and the transmission system intermediate frequency may be a reception wave and a transmission wave, respectively.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing an orthogonal modulator / demodulator according to an embodiment of the present invention.
In FIG. 1, reference numeral 11 is a reference oscillator comprising a crystal or the like, 12 is a local oscillator for quadrature detection whose input side is connected to the output side of the reference oscillator 11, and 13 is a transmission whose input side is connected to the output side of the reference oscillator 11. This is a local oscillator for system intermediate frequency generation MIX.
[0011]
Further, in FIG. 1, 14 is connected to the output terminal of the first input terminal 14a is orthogonal detection for the local oscillator 12, also the intermediate frequency signal f IFR receiving system is input to the second input terminal 14b In the quadrature detection circuit 15, the first input terminal 15 a is connected to the output terminal of the quadrature detection local oscillator 12, and the second input terminal 15 b is connected to the output terminal of the transmission system intermediate frequency generation MIX local oscillator 13. It is a mixer.
[0012]
In addition, the output terminal of the mixer 15 is connected to the first input terminal 16a, and the I (t) signal and the Q (t) signal (baseband signal) are respectively connected to the second and third input terminals 16b and 16c. The input quadrature modulation circuit 17 has the first input terminal 17a connected to the output terminal of the quadrature modulation circuit 16, and the second input terminal 17b connected to the output terminal of the transmission system intermediate frequency generation MIX local oscillator 13. Mixer.
[0013]
The operation of the embodiment will be described below.
The quadrature detection circuit 14 performs quadrature detection of the intermediate frequency signal f IFR of the reception system using the quadrature detection local oscillation frequency f IF output from the quadrature detection local oscillator 12 to obtain an I (t) signal and a Q (t) signal ( Baseband signal).
[0014]
The mixer 15 outputs a local oscillation frequency f IF for quadrature detection output from the local oscillator 12 for quadrature detection and a local oscillation frequency for transmission system intermediate frequency generation MIX (f IF + Δf) output from the local oscillator 13 for transmission system intermediate frequency generation MIX. ) To generate a quadrature modulation frequency Δf, which is output to the input terminal 16 a of the quadrature modulation circuit 16.
[0015]
The quadrature modulation circuit 16 modulates the input I (t) signal and Q (t) signal (baseband signal) with the quadrature modulation frequency Δf to obtain a modulated signal having the frequency Δf.
[0016]
The mixer 17 mixes the transmission system intermediate frequency generation MIX local oscillation frequency (f IF + Δf) output from the transmission system intermediate frequency generation MIX local oscillator 13 and the modulation signal frequency of the frequency Δf output from the quadrature modulation circuit 16. The intermediate frequency signal f IFT of the transmission system is obtained.
[0017]
According to the above configuration, the orthogonal detection local oscillator 12 and the transmission system intermediate frequency generation MIX local oscillator 13 are based on the oscillation frequency of the common reference oscillator 11, and the orthogonal modulation frequency output from the mixer 15 is used. Δf is also based on the oscillation frequency of the reference oscillator 11. If the intermediate frequencies f IFT and f IFR of the transmission system and the reception system are equal, the baseband signals of the transmission system and the reception system can be kept coherent.
[0018]
【The invention's effect】
As is clear from the above description, according to the present invention, one of the three local oscillators conventionally required is functionally realized by a mixer that mixes the local oscillation frequencies from the other two local oscillators. This makes it possible to reduce the number of local oscillators. Therefore, by reducing the number of local oscillators realized by the PLL configuration, the circuit scale can be reduced at a low cost, and orthogonality that is not easily affected by noise or the like. There is an effect that a modem can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an orthogonal modulator / demodulator according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a conventional quadrature modulator / demodulator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 Reference oscillator 12 Local oscillator for quadrature detection 13 Local oscillator for transmission system intermediate frequency generation MIX 14 Quadrature detection circuits 15 and 17 Mixer 16 Quadrature modulation circuit

Claims (1)

直交検波回路に与える第1の局部発振周波数を出力する直交検波用局部発振器と、
送信系中間周波数信号を生成するのに必要な第２の局部発振周波数を出力する送信系中間周波数生成用局部発振器と、
前記第１の局部発振周波数により受信系中間周波数信号を直交検波してベースバンド信号を生成する直交検波回路と、
前記第１の局部発振周波数と前記送信系中間周波数生成用局部発振器の第２局部発振周波数とを混合し、直交変調信号の生成に必要な第３の局部発振周波数を出力するミキサと、
前記第３の局部発振周波数により、入力されるベースバンド信号を変調して前記第３の局部発振周波数と同じ周波数の直交変調信号を生成する直交変調回路と、
前記直交変調信号に第２の局部発振周波数を混合して、前記受信系中間周波数信号と同じ周波数の前記送信系中間周波数信号を生成するミキサと、
前記直交検波用局部発振器及び送信系中間周波数生成用局部発振器の基準周波数を出力する基準発振器と、
を備える直交変復調器。A local oscillator for quadrature detection that outputs a first local oscillation frequency to be applied to the quadrature detection circuit;
A local oscillator for generating a transmission intermediate frequency that outputs a second local oscillation frequency required to generate a transmission intermediate frequency signal;
A quadrature detection circuit for generating a baseband signal by quadrature detection of a reception intermediate frequency signal using the first local oscillation frequency;
A mixer that mixes the first local oscillation frequency with the second local oscillation frequency of the transmission system intermediate frequency generation local oscillator, and outputs a third local oscillation frequency necessary for generating an orthogonal modulation signal;
An orthogonal modulation circuit that modulates an input baseband signal by the third local oscillation frequency to generate an orthogonal modulation signal having the same frequency as the third local oscillation frequency;
A mixer for mixing the quadrature modulation signal with a second local oscillation frequency to generate the transmission intermediate frequency signal having the same frequency as the reception intermediate frequency signal;
A reference oscillator that outputs a reference frequency of the orthogonal detection local oscillator and the transmission system intermediate frequency generation local oscillator;
An orthogonal modulator / demodulator.
JP33416297A 1997-12-04 1997-12-04 Quadrature modem Expired - Fee Related JP3943215B2 (en)

Priority Applications (1)

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JP33416297A JP3943215B2 (en) 1997-12-04 1997-12-04 Quadrature modem

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Application Number Priority Date Filing Date Title
JP33416297A JP3943215B2 (en) 1997-12-04 1997-12-04 Quadrature modem

Publications (2)

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JPH11168517A JPH11168517A (en) 1999-06-22
JP3943215B2 true JP3943215B2 (en) 2007-07-11

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