JPS6221460B2 - - Google Patents
Info
- Publication number
- JPS6221460B2 JPS6221460B2 JP55087051A JP8705180A JPS6221460B2 JP S6221460 B2 JPS6221460 B2 JP S6221460B2 JP 55087051 A JP55087051 A JP 55087051A JP 8705180 A JP8705180 A JP 8705180A JP S6221460 B2 JPS6221460 B2 JP S6221460B2
- Authority
- JP
- Japan
- Prior art keywords
- signal
- output
- circuit
- mixing
- electric field
- 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.)
- Expired
Links
- 230000005684 electric field Effects 0.000 claims description 43
- 239000002131 composite material Substances 0.000 claims description 4
- 238000000926 separation method Methods 0.000 description 12
- 238000000034 method Methods 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 4
- 230000003321 amplification Effects 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04H—BROADCAST COMMUNICATION
- H04H40/00—Arrangements specially adapted for receiving broadcast information
- H04H40/18—Arrangements characterised by circuits or components specially adapted for receiving
- H04H40/27—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95
- H04H40/36—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving
- H04H40/45—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving
- H04H40/72—Arrangements characterised by circuits or components specially adapted for receiving specially adapted for broadcast systems covered by groups H04H20/53 - H04H20/95 specially adapted for stereophonic broadcast receiving for FM stereophonic broadcast systems receiving for noise suppression
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/06—Receivers
- H04B1/16—Circuits
- H04B1/1646—Circuits adapted for the reception of stereophonic signals
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Computer Networks & Wireless Communication (AREA)
- Stereo-Broadcasting Methods (AREA)
Description
【発明の詳細な説明】
本発明はFMマルチプレツクス復調器に関し、
特にステレオ放送又は多チヤンネル放送復調の際
生ずる雑音を軽減するFMマルチプレツクス復調
器に関するものであり、集積回路化に適したFM
マルチプレツクス復調器に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an FM multiplex demodulator;
In particular, it relates to an FM multiplex demodulator that reduces noise that occurs when demodulating stereo broadcasts or multichannel broadcasts, and is suitable for integrated circuit implementation.
It concerns multiplex demodulators.
従来一般式にFMコンポジツト信号を使用した
FMステレオ放送を受信し復調した場合の信号対
雑音（Ｓ／Ｎ）特性は第１図に示す如くなる。Ａ
はステレオ復調の場合の信号対雑音（Ｓ／Ｎ）特
性で、Ｂはモノラル復調の場合の信号対雑音特性
（Ｓ／Ｎ）で、Ｃはステレオ復調時のチヤンネル
セパレーシヨン特性である。第１図において、入
力50dB以下の中電界以下になつたときにはモノ
ラル復調に比べステレオ復調時のＳ／Ｎは約
20dB悪化する。このステレオ復調時のＳ／Ｎ比
の劣化は避け得ないものであるが、FM受信時の
ノイズは非常に耳障りで、これを除去する工夫が
種々提案されている。その一つの方法として第２
図に示すように、FMマルチプレツクス復調回路
１００の左チヤンネル出力１００Ｌと右チヤンネ
ル出力１００Ｒとをコンデンサー１００′で結合
する方法が知られている。これはステレオ復調に
伴ない増加するノイズは左、右チヤンネルにて位
相が180゜異つている点と人間の目につきやすい
ノイズは可聴周波数帯中の高域に分布する点に着
目して高域のみモノラルとしてノイズを打消し、
且つ低域においては左・右のセパレーシヨンを保
つ方法である。 Conventionally, FM composite signals were used in the general formula.
The signal-to-noise (S/N) characteristics when receiving and demodulating FM stereo broadcasting are shown in Figure 1. A
is the signal-to-noise (S/N) characteristic in the case of stereo demodulation, B is the signal-to-noise characteristic (S/N) in the case of monaural demodulation, and C is the channel separation characteristic in the case of stereo demodulation. In Figure 1, when the input field is below 50 dB, the S/N during stereo demodulation is approximately
20dB worse. This deterioration of the S/N ratio during stereo demodulation is unavoidable, but the noise during FM reception is extremely annoying, and various methods have been proposed to remove it. The second method is
As shown in the figure, a method is known in which a left channel output 100L and a right channel output 100R of an FM multiplex demodulation circuit 100 are coupled by a capacitor 100'. This is based on the fact that the noise that increases with stereo demodulation has a 180° phase difference between the left and right channels, and that the noise that is easily noticeable to the human eye is distributed in the high range of the audible frequency band. Cancel noise as only monaural,
In addition, this method maintains separation between left and right in the low range.
この方法はモノラルにしてしまう前の救済策で
あり、モノラルほどのＳ／Ｎ比の改善はないとい
う欠点と、強電界時でもこの効果が作用してセパ
レーシヨン劣化が起きるという欠点がある。 This method is a remedy before converting to monaural, and has the drawback that it does not improve the S/N ratio as much as monaural, and also has the drawback that this effect acts even in the case of a strong electric field, causing separation deterioration.
本発明の目的は上記欠点を解決し、さらに弱電
界時にはモノラル以上のＳ／Ｎの改善を行なう
FMマルチプレツクス復調器を提供せんとするに
ある。 The purpose of the present invention is to solve the above-mentioned drawbacks and further improve the S/N more than monaural when the electric field is weak.
The purpose is to provide an FM multiplex demodulator.
即ち、本発明は弱電界時におけるステレオ復調
におけるノイズ低減を電界強度に応じた制御電圧
によりステレオ復調からモノラル復調へ切換える
ことにより行う。この切換えを急激に行なうと聴
感上の不自然さがある為に除々にステレオからモ
ノラルへ切換え、さらに弱電界時においてはモノ
ラル以上のＳ／Ｎ比改善を行うFMマルチプレツ
クス復調器を提供する。本発明によるFMマルチ
プレツクス復調器は、FMコンポジツト信号から
左および右チヤンネル信号を得るFMマルチプレ
ツクス復調回路と、前記右および左チヤンネル信
号を加算してモノラル信号を得る加算回路と、こ
の加算回路の出力に接続され前記モノラル信号の
高域周波数を遮断して出力するローパスフイルタ
と、前記左チヤンネル信号および前記ローパスフ
イルタの出力信号を受ける第１の混合回路と、前
記右チヤンネル信号および前記ローパスフイルタ
の出力信号を受ける第２の混合回路と、前記第１
および第２の混合回路に結合され、受信電界強度
を現わす制御信号に応答して、強電界時には前記
第１および第２の混合回路がそれぞれ前記左およ
び右チヤンネル信号を出力するように制御し、中
電界から弱電界の範囲では前記第１および第２の
混合回路がそれぞれ前記左チヤンネル信号と前記
ローパスフイルタの出力信号との混合信号および
前記右チヤンネル信号と前記ローパスフイルタの
出力信号との混合信号であつて弱電界になるに従
つて前記ローパスフイルタの出力信号の混合割合
が増大する混合信号を出力するように制御し、弱
電界時には前記第１および第２の混合回路が共に
前記ローパスフイルタの出力信号を出力するよう
に制御する制御回路とを備える。 That is, the present invention reduces noise in stereo demodulation in a weak electric field by switching from stereo demodulation to monaural demodulation using a control voltage depending on the electric field strength. Since abrupt switching causes unnatural hearing, the present invention provides an FM multiplex demodulator that gradually switches from stereo to monaural and improves the S/N ratio more than monaural in a weak electric field. The FM multiplex demodulator according to the present invention includes an FM multiplex demodulation circuit that obtains left and right channel signals from an FM composite signal, an adder circuit that adds the right and left channel signals to obtain a monaural signal, and a a low-pass filter connected to the output for cutting off high frequencies of the monaural signal and outputting the monaural signal; a first mixing circuit for receiving the left channel signal and the output signal of the low-pass filter; and a first mixing circuit for receiving the left channel signal and the output signal of the low-pass filter; a second mixing circuit receiving the output signal; and a second mixing circuit receiving the output signal;
and a second mixing circuit, in response to a control signal indicative of received field strength, controlling the first and second mixing circuits to output the left and right channel signals, respectively, when the electric field is strong. , in the range from a medium electric field to a weak electric field, the first and second mixing circuits generate a mixed signal of the left channel signal and the output signal of the low-pass filter, and a mixture of the right channel signal and the output signal of the low-pass filter, respectively. The signal is controlled to output a mixed signal in which the mixing ratio of the output signal of the low-pass filter increases as the electric field becomes weaker, and when the electric field becomes weaker, the first and second mixing circuits both pass through the low-pass filter. and a control circuit that controls the output signal to be output.
以下、図面を用いて本発明をより詳細に説明を
行なう。 Hereinafter, the present invention will be explained in more detail using the drawings.
第３図は本発明の一実施例を示すブロツク図で
ある。FMマルチプレツクス復調回路１には第１
の復調信号である左チヤンネル出力Ｌと第２の復
調信号である右チヤンネル出力Ｒの２つのステレ
オ出力があり、この２つのステレオ出力を加算回
路２で加算する。加算回路２の出力端では、ステ
レオ復調されたＬ・Ｒ信号出力は加算される為モ
ノラル信号となつて出力する。加算回路２の出力
のモノラル信号をローパスフイルタ３（以LPFと
呼ぶ）を通して高域周波数をしや断した第３の復
調信号であるモノラル信号Ｌ＋Ｒを出力する。ま
た、FMマルチプレツクス復調回路１の出力であ
る左チヤンネル出力ＬとLPF3を通した信号Ｌ＋
Ｒは、第１の混合回路４に入力されこの２つの信
号の混合の割合を制御回路６からのコントロール
信号により制御する。このコントロール信号によ
り制御された混合比で２つの信号は混合されて第
１の混合回路４の出力端子７へ出力される。ま
た、第２の混合回路５には、LPF３を通したモノ
ラル信号Ｌ＋ＲとFMマルチプレツクス復調回路
１の右チヤンネル出力Ｒとが入力され、制御回路
６からのコントロール信号により制御された混合
比で右チヤンネル出力ＲとLPF３を通したモノラ
ル信号Ｌ＋Ｒとが混合されて第２の混合回路５の
出力端子９に出力される。 FIG. 3 is a block diagram showing one embodiment of the present invention. The FM multiplex demodulation circuit 1 includes a first
There are two stereo outputs: a left channel output L, which is a demodulated signal, and a right channel output R, which is a second demodulated signal, and these two stereo outputs are added by an adder circuit 2. At the output end of the adder circuit 2, the stereo demodulated L and R signal outputs are summed and output as a monaural signal. The monaural signal output from the adder circuit 2 is passed through a low-pass filter 3 (hereinafter referred to as LPF), and a monaural signal L+R, which is a third demodulated signal in which high frequencies are cut off, is output. In addition, the left channel output L, which is the output of the FM multiplex demodulation circuit 1, and the signal L+ passed through the LPF3
R is input to the first mixing circuit 4, and the mixing ratio of these two signals is controlled by a control signal from the control circuit 6. The two signals are mixed at a mixing ratio controlled by this control signal and output to the output terminal 7 of the first mixing circuit 4. Further, the monaural signal L+R passed through the LPF 3 and the right channel output R of the FM multiplex demodulation circuit 1 are inputted to the second mixing circuit 5, and the mixing ratio controlled by the control signal from the control circuit 6 is adjusted to the right channel. The channel output R and the monaural signal L+R passed through the LPF 3 are mixed and output to the output terminal 9 of the second mixing circuit 5.
制御回路６は、制御回路６の入力端子８より入
力される信号により第１、第２の混合回路４，５
の混合の割合を制御するコントロール信号を発生
する。第１の混合回路４は強電界時には、印加さ
れたコントロール信号によつて、入力された信号
の左チヤンネル信号ＬとLPF３を通したモノラル
信号Ｌ＋Ｒのうち左チヤンネル信号Ｌだけを出力
し、中電界時から弱電界時には左チヤンネル信号
ＬとLPF３を通したモノラル信号Ｌ＋Ｒとの混合
比を変化させ、弱電界時にはLPF３を通したモノ
ラル信号Ｌ＋Ｒのみを出力するように制御され
る。 The control circuit 6 controls the first and second mixing circuits 4 and 5 by a signal input from an input terminal 8 of the control circuit 6.
generates a control signal to control the mixing ratio of the When the electric field is strong, the first mixing circuit 4 outputs only the left channel signal L of the left channel signal L of the input signal and the monaural signal L+R passed through the LPF 3, depending on the applied control signal. When the electric field is weak, the mixing ratio of the left channel signal L and the monaural signal L+R passed through the LPF 3 is changed, and when the electric field is weak, only the monaural signal L+R passed through the LPF 3 is output.
同様に第２の混合回路５は強電界時には入力さ
れた信号の右チヤンネル信号ＲとLPF３を通した
モノラル信号Ｌ＋Ｒのうち右チヤンネル信号Ｒの
みを出力し中電界時から弱電界時には右チヤンネ
ル信号ＲとLPFを通したモノラル信号Ｌ＋Ｒとの
混合比を変化させ弱電界時にはLPF３を通したモ
ノラル信号Ｌ＋Ｒのみを出力するように制御回路
６により制御される。 Similarly, the second mixing circuit 5 outputs only the right channel signal R of the input signal when the electric field is strong and the right channel signal R of the monaural signal L+R passed through the LPF 3, and outputs the right channel signal R when the electric field is medium to weak. The control circuit 6 changes the mixing ratio of the monaural signal L+R passed through the LPF 3 and outputs only the monaural signal L+R passed through the LPF 3 when the electric field is weak.
したがつて、制御回路６の入力端子８に電界強
度に応じた信号たとえば、FM受信器の信号強度
表示器（以下シグナルメーターと呼ぶ）の駆動信
号を入力すれば強電界時すなわちステレオ復調時
のＳ／Ｎ状態が良好な範囲には第１の混合回路４
の出力端子７には左チヤンネル信号Ｌ、第２の混
合回路５の出力端子９には右チヤンネル信号Ｒの
ステレオ信号が左・右チヤンネルセパレーシヨン
を劣化することなく出力され中電界から弱電界の
範囲すなわちステレオ復調時のＳ／Ｎがモノラル
復調時のＳ／Ｎに比べ悪化する範囲では第１、第
２の混合回路４，５には、ステレオ信号とモノラ
ル信号の混合比を電界強度により変化させ除々に
モノラル信号へと移行し、ステレオ復調時におけ
るＳ／Ｎの悪化を改善を行い、左・右チヤンネル
のセパレーシヨン量も除々にモノラルへと移行す
る。 Therefore, if a signal corresponding to the electric field strength, for example, a drive signal for a signal strength indicator (hereinafter referred to as a signal meter) of an FM receiver, is input to the input terminal 8 of the control circuit 6, it will be possible to detect the signal during strong electric field, that is, during stereo demodulation. The first mixing circuit 4 is in the range where the S/N condition is good.
A stereo signal of the left channel signal L is output to the output terminal 7 of the second mixing circuit 5, and the right channel signal R is output to the output terminal 9 of the second mixing circuit 5 without deteriorating the left/right channel separation. In the range where the S/N during stereo demodulation is worse than the S/N during monaural demodulation, the first and second mixing circuits 4 and 5 have a control system that changes the mixing ratio of the stereo signal and monaural signal depending on the electric field strength. The deterioration of S/N during stereo demodulation is improved by gradually transitioning to a monaural signal, and the amount of separation between the left and right channels is also gradually transitioning to monaural.
すなわち、中電界から弱電界の範囲では第１の
混合回路４の出力端子７には電界強度によつて混
合比が変化した左チヤンネル信号Ｌとモノラル信
号Ｌ＋Ｒの混合信号が出力され、第２の混合回路
５の出力端子９には電界強度によつて混合比が変
化した右チヤンネル信号Ｒとモノラル信号Ｌ＋Ｒ
の混合信号が出力される。さらに弱電界時は第１
の混合回路４の出力端子７と第２の混合回路５の
出力端子９はともにモノラル信号Ｌ＋Ｒを出力す
る。このモノラル信号Ｌ＋Ｒはノイズフイルター
として作用するLPF３を通して第１の混合回路４
の出力端子７と第２混合回路５の出力端子９に出
力されるモノラル信号Ｌ＋ＲはLPF３にて高域ノ
イズをカツトされた信号でモノラル信号としてさ
らにＳ／Ｎの改善が行なえる。 That is, in the range from a medium electric field to a weak electric field, a mixed signal of the left channel signal L and the monaural signal L+R whose mixing ratio changes depending on the electric field strength is output to the output terminal 7 of the first mixing circuit 4, and the second The output terminal 9 of the mixing circuit 5 receives a right channel signal R and a monaural signal L+R whose mixing ratio has changed depending on the electric field strength.
A mixed signal is output. Furthermore, when the electric field is weak, the first
The output terminal 7 of the second mixing circuit 4 and the output terminal 9 of the second mixing circuit 5 both output a monaural signal L+R. This monaural signal L+R is passed through the LPF 3 which acts as a noise filter to the first mixing circuit 4.
The monaural signal L+R outputted to the output terminal 7 of the second mixing circuit 5 and the output terminal 9 of the second mixing circuit 5 is a signal from which high-frequency noise has been removed by the LPF 3, and the S/N ratio can be further improved as a monaural signal.
第４図は本発明を実現する一具体例である。同
図中、１はFMマルチプレツクス復調回路、２は
加算回路、３はローパスフイルター、４は第１の
混合回路、５は第２の混合回路、６は制御回路、
７は第１の混合回路の出力端子、８は制御回路６
の入力端子、９は第２の混合回路の出力端子でそ
れぞれ第３図に対応している。また１０は電源供
給ラインである。 FIG. 4 shows a specific example of implementing the present invention. In the figure, 1 is an FM multiplex demodulation circuit, 2 is an addition circuit, 3 is a low-pass filter, 4 is a first mixing circuit, 5 is a second mixing circuit, 6 is a control circuit,
7 is the output terminal of the first mixing circuit, 8 is the control circuit 6
and 9 are the output terminals of the second mixing circuit, respectively corresponding to FIG. Further, 10 is a power supply line.
FMマルチプレツクス復調回路１においてトラ
ンジスター１０１のベースにステレオ合成信号が
入力され、38kHz副搬送波によりトランジスター
１０２，１０３，１０４，１０５にて時分割さ
れ、トランジスター１０７，１１０，１１１、抵
抗１１２，１１３で構成されるカレントミラー回
路のトランジスター１０７のコレクターに右チヤ
ンネル信号Ｒを、またトランジスター１０６，１
１４，１１５、抵抗１１６，１１７で構成される
カレントミラー回路のトランジスター１０６のコ
レクターに左チヤンネル信号２を出力する。トラ
ンジスター１０８，１０９、抵抗１２０，１２１
の回路は左・右チヤンネルのもれ成分をキヤンセ
ルする為の回路である。 In the FM multiplex demodulation circuit 1, a stereo composite signal is input to the base of a transistor 101, and is time-divided by transistors 102, 103, 104, 105 using a 38kHz subcarrier, and is composed of transistors 107, 110, 111, and resistors 112, 113. The right channel signal R is applied to the collector of the transistor 107 of the current mirror circuit, and the transistors 106 and 1
The left channel signal 2 is output to the collector of the transistor 106 of the current mirror circuit composed of the resistors 14 and 115 and the resistors 116 and 117. Transistors 108, 109, resistors 120, 121
The circuit is for canceling the leakage components of the left and right channels.
FMマルチプレツクス復調回路１の出力左チヤ
ンネル信号Ｌは加算回路２の第１入力トランジス
ター２０１と第１の混合回路４の第１入力トラン
ジスター４０１へ入力され、また右チヤンネル信
号Ｒは加算回路の第２の入力トランジスター２０
２と第２の混合回路５の第１の入力トランジスタ
ー５０１へ入力される。加算回路２に入力された
左チヤンネル信号Ｌと右チヤンネル信号Ｒはトラ
ンジスター２０１，２０２のコレクターで加算さ
れトランジスター２０３のコレクターに出力され
る。トランジスター２０３のコレクターに出力さ
れた信号はLPF３のコンデンサー３０１により高
域ノイズをカツトされたモノラル信号として第１
の混合回路４の第２の入力トランジスター４０２
と第２の混合回路５の第２の入力トランジスター
５０２へ入力される。 The output left channel signal L of the FM multiplex demodulation circuit 1 is input to the first input transistor 201 of the adder circuit 2 and the first input transistor 401 of the first mixing circuit 4, and the right channel signal R is input to the second input transistor of the adder circuit 4. input transistor 20
2 and the first input transistor 501 of the second mixing circuit 5. The left channel signal L and right channel signal R input to the adder circuit 2 are added by the collectors of transistors 201 and 202 and output to the collector of transistor 203. The signal output to the collector of the transistor 203 is the first monaural signal with high-frequency noise removed by the capacitor 301 of the LPF3.
The second input transistor 402 of the mixing circuit 4 of
and is input to the second input transistor 502 of the second mixing circuit 5.
第１の混合回路４はトランジスター４０３，４
０４，４０５，４０６の双差動増幅器構成となつ
ており、トランジスター４０３，４０６のベース
電圧とトランジスター４０４，４０５のベース電
圧の差すなわち制御回路６よりのコントロール電
圧によりトランジスター４０１に入力された左チ
ヤンネル信号Ｌとトランジスター４０２に入力さ
れたモノラル信号Ｌ＋Ｒとの混合する割合をコン
トロールされる。 The first mixing circuit 4 includes transistors 403, 4
04, 405, and 406, and the left channel input to the transistor 401 by the difference between the base voltages of the transistors 403, 406 and the base voltages of the transistors 404, 405, that is, the control voltage from the control circuit 6. The mixing ratio of the signal L and the monaural signal L+R input to the transistor 402 is controlled.
同様に第２の混合回路５もトランジスター５０
３，５０４，５０５，５０６の双差動増幅器構成
となつており制御回路６よりのコントロール電圧
によりトランジスター５０１に入力された右チヤ
ンネル信号Ｒとトランジスター５０２に入力され
たモノラル信号Ｌ＋Ｒとの混合する割合をコント
ロールされる。制御回路６はトランジスター６０
１，６０２の差動増幅器６００で構成され、第１
の混合回路４と第２の混合回路５の混合する割合
を制御するコントロール電圧はトランジスター６
０１，６０２の差動増幅器６００の伝達特性を利
用して発生する。トランジスター６０２のベース
には基準電圧源６１３の電圧をトランジスター６
０５、ダイオード６０６でレベルシフトして印加
しコントロール回路６の入力端子９には受信機の
中間周波増幅後から得たシグナルメーターの駆動
電圧を入力し、この電圧をトランジスター６０
３、ダイオード６０４でレベルシフトしてトラン
ジスター６０１のベースに印加する。差動増幅器
６００の出力電圧をトランジスタ６０７、ダイオ
ード６０８，６０９とトランジスター６１０、ダ
イオード６１１，６１２にてレベルシフトして第
１、第２の混合回路４，５を制御するコントロー
ル電圧となる。 Similarly, the second mixing circuit 5 also has a transistor 50.
It has a double differential amplifier configuration of 3,504,505,506, and the mixing ratio of the right channel signal R input to the transistor 501 and the monaural signal L+R input to the transistor 502 is determined by the control voltage from the control circuit 6. is controlled. The control circuit 6 is a transistor 60
Consisting of 1,602 differential amplifiers 600, the first
A control voltage for controlling the mixing ratio between the mixing circuit 4 and the second mixing circuit 5 is supplied to the transistor 6.
This is generated using the transfer characteristics of the differential amplifier 600 of 01,602. The voltage of the reference voltage source 613 is connected to the base of the transistor 602.
05, the signal meter driving voltage obtained after the intermediate frequency amplification of the receiver is inputted to the input terminal 9 of the control circuit 6 after being level shifted by the diode 606, and this voltage is applied to the transistor 60.
3. The level is shifted by the diode 604 and applied to the base of the transistor 601. The output voltage of the differential amplifier 600 is level-shifted by a transistor 607, diodes 608, 609, a transistor 610, and diodes 611, 612, and becomes a control voltage for controlling the first and second mixing circuits 4, 5.
たとえば、強電界時は制御回路６の入力端子８
に印加される電圧は基準電圧源６１３より高く、
したがつてトランジスター６０１は導通してトラ
ンジスター６０２はしや断となる。このときダイ
オード６０９のカソードとダイオード６１２のカ
ソードで発生するコントロール電圧は、ダイオー
ド６０９のカソードでの電圧の方がダイオード６
６１２のカソードでの電圧より低くなつている。
したがつて、第１の混合回路４において、トラン
ジスター４０３，４０６のベース電圧はトランジ
スター４０４，４０５のベース電圧よりも低いの
でトランジスター４０３，４０６はしや断とな
り、トランジスター４０４，４０５は導通とな
る。このときトランジスター４０１に入力された
左チヤンネル信号Ｌだけトランジスター４０７，
４０８，４０９で構成される出力回路より第１の
混合回路の出力端子７へ出力されトランジスター
４０２へ入力されたモノラル信号Ｌ＋Ｒは出力し
ない。 For example, in the case of a strong electric field, the input terminal 8 of the control circuit 6
the voltage applied to is higher than the reference voltage source 613;
Therefore, transistor 601 is turned on and transistor 602 is turned off. At this time, the control voltage generated at the cathode of diode 609 and the cathode of diode 612 is that the voltage at the cathode of diode 609 is higher than that at the cathode of diode 612.
612 is lower than the voltage at the cathode.
Therefore, in the first mixing circuit 4, the base voltages of the transistors 403, 406 are lower than the base voltages of the transistors 404, 405, so the transistors 403, 406 are turned off, and the transistors 404, 405 are turned on. At this time, only the left channel signal L input to the transistor 401 is transmitted to the transistor 407,
The monaural signal L+R, which is output from the output circuit composed of 408 and 409 to the output terminal 7 of the first mixing circuit and input to the transistor 402, is not output.
同様に第２の混合回路５においても、トランジ
スター５０３，５０６はしや断となり、トランジ
スター５０４，５０５は導通し、トランジスター
５０１に入力され左・右チヤンネル信号Ｒだけが
トランジスタ５０７，５０８，５０９で構成され
る出力回路より第２の混合回路５の出力端子９に
出力され、トランジスター５０２の入力されたモ
ノラル信号Ｌ＋Ｒは出力しない。また弱電界時に
は制御回路６の入力端子８に印加される電圧は基
準電圧源６１３の電圧値より低く、トランジスタ
ー６０１はしや断、トランジスター６０２は導通
となりダイオード６０９のカソード電圧はダイオ
ード６１２のカソード電圧より高くなる。したが
つて第１の混合回路において、トランジスター４
０３，４０６のベース電圧はトランジスター４０
４，４０５のベース電圧より高くなりトランジス
ター４０３，４０６は導通、トランジスター４０
４，４０５はしや断となりこのときトランジスタ
ー４０２に入力されたモノラル信号Ｌ＋Ｒだけ第
１の混合回路４の出力端子７に出力し、左チヤン
ネル信号Ｌは出力しない。 Similarly, in the second mixing circuit 5, transistors 503 and 506 are turned off, transistors 504 and 505 are turned on, and only the left and right channel signals R are input to transistor 501 and are composed of transistors 507, 508, and 509. The monaural signal L+R is output from the output circuit to the output terminal 9 of the second mixing circuit 5, and the monaural signal L+R input to the transistor 502 is not output. Further, in the case of a weak electric field, the voltage applied to the input terminal 8 of the control circuit 6 is lower than the voltage value of the reference voltage source 613, the transistor 601 is cut off, the transistor 602 is turned on, and the cathode voltage of the diode 609 is equal to the cathode voltage of the diode 612. becomes higher. Therefore, in the first mixing circuit, transistor 4
03,406 base voltage is transistor 40
The voltage becomes higher than the base voltage of transistor 4,405, transistors 403 and 406 become conductive, and transistor 40 becomes conductive.
4,405 is cut off, and at this time, only the monaural signal L+R input to the transistor 402 is output to the output terminal 7 of the first mixing circuit 4, and the left channel signal L is not output.
同様に第２の混合回路５においてもトランジス
ター５０３，５０６は導通し、トランジスター５
０４，５０５はしや断となりトランジスター５０
２に入力されたモノラル信号Ｌ＋Ｒだけ第２の混
合回路５の出力端子９に出力し右チヤンネル信号
Ｒは出力しない。 Similarly, in the second mixing circuit 5, transistors 503 and 506 are conductive, and the transistor 5
04,505 suddenly breaks and transistor 50
Only the monaural signal L+R input to the second mixing circuit 5 is outputted to the output terminal 9 of the second mixing circuit 5, and the right channel signal R is not outputted.
また、第１の混合回路４の出力端子７及び第２
の混合回路５の出力端子９に出力されるモノラル
信号Ｌ＋ＲはLPF３を通して高域ノイズをカツト
したモノラル信号Ｌ＋Ｒなので、モノラルとして
のＳ／Ｎ比の改善が行える。またLPF３のコンデ
ンサ３０１の容量値をえらぶことで高域ノイズの
減衰量を選ぶことができる。また中電界から弱電
界から弱電界領域においては制御回路６よりのコ
ントロール電圧は、制御回路６の入力端子８の入
力電圧に応じて変化し、したがつて第１の混合回
路４のトランジスター４０３，４０６とトランジ
スター４０４，４０５のベース電圧の差も制御回
路６の入力端子８の入力電圧に応じて変化する。
したがつてトランジスター４０１に入力された左
チヤンネル信号Ｌとトランジスタ４０２に入力さ
れたモノラル信号Ｌ＋Ｒを混合した信号が第１の
混合回路４の出力端子７に出力し、左チヤンネル
信号Ｌとモノラル信号Ｌ＋Ｒの混合の割合は制御
回路６の入力端子８の入力電圧に応じて変化す
る。 Further, the output terminal 7 of the first mixing circuit 4 and the second
Since the monaural signal L+R outputted to the output terminal 9 of the mixing circuit 5 is a monaural signal L+R with high frequency noise cut through the LPF 3, the S/N ratio as a monaural signal can be improved. Furthermore, by selecting the capacitance value of the capacitor 301 of the LPF 3, the amount of attenuation of high frequency noise can be selected. Further, in the medium electric field to weak electric field to weak electric field region, the control voltage from the control circuit 6 changes according to the input voltage at the input terminal 8 of the control circuit 6, and therefore the transistor 403 of the first mixing circuit 4, The difference between the base voltages of the transistors 406 and the transistors 404 and 405 also changes depending on the input voltage of the input terminal 8 of the control circuit 6.
Therefore, a signal obtained by mixing the left channel signal L input to the transistor 401 and the monaural signal L+R input to the transistor 402 is output to the output terminal 7 of the first mixing circuit 4, and the left channel signal L and the monaural signal L+R are output to the output terminal 7 of the first mixing circuit 4. The mixing ratio changes depending on the input voltage at the input terminal 8 of the control circuit 6.
同様に第２の混合回路５の出力端子９にはトラ
ンジスタ５０１に入力された右チヤンネル信号Ｒ
とトランジスタ５０２に入力されたモノラル信号
Ｌ＋Ｒを混合した信号を出力し、この混合する割
合は制御回路６の入力端子８の入力電圧に応じて
変化する。また、差動増幅器６００の相互コンダ
クタンスを適当に選ぶことにより、混合比の変化
速度を選ぶことができる。 Similarly, the output terminal 9 of the second mixing circuit 5 receives the right channel signal R input to the transistor 501.
and the monaural signal L+R input to the transistor 502 are output, and the mixing ratio changes depending on the input voltage at the input terminal 8 of the control circuit 6. Further, by appropriately selecting the mutual conductance of the differential amplifier 600, the rate of change of the mixing ratio can be selected.
したがつて制御回路６の入力端子８に電界強度
に応じた信号たとえばFM受信器のシグナルメー
ターの駆動電圧を入力すれば、ステレオ復調時で
もＳ／Ｎ状態の良い強電界時は左チヤンネル信号
Ｌ、右チヤンネル信号Ｒのステレオ信号を左・右
チヤンネルのセパレーシヨンの劣化を行なわずに
出力し、中電界から弱電界のステレオ復調時の
Ｓ／Ｎ比より約20dB悪化する範囲ではステレオ
信号出力より徐々にモノラル信号出力へと移行
し、すなわち左・右チヤンネルのセパレーシヨン
を除々にモノラルへ移行してステレオ復調時の
Ｓ／Ｎ比の劣化の改善を行う。 Therefore, if a signal corresponding to the electric field strength, for example, the drive voltage of the signal meter of an FM receiver, is input to the input terminal 8 of the control circuit 6, the left channel signal L will be output even during stereo demodulation in the case of a strong electric field with good S/N condition. , the stereo signal of the right channel signal R is output without degrading the separation of the left and right channels, and within the range where the S/N ratio is approximately 20 dB worse than the S/N ratio during stereo demodulation in medium to weak electric fields, the stereo signal output is The signal output is gradually shifted to monaural signal output, that is, the separation of the left and right channels is gradually shifted to monaural, thereby improving the deterioration of the S/N ratio during stereo demodulation.
モノラル復調時のＳ／Ｎも悪化する弱電界時に
はLPFにより高域ノイズをカツトしたモノラル信
号としてＳ／Ｎの改善が行える。 In the case of a weak electric field where the S/N during monaural demodulation deteriorates, the S/N can be improved by using the LPF as a monaural signal with high-frequency noise cut.
第１図に本発明を用いた場合の特性図の１例を
実線Ａ，Ｄ，Ｅで示した。すなわち、実線Ｄは本
実施例による場合のチヤンネルセパレーシヨン特
性で、実線Ｅは本実施例による場合のＳ／Ｎ特性
を示したものである。 An example of a characteristic diagram when the present invention is used is shown in FIG. 1 by solid lines A, D, and E. That is, the solid line D shows the channel separation characteristic according to this embodiment, and the solid line E shows the S/N characteristic according to this embodiment.
このように特性曲線Ｄによれば強電界時ではセ
パレーシヨンの劣化はなく、中電界から弱電界の
範囲では除々にセノラルへ移行し弱電界ではモノ
ラルとなることが解る。同様に特性曲線Ｅより中
電界より弱電界の範囲においてはステレオ復調時
ＡのＳ／Ｎ特性へ移行し、さらに弱電界において
はモノラル復調時ＢのＳ／Ｎをより改善したＳ／
Ｎ特性となつていることが解る。 As described above, according to the characteristic curve D, it can be seen that there is no deterioration of the separation in the case of a strong electric field, and that it gradually shifts to cenoral in the range of medium to weak electric fields, and becomes monaural in a weak electric field. Similarly, characteristic curve E shows that in the range from medium electric field to weak electric field, the S/N characteristic shifts to that of A during stereo demodulation, and furthermore, in a weak electric field, the S/N characteristic of B during monaural demodulation is improved.
It can be seen that it has N characteristics.
第１図はFMマルチフレツクス復調器のＳ／Ｎ
特性曲線とチヤンネルセパレーシヨン特性曲線と
を示すグラフである。第２図はFM受信時の従来
のノイズ除去方法を示す図である。第３図は本発
明の一実施例を示すブロツク図である。第４図は
本発明の一実施例を実現する回路図である。
Ａ……ステレオ復調時のＳ／Ｎ特性曲線、Ｂ…
…モノラル復調時のＳ／Ｎ特性曲線、Ｃ……チヤ
ンネルセパレーシヨン特性曲線、Ｄ……本発明実
施の場合のチヤンネルセパレーシヨン特性曲線、
Ｅ……本発明実施の場合のＳ／Ｎ特性曲線、１…
…FMマルチプレツクス復調回路、２……加算回
路、３……ローパスフイルター、４……第１の混
合回路、５……第２の混合回路、６……コントロ
ール回路、７……第１の混合回路の出力端子、８
……コントロール回路の入力端子、９……第２の
混合回路の出力端子、１０……電源供給ライン、
１０１，１０２，１０３，１０４，１０５，１０
６，１０７，１０８，１０９，１１０，１１１，
１１４，１１５，１２２，１２５，１２６，２０
１，２０２，２０３，２０４，２０５，２０６，
４０１，４０２，４０３，４０４，４０５，４０
６，４０７，４０８，４０９，５０１，５０２，
５０３，５０４，５０６，５０７，５０８，５０
９，６０１，６０２，６０３，６０５，６０７，
６１０……トランジスター、１１２，１１３，１
１６，１１７，１１８，１１９，１２０，１２
１，１２４，１２７，２０７，２０８，２０９，
２１０，２１１，４１０，４１１，４１２，４１
３，５１０，５１１，５１２，５１３，６１４，
６１５，６１６，６１７……抵抗、１２２，６１
３……基準電圧源、３０１……コンデンサー、６
００……差動増幅器、６０４，６０６，６０８，
６０９，６１１，６１２……ダイオード、６１
８，６１９，６２０，６２１，６２２……定電流
源。
Figure 1 shows the S/N of the FM multiflex demodulator.
5 is a graph showing a characteristic curve and a channel separation characteristic curve. FIG. 2 is a diagram showing a conventional noise removal method during FM reception. FIG. 3 is a block diagram showing one embodiment of the present invention. FIG. 4 is a circuit diagram for realizing an embodiment of the present invention. A... S/N characteristic curve during stereo demodulation, B...
...S/N characteristic curve during monaural demodulation, C...Channel separation characteristic curve, D...Channel separation characteristic curve in the case of implementing the present invention,
E... S/N characteristic curve in case of implementing the present invention, 1...
...FM multiplex demodulation circuit, 2...Addition circuit, 3...Low pass filter, 4...First mixing circuit, 5...Second mixing circuit, 6...Control circuit, 7...First mixing circuit Output terminal of the circuit, 8
... Input terminal of the control circuit, 9 ... Output terminal of the second mixing circuit, 10 ... Power supply line,
101, 102, 103, 104, 105, 10
6,107,108,109,110,111,
114, 115, 122, 125, 126, 20
1,202,203,204,205,206,
401, 402, 403, 404, 405, 40
6,407,408,409,501,502,
503, 504, 506, 507, 508, 50
9,601,602,603,605,607,
610...Transistor, 112,113,1
16, 117, 118, 119, 120, 12
1,124,127,207,208,209,
210, 211, 410, 411, 412, 41
3,510,511,512,513,614,
615,616,617...Resistance, 122,61
3... Reference voltage source, 301... Capacitor, 6
00... Differential amplifier, 604, 606, 608,
609, 611, 612...Diode, 61
8,619,620,621,622...constant current source.
Claims (1)
ネル信号を得るFMマルチプレツクス復調回路
と、前記右および左チヤンネル信号を加算してモ
ノラル信号を得る加算回路と、この加算回路の出
力に接続され前記モノラル信号の高域周波数を遮
断して出力するローパスフイルタと、前記左チヤ
ンネル信号および前記ローパスフイルタの出力信
号を受ける第１の混合回路と、前記右チヤンネル
信号および前記ローパスフイルタの出力信号を受
ける第２の混合回路と、前記第１および第２の混
合回路に結合され、受信電界強度を現わす制御信
号に応答して、強電界時には前記第１および第２
の混合回路がそれぞれ前記左および右チヤンネル
信号を出力するように制御し、中電界から弱電界
の範囲では前記第１および第２の混合回路がそれ
ぞれ前記左チヤンネル信号と前記ローパスフイル
タの出力信号との混合信号および前記右チヤンネ
ル信号と前記ローパスフイルタの出力信号との混
合信号であつて弱電界になるに従つて前記ローパ
スフイルタの出力信号の混合割合が増大する混合
信号を出力するように制御し、弱電界時には前記
第１および第２の混合回路が共に前記ローパスフ
イルタの出力信号を出力するように制御する制御
回路とを備えるFMマルチプレツクス復調器。1: an FM multiplex demodulation circuit that obtains left and right channel signals from the FM composite signal; an adder circuit that adds the right and left channel signals to obtain a monaural signal; a first mixing circuit that receives the left channel signal and the output signal of the low-pass filter; and a second mixing circuit that receives the right channel signal and the output signal of the low-pass filter. is coupled to the first and second mixing circuits, and is coupled to the first and second mixing circuits in response to a control signal representing the received field strength.
The mixing circuits are controlled to output the left and right channel signals, respectively, and in the range from a medium electric field to a weak electric field, the first and second mixing circuits output the left channel signal and the output signal of the low-pass filter, respectively. and a mixed signal of the right channel signal and the output signal of the low-pass filter, in which the mixing ratio of the output signal of the low-pass filter increases as the electric field becomes weaker. and a control circuit that controls both the first and second mixing circuits to output the output signal of the low-pass filter when the electric field is weak.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8705180A JPS5711551A (en) | 1980-06-26 | 1980-06-26 | Fm multiplex demodulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP8705180A JPS5711551A (en) | 1980-06-26 | 1980-06-26 | Fm multiplex demodulator |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16327786A Division JPS62149231A (en) | 1986-07-11 | 1986-07-11 | Fm multiplex demodulation circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5711551A JPS5711551A (en) | 1982-01-21 |
| JPS6221460B2 true JPS6221460B2 (en) | 1987-05-13 |
Family
ID=13904137
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP8705180A Granted JPS5711551A (en) | 1980-06-26 | 1980-06-26 | Fm multiplex demodulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5711551A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6149532A (en) * | 1984-08-17 | 1986-03-11 | Pioneer Electronic Corp | Separation control circuit |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS49102301A (en) * | 1972-11-08 | 1974-09-27 | ||
| JPS5560356A (en) * | 1978-10-30 | 1980-05-07 | Hitachi Ltd | Stereo signal demodulation system |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS558372Y2 (en) * | 1975-04-18 | 1980-02-25 |
-
1980
- 1980-06-26 JP JP8705180A patent/JPS5711551A/en active Granted
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS49102301A (en) * | 1972-11-08 | 1974-09-27 | ||
| JPS5560356A (en) * | 1978-10-30 | 1980-05-07 | Hitachi Ltd | Stereo signal demodulation system |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5711551A (en) | 1982-01-21 |
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