JP4625278B2 - Noise squelch circuit - Google Patents

Noise squelch circuit Download PDF

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JP4625278B2
JP4625278B2 JP2004202613A JP2004202613A JP4625278B2 JP 4625278 B2 JP4625278 B2 JP 4625278B2 JP 2004202613 A JP2004202613 A JP 2004202613A JP 2004202613 A JP2004202613 A JP 2004202613A JP 4625278 B2 JP4625278 B2 JP 4625278B2
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squelch circuit
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眞之 伊藤
弘樹 本間
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株式会社五洋電子
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Description

本発明は、受信ノイズを検出してスピーカをオン／オフ制御する受信機のノイズスケルチ回路に関するものである。   The present invention relates to a noise squelch circuit of a receiver that detects reception noise and controls on / off of a speaker.

ＦＭ方式の受信機では、受信電界が弱いときに、ノイズ信号レベルが大きく、受信電界が強いときにはノイズ信号レベルが小さくなる。ノイズスケルチ回路では、この特性を利用し、ノイズ信号を整流したＤＣ電圧を観測し、判定することにより、スケルチ制御に用いている。   In the FM receiver, the noise signal level is large when the reception electric field is weak, and the noise signal level is small when the reception electric field is strong. The noise squelch circuit uses this characteristic to observe and determine a DC voltage obtained by rectifying the noise signal, and uses it for squelch control.

図３は従来のノイズスケルチ回路を含む受信機の全体回路図であり、図４は従来のノイズスケルチ回路の回路動作を示す説明図である。図３において受信機は、ＦＭ検波器１と、ＦＭ検波器１の出力側に接続される音声処理回路２と、音声処理回路２の出力側に設けられてその出力を増幅する低周波増幅器３と、低周波増幅器３の出力側に設けられたスピーカ４とを備える。   FIG. 3 is an overall circuit diagram of a receiver including a conventional noise squelch circuit, and FIG. 4 is an explanatory diagram showing a circuit operation of the conventional noise squelch circuit. In FIG. 3, the receiver includes an FM detector 1, an audio processing circuit 2 connected to the output side of the FM detector 1, and a low frequency amplifier 3 provided on the output side of the audio processing circuit 2 to amplify the output. And a speaker 4 provided on the output side of the low frequency amplifier 3.

また、この受信機はノイズスケルチ回路５と、このノイズスケルチ回路５の出力側に設けられ、ノイズスケルチ回路５の出力に基づいて低周波増幅器３を制限する制御回路６とを備えている。ノイズスケルチ回路５は、ハイパスフィルタ１１とローパスフィルタ１２とノイズ増幅器１３と整流器１４と平滑回路１５とが順次接続されている。   The receiver includes a noise squelch circuit 5 and a control circuit 6 provided on the output side of the noise squelch circuit 5 for limiting the low-frequency amplifier 3 based on the output of the noise squelch circuit 5. In the noise squelch circuit 5, a high-pass filter 11, a low-pass filter 12, a noise amplifier 13, a rectifier 14, and a smoothing circuit 15 are sequentially connected.

以下、動作について説明する。受信波はＦＭ検波器１で復調され変調信号成分とノイズ信号成分が出力される。これは音声処理回路２及び低周波増幅器３を通りスピーカ４へ出力されるが、一方、ノイズスケルチ回路５のハイパスフィルタ１１、ローパスフィルタ１２により制限されたある帯域のノイズ信号が取り出され、ノイズ増幅器１３を介して整流器１４に送られる。ＦＭ検波器１の出力復調信号を図４（ａ）に示し、整流器１４に入力されるノイズを図４の（ｂ）に示す。整流器１４ではノイズを整流してＤＣ電圧に変換し、平滑回路１５でリップルを低減した後、そのレベルを制御回路６で読み込み、判定しスケルチ制御する。   The operation will be described below. The received wave is demodulated by the FM detector 1 and a modulated signal component and a noise signal component are output. This is output to the speaker 4 through the audio processing circuit 2 and the low frequency amplifier 3, while a noise signal in a certain band limited by the high pass filter 11 and the low pass filter 12 of the noise squelch circuit 5 is taken out, and the noise amplifier 13 to the rectifier 14. The demodulated signal output from the FM detector 1 is shown in FIG. 4A, and the noise input to the rectifier 14 is shown in FIG. The rectifier 14 rectifies the noise and converts it into a DC voltage. After the ripple is reduced by the smoothing circuit 15, the level is read by the control circuit 6, and is determined and squelch controlled.

しかし、従来のノイズスケルチ回路５では、もし変調信号成分が大きく、フィルタの減衰が不足している場合、高周波ノイズ信号と共に変調波信号が整流される結果、整流器１４のＤＣ電圧出力が増加し、このため制御回路が誤動作することになるという問題があった。   However, in the conventional noise squelch circuit 5, if the modulation signal component is large and the attenuation of the filter is insufficient, the modulation wave signal is rectified together with the high frequency noise signal, so that the DC voltage output of the rectifier 14 increases. Therefore, there has been a problem that the control circuit malfunctions.

本発明は、受信波に含まれる変調信号成分がノイズ成分と一緒に整流され、整流器のＤＣ電圧が変化することにより制御回路が誤動作することを防止することができる受信機のノイズスケルチ回路を提供することを目的としている。   The present invention provides a receiver noise squelch circuit in which a modulation signal component included in a received wave is rectified together with a noise component, and a control circuit can be prevented from malfunctioning due to a change in the DC voltage of the rectifier. The purpose is to do.

上述した課題を解決するため、本発明に係るノイズスケルチ回路は、受信ノイズを検出してスピーカをオン／オフ制御する受信機のノイズスケルチ回路において、変調信号を反転増幅して前記変調信号の逆位相成分を抽出し、これを元信号に加算して加算信号を得ることで、前記変調信号から変調信号成分を除去する変調信号成分除去手段（第１ローパスフィルタ２１と、第２ローパスフィルタ２２及び反転増幅器２３の直列回路と、これらの出力を加算する加算器２４）と、前記変調信号成分除去手段の出力信号である前記加算信号に基づいて前記受信ノイズを検出する受信ノイズ検出器とを備えてなるものである。   In order to solve the above-described problem, a noise squelch circuit according to the present invention is a noise squelch circuit of a receiver that detects reception noise and controls on / off of a speaker, and inverts and amplifies a modulation signal to reverse the modulation signal. The phase component is extracted and added to the original signal to obtain an added signal, whereby modulation signal component removing means (first low-pass filter 21, second low-pass filter 22, and the like) removes the modulation signal component from the modulation signal. A series circuit of an inverting amplifier 23, an adder 24) for adding these outputs, and a reception noise detector for detecting the reception noise based on the addition signal which is an output signal of the modulation signal component removing means. It will be.

以上に詳述したように本発明によれば、変調された受信波に対して安定したスケルチ制御を実現できる。またフィルタのカットオフ周波数と反転増幅器のゲインを調整することにより、さまざまな変調信号に対して最適化した設定にすることが可能である。   As described above in detail, according to the present invention, stable squelch control can be realized for a modulated received wave. In addition, by adjusting the cutoff frequency of the filter and the gain of the inverting amplifier, it is possible to optimize the settings for various modulation signals.

以下、本発明の実施の形態について図面を参照しつつ説明する。図１は本実施の形態によるノイズスケルチ回路を含む受信機の全体回路図、図２は実施の形態の動作を示す説明図である。なお、図１において図３と同一符号は図３のそれらと同一又は相当物であり、ここでの説明を省略する。   Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall circuit diagram of a receiver including a noise squelch circuit according to the present embodiment, and FIG. 2 is an explanatory diagram showing the operation of the embodiment. 1, the same reference numerals as those in FIG. 3 are the same as or equivalent to those in FIG. 3, and description thereof is omitted here.

本実施の形態におけるノイズスケルチ回路５Ａは、第１ローパスフィルタ２１と、第１ローパスフィルタ２１に並列に設けられた第２ローパスフィルタ２２及び反転増幅器２３の直列回路と、これら第１ローパスフィルタ２１の出力と反転増幅器２３の出力を加算する加算器２４と、加算器２４の出力側に設けられたノイズ増幅器１３Ａと、ノイズ増幅器１３Ａの出力側に設けられた整流器１４及び平滑回路１５とを備えている。   The noise squelch circuit 5 </ b> A according to the present embodiment includes a first low-pass filter 21, a series circuit of a second low-pass filter 22 and an inverting amplifier 23 provided in parallel to the first low-pass filter 21, and the first low-pass filter 21. An adder 24 for adding the output and the output of the inverting amplifier 23; a noise amplifier 13A provided on the output side of the adder 24; a rectifier 14 and a smoothing circuit 15 provided on the output side of the noise amplifier 13A. Yes.

以下、本発明の実施の形態におけるノイズスケルチ回路５Ａの動作について、図２を用いて説明する。受信波は検波器で復調され、図２（ａ）で示すような変調信号成分とノイズ信号成分を含んだ復調信号が出力される。この信号は音声処理回路２を通り、低周波増幅器３で信号増幅されスピーカ４に出力される。弱電界において、ＦＭ受信機のノイズ信号は大きくなるため、ノイズスケルチ回路５Ａで低周波増幅器３を制御し、スピーカ４から大きいノイズ音が出ないようにする必要がある。   Hereinafter, the operation of the noise squelch circuit 5A in the embodiment of the present invention will be described with reference to FIG. The received wave is demodulated by a detector, and a demodulated signal including a modulated signal component and a noise signal component as shown in FIG. This signal passes through the audio processing circuit 2, is amplified by the low frequency amplifier 3, and is output to the speaker 4. Since the noise signal of the FM receiver becomes large in a weak electric field, it is necessary to control the low-frequency amplifier 3 with the noise squelch circuit 5A so that no loud noise is emitted from the speaker 4.

ノイズスケルチ回路５Ａは復調信号のノイズ信号成分レベルを検出し、受信電界強度を判定してスケルチの制御を行う。そこで、実施の形態におけるノイズスケルチ回路５Ａでは、まずＦＭ検波器１の出力復調信号をカットオフ周波数ｆLP1の第１ローパスフィルタ（ＬＰＦ−１）２１（通常は３０〜１００ｋＨｚ程度）に入力し、高周波成分を除去する。この信号を図２（ｂ）に示す。 The noise squelch circuit 5A detects the noise signal component level of the demodulated signal, determines the received electric field strength, and controls the squelch. Therefore, in the noise squelch circuit 5A in the embodiment, first, the output demodulated signal of the FM detector 1 is input to the first low-pass filter (LPF-1) 21 (usually about 30 to 100 kHz) having the cutoff frequency f LP1 . Remove high frequency components. This signal is shown in FIG.

また、もう一方は復調信号をｆLP1より低いカットオフ周波数ｆLP2の第２ローパスフィルタ（ＬＰＦ−２）２２（通常は５〜１０ｋＨｚ）に入力し、反転増幅器２３により反転増幅する。この信号を図２（ｃ）に示す。 On the other hand, the demodulated signal is input to a second low-pass filter (LPF-2) 22 (normally 5 to 10 kHz) having a cutoff frequency f LP2 lower than f LP1 , and is inverted and amplified by the inverting amplifier 23. This signal is shown in FIG.

次に逆位相の関係にあるこれら２つの信号を加算器２４で合成し、ｆLP2以下の低周波成分を除去する。このｆLP2以下の低周波数成分は音声等の変調信号の成分であり、これを除去してノイズ信号成分を抽出する。 Next, these two signals having an anti-phase relationship are combined by an adder 24 to remove low frequency components below f LP2 . The low frequency component below f LP2 is a component of a modulation signal such as voice, and this is removed to extract a noise signal component.

従来はハイパスフィルタにより低周波数を除去しているが、高次のフィルタが必要であり減衰量や回路規模の点などからトレードオフ条件が多く設計上制約が大きい。しかし、逆位相の信号を元信号に加算する方式ではＡＣ成分が打ち消しあうためフィルタの減衰量に依存せず、原理的に大振幅の復調信号に対しても効果が大きい。また、反転増幅器のゲインを可変して経路の違いによる差を調整して加算すれば、ｆLP2以下の低周波数成分に対する減衰量を最適化することが可能である。 Conventionally, low frequencies are removed by a high-pass filter, but a high-order filter is necessary, and there are many trade-off conditions due to the amount of attenuation and circuit scale, and design constraints are large. However, the method of adding an antiphase signal to the original signal cancels the AC component, so that it does not depend on the attenuation of the filter and is in principle effective for a large amplitude demodulated signal. Further, if the gain of the inverting amplifier is changed and the difference due to the difference in the path is adjusted and added, it is possible to optimize the attenuation amount for the low frequency component of f LP2 or less.

こうして加算された信号はノイズ増幅器１３Ａでレベル調整され、整流器１４でＤＣ電圧信号に変換される。この時ノイズ増幅器１３Ａのゲインは、ノイズスケルチ回路５Ａ全体を通してのダイナミックレンジが最適となるよう調整する。   The level of the added signal is adjusted by the noise amplifier 13A and converted to a DC voltage signal by the rectifier 14. At this time, the gain of the noise amplifier 13A is adjusted so as to optimize the dynamic range throughout the noise squelch circuit 5A.

整流器１４の入力ノイズ信号を図２の（ｄ）に示す。ＤＣ電圧信号は平滑回路１５でさらにリップルを除去して後、制御回路６に取り込まれる。制御回路６はこの観測された値を判定し、低周波増幅器３を制御し、スピーカ４の出力をオン／オフする。   An input noise signal of the rectifier 14 is shown in FIG. The DC voltage signal is further removed by the smoothing circuit 15 and then taken into the control circuit 6. The control circuit 6 determines the observed value, controls the low frequency amplifier 3, and turns on / off the output of the speaker 4.

本実施の形態によるノイズスケルチ回路を含む受信機の全体回路図である。1 is an overall circuit diagram of a receiver including a noise squelch circuit according to the present embodiment. 本実施の形態の動作を示す説明図である。It is explanatory drawing which shows operation | movement of this Embodiment. 従来のノイズスケルチ回路を含む受信機の全体回路図である。It is the whole circuit diagram of the receiver containing the conventional noise squelch circuit. 従来のノイズスケルチ回路の回路動作を示す説明図である。It is explanatory drawing which shows the circuit operation | movement of the conventional noise squelch circuit.

符号の説明Explanation of symbols

１ ＦＭ検波器、２ 音声処理回路、３ 低周波増幅器、４ スピーカ、５，５Ａ スケルチ回路、２１ 第１ローパスフィルタ、２２ 第２ローパスフィルタ、２３ 反転増幅器、２４ 加算器、１３，１３Ａ ノイズ増幅器、１４ 整流器、１５ 平滑回路、１６ 制御回路。   1 FM detector, 2 audio processing circuit, 3 low frequency amplifier, 4 speaker, 5, 5A squelch circuit, 21 first low pass filter, 22 second low pass filter, 23 inverting amplifier, 24 adder, 13, 13A noise amplifier, 14 rectifier, 15 smoothing circuit, 16 control circuit.

Claims (1)

受信ノイズを検出してスピーカをオン／オフ制御する受信機のノイズスケルチ回路において、
受信波の復調信号から変調信号成分を抽出するフィルタを経由した信号である変調信号を反転増幅して前記変調信号の逆位相成分を抽出し、これを前記復調信号から所定の周波数帯域外の周波数成分を除去するフィルタを経由した信号に加算して加算信号を得ることで、前記復調信号から前記変調信号成分を除去する変調信号成分除去手段と、
前記変調信号成分除去手段の出力信号である前記加算信号に基づいて前記受信ノイズを検出する受信ノイズ検出器とを備えてなるノイズスケルチ回路。 In a noise squelch circuit of a receiver that detects reception noise and controls on / off of a speaker,
A modulated signal that is a signal that has passed through a filter that extracts a modulated signal component from a demodulated signal of the received wave is inverted and amplified to extract an antiphase component of the modulated signal, and this is a frequency outside a predetermined frequency band from the demodulated signal. by then adding the signal having passed through a filter to remove components to obtain an addition signal, and the modulated signal component removing means for removing said modulation signal component from the demodulated signal,
A noise squelch circuit comprising: a reception noise detector that detects the reception noise based on the addition signal that is an output signal of the modulation signal component removal means.
JP2004202613A 2004-07-09 2004-07-09 Noise squelch circuit Expired - Fee Related JP4625278B2 (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56143728A (en) * 1980-04-10 1981-11-09 Nec Corp Detecting circuit for out-band signal or noise
JPH0433422A (en) * 1990-05-30 1992-02-04 Pioneer Electron Corp Radio receiver
JPH04114519A (en) * 1990-09-04 1992-04-15 Fujitsu Ten Ltd Squelch circuit
JP2002280914A (en) * 2001-03-21 2002-09-27 Oki Electric Ind Co Ltd Disturbance wave detecting squelch circuit and method for detecting the disturbance waves

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS56143728A (en) * 1980-04-10 1981-11-09 Nec Corp Detecting circuit for out-band signal or noise
JPH0433422A (en) * 1990-05-30 1992-02-04 Pioneer Electron Corp Radio receiver
JPH04114519A (en) * 1990-09-04 1992-04-15 Fujitsu Ten Ltd Squelch circuit
JP2002280914A (en) * 2001-03-21 2002-09-27 Oki Electric Ind Co Ltd Disturbance wave detecting squelch circuit and method for detecting the disturbance waves

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