JPS6057707A - Fm demodulator - Google Patents
Fm demodulatorInfo
- Publication number
- JPS6057707A JPS6057707A JP16714883A JP16714883A JPS6057707A JP S6057707 A JPS6057707 A JP S6057707A JP 16714883 A JP16714883 A JP 16714883A JP 16714883 A JP16714883 A JP 16714883A JP S6057707 A JPS6057707 A JP S6057707A
- Authority
- JP
- Japan
- Prior art keywords
- low
- pass filter
- signal
- output
- time constant
- 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
Links
Classifications
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03D—DEMODULATION OR TRANSFERENCE OF MODULATION FROM ONE CARRIER TO ANOTHER
- H03D3/00—Demodulation of angle-, frequency- or phase- modulated oscillations
- H03D3/02—Demodulation of angle-, frequency- or phase- modulated oscillations by detecting phase difference between two signals obtained from input signal
- H03D3/24—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits
- H03D3/241—Modifications of demodulators to reject or remove amplitude variations by means of locked-in oscillator circuits the oscillator being part of a phase locked loop
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Noise Elimination (AREA)
Abstract
Description
【発明の詳細な説明】
く技術分野〉
本発明はビデオテープレコーダ等に用いるに好適なＦＭ
復調装置に関するものである。[Detailed Description of the Invention] Technical Field> The present invention provides an FM suitable for use in video tape recorders, etc.
This invention relates to a demodulator.
〈従来技術と問題点〉
一般にビデオテープレコーダやビデオディスクプレーヤ
等の映像再生装置では、再生時に再生信号中のＦＭ搬送
波が急激に減衰したり或いは欠落することがままあシ、
このような場合ＦＭ復調装置の出力にスパイク状のノイ
ズが発生する。<Prior Art and Problems> In general, in video playback devices such as video tape recorders and video disc players, the FM carrier wave in the playback signal often rapidly attenuates or disappears during playback.
In such a case, spike-like noise occurs in the output of the FM demodulator.
そこで従来のこの種の映像再生装置では、このようなノ
イズ対策のためＦＭ復調装置の後段にノイズ除去装置を
挿入していたが、この場合回路構成が複雑化しコストア
ップとなっていた。Therefore, in the conventional video reproducing apparatus of this type, a noise removing device was inserted after the FM demodulator to counteract such noise, but in this case, the circuit configuration became complicated and the cost increased.
く目的〉
本発明はこのような点に鑑みなされたものであシ、搬送
波欠落時のノイズ発生を抑止でき後段にノイズ除去装置
を挿入する必要のないＦＭ復調装置を提供するものであ
る。Purpose of the Invention The present invention was made in view of the above points, and it is an object of the present invention to provide an FM demodulator that can suppress the generation of noise when a carrier wave is missing and does not require the insertion of a noise removal device at a subsequent stage.
さらに本発明では搬送波欠落時のみならず所望時に随時
復調出力をミュートすることができるＦＭ復調装置を提
供するものである。Furthermore, the present invention provides an FM demodulator that can mute the demodulated output not only when a carrier wave is missing but also at any desired time.
〈実施例〉
以下図面に示す実施例に従って本発明を説明する。図面
は本発明装置の１実施例を示し、ここでＩＩ″ｉ位相比
較器、２は電圧制御型発振器（ＶＣＯ）、３はローパス
フィルタであり、これらによってＰＬＬ（フェーズ・ロ
ックド・ループ）方式を採用した一般のＦＭ復調装置が
構成されている。そしてこの装置の復調動作は周知のよ
うに入力端子４にＦＭ変調された信号が供給されたとき
、このＦＭ変調信号は位相比較器１に加えられ、ここで
ＶＣＯ２からの発振信号と位相比較される。比較出力は
ローパスフィルタ３を経てＶＣＯ２に制御電圧として印
加されるとともに出力端子５に復調出力として導出され
る。<Examples> The present invention will be described below according to examples shown in the drawings. The drawing shows one embodiment of the device of the present invention, in which a phase comparator II''i, 2 a voltage-controlled oscillator (VCO), and 3 a low-pass filter are used to implement a PLL (phase-locked loop) system. The adopted general FM demodulation device is configured.As is well known, the demodulation operation of this device is such that when an FM modulated signal is supplied to the input terminal 4, this FM modulated signal is added to the phase comparator 1. Here, the phase is compared with the oscillation signal from the VCO 2. The comparison output is applied as a control voltage to the VCO 2 via a low-pass filter 3, and is also delivered to an output terminal 5 as a demodulated output.
本発明では上記のようなＰＬＬ方式のＦＭ復調装置にさ
らに第２のローパスフィルタ６、スイソー チング回路
７、搬送波レベル検出器８、スイッチコントロール回路
９を加えて構成したものである。The present invention is constructed by adding a second low-pass filter 6, a switch sorting circuit 7, a carrier wave level detector 8, and a switch control circuit 9 to the PLL type FM demodulator as described above.
なお、ここで第２のローパスフィルタ６の時定数はロー
パスフィルタ３の時定数に比較して十分大きいものとし
、またスイッチング回路７は定常動作時には図示するよ
うに第１のローパスフィルタ３側の端子■に接続されて
いるものとする。Note that the time constant of the second low-pass filter 6 is assumed to be sufficiently larger than that of the low-pass filter 3, and the switching circuit 7 is connected to the terminal on the first low-pass filter 3 side as shown in the figure during steady operation. ■Assume that it is connected to.
上記のように構成されたＦＭ復調装置では、定常時には
位相比較器１、ＶＣＯ２、第１のローパスフィルタ３及
びスイッチング回路７によりＰＬＬ回路が形成され、上
述したと同様の動作で出力端子５に復調出力が導出され
る。In the FM demodulator configured as described above, a PLL circuit is formed by the phase comparator 1, VCO 2, first low-pass filter 3, and switching circuit 7 during normal operation, and demodulation is performed at the output terminal 5 by the same operation as described above. An output is derived.
ところがいま、入力端子４に供給されるＦＭ変調信号の
搬送波が一時的に減少或いは欠落したとき、このことが
搬送波レベル検出器８Ｖｃて検出されスイッチコントロ
ール回路９が作動され、このときスイッチング回路７が
第２のローパスフィルタ６側の端子■に接続される。こ
の場合ローパスフィルタ６の時定数が大きいため、ＶＣ
Ｏ２に印加される制御電圧の変化が抑えられ、また出力
端子５に導出される復調出力もそれ以前の出力が保持さ
れた状態となる。このような結果搬送波の欠落時等に出
力端子５にスパイク状のノイズが導出されることはない
。However, now, when the carrier wave of the FM modulation signal supplied to the input terminal 4 temporarily decreases or is missing, this is detected by the carrier wave level detector 8Vc and the switch control circuit 9 is activated, and at this time the switching circuit 7 is activated. It is connected to terminal (2) on the second low-pass filter 6 side. In this case, since the time constant of the low-pass filter 6 is large, the VC
Changes in the control voltage applied to O2 are suppressed, and the demodulated output delivered to the output terminal 5 also maintains its previous output. As a result, spike-like noise is not generated at the output terminal 5 when a carrier wave is lost.
なお上記実施例において定常のＦＭ復調動作中に復調出
力をミュートしたい場合には、もう一つの入力端子ｌＯ
にミュート指令を与えれば、このときスイッチコントロ
ール回路９が作動され、スイッチング回路７は時定数の
大きな第２のローパスフィルタ６側の端子■に接続され
、ＶＣＯ２への制御電圧の変化が抑えられ、結果的に復
調出力がミュートされることになる。In the above embodiment, if you want to mute the demodulation output during steady FM demodulation, use another input terminal lO.
When a mute command is given to the VCO 2, the switch control circuit 9 is activated, the switching circuit 7 is connected to the terminal (3) on the second low-pass filter 6 side having a large time constant, and changes in the control voltage to the VCO 2 are suppressed. As a result, the demodulated output is muted.
〈効果〉
以上のように本発明によれば、ＰＬＬ回路を使用したＦ
Ｍ復調装置において、入力ＦＭ搬送波の一時的な欠落時
或いは急減時にＰＬＬ回路を構成シテいるローパスフィ
ルタを大きな時定数のものに切換えるようにしているた
め、従来装置のように復調出力にスパイク状ノイズが発
生される虞れはない。<Effects> As described above, according to the present invention, F
In the M demodulator, when the input FM carrier wave temporarily drops or suddenly decreases, the low-pass filter that makes up the PLL circuit is switched to one with a large time constant, so unlike conventional devices, spike-like noise is not generated in the demodulated output. There is no risk that this will occur.
さらにまた本発明によれば、所望時にローパスフィルタ
の時定数を切換えることにより、復調出力を随時ミュー
トすることも可能である。Furthermore, according to the present invention, it is also possible to mute the demodulated output at any time by switching the time constant of the low-pass filter when desired.
ｌ・・・位相比較器、２・・・ｖｃｏ、ａ・・・第１の
ローパスフィルタ、６・・・第２のローパスフィルタ、
７・・・スイッチング回路、８・・・搬送波レベル検出
器。
９・・・スイッチコントロール回路０l...phase comparator, 2...vco, a...first low-pass filter, 6...second low-pass filter,
7... Switching circuit, 8... Carrier wave level detector. 9...Switch control circuit 0
Claims (1)
Ｌ回路内に時定数の異なる２つのローパスフィルタとス
イッチング手段とを有し、入力ＦＭ搬送波レベルの減少
或いは欠落を検知したとき時定数の大きなローパスフィ
ルタに切換えるようにしたことを特徴とするＦＭ復調装
置。 ２、所望時に前記スイッチング手段を作動してローパス
フィルタの時定数を随時切換え復調出力をミュートでき
るようにした前記特許請求の範囲１記載のＦＭ復調装置
０[Claims] 1. An FM demodulator using a PLL circuit, which
FM demodulation characterized by having two low-pass filters with different time constants and a switching means in the L circuit, and switching to the low-pass filter with a larger time constant when a decrease or omission of the input FM carrier wave level is detected. Device. 2. The FM demodulator 0 according to claim 1, wherein the switching means is actuated when desired to change the time constant of the low-pass filter at any time and mute the demodulated output.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16714883A JPS6057707A (en) | 1983-09-08 | 1983-09-08 | Fm demodulator |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16714883A JPS6057707A (en) | 1983-09-08 | 1983-09-08 | Fm demodulator |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS6057707A true JPS6057707A (en) | 1985-04-03 |
Family
ID=15844307
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16714883A Pending JPS6057707A (en) | 1983-09-08 | 1983-09-08 | Fm demodulator |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6057707A (en) |
-
1983
- 1983-09-08 JP JP16714883A patent/JPS6057707A/en active Pending
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