JPS5910816Y2 - automatic frequency control circuit - Google Patents
automatic frequency control circuitInfo
- Publication number
- JPS5910816Y2 JPS5910816Y2 JP6806778U JP6806778U JPS5910816Y2 JP S5910816 Y2 JPS5910816 Y2 JP S5910816Y2 JP 6806778 U JP6806778 U JP 6806778U JP 6806778 U JP6806778 U JP 6806778U JP S5910816 Y2 JPS5910816 Y2 JP S5910816Y2
- Authority
- JP
- Japan
- Prior art keywords
- frequency
- signal
- tuning
- local oscillator
- output
- 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
Landscapes
- Channel Selection Circuits, Automatic Tuning Circuits (AREA)
- Superheterodyne Receivers (AREA)
Description
【考案の詳細な説明】
本考案は局部発振器の周波数を所定周波数に制御する自
動周波数制御回路に係り、特に同調操作時のヒステリシ
ス現象を除去するようにしたものである。[Detailed Description of the Invention] The present invention relates to an automatic frequency control circuit that controls the frequency of a local oscillator to a predetermined frequency, and is particularly designed to eliminate the hysteresis phenomenon during tuning operation.
たとえばＦＭチューナではフロントエンドのバリコンの
操作によって局部発振器の発振周波数を連続的に変化さ
せて同調操作を行なうようにしている。For example, in an FM tuner, tuning is performed by continuously changing the oscillation frequency of a local oscillator by operating a variable capacitor at the front end.
しかしながらこのようなものでは局部発振器の発振周波
数の変化は連続的なために、受信状態において正確に正
同調点に同調し、かつ維持することは極めて困難である
。However, in such a device, since the oscillation frequency of the local oscillator changes continuously, it is extremely difficult to accurately tune to and maintain the positive tuning point in the receiving state.
ところでＦＭ受信機のように受信電波の周波数が既知で
あれば、局部発振器の発振周波数を連続的に変化する必
要はなく、規定の中間周波数を得るための各受信電波に
対応した周波数で正確な発振出力が得られればよい。By the way, if the frequency of the received radio waves is known, as in the case of an FM receiver, there is no need to continuously change the oscillation frequency of the local oscillator, and it is not necessary to continuously change the oscillation frequency of the local oscillator. It is sufficient if oscillation output can be obtained.
たとえば放送電波の周波数は一定のステップをもって設
定し、我国で実施されているＦＭ放送ではＩＱＱ ｋＨ
ｚステップとなっている。For example, the frequency of broadcast radio waves is set in fixed steps, and in FM broadcasting conducted in Japan, IQQ kH
It is a z step.
このために上記周波数ステップに対応した所定の周波数
で発振する基準周波数発振器出力を基準にして局部発振
器の発振周波数を計数カウンタによりデイジタル的に検
出し、これをアナログ信号に変換して直流電圧を発生さ
せ、この直流電圧により局部発振器の発振周波数を制御
することが考えられている。To do this, a counter digitally detects the oscillation frequency of the local oscillator based on the output of a reference frequency oscillator that oscillates at a predetermined frequency corresponding to the frequency step, and converts this into an analog signal to generate a DC voltage. It has been considered to control the oscillation frequency of the local oscillator using this DC voltage.
すなわち上記直流電圧により、局部発振器の発振周波数
を上記基準周波数発振器で規定された周波数間隔で存在
するセッティングポイントに常に引戻すように制御する
ものである。That is, the DC voltage is used to control the oscillation frequency of the local oscillator so as to always return it to a setting point that exists at a frequency interval defined by the reference frequency oscillator.
しかしながらこのようなものでは局部発振器へ制御用の
直流電圧を与えたまま同調操作を行なうと、正同調点の
近くで発振周波数が引き込まれ、同調が見掛上緩かにな
り、しかもダイアル指針の指示する周波数目盛と実際の
受信周波数との間にズレを生じる原因にもなる。However, with such a device, if the tuning operation is performed while the control DC voltage is applied to the local oscillator, the oscillation frequency will be pulled in near the positive tuning point, making the tuning apparently looser, and the dial pointer will change. This can also cause a discrepancy between the indicated frequency scale and the actual received frequency.
本考案は上記の事情に鑑みてなされたもので同調操作中
は局部発振回路へ与える制御用の直流電圧を断ち、同調
操作を完了後、局部発振回路へ制御用の直流電圧を与え
て自動的に所定の同調周波数を維持できるようにし、容
易に正確な同調操作を行なうことができる自動周波数制
御回路を提供することを目的とするものである。This invention was developed in view of the above circumstances, and during the tuning operation, the control DC voltage applied to the local oscillation circuit is cut off, and after the tuning operation is completed, the control DC voltage is applied to the local oscillation circuit automatically. It is an object of the present invention to provide an automatic frequency control circuit that can maintain a predetermined tuning frequency and easily perform accurate tuning operations.
以下本考案の一実施例を図に示すブロック図を参照して
詳細に説明する。Hereinafter, one embodiment of the present invention will be described in detail with reference to the block diagram shown in the drawings.
アンテナ１で受信された信号、たとえばＦＭ放送信号を
、高周波増幅器２で増幅してミクサ３へ与え、局部発振
回路４の発振出力と混合して所定の中間周波数に変換す
る。A signal received by an antenna 1, for example, an FM broadcast signal, is amplified by a high frequency amplifier 2 and given to a mixer 3, where it is mixed with the oscillation output of a local oscillation circuit 4 and converted to a predetermined intermediate frequency.
そしてこの中間周波信号を中間周波増幅器５で増幅し、
検波器６で検波して低周波信号を得、図示しないスピー
力等から再生する。This intermediate frequency signal is then amplified by an intermediate frequency amplifier 5,
A low frequency signal is obtained by detection by a wave detector 6 and reproduced from a speaker power (not shown) or the like.
一方上記局部発振回路４の発振出力をブリスケーラ７で
分周後、ゲート８を介して１０ ｋＨｚ、１００ ｋＨ
ｚ、ＩＭＨｚ、１０ＭＨｚ、ｌＱＱＭＨｚにそれぞれ対
応する５段のＢＣＤカウンタ９， １０， １１， １
２， １３へ与えてカウントする。On the other hand, the oscillation output of the local oscillation circuit 4 is frequency-divided by a brise scaler 7, and then transmitted through a gate 8 to 10 kHz and 100 kHz.
5-stage BCD counters 9, 10, 11, 1 corresponding to z, IMHz, 10MHz, and lQQMHz, respectively
Give it to 2, 13 and count.
なお上記各カウンタ９，１０， １１， １２， １３
は局部発振回路の発振出力から受信周波数を逆算するた
めにオフセット信号発生器１４からオフセット信号を与
えて受信周波数に対応するＢＣＤ信号を得る。Note that each of the above counters 9, 10, 11, 12, 13
In order to calculate the reception frequency backward from the oscillation output of the local oscillation circuit, an offset signal is applied from the offset signal generator 14 to obtain a BCD signal corresponding to the reception frequency.
このＢＣＤ信号はラッチ、テ゛コーダ、ドライバ回路１
５を介して表示器１６に表示する。This BCD signal is used for latch, coder, driver circuit 1
5 on the display 16.
さらに最下位の桁のカウンタ９のカウント値をラツチ１
７を介してテ゛ジタルーアナログ変換器１８および数値
比較回路１９へ与える。Furthermore, the count value of counter 9 of the lowest digit is latch 1.
7 to a digital-to-analog converter 18 and a numerical comparison circuit 19.
なおゲート８、各カウンタ９， １０， １１， １２
， １３および゛ラツチ１７は基準発振器２０から与え
られる一定周波数の基準信号によって制御される。In addition, gate 8, each counter 9, 10, 11, 12
, 13 and latch 17 are controlled by a constant frequency reference signal provided by a reference oscillator 20.
また数値比較回路１９はラツチ１７の出力が３〜７にな
ったことを検出すると遅延回路２１を介してスイッチ２
２をＡＦＣ側へ駆動する。Further, when the numerical comparison circuit 19 detects that the output of the latch 17 has become 3 to 7, it passes the output to the switch 2 through the delay circuit 21.
2 to the AFC side.
このスイッチ２２は可動接点を局部発振回路４の可変容
量ダイオードに接続し、フリーラン側の固定接点には所
定電圧の電源２３を接続している。This switch 22 has a movable contact connected to a variable capacitance diode of the local oscillation circuit 4, and a fixed contact on the free run side connected to a power supply 23 of a predetermined voltage.
またデジタルーアナログ変換器１８のアナログ出力を増
幅器２４で増幅し、フィルタ２５を介して、スイッチ２
２のＡＦＣ側の接点へ接続している。Further, the analog output of the digital-to-analog converter 18 is amplified by the amplifier 24, and then passed through the filter 25 to the switch 2.
Connected to the AFC side contact of No.2.
なお１０ ｋＨｚをカウントするカウンタ９にはオフセ
ット値として５を与え、同調点においてカウント出力５
を得るようにしている。Note that the counter 9 that counts 10 kHz is given an offset value of 5, and the count output is 5 at the tuning point.
I'm trying to get it.
このような構或であれば図示しない同調ノブを操作すれ
ば局部発振回路４の発振周波数を変化させ所望の放送電
波を受信することができる。With such a structure, by operating a tuning knob (not shown), the oscillation frequency of the local oscillation circuit 4 can be changed and desired broadcast waves can be received.
なおこの場合１０ｋＨｚの桁が０になる１００ ｋＨｚ
毎にラッチ１７の出力は５となりそれを数値比較回路１
９で検出し、遅延回路２１を介してスイッチ２２をＡＦ
Ｃ側へ切換える。In this case, the 10kHz digit becomes 0, which is 100kHz.
Each time, the output of the latch 17 becomes 5, which is sent to the numerical comparison circuit 1.
9, and the switch 22 is activated via the delay circuit 21.
Switch to C side.
したがってラッチ１７の出力をアナログ変換したアナロ
グ信号を上記スイッチ２２を介して局部発振回路４へ与
えて発振出力周波数の自動周波数制御、すなわちロック
動作を行なうことができる。Therefore, an analog signal obtained by converting the output of the latch 17 into an analog signal can be applied to the local oscillation circuit 4 via the switch 22 to perform automatic frequency control of the oscillation output frequency, that is, a locking operation.
一方所定のゲート時間内にラツチ１７の出力が３〜７の
範囲から逸脱する、すなわち上記ゲート時間内に正同調
点より３０ｋＨｚ以上の変化を生じるとそれによって数
値比較回路１９の出力は消勢し上記ロックは解除される
。On the other hand, if the output of the latch 17 deviates from the range of 3 to 7 within the predetermined gate time, that is, if there is a change of 30 kHz or more from the positive tuning point within the gate time, the output of the numerical comparison circuit 19 is deenergized. The above lock is released.
したがってスイッチ２２はフリーラン側へ駆動され局部
発振回路４に電源２３から一定の電圧を与えることによ
って容易に正確な同調操作を行なうことができる。Therefore, the switch 22 is driven to the free run side, and by applying a constant voltage to the local oscillation circuit 4 from the power supply 23, accurate tuning operation can be easily performed.
なお、本考案は上記実施例に限定されるものではなく、
たとえば自動周波数制御をＦＭ検波器の出力に同調状態
に応じて得られる正負極性のＳ字特性の直流信号を用い
て局部発振回路の発振周波数を直流的に制御するものに
も応用できることは勿論である。Note that the present invention is not limited to the above embodiments,
For example, automatic frequency control can of course be applied to DC control of the oscillation frequency of a local oscillation circuit using a DC signal with S-shaped characteristics of positive and negative polarity obtained depending on the tuning state of the output of an FM detector. be.
さらに上記制御用の直流電圧に所定のリミットを設定し
てもよいし、電界強度、ＦＭ検波器の零点等を併用して
、電波の存在する同調点でのみロックを行なうようにし
てもよいし、ロック信号およびミューテイング信号を併
用し、ロック時のみ｛氏周波出力を出すようにしてもよ
い。Furthermore, a predetermined limit may be set on the DC voltage for control, or locking may be performed only at tuning points where radio waves are present, using electric field strength, the zero point of an FM detector, etc. , a lock signal, and a muting signal may be used in combination, and the frequency output may be output only when locked.
また可変容量ダイオードを用いたフロントエンドで制御
電圧を連続的に変化させて、自動スキャニング動作のス
タート、ストップを行ない、ストップ動作に応動して自
動周波数制御を動作させることもできる。It is also possible to start and stop the automatic scanning operation by continuously changing the control voltage using a front end using a variable capacitance diode, and to operate the automatic frequency control in response to the stop operation.
以上詳述したように本考案によれば同調操作中は局部発
振器への制御用の直流電圧を断ち、正同調点に同調して
制御用の直流電圧を自動的に与えるようにしたから同調
操作を容易かつ正確に行なえ、しかもこの正同調点を確
実に保持することができる自動周波数制御回路を提供す
ることができる。As detailed above, according to the present invention, the control DC voltage to the local oscillator is cut off during the tuning operation, and the control DC voltage is automatically applied when the local oscillator is tuned to the positive tuning point. It is possible to provide an automatic frequency control circuit that can easily and accurately perform this, and can also reliably maintain this positive tuning point.
図は本考案の一実施例を示すブロック図である。
４・・・局部発振器、９， １０， １１， １２，
１３・・・カウンタ、１８・・・デジタルーアナログ変
換器、１９・・・数値比較回路、２０・・・基準発振器
、２２・・・スイッチ。The figure is a block diagram showing one embodiment of the present invention. 4...Local oscillator, 9, 10, 11, 12,
13... Counter, 18... Digital-analog converter, 19... Numerical comparison circuit, 20... Reference oscillator, 22... Switch.
Claims (1)
このカウント値を所定の設定値と比較しこの差分をアナ
ログ変換した直流信号を局部発振器へ与えて発振周波数
を制御するようにしたものにおいて、上記カウント値の
変化量が上記ゲート時間に所定値を越えたときに同調操
作中とみなして上記直流信号を断つようにしたことを特
徴とする自動周波数制御回路。In a device in which the oscillation frequency of a local oscillator is counted for a predetermined gate time, this count value is compared with a predetermined set value, and this difference is converted into an analog DC signal, which is applied to the local oscillator to control the oscillation frequency. An automatic frequency control circuit characterized in that when the amount of change in value exceeds a predetermined value during the gate time, it is assumed that a tuning operation is in progress and the DC signal is cut off.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6806778U JPS5910816Y2 (en) | 1978-05-20 | 1978-05-20 | automatic frequency control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6806778U JPS5910816Y2 (en) | 1978-05-20 | 1978-05-20 | automatic frequency control circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS54170758U JPS54170758U (en) | 1979-12-03 |
| JPS5910816Y2 true JPS5910816Y2 (en) | 1984-04-04 |
Family
ID=28975603
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6806778U Expired JPS5910816Y2 (en) | 1978-05-20 | 1978-05-20 | automatic frequency control circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5910816Y2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR950009407B1 (en) * | 1993-09-21 | 1995-08-22 | 주식회사금성사 | Digital channel selecting device and its method |
-
1978
- 1978-05-20 JP JP6806778U patent/JPS5910816Y2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| JPS54170758U (en) | 1979-12-03 |
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