【０００１】[0001]
【産業上の利用分野】本発明はＦＭ信号の復調感度の自
動調整化に関し、特に集積回路（ＩＣ）に内蔵したＦＭ
信号の復調器（FM Demodulater）の復調感度を自動的に
調整することで無調整化を行った集積回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to automatic adjustment of demodulation sensitivity of FM signals, and more particularly to FM incorporated in an integrated circuit (IC).
The present invention relates to an integrated circuit in which the demodulation sensitivity of a signal demodulator (FM Demodulater) is automatically adjusted to eliminate adjustment.
【０００２】[0002]
【従来の技術】フィルタ回路やＦＭ信号の復調回路を集
積化する場合、集積回路（以下、ＩＣと略す。）内での
抵抗値，容量値の絶対精度は、あまりよくないため、Ｉ
Ｃ同しの間でこれらのバラ付きが生じて、各サンプルご
とに遮断周波数のズレや復調感度のズレが起きてしま
う。従来このようなＩＣ同しの間におけるフィルタ回路
の遮断周波数バラつきをなくすために、ＩＣ内での抵抗
値，容量値の相対的比精度は比較的良いことを利用し
て、遮断周波数を自動調整する回路が提案されている。
しかし、ＦＭ信号の復調回路の感度バラつきについては
自動調整されておらず、外部からの調整が必要であっ
た。フィルタの自動調整回路としては、例えば特開昭６
１−１７４８１０号公報，特昭６１−２８１６１３号公
報に記載されているものなどが知られている。2. Description of the Related Art When a filter circuit or an FM signal demodulation circuit is integrated, the absolute accuracy of the resistance value and the capacitance value in the integrated circuit (hereinafter abbreviated as IC) is not so good.
C These variations occur between the same, so that a cutoff frequency shift and a demodulation sensitivity shift occur for each sample. In order to eliminate variations in the cutoff frequency of the filter circuit between ICs, the relative cutoff frequency is automatically adjusted by utilizing the fact that the relative ratio accuracy of the resistance value and the capacitance value in the IC is relatively good. A circuit that does this has been proposed.
However, the variation in sensitivity of the FM signal demodulation circuit is not automatically adjusted, and adjustment from the outside is required. An automatic filter adjusting circuit is disclosed in, for example, Japanese Patent Laid-Open No.
Those described in JP-A-1-174810 and JP-B-61-281613 are known.
【０００３】[0003]
【発明が解決しようとする課題】ＦＭ信号の復調回路の
復調感度はＩＣ内の抵抗や、容量の絶対値バラつきによ
り、それぞれＩＣごとにバラついている。このためＦＭ
信号を再生したときの再生レベルが所定の値となるよう
に外部から調整する必要があった。本発明の目的はＩＣ
内で素子バラつきが起きても、復調感度変動の少ないＦ
Ｍ信号の復調回路を実現し、外部からの調整を省くこと
にある。The demodulation sensitivity of the FM signal demodulation circuit varies from IC to IC due to variations in absolute values of resistance and capacitance in the IC. For this reason FM
It was necessary to externally adjust the reproduction level when the signal was reproduced to a predetermined value. The object of the present invention is IC
Even if element variation occurs in the F
The purpose is to realize a demodulation circuit for the M signal and eliminate external adjustment.
【０００４】[0004]
【課題を解決するための手段】ＦＭ復調器として遅延線
型の回路を用いた場合、復調感度は遅延線もしくは移相
器のＣＲ積に比例する。ＩＣ内での素子の比精度（ペア
性）は比較的良好なため復調器でのＣＲ積ズレとフィル
タ部分のＣＲ積ズレはほぼ同じである。一方、ＩＣに集
積化されたフィルタは信号電圧を電流に変換する増幅器
と負荷容量から成る積分回路で構成される。遮断周波数
は増幅器の相互コンダクタンスと負荷容量で決まるた
め、どちらかを調整することでフィルタの遮断周波数を
制御できる。このフィルタの遮断周波数を制御する自動
調整回路は、そのＩＣ内の抵抗と容量の絶対値ズレを抵
抗値と容量値の積（ＣＲ積）のズレ量として検出し、フ
ィルタの遮断周波数を自動的に調整する。このためフィ
ルタの調整信号を復調器に用いることによりＣＲ積のズ
レによる復調感度ズレを補償することができる。When a delay line type circuit is used as the FM demodulator, the demodulation sensitivity is proportional to the CR product of the delay line or the phase shifter. Since the relative accuracy (pairability) of the elements in the IC is relatively good, the CR product deviation in the demodulator and the CR product deviation in the filter part are almost the same. On the other hand, the filter integrated in the IC is composed of an integrating circuit including an amplifier for converting a signal voltage into a current and a load capacitance. Since the cutoff frequency is determined by the transconductance of the amplifier and the load capacitance, the cutoff frequency of the filter can be controlled by adjusting either one. The automatic adjustment circuit that controls the cutoff frequency of the filter detects the deviation of the absolute value of the resistance and the capacitance in the IC as the deviation amount of the product of the resistance value and the capacitance value (CR product), and automatically determines the cutoff frequency of the filter. Adjust to. Therefore, by using the adjustment signal of the filter in the demodulator, it is possible to compensate the demodulation sensitivity shift due to the shift of the CR product.
【０００５】[0005]
【作用】フィルタの自動調整回路はある基準信号を２つ
に分け、一方は調整用フィルタを通して位相を回して位
相比較器に入力し、もう一方を直接位相比較器に入力
し、両者の位相差を検出してフィルタの調整信号として
調整用フィルタにフィードバックする。この結果、調整
用フィルタは所定の特性となるよう、ＣＲ積バラつきが
補償される。遅延線型のＦＭ信号復調器ではＦＭ信号は
リミッタにより波形整形された後、２分され一方は直接
掛け算器に入力され、他方は遅延線もしくは移相器を介
して前記掛け算器に入力される。この掛け算器の出力は
パルス幅変調された信号となるため、低域通過型フィル
タ（ＬＰＦ）を通すことにより、復調信号を得ることが
できる。この前記遅延線もしくは移相器の移送量はＣＲ
積に依存する。このＣＲ積バラつきによる遅延時間ズレ
はフィルタの調整信号を用いて補償され、復調感度は一
定となる。The automatic adjustment circuit of the filter divides a certain reference signal into two, one of which rotates the phase through the adjustment filter and inputs it to the phase comparator, and the other directly inputs it to the phase comparator to detect the phase difference between the two. Is detected and fed back to the adjustment filter as an adjustment signal of the filter. As a result, the CR filter variation is compensated so that the adjustment filter has a predetermined characteristic. In the delay line type FM signal demodulator, the FM signal is waveform-shaped by the limiter and then divided into two, one of which is directly input to the multiplier and the other of which is input to the multiplier through the delay line or the phase shifter. Since the output of this multiplier is a pulse width modulated signal, a demodulated signal can be obtained by passing it through a low pass filter (LPF). The transfer amount of the delay line or phase shifter is CR
Depends on the product. The delay time shift due to this CR product variation is compensated by using the adjustment signal of the filter, and the demodulation sensitivity becomes constant.
【０００６】[0006]
【実施例】以下、本発明の一実施例を図１及び図２を用
いて説明する。ＦＭ復調器１１について説明する前にフ
ィルタの自動調整回路２０の動作について説明する。基
準信号源１の信号は２分され、一方は直接位相比較器３
に入力され、他方は調整用フィルタ２を通過した後位相
比較器３に入力され、両者の位相差が検出される。位相
比較器３の出力は信号変換手段４によりフィルタの遮断
周波数調整信号に変換され、調整用フィルタ２に負帰還
される。調整用フィルタは増幅器と負荷容量で構成さ
れ、フィルタの遮断周波数調整信号で増幅器の相互コン
ダクタンスを変えることで遮断周波数を調整することが
できる。調整用フィルタ２として２次のアクティブフィ
ルタを用いた場合、フィルタの周波数特性は基準信号周
波数で、ちょうど位相が９０度まわる。つまり基準信号
周波数がフィルタのカットオフ周波数と一致する。通
常、自動調整される被調整フィルタは調整用フィルタと
等しいか、または相関の有るフィルタを用いる。これに
より被調整フィルタはフィルタの遮断周波数調整信号に
よって所定の周波数特性に調整される。さらに、調整用
フィルタ２をＩＣ内の素子（抵抗と容量）バラつきがな
い状態で基準信号周波数がカットオフ周波数と一致する
ように設計すれば、前記フィルタの遮断周波数調整信号
はＩＣ内のＣＲバラつきを補償する信号となる。つぎに
ＦＭ復調器の動作について説明する。ＦＭ信号５はリミ
ッタ６に入力され、方形波に波形整形された後、復調器
１１に入力される。復調器１１の出力には再生信号とＦ
Ｍ信号の２倍波が含まれており、低域通過型フィルタ
（ＬＰＦ）９にてＦＭ信号の２倍波を抑圧して再生信号
が取り出される。ＶＴＲ等の集積回路に内蔵されている
復調器１１の一般的構成は遅延線型ＦＭ復調器でリミッ
タ６の信号と、遅延線または移相器７を通過した信号を
掛け算（平衡変調）する回路である。本復調方式の入力
周波数対出力特性（ｆ−Ｖ特性）の例を図３に示す。遅
延線の遅延量をτとすると復調特性が折り変わる周波数
は ｆ＝１／２τ となる。復調感度Ｓ1 は Ｓ＝Ｅ0２τ となる。周波数ｆが０の時の復調電位Ｅ0 は掛け算器の
出力振幅で決まる。一般の回路では、この復調電圧Ｅ0
は負荷抵抗とそれに流れる電流で決まる。電流は抵抗値
に反比例するため復調電圧Ｅ0 は抵抗比で決まる。さら
に、ＩＣ内での素子比精度は良好なため、復調電圧Ｅ0
の絶対値は変化しない。しかしＩＣ内でのＣＲ積は前述
した様にバラつく。遅延線もしくは移相器７としてＩＣ
ではモノマルチバイブレータがよく用いられている。こ
の回路の遅延時間はエミッタ間容量とそれに流れる電流
の逆数に比例する。言い替えれば、容量と抵抗の積（Ｃ
Ｒ積）に比例する。この結果、復調感度もＣＲ積に比例
して変動する。遅延線もしくは移相器７の遅延量τ1 が
設計どうりの場合の復調特性をとすると、遅延線もし
くは移送器７の遅延量が多い場合（τ2 ）の復調特性は
のごとく復調感度は大きくなる。そこで前記フィルタ
の遮断周波数調整信号を用いて遅延線もしくは移相器７
の遅延時間を補正して、ＦＭ復調器１１の復調感度を自
動調整できる。また、遅延線としてアクティブフィルタ
を用いても、同様な結果を得ることが出来る。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Before describing the FM demodulator 11, the operation of the filter automatic adjustment circuit 20 will be described. The signal of the reference signal source 1 is divided into two, one of which is the direct phase comparator 3
Is input to the phase comparator 3 after passing through the adjustment filter 2, and the phase difference between the two is detected. The output of the phase comparator 3 is converted into a cutoff frequency adjusting signal of the filter by the signal converting means 4 and is negatively fed back to the adjusting filter 2. The adjustment filter is composed of an amplifier and a load capacitance, and the cutoff frequency can be adjusted by changing the transconductance of the amplifier with the cutoff frequency adjustment signal of the filter. When a second-order active filter is used as the adjustment filter 2, the frequency characteristic of the filter is the reference signal frequency, and the phase shifts by 90 degrees. That is, the reference signal frequency matches the cutoff frequency of the filter. Usually, the adjusted filter to be automatically adjusted uses a filter that is equal to or correlated with the adjustment filter. Accordingly, the filter to be adjusted is adjusted to have a predetermined frequency characteristic by the cutoff frequency adjustment signal of the filter. Furthermore, if the adjustment filter 2 is designed so that the reference signal frequency matches the cutoff frequency in the state where there is no variation in the elements (resistance and capacitance) in the IC, the cutoff frequency adjustment signal of the filter has CR variation in the IC. Will be a signal that compensates. Next, the operation of the FM demodulator will be described. The FM signal 5 is input to the limiter 6, shaped into a square wave, and then input to the demodulator 11. The output of the demodulator 11 is the reproduction signal and F
The second harmonic of the M signal is included, and the low-pass filter (LPF) 9 suppresses the second harmonic of the FM signal to extract the reproduction signal. The general structure of the demodulator 11 built in an integrated circuit such as a VTR is a delay line type FM demodulator which is a circuit for multiplying the signal of the limiter 6 and the signal passed through the delay line or the phase shifter 7 (balanced modulation). is there. An example of the input frequency vs. output characteristic (f-V characteristic) of this demodulation method is shown in FIG. When the delay amount of the delay line is τ, the frequency at which the demodulation characteristics change is f = 1 / 2τ. The demodulation sensitivity S1 is S = E0 2τ. The demodulation potential E0 when the frequency f is 0 is determined by the output amplitude of the multiplier. In a general circuit, this demodulation voltage E0
Is determined by the load resistance and the current flowing through it. Since the current is inversely proportional to the resistance value, the demodulation voltage E0 is determined by the resistance ratio. Further, since the element ratio accuracy in the IC is good, the demodulation voltage E0
The absolute value of does not change. However, the CR product in the IC varies as described above. IC as delay line or phase shifter 7
The mono-multivibrator is often used in. The delay time of this circuit is proportional to the capacitance between the emitters and the reciprocal of the current flowing through it. In other words, the product of capacitance and resistance (C
R product). As a result, the demodulation sensitivity also changes in proportion to the CR product. Given the demodulation characteristics when the delay amount τ1 of the delay line or the phase shifter 7 is as designed, the demodulation sensitivity when the delay amount of the delay line or the transporter 7 is large (τ2 ) is growing. Therefore, a delay line or phase shifter 7 is used by using the cutoff frequency adjustment signal of the filter.
By correcting the delay time of, the demodulation sensitivity of the FM demodulator 11 can be automatically adjusted. Also, the same result can be obtained by using an active filter as the delay line.
【０００７】他の具体的な実施例を図４を用いて説明す
る。第１の実施例において調整用フィルタ２と移相比較
器３と信号変換手段４を一つにまとめて自動調整回路２
０として示す。実際の回路ブロックでは復調器１１の出
力はディエンファシス回路を通過した後、低域通過型フ
ィルタ（ＬＰＦ）９に入力される。フィルタの自動調整
回路の出力信号はＬＰＦ９とＦＭ復調器１１の遅延線も
しくは移相器の７とＦＭ判別回路２１に入力される。Ｖ
ＴＲ等ＦＭ信号の復調の場合、VHS と S-VHSまたは Low
Band と High Band 等のように２種類のＦＭアロケー
ションをもつ信号が入力される。復調器１１ではＦＭ判
別回路２１の判別結果を受けて、適正な復調感度となる
ように遅延線もしくは移相器７の遅延時間を切替てい
る。このため入力されている信号がどちらのモードかを
判別するＦＭ判別回路２１が付加されている。ＦＭ判別
回路２１は一種のＦＭ復調器で、復調結果をあるスレッ
シュ電圧でコンパレートして VHS か S-VHS または Low
Band か High Band かを判別する。このＦＭ判別回路
２１の判別切り替わり周波数も遅延線の遅延時間もしく
は移相器の９０度移相がまわる周波数を正確に調整しな
くてはならない。このためフィルタの遮断周波数調整回
路の信号を用いてＦＭ判別回路２１の遅延線の遅延時間
もしくは移相器の移相量を自動調整している。本発明に
依ればＩＣ内部の素子バラつきを補償して復調器１１お
よびＦＭ判別回路２１の調整を自動化できる。Another specific embodiment will be described with reference to FIG. In the first embodiment, the adjusting filter 2, the phase shift comparator 3, and the signal converting means 4 are combined into one and the automatic adjusting circuit 2 is combined.
Shown as 0. In an actual circuit block, the output of the demodulator 11 passes through the de-emphasis circuit and then is input to the low pass filter (LPF) 9. The output signal of the filter automatic adjustment circuit is input to the LPF 9 and the delay line of the FM demodulator 11 or the phase shifter 7 and the FM discrimination circuit 21. V
For demodulation of FM signals such as TR, VHS and S-VHS or Low
Signals with two types of FM allocation such as Band and High Band are input. The demodulator 11 receives the discrimination result of the FM discrimination circuit 21 and switches the delay time of the delay line or the phase shifter 7 so that the demodulation sensitivity becomes appropriate. Therefore, an FM discriminating circuit 21 for discriminating which mode the input signal is in is added. The FM discriminating circuit 21 is a kind of FM demodulator, which compares the demodulation result with a certain threshold voltage to obtain VHS, S-VHS or Low.
Determine whether it is Band or High Band. As for the discrimination switching frequency of the FM discrimination circuit 21, the delay time of the delay line or the frequency at which the 90 ° phase shift of the phase shifter is rotated must be adjusted accurately. Therefore, the delay time of the delay line of the FM discriminating circuit 21 or the phase shift amount of the phase shifter is automatically adjusted using the signal of the cutoff frequency adjusting circuit of the filter. According to the present invention, the adjustment of the demodulator 11 and the FM discriminating circuit 21 can be automated by compensating for element variations inside the IC.
【０００８】[0008]
【発明の効果】本発明によれば、ＩＣ内の素子バラつき
による復調感度変化を補償でき、再生レベルの自動調整
かができる。According to the present invention, changes in demodulation sensitivity due to element variations in the IC can be compensated for, and the reproduction level can be automatically adjusted.
【図１】本発明の基本的構成を示すブロック図である。FIG. 1 is a block diagram showing a basic configuration of the present invention.
【図２】本発明の一実施例を示すブロック図である。FIG. 2 is a block diagram showing an embodiment of the present invention.
【図３】復調器の復調特性の一例を示す図である。FIG. 3 is a diagram showing an example of demodulation characteristics of a demodulator.
【図４】本発明の一実施例を示すブロック図である。FIG. 4 is a block diagram showing an embodiment of the present invention.
１…基準信号源、２…調整用フィルタ、３…位相比較
器、４…信号変換手段、５…ＦＭ信号源、６…リミッ
タ、７…遅延線もしくは移相器、８…掛け算器、９…Ｌ
ＰＦ、１０…復調信号出力、１１…復調器、２０…自動
調整回路、２１…ＦＭ判別回路、２２…ディエンファシ
ス回路。DESCRIPTION OF SYMBOLS 1 ... Reference signal source, 2 ... Adjustment filter, 3 ... Phase comparator, 4 ... Signal conversion means, 5 ... FM signal source, 6 ... Limiter, 7 ... Delay line or phase shifter, 8 ... Multiplier, 9 ... L
PF, 10 ... Demodulated signal output, 11 ... Demodulator, 20 ... Automatic adjustment circuit, 21 ... FM discrimination circuit, 22 ... De-emphasis circuit.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26063293AJPH07115328A (en) | 1993-10-19 | 1993-10-19 | FM signal demodulation circuit |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26063293AJPH07115328A (en) | 1993-10-19 | 1993-10-19 | FM signal demodulation circuit |
| Publication Number | Publication Date |
|---|---|
| JPH07115328Atrue JPH07115328A (en) | 1995-05-02 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26063293APendingJPH07115328A (en) | 1993-10-19 | 1993-10-19 | FM signal demodulation circuit |
| Country | Link |
|---|---|
| JP (1) | JPH07115328A (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6798678B2 (en) | 2001-01-24 | 2004-09-28 | Mitsubishi Denki Kabushiki Kaisha | Frequency voltage converter |
| US6850113B2 (en) | 2001-03-21 | 2005-02-01 | Sharp Kabushiki Kaisha | Demodulator and communication device using the same |
| US6977545B2 (en) | 2003-04-14 | 2005-12-20 | Sharp Kabushiki Kaisha | FM signal receiver and wireless communications device using same |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6798678B2 (en) | 2001-01-24 | 2004-09-28 | Mitsubishi Denki Kabushiki Kaisha | Frequency voltage converter |
| US6850113B2 (en) | 2001-03-21 | 2005-02-01 | Sharp Kabushiki Kaisha | Demodulator and communication device using the same |
| US6977545B2 (en) | 2003-04-14 | 2005-12-20 | Sharp Kabushiki Kaisha | FM signal receiver and wireless communications device using same |
| Publication | Publication Date | Title |
|---|---|---|
| US4881041A (en) | Pulse width distortion correction circuit | |
| EP0393717B1 (en) | Active filter circuit | |
| EP0018608A2 (en) | A noise removing apparatus | |
| EP0079097A1 (en) | Auto-tuned frequency discriminator | |
| JP2973491B2 (en) | NTSC / PAL signal discrimination circuit and active filter using this discrimination circuit | |
| US5450033A (en) | Frequency demodulation circuit | |
| JPH07115328A (en) | FM signal demodulation circuit | |
| US4349696A (en) | AM Stereophonic demodulator circuit for amplitude/angle modulation system | |
| GB2234650A (en) | Fm demodulating circuit with improved noise elimination | |
| US4605908A (en) | Disable circuit for a phase locked loop discriminator circuit | |
| US4633497A (en) | Separation control circuit | |
| JPS6244757B2 (en) | ||
| JPS6111012B2 (en) | ||
| JPS59219005A (en) | Quadrature detector | |
| JPS6230527B2 (en) | ||
| JPS5926681Y2 (en) | stereo demodulation circuit | |
| JPS5918741Y2 (en) | radio receiver | |
| JPS5924208Y2 (en) | Interfering signal detection circuit in FM stereo receiver | |
| JPH018024Y2 (en) | ||
| JPH033420A (en) | Pll circuit | |
| JP2002164742A (en) | FM demodulation circuit | |
| JPS594257A (en) | Carrier regenerative circuit | |
| JPH0134434B2 (en) | ||
| JPH0794951A (en) | Fm detection circuit | |
| JPH05110380A (en) | Automatic time constant adjustment circuit for filters |