JPH0697792A - Pulse frequency modulation system - Google Patents
Pulse frequency modulation systemInfo
- Publication number
- JPH0697792A JPH0697792A JP11638891A JP11638891A JPH0697792A JP H0697792 A JPH0697792 A JP H0697792A JP 11638891 A JP11638891 A JP 11638891A JP 11638891 A JP11638891 A JP 11638891A JP H0697792 A JPH0697792 A JP H0697792A
- Authority
- JP
- Japan
- Prior art keywords
- pulse frequency
- video signal
- circuit
- signal
- frequency modulation
- 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
Landscapes
- Picture Signal Circuits (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明はビデオ伝送の送受信装置
に使用するパルス周波数変調方式に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse frequency modulation method used in a transmitter / receiver for video transmission.
【０００２】[0002]
【従来の技術】従来のビデオ信号のパルス周波数変調方
式は、図２に示すようにコンデン１８により直流成分が
遮断されたビデオ信号をパルス周波数変調回路１２にお
いて、演算増幅器１６からの直流信号１７に応じてパル
ス周波数変調して出力し、この出力をパルス周波数復調
回路１３とローパスフィルタ１４とにより検出された直
流分を演算増幅器１６に入力していた。演算増幅器１６
は、検出された直流分とグランドＧレベルとを比較して
直流信号１７を出力し、パルス周波数変調回路１２がパ
ルス周波数変調を行う際の中心周波数のずれを制御して
いた。2. Description of the Related Art In the conventional pulse frequency modulation method of a video signal, a video signal of which DC component is blocked by a condenser 18 is converted into a DC signal 17 from an operational amplifier 16 in a pulse frequency modulation circuit 12 as shown in FIG. Accordingly, the pulse frequency is modulated and output, and the DC component detected by the pulse frequency demodulation circuit 13 and the low pass filter 14 is input to the operational amplifier 16. Operational amplifier 16
Compares the detected DC component with the ground G level and outputs a DC signal 17 to control the deviation of the center frequency when the pulse frequency modulation circuit 12 performs the pulse frequency modulation.
【０００３】[0003]
【発明が解決しようとする課題】この従来のパルス周波
数変調方式では、コンデンサにより直流成分を遮断した
ビデオ信号を用いていたため、ビデオ信号の平均レベル
（ＡＰＬ＝アベレージピクチャーレベル）変動を抑える
ことが困難であった。In this conventional pulse frequency modulation method, since the video signal in which the direct current component is blocked by the capacitor is used, it is difficult to suppress the fluctuation of the average level (APL = average picture level) of the video signal. Met.
【０００４】[0004]
【課題を解決するための手段】本発明のパルス周波数変
調方式は、入力のビデオ信号の平均レベル変動を抑圧し
第１のビデオ信号として出力するクランパー回路と、前
記第１のビデオ信号を直流信号に応じてパルス周波数変
調するパルス周波数変調回路と、前記パルス周波数変調
された第１のビデオ信号を復調し第２のビデオ信号とし
て出力するパルス周波数復調回路と、前記第１と第２の
ビデオ信号の直流レベルをそれぞれ検出する第１と第２
のローパルフィルタと、この第１と第２のローパスフィ
ルタからの出力が比較された差の前記直流信号を出力す
る演算増幅器とを有する。According to the pulse frequency modulation method of the present invention, a clamper circuit for suppressing an average level fluctuation of an input video signal and outputting it as a first video signal, and a DC signal for the first video signal. A pulse frequency modulation circuit for performing pulse frequency modulation according to the above, a pulse frequency demodulation circuit for demodulating the pulse frequency modulated first video signal and outputting it as a second video signal, and the first and second video signals 1st and 2nd to detect the DC level of
Low-pass filter and an operational amplifier that outputs the DC signal of the difference between the outputs from the first and second low-pass filters.
【０００５】[0005]
【実施例】次に、本発明について図面を参照して説明す
る。図１は本発明の一実施例のブロック図である。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.
【０００６】本実施例は、入力のビデオ信号の平均レベ
ル変動を抑圧し第１のビデオ信号ａとして出力するクラ
ンパー回路１と、第１のビデオ信号ａを直流信号７に応
じてパルス周波数変調するパルス周波数変調回路２とパ
ルス周波数変調された第１のビデオ信号ｂを復調し第２
のビデオ信号ｃとして出力するパルス周波数復調回路３
と、第１と第２のビデオ信号ａ，ｃの直流レベルをそれ
ぞれ検出する第１と第２のローパルフィルタ４，５とこ
の第１の第２のローパスフィルタ４，５からの出力が比
較された差の直流信号７を出力する演算増幅器６とを有
して構成される。In this embodiment, a clamper circuit 1 for suppressing an average level fluctuation of an input video signal and outputting it as a first video signal a, and a pulse frequency modulation of the first video signal a according to a DC signal 7. The pulse frequency modulation circuit 2 and the pulse frequency modulated first video signal b are demodulated to the second
Frequency demodulation circuit 3 for outputting as the video signal c
And the outputs from the first and second low pass filters 4 and 5 for detecting the DC levels of the first and second video signals a and c, respectively, and the outputs from the first and second low pass filters 4 and 5. And an operational amplifier 6 that outputs a DC signal 7 of the difference.
【０００７】次に動作について説明すると入力されたビ
デオ信号のＡＰＬ変動を抑えるクランパー回路１からの
第１のビデオ信号ａはパルス周波数変調回路２によりパ
ルス周波数変調され、送信される。その際、パルス周波
数変調されたビデオ信号ｂを分岐し、パルス周波数復調
回路３に入力し、復調された第２のビデオ信号ｃを得
る。第２のビデオ信号ｃの直流成分を第２のローパスフ
ィルタ５により検出する。クランパー回路１から第１の
ビデオ信号ａの直流成分を第１のローパスフィルタ５に
より検出する。第１と第２のビデオ信号の直流成分を演
算増幅器６により比較し、パルス周波数変調の際の中心
周波数のずれを検出する。そしてこの検出された中心周
波数のずれをパルス周波数変調回路２に直流信号７とし
て入力し、パルス変調の際の中心周波数のずれを修正す
る。The operation will now be described. The first video signal a from the clamper circuit 1 for suppressing the APL fluctuation of the input video signal is pulse frequency modulated by the pulse frequency modulation circuit 2 and transmitted. At that time, the pulse frequency-modulated video signal b is branched and input to the pulse frequency demodulation circuit 3 to obtain a demodulated second video signal c. The DC component of the second video signal c is detected by the second low pass filter 5. The DC component of the first video signal a from the clamper circuit 1 is detected by the first low pass filter 5. The DC components of the first and second video signals are compared by the operational amplifier 6 to detect the deviation of the center frequency during pulse frequency modulation. Then, the detected shift of the center frequency is input to the pulse frequency modulation circuit 2 as a DC signal 7, and the shift of the center frequency at the time of pulse modulation is corrected.
【０００８】[0008]
【発明の効果】以上説明したように本発明は、パルス周
波数変調回路に入力するビデオ信号と出力が復調された
ビデオ信号とが比較された直流信号によりパルス周波数
変調の中心周波数を制御することにより、入力のビデオ
信号の平均レベル変調を抑圧したパルス周波数変調を行
うことができる。As described above, according to the present invention, the center frequency of pulse frequency modulation is controlled by the DC signal obtained by comparing the video signal input to the pulse frequency modulation circuit with the demodulated output video signal. It is possible to perform pulse frequency modulation in which the average level modulation of the input video signal is suppressed.
【図１】本発明の一実施例のブロック図である。FIG. 1 is a block diagram of an embodiment of the present invention.
【図２】従来のパルス周波数変調方式の一例のブロック
図である。FIG. 2 is a block diagram of an example of a conventional pulse frequency modulation method.
１ クランパー回路 ２ パルス周波数変調回路 ３ パルス周波数復調回路 ４ 第１のローパスフィルタ ５ 第２のローパスフィルタ ６ 演算増幅器 1 Clamper Circuit 2 Pulse Frequency Modulation Circuit 3 Pulse Frequency Demodulation Circuit 4 First Low Pass Filter 5 Second Low Pass Filter 6 Operational Amplifier
Claims (1)
圧し第１のビデオ信号として出力するクランパー回路
と、前記第１のビデオ信号を直流信号に応じてパルス周
波数変調するパルス周波数変調回路と、前記パルス周波
数変調された第１のビデオ信号を復調し第２のビデオ信
号として出力するパルス周波数復調回路と、前記第１と
第２のビデオ信号の直流レベルをそれぞれ検出する第１
と第２のローパルフィルタと、この第１と第２のローパ
スフィルタからの出力が比較された差の前記直流信号を
出力する演算増幅器とを有することを特徴とするパルス
周波数変調方式。1. A clamper circuit for suppressing an average level fluctuation of an input video signal and outputting it as a first video signal, and a pulse frequency modulation circuit for pulse frequency modulating the first video signal according to a DC signal. A pulse frequency demodulation circuit for demodulating the pulse frequency modulated first video signal and outputting it as a second video signal, and a first frequency detecting circuit for detecting the DC levels of the first and second video signals, respectively.
And a second low-pass filter, and an operational amplifier for outputting the DC signal having a difference obtained by comparing the outputs from the first and second low-pass filters.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11638891A JPH0697792A (en) | 1991-05-22 | 1991-05-22 | Pulse frequency modulation system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11638891A JPH0697792A (en) | 1991-05-22 | 1991-05-22 | Pulse frequency modulation system |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0697792A true JPH0697792A (en) | 1994-04-08 |
Family
ID=14685790
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11638891A Pending JPH0697792A (en) | 1991-05-22 | 1991-05-22 | Pulse frequency modulation system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0697792A (en) |
-
1991
- 1991-05-22 JP JP11638891A patent/JPH0697792A/en active Pending
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 19990223 |