CISPR20讲稿.doc

CISPR 20 声音，电视广播接收机及有关设备抗扰度限值和测量方法一 CISPR 20所适用的产品分类：（见后表2所示）二 相关词语的定义1. Sound receiver2. television receiver3. associated equipment4. multifunction equipment5. disturbance6. Interference三 CISPR 20主要的测试项目以及RS公司对其测试项目的专用术语简称1. S1 : Input immunity (Differential mode)2. S2a : Immunity from conducted voltages 3. S2b : Immunity from conducted currents (Common mode)4. S3 : Immunity from radiated fields5. S4 : Screening effectiveness6. EFT : Electrical transients7. ESD : Electrostatic discharge四 性能判定1. Performance criteria A1.1 Evaluaation of audio quality用客观的方法来评定声音的抗扰度：采用信噪比S/NTelevision,FM Radio and associated equipment: S/N40dBAM Radio: S/N26dBCar Radio: S/N26dB1.2 Evaluaation of picture quality用主观的方法来评定图象的抗扰度：人眼观察的距离必须正对图象，观察距离要求为屏幕高度的6倍。结果：图象不能有任何可察觉的干扰图形，色彩损伤以及扭曲，图形的几何变化，图象对比度的变化及同步失真等现象。 （注：如果怀疑图象性能是否刚好可察觉，可通断骚扰信号几次） 对于Video tape or Video disk equipment,必须使用Test-TV-Set。2. Performance criteria B五 适用性1. Multifunction equipment1.1多功能设备的每种功能都必须满足相关的各种条款要求；1.2如果某功能不属于该标准的相关条款，必须单独满足其它标准的相关条款（如：A TV receiver provided with a telecommunication function,the requirements for the telecommunication port are verified in accordance with CISP 24）2. PC tuner cards必须使用在整个系统中进行测试3. IR units必须和主单元放在一起进行测试六 抗扰度测试前的一般要求1. Immunity measurements are performed by application of a wanted test signal and an unwanted signal to the equipment under test. These signals and methods of application are specified in follow;2. The Limit values for the wanted and unwanted signals specified for the input immunity correspond to a nominal antenna impedance of 75. For receivers with nominal antenna impedance other than 75,these limit values on the antenna terminals are modified, according to the following formula: Lz=L+10lg(Z/75)dB(uV);3. Measurement procedure for audio assessment :1.1 First the wanted test signal is applied to the equipment under test .This produces a wanted audio signal which is measured.1.2 The volume control of the equipment under test or test set-up is adjusted to set this audio signal at the required level(调整音量控制一般为50mW,对于汽车收音机为500mW).The wanted audio signal is then removed by switching off the modulation or the audio test signal.1.3 The “unwanted” disturbance signal is applied in addition and its frequency is swept through the test range; its level is kept an the relevant limit value.1.4 The evaluation of the interference is made by measuring the level of the unwanted output signal and comparing this to the wanted output signal level.4. Audio power-output measurement (见图2)七 抗扰度的测量1. Measurement of input immunity1.1 Sound receiversMeasuring set-up(见图3)1.1.1 Measurement with unwanted signals outside the FM band range（Limit见表3） 有用信号: level 60dB(uV),1kHz调频，频偏40kHz(注：测量立体声音，附加19kHZ纯音导频信号，频偏7.5kHz)无用信号: 1Khz调幅，调幅80% 1.1.2 Measurement with unwanted signals inside the FM band range（Limit见表4） 有用信号: level 60dB(uV),1kHz调频，频偏75kHz(汽车收音机为40Khz)(注：测量立体声音，附加19kHZ纯音导频信号，频偏7.5kHz)无用信号: 1Khz调幅，频偏40kHz1.2 Television receivers and video tape equipment (Limit见表5，6)Measuring set-up(见图4)有用信号：图象 VHF: level 70dB(uV),UHF: level 74dB(uV) 声音 1kHz调频，频偏30kHz,VHF: level (70-X)dB(uV)UHF: level (74-X) dB(uV) X=10dB对于输入声音信号是双声道的，第二个声音载频:VHF: level (70-Y) dB(uV)UHF: level (74-Y) dB(uV) Y=20dB也用1kHz调频，频偏30kHZ，并附加54.6875kHz导频信，频偏2.5kHz,用于识别两个独立的声音通道。 无用信号：见表51.3 Satellite television receivers 2. Measurement of immunity to RF voltage (common mode) at antenna terminal（Limit见表8）2.1 测量原理(见图5)2.2 Coupling units(见图C1,C2,C3,C4) Type AC, Type MC, Type LC, Type Sr2.3 Mesurement set-up and circuit(见图6) 2.3.1 Sound receivers FM: 有用信号：tuned 98Mhz, level 60dB(uV), 1kHz调频, 频偏40kHz AM: 有用信号：tuned 250kHz(LW),1Mhz(MW),16Mhz(SW),level 46dB(uV),调幅1kHz，30%幅度 无用信号：调幅1kHz,80%幅度 2.3.2 Televvision receivers 有用信号：图象 level 70dB(uV) 声音 1kHz调频, 频偏30kHz 无用信号：调幅1kHz,80%幅度3. Measurement of screening effectiveness (Limit见表8a)3.1 Mesurement set-up(见图7) 3.1.1 Televvision receivers 3.1.2 Sound