英语翻译Amplitude Modulation Amplitude modulation (AM) is a modulation technique in which the amplitude of a high frequency sine wave (usually at a radio frequency) is varied in direct proportion to that of a modulating signal.The modulating sign

英语翻译Amplitude Modulation Amplitude modulation (AM) is a modulation technique in which the amplitude of a high frequency sine wave (usually at a radio frequency) is varied in direct proportion to that of a modulating signal.The modulating sign
英语翻译
Amplitude Modulation
Amplitude modulation (AM) is a modulation technique in which the amplitude of a high frequency sine wave (usually at a radio frequency) is varied in direct proportion to that of a modulating signal.The modulating signal carries the required information and often consists of audio data,as in the case of AM radio broadcasts or two-way radio communications.The high frequency sine wave (the carrier) is modulated by adding the modulating signal to it in a mixer.A simplified AM radio transmitter system is shown below.A simple form of amplitude modulation was originally used to modulate audio voice signals onto a low-voltage direct current (dc) carrier on a telephone circuit.A microphone in the telephone handset acts as a transducer,and uses the sound waves produced by the human voice to vary the current passing through the circuit.At the other end of the telephone line,a second transducer (in the form of a small loudspeaker mounted in the remote handset) uses the varying voltage to produce sound waves that are close enough to the original speech patterns to be recognisable as the voice of the caller.Although the human voice is composed of frequencies ranging from 300 to approximately 20,000 hertz,the public switched telephone system limits the frequencies used to between 300 and 3,400 hertz,giving a total bandwidth of 3,100 hertz.This bandwidth is perfectly adequate for purely voice transmission,since the higher frequencies in the human voice (i.e.those above 3,100 hertz) are not really needed for recognisable speech reproduction.The use of a limited bandwidth also makes the telephone system much simpler from an engineering perspective.Whereas telephone signals can be transmitted at audio frequencies,the same is not really a practical proposition for radio transmissions.The main reason for this is that the optimum length of a radio antenna is a half or a quarter of a wavelength.Since a typical audio frequency of 3,000 hertz has a wavelength of approximately 100 kilometres,the antenna would need to have a length of 25 kilometres to be effective - not a realistic proposition.By comparison,a radio frequency of 100 megahertz would have a wavelength of approximately 3 metres,and could use an antenna 80 centimetres long.It becomes necessary,therefore,to use a radio frequency carrier signal in order to transmit audio

英语翻译Amplitude Modulation Amplitude modulation (AM) is a modulation technique in which the amplitude of a high frequency sine wave (usually at a radio frequency) is varied in direct proportion to that of a modulating signal.The modulating sign
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振幅调制
振幅调制（上午）是一种调制技术，其中振幅高频率的正弦波（通常在一个无线电频率）是成正比变化，调制信号。调制信号进行所需的信息，通常包括音频数据，如在案件是广播或双向无线电通信。高频率的正弦调制波（承运人）通过添加调制信号在混频器。一个简化的调幅广播发射系统，如下所示。一个简单的形式的振幅调制最初是用来调节音频信号到一个低压直流（直流）载波电话电路。麦克风的电话手机就像一个传感器，...

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振幅调制
振幅调制（上午）是一种调制技术，其中振幅高频率的正弦波（通常在一个无线电频率）是成正比变化，调制信号。调制信号进行所需的信息，通常包括音频数据，如在案件是广播或双向无线电通信。高频率的正弦调制波（承运人）通过添加调制信号在混频器。一个简化的调幅广播发射系统，如下所示。一个简单的形式的振幅调制最初是用来调节音频信号到一个低压直流（直流）载波电话电路。麦克风的电话手机就像一个传感器，并利用声波产生的人类的声音不同的电流通过电路。在另一端的电话线，一个传感器（在一个小扬声器安装在远程手机）使用不同的电压产生声波，足够接近于原始语音模式来识别对方的声音。虽然人类的声音是由频率范围从300到大约20000赫兹，公共电话交换系统限制的频率使用之间的300和3400赫兹，使总带宽3100赫兹。这个带宽是完全足够的纯粹的语音传输，因为较高的频率在人类的声音（即高于3100赫兹）真的不需要识别语音再现。利用有限的带宽，使得系统简单得多，从工程的角度。而电话信号可以传输音频频率，同样是不真的是一个实践命题的无线电传输。最主要的原因是，最佳长度的无线电天线一半或四分之一波长。因为一个典型的音频频率为3000赫兹的波长约100公里，天线将需要有一个长度为25公里，是有效的，而不是一个现实的命题。相比之下，一个无线电频率100兆赫将波长大约3米，并且可以使用一个天线80厘米长。有必要，因此，使用无线电频率的载波信号来传输音频

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振幅调制　　　　振幅调制(AM)是一种调制技术的振幅高频率的正弦波(通常是在一个广播频率)是多种多样的成正比的调制信号。在调制信号携带所需资料及通常包括音频数据,在案件的是广播或双向无线电通讯。高频率的正弦波调制(载体),通过增加调制信号,交际的人。一个简化系统是无线电发射器如下图所示。一个简单的形式的振幅调制最初是用于调节音频声音信号到低压直流(dc)载体对电话线路。一个麦克风电话手机作为一个传...

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振幅调制　　　　振幅调制(AM)是一种调制技术的振幅高频率的正弦波(通常是在一个广播频率)是多种多样的成正比的调制信号。在调制信号携带所需资料及通常包括音频数据,在案件的是广播或双向无线电通讯。高频率的正弦波调制(载体),通过增加调制信号,交际的人。一个简化系统是无线电发射器如下图所示。一个简单的形式的振幅调制最初是用于调节音频声音信号到低压直流(dc)载体对电话线路。一个麦克风电话手机作为一个传感器,并采用声波所产生的人类的声音以不同的电流通过这条赛道。在另一端的teleph

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