什么是bcd碼數據傳輸通訊

傳輸障礙 (Transmission Impairment)

In the data communication system, analog and digital signals go through the transmission medium. Transmission media are not ideal. There are some imperfections in transmission mediums. So, the signals sent through the transmission medium are also not perfect. This imperfection cause signal impairment.

在數據通信系統中，模擬和數字信號通過傳輸介質。 傳輸媒體并不理想。 傳輸介質存在一些缺陷。 因此，通過傳輸介質發送的信號也不完美。 這種缺陷會導致信號損傷 。

It means that signals that are transmitted at the beginning of the medium are not the same as the signals that are received at the end of the medium that is what is sent is not what is received. These impairments tend to deteriorate the quality of analog and digital signals.

這意味著在媒體開始處發送的信號與在媒體結束處接收的信號不同，即發送的內容與接收的內容不同。 這些損害往往會降低模擬和數字信號的質量。

后果 (Consequences)

For a digital signal, there may occur bit errors.

對于數字信號，可能會發生誤碼。

For analog signals, these impairments degrade the quality of the signals.

對于模擬信號，這些損害會降低信號質量。

損害原因 (Causes of impairment)

There are three main causes of impairment are,

造成損害的三個主要原因是：

Attenuation

衰減

Distortion

失真

Noise

噪聲

1)衰減 (1) Attenuation)

Here attenuation Means loss of energy that is the weaker signal. Whenever a signal transmitted through a medium it loses its energy, so that it can overcome by the resistance of the medium.

此處的衰減表示能量損失，即較弱的信號。 每當通過介質傳輸的信號都會損失其能量，因此可以通過介質的阻力克服。

• That is why a wire carrying electrical signals gets warm, if not hot, after a while. Some of the electrical energy is converted to heat in the signal.

  這就是為什么載有電信號的電線會在一段時間后變熱，甚至變熱的原因。 某些電能在信號中轉換為熱量。

• Amplifiers are used to amplify the signals to compensate for this loss.

  放大器用于放大信號以補償這種損耗。

• This figure shows the effect of attenuation and amplification:

  該圖顯示了衰減和放大的效果 ：

• 
  
  
  
  
  
  

• A signal has lost or gained its strength, for this purpose engineers use the concept of decibel(dB).

  信號丟失或增強了強度，為此，工程師使用分貝(dB)的概念。

• Decibel is used to measure the relative strengths of two signals or a signal at two different points.

  分貝用于測量兩個信號或兩個不同點的信號的相對強度。

• If a signal is attenuated then dB is negative and if a signal is amplified so the db is positive.

  如果信號衰減，則dB為負；如果信號放大，則db為正。

  Attenuation(dB) = 10log10(P2/P1)

  衰減(dB)= 10log10(P2 / P1)

  where P2 and P1 are the power of a signal at points1 and 2.

  其中P2和P1是點1和2處的信號功率。

2)失真 (2) Distortion)

If a signal changes its form or shape, it is referred to as distortion. Signals made up of different frequencies are composite signals. Distortion occurs in these composite signals.

如果信號改變其形式或形狀，則稱為失真。 由不同頻率組成的信號是復合信號。 這些復合信號中會發生失真。

• Each component of frequency has its propagation speed traveling through a medium and therefore, different components have different delay in arriving at the final destination.

  頻率的每個分量都具有通過介質傳播的傳播速度，因此，不同的分量在到達最終目的地時會有不同的延遲。

• It means that signals have different phases at the receiver than they did at the source.

  這意味著信號在接收器處的相位與在信號源處的相位不同。

• This figure shows the effect of distortion on a composite signal:

  該圖顯示了失真對復合信號的影響：

• 
  
  
  
  
  
  

3)噪音 (3) Noise)

Noise is another problem. There are some random or unwanted signals mix up with the original signal is called noise. Noises can corrupt the signals in many ways along with the distortion introduced by the transmission media.

噪音是另一個問題。 有一些隨機或不想要的信號與原始信號混合在一起稱為噪聲。 噪聲會以多種方式破壞信號，并破壞傳輸介質帶來的失真。

Different types of noises are:

不同類型的噪音是：

Thermal noise

熱噪聲

Intermodulation noise

互調噪聲

Crosstalk

相聲

Impulse noise

脈沖噪聲

a)熱噪聲 (a) Thermal noise)

The thermal noise is random motion of electrons in a conductor that creates an extra signal not originally sent by the transmitter.

熱噪聲是導體中電子的隨機運動，會產生額外的信號，該信號最初不是由發射器發送的。

It is also known as white noise because it is distributed across the entire spectrum (as the frequency encompass over a broad range of frequencies).

也被稱為白噪聲，因為它分布在整個頻譜中(因為頻率涵蓋了很寬的頻率范圍)。

b)互調噪聲 (b) Intermodulation noise)

More than one signal share a single transmission channel, intermodulation noise is generated.

多個信號共享一個傳輸通道，會產生互調噪聲。

For instance, two signals S1 and S2 will generate signals of frequencies (S1 + S2) and (s1 - S2), which may interfere with the signals of the same frequencies sent by the sender. due to If nonlinearity present in any part of the communication system, intermodulation noise is introduced.

例如，兩個信號S1和S2將生成頻率為(S1 + S2)和(s1-S2)的信號，這可能會干擾發送方發送的相同頻率的信號。 由于如果通信系統的任何部分都存在非線性，則會引入互調噪聲。

c)相聲 (c) Cross talk)

Cross talk is an effect a wire on the another. One wire acts as a sending antenna and the transmission medium acts as the receiving antenna.

串擾是一種相互影響的作用。 一根導線充當發送天線，傳輸介質充當接收天線。

Just like in telephone system, it is a common experience to hear conversation of other people in the background. This is known as cross talk.

就像在電話系統中一樣，在后臺聽到其他人的交談是一種常見的體驗。 這就是所謂的串擾。

d)脈沖噪聲 (d) Impulse noise)

Impulse noise is irregular pulses or spikes( a signal with high energy in a very short period) generated by phenomena like that comes from power lines, lightning, spark due to loose contact in electric circuits and so on.

脈沖噪聲是不規則的脈沖或尖峰(在很短的時間內具有高能量的信號)，是由電源線，雷電，電路接觸不良引起的火花等現象產生的。

It is a primary source of bit-errors in digital data communication that kind of noise introduces burst errors.

噪聲引入突發錯誤是數字數據通信中比特錯誤的主要來源。

翻譯自: https://www.includehelp.com/computer-networks/transmission-impairment.aspx

什么是bcd碼數據傳輸通訊

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