Emphasis and De - Emphasis ???

I read some datasheets talk about "emphasis" and "De - Emphasis" terminologies. What is it? Help me, Plz!

Thank you!

kiddy said:

I read some datasheets talk about "emphasis" and "De - Emphasis" terminologies. What is it? Help me, Plz!

Thank you!

Click to expand...

They are used for FM modulation and de-modulation. Emphasis or Pre-emphasis is added at the modulator side and increase the gain at high frequency against the boardcasting attenuation, and de-emphasis at de-modulator is to restore the normal gain at high freq. . The most popular emphasis filter is 50us, 75us, J.17

kiddy,
preemphasis is used to shape the spectrum of a signal so that its frequency components are more nearly equal. This improves the signal to noise ratio at the receiving end. At the receiver, deemphasis is used to resotre the origninal frequency spectrum.
Regards,
Kral

Thank you all.!

hi kiddy

emphasis: in this case is to emphasize higher frequency components, and de-emp..is the opposite to restore the signal

take an example of freq modulation: here the baseband signal before been fed to fm transmitter is been emphasized(in this case the at the receiver's output the noise distribution is kf^2, where k is a constant. which tells the higher freq components are affected by noise more than the lower freq)

so emphasize the higher freq of baseband input signal(so that higher freq have higher power)
now the noise has little effect on the higher freq components...

another example is tape recorder, while recording the recorder head, works well with lower freq (since its an inductance, its impedance is low for lower freq....and hence good response for lower freq) now when i emphasize the input signal, the recorder head's output is linear.

just go thro digital and analog communications by sam shanmugam...or simon haykin