Thread: Distortionless Transmission

In my Signal Analysis course, I learnt that for a distortionless transmission, the magnitude response of a channel should be constant and its phase reps should be linear. THe magnitude reps part is understood. But i'm a bit skeptical about the linear phase part. Could any one please clarify. I feel that phase reps also should be const.

At the same channel length, twice the frequency has twice the phase delay, right? So, a linear frequency increase has to have a linear phase increase, therefore phase response of the distortionless channel has to be linear.

Hi,

a signal is transmitted through a system without distortion, when all frequencies contained in the signal have the same delay. The frequency dependent delay is described by the group delay. If group delay is constant over frequency, all frequencies in the signal are delayed by the same amount.

Group delay on the other hand is the derivative of the phase response with respect to angular frequency. This derivative is only constant if the phase response is linear.
So this is the mathematical reason, why the phase response has to be linear for distortionless transmission.

no,u littlebit confused abt phase part.Linear phase means it directly proptional to frequency.because ω is always present.if u r not clear abt this then u may take help of any standard text of signal and system book eg openheim or lathi

During the transmission of signals, there is always a delay between the receiving end signal and the sending end signal. For the distortionless transmission there must be the uniform delay of all the frequency components.
If the phase is linear , delay=d(phase)/d(frequency) is constant..
if the phase is constant, the delay=0 which cannot be realised in the real transmission.