Q10Control System
Question
Q.10. What is all pass system? Also write its application.
Answer
An all-pass system has a magnitude response equal to unity (constant) at all frequencies but a frequency-dependent phase shift, achieved by pole-zero pairs symmetric about the jω-axis; used for phase/delay equalization without altering amplitude.
An all-pass network is one whose transfer function magnitude |G(jω)| = 1 for every frequency ω, i.e. it passes all frequency components with equal gain, while contributing a phase shift that varies with frequency. This is achieved using a zero in the right-half plane that mirrors a pole in the left-half plane, e.g. G(s) = (s-a)/(s+a) with a > 0. Its main application is as a phase equalizer/delay compensator in communication and control systems where phase or group-delay correction is needed without disturbing the amplitude response, and it is also used to model non-minimum-phase behavior in system identification.