Lecture #8 - Linear Phase

Question 1

What is a distortionless transmission?

Answer 1

System gives distortionless transmission if the form of the signal passed through that system is unaffected.

i.e. the o/p signal is a delayed and scaled replica of the input signal

Question 2

What must be done to the system to get distortionless transmission in frequency

Answer 2

1. System must amplify or attenuate each frequency component uniformly.

• The magnitude response must be uniform within the signal frequency band.

2. System must delay each freqeuncy component by the same number of samples.

Question 3

Outline the equations and graph for an ideal delay system

Question 4

What is the phase delay?

Answer 4

The relative delay imposed on individual frequency components of the input signal

Question 5

What happens if the phase delay is constant?

Answer 5

There’s distortionless transmission

Question 6

What is a linear-phase filter?

Answer 6

Phase varies linearly with /omega (frequency)

This means linear-phase filters do not introduce distortion to the shape of the waveform.

Question 7

A symmetry impulse response means what in phase?

Answer 7

Linear phase

Question 8

What is the difference between necessary and sufficient conditions?

Answer 8

1. Necessary; has to be fulfilled
2. Sufficient; other conditions must be fulfilled

Question 9

What does nonlinearity of the phase mean?

Answer 9

Results in time dispersion

Question 10

What’s the reality of implementing linear-phase in filters?

Answer 10

1. IIR filters transfer function; nearly impossible to implement
2. FIR filter transfer function; always possible to design with an exact linear-phase response

Question 11

What happens to the impulse response of the linear-phase FIR when the phase is linear?

Answer 11

1. The impulse is symmetric
2. IR is antisymmetric