What is meant by Phase Shifting?

Answer 1

Phase shifting basically means moving the reference from where the wave starts along x axis. For example, sine wave and cosine wave are basically similar, but have different starting points along x axis. Therefore, it's clear that shifting a sine wave by 90 degree towards negative infinity will give cosine wave.

Answer 2

Imagine two cars racing around a racetrack at the same speed, but one is a few feet ahead of the other. Since the speed is the same, their position with respect to each other does not change, yet they are not exactly 'lined up'. If you stand on the sidelines, you would see one car pass by before the other each time they go by, even though they are both going the same speed. The same situation can exist with two alternating voltages, for instance. They could both be the exact, same frequency, yet be 'out of step' with each other. If you looked at the two voltages on an oscilloscope, you would see the two waveforms peak at different places on the screen, almost like you were having double vision. This time difference (or offset) between two waveforms of equal frequency is phase shift. So, two recurring events that happen with equal regularity but not at the exact same time are said to be 'out of phase' with each other, or 'there is phase shift' between the two. If they do happen at the same time, they are 'in phase' or, there is 'no phase shift'between them. Have you ever heard someone say "you zigged when I zagged" or "whenever I am arriving, you seem to be leaving?" - phase shift! Or, if you walk down the sidewalk with someone, and when you step with your left foot they are stepping with their right foot, your feet are 'out of phase' with their feet. Even if you just put your left foot down a tenth of a second after your friend's left foot touches the ground, there is still a little phase shift between you. On the other hand, if you watch a marching band march, their feet are all 'in phase'. Phase shift is usually measured in degrees. One complete cycle of the recurring event is 360 degrees, same as the number of degrees in a complete circle. So, in the case of left foot / right foot above, the phase shift would be 180 degrees. This is the origin of the saying "180 degrees out" meaning the exact opposite.

Answer 3

Doppler shift is the observed effect to frequency or phase noted when the producer of a periodic wave and the observer of that periodic wave are moving with respect to each other.

The best example of this is the apparent change in frequency of a siren when an ambulance goes past you. Another example is red shift, where the color of a receding star shifts towards the red end of the visible light spectrum due to its velocity relative to the Earth.

When the propagation speed depends on the medium, such as for sound, the velocity of both the producer and observer relative to each other and to the medium must be considered. When the propagation speed does not depend on the medium, such as for light, only the velocity of producer and observer relative to each other need be considered.

Answer 4

· Amplitude shift keying · Frequency shift keying · Phase shift keying