# doppler efffect

Discussion in 'Wireless & RF Design' started by vj39, Oct 1, 2012.

1. ### vj39 Thread Starter Member

Feb 16, 2012
17
0
mti radars use doppler effect based on phase shift principle and cw radars use frequency shift...so is the phase and frequency shift in doppler effect real or apparent?...is it the phase shift which causes an apparent frequency shift or the other way round?...(newbie to radars)

2. ### K7GUH Member

Jan 28, 2011
191
23
At the risk of seeming too abrupt, I would observe that if it weren't real, you couldn't measure it. So, if it matters to you, please explain the full context of your question. We, the experts and the wannabees, have always failed at reading a poster's mind.

3. ### vj39 Thread Starter Member

Feb 16, 2012
17
0
when u consider a frequency modulated wave and phase modulated wave its hard to differentiate between the two without observing the modulating signal...
re framing my question
In Doppler effect is it the phase shift which causes the frequency shift or vice versa or is it both phase and frequency shift occurring simultaneously?

4. ### BMorse AAC Fanatic!

Sep 26, 2009
2,675
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5. ### vj39 Thread Starter Member

Feb 16, 2012
17
0
"The frequency of the sounds that the source emits does not actually change. To understand what happens, consider the following analogy. Someone throws one ball every second in a man's direction. Assume that balls travel with constant velocity. If the thrower is stationary, the man will receive one ball every second. However, if the thrower is moving towards the man, he will receive balls more frequently because the balls will be less spaced out. The inverse is true if the thrower is moving away from the man. So it is actually the wavelength which is affected; as a consequence, the received frequency is also affected. It may also be said that the velocity of the wave remains constant whereas wavelength changes; hence frequency also changes."(wikipedia)