[SOLVED] explanation of doppler shift if the angle is 90

[rawanayyoub]

Hi all,
Please I need an explanation a bout the Doppler effect; according to this equation :-
Δf = ( V/λ)cosΘ
where:-
Δf : is the Doppler frequency Shift
V : Vehicle speed
Θ : the separation angle between the direction of motion of the mobile and the direction of arrival of the wave

according to the equation If the vehicle is moving directly towards the transmitter Δf become positive that's related to Θ=0 & if the vehicle is moving directly away from the transmitter Δf become negative that's related to Θ= 180 ,If the vehicle is moving perpendicular to the angle of arrival of the transmitted signal Δf become zero that's related to Θ=90 for the last case I need an explanation why this happen or how it is happened , Please I need this explanation so badly.

Thanks for any help.
Rawan Ayyoub

 

[Mityan]

The doppler shift = 0 means that that you receive the same exact frequency that target radiated (or reflected), without any shift.
It moves perpendicular to you, it dont get closer or farther.

 

[rawanayyoub]

Dear Mityan , thanks for your replay. i have an explanation in this figure:

According to figure, If Rx moving to A location (which is far away from the source) or to B location (which is toward the source), then ∆L increase or decrease according to Rx velocity. In case Rx moving to C location (which is perpendicular of S-Rx line) then ∆L =0, although the receiver is in motion but it was assumed to be stationary and then No Doppler Shift.

I repeat my deepest thanks :smile:
Rawan Ayyoub