Axial ratio of circular vs 45 degree linear polarization question

[yefj]

Hello, Axial ratio is defined as the ratio between amplitude of one component of electric field and another component of electric field.
But this definition doesnt take into account the phase between them.
So technically if we have X-axes and Y-axes components withe the same amplitude and zero phase between them,then by the Axial ratio formula we will have 0dB as if its a circular polarization.
Where am i wrong in my logic?
Thanks.

 

[FvM]

Phase 0 means linear polarization, e.g. 45 degree rotated. No circular polarization without phase difference.

 

[yefj]

Hello VFM,both linear polarization with equal orthogonal amplitude and circular polarization.
Will have mathematickly the same Axial ratio.
That is the problem.
Axial ratio by itself cannot say if the fieal is circular.
We need 90 degree phase also?
correct?
AXIAL ratio cannot say if we have circular polarization.

 

[c_mitra]

Linear polarization means that all the waves that arrive at a given point have their electric fields aligned in one plane. A single wave (photon) is always plane polarized. A circularly polarized wave has the electric vector rotating (either clockwise or anti) if you look along the direction of propagation.

Now sitting at the detector (antenna) site and looking at the direction of the approaching wave, you will see either the electric vector in one plane (plane polarized), randomly distributed (unpolarized) or rotating (circularly polarized). Now your antenna (detector of the electric field) can sense the electric field if it is so oriented (for a dipole antenna can detect a plane polarised wave). If the electric field is at an angle, only the component of the electric field onto the antenna is detected.

 

[c_mitra]

View attachment 170927

This statement is correct; if you can restate your question in a different form (I cannot understand your question in the present form) I can perhaps (or someone else) can try to clarify and doubts.

This is a polar diagram; the electric fields are represented with the amplitude vector ("A" in Asin(wt)) and you can get an elliptically polarized wave if you do not have equal amplitudes for the two constituent waves (e.g., A1sin(wt) +A2sin(wt+phi)).