I measured the radiation pattern of a patch antenna using Agilent N9923A Vector Network Analyzer (VNA). The measurement setup involves:
1) Connecting horn antenna at first port of VNA (horn antenna = transmitting antenna)
2) Connecting my designed patch antenna at second port of VNA (patch antenna = receiving antenna)
3) Then by calculating the S21, I plotted the radiation pattern of patch antenna
Now my question is: Is the above mentioned procedure is the correct one for calculating the radiation pattern of my designed patch antenna ?
Please answer me.
This is correct - you will measure the radiation pattern of the antennas in the surroundings they were in. There may be reflections from nearby objects that may distort the pattern. You need to make sure that your horn is further away than twice the square of its diagonal divided by the wavelength, or the same for the antenna you are measuring if it is bigger, and that they are far enough apart that reflections between them don't cause ripples in the measurement for small changes in distance (half a wavelength). You also need to make sure you have the polarization correct. If you rotate the horn the size of the signal will probably change, so you need to be careful that you know which polarization you are measuring in which direction. Three schemes for defining polarization are defined by Ludwig.
To Malcolm white,
But, how to get phi=0 degrees and 90 degrees radiation pattern?
Which antenna rotation needs to be done?
Can you please provide any images or text regarding this
By Phi=0 and phi=90 I guess you mean two cuts at right angles to each other that cross directly in front of the antenna (Theta=0). You need to define these directions. Where is "forwards"? That is theta=0, and the two phi cuts cross in this direction. You have to define or decide what is phi=0 and phi=90 degrees. Perhaps phi=0 is in line with the feed? Usually for a rectangular patch or horn phi=0 might correspond to one axis of the patch, or to the horizontal direction if the antenna points sideways, and phi=90 the other axis of the patch, or to the vertical direction. Whatever you choose, put it in the results so other people know what you have done. For principal-plane cuts (phi=0 and 90) and linear polarization it is usual to measure with the polarization parallel to the plane of each cut and normal to the plane of each cut.
To Malcom white,
I agree with the information you provided.
I need the measurement process of those two cuts.
Thanks.
It is usual to rotate the antenna to be tested, about the 2 principal axes. Perhaps use a stepper motor? You need to use absorber so that when the antenna is pointing at the floor or wall the reflection does not add to the direct signal, which may be smaller.
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