I'm currently working on circular polarization Off-Body Antenna, i'm looking for the detailed steps to follow how to measure the axial ratio and plot the graph of (axial ratio vs frequency) using the lab volt material, that would be really appreciated !
thank you !
Please check the following:
Article Axial ratio measurements of single circularly polarized antennas
Article Antenna Pattern Measurement: Theory and Equations
https://www.keysight.com/upload/cmc_upload/All/ORFR-Theory.pdf
http://ocw.upm.es/teoria-de-la-senal-y-comunicaciones-1/antenna-design-and-measurement-techniques/contenido/laboratory-session-09.pdf
Use a linearly polarized antenna and rotate it while keeping it in the same position pointing at the antenna under test. The square root of the variation in received power is the axial ratio.
i don't understand what you mean about "whilw keeping it in the same position pointing at the antenna" since it's rotating ...please i need some more details about the conception as a scheme of the antenna positions.
thank you ...
If you point a linearly polarized antenna at the antenna you want to measure (Antenna Under Test, AUT), and spin the linearly polarized antenna around the axis that is the same as the line joining the two antennas, then, if the AUT is perfectly circularly polarized, the signal received by the linearly polarized antenna will not change in amplitude. If it does change, the ratio between the max and min is the axial ratio. You would need to repeat this for all directions from the AUT in which you wanted to know the radiation pattern. If the linear antenna is spun quickly then the AUT can be continuously moved slowly, so that the axial ratio can be measured continuously as the radiation pattern is measured. The signal can be measured using a power meter or network analyser, and it can be compared to another measurement, of a known gain antenna, if a gain measurement is required.
thank you so much Mr Spyridon K Chronopoulos and Mr Malcolm White, I've got good measures, the axial ratio measured is quite well :)
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