The direction of phasor determines whether polarization is left handed or right handed. For an observer viewing the wave approaching, the rotation of electric field vector in a stationary transverse plane is clockwise for left hand circular polarization as standardized by IEEE.
Nobody ever transmits circular polarization, but elliptical polarization, because here is always some of the wrong polarization present, except at a few directions where the polarization may be exact. You need to design for as good as your system requires. If two antennas have the same elliptical polarization, they can receive all of each other's power if the axes of the ellipses are lined up, but if the polarization axis isn't lined up then some of the power won't be received and there will be a loss of gain and sensitivity, and there will be cross-talk if two channels are on opposite polarizations. Circular polarization is good because it doesn't matter whether the antennas are the same way up, so long as they are pointing at each other. This isn't the case for elliptical or linear polarizations.
Elliptical polarization is the combination of two opposite circular polarizations of different sizes, and also the combination of a circular polarized and a linear polarized signal.
If you design for non-circular, that will set the limit for what you can achieve. You have to assume that some or all of the time most of the power radiated in the wrong polarization will be wasted. Satellites cost a lot of money to put into orbit, and the antennas, the amplifiers and their power supplies and solar panels all add weight, so anything in the design that wastes that power by putting it into the wrong polarization is very expensive in the weight needed to get even more power for the antenna design to waste. For a receiving antenna on earth, if there is enough extra power arriving, or you can afford a larger antenna (which has a narrower beam so is harder to point correctly), then you can use a poorly polarized antenna, unless the system uses opposite polarizations to separate channels.
- Badges
- Science topic
- Similar topics
- Vectorization