GPS antennas = circular polarized？

[senmeis]

Hi,

I read almost all the GPS antennas are circular polarized. Is it also true for satellite receiving antennas?

 

[volker@muehlhaus]

Yes, that would make best use of the available signal.

But I have already designed GNSS receive antennas with linear polarisation for special cases where circular was not possible.

 

[vfone]

Polarization loss between linear polarization (vertical or horizontal) and circular polarization is 3dB.
The average GPS free-space path loss is about 122dB (for average satellite altitude ~20200km). At this path loss, is not such important another 3dB extra loss.

 

[erik zhong]

Your answer is so clear. May I ask an another question. If there is an antenna which is lossless and has an uncertain polarization. If it has 2dB polarization loss when RX antenna is LFCP. What the polarization loss will be if the RX antenna is RHCP?

 

[vfone]

If you get about 2dB loss when the RX antenna is LHCP and more than 20dB loss if the RX antenna is RHCP, most probably the uncertain polarization antenna is circular LHCP.
If you get about 2dB for both RX circular polarization (LHCP or RHCP) means the uncertain polarization antenna have linear polarization (vertical or horizontal).