Type of antenna for 5.8 Ghz omni antenna
Should I try to make it circularly polarized also? If so, would I want a CP or vertically polarized receive antenna to match it?
Is it in the multipath evironment? If so, any omni-direction antenna will work since you will receive statistical waves. If multipath exists, i think polarlize of antenna is not a major problem. The radiation pattern is not a major concern. It seems that it will be a small antenna. If so, radiation efficiency is more critical parameter.
I think for 5.8GHz omi-directional. λ/2 dipole is suitable. You can achieve omi pattern when you place the PCB vertically. It should be linear polarization.
Well, there IS plenty of multipath, but it is not a mimo receiver so I am trying to mitigate the multipath.
There are actually 4 antennas and a SP4T switch, so I would prefer to print the antennas and the switch onto the same pcb. All the mmic switches have single ended outputs, so I will either have to use a balun at each output, or use a λ/4 antenna.
I was thinking of λ/4 transmit antennas on the pcb, and a circularly polarized receive antenna, thinking that then no matter how I rotated the transmit pcb, the receive antenna would pick up some of the signal. I am willing to take a 3 dB hit on the linear to circular polarization mismatch if I can avoid a 20 dB null as the TX pcb is rotated.
Obviously I am not an antenna guy! Is my thinking correct?
Check this document at page 4.
http://www.cushcraft.com/comm/suppor...tion-14B32.pdf
As you can see could be up to 10dB mismatch between a Linearly and Circularly polarized antennas (worst case).
Better choice seems to be using a linear polarized antenna and dual linearly polarized antenna?but is harder to be implemented.