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I've set up two antennas with Linear Polarization (LP) in both sides, in 2.4 GHz no more than 4 meters each other, but they are facing strongly obstruction object (like a big steel wall in they line of sight) so they EM waves are constantly reflecting. Even though I'm able to see signals in LP but they are too weak, (-80dBm according to RSSI) so I've been reading about Circular Polarization (CP) and how satellites uses this for accounting a lot of reflection along the path. Even if antennas distance is few meters I want to improve this communication and one thing that I have in mind is using CP in the receiver (can't use CP in the transmitter because of limited space). But CP could have advantage in multipath fading which is likely the environment I have.

The currently set up have antennas with 5 dBi gain in transmitter and 16 dBi in receiver. With vertical monopole 8 shape in the transmitter and Directional in the receiver. What do you recommend me for improving this communication? What things to account for?

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  • \$\begingroup\$ What sort of omnidirectional transmit antenna is giving you a gain of 5 dBi? \$\endgroup\$
    – Andy aka
    Commented Mar 3, 2015 at 13:38
  • \$\begingroup\$ This for example: l-com.com/… \$\endgroup\$
    – progloverfan
    Commented Mar 3, 2015 at 13:46
  • \$\begingroup\$ @Andyaka: "omnidirectional" is a very fuzzy term these days.. \$\endgroup\$
    – PlasmaHH
    Commented Mar 3, 2015 at 13:54
  • \$\begingroup\$ Ok you are right is not omnidirectional in the real sense. The typical donut shape for monopole antenna. Is omni in the H plane only. \$\endgroup\$
    – progloverfan
    Commented Mar 3, 2015 at 13:58
  • \$\begingroup\$ I'm happy with the definition of an omni but your gain might be too high and the significantly flat donut shape from an antenna with 5dBi gain might be largely wasted due to misalignment vertically. \$\endgroup\$
    – Andy aka
    Commented Mar 3, 2015 at 14:02

1 Answer 1

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A dipole with a gain of 5dBi might have an elevation radiation pattern quite similar to this Lower diagram: -

enter image description here

Note the lower of the diagrams - the beam width is quite tight and peaks at about 5dBi. Compare this with a regular dipole: -

enter image description here

Despite the peak elevation power only being around 2dBi (lower right hand diagram) there is good coverage over a broader angle compared with the higher gain dipole. This means that when there is significant differences in alignment between antennas (and the distance between them is short), the lower gain antenna is likely to outperform the higher gain antenna.

Pretty pictures taken from here

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  • \$\begingroup\$ I really like your answer!. I can't vote up because I don't have enough reputation. I like to vote this as accepted but I want information about the mixing polarization performance. CP and LP. But there is enough improvement about misalignment antennas and lower gain! \$\endgroup\$
    – progloverfan
    Commented Mar 3, 2015 at 14:49

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