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GNSS Antennas

Selecting a GNSS Antenna

  • Using a passive GNSS antenna is possible but not recommended. This requires a high RHCP antenna gain, good view of the sky, and a short matched/tuned 50 Ω input impedance line. This option may be appropriate to minimize BOM costs.
  • Best performance is achieved by using an active antenna with integrated LNA. The LNA gain must be >17dB for standard GPS-INS use.
  • For RTK and dual antenna (GPS compassing) use, the following characteristics are recommended: gain >26dB, multipath signal rejection, better signal to noise ratio, and improved carrier phase linearity.
  • Antennas with integrated SAW filter may be necessary to reject interference from near frequencies or harmonic signals, such as wireless and LTE.
  • For RTK and dual antenna applications we recommend dual feed (dual element) GNSS antennas

GNSS Antenna Integration Considerations

GNSS Antenna Ground Plane

A GNSS antenna ground plane blocks multipath signals, creating a shadow area for the antenna to hide in. The ground plane is acting as an RF blocking device. It is made of any material that attenuates (or totally blocks or reflects) RF signals. It creates a shadow area for the antenna to hide in. That shadow is a cone above the ground plane. Any signals that come down from the satellites and are bouncing back upward from the earth can’t get to the antenna. Only signals coming directly from above can get to the antenna. The distance of the physical antenna above the ground plane changes the shape of the RF blocked shadow area.

The signal gain on some antennas can be improved by increasing the ground plane size up to a given size. Beyond that given size the antenna gain is not affected much.

A ground plane width of 8 to 12 cm is typically large enough for most applications.

u-Blox: RF design considerations for GNSS receivers Application Note

Taoglas: GPS Patch Integration Application Note

electronics.stackexchange.com: How big a ground plane does a GPS antenna need?