External Antenna Considerations; Omni-Directional Antennas; Antenna Polarization - Airspan ASWipLL Quick Installation And Configuration Manual

AS W i p L L 9 0 0 M H z

External Antenna Considerations

This chapter discusses main issues when using third-party external antennas.
Notes:
1) To avoid unnecessary RF cable loss, use short-length cables and with low attenuation.
2) Antennas should have a VSWR of less than 1:1.5.
3) Ensure BSR and SPR/IDR use the same antenna polarity.
4) When using an omni-directional antenna, choose a type providing a wide vertical beam width of at
least 8° to allow connection of nearby CPEs.
5) Antennas must be DC grounded.
6) In accordance with FCC regulations for operating in unlicensed bands, BSR external antennas must
provide an EIRP of less than or equal to 36 dBm to prevent interference with other radios operating in the
unlicensed band.

3.1. Omni-Directional Antennas

In some scenarios, where capacity demand is relatively low, external omni-directional antenna use at the Base
Station may seem attractive. However, it is recommended to avoid using omni-directional antennas (if
possible), due to the following disadvantages that these antennas pose compared to directional antennas:
Higher sensitivity to external interferences.
Higher sensitivity to multipath, resulting in the following:
The root mean square (RMS) delay spread at the Base Station is substantially higher.
Multipath interference at the CPE side (when using omni-directional antenna at the Base Station) is
substantially higher. In fact, when using an omni-directional antenna, the existence of clear Fresnel
zone between BSR and SPR/IDR is insufficient to eliminate multipath interference, since multipath, in
this case, can be caused by reflections originating from obstacles outside the Fresnel zone.
Higher sensitivity to alignment. Since the omni-directional antenna gain is achieved by narrowing the
vertical beam width, a relatively low deviation in the antenna alignment results in severe signal attenuation

3.2. Antenna Polarization

The performance of ASWipLL 900 may vary dramatically depending on the polarization of antennas, i.e.
vertical or horizontal. Therefore, it is recommended that the operator, during installation, compare the
performance between horizontal and vertical polarization of external antennas, and use the polarization
providing the best performance.
Note: Some antennas support both horizontal and vertical polarization:
- Yagi
- 9 dBi antenna (Cat. No. 35000008)
- 6.5 dBi antenna (Cat. No. 35000009)
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Q u i c k I n s t a l l a t i o n & C o n f i g u r a t i o n G u i d e
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