Explain the antenna arrangement of space diversity used at cell site

5. Explain the antenna arrangement of space diversity used at cell site.

Space-Diversity Antennas Used at Cell Site:

Two-branch space-diversity antennas are used at the cell site to receive the same signal with different fading envelopes, one at each antenna. The degree of correlation between two fading envelopes is determined by the degree of separation between two receiving antennas. When the two fading envelopes are combined, the degree of fading is reduced. Here the antenna setup is shown in Fig. 5a.

Equation is presented as an example for the designer to use.

Ș = h/D = 11 (8.13-1)

where h is the antenna height and D is the antenna separation. From Eq., the separation d ≥ 8λ is needed for an antenna height of 100 ft (30 m) and the separation d ≥ 14λ is needed for an antenna height of 150 ft (50 m). In any omni cell system, the two space-diversity antennas should be aligned with the terrain, which should have a U shape as shown in Fig.5b. Space-diversity antennas can separate only horizontally, not vertically; thus, there is no advantage in using a vertical separation in the design.