[5] Space Diversity Calculation

Antenna separation

Theoretically, proper antenna separation is determined by the degree of fading correlation between both paths. The separation isvertical because the antennas are situated in two different layers of the atmosphere. In principle, the larger the separation between both antennas of a 1+1 system the better the improvement (less correlation) and consequently the larger the path length will be. The degree of correlation decreases exponentially and reaches a certain level for which no more detectable improvement is attained (the path length does not increase).

Several “rules of thumb” to find out reasonable antenna separation are found elsewhere in the literature. Two general such rules are frequently used,

Dsep (m)=200×lm

(1)

and

Dsep (m)=80/fGHz

(2)

where D_sep is the vertical separation in m, l_m and f_GHz are expressed in meter and GHz, respectively. Applying equation (1) and (2) to the studied frequency bands, the vertical antenna separations are as given in Table 1.

Frequency (GHz)	Dsep(m)=80/fGHz	Dsep (m)=200×lm
7/8	11.4	8.6
13	6.2	4.6
15	5.3	4.0
18	4.4	3.3

Table 1: Vertical antenna separation expressed in meters as obtained by equation (1) and (2).