27 Antenna configuration for horizontal and vertical separation 28 Horizontal & vertical spacing vs. antenna isolation The isolation according to increasing horizontal separation with fixed 1 m vertical separation is shown at Fig. 28. Interestingly, the isolation for the mixed horizontal and vertical separation is decreasing with the increase in horizontal separation distance. But this is still better than that in the case of simple horizontal isolation. Therefore, mixed horizontal and vertical separation may be more effective where use of same antenna pole for both BS antennas is not possible. 8.2.1.4 Result summary The measured isolation for all the antenna configurations considered is summarized in Table 5. If isolation with only the horizontal antenna configuration is considered, then a maximum of 76 dB isolation was measured with 3 m separation and 4° of electrical down-tilt. On the other hand, with vertically separated antennas, a maximum of 83 dB isolation was measured with 0.5 m separation and 4° of electrical down-tilt. However, the practical configuration may depend upon the environment of the base station antenna installation, as well as the required isolation for protecting the system performance. TABLE 5 Summary of antenna configuration and measured isolation Antenna configuration Measured isolation Horizontal separation 3 m/8 m 56 dB/61 dB Horizontal separation 3 m with 0°/+15°boresight angle rotation 56 dB/60 dB Horizontal separation 3 m with 0°/4°electrical down-tilt 56 dB/76 dB Vertical separation 0 m 70 dB Vertical separation 1 m with different antenna pole (horizontal separation 1 m) 76 dB Vertical separation 0.5 m with 0°/4°electrical down-tilt 76 dB/83 dB results may be compared to those obtained from the analytical formula in § 6. For 2 665 MHz the necessary horizontal separation to obtain 60 dB isolation is 9.0 or 2.85 m, depending on the antenna gain in the direction of the other antenna, which is not in contradiction with the results above. The analytical results for 2 665 MHz and a vertical edge-to-edge separation of 0.71 m is an isolation of 60 dB, somewhat lower than the measured results. 8.2.2 Measurements of horizontal separation in the 900, 1800 and 2 GHz bands Measurements of isolation due to horizontal separation of mono-band antennas have been carried out for 900, 1 800 and 2 000 MHz with antenna characteristics as defined in 6. The results are presented in Table 7, where the separation distance between the antennas is expressed as edgetoedge. 6
8.2.3.3 Measurement results The following tables show measurement results. Readings 1 and 2 correspond to measurements of the same scenario, but at different points in time. 8 Vertical isolation of item 1 (Vertical polarization ~ Vertical polarization) Sequence Frequency (MHz) Edge distance (m) Reading 1 (dB) Reading 2 (dB) Scenario 1 890 0.21 47.22 – Close 890 0.21 46.24 – Away 2 890 1.32 59.92 60.42 Close 890 1.32 60.15 61.00 Away 3 890 2.38 54.65 55.67 Close 890 2.38 61.26 60.86 Away 4 890 3.77 – – Close 890 3.77 64.68 64.46 Away TABLE 9 Vertical isolation of item polarization ~ 45° Sequence Frequency (MHz) Edge distance (m) Reading 1 (dB) Reading 2 (dB) Scenario 1 890 0.30 55.33 – Close 890 0.30 57.14 – Away 2 890 3.50 69.20 70.07 Close 890 3.50 71.50 – Away 3 830 3.50 60.77 – Away TABLE 10 Vertical isolation of item 3 (In phase 45° polarization) Sequence Frequency (MHz) Edge distance (m) Reading 1 (dB) Scenario 1 890 0.19 44.76 Close 890 0.19 55.06 Away 2 830 0.19 52.71 830 0.19 58.28 Away 3 890 3.62 61.27 Close 890 3.62 66.73 Away